北京市2020年春节期间空气质量影响因素分析

2020年春节期间由于新冠肺炎疫情的大范围暴发,包括北京在内的多个城市经济社会活动较长时间处于低水平状态。但是在此期间,北京市出现了两次(农历正月初二至初六、正月十六至十九)污染水平不逊于往年的重污染天气,成为社会各界关注的焦点。本文以北京市2016-2020年春节期间的空气质量为研究对象,首先运用多元线性回归法判断了气象因素以及经济和社会活动因素对四类污染物(PM_2.5、PM₁₀、NO_2和SO₂)的影响程度,进一步研究了在2020年春节期间的两次重污染时段内各个因素对PM_2.5的影响程度,最后运用双重差分法评估春节期间的疫情管控措施对北京市空气质量产生的影响。多元线性回归结果显示在2016-2020年春节期间:(1)气象因素对北京市的PM_2.5、PM₁₀、NO₂和SO₂四类污染物浓度的影响占主导地位,其中温度、湿度与四类污染物浓度变化均显著正相关,气压和降水与四类污染物浓度变化均显著负相关;(2)经济活动水平与NO₂浓度水平有显著正相关关系,说明随着经济活动水平强度的降低和交通流量的下降,NO₂浓度呈现出降低趋势,而PM_2.5、PM₁₀和SO₂与经济活动水平分别有正相关、正相关和负相关关系,但并不显著;(3)从社会活动来看,燃放烟花爆竹会增大PM_2.5、PM₁₀和SO₂浓度,同时假期变量对PM_2.5和SO₂的浓度变化也存在显著正向影响。对于2020年春节期间的两次重污染过程来说,气象依然是主要影响因素,但是各因素的贡献值有所不同;春节期间经济活动水平对正月初二至初六重污染过程的贡献较小(2%),而对正月十六至十九有明显的负影响(-20%)。双重差分法评估结果显示,疫情管控对PM₁₀和NO₂有缓解效果,而对PM_2.5和SO₂未见明显影响,这表示疫情管控措施对空气质量施加了影响。本文不仅识别出了春节期间气象因素、经济社会活动与北京市四类污染物浓度之间的关系,有助于厘清各因素对空气质量产生影响的方式,而且对进一步改善北京市及京津冀地区的空气质量具有重要启示意义。

Analysis on the influencing factors of air quality during the Spring Festival in Beijing in 2020

With the outbreak of COVID-19 during the Spring Festival in China,social and economic activities in many cities,including Beijing,remain at low levels for a few weeks.However,Beijing was shrouded in heavy smog for many days(from 2nd day to 6th day of lunar January,and from 16th day to 19th day of lunar January),which was comparable with the heavily polluted air quality and draw all attention of the whole society.This paper analyzes the air quality in Beijing during the epidemic to explain how heavy air pollution happens.The multiple linear regression is applied first to evaluate the impact of meteorological factors and economic and social activities on PM2.5,PM10,NO₂ and SO₂,and further explain the impact of various factors on PM25 during the two heavy pollution periods during the Spring Festival in 2020.Then we use the difference in differences method to assess the impact of the lockdown on the air quality in Beijing.Multiple linear regression results demonstrate that during the Spring Festival of 2016-2020:(1)meteorological factors have a dominating effect on the concentrations of PM2.5,PM10,NO₂ and SO₂ in Beijing,among which temperature and humidity are significantly positively correlated with the four pollutants,and pressure and precipitation are significantly negatively correlated with the four pollutants.(2)there is a significant positive correlation relationship between the level of economic activity and NO₂,indicating that with the intensity of the level of economic activity and the traffic flow decrease,the NO₂concentration also decreases,while PM2.5,PM10 and SO₂ have positive,positive and negative correlations respectively with the level of economic activity,but are not significant.(3)from the perspective of social activities,the firecrackers will increase the concentrations of PM2.5,PM10 and SO₂,and the holiday also has a significant positive effect on the concentrations of PM25 and SO2.Regarding the two heavy pollution periods during the Spring Festival in 2020,unfavorable meteorological conditions are still the main factor,but the contribution of each factor is different.Economic activity increases the air pollution level(2%)from the 2nd day to 6th day in lunar January but has a significant negative impact(-20%)from 16th day to 19th day in lunar January.The results of the difference in differences method show that the lockdown during the epidemic affects the air quality in Beijing.Specifically,the lockdown has a mitigating effect on PM₁₀ and NO₂,while no obvious effect on PM2.5 and SO₂.The paper helps to not only understand the relationship between meteorological factors and socioeconomic activities and the four types of pollutants in Beijing during the Spring Festival,but also clarify how various factors affect the air quality,which has a great significance to further improve the air quality in Beijing and the Beijing-Tianjin-Hebei region.