The unintended consequence of SO<sub>2</sub> and NO<sub>2</sub> regulations over China: increase of ammonia levels and impact on PM<sub>2.5</sub> concentrations

Abstract

<p><strong>Abstract.</strong> Air pollution, reaching hazardous levels in many Chinese cities has been a major concern in China over the past decades. New policies have been applied to regulate anthropogenic pollutant emissions, leading to changes in atmospheric composition and in particulate matter (PM) production. Increasing levels of atmospheric ammonia columns have been observed by satellite during the last years, in particular IASI observations reveal an increase of these columns by 15 % and 65 % from 2011 to 2013 and 2015, respectively, over Eastern China. In this paper we have performed model simulations for 2011, 2013 and 2015 in order to understand the origin of this increase, and in particular to quantify the link between ammonia and the inorganic components of particles: NH<sub>4(p)</sub><sup>+</sup> / SO<sub>4(p)</sub><sup>2−</sup> / NO<sub>3(p)</sub><sup>−</sup>. Interannual change of meteorology can be excluded as a reason: year 2015 meteorology leads to enhanced sulphate production over Eastern China which increases the ammonium and decreases the ammonia content which is contrary to satellite observations. Reductions in SO<sub>2</sub> and NO<sub>X</sub> emission between 2011 and 2015 of respectively −37.5 and −21 %, as constrained from satellite data, lead to decreased inorganic matter (by 14 % for NH<sub>4(p)</sub><sup>+</sup> + SO<sub>4(p)</sub><sup>2−</sup> + NO<sub>3(p)</sub><sup>−</sup>). This in turn leads to increased gaseous NH<sub>3(g)</sub> tropospheric columns, by as much as 24 % and 49 % (sampled corresponding to IASI data availability) from 2011 to 2013 and 2015 respectively, and thus can explain most of the observed increase.</p>

Understanding the Simulated Ammonia Increasing Trend from 2008 to 2015 over Europe with CHIMERE and Comparison with IASI Observations

“…These trends are considered as insignificant everywhere in Europe (except over parts of Albania and Greece, Figure 4b). This demonstrates that the impact of meteorology changes between 2008 and 2015 on NH 3 VCD trends may be weak over Europe, as already shown for other parts of the world (by WichinkKruit et al, [15] for the Netherlands, by Yu et al [16] for the United States, and by Lachatre et al [17] for Eastern China).…”

“…Using satellite observations from the Infrared Atmospheric Sounding Interferometer (IASI, [13]), Van Damme et al [11] also found a significant increase of +1.90 ± 0.43 %/yr over Western and Southern Europe from 2008 to 2018 in the NH 3 VCD. Different reasons have been raised to explain this NH 3 increase in the atmosphere, also observed over other parts of the world [14][15][16][17], including:…”

Simple Framework to Quantify the Contributions from Different Factors Influencing Aerosol pH Based on NHx Phase-Partitioning Equilibrium

“…This simplified equation between aerosol pH and influencing factors provides a unique tool to predict the pH response to atmospheric processes. For instance, the reduction of particulate sulfate or nitrate without changes in NH x concentration can release more NH 3 into gas phase , to make aerosol pH higher, but this increased amount, judged from , should have an upper limit constrained by the total NH x amount. Calculating the value of each component in and allows the contribution of each influencing factor to pH in different studies to be compared quantitatively, providing a convenient way to compare pH studies in different locations or time periods.…”

Trends of inorganic and organic aerosols and precursor gases in Europe: insights from the EURODELTA multi-model experiment over the 1990–2010 period

“…Particles in this size range can penetrate deeply into the respiratory system leading to respiratory and cardio-vascular problems. The formation mechanisms leading to the formation of secondary aerosols, especially the organic fraction, are complex, non-linear and still not fully understood (Bian et al, 2017;Lachatre et al, 2018;Tsigaridis et al, 2014).…”