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401.
Altitude dependence of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in surface soil from Tibetan Plateau, China 总被引:5,自引:0,他引:5
Pu Wang Qinghua Zhang Yawei Wang Thanh Wang Xiaomin Li Yingming Li Lei Ding Guibin Jiang 《Chemosphere》2009,76(11):1498-1504
Remote mountain areas besides high latitude regions are beginning to receive increased attention in studying the transport and behavior of persistent organic pollutants (POPs). In the present work, surface soil samples were collected from the Tibetan Plateau, the highest plateau in the world which includes the northern slope of Mt. Qomolangma, to investigate the levels and trends of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) along the altitudinal gradient. The average PCB and PBDE concentrations were 185.6 ng kg−1 dry weight (dw) (range 47.1–422.6 ng kg−1 dw) and 11.1 ng kg−1 dw (range 4.3–34.9 ng kg−1 dw), respectively. Regression analysis between the log-transformed TOC-normalized concentrations and the altitudes of the sampling sites showed two opposite trends with regard to altitude dependence: negative relationship with altitude below about 4500 m followed by a positive altitude dependence above this point. Considering minimum anthropogenic activities and very sparse precipitation in the north of Himalayas, the trends above 4500 m imply that the significant altitude dependence of these two groups of POPs were irrespective of pollution sources, but could be predicted by the global distillation effect involving cold condensation in high altitude mountain areas. Increasing levels of heavier congeners were found in higher altitude sites, although the lighter congeners were the main contributors to the total amount, suggesting that less volatile congeners seem to become enriched easier than those more volatile at higher altitudes in this region. 相似文献
402.
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404.
本文主要论述了"全寿命周期模式"这一当今各国水污染防治从末端走向起始,从集中走向集中与分散相结合的最新趋势,并结合宁夏水资源缺乏、经济基础薄弱的特殊情况,对当地水污染防治提出了相关对策. 相似文献
405.
A series of simulations under weakly to moderately stable boundary layers (SBLs) have been performed using the proposed subgrid-scale (SGS) model implemented into the Terminal Area Simulation System (TASS). The proposed SGS model incorporates some aspects of the two-part eddy viscosity SGS model of Sullivan et al. (1994) and further refinements which include the dependence of SGS mixing length on stratification, two-part separation of the SGS eddy diffusivity of heat, and more realistic empirical forms of Monin–Obukhov similarity functions. The potential temperature profiles from simulations clearly show a three-layer structure: a stable surface layer of strong gradients, a middle layer of small gradients, and an inversion layer on the top. The wind speed profiles show the formation of low level jet (LLJ). However, the sub-layer structures under moderately SBLs differ from those under weakly SBLs. Both the momentum and heat fluxes decrease almost linearly in the lower part of the SBL. The near surface values of the normalized turbulent kinetic energy (TKE/u
*
2) in all simulations are about 4 which is much less than the typical value of 5.5 under the neutral condition. The decay of turbulence first occurs in the area with large values of Richardson number (R
i<0.2). Generally, instantaneous values of the TKE and R
i at the various grid points are negatively correlated, but there is not a unique relationship between the two parameters. 相似文献
406.
407.
Alachlor has been widely used in agriculture all over the world. It is suggested that it may be a carcinogen and also an environmental estrogen. In this paper, the physiological and biochemical perturbations of crucian carp (Carassius auratus) exposed to alachlor at different concentrations over 60 days were investigated. The gonadosomatic index (GSI) and hepatosomatic index (HSI) were measured. The activity of hepatic antioxidant defense and detoxifying enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) and the content of glutathione (GSH) were determined and compared with the control group. The result showed that GSI and HSI decreased significantly (P<0.05) in almost all treatments. The activities of SOD, CAT and GST were induced continuously (P<0.05), while the content of reduced glutathione (GSH) was inhibited on the whole. These changes reflect that the antioxidant systems of the tested fishes were affected. The possible defense mechanistic implications about the changes were thus discussed. Furthermore, hepatic SOD and GST were sensitive to alachlor at low concentration, indicating that they might be potential biomarkers in early detection of alachlor contamination in aquatic ecosystems. 相似文献
408.
比较研究了β-环糊精(β-CD)对3株黄孢原毛平革菌(Phanerochaete chrysosporium)CGMCC5.776、GIM3.383和GIM3.393产锰过氧化物酶(MnP)和降解多环芳烃(PAHs)的影响.结果表明:3株菌都能分泌出高活性的MnP,β-CD能显著提高MnP的活性.加入2.0 g/Lβ-CD的体系培养到第12天时.酶活性最高达到2 912.5 U/L;而且β-CD能显著提高PAHs的降解率,两者之间存在较好的相关性.加入1.0 g/L β-CD的体系对比不加β-CD的体系,PAHs的降解率提高了1~2倍.PAHs的降解同时受到MnP活性、PAHs表观溶解度和分子结构稳定性等因素的影响. 相似文献
409.
分析了认证企业在建立环境目标、指标和管理方案中存在问题,提出了改进对策。 相似文献
410.