Ozone(O_(3))pollution is usually linked to warm weather and strong solar radiation,making it uncommon in cold winters.However,an unusual occurrence of four high O_(3)episode days(with maximum hourly concentrations exc...Ozone(O_(3))pollution is usually linked to warm weather and strong solar radiation,making it uncommon in cold winters.However,an unusual occurrence of four high O_(3)episode days(with maximum hourly concentrations exceeding 100 ppbv and peaking at 121 ppbv)was recorded in January 2018 in Lanzhou city,China.During these episodes,the average daytime concentration of total non-methane volatile organic compounds(TVOCs)reached 153.4±19.0 ppbv,with alkenes—largely emitted from the local petrochemical industry—comprising 82.3±13.1 ppbv.Here we show a photochemical box model coupled with a Master Chemical Mechanism to elucidate the mechanisms behind this unusual wintertime O_(3)pollution.We find that the typically low temperatures(−1.7±1.3°C)and weak solar radiation(263.6±60.7 W m^(-2))of those winter episode days had a minimal effect on the reactivity of VOCs with OH radicals.Instead,the ozonolysis of alkenes generated Criegee intermediates,which rapidly decomposed into substantial ROx radicals(OH,HO_(2),and RO_(2))without sunlight.This radical production led to the oxidation of VOCs,with alkene ozonolysis ultimately contributing to 89.6±8.7%of the O_(3)formation during these episodes.This mechanism did not activate at night due to the depletion of O_(3)by the NO titration effect.Furthermore,the findings indicate that a reduction of alkenes by 28.6%or NO_(x)by 27.7%in the early afternoon could significantly mitigate wintertime O_(3)pollution.Overall,this study unravels the unique mechanism of alkene-induced winter O_(3)pollution and offers a reference for winter O_(3)reduction strategies in the petrochemical industrial regions.展开更多
基金Research Grants Council(RGC)of the Government of the Hong Kong Special Administrative Region(PolyU 152124/21 E and N_PolyU530/20)research support scheme of Research Institute for Land and Space at The Hong Kong Polytechnic University(1-CD79)Start-up Fund for RAPs under the Strategic Hiring Scheme of the Hong Kong Polytechnic University(1-BD3T).
文摘Ozone(O_(3))pollution is usually linked to warm weather and strong solar radiation,making it uncommon in cold winters.However,an unusual occurrence of four high O_(3)episode days(with maximum hourly concentrations exceeding 100 ppbv and peaking at 121 ppbv)was recorded in January 2018 in Lanzhou city,China.During these episodes,the average daytime concentration of total non-methane volatile organic compounds(TVOCs)reached 153.4±19.0 ppbv,with alkenes—largely emitted from the local petrochemical industry—comprising 82.3±13.1 ppbv.Here we show a photochemical box model coupled with a Master Chemical Mechanism to elucidate the mechanisms behind this unusual wintertime O_(3)pollution.We find that the typically low temperatures(−1.7±1.3°C)and weak solar radiation(263.6±60.7 W m^(-2))of those winter episode days had a minimal effect on the reactivity of VOCs with OH radicals.Instead,the ozonolysis of alkenes generated Criegee intermediates,which rapidly decomposed into substantial ROx radicals(OH,HO_(2),and RO_(2))without sunlight.This radical production led to the oxidation of VOCs,with alkene ozonolysis ultimately contributing to 89.6±8.7%of the O_(3)formation during these episodes.This mechanism did not activate at night due to the depletion of O_(3)by the NO titration effect.Furthermore,the findings indicate that a reduction of alkenes by 28.6%or NO_(x)by 27.7%in the early afternoon could significantly mitigate wintertime O_(3)pollution.Overall,this study unravels the unique mechanism of alkene-induced winter O_(3)pollution and offers a reference for winter O_(3)reduction strategies in the petrochemical industrial regions.
