Zhenfei Liang, M.S.Advisor: Nick Basta

Environmental Science Graduate Program

Predicting Metal(loid) Phytoaccumulation from Soil Property and Chemical Extraction

CONTENTSINTRODUCTION

TRANSFER FROM SOIL TO PLANT

METAL(LOID) BIOAVAILABILITY

METHODS FOR PREDICTING PHYTOACCUMULATION

SOIL PROPERTY METHOD

CHEMICAL EXTRACTION METHOD

CONCLUSION

PERSPECTIVES

INTRODUCTION

Concern over metal contaminated soil

Introduction of metals into the food chain

Loss of vegetation cover induces through phytotoxicity

Cycling of metals to surface soil horizons by tolerant

plants to induce toxic effects on plants

(McLaughlin, 2001)

WHY BOTHER?

INTRODUCTION

Predicting plant uptake in contaminated soil

important, with regard to plant nutrition, crop

contamination, environmental quality

Measuring total metal content in soil may not

predict phytoaccumulation

TRANSFER FROM SOIL TO PLANT Controlling factors: geochemical,

climatic, biological, anthropogenic

Phytoaccumulation depends upon

abundance, speciation and binding

characteristics on soil surfaces,

governed by sorption,

complexation and redox processes

(Marschner, 1995; McBride, 1995; Sauvé et al., 2000; Kabata-Pendias, 2004; Patra et al., 2004; Moreno et al., 2005; Sterckeman et al., 2005; Rieuwerts et al., 2006; Kalis et al., 2007; Anawar et al., 2008; Römkens et al., 2009a; Rodrigues et al., 2010)

METAL(LOID) BIOAVAILABILITY Available fraction ≡ fraction of total amount of contaminant

present in a specific environmental compartment, within a

given time span, either available or can be made available for

uptake by organisms from either direct surrounding of the

organism or by ingestion of food

Bioavailability ≡ contaminant absorbed into the organism

and may cause an adverse or beneficial effect in the exposed

organism

METAL(LOID) BIOAVAILABILITY

METAL(LOID) BIOAVAILABILITY

Bioavailability reduces uncertainty in exposure

estimates and improves risk assessment from

contaminated plants

Accurate prediction of bioavailability improve

risk assessment in terrestrial ecosystems

(Peijnenburg et al., 1997; Sauvé et al., 1998; McLaughlin et al., 2000a; McLaughlin et al., 2000b; Peijnenburg et al., 2000; Weng et al., 2004; Dayton et al., 2006; Menzies et al., 2007; USEPA, 2007; Zhang et al., 2010)

METHODS FOR PREDICTING PHYTOACCUMULATION Plant bioassay takes a long time Prediction is hot topic, great progress, but still difficult, no

single one reliable method exists Mechanistic models & empirical models Soil contaminant measurement methods: Single Chemical Extraction

Chemical Speciation (sequential extraction or spectroscopy)

Diffusive Gradients in Thin Films (DGT) (Zhang and Davison, 1995)

Pore Water (PW) (McBride et al., 1997)

Windermere Humic Aqueous Model (WHAM) (Tipping, 1998)

Free Ion Activity Model (FIAM) (Sauvé et al., 1998)

Donnan Membrane Technique (DMT) (Temminghoff et al., 2000)

terrestrial Biotic Ligand Model (tBLM) (Di Toro et al., 2001)

HOW TO MEASURE?

SOIL PROPERTY METHOD

Modifying effect of soil property on correlation and

multiple-regression techniques routinely used to

examine the relationship between and among soil

properties and biological endpoints

Dominant soil properties to affect

phytoaccumulation: pH, OC, CEC, clay content, and

reactive Fe, Al, Mn oxides

(Basta et al., 2005; Fairbrother et al., 2007)

SOIL PROPERTY METHOD Soil samples: natural source (naturally uncontaminated or

contaminated), anthropogenic source (artificially spiked)

Studied metal(loid)s: As, Cd, Ce, Cr, Cu, La, Nd, Ni, Pb, Pr, Zn

Number of soils or study sites: 3 to 215

pH, OC, total content the most significant factors for prediction, pH

and OC negatively correlated with plant uptake, total content

positively correlated Empirical methodology, overlooking other abiotic or biotic factors

besides soil property

Soil properties inherently intercorrelated, necessitating techniques

to quantify the marginal contribution of each mitigating property

CHEMICAL EXTRACTION METHOD Mechanistically based, only extract very small proportion

of potential available (bioaccessible) pool

Extraction methods:

Single extraction procedure

Sequential extraction procedures

Enhancement with microscopic and spectroscopic techniques

(Peijnenburg et al., 1999; Basta and Gradwohl 2000; Peijnenburg et al., 2007)

† * p < 0.05, ** p < 0.01, *** p < 0.001.‡ Aboveground Leersia hexandra 0.688*, underground Juncus effuses 0.512*.

Soil samples: 2 naturally uncontaminated, 7 naturally contaminated, 3 natural soils

(plus naturally uncontaminated or contaminated), 1 combination of naturally

contaminated and artificially spiked

Studied metal(loid)s: As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, Zn

Number of soils or study sites: 1 to 53

Extraction tests:

H2O;

Neutral salt solutions: 0.01 M CaCl2, 0.05 M CaCl2, 0.01 M Ca(NO3)2, 0.05 M Ca(NO3)2, 0.1 M LiNO3, 0.1 M

NaNO3, 0.01 M Sr(NO3)2, 1 M NH4NO3, 1 M NH4Ac, 0.1 M (NH4)2SO4, 1 M NH4Cl, 1 M

MgCl2, 0.5 M NaHCO3, 1.0 M NaAc, 0.5 M KH2PO4;

Chelating agents: 0.01 M EDTA, 0.04 M EDTA, 0.05 M EDTA, 0.02 M AAAC-EDTA, 0.05 M AAAc-EDTA, 0.1 M

Na2EDTA, 0.05 M NH4-EDTA, Mehlich 3, AEM-EDTA, EDTA-NH4Ac, 0.005 M DTPA, AEM-

DTPA, 0.005 M DTPA-TEA, AB-DTPA, CaCl2-TEA-DTPA, DTPA-TEA-CaCl2;

Weak acids: 0.11 M HAc, 0.43 M HAc, 0.2 M C6H8O7;

Strong acids: HClc, 0.1 M HCl, 1 M HCl, 0.43 M HNO3, 0.5 M HNO3, HNO3/HClO4, HCl/HClO4, HCl/HNO3,

Mehlich 1;

Others: EPA 3050, TCLP, BCR, and rhizo

CHEMICAL EXTRACTION METHOD

CaCl2 significantly correlated in 6 studies

NH4OAc suitable in 3 studies

NH4Cl effective in 2 studies

Cd: 0.01 M CaCl2, 1 M NH4OAc, 1 M NH4NO3, 0.005 M DTPA-TEA

Zn: 0.01 M CaCl2, 1 M NH4OAc, 0.005 M DTPA-TEA, 1 M NaNO3

Pb: 0.01 M CaCl2, 1 M NH4OAc, 0.005 M DTPA-TEA, Mehlich 3

As: 0.01 M CaCl2, 1 M NaNO3, 0.1 M (NH4)2SO4, H2O

CHEMICAL EXTRACTION METHOD

(Gray et al., 1999; Krishnamurti et al., 2000; Song et al, 2004; Meers et al, 2005; Zhang et al, 2006; Meers et al.,2007; Vázquz et al., 2008; Zhang et al., 2010)

CONCLUSION

pH, OC, total content are the most

significant factors for predictionNeutral salt extractants provide the

most useful indicationNo single one prediction method is

recognized universally

PERSPECTIVES Soil property method based on spiked soils, most chemical

extraction method based on natural soils, metal(loid)

availability greater in spiked soils than naturally contaminated

The ability of regression equations from spiked soils, to predict

phytoaccumulation from naturally contaminated soils, or vice

versa

Prediction ability for other sources, such as inorganic fertilizer,

organic sewage sludge, manure byproducts

(Bolan et al., 2003; Bolan et al., 2004; Basta et al., 2005)

ACKNOWLEDGEMENTS• M.S. Committee Dr. Nick Basta Dr. Roman Lanno Dr. Jiyoung Lee

• Colleagues Shane Whitacre John Obrycki Brooke Stevens

OSU ESGP

ESGP

Thank you for your attentionQuestions and Comments?