This project supports rapid airborne measurements of bulk aerosol ionic composition during ACE-Asia (Aerosol Characterization Experiment). An automated instrument will be deployed on the C-130 research aircraft. The instrument consists of a particle-in-liquid sampler coupled to a dual channel ion chromatograph (IC) analysis system. The following ions can be measured with a sensitivity of about 5 pptv over a sample integration interval and duty cycle of about 4 minutes: chloride, nitrate, sulfate, sodium, ammonium, potassium, and calcium. Particles are collected directly into a liquid which is injected online and continuously into the ion chromatograph. The rapid ionic concentration measurements will be used to chemically characterize and study the evolution of the aerosol plumes advected from Asia. Another objective is to quantify the extent to which ionic components contribute to aerosol optical properties by synchronizing the airborne chemical and physical measurements.