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231.
232.
Accumulation of mercury and its effect on antioxidant enzymes in brain, liver, and kidneys of mice. 总被引:7,自引:0,他引:7
S Hussain A Atkinson S J Thompson A T Khan 《Journal of environmental science and health. Part. B》1999,34(4):645-660
The effect of mercuric chloride (HgCl2) on the activities of catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) and its effect on glutathione (GSH) content were evaluated in different organs (liver, kidneys, and brain) of mice after administration at 0, 0.25, 0.5 and 1.0 mg/kg/day for 14 days. The uptake of mercury shows that the kidneys accumulated the highest levels of mercury compare to brain and liver. The enzyme levels varied in mercury treated organs compare to control. A dose dependent increase of antioxidant enzymes occurred in the liver and kidneys. The increase in enzyme activities correlated with highest mercury accumulation in the kidneys and liver. Mercury is known to generate reactive oxygen species (ROS) in vivo and in vitro, therefore, it is likely that enzyme activities increased to scavenge ROS levels produced as a result of mercury accumulation. Glutathione content increased in liver and kidneys of mercury treated mice compare to control. The results showed that the highest oral dose of mercury significantly increased antioxidant enzymes in kidneys and liver. The increased antioxidant enzymes enhance the antioxidant potential of the organs to reduce oxidative stress. 相似文献
233.
Mark Thompson Jan Vlok Mathieu Rouget M. T. Hoffman Andrew Balmford R. M. Cowling 《Environmental management》2009,43(4):585-596
Improved techniques for measuring and monitoring the state of biodiversity are required for reporting on national obligations
to international and regional conservation institutions. Measuring the extent of grazing-related degradation in semi-arid
ecosystems has proved difficult. Here we present an accurate and cost-effective method for doing this, and apply it in a South
African semi-arid region that forms part of a globally significant biodiversity hotspot. We grouped structurally and functionally
similar vegetation units, which were expert-mapped at the 1:50,000 scale, into four habitat types, and developed habitat-specific
degradation models. We quantified degradation into three categories, using differences between dry and wet season values of
the Normalized Difference Vegetation Index (NDVI) for the three succulent karoo habitats, and the difference between maximum
and mean NDVI values for the subtropical thicket habitat. Field evaluation revealed an accuracy of 86%. Overall, degradation
was high: 24% of the study area was modeled as severely degraded, and only 9% as intact. Levels of degradation were highest
for bottomland habitats that were most exposed to grazing impacts. In sharp contrast to our methods, a widely used, broad-scale
and snapshot assessment of land cover in South Africa was only 33% accurate, and it considerably underestimated the extent
of severely degraded habitat in the study area. While our approach requires a multidisciplinary team, and in particular expert
knowledge on the characteristics and spatial delimitation of vegetation types, it is repeatable, rapid, and relatively inexpensive.
Consequently, it holds great promise for monitoring and evaluation programs in semi-arid ecosystems, in Africa, and beyond. 相似文献
234.
Christopher L. Thompson Raymond J. Supalla Derrel L. Martin Brian P. McMullen 《Journal of the American Water Resources Association》2009,45(6):1508-1518
Thompson, Christopher L., Raymond J. Supalla, Derrel L. Martin, and Brian P. McMullen, 2009. Evidence Supporting Cap and Trade as a Groundwater Policy Option for Reducing Irrigation Consumptive Use. Journal of the American Water Resources Association (JAWRA) 45(6):1508‐1518. Abstract: In the American West water is becoming an increasingly scarce resource. Obligations to bordering states, endangered species protection, and long‐term resource sustainability objectives have created a need for most western states to reduce the consumption of irrigation water. In Nebraska specifically, the Nebraska Department of Natural Resources (NDNR) and local Natural Resource Districts (NRDs) are meeting a large part of this need by using a regulatory approach, commonly called groundwater allocation. The cost of allocation, which occurs in the form of reduced economic returns to irrigation, could be greatly reduced by using an integrated cap and trade approach. Much like environmental cap and trade programs which are used to reduce the cost of limiting environmental pollution, the trading of capped groundwater allocations can reduce the cost of limiting water use. In an analysis of a typical case in the Nebraska Republican Basin, we found that the impact of a water market to trade groundwater allocations depended on the size of the allocation and on the characteristics of the land and irrigation systems involved in the trade. Potential economic benefits from trade ranged from US$0 to US$120 per 1,000 cubic meters traded, from US$25 to US$250 per 1,000 cubic meters of reduction in consumptive use, and from US$16 to US$50 per hectare of irrigated land in the region. The highest benefits occurred at relatively high allocations, which capped withdrawals at 65‐75% of the expected unrestricted pumping level. These gains from trade would be split between buyers and sellers based on the negotiated selling price. 相似文献
235.
236.
Conservation subdivision design has been promoted as a way to protect ecologically sensitive areas while maintaining housing densities comparable to standard subdivisions, but many developers and planners question the appeal of conservation design to consumers. This study was conducted to compare economic aspects of conservation subdivision design to standard subdivision design in the midwestern United States. Three methods were used to determine the value homebuyers have for embedded conservation features in residential areas: transactional analyses (to indicate the value homebuyers have expressed for such features in the past); hedonic analyses (to determine the proportion of present value of homes attributable to such features); and contingent valuation (to examine willingness to pay according to homebuyers' preferred features, an indicator of potential future investment). Transactional analyses were based on assessment and transaction data for homes in three conservation-oriented subdivisions and three standard subdivisions in Cedar Rapids, Iowa, United States. Hedonic price models were also derived from assessment and transaction data. Contingent valuation analyses were based on a survey of residents in the same six subdivisions. Transactional data indicated higher 5-year appreciation rates for conservation versus standard subdivision design. Hedonic price models revealed that well-integrated conservation features (e.g. protected stream corridors) within subdivisions have a positive effect on home prices. Sixty-six percent of all respondents indicated willingness to pay for more embedded open space. Maximum willingness to pay was related to several factors including income, gender, desired level of open space, and concern about urban development. Overall, these results indicate that consumer demand and willingness to pay for conservation subdivision design are positive and should not be considered a barrier to implementation. 相似文献
237.
Ingrid Elizabeth Van Putten Catherine Mary Dichmont Leo Ximenes Cabral Dutra Olivier Thébaud Roy Aijun Deng Eddie Jebreen Randall Owens Ricardo Pascual Mark Read Carolyn Thompson 《Regional Environmental Change》2016,16(5):1417-1431
A wide range of goals and objectives have to be taken into account in natural resources management. Defining these objectives in operational terms, including dimensions such as sustainability, productivity, and equity, is by no means easy, especially if they must capture the diversity of community and stakeholder values. This is especially true in the coastal zone where land activities affect regional marine ecosystems. In this study, the aim was firstly to identify and hierarchically organise the goals and objectives for coastal systems, as defined by local stakeholders. Two case study areas are used within the Great Barrier Reef region being Mackay and Bowen–Burdekin. Secondly, the aim was to identify similarities between the case study results and thus develop a generic set of goals to be used as a starting point in other coastal communities. Results show that overarching high-level goals have nested sub-goals that contain a set of more detailed regional objectives. The similarities in high-level environmental, governance, and socio-economic goals suggest that regionally specific objectives can be developed based on a generic set of goals. The prominence of governance objectives reflects local stakeholder perceptions that current coastal zone management is not achieving the outcomes they feel important and that there is a need for increased community engagement and co-management. More importantly, it raises the question of how to make issues relevant for the local community and entice participation in the local management of public resources to achieve sustainable environmental, social, and economic management outcomes. 相似文献
238.
Plastic production pellets collected from beaches of south west England contain variable concentrations of trace metals (Cr, Co, Ni, Cu, Zn, Cd and Pb) that, in some cases, exceed concentrations reported for local estuarine sediments. The rates and mechanisms by which metals associate with virgin and beached polyethylene pellets were studied by adding a cocktail of 5 μg L(-1) of trace metals to 10 g L(-1) pellet suspensions in filtered seawater. Kinetic profiles were modelled using a pseudo-first-order equation and yielded response times of less than about 100 h and equilibrium partition coefficients of up to about 225 ml g(-1) that were consistently higher for beached pellets than virgin pellets. Adsorption isotherms conformed to both the Langmuir and Freundlich equations and adsorption capacities were greater for beached pellets than for virgin pellets. Results suggest that plastics may represent an important vehicle for the transport of metals in the marine environment. 相似文献
239.
240.
Aristides Stamulis Joseph K. Thompson Harold F. Bogardus 《Journal of the Air & Waste Management Association (1995)》2013,63(11):709-712
Activated charcoal is widely used for the purification of air. Charcoal has a large surface area (ca. 1000 square meters per gram) and acts to purify air by adsorbing gaseous pollutants on its surface. When the capacity of the surface is exhausted, the charcoal is no longer effective and must be replaced. The carbon dioxide (CO2) pulse technique, developed at NRL, is a non-destructive method by which one can determine the remaining capacity, or the residual life of a charcoal bed before it has become exhausted. A dose of CO2 is injected into the air stream ahead of the charcoal bed and is eluted through the bed. The shape of the emerging CO2 elution peak is determined by the condition of the charcoal bed. For a new, unused charcoal bed the CO2 elution peak is considerably dispersed (flattened and broadened) due to adsorption and desorption at the charcoal surface. For a partially spent bed the elution peak is dispersed to a degree proportional to the remaining capacity of the bed. For a fully spent bed the CO2 elution peak is little affected by passage through the bed. The carbon dioxide puise technique has been shown to be indicative of charcoal capacity for a wide range of non-polar materials (such as hydrocarbons, alcohols, etc.), which are taken up primarily by physical adsorption. The method is essentially insensitive to relative humidity in the range between 10 and 70%. An adaptation of the method has been used for detection of leaks in a charcoal bed, such as those caused by channeling, faulty packing, etc. 相似文献