Studies on the biodegradation characteristics of parathion-methyl by Plesiomonas sp. (DLL-1) in soils and the influence factors

The biodegradation of parathion methyl by Plesiomonas sp. (DLL 1)in soils and the influence factors were studied both in laboratory and field test. The laboratory test results showed that effectial biodegradation of parathion methyl was happened in four different soils such as Jiangxi red soil,Jiangsu Taihu paddy soil、Northeast China black soil and Hebei sandy loam. the degradation half times of parathion meththyl in the above mentioned soils were 3 90?h、313?h、4 20?h and 2 91?h respectively,while they were 3 10?d,2 96?d,2 75?d and 111?d in the contrast test respectively. The laboratory test results also showed that the degradation percentage of parathion methyl in 24 hours was 86 0% 95 2% in Jiangsu Taihu paddy soil when the pesticide concentration was in the range of 1 5 to 450?mg/kg. The degradation percentages of parathion methyl were both more than 95% in 24 hours when the water content in soils were 50 % (modified upland field) and 150% (modified wet field) in laboratory test, while the degradation percentages of parathion methyl were 18 8% and 42 2% in the contrast test. The effective biodegradation of parathion methyl was taken place by DLL 1 bacteria in the open field test when the dosege of pesticide was in the range of 1 5 100?mg/kg.The suitable usage amount of DLL 1 bacteria was about 3?g/m\+2.