Vapor , pesticide

The most common methods for trapping pesticide vapors from air use adsorbents. Common air sampling adsorbents include charcoal (derived from petroleum or coconut) and synthetic polymeric materials, such as cross-linked polystyrene and open-cell polyurethane foam. Charcoal has been used for the cumulative sampling of volatile... 

Water samples were also collected from the drainage tile surrounding this concrete-lined pit. Other water samples were taken from sites remote from the pit location. Air samples for pesticide vapor analyses were collected in the vicinity of the pit. 

Air Samples. The atmospheres in the vicinity of the pits were sampled for pesticide vapors using XAD-2 resin and a vacuum pump ( 6). Collection efficiencies for this method were measured in the laboratory using simulated atmospheres and found to be 99.5% average for 10 pesticides spiked at 10 ng/L of air. 

A high volume Staplex air sampler with a vacuum capacity of 24 L/mln was placed horizontally on top of the berm facing towards the bed and operated for 2 hr. The air sampling procedure Including the preparation of the resin and extracting the captured pesticide vapors has been reported by Wehner et al. (3). 

Figure 1. Environmental chamber. A, air entrance B, air exit C, hygrotherm D, temperature and humidity probe E, Pyrex tray F, crystallizing dish G, air dispersion tube H, 12 rubber stoppers (covered with aluminum foil) I, pesticide vapor traps J, flow meter. Reproduced with permission from Ref. 18. Copyright 1983, Pergamon Press.

A number of complex chemical compounds (e.g., pesticides, vapors and fumes, automobile exhausts, petroleum distillates, foundry fumes, heterocyclic amines, solid particles) have caused adverse effects to humans and environment. Some persistent contaminants have originated from industrial sources. For example, DDT, mirex, PCBs, dioxin, and others have been traced in the atmosphere as toxic depositions causing concern to human health.3... 

Figure 4. High volume air sampler modified for holding solid sampling media for adsorbing pesticide vapors (2 )...

Table I. Pesticide Vapor Sampling Efficiencies of XAD-4 Resin and Polyurethane Foam in a High Volume Air Sampler3,b...

Figure 6. Arrangement for sampling pesticide vapors at three heights above a treated surface via a manifold interface (B) between XAD-packed tubes (C) and high volume air sampler motor (A) (51)...

Evidence was obtained recently that pesticide vapors may enter the air by still another mechanism, involving plant circulation and water loss (57). Rice plants were found to efficiently transport root-zone applied systemic carbamate insecticides via xylem flow to the leaves, eventually to the leaf surface by the processes of guttation and/or stomatal transpiration, and finally to the air by surface volatilization. Results from a model chamber showed that 4.2, 5.8, and 5.7% of the residues of carbaryl, carbofuran, and aldicarb, respectively, present in rice plants after root soaking vaporized within 10 days after treatment. The major process was evaporation of surface residues deposited by guttation fluid. 

Parmele, L.H. Lemon, E.R. Taylor, A.W. Micrometeorolog-ical measurement of pesticide vapor flux from bare soil and corn under field conditions. Water, Air, Soil Pollut., 1972, 1, 433. 

Turner, B.C. Glotfelty, D.E. Field air sampling of pesticide vapors with polyurethane foam. Anal. Chem., 1977,... 

The deviations observed between extrapolated estimates from GLC data, and direct measurements with the effusion measurements appear to be too large to be accounted for by extrapolation uncertainties. The best estimate can probably be obtained by fitting the combined data to the Clausius-Clapeyron equation (footnote b of Table IV). The obvious implication is that where possible, extrapolation of pesticide vapor pressures obtained at elevated temperatures be converted to interpolation by including a direct measurement at room temperature. In terms of the work described here, vapor pressure measurements requiring the DTA should be supplemented with Knudsen cell measurements. This would require a temperature at which the vapor pressure was 10 3 mm. or less. 

Secondly, much of any pesticide vapor escaping to 50 meters or more above the crop will ascend even higher by eddy diffusion and eventually reach the highly photochemically active ionosphere. I suggest that except for the destructive reactions occurring in the upper atmosphere, all life would probably have succumbed to intoxication by its own waste products, let alone by-products of the chemical industry. 

Figure 3.3 Low-volume pesticide vapor generator for determination of air sampling efficiencies...

Whatever their design, passive samplers will collect only pesticide vapors. Therefore, air measurements made with them will not always be appropriate for estimating total respiratory exposure, especially in the case of low-volatility pesticides and pesticides tracked indoors on soil particles. In addition, some pesticides may undergo chemical degradation on sorbents or in solvents over such long sampling periods. Therefore, internal standards or other means will need to be used to assure acceptable analyte recoveries. 

Splashes, errant sprays, mists, clouds, etc., of pesticide vapors, aerosols, hquids, dusts, and granules are potential sources of facial contact with the pesticides. Although facial contacts would be expected to occur less frequently than, for example, contact with the hands, the health consequences of the contacts are potentially more serious, especially for contacts with the eyes. 

Thermal loggers, also called thermal generators, use heat to vaporize a special oil formulation of a pesticide. As the pesticide vapor is released into the... 

Pesticide vapors move about easily in air. Fumigant pesticides are intended to form a vapor when they are released. Persons using fumigants must... 

---