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971.
Epidemiological studies suggesting the possibility of harmful effects on human (specifically children’s leukaemia) due to
long-term exposure to magnetic fields of extremely low frequency (e.g. 50/60 Hz) and relatively low values (i.e. over the
microtesla range) have stirred high activity in the topic of magnetic field mitigation. To reduce these fields, it is common
to use passive metal screens (e.g. plates made of aluminium or steel). To design them, effective and fast numerical computations
are highly desirable. In this article, a method is presented, which computes various parameters of screens in a given shielding
problem and yields magnetic field distribution and shielding factors. The method takes into consideration the 3D field distribution
and is able to solve systems with large aspect ratios (thin thickness in comparison with its other dimensions); this is a
common problem where other methods such as finite elements often experience difficulties. The presented method computes separately
the field inside and outside the screens. Afterwards, the solutions are “stitched” together along the border of the subregions.
Two practical examples are given of the developed numerical method. 相似文献
972.
Urbanization and its impact on groundwater: a remote sensing and GIS-based assessment approach 总被引:1,自引:0,他引:1
The perils of unplanned urbanization and increasing pressure of human activities on hydro-geomorphologic system often result
in modification of the existing recharge mechanism, which leads to many environmental consequences. In the present research,
an attempt has been made to investigate the applicability of remote sensing and geographical information system (GIS) in dealing
with spatial and temporal variability of dynamic phenomena, like urbanization and its impact on groundwater. This paper covers
primarily, quantitative and qualitative impacts of urban growth on the behavior of aquifer in Ajmer city (India). Urban growth
of the Ajmer city in last 17 years has been estimated from the satellite images. Database related to urbanization and groundwater
has been created in GIS. Groundwater recharge has been computed using a water balance approach known as Water Level Fluctuation
Methodology. Recharge estimation methodology has been implemented in GIS to introduce the spatial variability of hydro-geological
characteristics. Further, temporal and spatial variations in groundwater quality and quantity have been correlated with urban
growth using overlay analysis in GIS. The study reveals a general decline in water table and quality with urbanization. Further,
remote sensing and GIS technologies have been found useful in assessment of spatial and temporal phenomena of urbanization
and its impact on groundwater system. 相似文献
973.
François Munoz Franz Bogner Pierre Clement Graça S. Carvalho 《Journal of environmental psychology》2009
By using an original framework involving complementary statistical approaches, we investigated the environmental attitudes of 6379 pre-service and in-service teachers in 16 countries of Europe and its neighbourhood. To test hypotheses about the nature of environmental attitudes, we examined the variation across groups of individuals (between-class analysis), investigated the independent effects of several candidate explanatory factors (orthogonal analysis), and finally inspected potential relationships between conceptions on a variety of topics (co-inertia analysis). 相似文献
974.
From land cover change to land function dynamics: a major challenge to improve land characterization 总被引:36,自引:0,他引:36
Verburg PH van de Steeg J Veldkamp A Willemen L 《Journal of environmental management》2009,90(3):1327-1335
Land cover change has always had a central role in land change science. This central role is largely the result of the possibilities to map and characterize land cover based on observations and remote sensing. This paper argues that more attention should be given to land use and land functions and linkages between these. Consideration of land functions that provide a wide range of goods and services makes more integrated assessments of land change possible. The increasing attention to multifunctional land use is another incentive to develop methods to assess changes in land functions. A number of methods to quantify and map the spatial extent of land use and land functions are discussed and the implications for modeling are identified based on recent model approaches in land change science. The mixed use of land cover, land use and land function in maps and models leads to inconsistencies in land change assessments. Explicit attention to the non-linear relations between land cover, land use and land function is essential to consistently address land change. New methods to map and quantify land function dynamics will enhance our ability to understand and model land system change and adequately inform policies and planning. 相似文献
975.
C. Stoate A. Bldi P. Beja N.D. Boatman I. Herzon A. van Doorn G.R. de Snoo L. Rakosy C. Ramwell 《Journal of environmental management》2009,91(1):22-46
The impacts of agricultural land use are far-reaching and extend to areas outside production. This paper provides an overview of the ecological status of agricultural systems across the European Union in the light of recent policy changes. It builds on the previous review of 2001 devoted to the impacts of agricultural intensification in Western Europe. The focus countries are the UK, The Netherlands, Boreal and Baltic countries, Portugal, Hungary and Romania, representing a geographical spread across Europe, but additional reference is made to other countries. Despite many adjustments to agricultural policy, intensification of production in some regions and concurrent abandonment in others remain the major threat to the ecology of agro-ecosystems impairing the state of soil, water and air and reducing biological diversity in agricultural landscapes. The impacts also extend to surrounding terrestrial and aquatic systems through water and aerial contamination and development of agricultural infrastructures (e.g. dams and irrigation channels). Improvements are also documented regionally, such as successful support of farmland species, and improved condition of watercourses and landscapes. This was attributed to agricultural policy targeted at the environment, improved environmental legislation, and new market opportunities. Research into ecosystem services associated with agriculture may provide further pressure to develop policy that is targeted at their continuous provisioning, fostering motivation of land managers to continue to protect and enhance them. 相似文献
976.
Costa EA Campos VP da Silva Filho LC Greven HA 《Journal of environmental management》2009,90(2):1060-1068
In recent years, growing interest has focused on determining the performance of materials and evaluating the service life of structures exposed to various environmental forces. In this context, the determination of the aggressive potential of marine salts on mortars used as external renders is critical. The present study aimed to evaluate the spatial distribution of marine salts relative to distance from the sea. This was done by monitoring the deposition rate of chlorides and sulfates in wet candle sensors, located at nine stations scattered around the Metropolitan Region of Salvador, state of Bahia, Brazil. The study also determined the effectiveness of water-soluble salts at penetrating three different types of mortars of varying cement content via deposition and diffusion. The methodology employed enabled an evaluation of the efficiency of the monitoring sensors' measurement of the aggressiveness potential of local marine aerosol, and determination of the comparative performance of the three mortars tested, from the standpoint of resistance to salt penetration. The type and amount of salts captured both in solution and in powder samples extracted from the mortars were determined by ion chromatography. The analysis of the various types of mortars tested indicated which types are more resistant to the aggressive potential of the region's marine aerosol and the distance from the shore where local buildings are liable to be most strongly affected. 相似文献
977.
Chambers MK Ford MR White DM Barnes DL Schiewer S 《Journal of environmental management》2009,90(2):961-966
People living without piped water and sewer can be at increased risk for diseases transmitted via the fecal-oral route. One rural Alaskan community that relies on hauling water into homes and sewage from homes was studied to determine the pathways of fecal contamination of drinking water and the human environment so that barriers can be established to protect health. Samples were tested for the fecal indicator, Escherichia coli, and the less specific indicator group, total coliforms. Shoes transported fecal contamination from outside to floor material inside buildings. Contamination in puddles on the road, in conjunction with contamination found on all-terrain vehicle (ATV) tires, supports vehicle traffic as a mechanism for transporting contamination from the dumpsite or other source areas to the rest of the community. The abundance of fecal bacteria transported around the community on shoes and ATV tires suggests that centralized measures for waste disposal as well as shoe removal in buildings could improve sanitation and health in the community. 相似文献
978.
979.
There is growing concern that recreational shoreline angling activity may negatively impact littoral and riparian habitats
independent of any direct or indirect influences of fish harvest or fishing mortality through mechanisms such as disturbance
(e.g., trampling, erosion) and pollution (e.g., littering). We sampled a suite of aquatic and terrestrial variables (i.e.,
water quality, aquatic and terrestrial macrophytes, soil compaction, anthropogenic refuse) at 14 high shoreline angling-activity
sites (identified by way of interviews with conservation officers and angling clubs) within an urban area (Ottawa, Canada).
For each high angling-activity site, a nearby corresponding low angling-activity site was sampled for comparison. We found
that the percentage of barren area and soil compaction were greater in areas of high angling activity compared with areas
that experienced relatively low angling activity. In addition, terrestrial and aquatic macrophyte density, height, and diversity
were lower at high angling-activity sites. Angling- and non-angling-related litter was present in large quantities at each
of the high angling-activity sites, and comparatively little litter was found at low angling-activity sites. Collectively,
these findings indicate that shoreline angling does alter the riparian environment, contributing to pollution and environmental
degradation in areas of high angling intensity. With growing interest in providing urban angling opportunities and in response
to increasing interest in developing protected areas and parks, a better understanding of the ecologic impacts of shoreline
angling is necessary to address multiuser conflicts, to develop angler outreach and educational materials, and to optimize
management of angling effort to maintain ecologic integrity of riparian and aquatic ecosystems. 相似文献
980.
Dongmei Han Xing Liang Menggui Jin Matthew J. Currell Ying Han Xianfang Song 《Environmental management》2009,44(2):243-255
Based on analysis of groundwater hydrochemical and isotopic indicators, this article aims to identify the groundwater flow
systems in the Yangwu River alluvial fan, in the Xinzhou Basin, China. Groundwater δ2H and δ18O values indicate that the origin of groundwater is mainly from precipitation, with local evaporative influence. d-excess values lower than 10% in most groundwaters suggest a cold climate during recharge in the area. Major ion chemistry,
including rCa/rMg and rNa/rCl ratios, show that groundwater salinization is probably dominated by water–rock interaction (e.g.,
silicate mineral weathering, dissolution of calcite and dolomite and cation exchange) in the Yangwu River alluvial fan, and
locally by intensive evapotranspiration in the Hutuo River valley. Cl and Sr concentrations follow an increasing trend in
shallow groundwater affected by evaporation, and a decreasing trend in deep groundwater. 87Sr/86Sr ratios reflect the variety of lithologies encountered during throughflow. The groundwater flow systems (GFS) of the Yangwu
River alluvial fan include local and intermediate flow systems. Hydrogeochemical modeling results, simulated using PHREEQC,
reveal water–rock interaction processes along different flow paths. This modeling method is more effective for characterizing
flow paths in the intermediate system than in the local system. Artificial exploitation on groundwater in the alluvial fan
enhances mixing between different groundwater flow systems. 相似文献