Measuring Dry Deposition of Sea Spray Aerosol and Height of Aerosol Plume Using a Controlled Wave Pool

Abstract

Deposition of sea spray aerosols facilitates atmospheric corrosion of materials, requiring maintenance and replacement over time. However, the dimensions of sea spray aerosol plumes produced from breaking waves have not been well-characterized, limiting useful prediction of particle transport downwind and atmospheric corrosion. Therefore, this project aimed to measure sea spray aerosol production from breaking waves in a controlled environment at several elevations to obtain the height profile of an aerosol plume. Measurements were conducted using a 13.7 × 6.7 m pool with 1.5 m depth filled to 101.6 cm with Instant Ocean® at the Laboratory for Autonomous Systems (LASR), Naval Research Laboratory (NRL). Waves were generated to simulate a total of 525 wave crashes using fully automated pistons. Airborne concentrations, aerosol number size, and dry deposition fluxes were measured at 47, 153.7 and 260.4 cm above the water surface. Aerosol size distributions and dry deposition fluxes showed that coarse, salt-rich aerosols deposited mostly at 47 cm while submicron particles traveled further up to 153.7 and 260.4 cm. Furthermore, corrosion was evaluated at each elevation using C1010 witness coupons, Ag witness coupons, and corrosion sensors. Corrosion rates of C1010 were most severe at 153.7 cm, suggesting that corrosion may not necessarily be the most severe adjacent to the water surface. This study provided experimental data for initial plume conditions, including loss of particles by dry deposition, that could be used for modeling the transport of sea spray aerosols.