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101.
Spatial and temporal trends of organic contaminants in sediments along the Korean coast were estimated through a nationwide environmental monitoring program from 2001 to 2007. The concentrations of organic contaminants in sediments along the Korean coast were relatively low or moderate compared with foreign studies. The mean detection frequencies of organic contaminants during the seven years were highest for PAHs and PCDD/Fs, followed by PCBs, DDTs, TBT and HCHs in decreasing order. Based on published sediment quality guidelines, the ecological risks of persistent organic pollutants in sediments along the Korean coast were low, despite exceedances of the ERL at 2-6 sites for DDTs, and the TEL at 9-18 sites for PCDD/Fs. Nonparametric tests to assess temporal trends revealed significant decreasing trends for PCBs and PCDD/Fs at four and three sites, respectively (p < 0.05). These results reflect the effects of regulations on the use of those contaminants. 相似文献
102.
监测自然衰减技术(MNA)是修复地下水土有机污染最经济和有效的方法之一。在自然衰减的评价中,美国主要是从3个方面的证据来揭示自然衰减的发生:污染物质量减少;表征生物降解的地球化学指标的变化;通过微生物降解菌研究为生物降解提供直接证据。本文总结了目前国际上获取自然衰减证据的主要方法:污染物浓度变化趋势统计法、污染物质量守恒和质量通量分析法、溶质运移的解析模型、溶质运移的数值模型、地球化学证据方法、稳定同位素方法和微生物菌群研究等方法。我国在自然衰减评价方面的研究较少。由于自然衰减修复时间较长、修复效率较低,在实际应用中,联合运用强化衰减修复技术和MNA技术成为地下水土治理的主要发展趋势。 相似文献
103.
Low-income informal sector contexts are rife in practices that retain value of materials and goods, but in the academic literature and policy debates these practices are seldom considered as part of the circular economy (CE). This is a major omission in CE discourse, as over 60 percent of the world’s employed population is in the informal sector and many of them make their living from circularity practices. Hence, our paper advances a globally covering understanding of CE by focusing on local practices constituting CE in the overlooked contexts of low-income informal markets of emerging economies, and on the motives behind the practices. To that end we introduce the notion of Necessity-Driven Circular Economy, defined as a set of locally embedded and interlinked formal and informal practices aimed at restoring and retaining the value of goods and materials for as long as possible, based on economic necessity and opportunities for income generation. We substantiate this conceptual work with our empirical findings from low-income urban communities in Brazil, India, and Tanzania. This allows us to capture the essential characteristics of necessity-driven circular economy. These characteristics draw attention to the social and cultural embeddedness and the interweaving of consumption and production in necessity-driven circular economy, as opposed to the dominant techno-economic and industry-focused circular economy conceptualizations that are typical in academic discourse and portray developed country contexts. Finally, we discuss conceptual and practical relevance of necessity-driven circular economy and point out its system-level implications for policymakers and businesses. 相似文献
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Throughout the course of civilization, large rivers have played a major role in transport, water supply and human waste disposal. The pressure on these resources has greatly intensified over this century, but our ecological understanding of this most important class of freshwater environments remains poorly developed. 相似文献
108.
Transformations and hydraulic captures of petrochemical contaminants in a karst-fractured aquifer 总被引:2,自引:0,他引:2
Yudao Chen Xueyu Zhu Xueshun Zhu Yaping Jiang Qinglin Xie 《Environmental Geology》2000,39(11):1304-1308
The development of a petrochemical industry may be responsible for petrochemical contamination of karst-fractured aquifers
in an urban water supply system. In the Dawu Well Field, a karst-fractured aquifer in Zibo City, in the east of China, has
been seriously polluted by petrochemicals from the operation of petrochemical plants. More than 60 species of organic contaminants
have been detected in the water supply wells of the Liuhang-Hougao zone, in the west part of Dawu Well Field. Investigations
indicate that contaminants are transported from the petrochemical plants to the karst-fractured aquifer along karst fractures
and the Jinling Fault. In the groundwater, concentrations of pollutants vary with depth. Concentrations are greater with depth
because of the transmissibility of the Jinling fault. The local convective flow field has a significant influence on transportation
of contaminants. Hydraulic barriers can prevent the transportation of contaminants and they can be removed by extraction.
Received: 22 October 1999 · Accepted: 14 February 2000 相似文献
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在考虑对流弥散、平衡/非平衡双点吸附解吸、微生物降解等情况下,建立了土壤环境中有机污染物迁移转化的动力学模型,并给出了有限差分解。在此模型的基础上,详细讨论了有机污染物在土壤中的分布规律,并对一阶吸附解吸速率常数 和平衡吸附点位所占总点位的比例 进行了灵敏度分析。分析研究表明:参数 对于土壤中有机污染物浓度分布有着重要的影响,其影响程度又与非平衡吸附点位所占总点位的比例(1- )有关;污染后期土壤吸附相的存在,也会起到增加土壤水溶质浓度的作用,且 越大,这种作用越明显。 相似文献