Characteristics of Water-soluble Inorganic Ions inAerosol and Precipitation and their ScavengingRatios in an Urban Environment in Southwest China

摘要

Daily fine particulate matter (PM2.5) and precipitation samples were collected simultaneouslyat an urban site in southwest China in four segregated months in 2015 for measuring majorwater-soluble inorganic ions (WSIIs). Online hourly concentrations of PM10 and PM2.5 were alsomonitored, which showed annual mean concentrations of 67.8 and 41.6 μg m–3, respectively.PM2.5 showed the highest concentration in winter and lowest in summer. The annual meanconcentration of the total WSIIs was 20.3 μg m–3, accounting for about 48.7% of PM2.5. Amongthe total WSIIs in ambient PM2.5, SO42– was the predominant component (49.7%), followed byNH4+(24.1%) and NO3–(21.4%). NH4+and SO42– were the two most abundant ions in precipitation,followed by Ca2+ and NO3–. Seasonal patterns of the major inorganic ions in precipitation weresimilar to those in PM2.5, with the highest concentration in winter and lowest in summer. Themean scavenging ratios were 454, 445, 364, 456, and 394 for SO42–, NO3–, NH4+, Cl–, and K+, and116, 353, and 18 for gas SO2, HNO3, and NH3, respectively. The higher scavenging ratios ofparticulate ions than their gaseous precursors suggest the higher contributions of particles thangases to the total wet deposition.