Abstract
Abstract. In this study, a cruise campaign was conducted over marginal seas in China to measure the concentrations of condensation nuclei (Ncn), cloud condensation nuclei (Nccn) and other pollutants from day of year (DOY) 110 to DOY 135 of 2018. The ship self-emission signals were exhaustively excluded, and the mean values of Nccn during the cruise campaign were found to slightly increase from 3.2±1.1×103 cm−3 (mean ± standard deviation) at supersaturation (SS) of 0.2 % to 3.9±1.4×103 cm−3 at SS of 1.0 %, and the mean value for Ncn was 8.1±4.4×103 cm−3. Data analysis showed that marine traffic emissions apparently largely contributed to the increase in Ncn in the daytime, especially in the marine atmospheres over heavily traveled sea zones; however, the fresh sources made no clear contribution to the increase in Nccn. This finding was supported by the quantitative relations between Ncn and Nccn at SS = 0.2 %–1.0 % against the mixing ratios of SO2 in the ship self-emission plumes – i.e., a 1 ppb increase in SO2 corresponded to a 1.4×104 cm−3 increase in Ncn but only a 30–170 cm−3 increase in Nccn, possibly because of abundant organics in the aerosols. Smooth growth can be observed in the marine-traffic-derived particles, reflecting aerosol aging. The estimated hygroscopicity parameter (κ) values were generally as high as 0.46–0.55 under the dominant onshore winds, suggesting that inorganic ammonium aerosols likely acted as the major contributor to Nccn largely through aerosol aging processes of decomposing organics. Moreover, the influences of the new transported particles from the continent on the Ncn and Nccn in the marine atmosphere were investigated.
Highlights
Oceans occupy approximately 2/3 of the Earth’s surface, and water evaporation from oceans is a major source of moisture in the atmosphere
The number concentrations of aerosols (Ncn) greatly increased to 1.9±0.7×104 cm−3 at 08:00–21:00 LT on day of year (DOY) 110 when the ship cruised across the Yangtze River estuary
The atmospheric particles over marginal seas in China can be further transported to the remote northwest Pacific Ocean (NWPO) in spring under westerly winds – e.g., the Ncn observed over the NWPO in March–April 2014 was as high as 2.8±1.0×103 cm−3 and approximately half of that over marginal seas in China observed in March 2014 (Wang et al, 2019)
Summary
Oceans occupy approximately 2/3 of the Earth’s surface, and water evaporation from oceans is a major source of moisture in the atmosphere. In addition to sea-spray aerosols and secondarily formed aerosols from sea-derived gaseous precursors (O’Dowd et al, 1997; Clarke et al, 2006; Quinn and Bates, 2011; Blot et al, 2013; Fossum et al, 2018), marine traffic emits large amounts of aerosols and reactive gases (Chen et al, 2017). These pollutants may directly or indirectly contribute to CCN to some extent (Langley et al, 2010). The regression equations are valuable for the estimation of Ncn and Nccn from SO2 when the direct observations of Ncn and Nccn are not available
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