Enzyme activities in soil at increasing metal (Cu, Ni, Pb) doses and time-dependence in a model experiment

Abstract

Aim of this paper is to examine the effect of spiked copper (Cu), nickel (Ni) and lead (Pb) metal salts on the dehydrogenase (oxydo-reductase) and phosphatase (hydrolase) enzyme activities in a characteristic Hungarian soil, the pseudomycelliar chernozem. Pot-experiment was performed with a soil, originating from a spot of the Hungarian soil-information-monitoring (TIM) system of Bicserd. The added metal salts were used in water soluble forms and incorporated uniformly to the soil. Soils were treated with increasing metal concentrations to give the following metal amounts: 0, 50, 200, and 800 kg.ha^-1. Enzyme activities of the soil were analysed at the 0^th, 7 ^th, 14 ^th, and 28^th days after the metal addition. The laboratory model-experiment has been set up in three replicates.

Effects of metal salts were largely dependent on the chemical and physical properties of pseudomycelliar chernozem soil, the applied heavy metal-types, the doses of used metals and the elapsed time after the pollution. Considering the different metals, the copper prowed to be the most toxic one on the studied enzyme activities, whereas the lead induced those. By comparison with copper the nickel affected a smaller decrease in the soil microbial activity. The dehydrogenase, oxydo-reductase enzyme was found to be more sensitive parameter in comparison with the phosphatase, hydrolase enzyme among the studied condition. Studied enzymes and used methods are suggested, as fast and rather reliable tools for estimating the soil-resilience capacities at heavy metal pollution.