Department of Civil Engineering, ‡Department of Geosciences and Environment, and §Department of Technology, California State University, Los Angeles , 5151 State University Drive, Los Angeles, California 90032, United States.
Environ Sci Technol. 2014 Oct 21;48(20):12056-62. doi: 10.1021/es501829z. Epub 2014 Sep 30.
The potential impacts of CO2 leakage from a natural subsurface reservoir on soil and water quality were studied. Field measurements of soil pore CO2 concentrations and visual inspection of plants at Mammoth Mountain, CA, allowed the demarcation of tree-kill and non-tree-kill zones, with CO2 concentrations >100,000 ppm and ∼ 1,000 ppm, respectively. Soils collected from six sites along a transect stretching from the center of the tree-kill zone to an equidistant point into the non-tree-kill zone were analyzed for surface area and organic carbon content. Batch and column leaching tests were conducted to determine the extent of weathering induced by the presence of CO2 in the aqueous solution. Soils deep into the tree-kill area exhibited significantly higher surface areas (10.67 m(2)/g vs 2.53 m(2)/g) and lower organic carbon content (9,550 mg/kg vs 35,550 mg/kg). Batch results indicated that lower pH values (∼ 2) released higher concentrations of Mg, Si, Fe, and As, while, for soils in the tree-kill zone, longer-term batch results indicated higher releases at the higher pH of 5.5. Column experiments were used to compare the effects of pH adjusted using HCl vs CO2. For pore volumes (PV) < 100, CO2 enhanced trace element release. For 100 < PV < 10,000 concentrations of elements in the two systems were equivalent and steady. At PV > 10,000, after a drop in pH in the CO2 system, larger amounts of Fe and As were released, suggesting a CO2-induced dissolution of Fe-silicates/clays and/or reductive dissolution of Fe(3+) that releases Fe-bound arsenic. The specific role of pore water-dissolved CO2 on the release of trace elements is hitherto unknown. However, interactions of pore-water CO2 and the minerals in the Mammoth Mountain soils can cause the release of environmental pollutants.
研究了从天然地下储层中 CO2 泄漏对土壤和水质的潜在影响。在加利福尼亚州猛犸山进行的土壤孔隙 CO2 浓度现场测量和对植物的目视检查，将树木死亡区和非树木死亡区分开，CO2 浓度分别大于 100000ppm 和大约 1000ppm。从沿树木死亡区中心延伸到非树木死亡区等距点的一条测线上的六个地点采集的土壤，用于分析表面积和有机碳含量。进行了批量和柱浸出试验，以确定存在于水溶液中的 CO2 引起的风化程度。深入树木死亡区的土壤表现出明显更高的表面积（10.67m2/g 对 2.53m2/g）和更低的有机碳含量（9550mg/kg 对 35550mg/kg）。批量结果表明，较低的 pH 值（约 2）释放出更高浓度的 Mg、Si、Fe 和 As，而对于树木死亡区的土壤，较长时间的批量结果表明在较高的 pH 值 5.5 下释放更高。柱实验用于比较使用 HCl 与 CO2 调节 pH 的效果。对于孔隙体积（PV）<100，CO2 增强了微量元素的释放。对于 100<PV<10000，两种系统中的元素浓度相等且稳定。在 PV>10000 时，在 CO2 系统中的 pH 下降后，释放出更多的 Fe 和 As，这表明 CO2 诱导的 Fe-硅酸盐/粘土溶解和/或 Fe（3+）的还原溶解释放了与 Fe 结合的砷。孔隙水溶解 CO2 对微量元素释放的具体作用尚不清楚。然而，孔隙水 CO2 与猛犸山土壤中矿物质的相互作用可能导致环境污染物的释放。
