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51.
Daniel L. Tufford William D. Marshall 《Journal of the American Water Resources Association》2002,38(6):1625-1635
ABSTRACT: This study presents the results of fecal coliform (FC) sampling in the Rawls Creek, South Carolina, watershed during 1999 and 2000. The work was undertaken because the watershed is listed on the 303(d) list for South Carolina due to FC excursions. The watershed is 43.8 percent residential, 35 percent forest, 5.7 percent mixed urban, 4.9 percent commercial, and 4.8 percent agriculture. Samples were taken at 15 stations during eight field trips divided into two phases to characterize FC inputs from subbasins and to integrate results from upstream sampling. FC concentrations ranged from 135 to 730 colonies/100 ml. Results suggest that retention ponds in the area are a significant factor in attenuation of FC concentrations. Catchments with the largest contiguous impervious areas are the greatest source of FC. The highest concentrations of FC were observed at stations just downstream from a large detention basin that intercepts storm runoff from a large commercial area. Further analysis of the design and performance of that structure is suggested. The Koon Branch tributary is less than 20 percent of the land area in the watershed but may contribute 40 percent of the fecal loading. The results of this study confirm the importance of site assessments to aid understanding of nonpoint source pollution in complex watersheds. 相似文献
52.
Bruce M. Rothschild Larry D. Martin Brendan Anderson Alison Olcott Marshall Craig P. Marshall 《Die Naturwissenschaften》2013,100(8):789-794
Discovery of a fossil (30–35 million-year-old) urolith from Early Oligocene deposits in northeastern Colorado provides the earliest evidence for the antiquity of bladder stones. These are spherical objects with a layered phosphatic structure and a hollow center. Each layer is composed of parallel crystals oriented perpendicular to the surface. Macroscopic and microscopic examination and X-ray diffraction analysis, along with comparison with 1,000 contemporary uroliths, were used as evidence in the confirmation of this diagnosis. Raman microspectroscopy verified the presence of organic material between layers, confirming its biologic origin. 相似文献
53.
Nadine Marshall Paul Marshall Ameer Abdulla 《Journal of Environmental Planning and Management》2009,52(7):901-918
The social and economic ramifications of marine conservation strategies such as marine protected areas (MPAs) are important to consider prior to their implementation to ensure that they do not exceed the resilience of resource-users and that resource protection might be maximised through compliance and low resistance. This paper presents a framework in which the human dimensions can be more easily and usefully integrated into the design and delivery of conservation initiatives. The framework espouses quantifying (1) the level of dependency on the resource; (2) perceptions towards conservation initiatives; and (3) social resilience. The framework is applied in Salum, Egypt, which is the site of a prospective MPA. 相似文献
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55.
L. Zaibet S. Traore A. Ayantunde K. Marshall N. Johnson M. Siegmund-Schultze 《Environment, Development and Sustainability》2011,13(1):87-105
Rural livelihoods in West Africa depend largely on livestock. The sub-humid and humid zones of the region, however, are highly
affected by the tsetse flies, vector of trypanosomosis, by severely limiting livestock production and livelihood options.
Endemic ruminant livestock breeds are trypanotolerant, but perceived as inferior compared to other breeds in terms of productivity.
The paper shows trends of relative decline in endemic population as a result of increased crossbreeding, largely with zebu
cattle and Sahelian sheep and goats, and considerable decline in habitat quality due to forest conversion, logging activities
and bushfires. The trade-offs between livelihoods and income strategies and endemic ruminant and habitat conservation are
captured by an understanding of the socio-economic conditions and potential drivers of breed choices and forest use within
households and communities. The paper shows that livelihood analysis is an important step in understanding impacts and therefore
responses to development projects and to ensure that the poorest categories are not excluded from development interventions. 相似文献
56.
Long-term trends (i.e., 1985 through 1999; 14 1/2 yrs) of the phytoplankton community in Chesapeake Bay indicated patterns of increasing phytoplankton abundance and biomass associated with mainly diatoms and chlorophytes, and to a lesser degree dinoflagellates. Decreasing trends in productivity rates above the pycnocline were present over a shorter time period (10 1/2 yrs.), with evidence for increasing nitrogen limitation is indicated. Reduced light availability is inferred due to decreasing trends of Secchi depths and increased suspended solids trends, which were associated with decreasing trends in productivity rates. 相似文献
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58.
Computer simulation provides a powerful tool for comparing alternative designs of remediation processes. The software package FLUENT copes successfully with subsurface three-dimensional flow fields, multiple and directional permeabilities, wide spatial variations in subsurface gas velocities, and the presence of surface structures. FLUENT can provide an invaluable method for comparing remediation efficiencies among competing design alternatives. This article features case studies to illustrate the benefits that simulation studies provide before and during the initiation of remedial actions using bioventing. 相似文献
59.
A mathematical model widely applied in population studies and in assessment of the impact of exploitation on fish populations was applied to assess cadmium toxicity in laboratory populations ofDaphnia galeata mendotae. Over a range of toxicant concentrations, the birth rate of the population increased to balance the death rate and the population compensated for the increased mortality. The model describes the relation between toxicant concentration, toxicant-induced mortality, and equilibrium population size. Compensation for increased mortality is described in terms of the decrease in population size necessary to produce an increase in the birth rate that will balance the increased death rate. The relative capacity of different aquatic organisms to compensate for toxicant-induced mortality is examined and a relation between compensatory capacity and the innate capacity for increase is developed. 相似文献
60.
Marshall E. Wilcher 《The Environmentalist》1986,6(4):289-298
Summary An analysis of the recent acid rain debate in North America reveals that the policies and priorities of the various interested bodies with regard to this issue directly reflect their vested interests and in many instances their geographical location.Dr Marshall E. Wilcher is Assistant Professor in Political Science at the New Kensington Campus of Pennsylvania State University. 相似文献