Physical and Chemical Properties of Pesticides

Heller, S.R., Scott, K., Bigwood, D.W. (1989) The need for data evaluation of physical and chemical properties of pesticides The ARS pesticide properties database. J. Chem. Inf. Comput. Sci. 29, 159-162. 

Mackay et al. (1997) provide detailed examples of fugacity calculations to illustrate how variations in the physical and chemical properties of pesticides affect their partitioning among environmental media. Figure 3 displays the results from some of these calculations for three of the pesticides listed in Table 1. Consistent with the expectations described above, these computations predict that following their release into the hydro-logic system, the relatively water-soluble herbicide atrazine will come to reside mostly in the aqueous phase, the more hydrophobic insecticide... 

Water leaves the field either as surface mnoff, carrying pesticides dissolved in the water or sorbed to soil particles suspended in water, or as water draining through the soil profile, carrying dissolved pesticides to deeper depths. The distribution of water between drainage and mnoff is dependent on the amount of water appHed to the field, the physical and chemical properties of the soil, and the cultural practices imposed on the field. These factors also impact the retention and transformation processes affecting the pesticide. 

Disulfoton is a systemic insecticide/acaricide that belongs to the organophosphate class of pesticides. Pure disulfoton is a colorless oil with low volatility and water solubility, but is readily soluble in most organic solvents (Worthing 1987). Information regarding the physical and chemical properties of disulfoton is located in Table 3-2. 

Air sampling for occupational exposure to pesticides normally consists of measurement of pesticide concentrations in the worker s breathing zone, with a portable air-sampling pump and a sampling train which includes some type of collection device. The latter device, or sampling media, selected are based on the physical and chemical properties of the compound to be measured. Field workers may be exposed to chemical vapors, solid particulates or water-based aerosols. Examples of sampling media include membrane filters, sorbent tubes, polyurethane foam and charcoal. A discussion of pesticide exposure provides a useful review of methods for respiratory exposure measurement (Nigg etal, 1990). 

The clean-up of contaminated ground water poses problems that are different from contaminated surface waters, particularly because ground water is not easily accessible. Due to the typical slow movement of pollutants in the aquifer and the relatively low degree of dispersion, concentrations of contaminants can remain high and detection can be difficult. In the case of pesticides, some of the factors that may contribute to ground water contamination include physical and chemical properties of the pesticide, application methods used for their application, and characteristics of the soil and site. Once an aquifer is contaminated, its restoration as a usable... 

Some Physical and Chemical Properties of the Selected Organochlorinated Pesticides... 

The isolation of the above mentioned compounds, especially of pesticides, is mainly carried out by the extraction. The following clean-up is governed by the physical and chemical properties of the compounds to be analyzed. A very annoying factor in the analytical procedure is fat, which is extracted additionally by the solvent used. For this no uniform procedure exists. Contaminants in repurified extracts can be determined by different methods. GLC, HPLC, and DPP have found widespread utilization. 

Table 12.62 Important physical and chemical properties of modern pesticide representatives.

WHOPES has also established a database, which will be made available on the Internet through the WHO web site in the near future. The database contains the basic information that vector control professionals need to know for the day-to-day use of pesticides that have successfully completed evaluation under the Scheme, including type of application, recommended use, selected physical and chemical properties, basic toxicology, storage and handling, and reported cases of resistance (per species and country). 

As a result of pesticides widespread usage, they are now present at all environmental levels with different distributions related to their physical and chemical properties. Examples include ... 

Contamination of post-consumer PET (POSTC-PET) is the major cause of deterioration of its physical and chemical properties during reprocessing. POSTC-PET is contaminated with many substances (1) acid producing contaminants, such as poly(vinyl acetate) and PVC (2) water (3) coloring contaminants (4) acetaldehyde (5) other contaminants such as detergents, fuel, pesticides, etc., stored in PET bottles. 

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