Predicting Metal(loid) Phytoaccumulation/Phytoavailability from Soil Property and Chemical Extraction Method
A Graduate Defense Seminar will be presented by Zhenfei Liang, MS Candidate in ESGP, on Thursday (7/16) at 1:00 p.m. in 333 Kottman Hall. Zhenfei will present Predicting Metal(loid) Phytoaccumulation/Phytoavailability from Soil Property and Chemical Extraction Method.
Total content of metal(loid) is a poor indicator of phytoaccumulation/phytoavailability. Bioavailability processes are embedded within existing ecological risk frameworks to reduce uncertainty in exposure estimates and improve risk assessment. Using either dominant soil chemical/physical property method or surrogate soil chemical extraction method to predict phytoaccumulation/phytoavailability of contaminants has been widely accepted. Generally, the soil property method is empirically based, while the chemical extraction is mechanistically based. Soil pH, OM and total metal(loid) content are the most significant factors for prediction of phytoaccumulation/phytoavailability, with soil pH and OM being negatively correlated with plant uptake and total content positively correlated. While there is no consensus, neutral salt extractants (such as 0.01 M CaCl2, 1 M NH4Ac) appear to provide the most useful indication of metal(loid) phytoavailability across a range of metals of interest, although further research is required to guarantee the sufficiency of data. No single one prediction method is recognized universally. The distinction in literature resulting from contamination type, contamination source, sampling procedure, selection of test species, ecological endpoint, analysis technique, standardization, etc. further complicate the problem and render it sticky to reach unified standardization. Attention must be paid that some of the prediction relationships applied with the soil property method are based on spiked soils, while most of the regression equations established through the chemical extraction method are based on either naturally contaminated or uncontaminated soils. Very little information, of the ability of regression equations generated from spiked soils, exists to predict phytoaccumulation/phytoavailability from naturally contaminated soils, or vice versa. There are also research needs of using other ecological receptors (like animals and microorganisms) to assess metal(loid) bioavailability and establish correlation relationship.