The State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi Province 712100, PR China; Department of Civil, Geological and Environmental Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK S7N 5A9, Canada; CAS Center for Excellence in Quaternary Science and Global Change, Xian, Shaanxi 710061, China.
Department of Civil, Geological and Environmental Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK S7N 5A9, Canada.
Sci Total Environ. 2021 Jul 20;779:146429. doi: 10.1016/j.scitotenv.2021.146429. Epub 2021 Mar 13.
Knowledge of the controls affecting the release of contaminants from waste rock dumps is critical for developing strategies to mitigate downstream impacts on water quality. In this study, a three-dimensional model of a large coal waste rock dump constructed in the Elk Valley, British Columbia, Canada was developed to capture the impact of construction history (1981-2012) and solute transport on nitrate (NO) release over a 100-year timeframe. The model consisted of 21, one-dimensional finite element models that represented the temporal evolution of the dump. Nitrate, derived from undetonated blast products, was assumed to be present at the time of waste rock placement and was simulated as a conservative species. The simulated pattern of NO release to the surface water receptor occurred approximately 8 years before its measured arrival. This time lag is attributed to displacement of the water within a basal alluvial aquifer by dump effluent. The simulated patterns of historic releases corrected for the 8-year time lag, compare favourably with monitoring data and suggest the dominant hydrogeological and geochemical mechanisms are captured in the model. The model indicated the flushing of NO from the dump should be complete by about 2042 with a peak effluent concentration of NO in 2008. The addition of reclamation covers to the model resulted in an immediate decrease in the annual NO loading rate but extended the time frame for NO release from the dump relative to the no cover case. The model also showed that the timing of cover placement had little impact on NO release relative to the no cover case due to long duration of waste rock placement (~30 years) over a relatively large footprint.
了解影响废石堆中污染物释放的控制因素对于制定减轻对水质下游影响的策略至关重要。在这项研究中，为了捕捉施工历史（1981-2012 年）和溶质运移对硝酸盐（NO）在 100 年时间内释放的影响，建立了加拿大不列颠哥伦比亚省 Elk Valley 大型煤矸石堆的三维模型。该模型由 21 个一维有限元模型组成，代表了堆体的时间演化。假定在废石堆放时存在来源于未爆炸的爆破产物的硝酸盐，并将其模拟为保守物质。NO 释放到地表水受纳体的模拟模式大约在其测量到达之前 8 年发生。这种时间滞后归因于废石堆废水对基岩冲积含水层内水的置换。经 8 年时间滞后修正后的历史排放量模拟模式与监测数据吻合较好，表明模型中捕获了主要的水文地质和地球化学机制。该模型表明，到 2042 年左右，NO 从堆体中的冲洗应该完成，2008 年 NO 的峰值排放浓度。在模型中添加复垦覆盖层会立即降低每年的 NO 加载速率，但与无覆盖层的情况相比，会延长从堆体中释放 NO 的时间框架。该模型还表明，由于废石堆放时间较长（约 30 年）且占地面积较大，覆盖层的放置时间相对于无覆盖层的情况对 NO 释放的影响很小。
