Carbon monoxide production and emission by some Scottish soils

When mineral soils from woodland, grassland and arable environments in Central Scotland were air-dried, they became net sources of CO; production rates were greatly increased by ovendrying at 104°C. The soils also produced CO after sterilisation by autoclaving and gamma irradiation. It was concluded that the CO production process involved non-biological decomposition of humic materials; addition of such materials to soils enhanced production. When moist, the soils were normally net sinks for CO, but in the presence of 1000 ppmv of acetylene (an inhibitor of microbial oxidation of CO), they became net sources. Net CO emission was observed in a peatland, in the field, during the wetter months of the year. Here, the CO production was apparently due to a different process from that responsible for production in the dried soils, probably involving anaerobic microbial activity. A possible upper limit of 0.2 Tg y−1, for emissions of CO from northern hemisphere wetlands, was calculated on the basis of this part of the study.