Unexpected Contributions of Sea Spray and Lake Spray Aerosol to Inland Particulate Matter

Sea spray aerosol (SSA) and lake spray aerosol (LSA) from wave breaking contribute to particulate matter (PM) in coastal regions near oceans and freshwater lakes, respectively. However, SSA and LSA contributions to atmospheric aerosol populations in inland regions are poorly understood because of difficulties differentiating them from other inland sources when using bulk particle measurements. Herein, we show that SSA and LSA episodically contribute to atmospheric aerosol populations at a rural site in northern Michigan >700 and >25 km from the nearest seawater and Great Lakes sources, respectively. During July 2014, individual SSA and LSA particles were identified by single-particle mass spectrometry and electron microscopy and then combined with air mass trajectory analysis for source apportionment. SSA comprised up to 33 and 20% of PM mass (0.5-2.0 mu m) during two multiday transport events from Hudson Bay and a 3% average background outside these periods. LSA transported from Lake Michigan reached a maximum of 7% of PM mass (0.5-2 mu m) during a daylong high-wind event and contributed a 3% average background during the remainder of the study. The observation of SSA and LSA transported inland motivates further studies of the impacts of wave breaking particles on cloud formation and air quality at inland locations far from marine and freshwater sources.