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21.
本文根据鄂尔多斯高原逆温天气的形成,讨论了高原地区中小城镇大气污染的时空分布及控制污染的可行性途径。  相似文献   
22.
通过对影响我国农村居民消费需求不足的原因分析,认为我国农村居民收入水平偏低且增长缓慢是导致需求不足的关键因素。此外商品有效供给不足、农村的消费观念、消费环境和农村居民的文化素质也在一定程度上影响了农村居民的消费需求。  相似文献   
23.
To address the limited application of analytical and modelling techniques in prioritizing revegetation sites for dryland salinity (saline land) management, a case study of the Hodgson Creek catchment in Queensland, Australia, was conducted. An analytical framework was developed, incorporating the use of spatial datasets (Landsat 7 image, DEM, soil map, and salinity map), which were processed using digital image processing techniques and a geographic information system (GIS). Revegetation sites were mapped and their priority determined based on recharge area, land use/cover and sub‐catchment salinity. The analytical framework presented here enhances the systematic use of land information, widens the scope for scenario testing, and improves the testing of alternative revegetation options. The spatial patterns of revegetation sites could provide an additional set of information relevant in the design of revegetation strategies.  相似文献   
24.
In France, freshwater recreational fishing management does not sufficiently satisfy anglers. Fishing effort is too high creating congestion costs and environmental quality is low while there is a positive willingness-to-pay for improvements. These inefficiencies are explained by three phenomena. First, private property rights are attenuated under institutional pressure. Second, recreational fishing is managed as an open access resource over the whole territory. Finally, halieutic policies focus on the protection of environmental resources and are inefficient at maximizing the social rent provided by recreational fisheries. Fishing effort regulation and environmental services provision following the beneficiary-pays principle could improve collective welfare. Social pricing could ensure equity in access to the resource.  相似文献   
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Environmental Fluid Mechanics - Most studies on sediment transport and bedforms migration consider unlimited sediment supply conditions. However, areas where the sediment supply is limited are...  相似文献   
27.
Ornamental horticulture has been identified as an important threat to plant biodiversity and is a major pathway for plant invasions worldwide. In this context, the family Cactaceae is particularly challenging because it is considered the fifth most threatened large taxonomic group in the world; several species are among the most widespread and damaging invasive species; and Cactaceae is one of the most popular horticultural plant groups. Based on the Convention on International Trade in Endangered Species of Wild Flora and Fauna and the 11 largest online auction sites selling cacti, we documented the international cactus trade. To provide an in‐depth look at the dynamics of the industry, we surveyed the businesses involved in the cactus trade in South Africa (a hotspot of cactus trade and invasions). We purchased seeds of every available species and used DNA barcoding to identify species to the genus level. Although <20% of this trade involved threatened species and <3% involved known invasive species, many species were identified by a common name. However, only 0.02% of the globally traded cacti were collected from wild populations. Despite a large commercial network, all South African imports (of which 15% and 1.5% were of species listed as threatened and invasive, respectively) came from the same source. With DNA barcoding, we identified 24% of the species to genus level. Based on our results, we believe that if trade restrictions are placed on the small proportion of cacti that are invasive and there is no major increase in harvesting of native populations, then the commercial trade in cactus poses a negligible environmental threat. However, there are currently no effective methods for easily identifying which cacti are traded, and both the illicit harvesting of cacti from the wild and the informal trade in invasive taxa pose on‐going conservation challenges.  相似文献   
28.
近年来,燃煤电厂烟塔合一烟气排烟对近距离环境影响的不确定性,使其在国内的推广过程受到一定限制。准确判断烟塔合一排烟的环境影响,对于我国现有燃煤电厂烟气污染物的排放有着巨大的工程价值和明显的现实意义。利用国家环境保护某重点实验室中风洞试验平台,对燃煤电厂烟塔合一烟气污染物在近距离的扩散和传输行为,进行物理风洞试验以及数值模拟计算,并进行对比分析。结果表明:德国Austal2000模式的浓度预测并不精确;数值风洞也有其差异性,而物理风洞的结果在很大程度上符合现有的理论及国内工程实际。  相似文献   
29.
<正>Arsenic(As)is a well-recognized toxicant and carcinogen.Chronic exposure to inorganic arsenic causes a range of human cancers(e.g.,skin,bladder,and lung)and increases the risk of developing diabetes,hypertension,and cardiovascular and neurological diseases.The prevalence of arsenic species and the severity of their health effects continue to drive and demand for extensive research(Carlin et al.,2016).  相似文献   
30.
安乐 《海洋环境科学》2017,36(2):303-306, 312
对紫外分光光度法测定海水中石油类浓度进行了不确定度评定。通过对标准溶液、标准工作曲线拟合、前处理过程等影响测定结果的不确定度分量进行分析,计算出测定结果的扩展不确定度,并找出影响该不确定度的主要因素。结果表明,紫外分光光度法测定海水中石油类浓度的不确定度的主要来源是实验中前处理过程的不确定度,本次实验所测海水中石油类浓度的不确定度报告为19.98±1.326 mg/L。  相似文献   
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