[Analysis of Stable Carbon Isotope Characteristics of PM in Summer and Winter Season in Xinxiang City].

We study the seasonal variations of C ratios in aerosol fine particulate matter (PM) using 91 PM samples collected from Xinxiang, China, during the summer and winter in 2017. Mass concentrations of total carbon (TC), water soluble ions, and stable carbon isotope ratios (C) were determined. The mean concentrations of TC in the summer and winter were 11.78 μg·m and 26.6 μg·m, respectively. The C ratio in the summer ranged from -27.70‰ to -25.22‰. The daily C ratio fluctuated in the first half of the summer months (mean -26.96‰), whereas the C ratio in the second half of the summer was relatively stable (mean -25.69‰). The number of fires in the study area during the first half of the summer was quite different to the number during the second half of the summer, meanwhile, there was a positive correlation between the K concentration and the TC mass concentration (=0.62, <0.01). This indicates that biomass burning most likely contributed to variations in C. During the winter there was a significant negative correlation between winter RH and the TC/PM mass ratio (=0.68, <0.01), which suggests that SOA growth was dominant in the early stage of haze development, whereas the pollution period was dominated by SIA components. The ratio of C ranged from -26.72‰ to -23.49‰, and there was a difference between the variation of the C ratio in haze episode (when it was mainly enriched in the development stage) to that in the stage dominated by depletion.