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Abstract
There is a growing concern on the potential application of a direct current (DC) electric
field to soil for removing contaminants, but little is known about its impact on soil
enzyme activities. This study investigated the change of enzyme activities of a heavy
metal contaminated soil before and after electrokinetic (EK) treatments at lab-scale
and the mechanisms of EK treatment to affect soil enzyme activities were explored.
After treatments with 1-3 V cm(-1) of voltage gradient for 420 h, soil pH, electrical
conductivity (EC), soil organic carbon, dissolved organic carbon (DOC), soil heavy
metal concentration and enzyme activities were analyzed. The results showed that the
average removal efficiencies of soil copper were about 65% and 83% without and with
pH control of catholyte, respectively, and all the removal efficiencies of cadmium
were above 90%. The soil invertase and catalase activities increased and the highest
invertase activity was as 170 times as the initial one. The activities of soil urease
and acidic phosphatase were lower than the initial ones. Bivariate correlation analyses
indicated that the soil invertase and acidic phosphatase activities were significantly
correlated with soil pH, EC, and DOC at P<0.05, but the soil urease activities had
no correlation with the soil properties. On the other hand, the effects of DC electric
current on solution invertase and catalase enzyme protein activities indicated that
it had negative effect on solution catalase activity and little effect on solution
invertase activity. From the change of invertase and catalase activities in soil and
solution, the conclusion can be drawn that the dominant effect mechanism is the change
of soil properties by EK treatments.