Exploring wintertime regional haze in Northeast China: role of coal and biomass burning

Abstract

<p><strong>Abstract.</strong> As one of the intense anthropogenic emission regions across the relatively high latitude (> 40° N) areas on the Earth, Northeast China faces serious problem on regional haze during long winter with half a year. Aerosols in polluted haze in Northeast China are poorly understood compared with the haze in other regions of China such as North China Plain. Here, we for the first time integrated bulk chemical measurements with single particle analysis from transmission electron microscopy (TEM), nanoscale secondary ion mass spectrometer (NanoSIMS), and atomic force microscopy (AFM) to obtain morphology, size, composition, aging process, and sources of aerosol particles collected during two contrasting regional haze events (Haze-I and Haze-II) at an urban site and a mountain site in Northeast China, and further investigated the causes of regional haze formation. Haze-I evolved from moderate (average PM<sub>2.5</sub>: 76–108 μg/m<sup>3</sup>) to heavy pollution (151–154 μg/m<sup>3</sup>), with the dominant PM<sub>2.5</sub> component changing from organic matter (OM) (39–45 μg/m<sup>3</sup>) to secondary inorganic ions (94–101 μg/m<sup>3</sup>). Similarly, TEM observations showed that S-OM particles elevated from 29 % to 60 % by number at urban site and 64 % to 74 % at mountain site and 75–96 % of Haze-I particles included primary OM. Change of wind direction induced that Haze-I rapidly turned into Haze-II (185–223 μg/m<sup>3</sup>) with the predominant OM (98–133 μg/m<sup>3</sup>) and unexpectedly high K<sup>+</sup> (3.8 μg/m<sup>3</sup>). TEM also showed that K-OM particles increased from 4–5 % by number to 50–52 %. Our study revealed a contrasting formation mechanism of these two haze events: Haze-I was induced by accumulation of primary OM emitted from residential coal burning and further deteriorated by secondary aerosol formation via heterogeneous reactions; Haze-II was caused by long-range transport of agricultural biomass burning emissions. Moreover, we found that 75–97 % of haze particles contained tarballs, but only 4–23 % contained black carbon and its concentrations were low at 2.7–4.3 μg/m<sup>3</sup>. The results highlight that abundant tarballs are important light-absorbing brown carbon in Northeast China during winter haze and further considered in climate models.</p>

Chemical compositions and possible transportation of PM2.5 during two haze periods in a coastal city of the North China Plain

“…The results suggested that haze formation in this study might be affected by combustion sources. Cl À and Na + were mainly from industrial emissions and coal combustions (Zhang et al, 2017); K + can be from biomass and coal combustions (Zhang et al, 2020). The CCs of Cl À , Na + , K + with PM 2.5 were 0.83, 0.79, and 0.88, showing positive correlations.…”