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201.
The energy balance over land and oceans: an assessment based on direct observations and CMIP5 climate models 总被引:2,自引:0,他引:2
202.
203.
Experimental analysis of arsenic precipitation during microbial sulfate and iron reduction in model aquifer sediment reactors 总被引:4,自引:0,他引:4
Matthew F. Kirk Eric E. Roden Adrian J. Brealey 《Geochimica et cosmochimica acta》2010,74(9):2538-6788
Microbial SO42− reduction limits accumulation of aqueous As in reducing aquifers where the sulfide that is produced forms minerals that sequester As. We examined the potential for As partitioning into As- and Fe-sulfide minerals in anaerobic, semi-continuous flow bioreactors inoculated with 0.5% (g mL−1) fine-grained alluvial aquifer sediment. A fluid residence time of three weeks was maintained over a ca. 300-d incubation period by replacing one-third of the aqueous phase volume of the reactors with fresh medium every seven days. The medium had a composition comparable to natural As-contaminated groundwater with slightly basic pH (7.3) and 7.5 μM aqueous As(V) and also contained 0.8 mM acetate to stimulate microbial activity. Medium was delivered to a reactor system with and without 10 mmol L−1 synthetic goethite (α-FeOOH). In both reactors, influent As(V) was almost completely reduced to As(III). Pure As-sulfide minerals did not form in the Fe-limited reactor. Realgar (As4S4) and As2S3(am) were undersaturated throughout the experiment. Orpiment (As2S3) was saturated while sulfide content was low (∼50 to 150 μM), but precipitation was likely limited by slow kinetics. Reaction-path modeling suggests that, even if these minerals had formed, the dissolved As content of the reactor would have remained at hazardous levels. Mackinawite (Fe1 + xS; x ? 0.07) formed readily in the Fe-bearing reactor and held dissolved sulfide at levels below saturation for orpiment and realgar. The mackinawite sequestered little As (<0.1 wt.%), however, and aqueous As accumulated to levels above the influent concentration as microbial Fe(III) reduction consumed goethite and mobilized adsorbed As. A relatively small amount of pyrite (FeS2) and greigite (Fe3S4) formed in the Fe-bearing reactor when we injected a polysulfide solution (Na2S4) to a final concentration of 0.5 mM after 216, 230, 279, and 286 days. The pyrite, and to a lesser extent the greigite, that formed did sequester As from solution, containing 0.84 and 0.23 wt.% As on average, respectively. Our results suggest that As precipitation during Fe-sulfide formation in nature occurs mainly in conjunction with pyrite formation. Our findings imply that the effectiveness of stimulating microbial SO42− reduction to remediate As contamination may be limited by the rate and extent of pyrite formation and the solubility of As-sulfides. 相似文献
204.
Natural disasters as the end of the insurance industry? Scalar competitive strategies, Alternative Risk Transfers, and the economic crisis 总被引:1,自引:0,他引:1
The aftermath of Hurricane Katrina has piqued interest in the insurance industry, and this scrutiny has led to assumptions that the industry has become unstable and unprofitable with the increased incidence of disasters in highly-insured regions of the world. This paper challenges that assumption by arguing that the insurance industry has responded by spreading risk through scaled and networked recovery schemes. We found that because of competitive strategies of risk-spreading and displacement arrangements, the industry has actually profited as a whole. Regional insurance companies have always relied on the higher financial scales of the reinsurance industry in Munich, Zurich, and London. But with claims reaching into the billions of dollars, the reinsurance industry itself has raised premiums, spread risk farther afield, and jumped scale by spreading risk to futures markets called Alternative Risk Transfers (ARTs). However, the recession beginning in 2008 has called into question the viability of using futures markets as insurance. It is shown through a media analysis of four major business publications (The Economist, The New York Times, The Financial Times and The Wall Street Journal) how the industry responded to the costs of the 2004, 2005, and 2006 hurricane seasons. Because geography is rather new to this literature, this paper also offers a broad review of the insurance industry. 相似文献
205.
Eric BUFFETAUT 《地球学报》2010,31(Z1):7-9
The French pterosaur record extends from the Late Triassic to the end of the Cretaceous (Mazin et al., 2001 and references therein), with occurrences at various horizons of the Triassic, Jurassic and Creta-ceous, but the completeness and quality of the avail-able fossil material is highly variable. 相似文献
206.
Véronique Lavastre Corinne Le Gal La Salle Jean-Luc Michelot Sophie Giannesini Lucilla Benedetti Joël Lancelot Bernard Lavielle Marc Massault Bertrand Thomas Eric Gilabert Didier Bourlès Norbert Clauer Pierre Agrinier 《Applied Geochemistry》2010
Groundwaters from the Tithonian/Kimmeridgian, Oxfordian and Upper Dogger aquifers, within the eastern part of the Paris basin (France), were characterised using 3H, 14C and 36Cl, and noble gases tracers, to evaluate their residence times and determine their recharge period. This information is an important prerequisite to evaluating the confinement properties of the Callovo-Oxfordian clay formation sandwiched between the Oxfordian aquifer and the Dogger aquifer, currently being investigated by the French nuclear waste management agency (Andra) for radioactive waste disposal. Data presented in this paper are used to test 4 hypotheses. 相似文献
207.
208.
Dissolution rates of sediments obtained from the Oued Cherf reservoir were measured in closed-system batch reactors at 25 °C in fluids sampled concurrently from the same locations as the sediments. The BET surface areas of the sediments ranged from 16 to 45 m2/g and consisted primarily of quartz, calcite, and clay minerals. After a brief initial period, release rates of Si, Mg, Ca, Cl, SO4, and NO3 from these sediments are approximately linear with time over the course of the experiments, which lasted from 3 to 5 months. BET surface area normalized Si release rates ranged from 10–17.4 to 10–18.4 mol/cm2/s. These release rates match closely Si release rates from quartz and clay minerals determined from laboratory dissolution rates reported in the literature. This coherence suggests that laboratory measured silicate dissolution rates can be used with confidence to predict the dissolution behavior of sediments in natural surface waters. 相似文献
209.
Eric F. Lambin Sarah Ann Lise D’haen Ole Mertz Jonas Østergaard Nielsen Kjeld Rasmussen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2014,114(1):76-83
In an attempt to anticipate possible futures of drylands of West Africa in the face of rapid socio-economic and environmental changes, we developed four scenarios based on recent survey data, the literature and our knowledge of the region. The four scenarios are inspired by those developed by the Millennium Ecosystem Assessment: (1) ‘downward spiral’ characterized by rapid climate change, expansion of agriculture and chaotic urban growth; (2) ‘integrated economy’ with integrated land management, food production for local markets and rural–urban exchanges; (3) ‘open doors’ characterized by large-scale out-migrations, land grabbing by foreign companies and development aid and (4) ‘climate change mitigation’ with an increase in biofuel crops, land management for carbon capture and development of off-farm activities. We conclude that the Sahel region is most likely moving away from being a highly climate-dependent region based on agriculture towards a more open and diversified economy. West African countries have to find a balance between the new opportunities and risks created by economic globalization. 相似文献
210.
Marc Pons Peter A Johnson Martí Rosas Eric Jover 《International journal of geographical information science》2014,28(12):2474-2494
One main argument for modeling socio-ecological systems is to advance the understanding of dynamic correlations between various human and environmental factors, including impacts and responses to environmental change. We explore the shift in skier distribution among ski resorts taking into account the behavioral adaptation of individuals due to the impact of climate change on snow conditions. This analysis is performed at a regional scale by means of a coupled gravity and georeferenced agent-based model. Four different scenarios are considered. Two scenarios assume an increase of winter mean temperature of +2°C and +4°C, respectively, taking into account only natural snow conditions. Two additional scenarios add the effect of snowmaking to enhance the natural snow depth and extend the skiing season in the +2°C and +4°C base scenarios. Results show differing vulnerability levels, allowing the classification of ski resorts into three distinct groups: (1) highly vulnerable ski resorts with a strong reduction in visitors attendance for all climate change scenarios, characterized by unfavorable geographical and attractiveness conditions, making it difficult to ensure snow availability in the future; (2) low vulnerability ski resorts, with moderate reduction in season length during a high climate change scenario but no reduction (or even an increase) in a low one, characterized by ski resorts with a medium capacity and attractiveness to ensure enough snow conditions and capture skiers from other ski resorts; and (3) resilient ski resorts, with good conditions to ensure future snow-reliable seasons and outstanding attractiveness, allowing them to offer longer ski seasons than their competitors and potentially attracting skiers from other closed or marginal resorts. Ski resorts included in this last group increase their skier attendance in all climate change scenarios. Although similar studies in the literature foretell a significant reduction of the ski market in the near future, another probable effect outlined in this study is a redefinition of this market due to a redistribution of skiers, from vulnerable ski resorts to more resilient ones. 相似文献