Seasonal characteristics of the chemical composition of rainwaters from Salta city, NW Argentina

Major ions, pH and electrical conductivity (EC) were analyzed in rainwater samples collected at Salta city (NW Argentina) during the summer seasons of years 2010–2011 and 2011–2012. Precipitations in the area are characterized by low total dissolved load and slightly acidic pH. The pH values are in agreement with low concentrations of anthropogenic acid species such as NO₃⁻ and SO₄²⁻ and consistent with a low urban development. Data indicate that the high concentrations of dissolved Ca are probably associated with the existence of marble quarry mining in the valley. According to a below-cloud process, it is observed that during the dry season, dust particles and contaminants are concentrated in the lower troposphere and washed-out immediately after a rainfall occurred. This process is in part responsible for the chemical composition of the local rainwater. Apart from quarry mining activity, the area does not have significant extra atmospheric pollution linked to anthropogenic sources. The new data permit to establish the baseline of the chemical composition of the local rainwater.