During the Eleventh and Twelfth Five-Year Plan periods (2006–2015), the
national policy of total amount control of air pollutants (mainly through flue-gas
desulfurization, FGD) had led to SO 2 emissions declined by 50% (Fig. 8.1). But the
emission of NO x increased to 29 Tg year
À1 in 2012 (Fig. 8.1), result from the
increasing energy consumption in transportation sectors without adequate control
measures (Zhao et al. 2013). Meanwhile, the emission of NH 3 retained at a large
value around 10 Tg year
À1 since 2006 (Kang et al. 2016; Fig. 8.1). Subsequently, as
a result of significantly increasing emissions of reactive N but decreasing emissions
of S, N would be a prior contributor to acidic deposition. An increasing contribution
of N to acid deposition has been observed in several studies. In Chongqing,
southwest China, in response to the successful abatement of SO 2 emission, but not
of NO x , S deposition decreased significantly, whereas N deposition increased during
2008–2013 (Yu et al. 2017c). The increasing contribution of N was also observed
over China from the compiled results from the Acid Deposition Monitoring Network
in East Asia (EANET) and some other sites (Yu et al. 2017a; Itahashi et al. 2018). In
precipitation from 2006 to 2010, the NO 3
À concentration increased at a rate of
0.6 Æ 5.5 μeq L
À1 year
À1 (avg. 54.3 μeq L
À1 ), while the SO 4
2À concentration had a
decline trend of 20.3 Æ 8.8 μeq L
À1 year
À1 (avg. 230.6 μeq L
À1 ). At a nationwide
scale, the average NO 3
À deposition in precipitation increased from 5 kg N ha
À1
year
À1 in 2000 to 10 kg N ha
À1 year
À1 in 2015, while the average SO 4
2À deposition
declined from 48 kg S ha
À1 year
À1 in 2000 to 30 kg S ha
À1 year
À1 in 2015 (Fig. 8.2;
Yu et al. 2017a). Thus, the NO 3
À /SO 4
2À equivalence ratio in precipitation increased
significantly from 0.1 to 0.6 during this period (Fig. 8.2).
The N deposition lacked direct monitoring in China, especially on the long term
scale. The mean bulk N deposition from all available monitoring sites across China
showed an increasing trend from 13.2 kg N ha
À1 year
À1 in the 1980s to 21.1 kg N
ha
À1 year
À1 in the 2000s (Liu et al. 2013). The total inorganic N (TIN, including
NO 3
À and NH 4
+
) deposition at Tieshanping site near Chongqing city also showed a
significantly increase from 2001 to 2013 (from 9 to 38 kg N ha
À1 year
À1
; Yu et al.
2017c). The N deposition in forest ecosystems, normally larger than that in open areas
due to the canopy interception, has aroused great concerns in China. The wet deposition of N reviewed from the reports of 69 forests at 50 sites throughout China ranged
from 2.6 to 48.2 kg ha
À1 year
À1 and averaged at 16.6 kg ha
À1 year
À1 (Fang et al.
2011). Complied results from 38 typical forest stands showed that the N deposition in
throughfall had a large mean value of 14.0 kg ha
À1 year
À1 for NH 4
+
ÀN, 5.5 kg ha
À1
year
À1 for NO 3
À À N, and 21.5 kg ha
À1 year
À1 TIN, respectively (Du et al. 2014).
Recently, a study showed that the N deposition in throughfall ranged from 8.4 to
113 kg N ha
À1 year
À1
, with a mean value of 33.9 kg N ha
À1 year
À1
, at 22 subtropical
forest sites in southern China (Yu et al. 2018). In addition to monitoring, modelling
results have also suggested an increasing trend of N deposition, while S deposition has
started to decline since 2006 in China (Zhao et al. 2013). A series of modelling results
of total N and S deposition showed that the S deposition declined significantly after
2005, while the N deposition increased from 2005 to 2013 across China (Fig. 8.3).
Acid deposition was varied not only in time but also in space. Similar to Fig. 8.3, the
modelling results based on the Nested Air Quality Prediction Modelling System
8 Contribution of Atmospheric Reactive Nitrogen to Acid Deposition in China
159
national policy of total amount control of air pollutants (mainly through flue-gas
desulfurization, FGD) had led to SO 2 emissions declined by 50% (Fig. 8.1). But the
emission of NO x increased to 29 Tg year
À1 in 2012 (Fig. 8.1), result from the
increasing energy consumption in transportation sectors without adequate control
measures (Zhao et al. 2013). Meanwhile, the emission of NH 3 retained at a large
value around 10 Tg year
À1 since 2006 (Kang et al. 2016; Fig. 8.1). Subsequently, as
a result of significantly increasing emissions of reactive N but decreasing emissions
of S, N would be a prior contributor to acidic deposition. An increasing contribution
of N to acid deposition has been observed in several studies. In Chongqing,
southwest China, in response to the successful abatement of SO 2 emission, but not
of NO x , S deposition decreased significantly, whereas N deposition increased during
2008–2013 (Yu et al. 2017c). The increasing contribution of N was also observed
over China from the compiled results from the Acid Deposition Monitoring Network
in East Asia (EANET) and some other sites (Yu et al. 2017a; Itahashi et al. 2018). In
precipitation from 2006 to 2010, the NO 3
À concentration increased at a rate of
0.6 Æ 5.5 μeq L
À1 year
À1 (avg. 54.3 μeq L
À1 ), while the SO 4
2À concentration had a
decline trend of 20.3 Æ 8.8 μeq L
À1 year
À1 (avg. 230.6 μeq L
À1 ). At a nationwide
scale, the average NO 3
À deposition in precipitation increased from 5 kg N ha
À1
year
À1 in 2000 to 10 kg N ha
À1 year
À1 in 2015, while the average SO 4
2À deposition
declined from 48 kg S ha
À1 year
À1 in 2000 to 30 kg S ha
À1 year
À1 in 2015 (Fig. 8.2;
Yu et al. 2017a). Thus, the NO 3
À /SO 4
2À equivalence ratio in precipitation increased
significantly from 0.1 to 0.6 during this period (Fig. 8.2).
The N deposition lacked direct monitoring in China, especially on the long term
scale. The mean bulk N deposition from all available monitoring sites across China
showed an increasing trend from 13.2 kg N ha
À1 year
À1 in the 1980s to 21.1 kg N
ha
À1 year
À1 in the 2000s (Liu et al. 2013). The total inorganic N (TIN, including
NO 3
À and NH 4
+
) deposition at Tieshanping site near Chongqing city also showed a
significantly increase from 2001 to 2013 (from 9 to 38 kg N ha
À1 year
À1
; Yu et al.
2017c). The N deposition in forest ecosystems, normally larger than that in open areas
due to the canopy interception, has aroused great concerns in China. The wet deposition of N reviewed from the reports of 69 forests at 50 sites throughout China ranged
from 2.6 to 48.2 kg ha
À1 year
À1 and averaged at 16.6 kg ha
À1 year
À1 (Fang et al.
2011). Complied results from 38 typical forest stands showed that the N deposition in
throughfall had a large mean value of 14.0 kg ha
À1 year
À1 for NH 4
+
ÀN, 5.5 kg ha
À1
year
À1 for NO 3
À À N, and 21.5 kg ha
À1 year
À1 TIN, respectively (Du et al. 2014).
Recently, a study showed that the N deposition in throughfall ranged from 8.4 to
113 kg N ha
À1 year
À1
, with a mean value of 33.9 kg N ha
À1 year
À1
, at 22 subtropical
forest sites in southern China (Yu et al. 2018). In addition to monitoring, modelling
results have also suggested an increasing trend of N deposition, while S deposition has
started to decline since 2006 in China (Zhao et al. 2013). A series of modelling results
of total N and S deposition showed that the S deposition declined significantly after
2005, while the N deposition increased from 2005 to 2013 across China (Fig. 8.3).
Acid deposition was varied not only in time but also in space. Similar to Fig. 8.3, the
modelling results based on the Nested Air Quality Prediction Modelling System
8 Contribution of Atmospheric Reactive Nitrogen to Acid Deposition in China
159