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161.
Dale F. Rucker David A. Myers Brian Cubbage Marc T. Levitt Gillian E. Noonan Michael McNeill Colin Henderson Robert W. Lober 《Environmental monitoring and assessment》2013,185(1):995-1010
A characterization program has been developed at Hanford to image past leaks in and around the underground storage tank facilities. The program is based on electrical resistivity, a geophysical technique that maps the distribution of electrical properties of the subsurface. The method was shown to be immediately successful in open areas devoid of underground metallic infrastructure, due to the large contrast in material properties between the highly saline waste and the dry sandy host environment. The results in these areas, confirmed by a limited number of boreholes, demonstrate a tendency for the lateral extent of the underground waste plume to remain within the approximate footprint of the disposal facility. In infrastructure-rich areas, such as tank farms, the conventional application of electrical resistivity using small point-source surface electrodes initially presented a challenge for the resistivity method. The method was then adapted to directly use the buried infrastructure, specifically the steel-cased wells that surround the tanks, as “long” electrodes for both transmission of electrical current and measurements of voltage. Overcoming the drawbacks of the long electrode method has been the focus of our work over the past 7 years. The drawbacks include low vertical resolution and limited lateral coverage. The lateral coverage issue has been improved by supplementing the long electrodes with surface electrodes in areas devoid of infrastructure. The vertical resolution has been increased by developing borehole electrode arrays that can fit within the small-diameter drive casing of a direct push rig. The evolution of the program has led to some exceptional advances in the application of geophysical methods, including logistical deployment of the technology in hazardous areas, development of parallel processing resistivity inversion algorithms, and adapting the processing tools to accommodate electrodes of all shapes and locations. The program is accompanied by a full set of quality assurance procedures that cover the layout of sensors, measurement strategies, and software enhancements while insuring the integrity of stored data. The data have been shown to be useful in identifying previously unknown contaminant sources and defining the footprint of precipitation recharge barriers to retard the movement of existing contamination. 相似文献
162.
Gregory J. Pond Jeffrey E. Bailey Benjamin M. Lowman Michael J. Whitman 《Environmental monitoring and assessment》2013,185(2):1515-1540
Multimetric indices (MMIs) are routinely used by federal, state, and tribal entities to assess the quality of aquatic resources. Because of their diversity, abundance, ubiquity, and sensitivity to environmental stress, benthic macroinvertebrates are well suited for MMIs. West Virginia has used a statewide family-level stream condition index (WVSCI) since 2002. We describe the development, validation, and application of a geographically- and seasonally partitioned genus-level index of most probable stream status (GLIMPSS) for West Virginia wadeable streams. Natural classification strata were evaluated with reference site communities using mean similarity analysis and non-metric multidimensional scaling ordination. Forty-one metrics spanning six ecological categories (richness, composition, tolerance, dominance, trophic groups, and habits) were evaluated for sensitivity, responsiveness, redundancy, range and variability across seasonal (spring and summer) and regional (mountains and plateau) strata. Through a step-wise metric selection process, 8–10 metrics were aggregated to comprise four stratum-specific GLIMPSS models (mountain/plateau and spring/summer). A comparison of GLIMPSS with WVSCI exhibited marked improvements where GLIMPSS detecting greater stream impacts. A variation of the GLIMPSS, which differs only in the family-level taxonomic identification of Chironomidae (GLIMPSS (CF)), was comparable to the full GLIMPSS. These MMIs are robust yet practical tools for evaluating impacts to water quality, instream and riparian habitat, and aquatic wildlife in wadeable riffle-run streams based on sensitivity, responsiveness, precision, and independent validation. These models may be used effectively to detect degradation of the naturally occurring benthic community, assess causes of biological degradation, and plan and evaluate remediation of damaged stream ecosystems. 相似文献
163.
A method is described whereby dielectrophoresis of algal cells is used to perform rapid water quality analysis, specifically detecting the presence of CuSO4. The dielectric collection spectrum of the fresh water alga Selenastrum capricornutum was determined for a range of concentrations of CuSO4 from 25 mg L(-1) to 0.25 mg L(-1) for exposure times of 15 min and 18 h. In all cases increasing the concentration of CuSO4 reduced cell collection, but a step reduction was observed in collection between 2 mg L(-1) and 5 mg L(-1). This method has potential for forming a rapid, low-cost test for water quality with broad specificity and significantly reduced analysis time compared to current methods. 相似文献
164.
Dissolved hexavalent chromium concentrations were determined in river, estuarine and coastal waters of the Humber catchment in north-east England. Samples were collected, filtered, extracted on site and after storage for up to eight days. Hexavalent chromium concentrations did not change by more than 0.05 microg l(-1) (not significant, p = 0.05) over this period. Total chromium concentrations in the catchment were less than 1.0 microg l(-1). This is low in relation to the proposed Environmental Quality Standard. Hexavalent chromium accounted for between 27% and 100% of the total dissolved concentration, with an average of approximately 50%. The proportion of Cr(III) and Cr(VI) in the rivers and estuary were of the same range as previously measured in 1993. The addition of Cr(III) and Cr(VI) to fresh and saline water samples illustrates the complexity of the factors controlling chromium speciation in natural waters. The presence of oxidisable organic matter and the stabilising role of complexing organic ligands are proposed as the main controlling influences of redox speciation in filtered samples. 相似文献
165.
Comparing Costs of Onsite Best Management Practices to Nutrient Credits for Stormwater Management: A Case Study in Virginia 下载免费PDF全文
Alicia L. Nobles Jonathan L. Goodall G. Michael Fitch 《Journal of the American Water Resources Association》2017,53(1):131-143
Best management practices (BMPs) are widely used to mitigate impacts of increased impervious surfaces on stormwater runoff. However, there is limited detailed and up‐to‐date information available on the cost of designing, constructing, and maintaining BMPs over their lifetime. The objective of this study is to analyze BMPs recently constructed by the Virginia Department of Transportation (VDOT) to quantify their total cost per pound of phosphorus removed annually. A motivating factor for the study is recent changes to regulatory guidelines in Virginia which allow for full or partial substitution of purchased nutrient credits in lieu of constructing onsite BMPs to achieve compliance with stormwater quality regulations. Results of the analysis of nine BMPs found their cost ranged from $20,100 to $74,900, in 2014 dollars, per pound ($44,313‐$165,126 per kg) of phosphorus removed. Based on these results and assuming current credit prices procured by VDOT, purchasing nutrient credits is a cost‐effective option for the agency, especially when factoring in the cost of additional right of way for the BMP. Based on this finding, we expect compliance with stormwater quality regulations through credit purchases to become more widely used in Virginia. Moving forward, we suggest more direct tracking of BMP costs to support comparisons between BMP costs across a range of types and conditions to credit purchases for meeting stormwater regulations. 相似文献
166.
A novel method was developed to suppress membrane fouling in submerged membrane bioreactors. The method is based on the dielectrophoretic (DEP) motion of particles in an inhomogeneous electrical field. Using a real sample of biomass as feed, the fouling-suppression performance using DEP with different electrical field intensities (60–160 V) and different frequencies (50–1000 Hz) was investigated. The fouling-suppression performance was found to relate closely with the intensity and frequency of the electrical field. A stronger electrical field was found to better recover the filtrate flux. This is because of a stronger DEP force acting on the biomass particles close to the membrane's surface. Above an intensity and frequency value of 130 V and 1 kHz, respectively the permeate flux was reduced due to an electrothermal effect. 相似文献
167.
Arsenic and sulfur mineralization is a natural phenomenon occurring in hydrothermal systems where parameters like temperature and organic matter(OM) can influence the mobilization of the toxic metalloid in marine environments. In the present study we analyze the influence of temperature and OM(particularly sulfur-containing additives) on As and S precipitation based on the recent discovery of As-rich nanoparticles in the hydrothermal system near the coast of the Greek island Milos. To this end, ... 相似文献
168.
169.
Mirela G. Tulbure Michael C. WimberlyArvid Boe Vance N. Owens 《Agriculture, ecosystems & environment》2012,146(1):121-129
The U.S. Renewable Fuel Standard calls for 136 billion liters of renewable fuels production by 2022. Switchgrass (Panicum virgatum L.) has emerged as a leading candidate to be developed as a bioenergy feedstock. To reach biofuel production goals in a sustainable manner, more information is needed to characterize potential production rates of switchgrass. We used switchgrass yield data and general additive models (GAMs) to model lowland and upland switchgrass yield as nonlinear functions of climate and environmental variables. We used the GAMs and a 39-year climate dataset to assess the spatio-temporal variability in switchgrass yield due to climate variables alone. Variables associated with fertilizer application, genetics, precipitation, and management practices were the most important for explaining variability in switchgrass yield. The relationship of switchgrass yield with climate variables was different for upland than lowland cultivars. The spatio-temporal analysis showed that considerable variability in switchgrass yields can occur due to climate variables alone. The highest switchgrass yields with the lowest variability occurred primarily in the Corn Belt region, suggesting that prime cropland regions are the best suited for a constant and high switchgrass biomass yield. Given that much lignocellulosic feedstock production will likely occur in regions with less suitable climates for agriculture, interannual variability in yields should be expected and incorporated into operational planning. 相似文献
170.
Tobias Frische Michael Faust Wiebke Meyer Thomas Backhaus 《Environmental science and pollution research international》2009,16(5):593-603