When river water meets seawater: Insights into primary marine aerosol production

Jiyeon Park,Jiyi Jang,Young Jun Yoon,Sujin Kang,Hyojin Kang,Kihong Park,Kyung Hwa Cho,Jung-Hyun Kim,Manuel Dall'Osto,Bang Yong Lee

doi:10.1016/j.scitotenv.2021.150866

Abstract

The impact of inorganic salts and organic matter (OM) on the production of primary marine aerosols is still under debate. To constrain their impact, we investigated primary aerosols generated by a sea-spray generator chamber using surface water samples from rivers, estuaries, and seas that were collected along salinity gradients in two temperate Korean coastal systems and one Arctic coastal system. Salinity values showed an increasing trend along the river–estuary–coastal water transition, indicating the lowest amount of inorganic salts in the river but the highest amount in the sea. In river samples, the lowest number concentration of primary aerosol particles (1.01 × 103 cm−3) was observed at the highest OM content, suggesting that low salinity controls aerosol production. Moreover, the number concentration of primary aerosols increased drastically in estuarine (1.13 × 104 cm−3) and seawater (1.35 × 104 cm−3) samples as the OM content decreased. Our results indicate that inorganic salts associated with increasing salinity play a much larger role than OM in aerosol production in river-dominated coastal systems. Laboratory studies using NaCl solution supported the conclusion that inorganic salt is a critical factor in modulating the particles produced from river water and seawater. Accordingly, this study highlights that inorganic salts are a critical factor in modulating the production of primary marine aerosols.

Highlights

Primary marine aerosol or sea spray aerosol (SSA) particles, produced through wave breaking on the ocean surface (Gong, 2003) are the largest source of natural aerosols to the atmosphere; they have a significant impact on Earth's radiation equilibrium (Partanen et al, 2014) and climate (Cochran et al, 2017)
Because salinity can be defined as the amount of inorganic salt (e.g., NaCl, KCl, CaCl2, K2SO4, and MgSO4) dissolved in water (Williams and Sherwood, 1994), such salinity changes revealed the lowest amount of inorganic salts in the GRW samples but the highest amount in the GSW samples
The total number concentration of primary aerosol particles generated from the GRW samples (1.12 × 103 cm−3) was 8–12 times lower than that of primary aerosol particles generated from the GEW (9.39 × cm−3) and GSW (1.35 × cm−3) samples

Summary

Introduction

Primary marine aerosol or sea spray aerosol (SSA) particles, produced through wave breaking on the ocean surface (Gong, 2003) are the largest source of natural aerosols to the atmosphere; they have a significant impact on Earth's radiation equilibrium (Partanen et al, 2014) and climate (Cochran et al, 2017). When OM is incorporated into global model simulations (Gantt et al, 2009; O'Dowd et al, 2008), satellite-derived chlorophyll a (Chl a) is used as a proxy for surface ocean biological activity in an effort to parameterize the emission of sea spray organics This is based on findings from open oceans in the northeast Atlantic and the Southern Ocean, whereby Chl a was observed to be highly correlated with the OM fraction of ambient marine aerosols at both monthly and seasonal timescales (O'Dowd et al, 2004; O'Dowd et al, 2008; Sciare et al, 2009; Spracklen et al, 2008). Chl a concentrations may not be applicable to other regions such as coastal oceans, where phytoplankton-derived Chl a accounts for only a small fraction of the OM in surface waters (less than 0.4% of OM) (Gardner et al, 2006; Huot et al, 2007; Quinn et al, 2015)

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