engleski

Remobilization of trace metals from soils from areas impacted by war activities in Croatia

Metals in soils can be bound in different forms which can be less or more mobile and thus available for plant uptake, transport by soil solutions and possible contamination of adjacent water bodies. Extraction with various extractants can be applied to soils in order to assess the mobility of metals in these soils. Water extraction of soils at natural pH estimates the most labile fraction of the bound metals which can be leached from the solid phase by the soil solution. This extraction was applied to a number of soil samples collected in the frame of the project. Extraction was made on 1 g of dry soil (fraction < 2mm) which was extracted for 24 h on a mechanical shaker with 10 ml of Milli-Q water. The extract was centrifuged, filtered (<0.45 um) and metals were measured in appropriately diluted extracts by HR ICPMS. Results showed that the percentage of extracted metals was generally low and for most of the metals was lower than 1% of the total metal content in the solid phase. Higher percentages were obtained for very mobile macroelements such as K and Na (in average 6 and 15 %, respectively) and for some minor elements - As (in average 1.6 %) and Mo (8 %). However, in spite of the low percentage extracted from soil, the concentration of some metals in the extract was actually very high compared to the concentration of these metals in surface waters. In very contaminated soil samples concentrations up to several mg/l of Pb, Zn and Sb were obtained, suggesting high mobility of these metals in contaminated soils. In general, for anthropogenic metals as are Cd, Pb, Cu, Zn and Sb good correlation between concentration in the water extract and in the soil has been obtained indicating labile binding of these metals. In the case of antimony extraction with water proved to be a better indicator of soil contamination by Sb than extraction with nitric acid (the extraction method used for the determination of metals in the solid phase), indicating that some other digestion method should be used for Sb determination in the solid phase. The obtained results indicate that extraction with water can be a useful tool for estimating the weakly bound metal fraction in soils and for assessment of potential risk of metal contamination from soils highly polluted by toxic metals.

metals; remobilization; soil; war-related contamination; Croatia

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