Aging of mercury in a soil from the Amazon region contaminated by mining activity

• Grant number: 23/09811-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2023
• End date: March 31, 2025
• Field of knowledge: Physical Sciences and Mathematics - Geosciences
• Principal Investigator: Luís Reynaldo Ferracciú Alleoni
• Grantee: Raphael Assumpção Gealorenco da Silva
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated scholarship(s): 23/17502-0 - Spatial and temporal variability of mercury in soil contaminated by artisanal gold mining, BE.EP.IC

Abstract

Due to artisanal gold mining, high levels of mercury (Hg) in humans are common in the Brazilian Amazon region, particularly in indigenous communities. Most of the gold in these regions is extracted through artisanal mining, which can contaminate the soil and environment with Hg. The stability of contamination by Hg and its species in the soil solution can change over time, and this has direct implications for agricultural management and risk management. Soil organic matter (OM) can strongly interact with Hg and affect its speciation, solubility, mobility and toxicity, and the strong binding of Hg by MO is attributed to the coordination of Hg at reduced sulfur sites within the OM. Due to the importance of time in changing more reactive OM fractions, such as the dissolved fraction, we will evaluate the influence of aging on Hg fractions in soil contaminated by artisanal gold mining. The correlation between soil OM quality and Hg availability will also be investigated. Samples of a soil contaminated with Hg will be incubated in the laboratory for 0, 5, 1, 2, 6, 12, 24, 48, 72, 720, 2160, and 4320 h, which is equivalent to artificial aging of up to 180 days. The method used to access the geochemical fractions of Hg will be proposed by the Bureau Communautaire de Référence (BCR) of the European Union, which consists of using 0.11 M acetic acid solutions to extract the exchangeable/extractable fraction, 0.1 M of hydroxylamine hydrochloride for the reducible fraction, and ammonium acetate for the oxidizable fraction. The quality of soil OM will be assessed by physical fractionation to obtain total and dissolved levels of soil organic carbon. The results of this study should help to predict the impacts of Hg in this environment, as well as help in risk management of areas contaminated by Hg in northern Brazil.