Assessing the Effects of Wet Deposition: Observing Removal Timescales for Gases and Aerosols in Semi-Urban and Remote Areas
CHRISTOS STAMATIS, Chenyang Bi, Gabriel Isaacman-VanWertz,
Virginia Tech Abstract Number: 541
Working Group: Aerosol Chemistry
AbstractA substantial fraction of secondary organic aerosol (SOA) is formed through the multigenerational oxidation of reactive organic gases. Therefore any processes such as wet and dry deposition that remove gases, in particular lightly oxidized and/or condensable gases, will affect the thermodynamic equilibrium and the formation of SOA. Unfortunately, there are few direct observational constraints on the wet deposition of oxygenated gases and particles and their timescales of removal, leading to significant uncertainty regarding the impact of precipitation on aerosols. In this work we will present observationally constrained estimates of wet deposition timescales for gases and particles. Precipitation size distribution data from globally distributed sites in the Department of Energy Atmospheric Radiation Measurement (ARM) network and in Blacksburg, VA provided highly detailed measurements of precipitation characteristics, collocated with measurements of wet scavenging of particle size distributions. We combine these data with measurements of oxygenated gases across a range of volatilities collected during precipitation events in Blacksburg, Virginia using a proton-transfer time-of-flight mass spectrometer (VOCUS PTR-TOF MS) and a semi-volatile thermal desorption aerosol gas chromatograph (SV-TAG). Direct observations of removal are combined with precipitation data to calculate scavenging coefficients that are size-dependent (for particles) and solubility-dependent (for gases). Studying the real-world measurements from these diverse geographical locations will lead to an improved understanding of wet deposition timescales for gases and how precipitation parameters such as precipitation duration, intensity and size distribution affects aerosol chemical properties and mass.