The Variations of 13CH4 Flux and δ13 C in a Rice Paddy Field.

The variations of ¹³CH₄ flux and  δ¹³C in a rice paddy field.

Kentaro Katano*, Shujiro Komiya*, Kosuke Noborio**,

*Graduate School of Agriculture, Meiji University, Kanagawa, Japan

**School of Agriculture, Meiji University, Kanagawa, Japan

  In recent years, global climate change has become one of the biggest concerns. Increases in greenhouse gases (GHGs) concentration may be attributed to the global warming. Rice paddy fields are a major source of methane (CH₄)  in monsoon Asian countries. Methane is an end product of the decomposition of organic matter in soil under anaerobic conditions. Previous studies suggested that different methanogenetic pathways in rice paddy fields resulted in different isotopic signitures for CH₄ varing. It is, however, still not well understood the relationship between variations inδ¹³C of CH₄ in soil and ¹³CH₄ flux. The objective of this study was to elucidate the relationship between d ¹³C valuea of CH₄ in soil and ¹³CH₄ flux in rice paddy fields. For measuring δ¹³C values for CO₂ and CH₄, we used a cavity ring-down spectroscopy (CRDS) analyzer (model G3301-i, PICARRO Inc.). For measuring δ¹³C values and CH₄ concentration in soil, a static equilibrium method with a gas-permeable silicone tube was used to collect soil air. Flux of ¹³CH₄ above ground was measured by the closed chamber method using automatic chambers. We will discuss the relationship between d ¹³C values and flux variation in conjunction with soil and weather conditions.