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861.
J. Devereux Joslin 《Environmental management》1994,18(4):559-567
Concern about mercury pollution from atmospheric deposition has risen markedly in the last decade because of high levels of
mercury in freshwater fish from relatively pristine waters. Whereas high concentrations have been found principally in Canada,
the northern United States, and Scandinavia, they have also recently been observed throughout much of Florida. Recent surveys
of the Tennessee River system, however, have found no locations where fish levels exceed EPA guidelines for fish consumption.
This paper evaluates a number of factors that may cause certain regions in the northern hemisphere to experience unacceptable
fish mercury levels while other regions do not. Relevant regional differences include: (1) Waters of the Tennessee River system
are generally nonacidic (pH>6) and well buffered, whereas 16%, 22%, and 40% of the lakes in upper Midwest, Northeast, and
Florida, respectively, have acid-neutralizing capacities below 50 μeq/liter. Acidity correlates highly with fish mercury levels
in a number of lake surveys, and experimental manipulations of acidity have significantly raised fish mercury levels. (2)
The ratio of land area to water surface area in the Tennessee Valley averages about 30, whereas it is 15 in the upper Midwest
and 6 in Florida. Low ratios allow mercury in precipitation to be directly deposited to aquatic bodies, without an opportunity
for the mercury to be sequestered by terrestrial ecosystems. (3) Stream organic matter concentrations in Florida, the upper
Midwest, and Sweden are 2–10 times those in the Tennessee Valley. Mercury binds strongly to organic matter, and organic matter
transport in runoff is a major pathway by which mercury enters aquatic ecosystems. 相似文献
862.
Detection of a Toxic Product Released by a Polyurethane-Containing Film Using a Composting Test Method Based on a Mineral Bed 总被引:1,自引:0,他引:1
Maurizio Tosin Francesco Degli-Innocenti Catia Bastioli 《Journal of Polymers and the Environment》1998,6(2):79-90
The degradation of a film containing a 4,4diphenyl methane diisocyanate (MDI) poly(€-caprolactone)-based polyurethane was followed in a test system based on a mineral solid bed designed to facilitate analysis of break-down products released under composting conditions. The use of a mineral solid bed can help extraction and analytical procedures which could be hindered by the heterogeneous nature of compost. The fermentation conditions are typical of the composting environment and generate a powerfully degradative environment. The film fully disintegrated within 30 days of treatment. Analysis on the mineral bed extracts showed that: (i) about 40% of the initial polyurethane was still present in the bed extracts; (ii) this residue was strongly degraded in the poly(€-caprolactone) part, while the urethane part was almost completely recovered (from 80 to 95%, according to the measurement method); (iii) 4,4 diamino diphenyl methane (MDA), a very dangerous product of MDI, was released during biodegradation. The results indicate that a mineral bed can be employed to study degradation and metabolites formation in solid phase fermentation and that the MDI-based polyurethanes are not susceptible of a full degradation during composting and maintain the potential of a slow release of MDA into the environment after soil application. 相似文献
863.
大气细颗粒物(PM2.5)对心血管内皮细胞NOS的影响 总被引:5,自引:0,他引:5
运用体外试验方法,探讨了大气细颗粒物的心血管毒性及其可能的作用机制采集上海城区大气中的PM25,并以0.01、0.05、0.2、1 mg·mL-1剂量染毒大鼠心血管内皮细胞24 h后,观察PM2.5对心血管内皮细胞内总NOS,iNOS及cNOS活力等指标的影响.发现与对照组相比,0.2 mg·mL-1染毒组的心血管内皮细胞总NOS和iNOS活力显著增加,而cNOS活力显著降低,并且随着PM25染毒剂量的增加,存在剂量-反应关系.这一结果表明,PM2.5可通过诱导心血管内皮细胞的iNOS活性,对心血管系统产生氧化应激损伤,氧化应激作用可能是PM2.5心血管系统毒性的作用机制之一. 相似文献
864.
M. J. Goodwin R. J. Parkinson E. N. D. Williams J. R. B. Tallowin 《Agriculture, ecosystems & environment》1998,70(2-3)
The seasonal pattern of extractable soil P and soil solution P was determined for topsoil samples taken from a Cirsio-Molinietum fen-meadow community, and also for an adjacent agriculturally improved pasture in Devon, UK. Phosphorus concentration was investigated using three methods during 1993; Olsen's reagent (sodium bicarbonate) for soil P, centrifuging and polymeric suction cups for soil solution P. Solutions were extracted at two-weekly intervals during the spring and at monthly intervals during the summer. Phosphorus removed from both sites by centrifuging was in the range 5–30 μg dm−3 soil, in comparison with 1–6 mg kg−1 for Olsen P. Olsen P on the Cirsio-Molinietum was significantly lower than on the improved pasture in mid-March and mid-June. The concentration of P in soil solution removed by suction cups was below the level of detection (<2 μg dm−3) on the Cirsio-Molinietum. Suction cup P on the improved pasture peaked in April and May at 16–19 μg dm−3 soil. Herbage yield and P concentration were measured throughout the growing season. Above-ground standing crop was greater on the Cirsio-Molinietum than the improved pasture at the beginning of the grazing season, because of the large litter component on the former. Total P content of this material was only 1.81 kg P ha−1 on the Cirsio-Molinietum, in comparison with 5.58 kg P ha−1 on the improved pasture. Phosphorus concentration of plant material obtained by repeated defoliation was approximately 1.0 mg P g−1 DM on the Cirsio-Molinietum, whereas a clear seasonal trend, peaking at 3.5 mg P g−1 DM, was observed on the improved pasture. Phosphorus concentration of litter, grass and sedge from ungrazed plots on the Cirsio-Molinietum indicated distinct seasonal variations for the grass, with no seasonal pattern for the sedge component. 相似文献
865.
866.
酚类化合物的QSAR研究 总被引:7,自引:1,他引:7
直接应用化合物的分子结构式产生的结构描述参量研究了45个酚类化合物的麻醉毒性和分子结构之间的相关性。用多元回归分析和神经网络法建立了相应的数学模型,并用其预测了5个酚类化合物的麻醉毒性。结果表明,所提取的结构参量较好地反映这类化合物的结构特性,而用神经网络法所得结果优于多元回归分析结果。 相似文献
867.
以二恶英类(DIOXINs, DXNs)为代表的十二项物质是在环境中具有高残留性、高生物浓缩性和高生物毒性的物质,即POPs物质(PersistentOrganicPollutants,残留性有机污染物质)。控制和治理POPs物质是我国加入斯德哥尔摩公约后应尽的义务与责任。我国加入WTO后,国内产品若走向世界,二恶英标准的制定与评价是必不可少的,否则我们国家将受到沉重的打击。同时也是保证我国人民身心健康的重要保证。本文主要叙述了二英的毒性、我国现在的污染状况以及我们应该采取的措施。 相似文献
868.
869.
麻痹性贝毒素的毒理效应及检测技术 总被引:8,自引:0,他引:8
近年来世界各地,特别是我国浙江、广东等沿海地区赤潮发生过度频繁,许多赤潮生物分泌的毒素不但使其他海洋生物中毒,更会对人类健康造成潜在的危害。因此对赤潮毒素的研究已成为海洋环境科学研究的重要内容。麻痹性贝毒素是其中重要的一类赤潮藻毒素。它们毒性大,作用强,在全球的分布越来越广泛,并且已经在世界范围内造成了严重的危害,引起了国内外科学家的高度重视。本文详细综述了近年来国外在麻痹性贝毒素检测技术方面最新的研究进展,重点介绍了麻痹性贝毒素的化学结构、前处理技术和分析检测新技术及其毒性作用机理。 相似文献
870.