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941.
942.
通过对垫江县目前土地资源利用特点,存在问题及其原因的详细分析,结合垫法实际,提出了垫江县土地资源可持续利用分区的设想,针对各区不同的土地利用特点,提出了土地持续利用方向及主要措施。 相似文献
943.
水力侵蚀对路基表面稳定性的影响研究 总被引:4,自引:0,他引:4
通过降雨试验和天然降雨水土流失调查 ,笔者首先探讨了风化花岗岩地区路基表面水力侵蚀的表现形式和规律 ,其中 ,基床表层已填筑级配碎石的易于发生级配碎石粗粒化 ,未填筑级配碎石的易于发生沟蚀 ;裸露的路堤边坡水力侵蚀发生发展规律一般为 :沟蚀→边坡滑坍 ;裸露的路堑边坡水力侵蚀发生发展规律一般为 :溅蚀→面蚀→沟蚀→坍塌 ;片石护坡的路堤和路堑边坡易于发生潜蚀。然后分析了水力侵蚀对路基表面稳定性的影响 ,认为溅蚀和面蚀对路基表面稳定性的影响较小 ;沟蚀对路堤边坡表面稳定性的影响程度随侵蚀程度和工程进度具体情况而定。最后 ,提出了施工期路基表面防护的建议 相似文献
944.
This article provides an objective integrated environmental impact assessment of the Gulf War consequences. The environmental
damage was evaluated and found to be significantly exaggerated by the media and speculators. The total amount of burned crude
oil was calculated to be 52.5 million metric tons. Most air pollution field measurements were comparable to those found in
Western cities. The health impact associated with such exposure was found to be minimal. The total amount of oil released
into the marine environment ranged between 2 and 4 million barrels, much less than the early estimation of 12–14 million barrels.
The marine environment is expected to recover much faster than earlier anticipations. Unlike water and air, soil pollution
is likely to persist for some years to come. 相似文献
945.
ABSTRACT: A spatial decision support system (SDSS) was developed to assess agricultural nonpoint source (NPS) pollution using an NPS pollution model and geographic information systems (GIS). With minimal user interaction, the SDSS assists with extracting the input parameters for a distributed parameter NPS pollution model from user-supplied GIS base layers. Thus, significant amounts of time, labor, and expertise can be saved. Further, the SDSS assists with visualizing and analyzing the output of the NPS pollution simulations. Capabilities of the visualization component include displays of sediment, nutrient, and runoff movement from a watershed. The input and output interface techniques/algorithms used to develop the SDSS, along with an example application of the SDSS, are described. 相似文献
946.
本文阐述了黄泛平原土壤侵蚀的特点,对侵蚀的形式、程度及严重危害,作了比较详细的分析,并从宏观上提出了一些防治对策。 相似文献
947.
William L. Halvorson Dennis B. Fenn William R. Allardice 《Environmental management》1988,12(1):109-118
The multifaceted development of an erosion surface on Santa Barbara Island, Channel Islands National Park, California, has led to this study of the relationship between soils and vegetation. A dry Mediterranean climate and past attempts at farming and introductions of alien species have led to vegetative degradation accompanied by both gully and surface erosion. Soil and vegetation analyses show this erosion to be in a location of transition. The soils are Typic Chromoxererts (Vertisol Order) with high clay, salinity, and sodium contents. The vegetation is ecotonal in nature, grading from a principally alien annual grassland withAvena fatua andAtriplex semibaccata to a shrub community dominated by the nativeSuaeda californica. Management toward revegetation and stabilization of this island ecosystem will be difficult with high clay, saline-sodic soils and disturbed vegetation. 相似文献
948.
Quality control is a crucial aspect of database management, particularly for physicochemical parameters that are widely used
in modeling environmental fate processes. Complete rechecking of original studies to verify environmental fate parameters
is time consuming and difficult. This paper evaluates an alternative, more efficient approach to identifying database errors.
The approach focuses verification efforts on a targeted subset of entries by making use of the relationship between water
solubility (S) and soil organic carbon partition coefficient (K
oc
). Two regression equations, one selected from the literature and one calculated from entries in the database, were used to
evaluate the reasonableness of (S, K
oc
) pairs among control compared to the targeted outlier group from a total of 59 pesticides. Our hypothesis was that (S, K
oc
) pairs that lay far from the regression line were more likely to be in error than those that fit the regression. Database
values were checked against original studies.
Identified errors in the database included coding mistakes, miscalculations, and incorrect chemical identification codes.
The error rate in outlier (S, K
oc
) pairs was about twice that of pairs that conformed to the regression equation; however, the error rate differential was
probably not large enough to justify the use of this quality control method. Through our close scrutiny of database entries
we were able to identify administrative practices that led to mistakes in the data base. Resolution of these problems will
significantly decrease the number of future mistakes. 相似文献
949.
Jordan FL Sandrin SK Frye RJ Brusseau ML Maier RM 《Journal of contaminant hydrology》2004,74(1-4):19-38
A series of miscible-displacement column experiments were conducted under saturated flow conditions to systematically investigate the influence of physical and biological complexity on bacterial activity and fate in the presence and absence of a non-sorbing growth substrate, salicylate. Bacterial elution was monitored for three different systems; System I--a sterilized, inoculated, well-sorted sand, System II--a sterilized, inoculated, heterogeneous loamy sand (Hayhook), and System III--two different unsterilized loamy sands (Hayhook and Vinton) each with their associated indigenous microbial community. Results show that System I behaved ideally with respect to both cell and substrate transport, wherein: (1) growth occurred in response to substrate addition, (2) cell elution increased in response to the substrate pulse, and (3) breakthrough curves were reproducible for both substrate and cell elution. In contrast, System II showed ideal behavior with respect to substrate transport but showed variable behavior for cell transport. Further, there was no measurable growth in response to substrate addition and no increase in cell elution during the salicylate pulse. System III exhibited non-ideal behavior for both substrate and cell transport. Of particular interest is the fact that the indigenous communities of the two soils behaved differently. Specifically, for the Hayhook soil, an increased elution response was observed for the heterotrophic population while the salicylate-degrading community was preferentially retained in the column. In contrast for the Vinton soil, the substrate pulse did not elicit an elution response from either the heterotrophic or salicylate-degrading community from the culturable, indigenous Vinton microorganisms. For Systems II and III, the observed variability appears to be associated with the biological component of the system, since sterile controls were reproducible. This type of systematic study is critical for understanding cell and substrate transport behavior in complex, heterogeneous systems, and illustrates the potential uncertainty associated with measurements in such systems. 相似文献
950.