Boone Pickens School of Geology, 105 Noble Research Center, OK State University, Stillwater, OK 74078, USA.
Boone Pickens School of Geology, 105 Noble Research Center, OK State University, Stillwater, OK 74078, USA.
Sci Total Environ. 2016 Mar 1;545-546:57-66. doi: 10.1016/j.scitotenv.2015.12.043. Epub 2015 Dec 31.
We investigated the spatial variations in the concentrations of dissolved inorganic carbon (DIC), the stable carbon isotopic composition (δ(13)C) of DIC and the δ(13)C of carbonate precipitated from neutral mine drainage interacting with the atmospheric CO2(g). We assessed the chemical, DIC and δ(13)CDIC evolution of the mine drainage and the δ(13)C evolution of carbonate precipitates for a distance of 562 m from the end of an 8 km tunnel that drains a mine. Our results show that as the mine drainage interacts with atmospheric CO2(g) the outgassing of CO2 due to the high initial partial pressure of CO2 (pCO2) causes the DIC to evolve under kinetic conditions followed by equilibration and then under equilibrium conditions. The carbonate evolution was characterized by spatial increases in pH, decreasing concentrations of Ca(2+) and DIC and by the precipitation of carbonate. The δ(13)CDIC showed a larger enrichment from the tunnel exit to 38 m, moderate continuous enrichment to 318 m and almost no enrichment to 562 m. On the other hand, the δ(13)C of the carbonate precipitates also showed large enrichment from the tunnel exit to 38 m, moderate enrichment to 318 m after which the δ(13)C remained nearly constant. The enrichment in the δ(13)C of the DIC and the carbonate precipitates from 0 to 38 m from kinetic fractionation caused by CO2(g) outgassing was followed by a mix of kinetic fractionation and equilibrium fractionation controlled by carbon exchange between DIC and atmospheric CO2(g) to 318 m and then by equilibrium fractionation from 318 to 562 m. From the carbonate evolution in this neutral mine drainage, we estimated that 20% of the carbon was lost via CO2 outgassing, 12% was sequestered in sediments in the drainage ponds from calcite precipitation and the remainder 68% was exported to the local stream.
我们研究了溶解无机碳（DIC）浓度、DIC 的稳定碳同位素组成（δ(13)C）和与大气 CO2(g) 相互作用的中性矿山排水中碳酸盐沉淀的 δ(13)C 的空间变化。我们评估了矿山排水的化学、DIC 和 δ(13)CDIC 演化以及从 8 公里长的隧道末端延伸 562 米处的碳酸盐沉淀的 δ(13)C 演化。我们的结果表明，随着矿山排水与大气 CO2(g) 相互作用，由于初始 CO2 分压（pCO2）高，CO2 的逸出导致 DIC 在动力学条件下演化，然后达到平衡，最后达到平衡条件。碳酸盐的演化特征是 pH 值升高，Ca(2+)和 DIC 浓度降低，碳酸盐沉淀。δ(13)CDIC 从隧道出口到 38 米处表现出较大的富集，在 318 米处连续适度富集，在 562 米处几乎没有富集。另一方面，碳酸盐沉淀的 δ(13)C 也从隧道出口到 38 米处表现出较大的富集，在 318 米处适度富集，之后 δ(13)C 几乎保持不变。由于 CO2(g) 逸出引起的动力学分馏作用，DIC 和碳酸盐沉淀的 δ(13)C 从 0 到 38 米处发生富集，随后是动力学分馏和由 DIC 和大气 CO2(g) 之间的碳交换控制的平衡分馏的混合作用，从 318 米到 562 米处发生平衡分馏。从这种中性矿山排水中的碳酸盐演化，我们估计有 20%的碳通过 CO2 逸出损失，12%的碳通过方解石沉淀在排水池中被固定，其余的 68%的碳被输送到当地溪流。
