Departamento de Ciencias Geológicas, Universidad Católica Del Norte, Antofagasta, Chile; Centro de Estudio Del Agua Del Desierto, CEITSAZA, Universidad Católica Del Norte, Antofagasta, Chile; Instituto Milenio de Investigación en Riesgo Volcánico - CKELAR Volcanoes, Chile.
Department of Geology and Geophysics, Indian Institute of Technology-Kharagpur, Kharagpur, 721302, West Bengal, India.
Environ Pollut. 2022 Dec 1;314:120151. doi: 10.1016/j.envpol.2022.120151. Epub 2022 Sep 14.
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.
全球范围内，水文系统中的砷（As）污染广泛存在，而在造山环境中，砷的富集与区域构造和气候因素之间的联系仍未得到很好的理解。本研究通过评估智利的水文化学状况，为砷、构造和气候之间的关系提供了新的见解，智利是一个活跃的俯冲带，具有高度多样化的自然环境。选择的研究地点包括沿着四条连接智利海岸和安第斯山脉的区域横切线上的河流流域，这些横切线位于该国的北部、中部和南部地区。结果表明，地表水中的砷浓度与河流沉积物中的砷浓度呈正相关，且从智利北部到南部呈逐渐降低的趋势。相比之下，砷浓度与年平均降水量呈负相关，而年平均降水量在智利南部呈显著增加的趋势。从区域构造的角度来看，智利北部的安第斯山脉缩短幅度较大，地壳厚度较高，这导致地壳的污染和表面的砷含量增加。极低的降水率也与局部的砷富集以及饥饿的海沟有关，这可能有利于更高的板块耦合和缩短。相反，智利南部的安第斯山脉缩短幅度减小，相关的地壳厚度降低，导致地壳污染程度降低，从而成为地表沉积物和地表水的贫砷来源。高降水率进一步导致地表水的稀释、固相的潜在迁移以及大量的海沟沉积物，这些可能导致更低的板块耦合和缩短。在局部尺度上，智利北部的砷迁移潜力较低，在那里观察到沉积物中含有更多的含砷矿物，主要是更细的颗粒（<63μm）。在遇到的物理化学条件下，铁氧化物的丰度可能起到砷的次生表面汇的作用。
