Chemical behavior of the Sali River, Province of Tucuman, Argentina

Major ionic composition and other chemical parameters were determined at fi ve sampling stations on the Sali River (Province of Tucuman, Argentina). Th e heavy human usage of the river causes increased levels of dissolved ions, from the dissolution of halite and gypsum, and from the weathering of basi c sediments. Correlations demonstrate that sodium chloride and sulphate, an d calcium carbonate are the main contributors to dissolved ions in the rive r. In the polluted region, south of the Celestino Gelsi dam, the main sourc e of calcium and sulphate is the dissolution of gypsum. Large amounts of ha lite are also dissolved. Weathering of biotite, K-feldspar and albite are s uggested by the data. Conductivity, dissolved oxygen and organic matter all indicate severe contamination by organic matter (mainly from sugar-cane pr ocessing) in the lower course. The data also demonstrate a substantial impr ovement in water quality before the discharge of the river at the Rio Hondo dam. Data from the Colorado (a tributary of the Sali River) and Medina riv ers are also analyzed and compared.