Abstract
Abstract. Both organic carbon (OC) and elemental carbon (EC) were measured during PRIDE-PRD 2006 summer campaign by using a semi-continuous thermal-optical carbon analyzer at a rural site, Back Garden (BG), which is located 50 km to the northwest of Guangzhou City. Together with the online EC/OC analyzer, various kinds of instruments related to aerosol chemical properties were employed here, which provided a good opportunity to check data quality. The concentrations of OC correlated well with the mass of organic matter (OM) and water soluble organic carbon (WSOC), implying the reliability of the data measured in this campaign. The average OC concentrations in fine particle for three typical periods during the campaign (local emission influence, typhoon and precipitation and normal days) were 28.1 μgC m−3, 4.0 μgC m−3 and 5.7 μgC m−3, respectively; and EC were 11.6 μgC m−3, 1.8 μgC m−3, and 3.3 μgC m−3, respectively. The diurnal patterns of EC and OC during the campaign were higher at night and in early morning than daytime, which was probably caused by the primary emission and accumulation in the occurrence of low boundary layer. Compared with the constant diurnal enhancement ratios of EC, the enhancement ratio of OC (OC versus (CO-CObackground)) kept in a relative high level in the afternoon, with a similar diurnal profile to oxygenated organic aerosol (OOA), due to the strong photochemical formation of OC. Here, a modified EC tracer method was used to estimate the formation of secondary organic carbon (SOC). These results showed that the average SOC concentration (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 the average of 47%. The modified approach in this study proved to be effective and reliable for SOC estimation based on good correlations between estimated SOC versus OOA or WSOC, and estimated POC versus hydrocarbon-like organic aerosol (HOA).
Highlights
Carbonaceous aerosol is the main constituent (20–80 % of fine particle) in the particulate matter (Lim and Turpin, 2002)
Local emission influence days (8 % of total days) were characterized by high concentrations of carbonaceous aerosol starting from noon, 23 July to midnight, 25 July
A T0 site was an urban site located in the center of Mexico City. b T1 site was a suburb site in the down wind direction of Mexico City. c T2 site was a regional background site of Mexico City. d The concentrations of organic carbon (OC) and element carbon (EC) were the sum of the values in condensation mode (0.36-0.46μm) and droplet mode (0.8-1.1μm). e Personal communication. f The concentration of OC is calculated by organic matter (OM)/1.71. g Refer to the water soluble organic carbon (WSOC)/OC. h The data was calculated from oxygenated organic aerosol (OOA)/OA
Summary
Carbonaceous aerosol is the main constituent (20–80 % of fine particle) in the particulate matter (Lim and Turpin, 2002). High-time resolved estimation of POC and SOC contributions becomes an important and useful way to understand secondary organic formation processes (Lim and Turpin, 2002). A few studies on carbonaceous aerosol in the PRD region were conducted and relative high concentrations were usually detected, which were comparable to those in Beijing and Mexico City (Lin et al, 2009; Yu et al, 2009; Gnauk et al, 2008). A higher time resolution research of carbonaceous aerosol in PRD region is needed to explore primary emissions and secondary formation. The study focus was twofold: (1) to find the time variation characteristics of carbonaceous aerosol at a rural site of PRD; and (2) to distinguish and quantify the contributions of primary and secondary sources to carbonaceous aerosol
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
