Mineralogical controls on environmental mobility of arsenic from historic mine processing residues, New Zealand
Mineralogical controls on environmental mobility of arsenic from historic mine processing residues, New Zealand
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DOI：
10.1016/j.apgeochem.2007.12.030
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发表时间：
2008-06-01
影响因子：
3.4
通讯作者：
Craw, Dave
中科院分区：
文献类型：
--
作者：
Haffert, Laura;Craw, Dave
1908年至1951年，新西兰黑水Au矿进行了毒砂矿石的加工，矿山关闭后没有进行恢复。固体加工残留物中的高As浓度（高达40重量% As）是由于次生As矿物。研究中心的pH值范围从4.1到近中性。最初，所有经过加工的砷都是以毒砂（三氧化二砷多晶型物，As-III）的形式存在，这是毒砂焙烧的副产品。在焙烧炉附近，由于砷石溶解过程中溶解的砷浓度高，臭葱石沉淀。臭葱石的形成有两个主要后果。首先，臭葱石沉淀物胶结焙烧炉区域附近的地面，从而产生不可渗透的表面壳（高达30重量% As）并将风化的毒砂颗粒包封在胶结物内。其次，臭葱石的形成暂时固定了一些溶解的砷，这是在附近的毒砂溶解产生的。当所有可用的毒砂都溶解时，臭葱石变得可溶，并且溶解的As浓度由臭葱石溶解度控制，其比毒砂溶解度低至少两个数量级。下游Eh条件低于As-V/As-III边界，因此臭葱石不会沉淀，溶解的As浓度受砷石溶解度控制。溶解砷在某些地方高达52 mg/L，超过世界卫生组织现行饮用水指南0.01 mg/L的5200倍。这项研究表明，溶解砷浓度排放沃茨在历史矿山网站是依赖于处理技术和相关的矿物。(C)2008爱思唯尔有限公司保留所有权利。
Processing of arsenopyrite ore took place at Blackwater Au mine, New Zealand, between 1908 and 1951 and no rehabilitation was undertaken after mine closure. High As concentrations in solid processing residues (up to 40 wt% As) are due to secondary As minerals. Site pH regimes vary from 4.1 to circum-neutral. Originally, all processed As was present as arsenolite (arsenic trioxide polymorph, As-III), a by-product of arsenopyrite roasting. Near the roaster, scorodite precipitated as a result of the high dissolved As concentration during arsenolite dissolution. The formation of scorodite has two major consequences. Firstly, the scorodite precipitate cements the ground in the vicinity of the roaster area, thereby creating an impermeable surface crust (up to 30 wt% As) and encapsulating weathered arsenolite grains within the cement. Secondly, formation of scorodite temporarily immobilizes some of the dissolved As that is generated during nearby arsenolite dissolution. Where all the available arsenolite has dissolved, scorodite becomes soluble, and the dissolved As concentrations are controlled by scorodite solubility, which is at least two orders of magnitudes lower than arsenolite solubility. Downstream Eh conditions fall below the As-v/As-III boundary, so that scorodite does not precipitate and dissolved As concentrations are controlled by arsenolite solubility. Dissolved As reaches up to 52 mg/L in places, and exceeds the current WHO drinking water guideline of 0.01 mg/L by 5200 times. This study shows that dissolved As concentrations in discharge waters at historic mine sites are dependent on the processing technology and associated mineralogy. (C) 2008 Elsevier Ltd. All rights reserved.