Pablo L. Higueras received his PhD in Earth Sciences from the University of Granada (Spain) in 1994. He is the head of Instituto de Geología Aplicada in Universidad de Castilla-La Mancha and an academic of its School of Mines in Almadén (Ciudad Real). His research topics mainly include geochemistry, biogeochemistry, mining, potentially toxic elements, and mercury. In these fields, he and coworkers from all over the world have published some 150 JCR articles and have presented more than 250 communications in international conferences. Some selected references related with this article are as follows: 1. Gray, J.E.; Hines, M.E.; Higueras, P.L.; Adatto, I.; Lasorsa, B.K. (2004) Mercury Speciation and Microbial Transformations in Mine Wastes, Stream Sediments, and Surface Waters at the Almadén Mining District, Spain. Environmental Science and Technology, 38 (16), 4285–4292. https://doi.org/10.1021/es040359d. 2. Gray, J.E.; Plumlee, G.S.; Morman, S.; Higueras, P.L.; Crock, J.G.; Lowers, H.; Witten, M.L. (2010) In vitro studies evaluating leaching of mercury in mine waste calcine using simulated human body fluids. Environmental Science and Technology, 44: 4782–4788. https://doi.org/10.1021/es1001133.