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761.
于2015年以贵州省贵阳市饮用水源地红枫湖的水生食物链作为研究对象,通过测定不同营养级生物的汞含量及稳定碳氮同位素,并结合2007年红枫湖的数据,对比红枫湖水体的汞含量及水生食物链中的汞含量、食物链长度及生物放大率的变化。结果发现:相比于2007年,湖水中的总汞浓度降低了40%,但鱼体总汞和甲基汞含量分别增加了140%与210%,甲基汞在总汞中占的比例平均增加了18%。食物链长度增加一级,汞的生物放大率降低。可能的原因是:2008年政府对红枫湖进行综合治理后,水体富营养化程度降低,湖中食物链结构发生改变,鱼类生长速度减慢,使得鱼体内汞的生物稀释作用减弱,鱼体的汞含量相对升高。同时,高强度捕捞,使得鱼样个体普遍偏小,导致生物放大率较低。 相似文献
762.
763.
Bruce J. McGurk Thaddeus J. Edens David L. Azuma 《Journal of the American Water Resources Association》1993,29(1):85-94
ABSTRACT: Ten pairs of snow sensors were analyzed to investigate the feasibility of predicting snow water equivalent at high-elevation, telemetered snow sensor sites from lower-elevation sensors. The need for this analysis stems from an agreement between the California Department of Water Resources and the USDA Forest Service to temporarily allow snow sensors in California's wilderness areas so that a predictive relationship can be developed. After 10 or 15 years, the agreement calls for the sensors to be removed. Initial efforts to a priori select sensor pairs were based on proximity, colocation within a basin, and annual precipitation amount, but regression yielded poor fits (R2 < 0.65) and high standard errors in eight of the ten cases. Analysis of the results suggested that eleva-tional similarity was the most important selection criteria, and that all available sensors near the target site should be analyzed via a regression screening. Using elevation for selection and the regression screening, five sensors that initially had poor fits were reanalyzed. Each of the five sensors was paired with between two and five new sensors, and R2 values improved between 27 and 46 percent. Various data smoothing and editing algorithms were evaluated, but they rarely resulted in improved fits. 相似文献
764.
765.
Land use/land cover (LULC) has a profound impact on economy, society and environment, especially in rapid developing areas.
Rapid and prompt monitoring and predicting of LULC’s change are crucial and significant. Currently, integration of Geographical
Information System (GIS) and Remote Sensing (RS) methods is one of the most important methods for detecting LULC’s change,
which includes image processing (such as geometrical-rectifying, supervised-classification, etc.), change detection (post-classification),
GIS-based spatial analysis, Markov chain and a Cellular Automata (CA) models, etc. The core corridor of Pearl River Delta
was selected for studying LULC’s change in this paper by using the above methods for the reason that the area contributed
78.31% (1998)–81.4% (2003) of Gross Domestic Product (GDP) to the whole Pearl River Delta (PRD). The temporal and spatial
LULC’s changes from 1998 to 2003 were detected by RS data. At the same time, urban expansion levels in the next 5 and 10 years
were predicted temporally and spatially by using Markov chain and a simple Cellular Automata model respectively. Finally,
urban expansion and farmland loss were discussed against the background of China’s urban expansion and cropland loss during
1990–2000. The result showed: (1) the rate of urban expansion was up to 8.91% during 1998–2003 from 169,078.32 to 184,146.48 ha;
(2) the rate of farmland loss was 5.94% from 312,069.06 to 293,539.95 ha; (3) a lot of farmland converted to urban or development
area, and more forest and grass field converted to farmland accordingly; (4) the spatial predicting result of urban expansion
showed that urban area was enlarged ulteriorly compared with the previous results, and the directions of expansion is along
the existing urban area and transportation lines. 相似文献
766.
青岛市水资源问题探讨 总被引:1,自引:0,他引:1
较为详细地分析了青岛市城市供水现状、制约供水能力的主要因素,着眼于青岛市经济全面、协调与可持续发展,运用系统分析的观点,提出了解决青岛城市用水供需矛盾的可行性策略. 相似文献
767.
国土空间规划体系改革对人才培养提出了新的要求,构建新时代国土空间规划人才培养体系迫在眉睫。从人才培养和人才需求两个层面开展问卷调查,运用潜在冲突指数(PCI)等方法,研究中国国土空间规划相关专业的教育现状。结果表明:目前全国开设国土空间规划相关专业的高校约有261所,并呈现出开设类型多样化、办学层级多元化、学位学制差异化,以及硕博培养体系亟需完善等特征。从人才供给侧来看,学科基础的差异性导致了现有人才培养方案对规划基础理论掌握的要求各有侧重,但是各专业均表示出对规划工具应用、规划实践课程以及跨学科知识融合的强烈需求。而从人才需求侧来看,用人单位都重视多学科交叉复合型人才、理论与实践兼备的技术型人才以及基础理论扎实的专业型人才。为此,特从学科体系构建、基础理论研究、应用课程建设、专业评估机制和职业培训渠道等方面提出了国土空间规划人才培养体系革新思路。 相似文献
768.
769.
David A. Blair William D. Spronz Keith W. Ryan 《Journal of the American Water Resources Association》1999,35(5):1201-1212
The City of Cape May, New Jersey, draws its primary water supply from the Cohansey Aquifer, a unit serving residential, community, and industrial users throughout the Coastal Plain. By the year 2000, projected population growth will impose a peak water demand beyond available supplies. In addition, regional over-pumping threatens the Cohansey with saltwater intrusion, placing the city wells at risk by 1998. In the early-to mid 1990s, three broad categories of water-supply alternatives were evaluated by regional, state, and federal agencies — additional pumping from the Cohansey, conjunctive use of the Cohansey with other aquifers, and desalination of brackish groundwater. An approach was adopted in 1996 which derives up to 2 MGD from desalination of brackish groundwater, with the remaining peak demand satisfied by short-term pumpage from existing wells in the Cohansey. The first of two wells has been completed, yielding 1.4 MGD of brackish groundwater. Similar performance from the second well will exceed the design goal. When the initial system comes on line during the summer of 1998, New Jersey will have its first public water supply derived from desalinated groundwater. The use of desalinated groundwater balances competing demands for water resources in the southern Cape Region of New Jersey, allowing continued economic growth while reducing human impacts on a threatened aquifer. 相似文献
770.
华北及邻近地区的巨灾链 总被引:8,自引:1,他引:7
对华北及其邻近地区自清代以来特大地震和水灾构成的4次巨灾链进行了介绍,并初步探讨了它们的形成机制、预测指标及减灾对策。 相似文献