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61.
A new estimate of global methane flux from onshore and shallow submarine mud volcanoes to the atmosphere 总被引:3,自引:0,他引:3
A new estimate of global methane emission into the atmosphere from mud volcanoes (MVs) on land and shallow seafloor is presented. The estimate, considered a lower limit, is based on 1) new direct measurements of flux, including both venting of methane and diffuse microseepage around craters and vents, and 2) a classification of MV sizes in terms of area (km2) based on a compilation of data from 120 MVs. The methane flux to the atmosphere is conservatively estimated between 6 and 9 Mt y–1. This emission from MVs is 3–6% of the natural methane sources and is comparable with ocean and hydrate sources, officially considered in the atmospheric methane budget. The total geologic source, including MVs, seepage from seafloor, microseepage in hydrocarbon-prone areas and geothermal sources, would amount to 35–45 Mt y–1. The authors believe it is time to add this parameter in the Intergovernmental Panel on Climate Change official tables of atmospheric methane sources.GEM 相似文献
62.
北京地区大气主要温室气体的季节变化 总被引:7,自引:0,他引:7
摘 要:报道了北京主要温室气体浓度最新变化情况,采用1993—2002年北京主要温室气体周平均浓度的数据,用时间序列分解的方法对其季节变化进行了分析研究,并对造成北京主要温室气体季节变化的原因进行了初步探讨。分析发现北京大气CH4的季节变化范围在-49.2×10- 9~ 55.7×10- 9(V/V)之间,并呈现出双峰模态;北京大气CO2浓度的季节变化范围在-26.4×10- 6~ 34.0×10- 6(V/V)之间;北京大气 N 2 O浓度变化没有明显的季节变化特点。 相似文献
63.
Diffuse CO<Subscript>2</Subscript> degassing at Vesuvio,Italy 总被引:1,自引:0,他引:1
Francesco?FrondiniEmail author Giovanni?Chiodini Stefano?Caliro Carlo?Cardellini Domenico?Granieri Guido?Ventura 《Bulletin of Volcanology》2004,66(7):642-651
At Vesuvio, a significant fraction of the rising hydrothermal–volcanic fluids is subjected to a condensation and separation process producing a CO2–rich gas phase, mainly expulsed through soil diffuse degassing from well defined areas called diffuse degassing structures (DDS), and a liquid phase that flows towards the outer part of the volcanic cone. A large amount of thermal energy is associated with the steam condensation process and subsequent cooling of the liquid phase. The total amount of volcanic–hydrothermal CO2 discharged through diffuse degassing has been computed through a sequential Gaussian simulation (sGs) approach based on several hundred accumulation chamber measurements and, at the time of the survey, amounted to 151 t d–1. The steam associated with the CO2 output, computed assuming that the original H2O/CO2 ratio of hydrothermal fluids is preserved in fumarolic effluents, is 553 t d–1, and the energy produced by the steam condensation and cooling of the liquid phase is 1.47×1012 J d–1 (17 MW). The location of the CO2 and temperature anomalies show that most of the gas is discharged from the inner part of the crater and suggests that crater morphology and local stratigraphy exert strong control on CO2 degassing and subsurface steam condensation. The amounts of gas and energy released by Vesuvio are comparable to those released by other volcanic degassing areas of the world and their estimates, through periodic surveys of soil CO2 flux, can constitute a useful tool to monitor volcanic activity.Editorial responsibility: H. Shinohara 相似文献
64.
W. Thomas T. Ruppert M. Van Roozendael J. Verdebout D. Balis C. Meleti C. Zerefos 《Journal of Atmospheric Chemistry》2005,50(3):295-320
We focus on the retrieval of volcanic sulfur dioxide (SO2) emissions from an analysis of atmospheric UV backscatter spectra obtained by the Global Ozone Monitoring Experiment (GOME) spectrometer on board the ESA European Remote Sensing Satellite (ERS-2). Here, the last major eruptions of Mt. Etna on Sicily (Italy) in July/August 2001 and October/November 2002 provided an excellent opportunity to study the retrieval of SO2 columnar amounts from ground-based, LIDAR and satellite measurements. Our study shows that the bulk of emitted SO2 was confined in the troposphere, mainly between 700 hPa and 400 hPa which is confirmed by trajectory analysis, by LIDAR observations and AVHRR observations. The area of influence of Mt. Etna eruptions ranges from the Western Saharan Desert to Greece and the near east states and even down to the basin of Tschad, Africa. Our analysis revealed that information about the plume height of volcanic eruptions and aerosol parameters is necessary for a reliable quantitative retrieval of SO2 from space-borne sensor data at periods perturbed by volcanic eruptions. 相似文献
65.
活动断裂带的壤中气汞量测量研究 总被引:2,自引:0,他引:2
在覆盖区应用壤中气汞量测量研究活动断裂是一种新方法,它不仅能较准确地确定活动断裂的位置,还可以确定其产状,规模,活动性及相对强度,甚至可以作为确定断裂力学性质的参考,本文简棕了断裂带壤中气汞量测量的基本原理,并以长江三峡,长春,吉林等地利用该种方法研究活动断裂的成果为例,说明该项研究的效果及应用前景。 相似文献
66.
67.
The methane concentration in the atmosphere andsurface water was surveyed along 58° N acrossthe North Sea. In addition, the vertical methanedistribution in the water column was determined at sixstations along the transect. The methane contents ofthe surface water as well as in the water column wereextremely inhomogeneous. Input by freshwater fromriver discharge and injection of methane from thesediment were both observed. The survey continued fromthe western side of the North Sea to the Elbe Riverestuary. The Elbe River appears to have low methaneconcentrations compared to other European rivers, itsaverage input into the North Sea is estimated to be70 nmol s-1 of methane. Near 58° N,1°40' E, an abandoned drill site releases about 25 % ofthe North Sea's emission of methane to the atmosphere.The advective methane transport induced by watercirculation was assessed for May 16, 1994, using a 3-DNorth Sea circulation model. For the period of thissurvey, the North Sea's source strength foratmospheric methane is estimated using in situwind velocities. In comparison to the advectivetransport by the water circulation, the gas flux tothe atmosphere appears to be the dominant sink ofNorth Sea methane. This flux is estimated to bebetween 1500 · 106 mol a-1 and 3100 ·106mol a-1, depending on the relationbetween wind speed and gas transfer velocity. 相似文献
68.
Noble gas concentrations and isotopic compositions have been determined for four submarine volcanic glasses from the Valu Fa Ridge (VFR) in the southern Lau Basin. The samples are the least differentiated ones from this area, and they display enrichments in fluid-mobile elements similar to the nearby island arc. 3He/4He ratios are slightly below average MORB (6.8–7.8 times atmospheric), whereas Ne, Ar, Kr, and Xe have isotopic compositions very similar to air. Together with previously published data from the Valu Fa Ridge and other spreading segments in the Lau Basin, our data show a systematic latitudinal variation of increasing Ne, Ar, Kr, and Xe abundances from north to south as well as Ne and Ar isotopic compositions changing from MORB-like to atmosphere-like in the same direction. Moreover, isotopic compositions and noble gas abundances of the lavas correlate strongly with Ba/Nb ratios and H2O concentrations. Based on these observations and mass balance arguments, we propose that the atmospheric noble gases come from the subducting oceanic crust and are not due to shallow contamination with air dissolved in seawater or assimilation of old crust. Our data suggest that the noble gases released from the subducting slab are atmospheric and thus contain little or no solar He and Ne. In addition to the fact that ratios of He to heavy noble gases are small in aged ocean crust, He has possibly fractionated from the other noble gases due to its higher diffusivity, and thus He transport from the subducting slab into the mantle wedge is probably insignificant. We propose that the 3He/4He ratios lower than MORB observed in the VFR lavas result from radiogenic ingrowth of He in a highly depleted, and hence degassed, mantle wedge after the enrichment of U and Th released from the downgoing slab. 相似文献
69.
Bruce A. Callander 《GeoJournal》1997,42(1):55-63
IPCCs statement in its 1995 report (IPCC 1996) that a human influence was discernible in global climate has been widely quoted but often misunderstood. The character of the evidence underpinning this detection statement is explained so that its strengths and weaknesses can be better understood and the subtleties of its message better appreciated. To demonstrate the close linkage between the government-approved summary and the underlying chapters of the IPCC report the detailed evolution of the detection statement from first draft through to the form finally approved by the IPCC is described. 相似文献
70.
An aspect of global change currently not well understood is how processes operating on spatial scales finer than those used in recent global circulation models (GCMs) contribute to changes in atmospheric composition and the subsequent changes in climate. We use the ‘IPAT’ formulation as a framework to test relationships among social driving forces and user group greenhouse gas (GHG) emissions in northwestern North Carolina. Using regression, correlation, and bivariate mapping to examine relationships between a suite of socioeconomic variables and GHG emissions for the residential, commercial/industrial, and agricultural end‐user categories, we find that various measures of population and affluence serve equally well as explanatory variables. 相似文献