Sequential sampling of rainwater from Hurricane Irene was carried out inWilmington, NC, USA on 26 and 27 August 2011. Eleven samples were analyzedfor pH, major ions (Cl, NO, SO, Na,K, Mg, Ca, NH), dissolved organic carbon(DOC) and hydrogen peroxide (HO). Hurricane Irene contributed16% of the total rainwater and 18% of the total chloride wetdeposition received in Wilmington NC during all of 2011. This workhighlights the main physical factors influencing the chemical composition oftropical storm rainwater: wind speed, wind direction, back trajectory andvertical mixing, time of day and total rain volume. Samples collected earlyin the storm, when winds blew out of the east, contained dissolvedcomponents indicative of marine sources (salts from sea spray and low DOC).The sea-salt components in the samples had two maxima in concentration duringthe storm the first of which occurred before the volume of rain hadsufficiently washed out sea salt from the atmosphere and the second when backtrajectories showed large volumes of marine surface air were lifted. As thestorm progressed and winds shifted to a westerly direction, the chemicalcomposition of the rainwater became characteristic of terrestrial storms(high DOC and NH and low sea salt). This work demonstrates thattropical storms are not only responsible for significant wet deposition ofmarine components to land, but terrestrial components can also becomeentrained in rainwater, which can then be delivered to coastal waters viawet deposition. This study also underscores why analysis of one compositesample can lead to an incomplete interpretation of the factors thatinfluence the chemically divergent analytes in rainwater during extremeweather events.
展开▼
