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991.
The effort to transition energy sources away from dependence on fossil fuels has become highly divided along partisan lines in some countries, but the social-science literature has not yet caught up with this important problem. Policy-adoption studies do not address the specific problem of polarization and gridlock, and the literature on gridlock does not examine conditions for breaking gridlock for renewable energy and energy efficiency (REEE) policy. Qualitative research can help to fill the void by identifying strategies that legislators use for achieving support for REEE policy where there is gridlock, polarization, and/or strong opposition. Interview data from a stratified sample of US states reveals three strategies that state-government legislators use to enhance REEE policy development under these conditions: bring to the process countervailing industrial interests to align REEE with business; transfer decision making to public service commissions; and use extra-legislative consultation processes to develop stakeholder consensus.  相似文献   
992.
Objective: Suboptimal child restraint use includes incorrect and/or inappropriate restraint use and increases the risk of injury. Comfort has been suggested as an important factor impacting on optimal use of restraints by children. This article aims to examine the relationships between parent reported comfort and restraint misuse and age-appropriate restraint choice.

Methods: This is an analysis of data from a cross sectional observation study of child restraint use in New South Wales. Logistic regression was used to model the relationship between parent-reported comfort and restraint misuse and age-appropriate restraint choice.

Results: There was no significant relationship between either parent-reported comfort and restraint misuse or parent-reported comfort and age-appropriate restraint choice.

Conclusions: Parent perceptions of comfort of children in child restraints do not appear to be associated with incorrect child restraint use or age appropriate restraint choice. It is possible that the actual comfort of the child may be related to incorrect use but this remains to be tested. Further investigation of the relationship between parent-perceived comfort and the actual comfort of the child, as well as the impact of child comfort on optimal child restraint use is warranted.  相似文献   

993.
Abstract

Landfills represent a source of distributed emissions source over an irregular and heterogeneous surface. In the method termed “Other Test Method-10” (OTM-10), the U.S. Environmental Protection Agency (EPA) has proposed a method to quantify emissions from such sources by the use of vertical radial plume mapping (VRPM) techniques combined with measurement of wind speed to determine the average emission flux per unit area per time from nonpoint sources. In such application, the VRPM is used as a tool to estimate the mass of the gas of interest crossing a vertical plane. This estimation is done by fitting the field-measured concentration spatial data to a Gaussian or some other distribution to define a plume crossing the vertical plane. When this technique is applied to landfill surfaces, the VRPM plane may be within the emitting source area itself. The objective of this study was to investigate uncertainties associated with using OTM-10 for landfills. The spatial variability of emission in the emitting domain can lead to uncertainties of –34 to 190% in the measured flux value when idealistic scenarios were simulated. The level of uncertainty might be higher when the number and locations of emitting sources are not known (typical field conditions). The level of uncertainty can be reduced by improving the layout of the VRPM plane in the field in accordance with an initial survey of the emission patterns. The change in wind direction during an OTM-10 testing setup can introduce an uncertainty of 20% of the measured flux value. This study also provides estimates of the area contributing to flux (ACF) to be used in conjunction with OTM-10 procedures. The estimate of ACF is a function of the atmospheric stability class and has an uncertainty of 10–30%.  相似文献   
994.
Abstract

Since the early 1970s, researchers and data analysts have reported differences between weekday and weekend ozone concentrations, with higher ozone concentrations occurring on Sundays in some locations. At that time, the phenomenon was referred to as the “Sunday effect.” In the late 1980s, additional papers focused on weekday/weekend differences in air quality in the South Coast (Los Angeles) Air Basin.

Analyses of ozone concentrations measured at a number of locations in northern California reveal that average ozone concentrations are frequently higher on weekends than on weekdays. Violations of the California 0.09 ppm 1-hour air quality standard for ozone also occur in disproportionately greater frequency on weekends. We hypothesize that this phenomenon is based largely on the differences between weekday and weekend emission patterns. We believe that the observed differences may provide information regarding which pollutant reduction strategy, NOx or ROG control, may be more effective in reducing ambient ozone concentrations. For the northern California region, the presence of higher weekend ozone concentrations suggests the need for ROG control is greater than for NOx control. If both NOx and ROG are to be controlled, it is important to understand the interdependence of the two pollutants in forming ozone. With the current uncertainty and debate regarding official vehicular emission inventories, this phenomenon emphasizes the importance of using observation-based data to examine ambient pollution and emission relationships. This natural experiment of varying emissions provides an interesting test case for sophisticated air pollution model performance and evaluation.

Using a Bay Area emission inventory and an estimate of its change from weekday to weekend, combined with a generic Empirical Kinetic Modeling Approach (EKMA) diagram, we demonstrate the weekend effect. In addition, changes in the Bay Area emission inventory from 1980 to 1990, when combined with the EKMA diagram, also show why the weekend effect is more evident in the 1990s.

It is our hypothesis that the presence of the weekend effect, positive or negative, combined with changes in emission changes, provides a simple clue to whether an area is NOxor ROG limited with respect to ozone formation.  相似文献   
995.
Abstract

Evaporative loss of particulate matter (with aerodynamic diameter <2.5 μm, [PM2.5]) ammonium nitrate from quartz-fiber filters during aerosol sampling was evaluated from December 3, 1999, through February 3, 2001, at two urban (Fresno and Bakersfield) and three nonurban (Bethel Island, Sierra Nevada Foothills, and Angiola) sites in central California. Compared with total particulate nitrate, evaporative nitrate losses ranged from <10% during cold months to >80% during warm months. In agreement with theory, evaporative loss from quartz-fiber filters in nitric acid denuded samplers is controlled by the ambient nitric acid-to-particulate nitrate ratio, which is determined mainly by ambient temperature. Accurate estimation of nitrate volatilization requires a detailed thermodynamic model and comprehensive chemical measurements. For the 14-month average of PM2.5 acquired on Teflon-membrane filters, measured PM2.5 mass was 8–16% lower than actual PM2.5 mass owing to nitrate volatilization. For 24-hr samples, measured PM2.5 was as much as 32–44% lower than actual PM2.5 at three California Central Valley locations.  相似文献   
996.
Ozone is an ubiquitous air pollutant that affects both human health and vegetation. There is concern about the number of hours human populations in nonattainment areas in the United States are exposed to levels of 03 at which effects have been observed. As improvement in air quality is achieved, it is possible that 03 control strategies may produce distributions of 1-h 03 concentrations that result in different diurnal profiles that produce greater potential exposures to 03 at known effects levels for multiple hours of the day. These concerns have prompted new analysis of aerometric data. In this analysis, the change in the seasonally averaged diurnal pattern was investigated as changes in 03 levels occurred. For the data used in this analysis, 25 of the 36 sites that changed compliance status across years showed no statistically significant change in the shape of the average diurnal profile (averaged by 03 season). For 71 percent (10 out of 14) of the sites in southern California and Dallas-Fort Worth, Texas, that showed improvement in O3 levels (i.e., reductions in the number of exceedances over the years), but still remained in nonattainment, a statistically significant change in the shape of the seasonally averaged diurnal profile occurred. Based on the results obtained in this study, the evaluation of diurnal patterns may be useful for identifying the influence of changes in emission levels versus meteorological variation on attainment status. Using data from the southern California and Dallas-Fort Worth sites, which showed improvements in 03 levels, changes were observed in the seasonally averaged diurnal profiles. On the other hand, for the sites moving between attainment and nonattainment status, such a change in shape was generally not observed and it was possible that meteorology played a more important role than changes in emission levels relative to attainment status.  相似文献   
997.
分别在2014年春季和夏季三峡库区水华高发期,在库区北岸最大支流澎溪河流域从其河口处逆流而上至回水末端共布置8个采样点,对浮游藻类和环境因子进行了监测,运用数理统计分析手段,对浮游藻类的群落结构及其与环境因子的关系进行了分析.结果表明在4月中旬,除河口样点外,其他采样点水体出现分层,但断面多只有温跃层和滞温层,而没有混合层;上游水体层次间温差高于下游水体;各采样点的水深以及表层水体(水面向下至0.5 m深的水层)的水温、浊度、p H、电导率、溶解氧、叶绿素a、总氮和总磷的空间分布差异显著(ANOVA,P0.05);共检测到浮游藻类25种(属),丰度在(2.76~145.8)×10~4cell·L~(-1)之间,以角甲藻(Ceratium hirundinella)为主要优势藻,鱼腥藻(Anabaena sp.)为次优势藻;上游接近支流来水的样点S7(63.4×10~4cell·L~(-1))和S8(145.8×10~4cell·L~(-1))水华最为严重;硝酸盐氮、水温、p H、电导率和溶解氧是藻类生长的决定因子.在7月下旬,水体分层,趋势与春季相似;各采样点深度和0~0.5 m水层的水温、浊度、氧化还原电位、p H、电导率、叶绿素a、氨氮、硝酸盐氮、总氮和总磷的空间分布仍然差异显著(ANOVA,P0.05);共检测到浮游藻类46种(属),丰度在(9.56~278.88)×10~4cell·L~(-1)之间,总体以席藻(Phormidium sp.)为主要优势藻,鱼腥藻(Anabaena sp.)为次优势藻;下游接近澎溪河河口的样点S2(216.44×10~4cell·L~(-1))、S3(278.88×10~4cell·L~(-1))和S4(108.12×10~4cell·L~(-1))水华严重;浊度、水深、总氮、氧化还原电位、电导率和溶解氧是藻类生长的决定因子.水体分层与水华形成有重要关系.  相似文献   
998.
999.
Evans DM  Turley NE  Levey DJ  Tewksbury JJ 《Ecology》2012,93(5):1016-1025
Habitat corridors confer many conservation benefits by increasing movement of organisms between habitat patches, but the benefits for some species may exact costs for others. For example, corridors may increase the abundance of consumers in a habitat to the detriment of the species they consume. In this study we assessed the impact of corridors on insect herbivory of a native plant, Solanum americanum, in large-scale, experimentally fragmented landscapes. We quantified leaf herbivory and assessed fruit production as a proxy for plant fitness. We also conducted field surveys of grasshoppers (Orthoptera), a group of abundant, generalist herbivores that feed on S. americanum, and we used exclosure cages to explicitly link grasshopper herbivory to fruit production of individual S. americanum. The presence of corridors did not increase herbivory or decrease plant fruit production. Likewise, corridors did not increase grasshopper abundance. Instead, patches in our landscapes with the least amount of edge habitat and the greatest amount of warmer "core" area had the highest levels of herbivory, the largest cost to plant fruit production as a result of herbivory, and the most grasshoppers. Thus habitat quality, governed by patch shape, can be more important than connectivity for determining levels of herbivory and the impact of herbivory on plant fitness in fragmented landscapes.  相似文献   
1000.
Sustainable management of fisheries is often compromised by management delaying implementation of regulations that reduce harvest, in order to maintain higher catches in the short-term. Decreases or increases in fish population growth rate driven by environmental change, including ecosystem and climate change, affect the harvest that can be taken sustainably. If not acted on rapidly, environmental change could result in unsustainable fishing or missed opportunity for higher catches. Using simulation models of harvested fish populations influenced by environmental change, we explore how long fisheries managers can afford to wait before changing harvest regulations in response to changes in population growth. If environmental change causes population declines, delays greater than five years increase the probability of population collapse. Species with fast and highly variable population growth rates are more susceptible to collapse under delays and should be a priority for revised management where delays occur. Generally, the long-term cost of delay, in terms of lost fishing opportunity, exceeds the short-term benefits of overfishing. Lowering harvest limits and monitoring for environmental change can alleviate the impact of delays; however, these measures may be more costly than reducing delays. We recommend that management systems that allow rapid responses to population growth changes be enacted for fisheries management to adapt to ecosystem and climate change.  相似文献   
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