Chemical compositions and the impact of sea salt in atmospheric PM1 and PM2.5 in the coastal area

Abstract

The 11.5-h samples were collected at a coastal site and an urban site in the coastal area, Qingdao. PM1- and PM2.5-bound water-soluble inorganic ions (WSIIs), organic carbon (OC) and element carbon (EC) were analyzed in January and July 2019. PM2.5-bound elements were determined in July 2019. The results showed that the ∑WSIIs, OC and EC concentrations at the coastal site were significantly lower than those at the urban site, and their concentrations in winter were significantly higher than those in summer. Sea salt concentrations in PM2.5 were significantly higher than those in PM1 and were significantly correlated with the concentrations of secondary inorganic aerosol (SIA) and secondary organic carbon (SOC). The mean concentrations of total elements were 1258.35 ± 1033.43 and 1669.27 ± 808.53 ng m−3 at the coastal site and urban site, respectively. The health risk assessments for elements implied that the total non-carcinogenic risks via inhalation can be ignored and the total carcinogenic risks were within an acceptable level. Positive matrix factorization model (PMF) indicated secondary inorganic aerosols (31.13%), biomass burning (28.98%), aged sea salt (21.60%), coal combustion (10.91%) and crustal dust (7.39%) were major sources of WSIIs, OC and EC. Coal and biomass burning sources played more obvious roles at the urban site in winter but secondary inorganic aerosols and aged sea salt made more apparent contributions at the coastal site. The contribution of aged sea salt source was significantly increased from winter to summer. While the contributions of secondary inorganic aerosols, biomass burning, coal combustion and crustal dust were decreased. The concentration-weighted trajectory (CWT) model suggested that local areas from Shandong Province were important for secondary inorganic aerosols, biomass burning and coal combustion. The major source regions of aged sea salt source were the Yellow Sea, Jiangsu, Anhui and Eastern Shandong Provinces. Crustal dust was dominantly originated from Western Shandong Province.