Further Studies on Degradation of Fenitrothion in Soils

Abstract

The degradation of fenitrothion (I) and 3-methyl-4-nitrophenol (II), one of the major degradation products in soil, was studied, using 14C preparations labeled at the phenyl ring. In two kinds of aerobic upland soils, I and II degraded with an initial half-life of less than 7 days. A main degradation route of I was a cleavage of the P-O-aryl linkage, leading to the formation of II which underwent further metabolism to 14C02. In soils treated initially with II, a trace amount of 3-methyl-4-nitrocatechol was detected. When soils containing the bound 14C residues arising from I were mixed with fresh soil, 17.5 to 22.4° of the bound 14C was mineralized to 14C02 over 22-week period. In two kinds of submerged soils, I degraded mainly via reduction of the nitro group to the amino group with an initial half-life of less than 7 days. The resultant product was bound to the soils or metabolized further to the formylamino and acetylamino derivatives. In addition, a relatively large amount of 14C02 was evolved from the soils. When the conditions of the submerged soils were altered to those of aerobic upland by draining the flooded water, the bound 14C residues were partially mineralized to 14C02. Furthermore, the bound 14C residues in upland and submerged soils were hardly taken up by bean and rice plants, respectively.

Fate of aged tolclofos-methyl and diethofencarb residues in soil

“…Mikami et al reported that 18-22% of the unextracted bound residues was mineralized over a 22-week period using soil with added 14 Cfenitrothion. 13) Although the substituents in the phenyl ring are di erent between I and fenitrothion, a similar degree of mineralization irrespective of solvent extraction suggests that extraction by aqueous organic solvent even in the presence of acid does not signi cantly alter the bioavailability of bound residues. Based on these results, the unextracted bound residues not easily released by the usual extraction with aqueous organic solvent were claried to be mineralized upon their release by microbes.…”

“…5,6) e fractions of a pesticide and its metabolites bound to soil may be released over time and become available to plants and soil organisms. Although little is known about the nature of bound residues, 13 C-and 15 N-NMR spectroscopy has been applied to elucidate their chemical nature. [7][8][9] Mineralization experiments of bound residues have also been conducted to examine their bioavailability [10][11][12] and some micro ora showed mineralization ability towards bound residues remaining even a er Soxhlet extraction.…”

“…[7][8][9] Mineralization experiments of bound residues have also been conducted to examine their bioavailability [10][11][12] and some micro ora showed mineralization ability towards bound residues remaining even a er Soxhlet extraction. 13) e objective of the present study was to examine the fate of aged pesticide residues through mineralization experiments by taking account of the usual agronomical practices such as tillage and organic additions. Microbial activity in soil contributing to mineralization was mimicked by the addition of fresh soil, glucose and pulverized straw as model practices.…”

Behavior of paddy pesticides and major metabolites in the Sakura River, Ibaraki, Japan

“…Fenitrothion-oxon is also a minor metabolite produced by photodegradation of fenitrothion in water or soil. 51,52) Because oxons of organophosphorus insecticides hydrolyze faster than the parent compounds, 44) oxons can be expected to be present only rarely in paddy fields or rivers.…”

Mutagenic fate of insecticide fenitrothion in the environment—mutagenicity increases both by anaerobic biodegradation and photodegradation

“…After application, fenitrothion in the environment is transformed into various compounds by means of biological activity, chemical activity, and photolysis, and many researchers have investigated the resulting transformed products (TPs; Takimoto et al 1976;Spillner et al 1979;Adhya et al 1981;Mikami et al 1985a;Sato 1992;Shalini et al 1996;Alonso et al 1997;Hashizume et al 1997) and their proposed metabolic pathways.…”