An appraisal of the principal concerns and controlling factors for Arsenic contamination in Chile

Abstract

Although geogenic Arsenic (As) contamination is well-recognized in northern Chile, it is not restricted to this part of the country, as the geological conditions favoring As release to the human environment exist across the country as well, although not at the same level, based on comparatively fewer studies in central and southern Chile. The present work provides a critical evaluation of As sources, pathways, and controls with reports and case studies from across the country based on an exhaustive bibliographic review of its reported geogenic sources and processes that affect its occurrence, systematization, and critical revision of this information. Arc magmatism and associated geothermal activities, identified as the primary As sources, are present across the Chilean Andes, except for the Pampean Flat Slab and Patagonian Volcanic Gap. Metal sulfide ore zones, extending from the country's far north to the south-central part, are the second most important geogenic As source. While natural leaching of As-rich mineral deposits contaminates the water in contact, associated mining, and metallurgical activities result in additional As release into the human environment through mining waste and tailings. Moreover, crustal thickness has been suggested as a principal controlling factor for As release, whose southward decrease has been correlated with lower As values.

Figure 1

Findings of the two reviews of the studies on the health effects of As exposure in Latin America^,, with many of the reported studies reported from the Antofagasta Region of Chile, together with three other reviews documenting evolution of As research in Latin America, recent studies on its occurrence and natural sources. Basic scheme from Fig. 2 of Khan et al. used with permission.

Figure 2

Location of the places (mentioned in the "Arsenic situation in Chile") relevant to As-related studies in Chile (modified from Fig. 2 of Apata et al., with permission).

Figure 3

Variation of Arsenic (As) concentration in thermal waters of Chile (UTM Coordinates WGS 84/zones 18, 19S) with the locations where As concentration is above 1000 µg/L.

Figure 4

Location of Chilean metallogenic belts with the location of the major deposits and principal cities (source: Kura Mineral Resources website, kuraminerals.com/chile-mining, used here with permission) and the highest As concentrations in different segments of the Andes, proposed by Stern et al.. See the inset map (reproduced with permission) for the details of the tectonic elements and varying depth in kilometers to the Benioff zone, shown by the contours.