Determination of Elemental and Organic Carbon in PM2.5 in the Pearl River Delta Region: Inter-Instrument (Sunset vs. DRI Model 2001 Thermal/Optical Carbon Analyzer) and Inter-Protocol Comparisons (IMPROVE vs. ACE-Asia Protocol) |
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| Authors: | Cheng Wu Wai Man Ng Jingxiang Huang Dui Wu Jian Zhen Yu |
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| Affiliation: | 1. Division of Environment , Hong Kong University of Science and Technology , Kowloon , Hong Kong , China;2. Environmental Central Facility , Hong Kong University of Science and Technology , Kowloon , Hong Kong , China;3. Atmospheric Research Centre, Fok Ying Tung Graduate School , Hong Kong University of Science and Technology , Nansha , China;4. Institute of Tropical and Marine Meteorology, China Meteorological Administration , Guangzhou , China;5. Division of Environment , Hong Kong University of Science and Technology , Kowloon , Hong Kong , China;6. Atmospheric Research Centre, Fok Ying Tung Graduate School , Hong Kong University of Science and Technology , Nansha , China;7. Department of Chemistry , Hong Kong University of Science and Technology , Kowloon , Hong Kong , China |
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| Abstract: | Organic carbon (OC) and elemental carbon (EC) are operationally defined due to the lack of definitive standards. Consequently, their quantification is protocol dependent. IMPROVE and NIOSH are the two widely used thermal/optical protocols for OCEC analysis, differing in temperature programs and in the optical method for charring correction. The IMPROVE protocol is often implemented on a DRI analyzer while the NIOSH protocol is often implemented on a Sunset Laboratory Analyzer. Evaluation of the implementation of the IMPROVE protocol on the Sunset Laboratory analyzer or implementation of the NIOSH or NIOSH-derived protocols on the DRI analyzer has rarely been reported. We analyzed OC and EC in about 100 ambient samples collected in the Pearl River Delta in China by implementing the IMPROVE protocol and a NIOSH-derived (ACE-Asia) protocol on both a DRI Model 2001 analyzer and a Sunset Laboratory analyzer. The total carbon (TC) and EC filter loading as determined by the ACE-Asia protocol on the Sunset analyzer varied from 2.6 to 67.0 and 0.2 to 7.4 μg cm?2, respectively. Inter-instrument comparison indicates that the implementation of the IMPROVE protocol on the Sunset analyzer reports TC, EC, and OC measurements to be in good agreement with those made on the DRI analyzer. EC and OC analyzed using the ACE-Asia protocol are also in good agreements for measurements implemented on the Sunset and DRI analyzers. Inter-protocol comparison indicates consistency in TC determination but discrepancies in OC and EC, with the IMPROVE protocol reporting much higher EC than the ACE-Asia protocol. An analysis of different comparison scenarios reveals that the cause of the EC difference could be quantitatively attributed to temperature protocol (thermal effect) and optical pyrolysis correction method (reflectance vs. transmittance). The variation in EC concentrations was more pronounced in samples that produced more charred OC during thermal analysis. Copyright 2012 American Association for Aerosol Research |
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