3. Transboundary Transport
3.1 Estimated Acid Rain Transport and Deposition
Lacking detailed field data, modelling to date in Asia has focused on the dominant
acid rain precursor emitted in the course of energy use, namely, wet and dry deposition of
aerosol sulfate and gaseous SO2. These emissions of the latter come from the following
sources: natural sources refer to active volcanoes; anthropogenic sources comprise of:
regional shipping in port and sealanes; large point sources (>300 MWe power plants;
>900
MWt industrial facilities; and >20 kT SO2/year emitters); and area sources (including
industrial, domestic, and transportation emissions, the latter provided on a one by one
degree
resolution).
The atmospheric module used in the RAINS-ASIA model calculates the
concentrations
and deposition of sulfate and SO2 on a one by one degree resolution, using a multi-layer
advection model bound by night/day and time (five days or until the plumes depart from
the
modelling region) whereby the initial release branches into different trajectories. The
modelling employed collected values for 1990 observed wind speeds and temperature
from
upper air sondings, or interpolated from these points to positions required by the model,
as
well as precipitation data. The modelling is hampered by lack of data for oceans in
Northeast Asia.
[OH9, Met Stations, 5/17]
3.2 Estimated Deposition and Concentrations
As might be expected, calculated sulfur deposition is closely correlated with spatial
distribution and density of emissions. The regions in eastern and southern PRC and the
ROK
clearly show elevated sulfur deposition in the RAINS-ASIA model. The strong
continental
outflow of air from east Asia results in a high deposition latitudinal band 20-40o over
virtually the whole western Pacific ocean. Accumulated annual deposition is also
heavily
related to the annual precipitation patterns in southeastern China and Southeast Asia. In
most
areas, wet deposition of aerosol sulfate dominates the sulfate deposition process, whereas
in
the case of gaseous SO2, the dry and wet removal mechanisms are about the same in
importance.
Deposition varies strongly according to season because of wind and precipitation
seasonality; high emissions due to residential heating in winter months in northern Asia;
and
changes in chemical processes and rates due to season. Heavy precipitation occurs over
Northeast Asia in December-January-February; and the rainy season occurs in June-July-
August. More than 30 percent of cumulative annual wet deposition over the East Sea of
Korea/Sea of Japan occurs during winter. Volcanoes are also important, accounting for
nearly 30 percent of total deposition in Japan, for example.
The calculated annually-averages surface concentrations of aerosol sulfate and gaseous
SO2 reveal elevated values throughout Asia. Direct damage to sensitive crops and forest
ecosystems can occur at levels of 20-30 ęg/m3--levels exceeded in large areas of the
PRC
and Korea. Japanese deposition measured levels reveal high values in Kyushu, on the
East
Sea of Korea/Sea of Japan side of Honshu, and large urban areas. These values (ranging
from an annual 2-55 g-sulfate/m2 ) being higher than predicted by modelling work (1-4.8
g-
sulfate/m2). Perhaps this difference is due to the coarse resolution of modeling, and the
fact
that monitoring may be biased toward and by urban areas. In the course of the RAINS-
ASIA project, 43 sampling sites were established in 11 countries using low-cost passive
samplers to collect weekly or monthly SO2 levels during 1994 at sites chosen for distance
from major emitter sources and or in sensitive areas.
[OH10, monthly av. SO2 concentrations, 5/40]
[OH11, monthly av. sulfate surface concentration, 5/41]
[OH12, 5/42, observed/predicted sulfate deposition in Japan]
[OH13, 5/46, SO2 sampling sites]
Calcium deposition ("yellow rain") is an important dimension to acid rain in Asia which
is
absent in North America and Europe. East Asia experiences large-scale dust storms
which
come from strong cold fronts and strong winds which lift up dust high into the
atmosphere
from the PRC and Mongolia. The dust contains alkaline substances such as Ca, Mg, K,
and
Na which likely neutralizes some of the acid rain. Indeed, although sulfate levels in Asia
are
similar to those found in North America and Europe, the pH values of the rain are much
higher--due it seems to the availability of excess calcium in the wind-blown dust the
calculated values of which correlate closely with observational data.
The deposition rates calculated in the RAINS-ASIA modelling are highly uncertain.
Adjusting some parameters in the model showed it to be sensitive to emissions inventory
(and
particularly weak in relation to biomass fuels), the dispersion formula, the location of
sources
within the grid, wet removal rate constants, spotty or surrogate data for winds and rain
temporal and spatial variation--all these factors need to be validated, refined, and tested.
3.21 Acid Rain Import/Export
The atmospheric modeling and resultant deposition patterns provide suggestive figures
for
intra-regional (internal to each country) and transboundary deposition patterns. In the
PRC,
for example, the modelling done by RAINS-ASIA indicates that 82 percent of the sulfur
deposition arising from its emissions are deposited in the PRC, about 2 percent on Japan
and
the Korean Peninsula, and the other 15 percent on the oceans (except for a tiny fraction
on
Taiwan and Indochina).
In Table 1, for example, take Japan. Reading along the row, one finds that a total of
about 400,000 tonnes of sulfur were deposited on Japan in 1990, of which about half
came
from Japan itself about 7 percent from the ROK, about 10 percent from the PRC, and
about
30 percent from volcanoes. Of the cross-border deposition onto national territories in
Northeast Asia in 1990 (about 292,000 tonnes according to the model), the PRC was
responsible for 47 percent, the ROK about 29 percent, the DPRK about 23 percent, and
Japan only about 1 percent.
[OH14, Table 1]
Table 1: Northeast Asian Recipients/Sources of Sulfur Deposition,
1990
Source: G. Carmichael and R. Arndt, "Long Range Transport and
Deposition of Sulfur in Asia," RAINS-ASIA unpublished work in
progress, March 1995, p. 11.
3.3 Critical Loads and Levels
As noted earlier, sulfur deposition causes acidification. The highest level deposition
before
tolerance to acidification-related effects is exceeded is the critical load for that ecosystem.
Given an ecosystem's characteristics, the critical load is a function of the aerial
concentration of the pollutants that damages the ecosystem. The concentration at or
above
which damage occurs is known as the critical level. The higher the critical load, the less
sensitive the ecosystem is to increased acidity; and conversely, the lower the critical load,
the
more sensitive it is to increased acidity.
Both these concepts attempt to define the level of stress imposed by the assaulting
pollutant that threatens the ecological integrity of a natural system, that is, its structural
and
functional attributes. The former relate to aspects such species composition, diversity,
ratios between trophic levels, etc. The latter relates to nutrient transfer, energy flows, rate
processes, maintenance efficiency, and ecological efficiency. The damage that can occur
to
these ecosystem characteristics are direct and immediate, especially at a local level from
gaseous plumes; direct but occasional excessive levels that result in immediate damage
but
not in an irreversible, long term way; and long term, chronic excessive deposition that
changes soil chemistry to the point that ecosystem sustainability is threatened or
irreversibly
damaged.
Various methods have been developed to estimate critical loads for specific
ecosystems in Europe and North America given lack of field data. These include: 1) the
relative sensitivity approach which is based on parameters such as climate, geology, soil,
land use, and vegetation type; and 2) the Steady State Mass Balance Model which
concentrates on the ability of soils (from weathering and other processes) to buffer the
acidity, thereby relating vegetation types and tolerances to soil chemistry.
At the macro-level of regional acid rain analysis, the first objective is to establish
broad categories of critical loads at a low resolution compatible with the overall
transport/deposition model. The critical loads are driven by ecosystem considerations,
and
can be used to evaluate emission control strategies. Where emissions can be shown to
impose excess loads given a current or projected control strategy, the excess can be
defined
in terms of area or areal fraction of protected versus vulnerable ecosystems; and excess
values over critical loads for each area (at whatever resolution is the foundation of the
analysis--one by one degree in the case of RAINS-ASIA). At this stage, ecosystem
recovery
(or restoration if recovery is not feasible) is not integrated into assessments of acid rain
control strategy.
3.4 Ecosystem Sensitivity and Critical Load Exceedance
The sensitivity of a given ecosystem is determined by multiple variables and cannot
be determined a priori. Certainly, vegetation types may occur on sites with typical
acidity
buffering rates. But the buffering itself will vary as a function of soil chemistry response,
in
turn a function of multiple chemical and physical factors. Thus, an ecosystem may be
highly sensitive to increased acidity even though it has vegetation types that are highly
tolerant of increased acidity--because the background buffering rate is low. Conversely,
ecosystems with vegetation types that are highly intolerant of increased acidity
nonetheless
may be insensitive to higher acidity because high buffering rates. The RAINS-ASIA
project
used six factors to classify vegetation types into six sensitivity classes: soil buffering
ability;
soil moisture; flooding; nutrient circulation, rooting depth, and organic matter type;
stresses
such as temperature; and tolerance of Al (see Table 2).
[OH15, table 2]
[OH16, sensitivity according to vegetation type only 6/26]
Work to date in Asia has relied on detailed studies of the sensitivity of indicator
species to acidification. This approach simplifies greatly the complex interdependence of
species in actual ecosystems, and the existence of numerous limiting conditions and
thresholds which may not be represented prudently in the acidity level defined as
"acceptable" to the indicator species. Thus, it is crucial that detailed ecological studies be
conducted in a range of sensitive and significant ecosystems to identify indicator species
which capture the complexity and set conservative limits with respect to the whole
ecosystem, not just the dominant or indicator species in the ecosystem.
species to acidification. This approach simplifies greatly the complex interdependence of
species in actual ecosystems, and the existence of numerous limiting conditions and
thresholds which may not be represented prudently in the acidity level defined as
"acceptable" to the indicator species. Thus, it is crucial that detailed ecological studies be
conducted in a range of sensitive and significant ecosystems to identify indicator species
which capture the complexity and set conservative limits with respect to the whole
ecosystem, not just the dominant or indicator species in the ecosystem.
At the low level of resolution used in RAINS-ASIA, continental data sets for these
classes have been combined with three other major variables which together determine
overall relative sensitivity (climate, soil, geological data) have been mapped for Asia by
GIS manipulation. Once amalgamated, these maps show Northeast Asia to have a
ecosystems that are relatively highly sensitive to acidic deposition, especially in Japan
and
Korea where soils are already acidic and ecosystems have a low ability to buffer chronic
increases in acidity. (Note that at this level of resolution, local areas of low sensitivity
such
as paddy fields in areas containing highly sensitive ecosystems are not distinguished;
however, the RAINS-ASIA approach does compute the extent to which critical loads are
exceeded for different ecosystems contained in a mapping cell, allowing different risk
levels
of imposing damage to determine sensitivity. The areas found in Northeast Asia by
Table 2: Sensitivity of Ecosystem Types by Vegetation Type Only in Asia
Source: J.P. Hettelingh et al, "An Assessment Model for Acid Rain in Asia,"
work in progress, RAINS-ASIA, April 1995.
RAINS-ASIA to be most in excess of critical loads for acidity due to sulfur deposition in
1990 (at a 25 percentile critical load exceedence such that 75 percent of the ecosystems
are
protected) were Korea, and southern Japan.
The RAINS-ASIA modeling of sensitivity and critical load exceedence estimates are
highly uncertain, however. The range of environmental conditions and ecosystems in
Asia is
far greater than in Europe, along with related soil types and land uses. The calculated
results require urgent validation and refinement based on fieldwork. The crude, low
resolution identification of sensitive ecosystems in the RAINS-ASIA project should be
used
to identify the range and location of sample sites for such field work to identify the
impacts
of acid deposition, and to ensure consistency of approach and comparability of results
across
these studies.
Two such reports work are available so far, one in Japan, and one in China. The
Japanese study applied a variety of steady-state model formulae for calculating critical
load to
data collected for Gunma Prefecture (northwest of Tokyo). They found that each formula
resulted in different levels and spatial distribution of critical loads (in some cases,
negative)
for the same area and that much better estimates of vegetation-specific, base cation
uptake
and site-specific information on mineralogy and weathering rates are needed as well as
monitoring of acid deposition. In addition, local and widespread forest decline has been
reported over the last two decades at many locations in Japan. Causes include air
pollution,
wind and drought damage, insects and pathogens, and the direct and indirect effects of
acid
deposition. Detailed, controlled studies are needed, therefore, to determine the
contribution
of acid deposition to this decline.
The Chinese study examined current and prospective emissions in Guizhou Province
in southwest China relative to a map combining critical loads and critical levels. The
study
showed that a province-wide, even reduction of emissions was unnecessary so long as
emissions from three big cities are reduced, or the large point sources in these cities are
relocated to areas capable of absorbing more air pollution.
Meanwhile, the modeling presents a prima facie case that future deposition levels
present a major potential environmental problem for the region.
4.0 Control Costs and Economics
4.1 Control Options and Costs
Since the first and second generation scrubbers for SOx and NOx became available in the
1970s, utilities and industries have accumulated a vast operational experience with
abatement technologies. In Germany today, for example, all relevant emission sources
have
been regulated and in general, are required to be constructed and operated according to
best
available practices.
A comprehensive inventory of technological controls will include: 1) desulfurization
of fuel oil, coal, and diesel fuel before combustion; 2) desulfurization of fuels during
combustion by additive processes such as injecting limestone into the furnace with Su
removal rates of 50-60 percent at moderate costs albeit with a large waste stream, and
fluidized bed combustion; and post combustion capture by flue gas treatments, the most
popular of which are wet limestone scrubbers which can now remove 95 percent or more
of
the sulfur without imposing much higher costs, and even offset cost by recycling captured
Su
to the chemical industry (Wellman-Lord process). Typical investment and operating cost
functions are shown in Table 3 and can be simplified into a reduction cost curve as shown
in
Table 4.
[OH17, table 3, 4/35]
[OH18, table 4]
Two other important policy measures are: 3) changes in fuel mix toward those
containing less or no sulfur; and 4) increased efficiency of energy use on the supply and
demand sides. These approaches reduce the emissions to be cleaned in the course of
energy
use; and they abate the emissions in the first place by reducing the emitting activities.
They may be substantially cheaper than the control technological options and will be
adopted
often for non-acid rain motivations (such as lower cost of energy services, reducing
greenhouse gas emissions, modernization of plant, etc.).
Table 4: Emission Cost Control Curve
Source: D. Streets et al, "Emissions and Control," work in progress, RAINS ASIA,
April 1995, Table 4.19
Many of the control technologies used in the OECD and listed above--and related costs--
can
be transposed to the Asian region as broadly the same technological fixes are available.
But
use of OECD cost data--which reflect higher emission standards at this time--mean that
actual
costs in Asian countries may be overstated as the requirements are less stringent; and in
many cases, local inputs such as labor and materials for such technologies may be
substantially cheaper than in OECD countries.
In addition, technological controls on Asian energy conversion systems no longer used
in OECD countries including coal briquettes and wet particle scrubbers, low cost
adaptations
of OECD technologies, and technologies appropriate to local fuels (such as lignite, high
ash
coals as in the DPRK, etc) reflecting local labor and materials as costs, would diversify
the
technological options and shift the cost functions.
4.2 Economics of Emission Reductions
Using baseline and projected emission scenarios, the RAINS ASIA project developed
cumulative cost estimates for controlling SO2 emissions. The unabated projected SO2
emissions in 2020 in the "business as usual" scenario with no further controls than those
present today are 110 million tonnes, compared with about half that figure for the "best
available control technology" scenario. The latter reduction rate requires an estimated
$42
billion in the year 2000, rising to about $80 billion per year in 2020. Adopting energy
efficiency measures to reduce emissions (and assumed to not be charged to the SO2
account,
thereby relieving SO2 controllers of this responsibility), these costs fall to about $37
billion
and $58 billion respectively.
[OH19, Foell Figures 4 and 5, p. 8]
In the base "business as usual" case with no further controls, the cost falls to only
about $3 billion per year (or only $2 billion/year for the low energy scenario)--mostly
from
control costs adopted in Japan.
Only under the "best available control technology" scenario does excess deposition
fall to levels that might be regarded as even minimally acceptable in the RAINS-ASIA
models. The cost of the control technology options may be compared with the funds
required to develop electric power in APEC countries. Between 1991-2000, for
example,
one study estimates that an average of (1992)$55 billion/year will be needed for power
generation, transmission, and distribution, rising to (1992)$92.7 billion/year between
2000-
2010. Of this total, China will demand 62 percent in 1991-2001, rising to 60 percent
over
2000-2010; the NICs 19 falling to 14 percent; and ASEAN states, 19 falling to 17
percent.
Due to the absolute scarcity of investment capital, it is not surprising that the PRC is
reluctant to spend funds on sulfur emission controls--especially when (as we saw earlier)
a
substantial fraction of the eventual deposition is either on international commons (the
oceans)
or on other states. Indeed, the PRC reportedly has rejected Japan's efforts to fund
emission
controls with aid funds as unwarranted "green conditionality" and prefers to spend aid on
expanded coal-fired generation. Although the PRC has emphasized the adaptation of
environmental management technology, it is unlikely that cooperative projects such as
the
adaptation in Shanxi Province of Japanese limestone-gypsum wet flue gas desulfurization
will
be replicated widely enough to achieve significant reductions of projected emissions.
[OH20, Foell p. 10]
Unfortunately, the costs associated with the damage arising from exceeding critical
loads today or as projected in the future have not been estimated. Consequently, it is not
possible to quantify the benefits of avoiding the damage imposed by acid rain by
investments
on the scale referred to above.
Nor can the issue of who should pay to stop acid rain be elevated from a political
tussles rooted in scientific uncertainty, not to mention connections with preexisting
regional
animosities over unrelated issues that preclude even serious dialogue over such issues as
acid
rain--let alone cooperative action to address the problem.
What are the aesthetic and ecological values of forests worth to the Japanese people?
Are they and others willing to pay a price commensurate with the cost of avoiding these
emissions in the PRC and elsewhere to preserve elements of their environment which are
central to their national identity?
5. Conclusion
Assuming that 1) the acid rain issue can be extricated from political gridlock due to high
level geopolitical (and geoeconomic) issues in the region; and 2) assuming further that
not
only is the political will is forthcoming in wealthy states to invest substantial resources in
an
international effort but that 3) the major acid rain exporting states are willing to accept
aid on
a scale commensurate with the problem that they are creating--what then?
Returning to the conceptual framework outlined in section 1.4, we believe that at least
five steps must be taken to address effectively the nexus between energy, development,
and
environmental impacts that is embodied in the regional acid rain problem.
First, a much expanded political commitment and scientific effort must be made at a
regional level to monitor acid rain emissions, transport, deposition, and impacts analysis.
This enterprise itself requires major investment in technical assistance, training, provision
of
equipment, information exchange, and education based on the results to ensure that
awareness of the issue is not confined to a narrow strata of scientists but reaches all
sectors
of society. An effective capacity building program in each country and via the creation of
regional networks is needed to achieve this outcome.
Second, states in Northeast Asia might consider the utility of negotiating a subregional
convention on long range transboundary air pollution, adapting the European and North
American experience to local circumstances. This convention would provide the
framework
for on-going governance of a common pool resource--the atmospheric system and
terrestrial
absorptivity of deposited acid rain. As economic integration proceeds apace in Northeast
Asia, we believe that the environmental "subtext" will require explicit agreements to
regulate
and manage the impacts implied by such growth in sub-regional trade and investment.
Acid
rain is only one such dimensions of such sub-regional cooperation. But it is a crucial one
because the solutions entailed in solving the acid rain are needed badly to address a
number
of other regional environmental problems including oceans management, integrated
coastal
zone management, and wetlands and critical habitat maintenance for migratory birds.
As in Europe, such a convention would require states to increase greatly the
transparency of their emissions and control programs by such obligations as 1) submitting
annual reports and periodic reviews by independent scientific panels, combined with
monitoring programs of actual emissions and deposition, including transboundary fluxes;
2)
development of special manuals and guidelines for emission inventories and uniform
calculation of pollution control costs; 3) widespread dissemination of the documents and
reports to media, schools, and universities; 4) specialized information exchange and
increased scientific cooperation and expertise; 5) establishment and participation in
specialized working groups on topics such as impacts, assessment modeling, economic
aspects, control technologies, abatement strategies, etc.; 6) eventual expansion of the
convention beyond SOx and NOx to issues such as transboundary transport of persistent
organic compounds and emissions of heavy metals.
Third, "no regrets" measures such as energy efficiency and fuel switching to achieve
abatement of emissions at zero, low, or even negative marginal cost should be
implemented
immediately, along with institutional and pricing reforms which will also reduce
emissions.
Fourth, informed debate needs to be stimulated in the public in Asian states via better
coverage in the media, specific education and outreach programs, and opening the
political
and scientific dialogues a much higher degree of non-governmental participation--
something
to which all governments in the region committed themselves to at the 1992 UNCED
conference. Unless such broad-based constituencies emerge, one can predict confidently
that
little will be achieved.
Finally, the availability of financing will make or break the ability of states to control
emissions that lead to acid rain. Much more attention needs to be given to creative and
innovative ways of levering public and private capital into environmental concerns,
including
abatement of acid rain.