Atmos. Chem. Phys. Discuss., 12, 26995-27020, 2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Dynamics of the chemical composition of rainwater throughout Hurricane Irene
K. M. Mullaugh1,*, J. D. Willey1, R. J. Kieber1, R. N. Mead1, and G. B. Avery Jr.1
1Department of Chemistry and Biochemistry, University of North Carolina Wilmington, Wilmington, North Carolina 28403-5932, USA
*now at: Elon University, Elon, NC 27244, USA

Abstract. Sequential sampling of rainwater from Hurricane Irene was carried out in Wilmington, NC, USA on 26 and 27 August 2011. Eleven samples were analyzed for pH, major ions (Cl, NO3, SO42−, Na+, K+, Mg2+, Ca2+, NH4+), dissolved organic carbon (DOC) and hydrogen peroxide (H2O2). Hurricane Irene contributed 16% of the total rainwater and 18% of the total chloride wet deposition received in Wilmington NC during all of 2011. This work highlights the main physical factors influencing the chemical composition of tropical storm rainwater: wind speed, wind direction, air mass back trajectory and vertical mixing, time of day and total rain volume. Samples collected early in the storm, when winds blew out of the east, contained dissolved components indicative of marine sources (salts from sea spray and low DOC). The seasalt components in the samples had two maxima in concentration during the storm the first of which occurred before the volume of rain had sufficiently washed out seasalt from the atmosphere and the second when the air mass dipped to low elevations over the Atlantic Ocean followed by rapid vertical mixing. As the storm progressed and winds shifted to a westerly direction, the chemical composition of the rainwater became characteristic of terrestrial storms (high DOC and NH4+ and low seasalt). This work demonstrates that tropical storms are not only responsible for significant wet deposition of marine components to land, but terrestrial components can also become entrained in rainwater, which can then be delivered to coastal waters via wet deposition. This study also underscores why analysis of one composite sample can lead to an incomplete interpretation of the factors that influence the chemically divergent analytes in rainwater during extreme weather events.

Citation: Mullaugh, K. M., Willey, J. D., Kieber, R. J., Mead, R. N., and G. B. Avery Jr.: Dynamics of the chemical composition of rainwater throughout Hurricane Irene, Atmos. Chem. Phys. Discuss., 12, 26995-27020, doi:10.5194/acpd-12-26995-2012, 2012.
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