Reply on RC1

Lingyu Li

doi:10.5194/acp-2021-675-ac1

Abstract

Coordinated control of fine particulate matter (PM2.5) and ozone (O3) has become a new and urgent issue for China’s air pollution control. Biogenic volatile organic compounds (BVOCs) are important precursors of O3 and secondary organic aerosol (SOA) formation. China experienced a rapid increase in BVOC emissions as a result of increased vegetation biomass. We applied WRF-Chem3.8 coupling with MEGAN2.1 to conduct long-term simulations for impacts of BVOC emissions on O3 and SOA during 1981–2018, using the emission factors extrapolated by localized emission rates and annual vegetation biomass. In summer of 2018, BVOC emissions are 9.91 Tg (in June), which lead to an average increase of 8.6 ppb (16.75 % of the total) in daily maximum 8-h (MDA8) O3 concentration and 0.84 μg m−3 (73.15 % of the total) in SOA over China. The highest contribution to O3 is concentrated in the Great Khingan Mountains, Qinling Mountains, and most southern regions, while southern areas for SOA. Isoprene has the greatest contribution to O3 while monoterpene has the largest SOA production. BVOC emissions have distinguished impacts in different regions. Chengdu-Chongqing (CC) region has the highest O3 and SOA generated by BVOCs while Beijing-Tianjin-Hebei (BTH) region has the lowest. From 1981 to 2018, the interannual variation of BVOC emissions caused by increasing leaf biomass results in O3 concentration increasing by 7.38 % at an average rate of 0.11 ppb yr−1, and SOA increasing by 39.30 % at an average rate of 0.008 μg m−3 yr−1. Due to the different changing trends of leaf biomass by regions and vegetation types, O3 and SOA show different interannual variations. Fenwei Plain (FWP), Yangtze River Delta (YRD), and Pearl River Delta (PRD) regions have the most rapid O3 increment while the increasing rate of SOA in CC is the highest. BTH has the smallest enhancement in O3 and SOA concentration. This study will help to recognize the impact of historical BVOC emissions on O3 and SOA, and further provide the reliable scientific basis for the precise prevention and control of air pollution in China.

Highlights

In recent years, China suffers from more and more severe O3 pollution with continuously increasing O3 concentration in most regions (Liu et al, 2018a; Liu and Wang, 2020; Wang et al, 2017)
Chengdu-Chongqing (CC) region has the highest O3 and secondary organic aerosol (SOA) generated by Biogenic volatile organic compounds (BVOCs) while Beijing-Tianjin-Hebei (BTH) region has the lowest
From 1981 to 2018, the interannual variation of BVOC emissions caused by increasing leaf biomass results in O3 concentration increasing by 7.38% at an average rate of 0.11 ppb yr-1, and SOA increasing by 39.30% at an average rate of 0.008 μg m-3 yr-1

Summary

Introduction

China suffers from more and more severe O3 pollution with continuously increasing O3 concentration in most regions (Liu et al, 2018a; Liu and Wang, 2020; Wang et al, 2017). PM2.5 and O3 are currently important atmospheric pollutants affecting air quality in urban and regional areas of 35 China. Their coordinated prevention and control has become a new and urgent issue for China’s air pollution control. Volatile organic compounds (VOCs) are precursors of O3 and secondary organic aerosol (SOA) formation (Claeys et al, 2004; Hallquist et al 2009; Kota et al 2015), which can be emitted by biogenic and anthropogenic sources. The high BVOC emissions can lead to great increases by 29–49% in surface O3 concentration in most 45 southern urban areas (Li et al, 2018; Liu et al, 2018b; Situ et al, 2013; Wu et al, 2020) and contribute 70–75% to China’s total SOA formation in summer (Hu et al, 2017; Wu et al, 2020). It is essential to understand the emission characteristics of BVOCs and their impacts on the formation of O3 and SOA for making effective policies of secondary air pollution control in China

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