El valle de Lluta y su anomalía de arsénico: ¿Un fenómeno natural o una contaminación antrópica?

The Lluta River Basin in northern Chile is characterized by exceptionally high levels of arsenic in the soil, traditionally attributed to natural volcanic processes. However, this study reveals that historical sulfur mining operations have significantly exacerbated the arsenic contamination in the region. The Azufre River, a tributary of the Lluta River, originates on the western slopes of the Tacora volcano, where sulfur mining was a prominent industry throughout the 20th century. Remnants of these historical mining activities, including a tailings dam, still persist in the area. The primary objective of this research was to evaluate the impact of the tailings dam on arsenic concentrations in the soils of the Lluta River basin. The maximum arsenic concentration measured in soils upstream of the mining tailings was 292 mg/kg, establishing a baseline for arsenic levels in the region. Notably, however, the sample size for this study was limited, and further investigations with a larger dataset are necessary to confirm these findings. Statistical analysis comparing arsenic concentrations in soils upstream and downstream of the mining tailings provides compelling evidence of anthropogenic pollution originating from the tailings dam. This observation is further supported by elevated levels of other chalcophile elements (copper, lead, and zinc) and alterations in general soil characteristics (pH and electrical conductivity). In conclusion, while high arsenic levels in the Lluta River basin soils are a natural phenomenon, the acid drainage from the historical sulfur mine tailings dam has significantly aggravated the contamination.