[Analysis on the Characteristics of Oxidation Potential and Influence Sources of PM 2.5 in Baoding City in Winter].

In order to explore the characteristics of PM _2.5 oxidation potential and its impact sources in the suburbs of Baoding City in the winter of 2018, the dithiothreitol (DTT) method was used to determine the reactive oxygen species in PM _2.5 . Pearson correlation was used to analyze the relationship between the chemical components in PM _2.5 and the oxidation potential. PMF was used to analyze the pollution source of DTT _v . Firstly, the results showed that the average value of ρ (PM _2.5 ) in Baoding in winter was (140.96±70.67) μg·m ^-3 higher than the concentration of PM _2.5 in Beijing during the same period. Secondly, both the DTT _v and DTT _m values of the oxidation potential were higher during the day than those at night[DTT _v was (2.37±0.76) nmol·(min·m ³ ) ^-1 during the day and (2.14±1.17) nmol·(min·m ³ ) ^-1 at night; DTT _m was (0.96±0.60) pmol·(min·μg) ^-1 during the day and (0.76±0.41) pmol·(min·μg) ^-1 at night]. This showed that the atmospheric environment during the day was more conducive to the generation and survival of active oxygen. In addition, through the analysis of the correlation between DTT _v and carbohydrates, inorganic salt ions, OC, EC, and water-soluble metals, it was found that metal Fe, oxalate, and NH ₄ ⁺ had a high correlation with DTT _v both day and night (during the day: r =0.790, P <0.01, at night: r =0.960, P <0.01; during the day: r =0.609, P <0.01, at night: r =0.577, P <0.01; during the day: r =0.627, P <0.01, at night: r =0.586, P <0.01), and OC, levoglucan, mannan, and galactan were only highly correlated with DTT _v in the daytime ( r =0.675, P <0.01; r =0.701, P <0.01; r =0.662, P <0.01; r =0.671, P <0.01). Finally, according to the PMF source analysis, there were five main pollution sources that affected DTT _v :secondary sources (29.9%), biomass combustion (29.2%), dust (11.2%), mineral dust and industrial sources (8.6%), and traffic sources (21.1%). The influence of secondary sources and biomass combustion on DTT _v was dominant.