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931.
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
932.
大渡河上游地区景观格局与动态 总被引:38,自引:1,他引:37
利用卫星遥感资料,对大渡河上游地区金川、壤塘、马尔康三县18665km2土地的景观格局与动态进行分析。结果显示,1995~2000年,研究地区的景观破碎化程度有所下降,多样性增加,斑块形状不规则性增强。整个景观表现出以草地为基质,以林地变动为主要特征。5年间,有林地面积减少53687hm2,大部分转变为灌木林地和疏林地。有林地的空间动态,如斑块密度下降,形状趋于规则等,显示该地区森林减少主要是有计划采伐的结果。耕地面积的下降则表明当地退耕还林、还草的政策措施已初见成效。 相似文献
933.
934.
青藏铁路景观视觉管理系统研究 总被引:8,自引:0,他引:8
铁路建设需要设置取(弃)土场、砂石料点、施工营地等工程场地,这些工程场地如果设计不合理,必将对沿线景观造成破坏,进而对视觉产生强烈的冲击。该文参考美国林务局的“视觉管理系统(VisualManagementSystem,VMS)”和美国土地管理局的“视觉管理(VisualResourcesMana-gement,VRM)”,利用遥感(RS)和地理信息系统(GIS)技术,结合新建青藏铁路沿线景观特点和工程场地的位置、面积、所处的坡度、相对于铁路的距离、沿铁路方向的长度以及相对于本底景观的对比度,建立了新建青藏铁路沿线的景观视觉管理系统,定量分析和评价了铁路建设工程可能对高原景观带来的冲击,并为修改和重新设计工程场地提出了指导性建议。 相似文献
935.
岷江上游生态环境建设与经济可持续发展 总被引:12,自引:1,他引:11
岷江上游生态环境问题严重,森林破坏、植被生态功能退化、水土流失、生物多样性减少。在上游地区应加强退耕还林还草,建立生态型持续农业系统和生态文明示范区,调整产业结构,提高群众的综合素质,走可持续发展道路。 相似文献
936.
937.
938.
James E. Bollinger Laura J. Steinberg Andrew J. Englande James P. Crews Janet M. Hughes Cruz Velasco Karen H. Watanabe William R. Hartley Christopher M. Swalm Jeffrey M. Mendler LuAnn E. White William J. George 《Journal of the American Water Resources Association》2000,36(6):1375-1390
ABSTRACT: Nutrient data from all available sources for the lower Mississippi River were examined for potential differences among sampling agencies and geographic locations for the period between 1960 and 1998. Monthly means grouped by parameter, sampling location and agency, were calculated and compared as paired sets, excluding those months where data were not available for both sets. Some significant differences were found between various agencies collecting nutrient data on the river, as well as between various stretches of river, especially in the case of phosphorus nutrient data. Results were used to synthesize data sets from which a history of nutrient loading in the Mississippi River was determined. General trends in nitrate+nitrite, total Kjeldahl nitrogen, orthophosphate, total phosphorus and silica loads, as well as changes in nutrient proportions and the specific limiting nutrient (by month) are reported. This study provides a useful summary of contemporary and historical nutrient data that may assist in the evaluation of Mississippi River water quality and its potential effect on the Gulf of Mexico. 相似文献
939.
TaWei Soong William H. Ettinger 《Journal of the American Water Resources Association》2000,36(1):105-121
ABSTRACT: Effects of the 1993 flood on river water and sediment quality were investigated using historical data and data collected from the Illinois River and Upper Mississippi River in a post‐flood period. Overall the post‐flood results showed systematic reductions and individual changes in the water and sediment constituents. The reductions in sediment metals and nutrients were most obvious at the Keokuk and Lock and Dam 26 stations. By analyzing and comparing the physical changes to the changes in water and sediment constituents at each station, it was found that physical processes such as sediment entrainment and, more importantly, the removal of fine sediment to be the main causes for the reduced concentrations in sediment constituents. On the other hand, sediment redistribution and associated secondary contamination could have caused the emergence of several water and sediment constituents that were undetected before the flood. 相似文献
940.
对长江南京段水、悬浮物及沉积物中多氯有毒有机污染物进行了分析测定,由色谱/质谱测得的结果表明,水和沉积物中多氯有机污染物的浓度较低,低于欧洲主要河流中的含量水平.悬浮物中这类污染物总含量较高,为56.45~62.35μg/kg,而水中总含量仅为14.61~15.83ng/L.由于长江中污染物被充分稀释与混匀,各采样点的水和悬浮物中该类污染物的浓度变化不大,两相间具有较好的相关性.但各采样点的沉积物中多氯有机污染物含量差异甚大,表明悬浮物的沉积极不均一.沉积物中主要污染物是六氯苯(HCB)和它的代谢产物五氯苯(PeCB)以及滴滴涕(DDT)的代谢产物,其他多氯有机污染物含量很低. 相似文献