Effects Of Individual Copper, Zinc, Lead And Cadmium Pollution On Biological Activities Of Aquic Brown Soil

The thesis investigates the effects of copper (Cu),zinc (Zn),lead (Pb) and cadmium (Cd) individual pollution on soil microorganisms and their activities via pot culture and laboratory incubation experiments with aquic brown soil selected. The main purpose of this study was to provide some useful information for bioremediation, environmental quality evaluation and especial warning indication for soils contaminated by heavy metals. The tested soil treated with different content gradients of Cu, Zn, Pb and Cd taking non-added any metal soil as control. Soil respiration intensity, ammonization, nitrification, nitrogen fixation, cellulose decomposing intensity, the activities of phosphomonoesterase, saccharase, protease, urease, dehydrogenase polyphenol oxidase, nitrate reductase, L-asparaginase and the content of microbial biomass C, N, P were tested by taking the sample from the treated soils and the control. We took the third class of soil environment standard as the start treatment.The soils were added a content gradient of Cu, Zn, Pb and Cd respectively. The content gradient was designed as 400,800 and 1200 mg Cu2+kg-1 dried soil; 500,1000 and 1500 mg Zn2+ kg-1 dried soil; 500,1000 and 1500 mg Pb2+ kg-1 dried soil; 1,10 and 20 mg Cd2+kg-1 dried soil.The main results of this study are presented as follows:with the increase of the content of Cu, Zn, Pb and Cd, the microbial biomass C, N, P content of soils are all decrease. There are significant positive correlations between the content gradients of Cu, Zn, Pb and Cd, and metabolic quotient, while remarkable negative correlation were found between microbial quotient and the content of heavy metals.The activities of phosphomonoesterase, polyphenol oxidase and nitrate reductase were activated by Cu at low content and restrained at high content. However, the activities of protease, urease, dehydrogenase, saccharase, polyphenol oxidase, nitrate reductase,L-asparaginase all decrease under the Cu treatement. The activities of phosphomonoesterase,saccharase, polyphenol oxidase, nitrate reductase increase under the treatment of lower content of added Zn, but decrease at the highest content; while the activities of protease, urease, dehydrogenase, polyphenol oxidase, nitrate reductase, L-asparaginase increase with content of add Zn. The activities of phosphomonoesterase, saccharase, dehydrogenase, polyphenol oxidase in the application of Pb increase under certain content but significantly decrease with the following increase of content. The activities of other enzymes decrease as the content of Cd, except the increase of the activity of dehydrogenase at lower content. There are linear regressions between content and microbial biomass, respiration intensity, nitrogen fixation, ammonization, metabolic quotient and microbial quotient, the activities of protease, urease, dehydrogenase, L-asparaginase, respectively.Therefore,they can be used as indicated index of single heavy metal pollution.