title: Evaluation of 14C abundance in soil respiration using acclerator mass spectrometry.
abstract: To clarify the behavior of 14C in terrestrial ecosystems, 14C abundance in soil respiration was evaluated in an urban forest with a new method involving a closed chamber technique and 14C measurement by accelerator mass spectrometry (AMS). Soil respiration had a higher Delta14C than the contemporary atmosphere. This indicates that a significant portion of soil respiration is derived from the decomposition of soil organic matter enriched in 14C by atmospheric nuclear weapons tests, with a notable time lag between atmospheric 14C addition and re-emission from soil. On the other hand, delta14C in soil respiration demonstrated that 14C abundance ratio itself in soil-respired CO2 is not always high compared with that in atmospheric CO2 because of the isotope fractionation during plant photosynthesis and microbial decomposition of soil organic matter. The Delta14C in soil respiration was slightly lower in August than in March, suggesting a relatively high contribution of plant root respiration and decomposition of newly accumulated and/or 14C-depleted soil organic matter to the total soil respiration in August.
authors.affiliation: Radiation Protection Division, Japan Nuclear Cycle Development Institute, Tokai-mura, Naka-gun, Ibaraki 319-1194, Japan. koarashi.jun@jnc.go.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Koarashi
authors.forename: Takao
authors.initials: T
authors.lastname: Iida
authors.forename: Jun
authors.initials: J
authors.lastname: Moriizumi
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Asano
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis*; D001272:Atmosphere / Q000032:analysis; D002245:Carbon Dioxide / Q000032:analysis*; D002250:Carbon Radioisotopes / Q000032:analysis*; D002947:Cities; D017753:Ecosystem; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D007564:Japan; D013058:Mass Spectrometry / Q000379:methods; D012987:Soil / Q000032:analysis; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D014197:Trees
chemical_list: D000396:Air Pollutants, Radioactive; D002250:Carbon Radioisotopes; D012987:Soil; D012990:Soil Pollutants, Radioactive; D002245:Carbon Dioxide