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731.
In this work we present the results of an experimental study on the abatement of polychlorinated biphenyl (PCBs) in contaminated soil using a high energy milling technique, that promotes a reaction only by impact between milling bodies. A sample of soil from a controlled landfill was treated with powdered NaBH(4) using two different hydride/soil ratios (5 and 2.5% w/w). The efficiency of the dehalogenation/hydrogenation reaction was studied as a function of the milling time (3.5 up to 30 h). After each run, the total PCBs content and the production of inorganic chloride were measured. The complete abatement was obtained with a starting PCBs concentration of about 2600 mg/kg. The residual PCBs concentration resulted to be <0.2 mg/kg. The final products of the treatment were biphenyl and NaCl. Other toxic or hazardous organic by-products were not generated. Boron was found as boric acid.  相似文献   
732.
An ecological impact study was performed based on in situ biomarker assays with the waterflea Daphnia magna. The effects of metallurgic effluents on the energy metabolism, anti-oxidative metabolism and DNA damage were assessed in caged daphnids during a 4-week study. In situ survival and reproduction studies demonstrated a clear impact on these parameters in organisms exposed in the most polluted areas. At the downstream--sublethal--zone the organisms were disturbed within their tolerance limits, resulting in alterations of their energy metabolism. These data suggest an acclimation hypothesis, which was tested through the analysis of the energy metabolism of resident species: isopods and amphipods. These organisms had shifted to a decrease in their overall energy metabolism compared to the upstream region. This change in some biochemical processes suggests a selective advantage to cope with the prevailing environmental conditions. In addition, we found clear genotoxic effects caused by the industrial discharges that might correlate with a reduction in (long-term) survival.  相似文献   
733.
Introduced to Saskatchewan in the 1930s as a potential shelterbelt species, European buckthorn is now a prominent understory shrub in riparian woodland and shrub communities around Saskatoon. Locally, the Meewasin Valley Authority (MVA) is actively controlling buckthorn as part of its mandate to conserve natural heritage resources of the South Saskatchewan River Valley, with the goal of restoring the natural biodiversity of remnant patches of native vegetation. European buckthorn is normally dioecious, and MVA has chosen to treat only fruiting stems in an attempt to limit seed production. Two control techniques have been used. In one treatment, glyphosate was applied to stems after cutting; alternatively Garlon 4 Dow AgroSciences herbicide (active ingredient triclopyr) was applied as a chemical girdle directly to the stems using a streamline basal bark spray method. To date, more than 347,000 fruiting stems of buckthorn have been treated. Results indicate good initial progress in limiting seed production in dense buckthorn sites, but at a high cost. Although seed eradication is not a practical short-term goal for the Saskatoon buckthorn population, chemical girdling can substantially and strategically reduce seed and effectively limit spread. Field-tested strategies to reduce costs and improve efficiencies are discussed.  相似文献   
734.
The influence of pre-extractant, extractant, and post-extractant on total extracted amounts of P and organic P compound groups measured with 31P nuclear magnetic resonance (31P-NMR) in lacustrine sediment was examined. The main extractants investigated were sodium hydroxide (NaOH) and sodium hydroxide ethylenediaminetetraacetic acid (NaOH-EDTA) with bicarbonate buffered dithionite (BD) or EDTA as pre-extractants. Post extractions were conducted using either NaOH or NaOH-EDTA, depending on the main extractant. Results showed that the most efficient combination of extractants for total P yield was NaOH with EDTA as pre-extractant, yielding almost 50% more than the second best procedure. The P compound groups varying the most between the different extraction procedures were polyphosphates and pyrophosphates. NaOH with BD as pre-extractant was the most efficient combination for these compound groups.  相似文献   
735.
Increasing food demands are causing rapid transitions in farming systems, often involving intensified land and resource use. While transitioning has benefits regarding poverty alleviation and food outputs, it also causes environmental and social issues over time. This study aims to understand the transitions in farming systems in a region in Telangana, from 1997 to 2015, and their effect on livestock rearing and smallholder livelihoods. We also examine the impact of the transitions on lower caste groups and women in particular. We collected data using a combination of methods, i.e., a household survey, focus group discussions, and secondary data sources, to build a comprehensive picture of the transitions in the region. We found that subsistence mixed farming systems transitioned to market-orientated specialized systems over a short time span. As the transition process gained momentum, households either intensified their production or got marginalized. Technological interventions, development programs with integrated approaches, and market demand for certain agricultural produce triggered increased regional production but also led to the scarcity of water, land, and labor. The transitions marginalized some of the households, changed the role of livestock in farming, and have been inclusive of both lower caste groups and women in terms of increased ownership of large ruminants and access to technologies. However, for women specifically, further increase in workload in the context of farming is also found.  相似文献   
736.
737.
In southern India, tens of thousands of village-level irrigation systems (‘tanks’ and feeder channels) are in disrepair. This paper analyses the results of a local NGO effort that focused on awareness-raising and advice to bring about self-sustained community action for irrigation system restoration. After designing a model structure that contains both motivational and capacity (social capital) factors, it is found that (pre-existing) collective social capital, as measured through five simple indicators, strongly correlates with success of the NGO strategy. The intensity of the NGO’s effort shows a negative correlation with success, however. The discussion focuses on issues of social capital definition and measurement and the practical implications of the concept for environmental action, especially the difference between using existing social capital for environmental management versus the construction of social capital as a basis for later self-sustained environmental work. Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue.  相似文献   
738.
Marine rock-pools, commonly found along the Mediterranean coasts, are isolated patches of habitat characterised by large spatial and temporal variations. The phylogeography of Calobius quadricollis and C. urbanelliae, two sibling species of moss beetles (Coleoptera, Hydraenidae) inhabiting Italian temporary marine rock-pool ecosystems, were studied using mitochondrial cytochrome c oxidase subunit I (COI). Our data suggest a strong association between the scored genetic variability and the geographical distribution of populations sampled for both species. These analyses provided evidences of episodic species range expansion and fragmentation, recurrent “flush and crash” and bottleneck episodes probably occurring during the Glacial Cycles. The observed phylogeographical pattern is probably related to the historical and biogeographical processes of Mediterranean areas, as well as both to the ephemeral habitat tipology and limited dispersal ability of these beetles.  相似文献   
739.
740.
The study presents an approach that combined objective information such as sampling or experimental data with subjective information such as expert opinions. This combined approach was based on the Analytic Network Process method. It was applied to evaluate soil erosion risk and overcomes one of the drawbacks of USLE/RUSLE soil erosion models, namely that they do not consider interactions among soil erosion factors. Another advantage of this method is that it can be used if there are insufficient experimental data. The lack of experimental data can be compensated for through the use of expert evaluations. As an example of the proposed approach, the risk of soil erosion was evaluated in olive groves in Southern Spain, showing the potential of the ANP method for modelling a complex physical process like soil erosion.  相似文献   
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