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561.
This is a study of the scientific component of an effort to restore an urban river by removing a low-head dam. The Secor Dam
is owned by a local government entity near Toledo, Ohio. The proposed removal of the last structure impeding flow on the Ottawa
River has broad appeal, but the owner is concerned about liability issues, particularly potential changes to the flood regime,
the presence of contaminated sediments behind the dam, and possible downstream transport of reservoir sediments. Assessing
sediment contamination involved sediment sampling and analysis of trace metals and organic contaminants. Forecasting sediment
transport involved field methods to determine the volume and textural properties of reservoir and upstream sediment and calculations
to determine the fate of reservoir sediments. Forecasting changes in the flood regime involved HEC-RAS hydrological models
to determine before and after dam removal flood scenarios using LiDAR data imported into an ArcGIS database. The resulting
assessment found potential sediment contamination to be minor, and modeling showed that the removal of the dam would have
minimal impacts on sediment transport and flood hazards. Based on the assessment, the removal of the dam has been approved
by its owners. 相似文献
562.
Xiao Zhong Wenjun Zhang Tingting Li Jiayi Tang Xiaoli Liu Yuhang Liu 《环境科学学报(英文版)》2022,34(11):199-210
Chiral pesticides account for 30% of pesticides. Pesticides are inevitably leached into the groundwater by runoff. At the watershed level, the distribution characteristics of enantiomers in sediments collected from the river network of an agricultural area near the middle and lower reaches of the Yangtze River were tested, and their potential correlations with the physicochemical properties and microbial communities of the sediments were analyzed. The sediment pollution was serious at sites 8 and 9, with their pollution source possibly being agricultural or industrial sewage. Moreover, there were higher cumulative contents of pesticide residues at sites 4, 8, and 9. Specifically, Cycloxaprid was the most detected chiral pesticide in the study area, followed by Dinotefuran and Diclofop-methyl. Additionally, Ethiprole and Difenoconazole had strong enantioselectivity in the study area. Interestingly, the enantiomers of some chiral pesticides, such as Tebuconazole, had completely different distributions at different sites. Pearson correlation analysis showed that sediment catalase and microbial biomass carbon were important factors for enantioselectivity of chiral pesticides. The effect of sediment physicochemical properties on enantioselective distribution was achieved by influencing the microorganisms in the sediment. Furthermore, the enantioselective distribution of Tebuconazole was closely related to the genus Arenimonas. Overall, the enantioselective distribution of most of the chiral pesticides was positively correlated with the prokaryotic microbial community. This study provides empirical support for agricultural non-point source pollution caused by chiral pesticides, and also lays a research foundation for exploring the factors that affect the fate of chiral pesticides in the environment. 相似文献
563.
Quantifying sediment-associated metal dispersal using Pb isotopes: Application of binary and multivariate mixing models at the catchment-scale 总被引:1,自引:0,他引:1
Graham Bird Paul A. Brewer Mariyana Nikolova Mihail Mollov 《Environmental pollution (Barking, Essex : 1987)》2010,158(6):2158-2169
In this study Pb isotope signatures were used to identify the provenance of contaminant metals and establish patterns of downstream sediment dispersal within the River Maritsa catchment, which is impacted by the mining of polymetallic ores. A two-fold modelling approach was undertaken to quantify sediment-associated metal delivery to the Maritsa catchment; employing binary mixing models in tributary systems and a composite fingerprinting and mixing model approach in the wider Maritsa catchment. Composite fingerprints were determined using Pb isotopic and multi-element geochemical data to characterize sediments delivered from tributary catchments. Application of a mixing model allowed a quantification of the percentage contribution of tributary catchments to the sediment load of the River Maritsa. Sediment delivery from tributaries directly affected by mining activity contributes 42-63% to the sediment load of the River Maritsa, with best-fit regression relationships indicating that sediments originating from mining-affected tributaries are being dispersed over 200 km downstream. 相似文献
564.
Flood control failure: San Lorenzo River,California 总被引:2,自引:0,他引:2
The San Lorenzo River on the central California coast was the site of a major US Army Corps of Engineers flood control project in 1959. By excavating the channel below its natural grade and constructing levees, the capacity of the river was increased in order to contain approximately the 100 year flood. Production and transport of large volumes of sediment from the river's urbanizing watershed has filled the flood control project with sand and silt. The natural gradient has been re-established, and flood protection has been reduced to containment of perhaps the 30 year flood. In order for the City of Santa Cruz, which is situated on the flood plain, to be protected from future flooding,it must either initiate an expensive annual dredging program, or replan and rebuild the inadequately designed flood control channel. It has become clear, here and elsewhere, that the problem of flooding cannot simply be resolved by engineering. Large flood control projects provide a false sense of security and commonly produce unexpected channel changes. 相似文献
565.
Richard Lowrance Lee S. Altier J. Denis Newbold Ronald R. Schnabel Peter M. Groffman Judith M. Denver David L. Correll J. Wendell Gilliam James L. Robinson Russell B. Brinsfield Kenneth W. Staver William Lucas Albert H. Todd 《Environmental management》1997,21(5):687-712
/ Maryland, Virginia, and Pennsylvania, USA, have agreed to reduce nutrient loadings to Chesapeake Bay by 40% by the year 2000. This requires control of nonpoint sources of nutrients, much of which comes from agriculture. Riparian forest buffer systems (RFBS) provide effective control of nonpoint source (NPS) pollution in some types of agricultural watersheds. Control of NPS pollution is dependent on the type of pollutant and the hydrologic connection between pollution sources, the RFBS, and the stream. Water quality improvements are most likely in areas of where most of the excess precipitation moves across, in, or near the root zone of the RFBS. In areas such as the Inner Coastal Plain and Piedmont watersheds with thin soils, RFBS should retain 50%-90% of the total loading of nitrate in shallow groundwater, sediment in surface runoff, and total N in both surface runoff and groundwater. Retention of phosphorus is generally much less. In regions with deeper soils and/or greater regional groundwater recharge (such as parts of the Piedmont and the Valley and Ridge), RFBS water quality improvements are probably much less. The expected levels of pollutant control by RFBS are identified for each of nine physiographic provinces of the Chesapeake Bay Watershed. Issues related to of establishment, sustainability, and management are also discussed.KEY WORDS: Riparian forest buffers; Chesapeake Bay; Nonpoint source pollution; Nitrogen; Phosphorus; Sediment 相似文献
566.
底泥中多环芳烃的处理技术进展 总被引:3,自引:0,他引:3
底泥中多环芳烃(PAHs)的处理方法主要有物化处理和生物处理。物化处理方法有湿式空气氧化、溶剂浸提、热解吸等;生物处理有好氧处理和厌氧处理。物化处理速度快、效果明显,但能耗高、投资大;生物处理方法虽然能耗低,但速度慢、降解率较低。实际运用中宜发展物化和生物的组合工艺。 相似文献
567.
Polychlorinated organic compounds in Yangtse River sediments 总被引:7,自引:0,他引:7
Polychlorinated organic compounds (PCOCs) were analyzed in Yangtse River sediments. The results show that the concentrations of PCOCs in Yangtse River sediments followed the order of DDTs > HCB > HCHs > PCBs. High PCOCs concentrations were detected in sediments from station Y02a and Y02b, which are located in the main input of the Yangtse River (Nanjing section). Results also show that the PCOCs values were highly correlated with organic carbon content and heavy metal contamination. 相似文献
568.
Laboratory experiments were carried out to study the influence of temperature (24, 28 and 30 °C) and pH (1–10) on organic mercury (CH3HgCl) transfer and accumulation in an experimental ecotoxicological model. We followed the evolution of CH3HgCl in a basic model (water+air) by varying temperature and pH. In a second step, we completed the model by adding sediment and fish. We added CH3HgCl to water at the beginning of each experiment which was repeated at least three times. Results demonstrated that mercury was released from methylmercury into the air regardless of water pH and its concentration in the air increased with increasing pH. By contrast, in presence of sediment, almost all the mercury was fixed onto the sediment and no mercury was traced in air or in water. Interestingly, in the presence of sediment, the life span of fish under methylmercury exposure lasted longer despite their higher mercury body level content at their death. These results indicate that water is a bad exposure indicator for aquatic pollution. In case of chronic pollution, sediments, fish and aquatic plants are more appropriate indicators. 相似文献
569.
河流泥沙吸附石油的实验研究 总被引:1,自引:0,他引:1
研究河流中的泥沙对石油的吸附和解吸规律对建立水质数学模型及水质预测预报具有重要意义,可为水域石油污染的治理提供依据。本文根据静态实验研究成果,建立了通用的吸附反应方程,在水槽中进行了均匀输沙吸附实验,并用解析解进行计算与动态实验结果进行比较,其结果较为理想。最后对河流底沙的吸附进行了初步探讨,分析了石油向底沙层扩散的过程。 相似文献
570.