69 D32. Geochemistry (Posters)

Sunday, 22 October 2017
9:00 AM - 5:30 PM
Halls 4EF

STABLE ISOTOPE AND MAJOR ION GEOCHEMISTRY OF URBAN PRECIPITATION

Paper number: 69-40
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

Abstract

Analysis of precipitation from Columbus, Ohio has identified the stable isotopic and major ion content of urban precipitation and shown the effect of urban environment impacts on precipitation as determined by seasonality, volume, and event. The study provides an understanding of how continental cities influence local precipitation by defining a local meteoric waterline (LMWL) through stable hydrogen (δD) and oxygen (δ18O) isotope variations for central Ohio, and additionally by characterizing the chemical composition of precipitation. Samples were collected from April 2014 to July 2017 and analyzed using a Picarro Cavity Ring Down Spectroscopy Analyzer (Model L1102-i) for water isotopes for δ18O and δD and Thermo Scientific Dionex (ICS-2100 and DX-120) ion chromatography systems for major anion and cation concentrations. Collection sites included several locations in central Ohio on and near The Ohio State University Campus. Results showed lighter δ18O and δD signatures with higher d-excess in winter months and heavier signatures in summer months due to changes in temperature and precipitation source. The LMWL was determined as δD = 7.8*δ18O + 9.25 (R2 =.9768), slightly different from the global meteoric waterline (GMWL) δD = 8*δ18O + 10. The major ion concentrations in precipitation revealed the presence of urban and natural aerosols and indicated the occurrence of both atmospheric below-cloud scavenging and wash-out. Major ions included NO3-, SO42-, Cl-, NH4+, Ca2+, Mg2+, and K+, with concentrations differing by seasons and precipitation events. This LMWL provides isotopic ratios of δ18O and δD for the eastern continental United States, benefiting future precipitation studies in this region. Further, isotopic composition and chemical components of urban precipitation as determined by seasonality, volume, and event source highlight both the climatic factors controlling precipitation trends and the anthropogenic factors influencing precipitation chemistry.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-306089

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