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891.
Robert H. Webb H. Craig Ragland William H. Godwin Oennis Jenkins 《Environmental management》1978,2(3):219-233
The effects of off-road vehicles (ORVs) on the physical and chemical properties of 6 soil series were measured at Hollister Hills State Vehicular Recreation Area in central California. Accelerated soil erosion and the alteration of surface strength, bulk density, soil moisture, temperature, and soil nutrients were quantified to gain an insight into the difficulty of revegetating altered, or modified, areas.Erosion is severe at Hollister Hills, particularly in coarse grained soils on steep slopes. Erosion displaced 0.5 and 3.0 metric tons per square meter on 2 trails on gravelly sandy loam, and 0.3 metric tons/m2 from a trail on sandy loam. The surface strength and bulk density increased while the soil moisture decreased in gravelly sandy loam, coarse sandy loam, sandy loam, and clay. Clay loam had an increased surface strength with variably increased bulk density and no decrease in soil moisture. Diurnal temperature fluctuations increased and organic material and soil nutrients decreased in soil modified by vehicles.These property changes increase the erosion potential of the soil, impede germination of seedlings, and slow natural revegetation. Management methods in ORV-use areas should include planning trails by prior application of the universal soil loss equation and soil surveys, trail closure before complete loss of the soil mantle, and revegetation of closed areas. 相似文献
892.
Anne-Marie?DelortEmail author Bruno?Combourieu Nicolas?Haroune 《Environmental Chemistry Letters》2003,1(4):209-213
This article presents a short overview of selected recent papers using nuclear magnetic resonance (NMR) to investigate interactions between organic pollutants and soil components such as organic matter, clays, whole soils, and sediments. First, we describe solid state cross polarisation magic angle spinning (CP-MAS) experiments as the main tools to investigate covalent bonds. Second, we report NMR approaches allowing us to assess molecule mobility and to characterise non-covalent interactions. Those approaches include correlations between K
oc
values and soil organic matter functions determined by CP-MAS, 2H NMR fingerprints, relaxation time measurements, 19F and 1H high resolution (HR)-MAS experiments. 相似文献
893.
Stohlgren TJ Chong GW Schell LD Rimar KA Otsuki Y Lee M Kalkhan MA Villa CA 《Environmental management》2002,29(4):566-577
Basic information on where nonnative plant species have successfully invaded is lacking. We assessed the vulnerability of
22 vegetation types (25 sets of four plots in nine study areas) to nonnative plant invasions in the north–central United States.
In general, habitats with high native species richness were more heavily invaded than species-poor habitats, low-elevation
areas were more invaded than high-elevation areas, and riparian zones were more invaded than nearby upland sites. For the
100 1000-m2 plots (across all vegetation types), 50% of the variation in nonnative species richness was explained by longitude, latitude,
native plant species richness, soil total percentage nitrogen, and mean maximum July temperature (n = 100 plots; P < 0.001). At the vegetation-type scale (n = 25 sets of four 1000-m2 plots/type), 64% of the variation in nonnative species richness was explained by native plant species richness, elevation,
and October to June precipitation (P < 0.001). The foliar cover of nonnative species (log) was strongly positively correlated with the nonnative species richness at the
plot scale (r = 0.77, P < 0.001) and vegetation-type scale (r = 0.83, P < 0.001). We concluded that, at the vegetation-type and regional scales in the north–central United States, (1) vegetation types
rich in native species are often highly vulnerable to invasion by nonnative plant species; (2) where several nonnative species
become established, nonnative species cover can substantially increase; (3) the attributes that maintain high native plant
species richness (high light, water, nitrogen, and temperatures) also help maintain nonnative plant species richness; and
(4) more care must be taken to preserve native species diversity in highly vulnerable habitats. 相似文献
894.
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
895.
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
896.
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
897.
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
898.
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
899.
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
900.
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