Nighttime aqueous oxidation of fossil fuel emissions is a significant source of atmospheric secondary organic aerosols.However,the underlying mechanism of the aqueous processing remains unclear.Utilizing ultrahigh-res...Nighttime aqueous oxidation of fossil fuel emissions is a significant source of atmospheric secondary organic aerosols.However,the underlying mechanism of the aqueous processing remains unclear.Utilizing ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry of watersoluble organic carbon samples,we present field observations that reveal the aqueous-phase conversion of nitroaromatic compounds(NACs)and sulfur-containing aerosols from fossil fuel combustion at high relative humidity during a severe haze event in Beijing in the winter of 2016.We have confirmed that the ring-breaking oxidation of NACs can generate nitrous acid in the aqueous phase,which rapidly oxidizes sulfur dioxide(SO_(2))to sulfate.Subsequently,reactions between sulfate and unsaturated compounds contribute to the formation of aliphatic organosulfates.Our results elucidate a molecular-level understanding of the aqueous production of sulfur-containing aerosols from NACs and SO_(2) in wintertime urban haze.展开更多
Increases in free tropospheric ozone over the past two decades are mainly in the Northern Hemisphere that have been widely documented,while ozone trends in the Southern Hemisphere(SH)remain largely unexplained.Here we...Increases in free tropospheric ozone over the past two decades are mainly in the Northern Hemisphere that have been widely documented,while ozone trends in the Southern Hemisphere(SH)remain largely unexplained.Here we first show that in-situ and satellite observations document increases of tropospheric ozone in the SH over 1990–2015.We then use a global chemical transport model to diagnose drivers of these trends.We find that increases of anthropogenic emissions(including methane)are not the most significant contributors.Instead,we explain the trend as due to changes in meteorology,and particularly in transport patterns.We propose a possible linkage of the ozone increases to meridional transport pattern shifts driven by poleward expansion of the SH Hadley circulation(SHHC).The SHHC poleward expansion allows more downward transport of ozone from the stratosphere to the troposphere at higher latitudes,and also enhances tropospheric ozone production through stronger lifting of tropical ozone precursors to the upper troposphere.These together may lead to increasing tropospheric ozone in the extratropical SH,particularly in the middle/upper troposphere and in austral autumn.Poleward expansion of the Hadley circulation is partly driven by greenhouse warming,and the associated increase in tropospheric ozone potentially provides a positive climate feedback amplifying the warming that merits further quantification.展开更多
基金supported by the National Natural Science Foundation of China(42130513,42221001,22276099,and U24A20515)the Harvard-NUIST Joint Laboratory on Air Quality and Climate(JLAQC)。
文摘Nighttime aqueous oxidation of fossil fuel emissions is a significant source of atmospheric secondary organic aerosols.However,the underlying mechanism of the aqueous processing remains unclear.Utilizing ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry of watersoluble organic carbon samples,we present field observations that reveal the aqueous-phase conversion of nitroaromatic compounds(NACs)and sulfur-containing aerosols from fossil fuel combustion at high relative humidity during a severe haze event in Beijing in the winter of 2016.We have confirmed that the ring-breaking oxidation of NACs can generate nitrous acid in the aqueous phase,which rapidly oxidizes sulfur dioxide(SO_(2))to sulfate.Subsequently,reactions between sulfate and unsaturated compounds contribute to the formation of aliphatic organosulfates.Our results elucidate a molecular-level understanding of the aqueous production of sulfur-containing aerosols from NACs and SO_(2) in wintertime urban haze.
基金supported by the National Natural Science Foundation of China(41475112,41375072,and 41530423)the National Key Research and Development Program of China(2017YFC0210102)+1 种基金supported by the Chinese Scholarship Councilsupport from the Atmospheric Chemistry Program of the US National Science Foundation
文摘Increases in free tropospheric ozone over the past two decades are mainly in the Northern Hemisphere that have been widely documented,while ozone trends in the Southern Hemisphere(SH)remain largely unexplained.Here we first show that in-situ and satellite observations document increases of tropospheric ozone in the SH over 1990–2015.We then use a global chemical transport model to diagnose drivers of these trends.We find that increases of anthropogenic emissions(including methane)are not the most significant contributors.Instead,we explain the trend as due to changes in meteorology,and particularly in transport patterns.We propose a possible linkage of the ozone increases to meridional transport pattern shifts driven by poleward expansion of the SH Hadley circulation(SHHC).The SHHC poleward expansion allows more downward transport of ozone from the stratosphere to the troposphere at higher latitudes,and also enhances tropospheric ozone production through stronger lifting of tropical ozone precursors to the upper troposphere.These together may lead to increasing tropospheric ozone in the extratropical SH,particularly in the middle/upper troposphere and in austral autumn.Poleward expansion of the Hadley circulation is partly driven by greenhouse warming,and the associated increase in tropospheric ozone potentially provides a positive climate feedback amplifying the warming that merits further quantification.
