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Chapter 5

HEAVY METAL ANALYSIS

5.1. INTRODUCTION

Heavy metals are the chemical elements found in all kinds

of soils and sediments mostly with density greater than 5 g dm-1, the

very low general level of their content in soils and plants as well as the

biological role of most of them are microelements (Lacatusu, 1998).

Many of these metals find their way into the living systems through

air, water and food and tend to accumulate in the body, some of them

even in minor ·concentrations threaten to affect the metal dependent

enzyme catalyzed reactions in the body. At least 11 metals are known

to be essential for living organisms and these are Fe, Cu, Zn, Co, Mn,

Cr, Mo, V, Se, Ni and Sn. Essential metals always function in

combination with organic molecules and most commonly with proteins

either tightly bound in metallo-proteins or more loosely bound in

metal protein complexes (Brouwer et al., 1986). There is little evidence

that marine organisms ever suffer from metal deficiencies and

presumably the optimum concentrations are those that occur naturally.

Some heavy metals are essential to maintain human

metabolism, however, many may be poisonous at higher concentrations

(greater than the permissible limit), as they tends to bio-accumulate in

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human bodies making them dangerous and thereby poses great

health and environmental risks. The toxicity of heavy metals causes

morphological abnormalities, neuro-physiological disturbances, genetic

alteration of cell (mutation), terato-genesis and carcinogenesis.

In addition, heavy metals effect on enzymatic and hormonal activities

reduces growth and increases mortality (Idris, 2008).

Coastal and estuarine regions are the important sinks for

many persistent pollutants and they accumulate in organisms and

bottom sediments (Szefer et al., 1995). Sediments are essential

components of terrestrial and marine ecosystem. The marine sediments

are considered as sensitive indicators of both organic and inorganic

contamination in both spatial and temporal trends for monitoring the

marine environment (Larsen and Jensen, 1989). Sediments are important

carriers of heavy metals in the hydrological cycle because metals are

partitioned with the surrounding waters and they reflect the quality of

an aquatic system. Sediment-associated metals have the potential to be

ecotoxic due to their mobility and bioavailability, and this in turn affects

both ecosystems and human life through a process of bioaccumulation

and bio-magnification respectively (Buccolieri et al., 2006; Ip et al., 2007).

The analysis of heavy metals in marine sediments is

widely used to assess long-term anthropogenic inputs into the marine

environment (Fukushima et al., 1992; Ravichandran et al., 1995;

Li et al., 2010). The studies of metals like, Cr, Cd, Ni, Cu, Zn, Pb and

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Fe, which have an affinity for biota, and have nutrient-like distribution

in the oceans, are important. Metals such as Ni, Cd, Cr and Zn, etc.

are used in contamination studies in marine systems due to their

relationship with anthropogenic activities (Burton et al., 2004;

Munuz et al., 2004).

Metals enter the marine environment by two means:

natural processes (including erosion of ore-bearing rocks, wind-blown

dust, volcanic activity and forest fires); and processes derived from

human activities by means of atmospheric deposition, rivers, and

direct discharges or dumping (Clark, 2001). For some metals, natural

and anthropogenic inputs are of the same order (for example Hg and

Cd), whereas for others (for example Pb) inputs due to human

activities (Clark, 2001; Chatterjee et al., 2007). Once the metals are

released to the environment, they are transferred to the sediments

through adsorption onto suspended matter and subsequent

sedimentation (Hart, 1982).

Heavy metal contamination in terrestrial and aquatic

environments has significantly increased since the onset of the

industrial revolution (Forstner and Wittmann, 1981). The consequence

of heavy metal contamination is more serious in comparison to

organic or microbial contamination because heavy metals are cycled

between aqueous and particulate phases over a long period (Salomons

and Forstner, 1984).

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Heavy metals in the environment have many sources

(1) geologic weathering, (2) industrial processing of ores and metals,

(3) use of metals and metal compounds, (4) leaching of metals from

garbage and soil waste dumps, and (5) animal and human excrete

(Forstner and Wittmann, 1981).

Enrichment Factors are commonly used in the literature as

a means of identifying and quantifying human interference with global

element cycles. The geo-accumulation index (Igeo) was originally

defined by Muller (1979); Igeo is a quantitative measure of

contamination of aquatic sediments (Ridgway and Shimmield, 2002).

The spatial distribution of heavy metals in marine sediment

is of major importance in clarifying the pollution history of aquatic

systems (Rubio et al., 2001; Liu et al., 2003) and the study of the

seasonal variation of trace metals is important to assess the influence

of hydrographic changes because it plays a principal role in modifying

metals in sediments. It is therefore the goal of this study to provide

the spatial distribution and seasonal variation of trace metals in the

marine sediments from Visakhapatnam coast, Bay of Bengal, India.

5.2. REVIEW OF LITERATURE

Metals have exerted a profound influence on the course of

biological evolution, their modern day industrial usage, mainly during

the course of last fifty years has led to their bioaccumulation in the

environments (Moore and James, 1992).

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Valsecchi et al. (1995) reported that heavy metals appeared

to cause an alteration in the soil Carbon cycle, and modify energy

metabolism of soil Olicroflora leading to a decrease in the net

mineralization of soil organic matter. However other research has

shown that heavy metals at low concentrations, or inputs of heavy

metals with organic matter, stimulate bacterial growth and population

size (Dusek, 1995).

With the rapid industrialization and economic development

in coastal region heavy metals are continuing to be introduced to

estuarine and coastal environment around the world (Feng et al., 2004;

Romano et al., 2004; Santos et al., 2005).

Geochemical characteristics of the sediments can be used

to infer the weathering trends and the sources of pollution (e.g.,

Forstner and Salomons, 1980; Fedo et al., 1996; Nesbitt et al., 1996;

Nath et al., 2000). Therefore, chemical availability of metals on

sediments has been used to deduce the sources and pathways by

which major and trace elements have entered the marine environment

(Loring and Rantala, 1992).

Sediments are the main repository and source of heavy metals

in the marine environment and play an important role in the transport

and storage of potentially hazardous metals (Guevara et al., 2005;

Mason et al., 2006; Yu et al., 2009).

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Sediments are preferable monitoring ‘‘tools’’ since contaminant

concentrations are orders of magnitude higher and they show less

variation in time and space, allowing more consistent assessment of

spatial and temporal contamination (Tuncer et al., 2001; Beiras et al., 2003;

Caccia et al., 2003). Sediment analyses play an important role in

assessments of pollution status of marine environment.

Pollution of the natural environment by heavy metals is a

worldwide problem, because these metals are indestructible and most

of them have toxic effects on living organisms, when they exceed a

certain concentration (Nuremberg, 1984; Forstner, 1990; Harte et al., 1991;

Schuurmann and Market, 1998; MacFarlane and Burchett, 2000).

Arsenic, Cr, Cu, Mn, Ni and Fe are used as markers or

tracers of metal industries (Jervis et al., 1993; Nkono et al., 1999;

Kumar et al., 2001; Lin et al., 2002; Gallego et al., 2002; Loska et al., 2004).

Cadmium, Co, Pb, Sn, and Zn are known as the markers of

paint industries (Aksu et al., 1998; Yasar et al., 2001; Lin et al., 2002)

many of which are present in the study area.

Various studies have demonstrated sediments from coastal

areas greatly contaminated by heavy metals; therefore, the evaluation

of metal distribution in surface sediments is useful to assess pollution

in the marine environment (Jayaprakash et al., 2008; Pekey, 2006;

Buccolieri et al., 2006; Bellucci et al., 2002).

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Trace metals can be recirculated in the aquatic

environments via natural or anthropogenic processes and then back

to the water bodies, resulting in deterioration of the water quality and

long-term implication of human health and ecosystem (Fatoki and

Mathabatha, 2001; Ip et al., 2007).

The analysis of heavy metals in the sediments permits

detection of pollutants that may be either absent or in low

concentrations in the water column (Davies et al., 1991) and their

distribution in coastal sediment provides a record of the spatial and

temporal history of pollution in a particular region or ecosystem.

All heavy metals exert toxic effects at some concentration,

including mining, smelting, electroplating, and other industrial

processes that have metal residues in their wastes and by non-point

source surface runoff (Bakan and Ozkoc, 2007).

The accumulated potentially toxic metals are taken up by the

bottom-dwelling animals and their concentrations are seen increasing in

their tissues (Sulochanan et al., 2007; Rao et al., 2006, 2007, 2009;

Krishna Kumar et al., 2010) causing a threat to the ecosystem and

pose a risk to human health.

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The increasing heavy metals contamination of coastal

sediments is a cause of growing concern, since these elements are

highly persistent and may exert toxic effects at all levels of biological

organization from cells to population and community structure

(Chapman et al., 1988; Thompson et al., 2007; Koigoora et al., 2013).

Trace metal concentrations in sediments can be influenced

by variations in organic carbon content, grain size, carbonate and

sulfide content, Fe-Mn oxyhydroxide content (Adriano, 2001;

Roychoudhry, 2007), reduction/oxidation reactions, adsorption/

desorption, and physical transport or sorting, as well as anthropogenic

metal inputs (Luoma et al., 1997).

Studies on the Indian shelf region are limited when compared

to other regions of the world. Considerable work has been carried out

on the sediments of the west coast of India by Gogate et al. (1976)

Paropkari et al. (1978) and Bhosle et al. (1978), whereas, the inner

shelf of the Bay of Bengal of the east coast has received very much less

attention. Overall, the geochemical characters of surface sediments of the

Bay of Bengal, indicate that the metal distribution is mainly controlled

by their sediment texture and studies along the Visakhapatnam coast

(Satyanarayana et al., 1985; Raman, 1995), Puri to Port Novo

(Mohapatra et al., 1992), central east coast of India (Rao and Sarma, 1993)

and the Madras coast (Pragatheeswaran et al., 1986) were limited to

the northern part of the east coast of India.

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Jonathan and Rammohan (2003) reported that the

analyzed data confirms that metal pollution is a significant factor in

the coastal region off the Tuticorin coast, justifying the need for

suitable treatment plants as well as continued monitoring.

Jonathan et al. (2004) concluded that the heavy metals in

the sediments of Gulf of Munnar were indicative of the direct effect of

industrial discharge.

Alagarsamy (2006) studied the spatial and temporal

distribution of trace metals in surface sediments of the Mandovi

estuary and observed that the lowest metal concentrations during the

monsoon, compared to the pre- and post-monsoon.

Roychoudhry (2007) reported that minor variations in the

total trace metal content and depth profiles were observed seasonally,

despite drastic changes in the microbial activity, major ion chemistry

and in the vegetation pattern.

Sundararajan and Natesan (2010) reported that the heavy

metals in the Palk Bay sediments shown a relatively very low degree of

seasonal variation in the concentrations.

Various studies have demonstrated marine sediments from

industrialized coastal areas are greatly contaminated by heavy metals;

therefore, the evaluation of metal distribution in surface sediments is

useful to assess pollution in the marine environment (Salomons and

Forstner, 1984; Bellucci et al., 2002; Buccolieri et al., 2006).

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Based on examination of the Namibian shelf sediments,

major and trace element geochemistry reflects the complex

intermixture of several sedimentary components of minor metal

enrichments (Calvert and Price, 1983).

Detailed study on the surface sediments and mineralogical

composition of Sulu Sea and South China sea revealed that the

sediments are carbonate rich and the compositional variability of the

sediments is controlled to some extent by variations in sediment

supply from adjacent land mass (Calvert and Pederson, 1993).

Taliadouri and Varnavas (1995) observed an increase in trace

metal concentration in surface sediments from Thermaikos Gulf, mainly

attributable to sewage outfall, the industrial zone and the river input.

Valdes et al. (2005) concluded that the higher

concentrations of heavy metals in the Mejillones Bay surface

sediments might be associated with the flux of organic matter and the

water column’s persistent strong hypoxic environmental conditions.

Choi et al. (2006) suggested that the limited water flow and

reduced flushing have been proposed elsewhere as promoting heavy

metal pollution of sediments in constricted parts of estuaries.

Preda and Cox (2002) reported that all trace metals in

sediments of Coastal Pumicestone region, Australia were controlled by

the presence of Fe and Mn oxides, and the grain size of the sediment.

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5.3. SAMPLE PREPARATION AND EXPERIMENTAL PROCEDURE

The sediment samples collected along Visakhapatnam

coast; Lawson’s Bay in the north and Appikonda Beach in the south,

Bay of Bengal, India during three seasons viz., post-monsoon

(December 2009), pre-monsoon (May 2010) and monsoon (September

2011) were dried at 40°C, homogenized and powdered using an agate

mortar. About 0.5 g of the sediment sample was accurately weighed

into pre-cleaned glass vessel and digested at room temperature with

HNO3/HClO4 (4:1) mixture for 24 hours. Following, the suspensions

were evaporated at 120ºC until dryness. Then, 10% HNO3 was added

to residues. The final suspensions were filtered through Whatmann

Grade ‘A’ filter paper. The solution was transferred into a polyethylene

volumetric flask and diluted with Milli-Q water to 100 ml. One

milliliter of the solution was then diluted to 10 ml by adding HNO3

(Walting, 1981). Metal concentrations (Fe, Cd, Cr, Cu, Ni, Pb and Zn)

were measured using Inductively Coupled Plasma Optical Emission

Spectroscopy (ICP-OES, Perkin-Elmer, Optima 2100 DV, U.S. EPA

Method 6020, 1996) at Centre of Advanced study in Marine Biology,

Annamalai University (Plate 5.1). Suitable internal chemical standards

(Merck, Germany) were used to calibrate the instrument. Precision

and accuracy of the metal analysis were checked against the marine

sediment Standard Reference material from NIST. All glass wares and

plastic containers were washed with 10% nitric acid solution and

rinsed thoroughly with Milli-Q water.

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Plate 5.1. Photograph of ICP-OES

5.4. METHODS FOR ESTIMATING POLLUTION IMPACT

Number of calculation methods have been used for

quantifying the degree of metal enrichment in sediments by many

authors (Salomons and Forstner, 1984; Muller, 1969; Hokanson, 1980).

They have proposed pollution impact scales or ranges to convert the

calculated numerical results into broad descriptive bands of pollution

ranging from low to high intensity.

5.4.1. Enrichment factor (EF)

In the present study, enrichment factor was used to assess

the level of contamination and the possible anthropogenic impact in

sediments. To identify anomalous metal concentration, geochemical

normalization of the heavy metals data to a conservative element,

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such as Al, Fe, and Si was employed. Several authors have successfully

used iron to normalize heavy metals contaminants (Schiff and

Weisberg, 1999; Baptista Neto et al., 2000; Mucha et al., 2003). In this

study iron has used as a conservative tracer to differentiate natural

from anthropogenic components. According to Ergin et al. (1991) the

metal enrichment factor (EF) is defined as follows

Sample

Upper crustal average

Me

FeEF

Me

Fe

where, (Me/Fe)sample is the metal to Fe ratio in the samples,

(Me/Fe)Upper crustal average is the metal to Fe in the continental crust

(Wedepohl, 1995).

5.4.2. Index of geo-accumulation

To understand the current environmental status and the

extent of metal contamination with respect to natural environment,

other approaches should also be applied. A common criterion to

evaluate the intensity of heavy metal pollution in sediments is the geo-

accumulation index (Igeo), which was originally defined by Muller (1969)

to determine metals contamination in sediments, by comparing

current concentrations with pre-industrial levels and can be

calculated by the following equation

2log1.5

CnIgeo

Bn

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where, Cn is the measured concentration of the examined metal; Bn is

the background value of the metal n (Wedepohl, 1995) and the factor

1.5 is used to minimize the effect of possible variations in the

background values, which may be attributed to lithogenic variations

in the sediments for a given metal in the environment, as well as very

small anthropogenic influences (Ruiz, 2001).

5.5. RESULTS AND DISCUSSION

5.5.1. Spatial and seasonal distribution of trace metals

The spatial distribution and seasonal variations of major (Fe)

and some trace metals (Cd, Cr, Cu, Ni, Pb and Zn) in surface

sediments from Visakhapatnam coast collected in three different

seasons viz., post-monsoon, pre-monsoon and monsoon seasons are

shown in Figs. 5.1 to 5.7(a-c).

Iron (Fe)

Iron is the most abundant and consistent transition metal,

is also probably the most well-known metal in biological systems.

Recent evidences indicate that iron is an essential nutrient limiting

phytoplankton production in ocean (Coale et al., 1996) as well as in

some coastal upwelling environments (Hutchins and Bruland, 1998;

Firme et. al., 2001). The spatial distribution maps of Iron in post-

monsoon, pre-monsoon and monsoon seasons are shown in Fig. 5.1a-c.

The concentrations of Iron in the surface sediments of Visakhapatnam

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coast during post-monsoon varied between 1,782 and 11,392 µg/g,

while it varies in the range of 1,516 to 8,504 µg/g during pre-monsoon

and it varies in the range 670 to 8,748 µg/g during monsoon.

The maximum concentration was measured at V1, near Lawson’s bay

during post-monsoon and minimum was measured at V14, near

harbour during monsoon. The average concentration of Fe was higher

during Pre-monsoon compared to other two seasons. Concentrations

of Fe decreased seaward during post-monsoon and it increased seaward

during pre-monsoon and monsoon seasons. High concentrations of Iron

were observed in the northern region during post and pre-monsoon

seasons and it was observed in the southern region during monsoon.

Cadmium (Cd)

Cadmium is a very bio-tonic element, it has no biological

function and it is a highly toxic non-essential metal. The spatial

distribution maps of cadmium in post-monsoon, pre-monsoon and

monsoon seasons are shown in Fig. 5.2a-c. The concentrations of

cadmium in the shelf sediments of Visakhapatnam during post-

monsoon varied between 0.04 and 0.76 µg/g, while it varies in the

range of 0.04 to 0.36 µg/g during pre-monsoon and it varies in the

range 0.24 to 1.00 µg/g during monsoon. The maximum concentration

was observed at V19, near Gangavaram port during monsoon and

minimum was observed at V27, near AK beach during post-monsoon

and at V20 and V22, near Gangavaram port during pre-monsoon. The

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average concentration of Cadmium was higher during monsoon

compared to other two seasons. Concentrations of Cd decreased

seaward during post-monsoon and it increased seaward during pre-

monsoon and monsoon seasons. High concentrations of Cadmium

were observed in the northern region during post and pre-monsoon

seasons and it was observed in the southern region during monsoon.

The anthropogenic sources of cadmium in the study area includes the

primary uses of cadmium in electroplating other metals or alloys for

protection from corrosion, in photographic industry and in the

manufacture of storage batteries, pigments, glass ceramics and plastic

stabilizers. It was found that cadmium content is high in rock

phosphate, which is the raw material, for the manufacture of

phosphate fertilizers (Forstner and Wittmann, 1979).

Chromium (Cr)

Chromium is one of the least toxic of the trace elements on the

basis of it’s over supply and essentiality (Forstner and Wittmann, 1979).

Generally mammalian body can tolerate 100-200 times its total body

content of chromium without harmful effects. The spatial distribution

maps of chromium in post-monsoon, pre-monsoon and monsoon

seasons are shown in Fig. 5.3a-c. The concentrations of chromium in

the shelf sediments of Visakhapatnam during post-monsoon varied

between 27.26 and 58.50 µg/g, while it varies in the range of 10.16 to

30.66 µg/g during Pre-monsoon and it varies in the range 14.33 to

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62.27 µg/g during monsoon. The maximum concentration was

observed at V19, near Gangavaram port during monsoon and

minimum was observed at V19, near Gangavaram port during pre-

monsoon. The average concentration of Cr was higher during monsoon

compared to other two seasons. Concentrations of Cr decreased

seaward during post-monsoon and it increased seaward during

monsoon season. High concentrations of chromium were observed in

the northern region during post and pre-monsoon seasons and it was

observed in the southern region during monsoon. The anthropogenic

sources of chromium in Visakhapatnam coastal sediments are metal

plating, organic and petro-chemicals, fertilizers, petroleum refining

and industrial dyes. Of these sources, electroplating industry is the

major contributor of chromium.

Copper (Cu)

Copper is an essential micronutrient, which is widely

distributed in nature in free state as well as in combined state. It is

highly toxic to most aquatic plants. Inhibition of growth generally

occurs at 0.1 mg/l, regardless of test conditions and species. The

spatial distribution maps of copper in post-monsoon, pre-monsoon

and monsoon seasons are shown in Fig. 5.4a-c. The concentrations of

copper in the shelf sediments of Visakhapatnam during post-monsoon

varied between 8.40 and 47.32 µg/g, while it varies in the range

of 2.88 to 37.66 µg/g during Pre-monsoon and it varies in the range

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6.74 to 45.15 µg/g during monsoon. The maximum concentration was

observed at V1, near Lawson’s bay during post-monsoon and minimum

was observed at V19, near Gangavaram port during pre-monsoon.

The average concentration of Cu was higher during post-monsoon

compared to other two seasons. Concentrations of Cu decreased

seaward during post-monsoon and it increased seaward during

monsoon season. High concentrations of copper were observed in the

northern region during post and pre-monsoon seasons and it was

observed in the southern region during monsoon. One of the major

sources of copper in the study area is the contribution from the

anti-fouling paint for the hulls of ships (Clark, 2001). Copper is

characterized by strongly scattered anthropogenic influence. This

particularly relates to the uncontrolled waste dumps and liquid waste

from industries.

Nickel (Ni)

Nickel is essential at trace levels for human health (Moore

and Ramamoorthy, 1984). Acute toxicity arises from competitive

interaction with five essential elements calcium, cobalt, iron, copper

and zinc. Nickel can replace essential metals in the metallo-enzymes

resulting in the disruption of metabolic pathways (McGroth and

Smith, 1990). The spatial distribution maps of Nickel in post-monsoon,

pre-monsoon and monsoon seasons are shown in Fig. 5.5a-c. The

concentrations of Nickel in the shelf sediments of Visakhapatnam

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during post-monsoon varied between 17.76 and 34.04 µg/g, while it

varies in the range of 2.37 to 23.66 µg/g during Pre-monsoon and it

varies in the range 8.19 to 34.40 µg/g during monsoon. The maximum

concentration was observed at V3, near Lawson’s bay during monsoon

and minimum concentration was observed at V20, near Gangavaram

port during pre-monsoon. The average concentration of Ni was higher

during post-monsoon compared to other two seasons. Concentrations

of Ni decreased seaward during post and pre-monsoon seasons and it

increased seaward during monsoon season. High concentrations of

Nickel were observed in the northern region during post-monsoon and

monsoon seasons and it was observed in the southern region during

pre-monsoon. The connection between Ni and the nutrient cycle is

also reflected by high Ni contents found in marine organic matter

(Collier and Edmond, 1984). A third factor affecting Ni concentrations

in sediments is its tendency to bind to metals, especially sulfides to Fe

(pyrite). The anthropogenic sources of Nickel in the study area are the

use of Ni in steel and other alloys, electroplating, and batteries.

Lead (Pb)

Lead is ubiquitous in the environment, present usually in

small amounts from natural geological sources in all rock, soil, dust,

water and air. Lead is a non-essential metal and it is a highly toxic

metal. The spatial distribution maps of lead in post-monsoon,

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pre-monsoon and monsoon seasons are shown in Fig. 5.6a-c. The

concentrations of lead in the shelf sediments of Visakhapatnam

during post-monsoon varied between 16.20 and 36.08 µg/g, while it

varies in the range of 4.98 to 20.15 µg/g during Pre-monsoon and it

varies in the range 8.38 to 32.45 µg/g monsoon. The maximum

concentration was observed at V1, near Lawson’s bay during post-

monsoon and minimum concentration was observed at V22, near

Gangavaram port during pre-monsoon. The average concentration of

Pb was higher during post-monsoon compared to other two seasons.

Concentrations of Pb decreased seaward during post and pre-

monsoon seasons and it increased seaward during monsoon season.

High concentrations of lead were observed in the northern region during

post and pre-monsoon seasons and it was observed in the southern

region during monsoon. The relatively high acid-leachable Pb in the

surface sediments is mainly due to lead-based paint industries and

input of effluents from the thermal power plant very close to the coast

add additional stress to the high concentration of Pb (Jonathan and

Ram-Mohan, 2003; Velde et al., 2003). Increase in Pb concentrations

may be due to the direct input of nitrate compounds from external

sources, mainly from the aquaculture effluents, agricultural runoff

and domestic sewage (Purvaja and Ramesh, 2000; Subramanian, 2004).

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Zinc (Zn)

Zinc is one of the most essential trace elements in the

human body. It is a constituent of all cells, and several enzymes

depend upon it as a co-factor. Concern has arisen because of the

intimate connection of zinc with cadmium in the geosphere and

biosphere. The spatial distribution maps of zinc in post-monsoon,

pre-monsoon and monsoon seasons are shown in Fig. 5.7a-c. The

concentrations of zinc in the shelf sediments of Visakhapatnam

during post-monsoon varied between 31.00 and 154.00 µg/g, while it

varies in the range of 8.56 to 49.94 µg/g during Pre-monsoon and it

varies in the range 9.40 to 77.60 µg/g monsoon. The maximum

concentration was observed at V5, near Lawson’s bay during post-

monsoon and minimum concentration was observed at V22, near

Gangavaram port during pre-monsoon. The average concentration of

Zn was higher during post-monsoon compared to other two seasons.

Concentrations of Zn decreased seaward during post and pre-

monsoon seasons and it increased seaward during monsoon season.

In all the three seasons, high concentrations observed in the northern

region of the study area. The anthropogenic sources of zinc in

Visakhapatnam coastal sediments are the input of organic wastes into

the sea, which comes from municipal sewage, contributes to the Zn

increase in sediments (Alagarsamy, 2006).

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Fig. 5.1. Spatial distribution of Fe in Visakhapatnam coast, Bay of Bengal, India

during (a) post-monsoon, (b) pre-monsoon and (c) monsoon seasons

respectively

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Fig. 5.2. Spatial distribution of Cd in Visakhapatnam coast, Bay of Bengal, India

during (a) post-monsoon, (b) pre-monsoon and (c) monsoon seasons

respectively

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Fig. 5.3. Spatial distribution of Cr in Visakhapatnam coast, Bay of Bengal, India

during (a) post-monsoon, (b) pre-monsoon and (c) monsoon seasons

respectively

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Fig. 5.4. Spatial distribution of Cu in Visakhapatnam coast, Bay of Bengal, India

during (a) post-monsoon, (b) pre-monsoon and (c) monsoon seasons

respectively

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Fig. 5.5. Spatial distribution of Ni in Visakhapatnam coast, Bay of Bengal, India

during (a) post-monsoon, (b) pre-monsoon and (c) monsoon seasons

respectively

135

Fig. 5.6. Spatial distribution of Pb in Visakhapatnam coast, Bay of Bengal, India

during (a) post-monsoon, (b) pre-monsoon and (c) monsoon seasons

respectively

136

Fig. 5.7. Spatial distribution of Zn in Visakhapatnam coast, Bay of Bengal, India

during (a) post-monsoon, (b) pre-monsoon and (c) monsoon seasons

respectively

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5.5.2. Seasonal variations

The concentrations of trace metals indicate enrichment in

the samples which are very close to the shoreline and they vary in the

following order Fe > Zn > Cu > Cr > Pb > Ni > Cd (Pitchaimani et al., 2008).

Similar distribution patterns of Cd, Cr, Cu, Fe, Pb and Zn (except Ni)

indicate that the area is affected by coal fueled iron and steel

industries (Muthuraj and Jayaprakash, 2008). An important observation

is that, in general, lowest metal concentrations were found during the

pre-monsoon and monsoon seasons, compared to the post-monsoon

season.

Generally, post-monsoon is associated with increase of

metals, which become enriched in the accumulative phases of the

sedimentary material. Terrestrial transport appears to occur mostly

during monsoon, which is associated with higher river discharge and

bed-load movements. The concentrations of trace metals were decreased

seaward during post-monsoon, while it increased seaward during pre-

monsoon and post-monsoon seasons. Fe had high concentration

during pre-monsoon due to the spillage and transportation of iron

ores (Alagarsamy, 2006) in the harbour to the ships and also the low

flow conditions of the coastal waters in the study area which is

attributed to the change in current direction. Based on their average

concentration of trace metals, Cd and Cr were had high concentrations

during monsoon due to heavy rainfall, leading to high fluvial inputs

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which are carrying metals from industrial and agricultural wastes

might have been responsible for the increased concentration of Cd and

Cr in monsoon period (Padma and Periakali, 1998; Periakali and

Padma, 1998; Kamala-kannan et al., 2008). Cu, Ni, Pb and Zn had

high concentrations during post-monsoon due to the deposition of

these metals into the sediments from untreated effluents being

discharged into the coast via monsoonal runoff from Meghadrigedda

(Sarma et al., 1996) could be higher as the increased monsoonal water

flow. The point sources of metal pollution were mainly from thermal

power plant, Visakhapatnam steel plant, petrochemical industries,

fertilizer industries, paper mills, tanneries, polymers, lead and zinc

mining, zinc smelter, fertilizers, shipyard, metal alloy, shipping

industries, and oil refineries. Transportation to and from the

Visakhapatnam port and industrial activities also play a major role in

increasing the metal level in this region (Alagarsamy and Zhang, 2010).

In general, Cd, Cr and Ni levels were high in pre-monsoon, while Pb

and Cu were high in post-monsoon (Satyanarayana et al., 1995).

5.6. ENRICHMENT FACTOR

In order to determine, whether the trace metals were

originated from natural weathering processes or from anthropogenic

activities, enrichment factors were calculated for trace metals

concentrations in Visakhapatnam marine sediments measured for

three different seasons (post-monsoon, pre-monsoon and monsoon)

and were shown in Fig. 5.8a-c.

139

Fig. 5.8. Spatial distribution of enrichment factors in three different seasons

(a) post-monsoon, (b) pre-monsoon and (c) monsoon seasons respectively

140

The normalization technique enabled to assess the magnitude

of enrichment relative to naturally occurring concentrations rather

than relying on a limited number of measurements from the selected

areas (Alagarsamy et al., 2010). EF values less than 1.5 suggest that

the heavy metals may be entirely from natural weathering processes

and greater than 1.5 suggest an anthropogenic source. The EF values are

interpreted as the levels of metal pollution suggested by Chen et al. (2007).

Chen et al. (2007), suggested that EF < 1 indicates no

enrichment, EF = 1-3 indicates minor enrichment, EF = 3-5 indicates

moderate enrichment, EF = 5-10 indicates moderately severe enrichment,

EF = 10-25 indicates severe enrichment, EF = 25-50 indicates very

severe enrichment, and EF > 50 indicates extremely severe enrichment.

As indicated by their respective enrichment factor (EF)

values, the enrichment of heavy metals in surface sediments from the

Visakhapatnam shelf were decreased during post-monsoon in the

order of Cd > Pb > Ni > Cu > Zn > Cr, while it decreased during pre-

monsoon in the order of Cd > Cu > Pb > Ni > Cr > Zn and it decreased

during monsoon in the order of Cd > Pb > Ni > Cr > Cu > Zn.

Enrichment of cadmium, chromium, nickel, lead in surface sediments

from Visakhapatnam was higher during monsoon than pre-monsoon

and post-monsoon seasons, while Enrichment of copper and zinc was

higher during post-monsoon than pre-monsoon and monsoon seasons.

141

The high proportions of Pb, Cd and Zn imply that the

sediments are contaminated by the offshore drilling activities,

atmospheric deposition of finer particles, domestic effluent discharges

and the extensive use of paints (Yasar et al., 2001; Lin et al., 2002).

Enrichment of Cd, Pb and Ni could be due to the operation of

numerous oil refineries in the study area and also the shallow nature

of the offshore region facilitating the deposition of trace metals and

also due to the north-south long shore currents which are obstructed

and terminated in this region. The wave action process might help in

transportation, deposition and enrichment of trace metals from the

heavily industrialized region in the northern part of southeast coast of

India. Moreover, the higher values are also due to the dynamic

movement of finer sediments, local industrial activities and movement

of fishing/commercial vessels in this region.

5.7. INDEX OF GEO-ACCUMULATION (Igeo)

To find out the contamination level of heavy metals in

marine sediments, Index of geo-accumulation was calculated and is

shown in Fig. 5.9a-c.

On the basis of average Igeo values, the contamination by

heavy metals in surface sediments from Visakhapatnam shelf was in

the order of Cd > Pb > Ni > Zn > Cu > Cr during post-monsoon, while

it was in the order of Cd > Pb > Cu > Cr > Ni > Zn during pre-monsoon

and it was in the order of Cd > Pb > Ni > Cr > Cu > Zn during monsoon.

142

Muller scale (Muller, 1981) of sediment quality description is shown in

Table 5.1, the calculated results of Igeo values (Fig. 5.9a-c) indicate

that Cd can be considered as a strong pollutant in this study area in

all the three seasons. Cd showed unpolluted to strongly polluted and

other metals showed unpolluted to moderately polluted situation in

this region. The high Igeo values identified for cadmium in the study

area indicate that the surface sediments are extremely contaminated,

probably as a result of anthropogenic activities and provide a useful

means of distinguishing between the natural and anthropogenic

sources of metal entering in to the coastal zone.

Table 5.1. Description of the sediment quality (Muller, 1981)

Igeo value Class Quality of sediment

< 0 0 Unpolluted

0-1 1 From unpolluted to moderately polluted

1-2 2 Moderately polluted

2-3 3 From moderately polluted to strongly polluted

3-4 4 Strongly polluted

4-5 5 From strongly to extremely polluted

> 5 6 Extremely polluted

143

Fig. 5.9. Spatial distribution of geo-accumulation index in three different seasons

(a) post-monsoon, (b) pre-monsoon and (c) monsoon seasons respectively

144

5.8. CONCLUSION

An important observation is that, in general, lowest metal

concentrations were found during the pre-monsoon and monsoon

seasons, compared to the post-monsoon season. The concentrations

of trace metals were decreased seaward during post-monsoon, while it

increased seaward during pre-monsoon and post-monsoon seasons.

Cu, Ni, Pb and Zn had high concentrations during post-monsoon due

to the deposition of these metals into the sediments from untreated

effluents being discharged into the coast via monsoonal runoff from

Meghadrigedda could be higher as the increased monsoonal water

flow. The high EF and Igeo values identified for cadmium in the study

area indicate that the surface sediments are extremely contaminated,

probably as a result of anthropogenic activities and provide a useful

means of distinguishing between the natural and anthropogenic

sources of metal entering in to the coastal zone.