4.3 Mapping N Deposition in China
4.3.1 Emission Inventories Input to Model
Simulation of N deposition largely relies on emission inputs to the model, which
have both anthropogenic and natural sources. The Emission Database for Global
Atmospheric Research (EDGAR) is widely used in global simulations of N deposition (Zhang et al. 2012; Zhao et al. 2017b). Regional emission inventories such as
the Multi-Resolution Emission Inventory of China (MEIC; http://meicmodel.org)
and the Regional Emission in Asia (REAS; Kurokawa et al. 2013) provide emissions
at higher horizontal resolution with a focus on East Asia.
Natural Nr sources including lightning, soil and wildfires (biomass burning) are
important for deposition over remote areas. Lightning NO x emissions in the model
are often parameterized using cloud top height (Price and Rind 1992), upward mass
flux (Allen and Pickering 2002) and convective precipitation (Allen and Pickering
2002). Soil or biogenic NO x emissions are calculated based on the soil N pool and
meteorological conditions such as temperature and precipitation (Yienger and Levy
1995; Hudman et al. 2012; Zhao et al. 2017b) and can be sensitive to vegetation
(Chen et al. 2018). Biomass burning emissions of NO x and NH 3 , such as those in the
Global Fire Emissions Database (GFED) (van der Werf et al. 2006) and the Fire
INventory from NCAR (FINN) (Wiedinmyer et al. 2014), are often derived as the
product of burning area (mass) and emission factors.
4.3.2 Modelled Spatial Distribution of N Deposition
Global model simulations of N deposition have shown that East Asia is one of the
hotspots of N deposition (Galloway et al. 2004). Deposition rates over East Asia as
estimated by recent global models can reach more than 30 kg N ha
À1 year
À1 (Vet et al.
2014; Zhao et al. 2017b), and more than 90% of the N deposition is from anthropogenic sources. More than 40% of the terrestrial land area of East Asia exceeded a
‘critical load’ threshold of 10 kg N ha
À1 year
À1 for sensitive ecosystems, as indicated
by a global simulation of N deposition for the year 2000 (Dentener et al. 2006).
Global models typically have a grid resolution of a few hundred kilometres,
which makes it difficult to capture observed high deposition rates (Zhang et al.
2012; Lamarque et al. 2013). Regional models, with boundary conditions from
global models, can better characterize the spatial distribution of N deposition at
higher resolution. At a national scale, Zheng et al. (2014) calculated a total N
deposition to China in 2010 of 7.9 kg N ha
À1 year
À1 , much lower than interpolated
results using bulk N deposition observations (13–21 kg N ha
À1 year
À1
) (Liu et al.
2013; Jia et al. 2014; Zhu et al. 2015). Higher deposition rates were reported by Lu
and Tian (2014), which showed historical deposition rates of 12.6 kg N ha
À1 year
À1
in the 1960s, 18.6 kg N ha
À1 year
À1 in the 1980s and increasing to 20.1 kg N ha
À1
year
À1 in the 2000s.
74
L. Zhang et al.
4.3.1 Emission Inventories Input to Model
Simulation of N deposition largely relies on emission inputs to the model, which
have both anthropogenic and natural sources. The Emission Database for Global
Atmospheric Research (EDGAR) is widely used in global simulations of N deposition (Zhang et al. 2012; Zhao et al. 2017b). Regional emission inventories such as
the Multi-Resolution Emission Inventory of China (MEIC; http://meicmodel.org)
and the Regional Emission in Asia (REAS; Kurokawa et al. 2013) provide emissions
at higher horizontal resolution with a focus on East Asia.
Natural Nr sources including lightning, soil and wildfires (biomass burning) are
important for deposition over remote areas. Lightning NO x emissions in the model
are often parameterized using cloud top height (Price and Rind 1992), upward mass
flux (Allen and Pickering 2002) and convective precipitation (Allen and Pickering
2002). Soil or biogenic NO x emissions are calculated based on the soil N pool and
meteorological conditions such as temperature and precipitation (Yienger and Levy
1995; Hudman et al. 2012; Zhao et al. 2017b) and can be sensitive to vegetation
(Chen et al. 2018). Biomass burning emissions of NO x and NH 3 , such as those in the
Global Fire Emissions Database (GFED) (van der Werf et al. 2006) and the Fire
INventory from NCAR (FINN) (Wiedinmyer et al. 2014), are often derived as the
product of burning area (mass) and emission factors.
4.3.2 Modelled Spatial Distribution of N Deposition
Global model simulations of N deposition have shown that East Asia is one of the
hotspots of N deposition (Galloway et al. 2004). Deposition rates over East Asia as
estimated by recent global models can reach more than 30 kg N ha
À1 year
À1 (Vet et al.
2014; Zhao et al. 2017b), and more than 90% of the N deposition is from anthropogenic sources. More than 40% of the terrestrial land area of East Asia exceeded a
‘critical load’ threshold of 10 kg N ha
À1 year
À1 for sensitive ecosystems, as indicated
by a global simulation of N deposition for the year 2000 (Dentener et al. 2006).
Global models typically have a grid resolution of a few hundred kilometres,
which makes it difficult to capture observed high deposition rates (Zhang et al.
2012; Lamarque et al. 2013). Regional models, with boundary conditions from
global models, can better characterize the spatial distribution of N deposition at
higher resolution. At a national scale, Zheng et al. (2014) calculated a total N
deposition to China in 2010 of 7.9 kg N ha
À1 year
À1 , much lower than interpolated
results using bulk N deposition observations (13–21 kg N ha
À1 year
À1
) (Liu et al.
2013; Jia et al. 2014; Zhu et al. 2015). Higher deposition rates were reported by Lu
and Tian (2014), which showed historical deposition rates of 12.6 kg N ha
À1 year
À1
in the 1960s, 18.6 kg N ha
À1 year
À1 in the 1980s and increasing to 20.1 kg N ha
À1
year
À1 in the 2000s.
74
L. Zhang et al.