of toxic heavy metals, can partially counteract the fertilizing effect of N deposition
on plant growth (Bowman et al. 2008; Du et al. 2016; Tian et al. 2018; De Vries et al.
2014). In some extreme cases, excess N deposition can cause ecosystem N saturation, resulting in a reduction in biodiversity and primary productivity and
transforming the ecosystem to a net N source (Aber et al. 1998; Yue et al. 2019).
Currently, West Europe, the United States, China, and India are four hotpots of
reactive N emission and deposition (Dentener et al. 2006; Vet et al. 2014). However,
the temporal trends of reactive N emission and deposition differ in these regions. As
a result of substantial emission reduction of NO x and NH 3 , atmospheric deposition of
both nitrate and ammonium has leveled off in the Europe since the early 1990s
(Tørseth et al. 2012). In the United States, a reduction of NO x emissions has
substantially decreased nitrate deposition since the middle 1990s, while ammonium
deposition has grown continuously due to an absence of ammonia emission regulation (Li et al. 2016; Du 2016). In China, emissions of both NH 3 and NO x kept
increasing continuously during the period 1980–2010 and drove an enhancement of
N deposition (Liu et al. 2013, 2016b). The Chinese government has started to curb
NO x emissions since 2010, and satellite observations indicate a reduction of average
NO 2 column densities by 32% from 2011 to 2015 (Liu et al. 2016a). With the
increase in N use efficiency in agriculture together with stricter emission controls on
sulfur dioxide (SO 2 ) and NO x , both wet and dry N deposition stabilized and even
showed decreasing trends in China (Liu et al. 2016b; Yu et al. 2019). In contrast, as
driven by growing consumption of N fertilizers and fossil fuels, emissions of NO x
and NH 3 in India both have increased rapidly (Abrol et al. 2017). In view of an
absence of national mitigation strategies, the increase of emission and deposition of
reactive N will likely continue in India in next decades.
The environmental concerns have motivated integrated assessments of the change
in N cycle in the hotspot regions. The European Nitrogen Assessment first provided
an integrated and comprehensive evaluation of the sources, effects, and regulation
policy of reactive N at the European scale (Sutton et al. 2011). The Science Advisory
Board of the US Environmental Protection Agency also completed a national report,
to assess the current inputs, flows, and consequences of reactive N and to provide
specific management strategies to reduce the negative environmental impacts
(Doering et al. 2011). Recently, a group of Indian scientists have published a
national assessment on the sources of reactive N, the consequent environmental
and climate effects, and management options and policies (Abrol et al. 2017). These
assessments have substantially improved our understanding of anthropogenic alteration of N cycle and provide solid basis for N management in Europe, the United
States, and India. However, such an assessment is absent in China, even though
China currently is the largest emitter of reactive N and experiencing the highest level
of N deposition across the globe.
Since the early 2000s, monitoring, experimental, and modeling efforts have been
emerging explosively in China to assess the emission, atmospheric deposition, and
environmental effects of reactive N (Liu et al. 2011, 2017; Du et al. 2013; Tian et al.
2018). Based on a literature review, this book summarizes recent research on
(1) atmospheric reactive N in China from a global perspective (Chap. 1), (2) the
1 An Overview of Atmospheric Reactive Nitrogen in China from a Global Perspective
3
on plant growth (Bowman et al. 2008; Du et al. 2016; Tian et al. 2018; De Vries et al.
2014). In some extreme cases, excess N deposition can cause ecosystem N saturation, resulting in a reduction in biodiversity and primary productivity and
transforming the ecosystem to a net N source (Aber et al. 1998; Yue et al. 2019).
Currently, West Europe, the United States, China, and India are four hotpots of
reactive N emission and deposition (Dentener et al. 2006; Vet et al. 2014). However,
the temporal trends of reactive N emission and deposition differ in these regions. As
a result of substantial emission reduction of NO x and NH 3 , atmospheric deposition of
both nitrate and ammonium has leveled off in the Europe since the early 1990s
(Tørseth et al. 2012). In the United States, a reduction of NO x emissions has
substantially decreased nitrate deposition since the middle 1990s, while ammonium
deposition has grown continuously due to an absence of ammonia emission regulation (Li et al. 2016; Du 2016). In China, emissions of both NH 3 and NO x kept
increasing continuously during the period 1980–2010 and drove an enhancement of
N deposition (Liu et al. 2013, 2016b). The Chinese government has started to curb
NO x emissions since 2010, and satellite observations indicate a reduction of average
NO 2 column densities by 32% from 2011 to 2015 (Liu et al. 2016a). With the
increase in N use efficiency in agriculture together with stricter emission controls on
sulfur dioxide (SO 2 ) and NO x , both wet and dry N deposition stabilized and even
showed decreasing trends in China (Liu et al. 2016b; Yu et al. 2019). In contrast, as
driven by growing consumption of N fertilizers and fossil fuels, emissions of NO x
and NH 3 in India both have increased rapidly (Abrol et al. 2017). In view of an
absence of national mitigation strategies, the increase of emission and deposition of
reactive N will likely continue in India in next decades.
The environmental concerns have motivated integrated assessments of the change
in N cycle in the hotspot regions. The European Nitrogen Assessment first provided
an integrated and comprehensive evaluation of the sources, effects, and regulation
policy of reactive N at the European scale (Sutton et al. 2011). The Science Advisory
Board of the US Environmental Protection Agency also completed a national report,
to assess the current inputs, flows, and consequences of reactive N and to provide
specific management strategies to reduce the negative environmental impacts
(Doering et al. 2011). Recently, a group of Indian scientists have published a
national assessment on the sources of reactive N, the consequent environmental
and climate effects, and management options and policies (Abrol et al. 2017). These
assessments have substantially improved our understanding of anthropogenic alteration of N cycle and provide solid basis for N management in Europe, the United
States, and India. However, such an assessment is absent in China, even though
China currently is the largest emitter of reactive N and experiencing the highest level
of N deposition across the globe.
Since the early 2000s, monitoring, experimental, and modeling efforts have been
emerging explosively in China to assess the emission, atmospheric deposition, and
environmental effects of reactive N (Liu et al. 2011, 2017; Du et al. 2013; Tian et al.
2018). Based on a literature review, this book summarizes recent research on
(1) atmospheric reactive N in China from a global perspective (Chap. 1), (2) the
1 An Overview of Atmospheric Reactive Nitrogen in China from a Global Perspective
3