Soil Bioavailability of Cadmium, Lead, and Zinc in Areas of Zn-Pb Ore Mining and Processing (Bukowno, Olkusz)

The study was performed to determine bioavailable amounts of cadmium, lead, and zinc in soils contaminated through the years of Zn-Pb ore mining and processing near Olkusz, Poland, and to identify the environmental risk (RAC) associated with the occurrence of the most mobile forms of these metals in the soil. The authors analyzed topsoil samples for the basic physical and chemical parameters, as well as for total metal content (by aqua regia extraction), and for percentage of 1 M HCl- and 1 M NH4NO3-extractable fractions. Results were compared with the content of these metals in a common grass species, Agrostis capillaris. In the study region, Cd, Pb, and Zn content was (respectively, in mg∙kg-1): 0.5–33.5, 2–529, and 4–7877. This means that in more than 24%, 30%, and 38% of samples, respectively, metal content exceeded the limits defined by the Polish Environment Minister’s Regulation of September 9, 2002, with nearly 24% of soil samples contaminated by all three metals. Based on the Environment Minister’s Regulation of September 1, 2016, which is currently in force, and using the allowed limits for subgroup IV (industrial land), set at 15 mg∙kg-1 for Cd, 600 mg∙kg-1 for Pb, and 2000 mg∙kg-1 for Zn, the analysis also found excessive metal content in a considerable percentage of topsoil samples (33%, 13%, and 38%, respectively). The content of the studied elements in a common grass species, Agrostis capillaris, was significantly higher than the so-called natural content. A strict association was found between total Cd, Pb, and Zn content, and the potentially available 1 M HCl-extractable fraction. The environmental risk presented by the content of mobile Cd, Pb, and Zn forms, assessed in all the studied soil samples using Risk Assessment Codes (RAC), demonstrates very high environmental risk associated with Cd, high environmental risk associated with Zn, and moderate environmental risk associated with Pb