Single particle ATOFMS measurements of the chemical and physical properties of polluted and fresh air masses in Gosan, Korea

Real-time single particle mass spectrometry measurements were made during the Pacific Dust Experiment (PACDEX) to gain insight into the size-resolved aerosol mixing state at the Aerosol Brown Cloud Monitoring Station in Gosan, Korea. During the one month sampling period during April and May 2007, there were several distinct time periods with different sources contributing significantly to the observed aerosol. The different events include outflow from the Asian continent, a minor Asian dust event, clean marine periods, and episodes of local influence. The aerodynamic size and chemical composition of individual particles were measured in real time using an aerosol time-of-flight mass spectrometer (ATOFMS). This information provides insight into the sources of the aerosol during these different periods. The mixing state and light scattering properties obtained from the scattering signal recorded by the ATOFMS allow information regarding the radiative properties of distinct chemical classes to be determined. The data from the ATOFMS along with concurrent measurements of particle number concentration, size distribution, bulk scattering, and black carbon mass concentration provide broad insight into the evolution of the polluted air masses. Within the different air masses, the distinct particle types observed include fly ash, elemental carbon, dust, sea salt, and vanadium types. Processed and agglomerated particle types, such as elemental carbon with sea salt and elemental carbon with dust, were also observed and are thought contribute significantly to the radiative properties of the air mass. Particle aging was assessed using nitrate, sulfate, and ammonium. From these measurements information regarding different sources contributing to Asian outflow was determined. This information is necessary for understanding Asian outflow events. The mixing state of chemically different particle types and their associated light scattering properties observed by ATOFMS measurements are shown. The demonstrated variability of scattering properties within both the fresh and aged aerosol demonstrates the need to include these findings in future global climate models for complete evaluation of the earth's radiation budget.