W. E. Westlake

Uptake of a PCB (Aroclor 1254) from soil by carrots under field conditions

SummaryThe change in composition of Aroclor 1254 in soil was evident over an eleven-month period. Dissipation appeared to parallel the degree of chlorination. The lesser chlorinated biphenyls were slowly dissipated while the more highly chlorinated biphenyls were not appreciably affected. PCBs were absorbed by carrot roots; increasing translocation was associated with decreasing biphenyl chlorination. Since 97% of the residue was found in the peel, very little translocation occurred in the plant tissue.

Varying persistence of polychlorinated biphenyls in six California soils under laboratory conditions

Each fortified and control sample, moistened to 40~ saturation, was inoculated and kept in an enameled tray loosely covered with a glass plate to retard water evaporation, substrate volatilization, and photodecomposition. Thus, the substrates would be subject to possible microbial degradation, chemical degradation, and adsorption to soil colloids, but not losses due to leaching or soil transport. Properties of the soils used were determined by HERMANSON and RIBLE (1967) (See Table I).

Worker environment research: Dioxathion (delnav®) residues on and in orange fruits and leaves, in dislodgable particulate matter, and in the soil beneath sprayed trees

Deposits and residues of dioxathion disappear at similar rates on and in the rind of oranges and the leaves of orange trees; dislodgable residues on the leaves dissipate at the same rate as the penetrated residues. This fact is important in evaluating the potential hazard to workers in treated groves because their exposure to pesticide residues is principally through the dislodgable residues. Samples of vapor and particulate matter taken during violent shaking of the trees show that the exposure of workers is almost entirely through contact with, and inhalation of, particulate matter, dermal contact probably being the more important. In one experiment, pickers were used in trees sprayed with dust containing no toxicant to determine the actual weights of dust that are inhaled (using Unico air samplers) and that accumulate on their bare arms (by washing at ten-minute intervals). The data show that several times as much dust is contacted dermally than is inhaled. Washing the entire trees with a dilute detergent solution removes a significant part of the dislodgable residue; as much as 30 percent is removed 46 days after spraying. The data presented in this paper provide a guide for toxicologists to permit the design of tests required to evaluate hazards workers encounter in pesticide-citrus groves.

Persistence of parathion in six California soils under laboratory conditions

Persistence curves obtained for parathion in six California soils are partially dependent on soil type. The possibility that long-term, low-level parathion soil residues can exist is confirmed. Each soil was fortified at 20 ppm, kept in an enameled tray, and maintained at 30°C with a soil moisture level of approximately 40 percent of saturation. The parathion residue in Laveen loamy sand drops rapidly to about 0.2 ppm in 30 days. In Mocho silt loam, Linne clay, and Madera sandy loam, it drops to between one and two ppm in 30 days and gradually decreases to about 0.2 ppm in 130 days. The rapid parathion residue decline is attributed to microbial degradation. In Windy loam, the residue after eight months remains above three ppm. In two experiments differing slightly in soil moisture, the residue in Santa Lucia silt loam is about 1.5 ppm after eight months in one experiment and about 0.5 ppm after six months in the other. The latter two soil types give linear semi-logarithmic persistence curves, suggestive of degradation by hydrolysis.Aminoparathion, above the detectable level of one ppm, is not found in Madera sandy loam after fortification with parathion at 200 ppm. However, a sharp decline of the parathion residue after ten days suggests microbial degradation. Three ppm aminoparathion were recovered after seven days when Madera sandy loam was fortified at 20 ppm with parathion and submerged under water. In contrast, the degradation of parathion remaining in Windy loam (3.2 ppm) and Santa Lucia silt loam (2.2 ppm) 7.7 months after fortification is not greatly accelerated when flooded with water.

Expanded utility of the Beilstein flame test for organically bound halogens as a sensitive and specific flame photometric detector in the gas chromatographic determination of R-X compounds as illustrated with organochlorine pesticides

In 1962 we published (9) a brief note on the utility of the Beilstein flame test for organohalogen compounds as an adjunct (split stream) glc detector to signal their appearance in the emergent gas stream for facilitating their collection as organohalogen fractions for any purpose. We reported that about 0.17 ~g. of organically bound chlorine/second was visually detectable with the conditions and apparatus used at that time. We further stated that enhanced minimum detectability could be achieved by filter

Influence of some soil characteristics on the dissipation rate of landrin insecticide

SummaryThe rates of dissipation of Landrin from nonsterile soils were primarily dependent upon the soil type. The persistence half-lives of the Landrin applied ranged from <4 to >40 days in the 8 soils investigated. Rates of breakdown increased with increasing soil pH (above pH 7), indicating alkaline hydrolysis as the major cause of Landrin degradation; destructive microorganisms were also involved, however. Soil organic matter did not seem to be a major factor in Landrin degradation.

Determination of phosphoric acid, dimethyl p-methylthiophenyl ester in cottonseed

She insecticide GC-65061 (phosphoric acid, dimethyl ~-methylthiophenyl ester) is a potential acaricide and insecticide for use on cotton. A sensitive and reasonably specific method for determining residues of the compound in cottonseed was required to establish the levels that might be found following its use. A gas chromatographic procedure was developed, utilizing a phosphorussensitive detector, that provided the degree of minimum detectability (0.05 ppm) and specificity required for the study.