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1.
During the first 50 days of a long-term period of incubation of lake sediments with inorganic mercury (Hg(2+)), low concentrations of methylinercury were observed to build up. Upon continued incubation there was a rapid decrease in amount of methylmercury in the system and a concomitant evolution of volatile inorganic mercury (Hg(0)). Transfer of the mixed culture to growth media containing methylmercury resulted in the degradation of methylmercury and the volatilization of Hg(0). Four bacterial isolates were obtained from the mixed culture which, in pure culture, rapidly degraded methylmercury to methane and Hg(0). The presence of methane in head space gases was confirmed by flameionization gas chromatography, and the presence of Hg(0) in head space gases was confirmed by mass spectrometry. 相似文献
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甲烷泄露背景下碳酸盐岩的形成及其地球化学特征 总被引：1，自引：0，他引：1
甲烷泄露背景下形成的碳酸盐岩,特征上明显区别于正常海相碳酸盐岩。冷泉碳酸盐岩、震旦纪的盖帽碳酸盐岩均被认为是甲烷泄露背景下的产物,其碳同位素值都出现强烈的负漂移。研究认为,成岩中的碳源于天然气水合物分解产生的甲烷。冷泉碳酸盐岩与盖帽碳酸盐岩在结构、构造及矿物组分上很相似。对甲烷泄露背景下的碳酸盐岩的外观构造、岩石矿物特征、地球化学特征进行了分析,并阐述了这类碳酸盐岩的特征与其形成背景、过程、条件之间的关系。 相似文献
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Massive blocks of freshwater ice and frozen sediments protrude from shallow, saline lakes in the Andes of southwestern Bolivia and northeastern Chile. These ice islands range up to 1.5 kilometers long, stand up to 7 meters above the water surface, and may extend out tens of meters and more beneath the unfrozen lake sediments. The upper surfaces of the islands are covered with dry white sediments, mostly aragonite or calcite. The ice blocks may have formed by freezing of the fresh pore water of lake sediments during the "little ice age." The largest blocks are melting rapidly because of possibly recent increases in geothermal heat flux through the lake bottom and undercutting by warm saline lake water during the summer. 相似文献
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Jouzel J Petit JR Souchez R Barkov NI Lipenkov VY Raynaud D Stievenard M Vassiliev NI Verbeke V Vimeux F 《Science (New York, N.Y.)》1999,286(5447):2138-2141
Isotope studies show that the Vostok ice core consists of ice refrozen from Lake Vostok water, from 3539 meters below the surface of the Antarctic ice sheet to its bottom at about 3750 meters. Additional evidence comes from the total gas content, crystal size, and electrical conductivity of the ice. The Vostok site is a likely place for water freezing at the lake-ice interface, because this interface occurs at a higher level here than anywhere else above the lake. Isotopic data suggest that subglacial Lake Vostok is an open system with an efficient circulation of water that was formed during periods that were slightly warmer than those of the past 420,000 years. Lake ice recovered by deep drilling is of interest for preliminary investigations of lake chemistry and bedrock properties and for the search for indigenous lake microorganisms. This latter aspect is of potential importance for the exploration of icy planets and moons. 相似文献
5.
Beauchamp B Harrison JC Nassichuk WW Krouse HR Eliuk LS 《Science (New York, N.Y.)》1989,244(4900):53-56
Lower Cretaceous cold-seep fossil assemblages have been found in the Canadian Arctic Archipelago. Serpulid worm tubes and bivalves are most abundant in these communities; in contrast, fossils are scarce in the surrounding strata. The fossils are contained in an isotopically light (delta(13)C = -25 to -50 per mil) carbonate rock groundmass that is interpreted to have formed from bacterial oxidation of methane. The rocks were deposited at intermediate depth (相似文献
6.
以1990、1998和2007年Landsat-TM影像为数据源,利用RS和GIS技术,采用最大似然法、土壤动态度和转移矩阵3种研究方法对艾比湖流域土壤盐渍地现状、程度和发展趋势进行定量分析。结果表明:在1990～2007年,艾比湖土壤盐渍化程度日益加剧。其中,重度、中度、轻度盐渍地分别增加了1.40、89.60、476.16 km2,而非盐渍地减少了567.16 km2;重度盐渍地集中分布在阿拉山口附近及湖滨区上部,中度盐渍地主要位于湖滨区中部和接近外围下风区的沙漠地带,而轻度盐渍地广泛分布于艾比湖外围和绿洲的交汇处;面积增加最少的重度盐渍地主要由中度盐渍地部分转化,增加次之的中度盐渍地主要由轻度盐渍地部分转化,增加最多的轻度盐渍地主要由非盐渍地部分转化,而非盐渍地逐年减少。 相似文献
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Bradbury JP Leyden B Salgado-Labouriau M Lewis WM Schubert C Binford MW Frey DG Whitehead DR Weibezahn FH 《Science (New York, N.Y.)》1981,214(4527):1299-1305
Chemical, paleontological, and mineralogical analyses of a 7.5-meter core from the middle of Lake Valencia, Venezuela, have provided information on the paleoclimatic history of this low-elevation, low-latitude site for the last 13,000 years. The data show that dry climates existed in this region from 13,000 years before present (B.P.) until about 10,000 years B.P. The Lake Valencia Basin was occupied by intermittent saline marshes at that time. About 10,000 years B.P., a permanent lake of fluctuating salinity formed and arboreal plant communities replaced the earlier dominant xeric herbaceous vegetation and marsh plants. By 8500 years B.P., Lake Valencia reached moderate to low salinities and discharged water; the modern vegetation became established at that time. After 8500 years B.P., the lake twice ceased discharging as a result of reduced watershed moisture. The second of these drying episodes is still in progress and has been aggravated by human activities in the watershed. 相似文献
8.
A subsurface Apollo 16 soil, 61221, is much richer in volatile compounds than soils from any other locations or sites as shown by thermal analysis-gas release measurements. A weight loss of 0.03 percent during the interval 175 degrees to 350 degrees C was associated with the release of water, carbon dioxide, methane, hydrogen cyanide, hydrogen, and minor amounts of hydrocarbons and other species. These volatile components may have been brought to this site by a comet, which may have formed North Ray crater. 相似文献
9.
Waite JH Young DT Cravens TE Coates AJ Crary FJ Magee B Westlake J 《Science (New York, N.Y.)》2007,316(5826):870-875
Titan's lower atmosphere has long been known to harbor organic aerosols (tholins) presumed to have been formed from simple molecules, such as methane and nitrogen (CH4 and N2). Up to now, it has been assumed that tholins were formed at altitudes of several hundred kilometers by processes as yet unobserved. Using measurements from a combination of mass/charge and energy/charge spectrometers on the Cassini spacecraft, we have obtained evidence for tholin formation at high altitudes (approximately 1000 kilometers) in Titan's atmosphere. The observed chemical mix strongly implies a series of chemical reactions and physical processes that lead from simple molecules (CH4 and N2) to larger, more complex molecules (80 to 350 daltons) to negatively charged massive molecules (approximately 8000 daltons), which we identify as tholins. That the process involves massive negatively charged molecules and aerosols is completely unexpected. 相似文献
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人为补水对扎龙芦苇湿地甲烷排放的影响 总被引：1，自引：0，他引：1
为研究人为补水对芦苇湿地甲烷排放的影响,分别在补水前5 d、补水后10、20和30 d测定了扎龙芦苇湿地淹水区RH和未淹水区RA的甲烷排放通量。结果表明,补水后30 d RH水深由20 cm上升至120 cm,甲烷排放通量由3.13 mg/(m2·h)增至9.60 mg/(m2·h),是对照组CH的1.62倍;RA在补水后30 d水深达到10 cm,甲烷排放通量由2.80 mg/(m2·h)上升至18.96 mg/(m2·h),为对照组CA的5.31倍。补水期间,RH的水深增加刺激了芦苇生长,从而为甲烷产生提供了更多底物,并增强了厌氧条件,导致甲烷排放增大;RA淹水后,大量有机质分解为甲烷产生提供了碳源以及通气状况的改变是促进其甲烷大量排放的原因。研究表明人为补水过程促进了淹水区和非淹水区的甲烷排放,建议在评估湿地甲烷排放时应考虑人为补水因素。 相似文献
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反刍家畜胃肠道甲烷排放是重要的温室气体排放源,减少反刍家畜胃肠道甲烷排放有助于缓解全球温室效应和提高家畜饲养效率。本论文从中国反刍家畜胃肠道甲烷排放现状、瘤胃甲烷生成机制、甲烷生成的日粮营养影响因子和甲烷减排策略与潜力4个方面系统综述反刍家畜胃肠道甲烷排放的研究进展。目前,中国反刍家畜甲烷总排放量超过10 Tg,占全球胃肠道甲烷排放的比例超过15%。反刍家畜胃肠道甲烷排放主要来自瘤胃和后肠道,其中瘤胃甲烷占胃肠道甲烷生成总量的80%以上。二氧化碳还原路径利用瘤胃内的氢和二氧化碳合成甲烷,是瘤胃内生成甲烷的主要路径。瘤胃内的氢还可被相关微生物利用,合成挥发性脂肪酸和微生物蛋白等代谢产物,进而被机体利用。减少反刍家畜胃肠道甲烷排放的关键在于促进瘤胃内氢的利用,以及阻断瘤胃内的氢被甲烷菌利用合成甲烷。甲烷减排的日粮营养调控策略包括优化日粮组成、改善饲料品质、提高瘤胃流通速率、添加氢池和甲烷抑制剂等。大多数营养调控策略的甲烷减排效果小于40%,最新研制的3-NOP抑制剂的甲烷减排效果最高可达80%。但是,一些减排策略的产业化应用还受添加剂残留、抗生素禁用、食品安全、产品价格和消费者喜好等因素影响。牧场管理和遗传选育也是降低甲烷排放量的重要手段,过去100年来已实现每千克标准乳的甲烷排放量减排效果为57%。未来反刍家畜胃肠道甲烷研究将主要集中在低排放品种的遗传选育、不同营养调控策略间的组合效果、甲烷减排的经济效益和可持续性、家畜生长性能与健康、食品安全、消费者喜好等方面。 相似文献
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Studies on Technique of Reducing Methane Emission in a Rice-Duck Ecological System and the Evaluation of Its Economic Significance 总被引：7，自引：0，他引：7
XIANG Ping-an HUANG Huang HUANG Mei GAN De-xin ZHOU Yan FU Zhi-qiang 《中国农业科学(英文版)》2006,5(10):758-766
The rice-duck ecological system is one of the major practices of the traditional Chinese agriculture. A study on the effect of reducing methane emission using this practice provided theoretical and practical basis for further development and utilization of this classical agricultural technique. The effect of reducing methane emission and the economic benefits of rice-duck ecological system were studied by carrying out a field experiment and by using economic methodology. The daily variation of CH4 emission in late rice paddy field was basically consistent with the daily variation of atmospheric temperature. The highest emission occurred at the full tillering stage of late rice with a rate of 24.1 or 32.2 or 40.5 mg m^-2 h^-1 in no-tillage area with duck and no-tillage area without duck and conventional-tillage area without duck, respectively. The inhibition of methane emission was apparently effective in the rice-duck ecological system during the initial tillering stage and the full tillering stage. Compared to the no-tillage area without duck, methane emission decreased by 2.333 g m^-2. Compared to the conventional-tillage area without duck, methane emission decreased by 4.723 g m^-2. During the production period of late rice, the amount of methane emission in no-tillage area with duck was 3.373 g m^-2 lesser than that of no-tillage area without duck, and 5.59 g m^-2 less than that of conventional-tillage without duck area. The economic significance was analyzed. Farmers adopting the rice-duck ecological system obtained 2 166 and 4 207 RMB yuan ha^-1 more income than those who adopted a no-tillage without duck technique or conventional-tillage without duck technique, respectively. In addition to the reduction of the environmental pollution by methane emission, the farmers who adopted the rice-duck ecological system achieved economic benefits of 5 000 RMB yuan ha^-1, which was 2 206 and 4 274 RMB yuan ha^-1 more than those who adopted a no-tillage without duck technique and a conventional-tillage without duck technique, respectively. The rice-duck ecological system not only increased the economic benefits for farmers, but also reduced methane emission in rice paddy field. A sustainable agricultural production mode was formed. 相似文献
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Pliocene and Pleistocene fossil localities near the western shoreline of Lake Turkana, ranging in age between 1 million and 3.5 million years in age, have produced important new hominid specimens including most of a Homo erectus skeleton and a relatively complete early robust australopithecine cranium. The lacustrine, fluviatile, and terrestrial strata are designated the Nachukui Formation, which is subdivided into eight members. The distribution of sedimentary facies within the Nachukui Formation suggests that, as today, the Labur and Murua Rith ranges formed the western margin of the basin and were drained by eastward-flowing rivers that fed into the forerunner of the present lake or a major river system. There is also stratigraphic evidence for tectonic movement during the deposition of these sediments. Twenty-three of the tuffs observed in the succession occur also in the Koobi Fora Formation east of the lake and in the Shungura Formation of the lower Omo Valley and permit precise correlation among these three localities. Fortyseven fossiliferous sites from West Turkana have yielded more than 1000 specimens of 93 mammalian species. The mammalian fossils represent nine sequential assemblages that augment information about faunal and environmental change from elsewhere in the basin. 相似文献
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Acetic acid is an important petrochemical that is currently produced from methane (or coal) in a three-step process based on carbonylation of methanol. We report a direct, selective, oxidative condensation of two methane molecules to acetic acid at 180 degrees C in liquid sulfuric acid. Carbon-13 isotopic labeling studies show that both carbons of acetic acid originate from methane. The reaction is catalyzed by palladium, and the results are consistent with the reaction occurring by tandem catalysis, involving methane C-H activation to generate Pd-CH3 species, followed by efficient oxidative carbonylation with methanol, generated in situ from methane, to produce acetic acid. 相似文献
18.
试论吉兰泰盐湖的发育与资源保护问题 总被引：1，自引：0，他引：1
胡春元 《内蒙古林学院学报》1998,(2)
位于包头－吉兰泰断陷盆地西南部的吉兰泰盐湖,其发育过程大体经历了外泄湖、内陆湖与盐湖三个阶段。目前盐湖已发育为干盐湖,并有快速发展为沙下湖之趋势。湖盐开采中出现的晶间卤水水位下降、流沙入湖等问题既是盐湖演化的必然结果,又与开发中轻视资源保护有关。解决这些问题的办法是在顺应盐湖演化规律的基础上采取人工措施,延缓盐湖演化的速度,在盐湖演化为沙下湖之前完成全部采盐任务。 相似文献
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随着时代的发展,通过科技工作者的努力研究和农民的反复实践,逐渐形成了各种沼气生态农业模式,使沼气建设跳出了单纯围绕能源建设的小圈子,将农民生活、生产和生态农业紧密联系在一起,在促进农民脱贫致富、农业产业结构调整和农村经济的可持续发展等方面起着非常重要的作用。 相似文献
20.
内蒙古达里诺尔湖泊湿地动态的遥感监测 总被引：4，自引：0，他引：4
利用极轨气象卫星NOAA/AVHRR遥感监测资料,结合实地考察数据,绘制遥感影像图及植被指数图,统计了2000年至2005年,每年4月到9月达里诺尔湖的水域面积,分析了达里诺尔湖泊水体的年际变化,并结合1961年至2004年45年的气象数据,得出以下主要结论:(1)由于气候及人为因素,从2000年起至2003年达里诺尔湖泊的水域面积处于稳定波动状态,而2003年8月后湖泊面积减少,呈下降趋势。(2)在人为因素对环境的作用保持在1个较低水平时,研究区湖面变化与温度和降水的变化有较好的吻合关系,年均气温与湖面积之间存在负相关关系,降水量与湖泊面积之间基本呈正相关关系。(3)该地区气候的变化对湖区生态变化起着重要的作用,人类影响相对较弱,认为温度和降水是影响研究区湖泊面积和水位的主导因素。 相似文献