CO2矿化封存条件下玄武岩溶解反应速率模型

实施CO2补集与地质封存是目前降低大气中CO2含量、减轻温室效应的有效途径。在所能利用的封存方式中,CO2矿化封存最为安全、稳定。在能实施矿化封存的岩石介质中,玄武岩封存潜力巨大,且岩石溶解反应过程是矿化沉淀过程的基础;因此,研究玄武岩溶解反应速率十分必要。在构成玄武岩的单一矿物与缓冲溶剂的反应速率模型的基础上,提出不同温度下玄武岩样品在超临界CO2水溶液中的溶解速率模型,并通过室内实验,利用采自山东省临朐县的玄武岩岩心样品,在45~100 ℃、10 MPa条件下,与超临界CO2－纯水反应,并运用最小二乘法确定模型中相关参数。同时利用57 ℃、72 ℃、92 ℃ 3个温度下的模型计算值与实验值对模型进行验证,结果证明了模型的准确性和可靠性,研究结果可直接应用于CO2地质封存条件下玄武岩溶解速率的计算。     

The interactions between vegetation and erosion: new directions for research at the interface of ecology and geomorphology

Vegetation and processes of erosion and deposition are interactive. An objective of this paper is to review selected studies that emphasize the interdependencies. The reviews suggest new directions for research uniting ecology and geomorphology – the sub‐discipline of biogeomorphology. The research, which recently has become vigorous, includes the sources, movement, and fates of fluvial loads of sediment, organic carbon, nutrients, contaminants, and woody debris to low‐energy storage sites; the function of biota in causing soil evolution, stability, and sequestration of carbon; the development of new methods to characterize watersheds based on edaphic conditions; and the refinement of current empirical and conceptual models and dendrochronological techniques to measure landscape change. These well acknowledged topics and others less well anticipated ensure that biogeomorphology will remain vibrant. Published in 2011. This article is a US Government work and is in the publish domain in the USA.     

苏北盆地盐城组咸水层CO2 地质封存泄漏风险的全局敏感性分析

      基于对苏北盆地盐城组下段沉积旋回地层概化,建立了一个含有断层的二维剖面模型,采用TOUGH2/ECO2N 程序对 注入到深部咸水层中CO2 的运移分布特征及沿断层的泄漏过程进行了数值模拟。结果表明,尽管盐城组下段地层具有3层旋 回结构且砂岩层属高孔高渗储层,但由于泥层厚度较小且渗透率相对较高,多层封盖效果不佳。在存在导通断层时,CO2 泄露风险较大。应用Morris 法以断层中气相CO2 总量作为输出变量,对模型参数进行了全局敏感性分析。研究显示,当仅 改变断层参数时,与毛细压力相关的参数对气相CO2 沿断层泄漏影响程度最高;当考虑系统参数整体变化时则以砂岩含水 层和泥岩的渗透率敏感性最高,其次为与毛细压力相关的参数（进气压力、残余液体饱和度及孔隙分布指数）。两种情形下 孔隙度与盐度的敏感性均很小。     

Potential for Coal-to-Liquids Conversion in the United States—Fischer–Tropsch Synthesis

The United States has the world’s largest coal reserves and Montana the highest potential for mega-mine development. Consequently, a large-scale effort to convert coal to liquids (CTL) has been proposed to create a major source of domestic transportation fuels from coal, and some prominent Montanans want to be at the center of that effort. We calculate that the energy efficiency of the best existing Fischer–Tropsch (FT) process applied to average coal in Montana is less than 1/2 of the corresponding efficiency of an average crude oil refining process. The resulting CO₂ emissions are 20 times (2000%) higher for CTL than for conventional petroleum products. One barrel of the FT fuel requires roughly 800 kg of coal and 800 kg of water. The minimum energy cost of subsurface CO₂ sequestration would be at least 40% of the FT fuel energy, essentially halving energy efficiency of the process. We argue therefore that CTL conversion is not the most valuable use for the coal, nor will it ever be, as long as it is economical to use natural gas for electric power generation. This finding results from the low efficiency inherent in FT synthesis, and is independent of the monumental FT plant construction costs, mine construction costs, acute lack of water, and the associated environmental impacts for Montana.

深部咸水层CO2地质封存数值模拟参数的全局敏感性分析:以苏北盆地盐城组为例

基于对苏北盆地盐城组下段砂岩储层概化建立二维径向剖面模型,运用TOUGH2/ECO2N程序模拟深部咸水层中CO₂迁移分布过程。采用定性(Morris法)和定量(Sobol和EFAST法)全局敏感性分析方法,以储层中注入井处的压力、气相CO₂总量及CO₂气相羽扩散距离作为模型响应变量,对储层的水平渗透率、孔隙度、残余液体饱和度、孔隙分布指数、压缩系数、进气压力的倒数和盐度7个参数进行全局敏感性分析,讨论了咸水层的水文地质参数、盐度及其他模型参数对CO₂封存运移泄漏过程的影响。Morris和Sobol法的敏感性分析结果都表明,对于不同的响应变量,参数的敏感性排序不同：以注入井处的压力为响应变量时,孔隙度的敏感性最高;以气相CO₂总量和CO₂羽扩散距离为响应变量时,水平渗透率的敏感性最高。EFAST 1阶及总敏感度分析结果与Sobol分析结果基本一致,但EFAST法相对Sobol法计算更高效稳健,需要的样本数较少。     

祁连山地区不同植被生态系统固碳价值量估算及时空演变分析

基于改进的CASA模型测算祁连山地区植被净初级生产力（NPP）物质量, 并进一步基于光合作用方程式、 碳循环过程模型估算了研究区2005年、 2010年、 2015年植被、 土壤固碳量及价值, 旨在定量分析该区域不同植被生态系统植被、 土壤固碳价值时空演变情况, 为制定更科学合理的碳管理措施提供科学依据。研究表明： 祁连山地区2005 - 2015年植被、 土壤固碳价值呈递增趋势, 2005年、 2010年、 2015年植被、 土壤固碳价值分别为515.95、 356.56亿元; 491.05、 404.36亿元; 581.55、 465.65亿元, 土地类型的改变使得植被、 土壤固碳分别增长12.72%、 30.39%。从空间分布上看, 东部植被、 土壤固碳量明显高于西部, 林地固碳能力最高, 单位面积固碳量为10.19 t·hm^-2。草地是研究区分布最广的植被, 且其对该地区植被、 土壤固碳贡献比为51.13%、 49.34%。     

Mopping up leaking carbon: A natural analog at Wadi Namaleh,Jordan

Carbon capture and sequestration (CCS) is one of the important options available for partially stemming greenhouse gas emissions from large point sources. The possibility of leaking from deep storage needs to be addressed. The Wadi Namaleh area in southern Jordan provides an interesting case study of how excess CO₂ can be trapped in the form of carbonates in the near surface, even when the local geology is not obviously conducive for such a process.Carbonate veins are formed in surface alteration zones of rhyolite host rock in this arid region. The alteration zones are limited to areas where surface soil or colluvium are present. Oxygen, deuterium and carbon isotopes of the carbonates and near-surface ground water in the area suggest that the source of carbon is deep seated CO₂, and that the carbonate precipitated in local meteoric water under ambient temperature conditions. Analysis of strontium in the carbonate, fresh rhyolite and altered host shows that the source for calcium is aeolian. Trace elements show that metal and REE mobility are constrained to the alteration zone.Thus, interaction of H₂O, CO₂ and atmospheric wet and dry deposition lead to the formation of the clayey (montmorillonite) alteration zone. This zone acts to trap seeping CO₂ and water, and thus produces conditions of progressively more efficient trapping of carbon dioxide by means of a positive feedback mechanism. Replication of these conditions in other areas will minimize CO₂ leakage from man-made CCS sites.     

Advances in Study of Phytolith Carbon Sequestration in Terrestrial Ecosystems of China

Phytolith-Occluded Carbon (PhytOC), a relatively stable carbon fraction, plays an important role in biogeochemical carbon cycle and mitigation of global warming. The formation mechanisms of PhytOC, the influence factors of phytolith carbon sequestration, the advances in study of phytolith carbon sequestration, and the management for enhancing the potential of phytolith carbon sequestration in terrestrial ecosystems of China were summarized in this review. Finally, future researches on phytolith carbon sequestration in terrestrial ecosystems of China were prospected. Climates, vegetation types, soil circumstances, the chemical compositions of the phytoliths and other factors will directly or indirectly affect the potential of phytolith carbon sequestration. In China, the PhytOC production quantity in grassland, cropland, forest, wetland and shrub ecosystems is (0.6±0.1)×10⁶,(4.9±1.7)×10⁶,(1.9±0.4)×10⁶,(0.6±0.5)×10⁶ and (1.3±0.3)×10⁶ t CO₂/a, respectively. Application of silicon-containing fertilizer, cultivation of high-silicon plant, and traditional enhancement of the plant net primary productivity can significantly improve the potential of phytolith carbon sequestration in terrestrial ecosystems of China. Future studies should focus more on ①the mechanisms of phytolith formation in different plants, ②the phytolith carbon sequestration in underground parts of plants from different terrestrial ecosystems, ③the quantification of soil PhytOC in different terrestrial ecosystems. Furthermore, more comprehensive, economical and reasonable management practices of improving the potential of phytolith carbon sequestration should also be further studied in different terrestrial ecosystems.     

围封对沙漠化草地土壤理化性质和固碳潜力恢复的影响

过度放牧是科尔沁沙地退化的主要原因,禁牧围封可以有效地控制牲畜对植被-土壤系统的破坏,促进退化生态系统的有效恢复。以过度放牧后的沙漠化草地为对象,调查了禁牧围封13年后沙漠化草地土壤理化性质的变化特征,并分析了围封对土壤固碳潜力的影响。结果表明：（1）沙漠化草地围封13年后,土壤砂粒含量减少、粉粒和黏粒含量增加,且粉粒增加最为明显,平均含量增加123%;土壤容重在不同土壤深度均呈下降趋势。（2）围封后土壤有机质、全氮、速效氮和速效钾含量呈增加趋势,分别增加了102%、97%、123%和24%,但土壤有效磷和缓效钾呈减少趋势;土壤pH显著升高,阳离子交换量呈现增加趋势。（3）除土壤有效铁外,其余有效微量元素包括有效铜、有效锰和有效锌平均含量均呈增加趋势,分别增加44%、30%和82%。（4）土壤有机质与pH值、阳离子交换量、全氮、速效氮、速效钾、有效铜、有效锰、有效锌含量呈显著正相关关系。（5）沙漠化草地围封13年后,100 cm深度土壤有机碳储量增加393.45 g·m^-2,碳截存速率为30.27 gC·m^-2·a^-1。对于因持续过度放牧所导致的严重退化草地,禁牧围封可有效促进土壤有机质、养分和微量元素的增加,影响土壤质地及固碳潜力等的变化,但严重退化沙漠化草地的恢复需要一个长期的过程,土壤有机碳储量要恢复到科尔沁非沙漠化草地水平至少需要百年的时间尺度。