碳排放交易制度下城市减排的机会成本研究——基于中国碳排放试点城市的实证检验

作为全球气候治理的重要手段,碳排放交易制度受到了广泛的关注与讨论。基于此,本文采用我国2010-2016年城市面板数据,运用非参数方法构建方向性环境距离函数测算了2009-2015年城市减排的机会成本,计算结果显示,试点地区与非试点地区的碳排放的机会成本整体表现为上升的趋势,且试点地区的碳排放的机会成本总体低于非试点地区。在测算城市减排机会成本的基础上,运用双重差分法来检验碳排放交易制度的有效性。经检验发现：碳排放交易制度有利于降低城市减排的机会成本,然而由于碳排放交易制度还存在碳排放权初始分配制度缺失、碳排放交易制度的定价机制扭曲等问题,因此其对降低城市减排的机会成本作用较小,并且进一步通过对政策时间趋势的分析得出政策效应随时间推移而逐渐减弱。     

基于FAHP的功效系数法的岩质边坡稳定性分级

针对岩质边坡稳定性评价的模糊性与多指标性特点,采用模糊层次分析法确定Ⅰ、Ⅱ级指标权重,提高了0.1~0.9标度法所确定权重的客观性并克服了单一性,且避免了同一对指标比较时的不一致性,量化了不连续性基础指标。引入功效系数法对不同类型的基础指标进行功效系数值归一化求解,结合功效系数值与Ⅰ、Ⅱ级指标权重向量计算得出总功效系数值,据总功效系数值大小划分稳定性级别。在模糊层次分析法基础上,运用功效系数法对永吉岩质边坡进行稳定性评价、分级的结果与实际调查情况相符。证明该方法对岩质边坡稳定性分级具有很好的适用性与可靠性。     

Atmospheric lead pollution in fine particulate matter in Shanghai, China

The Pb-monitoring program was extended for 6 years from 2002 to 2007 at 17 representative urban sites (6 traffic, 5 industrial, and 6 residential sites), and 3 suburban sites to assess the lead pollution in fine particulate matter (PM2.5) after phasing out leaded gasoline in Shanghai. Compared with Pb levels reported in other places, the Pb pollution in Shanghai is still serious after phasing out leaded gasoline, which remains at high concentration range (213–176 ng/m3) in PM2.5 in winter. Significant spati...     

Research status,challenges and future prospects of renewable synthetic fuel catalysts for CO2 photocatalytic reduction conversion

Environmental Science and Pollution Research - In recent years, with global climate change, the utilization of carbon dioxide as a resource has become an important goal of human society to achieve...     

赤壁市生态旅游资源特色与开发

赤壁生态旅游资源丰富,特色鲜明,类型齐全,具有较大的开发价值。通过对赤壁市开发条件、开发力和客源市场的分析,作者指出了该市开发旅游资源的巨大前景,提出了建立七种不同类型生态旅游区的构想。     

Distribution and migration of 95Zr in a tea plant/soil system

(95)Zr is a primary radionuclide in the radioactive liquid efflux from a pressurized water reactor and one of the main radionuclides released after nuclear accidents. The fission yield of (95)Zr is as high as 6.2%, however, its environmental behavior has not been well documented. An experiment was conducted to evaluate the accumulation and distribution of (95)Zr in a tea plant/soil system. (95)Zr was accumulated primarily in the trunk of tea plants after being taken up from the soil. The radioactivity concentration of (95)Zr in the trunk increased slowly with time, then it reached a dynamic equilibrium 14 days after application. The radioactivity concentration of (95)Zr in the other parts of the tea plant was very low; only slighter greater than the detection limit. The results indicated that (95)Zr was not readily translocated in the tea plant. About 98.9% of applied (95)Zr was found to concentrate in the upper 5 cm layer after being sprayed onto the soil surface. The results indicated that (95)Zr could not readily move downwards with percolating water due to strong adsorption to surface soil.     

茶树-土壤生态系统中HTO的迁移与消长动态

采用模拟污染物的同位素示踪技术研究HTO（氚水）在茶树-土壤模拟生态系统中的迁移规律。测定了植物和土壤样品中两种形态氚（自由水氚和结合态氚）的比活度，并应用具有相互交换的双库室开系统模型确定了茶和土壤分室的拟合方程。结果表明：引入土壤中的HTO，不仅在系统积分室间转移和分配，而且迅速向系统外扩散；HTO中的氚以自由水氚和结合态氚形式存在于茶树中，以吸湿性水氚和结晶水氚存在于土壤，其中自由水氚（或吸湿性不氚）远大于结合态氚（或结晶水氚）；对实验数据进行回归分析得；茶树植株中的总氚比活度Ct(t)=314.09(e^-0.0569t-e^-0.3777t)，土壤中的总氚比活度Cs(t)=136.73e^-0.3777t 112.22e^-0.0569t。     

Re-Os同位素体系在金属矿床研究中的应用

Re－Os法能够对金属硫化物矿物直接进行同位素定年，并可以根据矿物的Os同位素初始比值探讨成矿物质来源。它的研究对象还包括黑色页岩和洋底含金属沉积物等。普通Os法可以用于铂族元素矿物定年和成矿物源区的讨论。近年由常规Re－Os法衍生的Os－Os法有可能避免前者在定年技术方面的一些困难。Re-Os同位素体系为成矿年代学研究提供了广阔的前景。     

鄂西清江流域发展生态旅游的探讨

本文从鄂西清江流域旅游资源的生态旅游潜力分析入手,概括了该流域生态旅游资源的类型,提出了在小流域范围内发展生态旅游的意见,为当地有关部门开展生态旅游提供了参考性依据,有利于实现该流域旅游景观资源的可持续利用     

Modeling the probability of freeway lane-changing collision occurrence considering intervehicle interaction

Objective: To better capture the relationships between lane-changing collisions and explanatory variables, a microscopic model is developed for freeway lane-changing collisions based on the interactions between lane-changing vehicles.

Methods: The model applies an intervehicle interaction structure to account for the occurrence mechanism of lane-changing collisions. The occurrence mechanism can be described as the failure of a vehicle driver of an adjacent lane in avoiding the lane-changing vehicle, which disturbs the smooth movement of the adjacent lane vehicle and requires the driver's brake action to avoid an angle collision. This model is examined using data collected from freeways in Washington State during 2010 to 2011 and validated using lane-changing collision data for the SR 520 freeway.

Results: The findings of this study show that generalized truck percentage has a significant decreasing effect on lane-changing collision risk, whereas average spacing and several roadway characteristics have significant increasing effects. The frequency of slight collisions during peak hours is higher than that during off-peak hours. Young female drivers are more likely to be involved in collisions during lane-changing than young male drivers, but the result for senior drivers is opposite, with older male drivers having a higher probability of lane-changing collisions than female drivers in the same age group.

Conclusion: The process of lane-changing collisions is a complicated maneuver. Truck percentage, average spacing, and good roadway characteristics, such as straight and level segment, in the target lane have a significant effect on the occurrence of lane-changing collisions. Age and gender are also 2 important factors contributing to the relationship between lane-changing collisions and explanatory variables.