Mercury in sediments from a drainage catchment basin of the au mining district of El Triunfo, B.C.S., Mexico

In the drainage basin of the gold Mining District El Triunfo (MD-ET), around 800,000 tons of tailings are exposed in open air to seasonal tropical storms and oxidative weathering. This enhances the mobility of trace elements caused by winds and hurricanes in summer, when water runs through the normally arroyo (dry river). To determine the content and distribution of Hg along the dry river from the MD-ET towards its discharge into the Pacific Ocean, sediments were analysed with a Flow Injection Mercury System (FIMS). Results were validated with certified reference materials. Total Hg in tailings and the ashes from abandoned oven samples ranged between 336 µg kg⁻¹ and 54,900 µg kg⁻¹, respectively. However, arroyo concentrations were lower than average Earth’s crust concentrations in more than 45% of the samples. The Normalized Enrichment Factor distribution indicates that Hg was introduced anthropogenically, possibly by the artisanal extraction methods used historically.