Fog geoengineering to abate local ozone pollution at ground level by enhancing air moisture

Abstract

High concentrations of ozone (O_3) at ground level in urban and industrial regions worldwide have long been a major air pollution issue, notably during daytime because sunlights induce the photochemical production of ozone. After a review of actual techniques to clean O_3 pollution in urban and industrial regions, I present a fog geoengineering scheme for abating ozone pollution at ground level by enhancing ambient moisture locally through spraying water mist into the atmosphere. This scheme is based on my results showing that ozone levels decrease with air relative humidity. For instance, the mean O_3 concentrations decrease from 70.0 to 21.2 ppbv when relative humidity increases from below 40% to more than 80%, in Hangzhou city at midday times (11:00–16:00) without precipitation, during the "ozone season" from May to October of 2017. The mechanism of fog geoengineering is that atmosphere moisture inhibits O_3 formation by lowering air temperature, decreasing the chain length of peroxy radical chemical amplifiers (HO_2, RO_2, and RC(O)O_2), and decreasing the chain length of NO_2 by enhancing particle water, and destroys the existing O3 photo-chemically by water vapor through catalytic O_3 destruction cycle. Ozone mitigation by fog geoengineering has several advantages such as being a nature-like process, quick response, technological feasibility, efficacy, relatively low cost, and cooling effects. The proposed fog geoengineering to decrease the local O_3 at ground level could potentially be on avenue for addressing heavy O_3 pollution during the hot summer in megacities globally as expected.

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