Both organic carbon (OC) and elemental carbon (EC) were measured duringPRIDE-PRD 2006 summer campaign by using a semi-continuous thermal-opticalcarbon analyzer at a rural site, Back Garden (BG), which is located 50 km tothe northwest of Guangzhou City. Together with the online EC/OC analyzer,various kinds of instruments related to aerosol chemical properties wereemployed here, which provided a good opportunity to check data quality. Theconcentrations of OC correlated well with the mass of organic matter (OM)and water soluble organic carbon (WSOC), implying the reliability of thedata measured in this campaign. The average OC concentrations in fineparticle for three typical periods during the campaign (local emissioninfluence, typhoon and precipitation and normal days) were28.1 μgC m?3, 4.0 μgC m?3and 5.7 μgC m?3, respectively;and EC were 11.6 μgC m?3, 1.8 μgC m?3, and3.3 μgC m?3, respectively. The diurnal patterns of EC and OC during the campaignwere higher at night and in early morning than daytime, which was probablycaused by the primary emission and accumulation in the occurrence of lowboundary layer. Compared with the constant diurnal enhancement ratios of EC,the enhancement ratio of OC (OC versus (CO-CObackground)) kept in arelative high level in the afternoon, with a similar diurnal profile tooxygenated organic aerosol (OOA), due to the strong photochemical formationof OC. Here, a modified EC tracer method was used to estimate the formationof secondary organic carbon (SOC). These results showed that the average SOCconcentration (normal days) at BG site was about 2.0 ± 2.3 μgC m?3,and the SOC fraction in OC could reach up to 80% with theaverage of 47%. The modified approach in this study proved to beeffective and reliable for SOC estimation based on good correlations betweenestimated SOC versus OOA or WSOC, and estimated POC versus hydrocarbon-likeorganic aerosol (HOA).
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