Greenhouse Gas (CH₄, CO₂, N₂O) Emissions from Estuarine Tidal and Wetland and Their Characteristics

Abstract

A closed flux chamber system was used for measuring major greenhouse gas (GHG) emission from tideland and/or wetland soils in estuarine area at Saemankum, Kunsan in southwestern Korea during from months of February to June 2006. Hourly averaged GHG soil emissions were measured two to three times a day during the ebb tide hours only. Site soils were analyzed for soil parameters (temperature, pH, total organic contents, N and C contents in soil) in the laboratory. Soil GHG fluxes were calculated based on the GHG concentration rate of change measured inside a closed chamber The analysis of GHG was conducted by using a Gas Chromatography (equipped with ECD/FID) at laboratory. Changes of daily, monthly GHGs' fluxes were examined. The relationships between the GHG emissions and soil chemical contents were also scrutinized with respect to gas production and consumption mechanism in the soil. Soil pH was pH <TEX>$7.47{\pm}0.49$</TEX> in average over the experimental period. Organic matter contents in sample soil was <TEX>$6.64{\pm}4.98\;g/kg$</TEX>, and it shows relatively lower contents than those in agricultural soils in Kunsan area. Resulting from the soil chemistry data, soil nitrogen contents seem to affect GHG emission from the tidal land surface. The tidal soil was found to be either source or sink for the major GHG during the experimental periods. The annual average of <TEX>$CH_{4}\;and\;CO_{2}$</TEX> fluxes were <TEX>$0.13{\pm}0.86\;mg\;m^{-2}h^{-1}\;and\;5.83{\pm}138.73\;mg\;m^{-2}h^{-1}$</TEX>, respectively, which will be as a source of these gases. However, <TEX>$N_{2}O$</TEX> emission showed in negative flux, and the value was <TEX>$-0.02{\pm}0.66\;mg\;m^{-2}h^{-1}$</TEX>, and it implies tidal land surface act as a sink of <TEX>$N_{2}O$</TEX>. Over the experimental period, the absolute values of gas fluxes increased with soil temperature in general. Averages of the ambient gas concentration were <TEX>$86.8{\pm}6.\;ppm$</TEX> in <TEX>$CO_{2},\;1.63{\pm}0.34\;ppm\;in\;CH_{4},\;and\;0.59{\pm}0.15\;ppm\;in\;N_{2}O$</TEX>, respectively. Generally, under the presence of gas emission from agricultural soils, decrease of gas emission will be observed as increase in ambient gas concentration. We, however, could not found significant correlation between the ambient concentrations and their emissions over the experimental period. There was no GHG compensation points existed in tide flat soil.