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Response of surface ozone concentration to emission reduction and meteorology during the COVID‐19 lockdown in Europe

ABSTRACT: Abstract The lockdown period (March–May 2020) during the COVID‐19 pandemic in Europe led to a reduction in the anthropogenic emissions of primary pollutants. For three‐quarters of over 1,100 available monitoring stations, the average nitrogen dioxide (NO2) concentrations decreased by at least 2.7 μg·m−3 (or 25%) compared with the average concentrations recorded during the same period of the previous seven years. This reduction was not specific to urban or rural areas because the relative reduction was of similar magnitude in both areas. The ozone (O3) response differed spatially, with positive anomalies in Northern Europe and negative anomalies in Southwestern Europe. Reduced cloudiness and related enhanced radiation in Northern Europe played a significant role in the increase of surface O3 concentrations by shifting the photochemical partitioning between NO2 and O3 toward more O3. The level of total oxidant (Ox = O3 + NO2) remained unchanged, except in Southwestern Europe where it decreased. Several episodes lasting a few days of a high level of total oxidants were observed in Northern Europe. The results illustrate the complexity of the atmospheric response to the unprecedented reduction in the emission of primary pollutants. Anomalies of (a) nitrogen dioxide (NO2) mean concentration and (b) ozone (O3) mean concentration at European Air Quality e‐Reporting database (AirBase) stations in 2020 compared with the previous seven years (2013–2019) for the period March 18–May 18, 2020. Dots are coloured according to the anomalies in concentration (μg·m−3) and sized proportionally to the relative change (%). Black dots correspond to stations with < 30% of available data.

SUBMITTER: Deroubaix A

PROVIDER: S-EPMC8206774 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Climate and air quality change due to COVID-19 lockdown (LCD) are extremely concerned subjects of several research recently. The contribution of meteorological factors and emission reduction to air pollution change over the north of Morocco has been investigated in this study using the framework generalized additive models, that have been proved to be a robust technique for the environmental data sets, focusing on main atmospheric pollutants in the region including ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter (PM2.5 and PM10), secondary inorganic aerosols (SIA), nom-methane volatile organic compounds and carbon monoxide (CO) from the regional air pollution dataset of the Copernicus Atmosphere Monitoring Service. Our results, indicate that secondary air pollutants (PM2.5, PM10 and O3) are more influenced by metrological factors and the other air pollutants reported by this study (NO2 and SO2). We show a negative effect for PBHL, total precipitation and NW10M on PM (PM2.5 and PM10 ), this meteorological parameters contribute to decrease in PM2.5 by 9, 2 and 9% respectively, before LCD and 8, 1 and 5% respectively during LCD. However, a positive marginal effect was found for SAT, Irradiance and RH that contribute to increase PM2.5 by 9, 12 and 18% respectively, before LCD and 17, 54 and 34% respectively during LCD. We found also that meteorological factors contribute to O3, PM2.5, PM10 and SIA average mass concentration by 22, 5, 3 and 34% before LCD and by 28, 19, 5 and 42% during LCD respectively. The increase in meteorological factors marginal effect during LCD shows the contribution of photochemical oxidation to air pollution due to increase in atmospheric oxidant (O3 and OH radical) during LCD, which can explain the response of PM to emission reduction. This study indicates that PM (PM2.5, PM10) has more controlled by SO2 due to the formation of sulfate particles especially under high oxidants level. The positive correlation between westward wind at 10 m (WW10M), Northward Wind at 10 m (NW10M) and PM indicates the implication of sea salt particles transported from Mediterranean Sea and Atlantic Ocean. The Ozone mass concentration shows a positive trend with Irradiance, Total and SAT during LCD; because temperature and irradiance enhance tropospheric ozone formation via photochemical reaction.This study shows the contribution of atmospheric oxidation capacity to air pollution change.Supplementary informationThe online version contains supplementary material available at 10.1007/s00477-022-02224-z.

Project description:With the implementation of COVID-19 restrictions and consequent improvement in air quality due to the nationwide lockdown, ozone (O3) pollution was generally amplified in China. However, the O3 levels throughout the Guangxi region of South China showed a clear downward trend during the lockdown. To better understand this unusual phenomenon, we investigated the characteristics of conventional pollutants, the influence of meteorological and anthropogenic factors quantified by a multiple linear regression (MLR) model, and the impact of local sources and long-range transport based on a continuous emission monitoring system (CEMS) and the HYSPLIT model. Results show that in Guangxi, the conventional pollutants generally declined during the COVID-19 lockdown period (January 24 to February 9, 2020) compared with their concentrations during 2016-2019, while O3 gradually increased during the resumption (10 February to April 2020) and full operation periods (May and June 2020). Focusing on Beihai, a typical Guangxi region city, the correlations between the daily O3 concentrations and six meteorological parameters (wind speed, visibility, temperature, humidity, precipitation, and atmospheric pressure) and their corresponding regression coefficients indicate that meteorological conditions were generally conducive to O3 pollution mitigation during the lockdown. A 7.84 μg/m3 drop in O3 concentration was driven by meteorology, with other decreases (4.11 μg/m3) explained by reduced anthropogenic emissions of O3 precursors. Taken together, the lower NO2/SO2 ratios (1.25-2.33) and consistencies between real-time monitored primary emissions and ambient concentrations suggest that, with the closure of small-scale industries, residual industrial emissions have become dominant contributors to local primary pollutants. Backward trajectory cluster analyses show that the slump of O3 concentrations in Southern Guangxi could be partly attributed to clean air mass transfer (24-58%) from the South China Sea. Overall, the synergistic effects of the COVID-19 lockdown and meteorological factors intensified O3 reduction in the Guangxi region of South China.

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Response of surface ozone concentration to emission reduction and meteorology during the COVID‐19 lockdown in Europe

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