ABSTRACT
Residues of nitrofen in farm soils, persistence of nitrofen in field microplots, mobility of nitrofen in natural soils and the role of microbial flora in its degradation were studied. Muck soils from vegetable farms in southwestern Ontario contained up to 35 ppm nitrofen in mid-season (August), which decreased to 18 ppm by October. The herbicide was less persistent in sand than in muck. Degradation was slightly faster in sand and muck soils receiving two sprays, than in those sprayed once. From an initial deposit of ca. 2 and 10 ppm resp., in sand and muck field microplots, ca. 2 and 15% persisted after 16 wk. Leaching of nitrofen by water through sand was negligible, and it was even more strongly adsorbed onto organic soil. Natural microbial flora seemed to play an important role in the degradation of nitrofen in soil. Ca. 15 and 38% resp., of the initial concentration persisted in natural sandy loam and muck 16 wk after treatment at 10 ppm, whereas about 94 and 82% resp., persisted in sterilized sandy loam and muck at the same period.
Subject(s)
Herbicides/analysis , Pesticide Residues/analysis , Phenyl Ethers/analysis , Hydrogen-Ion Concentration , Ontario , Soil Pollutants/analysis , Time FactorsABSTRACT
The relative toxicity of endosulfan, its isomers, and formulated products to the freshwater fish Labeo rohita was tested. The 96-h LC50 values showed that toxicity decreased in the following order: isomer A, 35% emulsifiable concentrate, technical endosulfan, 4% dust, and isomer B. The principal method of detoxification was by formation of endosulfan ether in the liver, Endosulfant, at both sublethal and lethal doses, enhanced oxygen consumption in L. rohita. Histological studies showed minor changes in the liver only.
