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81.
Minerals on earth whose crystalline order has been reduced by radioactive decay of contained atoms are termed “metamict.” They are rare and few because in most crystalline solids, atoms and vacancies are relatively mobile at terrestrial temperatures, and radiation damage tends to be self-annealing. This is not the case in the extreme cold of deep space. Below roughly 100 K, reduced vacancy mobility allows cosmic ray and solar wind induced lattice defects to endure and accumulate for eons, reaching energy densities of up to MJ kg−1 in some materials. We examine the possible effects of the release of energy stored in cold deep-space materials when solid-state defects recombine upon warming due to impacts, gravitational infall, or perihelion. Dimensional analysis suggests energetic defect recombination in radiation-damaged “xenomict” solids in comets, and planetesimals may, in some circumstances, raise internal temperatures enough to melt ice and volatilize frozen gases. We speculate that this may account for some cometary outbursts and Deep Impact experiment results. Calorimetric experiments on appropriately irradiated natural and synthetic materials are needed to further quantify these mechanisms.  相似文献   
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The in situ degradation of chlorinated ethenes was assessed in an anaerobic aquifer using stable isotope fractionation approaches, microcosm studies and taxon specific detection of specific dehalogenating groups of bacteria. The aquifer in the Bitterfeld/Wolfen region in Germany contained all chlorinated ethenes, benzene and toluene as contaminants. The concentrations and isotope composition of the chlorinated ethenes indicated biodegradation of the contaminants. Microcosm studies confirmed the presence of in situ microbial communities capable of the complete dechlorination of tetrachloroethene. Taxon specific investigation of the microbial communities indicated the presence of various potential dechlorinating organisms including Dehalococcoides, Desulfuromonas, Desulfitobacterium and Dehalobacter. The integrated approach, using metabolite spectra, molecular marker analysis and isotope studies, provided several lines of evidence for natural attenuation of the chlorinated ethenes.  相似文献   
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A radiative transfer model and photochemical box model are used to examine the effects of clouds and aerosols on actinic flux and photolysis rates, and the impacts of changes in photolysis rates on ozone production and destruction rates in a polluted urban environment like Houston, Texas. During the TexAQS-II Radical and Aerosol Measurement Project the combined cloud and aerosol effects reduced j(NO2) photolysis frequencies by nominally 17%, while aerosols reduced j(NO2) by 3% on six clear sky days. Reductions in actinic flux due to attenuation by clouds and aerosols correspond to reduced net ozone formation rates with a nearly one-to-one relationship. The overall reduction in the net ozone production rate due to reductions in photolysis rates by clouds and aerosols was approximately 8 ppbv h?1.  相似文献   
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While process safety regulations and standards have been in place in western countries for more than two decades, China has only recently started to officially embrace these issues with the adoption of its Process Safety Management (PSM) regulation AQ/T 3034-2010 (SAWS, 2010). However, compliance with this regulatory framework requires substantial resources and may therefore appear too complex to be efficiently implemented by small and medium sized enterprises (SMEs) in the chemical sector. This is of particular relevance as about 99% of chemical companies in China are SMEs, accounting for more than 80% of all chemical accidents. To address this issue, additional local regulations and planning activities related to process safety have been implemented in China, including the establishment of hundreds of chemical industry parks. Some of the process safety problems faced by chemical industry parks are identified and discussed in this paper. To help solve these problems, UNEP's “Responsible Production approach for Chemical Hazards Management along the Value-Chain” is introduced in this paper and suggested as a simplified PSM approach targeted specifically at SMEs which, regardless of handling hazardous chemicals in their daily operations, may not have the knowledge or capacity to efficiently implement PSM and may not fall in the scope of the PSM regulation AQ/T 3034-2010. By introducing PSM to SMEs in a more manageable way, relevant steps can be progressively implemented by companies towards full compliance with the current regulatory framework, contributing to increased safety in chemical industry parks in China.  相似文献   
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Towards a Formal Framework of Vulnerability to Climate Change   总被引:7,自引:0,他引:7  
There is confusion regarding the notion of “vulnerability” in the climate change scientific community. Recent research has identified a need for formalisation, which would support accurate communication and the elimination of misunderstandings that result from the use of ambiguous terminology. Moreover, a formal framework of vulnerability is a prerequisite for computational approaches to its assessment. This paper presents an attempt at developing such a formal framework. We see vulnerability as a relative concept in the sense that accurate statements about vulnerability are possible only if one clearly specifies (1) the entity that is vulnerable, (2) the stimulus to which it is vulnerable and (3) the preference criteria to evaluate the outcome of the interaction between the entity and the stimulus. We relate the resulting framework to the Intergovernmental Panel on Climate Change conceptualisation of vulnerability and two recent vulnerability studies. This paper is dedicated to the memory of Gerhard Petschel-Held, whose pioneering work on syndromes of global change has been a source of inspiration for us and for others across various schools of thought on vulnerability.  相似文献   
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In a 50- to 70-year-old mixed stand of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.) in Germany, tree cohorts have been exposed to double ambient ozone (2×O3) from 2000 through 2007 and can be compared with trees in the same stand under the ambient ozone regime (1×O3). Annual diameter growth, allocation pattern, stem form, and stem volume were quantified at the individual tree and stand level. Ozone fumigation induced a shift in the resource allocation into height growth at the expense of diameter growth. This change in allometry leads to rather cone-shaped stem forms and reduced stem stability in the case of spruce, and even neiloidal stem shapes in the case of beech. Neglect of such ozone-induced changes in stem shape may lead to a flawed estimation of volume growth. On the stand level, 2×O3 caused, on average, a decrease of 10.2 m3 ha−1 yr−1 in European beech.  相似文献   
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