We project that the magnitude of avoided emissions and
deposition from implementing more effective control technologies
for mercury in Asian CFPPs is large (as a fraction of
current emissions levels), even when considering a scenario
where the Minamata Convention’s requirements for mercury
are consistent with existing, non-mercury-specific domestic
pollution and energy policy plans (MF). Even such a flexibly
designed Convention could lead to avoided emissions of 242
Mg in India and China in 2050 compared to a scenario with no
additional technology, which is equivalent to ∼12% of the total
global anthropogenic emissions in 2010.8 More than 60% of
these avoided emissions are from India, highlighting the
importance of India’s participation in any global requirements
for CFPPs. Despite the fact that mercury reduction efficiencies
in Chinese CFPPs are likely to be higher, the larger emissions
avoided in India reflect the fact that power sector emissions
contribute a larger fraction of total emissions in India across
technology scenarios (67−78%) than in China (12−24%),
where emissions from industrial processes represent the largest
fraction of 2050 projected emissions.
The benefits of these avoided emissions in terms of avoided
deposition are concentrated regionally in Asia, particularly in
India, where the difference reaches a maximum of ∼30 μg·m−2.
However, deposition differences between the NAC and MF
technology scenarios in the U.S. and Europe, are also ∼5% of
current deposition. Moreover, global benefits occur through
avoided enrichment to oceans, particularly to the Pacific and
Indian Oceans, from which many of the fish in the global
seafood market are sourced.60,62 Qualitatively, this distribution
of benefits is robust to the IPR assumption (see SI, Figure S3),
though regions outside of Asia receive a larger share of benefits.
The definition of BAT for CFPPs under the Convention is
being discussed in a technical working group, and will also be
discussed during future conferences of parties. We show that
these definitions can have a substantial impact on environmental
mercury: differences in stringency of required control
technologies (MF vs MS) could result in emissions differences
in India and China of 173 Mg combined in 2050, which is
roughly the total estimated emissions from India in 2005.9
Increased stringency in the definition of BAT could also avoid
growth in power sector emissions over present-day levels in
China, though this is unlikely for India. The majority of benefits
of increased stringency in terms of deposition are captured by
India and China, suggesting that there is a strong domestic
incentive for these two countries to take further actions beyond
a flexible BAT. In the model simulation, 73% by mass of the
173 Mg avoided emissions between MF and MS would have
been deposited in India and China. This pattern is due to the
speciation of modeled emissions reductions between MF and
MS, as all Indian emissions reductions are in Hg2+/P, forms that
contribute most strongly to regional pollution.
For the power sector, the emissions gap between technology
scenarios (A1B:NAC − A1B:MS) is comparable to, but smaller
than, that between energy and development scenarios
(A1B:NAC − B1:NAC), with the former being 94% of the
latter for China, and 74% for India. This result underscores the
importance of energy and development trajectories for mercury
emissions. While moving toward more effective mercury
control technologies in China and India can mitigate some of
the emissions growth associated with aggressive increases in
coal consumption for the power sector, avoiding coal
consumption and transitioning toward less carbon-intensive
energy sources is likely necessary for reducing emissions from
present-day levels. Both Indian and Chinese governments have
stated goals to increase renewable capacity, and to pursue
demand-side management of electricity, for instance through
energy efficiency targets.18,64 A recent agreement between
China and Russia on natural gas also suggests a shift toward
Russian-exported gas-fired power plants in the future. Avoided
consumption of coal could also be an important facet of a
mercury emissions mitigation strategy.
Several assumptions made in the chemical transport
modeling present opportunities for future exploration. Without
locational data on Chinese and Indian power sector emissions,
emissions were scaled uniformly across countries, based on
2005 spatial distributions.65 This approach does not capture
real spatial patterns, particularly as substantial new coal
generation capacity will be built by 2050. The distribution of
these new plants, particularly on the East−West axis, may have
implications for transboundary transport to countries down-
Environmental Science & Technology Policy Analysis
DOI: 10.1021/acs.est.5b00074
Environ. Sci. Technol. 2015, 49, 5326−5335
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wind; however, the present analysis still offers insight into
global distributional impacts, at the regional scale. Better spatial
data could also provide further insight into the deposition
patterns of divalent mercury within India and China.
Our projections suggest that under the Convention, Asian
CFPP emissions will be avoided, but will likely increase from
present-day, consistent with previous estimates that Minamata
will result in avoided emissions increases;66 however, total
deposition benefits from these avoided emissions are likely to
be larger than our estimates, which only take into account the
impact of primary emissions changes. The mercury simulation
used for this study does not completely account for the legacy
impacts of anthropogenic emissions: primary anthropogenic
emissions once deposited to terrestrial and aquatic ecosystems
join a legacy pool of mercury that can continue to cycle through
air, water, and land. Because primary emissions also enrich
legacy pools in ocean and soil reservoirs, by 2050, re-emissions
from these pools may contribute >50% of global deposition.
67,68 However, while the legacy anthropogenic contribution
to total deposition by 2050 under an A1B scenario may be
significant,68 we address here the dif ference between technology
scenarios. The influence of legacy emissions is less substantial
in the difference calculation, which is small compared to
projected overall changes in the global mercury budget. Using a
global box model developed by Amos et al.,67,69 we estimate
that accounting for legacy effects could increase deposition
differences between NAC and MF and MF and MS by ∼30%
by mass (additional details are provided in SI, Table S5).
Because legacy pools are likely to increase global background
concentrations of mercury, their inclusion will not substantially
change the modeled spatial patterns of deposition.
The effects of climate change could also have additional
impacts on global mercury transport that we do not account for
in this analysis. Climate change is likely to impact mercury
biogeochemical cycling through increased volatilization from
ocean and soil reservoirs (which will increase the influence
from legacy mercury), increased plant respiration and wildfires,
changes to oxidant concentrations, and changes to food webs,
among other factors.70−72 Exploring the coupled effects of
direct anthropogenic mercury emissions changes and climate
change will be critical for understanding to what extent there
will be a “climate penalty” on policy efforts to reduce mercury
pollution.70 These interactions between future energy and
development trajectories, climate change, and mercury
biogeochemical cycling suggest that beyond technology choices
for the power sector itself, a broader consideration of energy
and development choices will be necessary to understand future
mercury emissions trajectories and their impacts.