engleski

Response of soil dehydrogenase activity to salinity and cadmium species

Greater understanding of the microbial activity role in metal mobilization processes in soil is of major importance. The objective was to study the effect of major Cd species in solution of a saline soil on dehydrogenase activity (DHA). Hypothesis is that (i) under increased soil salinity, more mobile Cd species with diverse effect on DHA may be generated (i.e., CdCln 2-n) ; and that (ii) DHA may correlate to organically complexed Cd species. In a greenhouse pot experiment, NaCl salinity (50 and 100 mM) was applied to control soil and soil spiked with Cd (5 and 10 mg kg-1). Soil total and available (CaCl2 extractable) Cd concentrations were measured, and DHA determined using 2, 3, 5- triphenyltetrazolium chloride (TTC) method. Speciation was calculated from results of soil solution ion analysis using geochemical equilibriummodel Visual MINTEQ. DHAwas reduced with increased soil salinity and Cd contamination, but only compared with control soil. Although weak, negative correlation between DHA and CdCln 2-n complexes in soil solution suggested their higher inhibitory effect on DHA than other Cd species. Positive correlation between DHA and organically complexed Cd indicated that raised microbial activity may increase the proportion of organically complexed Cd in the soil solution. Cd toxicity to soil microorganisms can be accentuated in a saline environment, which may be an issue of great importance for agricultural production in coastal areas. Microbial activity may via releasing organic substances in soil solution significantly change cadmium complexation and mobility in soil, an aspect which has often been overlooked.

Soil microbial activity ; Contamination ; Cd complexation ; Cd bioavailability

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