Bioavailability of Pb before and after remediation of contaminated soil


Domen Lestan, Neza Finzgar, and Boštjan Kos. Agronomy Department, University of Ljubljana, Biotechnical Faculty, Jamnikarjeva 101, Ljubljana, 1000, Slovenia
Our report compares the efficiency of Pb bioavailability reduction of different remediation (Pb bioavailability stripping and Pb immobilization) techniques, which were used to treat Pb contaminated soils. In the soil-plant environment, heavy metal bioavailability is generally interpreted as the fraction of the total metal that interacts with the plant roots, while in humans it refers to metal solubility in the stomach and subsequent transmission across the gastro-intestinal tract. Soil metal bioavailability depends on physical, biological and chemical characteristics of the medium and is reflected in the metal soil fractionation. In the simulated heap leaching with 10, 20, 30 and 40 mmmol/kg of biodegradble chelate [S,S]ethylenediamine disuccinate (EDDS) 4.35, 17.51, 24.96 and 31.35 % of the total initial Pb was removed from the soil, respectively. In the bench-scale soil washing tests with EDDS and ethylenediamine tetraacetate (EDTA), imitating the technique of ex situ soil washing in a reactor, up to 49.0 and 74.5 % of the total initial Pb was removed, respectively. Pb in soil was immobilized by apatite and Slovacite amendment, any by vitrification using microwaves. Before and after remediation the Pb soil fractionation was assessed by sequential extractions. Oral bioavailability of Pb was determined in vitro using Ruby's physiologically based extraction test. Pb soil phytoavailability was determined by measuring Pb in roots and aboveground biomass of the reported Pb hyperaccumulator Thlaspi goesingense.