Acid rain links to CH4 emissions from wetlands.
A variety of approaches, spanning a range of spatial and temporal scales, were applied
to the investigation of the effects of low dose SO/- deposition, at rates comparable to
those experienced in acid rain impacted areas, on methane (CH4) emissions from natural
Over two years of experimental manipulation of S042- deposition to a peatland in
northeast Scotland, CH4 emissions were suppressed by around 40%. There was no
significant difference in suppression of CH4 flux within the sol- deposition range of
25-100 kg-S ha-1yr-l. In a similar short-term controlled environment SO/- manipulation
experiment, the suppressive effect of SO/- was found to be independent of the
simulated SO/- deposition rate within a range of 15-100 kg-S ha-1yr-l. The possibility
that suppression of CH4 fluxes may have been the result of a 'salt effect' was ruled out.
Both temperature and water table controlled the extent of CH4 flux suppression in acid
rain impacted wetlands.
Sulfate reduction potential in SO/- treatments were found to be 10 times larger than in
control plots, suggesting that long-term suppression of CH4 fluxes is the result of the
formation of an enlarged population of competitively superior sulfate reducing bacteria.
SO/- concentrations were smaller in peat pore water from SO/- treatments than from
controls. This is possibly the result of a stimulated SO/- reducing community
scavenging available SO/-, thereby decreasing concentrations to below ambient levels.
In northern peatlands (>50°) the effect of SO/- deposition at 1990 rates may have been
sufficient to reduce emissions from these systems by around 15% annually. Globally,
the effect of acid rain SO/- deposition may be sufficient to reduce CH4 emissions by as
much as 22-28 Tg by 2030, which places this interaction within the same size category
as many other components of the global CH4 budget that have received far greater