Abstract

The Lluta valley (Arica and Parinacota Region, Chile) is the site of a very unusual natural phenomenon where the soils in the valley are both saline and acidic. Soil conductivity was in the range of 1.4-16 dS/m (saturated paste extract) and 0.2-2.2 dS/m (1/5 soil/water extract). Soil pH was in the range of 5.1-6.9 (water), 4.9-6.3 (0.01 M CaCl2), and 4.4-6.0 (1 M KCl) at a soil/solution ratio of 1/2.5. Acidic soils are rare in arid regions, and their occurrence in the Lluta valley is attributed to the unusually low pH (below 2) of the Azufre River, which may be related to volcanic activity in the area. The situation is further exacerbated by acidic run-off from old sulfur mine tailings.