Urban dust and central Ohio precipitation

Anne Carey, Susan Welch, W Lyons
Herein we examine the solubility of dust collected during a long-term study of the stable isotopic composition of precipitation in Columbus, Ohio, the 15 th 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 Ca 2+ and anions (Cl-and SO 4 2-) by ion chromatography. Chloride concentrations are low, ranging from >1 μM L-1 to
more » ... 26 μM L-1 , and are uncorrelated to Ca 2+. Soluble, sea salt-corrected Ca 2+ 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 Ca 2+ concentration in our samples was 26 μM L-1. Mean sea salt-corrected Ca 2+ 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 Ca 2+ 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.