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排序方式: 共有106条查询结果,搜索用时 15 毫秒
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应用水质模型方法研究河流污染控制 总被引:6,自引:1,他引:6
应用水质模型对河流污染控制进行研究,经济、方便、有效。讨论了水质模型方法的原理、必然性、种类、建立步骤和应用范围,并以黄浦江为例,对水质模型的建立与应用进行了说明。 相似文献
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思茅地区乡镇企业的发展迅速,污染物排放剧增,与1989年相比,1995年的废水,废气和固体废排放量分别增加了439.5%、26.65%和16.62%,给当地环境带带来不利影响。为此,必须集中布局,优化产品,加强领导,加大科技投入,走可持续发展之路。 相似文献
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按提供产品的类别,乡镇尺度空间由生态空间、农业空间和建设空间组成,这3部分空间共同承载着乡镇社会经济发展的重任。坚持生态保护对发展的约束与支撑功能并存的理念,建立以生态约束为前提,并与开发建设协同推进的分区指标体系、技术方法及应用模式,是生态文明战略下空间功能分区的有益探讨。以南京市六合区雄州街道为案例,借助Arc GIS空间分析工具,采用互斥性矩阵分类法,通过对生态约束、农业发展、工业发展与人居环境等建设开发适宜性的单项与综合评价的集成,构建生态、农业和建设空间布局的总体架构,实现了街镇空间功能的整合与科学定位;划分禁止建设区、限制建设区、适宜建设区和已建设区等四大类功能区,并提出各功能区的生态环境保护措施与产业发展导向,为实施区域发展与生态保护的协同推进提供了依据。 相似文献
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Zheng J Wu F Yamada M Liao H Liu C Wan G 《Environmental pollution (Barking, Essex : 1987)》2008,152(2):314-321
Studies on the distribution and isotope compositions of fallout Pu are important for source characterization of possible future non-fallout Pu contamination in aquatic environments, and useful for dating of recent sediments to understand the pollution history of environmental contaminants. We present the historical record of atmospheric Pu fallout reconstructed from a sediment core from Lake Hongfeng, China. The Pu activity profile was in agreement with the 137Cs profile. Inventories were 50.7 Bq m(-2) for 239+240Pu and 1586 Bq m(-2) for 137Cs. The average 240Pu/239Pu atom ratio was 0.185+/-0.009, indicating that Pu originated from global stratospheric fallout rather than from direct tropospheric or close-in fallout from the Chinese nuclear testing conducted in the 1970s. Our data suggested that Lake Hongfeng would be an ideal setting for monitoring atmospheric fallout and environmental changes in this region. 相似文献
7.
To study the Pu concentration and isotope ratio distributions present in China, the 239+240Pu total activities and 240Pu/239Pu atom ratios in core soil samples from Hubei Province in central China were investigated using Accelerator Mass Spectrometry (AMS). The activities ranged from 0.019 to 0.502 mBq g−1 and the 239+240Pu inventories of 45 and ∼55 Bq m−2 agree well with that expected from global fallout. The 240Pu/239Pu atom ratios in the soil ranged from 0.172 to 0.220. The ratios are similar to typical global fallout values. Hence, any close-in fallout contribution from the Chinese nuclear weapons tests, mainly conducted in the 1970s, must have either been negligible or had a similar 240Pu/239Pu ratio to that of global fallout. The top 10 cm layer of the soil contributes ∼90% of the total inventory and the maximum concentrations appeared in the 2-4 cm or 4-6 cm layers. It is suggested that climatic conditions and organic content are the two main factors that affect the vertical migration of plutonium in soil. 相似文献
8.
Characterization of plutonium in deep-sea sediments of the Sulu and South China Seas 总被引:1,自引:0,他引:1
Wei Dong Jian Zheng Qiuju Guo Shaoming Pan 《Journal of environmental radioactivity》2010,101(8):622-1899
Anthropogenic Pu isotopes are important geochemical tracers for sediment studies. Their distributions and sources in the water columns as well as the sediments of the North Pacific have been intensively studied; however, information about Pu in the Southeast Asian seas is limited. To study the isotopic composition of Pu, and thus to identify its sources, we collected sediment core samples in the South China Sea and the Sulu Sea during the KH-96-5 Cruise of the R/V Hakuho Maru. We analysed the activities of 239+240Pu and the atom ratios of 240Pu/239Pu using isotope dilution sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS). The 240Pu/239Pu atom ratios in the sediments of both areas (inventory weighted mean: 0.251 for the South China Sea and 0.280 for the Sulu Sea) were higher than the global fallout value (0.178 ± 0.019), suggesting the existence of Pu from the Pacific Proving Grounds in the North Pacific. Low inventories of 239+240Pu in sediments were observed in the South China Sea (3.75 Bq/m2) and the Sulu Sea (1.38 Bq/m2). Most of the Pu input is still present in the water column. Scavenging and benthic mixing processes were considered to be the main processes controlling the distribution of Pu in the deep-sea sediments of both study areas. 相似文献
9.
S.M. Pan S.G. TimsX.Y. Liu L.K. Fifield 《Journal of environmental radioactivity》2011,102(10):930-936
A sediment core collected from the sub-aqueous delta of the Yangtze River estuary was subjected to analyses of 137Cs and plutonium (Pu) isotopes. The 137Cs was measured using γ-spectrometry at the laboratories at the Nanjing University and Pu isotopes were determined with Accelerator Mass Spectrometry (AMS), measurements made at the Australian National University. The results show considerable structure in the depth concentration profiles of the 137Cs and 239+240Pu. The shape of the vertical 137Cs distribution in the sediment core was similar to that of the Pu. The maximum 137Cs and 239+240Pu concentrations were 16.21 ± 0.95 mBq/g and 0.716 ± 0.030 mBq/g, respectively, and appear at same depth. The average 240Pu/239Pu atom ratio was 0.238 ± 0.007 in the sediment core, slightly higher than the average global fallout value. The changes in the 240Pu/239Pu atom ratios in the sediment core indicate the presence of at least two different Pu sources, i.e., global fallout and another source, most likely close-in fallout from the Pacific Proving Grounds (PPG) in the Marshall Islands, and suggest the possibility that Pu isotopes are useful as a geochronological tool for coastal sediment studies. The 137Cs and 239+240Pu inventories were estimated to be 7100 ± 1200 Bq/m2 and 407 ± 27 Bq/m2, respectively. Approximately 40% of the 239+240Pu inventory originated from the PPG close-in fallout and about 50% has derived from land-origin global fallout transported to the estuary by the river. This study confirms that AMS is a useful tool to measure 240Pu/239Pu atom ratio and can provide valuable information on sedimentary processes in the coastal environment. 相似文献
10.
Oikawa S Watabe T Inatomi N Isoyama N Misonoo J Suzuki C Nakahara M Nakamura R Morizono S Fujii S Hara T Kido K 《Journal of environmental radioactivity》2011,102(3):302-310
A radioactivity survey was launched in 1991 to determine the background levels of 239+240Pu in the marine environment off a commercial spent nuclear fuel reprocessing plant before full operation of the facility. Particular attention was focused on the 240Pu/239Pu atom ratio in seawater and bottom sediment to identify the origins of Pu isotopes. The concentration of 239+240Pu was almost uniform in surface water, decreasing slowly over time. Conversely, the 239+240Pu concentration varied markedly in the bottom water and was dependent upon the sampling point, with higher concentrations of 239+240Pu observed in the bottom water sample at sampling points having greater depth. The 240Pu/239Pu atom ratio in the seawater and sediment samples was higher than that of global fallout Pu, and comparable with the data in the other sea area around Japan which has likely been affected by close-in fallout Pu originating from the Pacific Proving Grounds. The 240Pu/239Pu atom ratio in bottom sediment samples decreased with sea depth. The land-originated Pu is not considered as the reason of the increasing 239+240Pu concentration and also decreasing the 240Pu/239Pu atom ratio with sea depth, and further study is required to clarify it. 相似文献