Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2E3, Canada.
Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada.
Sci Total Environ. 2016 Nov 15;571:699-710. doi: 10.1016/j.scitotenv.2016.07.039. Epub 2016 Jul 19.
Froth treatment thickened tailings (TT) are a waste product of bitumen extraction from surface-mined oil sands ores. When incubated in a laboratory under simulated moist oxic environmental conditions for 450d, two different types of TT (TT1 and TT2) exhibited the potential to generate acid rock drainage (ARD) by producing acid leachate after 250 and 50d, respectively. We report here the release of toxic metals from TT via ARD, which could pose an environmental threat if oil sands TT deposits are not properly managed. Trace metal concentrations in leachate samples collected periodically revealed that Mn and Sr were released immediately even before the onset of ARD. Spikes in Co and Ni concentrations were observed both pre-ARD and during active ARD, particularly in TT1. For most elements measured (Fe, Cr, V, As, Cu, Pb, Zn, Cd, and Se), leaching was associated with ARD production. Though equivalent acidification (pH2) was achieved in leachate from both TT types, greater metal release was observed from TT2 where concentrations reached 10,000ppb for Ni, 5000ppb for Co, 3000ppb for As, 2000ppb for V, and 1000ppb for Cr. Generally, metal concentrations decreased in leachate with time during ARD and became negligible by the end of incubation (450d) despite appreciable metals remaining in the leached TT. These results suggest that using TT for land reclamation purposes or surface deposition for volume reduction may unfavorably impact the environment, and warrants application of appropriate strategies for management of pyrite-enriched oil sands tailings streams.
泡沫处理尾矿（TT）是从露天开采的油砂矿石中提取沥青的一种副产品。当在实验室中模拟潮湿有氧环境条件下孵育约 450 天时，两种不同类型的 TT（TT1 和 TT2）分别在 250 天和 50 天后产生酸性浸出液，显示出产生酸性岩石排水（ARD）的潜力。我们在这里报告了通过 ARD 从 TT 释放有毒金属的情况，如果不对油砂 TT 矿床进行妥善管理，这可能会对环境构成威胁。定期收集的浸出液样品中的痕量金属浓度表明，即使在 ARD 发生之前，Mn 和 Sr 也会立即释放。在 ARD 之前和活跃的 ARD 期间都观察到 Co 和 Ni 浓度的峰值，特别是在 TT1 中。对于测量的大多数元素（Fe、Cr、V、As、Cu、Pb、Zn、Cd 和 Se），浸出与 ARD 生产有关。尽管两种 TT 类型的浸出液都达到了等效的酸化（pH2），但 TT2 中释放的金属量更大，其中 Ni 的浓度达到 10000ppb，Co 达到 5000ppb，As 达到 3000ppb，V 达到 2000ppb，Cr 达到 1000ppb。通常，在 ARD 期间，金属浓度随时间在浸出液中下降，并且在孵育结束时（约 450 天）变得可以忽略不计，尽管在浸出的 TT 中仍存在相当数量的金属。这些结果表明，使用 TT 进行土地复垦或表面沉积以减少体积可能会对环境产生不利影响，因此需要应用适当的策略来管理富含黄铁矿的油砂尾矿流。
