Department Exploitation and Prospecting of Mines, University of Oviedo, Asturias, Spain.
Department Biology of Organisms and Systems, University of Oviedo, Asturias, Spain.
Environ Sci Pollut Res Int. 2024 Feb;31(7):11081-11095. doi: 10.1007/s11356-024-31888-z. Epub 2024 Jan 13.
Mercury (Hg) is a toxic metal that can cause adverse effects for the health of ecosystems. The Caudal River is one of the main rivers in the Asturias region (NW Spain), whose basin is highly anthropized, hosting several Hg mines, closed in the last century. Arsenic (As) is also found in the mineral paragenesis of the Hg deposits, posing a greater environmental risk. In the mining sites, remaining old facilities and tailings continue to release these elements into the environment. In this work, samples of fluvial sediments and water were taken, both in areas affected by anthropic activity and in pristine areas, in order to establish the background levels for the critical elements. The mineralogical study of the sediments, combined with EDS microanalysis, is useful to identify mineralogical traps such as Fe oxides or clays to retain the As. The As content in all sampled sediments is above the threshold effect levels (TEL), the possible effect range within which adverse effects occasionally occur, according to the Canadian Sediment Quality Guidelines for the Protection of Aquatic Life. This fact is related to a naturally high geochemical background in the basin, due to the existing mineral deposits. The PEL threshold (the probable effect range within which adverse effects frequently occur) is exceeded by more than an order of magnitude in the sediments downstream of the Hg mines. In these points, the As content in the water, exceeding 700 μg L As, is also above the quality standard established in Spanish legislation. As a result, the Caudal River tributaries in the lower part of the basin do not reach a good ecological state, according to the Hydrological Planning Office, and in some cases their state is deficient, showing low richness and high dominance of macroinvertebrates. Although the concentrations decrease with distance from the source, these findings justify the low ecological quality of the affected watercourses.
汞（Hg）是一种有毒金属，会对生态系统的健康产生不利影响。考达尔河是西班牙西北部阿斯图里亚斯地区的主要河流之一，其流域高度人为化，有几个汞矿，这些汞矿在上个世纪已经关闭。砷（As）也存在于汞矿床的矿物共生体中，构成了更大的环境风险。在采矿区，遗留的旧设施和尾矿仍在向环境中释放这些元素。在这项工作中，采集了河流沉积物和水的样本，这些样本取自受人为活动影响的地区和原始地区，以便为关键元素确定背景水平。沉积物的矿物学研究，结合 EDS 微分析，有助于识别矿物学陷阱，如铁氧化物或粘土，以保留砷。所有采样沉积物中的砷含量都超过了阈效应水平（TEL），根据加拿大保护水生生物的沉积物质量指南，这是偶尔发生不利影响的可能影响范围。这一事实与盆地中存在的矿物矿床导致的自然高地球化学背景有关。在汞矿下游的沉积物中，超过 PEL 阈值（经常发生不利影响的可能影响范围）一个数量级以上。在这些点上，水中的砷含量超过 700μg/L 的砷，也超过了西班牙立法规定的质量标准。因此，根据水文规划办公室的数据，流域下游的考达尔河支流没有达到良好的生态状态，在某些情况下，它们的状态是不足的，表现为底栖无脊椎动物的丰富度低和优势度高。尽管浓度随距离源的距离而降低，但这些发现证明了受影响水道的低生态质量是合理的。
