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排序方式: 共有105条查询结果,搜索用时 125 毫秒
1.
Deurer M Sivakumaran S Ralle S Vogeler I McIvor I Clothier B Green S Bachmann J 《Journal of environmental quality》2008,37(3):915-924
A new method to diagnose the environmental sustainability of specific orchard management practices was derived and tested. As a significant factor for soil quality, the soil carbon (C) management in the topsoil of the tree-row of an integrated and organic apple orchard was selected and compared. Soil C management was defined as land management practices that maintain or increase soil C. We analyzed the impact of the soil C management on biological (microbial biomass C, basal respiration, dehydrogenase activity, respiratory quotient) and physical (aggregate stability, amount of plant-available water, conductive mean pore diameter near water saturation) soil properties. Soil in the alley acted as a reference for the managed soil in the tree row. The total and hot-water-extractable C amounts served as a combined proxy for the soil C management. The soil C management accounted for 0 to 81% of the degradation or enhancement of biophysical soil properties in the integrated and organic system. In the integrated system, soil C management led to a loss of C in the top 0.3 m of the tree row within 12 yr, causing a decrease in microbial activities. In the tree row of the organic orchard, C loss occurred in the top 0.1 m, and the decrease in microbial activities was small or not significant. Regarding physical soil properties, the C loss in the integrated system led to a decrease of the aggregate stability, whereas it increased in the organic system. Generally, the impact of soil C management was better correlated with soil microbial than with the physical properties. With respect to environmental soil functions that are sensitive to the decrease in microbial activity or aggregate stability, soil C management was sustainable in the organic system but not in the integrated system. 相似文献
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3.
We studied the validity of mid-trimester amniotic fluid testosterone and FSH in the diagnosis of fetal sex in abnormal fetuses and in twins. It was found that the testosterone/FSH ratio, but not the level of the individual hormones, was an excellent criterion for fetal sex diagnosis. In a control group of 32 female and 34 male fetuses, the testosterone/FSH ratio was diagnostic. In two cases the values were indeterminate and fetal sex could not be predicted, but there were no false diagnoses. The abnormalities of the fetuses were diagnosed by karyotype analyses or raised levels of α-fetoprotein. It was found that neither autosomal trisomies nor X-chromosome aneuploidy or neural tube defect interfered with the diagnostic value of the hormonal approach. The twin study included 14 pairs, three of whom were discordant for sex. In all twins the fetal sex diagnosis was appropriate. In co-twins of the same sex the hormone levels were very close to each other. 相似文献
4.
The uptake of particulates by an urban woodland: site description and particulate composition 总被引:24,自引:0,他引:24
Freer-Smith PH Holloway S Goodman A 《Environmental pollution (Barking, Essex : 1987)》1997,95(1):27-35
Woodlands may improve local air quality by increasing the uptake rates of gaseous, particulate and aerosol pollutants from the atmosphere and can also act as relatively permanent sinks for some pollutants. Rough Wood, Walsall was selected for a study of the material which accumulates on tree foliage because of its location in a densely populated urban area, and its proximity to a motorway with high traffic flow (the M6) and to other pollutant sources. Methods were developed for leaf washing to allow determination of the quantity of dust and the identification of the dust particles present on oak leaves. Elemental analysis of particles was also undertaken using scanning electron microscopy coupled with electron probe microanalysis. A large proportion of particles were organic in origin. Of the inorganic particles, the majority contained silicon and aluminium in varying proportions suggesting that they were soil derived. Some particles were clearly identified as the products of combustion, and sea or road salt was present on leaf surfaces. Some particles contained copper, tin and titanium which may reflect the proximity of Rough Wood to local metal workings. The number of particles counted on leaf surfaces decreased as distance from the motorway increased. 相似文献
5.
Maurer Edwin P. Roby Nicholas Stewart-Frey Iris T. Bacon Christopher M. 《Regional Environmental Change》2017,17(8):2421-2432
Regional Environmental Change - In addition to periodic long-term drought, much of Central America experiences a rainy season with two peaks separated by a dry period of weeks to over a month in... 相似文献
6.
Cr(VI) is far more soluble and toxic than Cr(III). Sediment pore water was investigated in a river adjacent to the property of a large former tannery, into which Cr-contaminated effluent was discharged over a 55-year period, and where extremely high Cr concentrations have been found in the sediments. Dialysis cells, or peepers, were used to generate depth profiles of Cr concentration in sediment pore water. Samples were analyzed for total Cr using inductively coupled plasma-mass spectrometry (ICP-MS) and for Cr species using high performance liquid chromatography (HPLC)-ICP-MS. The results show an absence of Cr(VI) in all samples. Furthermore, incomplete recovery of Cr(VI) added to the samples collected at the locations with highest sediment Cr concentrations indicate strong reducing conditions at those locations, which are not conducive to the presence of Cr(VI). 相似文献
7.
David C. Carslaw Paul S. Goodman Frank C.H. Lai Oliver M.J. Carsten 《Atmospheric environment (Oxford, England : 1994)》2010,44(23):2674-2680
In recent years sophisticated technologies have been developed to control vehicle speed based on the type of road the vehicle is driven on using Global Positioning Systems and in-car technology that can alter the speed of the vehicle. While reducing the speed of road vehicles is primarily of interest from a safety perspective, vehicle speed is also an important determinant of vehicle emissions and thus these technologies can be expected to have impacts on a range of exhaust emissions. This work analyses the results from a very large, comprehensive field trial that used 20 instrumented vehicles with and without speed control driven almost 500,000 km measuring vehicle speed at 10 Hz. We develop individual vehicle modal emissions models for CO2 for 30 Euro III and Euro IV cars at a 1-Hz time resolution. Generalized Additive Models were used to describe how emissions from individual vehicles vary depending on their driving conditions, taking account of variable interactions and time-lag effects. We quantify the impact that vehicle speed control has on-vehicle emissions of CO2 by road type, fuel type and driver behaviour. Savings in CO2 of ≈6% were found on average for motorway-type roads when mandatory speed control was used compared with base case conditions. For most other types of road, speed control has very little effect on emissions of CO2 and in some cases can result in increased emissions for low-speed limit urban roads. We also find that there is on average a 20% difference in CO2 emission between the lowest and highest emitting driver, which highlights the importance of driver behaviour in general as a means of reducing emissions of CO2. 相似文献
8.
Siddhartha Bagchi Alvin S. Goodman 《Journal of the American Water Resources Association》1979,15(2):536-549
ABSTRACT: This paper focuses on the development and testing of a mathematical model of an emergency ground water supply operated principally during periods of low streamflow. The process of ground water withdrawal and recharge is simulated taking account of streamflow, water demand, evapotranspiration, natural and artificial recharge and increased evapotranspiration due to artificial recharge, ground water pumpage, and streamflow contribution to pumped water. The model determines whether natural recharge is possible in less time than the return period of drought and also whether artificial recharge is needed. By simulating operation over a long period of time, the model can examine different droughts of short and long duration and can test the operating rules for ground water storage development in an area. Submodels analyze the components of the operating process including ground water flow into the stream, seepage losses, stream portion of well discharge due to induced infiltration and recharge from rainfall or water spreading. The model has been tested for areas in the humid northeastern United States. 相似文献
9.
Summary. A diverse group of brown seaweeds produce bouquets of C11 metabolites, some of which act as pheromones that cue gamete release or attract sperm to eggs following release. We demonstrate
that these C11 metabolites and their degradation products also frequently and strongly deter feeding by the herbivorous amphipod Ampithoe longimana, but rarely by the herbivorous sea urchin Arbacia punctulata. Across the range of concentrations tested, seven of twelve C11 metabolites or mixtures that we tested deterred feeding by the amphipod, but only two of eleven deterred the sea urchin.
For those compounds where we could rigorously contrast the magnitude of deterrence against the amphipod with the magnitude
of deterrence against the urchin, the amphipod was deterred significantly more than the urchin by five of six metabolites.
Thus, C11 compounds were more frequently and more strongly deterrent to the amphipod than to the sea urchin. These findings for C11 metabolites conflict with previous investigations, where other classes of seaweed chemical defenses have been shown to deter
feeding by large mobile herbivores like urchins and fishes but to be relatively ineffective against mesograzers, especially
the species of amphipod that we used here. Our results suggest that C11 metabolites are unusual among the known seaweed chemical defenses in that they are especially effective against mesograzers,
which often consume seaweed spores, zygotes, and juveniles. The high concentrations of C11 metabolites in brown algal eggs could allow these defenses to be especially important in defending gametes, zygotes, or young
sporelings from herbivorous mesograzers.
Received 26 February 1998; accepted 9 April 1998. 相似文献
10.
S. L. Goodman W. Seabrooke S. A. Jaffry 《Journal of Environmental Planning and Management》1998,41(3):313-336
Measuring the economic value of environmental quality is useful to evaluate policies that affect the use of natural resources. This paper presents the findings of a contingent valuation (CV) survey designed to measure non-use values for the natural coastal environment.This was attempted through evaluating public and scientific values of conservation quality. The results suggest that public perceptions of conservation quality are multidimensional,and that it may be difficult for some individuals to express their preferences for the conservation value of natural resources in monetary terms. Additionally, public and scientific judgments differ concerning some of the physical attributes imparting conservation value. These findings have important implications on efforts to consider environmental quality in land and coastal use decisions. 相似文献