In situ CO_2 profiles with complementary monitoring of O_2 in a drained peat layer(Soil Physics)

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Peatlands can export large amounts of carbon in various forms, including surface gas emissions and the discharge of dissolved carbon under aerobic/anaerobic soil degradation. Therefore, an apparent imbalance can be expected between gaseous CO_2 production and O_2 consumption in unsaturated peat layers. The present study monitored profiles of soil CO_2 and O_2 in Bibai mire, Hokkaido, Japan, with the aim of examining the apparent imbalance between the two gases. The CO_2 abundance to the atmospheric level did not exceed the O_2 deficit because the CO_2 concentrations were 0.21, 0.75 and 2.92%, whereas the O_2 concentrations were 19.71, 18.05 and 9.51% at depths of 10, 20 and 30cm, respectively. This shortage of CO_2 abundance implied that a remarkable amount of CO_2 dissolved into the liquid phase. The dissolved CO_2 mass on the basis of Henry's law ranged from 1.72 to 159.3 mmol m^<-2> (10cm)^<-1>, and was 1.59-5.25-fold greater than the gaseous CO_2 mass. The mass balance analyses showed that the CO_2 production rate in the gaseous phase at a depth of 20cm ranged from 6.52 to 23.11 mmol m^<-2> (10cm)^<-1> day^<-1>, equivalent to 43% on average of the O_2 consumption rate. This CO_2 production rate contributed to less than 10% of the gaseous CO_2 produced in the unsaturated peat layer, which had a maximum thickness of 40cm, implying the existence of a large CO_2 source in the peat layer, including in the saturated zone. The mass balance analyses also showed that the residence time of CO_2 in the gaseous phase alone was 0.351 day, whereas that in the whole peat soil matrix was 0.919 day at a depth of approximately 20cm, suggesting that high water content serves as a tentative storage for gaseous CO_2 in peatlands.
社団法人日本土壌肥料学会の論文

In situ CO_2 profiles with complementary monitoring of O_2 in a drained peat layer(Soil Physics)

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