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The unexpected effect of SO<sub>2</sub> and NO<sub>2</sub> emission reductions over China:strong and rapid increase of atmospheric ammonia levels

By Mathieu Lachatre, Audrey Fortems-Cheiney, Gilles Foret, Guillaume Siour, Gaëlle Dufour, Lieven Clarisse, Cathy Clerbaux, Pierre-François Coheur and Martin Van Damme


International audienceAir pollution, reaching hazardous levels in many Chinese cities has been a major concern in China over the pastdecades. New policies have been applied to regulate anthropogenic pollutant emissions, leading to changes inatmospheric composition and in particulate matter (PM) production. Increasing levels of atmospheric ammoniacolumns have been observed by satellite during the last years, in particular IASI observations reveal an increaseof these columns by 15% and 65% from 2011 to 2013 and 2015, respectively, over Eastern China. For thisperiod, it appears that ammonia emissions have remained almost identical. In our study, we have performed modelsimulations (with CHIMERE 3D CTM) for 2011, 2013 and 2015 in order to understand the origin of this rapidand substantial increase, and in particular to quantify the link between ammonia and the inorganic componentsof particles: NH4+(p) / SO42-(p) / NO3-(p). Interannual change of meteorology can be excluded as a reasonfor ammonia increase: year 2015 meteorology leads to enhanced sulphate production over Eastern China, whichincreases the ammonium production and decreases the ammonia content which is contrary to satellite observations.Reductions in SO2and NOX emission between 2011 and 2015 of respectively -38 and -21%, as constrained fromsatellite based OMI instrument observations, lead to decreased inorganic matter (by 14% for NH4+(p) + SO42-(p)+ NO3-(p)). This in turn leads to increased gaseous NH3(g) tropospheric columns, by as much as 24% and 49%(filtering model data following IASI data availability) from 2011 to 2013 and 2015 respectively, and thus canexplain most of the observed increase

Topics: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDE]Environmental Sciences
Publisher: HAL CCSD
Year: 2019
OAI identifier: oai:HAL:insu-02264990v1
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