COPPER IN SELECTED SOILS AND THEIR CAPACITY FOR REGULATING ITS SOLUTION CONCENTRATIONS

摘要

Investigations were carried out on seven soil samples collected in the vicinity of the Glogow Copper Smelter (Poland). The sampled areas have been formerly used for agricultural purposes, but with the increase in metals contamination they were afforested by poplars. Chemical tests were made in order to assess the potential capacity of soils for regulating the transfer of Cu ions from the solid phase to the solution and vice-versa. For this purpose, alkali and acid buffering curves were elaborated, and batch studies were additionally run in order to evaluate the maximal buffering capacity (MBC) developed by soils towards Cu ions. The results revealed that the potentially available Cu fraction, (DTPA_(Cu)) represented from 23 to 40% of the total Cu content. These relatively high levels may be attributed to the anthropogenic origin of this metal, hence the high lability enhancing its bioavailability. Alkali and acid buffer characteristics revealed that soils exhibited relatively less resistance to alkalization since pH changes varied between 5.1 and 12.9. On the other hand notable resistance to acid impact was observed, particularly for soils containing carbonates, and both high level of organic carbon (C_(org)) and silt + clay, respectively. The MBC values followed a sequence, which was not consistent with buffer curve shapes in the acid zone. On the basis of soil capacities for regulating copper equilibrium concentrations (C_e-Cu), two groups may be set: group I - with the range 0.002 - 0.38 mmol_cdm~(-3) and group II: 0.003 - 2.78 mmol_cdm~(-3). In the case of soils of the group I, no threats could be evocated, since Cu potential uptake and its transfer to the food chain should be markedly limited, reversely to soils of the group II, where Cu toxicity is unavoidable. Mechanisms involved in copper geochemical dynamics as well as the resulting consequences for agricultural and environmental media are strictly regulated by the buffer properties of soils.