Evaluation of heavy metals accessibility in poluted soils from Mežica valley

Abstract

The bioaccessibility and mobility of Pb and Zn were determined in twelve soil samples taken around nursery schools and schools and from vegetable gardens and backyards in Mežiška Valley, Slovenia. The concentrations of Pb ranged from 469 to 4333 mg kg-1 and of Zn from 313 to 8670 mg kg-1. In eleven (Pb) and nine (Zn) samples they were higher than the critical values set by the Slovenian legislature (Ur.l.RS No. 68, 1996). The Pb and Zn mobility was determined using the Toxicity Characteristic Leaching Procedure (TCLP) and was in every sample lower than the values set by US EPA for hazardous waste. The concentrations of Pb and Zn in the test plant lattuce (Lactuca sativa L.) were bellow the detection limit of the analytical instrument (Atomic Absorption Spectrophotometer). The bioacessibility of Pb in soil samples and soil dust in the human gastro-intestinal tract was determined in vitro using PBET (Physiologically Based Extraction Test). 2.8 - 22.8 % of the total soil Pb content was available from the simulated stomach and 1.2 - 9.0 % from the intestinal phase. The concentrations of bioaccessible Pb were higher in the soil than in the soil dust.