ABSTRACT
For the most part of the Copiapó River (between 20–100 km from the headwaters, corresponding to Lautaro Reservoir and Piedra Colgada sector respectively), Arsenic content is below the Chilean norm for potable water of 0.01 mg/L. However, in its catchment area located in the Andean Cordillera, some of the tributaries have relatively higher arsenic concentration, of both geogenic and anthropogenic origin, affirmed by the presence of arsenic bearing mineralization and mining activities in the area. A spike in the Arsenic concentration can be observed close to the city of Copiapó (Km. 100 from the headwaters) can be attributed to a local contamination source that not only contributes arsenic, but a wide spectrum of different metals. Downstream, Piedra Colgada onwards, arsenic concentration increases again. This increase however is due to contribution from very old (not dated, but chemically highly evolved) aquifer in that sector that has elevated arsenic concentration.
