national perspective, therefore, the strategy of air pollution control needs increasingly to stress the conditions in those areas in the future.
14.3.3 Policy Implications
The emissions of base cations and SO 2 could serve as indicators for ecosystem
acidification. From 2005 to 2014, Ca emissions are estimated to have declined by
31% (updated from Zhao et al. 2013), while SO 2 emissions (STD case by Xia et al.
(2016)) by only 20%. In contrast, the US emissions of SO 2 and PM 10 (as a surrogate
for base cations) are reported to decrease by 36% and 24%, respectively, from 1990
to 2005 (USEPA 2012). From the long-term observation of a forest catchment
(Likens et al. 1996), however, the abatement of SO 2 was insufficient to protect
surface waters and forest soils against further anthropogenic acidification in the
Northeastern USA. During 2005–2010, the US SO 2 emissions were further reduced
by 50%, but the PM 10 emissions were kept relatively stable. Comparing the conditions between the two countries, the smaller percentage of SO 2 reduction than that of
base cation reduction implied that the recovery of acidification in China could be
more difficult under current emission abatement pathway than the USA experienced
in 1990–2010. A long-term study revealed an association between reduced PM
concentrations and elevated acidity of precipitation at many monitoring sites in
China, and it could not be explained by changes in emissions from natural sources
(Tang et al. 2010). The observation suggested the enhanced risks of ecosystem
acidification resulting from the reduced base cations of anthropogenic origin over
the country. Since China’s efforts on PM control will definitely continue in order to
alleviate aerosol pollution and to avoid public health damages, little other choice is
available to reduce acidification but to conduct even more strict SO 2 controls.
Emission inventory studies find that SO 2 comes mainly from stationary combustion sources (e.g., power and industrial boilers) while NO X from both stationary and
mobile sources. As the lifetimes and emission intensities are similar for SO 2 and
NO 2 , the contribution of transportation to air quality can be evaluated based on the
ratio of NO 2 to SO 2 VCDs. Figure 14.8a–c illustrates the spatial pattern of NO 2 to
SO 2 VCD ratio in China for 2005, 2012, and 2014, respectively. In 2005, large ratios
were found in developed areas including Beijing, PRD, and Zhejiang province
(Fig. 14.8a). The shares of transportation to total NO X emission in BTH (39%),
YRD (27%), and Guangdong province (29%) were larger than the national level of
24%, and the shares reached 40% and 46% for Beijing and Shanghai, respectively.
In 2014, the shares grew to 44%, 55%, 33%, and 30% for Beijing, Shanghai,
Guangdong, and the whole country, respectively, even with staged implementation
of on-road vehicle emission standards (Xia et al. 2016). The main reasons for the
elevated contribution of transportation included the fast growth in the on-road
vehicle numbers and the increased emissions from non-road sources. The areas
with large NO 2 to SO 2 ratio kept expanding over time to the YRD region, the
whole Eastern China, the SB, and several provincial capital cities in Western and
14 National Regulation of SO 2 and NO x Emissions in China
327
14.3.3 Policy Implications
The emissions of base cations and SO 2 could serve as indicators for ecosystem
acidification. From 2005 to 2014, Ca emissions are estimated to have declined by
31% (updated from Zhao et al. 2013), while SO 2 emissions (STD case by Xia et al.
(2016)) by only 20%. In contrast, the US emissions of SO 2 and PM 10 (as a surrogate
for base cations) are reported to decrease by 36% and 24%, respectively, from 1990
to 2005 (USEPA 2012). From the long-term observation of a forest catchment
(Likens et al. 1996), however, the abatement of SO 2 was insufficient to protect
surface waters and forest soils against further anthropogenic acidification in the
Northeastern USA. During 2005–2010, the US SO 2 emissions were further reduced
by 50%, but the PM 10 emissions were kept relatively stable. Comparing the conditions between the two countries, the smaller percentage of SO 2 reduction than that of
base cation reduction implied that the recovery of acidification in China could be
more difficult under current emission abatement pathway than the USA experienced
in 1990–2010. A long-term study revealed an association between reduced PM
concentrations and elevated acidity of precipitation at many monitoring sites in
China, and it could not be explained by changes in emissions from natural sources
(Tang et al. 2010). The observation suggested the enhanced risks of ecosystem
acidification resulting from the reduced base cations of anthropogenic origin over
the country. Since China’s efforts on PM control will definitely continue in order to
alleviate aerosol pollution and to avoid public health damages, little other choice is
available to reduce acidification but to conduct even more strict SO 2 controls.
Emission inventory studies find that SO 2 comes mainly from stationary combustion sources (e.g., power and industrial boilers) while NO X from both stationary and
mobile sources. As the lifetimes and emission intensities are similar for SO 2 and
NO 2 , the contribution of transportation to air quality can be evaluated based on the
ratio of NO 2 to SO 2 VCDs. Figure 14.8a–c illustrates the spatial pattern of NO 2 to
SO 2 VCD ratio in China for 2005, 2012, and 2014, respectively. In 2005, large ratios
were found in developed areas including Beijing, PRD, and Zhejiang province
(Fig. 14.8a). The shares of transportation to total NO X emission in BTH (39%),
YRD (27%), and Guangdong province (29%) were larger than the national level of
24%, and the shares reached 40% and 46% for Beijing and Shanghai, respectively.
In 2014, the shares grew to 44%, 55%, 33%, and 30% for Beijing, Shanghai,
Guangdong, and the whole country, respectively, even with staged implementation
of on-road vehicle emission standards (Xia et al. 2016). The main reasons for the
elevated contribution of transportation included the fast growth in the on-road
vehicle numbers and the increased emissions from non-road sources. The areas
with large NO 2 to SO 2 ratio kept expanding over time to the YRD region, the
whole Eastern China, the SB, and several provincial capital cities in Western and
14 National Regulation of SO 2 and NO x Emissions in China
327