key: cord-0777318-ssnzv437 authors: Wu, Cui-Lin; Wang, Hong-Wei; Cai, Wan-Jin; He, Hong-Di; Ni, An-Ning; Peng, Zhong-Ren title: Impact of the COVID-19 lockdown on roadside traffic-related air pollution in Shanghai, China date: 2021-02-18 journal: Build Environ DOI: 10.1016/j.buildenv.2021.107718 sha: a62bb7ef184b2eb1aecd974691a9d2e8ac567398 doc_id: 777318 cord_uid: ssnzv437 The outbreak of COVID-19 has significantly inhibited global economic growth and impacted the environment. Some evidence suggests that lockdown strategies have significantly reduced traffic-related air pollution (TRAP) in regions across the world. However, the impact of COVID-19 on TRAP on roadside is still not clearly understood. In this study, we assessed the influence of the COVID-19 lockdown on the levels of traffic-related air pollutants in Shanghai. The pollution data from two types of monitoring stations—roadside stations and non-roadside stations were compared and evaluated. The results show that NO(2), PM(2.5), PM(10), and SO(2) had reduced by ∼30–40% at each station during the COVID-19 pandemic in contrast to 2018–2019. CO showed a moderate decline of 28.8% at roadside stations and 16.4% at non-roadside stations. In contrast, O(3) concentrations increased by 30.2% at roadside stations and 5.7% at non-roadside stations. This result could be resulted from the declined NOx emissions from vehicles, which lowered O(3) titration. Full lockdown measures resulted in the highest reduction of primary pollutants by 34–48% in roadside stations and 18–50% in non-roadside stations. The increase in O(3) levels was also the most significant during full lockdown by 64% in roadside stations and 33% in non-roadside stations due to the largest decrease in NO(2) precursors, which promote O(3) formation. Additionally, Spearman's rank correlation coefficients between NO(2) and other pollutants significantly decreased, while the values between NO(2) and O(3) increased at roadside stations. significant reduction in criteria air pollutants levels (e.g., NO x , SO 2 , PM 2.5 , PM 10 , and CO) 48 during the COVID-19 lockdown period across the world's most polluted cities (e.g. 49 Wuhan, Bangalore, Beijing, Bangkok, Delhi, Nanjing, New York, and Milan), due to the 50 absence of motor vehicle traffic and suspended manufacturing within lockdown 51 restrictions [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] . For instance, [16] observed the significant reduction in ambient 52 PM 10 , PM 2.5 , NO 2 and SO 2 levels in Delhi and Mumbai cities during post-lockdown 53 J o u r n a l P r e -p r o o f phase in comparison with the same time span in 2019 (by almost 55%, 49%, 60% and 54 19%, and 44%, 37%, 78% and 39%, respectively). In another study, over 300 cities in 55 China experienced a huge decrease in the concentrations of critical air pollutants (PM 2.5 , 56 PM 10 We compared the air quality changes between the roadside and non-roadside stations 198 to quantitatively evaluate the impacts of the COVID-19 lockdown on TRAP in Shanghai. In contrast, non-roadside monitoring stations showed a slightly higher increase during the 302 night, which may be linked to the decrease in nitrogen oxide production in non-roadside 303 areas. This phenomenon would have decreased nitric acid concentrations and 304 hydrocarbon oxidisation, leading to a reduction in O 3 consumption at night [50] . As an 305 industrial sector pollutant, we observed significant differences in SO 2 between the 306 daytime and night-time at roadside stations (33.5% vs. 24.5%). However, the percentage 307 decrease at non-roadside areas was almost the same (39% vs. 38.5%). 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I agree that I will disqualify myself from reviewing, editing, or participating in editorial decisions about any Journal of Building and Environment submission that deals with a matter in which either I or a member of my immediate family (ie, my spouse, domestic partner, or minor children) have direct financial interest or a competing financial interest (eg, employment or affiliation, grants or funding, consultancies, honoraria, stock ownership or stock options, expert testimony, royalties, or patents filed, received, or pending). This also applies to the past 5 years and the foreseeable future.I also agree that I will not use any confidential information obtained from my activities with Journal of Building and Environment to further my own or others financial interests.Yours faithfully, Hong-di He On behalf of all authors Feb 8, 2021