Asia is experiencing rapid economic and population growth. It
is estimated that by the year 2010 over 4 billion people will
be living in eastern Asia and the Indian sub-continent. Additionally,
these countries are experiencing phenomenal economic expansion.
For example, China has experienced 9.5% growth in its GDP between
1980 and 1990 (Hoffman, 1994). This rapid growth in the many Asia
economies has resulted in significant growth in the region's energy
needs (Akimoto and Narita, 1994, and Siddiqi, 1996). Coal is becoming
the primary choice for energy production within this region. In
1987, coal accounted for 76 and 35% of the primary energy consumption
in China and South Korea, respectively, (Shrestha and Bhattacharya,
This growth has not come without environmental consequences. Asia
is experiencing a rapid increase in air pollutant emissions (Rodhe
et al., 1992 and Kato et al., 1991), with growth in sulfur oxide
emissions paralleling the region's expanding energy needs (Foell
et al., 1995 and Qi et al., 1995). Over the past two decades China's
SO2 emissions have grown by more than a factor of three (Cofala,
1995) and this trend is expected to continue. Asia's total SO2
emissions may increase by another factor of three between 1990
and the year 2020 (Foell et al., 1995).
The impact of Asia's deteriorating air quality could have wide-ranging
consequences for the region. Many urban centers in Northeast Asia
have air pollution levels exceeding WHO ambient standards (Mage
et al., 1996 and Florig, 1995). Acidic precipitation is being
reported throughout the region (Khemani et al., 1989, Mohammed
and Kamsah, 1993, Wang and Wang, 1995), with many areas already
receiving levels which exceed the acidic carry capacity of their
soils (Hettelingh et al., 1995). According to a recent study conducted
by the Chinese Research Academy of Environmental Sciences, 40%
of China is affected by acid rain causing US$1.6 billion worth
of damage to crops, forests and property annually (Walsh, 1995).
The transport and fate of sulfur in Asia is an area of increasing
environmental interest and concern (Carmichael and Arndt, 1995,
Robertson et al., 1996, Arndt et al., 1996, Sato et al., 1996,
and Sharma et al., 1995) as countries receive growing amounts
of sulfur from neighboring and even distant countries (Ichikawa
and Fujita, 1995, and Arndt et al., 1996b).
In this paper we assess the vulnerability of Northeast Asia to
the problems of long range transport of pollutants and acidic
deposition. This will be accomplished by looking at the present
situation and then exploring the future situation that may result
from the growth in energy use as discussed in Streets (1996b).
The following discussion is organized in terms of overriding questions
regarding acid deposition in Northeast Asia.
In discussing acidic deposition it is important for us to realize
that the relationships between the emissions of pollutants and
the resultant acid deposition are difficult to determine because
of the number and nature of the processes that occur. Acidic deposition
arises as a result of several chemical and physical processes
which convert primary pollutants such as sulfur dioxides and nitrogen
oxides into more strongly acidic (secondary) pollutants. Sulfur
and nitrogen containing species along with reactive hydrocarbons
are emitted from a variety of anthropogenic and natural sources.
These compounds are mixed, transported, reacted, and finally removed
from the air back to the earth's surface. Sulfur dioxide is converted
by chemical reactions in the atmosphere in the presence of sunlight
and water vapor into sulfuric acid, or, depending on the meteorological
conditions and the local availability of oxidizing substances,
the sulfur dioxide (SO2) may be transported hundreds of kilometers
before it reacts. Some SO2 may also be deposited in gaseous form
directly to the earth's surface. Some SO2 may be absorbed into
cloud droplets, where it may undergo chemical reactions which
produce sulfuric acid. This acid may be removed from the atmosphere
through the formation of precipitation, or it may be injected
into the gas phase through evaporation processes.
In a somewhat similar manner, nitrogen oxides (NO and NO2, referred
to together as NOx) can be transported, dry deposited,
or reacted to form nitric acid. Gaseous nitric acid is usually
absorbed immediately into available cloud water and is eventually
returned to the earth as nitrate ion in precipitation. Organic
acids, may also be formed from emitted reactive hydrocarbons,
and end up in precipitation. These acidic species cause an acidification
of the precipitation (rainwater is classified acidic if the pH
is less than 5.6), which in turn can result in adverse environmental
impacts. However, pH by itself only tells part of the story. It
is not the pH of the rainwater that causes the environmental problems,
but rather the response of plants and soils to the chemical constituents
of the rainwater. Of most concern is the presence of strong acids
such as sulfuric and nitric acids. Thus to assess acidic deposition
in Asia we must look at the chemical composition of the precipitation.
Acid deposition monitoring in Northeast Asia began in the early
1980's. The history of acid rain monitoring in Japan and a summary
of the results are nicely presented in papers by Hara (1993) and
Murano et al., (1993). The first long term measurements of precipitation
chemistry in Japan were undertaken by the Japan Meteorological
Agency, as part of the World Meteorological Organization, global
precipitation network. They have been monitoring precipitation
chemistry at Ryouri (located in northern Japan facing the Pacific
Ocean) since 1976. In 1983 the Japan Environmental Agency (JEA)
organized the Committee of Acid Deposition to launch a 5-year
project on acid deposition monitoring, which has continued to
the present day. The measurements at Ryouri show that the pH levels
were 5.2 in the late 1970's and now are below 4.7 (pH is a logarithmic
scale so this indicates an increase in acidity of ~ 5 times).
The acidity is due predominately to sulfate and nitrate, with
sulfate contributing 3 times more acidity than nitrate. The amount
of sulfate deposited at this site has remained fairly constant,
but the nitrate levels have continued to increase. This location
tends to be most heavily influenced by Japanese emissions, and
thus the deposition follows the general trends in Japanese emissions
discussed in Streets (1996b), where SO2 has decreased while NOx
emissions have increased during this time period.
Examination of the JEA network, which provides information from
29 sites throughout Japan, shows that the pH values (annual values)
range from 4.3 to 5.3, with sulfate again being the major acid
followed by nitrate. (A map summarizing the pH values in Japan
is shown in Figure 1.) Thus, the precipitation throughout Japan
is classified as acidic. However, no discernible trend in pH with
respect to time is apparent from these data. These values can
be compared to those measured in Europe and North America (also
shown in Figure 1) where the values range from 4.4 to 6.5 and
4.2 to 5.6, respectively. The pH levels in Japan are similar to
those measured in areas in Europe and North America where acid
deposition problems have occurred.
In Japan there have been impacts which are being associated with
acid deposition. Sekiguichi (1987) reported dieback of Japanese
Cedar in a wide region covering the western and northwestern areas
of the Kanto plain. The cause has been discussed in terms of acidification
of the soils, as well as magnesium deficiency, exposure to atmospheric
ozone, excess supply of nitrogen compounds, and water deficiencies.
A distinctive fact which is often missed when looking at precipitation
chemistry in Asia is the role of bases. For example, Northeast
Asia is characterized by high levels of ammonium and calcium.
These constituents arise from agricultural activities (e.g., livestock
and human wastes, and fertilizers in the case of ammonia) and
from windblown dust (kosa, yellow sand in the case of calcium)
and are basic, meaning that they can neutralize the strong acids.
Although the levels of the strong acids (e.g., sulfate and nitrate)
in precipitation are frequently equal to or greater than those
measured in other areas the pH values remain high due to the presence
of these bases. In the case of Japan, their monitoring data suggests
that ~50% of the strong acids are neutralized by these basic compounds.
China began a comprehensive survey of acid deposition in 1982,
under the auspices of the Chinese National Environmental Protection
Agency. These data have been analyzed by Wang and Wang (1995).
The pH values of rainwater vary remarkably throughout China (see
Figure 2). In the western half of China the pH values range from
6 to 7, indicating that the rain is not acidic but actually is
basic! In the southeastern regions, the pH levels are strongly
acidic, with annual mean values falling below 4.0. The northeast
regions of China have pH levels which are higher than those in
the south, but which are still acidic. The contour of pH levels
equal to 5.6 extends just to the west of Beijing and along the
eastern edge of the Greater Khingan mountain range. A comparison
of the situation in 1982 with that at the present time shows clearly
that the extent of the geographical region receiving acidic deposition
has expanded greatly during the last decade. The regions receiving
acidic deposition in 1982 were restricted to the southeast regions
well below Beijing. The area receiving acid deposition has increased
by 600,000 - 700,000 km2 since 1982 (Wang et al., 1993)!
The contrast between the north and south regions of China is important.
Throughout China sulfate dominates the strong acids in the rainwater.
The levels of sulfate in the rainwater are similar in both the
north and the south. However, the northern regions (approximately
that region north of the Yangtze river), are heavily influenced
by wind blown soils. Highly basic soils originating from the Taklimakan
and Gobi deserts are blown throughout this region and serve to
neutralize the strong acids arising from air pollutants in the
northern regions. However, as indicated by this data, the strong
acids are now often exceeding the capacity of this natural buffer,
and the regions of acid deposition are expanding. This situation
is important in other regions of Asia as well. A similar situation
exists now in India, where large quantities of strong acids are
being deposited, but where the pH levels remain relatively high
due to alkaline soils associated with their arid regions. However,
pH levels are becoming acidic as the levels of strong acids rise
with their increased use of fossil fuel.
Acid deposition data throughout Asia has been reviewed by Ayers
and Hara (1996). A similar picture as that described above emerges
when we look at acid deposition in Korea, Taiwan, Hong Kong and
other regions of Asia.
The observational data shows that acidic deposition occurs throughout
Northeast Asia, and that it is due predominately to sulfur species
at present, but with a growing contribution due to nitrate. An
important question to address is what fraction of the acid deposition
at a given location is due to local emissions? versus that due
to pollutants which arise from activities located in another county,
prefecture or country? A recent analysis of sulfur deposition
in Japan conducted by Dr. Fujita (1996) at Central Research Institute
for Electric Power Industry (CRIEPI), which utilized present measurements
and estimates of sulfur emissions, concludes that Japan receives
more sulfur deposition than can be attributed to its own emissions!
Figure 1. Rainwater pH in Japan as measured in the JEA Phase-II
Survey. Also shown are pH values in Europe and USA. From Hara
(1993). [available in hard-copy version only]
Figure 2. Rainwater pH in China in 1982 and 1992 (from Wang et
al., 1995) [available in hard-copy version only]
This suggests that transboundary pollutant transport is already
an important occurrence in this region. The possibility of a significant
contribution of long range transport of pollutants to acid deposition
in the region, should come as no surprise. People in Northeast
Asia are well aware of the long range transport of dust. During
spring months dust storms (also referred to as yellow sand or
kosa) over the central China deserts transport large quantities
of dust into the middle troposphere. The resulting dust clouds
travel behind cold fronts and can be transported thousands of
kilometers away from the source regions (Merrill et al., 1985).
During the peak season for dust storms (April, May and June) the
region is under the influence of westerly flows so that the dust
is transported over Korea and Japan and out into the central Pacific
Ocean. It is estimated that the airborne transport and subsequent
deposition of dust accounts for 20 to 70% of the total mineral
material input into the Yellow Sea. This appreciation of dust
transport from China, coupled with China's growing sulfur emissions,
has resulted in eyes focused towards China as a logical source
of Korea's and Japan's excess acid deposition.
Such dust studies, along with the analysis of aerosol and precipitation
chemistry measurements, and modeling studies support the idea
that transboundary transport is a common occurrence in this region.
Transboundary transport in Northeast Asia is no longer in doubt
scientifically, and is beginning to be recognized politically.
How and where sulfur (and other pollutants transported long distances)
will be deposited is an area of increasing environmental concern
(Rodhe et al., 1992 and Hordijk et al., 1995). A number of models
have been developed to understand the transport and deposition
of sulfur in the region (including among others: Robertson et
al., 1995; Sato et al., 1996; Arndt et al., 1995; Kotamarthi and
Carmichael, 1990; Ichikawa and Fujita, 1995; Katatani et al.,
1992). These models assist investigators in understanding the
impact of current emissions on sulfur deposition in Asia and anticipating
how projected emissions may affect the region's environment in
To better understand how future emissions may affect acidification
in Asia, it is necessary to develop relationships between sources
of sulfur and their resulting deposition patterns. As part of
the RAINS-ASIA Project (Foell et al., 1995) a long range transport
model (ATMOS) was developed for studying the transport and deposition
of sulfur in Asia (Arndt et al., 1996, Arndt and Carmichael, 1995).
The ATMOS model calculates the deposition from each emission source
directly, allowing deposition from a specific point source, region,
or country to be analyzed separately.
We have used this model to investigate source-receptor relationships
for Asia and have calculated sulfur deposition for the Base Year
1990, using the SO2 emission inventory described in Streets (1996b).
The gridded SO2 emissions for 1990 are shown in Figure 3. Shown
are the emissions from all anthropogenic sources included in the
model (LPS and area sources), shipping and volcanoes. The areas
of high population and intense industrial activity are clearly
depicted. Northeast Asia represents the region with the highest
emissions. The model calculated annual total deposition in grams-sulfur
per meter squared per year (g-S/m2-yr)is presented in Figure 4.
This map provides an Asia-wide perspective on acid deposition.
There are very few regions in Asia which are not impacted by sulfur
deposition. The high sulfur deposition regions follow closely
the spatial distribution and the density of the emissions. For
example, the dense emission regions in eastern and southern China,
South Korea, northern Thailand, and eastern India all show elevated
sulfur deposition. The highest annual deposition (~10.5 g-S/m2-yr)
occurs around the city of Chongqing in Sichuan province. The strong
continental outflow of sulfur from East Asia is also clearly depicted.
Sulfur emissions in the latitude band 20o to 40o
N result in high sulfur deposition virtually throughout the western
Pacific Ocean at these latitudes, with Japan and Korea displaying
deposition levels ranging from 0.5 to 6 g-S/m2-yr. It is interesting
to note that we estimate that ~70% of the emissions in Asia are
deposited within the study region, with the remainder being transported
out of the region (and into the central Pacific Ocean, and even
to North America! This is similar to estimates for the fate of
emissions from North American and Western European emissions (Welpdale,
Figure 3. 1990 annual sulfur emissions AND
Figure 4. Calculated 1990 sulfur deposition [available in hard-copy
The ATMOS model calculates the deposition from each source directly
and this information can be used to analyze a variety of policy-related
questions. For example, the deposition from a specific LPS, region,
or country can be viewed separately. This information can also
be used to identify which sources contribute to the deposition
at a specified receptor, and can be aggregated to provide source-receptor
information at a country-to-country or region-to-region level.
(Please note that the source-receptor information presented is
based on only one year of meteorology and must be considered preliminary.)
This information related to source-receptor relationships is of
great interest in the region. The interaction between emission
sources and their resulting deposition patterns in Northeast Asia
is of particular interest since this region has the highest sulfur
emissions in Asia (Hara, 1994; Huang et al., 1995; and Murano
et al., 1993).
The sources of sulfur deposition at five locations within Japan
are presented in Figure 5. Shown are the contributions to the
"controllable" sulfur (i.e., that due to anthropogenic
activity). The variation in Japan's deposition is driven by volcanic,
Chinese, South Korean, and Japanese emissions. China's influence
is shown to be most evident along the western coast of Honshu
and the island of Kyushu, with the smallest impact on Hokkaido
in the north. Although Japanese sources are the primary source
of anthropogenic deposition throughout Japan, their contribution
is highest in eastern Japan, accounting for over 60% of the total
deposition. The influence of volcanic emissions on Japan's deposition
pattern is also evident, particularly on Hokkaido. Here large
emissions from volcanic sources and small influences from anthropogenic
sources result in volcanoes accounting for over 60% of the total
deposition. Please note that Russian emissions are not included
in the analysis. These emissions would have their largest impact
on Japan's northern regions, where they are estimated to increase
acid deposition by 10 to 20% (Ichikawa and Fujita (1995).
More explicit information is seen by examining the 1990 source-receptor
relations for the 23 regions in Northeast Asia as defined in Streets
(1996b). This information is presented in Table 1. Each row represents
deposition on a specific region (i.e., the receptor location),
while each column represents the per cent contribution of deposition
due to emissions originating from the designated source
regions. For example, from the row Kyushu-Okinawa we see that
20% of the deposition is due to its own emissions, while 21% comes
from emissions in Pusan, South Korea, and an additional 8% comes
from emissions in Jiangsu, China. As another example, we see that
in Shanghai only 53% of the anthropogenic sulfur deposition comes
from its own emissions, with emissions from Jiangsu and Zhejiang
Provinces, providing 24% and 18%, respectively. This table clearly
identifies that sulfur deposition at a particular receptor can
be affected by emissions located hundreds of kilometers away.
Table 2 illustrates the role that China plays in the region in
regards to acid deposition. China accounts for ~65% (~22 million
tonnes of SO2 per year) of the total emissions in Asia. Of China's
emissions, 83% and 14% are deposited on China and the region's
oceans, respectively. The remaining 3% falls on other nations
(i.e. 0.8% on N. Korea and 0.5% on Japan). Column three presents
the fraction of the country's total deposition resulting from
China. For example, 98% of the sulfur deposited in China is from
Chinese sources while 35% and 39% of the sulfur deposited in North
Korea and Vietnam, respectively, is due to Chinese emissions.
This table provide an interesting perspective on the region's
deposition. Although 97% of China's emissions deposited in the
region fall either within China or on the region's oceans, we
see that the remaining 3% can account for significant percentages
of the neighboring countries' total deposition !
Figure 5. Calculated annual sulfur deposition sources and their
fraction contributions for five locations in Japan. [available
in hard-copy version only]
Another important point in this regard is that the transport patterns
show significant variation throughout the year with continental
outflow during the winter and spring and onshore flows during
the summer and fall. These flow fields combine with precipitation
patterns to significantly alter the source-receptor relationships
during the year. Throughout much of Northeast Asia deposition
amounts exhibit similar patterns with minimum deposition occurring
in the winter and spring and maximum values in the summer.
During the winter and spring months, low precipitation levels
over the northern half of China result in the sulfur emitted in
this area experiencing very little wet removal. As a result, this
sulfur is transported farther from its point of origin then similar
emissions released during the summer months when precipitation
is higher and the pollutant is more likely to be washed out closer
to its point of origin. Hence, SO2 released in northern China
during the winter and spring months has a longer "lifetime"
then its summer-time counterpart. Additionally, the presence of
strong prevailing westerlies during the winter and spring cause
the pollutant to be carried farther from its source location.
As a result of these greater transport distances a higher fraction
of the emitted SO2 is converted to sulfate. The net
effect is that Chinese emissions are more likely to be deposited
within China during the summer than during the winter. These factors
can be quantified by comparing where Chinese emissions are deposited
throughout the year. China's deposition on its own soils is over
50% higher during the summer as compared to winter, despite the
fact that due to the domestic heating cycle sulfur emissions in
the winter months are 16% higher than during the summer months.
Rodhe and Granat (1984) reported a similar phenomenon for European
Table 1. Regional source-receptor relationships for Eastern Asia [available in hard copy only]
Table 2. China's contribution to controllable sulfur deposition
in the region, expressed both as a percentage of China's total
deposition in the region and as a percentage of the receptor-
country's total deposition.
Winter precipitation along the western coast of Japan is quite
high when compared with other northern latitude locations in Northeast
Asia. This acts as a strong mechanism for removal of airborne
sulfur species. The greater transport of sulfur away from the
Chinese mainland during the winter, along with the elevated precipitation
levels in western Japan during the winter, results in high deposition
of acidic species in Japan during the winter. Furthermore, the
contribution of Chinese sources to acid deposition in Japan is
2 to 3 times higher for the winter and spring then for summer
and autumn. The same phenomenon is found when comparing winter
and summer deposition from South Korea. Deposition on Japan due
to South Korean sources is over two times higher during the winter
than it is in the summer. In contrast, during the summer, when
on-shore winds predominate, sulfur from Japanese sources reaches
South Korea. Transport out of the study area is also higher during
the winter and spring months.
The important point from the above discussion is that in Northeast
Asia, source-receptor relationships can vary by season with a
country (or region) changing from being downwind of other countries
sulfur emissions, to being the upwind source of acid deposition.
A detailed evaluation of model performance is not pssible due
to a lack of a comprehensive observational data set for acid deposition
throughout Asia. However, the model has been compared to various
data sets in the region. For example, CRIEPI has developed an
air quality monitoring network in East Asia with locations in
Japan, South Korea, China, and Taiwan (CRIEPI, 1994). This network
reflects a widespread variation in geographic locations and emission
source magnitudes. The observed annual averaged sulfate concentrations
at 16 locations throughout these four countries are presented
along with model calculated concentrations in Figure 6. The model
captures both the spatial variation and magnitude of the observed
values at most locations. The model calculated deposition values
have also been compared with JEA monitoring networks in Japan
discussed previously (Arndt et al., 1996). Although the model
has a tendency to under-predict deposition, especially at those
monitoring sites located near major urban areas, the model does
accurately capture the spatial variability in the sulfur deposition.
Furthermore, Murano (1994) found that wet sulfate deposition accounts
for over half of the sulfate deposition on Japan. Of the estimated
1 Tg S deposited on Japan each year Fujita (1996), ~70% is due
to wet deposition (Ichikawa and Fujita, 1995). The ATMOS model
results are consistent with these estimates, predicting that 60%
of the total deposition in Japan is due to wet removal processes.
The model predictions have also been compared with observations
from a SO2 monitoring network in Asia (Carmichael et al., 1995).
In addition to capturing annual averages, the model also captures
monthly variations in concentrations at these locations. The model
provides a reasonable representation of the seasonal variation
of monthly concentrations and captures the maximum and minimum
seasons at most locations. The model also captures the wide variations
in concentration levels between the different sites. For example,
while Yangyang, South Korea, experiences monthly average concentrations
as high as 10 mg m-3, Mersing,
Malaysia, has monthly values less than 1 mg
m-3, the model results correctly reflect this variation. The influence
of precipitation on the concentrations at these locations is also
captured. The winter monsoons over Southeast Asia serve to decrease
concentrations in Thailand and Malaysia during this time. Similarly,
the rainy season in South Korea also results in corresponding
low SO2 concentrations at that time. Due to the coarseness of
the model, local influences can be lost in the calculated values.
Figure 6. Comparison of observed (CRIEPI, 1994) and ATMOS predicted
annual sulfate concentrations.
These preliminary results, while identifying the need to perform
a rigorous model evaluation, provide some confidence that the
model can provide a reasonable representation of Asia's deposition
Some preliminary work on comparing and contrasting acid deposition
models applied to Northeast Asia has begun. These have included
comparing CRIEPI (Ichikawa and Fujita, 1995) and ATMOS trajectory
model results with eulerian results using the STEM model (Carmichael
et al., 1991) and the model of Murao (Katatani et al., 1992).
These findings have been reported by Phadnis et al., (1996) and
Katatani (1996). In general the models are relatively consistent
in their prediction of total sulfur deposition.
Although the predictions of total deposition are quite consistent
between the various models, there are important differences between
the calculated source-receptor relationships. For example, as
presented above we estimate that China accounts for ~17% of Japan's
controllable acid deposition. Source-receptor relationships
in East Asia have also been investigated by Huang et al. (1995)
and Ichikawa and Fujita (1995). Their calculated contribution
of Chinese sources to Japan's deposition present markedly different
estimates of the role that long-range transport plays in Japan's
over-all deposition. Huang et al. estimate that China accounts
for only 3.5% of Japan's total sulfur deposition. They found that
over 93% of the sulfur deposited within Japan was from either
Japanese anthropogenic or volcanic sources. In contrast, Ichikawa
and Fujita (1995) estimate China to be a major source of wet sulfate
deposition in Japan, accounting for one-half of the anthropogenic
deposition. Our estimate falls between these values. We have begun
to study the reasons for the differences between these findings.
We have found that the variations in source-receptor relationships
are largely due to differences in removal rates and chemical conversion
rates assumed in the models. For example, the use of a low removal
rate (such as is the case in Ichikawa and Fujita (1995)) results
in a greater transport of sulfur away from source locations, and
thus a larger contribution to Japan's deposition from emissions
There is clearly a great need to conduct more model comparisons
and fundamental studies to better determine the most suitable
parameters for use in modeling studies in Northeast Asia. Until
such studies are done all source-receptor relationships - including
those shown in Table 2 - must be treated with extreme caution.
Moreover, these estimates are not yet sufficiently robust to serve
as the foundation for policy analysis related to allocation of
responsibility and liability for transboundary air pollution in
the Northeast Asian region. Conversely, the models already demonstrate
clearly the need to address the issue of acid deposition at the
source - whatever the ultimate transboundary distribution of the
acid rain precursors. Clearly, this is an important area which
requires further work. Such studies are planned as part of the
RAINS-Asia Phase-II project.
The environmental implications of sulfur deposition cannot be
evaluated simply by examining the sulfur deposition amounts at
a specific location. Rather, deposition values must be compared
with the ability of the receptor locations to assimilate the sulfur
deposited. The environmental impacts of sulfur deposition in Asia
are being assessed through use of estimates of critical loads
(Hettelingh, 1991). A critical load is the maximum level of pollutant
that can be deposited on a specific location without environmental
damage and provides a means for assessing the environmental risks
arising from sulfur deposition. The concept of critical loads
is widely accepted in Europe (Hettelingh, 1995) and is beginning
to be seriously studied in Asia (Xie et al., 1995). In this study
we compare critical loads with the estimates of sulfur deposition
to identify which ecosystems may be at risk under various emission
scenarios. The areas identified in this way should be viewed simply
as regions at potential risk, and the prediction of damage
based on the concept of critical loads in Asian countries awaits
Presented in Figure 7 are the calculated sulfur exceedances (i.e.,
the difference between sulfur deposition and the sulfur 20% critical
loads levels which represents sulfur deposition amounts that protect
80% of the ecosystems) for 1990. To account for uncertainties
in the estimate of critical loads, we chose to use the 20%-levels
in our analysis, which are more lenient then the 5%-levels used
in Europe All colored areas indicate those regions where sulfur
deposition exceeds the critical load, and thus those areas where
ecosystems are predicted to be at risk. Vast regions of Asia are
predicted to be in excess of the critical load. These areas include
vast regions of east and south China, South Korea, southern Japan,
Taiwan, and areas in India, Bangladesh, Thailand, Malaysia and
Figure 7. Calculated sulfur exceedances for 1990. [available in
hard-copy version only]
The rapid increase in energy consumption in Asia will certainly
result in a large growth in sulfur emissions. Without the introduction
of additional emissions controls to counter this growth, elevated
pollutant levels can be anticipated in this region. To understand
the potential future damage (i.e., risk) to the region's
ecosystems, several energy and emission scenarios were evaluated.
Specifically those scenarios outlined in Streets (1996b) were
utilized. These consisted of: the "business-as-usual"
scenario (BAS); the best available technology (BAT) scenario;
the advanced control technology (ACT) scenario; the basic control
technology (BCT) scenario; and a high energy efficient scenario
(HEF). Each of these were used to project SO2 emission into the
year 2020, and the resulting acid deposition was calculated using
these new emissions (but with the assumption that the meteorology
was not changed as a result of these emissions).
The BAS growth is designated as the continued increase in energy
consumption without further sulfur emissions controls or modifications
to energy production methods (e.g., replacement of coal burning
with natural gas usage or reduction of biomass burning). By maintaining
current emission practices it is estimated that emissions will
reach three times the current levels by the year 2020 except in
Japan. Using these emissions, the sulfur deposition and exceedances
for the year 2020 were calculated and the 2020 exceedances are
shown in Figure 8. Under the assumptions of this BAS scenario,
excess deposition would reach unprecedented levels in some regions.
We calculate that critical loads would be exceeded by between
two and five grams sulfur per square meter per year in large parts
of central and eastern China. The highest excess deposition (up
to 15 to 20 grams sulfur per square meter per year) is calculated
for some ecosystems in Korea, and in the Sichuan and Shanghai
provinces. These values are greater than the highest levels ever
measured in the Black Triangle region of eastern Europe! In Japan,
the region where ecosystems are identified to be at risk to acid
deposition extend from Kyushu through central Honshu, and cover
more than half of the country.
Although the current state of scientific knowledge does not yet
allow drawing conclusions about the environmental damage implied
with such excess deposition, the fact that sulfur deposition will
be more than ten times above the sustainable levels in large areas
may give reason for serious concern. To derive more specific information
on potential environmental threats, the RAINS-ASIA model enables
the examination of conditions for various types of ecosystems
individually. We conclude that the growth of sulfur deposition
could have a severe negative influence on the conditions of many
important agricultural crops in Asia. The fact that the major
rice growing areas in Asia (e.g., in China, and Korea) would experience
excess deposition of up to 15 grams per square meter per year
is cause for serious concern.
Figure 8. Calculated sulfur exceedances for various emission control
scenarios for the year 2020[available in hard-copy version only]
Obviously, acid deposition represents only one potential cause
for environmental damage. Our analysis shows that high deposition
is always linked to high levels of ambient concentrations. We
estimate that in this BAS scenario that the SO2 levels in the
rice growing regions in China would reach up to 60 micrograms
SO2/m3. Although specific analysis of dose-response relationships
for rice paddies is still lacking, a rough extrapolation of the
threshold levels (concentrations above which negative impacts
are expected) for similar ecosystems (which range usually from
20 to 30 micrograms SO2/m3, see e.g. IUFRO, 1978) suggests that
these levels are two to three higher than the threshold values.
High ambient levels of SO2 concentrations resulting from this
scenario do not only imply serious risks to natural and agricultural
ecosystems, but also impose a serious threat to human health.
One of the first and most visible signals is the deterioration
of urban air quality in large metropolitan agglomerations in Asia.
Our results indicate that this unabated scenario would lead to
air pollution levels which exceed the WHO guideline of 40-60 micrograms
SO2/m3 (annual average - WHO, 1979) throughout large parts of
the region. We have recently explored this aspect in more detail
in the Jiangsu and Shanghai areas (Chang et al., 1996). From a
human health risk standpoint, we confirmed the fact that large
regions are currently being exposed to SO2 concentrations in excess
of the WMO long-term exposure guideline, with isolated regions
having concentrations in excess of the short-term exposure guidelines.
The situation forecasted for 2010 was markedly different with
essentially the entire domain exceeding the long-term guidelines
and significant regions exposed to concentrations well in excess
of the short-term guidelines. Adverse risks to increased levels
of ambient sulfate aerosol were also identified as another growing
health concern in the region. These results suggest that the public
health impacts in China due to the rapid rise in emissions will
be large, and in many locations will be more significant that
the impacts due to acid deposition. The issues of human health
and acidic deposition should be treaty as a common problem since
they both are a result of the high and growing emissions of SO2.
The results from our study also suggest that the continued growth
of sulfur emissions may have profound impacts on the agricultural
productivity of the region. The lower Yangzte River delta and
the northern regions are projected to be at risk to both direct
and indirect effects of air pollution and acid deposition. The
central regions of Jiangsu, while projected not to be at risk
to acid deposition, are identified to be at risk due to high levels
of ambient SO2. These preliminary results indicate the nature
of the potential impacts and the challenges that this region faces
over the next few decades. Although this paper looked solely at
the effects of increases in sulfur emissions, the attendant increase
in NOx emissions will also pose additional environmental concerns
through increases in ambient ozone levels, and acid deposition
(via nitric acid).
As outlined above it can be expected that the growth in SO2 emissions
associated with the envisaged evolution of energy use gives reason
for serious concern about maintaining sustainable conditions for
natural and agricultural ecosystems in Asia. If no countermeasures
are taken, our results suggest a degradation of the environmental
quality to unprecedented levels. In response to the finding of
the previous section we explored the environmental benefits of
alternative strategies for reducing SO2 emissions.
The BAT scenario explores ecological improvements offered by advanced
technology as a means to reduce emissions. The measures considered
in this scenario represent the current technological standards
in many industrialized countries. In particular, wet flue gas
desulfurization (WFGD) processes are assumed for all industrial
and power plant boilers burning coal and oil, including retrofits
of the existing boiler stock. In the residential/commercial (domestic)
sector and in the transport sector the use of low sulfur fuels
(low sulfur coal, low sulfur oil) is assumed for all small sources.
Advanced emission control methods applied to the fuel consumption
levels as suggested by the reference energy scenario could drastically
reduce SO2 emissions in Asia below the current levels. Between
1990 and 2020, SO2 emissions from Northeast Asia would decline
by ~60 percent, despite the assumed growth in energy consumption.
Since control technologies work most effectively at large sources,
the relative contribution from large point sources declines from
16 percent in 1990 to less than nine percent in 2020. Note, that
this is in contrast to the unabated scenario, in which the share
of large point sources increases to 25 percent. Not surprisingly,
declining emissions would result in substantial reductions in
sulfur deposition. Most interesting, however, is a comparison
between the diminished deposition and the critical loads. As displayed
in Figure 8, a general use of advanced emission control technologies
brings down sulfur deposition below the critical loads throughout
most of the region. However, even under this scenario exceedances
of critical loads remain in southeastern China and Korea, where
sensitive ecosystems are located in regions with intense economic
activity. Japan's risk to acid deposition is essentially eliminated
under this scenario.
The scenario shows that, despite the more than three-fold increase
in energy consumption expected for the next few decades, sustainable
conditions - at least in terms of sulfur deposition - could be
achieved by advanced technologies for most of the Asian ecosystems.
As already discussed in Streets (1996b), the success in
ecosystem protection achievable with advanced control technologies,
however, has its price. In the year 2020 full application of advanced
emission control technologies would require US$35 billion per
year (1990 dollars), which is about 0.6 percent of the regional
GDP assumed for the underlying energy scenario. For comparison,
the relative costs for the latest agreement on reducing sulfur
emissions in Europe (the Oslo protocol) were only about one third
of this level (0.2 percent of the GDP; Amann et al., 1994).
It should be pointed out that there exists a wide range in burdens
to the various national economies: Whereas for some countries
with highly developed economies (e.g., Japan) the abatement costs
are comparably low (0.05 and 0.06 percent, respectively), developing
countries with a heavy reliance on coal face substantially higher
burdens (e.g., China, 1.7 percent). In Europe, the highest share
of GDP for the latest agreement was 0.8 percent.
Since the environmental benefits of such a strategy cannot yet
be quantified in monetary terms, a definite answer about the cost-benefit
ratio of fully applying western emission control standards cannot
be derived yet. It has to be observed, however, that the costs
associated with such a strategy would put significant burdens
on many developing economies in the region. Consequently, below
we search for alternative, perhaps more cost-effective, solutions
to reduce source emissions in Asia.
An obvious option for cost-savings would be to select only the
most cost-effective measures to reduce emissions. If structural
changes in the energy system, such as energy conservation measures
and fuel substitution, are left aside for a moment, the remaining
technologies show a wide range of cost-effectiveness. A rational
policy could therefore request only the most cost-effective measures,
thereby reducing the achieved emission reductions to some degree,
but to a greater extent also the involved costs. To follow this
idea further, we constructed a scenario which assumed that only
advanced control technologies (wet flue gas desulfurization WFGD)
were applied in new, large emission sources in the power plant,
the industrial and refinery sectors. In this scenario, emissions
from existing power stations and from small sources in the industry
are assumed to be controlled through the use of low sulfur fuels
(50 percent share of low sulfur coal and oil). Also in the domestic
and transport sectors low sulfur fuels are prescribed. For Japan
and Taiwan, however, the scenario assumes compliance with current
national legislation. This is the 'advanced control technology'
As expected, restricting advanced measures to certain sources
lowers the emission reductions. Whereas the BAT strategy would
cut total SO2 emissions in Northeast Asia by ~60% in 2020, the
ACT scenario produces a 40 percent increase of emissions. However,
this level is still less than half of the unabated levels. Selecting
only the most cost-effective measures cuts down costs, from more
than US$ 35 billion/year (costs for the BAT scenario in 2020)
to US$ 14 billion/year (costs drop by about 60 percent). Consequently,
in terms of GDP this strategy would take 0.25 percent, which is
already close to the 0.21 percent level currently discussed in
Europe. Due to country-specific structural differences, the actual
situation varies considerably among countries. In China, where
the BAT strategy would consume 1.7 percent of GDP, limiting measures
to the more cost-effective technologies will reduce the share
to 0.6 percent of the GDP. (Please note that these estimates assume
all the costs are attributed to emission reductions only.) As
shown in Figure 8, under this scenario areas with serious excess
deposition are restricted to Korea and some Chinese provinces,
whereas in most other regions the deposition could be maintained
below the critical loads.
Although emission control costs are reduced significantly in the
ACT scenario, the construction of such emission control devices
according to world standards requires substantial technical know-how
and capital investments. Experience shows that developing countries
often have limited access to the necessary technical and financial
resources needed to implement advanced technological solutions.
Consequently, preference is often given to less advanced approaches
readily available on the domestic market, which are also often
less capital intensive. To explore the economic and ecological
features of strategies that give preference to domestic technologies
an indicative scenario was constructed, in which use is made of
domestically available control technologies. Therefore, instead
of installing standard flue gas desulfurization units at large
power stations, emissions from these sources would be controlled
through more basic technologies with low capital requirements.
The 'basic control technology' (BCT) scenario assumes that in
China emissions from new large point sources are controlled by
domestic technology (with a typical removal efficiency of about
50 percent) rather than by advanced flue gas cleaning methods
(with efficiencies of more than 90 percent). For small sources
in the industrial and domestic sector the use of low sulfur fuels
is assumed. Under this scenario SO2 emissions for the Northeast
Asia region are increased from the 1990 levels by ~70%, but are
60% of the unabated 2020 emissions. It is interesting to note
however that total costs are essentially the same as those for
the ACT scenario as discussed in Streets (1996b).
Figure 8 shows excess deposition for the BCT scenario. Compared
to the ACT scenario the increase in emissions from the large point
sources results in a situation whereby many parts of eastern China
face excess deposition of more than two grams per square meter
per year, with peak exceedances in the Sichuan and Shanghai provinces
of about ten grams. Consequently, it can be concluded that in
the long run a strategy relying solely on control technologies
with modest removal efficiencies will not be able to preserve
important agricultural areas from serious excess deposition. This
scenario maintains the present (1990) levels of risk in Japan
and South Korea.
The advanced control technology scenario made a step towards increasing
cost-effectiveness in comparison to the best available technology
scenario by selecting only the most effective measures. A further
reduction of costs, without increasing environmental damage, could
be achieved by directing advanced control measures to ecologically
sensitive areas and relaxing control requirements at less sensitive
locations. It should be mentioned that China is currently exploring
similar approaches by requesting only power stations in ecologically
sensitive regions to reduce emissions (rational siting of plants,
Zhao et al., 1995). As an illustrative example, Amann and
Cofala (1996) explored a scenario for China that applies advanced
emission control measures to only those provinces where significant
excess deposition would occur without such measures (see Table
3). Emissions and control costs for these three countries in the
LACT scenario are shown in Table 4. These results show that lower
emissions, and thus substantial environmental protection, could
be achieved at 70% of the cost of the BCT or ACT scenarios.
Furthermore in some cases a few sources dominate the cause of
acid deposition in a region. For example one of the 'hot spots'
of sulfur deposition, with exceedance of critical loads of more
than ten grams sulfur/m2/year, occurs in the Chinese Sichuan province.
Table 5 shows that specific point sources make a significant,
and often dominant, contribution to local deposition (e.g., the
Chengdu power station contributes about 30 percent of total deposition
to grid 105 degrees East, 30 degrees North). Consequently, measures
that focus on a few specific sources could significantly improve
the local situation.
North-eastern plain, Heilongjiang
(thousand tons SO2)
|Costs, million US $|
for the reference scenario for the year 2020 in milligrams sulfur/m2/year
(note that those power stations designated with an N
are only foreseen for the year 2020 and do not yet exist!)
|Receptor in Sichuan (30_ N, 105_ E)|
|China, Sichuan||China, LPS N25 (Chengdu)|
|China, Chongqing||China, LPS N24 (Jianqou)|
|China, Yunnan||China, LPS 56 (Baima)|
|China, Shaanxi-G.||China, LPS 4 (Chongqing)|
|China, Guizhou||China, LPS N1 (Luohang)|
|China, Guiyang||China, LPS N65 (Douba)|
|China, West Tibet||China, LPS N66 (Huayinshan)|
|China, Hubei||China, LPS N59 (Xigu)|
|China, Hebei||China, LPS 11 (Qinzhen)|
|China, Hunan||China, LPS N22 (Jingyuan)|
|China, Other Provinces||China, 10 other LPS|
|India, all sources|
|TOTAL DEPOSITION||Critical Load (25 percentile)|
Another way to limit environmental impacts would be to consider
relocating coal power stations which make significant contributions
to excess deposition in sensitive ecosystems in the baseline scenario,
to less sensitive regions. As an illustration Amann and Colfalo
(1996) evaluated the impact of relocating four sources planned
for construction in the heavily polluted region of the Sichuan
province to the northern part of the country. Even under the assumption
that the relocated power stations would not be equipped with desulfurization
technologies, excess deposition in the hot spots declined compared
to the baseline reference scenario. For instance, in the Sichuan
province excess deposition in the grids affected by the moved
sources decreased by about five to six g/m2-yr, whereas, due to
the large tolerance of acid deposition of the ecosystems in the
new locations, no major areas would experience excess deposition
as a result of this measure.
All the scenarios discussed above are based on certain assumptions
about the development of the economies and of energy intensities.
However, the volumes and the structural composition of energy
supply also have a critical influence on the level of emissions.
These contributing factors imply that not only will emission levels
be crucially dependent on the energy scenario, but also that energy
policies promoting energy efficiency and use of cleaner fuels
are important instruments to reduce pollution and pollution control
To illustrate this fact calculations were performed using a control
strategy based on the energy efficiency pathway (HEF scenario).
As discussed in Streets (1996b), the HEF pathway results in a
40% decrease in SO2 emissions in Northeast Asia, relative to the
unabated BAS emission. Consequently, emission control strategies
based on the energy efficiency pathway provide better protection
for the ecosystems than would result from the base case. The excess
sulfur deposition for this HEF case is shown in Figure 8. As expected
the exceedance map shows that the vulnerability of Northeast Asia
under this scenario is substantially improved relative to the
BAS situation, and accomplishes improvements similar (but no quite
as effectively) as those for the BCT scenario. Combining energy
efficiency with controls as discussed above is an obvious strategy
which would yield long term benefits.
Finally it is illustrative to look at the impact of the various
control strategies on the deposition at a specific receptor. We
chose a receptor located in southern Honshu, Japan. The annual
calculated sulfur deposition for the various scenarios at this
site are summarized in Table 6. This particular site is presently
receiving an excess deposition of ~100 mg-S/m2/yr (calculated
as the difference between the total deposition and the 5% critical
load). Under the BAS assumptions, by the year 2020 it would be
receiving an excess deposition of nearly 10 times the present
levels! Only the BAT and ACT scenarios are projected to reduce
future depositions at this site below the critical levels. Another
interesting point is that the scenarios also influence the source-receptor
relationships. Also shown in Table 6 are the sources of the deposition
at this receptor location for the various scenarios. At present
Japanese emissions contribute ~17% to the deposition at this site.
Under the BAS scenario, Japan's contribution decreases by a factor
of 2, while the contributions from China and South Korea increase.
Under the BCT and ACT scenarios the importance of Chinese emissions
grows to nearly 50%, while that due to South Korea sources decreases
to ~25%. Under the BAT scenario the contribution due to Japanese
sources increases (to ~25%), but China and South Korea still contribute
22% and 53%, respectively.
|5% Critical Load||415||415||415||415||415||415|
The present situation in Northeast Asia is that high levels of
acidic compounds, predominately sulfate and nitrates, are being
deposited throughout the region. The levels of acid deposition
are sufficiently high to put ecosystems at risk (as estimated
by critical loads for Asia) in vast regions including southern
China, South Korea, Taiwan, and southern Japan. The situation
would be worse if it were not for the fact that Northeast Asia
has high levels of wind blown soils which neutralize an appreciable
fraction of the strong acids. Model calculations suggest that
transboundary transport already contributes to acid deposition
in Korea and Japan.
This situation most likely will change dramatically as a consequence
of the very high economic and population growth rates of the region.
The expansion of fossil fuel energy systems, combined with a major
fuel shift to indigenous coal, will undoubtedly result in a significant
increase in atmospheric emissions for the Asian countries. Substantial
portions of these emissions will be transported by winds hundreds
of kilometers from their source. To help quantify and anticipate
environmental impacts associated with these emissions it is imperative
that we develop a greater understanding of the mechanisms of long
range transport of pollutants in Asia. Increased monitoring and
modeling activities will be needed, which could be conducted as
regional and/or bi-lateral initiatives. These activities are necessary
because there is considerable uncertainty associated with modeling
sulfur deposition in a region as large as Asia. The lack of a
comprehensive observation network prevents us from rigorously
evaluating model performance in Northeast Asia. This situation
will improve as a result of the Japan JEA-lead activity on establishing
an acid deposition monitoring network for Asia. This network has
been discussed at four expert meetings and is now in the implementation
phase (JEA, 1995). Furthermore, the modeling activity discussed
in this paper as well as most other attempts, make use of parameterizations
which have been derived based on modeling studies at the mid-latitudes
in North America and Europe. There is still uncertainty as to
how well these values capture the wide variations in geographical
features and latitudinal variations associated with Asia. Although
extensive experience can be drawn from Europe and North America,
the Asian situation is sufficiently different in terms of mixes
of pollutants, meteorology, etc., that what we need is Asian-specific
information on the mechanisms of acid deposition and long range
transport. There is a clear need to conduct more model comparisons
and fundamental studies to better determine the most suitable
parameters for use in modeling studies in Northeast Asia. Until
such studies are done all source-receptor relationships must be
treated with extreme caution. Moreover, the present estimates
are not yet sufficiently robust to serve as the foundation for
policy analysis related to allocation of responsibility and liability
for transboundary air pollution in the Northeast Asian region.
Conversely, the models already demonstrate clearly the need to
address the issue of acid deposition at the source - whatever
the ultimate transboundary distribution of the acid rain precursors.
The present trends in energy consumption in the region impose
significant environmental threats to a variety of ecosystems in
large parts of Asia. Within the next two to three decades, as
the regional SO2 emissions increase, sulfur deposition levels
are anticipated which are higher than those observed in Europe
and North America during the 1970s and 1980s, and in some cases
will most probably exceed those observed previously in the most
polluted areas in central and eastern Europe. This increase in
SO2 emissions will severely threaten the sustainable basis of
many natural and agricultural ecosystems in the region. Taking
the critical loads as an indicator for sustainable levels of acid
deposition, future sulfur deposition will exceed critical loads
by more than a factor of ten in wide parts of Asia. These levels
of sulfur deposition would cause significant changes in the soil
chemistry over wide areas in Asia, affecting growing conditions
for many natural ecosystems and agricultural crops. Furthermore,
ambient levels of SO2 would exceed WHO health guidelines not only
in cities, but also in many rural regions. If no countermeasures
are taken, our results suggest a degradation of the environmental
quality to unprecedented levels.
There are a variety of measures that could be taken to reduce
SO2 emissions and thereby avoid widespread excess deposition in
the region. Advanced emission control technologies could reduce
emissions below current levels even in a high growth energy scenario,
albeit at extremely high costs. Illustrative scenarios demonstrate
the potential for an increase in the cost-effectiveness of strategies
if measures are focused on specific fuels, technologies, economic
sectors, emission sources or ecologically sensitive regions. All
of these activities make a difference. Energy planning is also
an important factor for controlling adverse environmental effects,
in particular acidification. The development of carefully designed
energy systems is of particular importance for controlling emissions
in those countries considering an expansion or replacement of
the present energy infrastructure.
However, the situation in Northeast Asia is probably bleaker than
we have discussed. Most of this paper has focused on sulfur as
the main component of acid deposition. While this is generally
true in this region, the contribution of nitric acid is rising
along with the increase in NOx emissions as discussed in Streets
(1996b). The attendant increase in NOx emissions will not only
lead to an increase in acid deposition, but will also pose additional
environmental concerns through increases in ambient ozone levels.
Increasing levels of ozone have significant environmental impacts,
including human health and reduction in crop yields. Initial work
by Chameides et al. (1994) have suggested that the increase in
NOx emissions and fertilizer use in Northeast Asia, may lead to
ozone levels sufficiently high to threaten rice, wheat and corn
production. Ozone, like acid deposition, is a regional problem,
which will require regional cooperation and emission reduction
policies to control.
Ammonia presents still another concern. Because of the predominately
rural and agricultural nature of large portions of Northeast Asia,
emissions of ammonia, associated with livestock and the intensive
use of fertilizers to meet the growing demand for food, are increasing
even more rapidly than emissions of SO2 and NOx
(Galloway, 1995). As discussed previously, ammonia in rainwater
acts as a base, neutralizing the strong acids, and elevating the
pH of precipitation. However, after it is deposited on soils biochemical
processes cause ammonia to act as a strong acidifying agent. Thus,
ammonia may be masking the extent of the problem of acid deposition
in Asia as measured by pH alone, and may actually be contributing
significantly to ecosystem damage (as is the case in the Netherlands).
The role of ammonia in this regard is not yet well characterized
in Northeast Asia, but its study should be given high priority.
The inclusion of ammonia into the acid deposition arena requires
the simultaneous consideration of energy and food security policies.
Finally, the regional aspect of acid deposition pose a significant
challenge to the region. The Asian situation is much different
than that in Europe and USA when they encountered acid deposition
as a significant problem. In Europe, the UN Economic Commission
for Europe (UNECE) provided a forum for countries to discuss the
problem and develop policies aimed at reducing sulfur and nitrogen
emissions. Under the auspices of UNECE the Convention on Long
Range Transport of Air Pollutants (LRTAP) was first signed in
1979. In addition, there were active collaborations and joint
research activities among the countries looking at various aspects
of the problem providing scientific input into the deliberations.
Both research and policy fora will need to be further developed
in Asia to address the challenges presented by these regional
Acknowledgments: Much of the work upon which
this paper is based was based on research supported in part by
funds from The World Bank and The Asian Development Bank as part
of the RAINS-ASIA project. Special thanks to the collaborators
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