Vigneault B, Campbell P G, Tessier A, De Vitre R
INRS-Eau, Université du Quebec, Sainte-Foy, Canada.
Water Res. 2001 Mar;35(4):1066-76. doi: 10.1016/s0043-1354(00)00331-6.
The objective of this study was to assess the effectiveness of an engineered shallow water cover in reducing the oxidation of sulfidic mine tailings and thus preventing the development of acid rock drainage. Fresh tailings were submerged under a 0.3-m water cover in experimental field cells. From 1996 to 1998, we followed the chemistry of the interstitial water near the tailings-overlying water interface using in situ dialysis, and determined pH and dissolved oxygen (DO) profiles across the tailing water interface using micro-electrodes. Penetration of DO into the tailings was limited to <7 mm, even in the presence of DO produced by benthic periphyton. Anoxia in the tailings was further demonstrated by the appearance of dissolved sigmaH2S, Fe and Mn in pore water at depths -1.5 cm below the interface. However, there was clear evidence of surface oxidation of the mine tailings at the mm scale (i.e., DO depletion, coupled with localized increases in [H+] and [SO4(2-)]). Mobilization of Cd and Zn from this surface layer was indicated by the presence of sub-surface peaks in the concentrations of these two metals in the tailings interstitial water and by a change in their solid phase partitioning from refractory to more labile fractions. In contrast, mobilization of Cu from tailings was less evident. Unlike previous reports, which suggested that submerged tailings were effectively inert, our results show alteration of the superficial layer over time.
本研究的目的是评估一种人工浅水覆盖层在减少硫化矿尾矿氧化从而防止酸性岩排水形成方面的有效性。新鲜尾矿被置于实验场地单元中0.3米深的水覆盖层之下。从1996年到1998年，我们使用原位透析法跟踪尾矿 - 上覆水界面附近间隙水的化学性质，并使用微电极测定尾矿水界面上的pH值和溶解氧（DO）剖面。即使在存在底栖附生植物产生的溶解氧的情况下，溶解氧渗入尾矿的深度也限制在<7毫米。尾矿中孔隙水在界面以下-1.5厘米深度处出现溶解态的总硫化氢、铁和锰，进一步证明了尾矿中的缺氧状态。然而，有明确证据表明在毫米尺度上尾矿存在表面氧化现象（即溶解氧消耗，同时[H⁺]和[SO₄²⁻]局部增加）。尾矿间隙水中这两种金属的浓度在次表层出现峰值，以及它们的固相分配从难熔部分变为更不稳定部分，表明镉和锌从该表层发生了迁移。相比之下，尾矿中铜的迁移不太明显。与之前认为淹没尾矿实际上是惰性的报道不同，我们的结果表明表层随时间发生了变化。
