Laboratory Investigations of Weathering of Soils from Mammoth Mountain, CA, a Naturally CO2-Impacted Field Site

详细信息    查看全文

• 作者：Helen Sanchez ; Gustavo Menezes ; Andre Ellis ; Claudia Espinosa-Villegas ; Crist Khachikian
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：October 21, 2014
• 年：2014
• 卷：48
• 期：20
• 页码：12056-12062
• 全文大小：358K
• ISSN：1520-5851

文摘

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 鈭?,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 m²/g vs 2.53 m²/g) and lower organic carbon content (9,550 mg/kg vs 35,550 mg/kg). Batch results indicated that lower pH values (鈭?) 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 Fe³⁺ 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.