Influence of different acidic gases and relative humidity on the chlorine loss of marine aerosols
不同酸性气体及相对湿度对海盐氯损耗过程的影响

In this work, we investigated the influence of various acidic gases and relative humidity on depletion of chloride on sea salt aerosols at three locations in the Pearl River Delta Region using online chemical composition data obtained by MARGA. The three locations include Nancun (NC) in Guangzhou, Xichong (XC) and Zhuzilin (ZZL) in Shenzhen. Chloride depletion reached an average of 48.0% at ZZL and 56.9% at XC, typically peaking around 14:00. The major acidic gases were HNO2 and SO2 and the major alkaline gas was NH3 at all three stations, but their proportions differed among the stations. At XC, HNO2 was the most abundant (42%), followed by SO2 (32%). At ZZL, NH3 and SO2 accounted for 36% and 34%, respectively. At NC, SO2 dominated (58%), followed by NH3 (20%), while HNO2 only accounted for 7%. We further explored the sources of HCl, including the reactions with HNO3 and H2SO4 and the volatilization of NH4Cl. At XC and ZZL, HCl and HNO3 showed very good correlation (R2XC=0.689,R2ZZL=0.594), suggesting that HCl was primarily from the reaction of HNO3 with NaCl. At NC in Guangzhou, the two species had a weak correlation (R2NC=0.295), likely suggesting the presence of other chloride depletion pathways. In addition, we found that the extent of chloride loss was larger under lower relative humidity conditions.