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841.
人工神经网络在水环境质量评价中的应用 总被引:7,自引:0,他引:7
为了将人工神经网络应用于水环境质量评价,应用了人工神经网络B—P算法,构造了水环境质量评价模型,该模型应用于实例评价结果表明,人工神经网络用于环境质量评价具有客观性,通用性和实用性。 相似文献
842.
阐述了地表移动与变形预计理论在矿山开发项目环境影响评价工作中的必要性,着重介绍了典型曲线预计法建立的方法及预计的步骤. 相似文献
843.
《环境科学学报(英文版)》2023,35(7):202-212
The excessive accumulation of potentially toxic metals (Pb and Cd) in coastal wetlands is among the main factors threatening wetland ecosystems. However, the effects of water table depth (WTD) on the risk and binding mechanisms of potentially toxic metals in sediments remain unclear. Here, sediments from different WTD obtained from a typical coastal wetland were evaluated using a newly developed strategy based on chemical extraction methods coupled with high-resolution spectroscopy. Our findings indicated that the WTD of the coastal wetland fluctuates frequently and the average enrichment factor for Pb was categorized as minor, whereas Cd enrichment was categorized as moderate. High-resolution spectroscopy techniques also demonstrated that organic functional groups and partly inorganic compounds (e.g., Fe-O/Si-O) played a vital role in the binding of Pb and Cd to surface sediments. Additionally, mineral components rather than organic groups were mainly bound to these metals in the bottom sediments. Collectively, our findings provide key insights into the potential health effects and binding characteristics of potentially toxic metals in sediments, as well as their dynamic behavior under varying sediment depths at a microscale. 相似文献
844.
845.
水土流失既是资源问题,又是生态环境问题。土壤侵蚀对人类生存和发展构成了严重威胁,成为制约可持续发展的障碍因素。以鄂西北丹江口库区郧西县坡面径流小区为试验点,通过分析小区的实地观测数据,建立坡面土壤侵蚀定性评价指标体系,并将数量化理论II作为有效的数学方法,建立郧西县坡面径流小区土壤侵蚀强度评价模型,对参与建立模型的样本进行回归分析,其准判率达到800%以上,并且利用该模型对其他年份坡面土壤侵蚀强度实测数据进行对比验证,得到土壤侵蚀强度分级的精度较高。研究表明,建立的郧西县坡面径流小区土壤侵蚀强度评价模型有较好的适用性与可靠性,可为郧西县及类似自然地理环境的其他区域水保工作起到一定指导意义 相似文献
846.
There are currently no widely accepted procedures for comparing the performance of global environmental assessments (GEAs) and this may be a barrier to improving their methodology. To encourage greater self-reflection within the GEA community, it is proposed to introduce consistent evaluation approaches. Two elements from current evaluation practice are reviewed here that could be particularly useful for evaluating GEAs. The first are logic models which provide a transparent visual mapping of how activities in a GEA are intended to have impacts on policies. The second are performance metrics. It is proposed that GEAs adopt two kinds of metrics: (i) A common generic set for use in all GEAs to provide a basis for comparing the performance of GEAs, and (ii) a specific set of measureable metrics for each particular GEA derived from/linked to the generic set. Although many issues arise in applying these and other elements from evaluation theory and practice to GEAs, the potential benefits are greater comparability of GEA performance and new knowledge about how to improve them. This Short Communication is part of a Special Issue on solution-oriented GEAs. 相似文献
847.
Climate change, population growth and socio-structural changes will make meeting future food demands extremely challenging. As wheat is a globally traded food commodity central to the food security of many nations, this paper uses it as an example to explore the impact of climate change on global food supply and quantify the resulting greenhouse gas emissions. Published data on projected wheat production is used to analyse how global production can be increased to match projected demand. The results show that the largest projected wheat demand increases are in areas most likely to suffer severe climate change impacts, but that global demand could be met if northern hemisphere producers exploit climate change benefits to increase production and narrow their yield gaps. Life cycle assessment of different climate change scenarios shows that in the case of one of the most important wheat producers (the UK) it may be possible to improve yields with an increase of only 0.6% in the emission intensity per unit of wheat produced in a 2 °C scenario. However, UK production would need to rise substantially, increasing total UK wheat production emissions by 26%. This demonstrates how national emission inventories and associated targets do not incentivise minimisation of global greenhouse gas emissions while meeting increased food demands, highlighting a triad of challenges: meeting the rising demand for food, adapting to climate change and reducing emissions. 相似文献
848.
渤海海域生态系统服务功能价值评估 总被引:9,自引:0,他引:9
客观评估海洋生态系统服务功能价值。对于生态环境保护以及海洋综合管理具有重要意义。以海洋生态系统服务功能分类为基础.构建了食品生产、提供基因资源、氧气生产和气候调节、废弃物处理、生物控制、休闲娱乐、科研文化、初级生产、物种多样性维持等九项服务功能价值的评估方法。以渤海为研究区域.对上述九项生态系统服务功能价值进行了定量评价。结果表明。渤海海域九项生态系统服务功能的价值为81703亿元.相当于近期环渤海地区生产总值的1.73倍.其中直接使用价值为12873亿元,间接使用价值68830亿元.间接使用价值远大于直接使用价值;渤海海域生态系统服务价值,以支持功能价值为主,占生态系统服务功能总价值的74.68%。此外.认为海洋生态系统服务功能分类和价值评价方法有待进一步完善.渤海海域生态系统服务功能价值的评估值与实际有偏差。 相似文献
849.
850.
为了在事故发生之前对苯储罐进行风险评价,提出1种基于BP神经网络的泄漏事故风险评价方法,利用该方法构建了苯储罐的风险评价模型,并对模型进行了训练及验证。研究结果表明:BP神经网络成功完成了建模任务,且模型训练结果较好,可利用基于BP神经网络所构建的苯泄漏事故风险评价模型对苯储罐发生泄漏事故的风险进行评价。 相似文献