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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?
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