title: Variation of atmospheric14CO2and its spatial distribution.
abstract: The atmospheric14CO2is usually presented in the Δ14C notation, which cannot reflect its absolute quantity change. This article presents the atmospheric radiocarbon activity concentrations (aacn, reported in mBq/m3) in recent years at nine observation stations. The aacnat Schauinsland decrease from 1977 to 1993 but between 1993 and 2003 keeps at a relative steady state. Atmospheric aacns were higher in the northern hemisphere than that in the southern hemisphere. The aacns in the northern hemisphere show clear seasonal cycle with higher value in winter and lower value in summer, while this seasonality is not obvious in the southern hemisphere. Vegetation plays as a role of sink in summer and a role of source in winter, and atmosphere-biosphere radiocarbon exchange might be the main driver of the aacns seasonality. The annual mean aacns in both hemispheres show slightly increasing trends since 2002, which may be mainly caused by decreasing air-sea14C flux as the air-sea14C gradient decline.
authors.affiliation: SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710061, China; Xi'an AMS Center, Xi'an, 710061, China. Electronic address: wusg@ieecas.cn.
authors.forename: Shugang
authors.initials: S
authors.lastname: Wu
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001272:Atmosphere / Q000737:chemistry*; D002245:Carbon Dioxide / Q000032:analysis*; D004784:Environmental Monitoring
chemical_list: D000393:Air Pollutants; D002245:Carbon Dioxide
keywords: Activity concentration; Atmospheric (14)CO(2); Biosphere/atmosphere interactions; Carbon cycling; Evolution of the atmosphere; Geochemical cycles; Radiocarbon