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1.
1 Introduction As one of the most important greenhouse gases, atmospheric carbon dioxide (CO2) has increased in concentration rapidly since preindustrial times[1―4] and significantly contributes to the climate change[5] caused by anthropogenic emissions. Documentation of the global carbon cycle has been critical for under-standing the causative relationships between green-house gases and climate change. For example, the CO2 level in the atmosphere has been monitored at many sites worldwide … 相似文献
2.
The oxygen minimum zones (OMZs) are recognized as intense sources of N 2O greenhouse gas (GHG) and could also be potential sources of CO 2, the most important GHG for the present climate change. This study evaluates, for one of the most intense and shallow OMZ, the Chilean East South Pacific OMZ, the simultaneous N 2O and CO 2 fluxes at the air–sea interface. Four cruises (2000–2002) and 1 year of monitoring (21°–30°–36°S) off Chile allowed the determination of the CO 2 and N 2O concentrations at the sea surface and the analysis of fluxes variations associated with different OMZ configurations. The Chilean OMZ area can be an intense GHG oceanic local source of both N 2O and CO 2. The mean N 2O fluxes are 5–10 times higher than the maximal previous historical source in an OMZ open area as in the Pacific and Indian Oceans. For CO 2, the mean fluxes are also positive and correspond to very high oceanic sources. Even if different coupling and decoupling between N 2O and CO 2 are observed along the Chilean OMZ, 65% of the situations represent high CO 2 and/or N 2O sources. The high GHG sources are associated with coastal upwelling transport of OMZ waters rich in N 2O and probably also in CO 2, located at a shallow depth. The integrated OMZ role on GHG should be better considered to improve our understanding of the past and future atmospheric CO 2 and N 2O evolutions. 相似文献
3.
The concentrations of CH 4 in the atmosphere over the past 2000 years have been deduced by extracting and analyzing the air in bubbles embedded in the
Dasuopu ice core, Qing-hai-Tibetan Plateau. Upon analyzing 57 ice core samples we found that the concentration of CH 4 200 years ago and earlier was 0.85 μ mol· mol -1 or about 40% of present atmospheric CH 4 levels over Qinghai-Tibetan Plateau. A rapid and significant increase of atmospheric CH 4 started about 200–250 a ago. For a given age before 19th century, the Dasuopu CH 4 concentrations were about 15%-20% higher than those in Antarctic and Greenland references. It was also found that the Dasuopu
CH 4 concentrations changed more frequently, and its fluctuations could reflect the temperature change sensitively. 相似文献
4.
内陆水体是大气CO 2收支估算的重要组成部分。农业流域分布着大量池塘景观水体,且具备蓄洪抗旱、消纳污染、水产养殖等多种功能。但是,农业流域不同功能的小型池塘CO 2排放特征尚不清楚。本研究以极具农业流域代表性的烔炀河流域为研究对象,选取流域中用于水产养殖(养殖塘)、生活污水承纳(村塘)、农业灌溉(农塘)、蓄水(水塘)的4个功能不同的景观池塘,基于为期1年的野外实地观测,以明确农业流域小型池塘CO 2排放特征。结果表明,不同功能池塘水体CO 2排放差异显著,受养殖活动、生活污水输入和农田灌溉等人类活动影响,养殖塘((80.37±100.39) mmol/(m 2·d))、村塘((48.69±65.89) mmol/(m 2·d))和农塘((13.50±15.81) mmol/(m 2·d))是大气CO 2的热点排放源,其CO 2排放通量分别是自然蓄水塘((4.52±23.26) mmol/(m 2·d))的18、11和3倍。统计分析也表明,该流域池塘CO 2排放变化总体上受溶解氧、营养盐等因素驱动。4个不同景观池塘CO 2排放通量全年均值为(37.31±67.47) mmol/(m 2·d),是不容忽视的CO 2排放源,其中养殖塘和村塘具有较高的CO 2排放潜力,在未来研究中需要重点关注。 相似文献
5.
Based on summer observations of stable isotope of precipitation at Muztagata, western China, during 2002-2003, this paper
presents the relationship between δ
18O in precipitation and air temperature, and discusses the effect of moisture transport on δ
18O in precipitation. Results show that air temperature correlates positively with δ
18O in precipitation, and the temperature effect controls the δ
18O of precipitation in this area. The Muztagata region exhibits high δ
18O values in summer precipitation, similar to those shown at stations in adjacent regions. According to the results of our
model set up to trace the moisture trajectories, the westerlies and local moisture circulation contribute to variations of
oxygen isotopes in precipitation. In addition, the impacts of the moisture transport distance, the moisture transport level,
and the incursion of the polar air mass also influence the variations of δ
18O in precipitation. The moisture origins and transport mechanisms also contribute to the variation of δ
18O in precipitation at Muztagata. 相似文献
6.
Soil H 2 and CO 2 surveys were carried out along seven active faults and around the aftershock region of the 2000 Tottori-ken Seibu earthquake
in Japan. Diffuse CO 2 effluxes were also measured along one fault and around the 2000 aftershock region. The results show highly variable H 2 concentration in space and time and it seems that the maximum H 2 concentration at each active fault correlates with fault activity as exemplified by the time of the latest big earthquakes.
Even though observed H 2 concentrations in four faults were markedly lower than those collected previously in the latter half of the 1970s, it is
evident that the higher H 2 concentrations in this study are due to the addition of the fault gases. Comparing the chemical composition of trapped gases
(H 2: 5–20% and CO 2/H 2: 0.5–12) in fractured rocks of drill cores bored at the Nojima fault, a soil gas sample with the highest H 2 concentration showed large amounts of the trapped fault gas, diluted with atmospheric component. The profile experiment across
a fracture zone at the Yamasaki fault showed higher H 2 concentrations and lower CO 2/H 2 ratios as was observed in soil gas from the fracture zone. A few days after the 2000 Tottori-kei Seibu earthquake, no CO 2 effluxes related to the occurrence of earthquakes were observed at the aftershock region. However, only above the epicenter
zone, relatively high H 2 concentrations in soil gases were observed. 相似文献
7.
The long-term effect of elevated CO2 concentrations on needle dark respiration of two coniferous species-Pinus koraiensis and Pinus sylvestriformis on the Changbai Mountain was investigated using open-top chambers. P. Koraiensis and P. Sylvestriformis were exposed to 700,500μmol·mol-1 CO2 and ambient CO2(approx.350 μmol·mol-1)for four growing seasons. Needle dark respiration was measurd during the second, third and fourth growing seasons' exposure to elevated CO2.The results showed that needle dark respiration rate increased for P. Koraiensis and P. Sylvestriformis grown at elevated CO2 concentrations during the second growing season, could be attributed to the change of carbohydrate and/or nitrogen content of needles. Needle dark respiration of P. Koraiensis was stimulated and that of P. Sylvestriformis was inhibited by elevated CO2 concentrations during the third growing season. Different response of the two tree species to elevated CO2 mainly resulted from the difference in the growth rate. Elevated CO2 concentrations inhibited needle dark respiration of both P. Koraiensis and P. Sylvestriformis during the fourth growing season. There was consistent trend between the short-term effect and the long-term effect of elevated CO2 on needle dark respiration in P. Sylvestriformis during the third growing season by changing measurement CO2 concentrations. However, the short-term effect was different from the long-term effect for P. Koraiensis. Response of dark respiration of P. Koraiensis and P. Sylvestriformis to elevated CO2 concentrations was related to the treatment time of CO2 and the stage of growth and development of plant. The change of dark respiration for the two tree species was determined by the direct effect of CO2 and long-term acclimation. The prediction of the long-term response of needle dark respiration to elevated CO2 concentration based on the short-term response is in dispute. 相似文献
8.
Taking Huanglong Ravine and Kangding, Sichuan, and Xiage, Zhongdian, Yunnan, as examples, the authors summarize the hydrogeochemical
and carbon stable isotopic features of the geothermal CO 2-water-carbonate rock system and analyze the CO 2 sources of the system. It was found that the hydrogeochemical and carbon stable isotopic features of such a system are different
from those of shallow CO 2-water-carbonate rock system, which is strongly influenced by biosphere. The former has higher CO 2 partial pressure, and is rich in heavy carbon stable isotope. In addition, such a geothermal system is also different from
that developed in igneous rock. The water in the latter system lacks Ca 2+, and thus, there are few tufa deposits on ground surface, but it is rich in light carbon stable isotope. Further analysis
shows that CO 2 of the geothermal CO 2-water-carbonate rock system is a mixture of metamorphic CO 2 and magmatic CO 2. 相似文献
9.
Surface partial pressure of CO 2 ( pCO 2), temperature, salinity, nutrients, and chlorophyll a were measured in the East China Sea (ECS; 31°30′–34°00′N to 124°00′–127°30′E) in August 2003 (summer), May 2004 (spring), October 2004 (early fall), and November 2005 (fall). The warm and saline Tsushima Warm Current was observed in the eastern part of the survey area during four cruises, and relatively low salinity waters due to outflow from the Changjiang (Yangtze River) were observed over the western part of the survey area. Surface pCO 2 ranged from 236 to 445 μatm in spring and summer, and from 326 to 517 μatm in fall. Large pCO 2 (values >400 μatm) occurred in the western part of the study area in spring and fall, and in the eastern part in summer. A positive linear correlation existed between surface pCO 2 and temperature in the eastern part of the study area, where the Tsushima Warm Current dominates; this correlation suggests that temperature is the major factor controlling surface pCO 2 distribution in that area. In the western part of the study area, however, the main controlling factor is different and seasonally complex. There is large transport in this region of Changjiang Diluted Water in summer, causing low salinity and low pCO 2 values. The relationship between surface pCO 2 and water stability suggests that the amount of mixing and/or upwelling of CO 2-rich water might be the important process controlling surface pCO 2 levels during spring and fall in this shallow region. Sea–air CO 2 flux, based on the application of a Wanninkhof [1992. Relationship between wind speed and gas exchange over the ocean. Journal of Geophysical Research 97, 7373–7382] formula for gas transfer velocity and a set of monthly averaged satellite wind data, were −5.04±1.59, −2.52±1.81, 1.71±2.87, and 0.39±0.18 mmol m −2 d −1 in spring, summer, early fall, and fall, respectively, in the northern ECS. The ocean in this study area is therefore a carbon sink in spring and summer, but a weak source or in equilibrium with the atmosphere in fall. If the winter flux value is assumed to have been the mean of autumnal and vernal values, then the northern ECS absorbs about 0.013 Pg C annually. That result suggests that the northern ECS is a net sink for atmospheric CO 2, a result consistent with previous studies. 相似文献
10.
The study by the eddy covariance technique in the alpine shrub meadow of the Qinghai-Tibet Plateau in 2003 and 2004 showed that the net ecosystem carbon dioxide exchange (NEE) exhibited noticeable diurnal and annual variations, with more distinct daily changes during the warmer seasons. The CO2 emission of the shrub ecosystem culminated in April and September while the CO2 absorption capacity reached a maximum in July and August. The absorbed carbon dioxide during the two consecutive years was 231.4 and 274.8 g CO2·m−2 respectively, yielding an average of 253.1 gCO2·m−2 per year: that accounts for a large proportion of absorbed CO2 in the region. Obviously, the diurnal carbon flux was negatively related to temperature, radiation and other atmospheric factors. Still, minute discrepancies in kurtosis and duration of carbon emission/absorption were detected between 2003 and 2004. It was found that the CO2 flux in the daytime was similarly affected by photosynthetic photon flux density in both years. Temperature appears to be the most important determinant of CO2 flux: specifically, the high temperature during the plant growing season inhibits the carbon absorption capacity. One potential explanation is that soil respiration is enhanced under such condition. Analysis of biomass revealed that the annual net carbon fixed capacity of aboveground and belowground biomass was 544.0 in 2003 and 559.4 g C·m−2 in 2004, which coincided with the NEE absorption capacity (63.1 g C·m−2 in 2003 and 74.9 g C·m−2 in 2004) in the corresponding plant growing season. 相似文献
11.
Near-surface soil CO 2 gas-phase concentration ( C) and concomitant incident rainfall ( Pi) and through-fall ( Pt) depths were collected at different locations in a temperate pine forest every 30 min during the 2005 and 2006 growing seasons (and then averaged to the daily timescale). At the daily scale, C temporal variations were well described by a sequence of monotonically decreasing functions interrupted by large positive jumps induced by rainfall events. A stochastic model was developed to link rainfall statistics responsible for these jumps to near-surface C dynamics. The model accounted for the effect of daily rainfall variability, both in terms of timing and amount of water, and permitted an analytical derivation of the C probability density function (pdf) using the parameters of the rainfall pdf. Given the observed positive correlation between daily C and soil CO 2 fluxes to the atmosphere ( Fs), the effects of various rainfall regimes on the statistics of Fs can be deduced from the behavior of C under different climatic conditions. The predictions from this analytical model are consistent with flux measurements reported in manipulative experiments that varied rainfall amount and frequency. 相似文献
12.
The southern Yellow Sea (SYS), located to the north of the East China Sea (ECS), was considered part of the ECS when Tsunogai et al. (1999) proposed the “continental shelf pump” (CSP) hypothesis. However, the original CSP carbon dioxide (CO 2) uptake flux (2.9 mol C m −2 yr −1) appears to have been overestimated, primarily due to the differences between the SYS and the ECS in terms of their CO 2 system. In this paper, we estimated air-sea CO 2 fluxes in the SYS using the surface water partial pressure of CO 2 ( pCO 2) measured in winter, spring, and summer, as well as that estimated in fall via the relationship of pCO 2 with salinity, temperature, and chlorophyll a. The results indicate that overall, the entire investigated area was a net source of atmospheric CO 2 during summer, winter, and fall, whereas it was a net sink during spring. Spatially, the nearshore area was almost a permanent CO 2 source, while the central SYS shifted from being a CO 2 sink in spring to a source in the other seasons of the year. Overall, the SYS is a net source of atmospheric CO 2 on an annual scale, releasing ∼7.38 Tg C (1 Tg=10 12 g) to the atmosphere annually. Thus, the updated CO 2 uptake flux in the combined SYS and ECS is reduced to ∼0.86 mol C m −2 yr −1. If this value is extrapolated globally following Tsunogai et al. (1999), the global continental shelf would be a sink of ∼0.29 Pg C yr −1, instead of 1 Pg C yr −1 (1 Pg=10 15 g).The SYS as a net annual source of atmospheric CO 2 is in sharp contrast to most mid- and high-latitude continental shelves, which are CO 2 sinks. We argue that unlike the ECS and the North Sea where carbon on the shelf could be exported to the open ocean, the SYS lacks the physical conditions required by the CSP to transport carbon off the shelf effectively. The global validity of the CSP theory is thus questionable. 相似文献
13.
The environmental and biogeochemical information extracted from the sediments collected from the northern shelf of the South
China Sea shows that terrigenous inputs of phosphorus into the sea remained relatively constant, and the variation of phosphorus
contents at different depths was caused by climatic and environmental changes. The findings also suggest that the vertical
variation of phosphorus content was opposite to those of calcium carbonate and cadmium, and the functional correlation between
CO 2 and PO
4
3−
in seawater was given by calculating the chemical equilibrium, indicating that the accumulation of marine sedimentary phosphorus
may have something to do with the variation of atmospheric CO 2. The decreased phosphorus accumulation as well as the correspondingly-increased calcium carbonate content might be one of
key factors causing glacial atmospheric CO 2 decline. 相似文献
14.
We present an uncertainty analysis of ecological process parameters and CO 2 flux components ( R
eco, NEE and gross ecosystem exchange ( GEE)) derived from 3 years’ continuous eddy covariance measurements of CO 2 fluxes at subtropical evergreen coniferous plantation, Qianyanzhou of ChinaFlux. Daily-differencing approach was used to
analyze the random error of CO 2 fluxes measurements and bootstrapping method was used to quantify the uncertainties of three CO 2 flux components. In addition, we evaluated different models and optimization methods in influencing estimation of key parameters
and CO 2 flux components. The results show that: (1) Random flux error more closely follows a double-exponential (Laplace), rather
than a normal (Gaussian) distribution. (2) Different optimization methods result in different estimates of model parameters.
Uncertainties of parameters estimated by the maximum likelihood estimation (MLE) are lower than those derived from ordinary
least square method (OLS). (3) The differences between simulated R eco, NEE and GEE derived from MLE and those derived from OLS are 12.18% (176 g C·m −2·a −1), 34.33% (79 g C·m −2·a −1) and 5.4% (92 g C·m −2·a −1). However, for a given parameter optimization method, a temperature-dependent model (T_model) and the models derived from
a temperature and water-dependent model (TW_model) are 1.31% (17.8 g C·m −2·a −1), 2.1% (5.7 g C·m −2·a −1), and 0.26% (4.3 g C·m −2·a −1), respectively, which suggested that the optimization methods are more important than the ecological models in influencing
uncertainty in estimated carbon fluxes. (4) The relative uncertainty of CO 2 flux derived from OLS is higher than that from MLE, and the uncertainty is related to timescale, that is, the larger the
timescale, the smaller the uncertainty. The relative uncertainties of R eco, NEE and GEE are 4%−8%, 7%−22% and 2%−4% respectively at annual timescale.
Supported by the National Natural Science Foundation of China (Grant No. 30570347), Innovative Research International Partnership
Project of the Chinese Academy of Sciences (Grant No. CXTD-Z2005-1) and National Basic Research Program of China (Grant No.
2002CB412502) 相似文献
15.
水库近岸湿地(消落区)温室气体(CO 2、CH 4)产汇是水库温室气体效应问题的重要组成部分.本文以三峡水库支流澎溪河的白家溪、养鹿两处大面积消落区为研究对象,于2010年6 9月水库低水位运行期间,对近岸消落区土-气界面CO 2、CH 4通量进行监测.白家溪消落区土-气界面CO 2通量均值为12.38±2.42 mmol/(m 2·h);CH 4通量均值为0.0112±0.0064 mmol/(m 2·h).养鹿消落区CO 2、CH 4通量均值分别为10.54±5.17、0.14±0.16 mmol/(m 2·h).总体上,6 9月土-气界面CO 2通量呈增加趋势,而CH 4通量水平呈现显著的递减趋势.消落区土地出露后植被恢复,在一定程度上促进了土壤有机质含量的增加,使得6 9月CO 2释放通量的总体趋势有所增加.消落区退耕后,其甲烷氧化菌的活性得到恢复,加之在土地出露曝晒过程中土壤透气性增强,使得消落区土壤对大气中CH 4吸收氧化潜势增强.尽管如此,仍需进一步的研究以明晰消落区土-气界面CO 2、CH 4产汇的主要影响因素. 相似文献
16.
河流作为连接陆地和海洋碳库之间的通道,是全球内陆水体碳排放最主要的载体,在全球碳循环中发挥着至关重要的作用。全球河流水-气界面二氧化碳(CO 2)脱气显著的时间异质性特征研究有助于深入理解其碳循环过程与机制,也为准确评估碳通量以及完善碳循环模型提供了科学支撑。本文系统梳理了国内外的相关研究成果,总结了目前河流CO 2脱气通量在昼夜、季节以及多年尺度上的动态变化及其影响因素,指出其昼夜变化与季节变化存在一定的周期性,并对不同空间尺度上CO 2脱气通量的时间差异进行讨论。同时分析当前研究中的不足,认为缺乏河流二氧化碳分压( pCO 2)与CO 2脱气系数( k)高分辨率且长期连续的直接测量,限制了河流CO 2脱气通量时间尺度变化的周期性及相互之间关系的厘定,使得气候变化与人类活动对河流CO 2脱气时间动态的影响仍然难以量化与预测。最后,根据目前存在的问题,展望了未来的研究重点,为全球河流水-气界面碳循环过程与机制、模型研究提供新的思路与方向,以及可以更准确地评估和预测未来河流碳排放的变化趋势。 相似文献
17.
The Ketzin project provides an experimental pilot test site for the geological storage of CO 2. Seismic monitoring of the Ketzin site comprises 2D and 3D time-lapse experiments with baseline experiments in 2005. The first repeat 2D survey was acquired in 2009 after 22 kt of CO 2 had been injected into the Stuttgart Formation at approximately 630 m depth. Main objectives of the 2D seismic surveys were the imaging of geological structures, detection of injected CO 2, and comparison with the 3D surveys. Time-lapse processing highlighted the importance of detailed static corrections to account for travel time delays, which are attributed to different near-surface velocities during the survey periods. Compensation for these delays has been performed using both pre-stack static corrections and post-stack static corrections. The pre-stack method decomposes the travel time delays of baseline and repeat datasets in a surface consistent manner, while the latter cross-aligns baseline and repeat stacked sections along a reference horizon.Application of the static corrections improves the S/N ratio of the time-lapse sections significantly. Based on our results, it is recommended to apply a combination of both corrections when time-lapse processing faces considerable near-surface velocity changes. Processing of the datasets demonstrates that the decomposed solution of the pre-stack static corrections can be used for interpretation of changes in near-surface velocities. In particular, the long-wavelength part of the solution indicates an increase in soil moisture or a shallower groundwater table in the repeat survey.Comparison with the processing results of 2D and 3D surveys shows that both image the subsurface, but with local variations which are mainly associated to differences in the acquisition geometry and source types used. Interpretation of baseline and repeat stacks shows that no CO 2 related time-lapse signature is observable where the 2D lines allow monitoring of the reservoir. This finding is consistent with the time-lapse results of the 3D surveys, which show an increase in reflection amplitude centered around the injection well. To further investigate any potential CO 2 signature, an amplitude versus offset (AVO) analysis was performed. The time-lapse analysis of the AVO does not indicate the presence of CO 2, as expected, but shows signs of a pressure response in the repeat data. 相似文献
18.
Automated detection of fog and low stratus in nighttime satellite data has been implemented on the basis of numerous satellite
systems in past decades. Commonly, differences in small-droplet emissivities at 11 μm and 3.9 μm are utilized. With Meteosat SEVIRI, however, this method cannot be applied with a fixed threshold due to instrument design:
The 3.9 μm band is exceptionally wide and overlaps with the 4 μm CO 2 absorption band. Therefore, the emissivity difference varies with the length of the slant atmospheric column between sensor
and object. To account for this effect, the new technique presented in this paper is based on the dynamical extraction of
emissivity difference thresholds for different satellite viewing zenith angles. In this way, varying concentrations of CO 2 and column depths are accounted for. The new scheme is exemplified in a plausibility study and shown to provide reliable
results. 相似文献
19.
An extensive laboratory study was conducted to measure the interfacial tension (IFT) between CO 2 and brine consisting in equal molal concentrations of NaCl and CaCl 2. The experiments were repeated at various pressures, temperatures and salinities that are representative of conditions prevailing during CO 2 storage in deep saline aquifers. The dependence of CO 2/brine IFT on pressure and temperature is similar to that previously reported for the systems: CO 2/NaCl solution and CO 2/CaCl 2 solution. CO 2/brine IFT increases linearly with water salinity and the magnitude of this increase was found equal to the sum of the individual CO 2/NaCl solution and CO 2/CaCl 2 solution IFT increments, indicating a strong additive effect on IFT when the brine is composed of various salts. 相似文献
20.
Step heating experiments on ultra-high pressure (UHP) mcks from the Dabie Mountain shows a majority of CO 2 in fluid inclusion (excluding H 2O); CO is also a significant component, with a small content of N 2 and CH 4. Carbon isotopic composition of CO 2 in fluid of metamorphic climax stage (- 25%0- - 30%0) is different from that of mantle carbon, indicating that UHP rocks did not experience obvious transformation by mantle fluids
despite their subduction depth. CO 2 was derived from carbon matter in the pmtoliths of UHP rocks in a relatively confined system, showing that the UHP rocks
subsided quickly and uplifted quickly from the mantle.
Current organization: Research Institute of Petroleum Exploration and Development, Beijing 100083, China. 相似文献
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