Influence of toxic metals on activity of acid and alkaline phosphatase enzymes in metal-contaminated landfill soils

A study was conducted to determine the effect of toxic metals on soil acid phosphatase (EC 3.1.3.2) and alkaline phosphatase (EC 3.1.3.1) enzyme activities in landfill soils. The enzyme activities were consistently higher in the landfill soils than in an uncontaminated alluvial soil. The landfill soils contained higher concentrations of metals (iron, manganese, cadmium, lead, zinc, copper) than did the alluvial soil. Enzyme activities were negatively correlated with the metals, with inhibition increasing with the bioavailability of the metals. It is suggested that the metals affected enzyme activities by behaving synergistically or additively with each other. Although the landfill soils had higher enzyme activities than the alluvial soil due to higher organic matter concentrations, the ratios of enzyme activity/organic carbon indicated that inhibition of enzyme synthesis and stability had occurred due to metal stress.