Effect of gasoline formulation on the formation of photosmog: a box model study

Based on exhaust gas analyses from the combustion of five different types of gasoline in a passenger car operated on a chassis dynamometer, box model simulations of the irradiation of exhaust/NOx/air mixtures using an established chemical mechanism for a standardized photosmog scenario were performed. The fuel matrix used covered wide fractional ranges for paraffinic, olefinic, and aromatic hydrocarbons. Two fuels also contained methyl tertiary butyl ether (MTBE). The different O3 profiles calculated for each run were compared and interpreted. The O3 levels obtained were strongly influenced by the exhaust gas concentrations of aromatic and olefinic hydrocarbons. The higher exhaust content of these compounds caused higher O3 production in the smog system investigated. The conclusion of the present study is that the composition of gasoline cannot be taken directly for the estimation of the emissions' O3 creation potential from its combustion. Variation of the dilution in the different calculations showed evidence for an additional influence of transport effects. Accordingly, further detailed exhaust gas analyses followed by more complex modeling studies are necessary for a proper characterization of the relationship between fuel blend and gasoline combustion products.     

Biological dehalogenation and halogenation reactions

A large number of halogenated compounds is produced by chemical synthesis. Some of these compounds are very toxic and cause enormous problems to human health and to the environment. Investigations on the degradation of halocompounds by microorganisms have led to the detection of various dehalogenating enzymes catalyzing the removal of halogen atoms under aerobic and anaerobic conditions involving different mechanisms. On the other hand, more than 3500 halocompounds are known to be produced biologically, some of them in great amounts. Until 1997, only haloperoxidases were thought to be responsible for incorporation of halogen atoms into organic compounds. However, recent investigations into the biosynthesis of halogenated metabolites by bacteria have shown that a novel type of halogenating enzymes, FADH(2)-dependent halogenases, are involved in biosyntheses of halogenated metabolites. In every gene cluster coding for the biosynthesis of a halogenated metabolite, isolated so far, one or several genes for FADH(2)-dependent halogenases have been identified.     

Deposition, Verteilung sowie Bedeutung für den Menschen und sein Nahrungsnetz

Since the introduction of automotive exhaust catalysts in 1984, an intensive discussion started about the emission of platinum group metals and their effect on mankind and the environment. Several platinum compounds are known to be potent sensitizers, even at very small doses. In spite of both the scientific and public interest in this important field, the collection and coordination of scientific research and its conclusions continues to be a lacking. The present results from analytical chemistry, ecology, toxicology and occupational medicine are summarized here. This state of the art indicates the great need for further investigations concerning especially the assessment of emission sources and bioavailability studies for platinum as well as palladium and rhodium.     

Economists' opinions on environmental policy instruments: Analysis of a survey

Incentive instruments (effluent charges) are theoretically expected to be preferred to direct regulations (individual emission ceilings) by university-employed, theoretically inclined politically right-wing, professional economists living in a market-oriented country, ceteris paribus. Public sector employed, politically left-wing, professional economists living in a country with a long tradition of government involvement prefer the regulatory approach, ceteris paribus. These theoretical hypotheses tend to be supported by a bivariate probit analysis based on a survey of more than 1400 economists in five countries.     

渔民的利益和合作:瑞典沿岸渔业共同管理的前提

本文在"共同管理"、"参与性管理"或"地方管理"等概念下用不同的理念探讨了渔民参与渔业管理的问题.瑞典渔业范围内的经验研究阐明了关于渔民参与渔业管理先决条件的新观点.在影响成败的重要因素中,我们这里着重探讨了其中两个:渔民利益的明确表达、组织及代表问题和通常参与资源管理合作的各群体即:渔民、政府管理人员以及研究人员之间的信任.本文所概述的研究论及了渔民在资源管理、地方渔业管理方面的利益以及渔民的参与.连接这三个主题的问题是:在渔业管理中如何更好地反映渔民的利益?利益与信任,即"软事实",对于渔业管理和参与的成败而言,可以犹如所有权、资源的数量和质量或资源的货币价值之类的"硬事实"一样的重要.