Post-application volatilization

Localized, or field-scale, studies generally assess pesticides drifting off-target during application or from post-application volatilization over short sampling intervals. The... 

Taylor, A.W. Post-application volatilization of pesticides under field conditions. J. Air Pollut. Contr. Assoc., 1978, 28, 922. 

Upon release the formulated control agent is partitioned between the air, the forest vegetation and the forest floor. It is the post application loss of insecticides from conifers which is the subject of the following discussion. Volatilization has become increasingly recognized as a significant factor which limits the efficiency of pesticides and provides a major pathway to general environmental contamination. 

In the absence of direct field measurements of pesticide fluxes eminating from a sprayed forest a series of suppositions may be drawn from similar observations of losses from treated agricultural crops. The volatilization of dieldrin and heptachlor from a grass pasture was characterized by rather marked diurnal variations in vertical flux intensities of both insecticides during the initial days post application (12). The authors concluded that the volatilization ceased or was greatly reduced with decreased solar radiance. Estimated relative vapour concentrations of dieldrin rapidly declined from saturation 2 hours post application to 10% by evening. This parameter reached a maximum of 30 - 40% on day 2 and 20 - 25% on day 3. Although the saturated vapour concentration of heptachlor is approximately fifty... 

Of special interest is post-application exposure of toddlers and children, who tend to play on the floor and show extensive mouthing behavior (Davis and Ahmed, 1998 Groot et al., 1998). Toddlers and children contact residues which have settled on the floor by wiping the floor and stirring up dust. Semivolatile and volatile pesticides evaporate and absorb onto various surfaces, including babies toys, which have extensive contact with children (Gurunathan et al., 1998). In addition, the low body weight compared to adults is a risk factor for toddlers and children. 

Nearly all polymerization processes and products require a post-reaction process to remove and reduce to an acceptable level residual monomer(s), solvent or diluent. End use properties can be adversely affected by high levels of residuals through toxicity, odor, or poor physical properties. In the cases of residual solvent or diluent, a separation process involving the evaporation of the volatile components (devolatilization) can be used. Devolatilization can be used for residual monomer removal, but completing the polymerization of monomer is an attractive alternative when applicable. Polymerization finishing is usually accomplished with an increase in temperature to kick-off a finishing initiator or the addition of an initiator. (D For the dispersion... 

In fibre applications, the high volatility of monomeric HALS such as HALS-1 made it susceptible to loss during post extrusion heat treatments such as tentering. This is presumably related to the relatively high volatility of HALS-1 which is a result of its low molecular weight and... 

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