This project will make PILS (Particle-into-Liquid Sampler) measurements on the AEROMMA WP-3 NOAA aircraft to provide aerosol composition data for the AEROMMA Campaign. The PILS is a well-established aerosol collection device that provides a liquid sample containing dissolved aerosol particles which can be analyzed by various methods. These measurements will provide high chemical specificity of sulfur species to complement other aerosol composition measurements to be deployed, such as aerosol mass spectrometry, and will be used to address the following research questions: (1) What are the differences in the type of sulfate observed in urban vs. marine emissions? (2) How important of a source is biomass burning in the study region during summer? How does it compare to winter? (3) What is the pH of the aerosol in the study region in summer? How does it compare to winter? Overall, the project will help provide information that can aid in guiding emission control strategies aimed at helping to meet air quality standards to protect human health.