This study explores interactions between As and Fe(III) minerals, predominantly schwertmannite and jarosite, in acid mine drainage (AMD) via observations at a former mine site combined with mineral formation and transformation experiments. Our objectives were to examine the effect of As on Fe(III) mineralogy in strongly acidic AMD while also considering associated controls on As mobility. AMD at the former mine site was strongly acidic (pH 2.4 to 2.8), with total aqueous Fe and As decreasing down the flow-path from ∼400 to ∼20 mg L^–1 and ∼33,000 to ∼150 μg L^–1, respectively. This trend was interrupted by a sharp rise in aqueous As(III) and Fe(II) caused by reductive dissolution of As-bearing Fe(III) phases in a sediment retention pond. Attenuation of Fe and As mobility occurred via formation of As(V)-rich schwertmannite, As(V)-rich jarosite, and amorphous ferric arsenate (AFA), resulting in solid-phase As concentrations spanning ∼13 to ∼208 g kg^–1. Schwertmannite and jarosite retained As(V) predominantly by structural incorporation involving AsO₄-for-SO₄ substitution at up to ∼40 and ∼22 mol %, respectively. Arsenic strongly influenced Fe(III) mineral formation, with high As(V) concentrations causing formation of AFA over schwertmannite. Arsenic also strongly influenced Fe(III) mineral evolution over time. In particular, increasing levels of As(V) incorporation within schwertmannite were shown, for the first time, to enhance the transformation of schwertmannite to jarosite. This significant discovery necessitates a re-evaluation of the prevailing paradigm that As(V) retards schwertmannite transformation.

中文翻译：

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砷对酸性矿山排水中 Schwertmannite 和 Jarosite 形成的影响以及对砷迁移率的耦合影响

本研究通过对前矿场的观察结合矿物形成和转化实验，探讨了酸性矿山排水 (AMD) 中 As 和 Fe(III) 矿物（主要是施维特曼铁矿和黄钾铁矾）之间的相互作用。我们的目标是检查 As 对强酸性 AMD 中 Fe(III) 矿物学的影响，同时还考虑对 As 迁移率的相关控制。前矿场的 AMD 呈强酸性（pH 2.4 至 2.8），总含水 Fe 和 As 沿着流路从~400 至~20 mg L ^–1和~33,000 至~150 μg L ^–1， 分别。这种趋势被沉积物滞留池中含砷 Fe(III) 相还原溶解引起的含水 As(III) 和 Fe(II) 的急剧上升所中断。通过形成富含 As(V) 的施韦特曼铁矿、富含 As(V) 的黄钾铁矾和无定形砷酸铁 (AFA)，Fe 和 As 的流动性减弱，导致固相 As 浓度范围为 ~13 至 ~208 g kg ^{– 1} . Schwertmannite 和黄钾铁矾主要通过涉及 AsO ₄ -for-SO _{4 的}结构掺入保留 As(V)取代率分别高达 ~40 和 ~22 mol%。砷强烈影响 Fe(III) 矿物的形成，高 As(V) 浓度导致 AFA 在施维特曼石上的形成。随着时间的推移，砷也强烈影响 Fe(III) 矿物的演化。特别是，首次显示在施韦特曼铁矿中掺入 As(V) 的水平增加，以促进施韦特曼铁矿向黄钾铁矾的转化。这一重大发现需要重新评估 As(V) 阻碍施维特曼石转变的普遍范式。