DISTRIBUTION AND POTENTIAL MOBILIZATION OF AS, CU, AND ZN IN THE CAMARONES RIVER BASIN, SURIRE SALT FLAT, AND CARITAYA DAM, NORTHERN CHILE

The Camarones River Basin, Surire Salt Flat, and Caritaya Dam are located in northern Chile at elevations ranging from sea level to 4,250 m a.s.l. The climate and precipitation varies from west-east with (20 to more than 200 mm/year in the east, at higher elevations). Precipitation occurs in the summer (December to May). In addition, these basins have low population densities and limited anthropogenic activities that include mining (B at Surire and small Cu operations along the coast) as well as agriculture (Camarones River Valley).

During March (summer) and July (winter) of 2019, two sampling campaigns were performed in the Camarones River, Surire Salt Flat, and Caritaya Dam (winter). The sites were selected to identify the main trace elements present and their potential of mobilization in contrasting seasons. Water samples were filtered (0.22 µm) and acidified (HNO₃) in the field and were analyzed by ICP-MS at the PUCV (Valparaíso, Chile). Sediment samples were sieved, and the fraction lower than 63 µm was digested and quantified by ICP-OES at UCN (Antofagasta, Chile). These sediments were subjected to sequential digestions at the same facility.

The studied sites present slightly alkaline pH and oxidizing water in winter and summer. Dissolved As concentrations are well above the national regulations, yet Cu and Zn are lower. Regarding sediment concentrations, As and Cu tend to increase in winter, and Zn presents similar values in both seasons. The potential of mobilization was higher for As during the summer and was similar for Cu and Zn in summer and winter. Finally, when comparing results from the different basins, the highest concentrations of As and Zn in water were found in Caritaya and Camarones, respectively, while sediments at Caritaya, Caritaya-Surire, and Caritaya-Camarones presented the highest concentrations of As, Cu, and Zn, respectively. The potential of mobilization is similar for these elements in these basins.