Urban dust and central Ohio precipitation

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Urban dust and central Ohio precipitation

Anne E. Carey, Susan A. Welch, W. Berry Lyons

Pp 31-37


Herein we examine the solubility of dust collected during a long-term study of the stable isotopic composition of precipitation in Columbus, Ohio, the 15th largest city in the United States. Samples were collected in a stationary, open, exposed rain collector so that between rain events dry deposition was obtained. Rain and snow samples collected during 2014–2016were analyzed for Ca2+and anions (Cl- and SO42-) by ion chromatography. Chloride concentrations are low, ranging from >1 μM L-1 to 26 μM L-1, and are uncorrelated to Ca2+. Soluble, sea salt-corrected Ca2+concentrations ranged from 6 to 124 μM L-1. Our results are compared to a longer term dataset (1999–2015) from the National Atmospheric Deposition Program (NADP) of wet deposition samples collected 50 km southwest of Columbus. Mean sea salt-corrected Ca2+ concentration in our samples was 26 μM L-1. Mean sea salt-corrected Ca2+ concentrations in NADP samples was significantly lower (p=0.0001), at 5.6 μM L-1 with a range of 0.23–75 μM L-1. Dry deposition between precipitation events plays a major role in Ca2+ input to the city landscape. It is unclear whether this soluble calcium is from a local urban source or a regional agricultural source. SEM analysis is used to determine mineralogy of dust input to our samples and possible source of the dissolved calcium observed.

Keywords: Urban deposition; Calcium; Columbus, Ohio, USA