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11.
R. A. Olson Edwin C. Seim John Muir 《Journal of the American Water Resources Association》1973,9(2):301-311
ABSTRACT Rainfall, stream flow and groundwater have been sampled systematically throughout Nebraska since 1970 and analyzed for mineral N and P and the character of any sediments contained. Fallout N and P in rainfall ranges from 5–14 pounds N and 1 pounds P/A/yr, increasing from west to east across the state with increasing rainfall. The amount of NH4-N is essentially double that of NO3-N. The mean concentration of 2ppm N in rainfall is four times the mean N concentration of streams, demonstrating a substantial depolluting action of soils and growing crops. Where nutrient levels of streams are elevated, cause can usually be traced especially to industrial, sewage or livestock waste intrusion and not to crop production practices. The only significant quantity of nutrient N and P induced by cultivation is that accompanying sediments from eroded fields. The P content of Nebraska groundwater has remained essentially constant during the past 10 years while average NO3-N has increased slightly, a period during which farmer fertilizer use quadrupled. During the same time, irrigation acreage has increased by 50%, livestock numbers by 30%, with corresponding growth in human population and attendant industries. Indications are that irrigation practice has contributed more than any other factor to the small increase in groundwater NO3-N recorded. Individual cases do exist where groundwater NO3-N has increased substantially, especially in areas of intensive irrigation agriculture on very sandy soils and elsewhere with irrigation development in the proximity of ancient NO3-N deposits in mantlerock above the water table. 相似文献
12.
Roy Burke James P. Heaney Edwin E. Pyatt 《Journal of the American Water Resources Association》1973,9(3):433-447
ABSTRACT The problem of water resources management can be viewed as one requiring the existence and application of some type of “collective decision” mechanism. Currently, the general water resource decision problem is solved using an “individual decision” format without explicit consideration of the dominant social decision system. This paper demonstrates the need for blending technical planning activities with organized societal processes and then proposes a specific public decision framework to satisfy this requirement. The key element in this planning framework is a generalized “bargaining arena” which serves to link technical activities with the social system. Using this bargaining device we can (1) specify policy at a local level, (2) incorporate “social decision” rules into the planning process, and (3) provide local access to the decision process. A simple case of regional water quality management is used to describe the application of this planning procedure and to offer encouragement for successful use in more complex real-world cases. 相似文献
13.
Woodard KR French EC Sweat LA Graetz DA Sollenberger LE Macoon B Portier KM Rymph SJ Wade BL Prine GM Van Horn HH 《Journal of environmental quality》2003,32(3):996-1007
In northern Florida, year-round forage systems are used in dairy effluent sprayfields to reduce nitrate leaching. Our purpose was to quantify forage N removal and monitor nitrate N (NO3(-)-N) concentration below the rooting zone for two perennial, sod-based, triple-cropping systems over four 12-mo cycles (1996-2000). The soil is an excessively drained Kershaw sand (thermic, uncoated Typic Quartzip-samment). Effluent N rates were 500, 690, and 910 kg ha(-1) per cycle. Differences in N removal between a corn (Zea mays L.)-bermudagrass (Cynodon spp.)-rye (Secale cereale L.) system (CBR) and corn-perennial peanut (Arachis glabrata Benth.)-rye system (CPR) were primarily related to the performance of the perennial forages. Nitrogen removal of corn (125-170 kg ha(-1)) and rye (62-90 kg ha(-1)) was relatively stable between systems and among cycles. The greatest N removal was measured for CBR in the first cycle (408 kg ha(-1)), with the bermudagrass removing an average of 191 kg N ha(-1). In later cycles, N removal for bermudagrass declined because dry matter (DM) yield declined. Yield and N removal of perennial peanut increased over the four cycles. Nitrate N concentrations below the rooting zone were lower for CBR than CPR in the first two cycles, but differences were inconsistent in the latter two. The CBR system maintained low NO3(-)-N leaching in the first cycle when the bermudagrass was the most productive; however, it was not a sustainable system for long-term prevention of NO3(-)-N leaching due to declining bermudagrass yield in subsequent cycles. For CPR, effluent N rates > or = 500 kg ha(-1) yr(-1) have the potential to negatively affect ground water quality. 相似文献
14.
Edwin D Geetha VR Vishwanathan H Usha Rani MV 《Journal of environmental biology / Academy of Environmental Biology, India》2002,23(4):373-376
Common use of antimutagens and anticarcinogens in everyday life is an effective measure for preventing human cancer and genetic diseases. Antioxidant properties of tea have vast potential as protective agents against diverse toxic effects. The present study was aimed to evaluate the role of aqueous clonal tea extracts (green tea, oolong tea and black tea) in modulating the genotoxic damage induced by cyclophosphamide (CP), a commonly used chemotherapeutic drug and a well-known mutagen and clastogen. All the three tea extracts at 1 and 2% concentration did not increase the frequency of micronucleated polychromatic erythrocytes (MPE) in bone marrow cells of mice when administered individually. The tea extracts decreased the micronuclei (MN) induced by CP. Therefore, regular intake of tea may improve the antioxidant status in in vivo and thereby reduce the risk of cancer and coronary heart disease. 相似文献
15.
Construction of the 1913 Los Angeles aqueduct system had a different effect on vegetation productivity, diversity, and stability in the Mojave Desert than did construction of the 1970 aqueduct. Drastic disturbance was found to impede vegetation recovery, whereas slight disturbance sometimes enhanced vegetation. Comparisons of productivity, diversity, and stability measures for both aqueducts show apparent similarities of vegetation cover, biomass, and density. However, these similarities often vanish when one considers qualitative factors, such as proportion of long-lived species and typical cominants of undisturbed communities. Percentage composition of common long-lived perennials represents a good qualitative measure to supplement quantitative comparisons. Enhancement of vegetation along the right-of-way transects of the 1913 aqueduct shows considerable recovery, owing to the more than 65 years that have passed since construction. 相似文献
16.
Donald J. Epp C. Edwin Young 《Journal of the American Water Resources Association》1981,17(2):215-224
ABSTRACT: Varying treatment levels to meet seasonal variation in assimilative capacity of streams can reduce total costs of treatment. A mathematical model of a Pennsylvania stream based on a theoretically sound approximation of the physical relationships underlying the distribution of DO in a river system was used to determine discharge constraints for an economic optimization model which produced estimates of sewage treatment cost savings. Increasing the number of flow periods during the year enhances cost reducing opportunities even when land application processes are considered. Also, the least cost treatment process for year around operation may not be the least costly under multiple flow period management. 相似文献
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19.
Edwin Zaccaï 《Environment, Development and Sustainability》2008,10(1):51-67
A global analysis shows that considerable forces contribute nowadays to the perpetuation of the so-called “developed” model of consumption, and its extension to growing parts of the world, despite reiterated calls for “modification of production and consumption patterns”. Environmental product regulation can be situated in this general perspective. This paper returns to the framing of policies devoted to ecologically sustainable consumption, taking the example of the Integrated product policy at the European level. How are the objectives of such policies defined? What instruments are privileged? Comparing theoretical approaches with policy design, we focus on the role devoted to consumers in these contexts. Bringing in literature evidence, survey results and findings from an original study, we argue that appropriate knowledge of the diversity of consumers’ attitudes and about the limitations of their possible actions is not properly taken into account in product policies, notably when information and voluntary tools are dominant. From this point of view, environmental product regulations are well justified, but they should, as all policy instruments implicating consumers, take careful notice of their situation. 相似文献
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