Wet precipitation in northern Argentina: chemical characterization of soluble components in the Lerma Valley, Salta.

Abstract

Soluble components in rainwater were studied in Valle de Lerma (Salta-Argentina). The studied area is located in the central south area of Salta Province in the Cordillera Oriental region, Northwest Argentina. The largest urban area corresponds to Salta city, where sample collection and analysis of rainwater were performed between 2009 and 2012 periods. Conductivity and pH were measured on each sample, and major (Cl-, NO3-, SO42-, Na, Mg, K, Ca) and trace elements (Al, Mn, Co, Cu, Zn, As, Sb, Ba and Pb) were analyzed. Multivariate statistical calculation and enrichment factor were applied to the obtained data. Atmospheric dust collected on the same sampling stations were used as reference for enrichment factors calculations. The local rainwater presents significant enrichment in Ca, Cu, Zn, As, Sb and Pb while statistical analyses indicate a direct correlation between them. The association of elements in the rainwater is similar to those for the polymetallic ore deposits outcropping in the Puna-Altiplano region, which are located to west of the study area. Satellite images as well as previous research indicates transport of atmospheric dust from the Puna-Altiplano to the East, where Valle de Lerma is suited. We conclude that this phenomenon gives a particular print to the chemistry of the rainwater in this area. This work corresponds to the first study of the rainwater’s chemical composition in this region. As Salta city lacks of significant air pollution or major sources from anthropogenic activities, the data on this paper establish the background of the Valle de Lerma rainwater geochemistry.