The solid-state partitioning, distribution, and mineralogical associations of arsenic and antimony: Integrated findings from the Altiplano Puna, South America and international comparisons

Abstract

Arsenic (As) and antimony (Sb) are potentially hazardous metalloids and their presence in the environment is often related to mineral deposits, mines, and thermal springs. Despite their similar chemical properties, the distribution and behavior of As and Sb in nature has been shown to differ. In order to contribute to a better understanding of As and Sb in the environment as well as the important parameters controlling their mobility, this study presents a synthesis of geochemical results in the Altiplano-Puna of Chile and Bolivian Sb belt. Analyses include (i) solid-state partitioning, (ii) mineralogical studies and (iii) concentrations of both metalloids in groundwater, surface water, porewater, and fluvial and lake sediments in distinct seasons. Consistencies were found between the mobilization patterns of As and Sb in the studied sites where As is generally more mobile than Sb; however, mining-affected areas in the Bolivian Sb belt tend to be associated with a higher proportion of mobile Sb. From a mineralogical standpoint, As is generally associated with iron oxides and hydroxides and As-bearing pyrites, while Sb is linked to iron oxides, hydroxides, and clay-sized phyllosilicates. When compared to different metallogenic settings outside the Altiplano-Puna plateau (the Loa River Basin of northern Chile and Xikuangshan Mine in China), the following conclusions are consistent with the results obtained from the Altiplano-Puna: dissolved Sb concentrations tend to decrease with distance from the respective mining facility, the mobility of Sb is typically lower than As, and the preferred mineralogical associations are iron oxides and hydroxides. Finally, based on the seasonal analysis of As and Sb, it is conceptualized that wetlands behave as a source of As and as a sink and source of Sb depending on the water column; in addition, consideration must be taken regarding aeolian weathering.