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531.
Gregory A. Graves Yongshan Wan Dana L. Fike 《Journal of the American Water Resources Association》2004,40(6):1405-1419
ABSTRACT: Starting in 1998, a study was conducted to characterize storm water quality from predominant land use types in a coastal watershed along the south central coast of Florida, namely citrus, pasture, urban, natural wetland, row crop, dairy, and golf courses. Sixty‐three sampling sites were located at strategic points on drainage conveyances for each of seven specific land use areas. Runoff samples were collected following storm events that met defined rainfall criteria for a period of 30 months. Nitrogen (N), phosphorus (P), heavy metals, pesticides, and other water quality parameters were determined, and the results were analyzed to compare and characterize land uses as relative sources for these constituents in runoff. Results showed that runoff from most land use types had low dissolved oxygen concentration and that sediment and nutrient concentrations were closely related to land use, particularly to the amount of fertilizer applied in each land use. Among the eight heavy metals tested, copper was the most frequently detected and was mostly associated with runoff from citrus and golf course land uses. High levels of arsenic were also detected in golf course runoff. The most frequently detected pesticide was simazine from citrus. The information and methodologies presented may facilitate pollution source characterization and ecological restoration efforts. 相似文献
532.
Gregory W. Characklis 《Journal of the American Water Resources Association》2004,40(3):615-630
ABSTRACT: An analysis is undertaken to determine the conditions under which membrane desalination becomes an economically preferable alternative for treating brackish water supplies. While membrane desalination is more expensive than conventional treatment, it affords benefits beyond those of conventional processes by reducing salinity related damages. An important and largely unexplored issue regards how the added cost of desalination compares to its benefits in terms of damages avoided. A comparative analysis is undertaken over a range of scenarios with the objective of identifying the treatment technology the leads to the lowest “total economic cost,” a term described by the sum of costs related to supply, treatment, and salinity related damages. Using data from a representative region, desalination yields the lowest total economic cost for source waters that exceed “threshold” salinity concentrations below 1,000 mg/l total dissolved solids (TDS). In instances where standard conventional processes require upgrades to maintain compliance with pending regulations (e.g., disinfection byproducts), the cost gap between membrane and conventional processes is reduced and the threshold concentration lowered. Given the inherent uncertainty in both treatment cost and damage estimates, a sensitivity analysis is conducted to determine which factors have the greatest impact on the treatment decision. Results suggest that considering salinity related damages when selecting a treatment technology makes membrane desalination of brackish waters economically attractive under a wider range of circumstances. 相似文献
533.
Paul A. Nelson James D. Gregory 《Journal of the American Water Resources Association》1988,24(4):743-748
ABSTRACT: Variation of in situ measured saturated hydraulic conductivity (KS) with stand age was examined in drained and intensively managed loblolly pine (Pinus taeda L.) plantations on very poorly drained Bayboro loam soils. Stand ages studied were 1-year-old and 14-years old. No differences in Ks values were found between the stand ages. In addition, no differences in core measured soil properties were found between the stand ages, indicating that there were no differences in the pore structure of the soil matrix. There was large variation of Ks within stands and between stands within ages. The mean within stand Ks values ranged from 0.66 cm/hr to 4.85 cm/hr. The frequency of tests exhibiting pipe flow through large non-capillary voids was significantly greater in the older stands; however, the continuity of the voids in the soil, and whether or not non-Darcy type flow would occur in a saturated profile, could not be determined. 相似文献
534.
Lauren E. Hay Gregory J. McCabe 《Journal of the American Water Resources Association》2002,38(3):847-860
ABSTRACT: A monthly water‐balance (WB) model was tested in 44 river basins from diverse physiographic and climatic regions across the conterminous United States (U.S.). The WB model includes the concepts of climatic water supply and climatic water demand, seasonality in climatic water supply and demand, and soil‐moisture storage. Exhaustive search techniques were employed to determine the optimal set of precipitation and temperature stations, and the optimal set of WB model parameters to use for each basin. It was found that the WB model worked best for basins with: (1) a mean elevation less than 450 meters or greater than 2000 meters, and/or (2) monthly runoff that is greater than 5 millimeters (mm) more than 80 percent of the time. In a separate analysis, a multiple linear regression (MLR) was computed using the adjusted R‐square values obtained by comparing measured and estimated monthly runoff of the original 44 river basins as the dependent variable, and combinations of various independent variables [streamflow gauge latitude, longitude, and elevation; basin area, the long‐term mean and standard deviation of annual precipitation; temperature and runoff; and low‐flow statistics (i.e., the percentage of months with monthly runoff that is less than 5 mm)]. Results from the MLR study showed that the reliability of a WB model for application in a specific region can be estimated from mean basin elevation and the percentage of months with gauged runoff less than 5 mm. The MLR equations were subsequently used to estimate adjusted R‐square values for 1,646 gauging stations across the conterminous U.S. Results of this study indicate that WB models can be used reliably to estimate monthly runoff in the eastern U.S., mountainous areas of the western U.S., and the Pacific Northwest. Applications of monthly WB models in the central U.S. can lead to uncertain estimates of runoff. 相似文献
535.
Jean M. Sogbedji Gregory F. Mclsaac 《Journal of the American Water Resources Association》2002,38(6):1753-1765
ABSTRACT: Evaluation of the applicability and validity of hydrologic simulation models for various cropping systems in different hydrogeologic and soil conditions is needed for a range of spatial scales. We calibrated and tested the ADAPT model for simulating streamflow from 552 to 1,985 km2 watersheds in central Illinois, where more than 79 percent of the land is used for maize‐soybean production and tile drainage is common. Model calibration was performed with a seven year period (1987 through1993) of measured streamflow from one of the watersheds, and model testing was done using independent weather and measured streamflow data from the two neighboring watersheds for the same seven year period. Simulations of annual streamflow were accurate with a coefficient of determination and Willmott's index of agreement of 0.98 and 0.99, respectively. For simulation of monthly streamflow, Willmott's index of agreement ranged from 0.93 to 0.95. For simulation of daily streamflow, Willmott's index of agreement ranged from 0.84 to 0.85. The daily simulations challenged the temporal and spatial resolution of our measured precipitation data. Discrepancies between simulated and measured data may result from the model's inability to effectively address frozen soils and snowmelt runoff processes and in accurately representing evapotranspiration. 相似文献
536.
Catherine E. deRivera Natasha Gray Hitchcock Sarah J. Teck Brian P. Steves Anson H. Hines Gregory M. Ruiz 《Marine Biology》2007,150(6):1275-1288
Introduced populations can cause ecological and economic damage and are difficult to eradicate once they have established.
It is therefore important to be able to predict both where species may become established and their capacity to spread within
recipient regions. Here, we use a new method to assess potential for intraregional spread of a marine crab introduced to North
America, Carcinus maenas. We determined survivorship and development rates throughout a range of temperatures in the laboratory for C. maenas larvae from non-native populations on the Atlantic and Pacific coasts of North America. The larvae exhibited narrower physiological
tolerances than adults, and no lab-cultured larvae completed larval development below 10.0°C or above 22.5°C. Survivorship
peaked at intermediate water temperatures of 12.5–20.0°C, and development time decreased with increasing temperatures within
this range. Based upon these laboratory development rates, we used nearshore sea-surface temperature data from both coasts
of North America to predict development times required for larvae at different months and sites. Taken together, survivorship
and development data indicate that C. maenas has the capacity to continue its northward spread and establish populations at numerous additional sites in North America.
Moreover, decadal temperature data at two Alaskan sites predicted little variability in development duration across years,
suggesting that development duration predictions are robust to interannual water temperature differences. 相似文献
537.
Arsenic mobility in contaminated lake sediments 总被引:6,自引:0,他引:6
Nikolaidis NP Dobbs GM Chen J Lackovic JA 《Environmental pollution (Barking, Essex : 1987)》2004,129(3):479-487
An arsenic contaminated lake sediment near a landfill in Maine was used to characterize the geochemistry of arsenic and assess the influence of environmental conditions on its mobility. A kinetic model was developed to simulate the leaching ability of arsenic in lake sediments under different environmental conditions. The HM1D chemical transport model was used to model the column experiments and determine the rates of arsenic mobility from the sediment. Laboratory studies provided the information to construct a conceptual model to demonstrate the mobility of arsenic in the lake sediment. The leaching ability of arsenic in lake sediments greatly depends on the flow conditions of ground water and the geochemistry of the sediments. Large amounts of arsenic were tightly bound to the sediments. The amount of arsenic leaching out of the sediment to the water column was substantially decreased due to iron/arsenic co-precipitation at the water-sediment interface. Overall, it was found that arsenic greatly accumulated at the ground water/lake interface and it formed insoluble precipitates. 相似文献
538.
Paul E. Flathman Bryon J. Krupp Paul Zottola Jason R. Trausch John H. Carson Ruji Yao Gregory J. Laird Patrick M. Woodhull Douglas E. Jerger Paul R. Lear 《补救:环境净化治理成本、技术与工艺杂志》1996,6(2):57-79
In-situ biological solid-phase (or land) treatment was cost-effectively used to remediate 1,500 cubic yards (1,100 m3) of contaminated soil within three months of field operation following spillage of an estimated 12,000 gallons (45,000 L) of vinyl acetate from a railroad tank car onto surface soil. The vinyl acetate rapidly hydrolyzed to acetate and acetaldehyde with concentrations ranging up to 22,000 and 3,000 mg/kg, respectively. Ethanol, a metabolic intermediate, was found to accumulate in soil to concentrations as high as 280 mg/kg. The estimate for excavation, transportation, and disposal of the contaminated soil as a special waste, and for backfilling of the excavated area, was $850,000. The cost for biological remediation of the contaminated soil was $400,000, which was less than half the cost of excavation. In-situ biological treatments have been used to readily remove contaminants, such as acrylonitrile, styrene, butylcellosolve, ethylacrylate, and n-butylacrylate, at other sites involving railroad incidents. 相似文献
539.
540.
Zoran S. Petrović Yijin Xu Jelena Milić Gregory Glenn Artur Klamczynski 《Journal of Polymers and the Environment》2010,18(2):94-97
Thermoplastic urethanes based on polyricinoleic acid soft segments and MDI/BD hard segments with varied soft segment concentration
were prepared. Soft segment concentration was varied from, 40 to 70 wt%. Biodegradation was studied by respirometry. Segmented
polyurethanes with soft segments based on polyricinoleic acid degrade relatively slow losing about 11% carbon after 30 days,
but faster than corresponding petrochemical polyesterurethanes. Since biodegradation proceeds mainly through the soft segments,
higher soft segment content polymers displayed slightly higher biodegradation. Polyurethanes with dispersed hard domains in
the soft phase displayed slightly faster biodegradation than those with co-continuous morphology. Polyester diol degrades
slower than castor oil but significantly faster than the polyurethanes with built in soft segments from the same diol. Castor
oil biodegrades slower than soybean oil. 相似文献