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排序方式: 共有791条查询结果,搜索用时 78 毫秒
51.
S.M. Eldridge C.R. Chen Z.H. Xu P.N. Nelson S.E. Boyd I. Meszaros K.Y. Chan 《Waste management (New York, N.Y.)》2013,33(11):2157-2169
Using solid state 13C NMR data and elemental composition in a molecular mixing model, we estimated the molecular components of the organic matter in 16 recycled organic (RO) wastes representative of the major materials generated in the Sydney basin area. Close correspondence was found between the measured NMR signal intensities and those predicted by the model for all RO wastes except for poultry manure char. Molecular nature of the organic matter differed widely between the RO wastes. As a proportion of organic C, carbohydrate C ranged from 0.07 to 0.63, protein C from <0.01 to 0.66, lignin C from <0.01 to 0.31, aliphatic C from 0.09 to 0.73, carbonyl C from 0.02 to 0.23, and char C from 0 to 0.45. This method is considered preferable to techniques involving imprecise extraction methods for RO wastes. Molecular composition data has great potential as a predictor of RO waste soil carbon and nutrient outcomes. 相似文献
52.
G. N. Rao J. N. Beck H. E. Murray D. J. Nyman 《Journal of the American Water Resources Association》1991,27(1):47-58
ABSTRACT: Specific capacity data obtained from Well Construction reports which are available from USGS offices, can provide useful estimates of tranamissivity (T), and hydraulic conductivity (K), of an aquifer. The Chicot Aquifer in Louisiana is one of the largest sources of fresh ground water in North America. Hydrologic data collected for the Chicot Aquifer indicate that specific capacity tests can be used in estimating local and regional values for T and K, if the Cooper-Jacob equation for transient flow is used with proper corrections for well loss and partial penetration. Where full scale pumping test data are scarce, specific capacity test data that are adequately distributed spatially can be used to map changes in T and K values and can be summarized statistically to indicate applicable regional values. A computer program called “TGUESS” which is available from International Ground Water Modeling Center, Holcomb Research Institute, was used in this study. The contour maps for T and K values are prepared for different well depth intervals to avoid wide variation of values. 相似文献
53.
Gregory M. Clark Robert S. Williams 《Journal of the American Water Resources Association》1991,27(1):93-100
ABSTRACT: Batch-mixing experiments were used to help identify lithologic and mineralogic sources of increased concentrations of dissolved solids in water affected by surface coal mining in northwestern Colorado. Ten overburden core samples were analyzed for mineral composition and mixed with distilled water for 90 days until mineral-water equilibrium was reached. Between one day and 90 days after initial contact, specific conductance in the sample mixtures had a median increase of 306 percent. Dissolved-solids concentrations ranged from 200 to 8,700 mg/L in water samples extracted from the mixtures after 90 days. Mass. balance simulations were conducted using the geochemical models BALANCE and WATEQF to quantify mineral-water interactions occurring in five selected sample mixtures and in water collected from a spring at a reclaimed mine site. The spring water is affected by mineral-water interactions occurring in all of the lithologic units comprising the overburden. Results of the simulations indicate that oxidation of pyrite, dissolution of dolomite, gypsum, and epsomite, and cation-exchange reactions are the primary mineral-water interactions occurring in the overburden. Three lithologic units in the overburden (a coal, a sandstone, and a shale) probably contribute most of the dissolved solids to the spring water. Water sample extracts from mixtures using core from these three units accounted for 85 percent of the total dissolved solids in the 10 sample extracts. Other lithologic units in the overburden probably contribute smaller quantities of dissolved solids to the spring water. 相似文献
54.
Heinz G. Stefan .Ruochuan Gu 《Journal of the American Water Resources Association》1991,27(6):967-978
ABSTRACT: Forced artificial mixing of temperature-stratified ponds, or small lakes or reservoirs, by liquid jets can enhance water quality and can also be energy efficient. Based on previous studies of jet mixing mechanics of stratified water bodies, a conceptual design approach is presented. The main “operational” and “system” design parameters are considered in the proposed method. Using minimization of a total cost estimate as a criterion, an iterative method for the selection of the number and size of the jets is developed and illustrated. 相似文献
55.
Peter M. Allen Jeffrey C. Arnold Bruce W Byars 《Journal of the American Water Resources Association》1994,30(4):663-671
ABSTRACT: There is considerable potential for use of channel dimension data in planning-level models for resource and impact assessment. The channel dimension data is used to route flows and sediment through the basin. The cost of obtaining actual surveyed data for large watersheds is typically prohibitive. Predictive equations have been developed based on 674 stations from watersheds across the United States which encompass a wide variety of channel types and sizes. These equations were tested against an independent data set and found to be adequate for use in planning-level models. Future research is advocated which would include data from regions and stream types not included in this study. 相似文献
56.
Emmet M. Owens Steven W. Effler Francesco Trama 《Journal of the American Water Resources Association》1986,22(2):219-227
ABSTRACT: The thermal stratification characteristics of a flow-augmentation reservoir, Round Valley Reservoir, New Jersey, and attendant driving conditions were documented and analyzed for portions of three years. Substantial differences in the thermal stratification regime of the reservoir occurred in response to the documented changes in meteorological, operating, and light penetration conditions. The features of stratification that were affected included: the depth of the upper mixed layer, the average temperature of the epilimnion, the temperature gradient in the metalimnion, and the average temperature in the hypolimnion. 相似文献
57.
Quang M. Nguyen Martha W. Gilliland 《Journal of the American Water Resources Association》1988,24(1):103-111
ABSTRACT: Effects of no-flow river conditions on the quantity and quality of water in the Platte River well field of the City of Grand Island, Nebraska, were examined utilizing a finite-difference computer simulation model specifically developed for this well field. Results suggest that the effects of these no-flow periods on water quality may be most important. In particular, the no-flow periods eliminate the hydraulic barrier between the well field and an area north of the River that is contaminated with nitrate (concentrations in the 20 to 40 mg/1 NO3-N range). They also change the direction and velocity of movement of the contaminated ground water. Simulation results indicate that contaminated ground water moves toward the well field with a velocity of 0.42 ft/d after 30 days of no-flow and 1.43 ft/d after 180 days of no-flow. Limiting no-flow conditions to 10 consecutive days would protect the well field. 相似文献
58.
59.
Peter M. Allen Jeffrey G. Arnold Walter Skipwith 《Journal of the American Water Resources Association》2002,38(5):1477-1492
ABSTRACT: Major erosion of urban stream channels is found in smaller basins in the North Texas study area with contributing drainage areas of less than ten square miles. Within these basins, four basic channel types are identified based on bed and bank lithologies: alluvial banks and bottoms, alluvial banks and gravel bottoms, alluvial banks with rock bottoms, and rock banks with rock bottoms. Most channels (75 percent) have alluvial banks with gravel or rock bottoms. Channel slopes are steep (.38 to.76 percent). Rock consists predominantly of shale and limestone. Channel cross sections are divided into the following four zones based on weathering, scour and entrainment mechanisms: soil zone, slake zone, rock zone and bed material zone. Erodibility of the channels is determined using multiple techniques including reach hydraulics and stream power computations, submerged jet testing, slab entrainment thresholds, and slake durability rates. Procedures are based on both empirical and modeled time series estimates of channel erosion. Field and modeled results support rates of erosion of up to four inches per year. Rates are tied to flow regime, climate, and type of channel bed and banks. 相似文献
60.
Rebecca J. Wade Bruce L. Rhoads Jose Rodriguez Melinda Daniels David Wilson Edwin E. Herricks Fabian Bombardelli Marcelo Garcia John Schwartz 《Journal of the American Water Resources Association》2002,38(4):931-944
ABSTRACT: Many urban and suburban communities in the Midwest are seeking to establish sustainable, morphologically and hydraulically varied, yet dynamically stable fluvial systems that are capable of supporting healthy, biologically diverse aquatic ecosystems — a process known as stream naturalization. This paper describes an integrated research program that seeks to develop a scientific and technological framework to support two stream naturalization projects near Chicago, Illinois. The research program integrates theory and methods in fluvial geomorphology, aquatic ecology, hydraulic engineering and social theory. Both the conceptual and the practical challenges of that integration are discussed. Scientific and technical support emphasize the development of predictive tools to evaluate the performance of possible naturalization designs at scales most appropriate to community based projects. Social analysis focuses on place based evaluations of how communities formulate an environmental vision and then, through decision making, translate this vision into specific stream naturalization strategies. Integration of scientific and technical with social components occurs in the context of community based decision making as the predictive tools are employed by project scientists to help local communities translate their environmental visions into concrete environmental designs. Social analysis of this decision making process reveals how the interplay between the community's vision of what they want the watershed to become, and the scientific perspective on what the watershed can become to achieve the community's environmental goals, leads to the implementation of specific stream naturalization practices. 相似文献