activities rather than the change in fertilizer types, so the emissions in REAS
continued to increase in recent years. Moreover, we took into account the local
environmental conditions (soil pH, wind speed, etc.) and agricultural practices and
used field results from Chinese studies to correct the EFs, whereas REAS employed
only uniform EFs based on European studies and applied these across the whole of
China. Fu et al. (2015) recently estimated synthetic fertilizer NH 3 emissions at
approximately 3.0 Tg in 2011 using the bi-directional CMAQ model coupled to an
agro-ecosystem model, which is similar to the value of 2.8 Tg for the same year and
supports the reliability of Kang et al. (2016).
The estimates of Kang et al. (2016) are in agreement with those of Zhao and
Wang (1994), Streets et al. (2003), and Yamaji et al. (2004). The majority of the
previous inventories used European-based EFs, which could introduce significant
inaccuracies. Kang et al. (2016) employed a mass-flow approach and considered
three different livestock rearing systems, as well as four phases of manure management based on local agricultural practices. The EFs used in Kang et al. (2016) were
also refined according to environmental conditions. Hence, the estimations of Kang
et al. (2016) employed more realistic parameters, and the differences between the
present study and previous ones are expected. Paulot et al. (2014) estimated the
annual NH 3 emissions of 10.4 Tg using a global 3D chemical transport model in
2005–2008, while Kang et al. (2016) estimated 10.2 Tg for the same period, and
Huang et al. (2012) estimated 9.8 Tg in 2006. The three results are quite close.
Excellent qualitative agreement was found for spatial distribution between Kang
et al. (2016) and the global NH 3 column retrieved by the IASI satellite (Van Damme
et al. 2014). Several emission hotspots are shown, including the North China Plain,
Sichuan, and Xinjiang provinces (near Ürümqi and in Dzungaria), and the region
around the Tarim Basin was also detected by the IASI sensor.
2.5 Impact of SO 2 Mitigation on Elevated NH 3
Concentration
The North China Plain has been identified as a significant hotspot of ammonia (NH 3 )
due to extensive agricultural activities. Satellite observations suggest a significant
increase of about 30% in tropospheric gas-phase NH 3 concentrations in this area
during 2008–2016 (Fig. 2.10a). However, the estimated NH 3 emissions decreased
slightly by 7% because of changes in Chinese agricultural practices, i.e., the transition
in fertilizer types from ammonium carbonate fertilizer to urea, and in the livestock
rearing system from free-range to intensive farming. We note that both the emissions
of sulfur dioxide (SO 2 ) and its column concentrations derived from satellite observations have rapidly declined by about 60% over the recent few years (Fig. 2.10b). By
integrating measurements from ground and satellite, a long-term anthropogenic NH 3
emission inventory, and chemical transport model simulations, we find that this large
SO 2 emission reduction is responsible for the NH 3 increase over the North China
Plain. The simulations for the period 2008–2016 demonstrate that the annual average
2 Anthropogenic Emissions of SO 2 , NO x , and NH 3 in China
33
continued to increase in recent years. Moreover, we took into account the local
environmental conditions (soil pH, wind speed, etc.) and agricultural practices and
used field results from Chinese studies to correct the EFs, whereas REAS employed
only uniform EFs based on European studies and applied these across the whole of
China. Fu et al. (2015) recently estimated synthetic fertilizer NH 3 emissions at
approximately 3.0 Tg in 2011 using the bi-directional CMAQ model coupled to an
agro-ecosystem model, which is similar to the value of 2.8 Tg for the same year and
supports the reliability of Kang et al. (2016).
The estimates of Kang et al. (2016) are in agreement with those of Zhao and
Wang (1994), Streets et al. (2003), and Yamaji et al. (2004). The majority of the
previous inventories used European-based EFs, which could introduce significant
inaccuracies. Kang et al. (2016) employed a mass-flow approach and considered
three different livestock rearing systems, as well as four phases of manure management based on local agricultural practices. The EFs used in Kang et al. (2016) were
also refined according to environmental conditions. Hence, the estimations of Kang
et al. (2016) employed more realistic parameters, and the differences between the
present study and previous ones are expected. Paulot et al. (2014) estimated the
annual NH 3 emissions of 10.4 Tg using a global 3D chemical transport model in
2005–2008, while Kang et al. (2016) estimated 10.2 Tg for the same period, and
Huang et al. (2012) estimated 9.8 Tg in 2006. The three results are quite close.
Excellent qualitative agreement was found for spatial distribution between Kang
et al. (2016) and the global NH 3 column retrieved by the IASI satellite (Van Damme
et al. 2014). Several emission hotspots are shown, including the North China Plain,
Sichuan, and Xinjiang provinces (near Ürümqi and in Dzungaria), and the region
around the Tarim Basin was also detected by the IASI sensor.
2.5 Impact of SO 2 Mitigation on Elevated NH 3
Concentration
The North China Plain has been identified as a significant hotspot of ammonia (NH 3 )
due to extensive agricultural activities. Satellite observations suggest a significant
increase of about 30% in tropospheric gas-phase NH 3 concentrations in this area
during 2008–2016 (Fig. 2.10a). However, the estimated NH 3 emissions decreased
slightly by 7% because of changes in Chinese agricultural practices, i.e., the transition
in fertilizer types from ammonium carbonate fertilizer to urea, and in the livestock
rearing system from free-range to intensive farming. We note that both the emissions
of sulfur dioxide (SO 2 ) and its column concentrations derived from satellite observations have rapidly declined by about 60% over the recent few years (Fig. 2.10b). By
integrating measurements from ground and satellite, a long-term anthropogenic NH 3
emission inventory, and chemical transport model simulations, we find that this large
SO 2 emission reduction is responsible for the NH 3 increase over the North China
Plain. The simulations for the period 2008–2016 demonstrate that the annual average
2 Anthropogenic Emissions of SO 2 , NO x , and NH 3 in China
33