AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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A Two-Year Study of Carbonaceous Aerosols in Ambient PM2.5 at a Regional Background Site for Western Yangtze River Delta, China
DONG CHEN, Hongfei Cui, Yu Zhao, Nanjing University
Abstract Number: 45 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract To analyze the characteristics of regional background carbonaceous aerosols in western Yangtze River Delta (YRD), hourly organic carbon (OC) and elemental carbon (EC) in fine particular matter (PM$_(2.5)) were measured with a semi-continuous carbon analyzer at a suburban site in upwind Nanjing from June 2013 to May 2015. Relatively low OC, EC and OC/EC were observed compared to other studies conducted in Nanjing. The reasons include the limited primary emissions around the observation site, the improved emission controls in recent years, large contribution of traffic sources, and the use of denuder to reduce positive artifact in OC measurement. Resulting from the stable atmosphere conditions, the highest concentrations of carbonaceous aerosols were found in both winters, with average OC and EC observed at 11.8±10.0 and 5.9±3.4μg/m$^3 for the first one, and 8.1±5 and 4.5±2.4μg/m$^3 for the second one, respectively. Compared to 2013, reduced OC and EC were found in summer and autumn 2014, demonstrating the benefits of emission control polices implemented for the Nanjing Youth Olympic. Good correlation between OC and EC was found in winter indicating the common sources including traffic and coal combustion. Using the EC-tracer method, the highest SOC concentrations of each year were estimated in autumn for 2013-2014 (4.5 μg/m$^3) and in spring for 2014-2015 (2.4 μg/m$^3), while the largest SOC/OC appeared in summer attributed mainly to the enhanced oxidation rate for SOC generation from high temperature. For the hazy event in winter 2013, the back trajectories of air masses suggested that heavy pollution were from eastern Jiangsu, northern Anhui and Jiangsu, downtown Nanjing, and Shanghai. Secondary aerosol formation played an important role indicating by the mass fraction of OC and increased OC/EC in PM$_(2.5). In the harvest season, biomass burning was estimated to contribute 51% and 16 % of OC and EC concentrations, respectively.