In much of the world, seasonal weather patterns cause a flush of dissolved contaminants from mined areas at the beginning of wet seasons. However, on parts of New Zealand’s west coast, the annual rainfall exceeds 6000 mm/year, with frequent rain days regardless of season; in these conditions, chemically rich flushes are short-lived and subsequently diluted. We studied two historic underground mine sites on the Denniston Plateau. Historic drainages from the Coalbrookdale workings into the Cascade Mine area discharge between ≈ 100 and ≈ 1000 L/s, depending on rainfall volume and frequency. The frequent rain on the plateau dilutes the Coalbrookdale discharge waters, increasing its pH and decreasing dissolved AMD constituents. During short-term high rainfall events, the increased flow causes a flush of stored AMD for less than 10 h, with decreased pH and increased dissolved concentrations of AMD constituents. In contrast, historic drainage at the Sullivan Mine showed little response to rainfall and there was virtually no changes in chemistry during or after high rainfall events. While negative downstream impacts occur at both sites, this study showed that quantification of the variability within a site’s flow regime is critical in understanding the impact of a mine site’s AMD in high rainfall areas.

中文翻译：

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新西兰历史地下煤矿降雨增强酸性矿山排水的稀释过程

在世界大部分地区，季节性天气模式会在雨季开始时导致矿区溶解污染物大量涌出。然而，新西兰西海岸的部分地区，年降雨量超过6000毫米/年，无论季节如何，都有频繁的下雨天；在这些情况下，富含化学物质的冲洗液是短暂的，随后会被稀释。我们研究了丹尼斯顿高原上两个历史悠久的地下矿场。从 Coalbrookdale 工作区到 Cascade 矿区的历史排水量在 ≈ 100 和 ≈ 1000 L/s 之间，具体取决于降雨量和频率。高原上频繁的降雨稀释了 Coalbrookdale 排放水，提高了其 pH 值并降低了溶解性 AMD 成分。在短期高降雨事件期间，增加的流量导致储存的 AMD 冲刷不到 10 小时，随着 pH 值降低和 AMD 成分的溶解浓度增加。相比之下，沙利文矿的历史排水系统对降雨几乎没有反应，并且在高降雨事件期间或之后几乎没有化学变化。虽然两个站点都发生了负面的下游影响，但本研究表明，对站点流态变化的量化对于了解矿区 AMD 对高降雨区的影响至关重要。