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

• Metal concentration data has a good spatial structure and little variation.
• Remediation has potential to reduce Pb and Zn contaminated area.
• EDTA soil washing exhibits little scale-dependency of extraction efficiency.
• Remediation reduced the bio-accessibility of residual Pb and Zn.
• Geostatistics allows targeting of remediation actions.

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 15518 mg kg− 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 60 mmol EDTA per kg of soil and 75 and 34% of Pb and Zn with 120 mmol 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 19.4 km2 and that soil remediation (60 mmol 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.