8.2 Increasing Contribution of Atmospheric N to Acid
Deposition in China
After the 1960s, exponential growth of the human population and industrialization in
China, accompanied by increased energy demand, has enhanced the emission of SO 2
due to greater coal combustion (Fig. 8.1). However, NO x emission was far less than
SO 2 emission (Fig. 8.1; NO x /SO 2 <0.5). The atmospheric S contributed to major acid
deposition at that time, indicated by high SO 4
2À
/NO 3
À equivalence ratio in precipitation. The equivalence ratio of NO 3
À /SO 4
2À in precipitation was less than 0.2
(Fig. 8.2, e.g., only 0.16 Æ 0.05 in 1986, based on the survey of ten cities across
China; Wang and Wang 1996; Hao et al. 1998).
Although a series of strategies for the suppression of acid rain has been
implemented since the 1990s in seriously affected areas (Deng et al. 2009; Zhang
et al. 2010), energy production in China was still dominated by coal for the next
decades, and the emission of SO 2 further increased from 13 to 20 Tg year
À1 during
1990–2000 and rapidly to 34 Tg year
À1 by 2006 (Fig. 8.1). During that period, NO x
emission increased from 6 to 21 Tg year
À1 , but NH 3 emission increased slightly
and/or remained stable (Fig. 8.1). The emission ratio of NO x /SO 2 was about 0.6
(Fig. 8.1). Correspondingly, the NO 3
À
/SO 4
2À equivalence ratio in precipitation
stabilized at around 0.1 before 2000 and then increased to 0.3 in 2006 (Fig. 8.2).
Observational studies at several forests in southern China during 2001–2003 showed
that the annual bulk S deposition ranged from 24 to 160 kg S ha
À1 year
À1 , whereas
bulk N deposition only ranged 6–44 kg N ha
À1 year
À1 (Larssen et al. 2006). On a
national scale, the SO 4
2À deposition (33–55 kg S ha
À1 year
À1 ) had much larger
values than NO 3
À deposition (3.3–7.9 kg N ha
À1 year
À1 ) in precipitation during
1990–2005 (Fig. 8.2), manifesting the sulfur still contributed to major acid
deposition.
Fig. 8.1 SO 2 , NO x , and NH 3 emissions in China during 1990 and 2015 (MEIC for China, www.
meicmodel.org)
8 Contribution of Atmospheric Reactive Nitrogen to Acid Deposition in China
157
Deposition in China
After the 1960s, exponential growth of the human population and industrialization in
China, accompanied by increased energy demand, has enhanced the emission of SO 2
due to greater coal combustion (Fig. 8.1). However, NO x emission was far less than
SO 2 emission (Fig. 8.1; NO x /SO 2 <0.5). The atmospheric S contributed to major acid
deposition at that time, indicated by high SO 4
2À
/NO 3
À equivalence ratio in precipitation. The equivalence ratio of NO 3
À /SO 4
2À in precipitation was less than 0.2
(Fig. 8.2, e.g., only 0.16 Æ 0.05 in 1986, based on the survey of ten cities across
China; Wang and Wang 1996; Hao et al. 1998).
Although a series of strategies for the suppression of acid rain has been
implemented since the 1990s in seriously affected areas (Deng et al. 2009; Zhang
et al. 2010), energy production in China was still dominated by coal for the next
decades, and the emission of SO 2 further increased from 13 to 20 Tg year
À1 during
1990–2000 and rapidly to 34 Tg year
À1 by 2006 (Fig. 8.1). During that period, NO x
emission increased from 6 to 21 Tg year
À1 , but NH 3 emission increased slightly
and/or remained stable (Fig. 8.1). The emission ratio of NO x /SO 2 was about 0.6
(Fig. 8.1). Correspondingly, the NO 3
À
/SO 4
2À equivalence ratio in precipitation
stabilized at around 0.1 before 2000 and then increased to 0.3 in 2006 (Fig. 8.2).
Observational studies at several forests in southern China during 2001–2003 showed
that the annual bulk S deposition ranged from 24 to 160 kg S ha
À1 year
À1 , whereas
bulk N deposition only ranged 6–44 kg N ha
À1 year
À1 (Larssen et al. 2006). On a
national scale, the SO 4
2À deposition (33–55 kg S ha
À1 year
À1 ) had much larger
values than NO 3
À deposition (3.3–7.9 kg N ha
À1 year
À1 ) in precipitation during
1990–2005 (Fig. 8.2), manifesting the sulfur still contributed to major acid
deposition.
Fig. 8.1 SO 2 , NO x , and NH 3 emissions in China during 1990 and 2015 (MEIC for China, www.
meicmodel.org)
8 Contribution of Atmospheric Reactive Nitrogen to Acid Deposition in China
157