Technical note: Towards a stronger observational support for haze pollution control by interpreting carbonaceous aerosol results derived from different measurement approaches

Abstract. As China’s fine particulate matter (PM_2.5) has decreased nationwide during the last decade, further improvement of air quality became more challenging, imposing higher requirements on the observational support for the understanding of aerosol sources. This was particularly the case for the severe cold climate region in Northeast China, which suffered from relatively slow decreasing rate and high exposure risk of PM_2.5. Here we evaluated carbonaceous aerosol data measured by different sampling and analytical approaches, based on field campaigns conducted during a frigid winter and an agricultural-fire impacted spring in Harbin. For both the high- and low-volume sampling, a total of four sets of organic and elemental carbon results were derived by applying two commonly-used temperature protocols (IMPROVE-A, i.e., IMPV, and NIOSH) to both untreated filters and those extracted by methanol. Only the IMPV-based results measured before the extraction were found to be indicative of aerosol sources, e.g., in reasonable accordance with secondary aerosol formation in winter and open burning impacts in spring. Thus the analytical method of IMPROVE-A on untreated samples was recommended for future field observations and source apportionments of PM_2.5 in the studied region. In addition, although the low- and high-volume samplers typically led to comparable measurement results for various species, exceptions were identified for water-soluble potassium (K⁺) and some fire-emitted chromophores. We suggested that K⁺ detected by different PM_2.5 samplers may not be directly comparable, and K⁺ should be used with caution as a biomass burning tracer for studies relying on high-volume measurements.