Environmental Controls on New Particle Formation Over a Forested Region in the Southeastern U.S.A. During One Year

Abstract:

We investigate the environmental controls on ambient aerosol formation events from one year of measurements at a new research site in central Virginia. The Sweet Briar College Land-Atmosphere Research Station (SBC-LARS) features a 37-meter tower within a ~30 year-old loblolly pine plantation that is surrounded by mixed deciduous forest at the eastern edge of the Blue Ridge Mountains. The tower supports meteorological instruments at three different heights (2, 26, and 37 meters) and two air sampling inlets located above the canopy. The inlets draw air samples into a climate-controlled shed where precursor gas concentrations (ozone, sulfur dioxide, and nitrogen oxides) are determined by gas analyzers. Aerosol size distributions between 10 and 470 nm were measured by a Scanning Mobility Particle Sizer (SMPS), and between 0.3 and 10 μm by an Optical Particle Sizer (OPS) every three minutes. For this study, aerosol size distributions from July 2014 through August 2015 were analyzed along with HYSPLIT backwards trajectories, meteorological measurements, and gas concentrations to investigate controls on new particle formation (NPF). Results indicate a strong dependence of NPF occurrence on parent air mass, with higher probabilities of occurrence in air masses with low relative humidity and abundant insolation. Proxy sulfuric acid concentration and ozone concentration also varied significantly between NPF event types.