Fenitrothion volatilization

Metcalf, C.D., McLeese, D.W., and Zitko, V. Role of volatilization of fenitrothion from fresh water, Chemosphere, 9(3) 151-155, 1980. 

Their volatilization from litter on the forest floor will also be appreciable. With the possible exception of carbaryl, their volatilization after being washed into the soil will be relatively low or insignificant because of their low volatility, low Henry s constants, Kh> and/or their high rates of degradation in the soil environment. The rapid disappearance of the phenoxy herbicides (2, 31) and the insecticide, fenitrothion (28) from vegetation and the forest floor is supporting evidence that volatilization is an important pathway for loss of applied pesticides from the forest canopy and litter on the forest floor. 

There are relatively few studies which relate to volatilization of pesticides from conifers. Yule et al.(16) have monitored the level of phosphorus in air (both vapours and particulate material) at five sites in New Brunswick during a spraying season in which 300 tons of fenitrothion were applied to over 10b ha. Average daily concentrations ranged up to 3 ug/tri and were generally between 0.5 and 1.5 ug/nrr (background 0.5 ug/m ). The atmosphere contamination was due partly to local application and partly to downwind drift of pesticide. 

Movement and degradation of fenitrothion in the water/sed-iment model The concentration of fenitrothion in non-autoclaved and autoclaved stream waters in the presence of sediment are shown in Figure 4. The concentration of fenitrothion decreased rapidly in water and increased rapidly in sediment, showing that fenitrothion has a greater tendency than aminocarb for translocation from water to sediment. Within 15 h, 94% (open flask) and 89% (closed flask) of the chemical in the non-autoclaved samples was lost from the aqueous phase and the corresponding concentrations in sediment were 43% and 66% respectively. The rapid translocation of this compound from water to sediment was probably due to its lipophilic nature (], ). Such a phenomenon was not very significant for aminocarb because it was present in water as a cationic species at pH 6.0. At the end of the experimental period (75 h), only 0.2% and 0.5% of the chemical remained in water whereas the sediments contained 19% and 31% of the fortified levels respectively. The rapid loss in the open flask is primarily attributable to volatilization coupled with some microbial degradation. In the absence of volatilization (closed flasks), the decrease in concentration in both the phases was lower. The presence of sediment therefore,... 

In conclusion, water/sediment model studies suggest that the dissipation pathways for aminocarb and fenitrothion would be primarily via volatilization and microbial action as schematically represented in Figure 5. 

Although the paths of dissipation of fenitrothion in aquatic systems are well known, their relative importance needs to be established at the pg/L concentrations observed in field studies. For example, volatilization has been suggested as a major path of loss from lakes (6) but has not been measured directly. The relative contribution of photolysis under shaded and unshaded conditions has also not been studied. 

The study was designed to examine the effect of sunlight intensity, the importance of volatilization and the extent of partitioning of fenitrothion and degradation products into sediment, plants and fish under field conditions. 

Volatilization of AF or MNP is unlikely however since they have smaller Kg values than fenitrothion. 

Predicted and calculated flux of fenitrothion from water were similar although values were arrived at independently. Both results suggest that volatilization from water is slow compared to other paths of degradation of the insecticide which confirms predictions of the two-film theory of volatilization (17)(18). Losses of fenitrothion from surface films have been shown to be very rapid (2 ) but a surface film was not formed in the present work because the insecticide was mixed into the upper 10 cm of the water column. 

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