production), energy consumption, and the amount of vehicles. This means that
human activities over the 40-year time period had a large impact on PM 2.5 in Beijing.
It must be noted that the slopes of PM 2.5 /energy consumption and PM 2.5 /vehicle
amount increase significantly after 2004, indicating the increased influence of
emissions from these two items on PM 2.5 in recent years.
After the widely regarded haze event over North China in January 2013, the
Chinese government delivered the Air Pollution Prevention and Control Action Plan
(simplified as the Action Plan hereafter) to deal with the severe air pollution in
China. The Action Plan aims for a 10% decrease in the PM 2.5 concentration across
the entire country and 25%, 20%, and 15% decreases over Jing-Jin-Ji, the Yangtze
River Delta, and the Pearl River Delta, respectively. Zhao et al. (2013) reported a
decrease in aerosol optical depth (AOD) over East Central China from 2006 to 2015,
indicating the success of the strict emission control strategies. Figure 6.2 shows the
deseasonalized monthly mean PM 2.5 concentrations in Beijing, Shanghai, and
Guangzhou from April 2014 to June 2018. The PM 2.5 concentration in Beijing and
Shanghai decreased significantly over 5 years at rates of 6.76 μg/(m
3
Áyear)
( p < 0.001) for Beijing and 4.68 μg/(m
3
Áyear) ( p < 0.001) for Shanghai, but it
shows no significant trend for PM 2.5 in Guangzhou (the p value >0.1 was larger than
α of 0.05).
Long-term trend of NO x and NH 3 over China has been retrieved from satellite
data due to the lack of surface observations (Krotkov et al. 2016; Liu et al. 2017b;
Warner et al. 2017). Figure 6.3 displays the monthly and annual trend of the
OMI-retrieved NO 2 column and IASI-retrieved NH 3 over China (Liu et al. 2017b).
The NO 2 column increases from 2005 to 2011 and then decreases. The average
increasing rate for the warm season (April to September) is 0.063 Â 10
15 molec
cm
À2 year
À1 (4.07% year
À1 ). Krotkov et al. (2016) reported a temporary decrease in
the NO 2 column over the North China Plain in 2008 due to the Olympic Games and a
dramatic 50% increase from 2009 to 2011. The warm season decrease rate for the
NO 2 column over China was 0.072 Â 10
15 molec cm
À2 year
À1 (3.62% year
À1 ) from
2011 to 2015 due to the emission abatement target that was set for the 12th 5-year
plan (FYP). For the North China Plain, the NO 2 column decreased by approximately
40% from 2014 to 2015 (Krotkov et al. 2016). The decrease in the NO 2 column
indicates the abatement of NO x emissions from China. With the reduction of NO x
emissions, AOD and PM 2.5 also decreased in in recent years.
IASI-retrieved NH 3 over China increased at a rate of 0.188 Â 10
15 molec cm
À2
year
À1 (2.37% year
À1 ) in the warm season from 2008 to 2014, wherein the absolute
increase in the NH 3 column is much higher than that of the NO 2 column. There was a
sharp increase of more than 50% in the NH 3 column from 2014 to 2015. The
increase in the NH 3 column can be explained by the lack of NH 3 emission control
in China and by the decrease in SO 2 and NO x emissions (Warner et al. 2017). The
use of N fertilizer is the most important source for NH 3 , and a “Zero Increase Action
Plan” was announced by the Ministry of Agriculture, aimed at no further increase in
N fertilizer use in 2020 on the basis of 2015 use (Liu et al. 2016). If this plan is
effective, the increase rate of NH 3 emission from China would decrease.
122
Y. Pan et al.
human activities over the 40-year time period had a large impact on PM 2.5 in Beijing.
It must be noted that the slopes of PM 2.5 /energy consumption and PM 2.5 /vehicle
amount increase significantly after 2004, indicating the increased influence of
emissions from these two items on PM 2.5 in recent years.
After the widely regarded haze event over North China in January 2013, the
Chinese government delivered the Air Pollution Prevention and Control Action Plan
(simplified as the Action Plan hereafter) to deal with the severe air pollution in
China. The Action Plan aims for a 10% decrease in the PM 2.5 concentration across
the entire country and 25%, 20%, and 15% decreases over Jing-Jin-Ji, the Yangtze
River Delta, and the Pearl River Delta, respectively. Zhao et al. (2013) reported a
decrease in aerosol optical depth (AOD) over East Central China from 2006 to 2015,
indicating the success of the strict emission control strategies. Figure 6.2 shows the
deseasonalized monthly mean PM 2.5 concentrations in Beijing, Shanghai, and
Guangzhou from April 2014 to June 2018. The PM 2.5 concentration in Beijing and
Shanghai decreased significantly over 5 years at rates of 6.76 μg/(m
3
Áyear)
( p < 0.001) for Beijing and 4.68 μg/(m
3
Áyear) ( p < 0.001) for Shanghai, but it
shows no significant trend for PM 2.5 in Guangzhou (the p value >0.1 was larger than
α of 0.05).
Long-term trend of NO x and NH 3 over China has been retrieved from satellite
data due to the lack of surface observations (Krotkov et al. 2016; Liu et al. 2017b;
Warner et al. 2017). Figure 6.3 displays the monthly and annual trend of the
OMI-retrieved NO 2 column and IASI-retrieved NH 3 over China (Liu et al. 2017b).
The NO 2 column increases from 2005 to 2011 and then decreases. The average
increasing rate for the warm season (April to September) is 0.063 Â 10
15 molec
cm
À2 year
À1 (4.07% year
À1 ). Krotkov et al. (2016) reported a temporary decrease in
the NO 2 column over the North China Plain in 2008 due to the Olympic Games and a
dramatic 50% increase from 2009 to 2011. The warm season decrease rate for the
NO 2 column over China was 0.072 Â 10
15 molec cm
À2 year
À1 (3.62% year
À1 ) from
2011 to 2015 due to the emission abatement target that was set for the 12th 5-year
plan (FYP). For the North China Plain, the NO 2 column decreased by approximately
40% from 2014 to 2015 (Krotkov et al. 2016). The decrease in the NO 2 column
indicates the abatement of NO x emissions from China. With the reduction of NO x
emissions, AOD and PM 2.5 also decreased in in recent years.
IASI-retrieved NH 3 over China increased at a rate of 0.188 Â 10
15 molec cm
À2
year
À1 (2.37% year
À1 ) in the warm season from 2008 to 2014, wherein the absolute
increase in the NH 3 column is much higher than that of the NO 2 column. There was a
sharp increase of more than 50% in the NH 3 column from 2014 to 2015. The
increase in the NH 3 column can be explained by the lack of NH 3 emission control
in China and by the decrease in SO 2 and NO x emissions (Warner et al. 2017). The
use of N fertilizer is the most important source for NH 3 , and a “Zero Increase Action
Plan” was announced by the Ministry of Agriculture, aimed at no further increase in
N fertilizer use in 2020 on the basis of 2015 use (Liu et al. 2016). If this plan is
effective, the increase rate of NH 3 emission from China would decrease.
122
Y. Pan et al.