Biogenic New Particle Formation in the Presence of SO2 and Ammonia
VIGNESH VASUDEVAN GEETHA, Lee Tiszenkel, Shanhu Lee,
The University of Alabama in Huntsville Abstract Number: 249
Working Group: Aerosol Chemistry
AbstractNew particle formation (NPF) is the major source of cloud condensation nuclei. Whereas NPF has been frequently observed in boreal forests with abundant monoterpenes, NPF occurs very rarely in deciduous forests with dominant emissions of isoprene. Typically, laboratory studies of biogenic NPF have been conducted mostly from oxidation reactions of monoterpene (and some isoprene), while many forests are also affected by transported plumes containing SO
2 (and hence sulfuric acid). Also, ammonia is ubiquitous in the atmosphere and abundant in forests. Still, laboratory studies of multicomponent biogenic NPF are very scarce. We have conducted NPF experiments in the Tandem Aerosol Nucleation and Growth Environment Tube (TANGENT) from α-pinene and isoprene oxidized with ozone in the presence of SO
2 and ammonia. Particle size distributions in the size range from 1-100 nm are measured with PSM (Particle Size Magnifier) and SMPS (scanning mobility particle sizer). Sulfuric acid and ammonia are measured in real-time with two CIMSs (chemical ionization mass spectrometers). The chemical composition of HOMs (highly oxygenated organic molecules) is measured online with HrTOF-CIMS (high-resolution time of flight chemical ionization mass spectrometer), and offline with LC-ESI (liquid chromatography-electrospray ionization) high-resolution Orbitrap mass spectrometer. In this talk, we will discuss how SO
2 and ammonia affect the biogenic aerosol nucleation rate and growth rate and the chemical composition of HOMs in the gas and particle phase. These results will help to better understand the biogenic NPF processes under conditions that mimic the mixed deciduous forests in the United States.