A variety of approaches, spanning a range of spatial and temporal scales, were applied to the investigation of the effects of low dose SO<sub>4</sub><sup>2-</sup> deposition, at rates comparable to those experienced in acid rain impacted areas, on methane (CH<sub>4</sub>) emissions from natural wetlands. Over two years of experimental manipulation of SO<sub>4</sub><sup>2-</sup> deposition to a peatland in northeast Scotland, CH<sub>4</sub> emissions were suppressed by around 40%. There was no significant difference in suppression of CH<sub>4</sub> flux within the sol- deposition range of 25-100 kg-S ha<sup>-1</sup>yr<sup>-1</sup>. In a similar short-term controlled environment SO<sub>4</sub><sup>2-</sup> manipulation experiment, the suppressive effect of SO<sub>4</sub><sup>2-</sup> was found to be independent of the simulated SO<sub>4</sub><sup>2-</sup> deposition rate within a range of 15-100 kg-S ha<sup>-1</sup>yr<sup>-1</sup>. The possibility that suppression of CH<sub>4</sub> fluxes may have been the result of a 'salt effect' was ruled out. Both temperature and water table controlled the extent of CH<sub>4</sub> flux suppression in acid rain impacted wetlands. Sulfate reduction potential in SO<sub>4</sub><sup>2-</sup> treatments were found to be 10 times larger than in control plots, suggesting that long-term suppression of CH<sub>4</sub> fluxes is the result of the formation of an enlarged population of competitively superior sulfate reducing bacteria. SO<sub>4</sub><sup>2-</sup> concentrations were smaller in peat pore water from SO<sub>4</sub><sup>2-</sup> treatments than from controls. This is possibly the result of a stimulated SO<sub>4</sub><sup>2-</sup> reducing community scavenging available SO<sub>4</sub><sup>2-</sup>, thereby decreasing concentrations to below ambient levels. In northern peatlands (>50°) the effect of SO<sub>4</sub><sup>2-</sup> 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<sub>4</sub><sup>2-</sup> deposition may be sufficient to reduce CH<sub>4</sub> 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 CH<sub>4</sub> budget that have received far greater attention.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:367994 |
| Date | January 2000 |
| Creators | Gauci, Vincent |
| Publisher | Open University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://oro.open.ac.uk/58051/ |
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