The hydromagnesite playas of Atlin, British Columbia, Canada: A biogeochemical model for CO2 sequestration
The hydromagnesite playas of Atlin, British Columbia, Canada: A biogeochemical model for CO2 sequestration
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DOI：
10.1016/j.chemgeo.2009.01.012
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发表时间：
2008-07
期刊：
影响因子：
3.9
通讯作者：
I. Power;S. Wilson;J. Thom;G. Dipple;J. Gabites;G. Southam
中科院分区：
文献类型：
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作者：
I. Power;S. Wilson;J. Thom;G. Dipple;J. Gabites;G. Southam
人为温室气体排放可以通过硅酸镁矿物的碳化形成碳酸镁矿物来封存二氧化碳 (CO2) 来抵消。加拿大不列颠哥伦比亚省阿特林的水菱镁矿 [Mg5(CO3)4(OH)2·4H2O] 沼泽地提供了一个在流域范围内研究矿物碳化作用的自然模型。在近地表条件下，二氧化碳被参与基岩风化和碳酸盐矿物沉淀的微生物以生物地球化学方式封存。本研究的目的是在二氧化碳封存生物地球化学模型的背景下描述地下水补给区的风化状况和普拉亚的沉积环境，重点关注加速矿物碳化的微生物过程。具有超镁铁质基岩的地区，例如阿特林，代表了矿物碳酸化原料的最佳潜在来源。与下面的超镁铁质母质相比，土壤剖面的元素组成显示出 MgO 的显着损耗和 SiO2 的富集。将抛光的蛇纹石立方体放置在地下水补给区针叶林土壤的有机层中三年。检索后，通过扫描电子显微镜观察，立方体表面已被与表面凹坑相关的细菌定植。土壤中有机物的降解产生了螯合剂和酸，这些螯合剂和酸促进了蛇纹岩的化学风化，预计会对阿特林富含镁的基岩产生类似的影响。位于东南部普拉亚湿地附近的一口井地下水的稳定碳同位素表明，约 12% 的溶解无机碳现代起源于土壤二氧化碳。水菱镁矿高原的矿物学和同位素地球化学表明，存在三种不同的沉积环境：（1）湿地，其特征是通过蒸发浓缩的水中碳酸盐矿物的生物辅助沉淀，（2）导致形成固结文石沉积物的孤立湿地部分，以及（3）出现的草原环境，其中蒸发产生水菱镁矿堆。对东南部普拉亚湿地沉积物的检查表明，蓝藻、硫酸盐还原菌和硅藻有助于为碳酸盐矿物的沉淀创造有利的地球化学条件。阿特林遗址作为生物地球化学模型，对于利用被动微生物、地球化学和物理过程创建碳汇具有重要意义，这些碳汇有助于硅酸镁的矿物碳化。这些过程可以通过在人工或自然环境中创造类似于阿特林遗址的条件来实现二氧化碳封存的目的，其中适合碳酸镁沉淀。鉴于世界各地存在大量富含镁的基岩，这项研究对于降低大气二氧化碳浓度和应对全球气候变化具有重要意义。
Anthropogenic greenhouse gas emissions may be offset by sequestering carbon dioxide (CO2) through the carbonation of magnesium silicate minerals to form magnesium carbonate minerals. The hydromagnesite [Mg5(CO3)4(OH)2·4H2O] playas of Atlin, British Columbia, Canada provide a natural model to examine mineral carbonation on a watershed scale. At near surface conditions, CO2is biogeochemically sequestered by microorganisms that are involved in weathering of bedrock and precipitation of carbonate minerals. The purpose of this study was to characterize the weathering regime in a groundwater recharge zone and the depositional environments in the playas in the context of a biogeochemical model for CO2sequestration with emphasis on microbial processes that accelerate mineral carbonation. Regions with ultramafic bedrock, such as Atlin, represent the best potential sources of feedstocks for mineral carbonation. Elemental compositions of a soil profile show significant depletion of MgO and enrichment of SiO2in comparison to underlying ultramafic parent material. Polished serpentinite cubes were placed in the organic horizon of a coniferous forest soil in a groundwater recharge zone for three years. Upon retrieval, the cube surfaces, as seen using scanning electron microscopy, had been colonized by bacteria that were associated with surface pitting. Degradation of organic matter in the soil produced chelating agents and acids that contributed to the chemical weathering of the serpentinite and would be expected to have a similar effect on the magnesium-rich bedrock at Atlin. Stable carbon isotopes of groundwater from a well, situated near a wetland in the southeastern playa, indicate that ∼12% of the dissolved inorganic carbon has a modern origin from soil CO2. The mineralogy and isotope geochemistry of the hydromagnesite playas suggest that there are three distinct depositional environments: (1) the wetland, characterized by biologically-aided precipitation of carbonate minerals from waters concentrated by evaporation, (2) isolated wetland sections that lead to the formation of consolidated aragonite sediments, and (3) the emerged grassland environment where evaporation produces mounds of hydromagnesite. Examination of sediments within the southeastern playa–wetland suggests that cyanobacteria, sulphate reducing bacteria, and diatoms aid in producing favourable geochemical conditions for precipitation of carbonate minerals. The Atlin site, as a biogeochemical model, has implications for creating carbon sinks that utilize passive microbial, geochemical and physical processes that aid in mineral carbonation of magnesium silicates. These processes could be exploited for the purposes of CO2sequestration by creating conditions similar to those of the Atlin site in environments, artificial or natural, where the precipitation of magnesium carbonates would be suitable. Given the vast quantities of Mg-rich bedrock that exist throughout the world, this study has significant implications for reducing atmospheric CO2concentrations and combating global climate change.