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11.
The octachlorodibenzo-p-dioxin (OCDD) concentrations have been determined in aged samples of commercial pentachlorophenol (PCP), in wood protection formulations containing PCP and in wood treated with PCP as a preservative or as an anti-sapstain treatment. The concentrations of OCDD found in the various samples are within the range expected from the amount of commercial PCP initially present in the samples. In view of the known stability of OCDD the results are interpreted as indicating that the formulation, treatment and ageing processes have not led to any substantial conversion of PCP to OCDD; although one result indicates that outdoor exposure of treated samples increased the OCDD concentration by a factor of approximately 2 after years. Analysis of aged samples of treated wood indicate that OCDD is lost much less rapidly from the wood than PCP. 相似文献
12.
Solubilities in fats ranging from 0.88 g l?1 to completely miscible are reported for twelve organic chemicals. Comparison of these and other literature values with bioconcentration factors and octanol: water partition coefficients indicate that fat solubility is not a reliable predictor for either parameter. The results for the solubilities of seven chemicals in eight different fats cover a restricted range, indicating that the composition of the fat is not a critical parameter in determining the solubility. 相似文献
13.
Microbial grazing by two species of meiofaunal harpacticoid copepods (Heteropsyllus nunni and Thompsonula hyaenae) was determined by uptake of radioactive labels following their introduction into natural sediments from a low-energy intertidal site in Florida (29°5440N; 84°3130W) in May 1986. Grazing was related to three methods of radioactive-label introduction: injection, porewater replacement, and slurry. Uptake of label by harpacticoids was examined using two dual-label combinations, 3H-thymidine/14C-bicarbonate and 3H-thymidine/14C-acetate. The injection and porewater-replacement methods yielded statistically indistinguishable results. Results obtained by the slurry method differed significantly from the other two methods. We suggest that the unique results obtained in the slurry method were a consequence of the disruption of microbial-meiofaunal spatial relationships. 相似文献
14.
The uptake, metabolism and discharge of two polycyclic aromatic hydrocarbons, 14C-naphthalene and 3H-3,4-benzopyrene, were studied in 3 species of marine fish (mudsucker or sand goby, Gillichthys mirabilis; sculpin, Oligocottus maculosus; sand dab, Citharichthys stigmaeus). The path of hydrocarbons through the fish included entrance through the gills, metabolism by the liver, transfer of hydrocarbons and their metabolites to the bile, and, finally, excretion. The gall bladder was a major storage site of labeled hydrocarbons and their metabolites. The major product of 2H-3,4-benzypyrene metabolism was tentatively identified as 7,8-dihydro-7,8-dihydroxybenzopyrene. The 14C-naphthalene was metabolized to 1,2-dihydro-1,2-dihydroxynaphthalene after 24 h exposure. The urine appeared to the major avenne for discharge of labeled hydrocarbon from the body. Our laboratory results indicated that certain polycyelic aromatic hydrocarbons were rapidly taken up from seawater by the above fish, but detoxification mechanisms existed for efficient removal of these compounds from their body tissues. 相似文献
15.
With >80 million United States households engaged in lawn and gardening activities, increasing sustainability of lawn care is important. Mowing height is an easily manipulated aspect of lawn management. We tested the hypothesis that elevated mowing of tall fescue lawn grass promotes a larger, more diverse community of arthropod natural enemies which in turn provides stronger biological control services, and the corollary hypothesis that doing so also renders the turf itself less suitable for growth of insect pests. Turf-type tall fescue was mowed low (6.4 cm) or high (10.2 cm) for two growing seasons, natural enemy populations were assessed by vacuum sampling, pitfall traps, and ant baits, and predation and parasitism were evaluated with sentinel prey caterpillars, grubs, and eggs. In addition, foliage-feeding caterpillars and root-feeding scarab grubs were confined in the turf to evaluate their performance. Although some predatory groups (e.g., rove beetles and spiders) were more abundant in high-mowed grass, predation rates were uniformly high because ants, the dominant predators, were similarly abundant regardless of mowing height. Lower canopy temperatures in high-mowed grass were associated with slower growth of grass-feeding caterpillars. Higher lawn mowing reduces fuel consumption and yard waste, and promotes a deep, robust root system that reduces need for water and chemical inputs. Although in this study elevated mowing height did not measurably increase the already-high levels of predation, it did suggest additional ways through which bottom-up effects on insect pest growth might interact with natural enemies to facilitate conservation biological control. 相似文献
16.
17.
In this work, the potential for natural attenuation (NA) of Cr(VI) is evaluated for sub-wetland ground water at a chromium-contaminated site in Connecticut, incorporating the experimental findings of previous work at the site. Experimental data is assessed through long-term attenuation capacity calculations and modeling, which incorporates statistical uncertainty of parametric values. The NA evaluation yielded the following results: (1) Significant increases in Cr(VI) concentration and extremely long chromium source dissolution timeframes are required to exceed the attenuation capacity of the sub-wetland region soils studied in this work; and (2) Based on the 1-D transport modeling and incorporating input parameter uncertainty, there is an approximately 92% and 98% probability that the applicable regulatory criteria will not be exceeded at Point C, near a river which serves as the receptor, for the cases of (1) sorption of Cr(VI) only and (2) pseudo first order disappearance of Cr(VI) from the aqueous phase only, respectively. 相似文献
18.
We investigated physiological traits associated with a reproductive-resting stage in adult female harpacticoid copepods,
Coullana canadensis (Willey). Our hypothesis was this stage represents a life-history strategy that could increase fitness by improving winter
survivorship and future reproductive success in spring. To test if physiological rates are suppressed in this stage, we compared
gut-cell morphology, nitrogen excretion rates, enzyme activities, and phytoplankton grazing rates of reproductive-resting
and reproductive females reared in the laboratory under high food conditions. Copepods came from laboratory cultures originating
from individuals collected in Maine and Maryland, USA in 1990. Reproductive-resting females had lower physiological rates,
and the surface area of gut-cells was reduced compared to reproductive females. Distinct morphological differences in the
distribution of lipids between reproductive and reproductive-resting females were observed under light and electron microscopy,
the latter having a diffuse accumulation of lipid in the area normally occupied by the ovaries. Differences in lipid composition
were also found. Reproductive copepods had a significantly higher ratio (%) of polar lipids to total lipid, and a lower proportion
of triacylglycerols compared to reproductive-resting copepods. These laboratory findings are consistent with the hypothesis
that the reproductive-resting stage in C. canadensis is an adaptive response to increase winter survival.
Received: 29 May 1996 / Accepted: 3 December 1997 相似文献
19.
The results of analyses for polychlorodibenzofuran (PCDF) content in two samples of polychlorobiphenyl (PCB) from used electrical transformers are presented and discussed. In neither sample was there evidence for enhanced PCDF concentrations even though one of them had been subjected to overheating while in service. 相似文献
20.
Results of analyses of eight samples of technical pentachlorophenol conducted by three different analytical methods are presented and discussed. 相似文献