Spatial distribution of metal contamination before and after remediation in the Meza Valley, Slovenia

Abstract

Geostatistical technique was used to predicted spatial reduction of metal contamination after applying EDTA-based soil remediation. Soil samples from 268 locations in the Meza Valley, Slovenia with Pb and Zn concentrations up to 8955 and 15518mgkg−1 were extracted with the chelating agent ethylenediamine tetraacetate (EDTA). On average, 63 and 22% of Pb and Zn, respectively, were removed with washing solution containing 60mmol EDTA per kg of soil and 75 and 34% of Pb and Zn with 120mmol EDTA kg−1 soil. Spatial structure analysis revealed a good spatial structure and little spatial variation of data, which were further interpolated using Empirical Bayesian kriging to produce a continuous surface of Pb and Zn concentrations before and after remediation. Geostatistical simulations showed that the contaminated area covers 19.4km2 and that soil remediation (60mmol EDTA kg−1) has the potential to reduce the area with Pb and Zn above the critical regulatory threshold limit by 91 and 42%, respectively. Validated by pilot-scale remediation trials, soil extractions exhibit little scale-dependency of extraction efficiency. EDTA extraction also significantly reduced the bio-accessibility of toxic metals that remained in the soil after remediation using the unified bio-accessibility method. Pb and Zn concentrations accessible from the simulated intestinal phase were reduced by up to 99 and 96%, respectively.