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931.
利用FLEXPART模式反演中国区域SF6排放量 总被引:1,自引:0,他引:1
六氟化硫(SF_6)是一种长寿命卤代温室气体,被列为《京都议定书》限排物种.随着经济高速发展,中国的SF6排放量受到世界各国的关注.采用传统的"自下而上"清单方法估算SF6排放量时,所需排放因子、活动水平数据的准确性和时效性存在较大局限.因此,本文利用拉格朗日粒子扩散模式FLEXPART,结合2009年北京上甸子区域大气本底站SF6浓度观测资料,尝试建立中国区域SF6排放量的反演方法.结果表明,初步反演的2009年中国区域SF6排放量为1.25×103(0.53×103~1.97×103)t·a-1,与文献结果相当,源排放量的不确定性从1.05×103t·a-1减小到0.72×103t·a-1.与先验源相比,反演源的相关系数从0.37提高到0.43,均方根误差减小了2.64%. 相似文献
932.
Brooke E. Buckley Walter W. Piegorsch R. Webster West 《Environmental and Ecological Statistics》2009,16(1):53-62
In modern environmental risk analysis, inferences are often desired on those low dose levels at which a fixed benchmark risk
is achieved. In this paper, we study the use of confidence limits on parameters from a simple one-stage model of risk historically
popular in benchmark analysis with quantal data. Based on these confidence bounds, we present methods for deriving upper confidence
limits on extra risk and lower bounds on the benchmark dose. The methods are seen to extend automatically to the case where
simultaneous inferences are desired at multiple doses. Monte Carlo evaluations explore characteristics of the parameter estimates
and the confidence limits under this setting.
相似文献
R. Webster WestEmail: |
933.
上海崇明县植被覆盖度动态变化遥感监测研究 总被引:4,自引:0,他引:4
植被覆盖度是用于描述和评价生态系统的重要参数。基于1989、2001、2006年的TM/ETM+遥感数据,以上海市崇明县为研究区域,利用改进的像元二分模型,估算出不同时期内崇明县的植被覆盖度,并对其变化进行了定量分析。结果表明:1989-2001年,植被覆盖度负向变化地表约10.17%,正向变化约20.58%,乡镇和湿地区域正向变化的面积大于负向变化,农场区域则相反;2001-2006年,负向变化约29.1%,正向变化约12%,农场和湿地区域正向变化的面积大于负向变化,乡镇区域则相反,并且随着城市化进程的深入,各土地用地类型的植被覆盖度变化在一定程度上都呈现出生态退化的趋势。 相似文献
934.
Assisted migration (AM) is the translocation of species beyond their historical range to locations that are expected to be more suitable under future climate change. However, a relocated population may fail to establish in its donor community if there is high uncertainty in decision-making, climate, and interactions with the recipient ecological community. To quantify the benefit to persistence and risk of establishment failure of AM under different management scenarios (e.g., choosing target species, proportion of population to relocate, and optimal location to relocate), we built a stochastic metacommunity model to simulate several species reproducing, dispersing, and competing on a temperature gradient as temperature increases over time. Without AM, the species were vulnerable to climate change when they had low population sizes, short dispersal, and strong poleward competition. When relocating species that exemplified these traits, AM increased the long-term persistence of the species most when relocating a fraction of the donor population, even if the remaining population was very small or rapidly declining. This suggests that leaving behind a fraction of the population could be a robust approach, allowing managers to repeat AM in case they move the species to the wrong place and at the wrong time, especially when it is difficult to identify a species’ optimal climate. We found that AM most benefitted species with low dispersal ability and least benefited species with narrow thermal tolerances, for which AM increased extinction risk on average. Although relocation did not affect the persistence of nontarget species in our simple competitive model, researchers will need to consider a more complete set of community interactions to comprehensively understand invasion potential. 相似文献
935.
旅游业碳排放效率是考量旅游经济增长与生态环境关系的重要指标,对旅游业碳排放效率的有效测度和分析是实现旅游业节能减排与可持续发展的基础支撑.采用“自下而上”法核算2001—2015年我国旅游业能源消耗量与碳排放量(不含港澳台及西藏自治区数据,下同);继而运用非期望产出SBM模型对旅游业碳排放效率进行测度,并通过空间自相关分析揭示其空间特征;最后采用Malmquist指数(MI)评估旅游业碳排放效率的动态趋势.结果表明:①研究期内我国旅游业总体碳排放效率较低,平均水平为60%;各年度达到最佳生产前沿面(旅游业碳排放效率值为1)的省(市、自治区)(简称“省区”)数量较少,绝大多数省区的碳排放效率具有较大改善空间;旅游业碳排放效率水平存在明显的省际差异;东、中、西部地区的效率存在梯度差,形成“东高西低”的空间格局.②Moran's I指数和LISA聚类图显示,各省区旅游业碳排放效率存在明显的正向空间相关性,在空间分布上呈现出显著的地理聚集特征,形成“高—高”型与“低—低”型聚集区,空间联动格局尚未形成.③2001—2015年MI均在1以上(2004年除外),且总体平均值高达1.195,体现出持续改善的态势;各省区碳排放效率的提升来源于技术进步与技术效率双重贡献,其中,技术进步是促进旅游业碳排放效率提升的主要贡献因素.研究显示,我国旅游业碳排放效率的空间分布不均衡,但整体呈现持续上升的态势,各省区在依赖技术进步提高碳排放效率的同时,要注重全局空间联动格局的形成,最终实现低碳旅游业的协调发展. 相似文献
936.
Forest management often represents a balance between social, economic, and ecological objectives. In the eastern United States, numerous studies have established that terrestrial salamander populations initially decline in abundance following timber harvest, yet the large‐scale and long‐term consequences are relatively unknown. We used count data from terrestrial survey points to examine the relation between salamander abundance and historic timber harvest while accounting for imperfect detection of individuals. Overall, stream‐ and terrestrial‐breeding salamanders appeared to differ by magnitude of population decline, rate of population recovery, and extent of recolonization from surrounding forest. Specifically, estimated abundance of both species groups was positively associated with stand age and recovery rates were predicted to increase over time for red‐legged salamanders (Plethodon shermani) and decrease in stream‐breeding species. Abundance of stream‐breeding salamanders was predicted to reach a peak by 100 years after timber harvest, and the population growth rate of red‐legged salamanders was predicted to undergo a significant increase 100 years after harvest. Estimated abundance of stream‐breeding salamanders in young forest stands was also negatively associated with the distance to adjacent forest, a result that suggests immigration has a role in the recovery of these species. Our results indicate that salamander abundance in young forest stands may be only modestly lower than in more mature forest but that full recovery from timber harvest may take a substantial amount of time and that species life history may affect patterns of recovery. Historia de Vida como un Vaticinador de la Tasa de Recuperación de una Salamandra a la Colecta de Madera en los Bosques del Sur de los Apalaches, E.U.A 相似文献
937.
938.
Chao‐Hsien Liaw Yao‐Lung Tsai Mow‐Soung Cheng 《Journal of the American Water Resources Association》2006,42(2):311-322
The Keelung River Basin in northern Taiwan lies immediately upstream of the Taipei metropolitan area. The Shijr area is in the lower basin and is subject to frequent flooding. This work applies micromanagement and source control, including widely distributed infiltration and detention/ retention runoff retarding measures, in the Wudu watershed above Shijr. A method is also developed that combines a genetic algorithm and a rainfall runoff model to optimize the spatial distribution of runoff retarding facilities. Downstream of Wudu in the Shijr area, five dredging schemes are considered. If 10‐year flood flows cannot be confined in the channel, then a levee embankment that corresponds to the respective runoff retarding scheme will be required. The minimum total cost is considered in the rule to select from the regional flood mitigation alternatives. The results of this study reveal that runoff retarding facilities installed in the upper and middle parts of the watershed are most effective in reducing the flood peak. Moreover, as the cost of acquiring land for the levee embankment increases, installing runoff retarding measures in the upper portion of the watershed becomes more economical. 相似文献
939.
中国经济转型阶段建设用地增长极限计量研究 总被引:14,自引:4,他引:14
论文以中国经济发展进程中的建设用地增长态势为研究起点,在把握经济发展与建设用地增长规律的基础上,提出建设用地增长极限命题;通过构建边际模型,计量建设用地增长的极限时点,进而剖析时空变化规律。结果表明:①1978-2000年间中国经济发展与建设用地增长具有周期性波动特征,两者波动周期基本一致;②中国建设用地增长极限平均时点为2047年左右,不同省(市)建设用地增长极限特征不论时间纵向还是空间横向比较,都大致沿东南-西北线依次分级;③东部地区较早达到建设用地增长极限,其中上海、江苏和广东等11个省(市)早于全国平均时点,河北、四川和青海等其余19个省(市)晚于全国平均水平,东部地区建设用地增长压力较大,中、西部地区增长压力相对较小。最后,论文提出提高中、西部地区的土地利用效率,控制粗放利用,鼓励技术创新等加快逼近建设用地增长极限的政策和建议。 相似文献
940.