Skousen J, Simmons J, McDonald L M, Ziemkiewicz P
Plant and Soil Sciences, National Mine Land Reclamation Center, West Virginia University, Morgantown, WV 26506, USA.
J Environ Qual. 2002 Nov-Dec;31(6):2034-44. doi: 10.2134/jeq2002.2034.
Acid-base accounting (ABA) is an analytical procedure that provides values to help assess the acid-producing and acid-neutralizing potential of overburden rocks prior to coal mining and other large-scale excavations. This procedure was developed by West Virginia University scientists during the 1960s. After the passage of laws requiring an assessment of surface mining on water quality, ABA became a preferred method to predict post-mining water quality, and permitting decisions for surface mines are largely based on the values determined by ABA. To predict the post-mining water quality, the amount of acid-producing rock is compared with the amount of acid-neutralizing rock, and a prediction of the water quality at the site (whether acid or alkaline) is obtained. We gathered geologic and geographic data for 56 mined sites in West Virginia, which allowed us to estimate total overburden amounts, and values were determined for maximum potential acidity (MPA), neutralization potential (NP), net neutralization potential (NNP), and NP to MPA ratios for each site based on ABA. These values were correlated to post-mining water quality from springs or seeps on the mined property. Overburden mass was determined by three methods, with the method used by Pennsylvania researchers showing the most accurate results for overburden mass. A poor relationship existed between MPA and post-mining water quality, NP was intermediate, and NNP and the NP to MPA ratio showed the best prediction accuracy. In this study, NNP and the NP to MPA ratio gave identical water quality prediction results. Therefore, with NP to MPA ratios, values were separated into categories: <1 should produce acid drainage, between 1 and 2 can produce either acid or alkaline water conditions, and >2 should produce alkaline water. On our 56 surface mined sites, NP to MPA ratios varied from 0.1 to 31, and six sites (11%) did not fit the expected pattern using this category approach. Two sites with ratios <1 did not produce acid drainage as predicted (the drainage was neutral), and four sites with a ratio >2 produced acid drainage when they should not have. These latter four sites were either mined very slowly, had nonrepresentative ABA data, received water from an adjacent underground mine, or had a surface mining practice that degraded the water. In general, an NP to MPA ratio of <1 produced mostly acid drainage sites, between 1 and 2 produced mostly alkaline drainage sites, while NP to MPA ratios >2 produced alkaline drainage with a few exceptions. Using these values, ABA is a good tool to assess overburden quality before surface mining and to predict post-mining drainage quality after mining. The interpretation from ABA values was correct in 50 out of 52 cases (96%), excluding the four anomalous sites, which had acid water for reasons other than overburden quality.
酸碱平衡核算（ABA）是一种分析程序，它能提供相关数值，以帮助在煤矿开采和其他大规模挖掘之前评估覆盖岩层产生酸性物质和中和酸性物质的潜力。该程序由西弗吉尼亚大学的科学家在20世纪60年代开发。在通过要求评估地表采矿对水质影响的法律之后，ABA成为预测采矿后水质的首选方法，并且地表煤矿的许可决策很大程度上基于ABA确定的数值。为了预测采矿后的水质，将产生酸性物质的岩石量与中和酸性物质的岩石量进行比较，从而得出该场地水质（酸性或碱性）的预测结果。我们收集了西弗吉尼亚州56个采矿场地的地质和地理数据，这使我们能够估算总覆盖层数量，并根据ABA为每个场地确定最大潜在酸度（MPA）、中和潜力（NP）、净中和潜力（NNP）以及NP与MPA的比率。这些数值与采矿场地上泉水或渗水的采矿后水质相关联。覆盖层质量通过三种方法确定，宾夕法尼亚州研究人员使用的方法在覆盖层质量方面显示出最准确的结果。MPA与采矿后水质之间的关系较差，NP处于中等水平，而NNP以及NP与MPA的比率显示出最佳的预测准确性。在本研究中，NNP和NP与MPA的比率给出了相同的水质预测结果。因此，根据NP与MPA的比率，将数值分为几类：<1应产生酸性排水，1至2之间可能产生酸性或碱性水条件，>2应产生碱性水。在我们的56个地表采矿场地中，NP与MPA的比率从0.1到31不等，有六个场地（11%）不符合使用此分类方法的预期模式。两个比率<1的场地并未如预测那样产生酸性排水（排水呈中性），四个比率>2的场地在不应产生酸性排水时却产生了酸性排水。后四个场地要么开采速度非常缓慢，要么有不具代表性的ABA数据，要么从相邻的地下矿井接收水，要么有一种会使水质恶化的地表采矿作业方式。总体而言，NP与MPA的比率<1的场地大多产生酸性排水，1至2之间的场地大多产生碱性排水，而NP与MPA的比率>2的场地除少数例外产生碱性排水。利用这些数值，ABA是在地表采矿前评估覆盖层质量以及预测采矿后排水质量的良好工具。在52个案例中的50个（96%）中，不包括四个因覆盖层质量以外原因产生酸性水的异常场地，ABA数值的解释是正确的。
