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91.
Importance of Sediment–Water Interactions in Coeur d’Alene Lake,Idaho, USA: Management Implications 总被引:1,自引:0,他引:1
Kuwabara JS Carter JL Topping BR Fend SV Woods PF Berelson WM Balistrieri LS 《Environmental management》2003,32(3):348-359
A field study at Coeur dAlene Lake, Idaho, USA, was conducted between October 1998 and August 2001 to examine the potential importance of sediment–water interactions on contaminant transport and to provide the first direct measurements of the benthic flux of dissolved solutes of environmental concern in this lake. Because of potential ecological effects, dissolved zinc and orthophosphate were the solutes of primary interest. Results from deployments of an in situ flux chamber indicated that benthic fluxes of dissolved Zn and orthophosphate were comparable in magnitude to riverine inputs. Tracer analyses and benthic-community metrics provided evidence that solute benthic flux were diffusion-controlled at the flux-chamber deployment sites. That is, effects of biomixing (or bioturbation) and ground-water interactions did not strongly influence benthic flux. Remediation efforts in the river might not produce desired water-quality effects in the lake because imposed shifts in concentration gradients near the sediment–water interface would generate a benthic feedback response. Therefore, development of water-quality models to justify remediation strategies requires consideration of contaminant flux between the water column and underlying sediment in basins that have been affected by long-term (decadal) anthropogenic activities. 相似文献
92.
Measuring Plant Diversity in the Tall Threetip Sagebrush Steppe: Influence of Previous Grazing Management Practices 总被引:2,自引:0,他引:2
In July 2000, a 490-ha wildfire burned a portion of a long-term grazing study that had been established in 1924 at the US Sheep Experiment Station north of Dubois, Idaho, USA. Earlier vegetation measurements in this tall
threetip sagebrush (Artemisia tripartita spp. tripartita) bunchgrass plant community documented significant changes in vegetation due to grazing and the timing of grazing by sheep. A study was initiated in May 2001 using 12 multiscale modified Whittaker plots to determine the consequences of previous grazing practices on postfire vegetation composition. Because there was only one wildfire and it did not burn all of the original plots, the treatments are not replicated in time or space. We reduce the potential effects of psuedoreplication by confining our discussion to the sample area only. There were a total of 84 species in the sampled areas with 69 in the spring-grazed area and 70 each in the fall- and ungrazed areas. Vegetation within plots was equally rich and even with similar numbers of abundant species. The spring-grazed plots, however, had half as much plant cover as the fall- and ungrazed plots and the spring-grazed plots had the largest proportion of plant cover composed of introduced (27%) and annual (34%) plants. The fall-grazed plots had the highest proportion of native perennial grasses (43%) and the lowest proportion of native annual forbs (1%). The ungrazed plots had the lowest proportion of introduced plants (4%) and the highest proportion of native perennial forbs (66%). The vegetation of spring-grazed plots is in a degraded condition for the environment and further degradation may continue, with or without continued grazing or some other disturbance. If ecosystem condition was based solely on plant diversity and only a count of species numbers was used to determine plant diversity, this research would have falsely concluded that grazing and timing of grazing did not impact the condition of the ecosystem. 相似文献
93.
Differences between scientist and policy-maker response types and times, or the “how” and “when” of action, constrain effective
water resource management in suburbanizing watersheds. Policy-makers are often rushed to find a single policy that can be
applied across an entire, homogeneous, geopolitical region, whereas scientists undertake multiyear research projects to appreciate
the complex interactions occurring within heterogeneous catchments. As a result, watershed management is often practiced with
science and policy out of synch. Meanwhile, development pressures in suburban watersheds create changes in the social and
physical fabric and pose a moving target for science and policy. Recent and anticipated advances in the scientific understanding
of urbanized catchment hydrology and pollutant transport suggest that management should become increasingly sensitive to spatial
heterogeneities in watershed features, such as soil types, terrain slopes, and seasonal watertable profiles. Toward this end,
policy-makers should encourage funding scientific research that characterizes the impacts of these watershed heterogeneities
within a geopolitical zoning and development framework. 相似文献
94.
Contamination of groundwater, surface water and soil by explosives has occurred at military sites throughout the world as a result of manufacture of explosive compounds, assembly of munitions, and deployment of explosives containing devices. Due to the adverse effects of explosives on humans and other natural receptors, a low cost means of decontaminating these areas of contamination is needed. Base-induced transformation of explosives has shown promise as a rapid, low cost, and minimally resource-intensive technology for detoxifying explosives in soil and water. In order to understand the reaction mechanism, a reaction mixture of 2:1:1 (water:2,4,6-trinitrotoluene (TNT):1 N KOH) was analyzed by UV/VIS spectrometry from 190 to 1,100 nm. Time course measurements were conducted at 25, 20, 15, and 12 degrees C. A factor analysis program was used to analyze the spectral data. Principal component analysis indicated that six principal components explained the spectra to within experimental error, with four factors explaining the majority of the variance. Test spectral vectors for four components were developed, including TNT, two intermediates, and the final product, and were tested against the abstract vectors. Two possible reaction mechanisms were suggested and tested to explain the spectral data. 相似文献
95.
Dichloroacetic acid (DCAA) is produced during the oxidation of trichloroethylene. It is also produced in drinking water treatment as a disinfection by-product. DCAA is a problem material, because of its toxicity. The objective of this research is to find the final products and the reaction pathway of the DCAA decomposition by hydrolysis, and to increase the hydrolysis rate. The removal of both chlorine atoms in DCAA structure was achieved with hydrolysis at around 75 degrees C, and the final products were oxalic acid and glycolic acid. The reaction pathway was the production of oxalic acid and glycolic acid from two glyoxylic acid molecules by Cannizzaro reaction after the glyoxylic acid production from dechlorination of DCAA with hydrolysis. The hydrolysis rate of DCAA was increased with the use of 90% ethanol solution as solvent. The activation energy of DCAA was about 80 kJ/mol in it, while it was around 105 kJ/mol in water. 相似文献
96.
Stream Invertebrate Communities, Water Quality, and Land-Use Patterns in an Agricultural Drainage Basin of Northeastern Nebraska, USA 总被引:2,自引:0,他引:2
We used invertebrate bioassessment, habitat analysis, geographic information system analysis of land use, and water chemistry
monitoring to evaluate tributaries of a degraded northeast Nebraska, USA, reservoir. Bimonthly invertebrate collections and
monthly water chemistry samples were collected for two years on six stream reaches to identify sources contributing to reservoir
degradation and test suitability of standard rapid bioassessment methods in this region. A composite biotic index composed
of seven commonly used metrics was effective for distinguishing between differentially impacted sites and responded to a variety
of disturbances. Individual metrics varied greatly in precision and ability to discriminate between relatively impacted and
unimpacted stream reaches. A modified Hilsenhoff index showed the highest precision (reference site CV = 0.08) but was least
effective at discriminating among sites. Percent dominance and the EPT (number of Ephemeroptera, Plecoptera, and Trichoptera
taxa) metrics were most effective at discriminating between sites and exhibited intermediate precision. A trend of higher
biotic integrity during summer was evident, indicating seasonal corrections should differ from other regions. Poor correlations
were evident between water chemistry variables and bioassessment results. However, land-use factors, particularly within 18-m
riparian zones, were correlated with bioassessment scores. For example, there was a strong negative correlation between percentage
of rangeland in 18-m riparian zones and percentage of dominance in streams (r
2
= 0.90, P < 0.01). Results demonstrate that standard rapid bioassessment methods, with some modifications, are effective for use in this agricultural
region of the Great Plains and that riparian land use may be the best predictor of stream biotic integrity. 相似文献
97.
为了反映岩质边坡在节理面注浆后的变形效应,首先,通过室内试验,分析注浆前后岩体变形和破坏的全过程,以探讨其抗剪性能(粘结力c和内摩擦角φ)的变化;然后,基于理想弹塑性本构模型的Mohr-Cou-lomb准则,运用拉格朗日元数值方法(FLAC3D),对岩坡注浆前后变形效应(水平位移、垂直位移、剪应变增量)进行模拟。结果表明:注浆加固后,岩体的位移场变得均匀和连续,节理面处的较大位移受到抑制,边坡的整体性得到提高,有利于边坡的稳定性。 相似文献
98.
Steven J. Paustian Robert L. Beschta 《Journal of the American Water Resources Association》1979,15(1):144-154
ABSTRACT: Armored stream segments may affect the suspended sediment regime of small mountain streams in western Oregon by the release of fine sediments stored in the bed gravels. Sieve analysis of bed materials indicated that at least 30 percent of the suspended sediment yield for the 1975–76 winter had been stored in the streambed. Suspended sediment concentrations during storm-generated runoff were influenced by stream discharge and hydrograph characteristics. Sediment-discharge relations for individual storms were characterized by hysteresis loops. A seasonal flushing of fines was shown by a progressive decrease in the ratio of suspended sediment to stream discharge during the winter runoff period. 相似文献
99.
John W. Hanna Steven F. Philipp Gary W. Mullins 《Journal of the American Water Resources Association》1978,14(1):179-189
Abstract: Opportunities for the development of an amalgam of park and leisure-oriented commercial establishments in urban-core waterfont settings exist in many U.S. cities. Public awareness of the need to enhance the environmental quality of these waterfont areas has resulted in a demand for planning and implementation action. However, the lack of understanding of urban political systems has been an inhibiting factor in the development of this park/ business concept. The major factors that influence the decision-making process leading to the development of urban-core waterfronts for park/business use are identified inthis paper. Understanding this decision-making process can aid project implementation and avoid waste of planning effort in time, dollars, and productivity. 相似文献
100.
Circular economy (CE), with its basic principle of Reduce, Reuse, and Recycle, has been determined as the key strategy for the national development plan by the Chinese government. Given the economy-wide material flow analysis (EW-MFA) that leaves the inner flow of resource reutilisation unidentified, the reutilisation-extended EW-MFA is first introduced to evaluate and analyse the material input, solid waste generation, and reutilisation simultaneously. The total amount of comprehensive reutilisation (CR) is divided into three sub-flows, namely, reutilisation, recycle, and reuse. Thus, this model is used to investigate the resource CR in China from 2000 to 2010. China’s total amount of CR and its sub-flows, as well as the CR rate, remain to have a general upward trend. By the year 2010, about 60% of the overall solid waste generation had already been reutilised, and more than 20% of the total resource requirement was reutilised resource. Moreover, the growth patterns of the CR sub flows show different characteristics.Interpretations of resource reutilisation-related laws and regulations of CE and the corresponding policy suggestions are proposed based on the results. 相似文献