Role of tectonics and climate on elevated arsenic in fluvial systems: Insights from surface water and sediments along regional transects of Chile. (1st December 2022)

• Record Type: Journal Article
• Authors: Tapia, Joseline; Mukherjee, Abhijit; Rodríguez, María Pía; Murray, Jesica; Bhattacharya, Prosun
• Is Part Of: Environmental pollution. Volume 314(2022)
• Publication Date: 2022-12-01
• Subjects: Arsenic -- Fluvial systems -- Tectonics -- Climate -- Mobilization; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2022.120151
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Globally, arsenic (As) contamination is widespread in hydrological systems and the link between As enrichment and regional tectonic and climatic factors is still not well understood in orogenic environments. This work provides new insights on the relationship between As, tectonics, and climate by assessing the hydrochemistry of Chile, an active subduction zone with highly diverse natural settings. Selected study sites include fluvial courses along four regional transects connecting the Chilean coast to the Andes Cordillera in the northern, central, and southern areas of the country. The results indicate that As concentrations in surface water and fluvial sediments show a general positive correlation to crustal thickness and they tend to decrease progressively from northern to southern Chile. In contrast, As concentrations are negatively correlated to average annual precipitation which shows a significant increase toward southern Chile. From a regional tectonic perspective, northern Chile presents greater Andes shortening and higher crustal thicknesses, which induces increased crustal contamination and As content at the surface. Extremely low precipitation rates are also tied to local As enrichment and a sediment-starved trench that might favor higher plate coupling and shortening. On the contrary, decreased shortening of the Andes in southern Chile and related lower crustal thickness induces lower crustal contamination, thus acting as an As-poor provenance for surficial sediments and surface water. High precipitation rates further induce dilution of surface water, potential mobilization from the solid phase, and a significant amount of trench sediments that could induce lower plate coupling and lower shortening. At the local scale, a low potential for As mobilization was found in northern Chile where a greater distribution of As-bearing minerals was observed in sediments, mostly as finer particles (<63 μm). The abundance of Fe-oxides potentially acts as a secondary surficial sink of As under the encountered physicochemical conditions. Graphical abstract: Image 1 Highlights: The concentration and mobility of As were assessed in contrasting settings of Chile. Arsenic shows an increase with crustal thickness and decrease with precipitation. Shortening of the Andes and crustal contamination are related to surficial As. The main observed mineralogy is tied to geologic and climatic factors.