AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
NOx-related Increases of Biogenic Secondary Aerosols (bSOA) in Summertime Southeastern U.S.
JUN LIU, Lynn Russell, Megan Claflin, Paul Ziemann, Nga Lee Ng, Havala Pye, Benjamin Murphy, Karena McKinney, Jason Surratt, Scripps Institution of Oceanography
Abstract Number: 634 Working Group: Aerosol Chemistry
Abstract During the 2013 Southern Oxidant and Aerosol Study, Fourier Transform Infrared Spectroscopy (FTIR) and Aerosol Mass Spectrometer (AMS) measurements of submicron mass were collected at Look Rock (LRK), Tennessee, and Centreville (CTR), Alabama. CTR had higher concentrations of many aerosol and gas phase atmospheric components than LRK; for example, carbon monoxide, sulfate and organics concentrations were ~2 times higher at CTR. Despite these different concentration levels, the time series at LRK and CTR had moderate correlations of r= 0.51, 0.54 and 0.47 for carbon monoxide, submicron sulfate, and submicron non-refractory organic components (respectively). However, NOx had a very low correlation (r=0.08) between the sites with nighttime-to-early-morning peaks 3~10 times higher at CTR than at LRK. Organic Mass (OM), extinction and absorption had a maximum in the afternoon at both sites but increased again during nighttime only at CTR. OM sources were apportioned using Positive Matrix Factorization (PMF) of both AMS and FTIR. Three very similar factors were identified on both sites from FTIR, identified as Fossil Fuel Combustion (FFC) related organic aerosols, Mixed Organic Aerosols (MOA) and Biogenic Organic Aerosols (BOA). FFC was related to anthropogenic combustion emissions and MOA is likely associated with sulfate-related selective uptake of isoprene-related secondary organic components. The BOA spectrum from FTIR is similar (cosine similarity > 0.6) to that of lab-generated OA at high NOx conditions, The BOA fraction in the mornings was 51% higher at CTR than at LRK, and the FFC fraction was 18% higher at CTR than at LRK. These higher OM concentrations are consistent with higher atmospheric oxidation capacity associated with the higher NOx levels at CTR. The bigger difference in BOA fractions shows a bigger NOx effect on BOA than on the MOA.