Natural and anthropogenic sources of solutes in the wet precipitation of a densely populated city of Southern South America

• Published in: Chemosphere (Oxford) 2022-01, Vol.287, p.132307-132307, Article 132307
• Main Authors: Garcia, M.G., Lecomte, K.L., Depetris, P.J.
• Format: Article
• Language: English
• Subjects: Alkaline rainwater– heavy metals; Enrichment factors; Geogenic contaminants; REE patterns
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2021.132307

The chemistry of rainwater is controlled by the interaction among water, airborne particles and gas sources, whether natural or human-made. This article analyzes the chemical composition dynamics of individual rainfall events collected over a three-year period in the densely populated city of Córdoba (Argentina). The main purpose is to identify the natural and/or anthropogenic sources, and the extent to which they determine the seasonal chemical signature exhibited by wet precipitation in the heart of the South Eastern South America. The results reveal that, despite geogenic components are only minor constituents of the airborne particles in downtown Córdoba, they appear to be the main source of solutes in rainwaters, also responsible for the alkaline water pH that predominates most of the year. This fraction mostly corresponds to wind-blown soil particles transported either from local or distant sources, with rare earth elements (REE) patterns similar to those of rainwaters produced during the dry season. Anthropogenic contributions are only evident during the wet season, when rainwater shows REE patterns similar to those of industrial emissions and exhibits moderate enrichment of heavy metals such as Cu and Zn, derived from soluble compounds used in agricultural activities (e.g, sowing, fertilizing). With the exception of these two metals, the remaining heavy metals are depleted in rainwater suggesting that the airborne conveying compounds (mostly anthropogenic) are barely soluble. [Display omitted] •Regional loess sediments imprint the chemical signature to rainwater.•The influence of human activity on the rainwater chemical composition accounts for 18% of the total variance.•Cu and Zn derived from agrochemicals are moderately enriched in rainwater during the summer wet months.•Alteration of suspended loess particles determine relatively high concentrations of regional geogenic contaminants, As and F.•Natural and anthropogenic acidity is neutralized by carbonates spread in loess.