title: Pb, Zn and Cd mobility, availability and fractionation in aged soil remediated by EDTA leaching.
abstract: Soil washing remediation techniques usually remove only the labile heavy metal (HM) species from the soil, leaving the residual ones in less available/mobile forms, thus disturbing the chemical equilibrium among different species of HM in the soil. Re-establishing such equilibrium and shifting HM back to more available/mobile chemical forms could occur after exposing the remediated soil to environmental abiotic (ageing) factors. Contaminated soil from a smelter site (Pb 4600 mg kg(-1), Zn 1800 mg kg(-1), Cd 30 mg kg(-1)) was leached with increasing EDTA concentrations (2.5, 5.0, 10.0, 20.0, 40.0 and 4-consecutive steps of 40.0 mmol EDTA kg(-1) of soil). A gradient of removed HM was reached: from 6% to 73% of initial Pb, from 3% to 23% of initial Zn and from 17% to 74% of initial Cd were removed. Repetitive temperature changes (105 degrees C and -20 degrees C) were used to mimic abiotic factors acting on residual HM after EDTA soil leaching in saturated soil at 10% and 90% of soil water holding capacity. Fractionation using sequential extractions, mobility, and phytoavailability of Pb, Zn and Cd and Pb oral bioavailability were determined for aged and non-aged soil. The ageing treatment consistently lowered HM phytoavailability in the original (non-leached) and all treated (chelant-leached) soils. However, Pb, Zn and Cd behaved differently from each other; Pb mobility increased, Cd mobility decreased, while Zn mobility did not change. The results indicate that abiotic (ageing) processes change the availability/mobility of residual HM in all leaching treatments and should thus be considered in final remediation effectivity evaluation.
authors.affiliation: Agronomy Department, Biotechnical Faculty, University of Ljubljana, Center for Soil and Environmental Science, Ljubljana, Slovenia.
authors.forename: Metka
authors.initials: M
authors.lastname: Udovic
authors.forename: Domen
authors.initials: D
authors.lastname: Lestan
mesh_terms: D002104:Cadmium / Q000032:analysis* / Q000737:chemistry; D005591:Chemical Fractionation; D004492:Edetic Acid / Q000737:chemistry*; D004787:Environmental Pollution / Q000517:prevention & control*; D006863:Hydrogen-Ion Concentration; D007854:Lead / Q000032:analysis* / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis*; D013696:Temperature; D015032:Zinc / Q000032:analysis* / Q000737:chemistry
chemical_list: D012989:Soil Pollutants; D002104:Cadmium; D007854:Lead; D004492:Edetic Acid; D015032:Zinc