Parathion degradation

Studies have found that methyl parathion degrades more rapidly in anaerobic soil than in aerobic soils (Adhya et al. 1981, 1987 Brahmaprakash et al. 1987). An average half-life of 64 days was determined for nonflooded (aerobic) soils compared to an average half-life of 7 days in flooded (anaerobic) soils (Adhya et al. 1987). In experiments with " C-labeled methyl parathion, 35% of the labeled compound was recovered from nonflooded soil after 28 days, compared with 9% recovered from flooded soil (Brahmaprakash et al. 1987). 

Ou L, Rao PS, Davidson JM. 1983. Methyl parathion degradation in soil Influence of soil-water tension. Soil Biol Biochem 15 211-215. 

Parathion degraded on both glass surfaces and on bean plant leaves. Metabolites reported were paraoxon, 4-nitrophenol, and a compound tentatively identified as 5-ethyl parathion (El-Refai and Hopkins, 1966). Upon exposure to high intensity UV light, parathion was altered to the following photoproducts paraoxon, 0,5-diethyl 0-4-nitrophenyl phosphorothioate, 0,0-diethyl 5-4-nitrophenyl phosphorothioate, 0,0-bis(4-nitrophenyl) 0-ethyl phosphorothioate, 0,0-bis(4-nitrophenyl) 0-ethyl phosphate, 0,0-diethyl 0-phenyl phosphorothioate, and 0,0-diethyl 0-phenyl phosphate (Joiner et al., 1971). 

Rao. P.S.C. and Sethunathan. N. Effect of ferrous sulfate on parathion degradation in flooded soil, J. Environ. Set Health, B14(3) 335-351,1979. 

Fig. 16.15 Parathion degradation on kaolinite as affected by clay water content incubation period 15 days. (Saltzman et al. 1974)...

Fig. 16.16 Percentage of water-phase parathion degradation product recovered from montmo-rillonitic (1) and kaolinitic (2) soils, with (A) the same organic matter (OM) content and (B) different organic matter content. (Yaron 1975)...

Fig. 16.35 Pathway of parathion degradation in soil. Reprinted from Nelson LM, Yaron B, Nye PH (1982) Biologically-induced hydrolysis of parathion in soil. Soil Biol Biochem 14 223-227. Copyright 1982 with permission of Elsevier...

Figure 12. Parathion degradation with time in the presence of five other formulated pesticides. , amount in soil and water o, amount in water.

FIGURE 8.2 Effect of organophosphate hydrolase on methyl parathion degradation. 

Barles, R. W., Daughton, G. C. Hsieh, D. P. (1979). Accelerated parathion degradation in soil inoculated with acclimated bacteria under field conditions. Archives of Environmental Contamination and Toxicology, 8, 647-60. 

Parathion degrades more readily in nonsaline soil than in saline soil imder flooded conditions. In nonsaline soil, no parathion was detected after 20 days. Degradation yields observed in various soils with varying amounts of salinity ranged from 10 to 50% after the 20-day period (Reddy and Sethunathan, 1985). Six years after applying parathion to soil at concentrations of 30,000-95,000 ppm, very small concentrations were detected at the 9 cm below the surface (Wolfe et al., 1973). 

Sethunathan, N. Or nic Matter and Parathion Degradation in Flooded Soil, Soil Biol. Biochem., 5(5) 641-644 (1973). 

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