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Septic system leachfields can release dissolved nitrogen in the form of nitrate into ground water, presenting a significant source of pollution. Low cost, passive modifications, which increase N removal in traditional leachfields, could substantially reduce the overall impact on ground water resources. Bench-scale laboratory models were constructed to evaluate the effect of placing an organic layer below the leachfield on total N removal. The organic layer provides a carbon source for denitrification. Column units representing septic leachfields were constructed with sawdust-native soil organic layers placed 0.45 m below the influent line and with thicknesses of 0.0, 0.3, 0.6, and 0.9 m. Using a synthetic septic tank effluent, NO(3)-N concentrations at 3.8 m below the influent line were consistently below 1 mg L(-1) during 10 months of operation compared with a NO(3)-N concentration of nearly 12 mg L(-1) in the control column. The average total N removal increased from 31% without the organic layer to 67% with the organic layer. Total N removal appeared limited by the extent of organic N oxidation and nitrification in the 0.45-m aerobic zone. Design modifications targeted at improving nitrification above the organic layer may further increase total N removal. Increased organic layer thicknesses from 0.3 m to 0.9 m did not significantly improve average total N removal, but caused a shift in residual nitrogen from organic N to ammonia N. Results indicate that addition of a layer of carbon source material at least 0.3 m thick below a standard leachfield substantially improves total N removal. 相似文献
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创刊于1972年12月的《文教资料简报》是由南京师范学院(1984年易名为南京师范大学)内部编印的资料性月刊,主要目的是为文科教研服务。本文回顾该刊从创办至拥有"统一刊号"、从非正式出版物至成为正式出版物的历史沿革,具体观照该刊的编辑理念,总结该刊的内容特色、文献价值及经验启示。 相似文献
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Hiller Edgar Pilková Zuzana Filová Lenka Jurkovič Ľubomír Mihaljevič Martin Lacina Petr 《Environmental science and pollution research international》2021,28(5):5455-5471
Environmental Science and Pollution Research - It is well known that road transport emits various trace elements into the environment, which are deposited in soils in the vicinity of roads,... 相似文献
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The sensitivity of the United States Forest Health Monitoring network to outbreaks of defoliating insects was examined by means of a simulation study. A model constructed specifically for the study was used to generate a wide variety of defoliation patterns in forested landscapes. Forest configuration was that of Minnesota, USA, as expressed by the GAP land cover classification. Combinations of model parameters were based on a Latin Hypercube sample. The relationship between the average number of plots defoliated and outbreak characteristics was then examined via multiple regression. Both theoretical and model results pointed to a strong, linear relationship between the average number of plots defoliated and outbreak size. Model results provided additional insight, suggesting a significant relationship between the average number of plots defoliated and other outbreak characteristics after outbreak size was taken into account. 相似文献
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The provision of sheltered housing for sale in Scotland has experienced rapid growth since the opening of the first scheme in 1982. Development has been geographically concentrated in a small number of inner city and rural (coastal) areas. The expectation of continued rapid expansion is unlikely if recent trends of slower growth continue. This paper uses evidence from interviews with developers and owners of sheltered and mainstream housing, to examine the possible future contribution of the private market. On the basis of such evidence it raises questions about the relevance of some existing planning policies. 相似文献
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During the period of 1972 through 1993, Environmental Concern Inc. (EC) and its recent (1989) affiliate Environmental Construction
Company (ECC) have completed 216 marsh construction projects to control upland bank erosion in tributaries of the Maryland
portion of Chesapeake Bay. Of these projects, 26 have involved marsh construction on unaltered existing shores and 190 have
utilized marsh construction on shores that have been restored to former increased elevations through shoreline filling and
grading. This paper describes the latter restoration technique. Throughout the 21-year period of applying the technique for
long-term upland bank erosion control, refinements to the design standards and criteria for site suitability have been made
so as to optimize its successful application. As a result of this experience, a reliable bioengineering restoration technique
has evolved to control upland bank erosion. This paper describes the details of this successful technique through a review
of: (1) its objectives and benefits, (2) suitability of sites for its application, (3) the design of its shore restoration,
(4) its construction, (5) its maintenance, and (6) comparison of its cost with those of structural techniques for bank erosion
control. Although the technique has only been applied in the Maryland portions of Chesapeake Bay, its applicability should,
with modifications, be broadly applicable to all water bodies. 相似文献