河南省春节和疫情影响情景下PM2.5组分特征

2020年1月我国爆发了新型冠状病毒疫情，期间我国各地区大气污染源排放特征发生了显著改变.为研究该情景下PM_2.5组分特征，本研究于2020年1月1日~2月13日利用在线观测仪器对郑州、安阳和新乡市进行连续观测.根据春节假期和疫情爆发，将研究时期分为春节前（1月1~23日）、春节疫情期（1月24~31日）和节后疫情期（2月1~13日）.受疫情和有利的气象条件影响，节后疫情期间郑州、安阳和新乡市除O₃外其它污染物浓度较春节前均明显下降，其中NO₂和PM_2.5的降幅分别为65%、52%、72%和51%、55%、54%，但是污染物浓度仍较高，表明未来河南省冬季大气污染的较大幅度改善面临巨大挑战.从颗粒物组分来看，二次无机盐和有机物是观测期间PM_2.5的主要组分.春节疫情期3个城市受烟花爆竹的影响较小，并且硝酸根和扬尘的贡献相比春节前轻微下降.节后疫情期间郑州、安阳和新乡市PM_2.5中硝酸根浓度和占比显著下降，占比降幅为10.6%、4.1%和4%；硫酸根和有机物的占比上升，其中二次有机碳的贡献增大.以郑州市为例分析硝酸盐生成，相比春节前，节后疫情期间不同污染时段硝酸根的占比均下降，但硝酸根仍是污染时段PM_2.5中占比最高的组分.日变化特征表明节后疫情期间大气中O₃浓度和湿度的增高可能促进了NO₂的转化，因此下一步应采取PM_2.5和O₃的协同管控，重视NO₂和VOCs的协同减排.

Chemical composition characteristics of PM2.5 in Henan Province during the Spring Festival and COVID-19 outbreak

In January 2020, a new coronavirus epidemic broke out in China, when the emission characteristics of air pollution have changed significantly. To study the characteristics of PM_2.5 components under this scenario, a series of online observation instruments were used in Zhengzhou, Anyang, and Xinxiang cities from January 1 to February 13, 2020. The study period is divided into pre-holiday (January 1 to 23), mid-holiday outbreak (January 24 to 31), and post-holiday outbreak (February 1 to 13) based on the Spring Festival holiday and the outbreak of the epidemic. Affected by the outbreak and favorable meteorological conditions, the concentrations of other pollutants except O₃ in the three cities during the post-holiday outbreak were significantly lower than those during pre-holiday, especially NO₂ decreased by 65%, 52%, and 72% and PM_2.5 decreased by 51%, 55%, and 54%, respectively. Note that the pollutants remained high concentration, indicating that a large improvement in winter air quality in Henan Province will face great challenges in the future. Secondary inorganic aerosols and organic matter were the main components of PM_2.5 during the observation periods. During the mid-holiday outbreak, the three cities were less affected by fireworks, and the contribution of nitrate and dust decreased slightly compared to before the pre-holiday. After the holiday, the proportions of nitrate decreased by 10.6%, 4.1%, and 4% in Zhengzhou, Anyang, and Xinxiang, respectively. In contrast, the proportions of sulfate and secondary organic carbon increased. Taking Zhengzhou City as an example to analyze the formation of nitrate, compared to pre-holiday, the proportions of nitrate under different pollution levels in the post-holiday outbreak have decreased, but nitrate was still the highest proportion of PM_2.5 during the polluted period. The characteristics of diurnal variation indicate that the increase in O₃ concentration and humidity in the atmosphere during the post-holiday outbreak may promote the conversion of NO₂. Therefore, the next step should be to adopt the coordinated management and control of PM_2.5 and O₃ and pay attention to the coordinated reduction of NO₂ and VOCs.