Spatial and temporal variability of mercury in soil contaminated by artisanal gold mining

• Grant number: 23/17502-0
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• Start date: August 01, 2024
• End date: November 30, 2024
• Field of knowledge: Physical Sciences and Mathematics - Geosciences
• Principal Investigator: Matheus Bortolanza Soares
• Grantee: Raphael Assumpção Gealorenco da Silva
• Supervisor: Owen Duckworth
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Institution abroad: North Carolina State University (NC State), United States
• Associated to the scholarship: 23/09811-3 - Aging of mercury in a soil from the Amazon region contaminated by mining activity, BP.IC

Abstract

Mercury (Hg) is a potentially toxic element that has been considered by the World Health Organization as one of the top ten chemicals of concern. A major source of Hg emissions is artisanal and small-scale gold mining, contributing to almost 38% of total emissions into the atmosphere. Once in the environment, the Hg can form a large number of species, such as volatile species (Hg0 and dimethylmercury), oxidized species (Hg+, Hg+2, Hg2+2), salts (HgS, Hg(CN)2, HgCl2, HgSO4), soluble complexes (²-HgS, ±-HgS), or solid phases in association with, Fe (oxyhydr)oxides, (co)precipitates of HgFeS, and other minerals. The distribution and stability of Hg species is influenced by the geochemical environment as well as time. For example, the contact time (aging) of Hg in the soil may favor the transformation of some Hg species that are mediated by microbial activity, such as methylated Hg species. Because of the associated health and environmental issues, it is essential to understand the dynamics of Hg in time and space. To better understand the biochemical transformations of Hg in soils, we will use a Hg aging experiment for 180 days paired to the X-ray photoelectron spectroscopy (XPS) and Time-of flight secondary-ion mass spectrometry (ToF-SIMS) to investigate the speciation of Hg as well as its spatial distribution in soils. Results will elucidate the effect of aging on the availability of Hg and its correlation with other chemical elements in the soil.