Effects of Nanoscale Pores in Soils on Carbon Evolution under Extremely Dry Conditions(Environment)

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Soil carbon evolution under the lowest moisture conditions varies considerably among experimental systems/techniques, leading to discrepancies in the estimations from carbon dynamics models under low moisture conditions. We focused our study on clarifying the regulating factors of soil carbon evolution under the lowest moisture conditions by conducting laboratory experiments under precisely controlled conditions. Nanoscale porosity and surface properties of these soils were determined to analyze the role of residual water in the carbon evolution processes in dry soils. Laboratory incubation showed that the carbon evolution from a microporous (D < 2 nm) volcanic soil proceeded even at -100 kJ kg^<-1> water potential (WP) in contrast to the carbon evolution from a phyllosilicate alluvial soil. Pore-size estimation and ^1H-NMR spectroscopy showed that the carbon evolution at -100 kJ kg^<-1> WP proceeded through the utilization of nanopore-water in soils. Batch sorption experiment suggested that the surface affinity of the soils to dissolved organic matter (DOM) had enhanced carbon evolution by attracting DOM into hydrophilic spheres of the soil at -100 kJ kg^<-1> WP. Solid-state ^<13>C-NMR of organic matter samples (incubated in the absence of soils) suggested that the chemical alteration of the samples was significant for aliphatic components, while the alteration was not observed in the samples incubated at -100 kJ kg^<-1> WP. This fact also indicated the contribution of nanoscale pores in the volcanic components to carbon evolution. Application of the experimental results to several biogeochemical models revealed that both volumetric water content and WP are required to estimate carbon evolution under low moisture conditions. A microhabitat model showed that the carbon evolution at -100 kJ kg^<-1> WP could be attributed to extracellular enzymatic processes or other abiotic processes rather than to the activities of living microorganisms.
社団法人日本土壌肥料学会の論文

Effects of Nanoscale Pores in Soils on Carbon Evolution under Extremely Dry Conditions(Environment)

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