北京市环境空气过氧乙酰基硝酸酯污染特征及其影响因素研究

Characteristics and Influencing Factors of Peroxyacetyl Nitrate Pollution in Ambient Air in Beijing

过氧乙酰基硝酸酯(PAN)是大气光化学污染指示物之一,研究PAN的污染特征及其影响因素对大气污染防治至关重要。本研究于2019年4-11月在北京市典型城区开展了PAN及其影响因素的综合观测,分析了PAN的污染特征以及各影响因素与PAN的相关关系,利用多元线性回归法构建了PAN浓度的经验方程并进行了验证。结果表明:①观测期间,PAN浓度平均值为15.86μg/m^(3);在光化学反应较为活跃的6月、7月和9月,PAN浓度高于其他月份;昼间PAN浓度高于夜间。②在光化学污染期间,PAN浓度与同时刻的O_(3)浓度、8 h前的NO浓度、8 h后的NO_(2)浓度、3 h后的NO与NO_(2)浓度之比、5 h前的丙烷浓度、同时刻的丙酮浓度、2h前的太阳辐射、2h前的紫外辐射、同时刻的相对湿度和同时刻的温度均具有较好的线性相关关系,这与“丙烷-丙酮-PAN”反应机理较为相符。③基于上述参数构建PAN浓度多元线性回归方程,并利用6月22-24日的观测结果进行验证,绝对误差范围为0.36~9.72μg/m^(3),为PAN浓度估算提供了一种可行的计算方法。研究显示,通过降低NO、丙烷和丙酮浓度以及削弱辐射强度、增湿、降温等手段能够降低若干小时后的PAN浓度,从而缓解大气光化学污染。

Peroxyacetyl nitrate(PAN)is a typical indicator of atmospheric photochemical pollution.Studying the characteristics and influencing factors of PAN is of great significance for the prevention and control of air pollution.Based on on-site observations in urban area of Beijing from April to November 2019,this study analyzed the pollution characteristics of PAN and the correlation between various influencing factors and PAN,and constructed and verified the multiple linear regression empirical equation of PAN concentration.The results show that:(1)The average concentration of PAN during the observation period was 15.86μg/m^(3).In June,July,and September,the photochemical reaction was more active,and the PAN concentration was higher than in other months.PAN concentrations were higher during the day than at night.(2)During the photochemical pollution period,PAN concentrations showed good linear correlation with simultaneous O_(3) concentrations,NO concentrations from 8 hours earlier,NO_(2) concentrations from 8 hours later,the ratio of NO to NO_(2) concentrations after 3 hours,propane concentrations from 5 hours earlier,simultaneous acetone concentrations,simultaneous acetaldehyde concentrations,solar radiation from 2 hours earlier,ultraviolet radiation from 2 hours earlier,simultaneous relative humidity,and simultaneous temperature,which was consistent with the‘propane-acetone-PAN’reaction mechanism.(3)Based on the above parameters,a multiple linear regression equation for PAN concentration was constructed and validated using the observations results from June 22nd to 24th.The absolute error range was 0.36-9.72μg/m^(3),which provides a feasible method for estimating PAN concentration.The research indicated that by reducing the concentrations of NO,propane,and acetone,weakening the radiation intensity,increasing humidity,and lowering the temperature,the concentration of PAN can be reduced within a few hours,thereby mitigating atmospheric photochemical pollution.