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241.
Landscape Planning for Agricultural Nonpoint Source Pollution Reduction III: Assessing Phosphorus and Sediment Reduction Potential 总被引:2,自引:0,他引:2
Riparian buffers have the potential to improve stream water quality in agricultural landscapes. This potential may vary in
response to landscape characteristics such as soils, topography, land use, and human activities, including legacies of historical
land management. We built a predictive model to estimate the sediment and phosphorus load reduction that should be achievable
following the implementation of riparian buffers; then we estimated load reduction potential for a set of 1598 watersheds
(average 54 km2) in Wisconsin. Our results indicate that land cover is generally the most important driver of constituent loads in Wisconsin
streams, but its influence varies among pollutants and according to the scale at which it is measured. Physiographic (drainage
density) variation also influenced sediment and phosphorus loads. The effect of historical land use on present-day channel
erosion and variation in soil texture are the most important sources of phosphorus and sediment that riparian buffers cannot
attenuate. However, in most watersheds, a large proportion (approximately 70%) of these pollutants can be eliminated from
streams with buffers. Cumulative frequency distributions of load reduction potential indicate that targeting pollution reduction
in the highest 10% of Wisconsin watersheds would reduce total phosphorus and sediment loads in the entire state by approximately
20%. These results support our approach of geographically targeting nonpoint source pollution reduction at multiple scales,
including the watershed scale. 相似文献
242.
Agricultural non–point source (NPS) pollution poses a severe threat to water quality and aquatic ecosystems. In response,
tremendous efforts have been directed toward reducing these pollution inputs by implementing agricultural conservation practices.
Although conservation practices reduce pollution inputs from individual fields, scaling pollution control benefits up to the
watershed level (i.e., improvements in stream water quality) has been a difficult challenge. This difficulty highlights the
need for NPS reduction programs that focus efforts within target watersheds and at specific locations within target watersheds,
with the ultimate goal of improving stream water quality. Fundamental program design features for NPS control programs—i.e.,
number of watersheds in the program, total watershed area, and level of effort expended within watersheds—have not been considered
in any sort of formal analysis. Here, we present an optimization model that explores the programmatic and environmental trade-offs
between these design choices. Across a series of annual program budgets ranging from $2 to $200 million, the optimal number
of watersheds ranged from 3 to 27; optimal watershed area ranged from 29 to 214 km2; and optimal expenditure ranged from $21,000 to $35,000/km2. The optimal program configuration was highly dependent on total program budget. Based on our general findings, we delineated
hydrologically complete and spatially independent watersheds ranging in area from 20 to 100 km2. These watersheds are designed to serve as implementation units for a targeted NPS pollution control program currently being
developed in Wisconsin. 相似文献
243.
Hamilton TF Martinelli RE Kehl SR McAninch JE 《Journal of environmental monitoring : JEM》2008,10(10):1134-1138
We have determined the level and distribution of gamma-emitting radionuclides, plutonium activity concentrations, and 240Pu/239Pu atom ratios in tissue samples of giant clam (Tridacna gigas and Hippopus hippopus), a top snail (Trochus nilaticas) and sea cucumber (Holothuria atra) collected from different locations around Enewetak Atoll. The plutonium isotopic measurements were performed using ultra-high sensitivity accelerator mass spectrometry (AMS). Elevated levels of plutonium were observed in the stomachs (includes the stomach lining) of Tridacna clam (0.62 to 2.98 Bq kg(-1), wet wt.), in the soft parts (edible portion) of top snails (0.25 to 1.7 Bq kg(-1)), wet wt.) and, to a lesser extent, in sea cucumber (0.015 to 0.22 Bq kg(-1), wet wt.) relative to muscle tissue concentrations in clam (0.006 to 0.021 Bq kg(-1), wet wt.) and in comparison with previous measurements of plutonium in fish. These data and information provide a basis for re-evaluating the relative significance of dietary intakes of plutonium from marine foods on Enewetak Atoll and, perhaps most importantly, demonstrate that discrete 240Pu239Pu isotope signatures might well provide a useful investigative tool to monitor source-term attribution and consequences on Enewetak Atoll. One potential application of immediate interest is to monitor and assess the health and ecological impacts of leakage of plutonium (as well as other radionuclides) from a low-level radioactive waste repository on Runit Island relative to background levels of fallout contamination in Enewetak Atoll lagoon. 相似文献
244.
245.
The US Army Corps of Engineers often requires wetland creation or restoration as compensation for wetlands damaged during
development. These wetlands are typically monitored postconstruction to determine the level of compliance with respect to
site-specific performance standards. However, defining appropriate goals and measuring success of restorations has proven
difficult. We reviewed monitoring information for 76 wetlands constructed between 1992 and 2002 to summarize the performance
criteria used to measure progress, assess compliance with those criteria, and, finally, to evaluate the appropriateness of
those criteria. Goals were overwhelmingly focused on plant communities. Attributes used to assess the quality of restored
plant communities, including percent native species and the Floristic Quality Index, increased over time but were apparently
unrelated to the number of species planted. Compliance frequencies varied depending on site goals; sites often failed to comply
with criteria related to survival of planted vegetation or requirements that dominant plant species should not be exotic or
weedy, whereas criteria related to the establishment of cover by vegetation or by wetland-dependent plants were often met.
Judgment of a site’s success or failure was largely a function of the goals set for the site. Some performance criteria were
too lenient to be of value in distinguishing failed from successful sites, whereas other criteria were unachievable without
more intensive site management. More appropriate goals could be devised for restored wetlands by basing performance standards
on past performance of similar restorations, identifying consistent temporal trends in attributes of restored sites, and using
natural wetlands as references. 相似文献
246.
247.
Landscape Planning for Agricultural Nonpoint Source Pollution Reduction I: A Geographical Allocation Framework 总被引:1,自引:1,他引:0
Agricultural nonpoint source pollution remains a persistent environmental problem, despite the large amount of money that
has been spent on its abatement. At local scales, agricultural best management practices (BMPs) have been shown to be effective
at reducing nutrient and sediment inputs to surface waters. However, these effects have rarely been found to act in concert
to produce measurable, broad-scale improvements in water quality. We investigated potential causes for this failure through
an effort to develop recommendations for the use of riparian buffers in addressing nonpoint source pollution in Wisconsin.
We used frequency distributions of phosphorus pollution at two spatial scales (watershed and field), along with typical stream
phosphorus (P) concentration variability, to simulate benefit/cost curves for four approaches to geographically allocating
conservation effort. The approaches differ in two ways: (1) whether effort is aggregated within certain watersheds or distributed
without regard to watershed boundaries (dispersed), and (2) whether effort is targeted toward the most highly P-polluting
fields or is distributed randomly with regard to field-scale P pollution levels. In realistic implementation scenarios, the
aggregated and targeted approach most efficiently improves water quality. For example, with effort on only 10% of a model
landscape, 26% of the total P load is retained and 25% of watersheds significantly improve. Our results indicate that agricultural
conservation can be more efficient if it accounts for the uneven spatial distribution of potential pollution sources and the
cumulative aspects of environmental benefits. 相似文献
248.
Daniel J. St. Germain Donald K. Cohen Jeffrey J. Frederick 《Journal of the American Water Resources Association》2008,44(5):1337-1346
Abstract: The residents of Nassau County Long Island, New York receive all of their potable drinking water from the Upper Glacial, Jameco/Magothy (Magothy), North Shore, and Lloyd aquifers. As the population of Nassau County grew from 1930 to 1970, the demand on the ground‐water resources also grew. However, no one was looking at the potential impact of withdrawing up to 180 mgd (7.9 m3/s) by over 50 independent water purveyors. Some coastal community wells on the north and south shores of Nassau County were being impacted by saltwater intrusion. The New York State Legislature formed a commission to look into the water resources in 1972. The commission projected extensive population growth and a corresponding increase in pumping resulting in a projected 93.5 to 123 mgd (4.1 to 5.5 m3/s) deficit by 2000. In 1986, the New York Legislature passed legislation to strengthen the well permit program and also establish a moratorium on new withdrawals from the Lloyd aquifer to protect the coastal community’s only remaining supply of drinking water. Over 30 years has passed since the New York Legislature made these population and pumping projections and it is time to take a look at the accuracy of the projections that led to the moratorium. United States Census data shows that the population of Nassau County did not increase but decreased from 1970 to 2000. Records show that pumping in Nassau County was relatively stable fluctuating between 170 and 200 mgd (7.5 to 8.8 m3/s) from 1970 to 2004, well below the projection of 242 to 321 mgd (10.6 to 14.1 m3/s). Therefore, the population and water demand never grew to projected values and the projected threat to the coastal communities has diminished. With a stable population and water demand, its time to take a fresh look at proactive ground‐water resource management in Nassau County. One example of proactive ground‐water management that is being considered in New Jersey where conditions are similar uses a ground‐water flow model to balance ground water withdrawals, an interconnection model to match supply with demand using available interconnections, and a hydraulic model to balance flow in water mains. New Jersey also conducted an interconnection study to look into how systems with excess capacity could be used to balance withdrawals in stressed aquifer areas with withdrawals in unstressed areas. Using these proactive ground‐water management tools, ground‐water extraction could be balanced across Nassau County to mitigate potential impacts from saltwater intrusion and provide most water purveyors with a redundant supply that could be used during water emergencies. 相似文献
249.
Adaptive Management of Nonnative Species: Moving Beyond the “Either-Or” Through Experimental Pluralism 总被引:2,自引:2,他引:0
Jason M. Evans Ann C. Wilkie Jeffrey Burkhardt 《Journal of Agricultural and Environmental Ethics》2008,21(6):521-539
This paper develops the outlines of a pragmatic, adaptive management-based approach toward the control of invasive nonnative
species (INS) through a case study of Kings Bay/Crystal River, a large artesian springs ecosystem that is one of Florida’s
most important habitats for endangered West Indian manatees (Trichechus manatus). Building upon recent critiques of invasion biology, principles of adaptive management, and our own interview and participant–observer
research, we argue that this case study represents an example in which rigid application of invasion biology’s a␣priori imperative
to minimize INS has produced counterproductive results from both an ecological and social standpoint. As such, we recommend
that INS control in Kings Bay should be relaxed in conjunction with an overall program of adaptive ecosystem management that
includes meaningful participation and input from non-institutional stakeholders. However, we also note that adaptive management
and INS control are by no means mutually exclusive, in Kings Bay or elsewhere. Instead, we suggest that adaptive management
offers a means by which INS control efforts can emerge from—and be evaluated through—ongoing scientific research and participatory
dialogue about the condition of specific places, rather than non-contextual assumptions about the harmfulness of INS as a
general class. 相似文献
250.
Chemical solutions for greywater recycling 总被引:1,自引:0,他引:1
Pidou M Avery L Stephenson T Jeffrey P Parsons SA Liu S Memon FA Jefferson B 《Chemosphere》2008,71(1):147-155
Greywater recycling is now accepted as a sustainable solution to the general increase of the fresh water demand, water shortages and for environment protection. However, the majority of the suggested treatments are biological and such technologies can be affected, especially at small scale, by the variability in strength and flow of the greywater and potential shock loading. This investigation presents the study of alternative processes, coagulation and magnetic ion exchange resin, for the treatment of greywater for reuse. The potential of these processes as well as the influence of parameters such as coagulant or resin dose, pH or contact time were investigated for the treatment of two greywaters of low and high organic strengths. The results obtained revealed that magnetic ion exchange resin and coagulation were suitable treatment solutions for low strength greywater sources. However, they were unable to achieve the required level of treatment for the reuse of medium to high strength greywaters. Consequently, these processes could only be considered as an option for greywater recycling in specific conditions that is to say in case of low organic strength greywater or less stringent standards for reuse. 相似文献