Pollution-Derived Br2 Boosts Oxidation Power of the Coastal Atmosphere

• DOI: 10.1021/acs.est.2c02434
• Publication Date: 2022-08-10T23:09:26Z
• Authors: Men Xia; Tao Wang; Zhe Wang; Yi Chen; Xiang Peng; Yunxi Huo; Weihao Wang; Qi Yuan; Yifan Jiang; Hai Guo; Chiho Lau; Kenneth Leung; Alfred Yu; Shuncheng Lee
• Keywords: Peroxyacetyl nitrate; Atmospheric chemistry; Isoprene; Mixing ratio

The bromine atom (Br•) has been known to destroy ozone (O3) and accelerate the deposition of toxic mercury (Hg). However, its abundance sources outside polar regions are not well-known. Here, we report significant levels molecular (Br2)─a producer Br•─observed at a coastal site in Hong Kong, with an average noontime mixing ratio 5 ppt. Given short lifetime Br2 (∼1 min noon), this finding reveals large daytime source. On basis laboratory field evidence, show that observed is generated by photodissociation particulate nitrate (NO3-) reactive uptake dinitrogen pentoxide (N2O5) on aerosols important nighttime Model-calculated Br• concentrations comparable OH radical─the primary oxidant troposphere, accounting for 24% oxidation isoprene, 13% increase net O3 production, nearly 10-fold production rate HgII. Our findings reveal bromines play larger role atmospheric chemistry air quality polluted maritime areas than previously thought. results also suggest tightening control emissions two conventional pollutants (NOx SO2)─thereby decreasing aerosol acidity─would alleviate halogen radical adverse impact quality.