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71.
An Aquifer Vulnerability Assessment of the Paluxy Aquifer, Central Texas, USA, Using GIS and a Modified DRASTIC Approach 总被引:9,自引:1,他引:8
D epth to water, net Recharge, Aquifer media, Soil media,
Topography, Impact of the vadose zone, and
Conductivity of the aquifer). Using such an approach allows one to investigate the potential for groundwater contamination
on a regional, rather than site-specific, scale. Based upon data from variables such as soil permeability, depth to water,
aquifer hydraulic conductivity, and topography, subjective numerical weightings have been assigned according to the variable's
relative importance in regional groundwater quality. The weights for each variable comprise a GIS map layer. These map layers
are combined to formulate the final groundwater pollution potential map. Using this method of investigation, the pollution
potential map for the study area classifies 47% of the area as having low pollution potential, 26% as having moderate pollution
potential, 22% as having high pollution potential, and 5% as having very high pollution potential. 相似文献
72.
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75.
Diversity and host range of foliar fungal endophytes: are tropical leaves biodiversity hotspots? 总被引:2,自引:0,他引:2
Fungal endophytes are found in asymptomatic photosynthetic tissues of all major lineages of land plants. The ubiquity of these cryptic symbionts is clear, but the scale of their diversity, host range, and geographic distributions are unknown. To explore the putative hyperdiversity of tropical leaf endophytes, we compared endophyte communities along a broad latitudinal gradient from the Canadian arctic to the lowland tropical forest of central Panama. Here, we use molecular sequence data from 1403 endophyte strains to show that endophytes increase in incidence, diversity, and host breadth from arctic to tropical sites. Endophyte communities from higher latitudes are characterized by relatively few species from many different classes of Ascomycota, whereas tropical endophyte assemblages are dominated by a small number of classes with a very large number of endophytic species. The most easily cultivated endophytes from tropical plants have wide host ranges, but communities are dominated by a large number of rare species whose host range is unclear. Even when only the most easily cultured species are considered, leaves of tropical trees represent hotspots of fungal species diversity, containing numerous species not yet recovered from other biomes. The challenge remains to recover and identify those elusive and rarely cultured taxa with narrower host ranges, and to elucidate the ecological roles of these little-known symbionts in tropical forests. 相似文献
76.
Ma Li Yu Zhuo Jiao Yan Lin Lin Zhong Wei Day Sara W. Postlethwaite Arnold Chen Hong Li Qiang Yin Heliang Wang Gang 《Environmental science and pollution research international》2021,28(28):37498-37505
Environmental Science and Pollution Research - The widespread epidemic of the COVID-19 in developed countries such as Europe and the USA has sparked many speculations. What factors caused the rapid... 相似文献
77.
Arnold J. H. van Vliet Wichertje A. Bron Sara Mulder Wout van der Slikke Baudewijn Odé 《Regional Environmental Change》2014,14(3):997-1008
We determined whether climate change in the Netherlands has caused phenological changes since 1868. We analysed over 150,000 plant phenological observations of 320 plant species, obtained by four volunteer networks and one series collected by Mr. Braaksma. With the network data, we compared the timing of life cycle events in three different periods: 1894–1932 (Period 1), 1940–1968 (Period 2) and 2001–2010 (Period 3). For the Braaksma series, we compared the periods 1953–1968 (Period A) with 1969–1992 (Period B). We conclude that until the beginning of the 1990s, there have been no significant changes in the timing of life cycle events. The timing of life cycle events in Period 3 showed an average advance of flowering, leaf unfolding and fruit ripening of 14 days compared with Period 1 and 13 days compared with Period 2. Some species have advanced up to over 35 days. Autumn events occurred up to an average of 7 days later in Period 3 compared to earlier periods. This study shows that, based on network data, changes in climate explain on average 66 % of the variation in timing of phenological events from year to year. For the Braaksma data, this is 38 %. The expected future changes in climate will undoubtedly result in a further lengthening of the growing season. We believe that phenological networks, supported by thousands of volunteers, are needed to quantify, analyse, predict and communicate these phenological changes so various sectors in society can adapt to these changes and prevent significant socio-economic impacts. 相似文献
78.
Bielmyer GK Arnold WR Tomasso JR Isely JJ Klaine SJ 《Environmental monitoring and assessment》2012,184(5):2797-2804
Copper sheeting is a common roofing material used in many parts of the world. However, copper dissolved from roof sheeting
represents a source of copper ions to watersheds. Researchers have studied and recently developed a simple and efficient model
to predict copper runoff rates. Important input parameters include precipitation amount, rain pH, and roof angle. We hypothesized
that the length of a roof also positively correlates with copper concentration (thus, runoff rates) on the basis that runoff
concentrations should positively correlate with contact time between acidic rain and the copper sheet. In this study, a novel
system was designed to test and model the effects of roof length (length of roof from crown to the drip edge) on runoff copper
concentrations relative to rain pH and roof angle. The system consisted of a flat-bottom copper trough mounted on an apparatus
that allowed run length and slope to be varied. Water of known chemistry was trickled down the trough at a constant rate and
sampled at the bottom. Consistent with other studies, as pH of the synthetic rainwater decreased, runoff copper concentrations
increased. At all pH values tested, these results indicated that run length was more important in explaining variability in
copper concentrations than was the roof slope. The regression equation with log-transformed data (R
2 = 0.873) accounted for slightly more variability than the equation with untransformed data (R
2 = 0.834). In log-transformed data, roof angle was not significant in predicting copper concentrations. 相似文献
79.
Development and Testing of a Physically Based Model of Streambank Erosion for Coupling with a Basin‐Scale Hydrologic Model SWAT 下载免费PDF全文
B. Narasimhan P.M. Allen S.V. Coffman J.G. Arnold R. Srinivasan 《Journal of the American Water Resources Association》2017,53(2):344-364
A comprehensive streambank erosion model based on excess shear stress has been developed and incorporated in the hydrological model Soil and Water Assessment Tool (SWAT). It takes into account processes such as weathering, vegetative cover, and channel meanders to adjust critical and effective stresses while estimating bank erosion. The streambank erosion model was tested for performance in the Cedar Creek watershed in north‐central Texas where streambank erosion rates are high. A Rapid Geomorphic field assessment (RAP‐M) of the Cedar Creek watershed was done adopting techniques developed by the Natural Resources Conservation Service (NRCS), and the stream segments were categorized into various severity classes. Based on the RAP‐M field assessment, erosion pin sites were established at seven locations within the severely eroding streambanks of the watershed. A Monte Carlo simulation was carried out to assess the sensitivity of different parameters that control streambank erosion such as critical shear stress, erodibility, weathering depth, and weathering duration. The sensitive parameters were adjusted and the model was calibrated based on the bank erosion severity category identified by the RAP‐M field assessment. The average observed erosion rates were in the range 25‐367 mm year?1. The SWAT model was able to reasonably predict the bank erosion rates within the range of variability observed in the field (R2 = 0.90; E = 0.78). Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series. 相似文献
80.
A detailed Life Cycle Assessment (LCA) has been conducted for the manufacture, use and disposal of polypropylene tree shelters, which are used to protect young seedlings in the first few years of growth. The LCA was conducted using Simapro software, the Ecoinvent database and ReCiPe assessment methodology. Detailed information on materials, manufacturing, packaging and distribution of shelters was obtained from Tubex Ltd. in South Wales, UK. Various scenarios based on different forest establishment methods, with or without tree shelters were derived and analysed using data from published literature and independent sources. The scenarios included commercial forestry in northern temperate conditions, amenity forest establishment in temperate conditions, and forest establishment in semi-arid conditions. For commercial forestry, a reduction in required seedling production and planting as well as additional time-averaged wood production led to significant benefits with tree shelters, both compared to unprotected and fenced cases. For the amenity forest scenarios, tree shelter use had a net environmental impact, while for semi-arid forestry, the benefits of reduction in water use outweighed shelter production impacts. The current practice of in-situ degradation was compared to collection and disposal and it was found that in-situ degradation was slightly preferable in terms of overall environmental impact. Use of biopolymer-based shelters would improve the environmental performance slightly. 相似文献