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41.
北京市周边地区河道污染现状分析 总被引:1,自引:1,他引:0
北京市周边水环境污染日益严重,已经成为遏制本地区经济和社会发展的瓶颈。通过详细调查北京市周边地区主要河流的水质状况,从时间、空间的角度分析了河流水质的变化规律。分析发现:(1)污水收集管网的雨污合流以及初雨带来的面源污染严重影响了丰水期的水质,故丰水期的水质较枯水期差。(2)北京奥运会之后,许多关闭的企业相继开张排放污水,导致河流水质迅速变差,另外奥运旅游转为农家乐休闲自助游,也带来了较为严重的水质污染。(3)10个监测点的水质状况不达标率超过60%,已经成为河道水质治理和改善的重点关注对象。研究表明,河流非点源污染对河流水质影响日显突出;点源污染与产业结构及发展模式具有非常重要的正相关性,故合理调整该地区的产业结构和发展模式已势在必行。 相似文献
42.
An index system for evaluation of technologies for urban river rehabilitation was proposed and discussed. The index system includes indicators of cost, resources, environmental improvement, and social effects. The calculation method for an objective value of each index based on its attributes and weights was presented. The Foshan Channel, which is a seriously polluted, black and malodorous urban river in Foshan City, China, was selected as a case study. The values of the attributes and the weights of the indices for the Foshan Channel were determined. The technologies for the rehabilitation of the Foshan Channel were evaluated based on this index system. Finally, a rehabilitation scheme for the Foshan Channel was proposed. 相似文献
43.
Wyzga B 《Environmental management》2001,28(3):341-358
River engineers use sediment transport formulas to design regulated channels in which the river's ability to transport bedload
would remain in equilibrium with the delivery of materials from upstream. In gravel-bed rivers, a number of factors distort
the simple relationship between particle size and hydraulic parameters at the threshold of sediment motion, inherent in the
formulas. This may lead to significant errors in predicting the bedload transport rates in such streams and hence to instability
of their regulated channels. The failure to recognize a nonstationary river regime may also result in unsuccessful channelization.
Rapid channel incision has followed channelization of the main rivers of the Polish Carpathians in the 20th century. A case
study of the Raba River shows that incision has resulted from the increase in stream power caused by channelization and the
simultaneous reduction in sediment supply due to variations in basin management and a change in flood hydrographs. Calculations
of bedload transport in the river by the Meyer-Peter and Müller formula are shown to have resulted in unrealistic estimates,
perhaps because the different degree of bed armoring in particular cross-sections was neglected. It would have been possible
to avoid improper channelization if the decreasing trend in sediment load of the Carpathian rivers had been recognized on
the basis of geomorphological and sedimentological studies. Allowing the rivers to increase their sinuosity, wherever possible
without an erosional threat to property and infrastructure, and preventing further in-stream gravel mining are postulated
in order to arrest channel incision and reestablish the conditions for water and sediment storage on the floodplains. 相似文献
44.
Burchard H. Heede 《Environmental management》1991,15(2):251-255
Timber was harvested on South Fork of Thomas Creek, White Mountains of Arizona, USA, for the first time in 1978–1979. This
caused significant increases in annual flow volumes and annual instantaneous peak flows. North Fork remained untouched, but
both streams were in disequilibrium before harvest time. Due to wetter years during the postharvest period, North Fork also
experienced some flow increases, but the difference was not significant. Flow increases cause increased erosion in disequilibrium
channels. While in South Fork channel cross sections enlarged by 10% since preharvest time, those in North Fork enlarged by
only 2.5%. The number of knickpoints tripled in South Fork, which was about double that in North Fork. Knickpoint development
resulted in destruction of the natural control structures (log steps and transverse gravel bars) in South Fork (47%), while
in North Fork they increased by 23%. Knickpoints are scarps on the channel bed that have the appearance of gully headcuts.
The tripling of the number of knickpoints signifies that adjustment processes of the bed profile are intensified drastically
in South Fork. The geomorphic changes signify that due to increases in discharge, the extent of disequilibrium is exacerbated
in South Fork. Yet, volumes of erosion are relatively small, as will be sediment volumes leaving the watershed at a given
time, because of the stepwise sediment transport occurring in this ephemeral stream. 相似文献
45.
武汉市沙湖港富营养化状况分析与评价 总被引:2,自引:2,他引:0
根据2007年6月~2008年6月对武汉市沙湖港的水质监测,探讨了沙湖港水质变化特征和富营养化水平。结果表明:沙湖港DO一般在0~2.5mg/L范围内,为缺氧性环境。除硝酸盐氮未超标,氨氮、总氮和总磷均超标。根据地表水环境质量标准(GB3838-2002)中Ⅳ类标准,在各监测点的超标率,总磷均为100%,氨氮分别为86%、95%、100%、100%,总氮分别为90%、95%、95%、95%。总磷平均浓度大于0.660mg/L,为极富营养状态;总氮平均浓度大于4.60mg/L,为极富营养状态。丰水期流量大,氨氮、硝酸盐氮、总磷浓度低于枯水期和平水期。汇入沙湖港的东湖港对氨氮、总磷贡献较大,氨氮浓度偏高,最高达18.30mg/L。总氮是主要污染物,污染指数范围9.49~1.39。氮是沙湖港水体富营养化的限制因素,建议重点控制氮的含量。 相似文献
46.
探讨了通过气相色谱仪双通道检测室内空气中总挥发性有机化合物的可行性.建立了前、后双通道的苯、甲苯、乙酸丁酯、乙苯、苯乙烯、对(间)二甲苯、邻二甲苯、正十一烷等9种典型有机污染物的外标曲线,各组分相关系数R2为0.9995~1,并通过各自的标准曲线来计算其标样考核结果,对比标样真实浓度值,验证前、后双通道的准确性以及相互... 相似文献
47.
Françoise Henry Céline Mahfouz Alice Delegrange Lucie Courcot 《Chemistry and Ecology》2017,33(4):271-280
Mercury (Hg) in fish can present a potential risk to wildlife and human consumers. Mercury levels were determined in 12 fish species and 2 invertebrate species from the French coast of the Eastern English Channel collected in June and November 2012. Total mercury concentrations in the muscle tissues ranged between 0.04 and 1.63 µg g-1 (d.w.). Dab and sandeel displayed a significant positive correlation between Hg concentrations and fish length. Seasonal differences in Hg concentrations were observed for dab and shrimp. The lesser weever showed significantly higher concentrations of Hg (0.97 ± 0.34 µg g-1 d. w.) than all other species. Gobies and sprat, which had the smallest size, showed significantly lower concentrations than herring, whiting, pout and sardine. Among the considered species, flatfish such as dab, flounder, plaice and sole displayed intermediate levels of Hg. In the present study, the fish age expressed as specimen length seems to be one of the major factors governing Hg contents in muscle tissues. Finally, mercury concentrations in commercial fish from the Eastern English Channel were below the levels fixed by the European Union for total mercury in edible parts of fish products. 相似文献
48.
49.
The Kings Cross/St. Pancras area has been a rail transport hub from Central London to the Midlands and North Eastern England
since the middle of the nineteenth century and dust from the Kings Cross railway lands was even described by Charles Dickens.1 The Channel Tunnel high speed Rail Link (CTRL) is being constructed between 2001 and 2007 to connect continental Europe to
Central London. The CTRL and associated development will help regenerate an area that is surrounded by deprived high density
housing estates. London Borough of Camden has set up an extensive particulate monitoring programme to determine if there are
any health impacts on local residents from emissions from the demolition and construction work. This article assesses the
results from particulate measurements in 2003–2004 and compares this to baseline conditions before the redevelopment work
began. The evidence suggests that although 2003 had higher than average pollution levels in the UK as a whole, even higher
levels of particulates in the size range PM10–PM2.5 (defined as PMcoarse) were measured in Kings Cross. Due to the size of these particulates, they tend to be released from construction works rather
than transport or secondary particulate sources. Concentrations in 2004 were lower than 2003, but this was primarily due to
meteorological conditions. The paper also looks at the health of the local population and discusses whether these elevated
levels are creating a problem and legally constitute a statutory nuisance. The Council continues to work with the contractors
to try and ensure best practical means to minimise dust emissions and their effect on local residents.
1Our Mutual Friend 相似文献
50.