Ilyashuk Boris, Ilyashuk Elena
Department of Ecology, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria.
ACS ES T Water. 2024 Nov 13;4(12):5264-5274. doi: 10.1021/acsestwater.4c00263. eCollection 2024 Dec 13.
Little is known to date about the processes governing natural acid rock drainage (NARD) generated by rock glaciers. We used paragneiss samples from a catchment with NARD generated by a rock glacier in the Italian Alps for long-term leaching experiments under conditions that are possible within rock glaciers. The findings clearly suggest that at a low acid neutralization capacity of the rock, the dissolution of sulfide minerals, even if they are present in trace amounts, may be the most important process that controls the groundwater acidity at 1 °C, a typical temperature of groundwater discharge from rock glaciers. The acidic conditions increase the solubility and mobility of aquifer lithology-specific trace elements, and concentrations of some heavy metals of geogenic origin (e.g., Mn and Ni) may greatly exceed health standards after a six month interaction of water with paragneisses. Diurnal freeze-thaw cycles were found to be 6-7 times more effective in transformation of coarse rock fragments to fine-grained debris with fresh, reactive mineral surfaces, compared with temperatures above freezing. Cyclic freezing favors an enhanced formation of amorphous silica, a highly effective adsorbent for metal ions, and its redissolution within unfrozen layers of rock glaciers may represent an additional source of trace elements.
迄今为止，关于岩石冰川产生的自然酸性岩石排水（NARD）的控制过程知之甚少。我们使用了来自意大利阿尔卑斯山一个集水区的副片麻岩样本，该集水区的岩石冰川产生了NARD，用于在岩石冰川内部可能出现的条件下进行长期淋溶实验。研究结果清楚地表明，在岩石的酸中和能力较低时，硫化物矿物的溶解，即使其含量微量，也可能是控制1°C（岩石冰川地下水排放的典型温度）下地下水酸度的最重要过程。酸性条件会增加含水层岩性特定微量元素的溶解度和迁移率，并且在水与副片麻岩相互作用六个月后，一些地质来源的重金属（如锰和镍）的浓度可能会大大超过健康标准。研究发现，与高于冰点的温度相比，昼夜冻融循环在将粗岩石碎片转化为具有新鲜、活性矿物表面的细粒碎屑方面的效果要高6至7倍。循环冻结有利于增强无定形二氧化硅的形成，无定形二氧化硅是一种对金属离子非常有效的吸附剂，其在岩石冰川未冻结层内的再溶解可能是微量元素的另一个来源。
