Elucidating pollution characteristics, temporal variation and source origins of carbonaceous species in Xinxiang, a heavily polluted city in North China

In order to understand temporal variations, sources origins of carbonaceous components in Xinxiang, an industry city in North China, high time resolution of OC and EC were observed from March 2021 to February 2022. The results illustrated annual average OC and EC concentrations were 5.76 ± 3.65 and 0.83 ± 0.56 μg m−3, respectively. Obvious seasonal and monthly fluctuations of carbonaceous components were observed with high values in cold seasons and low levels in warm seasons. Meanwhile, diurnal variation patterns of carbonaceous species illustrated temporal evolution of boundary layer height (BLH) and variation in emission intensity strongly affected carbonaceous component levels. In addition, obvious correlations between OC and EC (p < 0.001) were found with higher correlation coefficient in autumn, demonstrating they were be likely to originate from similar sources or POC contributed more to OC. The minimum R squared (MRS) method was adopted to calculate second organic carbon (SOC) concentration, represented 52%, 53%, 33%, and 52% of OC in spring, summer, autumn, and winter, respectively. Moreover, two different formation pathways (photochemical oxidation and heterogeneous reactions) of SOC were found in diverse seasons. Furthermore, nonparametric wind regression (NWR) method and potential source contribution function (PSCF) showed the sources from southeast, southwest, and northwest areas were considered as important contributors of carbonaceous species in Xinxiang. This work elucidates the significance of strict control precursors of carbonaceous components and the pressing requirements for coordinated inter−regional prevention and control of air pollution for further improving air quality.