title: Δ14CO2from dark respiration in plants and its impact on the estimation of atmospheric fossil fuel CO2.
abstract: Radiocarbon (14C) has been widely used for quantification of fossil fuel CO2(CO2ff) in the atmosphere and for ecosystem source partitioning studies. The strength of the technique lies in the intrinsic differences between the14C signature of fossil fuels and other sources. In past studies, the14C content of CO2derived from plants has been equated with the14C content of the atmosphere. Carbon isotopic fractionation mechanisms vary among plants however, and experimental study on fractionation associated with dark respiration is lacking. Here we present accelerator mass spectrometry (AMS) radiocarbon results of CO2respired from 21 plants using a lab-incubation method and associated bulk organic matter. From the respired CO2we determine Δ14Cresvalues, and from the bulk organic matter we determine Δ14Cbomvalues. A significant difference between Δ14Cresand Δ14Cbom(P < 0.01) was observed for all investigated plants, ranging from -42.3‰ to 10.1‰. The results show that Δ14Cresvalues are in agreement with mean atmospheric Δ14CO2for several days leading up to the sampling date, but are significantly different from corresponding bulk organic Δ14C values. We find that although dark respiration is unlikely to significantly influence the estimation of CO2ff, an additional bias associated with the respiration rate during a plant's growth period should be considered when using Δ14C in plants to quantify atmospheric CO2ff.
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; Xi'an AMS Center, Xi'an 710061, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Xiaohu
authors.initials: X
authors.lastname: Xiong
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; Xi'an AMS Center, Xi'an 710061, China. Electronic address: weijian@loess.llqg.ac.cn.
authors.forename: Weijian
authors.initials: W
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; Xi'an AMS Center, Xi'an 710061, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Cheng
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; Xi'an AMS Center, Xi'an 710061, China.
authors.forename: Shugang
authors.initials: S
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; Xi'an AMS Center, Xi'an 710061, China.
authors.forename: Zhenchuan
authors.initials: Z
authors.lastname: Niu
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; Xi'an AMS Center, Xi'an 710061, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Du
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; Xi'an AMS Center, Xi'an 710061, China.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; Xi'an AMS Center, Xi'an 710061, China.
authors.forename: Yunchong
authors.initials: Y
authors.lastname: Fu
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; Xi'an AMS Center, Xi'an 710061, China.
authors.forename: George S
authors.initials: GS
authors.lastname: Burr
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data*; D001272:Atmosphere / Q000737:chemistry; D002245:Carbon Dioxide / Q000032:analysis*; D002247:Carbon Isotopes / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods*
chemical_list: D000393:Air Pollutants; D002247:Carbon Isotopes; D002245:Carbon Dioxide
keywords: Carbon cycle; Dark respiration; Fossil fuel CO(2); Plant; Δ(14)C