[M-IS13] 生物地球化学

[MIS13-05] 土壌で普遍的に起こる炭素・窒素安定同位体比および放射性炭素濃度の変動とその規定因子：微生物代謝・鉱物表面反応・団粒化

*和穎 朗太¹、梶浦 雅子¹、井上 弦²、浅野 眞希³、早川 智恵⁴ (1.農研機構 農業環境変動研究センター、2.長崎総合科学大学、3.筑波大学 環境生命系、4.東京大学農学生命科学研究科)

キーワード：土壌、炭素隔離、有機物・鉱物相互作用、炭素，窒素安定同位体、放射性炭素、鉱物学

Organic matter (OM) in soil represents the largest carbon pool on land. The production of CO2 via microbial degradation of soil OM therefore has a strong impact on global C cycle and anticipated global warming. Previous studies have shown that any soil holds multiple OM pools of varying stability against microbial attack. Growing number of studies suggests protective effect of specific mineral phases and mineral matrix. OM, however, interacts with soil minerals in highly complex ways including co-precipitation of organic ligands with multivalent metals at molecular scale and physical aggregation of OM with mineral particles at micron and larger scales.

Here we examined the relationship between the isotopic compositions (C-13, C-14, and N-15) and mineralogical characteristics (surface area and elemental composition, pedogenic metal oxides) among density fractions using a range of surface soils of contrasting mineralogy including volcanic soils rich in short-range-order minerals and much more weathered soils from both agricultural and natural systems. Each soil was separated into 4-7 density fractions after mechanical shaking with sodium polytungstate. From LF to higher-density fractions, We assessed how C aging is related to C13 and N15 enrichment and to what extent these isotopic variations among the fractions were controlled by the mineralogical characteristics.