EFFECTS OF COPPER AND ZINC ON SOIL MICROBIAL ENZYMES

The adverse effect of Cu and Zn (300, 600 and 900 mg kg(-1) soil) soil contamination on four enzymes (phosphatase, invertase, amylase and dehydrogenase) was studied for short-term (7 days) and long-term (30 days) exposure in microcosms' experiments. Evaluating the rate of inhibition on enzymes activities, Cu proved to be more toxic than Zn. The enzymes studied can be arranged in terms of their sensitivity to Cu and Zn as follows: dehydrogenase > phosphatase > amylase > invertase. Most of the adverse effects on enzymes activities were recorded in the first week after heavy metal amendments following by slow recovery, except in the samples of the highest level of contamination. Stimulation effects were noticed on amylase and invertase activities. It was not found any significant correlation between metal concentrations (total and water soluble) and the rate of enzymes' inhibition.