Seasonal variation of atmospheric dimethylsulfide at Amsterdam Island in the southern Indian Ocean     

B. C. Nguyen  N. Mihalopoulos  S. Belviso 《Journal of Atmospheric Chemistry》1990,11(1-2):123-141

Daily measurements of atmospheric concentrations of dimethylsulfide (DMS) were carried out for two years in a marine site at remote area: the Amsterdam Island (37°50S–77°31E) located in the southern Indian Ocean. DMS concentrations were also measured in seawater. A seasonal variation is observed for both DMS in the atmosphere and in the sea-surface. The monthly averages of DMS concentrations in the surface coastal seawater and in the atmosphere ranged, respectively, from 0.3 to 2.0 nmol l^-1 and from 1.4 to 11.3 nmol m^-3 (34 to 274 pptv), with the highest values in summer. The monthly variation of sea-to-air flux of DMS from the southern Indian Ocean ranges from 0.7 to 4.4 mol m^-2 d^-1. A factor of 2.3 is observed between summer and winter with mean DMS fluxes of 3.0 and 1.3 mol m^-2 d^-1, respectively.  相似文献   

基于遥感的城市热岛效应研究   总被引：15，自引：0，他引：15  

杨英宝  苏伟忠  江南 《地理与地理信息科学》2006,22(5):36-40

热红外遥感和气候学的交叉融合为城市热岛效应提供了新的研究方法。从城市热岛的空间分布与土地利用类型、植被覆盖关系、人为热关系以及城市热岛效应演变4方面分析热红外遥感在城市热岛研究中的应用现状;探讨目前存在的两个主要问题:城市地物真实温度难以获取,遥感和气候模型结合不密切;提出遥感和气候模型结合以及多平台、多尺度、多角度遥感的综合应用等是城市热岛效应遥感研究的发展趋势。  相似文献   

The ＂CO2-rich gas vents＂ of Mt. Amiata volcano （Tuscany, Central Italy）： Geochemistry,genetic mechanism and hazard evaluation     

Franco Tassi Orlando Vaselli Elena Lognoli Fabrizio Cuccoli Barbara Nisi Elena Ramaldi Sandro Moretti Luca Lombardi Bruno Capaccioni 《中国地球化学学报》2006,25(B08):70-71

Mt. Amiata （Southern Tuscany, Central Italy） is an extinct Quaternary volcano located in an area still marked by high heat-flow that is caused by deep seated （6-10 km） hot masses related to Pliocene magmatic activity. The anomalous geothermal gradient gives rise, within the Mesozoic limestone formation （Tuscan series）, to geothermal systems that fed the Ca-SO4 thermal springs characterizing this area. Besides of thermal fluids, several cold, dry CO2-rich gas emissions seep out on the NE flank of the volcano. These gas vents mostly consist of large sub-circular craters at variable depth and diameter （5-15 m and 10-50 m, respectively）, and represent a serious hazard for the local population, as testified by the several asphyxia casualties that have been repeatedly occurred within these morphological depressions. In this work, the chemical and isotopic compositions of the Mt. Amiata ＂CO2-rich gas vents＂ and the estimation of both the CO2 flux from the soil and the CO2 distribution in air of their surroundings, has been carried out in order to： （1） assess the origin of gases, （2） recognize the mechanism of formation for these gas emissions and their relationship with local tectonics, and （3） to evaluate the CO2 hazard in the high flux emanations. The chemical composition of the gases is largely dominated by CO2 （up to 98 % by vol） and shows relatively high concentrations of N2, CH4 and H2S （up to 1.1%, 0.9% and 3.9 % by vol, respectively）. These features, coupled with the carbon and nitrogen isotopic signatures, suggest that the origin of the main gas compounds may be related to the contribution of deep （i.e., thermometamorphic processes on carbonate formations for CO2） and shallow （i.e. thermal decomposition of organic material for CH4, N2 and H2S） sources.  相似文献   

Total gaseous mercury emissions from mercury-enriched soil in Guizhou, China     

Xinbin FENG Shaofeng WANG Guangle QIU Yamin HOU Shunlin TANG 《中国地球化学学报》2006,25(B08):243-244

Guizhou is located in the Circum-Pacific Global Mercuriferous Belt, and mercury concentrations in soil in this area are enriched. In-situ total gaseous mercury （TGM） exchange fluxes between air and soil surface were intensively measured at four sampling sites in Guiyang from 21 May to 16 June, 2003, and five sites in the Lanmuchang mercury mining area in December 2002 and May 2003, respectively. The in-situ Hg flux measurement was conducted with a dynamic flux chamber （DFC） of quartz. Overall, net emissions were obtained from all sampling sites. Soil mercury concentration and solar radiation have been proved to be the two most important parameters to control mercury emissions from soil. Meanwhile, rain events can enhance mercury emission rate significantly.  相似文献   

Urban lightning climatology and GIS: An analytical framework from the case study of Atlanta, Georgia     

J. Anthony Stallins  Mace L. Bentley 《Applied geography (Sevenoaks, England)》2006,26(3-4):242-259

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Palaeovariations in the East-Asian Monsoon Regime Geochemically Recorded in Varved Sediments of Lake Sihailongwan (Northeast China, Jilin Province). Part 2: a 200-Year Record of Atmospheric Lead-210 Flux Variations and its Palaeoclimatic Implications     

Georg Schettler  Jens Mingram  Jörg F. W. Negendank  Liu Jiaqi 《Journal of Paleolimnology》2006,35(2):271-288

Palaeovariations of the atmospheric ²¹⁰Pb flux in Northeast China (Long Gang area, Jilin province), quantified by high resolution ²¹⁰Pb measurements on seasonally laminated sediments of Lake Sihailongwan are presented on decadal scale. The mean flux of unsupported ²¹⁰Pb between 1790 and 1970 for the centre of the lake basin is 517 Bq m⁻² yr⁻¹ with maximum deviations between −23% and +27% of this value. Flux rates above this average were found between 1783 and 1813, around 1836, and between 1860 and 1901. The mean ²¹⁰Pb^exc flux rates derived were clearly lower around 1821, 1908, 1930, and 1953. The ²¹⁰Pb^exc flux reached its minimum of 344 Bq m⁻² yr⁻¹ during the period 1977–1982. The atmospheric flux of unsupported ²¹⁰Pb is correlated with the precipitation frequency during the summer monsoon and shows coinciding variability with geochemical proxies that document the groundwater inflow into the lake. Al₂O₃-rich dust of remote provenance scavenged by wet-deposition in the rainy season is the major carrier of the atmospheric ²¹⁰Pb^exc flux.  相似文献   

Geothermal evidence for fluid flow through the gas hydrate stability field off Central Chile—transient flow related to large subduction zone earthquakes?     

Ingo Grevemeyer  Norbert Kaul  Juan L. Diaz-Naveas 《Geophysical Journal International》2006,166(1):461-468

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Palaeovariations in the East-Asian Monsoon Regime Geochemically Recorded in Varved Sediments of Lake Sihailongwan (Northeast China, Jilin Province). Part 1: Hydrological Conditions and Dust Flux   总被引：2，自引：0，他引：2  

Georg Schettler  Qiang Liu  Jens Mingram  Jörg F. W. Negendank 《Journal of Paleolimnology》2006,35(2):239-270

The varved sediments of the dimictic Lake Sihailongwan (Long Gang mountain area, Jilin Province, Northeast China) represent a palaeoclimatic archive which documents the local precipitation frequency during the summer monsoon, and variations in the aeolian flux of dust with their remote sources in the arid and semi-arid regions of inner Asia. Based on a detailed discussion of sediment genesis in Lake SHL, dust flux rates and palaeohydrological conditions were reconstructed on a decadal scale over the past 220 years. The aeolian influx by dry and wet deposition was quantified and characterised in its chemical composition. Photosynthetic production in the lake is positively correlated with the inflow of nutrient-rich groundwater. The groundwater discharge largely reflects the strength of the summer monsoon. Net accumulation rates for biogenic silica were determined for annually laminated sediments from the centre of the U-shaped lake basin based on sediment data. In a Si-balance model of the modern lake, the depositional flux of biogenic silica could be independently quantified on the base of hydrochemical monitoring data. Comparison of the both estimates allowed to asses the focussing of the particle flux in the lake. Though water retention in Lake SHL is rather high (ca. 30 years), changes in the hydrological conditions are sensitively recorded in the sediments because (i) nutrient-rich groundwater discharges into the productive zone of the lake, (ii) a substantial proportion of the total dissolved Si-inventory of the mixed lake (ca. 30%) is annually consumed by diatom growth, and (3) sediment accumulation is substantially focussed towards the flat bottom of the lake basin. The bulk siliciclastic sediment fraction (ca. 75 wt.%) largely originates from influx of dust of remote provenance. In sediment thin-sections, the dry-deposited dust fraction is microscopically identifiable as seasonal silt layer. Aeolian input by wet-deposition shows a distinctly higher variability than the influx of dust by dry-deposition. As diatom production, wet-deposition of dust is positively correlated with the rainfall during the summer monsoon. The inferred positive correlation between rainfall and dust flux during the summer monsoon implies that dust deposition is determined by the out-wash efficiency of mineral particles for a permanent high atmospheric dust concentration over Northeast China in the last 220 years.  相似文献   

胞外聚合物对膜生物反应器运行性能的影响   总被引：3，自引：1，他引：3  

张凤君  王顺义  邓锡斌  赵芝清  沙娜  王鹤 《吉林大学学报(地球科学版)》2006,(Z1)

膜生物反应器处理污水过程中,依据胞外聚合物(EPS)、蛋白质、多糖、粘度等参数随时间的变化趋势以及对膜通量的影响,求出上述参数及蛋白质/多糖的比值与膜通量间的相关系数分别为0.28、0.57、0.38、0.14、0.70。结果表明:蛋白质/多糖的比值与膜通量的衰减速度两者相关系数最大。  相似文献   

Application of membrane technology for water treatment： Ultrasound-associated cleaning of fouled microfiltration membranes     

Rui CHEN Xiaoli WANG Yonggang ZHANG Xueqi FU 《中国地球化学学报》2006,25(B08):128-129

The use of membranes is a widely employed, versatile, and effective separation process. One of the limiting aspects in applying microfiltration （MF） for wastewater treatment is that of problems with membrane fouling and consequent flux reduction. Membrane fouling occurs by the irreversible deposition of retained particles, colloids, macromolecules, salts, etc. at the membrane surface and/or inside the membrane. The predominant fouling mechanisms observed with MF membranes are classified as three categories： the build-up of a cake layer on the membrane surface, blocking of membrane pores, and adsorption of fouling material on the membrane surface or in the pore walls. Although many techniques have been developed to overcome fouling, studies on membrane cleaning still seem to be insufficient for practical membrane filtration systems. Current membrane cleaning technologies include hydraulic, chemical, and mechanical methods. Ultrasound （US） has been widely used as a method of cleaning materials because of the cavitation phenomenon. In this study, US cleaning technique was applied to removing the fouling of polyvinglidenefluoride （PVDF） MF membrane, which was used to treat yeast cell and isolated soybean protein （ISP） solution, respectively. The US employed 40 kHz frequency and the output power of 1.43-2.85 W/cm^2. The evolution of the cleaning effect is followed by the measurements of the flux recovery rate （FRstat） and the cleaning time cycle. Results showed that the membrane property, which was fouled by yeast cell solution, could be recovered by water cleaning with US irradiation. And the cleaning time with the same FRstat decreased with the increase of US intensity.  相似文献