Exploring the variation of black and brown carbon during COVID-19 lockdown in megacity Wuhan and its surrounding cities, China

• Published in: The Science of the total environment 2021-10, Vol.791, p.148226-148226, Article 148226
• Main Authors: Wang, Qinglu, Wang, Lili, Tao, Minghui, Chen, Nan, Lei, Yali, Sun, Yang, Xin, Jinyuan, Li, Tingting, Zhou, Jingxiang, Liu, Jingda, Ji, Dongsheng, Wang, Yuesi
• Format: Article
• Language: English
• Subjects: Black carbon; Brown carbon; Carbon - analysis; China; Cities; Communicable Disease Control; COVID-19; Environmental Monitoring; Humans; Light absorption; SARS-CoV-2; Soot - analysis
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.148226

Absorbing carbonaceous aerosols, i.e. black and brown carbon (BC and BrC), affected heavily on climate change, regional air quality and human health. The nationwide lockdown measures in 2020 were performed to against the COVID-19 outbreak, which could provide an important opportunity to understand their variations on light absorption, concentrations, sources and formation mechanism of carbonaceous aerosols. The BC concentration in Wuhan megacity (WH) was 1.9 μg m−3 during lockdown, which was 24% lower than those in the medium-sized cities and 26% higher than those in small city; in addition, 39% and 16–23% reductions occurred compared with the same periods in 2019 in WH and other cities, respectively. Fossil fuels from vehicles and industries were the major contributors to BC; and compared with other periods, minimum contribution (64–86%) mainly from fossil fuel to BC occurred during the lockdown in all cities. Secondary BrC (BrCsec) played a major role in the BrC light absorption, accounting for 65–77% in WH during different periods. BrCsec was promoted under high humidity, and decreased through the photobleaching of chromophores under higher Ox. Generally, the lockdown measures reduced the BC concentrations significantly; however, the variation of BrCsec was slight. [Display omitted] •BC decreased by 16–39% during lockdown compared with the same period in 2019.•Compared with other periods, the minimum contribution (64–86%) mainly from fossil fuel to BC occurred during lockdown.•Secondary BrC accounts for 75% to the total BrC at 370 nm during the lockdown.•Secondary BrC absorption was promoted (decreased) under higher humidity (Ox).•The decline of primary pollutants is more obvious than secondary due to lockdown.