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1.
Ammonia concentration gradients above a Douglas fir canopy were measured from 16 August to 31 December 1989 by two automated high-precision thermodenuders at the location Speulderbos in The Netherlands. Concentration gradients were used to calculate the dry deposition flux of ammonia via flux-gradient theory. Meteorological data were obtained from a nearby tower. Ammonia concentrations were highly variable with highest values during the night. Concentration gradients were very small during daytime and quite large at night. Median values of the calculated deposition flux and deposition velocity were 0.1 microg m(-2) s(-1) and 3.2 cm s(-1) respectively (N=1624). 相似文献
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Zimmer AT 《Journal of environmental monitoring : JEM》2002,4(5):628-632
Recent research has indicated that insoluble ultrafine aerosols (ie., particles whose physical diameters are less than 100 nm) may cause adverse health effects due to their small size, and that toxicological response may be more appropriately represented by particle number or particle surface area. Unfortunately, current exposure criteria and the associated air-sampling techniques are primarily mass-based. Welding processes are high-temperature operations that generate substantial number concentrations of ultrafine aerosols. Welding aerosols are formed primarily through the nucleation of metal vapors followed by competing growth mechanisms such as coagulation and condensation. Experimental results and mathematical tools are presented to illustrate how welding metallurgy influences the chemical aspects and dynamic processes that initiate and evolve the resultant aerosol. This research suggests that a fundamental understanding of metallurgy and aerosol physics can be exploited to suppress the formation of undesirable chemical species as well as the amount of aerosol generated during a welding process. 相似文献
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热带沿海地区正在被日益用于旅游开发。那里丰富的自然海洋景色、珊瑚礁和温暖的海水以及通常友好的民俗文化,使之众多观光者的向往的地方。尽管沿海旅游业为地方及国家创造了大量的经济财富,但这种发展的代价常常是沿海环境退化。产生这种现象的原因通常是环境计划不善以及缺乏对社会-文化问题的考虑。本文对斯里兰卡的希卡杜沃 市海洋保护区的情况进行分析,在这些地方,旅游业的发展几乎使当地沿海环境遭到毁灭性破坏。文中考 相似文献
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采用道化学公司火灾、爆炸危险指数法对中国石化某厂综合储罐区进行安全评价,得出了其安全措施补偿前后的火灾、爆炸指数(F&EI)、危险等级、暴露半径、暴露面积以及暴露体积等。结果表明,该企业综合储罐区采取的安全措施较为适用,能降低火灾、爆炸事故发生的概率和事故损害. 相似文献
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OBJECTIVES: Zero tolerance (ZT) laws have been effective in reducing alcohol-related crashes among underage drivers. However, enforcement in some states has not been rigorous, and ZT offenses may not be viewed as serious offenses. On July 1, 1994, the state of Washington implemented a ZT law that allowed police to request a test for alcohol on suspicion of either a ZT or driving-under-the-influence (DUI) offense. The present study examined effects of the ZT law on arrests and case dispositions among underage offenders as a function of blood alcohol concentration (BAC) and post-law patterns of recidivism. METHODS: Times-series analyses examined the effects of the ZT law on trends in arrests of underage drivers between 1991 and 1999. Based on arrest records matched with driver's license records, the effects of the law on dispositions of alcohol-related offenses among underage drivers were examined, and rates of recidivism among underage offenders were examined for the period following the ZT law. RESULTS: There was a substantial increase in arrests of underage drivers beginning immediately after implementation of the ZT law, especially among drivers with low BACs. The types of court or administrative dispositions received by underage offenders changed markedly after the ZT law was implemented. Underage offenders with lower BACs became far more likely to receive alcohol-related convictions and/or license suspensions. However, the percentage of underage offenders with higher BACs receiving DUI convictions declined as some of these offenders received the lesser ZT disposition. After the ZT law, underage offenders with BACs of 0.10 g/dL or higher were more likely to recidivate than those with lower BACs, but appreciable proportions of drivers were re-arrested for another alcohol offense, whatever the BAC and however they were penalized. CONCLUSIONS: Implementation of Washington's law indicates that a ZT law can increase the likelihood that an underage person will be sanctioned for drinking and driving. However, recidivism remains an issue as more than one in four underage drivers arrested with low BACs subsequently were re-arrested. 相似文献
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Objective
To examine parental decisions about vehicles driven by teenagers and parental knowledge of vehicle safety.Methods
About 300 parents were interviewed during spring 2006 in Minnesota, North Carolina, and Rhode Island while teenagers took their first on-road driving tests.Results
Fewer than half of parents surveyed said teenagers would be the primary drivers of the chosen vehicles. Parents most often cited safety, existing family vehicle, and reliability when explaining the choices for their teenagers’ vehicles. About half of the vehicles intended for teenagers were small/mini/sports cars, pickups, or SUVs — vehicles considered less safe for teenagers than midsize/large cars or minivans. A large majority of vehicles were 2001 models or earlier. Vehicles purchased in anticipation of adding a new driver to the family were more likely to be the sizes/types considered less safe than vehicles already owned. Few parents insisted on side airbags or electronic stability control, despite strong evidence of their safety benefits. Even when asked to identify ideal vehicles for their teenagers to drive, about half of parents identified less safe vehicle sizes/types. Most parents knew that midsize/large vehicles are safer than small vehicles, and at least half of parents said SUVs and pickups are not safe for teenage drivers, citing instability.Conclusions
The majority of parents understood some of the important criteria for choosing safe vehicles for their teenagers. However, parents actually selected many vehicles for teenagers that provide inferior crash protection.Impact on industry
Vehicle safety varies substantially by vehicle size, type, and safety features. Many teenagers are driving inferior vehicles in terms of crashworthiness and crash avoidance. 相似文献8.
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To ensure science better informs the decision-making process, researchers and policy/program managers need to understand and respect each other's way of working, culture and operational timelines. However, there is little practical guidance on how this should be done and even less documented experience with specific mechanisms that better link these two groups. The published literature on information transfer has largely emphasized the dissemination of standard packages of information to ill-defined constituencies whose needs for scientific information are not well understood. Environment Canada's National Water Research Institute, on behalf of the Canadian Council of Ministers of the Environment, led a series of “Linking Water Science to Policy Workshops” as one such mechanism by which recent science could be delivered to practitioners, and practitioners could identify their research needs to scientists and research managers. There is a pressing need to explore and share experiences using creative mechanisms for sustained dialogue and networking between scientists and policy and program managers. The lessons learned from the workshop series and the need for science to continually inform the decision-making process has particular relevance for Canada's Ecosystem Initiatives given their integrated, place-based focus on long-term restoration and protection, and the challenge of continually changing ecosystems.The Canadian Crown reserves the right to retain a non-exclusive, royalty free licence in and to any copyright. 相似文献