Geomicrobiology and GeoHealth Labs have a new publication in Enviroments

Environments: "Molecular and Ionic Signatures in Rainwater: Unveiling Sources of Atmospheric Pollution."

Grace Stamm, a geology minor and the first author of this paper, led the study on molecular and ionic signatures in rainwater, unveiling sources of atmospheric pollution. Grace, her student assistantship, and another undergraduate, Arka Bhattacharjee (co-author), were supported through the NSF award (EAR: 2502654), Impact of Extreme Weather Events on Biogeochemical Cycling and Microbial Dynamics: Assessing Post-Hurricane Helene Shifts in the Oconee River Watershed.

This study reveals that rainwater in semiurban Athens, Georgia, acts as a dynamic vehicle for both nutrient ions and a complex suite of organic contaminants, exposing hidden dimensions of atmospheric contamination. It shows that during extreme events, river water chemistry is shaped not only by stormwater runoff but also by the often-overlooked influence of atmospheric deposition. 

Authors: 

Grace Stamm^1,2, Arka Bhattacharjee¹, Gayatri Basapuram¹, Avishek Dutta^1,3, and Srimanti Duttagupta¹

     ^{1 - Department of Geology, University of Georgia, Athens, GA 30602, USA; grace.stamm@uga.edu (G.S.)}

     ^{2 - Department of Physics and Astronomy, University of Georgia, Athens, GA 30602, USA}

     ^{3 - Savannah River Ecological Laboratory, University of Georgia, Aiken, SC 29802, USA}

Abstract

Atmospheric deposition through rainfall plays a significant role in transporting various anthropogenic contaminants to terrestrial and aquatic ecosystems. However, rainwater’s integrated ionic and molecular composition remains underexplored in semiurban environments. This study provides a comprehensive chemical characterization of rainwater collected during seven precipitation events from February to April 2025 in Athens, Georgia, USA. This semiurban area is characterized by substantial vehicular traffic, seasonal agricultural activities, and ongoing construction, while lacking significant industrial emissions. Targeted spectrophotometric analyses revealed heightened concentrations of nitrate (ranging from 2.0 to 4.3 mg/L), sulfate (17 to 26 mg/L), and phosphate (2.4 to 3.1 mg/L), with peak concentrations observed during high-intensity rainfall events. These findings are consistent with enhanced wet scavenging of atmospheric emissions. Concurrently, both targeted and non-targeted gas chromatography-mass spectrometry (GC-MS) analyses identified a diverse array of organic pollutants in the rainwater, including organophosphate, organochlorine, and triazine pesticides; polycyclic aromatic hydrocarbons (PAHs); plasticizers; flame retardants; surfactant degradation products; and industrial additives such as bisphenol A, triclosan, and nicotine. Furthermore, several legacy contaminants, such as organochlorines, were detected alongside currently utilized compounds, including glyphosate and its metabolite aminomethylphosphonic acid (AMPA). The concurrent presence of elevated anion and organic pollutant levels during significant storm events suggests that atmospheric washout can be the primary deposition mechanism. These findings underscore the capability of semiurban atmospheres to accumulate and redistribute complex mixtures of pollutants through rainfall, even in the absence of large-scale industrial activity. The study emphasizes the importance of integrated ionic and molecular analyses for uncovering concealed pollution sources. It highlights the potential of rainwater chemistry as a diagnostic tool for monitoring atmospheric contamination in urbanizing environments.

Keywords: rainwater chemistry; atmospheric deposition; non-targeted analysis; organic micropollutants; plasticizers