Dehydrogenase, urease and phosphatase activities as affected by Pb contamination in the Soil

Heavy metals contamination in soil has taken great attention in recent years mainly because of the public awareness as environmental issue. This may adversely affect the soil ecology by microbial loss and changes in enzymatic activities. Soil enzymes are important indicators of soil environmental quality and have been used in the national and international monitoring programs. The present study was conducted to investigate the impact of lead (Pb) on activities of three soil enzymes (dehydrogenase, urease and phosphatase). The soil was spiked with 0, 200, 400, 600, 800 and 1000 mg kg(-1) Pb and the activities of enzymes were determined at 0, 15, 30, 45 and 60 days after Pb contamination (DAC) in the soil. Results indicated that the declining rate of enzymes activity was comparatively higher from start to 30 DAC, than from 30 to 60 DAC. The significant inhibition (P<0.05) of dehydrogenase activity in Pb contaminated soil started from 15 DAC, while urease and phosphatase declined significantly from start to the end for all Pb treatments except for 200 mg kg(-1) Pb. Up to 60 DAC, more than 50% decrease in all the three enzymes activity compared to their initial value was observed under 1000 mg kg(-1) Pb treatment. This study concludes that Pb contamination in soil has adverse effects on the activities of dehydrogenase, urease and phosphatase.