better spatial coverage. For example, NH 3 tropospheric columns from the Tropospheric Emissions Spectrometer (TES) (Beer 2006) and NO 2 tropospheric columns
from the Ozone Monitoring Instrument (OMI) have been applied to evaluate model
results in China (Zhao et al. 2015, 2017a).
Regarding spatial distribution, model simulations (Zheng et al. 2014, Lu and Tian
2014, Zhao et al. 2017a) all show higher N deposition rates over East China (>15 kg
N ha
À1 year
À1 ) than Western China (<10 kg N ha
À1 year
À1 ) due to the higher level
of economic growth and agricultural activities in the former, being consistent with in
situ measurements (Jia et al. 2014; Zhu et al. 2015; Xu et al. 2015). The top panel of
Fig. 4.2 shows the spatial distribution of the annual N deposition to China using the
model results of Zhao et al. (2017a). The highest N deposition rates are concentrated
in North China, Central China, Eastern China and the Sichuan Basin (Zheng et al.
2014; Zhao et al. 2017a). Over some provinces, such as Henan, Hubei, Hunan,
Jiangsu and Anhui, average deposition rates can reach more than 40 kg N ha
À1
year
À1 .
There are also some regional-scale simulations at finer resolutions, which may
better capture the spatial variation and extreme values in the high deposition areas. The
average (maximum in parentheses) N depositions over the North China Plain (Zhang
et al. 2011), Guangdong province (Huang et al. 2015) and Yangtze River Basin
(Xu et al. 2018) are simulated to be 47 kg N ha
À1 year
1 (80 kg N ha
À1 year
À1
),
26 kg N ha
À1 year
À1 (75 kg N ha
À1 year
À1
) and 33 kg N ha
À1 year
À1 (55 kg N ha
À1
year
À1
), respectively. These regional simulations of N deposition show significant
spatial variations. For example, N deposition fluxes in Guangdong province range
from less than 10 kg N ha
À1 year
À1 over the coastal area to more than 70 kg N ha
À1
year
À1 in central (Guangzhou city) and southwestern (Maoming city) areas (Huang
et al. 2015).
Model sensitivity simulations by turning on/off specific sources can be applied to
assess the source contributions of N deposition. Eighty-nine percent of NH x deposition and 82% of NO y deposition over the terrestrial land area of China are from
domestic anthropogenic emissions, 6–7% of NH x and NO y deposition are contributed by foreign anthropogenic emissions, and 4% of NH x and 10% of NO y deposition are from natural sources (Zhao et al. 2017a). Because of intensive agriculture
activities, ammonia emissions from fertilizer use and manure management are the
most important deposition sources over many regions in China. For example, over
the Yangtze River Basin, where average N deposition exceeds 35 kg N ha
À1 year
À1 ,
agricultural sources contribute 51% of total N deposition and the other 49% are from
industry (13%), power plants (9%), transportation (9%) and domestic and natural
sources (18%) (Xu et al. 2018). Though the lifetime of Nr is relatively short, the
export of Nr cannot be neglected over highly polluted areas. The N deposition
budget over the North China Plain simulated by Zhang et al. (2011) shows that
annually 1981 Gg N is exported out of the North China Plain, which accounts for
more than 60% of total emissions of NH 3 and NO x in this region.
A large fraction of Nr emitted in East Asia is also exported and deposited to the
downwind northwestern Pacific Ocean (Dentener et al. 2006, Sanderson et al. 2008),
increasing N nutrient availability in the ocean (Kim et al. 2011). Twenty-three
76
L. Zhang et al.
from the Ozone Monitoring Instrument (OMI) have been applied to evaluate model
results in China (Zhao et al. 2015, 2017a).
Regarding spatial distribution, model simulations (Zheng et al. 2014, Lu and Tian
2014, Zhao et al. 2017a) all show higher N deposition rates over East China (>15 kg
N ha
À1 year
À1 ) than Western China (<10 kg N ha
À1 year
À1 ) due to the higher level
of economic growth and agricultural activities in the former, being consistent with in
situ measurements (Jia et al. 2014; Zhu et al. 2015; Xu et al. 2015). The top panel of
Fig. 4.2 shows the spatial distribution of the annual N deposition to China using the
model results of Zhao et al. (2017a). The highest N deposition rates are concentrated
in North China, Central China, Eastern China and the Sichuan Basin (Zheng et al.
2014; Zhao et al. 2017a). Over some provinces, such as Henan, Hubei, Hunan,
Jiangsu and Anhui, average deposition rates can reach more than 40 kg N ha
À1
year
À1 .
There are also some regional-scale simulations at finer resolutions, which may
better capture the spatial variation and extreme values in the high deposition areas. The
average (maximum in parentheses) N depositions over the North China Plain (Zhang
et al. 2011), Guangdong province (Huang et al. 2015) and Yangtze River Basin
(Xu et al. 2018) are simulated to be 47 kg N ha
À1 year
1 (80 kg N ha
À1 year
À1
),
26 kg N ha
À1 year
À1 (75 kg N ha
À1 year
À1
) and 33 kg N ha
À1 year
À1 (55 kg N ha
À1
year
À1
), respectively. These regional simulations of N deposition show significant
spatial variations. For example, N deposition fluxes in Guangdong province range
from less than 10 kg N ha
À1 year
À1 over the coastal area to more than 70 kg N ha
À1
year
À1 in central (Guangzhou city) and southwestern (Maoming city) areas (Huang
et al. 2015).
Model sensitivity simulations by turning on/off specific sources can be applied to
assess the source contributions of N deposition. Eighty-nine percent of NH x deposition and 82% of NO y deposition over the terrestrial land area of China are from
domestic anthropogenic emissions, 6–7% of NH x and NO y deposition are contributed by foreign anthropogenic emissions, and 4% of NH x and 10% of NO y deposition are from natural sources (Zhao et al. 2017a). Because of intensive agriculture
activities, ammonia emissions from fertilizer use and manure management are the
most important deposition sources over many regions in China. For example, over
the Yangtze River Basin, where average N deposition exceeds 35 kg N ha
À1 year
À1 ,
agricultural sources contribute 51% of total N deposition and the other 49% are from
industry (13%), power plants (9%), transportation (9%) and domestic and natural
sources (18%) (Xu et al. 2018). Though the lifetime of Nr is relatively short, the
export of Nr cannot be neglected over highly polluted areas. The N deposition
budget over the North China Plain simulated by Zhang et al. (2011) shows that
annually 1981 Gg N is exported out of the North China Plain, which accounts for
more than 60% of total emissions of NH 3 and NO x in this region.
A large fraction of Nr emitted in East Asia is also exported and deposited to the
downwind northwestern Pacific Ocean (Dentener et al. 2006, Sanderson et al. 2008),
increasing N nutrient availability in the ocean (Kim et al. 2011). Twenty-three
76
L. Zhang et al.