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Graduate Theses and Dissertations Graduate School

2006

Gold mining in a tropical rainforest: Mercurysorption to soils in the mining region of Arakaka-Mathew's Ridge, GuyanaJoniqua A'ja HowardUniversity of South Florida

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Scholar Commons CitationHoward, Joniqua A'ja, "Gold mining in a tropical rainforest: Mercury sorption to soils in the mining region of Arakaka-Mathew'sRidge, Guyana" (2006). Graduate Theses and Dissertations.http://scholarcommons.usf.edu/etd/2564

Gold Mining in a Tropical Rainforest:

Mercury Sorption to Soils in the Mining Region of Arakaka-Matthew's Ridge, Guyana

by

Joniqua A'ja Howard

A thesis submitted in partial fulfillment of the requirements for the degree of

Master of Science in Environmental Engineering Department of Civil and Environmental Engineering

College of Engineering University of South Florida

Major Professor: Maya Trotz, Ph.D. Daniel Yeh, Ph.D.

Nooren Poor, Ph.D.

Date of Approval: September 16, 2006

Keywords: iron oxide, batch equilibrium sorption, cold vapor analysis, THg,TLM

© Copyright 2006, Joniqua A'ja Howard

DEDICATION

This is for my ancestors, grandparents, and the many storms I encountered.

Sankofa!

ACKNOWLEDGEMENTS

“It is God who arms me with strength and makes my way perfect. He makes my feet like

the feet of a deer; he enables me to stand on the heights,…broaden the path beneath me,

so that my ankles do not turn…pursue my enemies and overtake them;.. and crush them

so that they could not rise... “–Psalms 18-32-36-

Also, I must extend my deepest gratitude and appreciation for my major professor, Dr.

Maya Trotz, and my committee members (Dr. Poor and Dr. Yeh) for helping me

formulate my thesis and challenging me throughout this period. Special thanks to my

family, close spiritual cheerleaders (Erlande Omisca and Quenton Bonds), my Bridge to

Doctorate Family, Mr. Benard Batson, and my lab buddies (Melody Nocon, Mike

“Austin” Roe, and Douglas Oti) for all their support during this challenging time. Most

importantly I must thank the National Science Foundation’s Bridge to Doctorate and GK-

12 STARS programs for the financial support.

“Remember this: Whoever sows sparingly will also reap sparingly, and whoever sows

generously will also reap generously.”– 2 Cor. 9:6, NIV. –

i

TABLE OF CONTENTS

LIST OF TABLES............................................................................................................. iii

LIST OF FIGURES .............................................................................................................v

ABSTRACT...................................................................................................................... vii

CHAPTER 1: INTRODUCTION........................................................................................1

1.1 Motivation and Research Objectives ...............................................................1

1.2 Scope of Work and Approach...........................................................................2

CHAPTER 2: BACKGROUND..........................................................................................3

2.1 Introduction.......................................................................................................3

2.2 Mercury and its Health Effects ..........................................................................3

2.3 Mercury and its Uses .........................................................................................5

2.4 Impacts of Artisinal Gold Mining in South America.........................................6

2.5 Mercury Fate in the Aquatic Environment ........................................................8

2.5.1 Mercury Sorption.................................................................................9

2.6 Guyana .............................................................................................................13

CHAPTER 3: MATERIALS AND METHODS ...............................................................17

3.1 Introduction.....................................................................................................17

3.2 Materials ..........................................................................................................17

3.2.1 Glassware .........................................................................................17

3.2.2 Reagents ...........................................................................................17

3.2.3 Kemiron/Sediments ..........................................................................18

ii

3.3 Analytical Procedures ......................................................................................19

3.3.1 Cold Vapor Atomic Adsorption .......................................................19

3.3.2 Scanning Electron Microscopy/Electron Dispersive Spectroscopy....................................................................................21

3.4 Batch Equilibrium Sorption Experiments.......................................................21

CHAPTER 4: RESULTS AND DISCUSSION................................................................26

4.1 Introduction.....................................................................................................26

4.2 Total Mercury Analysis ..................................................................................26

4.3 BET SEM/EDS and XRD...............................................................................28

4.4 Batch Equilibrium Sorption .............................................................................34

CHAPTER 5: SUMMARY, CONCLUSION, AND RECOMMENDATIONS FOR FUTURE WORK..............................................................................42

5.1 Introduction......................................................................................................42

5.2 Summary of Results and Conclusions .............................................................42

5.3 Recommendations for Future Work................................................................44

REFERENCES ..................................................................................................................46

APPENDICES ...................................................................................................................54

Appendix A: Abridged Experimental Results .......................................................55

iii

LIST OF TABLES

Table 2.1: Current regulatory limits and guidelines for mercury set by the US Environmental Protection Agency and the World Health Organization ...........4

Table 2.2: Mercury concentrations in sediment and water samples from different parts of the world. ..............................................................................................7

Table 2.3: Historical background total mercury concentrations..........................................8

Table 2.4: Content of various elements in soils.................................................................10

Table 3.1: Optimal working conditions for Hg determination in sediments using CVAAS............................................................................................................20

Table 3.2: Conditions used for batch adsorption studies (1000 ppb Hg = 0.5E-5M) ...............................................................................22

Table 3.3: Formation constants for Hg2+ species, Log K’s for ionic strength ...................23

Table 4.1: Total mercury concentrations in Matthew’s Ridge/Arakaka area ....................27

Table 4.2: Summary of batch equilibrium sorption studies...............................................36

Table A.1: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Pakera Creek sediment (1.1) ..................................................................................................55

Table A.2: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Pakera Creek sediment (1.2) ..................................................................................................56

Table A.3: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Philip’s Mine tailings (2.1) .....................................................................................................57

iv

Table A.4: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Philip’s Mine tailings (2.2) .....................................................................................................58

Table A.5: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Kemiron (3.1)...............................59

Table A.6: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Kemiron (3.2)...............................60

Table A.7: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Kemiron (3.3)...............................60

Table A.8: 1,000 ppb Hg (Hg(NO3)2) sorption on 0.1 g Kemiron (4.1)............................61

Table A.9: 1,000 ppb Hg (HgCl2) sorption on 0.1 g Pakera Creek (5.1)...........................62

Table A.10: 1,000 ppb Hg (HgCl2) sorption on 0.1 g Philip’s Mine (5.2) ........................62

Table A.11: 1,000 ppb Hg (HgCl2) sorption on 0.1 g Kemiron (5.3)................................63

Table A.12: EDS quantification (Arakaka Creek).............................................................64

Table A.13: EDS quantification (Kemiron).......................................................................64

Table A.14: EDS quantification (Philip’s Mine) ...............................................................64

Table A.15: EDS quantification (Pakera Creek)................................................................65

Table A.16: EDS quantification (Pakera Creek (2)) ..........................................................65

v

LIST OF FIGURES

Figure 2.1: (A) Historical trend in nominal and real gold price = 100*(nominal average annual gold price/ average annual US CPI (all items urban consumers, 1982-1984=100). 2006 averaged from January to May). (B) Estimated global mercury use in the world in 2000 for a total of 3,386 metric tons ..............................................................................................6

Figure 2.2: Some of the transformations involved in the cycling of mercury ....................9

Figure 2.3: Depiction of the solid-water interface and sorption interpretation.................11

Figure 2.4: Map of northern portion of Guyana and test site (Arakaka) plus sites where previous studies have been published .................................................14

Figure 3.1: Speciation of 1E-5 M Hg2+.............................................................................24

Figure 3.2: Speciation of 5E-4 M Hg2+.............................................................................24

Figure 3.3: Speciation of 5E-4 M Hg2+ with 0.001M Cl- .................................................25

Figure 4.1: SEM images of Kemiron for particles up to 38 μm in diameter ....................30

Figure 4.2: SEM image of Pakera Creek particles up to 38 μm in diameter ....................30

Figure 4.3: SEM image of Philip’s Mine for particles up to 38 μm in diameter...............30

Figure 4.4: EDS spectra and chemical quantification table for Philip’s Mine tailings..............................................................................................................31

vi

Figure 4.5: EDS spectra and chemical quantification for Pakera Creek............................31

Figure 4.6: EDS spectra and chemical quantification for Kemiron...................................32

Figure 4.7: XRD spectra for Philip’s Mine tailings...........................................................33

Figure 4.8: XRD spectra for Kemiron ..............................................................................33

Figure 4.9: Sediment samples (Kemiron, Pakera Creek, and Philip’s Mine) ....................34

Figure 4.10: Typical standards curve for THg analysis using CVAAS ............................35

Figure 4.11: Hg sorption to 0.5 g/L Kemiron ....................................................................37

Figure 4.12: Hg sorption to 0.5 g/L Pakera Creek sediment .............................................37

Figure 4.13: Hg sorption to 0.5 g/L Philip’s Mine tailings................................................38

Figure 4.14: Hg sorption to 0.5 g/L of soil for 1,000 ppb Hg (from HgCl2) .....................39

Figure 4.15: Hg sorption to 0.5 g/L of soil for 1,000 ppb Hg (from HgCl2 and Hg(NO3)2) .........................................................................39

vii

GOLD MINING IN A TROPICAL RAINFOREST:

MERCURY SORPTION TO SOILS IN THE MINING REGION OF ARAKAKA-

MATTHEW'S RIDGE, GUYANA

Joniqua Aja Howard

ABSTRACT

Gold mining by artisinal (small-medium scale) miners causes an immense amount of

damage to the environment (i.e. soil erosion, mobilization of heavy metals, etc.).1, 2 One

of the most popular gold mining techniques employed by artisinal miners in Guyana is

mercury amalgamation. During the amalgamation process approximately 300 metric

tons/yr 11, 12 of mercury is used. Mercury once in the environment can be transported

through the air, soil, and water column. It is estimated that 90-99% of total mercury

(THg) is associated with the sediment. An understanding of the geochemical conditions

that affect the fate of mercury in soils, which can act as potential sinks or sources for

mercury, can provide solutions for reduced environmental impacts of mercury

contamination.

Local Guyanese agencies have become concerned with the quality of the water, soil,

biota, and human impact in remote locations in the interior of Guyana. Therefore, soil

samples were collected from two local mines in Guyana’s Arakaka-Mathew’s Ridge area.

Two soil samples (Pakera Creek and Philip’s Mine) and a commercially available iron-

oxide sorbent, Kemiron, underwent CVAAS, BET surface area analysis, electron

dispersion spectroscopy, and x-ray diffractometry. THg concentrations for recovered soil

samples were approximately 300 ng/kg. In addition, samples were subjected to batch

equilibrium sorption studies as a function of pH and mercury species/concentration added

viii

as Hg(NO3)2 and HgCl2. All samples showed significant amounts of sorption between

pH 3-9 for 100-1,000 ppb Hg added as Hg(NO3)2. When HgCl2.was added to the batch

reactor containing Kemiron, an iron-oxide surface, the adsorption behavior of Hg2+

decreased. Philip’s Mine solids, characterized as silicon dioxide by BET, had the lowest

surface area (4 m2/g) and sorption when added as Hg(NO3)2 and HgCl2. On the other

hand, Kemiron and Pakera Creek displayed similar sorption behaviors with high sorption

across all pH ranges. This may be due to similar chemistry and larger surface areas.

Surface loadings were 200 mg/kg and 2,000 mg/kg for experiments with 100 ppb Hg and

1,000 ppb Hg, respectively. Further analysis is required to identify the binding

mechanisms between mercury and samples as well as the role of organic matter content

on samples.

CHAPTER 1: INTRODUCTION

1.1 Motivation and Research Objectives

Mercury pollution due to gold mining has been widely studied in the Amazon River

Basin1, which includes Brazil, Venezuela and the Guianas. Most of the mercury

pollution studies have been conducted in Brazil with a very limited amount of research

coming out of the much smaller Guyana (British Guyana). In Guyana there has been an

increase in mercury loading in the environment and a significant expansion in the number

of permits held by artisinal (small- and medium-scale placer deposit mines) that utilize

mercury for gold extraction 2. Not surprisingly, local agencies like the Guyana

Environmental Protection Agency and the World Wildlife Federation Guianas 3 have

become progressively concerned with the quality of the water, soil, biota, and human

impact in these particular mining areas that are remotely located in the interior of

Guyana. An opportunity arose in May 2005 to accompany a team of investigators into

two mining districts in Guyana (Arakaka and Mathew’s Ridge) under a WWF sponsored

project. From that visit, the Trotz research laboratory at USF obtained soil samples from

the area and pursued further studies on those samples. The WWF study also included

hair, water and fish samples, however, these results remain unavailable as the local

agency, the Institute of Applied Science and Technology, has not completed the research

as of June 2006.

The main objective of this research was to determine the sorptive capabilities of the

Guyanese soils located close to small-medium scale-mining operations in the Arakaka

and Mathew’s Ridge region.

1

These soils can act as potential sinks or sources for mercury and an understanding of

geochemical conditions that affect the fate of mercury can inform solutions for reduced

environmental impacts of mercury contamination in mining activities.

1.2 Scope of Work and Approach

A general overview of the work conducted in this research includes the evaluation of soil

samples collected from Guyana’s Mathew’s Ridge and Arakaka mining districts by BET

surface area analysis, electron dispersion spectroscopy, and X-ray diffractometry for soil

characterization. In addition to soil digestion for total mercury content, batch equilibrium

studies were conducted to understand inorganic mercury sorption on the soils from

Guyana and a commercially available iron oxide sorbent, Kemiron. Mercury

quantification was done using cold-vapor atomic absorption spectroscopy (CVAAS).

These batch equilibrium sorption studies were evaluated as a function of pH and mercury

concentration and mercury species (HgCl2 or Hg(NO3)2). Sorption studies assessed the

ability of sediment to uptake mercury concentrations of 100, 200, and 1,000 μg/L.

This thesis is arranged according to the following format:

• Chapter 2, Background. The background describes the mining environment in

Guyana and discusses mercury chemistry and research.

• Chapter 3, Materials and Methods. This section provides information on the

materials used and experimental and analytical methods used for the work done in

this thesis.

• Chapter 4, Results and Discussion. This section presents and discusses the results

of the experimental data.

• Chapter 5, Conclusion. The last section summarizes the research findings and

makes recommendations for future research.

2

CHAPTER 2: BACKGROUND

2.1 Introduction

This chapter provides an overview of mercury pollution and how it relates to small scale

gold mining operations in Guyana. Also reviewed are mercury transformations in aquatic

systems, health impacts, and the laws/regulations governing the usage of mercury.

2.2 Mercury and its Health Effects

Located on the periodic table as element number 80, mercury is a transition metal which

exists at room temperature as “liquid silver”, known in Latin as hydragyrum. It is both a

natural (e.g. volcanoes) and anthropogenic (e.g. mined ore) contaminant that causes

deleterious human health effects including impaired mental function, neurological

disorders and kidney damage. It is a transition metal commonly found in three oxidation

states (Hg(0), Hg(I), and Hg(II)) and is unique because its elemental state can vaporize at

room temperature. Mercury can transform into methylmercury, the most toxic form

known. Bioaccumulation and biomagnification of methyl mercury occurs to a relatively

high extent in aquatic systems 4-6, making fish consumption the leading route of human

exposure. As a result, United States Environmental Protection Agency (USEPA)

recommended surface and drinking water limits are 12 ng/L and 2000 ng/L total

inorganic mercury, respectively. Table 2.1 lists some guidelines/regulatory limits

currently in effect for mercury.

3

Unlike xenobiotics, mercury is found naturally in the environment and does not degrade

over time, but rather bioaccumulates and biomagnifies. Mercury bioaccumulation

usually occurs in the fatty tissues of fish and is largely magnified in large predatory

species such as salmon, shark, and king mackerel. According to the 2001 USEPA Fish

Advisory warning, about 90% -100% of adult fish contain methylmercury, which

accumulates in the fish muscle bound to proteins. In Minamata, Japan over 3,000 people

suffered from physical deformities, emotional disorders, and oftentimes death due to the

Chisso (“Nitrogen”) Corporation’s release of mercury into the Minamata Bay. The

Chisso Corporation, a chemical manufacturing plant, released approximately 27 tons of

mercury-laced waste into Minamata Bay from 1932 to 1968 where the local diet included

the daily consumption of fish from the bay. As a result of excessive consumption of

mercury-laced fish, residents began to develop signs of methylmercury poisoning, which

became known as “Minamata Disease”.

Table 2.1: Current regulatory limits and guidelines for mercury set by the US Environmental Protection Agency and the World Health Organization.

USEPA WHO Drinking Water MCL (μg/L – inorganic Hg) [4] 2 67 Recommended Surface Water (ng/L) 12 Permissible Hair (μg/g) 11.1 10-208 Urine (μg/g) below 10Fish (μg/g) dry weight (fish-type dependent) 0.5* 2.57

*Same for USFDA

According to the EPA and WHO, consumption of fish containing methyl-mercury should

be limited to an intake of less than 1 ng/g and based on three factors: (1) fish size and

type, (2) regular dietary intake, and (3) location. The agencies recommend that pregnant

woman and children reduce their intake of mercury-laced fish due to mercury’s ability to

be a neurotoxin.

4

2.3 Mercury and its Uses

Various physical, chemical and biological processes influence mercury speciation and

transfer between soil, water, and air and atmospheric deposition has been identified as the

main route of aquatic mercury contamination in non-mining areas of temperate and cold

regions where the bulk of scientific research has been conducted to date. Difficulties still

remain in understanding global inputs to localized systems due to lack of data and

understanding of complex processes governing mercury transformation and emission 9, 10.

In 1995, estimated global anthropogenic contributions to atmospheric mercury emissions

were 2,200 metric tons/yr with power plants being the largest contributor 11 and artisinal

gold mining next with a reported 300 metric tons/yr 11, 12. In terms of use, artisinal gold

and silver mining use nearly 20% of the 3,386 metric tons of mercury produced per year;

batteries and chlor-alkali processes account for 32% and 24% 13 (Figure 2.1). There is

great variation on these estimates because of difficulties with accounting and lack of

enforcement and regulations in some countries. Figure 2.1 depicts the historical trend on

the price of gold and distribution for various processes.

Artisinal gold mining, also referred to as small- to medium- scale mining, describes

mines that use extremely simple (mercury used as an amalgam with no proper processes

regulating releases to the environment) methods for gold recovery from various sizes of

land throughout the world. Mercury has been used for centuries to recover gold and

recent mining activities depend even more heavily on it since most gold is now found in

the very fine fractions of ore. The popularity of mercury use in artisinal mining derives

from its affordability, availability, simplicity of use and lack of regulations governing use

and disposal14. These mines employ an estimated 11.5 to 13.2 million people either

directly or indirectly, in 55 different countries15. These numbers and the use of mercury

will likely increase as gold prices continue to rise and other alternatives for livelihood

and cleaner, affordable processes are not developed. China and Indonesia account for the

bulk of mercury emissions from gold mining whilst approximately 10-30 tons per year

come from countries like Brazil and Venezuela16. The tropical rainforests in the Amazon

5

represent one of the world’s most biodiverse environments that is currently under threat

from artisinal gold mining, deforestation and industrialization.

Figure 2.1: (A) Historical trend in nominal (www.goldprices.com/Goldhistory.htm accessed 7/15/06) and real gold price = 100*(nominal average annual gold price/ average annual US CPI (all items urban consumers, 1982-1984=100). 2006 averaged from January to May) 17. (B) Estimated global mercury use in the world in 2000 for a total of 3,386 metric tons 13.

2.4 Impacts of Artisinal Gold Mining in South America

The typical process used in artisinal mines begins with hydraulic crushing of ore. The ore

is then passed over a sluice box containing a mat to trap gold particles, which are then

recovered by mercury in an amalgam. The amalgam is heated to vaporize the mercury to

recover gold. Though retorts exist for capturing mercury, they are not widely used by

miners. The bulk of studies to date have been conducted in Brazil where mercury

releases from deforestation and industrialization compound the difficulties in estimating

individual sources. Only recently has more research been done in French Guiana,

Suriname and Guyana, which have significantly less inputs from deforestation. Tables

2.2 and 2.3 show some of the sediment, soil and water concentrations found in the

literature.

6

High levels of mercury in indigenous populations of the Amazon basin in Brazil and

Guyana have been reported 18 and linked to the consumption of fish, their primary protein 19. With the exception of disaster areas, hair mercury concentrations of vulnerable groups

(women of reproductive age) in the Amazon are amongst the highest in the world 18.

Table 2.2: Mercury concentrations in sediment and water samples from different parts of the world.

Sediment Unfiltered Water Location Hg 20, 21 (ng/g)

Methyl Hg (ng/g)

Hg (ng/L)

Methyl Hg(ng/L)

Artisinal Au mines, Guyana*22 Artisinal Au mines, Suriname 23 mine wastes streams below mines uncontaminated baselines Amazon basin 24-26 streams affected by mining upstream from mining Antartica streams and lakes Slovenia Hg mine 27 streams affected by mining upstream from mining28 Worldwide background rivers and lakes

5-1200

5.5-200 110-150 14-48

24-406 67-93

1-219 -

-

<0.02-0.83 1.2-1.4

0.03-0.08

0.07-1.9 -

<1 – 0.49 -

-

11-930 -

6.4-10

2.9-33 2.2-2.6 0.27-1.9

18-322

<3 0.1-3.5

-

0.05-3.8 -

0.08-0.28

0.2-0.6 -

0.019-0.33

18-60 0.6 -

*samples collected for this study in May 2005.

Other indigenous populations of the region, e.g. the Maroons in Suriname, also showed

high levels of mercury in urine, which was correlated with proximity to mining activity29.

Studies in Brazil, Suriname, and French Guiana show that piscivorous fish have the

highest mercury concentrations 30-33 and that concentrations increase as a function of

rivers potentially affected by gold mining or industrial sites 31, 33 31. In Suriname,

researchers found that increased turbidity due to mining activities resulted in a layer of

finer particles (< 100 μm) on river sediments which may contribute to negative effects on

local fish populations 34. The turbidity in rivers close to artisinal gold mines in Guyana

and Suriname was also linked to higher mercury concentrations 22, 34. In Guyana, higher

mercury concentrations were found downstream from mining, but researchers could not

tell whether mercury contamination was caused by current amalgamation use or whether

7

it is actually mobilized from the ore itself 2, 22. Whilst these studies provide vital

information on the extent of contamination and the form of contamination based on

spectroscopic or sequential leach analysis, they provide limited information on the

lability, reactivity, and bioavailability of the mercury found.

Table 2.3: Historical background total mercury concentrations.2 Hg Concentrations within various media in mining locations within the humid tropics of

South America Location/media Hg range Reference

Channel sediments (ng/kg) Global background 70 (mean) Turekian, 1971 Poconé area, Brazil 23-198 Von Tümpling et al., 1995 Madiera River, Brazil 50-280 Pfeiffer et al., 1991 Madiera River, Brazil 30-350 Malm et al., 1990 Mazaruni River (Bartica), Guyana 77 (mean) Miller and Lechler, 2003 Essequibo River (Bartica), Guyana 42 (mean) Miller and Lechler, 2003

Soils (ng/kg) (*Ferralitic flood plain soils*) Background 20-50 Pierce et al., 1970 French Guiana 122-318 Rouletand Lucotte, 1995 Madiera River, Brazil 27-54 Malm et al., 1990 Madiera River, Brazil 30-180 Pfeiffer et al., 1991 Madiera River, Brazil 232-406 Lechler et al., 2000 Mazaruni River Basin (Bartica), Guyana 5-83 Miller and Lechler, 2003 Essequibo River Basin (Bartica), Guyana 44-228 Miller and Lechler, 2003

Water (ng L-1) Global Background 1-3 Gustin et al., 1994 Poconé area, Brazil <0.040b Lacerda et al.,1990 Madeira River, Brazil <40-9970b Malm et al., 1990 Madiera River, Brazil 20.0-510 Pfeiffer et al., 1991

b - prior to the use of ultra-clean laboratory procedures

2.5 Mercury Fate in the Aquatic Environment

Various chemical (e.g. sorption, precipitation, photoinduced volatilization) and biological

(methylation or demethylation) processes influence the speciation of mercury in aquatic

systems and extensive research has been done using both model and real conditions to

understand them and the few examples given next just barely capture the complexities.

Some of these processes are depicted in Figure 2.2 and are discussed further in the next

few paragraphs. Gaseous mercury compounds in the atmosphere deposit into the

8

hydrosphere by precipitation or wet deposition (rain, snow, sleet, hail, or mist),

particulate deposition and vapor adsorption (dry deposition), resulting in increased levels

of mercury. Once in the water compartment, mercury undergoes biogeochemical and

photo-oxidation transformation. Mercury is distributed between chemical species

including inorganic divalent mercury (II) and organic mercury (methyl-mercury –

CH3Hg). The dominant species include HgCl2, HgCl42-, Hg2+, Hg, and Hg species sorbed

onto mineral oxides, and organomercury species35. Mercury also forms solid HgS(s)

which is usually, but not always, found under reducing environments (either in sediment

or in biofilms in water column).

Wate

Hg0 (g) Algae

Bacteria CH3HgHg(IIBacteria

Hg(II)- particle

MeHg- particle

Hg- colloi

MeHg-colloi

Air Hg0 (g) Hg(II)

Sunlight

Sediment CH3Hg+Hg(II)Bacteria

HgS

Phyto- plankton

Fish

Zoo- plankton

Figure 2.2: Some of the transformations involved in the cycling of mercury36.

2.5.1 Mercury Sorption

According to Lindsey37 surface sediments in aquifers, lakes, and rivers contain metals in

particular iron and aluminum as well as silica which represent the most abundant mineral

oxides (Table 2.4). Mineral oxides play an important role in the speciation of mercury.

Mineral oxides (e.g. iron and aluminum oxides like goethite and gibbsite respectively)

form amphoteric surface groups when in contact with water. By definition, amphoteric

groups can have positive, negative or neutral charges along the surface/water interface

9

and can accept or lose protons depending on the pH of the solution. The behavior of the

surface/water interface has been modeled using various surface complexation models.

These empirical models include the Constant Capacitance (CC), Diffuse Double Layer

(DD), CD-Music (CD-M), and triple layer (TLM) models. Figure 2.3 uses the triple layer

model to represent a mineral oxide surface showing the different types of surfaces

charges. In this model, the o-plane, that closest to the mineral oxide surface, contains the

amphoteric surface functional groups (XO-, XOH+, XOH), where X is the main ion to

which the surface functional group is associated (e.g. Fe, Al, Si).

Table 2.4: Content of various elements in soils 37.

Metal Selected Average for soils (ng/g) Common Range for Soils (ng/g) Al 71,000 10,000-300,000 Fe 38,000 7,000-550,000 Mn 600 20-3,000 Cu 30 2-100 Cr 100 1-1000 Cd 0.06 0.01-0.70 Zn 50 10-300 As 5 1.0-50 Ni 40 5-500 Ag 0.05 0.01-5 Pb 10 2-200 Hg 0.03 0.01-0.3

10

Figure 2.3: Depiction of the solid-water interface and sorption interpretation.

Therefore, under acidic conditions (or below the pKa of the mineral oxide) the overall

number of positively charged surface sites would increase while under more alkaline

conditions (above the pKa of the mineral oxide) the positive sites would diminish and

vice versa would occur for negatively charged surface sites. Sorbing ions can lose their

spheres of hydration and form a strong covalent bond with the surface in the o-plane (e.g.

SOHg) or they can retain their spheres of hydration and form electrostatic bonds with the

surface in the β-plane (e.g. SO-…..Hg2+). Ions in the diffuse layer and further away from

the surface do not form any electrostatic or covalent bonds with the surface.

Mercury (II) sorption to clays 38, 39 and mineral oxides of iron 40-44, aluminum 40, 42, 45,

and silicon, some of the most common sediment constituents,45-47 typically increases as a

function of pH until it reaches a maxima then decreases in the higher pH regions. Methyl

mercury sorption to goethite and kaolin, on the other hand was found to be much lower

than inorganic Hg(II) sorption 39. The presence of ligands (e.g. chloride, sulfate,

phosphate), other heavy metals (e.g. Ni(II), Pb(II)), and/or organic matter can influence

mercury sorption to mineral oxide surfaces through various processes including

11

competition for surface sites, changes in the surface charge, formation of ternary surfaces

and formation of more stable aqueous complexes 42, 44-48.

In most sediments and natural waters, natural organic matter (NOM) can be found. NOM

consists of carbon-based polyligands with various functional groups including carboxylic

and thiols. Natural organic matter is known to form extremely strong complexes with

mercury 49-51, thereby affecting desorption kinetics from mineral oxides and even

bioavailability 52, 53. Mineral oxide surfaces have been functionalized with synthetic

organic acid to increase the removal of mercury from aqueous solutions 54. These effects

vary, however, depending on the biogeochemical conditions, the form of mercury, the

site and the type of natural organic matter (NOM). For example, fulvic acid, the

hydrophilic fraction of NOM, increased mercury sorption on goethite 41, but decreased

sorption of both Hg(II) and methyl mercury from kaolin 39. NOM has different

functional groups (e.g. carboxylic, phenolic, thiol) that play important roles in

complexing mercury thereby causing a distribution of binding affinities 55, 56.

Methylation and demethylation of mercury can occur via abiotic and microbial pathways 55. Researchers found that dissolved organic matter (DOM) influenced the abiotic, photo-

induced methylation rates of mercury 57. Recent studies on mercury volatilization (to

Hg(0)) found that the presence of NOM decreased volatilization in aqueous solutions, but

that mercury volatilization in real lake samples was significant in sunlight 58.

Nanoparticles like iron oxides may play a major role in the transport of heavy metals in

natural systems 59. Indeed, mercury concentrations downstream of Surinamese and

Guyanese artisinal gold mines were positively correlated with turbidity and the finer

fractions of suspended solids 22, 23. In fact, the majority of the mercury in the Guyanese

samples, including depth profiles from unmined ore, was associated with organic matter 22. This is not surprising given the high forest cover of this area. Based on the literature

review one would expect that the combination of high organic matter and suspended

tailings to have a significant effect on the processes governing mercury speciation and

transport close to artisinal mines.

12

2.6 Guyana

Guyana (located on the north east coast of South America and bordered by Brazil,

Suriname and Venezuela) more closely resembles the English-speaking islands of the

Caribbean with respect to history, language, and culture than its South American

neighbors. It is 214,970 km2 with a population of 765,283 the majority of whom reside

in the coastal area and in poverty 60, 61. Many of Guyana’s indigenous peoples

(Amerindians) reside in the interior regions of the country and are dependent upon the

natural environment for survival and economic resources. The main activities include

manicole palm harvesting, logging, subsistence farming and activities associated with

gold mining. Gold mining has been carried out in Guyana for over 100 years 60-63. The

artisinal gold miners as well as gaimperos or pork knockers, illegal miners, use simple

extraction techniques to quickly recover gold from placer (alluvial, colluvial, or elluvial)

deposits such as land dredging, simple panning techniques, or amalgamation. In the

Barima/Waini area of Region 1, where natives of the Arawak, Carib, and Warau Tribes

reside, gold mining is carried out using the mercury amalgamation process 61.

In Guyana, artisinal gold miners make up approximately 95% of all the miners while the

remaining 5% are from large scale operations. In the large-scale mining sector, miners

use sophisticated equipment and cyanide (HCN) to extract gold from ore. In particular

large scale companies such as OMAI Gold LTD. located in Region 8 utilizes cyanide.

This method of extraction in mining is preferred due to its higher yield of gold recovery

than by the mercury amalgamation. However, due to the economical factors, limited

technology, and easy availability, small-scale miners use elemental mercury.

13

Figure 2.4: Map of northern portion of Guyana and test site (Arakaka) plus sites where

previous studies2,22 have been published.

Figure 2.4 provides a map with the location of the site (Arakaka) plus two rivers for

which the work of the Mazaruni22 and Potero22 have been published. Previous sampling

for mercury in the Wai Wai district, at the most Southernly part of Guyana (not shown on

Figure 2.4) revealed that the Amerindians there had the highest mercury hair

concentrations of a range of Guyanese; fish concentrations were at WHO levels and they

consumed five meals of fish per day 64. The WWF conducted studies at the two gold

mining sites in Guyana, Isseneru, located off of the Mazaruni River (1997, and 2000 65),

Mathew’s Ridge (2005, data not processed as yet) and Arakaka (2005). Isseneru is an

Amerindian village where over 90% of residents surveyed had greater than 14 μg/g hair

concentrations 65 (recommended USEPA permissible limit is 11 μg/g). Singh65, 66

reported that in a total of 168 fish samples collected from Guyana’s Kurupung and

Isseneru areas the average concentration of mercury was 0.315 and 0.928 ng/g THg

which exceeds the United States Food and Drug Administration guidelines limits of 0.5

ng/g (Table 2.1). In addition, Singh66 correlated that elevated levels were due to average

local dietary fish consumptions being 3-4 times per week as well as an association with

14

mercury emanating from the natural environment. Apart from the extensive sediment

sampling that was done along the Mazaruni and Potaro Rivers (indicated on Figure 2.4),

further studies on human levels of contamination and fate of mercury and source of

mercury are obviously needed in Guyana.

Region 1, commonly known as the Northwest district, contains the towns of Arakaka and

Mathew’s Ridge. Arakaka and Mathew’s Ridge cover a land area of approximately

0.0084 km2. This zone is geologically underlain by Precambrian rocks and a 0.001 km2

section of a greenstone belt, an area underlain by metamorphosed volcanic and

sedimentary rocks that contain chlorites, which borders the Iroma and Waini Rivers.

Within Arakaka and Mathew’s Ridge there are or were several industries that include

manganese mining, diamond drilling, and gold mining 63. However, the dominant

commerce today is gold mining. Arakaka is the location of small- to- medium scale gold

mining, and many miners and their families reside in the nearby town of Mathew’s

Ridge. Residents within this area are dependent on the natural water ways for the

collection of fish, the principle source of protein. Drinking water sources include rain

catchments, upstream springs, and river water. A survey done by the WWF-IAST team

in 2005 identified the main sources of drinking water for Arakaka as the Barima River

and rain water.

Mercury amalgamation is the process by which gold is extracted from ore via the usage

of liquid mercury. With a legal mining workforce of roughly 11,000, Guyana’s small

scale mines use the following conventional gold mining process: (1) tree removal by

logging, (2) land dredging or the use of hydraulic pressure to extract alluvial deposits,

sediment that have been settled by water, (3) collection of ore placed on a sluice box for

manual or mechanical gravitational agitation to settle gold deposits, (4) addition of Hg to

the final concentrate (settled gold/ore deposits) that has been shaken off of sluice mats ( It

has been estimated that for every 1 kg of concentrate there is 14 grams of mercury

required to form an amalgamate 67 or oftentimes approximately 30 grams of mercury is

rubbed off on the final concentrate retained on the sluice mats, 63 which is considered an

15

illegal mining practice); (5) followed by a simple panning technique that washes excess

sediment particles from ore to the final recovery process or roasting technique.

Controversy does exist over whether mercury contamination in the Amazon is due to

burning of forests (the ferraltic soils have high background mercury concentrations),

mobilization of ore during mining, input of mercury from amalgamation processes or

atmospheric deposition (with a non- localized mercury source). Atmospheric deposition

has been identified as the main source of contamination, especially to remote areas of the

world 68. In an attempt to model mercury concentrations in the Florida Everglades

researchers found that atmospheric deposition played a major role and noticed that

mercury concentrations increased as a function of the amount of precipitation 9. Few

studies have attempted to measure atmospheric deposition rates in the Amazonian region 69 and mercury concentrations downstream from mining have always been lower than

upstream concentrations suggesting that atmospheric deposition is not as significant as

mining in these areas 21. The literature suggests that higher mercury concentrations are

found downstream from artisinal mines and are directly linked with fines fractions 22, 34.

16

CHAPTER 3: MATERIALS AND METHODS

3.1 Introduction

This chapter describes the materials and methods used in this thesis. It provides a detailed

description of the experimental and analytical procedures used.

3.2 Materials

3.2.1 Glassware

All glassware was washed with a 10% Liquinox detergent and rinsed with MilliQ water

prior to soaking in 1 N NaOH. After one hour glassware was rinsed with MilliQ water

and soaked in 10% HNO3 for an additional hour. The glassware was then rinsed multiple

times with MilliQ water again and allowed to air dry before usage.

Polycarbonate reactor vessels and 10 mL polycarbonate centrifuge tubes were cleaned

separately in a similar fashion as glassware except a q-tip was used to scrub the

containers free of remaining particulate matter and acid and base concentrations were an

order of magnitude lower. All rinse exercises were conducted three times before

proceeding.

3.2.2 Reagents

Mercury stock solutions were prepared in 100 mL glass volumetric flasks by dissolving

Fisher Brand mercuric chloride (M168-100) or mercuric nitrate in a 5% nitric acid

solution. Concentrations of the Hg stock solutions were measured against a calibration

curve prepared using cold vapor atomic absorption of mercury standards. Mercury

17

calibration standards of 5, 10, 20, 30, 50, 70, and 100 ppb (μg/L) were made using a

10,000 ppm (mg/L) mercury stock solution in 5% nitric acid from CentriPrep that was

diluted with 5% hydrochloric acid.

All solutions (slurries and standards) had background electrolyte concentrations of 0.1 N

NaNO3 (Fisher Brand Certified ACS sodium nitrate crystals (S343-500)).

The pH of slurry was varied using 0.1 N NaOH and 0.1 N HNO3. Both acid and base

were standardized using standard methods. MilliQ water was used for all experiments

and analysis.

Acid and reductant solutions for cold vapor atomic absorption analysis were 5% HCl and

10% w/v stannous chloride (LabChem Inc LC25180-1), respectively. A bulk volume of

5% hydrochloric acid solutions were made with 32% w/v HCl (Fisher) and diluted with

MilliQ water. Bulk solutions were stored in 1 L Nalgene high density polyethelyne

bottles.

3.2.3 Kemiron/Sediments

As described by Lindsey37 soils in the environment are principally composed of

aluminum, iron, or manganese oxides. Kemiron, a commercially available iron hydroxide

material was used as a model iron oxide. Kemiron was obtained from Kemiron

Company, U.S.A. It is highly porous with pore sizes ranging from 0.003 μm to 328 μm

and a particle diameters of less than or equal to 600 μm. This commercially available

iron hydroxide material is commonly used as an absorbent in water and waste water

treatment plants. Its principal benefit is to remove turbidity, reduce BOD/TOC/DBP,

precipitate phosphates, condition sludge, reduce bacteria, remove heavy metals, as well

as provide odor and corrosion control.

18

Sediment samples were collected from the Arakaka/Mathew’s Ridge region of Guyana in

May 2005 by the Institute of Applied Science and Technology (IAST) under a project

funded by the Guyana WWF office. These samples were collected in HDPE containers

and included the top 10 cm of sediment from the bottom of the water body tested. They

were stored on ice until airlifted to the IAST laboratory. Once there they were air dried

on filter paper, ground in a mortar and placed in doubly-bagged plastic storage bags.

They were then shipped to the laboratory at USF where they were stored in a freezer until

further use. The Philips Mine Tailings sample was collected by researchers at USF

during the same time period from the tailings pond right under a sluice box at a mine in

Arakaka. The sample was was taken from the surface and placed directly into a sealed

plastic storage bag.

Kemiron and selected sediment samples were ground using a mortar and pestle and

sieved using ASTM-E11, a stainless steel sieve of mesh size 400 (< 38 μm). The sieved

fraction less than 38 μm was stored in doubly sealed plastic storage bags in a sealed

HDPE container. Size fractions of < 38 μm were selected for batch adsorption studies to

decrease equilibration times. A five-point Braunauer, Emmett, and Teller (BET) surface

area analysis was done on Kemiron and selected soil samples using a Coulter SA2300

Surface Area Analyzer. The Kemiron and soils were dried at 80 oC for 18 hours and

outgassed with helium at 80oC for 3 hours. XRD testing was based on particle size

fractions of < 38μm while utilizing the back loading technique.

3.3 Analytical Procedures

3.3.1 Cold Vapor Atomic Adsorption

The Varian 240FS-AAS coupled with a Varian VGA77 attachment were used for the

mercury cold vapor analysis technique also known as cold vapor atomic absorption

spectroscopy (CVAAS). CVAAS analysis was used to determine total mercury

concentrations, THg, in sediment samples.

19

Mercury speciation was not conducted in this study. Before samples were analyzed using

the manual CVAAS technique, all samples were acidified to 0.5% HCl.

Due to the analytical sensitivity when testing for trace levels of mercury extreme care

was exercised. Therefore the capillaries for the acid, reductant, and sample lines of the

continuous vapor flow VGA77 were adjusted to an uptake rate of 1 mL/min, 1 mL/min,

and 8 mL/min, respectively, and a mercury flow-through cell was attached to the Mark V

burner head of the Varian 240FS. Optimal working conditions for the Varian 240FS-

AAS equipped with a VGA77 are outlined in Table 3.1.

Table 3.1: Optimal working conditions for Hg determination in sediments using CVAAS.

Parameters (Varian 240FS) Wavelength (nm) 253.7 Slit Width (nm) 0.5 Lamp Current 4 Integration time (s) 3

Vapor Generator (VGA 77) Acid uptake tube (mL/min) 1 Reductant uptake tube (mL/min) 1 Sample uptake tube (mL/min) 8 Argon* or Nitrogen Gas 99.99% pure Perimissible pressure range*** 43-57 psi

Reagents Usage

5% Hydrochloric Acid, (from concentrated) Acid Line, Reagent Water*, Preservation*

20% (w/v) Stannous Chloride Reductant Line 5% Nitric Acid, concentrated** Reagent water, preservation Notes: * - used in this study ** - suggested (Varian, 1985) *** - recommended pressure is 50 psi

20

The calibration standards for the CVAAS technique were prepared from a 1,000 mg/L

(10-6 μg/L) stock solution manufactured by CentriPrep. Calibration standards of 5, 10, 20,

30, 50, 70, and 100 μg/L were prepared fresh daily. The detection limit for Hg using the

VGA77 and 240FS was 2 μg/L (ppb).

3.3.2 Scanning Electron Microscopy/Electron Dispersive Spectroscopy

The Hitachi SEM Model 4105S was used to observe surface characteristics of sediment

samples. Working conditions for the SEM were between 20 to 17 KeV to reduce the

amount of particle charging at the surface while under a high pressure vacuum of 90

torrs. Sample size fractions of < 38 μm for Philip’s Mine Tailings and Kemiron were

used. To prepare samples for analysis by SEM a small strip of carbon tape was adhered

to the surface of the metal mounting plate. Next, soil samples were distributed evenly on

to the surface of the carbon tape using a pair of metal tweezers then inverted/lightly

tapped to ensure that there were no lose particles. Following procedures outlined in the

SEM/EDS protocol distributed by the Material Science Research Center at the University

of South Florida samples were carefully loaded into the SEM for analysis.

3.4 Batch Equilibrium Sorption Experiments

The batch equilibrium experiment was setup by acid washing a 250-mL Nalgene

polycarbonate reaction vessel with a screw cap and drilled holes for easy insertion of

electrodes and sample ports. Background electrolyte solution of 0.1 N sodium nitrate

(Fisher Brand Certified A.C.S. crystals, Cat. # S343-500) and approximately 0.1 g of soil

were mixed to form a slurry in the polycarbonate vessel. Then the initial pH of the

slurry was analyzed, then the vessel was covered with parafilm and the slurry was

allowed to equilibrate overnight at room temperature, 25˚C. A Teflon magnetic stir bar

was used to continuously stir the slurry overnight. After equilibration, 8 mL of the slurry

were pipetted into a 10-mL Nalgene test tube with screw cap. This sample represented

the initial background mercury concentration (Cblank) and the value was subtracted from

all other concentrations found after mercury addition. The stock mercury solution was

21

then added to give a total added concentration, Cintial. The pH was adjusted to varying pH

values of 3-10 8-mL samples collected at. pH adjustments with 0.1 N NaOH and 0.1 N

HNO3. Once all samples were collected they were placed on an end-over-end shaker for

24 hours to equilibrate. After the 24-hour batch reaction on the end over end Lab Quake

Shaker, samples were analyzed for pH using an Orion Ross 8103BNU pH electrode and

the Orion Duo 940A pH meter. Samples were then filtered using a 0.1 μm disposable

syringe filter, acidified to 0.5% hydrochloric, acid and analyzed for Hg by CVAAS. This

represented the amount of mercury remaining in solution, Csolution.

The amount of mercury removed during the experiment was calculated from:

% removed = [Cintial – Cblank – Csolution]/Cintial

All waste materials were discarded in a double-sealed plastic storage bag following

disposal instructions established by the University of South Florida’s Environmental

Health and Safety department. Equilibrium batch sorption experiments were done on

three solid samples (Kemiron, Pakera Creek, and Philips Mine) at varying mercury

concentrations of 100, 200, and 1,000 ppb (µg/L). The following batch adsorption

studies were conducted on solid samples:

Table 3.2: Conditions used for batch adsorption studies (1000 ppb Hg = 0.5E-5M).

Sample [THg] (made from Hg(NO3)2)

[THg] (made from

HgCl2

Background Electrolyte

Particle size (μm)

Kemiron 100, 1000 ppb 1000 ppb 0.1N NaNO3 < 38 Philips Tailings 100 ppb, 200 ppb,

1000 ppb 1000 ppb 0.1N NaNO3 < 38

Pakera Creek 100 ppb, 1000 ppb 1000 ppb 0.1N NaNO3 --

Experiments were also conducted using solutions of Hg(NO3)2 and HgCl2 at 0.1 N

NaNO3 in the absence of any solids.

22

This was used to provide information on the amount of mercury that could be sorbed to

the surface of the container and filter or photovolatilized during the experiment. These

control experiments resulted in less than 5% removal of mercury. Most experiments

were duplicated.

Table 3.3 provides formation constants that were used to determine Hg speciation under

experimental conditions used in this thesis assuming that mercury was added as Hg2+

either as a Hg(NO3)2 or HgCl2. The two possible Hg(II) precipitates are Hg(OH)2(s) and

HgCl2(s). Figures 3.1 and 3.2 show Hg(II) speciation if a total of 1E-5 M and 5E-4 M Hg

was added to solution and Hg(OH)2(s) was allowed to precipitate. At 1E-5 M, all of the

Hg2+ remains in solution and the dominant species between pH 4 and 10 is the uncharged

Hg(OH)2. At 5E-4 M, the main species across pH 4 and 10 remains the same, however,

the concentration is high enough for Hg(OH)2(s) precipitation. Hg spiked experiments in

this thesis were all below 1E-5 M HgT therefore no precipitation was expected. Figure 3.3

shows Hg2+ speciation for a 1E-5 M total Hg concentration in the presence of chloride

where the dominant species are uncharged HgCl2 and HgOHCl up to around pH 8. These

species dominate even more as chloride concentrations increase. Again, at the

concentration of 1E-5 M, which was above experimental concentrations, no precipitates

formed.

Table 3.3: Formation constants for Hg2+species, Log K’s for ionic strength = 0.

Equilibrium Reaction Log K HgP

2+P + OHPP

-PP = Hg(OH)P

+PP 10.6

HgP

2+P + 2OHPP

-P = Hg(OH)B2BB B 21.8

HgP

2+P + 3OHPP

-P = Hg(OH)B3PBB

-P 20.9

HgP

2+P + ClP

- P

P = HgClP

+PP P 7.2

HgP

2+P + 2ClP

-P = HgClB2BP P

P B B 14.0 HgP

2+P + 3ClP

-P = HgClP

3-PP P

P P 15.1 HgP

2+ P+ 4ClP

-P

P = HgClBPB4PB

2-P 15.4

HgP

2+P + ClP

-P + OHPP

PP

- P= HgOHCl 18.1

HgP

2+P + 2OHPP

-P = Hg(OH)B2(s)BB B 25.4

HgP

2+P + 2ClP

- P

P = HgClBB2(s)BB 14.21 P

23

pC-pH Diagram for 1E-5 M HgT, Hg(OH)2(s) allowed to precipitate

0

5

10

15

20

25

30

0 2 4 6 8 10 12 14

pH

pC

Hg2+HgOH+Hg(OH)2Hg(OH)3

Hg2+

Hg(OH)+

Hg(OH)2

Hg(OH)3-

Figure 3.1: Speciation of 1E5 M Hg2+.

pc-pH Diagram for 5E-4 M Hg2+. Hg(OH)2(s) allowed to precipitate

0

5

10

15

20

25

30

0 2 4 6 8 10 12 14

pH

pC

Hg2+HgOH+Hg(OH)2Hg(OH)3-

Hg2+

Hg(OH)+

Hg(OH)2

Hg(OH)3-

Figure 3.2: Speciation of 5E-4 M Hg2+.

24

pC-pH Diagram for 1E-5 M Hg2+ and 1E-3 M Cl-. Hg(OH)2(s) and HgCl2(s)

allowed to precipitate.

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14

pHpC Hg2+

HgCl+HgCl2HgCl3HgCl4Hg(OH)+Hg(OH)2Hg(OH)3-HgOHCl

HgCl2 Hg(OH)2HgOHCl

Figure 3.3: Speciation of 1E-5M Hg2+ with 0.001M Cl-.

25

CHAPTER 4: RESULTS AND DISCUSSION

4.1 Introduction

Presented in this chapter are the experimental results for sediments from Guyana’s

Arakaka/Mathew’s Ridge mining region and model mineral oxide: total mercury

concentrations by cold vapor atomic absorption analysis (CVAAS), surface area analysis,

scanning electron microscopy (SEM), and electron dispersive spectroscopy (EDS/XRD).

Results from equilibrium sorption experiments are also presented.

4.2 Total Mercury Analysis

Total mercury sediment loadings were determined for all samples collected by Guyana’s

Institute of Applied Science during May 2005 for the Guyana WWF office. For total

mercury concentrations, samples were sent to a Tampa-based environmental wet

chemistry laboratory, Advanced Environmental Labs (AEL). AEL digestion methods

were based on Standard Methods 6971 for manual cold-vapor atomic adsorption analysis

and the results are summarized in Table 4.1.

Samples collected from the Arakaka area (Arakaka Creek #12, Arakaka Creek #3, and

Arakaka Creek #8) exhibited total mercury concentrations close to global and local

background concentrations of 70 ng/kg 70 and 42-77 ng/kg 2 respectively. Mercury

levels in the remaining samples were within a range of 98-300 ng/kg which are similar to

levels reported in the Brazilian Amazon mining areas (180-406 ng/kg ) 71, 72.

26

Elevated mercury levels in tropical rainforests are enhanced by temporal variations 73;

organic content 35, 74; proportion of iron containing minerals 35, rainfall 35, 75, soil

microbial activity 35, 76, and the extent of pollution. Mine waste sediment, Philip’s Mine,

contained the highest total mercury concentrations when compared to other samples

collected from the area (excluding Water Source for MWJ), which was consistent with

mine tailings or waste results obtained from Gray et al.77

Table 4.1: Total mercury concentrations in Mathew's Ridge/Arakaka area.

THg in Region 2 of Guyana

Sample ID THg

(ng/g)

Coordinates78 (DMS)

Elevation78 (ft)

Arakaka Creek #9 (Up Falls Top) 98 N07° 35.167 W060° 01.183 29 Arakaka Creek #12 (Bamboo Creek) 41 N07° 34.799 W060° 00.13

13

Arakaka Creek #13 73 N07° 34.762 W060° 01.170 91 Arakaka Creek #8 (Down Manicora) 61 N07° 34.784 W060° 00.186 145 Pakera Creek #5 200 Arakaka Creek #1 (Near River) 130 N07° 35.431 W059° 58.714 63 Pakera Creek Reservoir #14 290 N07° 29.508 W060° 08.044 21 Control Arakaka Creek #10 (Ravine Off Red Hill)

110 N07° 35.574 W059° 59.378 62 Sediment Arakaka #4 180 N07° 34.761 W060° 01.183 29 Water Source For MWJ (#1) 1200 -- -- -- Philips Tailings #1 300 -- -- -- Minab #7 200 N07° 29.956 W060° 09.238 63 Soldier Pool #6 190 N07° 29.359 W060° 11.120 54

Three of the samples with the highest concentrations were further analyzed to describe

the possible fate/transport of mercury in the aquatic environment. Limited quantities of

sediment, “Water source for MWJ”, prevented adsorption studies with this sample even

though its mercury loadings were highest amongst the sampled sediments/soils.

27

4.3 BET SEM/EDS and XRD

BET, SEM imaging coupled with EDS/EDX spectra for individual samples of Kemiron,

Pakera Creek #14, and Philips Tailings #1 were collected to determine particle

morphology, surface area, and chemical information. BET surface areas were 40 m2/g,

25.8 m2/g and 4 m2/g for Kemiron, Pakera Creek #14, and Philip’s Tailings #1,

respectively. The low surface area of the ground Philip’s Mine tailings was expected

since the material resembled an iron oxide -coated sand and sand usually has a very low

surface area. Figures 4.1-4.3 show the SEM images of these three samples. The

Kemiron surface appears porous with small (~2 μm) particle deposits on the surface. The

Pakera Creek and Kemiron samples both showed surfaces consisting of particle

agglomerations that were flaky in nature. EDS/EDX and the corresponding SEM images

in Figure 4.4 – 4.6 suggest that carbon weight percentages are 45.76%, 40.38%, and 8.24

for Philips Mine, Pakera Creek, and Kemiron solids, respectively. High carbon contents

for Philip’s Mine and Pakera Creek solids may be indicative of high organic matter

content, which was expected given that the sampling location was in a tropical rainforest.

This high organic matter content may contribute to the flaky aggregate appearance seen

in the Philip’s Mine and Pakera Creek samples. The presence of organic matter may

influence the adsorption of trace metals. Paktunc et al. 22 found high concentrations of

organic matter in the sediments of the Potaro River in Guyana, even in unmined ore next

to a mining pit. Kemiron, a commercially available iron oxide showed low C content,

which was expected. It should be noted that a carbon based tape was actually used to

secure the sample on the holder for SEM and this may contribute to some background

carbon concentrations being recorded for the Kemiron sample.

In addition, the weight percentage of mercury in the Kemiron sample was 1.76% where

as Pakera Creek and Philip’s Mine samples were 0.61% and 0.77%, respectively. This

increased weight percent determined in the Kemiron sample may be due to contamination

during the sample loading and prepping process for the SEM/EDS analysis. The sample

results for Pakera Creek (Figure 4.5) and Philip’s Mine (Figure 4.4) also show high iron

and aluminum concentrations, suggesting the presence of iron and aluminum oxides.

28

Physical characteristics and MRD PW 3060/20 XRD spectras when compared against the

online database suggest that the mineralogy of soil samples collected from Philips Mine

were predominately quartz with an iron oxide coating (Figure 4.7). On the other hand,

the Kemiron samples were composed of predominately iron hydroxide (Figure 4.8).

29

Figure 4.1: SEM image of Kemiron for particles up to to 38 μm in diameter.

Figure 4.2: SEM image of Pakera Creek for particles up to to 38 μm in diameter.

Figure 4.3: SEM image of Philip’s Mine for particles up to to 38 μm in diameter.

30

Philip s T ailings

E lem W t % A t%

C K 45 .76 56.35

O K 40 .53 37.47

A l K 4 .32 2 .37

Si K 5 .91 3 .11

S 0.01 0

B a 0 .42 0 .05

Fe K 2 .28 0.6

H g L 0 .77 0 .06

Philip s T ailings

E lem W t % A t%

C K 45 .76 56.35

O K 40 .53 37.47

A l K 4 .32 2 .37

Si K 5 .91 3 .11

S 0.01 0

B a 0 .42 0 .05

Fe K 2 .28 0.6

H g L 0 .77 0 .06

Figure 4.4: EDS spectra and chemical quantification table for Philip’s Mine tailings.

Figure 4.5: EDS spectra and chemical quantification for Pakera Creek.

31

Figure 4.6: EDS spectra and chemical quantification for Kemiron.

32

Figure 4.7: XRD spectra for Philip’s Mine tailings.

Figure 4.8: XRD spectra for Kemiron.

33

4.4 Batch Equilibrium Sorption

Figure 4.9: Sediment samples (Kemiron, Pakera Creek, and Philips Mine).

The transport and fate of mercury in the aqueous compartment is directly influenced by

sorption to particle surfaces 79. Many batch equilibrium sorption experiments have been

conducted for the sorption of mercury (II) to various mineral oxide surfaces 46, 48. Batch

equilibrium sorption studies performed in this study are summarized in Table 4.2. Based

on the speciation plots in Chapter 3, no solid precipitates should form at the

concentrations used in the batch equilibrium sorption experiments. This was confirmed

by testing the aqueous mercury concentration as a function of pH when no solid was

present. Hence, the experiments using solid samples should reflect only adsorption

mechanisms.

34

Aqueous, 1000ppb Hg Standards Curve

y = 0.0049x - 0.0054R2 = 0.9986

0

0.1

0.2

0.3

0.4

0.5

0.6

0 20 40 60 80 100

Concentration

abso

rban

ce

Figure 4.10: Typical standards curve for THg analysis using CVAAS. New standards and standards curves were generated each time the instrument was run.

A typical standard curve for total mercury concentrations remaining in solution is shown

in Figure 4.10. The calibration was linear between 5 ppb and 100 ppb with less than 2%

RSD for all readings. Figures 4.11 to 4.13 plot mercury sorption as a function of pH onto

the three solid samples when mercury was added as Hg(NO3)2. For Kemiron and Pakera

solids, mercury sorption remained high across the pH region 3-9. Cationic sorption

generally shows increased sorption with pH and though this may be true for these solid

samples, the surface loading may still be too low to see that trend. For the case of

Kemiron when mercury concentrations were increased to 1,000 ppb, close to 100% was

still sorbed. This high concentration would actually mean a surface loading of 2000

mg/kg (µg/g), which shows significant potential for Kemiron as a sorbent in remediation.

Mercury sorption on Philip’s Mine tailings had the lowest of the three solids and could be

reflective of the lower surface area (an order of magnitude lower than Kemiron).

35

The Hg surface loadings on the Philip’s Mine tailings varied from 120 to 190 mg/kg

(µg/g) which was significantly higher than the results obtained from the field. The high

capacity of these solids to sorb mercury indicates their potential as sinks for mercury in

the environment.

Table 4.2: Summary of batch equilibrium sorption studies.

Solid

Solid

Concentration

(g/L)

Hg THg

(ppb)

THg

(M) Electrolyte

Ionic

Strength

Amount

sorbed/

amount of

sediment

at pH ≈ 7*

None -- HgCl2 1000

5E-6 NaNO3 0.1 --

None -- Hg(NO3)2 1000

5E-6 NaNO3 0.1 --

Kemiron 0.5 HgCl2 1000

5E-6 NaNO3 0.1 6530.61

Kemiron 0.5 Hg(NO3)2 1000

5E-6 NaNO3 0.1 9843.58

Kemiron 0.5 Hg(NO3)2 100

5E-7 NaNO3 0.1 990.39

Pakera

Creek 0.5 HgCl2 1000

5E-6 NaNO3 0.1 9671.18

Pakera

Creek 0.5 Hg(NO3)2 100

5E-7 NaNO3 0.1 922.97

Philip’s

Mine 0.5 HgCl2 1000

5E-6 NaNO3 0.1 8242.31

Philip’s

Mine 0.5 Hg(NO3)2 100

5E-7 NaNO3 0.1 995.66

*Calculations are based on data results for ≈pH 7 located in Appendix A.

36

Figure 4.11: Hg sorption to 0.5 g/L Kemiron.

Figure 4.12: Hg sorption to 0.5 g/L Pakera Creek sediment.

37

Figure 4.13: Hg sorption to 0.5 g/L Philip’s Mine tailings.

Since speciation of mercury changes in the presence of chloride ions, batch sorption

equilibrium using sodium nitrate as a background electrolyte and mercuric chloride as the

stock mercury concentration are outlined in Table 4.2.

Samples prepared by the addition of mercuric chloride are shown in Figure 4.14. In the

Kemiron samples depicted in Figure 4.15, sorption of mercury added as mercuric

chloride is lower when compared to Kemiron samples prepared from mercuric nitrate.

38

Figure 4.14: Hg sorption of 0.5 g/L of soil for 1,000 ppb Hg (from HgCl2).

Hg sorption to 0.1g/200mL Kemiron For 1000ppb Hg, 0.1N NaNO3

0%

20%

40%

60%

80%

100%

2 3 4 5 6 7 8 9 10 11

pH

% s

orbe

d

Hg added as HgCl2 Hg added as Hg(NO3)2

Figure 4.15: Hg Sorption of 0.5 g/L of soil for 1,000 ppb Hg (from HgCl2 and Hg(NO3)2).

39

Sorption characteristics for natural soil samples collected from Guyana which were

prepared to a total mercury concentration of 1,000 ppb using HgCl2 stock solution

indicate that in alkaline conditions (pH 8-10) sorption at the surface-mineral interface is

relatively higher when compared to highly acidic conditions (pH 3-5) (Figure 4.14).

However, when above pH 5 a distinct difference in sorption is observed for the

commercially available iron-oxide soil prepared with HgCl2 when compared to natural

samples. It appears that sorption begins to decrease above pH 5 in the Kemiron samples.

The behavior of mercury (II) at the solid/water interface by batch experiments has been

studied widely 42, 46. Kim et al. 42 examined the effects of chloride and sulfate, common

complexing ligands, to mineral sorbents of goethite (alpha-FeOOH), gamma-alumina

(gamma-Al2O3), and bayerite (beta-Al(OH)3) by extended x-ray adsorption fine structure

(EXAFS) spectroscopy. By measuring the uptake of Hg (II) at pH 6 with an initial

mercury concentration of 0.5 mM, Kim et al. 42 illustrated that the presence of chloride

with concentrations of 10-5 to 10-2 M resulted in the reduction of mercury (II) sorption.

Bonnissel-Gissinger et al. 46 modeled the sorption of Hg (II) onto amorphous silica

(Aerosil 200) and α-FeOOH, goethite (Bayferrox 910), using various 68 pH conditions.

The results by Bonnissel-Gissinger et al. 46 for the mineral sorbent, goethite, were

consistent with data results from Kim et al 42 which suggests that the presence of chloride

limited the sorption of mercury to oxide surfaces due to the formation of stable metal–

ligand aqueous complexes that do not absorb. However, Bonnissel-Gissinger et al.46

further suggested that the structures of the oxides (Aerosil 200) and iron-oxides did not

influence the sorptive capabilities of the samples. Wang et al.68 examined the influence

of chloride/mercury molar ratio and pH on the adsorption of mercury by poorly

crystalline oxides of Al, Fe, Mn, and Si. They reported that as the molar ratio of Cl/Hg

increased, sorption decreased due to the formation of aqueous Hg-Cl complexes.

The results from Figure 4.14 combined with the spectroscopic results presented in

Figures 4.4 and 4.5, revealed a high organic content in the natural samples of Philip’s

Mine tailings and Pakera Creek sediment: 45.76% and 40.38% by weight, respectively..

The organic portion of the natural samples likely provided stronger complexing sites

40

when compared to Kemiron (8.24% by weight). According to the investigation of

mercury distribution in waters of the coastal lagoons of Rio de Janeiro, Brazil, Lacerda

and Goncalves80 found that most dissolved mercury was strongly bonded to refractory

organic colloids. The Kemiron has the largest surface area of the three solids tested

which from a strictly sorption perspective would be expected to have the highest sorption

capacity. The type of mineral oxide or the presence of other complexing ligands in the

system resulted in the aqueous chloride complexes out-competing the Kemiron for

mercury more than the real sediment samples. This was especially true above pH 5. The

Philip’s Mine samples, which had a very low surface area also showed a strong binding

capacity for mercury. These tailings also show significant amounts of carbon and it is

reasonable to assume that that carbon is in the form of natural organic matter since no

carbonate minerals were identified by XRD. For the experiment with mercuric chloride,

the natural organic matter appeared to play a major role in competing with aqueous

mercury chloride complexes in the real sediment samples.

Hence, in this tropical rainforest region, natural organic matter (NOM) may have play a

significant role in mercury distributions. Further studies are needed to understand the

effect NOM has on mercury speciation/transformation reactions like abiotic photolysis.

A 24-hour equilibration time was used for all experiments. Kinetic tests were not

performed to validate this choice of equilibration period. Based on previous literature it

is possible that longer equilibration times were needed for batch reactor experiments.

41

CHAPTER 5: SUMMARY, CONCLUSION, & RECOMMENDATIONS FOR FUTURE

WORK

5.1 Introduction

The bioavailability, speciation, fate and transport of mercury in the environment can be

influenced by several natural and anthropogenic activities like soil degassing, volcanic

eruptions, mining, and industrial waste discharge. This section provides a summary of the

experimental results, conclusions, and recommendations for future work.

5.2 Summary of Results and Conclusions

The main objectives for studies on the samples collected from Guyana’s Mathews

Ridge/Arakaka area were to provide the following:

• Determine total mercury concentrations within the soil compartment

o Total mercury concentrations of the collected soil/sediment samples were

within the range of background mercury loadings reported in the

Amazonian mining districts (180-406 ng/kg 2, 22). One sample, MWJ,

reported mercury loadings of 1200 ng/kg. The samples were ground and

mixed prior to analysis and hence the results represent average loadings.

• Physical/Chemical characterization of soil samples

o Philip’s Mine tailings and Pakera Creek sediment as well as a

commercially available iron oxide, Kemiron, were subjected to BET

surface area, XRD, SEM/EDS analysis. The Philips Tailings had the

lowest surface area (4 m2/g) whilst Kemiron had the highest (40 m2/g).

SEM/EDS showed that the Philip’s Mine and Pakera Creek samples had

42

high carbon content likely due to the presence of natural organic matter;

however results may be inaccurate due to possible cross contamination of

sampling due to loading procedures. XRD identified goethite as the main

iron oxide phase present in Kemiron and SEM/EDS suggested that surface

impurities may include mercury. The ground (less than 38 μm) Kemiron

sample showed a porous surface with crystalline particle deposits.

• Determine the potential for mercury sorption by soil samples based on batch

reactor studies

o Simultaneous acidification of ground and surface waters can lead to an

increase in the mobility of mercury bound to soils and sediments 48.

Similarly, soils and sediments can act as potential sinks for mercury in the

environment. Batch adsorption studies of mercury on the Philip’s Mine

tailings, Pakera Creek sediments and Kemiron showed significant sorption

between pH 3 and 9 for conditions of 1 g/L solid and 100-1000 ppb Hg

added as Hg(NO3)2. The Philip’s Mine tailings sample showed the lowest

sorption and this was expected based on its low surface area compared

with Kemiron or the Pakera Creek sample. The Pakera Creek and

Kemiron samples showed similar behavior with high sorption across all

pH ranges and surface loadings around 200 mg/kg for the 100 ppb Hg

experiments and 2000 mg/kg for experiments with 1000 ppb Hg.

o Adsorption behavior of Hg2+ onto commercially available Kemiron, an

iron-oxide surface, exhibited decreased sorption patterns when mercuric

chloride was added to the system compared to the addition of mercuric

nitrate.

43

5.3 Recommendations for Future Work

• Further identification of binding mechanisms between mercury and sediment

samples is needed. This will include both sequential leaching techniques and

further spectroscopic analysis and modeling.

• Study of the role of organic matter in mercury mobility. This will include

quantification of organic matter content of soil/sediment samples as well as

mercury partitioning to these phases.

• Kinetic tests should be conducted to predict the possible fate and transport of

mercury (II) in soils.

• Future sampling in Guyana should be accomplished, especially in areas with

higher mercury concentrations, and better correlations made with aqueous

environmental parameters (pH, turbidity, alkalinity, TDS). Partnerships with the

local community and non-governmental organizations should be sought to not

only ensure continued access to the sampling sites and collected data, but also for

the sustained development of solutions to the potential pollution problems.

• The use of Kemiron as a sorbent for mercury under various geochemical

conditions including the presence of organic matter and other competing ions

should be further explored. This could lead to its further use as a remediation

procedure.

This research project examined the sorptive capabilities of sample Guyanese soils located

close to small-to-medium scale mining operations in the Arakaka and Mathew’s Ridge

region. These soils can act as potential sinks or sources for mercury and an

understanding of geochemical conditions that affect the fate of mercury can inform

solutions for reduced environmental impacts of mercury contamination. The motivation

for the work lies in understanding and reducing the environmental impact of mercury

used in the mining sector. This region is populated by scattered communities with

limited access to health care, analytical labs or centralized or coordinated drinking water

treatment and distribution systems. As local organizations like the Guyana WWF attempt

to assess the extent of mercury contamination and human exposure, a sustained

44

relationship with studied communities is definitely needed. More importantly,

multidisciplinary teams of researchers should be encouraged to further this work and

provide opportunities that not only further scientific research, but provides both

immediate and long term solutions to the local community. In a politically fragile

environment like Guyana, ways to form partnerships with local communities and non

governmental organizations are encouraged.

45

REFERENCES

1. Lacerda, L. D.; Goncalves, G. O., Mercury Distribution and Speciation in Waters of the Coastal Lagoons of Rio De Janeiro, Se Brazil. Marine Chemistry 2001, 76, (1-2), 47-58.

2. Miller, J. R.; Lechler, P. J.; Bridge, G., Mercury Contamination of Alluvial Sediments within the Essequibo and Mazaruni River Basins, Guyana. Water Air and Soil Pollution 2003, 148, (1-4), 139-166.

3. WWF-Guianas Guianas Forests and Environmental Coneservation Program: Mercury Impact Assessment Project; 2004.

4. Monson, B. A.; Brezonik, P. L., Seasonal Patterns of Mercury Species in Water and Plankton from Softwater Lakes in Northeastern Minnesota. Biogeochemistry 1998, 40, (2-3), 147-162.

5. Watras, C. J.; Back, R. C.; Halvorsen, S.; Hudson, R. J. M.; Morrison, K. A.; Wente, S. P., Bioaccumulation of Mercury in Pelagic Freshwater Food Webs. Science of the Total Environment 1998, 219, (2-3), 183-208.

6. Kim, J. P.; Burggraaf, S., Mercury Bioaccumulation in Rainbow Trout (Oncorhynchus Mykiss) and the Trout Food Web in Lakes Okareka, Okaro, Tarawera, Rotomahana and Rotorua, New Zealand. Water Air and Soil Pollution 1999, 115, (1-4), 535-546.

7. WHO Guidelins for Drinking-Water Quality: Incororating First Addendum. Volume 1, Recommendations. - 3rd Edition. http://www.who.int/entity/water_sanitation_health/dwq/gdwq0506.pdf (7/5/06).

8. Klatutau-Guimaraes, M. D. N.; D'ascencao, R.; Caldart, F. A., Analysis of Genetic Susceptibility to Mercury Contamination Evaluated through Molecular Biomarkers in at-Risk Amazon Amerindian Populations. Genetic Molecular Biology 2005, 28, (4), 827-832.

9. Atkeson, T.; Pollman, C.; Keeler, G. Integrating Atmospheric Mercury Deposition and Aquatic Cycling in the Florida Everglades: An Approach for Conducting

46

a Total Maximum Daily Load Analysis for an Atmospherically Derived Pollutant. Integrated Summary Final Report; Florida Department of Environmental Protection: 2002.

10. Ebinghaus, R.; Tripathi, R. M.; Wallschlager, D.; Lindberg, S. E., Natural and Anthropogenic Mercury Sources and Their Impact on the Air-Surface Exchange of Mercury on Regional and Global Scales. In Mercury Contaminated Sites. Characterization, Risk Assessment and Remediation, Springer-Verlag Berlin Heidelberg: New York, 1999.

11. UNEP, Global Mercury Assessment. In 2002.

12. Lacerda, L. D., Global Mercury Emissions from Gold and Silver Mining. Water, Air and Soil Pollution 1997a, 97, 209-221.

13. EPA Epa's Roadmap for Mercury. http://www.epa.gov/mercury/pdfs/V_InternationalHg.pdf.

14. Hylander, L. D., Global Mercury Pollution and Its Expected Decrease after a Mercury Trade Ban. Water Air and Soil Pollution 2001, 125, (1-4), 331-344.

15. Veiga, M. M.; Hinton, J. J., Abandoned Artisanal Gold Mines in the Brazilian Amazon: A Legacy of Mercury Pollution. Natural Resources Forum 2002, 26, (1), 15-26.

16. Veiga, M. M.; Maxson, P. A.; Hylander, L. D., Origin and Consumption of Mercury in Small-Scale Gold Mining. Journal of Cleaner Production 2006, 14, (3-4), 436-447.

17. Statistics., U. S. D. o. L. B. o. L. Cpi All Urban Consumers. . www.bls.gov/data (7/15/06).

18. Barbosa, A. C.; Dorea, J. G., Indices of Mercury Contamination During Breast Feeding in the Amazon Basin. Evironmental Toxicology and Pharmocology 1998, 6, (2), 71-79.

19. Barbosa, A. C.; Boischio, A. A.; East, G. A.; Ferrari, I.; Goncalves, A.; Silva, P. R. M.; Dacruz, T. M. E., Mercury Contamination in the Brazilian Amazon - Environmental, and Occupational Aspects. Water Air and Soil Pollution 1995, 80, (1-4), 109-121.

47

20. Charlet, L.; Roman-Ross, G.; Spadini, L.; Rumbach, G., Solid and Aqueous Mercury in Remote River Sediments (Litany River, French Guyana, South America). Journal De Physique IV 2003, 107, 281-284.

21. Spadini, L.; Charlet, L., Distribution of Anthropogenic Mercury in French Guyana River Sediments Downstream from Gold Mining Sites. Journal De Physique Iv 2003, 107, 1263-1266.

22. Paktunc, D.; Smith, D.; Couture, R., Mineralogical and Geochemical Characterization of Sediments and Suspended Particulate Matter in Water from the Potaro River Area, Guyana: Implications for Mercury Sources. In Applied Mineralogy, Pecchio, M.; Andrade, F. R. D.; D'agostino, L. Z.; Kahn, H.; Sant'agostino, L. M.; Tassinari, M. M. M. L., Eds. ICAM-BR: Sao Paolo, 2004; pp 379-382.

23. Gray, J. E.; Labson, V. F.; Weaver, J. N.; Krabbenhoft, D. P., Mercury and Methylmercury Contamination Related to Artisanal Gold Mining, Suriname. Geophysical Research Letters 2002, 29, (23).

24. Nriagu, J. O.; Pfeiffer, W. C.; Malm, O.; Desouza, C. M. M.; Mierle, G., Mercury Pollution in Brazil. Nature 1992, 356, (6368), 389-389.

25. Maurice-Bourgoin, L.; Quiroga, I.; Guyot, J. L.; Malm, O., Mercury Pollution I the Upper Beni River, Amazonian Basin: Bolivia. Abio 1999, 28, 302-306.

26. Hylander, L. D.; Meili, M.; Oliveira, L. J.; Silva, E. D. E.; Guimaraes, J. R. D.; Araujo, D. M.; Neves, R. P.; Stachiw, R.; Barros, A. J. P.; Silva, G. D., Relationship of Mercury with Aluminum, Iron and Manganese Oxy-Hydroxides in Sediments from the Alto Pantanal, Brazil. Science of the Total Environment 2000, 260, (1-3), 97-107.

27. Hines, M. E.; Horvat, M.; Faganeli, J.; Bonzongo, J. C. J.; Barkay, T.; Major, E. B.; Scott, K. J.; Bailey, E. A.; Warwick, J. J.; Lyons, W. B., Mercury Biogeochemistry in the Idrija River, Slovenia, from above the Mine into the Gulf of Trieste. Environmental Research 2000, 83, (2), 129-139.

28. Kannan, K.; Smith, R. G.; Lee, R. F.; Windom, H. L.; Heitmuller, P. T.; Macauley, J. M.; Summers, J. K., Distribution of Total Mercury and Methyl Mercury in Water, Sediment, and Fish from South Florida Estuaries. Archives of Environmental Contamination and Toxicology 1998, 34, (2), 109-118.

29. de Kom, J. F. M.; van der Voet, G. B.; de Wolff, F. A., Mercury Exposure of Maroon Workers in the Small Scale Gold Mining in Surinam. Environmental Research 1998, 77, (2), 91-97.

48

30. Barbosa, A. C.; de Souza, J.; Dorea, J. G.; Jardim, W. F.; Fadini, P. S., Mercury Biomagnification in a Tropical Black Water, Rio Negro, Brazil. Archives of Environmental Contamination and Toxicology 2003, 45, (2), 235-246.

31. Mol, J. H.; Ramlal, J. S.; Lietar, C.; Verloo, M., Mercury Contamination in Freshwater, Estuarine, and Marine Fishes in Relation to Small-Scale Gold Mining in Suriname, South America. Environmental Research 2001, 86, (2), 183-197.

32. Durrieu, G.; Maury-Brachet, R.; Boudou, A., Goldmining and Mercury Contamination of the Piscivorous Fish, Hoplias Aimara in French Guiana (Amazon Basin). Ecotoxicology and Environmental Safety 2005, 60, (3), 315-323.

33. Mirlean, N.; Larned, S. T.; Nikora, V.; Kutter, V. T., Mercury in Lakes and Lake Fishes on a Conservation -Industry Gradient in Brazil. Chemosphere 2005, 60, 226-236.

34. Mol, J. H.; Ouboter, P. E., Downstream Effects of Erosion from Small-Scale Gold Mining on the Instream Habitat and Fish Community of a Small Neotropical Rainforest Stream. Conservation Biology 2004, 18, (1), 201-214.

35. Fergusson, J. E., The Heavy Elements: Chemistry, Environmental Impact and Health Effects. Pergamon Press: 1990; p 429-524.

36. Gill, G. Biogeochemical Controls on Monomethyl Mercury Production in Aquatic Systems. http://gill.tamug.tamu.edu/OCNG647/Presentation/MethylMercuryProduction.ppt#262,1,Biogeochemical Controls on Monomethyl Mercury Production in Aquatic Systems.

37. Lindsay, W. L., Chemical Equilibria in Soils. Wiley: 1979.

38. Sarkar, D.; Essington, M. E.; Misra, K. C., Adsorption of Mercury(Ii) by Kaolinite. Soil Sci Soc Am J 2000, 64, (6), 1968-1975.

39. de Diego, A.; Tseng, C. M.; Dimov, N.; Amouroux, D.; Donard, O. F. X., Adsorption of Aqueous Inorganic Mercury and Methylmercury on Suspended Kaolin: Influence of Sodium Chloride, Fulvic Acid and Particle Content. Applied Organometallic Chemistry 2001, 15, (6), 490-498.

40. Kim, C. S.; Rytuba, J. J.; Brown, G. E., Exafs Study of Mercury(Ii) Sorption to Fe- and Al-(Hydr)Oxides I. Effects of Ph. Journal of Colloid and Interface Science 2004, 271, (1), 1-15.

49

41. Backstrom, M.; Dario, M.; Karlsson, S.; Allard, B., Effects of a Fulvic Acid on the Adsorption of Mercury and Cadmium on Goethite. Science of the Total Environment 2003, 304, (1-3), 257-268.

42. Kim, C. S.; Rytuba, J.; Brown, G. E., Exafs Study of Mercury(Ii) Sorption to Fe- and Al-(Hydr)Oxides - Ii. Effects of Chloride and Sulfate. Journal of Colloid and Interface Science 2004, 270, (1), 9-20.

43. Barrow, N. J.; Cox, V. C., The Effects of Ph and Chloride Concentration on Mercury Sorption by Goethite. Journal of Soil Science 1992, 43, (2), 295-304.

44. Gunneriusson, L.; Sjoberg, S., Surface Complexation in the H+-Goethite ([Alpha]-Feooh)-Hg (Ii)-Chloride System. Journal of Colloid and Interface Science 1993, 156, (1), 121-128.

45. Sarkar, D.; Essington, M. E.; Misra, K. C., Adsorption of Mercury(Ii) by Variable Charge Surfaces of Quartz and Gibbsite. Soil Science Society of America Journal 1999, 63, (6), 1626-1636.

46. Bonnissel-Gissinger, P.; Alnot, M.; Lickes, J. P.; Ehrhardt, J. J.; Behra, P., Modeling the Adsorption of Mercury(Ii) on (Hydr)Oxides Ii: Alpha-Feooh (Goethite) and Amorphous Silica. Journal of Colloid and Interface Science 1999, 215, (2), 313-322.

47. Mac Naughton, M. G.; James, R. O., Adsorption of Aqueous Mercury (Ii) Complexes at the Oxide/Water Interface Journal of Colloid and Interface Science 1974, Volume 47, (2), 431-440.

48. Tiffreau, C.; Lutzenkirchen, J.; Behra, P., Modeling the Adsorption of Mercury(II) on (Hydr)Oxides .1. Amorphous Iron-Oxide and Alpha-Quartz. Journal of Colloid and Interface Science 1995, 172, (1), 82-93.

49. Han, S. H.; Gill, G. A.; Lehman, R. D.; Choe, K. Y., Complexation of Mercury by Dissolved Organic Matter in Surface Waters of Galveston Bay, Texas. Marine Chemistry 2006, 98, (2-4), 156-166.

50. Aijun, Y.; Changle, Q.; Shusen, M.; Reardon, E. J., Effects of Humus on the Environmental Activity of Mineral-Bound Hg: Influence on Hg Volatility. Applied Geochemistry 2006, 21, (3), 446-454.

50

51. Khwaja, A. R.; Bloom, P. R.; Brezonik, P. L., Binding Constants of Divalent Mercury (Hg2+) in Soil Humic Acids and Soil Organic Matter. Environmental Science & Technology 2006, 40, (3), 844-849.

52. Sjoblom, A.; Meili, M.; Sundbom, M., The Influence of Humic Substances on the Speciation and Bioavailability of Dissolved Mercury and Methylmercury, Measured as Uptake by Chaoborus Larvae and Loss by Volatilization. Science of the Total Environment 2000, 261, (1-3), 115-124.

53. Yin, Y. J.; Allen, H. E.; Huang, C. P.; Sparks, D. L.; Sanders, P. F., Kinetics of Mercury(II) Adsorption and Desorption on Soil. Environmental Science & Technology 1997, 31, (2), 496-503.

54. Tonle, I. K.; Ngameni, E.; Njopwouo, D.; Carteret, C.; Walcarius, A., Functionalization of Natural Smectite-Type Clays by Grafting with Organosilanes: Physico-Chemical Characterization and Application to Mercury(II) Uptake. Physical Chemistry Chemical Physics 2003, 5, (21), 4951-4961.

55. Benoit, J. M.; Gilmour, C. C.; Heyes, A.; Mason, R. P.; Miller, C. L., Geochemical and Biological Controls over Methylmercury Production and Degradation in Aquatic Ecosystems. In Biogeochemistry of Environmentally Important Trace Elements. Washington, D.C., 2002.

56. Drexel, R. T.; Haitzer, M.; Ryan, J. N.; Aiken, G. R.; Nagy, K. L., Mercury(II) Sorption to Two Florida Everglades Peats: Evidence for Strong and Weak Binding and Competition by Dissolved Organic Matter Released from the Peat. Environmental Science & Technology 2002, 36, (19), 4058-4064.

57. Siciliano, S. D.; O'Driscoll, N. J.; Tordon, R.; Hill, J.; Beauchamp, S.; Lean, D. R. S., Abiotic Production of Methylmercury by Solar Radiation. Environmental Science & Technology 2005, 39, (4), 1071-1077.

58. Amyot, M.; Mierle, G.; Lean, D. R. S.; McQueen, D. J., Sunlight-Induced Formation of Dissolved Gaseous Mercury in Lake Waters. Environmental Science & Technology 1994, 28, (13), 2366-2371.

59. Waychunas, G. A.; Kim, C. S.; Banfield, J. F., Nanoparticulate Iron Oxide Minerals in Soils and Sediments: Unique Properties and Contaminant Scavenging Mechanisms. Journal of Nanoparticle Research 2005, 7, (4-5), 409-433.

60. Pelling, M., What Determines Vulnerability to Floods: A Case Study in Georgetown, Guyana. Environmental Problems 1997.

51

61. Vereecke, J., United Nations Development Programme, Country Office : Guyana, National Report on Indigenous Peoples and Development. In December 1994.

62. Vieira, R., Mercury-Free Gold Mining Technologies: Possibilities for Adoption in the Guianas. In Press, Corrected Proof.

63. Vieira, R., Mercury-Free Gold Mining Technologies: Possibilities for Adoption in the Guianas. Journal of Cleaner Production 2006, 14, (3-4), 448-454.

64. Coutoure, R., Personal Commnication. 1/13/2005.

65. Singh, D. J.; Rodrigues, M.; Best, W.; DBrowman, D.; Quik, J., Survey of Mercury Contamination in the Mazaruni River from Small Scale Mining Activity. In Environmental Studies Unit: 1997.

66. Singh, D.; Watson, C.; Mangal, S. Identification of the Sources and Assessment of the Levels of Mercury Contamination in the Mazaruni Basin in Guyana, in Order to Recommend Mitigation Measures; Institute of Applied Science and Technology 2001; pp 1-10.

67. Veiga, M. M., Mercury in Artisanal Gold Mining in Latin America: Facts, Fantasies and Solutions. In UNIDO - Expert Group Meeting, Vienna, 1997.

68. Wang, Q.; Kim, D.; Dionysiou, D. D.; Sorial, G. A.; Timberlake, D., Sources and Remediation for Mercury Contamination in Aquatic Systems--a Literature Review. Environmental Pollution 2004, 131, (2), 323-336.

69. Tessier, E.; Amouroux, D.; Grimaldi, M.; Stoichev, T.; Grimaldi, C.; Dutin, G.; Donard, O. F. X., Mercury Mobilization in Soil from a Rainfall Event in a Tropical Forest (French Guyana). Journal De Physique Iv 2003, 107, 1301-1304.

70. Applequi.Md; Turekian, K. K.; Katz, A., Distribution of Mercury in Sediments of New Haven (Conn) Harbor. Environmental Science & Technology 1972, 6, (13), 1123-&.

71. Lechler, P. J.; Miller, J. R.; Lacerda, L. D.; Vinson, D.; Bonzongo, J. C.; Lyons, W. B.; Warwick, J. J., Elevated Mercury Concentrations in Soils, Sediments, Water, and Fish of the Madeira River Basin, Brazilian Amazon: A Function of Natural Enrichments? Science Of The Total Environment 2000, 260, (1-3), 87-96.

52

72. Pfeiffer, W. C.; Malm, O.; Souza, C. M. M.; Delacerda, L. D.; Silveira, E. G.; Bastos, W. R., Mercury in the Madeira River Ecosystem, Rondonia, Brazil. Forest Ecology And Management 1991, 38, (3-4), 239-245.

73. de Lacerda, L. D., Updating Global Hg Emissions from Small-Scale Gold Mining and Assessing Its Environmental Impacts. Environmental Geology 2003, 43, (3), 308-314.

74. Dzombak, D. M.; Morel, F. M. M., Surface Complexation Modeling on Hydrous Ferric Oxide. John Wiley & Sons: New York, NY, 1990.

75. Lacerda, L. D.; Paraquetti, H. H. M.; Rezende, C. E.; Silva, L. F. F.; Silva, E. V.; Marins, R. V.; Ribeiro, M. G., Mercury Concentrations in Bulk Atmospheric Deposition over the Coast of Rio De Janeiro, Southeast, Brazil. Journal Of The Brazilian Chemical Society 2002, 13, (2), 165-169.

76. Guimaraes, J. R. D.; Meili, M.; Malm, O.; Brito, E. M. D., Hg Methylation in Sediments and Floating Meadows of a Tropical Lake in the Pantanal Floodplain, Brazil. Science Of The Total Environment 1998, 213, (1-3), 165-175.

77. Gray, J. E.; Hines, M. E.; Higueras, P. L.; Adatto, I.; Lasorsa, B., Mercury Speciation and Microbial Transformations in Mine Wastes, Stream Sediments, and Surface Waters at the Almaden Mining District, Spain. Environ. Sci. Technolo. 2004, 4285-4292.

78. Bera, S. Wwf Iast Mercury Impact Assessment Project-Region 1: Arakaka, Mathew's Ridge and Port Kaituma; IAST: Georgetown, Guyana, June 10, 2005, 2005; pp 1-5.

79. Kim, C. S.; Rytuba, J. J.; Brown, G. E., Geological and Anthropogenic Factors Influencing Mercury Speciation in Mine Wastes: An Exafs Spectroscopy Study. Applied Geochemistry 2004, 19, (3), 379-393.

80. Lacerda, G. O. G. L. D., Mercury Distribution and Speciation in Waters of the Coastal Lagoons of Rio De Janerio, Se Brazil. Marine Chemistry 2001, (76), 47-58.

53

APPENDICES

54

Appendix A: Abridged Experimental Data Results

Tabular report of the equilibrium sorption experiments discussed in Chapter 4. Data

results have been grouped according to sample name then by the mercury stock solution

(i.e. HgCl2 or Hg(NO3)2).

Table A.1: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Pakera Creek sediment (1.1).

Experiment 1.1:

100 ppb Hg (Hg(NO3)2) Sorption on 0.1 g Pakera Creek

Sediment

Background electrolyte: 0.1 N sodium nitrate

pH

THg (ppb) % Hg Sorbed

3.68 5.11 95%

3.97 4.90 95%

5.26 2.11 98%

5.41 4.45 96%

5.63 3.13 97%

5.69 1.57 98%

5.84 0.63 99%

5.86 2.95 97%

6.01 4.72 95%

6.90 7.70 92%

7.31 4.11 96%

55

Appendix A: (Continued)

Table A.2: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Pakera Creek sediment (1.2).

Experiment 1.2:

100 ppb Hg Sorption on 0.1 g Pakera Creek Sediment

Background electrolyte: 0.1 N sodium nitrate

pH

THg (ppb) % Hg Sorbed

3.10 5.47 90%

5.27 5.04 90%

6.02 5.51 89%

6.49 5.04 90%

6.70 6.66 88%

6.75 5.64 89%

6.91 5.57 89%

7.16 10.51 84%

7.40 1.06 84%

7.80 5.43 90%

9.34 5.28 90%

56

Appendix A: (Continued)

Table A.3: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Philip’s Mine tailings (2.1).

Experiment 2.1:

100 ppb Hg (Hg(NO3)2) Sorption on 0.1 g Philip’s

Mine tailings

Background electrolyte: 0.1 N sodium nitrate

pH THg (ppb) % Hg Sorbed

3.10 7.83 92%

3.39 5.47 95%

3.54 6.33 94%

4.10 31.07 69%

4.52 34.95 65%

4.85 32.95 67%

5.51 9.47 91%

5.63 92.76 7%

5.79 12.90 87%

5.87 7.60 92%

7.38 4.97 95%

57

Appendix A: (Continued)

Table A.4: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Philip’s Mine tailings (2.2).

Experiment 2.2:

100 ppb Hg (Hg(NO3)2) Sorption on 0.1 g Philip’s

Mine tailings

Background electrolyte: 0.1 N sodium nitrate

pH THg (ppb) % Hg Sorbed

3.57 0.72 89%

3.96 18.06 71%

6.34 7.55 76%

6.47 5.87 83%

7.30 0.75 71%

9.56 0.43 88%

58

Appendix A: (Continued)

Table A.5: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Kemiron (3.1).

Experiment 3.1:

100 ppb Hg (Hg(NO3)2) Sorption on 0.1 g Kemiron

Background electrolyte: 0.1 N sodium nitrate

pH THg (ppb) % Hg Sorbed

4.37 0.18 100%

4.71 0.10 100%

5.08 0.06 100%

5.39 0.10 100%

5.98 0.35 100%

6.58 0.35 100%

7.29 0.27 100%

7.44 0.30 100%

8.21 0.13 100%

59

Appendix A: (Continued)

Table A.6: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Kemiron (3.2).

Experiment 3.2:

100 ppb Hg (Hg(NO3)2) Sorption on 0.1 g Kemiron

Background electrolyte: 0.1 N sodium nitrate

pH THg (ppb) % Hg Sorbed

4.24 0.09 96%

5.49 0.11 96%

6.24 0.41 96%

6.93 0.19 96%

7.74 0.41 96%

9.03 0.39 96%

Table A.7: 100 ppb Hg (Hg(NO3)2) sorption on 0.1 g Kemiron (3.3).

Experiment 3.3:

100 ppb Hg (Hg(NO3)2) Sorption on 0.1 g Kemiron

Background electrolyte: 0.1 N sodium nitrate

pH THg (ppb) % Hg Sorbed

4.07 0.13 96%

5.07 1.76 96%

6.26 0.27 96%

7.38 0.40 96%

8.03 1.67 95%

60

Appendix A: (Continued)

Chapter 4.4: Equilibrium sorption experiments. Kemiron; Hg Spike from mercuric

nitrate with varied total mercury concentrations of 200 and 1,000 ppb.

Table A.8: 1,000 ppb Hg (Hg(NO3)2) sorption on 0.1 g Kemiron (4.1).

Experiment 4.1:

1000 ppb Hg (Hg(NO3)2)Sorption on 0.1 g Kemiron

Background electrolyte: 0.1 N sodium nitrate

pH THg (ppb) % Hg Sorbed

3.07 8.85 99%

3.66 10.26 99%

3.92 10.64 99%

4.53 11.68 99%

4.97 13.66 99%

5.99 14.70 99%

6.45 15.64 98%

7.95 16.77 98%

9.62 17.91 98%

9.92 18.38 98%

61

Appendix A: (Continued)

Chapter 4.4: Equilibrium sorption experiments for all samples (Pakera Creek, Philips

Tailings, and Kemiron); Hg spike from mercuric chloride with varied total mercury

concentrations of 1,000ppb.

Table A.9: 1,000 ppb Hg (HgCl2) sorption on 0.1 g Pakera Creek (5.1).

Experiment 5.1:

1,000 ppb Hg Sorption on 0.1 g Pakera Creek Background electrolyte: 0.1 N sodium nitrate

pH THg (ppb) % Hg Sorbed

2.86 430.32 57% 3.4 390.38 61%

4.84 294.61 71% 6.85 32.88 97% 8.74 37.21 96% 5.57 80.96 92% 4.43 307.59 69%

Table A.10: 1,000 ppb Hg (HgCl2) sorption on 0.1 g Philip’s Mine (5.2).

Experiment 5.2:

1,000 ppb Hg Sorption on 0.1 g Philip’s Mine tailings Background electrolyte: 0.1 N sodium nitrate

pH THg (ppb) % Hg Sorbed

2.68 256.92 74% 4.6 241.06 76%

6.23 175.77 82% 5.36 233.27 77% 8.67 55.10 94% 8.88 55.38 94% 9.04 44.52 96%

62

Appendix A: (Continued)

Chapter 4.4: Equilibrium sorption experiments for all samples (Pakera Creek, Philips

Tailings, and Kemiron); Hg spike from mercuric chloride with varied total mercury

concentrations of 1,000 ppb.

Table A.11: 1,000 ppb Hg (HgCl2) sorption on 0.1 g Kemiron (5.3).

Experiment 5.3:

1000 ppb Hg Sorption on 0.1 g Kemiron Background electrolyte: 0.1 N sodium nitrate

pH THg (ppb) % Hg Sorbed

2.84 356.36 64% 3.28 383.67 62% 4.44 380.88 62% 4.94 367.42 63% 5.46 302.80 70% 6.35 346.94 65% 8.51 462.04 54%

63

Appendix A: (Continued)

Chapter 4.3: EDS Quantification Results

All electron dispersion graphic signals and quantification results were taken at 25kV with

a tilt of 30 and take-off of 36.31 at total counts of 100.0 seconds.

Table A.12: EDS quantification Table A.13: EDS quantification (Arakaka Creek) (Kemiron)

Arakaka Creek Kemiron <38μm

Elem Wt % At% K-Ratio Elem Wt % At% K-Ratio

C K 23.41 33.41 0.0398 C 8.24 16.29 0.0208

O K 44.23 47.39 0.1115 O 41.64 61.72 0.1699

F K 1.02 0.92 0.0015 Mg 3.44 3.36 0.0095

Al K 1.46 0.93 0.0092 Ca 0.44 0.26 0.0042

Si K 27.65 16.88 0.2069 Fe 42.12 17.9 0.3893

Fe K 1.29 0.4 0.0113 Hg 1.76 0.21 0.0127

HgL 0.95 0.08 0.0066 Pb 2.39 0.27 0.0169

Table A.14: EDS quantification (Philip’s Mine)

Philips Tailings

Elem Wt % At% K-Ratio

C K 44.79 55.87 1.0192

O K 39.14 36.66 1.0038

Al K 4.34 2.41 0.9382

Si K 7.6 4.05 0.9662

K K 0.15 0.06 0.912

Ca K 0.02 0.01 0.9357

Ti K 0.34 0.11 0.8588

Fe K 2.88 0.77 0.8585

Hg L 0.74 0.05 0.6569

64

Appendix A: (Continued)

Chapter 4.3: EDS Quantification Results

All electron dispersion graphic signals and quantification results were taken at 25kV with

a tilt of 30 and take-off of 36.31 at total counts of 100.0 seconds.

Table A.15: EDS quantification Table A.16: EDS quantification (Pakera Creek) (Pakera Creek (2))

Pakera Creek Pakera Creek

Elem Wt % At% K-Ratio Elem Wt % At% K-Ratio

C 22.2 32.48 0.0438 C 40.38 53.03 0.1123

O 45.93 50.44 0.1256 O 38 37.47 0.0843

Al 7.68 5.00 0.044 Fe 8.42 2.38 0.224

Si 15.25 9.54 0.0964 Al 4.58 2.68 0.0263

S 0.06 0.03 0.0004 Si 7.51 4.22 0.05

Cl 0.11 0.05 0.0008 K 0.22 0.09 0.002

K 0.53 0.24 0.0045 Ti 0.22 0.07 0.002

Ba 0.94 0.12 0.0079 Mn 0.05 0.02 0.0005

Mn 1.07 0.34 0.0093 Hg 0.61 0.05 0.0042

Fe 5.31 1.67 0.0468

Hg 0.93 0.08 0.0065

65