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Trichloroacetic acid (TCAA) is a member of the family of compounds known as chloroacetic acids, which includes mono-, di- and trichloroacetic acid. The significant property these compounds share is that they are all phytotoxic. TCAA once was widely used as a potent herbicide. However, long after TCAA's use as a herbicide was discontinued, its presence is still detected in the environment in various compartments. Methods for quantifying TCAA in aqueous and solid samples are summarized. Concentrations in various environmental compartments are presented, with a discussion of the possible formation of TCAA through natural processes. Concentrations of TCAA found to be toxic to aquatic and terrestrial organisms in laboratory and field studies were compiled and used to estimate risk quotients for soil and surface waters. TCAA levels in most water bodies not directly affected by point sources appear to be well below toxicity levels for the most sensitive aquatic organisms. Given the phytotoxicity of TCAA, aquatic plants and phytoplankton would be the aquatic species to monitor for potential effects. Given the concentrations of TCAA measured in various soils, there appears to be a risk to terrestrial organisms. Soil uptake of TCAA by plants has been shown to be rapid. Also, combined uptake of TCAA from soil and directly from the atmosphere has been shown. Therefore, risk quotients derived from soil exposure may underestimate the risk TCAA poses to plants. Moreover, TCE and TCA have been shown to be taken up by plants and converted to TCAA, thus leading to an additional exposure route. Mono- and di-chloroacetic acids can co-occur with TCAA in the atmosphere and soil and are more phytotoxic than TCAA. The cumulative effects of TCAA and compounds with similar toxic effects found in air and soil must be considered in subsequent terrestrial ecosystem risk assessments. 相似文献
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Seventy-five samples of the crustacean fauna associated with the coral Madracis mirabilis (Duchassaing and Michelotti) were obtained at five sites along the west coast of Barbados in 1985. Samples were analyzed to determine whether any community response to eutrophication was evident. Ordination (multidimensional scaling) and classification (group average clustering) based on Bray-Curtis dissimilarity measures separated the fauna of highly eutrophied sites from those that were less eutrophied. Dominance plots based on relative abundance and log-normal plotting methods were ineffective in distinguishing the fauna of eutrophied sites. The crustacean fauna responded to eutrophication mainly by reduction of density of animals. No differences in species richness, number of site endemic species or rare species were observed between highly eutrophied and less eutrophied sites. Nine indicator species of eutrophy were identified on the basis of strong density differences between sites. 相似文献
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Louis P. Lue C.C. Lewis Veronica E. Melchor 《Journal of environmental science and health. Part. B》2013,48(3):343-354
Abstract Aldicarb, Temik® 15 G, was incorporated in furrows at 3.37 and 6.73 kg ai (active ingredent)/ha and carrots (Caucus carota L.) were directly seeded on the same day. The numbers of nematode larvae were significantly suppressed in the treated plots; averages were 249, 74, and 51/ 50 cc soil samples for control (0), 3.37 and 6.73 kg ai/ha, respectively. Aldicarb treatment resulted in a 28% yield increase as compared to the untreated. Aldicarb residue in carrots was 28 ppb for the low treatment and 46 ppb for the high. Residual levels in soil of high treatment declined from 6l to 31 ppb during two weeks prior to harvest, meanwhile, those in the low decreased slightly from 13 to 12 ppb. Carrots placed in hydroponic solution containing aldicarb 14.5 ppm for 6 days, had an aldicarb residue of 10.26 ppb and the hydroponic solution, 2.7 ppb. Persistence of aldicarb residue was in carrot > in soil > in hydroponic solution. 相似文献
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