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961.
The state of North Carolina's Department of Environment and Natural Resources (NCDENR) conducts routine water quality monitoring
throughout the state to assess the health of aquatic systems. The current study reports the results of a retrospective (1990–2000)
ecological risk assessment of six heavy metals (arsenic, cadmium, copper, lead, mercury, and zinc) in 17 North Carolina basins
that was conducted to estimate the risk of heavy metal toxicity to freshwater organisms and assess the sufficiency of NCDENR's
monitoring data to identify water-quality-related ecological threats. Acute and chronic ecotoxicological thresholds (ETs)
were calculated for each metal based upon the 10th percentile of species sensitivity distributions and were normalized for
water hardness. Statewide probabilities (expressed as percentages) of a random sample exceeding acute or chronic ETs among
the six metals ranged from 0.01% to 12.19% and 0.76% to 21.21%, respectively, with copper having the highest and arsenic and
mercury the lowest risk. Basin-specific probabilities varied significantly depending upon water hardness and presumably watershed
development. Although the majority of specific sites where data were collected were at low risk for metal toxicity, some specific
sites had a high probability of toxic events associated with one or more metals. Analytical detection limits for metals were
frequently higher than estimated chronic ET, limiting the ability to assess the risk of chronic toxicity in soft-water basins.
Results suggest risk-based criteria may be useful for assessing and validating the sufficiency of monitoring programs and
prioritizing management goals. 相似文献
962.
Legitimizing Fluvial Ecosystems as Users of Water: An Overview 总被引:6,自引:0,他引:6
Naiman RJ Bunn SE Nilsson C Petts GE Pinay G Thompson LC 《Environmental management》2002,30(4):455-467
We suggest that fluvial ecosystems are legitimate users of water and that there are basic ecological principles guiding the
maintenance of long-term ecological vitality. This article articulates some fundamental relationships between physical and
ecological processes, presents basic principles for maintaining the vitality of fluvial ecosystems, identifies several major
scientific challenges and opportunities for effective implementation of the basic ecological principles, and acts as an introduction
to three specific articles to follow on biodiversity, biogeochemistry, and riparian communities. All the objectives, by necessity,
link climate, land, and fresh water. The basic principles proposed are: (1) the natural flow regime shapes the evolution of
aquatic biota and ecological processes, (2) every river has a characteristic flow regime and an associated biotic community,
and (3) aquatic ecosystems are topographically unique in occupying the lowest position in the landscape, thereby integrating
catchment-scale processes. Scientific challenges for the immediate future relate to quantifying cumulative effects, linking
multidisciplinary knowledge and models, and formulating effective monitoring and assessment procedures. Additionally, forecasting
the ecological consequences of changing water regimes is a fundamental challenge for science, especially as environmental
issues related to fresh waters escalate in the next two to three decades. 相似文献
963.
The Cache River of southernmost Illinois is used as a case study for developing and demonstrating an approach to quantitatively
link (1) national agricultural policy and global agricultural markets, (2) landowner's decisions on land use, (3) spatial
patterns of land use at a watershed scale, and (4) hydrologic impacts, thus providing a basis to predict, under a certain
set of circumstances, the environmental consequences of economic and political decisions made at larger spatial scales. The
heart of the analysis is an estimation, using logistic regression, of the affect of crop prices and Conservation Reserve Program
(CRP) rental rates on farmland owner's decisions whether to reenroll in the CRP or return to crop production. This analysis
shows that reasonable ranges for crop prices (80%–150% of 1985–1995 values) and CRP rental rates (0–125% of 1985–1995 rates)
result in a range of 3%–92% of CRP lands being returned to crop production, with crop prices having a slightly greater effect
than CRP rental rates. Four crop price/CRP rental rate scenarios are used to display resulting land-use patterns, and their
effect on sediment loads, a critical environmental quality parameter in this case, using the agricultural non point source
(AGNPS) model. These scenarios demonstrate the importance of spatial pattern of land uses on hydrological and ecological processes
within watersheds. The approach developed can be adapted for use by local governments and watershed associations whose goals
are to improve watershed resources and environmental quality. 相似文献
964.
从分析我国1998年抗洪救灾的事实出发,探讨了洪涝灾害产生的原因,分析了生态环境严重破坏带来的严重影响;据此,确立保护生态环境是根治洪涝灾害的战略措施,并从城市可持续发展的高度提出了建议。 相似文献
965.
966.
生态城市的内涵与理论基础 总被引:1,自引:0,他引:1
刘天齐 《中国环境管理干部学院学报》2000,(2)
当前我国的城市发展建设中,有相当多的城市制定环境保护规划、建设生态城市。本文对生态城市的内涵和理论基础进行论述,以期对生态城市建设有所助益。 相似文献
967.
Alan E. Haberstock Henry G. Nichols Mark P. DesMeules Jed Wright Jon M. Christensen Daniel H. Hudnut 《Journal of the American Water Resources Association》2000,36(6):1271-1286
ABSTRACT: Successful restoration of declining anadromous species is dependent upon effective riparian buffer zone management. Natural resource managers, policy developers and local conservation groups require science‐based information concerning the width at which a given buffer will be effective for its stated purpose. This paper summarizes a method developed in 1999 to determine effective riparian buffer widths for Atlantic salmon habitat protection as part of the Atlantic Salmon Conservation Plan for Seven Maine Rivers. A major assumption of the method is that no two buffers are alike with respect to their effectiveness and that various buffer characteristics dictate the required width for a given level of effectiveness. The method uses a predictive model that generates suggested riparian buffer widths as a function of specific, measurable buffer characteristics (such as slope, soil characteristics, and plant community structure and density) that affect buffer function. The method utilizes a variable‐width, two‐zone approach and specifies land uses that are consistent with desired buffer function within the two zones. 相似文献
968.
Glenn E. Moglen 《Journal of the American Water Resources Association》2000,36(6):1391-1400
ABSTRACT: The NRCS curve number approach to runoff estimation has traditionally been to average or “lump” spatial variability into a single number for purposes of expediency and simplicity in calculations. In contrast, the weighted runoff curve number approach, which handles each individual pixel within the watershed separately, tends to result in larger estimates of runoff than the lumped approach. This work proposes further enhancements that consider not only spatial variability, but also the orientation of this variability with respect to the flow aggregation pattern of the drainage network. Results show that the proposed enhancements lead to much reduced estimates of runoff production. A revised model that considers overland flow lengths, consistent with existing NRCS concepts is proposed, which leads to only mildly reduced runoff estimates. Although more physically‐based, this revised model, which accounts directly for spatially distributed curve numbers and flow aggregation, leads to essentially the same results as the original, lumped runoff model when applied to three study watersheds. Philosophical issues and implications concerning the appropriateness of attempting to disaggregate lumped models are discussed. 相似文献
969.
970.
Timothy O. Randhir John G. Lee 《Journal of the American Water Resources Association》2000,36(3):595-608
ABSTRACT: Enforceable standards play a crucial role in the design and implementation of most water quality policies. The impacts of these standards on farm income and nonpoint source (NPS) pollution can provide valuable information to develop economic policies that can improve water quality with minimal loss in income and minimal risk. This study uses an integration of nonlinear programming and a simulation model to assess the impacts of enforceable standards at technology and farm boundary levels. The results indicate that the type of pollutant regulated, enforcement type, and the level of standard had a significant impact on farm income and water quality. Choice of farm boundary standards over technology standards is dependent on the impact of the policy on other NPS pollutants, in addition to the reduction of nitrate and phosphorus pollutants. Enforcing farm boundary standards on nitrates had desirable effects on subsurface and percolate nitrogen and variance in income. Technology standards were uncertain in their effects because of the restriction on the choice of technologies available to farmers. A comparative policy analysis considering incentives, multiple impacts, transaction costs of implementation, and regional consideration is important to an effective policy design. 相似文献