Marine Carbon Sequestration: Current Situation,Problems and Future

Abuse of fossil energy resources results in the excessive discharge of greenhouse gases, especially CO₂, enhancing the trend of global climate warming. Carbon sequestration is an important method to lower the increasing rate of CO₂ concentration in the atmosphere. Marine carbon sequestration is a novel idea for reducing CO₂ emission, and its reservoir mainly includes seawater and submarine sediment, which not only possess a great potential capacity of carbon sequestration, but also have high safety in relation to continental reservoirs. In this paper, we expounded the technique principle and mechanisms of marine carbon sequestration, potential capacity and time duration of marine carbon sequestration, main factors influencing marine carbon sequestration, CO₂ injection technique, impacts on marine biota from over emission of CO₂ and technique monitoring the leakage of CO₂. Finally, a prospect of marine carbon sequestration was proposed, and its hot topics were accordingly pointed out.     

Carbon Reduction Policies: A Regional Comparison of Their Contributions to CO2 Abatement in Six Carbon Trading Pilot Schemes in China

The contributions of carbon reduction policies were evaluated and compared for six carbon trading pilot schemes in China, in four municipalities(Beijing, Shanghai, Tianjin, and Chongqing) and two provinces(Guangdong and Hubei). The carbon emissions accounting method of the Intergovernmental Panel on Climate Change was used to calculate the actual CO2 and the support vector machine model was used to predict CO2. Chinese carbon reduction policies abated CO2 in the six carbon trading pilot schemes after the comprehensive policies came into force. However, the contribution of policies to CO2 abatement varied among regions, and the effect of carbon reduction policy on municipality pilot schemes was greater than on provincial pilot schemes. The largest contribution of carbon reduction policy to CO2 abatement was 28.3%, for the pilot carbon trading scheme in Beijing, and the smallest contribution was 3.7%, for that in Hubei. It is crucial to consider “carbon leakage” and a carbon trading linking program in order to evaluate the effects of carbon reduction policies.     

大洋俯冲和大陆碰撞沿走向的转换动力学及流体-熔体活动的作用

为了深入探讨大洋俯冲和大陆碰撞沿走向的转换及其动力学特征,同时更好的理解俯冲-碰撞带的流体-熔体活动及其效应,我们建立了一系列三维空间的大尺度、高分辨率的动力学数值模型。模拟结果显示,在板块会聚过程中,流体-熔体活动可以降低周围岩石的流变强度及两个板块之间的耦合作用,并能够促进大陆碰撞带俯冲板块的断离。同时,俯冲-碰撞带的空间转换模型揭示其深部结构存在巨大的沿走向的差异性,大陆碰撞带发生俯冲板块断离,而大洋俯冲板块持续下插。并且上覆板块的地壳物质发生从陆-陆碰撞带向洋-陆俯冲带的侧向逃逸。这种三维空间中沿走向的差异性俯冲-碰撞模式与中-东特提斯构造带相吻合,并揭示其动力学机制。     

Thermo‐hydro‐mechanical modeling with Langmuir's adsorption isotherm of the CO2 injection in coal

In this paper, we used a theoretical model for the variation of Eulerian porosity, which takes into account the adsorption process known to be the main mechanism of production or sequestration of gas in many reservoir of coal. This process is classically modeled using Langmuir's isotherm. After implementation in Code_Aster, a fully coupled thermo‐hydro‐mechanical analysis code for structures calculations, we used numerical simulations to investigate the influence of coal's hydro‐mechanical properties (Biot's coefficient, bulk modulus), Langmuir's adsorption parameters, and the initial liquid pressure in rock mass during CO₂ injection in coal. These simulations showed that the increase in the values of Langmuir's parameters and Biot's coefficient promotes a reduction in porosity because of the adsorption process when the gas pressure increases. Low values of bulk modulus increase the positive effect (i.e., increase) of hydro‐mechanical coupling on the porosity evolution. The presence of high initial liquid pressure in the rock mass prevents the progression of injected gas pressure when CO₂ dissolution in water is taken into account. Copyright © 2014 John Wiley & Sons, Ltd.     

On the discovery of CO nighttime emissions on Titan by Cassini/VIMS: Derived stratospheric abundances and geological implications

We present a quantitative analysis of CO thermal emissions discovered on the nightside of Titan by Baines et al. [2005. The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/VIMS. Earth, Moon, and Planets, 96, 119–147]. in Cassini/VIMS spectral imagery. We identify these emission features as the P and R branches of the 1-0 vibrational band of carbon monoxide (CO) near 4.65 μm. For CH₃D, the prominent Q branch of the ν₂ fundamental band of CH₃D near 4.55 μm is apparent. CO₂ emissions from the strong v₃ vibrational band are virtually absent, indicating a CO₂ abundance several orders of magnitude less than CO, in agreement with previous investigations. Analysis of CO emission spectra obtained over a variety of altitudes on Titan's nightside limb indicates that the stratospheric abundance of CO is 32±15 ppm, and together with other recent determinations, suggests a vertical distribution of CO nearly constant at this value from the surface throughout the troposphere to at least the stratopause near 300 km altitude. The corresponding total atmospheric content of CO in Titan is 2.9±1.5×10¹⁴ kg. Given the long lifetime of CO in the oxygen-poor Titan atmosphere (0.5–1.0 Gyr), we find a mean CO atmospheric production rate of 6±3×10⁵ kg yr⁻¹. Given the lack of primordial heavy noble gases observed by Huygens [Niemann et al., 2005. The abundances of constituents of Titan's atmosphere from the GCMS on the Huygens probe. Nature, 438, 779–784], the primary source of atmospheric CO is likely surface emissions. The implied CO/CH₄ mixing ratio of near-surface material is 1.8±0.9×10⁻⁴, based on an average methane surface emission rate over the past 0.5 Gyr of 1.3×10⁻¹³ gm cm⁻² s⁻¹ as required to balance hydrocarbon haze production via methane photolysis [Wilson and Atreya, 2004. Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. J. Geophys. Res. 109, E06002 Doi:10.1029/2003JE002181]. This low CO/CH₄ ratio is much lower than expected for the sub-nebular formation region of Titan and supports the hypothesis [e.g., Atreya et al., 2005. Methane on Titan: photochemical-meteorological-hydrogeochemical cycle. Bull. Am. Astron. Soc. 37, 735] that the conversion of primordial CO and other carbon-bearing materials into CH₄-enriched clathrate-hydrates occurs within the deep interior of Titan via the release of hydrogen through the serpentinization process followed by Fischer–Tropsch catalysis. The time-averaged predicted emission rate of methane-rich surface materials is 0.02 km³ yr⁻¹, a value significantly lower than the rate of silicate lava production for the Earth and Venus, but nonetheless indicative of significant active geological processes reshaping the surface of Titan.     

3种星虫线粒体16S rRNA、COI和Cyt b基因片段的序列比较

对裸体方格星虫(Sipunculus nudus)、可口革囊星虫(Phascolosoma esculenta)和澳洲管体星虫(Siphonosoma australe)的线粒体16S rRNA、COI和细胞色素b(Cytb)基因片段序列进行比较,并对其系统发生进行了初步探讨。采用PCR方法得到总长度分别为531～544bp(16S)、652～675bp(COI)和406～453bp(Cytb)的线粒体片段。片段碱基A+T比例较高(16S rRNA基因58.3%,COI基因56.9%,Cytb基因59.5%)。16S rRNA片段存在169个碱基变异位点(其中包括167个简约信息位点)和44个碱基插入/缺失,种内个体间变异较小;COI片段有512个碱基(333个简约信息位点)存在变异,79个碱基插入/缺失;Cytb片段存在347个碱基(318个简约信息位点)变异位点,16个碱基插入/缺失。数据分析结果支持3种星虫和环节动物的分类地位较近,与软体动物较远的分类观点。此外,裸体方格星虫与澳洲管体星虫之间亲缘关系较近(D=0.3159、0.3156、0.2361)。认为3种星虫线粒体16S rRNA、COI和Cytb基因在种间存在明显的多态性,证实了三种基因序列均普遍适用于星虫种及以上阶元的系统学分析。     

Multilayer distribution of carbon dioxide system in surface water of the Yellow Sea in spring

Surface water can be divided into three layers from top downward: surface microlayer (SML, thickness≤50 μm), subsurface layer (SSL, ≈25 cm) and surface layer (SL, 1–5m), among which the SML plays an important role on sea-air interaction because of its unique physical-chemical property. Carbon dioxide system including DIC (dissolved inorganic carbon), Alk (alkalinity), pH and pCO2 (partial pressure of CO2) in multilayered waters of the Yellow Sea was studied for the first time in March and May 2005. The results show that: DIC and Alk are obviously enriched in SML. The contents of DIC, Alk and pCO2 become lower in turn from SML, SSL to SL, higher in March and lower in May, whereas for pH it was opposite. The relationship between DIC and Alk is clearly positive, but negative between pH and pCO2. Meanwhile, pCO2 and temperature/salinity is also in positive relation, pCO2 decreases with latitude increase. DIC and Alk show a similar variation trend with the maximum at 02:00–03:00, but pH and pCO2 show an opposite pattern. In addition, the distribution patterns are similar to each other in the three layers. The Yellow Sea is shown to be a sink of atmospheric CO2 in spring by two methods: (1) comparing pCO2 in seawater and atmosphere; (2) turning direction of “pH-depth” curve. Calculation on the base of pCO2 data in SML in four models shows that carbon flux in spring in the area was about -6.96×106 t C.     

Geochemical features of the geothermal CO2-water-carbonate rock system and analysis on its CO2 sources--Examples from Huanglong Ravine and Kangding, Sichuan, and Xiage, Zhongdian, Yunnan

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 CO2-water-carbonate rock system and analyze the CO2 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 CO2-water-carbonate rock system, which is strongly influenced by biosphere. The former has higher CO2 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 Ca2+, and thus, there are few tufa deposits on ground surface, but it is rich in light carbon stable isotope. Further analysis shows that CO2 of the geothermal CO2-water-carbonate rock system is a mixture of metamorphic CO2 and magmatic CO2.     

Impact of Non-Methane Hydrocarbons on Tropospheric Chemistry and the Oxidizing Power of the Global Troposphere: 3-Dimensional Modelling Results

The impact of natural and anthropogenicnon-methane hydrocarbons (NMHC) on troposphericchemistry is investigated with the global,three-dimensional chemistry-transport model MOGUNTIA.This meteorologically simplified model allows theinclusion of a rather detailed scheme to describeNMHC oxidation chemistry. Comparing model resultscalculated with and without NMHC oxidation chemistryindicates that NMHC oxidation adds 40–60% to surfacecarbon monoxide (CO) levels over the continents andslightly less over the oceans. Free tropospheric COlevels increase by 30–60%. The overall yield of COfrom the NMHC mixture considered is calculated to beabout 0.4 CO per C atom. Organic nitrate formationduring NMHC oxidation, and their transport anddecomposition affect the global distribution of NO _x and thereby O₃ production. The impact of theshort-lived NMHC extends over the entire tropospheredue to the formation of longer-lived intermediateslike CO, and various carbonyl and carboxyl compounds.NMHC oxidation almost doubles the net photochemicalproduction of O₃ in the troposphere and leads to20–80% higher O₃ concentration inNO _x -rich boundarylayers, with highest increases over and downwind ofthe industrial and biomass burning regions. Anincrease by 20–30% is calculated for the remotemarine atmosphere. At higher altitudes, smaller, butstill significant increases, in O₃ concentrationsbetween 10 and 60% are calculated, maximizing in thetropics. NO from lightning also enhances the netchemical production of O₃ by about 30%, leading to asimilar increase in the global mean OH radicalconcentration. NMHC oxidation decreases the OH radicalconcentrations in the continental boundary layer withlarge NMHC emissions by up to 20–60%. In the marineboundary layer (MBL) OH levels can increase in someregions by 10–20% depending on season and NO _x levels.However, in most of the MBL OH will decrease by10–20% due to the increase in CO levels by NMHCoxidation chemistry. The large decreases especiallyover the continents strongly reduce the markedcontrasts in OHconcentrations between land and oceanwhich are calculated when only the backgroundchemistry is considered. In the middle troposphere, OHconcentrations are reduced by about 15%, although dueto the growth in CO. The overall effect of thesechanges on the tropospheric lifetime of CH₄ is a 15%increase from 6.5 to 7.4 years. Biogenic hydrocarbonsdominate the impact of NMHC on global troposphericchemistry. Convection of hydrocarbon oxidationproducts: hydrogen peroxides and carbonyl compounds,especially acetone, is the main source of HO _x in theupper troposphere. Convective transport and additionof NO from lightning are important for the O₃ budgetin the free troposphere.     

一个考虑二氧化碳的非线性气侯模式

建立一个包含年平均二氧化碳含量「ＣＯ２」、下垫面温度、边界层气温以及云量的零气候模式,用于研究ＣＯ２对气候的影响,结果表明,该模式能模拟出现代气候态以及「ＣＯ２」变化的趋势。进而用与该模式相应的现代气候平衡态的偏差方程,考察了在ＣＯ２的作用下,气候系统由定常态到周期态再到混沌态的演变过程。