氯氟烃及其替代物

近年来,臭氧衰竭比原先预料的更严重,对人类健康和环境构成了严重威胁。“蒙特利尔议定书”和“大气清洁法案”要求2000年要完全清除致臭氧衰竭物质——氯氟烃(CFCs)的生产和使用。目前,世界各地积极开发CFCs的替代物,以加速转换。虽然已开发的氧氯氟烃(HCFCs)、氢氟烃(HFCs)等替代物与CFCs相比还有一定缺点,但最终一定会实现替代转换。     

SEDIMENT OXYGEN DEMAND IN THE ARROYO COLORADO RIVER1

ABSTRACT: The lower reaches of the Arroyo Colorado have historically failed to meet their use under subsection 303(b) of the U.S. Clean Water Act due to fecal coliform bacteria and low dissolved oxygen (DO). Fish kills, especially at the tidal confluence at the Port of Harlingen, Texas, have been reported. Oxygen demand from sediment (SOD) for a river typically has two states‐diffusion limited SOD (SOD) and potential SOD (pSOD), expressed when sediment is resuspended through increased flow or other disturbances. The objective of this research was to measure SOD in the Arroyo Colorado River in situ, estimate pSOD ex situ, and evaluate the relationship between SOD and the depositional environment. We measured SOD and pSOD in the Arroyo Colorado River at up to eight sites over three sampling events. We identified the sample sites based on a modified Rosgen geomorphic index for streambed stabilization. Sites with high sediment deposition potential had high SOD. The average values of SOD between sites were 0.62 g/m²/day (standard deviation 0.38 g/m²/day) and ranged from 0.13 to 1.2 g/m²/day. Potential SOD values ranged from as low as 19.2 to as high as 2,779 g/m³ sediment/ day. Potential SOD can serve as an indicator of the possible impact of SOD from resuspended sediment in stream systems.     

Hamburgers and the Rainforest – a Review of Issues and Evidence

This paper examines the relationship between North American beef consumption and deforestation in South and Central America. Some writers have argued that consumption of hamburgers in North America, particularly hamburgers consumed in fast food restaurants, contributes to the depletion of the rainforest in South and Central America. We survey the published policy literature on the causes of rainforest depletion in the region. We also review the published estimates of the rate and extent of clearing of rainforest that has occurred in South and Central America since 1970. Finally, we review the data on beef imports and consumption in Canada and the United States in a effort to assess the importance of South and Central America as suppliers of beef to the North American market. We conclude that the relationship between beef consumption in North America should not be considered an important cause of forest depletion in South and Central America. Domestic policies and market forces in the countries where rainforests are located are the leading causes of rainforest depletion in this region. This lesson seems to have been lost on some popular and even some textbook writers on this subject. This revised version was published online in August 2006 with corrections to the Cover Date.     

Sustainability and comanagement of subsistence hunting in an indigenous reserve in Guyana

Although hunting is a key component of subsistence strategies of many Amazonians, it is also one of the greatest threats to wildlife. Because indigenous reserves comprise over 20% of Amazonia, effective conservation often requires that conservation professionals work closely with indigenous groups to manage resource use. We used hunter‐generated harvesting data in spatially explicit biodemographic models to assess the sustainability of subsistence hunting of indigenous Waiwai in Guyana. We collected data through a hunter self‐monitoring program, systematic follows of hunters, and semistructured interviews. We used these data to predict future densities of 2 indicator species, spider monkeys (Ateles paniscus) and bearded sakis (Chiropotes sagulatus), under different scenarios of human population expansion and changing hunting technology. We used encounter rates from transect surveys and hunter catch‐per‐unit effort (CPUE) to validate model predictions. Paca (Cuniculus paca) (198 /year), Currosaw (Crax alector) (168), and spider monkey (117) were the most frequently harvested species. Predicted densities of spider monkeys were statistically indistinguishable from empirically derived transect data (Kolmogorov–Smirnov D = 0.67, p = 0.759) and CPUE (D = 0.32, p = 1.000), demonstrating the robustness of model predictions. Ateles paniscus and C. sagulatus were predicted to be extirpated from <13% of the Waiwai reserve in 20 years, even under the most intensive hunting scenarios. Our results suggest Waiwai hunting is currently sustainable, primarily due to their low population density and use of bow and arrow. Continual monitoring is necessary, however, particularly if human population increases are accompanied by a switch to shotgun‐only hunting. We suggest that hunter self‐monitoring and biodemographic modeling can be used effectively in a comanagement approach in which indigenous parabiologists continuously provide hunting data that is then used to update model parameters and validate model predictions.     

利用沉积色素恢复湖泊古紫外强度研究综述

自从南极臭氧空洞被发现以来,平流层臭氧浓度下降导致到达地表的紫外辐射增强的现象引起了人们的广泛关注,目前这一状况还在不断加剧并将在未来很长一段时间里持续下去。为了更好地理解这种现象在长时间尺度上的意义以及合理预测未来地球表面紫外环境的变化以及生态系统的响应过程,科学家开始尝试恢复历史时期地球表面紫外辐射的变化。Scytonemin是蓝绿藻细胞外鞘上的一种抗UV色素,高UV强度照射能够促使细胞合成更多的这种色素以保护细胞免受紫外辐射的伤害,并且这种色素在湖泊沉积物中能够很好地保存。因此,我们可以通过分析不同时间段蓝绿藻细胞的scytonemin含量来反映历史时期湖泊紫外环境的变化。进一步的研究可以推测造成这种变化的原因以及生态系统对这些过程的响应,为预测未来地表紫外环境的变化及生态系统的响应提供合适的理论和证据。     

煤炭资源耗减价值及其“利益共享、风险共担”补偿机制研究

煤炭行业清费建税,资源税从价计征引起了社会各界对资源税费制度改革的热议,而资源耗减价值是资源税费制度改革的重要依据之一。将资源回采率纳入使用者成本模型,科学计量了我国2000-2011年间煤炭资源的耗减价值。分析表明:2000-2011年间,4%折现率下煤炭资源耗减价值增加了22倍之多,而资源税费却仅仅增长了7倍,煤炭资源耗减价值与资源税费实际征收额之间存在有巨大缺口得不到补偿;国家资源所有者权益的实现度与煤炭经济形势呈逆向分布,煤炭工业利润率的上升并没有带来国家资源所有者权益的增加,导致这种错位的原因与我国不合理的资源税收机制有很大关系;资源税税率的理论区间为1.11%-8.85%,与国家规定的2%-10%高度重合,从而说明国家决策的合理性。为使资源所有者权益的实现度与煤炭工业经济形势相"挂钩",以资源税收入等于资源耗减价值为切入点,对资源所有者权益的实现度进行数理分析,求得了资源税税率与当期资源价格的关系,发现固定税率的资源税难以适应市场波动,于是提出"资源税+利润税"的组合税收工具,确定了利润税的起征点,计算得出了资源税和利润税的税率组合。该组合税制在一定程度上能够平抑经济周期对煤炭工业造成的影响,同时又维护国家资源所有者权益,从而实现国家与煤炭工业"利益共享、风险共担"。     

The Interior-to-Edge Breakpoint Distance as a Guideline for Nature Conservation Policy

A method is proposed to quantify disturbance impact on isolated habitats. For every landscape patch, the breakpoint distance, defined as the penetration distance for which equality of interior and edge habitat is observed, can be calculated. Disturbance with equal impact at all patch sides is assumed. Effects of patch compactness, size, convolution, and perforation are discussed. The potential use of the measure for nature reserve design is discussed. The breakpoint distance follows the reserve design guidelines for individual patches, based on island biogeography and is consistent with the form and function principle. A large breakpoint distance is preferred for natural habitats. Small size, small compactness, intense convolution, and the occurrence of many gaps depress the breakpoint distance.     

Variability of tropospheric hydroperoxides at a coastal surface site in Antarctica

The annual cycles of hydrogen peroxide (H₂O₂) and methylhydroperoxide (MHP) have been investigated at a remote site in Antarctica in order to study seasonal variations as well as chemical processes in the troposphere. The measurements have been performed from March 1997 to January 1998 and in February 1999 at the German Antarctic research station Neumayer which is located at 70°39′S, 8°15′W. The obtained time series for hydrogen peroxide and methylhydroperoxide in near-surface air represents the first all-year measurements in Antarctica and indicates clearly the occurrence of seasonal variations. During polar night mean values of 0.054±0.046 ppbv (range<0.03–0.11 ppbv) for hydrogen peroxide and 0.089±0.052 ppbv (range<0.05–0.14 ppbv) for methylhydroperoxide were detected. At the sunlit period higher Mixing ratios were found, 0.20±0.13 ppbv (range<0.03–0.91 ppbv) for hydrogen peroxide and 0.19±0.10 ppbv (range<0.05–0.89 ppbv) for methylhydroperoxide. Occasional long-range transport of air masses from mid-latitudes caused enhanced peroxide concentrations at polar night. During the period of stratospheric ozone depletion we observed peroxide mixing ratios comparable to typical winter levels.     

STREAM DEPLETION BY WELLS IN THE SOUTH PLATTE BASIN-COLORADO1

The agricultural production from the Lower South Platte Basin in Colorado represents a significant portion of the state economy. Until the early 1950's the production had developed almost exclusively by use of river water. Drought conditions combined with improved well technology resulted in an inordinate amount of well development in the valley during the period 1952-56. These wells were used for supplemental supply in many cases, but the application of sprinkler irrigation brought many acres of here-to-fore dry land into irrigated production. As a result of the vast amounts of groundwater withdrawal by the newly developed wells, senior surface appropriators found a decreasing amount of water available for use in the streams. The legislature, observing the doctrine of prior appropriation, ruled that all surface and ground water in a tributary would be treated and administered as one resource. This, of course, spelled doom for the well-oriented segment of the economy. Analysis of a segment of the river on an inflow-outflow basis was made with careful determination of all inflow-outflow in the study reach to include correlations required to determine ungaged side-channel in-flow and unmetered irrigation wells. Results indicate that wells have intercepted normal return flows to the river resulting in a decreased amount of surface water during the irrigation season. Stream depletion appears to equal the expected consumptive use of well water which ranged between 40% to 50% of the groundwater extraction.     

Beyond depletion: Daily self-control motivation as an explanation of self-control failure at work

The organizational self-control literature usually applies resource perspectives that explain self-control failure at work by depletion of self-control resources. However, these perspectives neglect the role of self-control motivation. On a daily level, we examine several self-control aspects (resources, motivation, demands, and effort) as predictors of a manifestation of self-control failure at work, namely, daily counterproductive work behavior toward the organization (CWB-O). Additionally, we investigate self-control effort as a mechanism predicting the depletion of self-control resources throughout the day. We analyzed data from 155 employees in a 2-week diary study with 2 daily measurement points. Multilevel path modeling showed that self-control motivation and self-control demands, but not self-control resource depletion, predicted self-control effort. There was an indirect effect from self-control motivation on CWB-O via self-control effort but no indirect effect from self-control demands on self-control resource depletion throughout the day via self-control effort. Findings suggest that self-control motivation is a crucial factor explaining self-control failure at work and cast further doubt on the idea that exerted self-control effort is the only mechanism leading to self-control resource depletion.