Seasonal and spatial distribution of mercury in stream sediments from Almadén mining district

A significant risk of mercury (Hg) transfer from sediments to the aquatic environment is identified, particularly during dry periods, due to increased organic Hg fractions. The study, conducted in Almadén's Valdeazogues River—one of the world's largest Hg mining districts—revealed that while Hg is predominantly stored as residual cinnabar, a substantial organic fraction also plays a critical role. Using BCR sequential extraction on nine sites over six time periods, researchers found seasonal variations: wet seasons favor residual Hg, whereas dry seasons enhance organic Hg availability, heightening ecological risk. Exchangeable/carbonate and Fe-Mn oxide phases showed minimal seasonal susceptibility. The findings underscore the need for seasonal monitoring to mitigate Hg's impact on aquatic ecosystems.

Garcia-Ordiales, E., Higueras, P., Esbrí, J. M., Roqueñí, N., & Loredo, J. (2018). Seasonal and spatial distribution of mercury in stream sediments from Almadén mining district. Geochemistry: Exploration, Environment, Analysis, 19(2), 121–128. https://doi.org/10.1144/geochem2018-029