Abstract:Effects of pesticide-contaminat ion on population and activity of sulfat-ereducing bacteria(SRB)were invest igated in three paddy soils,Huangsong paddy soil developed from shallow-marine deposit of intermediate lake deposit,Red paddy soil developed from alluvial deposit and Purple paddy soil developed from parent material of neutral purple sandstone and shale,4 weeks after the soils were applied with insecticide(carbofuran),fungicide(carbendazim)and herbicide(butachlor)at different concentrations.The results showed that population and the sulfate-reducing activity of SRB in Purple paddy soil,Huangsong paddy soil and Red paddy soil ranged(66.83~127.81)×104,(45.87~105.07)×104,(3.81~61.62)×104 cells per gram dried soil,respect ively,and S-2(7.14~11.57),(6.84~9.07),(1.91~6.67)Lg d-1g-1 dried soil,respectively,and that the sulfate-reducing activity was positive relativity to the population of SRB in paddy soil.The population of SRB and the sulfate-reducing activity were increased by addition of carbofuran(1 mg kg-1 dried soil)or butachlor(1 mg kg-1 dried soil)in paddy soils,but significantly inhibited by addition of butachlor(50 mg kg-1 dried soil),carbofuran(5 mg kg-1 dried soil)and carbendazim(50 mg kg-1 dried soil)in paddy soil till 7 d,14 d and 7 d,respectively.Then the inhibition effects of the contaminants were gradually attenuating.Eventually pesticide or metabolism of pesticide became contributive to the population of SRB and their sulfate-reducing activity.