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Due to frequent soil Cd contamination and wide use of butachlor in China,there is a need to assess their combined toxicity to soil microorganisms.The combined effects of cadmium(Cd,10 mg kg-1 soil) and herbicide butachlor(10,50,and 100 mg kg-1 soil) on enzyme activities and microbial community structure in a paddy soil were assessed using the traditional enzyme assays and random amplified polymorphic DNA(RAPD) analysis.The results showed that urease and phosphatase activities were significantly reduced by high butachlor concentration(100 mg kg-1 soil).When the concentrations of Cd and butachlor added were at a ratio of 1:10,urease and phosphatase activities were significantly decreased whereas enzyme activities were greatly improved at the ratio of 1:5,which indicated that the combined effects of Cd and butachlor on soil urease and phosphatase activities depended largely on their addition concentration ratios.Random amplified polymorphic DNA(RAPD) analysis showed loss of original bands and appearance of new bands when compared with the control soil.Random amplified polymorphic DNA fingerprints suggested substantial differences between the control and treated soil samples,with apparent changes in the number and size of amplified DNA fragments.The addition of high concentration butachlor and the combined impacts of Cd and butachlor significantly affected the diversity of the microbial community.RAPD analysis in conjunction with other biomarkers such as soil enzyme parameters would prove a powerful ecotoxicological tool.Further investigations should be carried out to understand the clear link between RAPD patterns and enzyme activity.
Due to frequent soil Cd contamination and wide use of butachlor in China, there is a need to assess their combined toxicity to soil microorganisms. The combined effects of cadmium (Cd, 10 mg kg -1 soil) and herbicide butachlor (10,50, and 100 mg kg -1 soil) on enzyme activities and microbial community structure in a paddy soil were assessed using the traditional enzyme assays and random amplified polymorphic DNA (RAPD) analysis. The results showed that urease and phosphatase activities were significantly reduced by high butachlor concentration (100 mg kg-1 soil) .When the concentrations of Cd and butachlor added were at a ratio of 1: 10, urease and phosphatase activities were significantly decreased at enzyme activity were greatly improved at the ratio of 1: 5, which that the combined effects of Cd and butachlor on soil urease and phosphatase activities depended largely on their addition concentration ratios. Random amplified polymorphic DNA (RAPD) analysis showed loss of original bands and appearance of new bands when compared with the control soil. Random amplified DNA fingerprints suggested substantial differences between the control and treated soil samples, with apparent changes in the number and size of amplified DNA fragments. The addition of high concentration butachlor and the combined impacts of Cd and butachlor significantly affected the diversity of the microbial community .RAPD analysis in conjunction with other biomarkers such as soil enzyme parameters would prove a powerful ecotoxicological tool. Future investigations should be carried out to understand the clear link between RAPD patterns and enzyme activity .