Analysis of concentrations of nitrate salts of PM2.5 in downwind marine atmospheres related to gas-particle partitioning and different sources in China

Abstract

In order to explore the concentration characteristics and sources of major inorganic ions in marine atmospheric PM2.5, this study explores the concentration features of major inorganic ions in PM2.5 under the marine atmospheric observations of the offshore ~2000 km coastline of China in the downwind direction of the land-based sources. The observation results showed that the concentration of NO3- ranged from 0.03-10 μg m-3 with a variation of three orders of magnitude, and the main contributing species in PM2.5 was NO3- in the high concentration level observation period. The E-AIM results showed that NH3, HNO3 did not reach thermodynamic equilibrium with NH4+, NO3-, and ammonium nitrate was in volatile state, both during the day and at night. The results of the source analysis using PMF showed that there were three factors with identifiable contributions to NO3-, with Factor 1 considered to be a source of ship emissions, Factor 2 reflecting aerosols under low and medium pollution scenarios, and Factor 3 being aerosols under heavy pollution scenarios. Factor 3 was the main contributing source of NO3- concentration with a contribution of 84%, followed by Factor 2 (contribution of 15%) and the lowest contribution by Factor 1 (0.7%).