首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   83篇
  免费   4篇
安全科学   1篇
废物处理   8篇
环保管理   31篇
综合类   3篇
基础理论   14篇
污染及防治   20篇
评价与监测   6篇
社会与环境   3篇
灾害及防治   1篇
  2020年   5篇
  2019年   2篇
  2018年   4篇
  2017年   2篇
  2016年   4篇
  2015年   1篇
  2014年   5篇
  2013年   4篇
  2012年   6篇
  2011年   8篇
  2010年   1篇
  2009年   5篇
  2008年   10篇
  2007年   2篇
  2006年   1篇
  2005年   6篇
  2004年   5篇
  2003年   1篇
  2002年   3篇
  2001年   2篇
  2000年   2篇
  1999年   1篇
  1997年   1篇
  1988年   2篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
排序方式: 共有87条查询结果,搜索用时 453 毫秒
71.
Feedlots are potential point sources for the flow of antibiotics into the environment due to common use of antibiotics such as sulfamethazine, chlortetracycline and tylosin. Hence soils and manures originating from a grassland control, an experimental and a commercial feedlot were analyzed and mass balances were calculated for these antibiotics. Up to 9990 μg kg−1 sulfamethazine and 401 μg kg−1 chlortetracycline on a dry matter basis were determined in feedlot manure. Soil concentrations were two orders of magnitude smaller. This corresponds to 7-40% of the calculated residual amount. In the commercial feedlot chlortetracycline was found down to soil depths of −40 cm; sulfamethazine was still detectable 1 year after medication. Sulfamethazine and chlortetracycline were additionally determined in manure of a control treatment in the experimental feedlot where cattle never received antibiotics. This was attributed to runoff from upslope pens. Consequently, antibiotics partially persist within feedlots and may be dislocated into the surrounding environment by vertical transport and runoff.  相似文献   
72.
Microbial and plant ecology of a long-term TNT-contaminated site   总被引:1,自引:0,他引:1  
The contamination of the environment with explosive residues presents a serious ecological problem at sites across the world, with the highly toxic compound trinitrotoluene (TNT) the most widespread contaminant. This study examines the soil microbial community composition across a long-term TNT-contaminated site. It also investigates the extent of nitroaromatic contamination and its effect on vegetation. Concentrations of TNT and its metabolites varied across the site and this was observed to dramatically impact on the extent and diversity of the vegetation, with the most heavily contaminated area completely devoid of vegetation. Bryophytes were seen to be particularly sensitive to TNT contamination. The microbial population experienced both a reduction in culturable bacterial numbers and a shift in composition at the high concentrations of TNT. DGGE and community-level physiological profiling (CLPP) revealed a clear change in both the genetic and functional diversity of the soil when soil was contaminated with TNT.  相似文献   
73.
We investigated the acute impact of trinitrotoluene (TNT) contamination of soil on the aerobic bacterial community composition and function. The contamination of the environment with explosive residues presents a serious problem at sites across the world, with the highly toxic compound TNT being the most widespread explosive contaminant. We investigated the acute impact of trinitrotoluene (TNT) contamination of soil on the aerobic bacterial community composition and function. Soil microcosms were amended with a range of concentrations of TNT for 30 days. A polyphasic approach encompassing culture-independent molecular analysis by DGGE, community-level physiological profiling (CLPP) and cell enumeration revealed that the amendment of soils with TNT resulted in a shift from slower growing k-strategists towards faster growing r-strategists. Pseudomonads became prevalent at high concentrations of TNT. Pollution induced community tolerance (PICT) was observed as TNT concentrations increased. Chemical analyses revealed that TNT was reduced to its amino derivatives, products of reductive microbial transformation. The transformation to amino derivatives decreased at high concentrations of TNT, indicative of inhibition of microbial TNT transformation.  相似文献   
74.
ABSTRACT

Mixing ratios of the criteria air contaminant nitrogen dioxide (NO2) are commonly quantified by reduction to nitric oxide (NO) using a photolytic converter followed by NO-O3 chemiluminescence (CL). In this work, the performance of a photolytic NO2 converter prototype originally designed for continuous emission monitoring and emitting light at 395 nm was evaluated. Mixing ratios of NO2 and NOx (= NO + NO2) entering and exiting the converter were monitored by blue diode laser cavity ring-down spectroscopy (CRDS). The NO2 photolysis frequency was determined by measuring the rate of conversion to NO as a function of converter residence time and found to be 4.2 s?1. A maximum 96% conversion of NO2 to NO over a large dynamic range was achieved at a residence time of (1.5 ± 0.3) s, independent of relative humidity. Interferences from odd nitrogen (NOy) species such as peroxyacyl nitrates (PAN; RC(O)O2NO2), alkyl nitrates (AN; RONO2), nitrous acid (HONO), and nitric acid (HNO3) were evaluated by operating the prototype converter outside its optimum operating range (i.e., at higher pressure and longer residence time) for easier quantification of interferences. Four mechanisms that generate artifacts and interferences were identified as follows: direct photolysis, foremost of HONO at a rate constant of 6% that of NO2; thermal decomposition, primarily of PAN; surface promoted photochemistry; and secondary chemistry in the connecting tubing. These interferences are likely present to a certain degree in all photolytic converters currently in use but are rarely evaluated or reported. Recommendations for improved performance of photolytic converters include operating at lower cell pressure and higher flow rates, thermal management that ideally results in a match of photolysis cell temperature with ambient conditions, and minimization of connecting tubing length. When properly implemented, these interferences can be made negligibly small when measuring NO2 in ambient air.

Implications: A new near-UV photolytic converter for measurement of the criteria pollutant nitrogen dioxide (NO2) in ambient air by CL was characterized. Four mechanisms that generate interferences were identified and investigated experimentally: direct photolysis of HONO which occurred at a rate constant 6% that of NO2, thermal decomposition of PAN and N2O5, surface promoted chemistry involving HNO3, and secondary chemistry involving NO in the tubing connecting the converter and CL analyzer. These interferences are predicted to occur in all NO2 P-CL systems but can be avoided by appropriate thermal management and operating at high flow rates.  相似文献   
75.
We examined patterns of concurrent multiple mating in a live-bearing poeciliid fish, the sailfin molly (Poecilia latipinna). We tested whether the probability of multiple paternity was related to female body size or fertility and whether the rate of multiple paternity varied among four populations that differed in their distributions of female body size and fertility. We analyzed data on mother and offspring genotypes for three polymorphic allozymes by three techniques, including a maximum-likelihood estimator that accounts for sampling error in both parental and offspring allele frequencies. The estimated rate of multiple paternity varied between 0.09 and 0.85, and the rate in one population varied seasonally between 0.33 (spring) and 0.85 (autumn). The variation in these rates was not associated with variation in body-size distributions among populations but was closely associated with variation in size-specific fertility: populations with greater variation in female fertility had higher multiple-paternity rates. Within two populations, logistic regression revealed that individual females of larger body size and greater size-specific fertility were more likely to carry multiply sired broods. This result is consistent with observations made in one of the populations 5 years earlier. In general, the results strongly suggest that the mating system varies markedly among conspecific populations of sailfin mollies and that larger, more fertile females are the objects of intermale competition. Received: 6 May 1996 / Accepted in revised form: 5 December 1996  相似文献   
76.
Based on high disposal and low recycling rates of electronic waste (e-waste) and continued exportation to developing countries, reliance on municipal responsibility for e-waste management has been unsuccessful in the United States. This case study examines Maine’s program, which was the first US state to mandate producer responsibility for recycling household e-waste. Maine’s program established a shared cost responsibility among producers, municipalities, and consumers. The study found that Maine’s program resulted in a significant reduction in disposal and a corresponding increase in environmentally sound recycling. In the first 3 years of the program, 6.406 million kg of household e-waste was collected and recycled for a population of 1.32 million. The new program, implemented in 2006, increased the number of e-waste items collected and recycled by 108% in the first year, 170% in the second year, and 221% in the third year. The program decreased direct economic costs to municipalities and households because of the shared cost approach and for the first time established costs for producers. There was no empirical evidence indicating that producers have or will improve the recyclability of electronic products to reduce recycling costs. While other weaknesses were that found potentially limit the adoption of Maine’s program, its positive aspects warrant consideration by other governments.  相似文献   
77.
Increasingly, Extended Producer Responsibility (EPR) and Product Stewardship (PS) frameworks are being adopted as a preferred policy approach to promote cost-effective diversion and recovery of post-consumer solid waste. Because the application of EPR/PS generally requires the creation of a separate and often parallel collection and/or management system, key to increasing the amount of waste recovered is to maximize the convenience of the collection system to maximize consumer participation. Convenient collection is often mandated in EPR/PS laws, however it is not defined. Convenience is a subjective construct rendering it extremely difficult to define. However, based on a dissection of post-consumer collection efforts under a generic EPR/PS system, this paper identifies and examines five categories of convenience – knowledge requirements, proximity to a collection site, opportunity to drop-off materials, the draw of the collection site, and the ease of the process—and the various factors of convenience within each of these categories. By using a simplified multiple criteria decision analysis, this paper proposes a performance matrix of criteria of convenience. Stakeholders can use this matrix to assist in the design, assessment, and/or implementation of a convenient post-consumer collection system under an EPR/PS framework.  相似文献   
78.
79.
80.
Human-caused changes in disturbance regimes and introductions of nonnative species have the potential to result in widespread, directional changes in forest community structure. The degree that plant community composition persists or changes following disturbances depends on the balance between local extirpation and colonization by new species, including nonnatives. In this study, we examined species losses and gains, and entry of native vs. exotic species to determine how oak forests in the Appalachian Mountains might shift in species composition following a gradient of pulse disturbances (timber harvesting). We asked (1) how compositional stability of the plant community (resistance and resilience) was influenced by disturbance intensity, (2) whether community responses were driven by extirpation or colonization of species, and (3) how disturbance intensity influenced total and functional group diversity, including the nonnative proportion of the flora through time. We collected data at three spatial scales and three times, including just before, one year post-disturbance, and 10 years post-disturbance. Resistance was estimated using community distance measures between pre- and one year post-disturbance, and resilience using community distance between pre- and 10-year post-disturbance conditions. The number of colonizing and extirpated species between sampling times was analyzed for all species combined and for six functional groups. Resistance and resilience decreased with increasing timber-harvesting disturbance; compositional stability was lower in the most disturbed plots, which was driven by colonization, but not extirpation, of species. Colonization of species also led to increases in diversity after disturbance that was typically maintained after 10 years following disturbance. Most of the community-level responses were driven by post-disturbance colonization of native forbs and graminoids. The nonnative proportion of plant species tended to increase following disturbance, especially at large spatial scales in the most disturbed treatments, but tended to decrease through time following disturbance due to canopy development. The results of this study are consistent with the theory that resources released by disturbance have strong influences on species colonization and community composition. The effects of management activities tested in this study, which span a gradient of timber-harvesting disturbance, shift species composition largely via an increase in species colonization and diversity.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号