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991.
Kazuhiro Sonoda J. Alan. Yeakley Christopher E. Walker 《Journal of the American Water Resources Association》2001,37(6):1517-1532
ABSTRACT: We investigated spatial and temporal relationships among surface and subsurface watershed attributes and stream nutrient concentrations in urbanizing Johnson Creek watershed in northern Oregon. We sampled stream water at eight urban and five nonurban locations from March 1998 through December 1999. We sampled eight wells distributed over the two primary aquifers in the watershed. Using a Geographic Information System (GIS), percentages of landuse attributes within a radius of 30, 91, and 152 m from each sample site were quantified. We analyzed relationships between (1) nutrient concentrations and percentage cover of different landuse attributes, and (2) nutrient concentrations and underlying hydrologic units. We did not find a significant relationship between ground water chemistry and stream water chemistry. We found elevated levels of phosphorus (P) concentrations correlated with urban landuse, while higher nitrogen (N) concentrations were correlated with nonurban (primarily agricultural) landuse. We concluded that elevated levels of N in nonurban areas of Johnson Creek watershed were associated with agricultural practices. We further concluded that urban development factors such as increases in storm drains, dry wells, and impermeable surfaces may be responsible for higher input of P to the stream in urbanizing areas of the Johnson Creek watershed. 相似文献
992.
The Lagoon Olho d'Água in Pernambuco State, Northeast Brazil has received increasing environmental concern due to significant stress from pollution in the catchment. The existing environmental problems are the result of great pressure from a broad range of human activities, especially in the last 10 years. Serious pollution exists mainly from some industrial and urban activities, which increased intensively after the eighties. There is a strong social and economical pressure for housing and construction near the lagoon, due to the available land nearby beaches and estuarine zone, and recently by growing tourism activities. Uncontrolled land use by low-income communities and the pressure for construction by developers have led to landfilling and to deterioration of water quality in the lagoon catchment. Improvement of the environmental conditions in the catchment needs integrated measures. Guidelines and some specific actions involving several institutions have been established and refer to sanitation and urban infrastructure as the main priorities. A main target is the construction of low-cost sewage system with smaller and decentralised treatment plants. 相似文献
993.
The cause-and-effect relationships existing in freshwater biogeocenoses and changing with time are conventionally divided into three groups: direct, directly mediated, and indirect. The possibility of using the indirect relationships for the control over natural systems is exemplified by a new scheme of eutrophication control and water quality improvement. 相似文献
994.
工业废水厌氧生物处理中的无机和有机毒性物质 总被引:7,自引:0,他引:7
介绍了有关工业废水厌氧生物处理中无机和有机毒性物质方面的重要研究成果。工业废水中的毒性物质一般会对甲烷菌产生可逆性抑制,驯化能够减轻或消除毒性物质对甲烷菌的抑制作用,厌氧工艺在适当条件下能够有效地去除工业废水中的多种毒性物质。 相似文献
995.
996.
浙北水稻主产区田间土-水磷素流失潜能 总被引:20,自引:4,他引:16
选取嘉善、余姚、德清、余杭 4个具有代表性浙北水稻主产区 ,研究了水田土 水磷素流失潜能及环境意义 .4稻区高水平磷肥投入促进了土壤富磷化 ,土壤Olsen-P积累的同时 ,相应地提高了土壤生物性有效磷、水浸提磷 ,并提高了土壤磷素的流失潜能 .稻区土壤在富磷化过程中 ,存在着土壤磷素的农学意义向环境意义方向演变的趋势 .在非植稻期 ,稻区农田水体 ,包括沟渠水、田表水、排渠水、暗管排水等总磷 (TP)平均超过了易诱发水体富营养化临界值 ,其中溶解磷 (DRP)占总磷 40% ;主要是源于绿肥田表水及部分排渠中的溶解磷对稻区外水体构成了直接危害 .在非植稻期 ,因稻区间农耕措施的差异导致了土壤富磷水平与对应田表水磷素水平不具相关性 ;在植稻期 ,施磷措施促进水田土壤富磷 ,相应地提高了田表水磷素水平 . 相似文献
997.
麦草畏除草剂厌氧降解可生化性测定 总被引:1,自引:1,他引:0
苯环由14C标记合成的麦草畏除草剂,厌氧降解反应至第7天,转化率达64%,有14C标记的CO2产生;第16天,转化率达91%,出现一种主要的中间代谢产物,有CH4产生;第27天,转化率达95%,仍然只有一种主要的中间代谢产物.麦草畏苯环的断裂量仅占总量的2.96%,转化成CO2的为0.74%,转化成CH4的为0.11%.在降解27d中,主要中间代谢产物是3,6-二氯水杨酸,占麦草畏总量的92.04%.3,6-二氯水杨酸的苯环没有被打开,可生化性极低,仍然继续污染环境研究结果为控制麦草畏对人体健康危害,进行生物修复工程,提供了重要的参考依据. 相似文献
998.
999.
1000.
Gregory M. Clark David K. Mueller M. Alisa Mast 《Journal of the American Water Resources Association》2000,36(4):849-860
ABSTRACT: Data from 85 sites across the United States were used to estimate concentrations and yields of selected nutrients in streams draining relatively undeveloped basins. Flow‐weighted concentrations during 1990–1995 were generally low with median basin concentrations of 0.020, 0.087, 0.26, 0.010, and 0.022 milligrams per liter (mg/L) for ammonia as N, nitrate as N, total nitrogen, orthophosphate as P, and total phosphorus, respectively. The flow‐weighted concentration of nitrate exceeded 0.6 mg/L in only three basins. Total nitrogen exceeded 1 mg/L in only four basins, and total phosphorus exceeded 0.1 mg/L in only four basins. The median annual basin yield of ammonia as N, nitrate as N, total nitrogen, orthophosphate as P, and total phosphorus was 8.1, 26, 86, 2.8, and 8.5 kilograms per square kilometer, respectively. Concentrations and yields of nitrate tended to be highest in northeastern and mid‐Atlantic coastal states and correlated well with areas of high atmospheric nitrogen deposition. Concentrations and yields of total nitrogen were highest in the southeastern part of the nation and in parts of the upper Midwest. In the northeast, nitrate was generally the predominant form of nitrogen, and in the southeast and parts of the upper Midwest, organic nitrogen was the dominant form. Concentrations of total phosphorus were generally highest in the Rocky Mountain and Central Plain states. 相似文献