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排序方式: 共有349条查询结果,搜索用时 15 毫秒
1.
使用2004~2015年的中国280个地级市的面板数据,对科技创新投入与环境全要素生产率间的非线性关系、内部影响机理和空间异质性进行分析,结果显示:科技创新投入与环境全要素生产率之间呈现倒N型关系,两个拐点的位置分别为7.722(2257.47万元)和9.610(14913.17万元);在外部资本进入、污染治理、市场规模效应3种影响路径中,科技创新投入影响下的外部资本进入对环境全要素生产率依然存在污染避难所的负向效应,科技创新投入与外部资本间效应为0.1363,外部资本与环境全要素生产率间效应为-0.0065;科技创新投入能够增强企业的污染治理技术并提高环境全要素生产率,三者间前后效应分别为-0.0277和-0.0311;科技创新的投入与高效益增强了市场规模效应,有效促进生产结构的转型进而提高环境全要素生产率,三者间前后效应为0.0186和0.4346.空间异质性中,外部资本进入与溢出效应带来的污染避难所负效应在中部地区显著,在西部和东北部地区不显著,而污染天堂正效应在东部地区存在但不显著;污染创新治理投入的技术正溢出效应在东部和西部地区效应显著,在中部和东北部不显著;科技创新投入与市场需求规模效应在空间区域无差异且显著为正.建议依据科技创新投入的不同影响路径来实施空间差异化策略.  相似文献   
2.
基于经过验证的三维水动力-水质模型,对珠江口夏季有机碳进行海陆源区分,并对海陆源有机碳的分布特征、贡献比重及其通量过程进行研究.结果表明,水平方向上,珠江口夏季陆源(海源)有机碳浓度从口门到外海逐渐降低(升高),在表、底层海水中平均浓度分别为1.45和0.87mg/L(0.97和1.05mg/L);垂直方向上,在层化水域陆源(海源)有机碳浓度从上到下逐渐递减(升高),在非层化水域海陆源有机碳浓度垂向分布较为均匀.珠江口夏季海源有机碳贡献率表层海水低于底层海水,平均贡献率为48.26%,沿向海方向海源有机碳贡献率逐渐增加--从内伶仃洋水域的4.43%逐渐提升到外伶仃洋东侧水域的81.20%.珠江口水动力条件复杂,在径流、潮汐、季风等因素的作用下陆源有机碳向海输送且向海输送量逐渐递减;海源有机碳在不同水域动力输送特征不同,西南水域向海输送,向海输送量逐渐递增;东北水域向岸输送,向岸输送量逐渐递减.陆源有机碳生化反应活性较弱,只有小部分被生化过程消耗,其迁移转化主要由沉降过程控制,而海源有机碳的迁移转化,则由口门的动力输送过程主控向外海的生化耗碳过程主控过渡.此外,海源有机碳沉降作用明显低于陆源有机碳,生化作用明显高于陆源有机碳.  相似文献   
3.
Long-term integrated monitoring is an important approach forinvestigating, detecting and predicing the effects ofenvironmental changes. Currently, European freshwaters,glaciers, forests and other narural and semi-natural ecosystemsand habitats are monitored by a number of networks establishedby different organisations. However, many monitoring programmeshave a narrow focus (e.g. targeting individual ecosystems) andmost have different measurement protocols and sampling design.This has resulted in poor integration of ecosystem monitoring ata European level, leading to some overlapping of efforts and alack of harmonised data to inform policy decisions. The need fora consistent pan-European long-term integrated monitoring ofterrestrial systems programme is recognised in the scientificcommunity. However, the design of such a system can be problematic, not least because of the constraints imposed bythe need to make maximum use of existing sites and networks.Based on the outcomes of the NoLIMITS project (Networking ofLong-term Integrated Monitoring in Terrestrial Systems), thisarticle reviews issues that should be addressed in designing aprogramme based on existing monitoring sites and networks. Fourmajor design issues are considered: (i) users' requirements,(ii) the need to address multiple objectives, (iii) role ofexisting sites and (iv) operational aspects.  相似文献   
4.
This paper uses a dynamic model to explore the issue of irrigation-induced salinity, which puts irrigation at risk in most irrigated areas throughout the world. We address the design of instruments that an irrigation district board could implement to induce irrigators to take sustainable irrigation decisions. In our approach, the irrigators located above an aquifer participate in the accumulation of groundwater, a stock pollution. We analyse input-based instruments to induce the agents to follow the optimal stock path.  相似文献   
5.
1 IntroductionMercury(Hg)asaglobalpollutanthascausedconcernworldwidesincetheendof 1980s.Itisemittedtotheatmospherefrombothanthropogenicandnaturalsources.Importantsourceoftheformeristhedischargefrom productionanduseofHgaswellasthecombustionoffossilfuels(Nri…  相似文献   
6.
高伟  白辉  严长安  陈岩 《环境科学学报》2019,39(9):3134-3143
过量氮输入是水体氮污染的关键驱动因子,解析氮输入的结构和时空变化模式成为氮素环境管理的重要基础和难点.基于1952—2016年长江经济带各地区氮活动数据,分别构建了天然氮输入和人为氮输入模型,评估了氮输入负荷的时空变化特征.结果表明:①长江经济带氮输入负荷总体越过EKC曲线拐点进入由增长向下降的发展阶段,拐点出现在人均GDP为35777~36299元·人-1时,发生时间为"十二五"时期,主要原因是化肥和食物输入下降;②氮输入负荷存在显著的时空差异,东部地区表现为倒U型,中部为S型,西部为J型,表明氮负荷存在从东向西的空间转移,西部地区成为氮输入负荷增长的热点地区,这与东部地区化肥施用量下降有关;③人为输入是长江经济带氮输入的主要来源,输入量及其占总输入的比例均呈现显著的增长趋势,空间上表现为从西到东部逐步递增的变化规律,与氮驱动力分布一致;④植被的多年平均固氮量为1771 kg·km-2·a-1,其中,非农作物的固氮速率为763 kg·km-2·a-1,植被固氮量的年际波动较小,天然输入对长江经济带总体氮输入影响较小.  相似文献   
7.
An integrated approach was developed to determine the critical levels of air pollution for ecological standard setting based on the unified index of biological response, by taking into account the effects of all pollution components simultaneously. An empirical model of plant productivity was taken as the dose response model for gaseous pollutant effect on the productivity of trees and the annual productivity of plants was used as the above mentioned index. The CO2 increase in the lower atmosphere was considered to potentially increase plant productivity and NO2 was estimated as neutral while being dangerous for plants as a chemical precursor of ozone or as a source of acidification. The maximum permissible chronic O3 and SO2 levels for trees were estimated and it was found that O3 is much more phytotoxic, as compared to SO2 , with a rather narrow range of permissible levels (27-33 ppb) which complicates its monitoring and control.  相似文献   
8.
IntroductionSincethefirstenvironmentalinputoutputmodel(EIOM)(Cumberland,1966)wasestablishedbyincorporatingenvironmentalfactorsint?..  相似文献   
9.
Summary The balance of evidence suggests a perceptible human influence on global ecosystems. Human activities are affecting the global ecosystem, some directly and some indirectly. If researchers could clarify the extent to which specific human activities affect global ecosystems, they would be in a much better position to suggest strategies for mitigating against the worst disturbances. Sophisticated statistical analysis can help in interpreting the influence of specific human activities on global ecosystems more carefully. This study aims at identifying significant or influential human activities (i.e. factors) on CO2 emissions using statistical analyses. The study was conducted for two cases: (i) developed countries and (ii) developing countries. In developed countries, this study identified three influential human activities for CO2 emissions: (i) combustion of fossil fuels, (ii) population pressure on natural and terrestrial ecosystems, and (iii) land use change. In developing countries, the significant human activities causing an upsurge of CO2 emissions are: (i) combustion of fossil fuels, (ii) terrestrial ecosystem strength and (iii) land use change. Among these factors, combustion of fossil fuels is the most influential human activity for CO2 emissions both in developed and developing countries. Regression analysis based on the factor scores indicated that combustion of fossil fuels has significant positive influence on CO2 emissions in both developed and developing countries. Terrestrial ecosystem strength has a significant negative influence on CO2 emissions. Land use change and CO2 emissions are positively related, although regression analysis showed that the influence of land use change on CO2 emissions was still insignificant. It is anticipated, from the findings of this study, that CO2 emissions can be reduced by reducing fossil-fuel consumption and switching to alternative energy sources, preserving exiting forests, planting trees on abandoned and degraded forest lands, or by planting trees by social/agroforestry on agricultural lands.  相似文献   
10.
利用长江经济带110个地市1990~2013年RD投入与经济增长水平的相关面板数据,通过单位根检验、协整性检验和面板数据模型,对RD经费投入和人员投入与区域经济增长的影响进行了分析。结果表明:1长江经济带各市的经济增长与RD投入存在长期稳定的关系,RD短期投入对区域经济增长的影响则存在着一定的滞后效应;2RD人员投入产出弹性高于RD经费投入,说明区域经济增长对RD人员的依赖性更大;3RD投入表现出东部地区高于中部地区,中部地区高于西部地区,但RD投入对区域经济增长的影响则表现出中西部大于东部的现象,造成这一现象的原因在于所处发展阶段的不同和东中西区域经济特征不同。最后,从加大RD经费投入强度、制定RD投入中长期计划等方面提出了促进区域经济增长的建议。  相似文献   
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