Measurement of 14C Concentrations of Stratospheric CO2 by Accelerator Mass Spectrometry. Issue 3 (18th July 2016)

• Record Type: Journal Article
• Authors: Nakamura, Toshio; Nakazawa, Takakiyo; Nakai, Nobuyuki; Kitagawa, Hiroyuki; Honda, Hideyuki; Itoh, Tomizo; Machida, Toshinobu; Matsumoto, Eiji
• Is Part Of: Radiocarbon. Volume 34:Issue 3(1992)
• Page Start: 745
• Page End: 752
• Publication Date: 2016-07-18
• Subjects: Radiocarbon dating -- Periodicals; 930.1028505
• DOI: 10.1017/S0033822200064031
• Languages: English
• ISSNs: 0033-8222

Abstract

Abstract : In order to measure the concentrations of anthropogenically influenced gases in the stratosphere, we have collected air samples from the lower stratosphere since 1985, by a balloon-borne cryogenic sampling method, developed at the Institute of Space and Astronautical Science (ISAS). Air samples of ≃16 liters at STP were collected in the stratosphere at altitudes from 18.6 to 30.4 km, over the northeastern part of Japan (39.5°N, 139–142°E), on 1 September 1989. We conducted 14 C analyses to study the vertical and horizontal air-mass movement in the stratosphere, and to investigate the air transport mechanism between troposphere and stratosphere. Carbon dioxide (containing a few mg carbon) was separated cryogenically from the air samples, and the 14 C concentration of the CO2 was measured by a Tandetron accelerator mass spectrometer, using Fe-graphite targets prepared by reducing CO2 on Fe-powder with hydrogen in a Vycor tube at 650°. The 14 C concentrations, expressed as Δ 14 C, of CO2 were 267–309‰ at altitudes of 21–30 km, and 134‰ at 19–20 km. The Δ 14 C values at 21–30 km were higher than those of the current tropospheric CO2, of around 80–200‰. The observed 14 C concentrations, higher in the stratosphere than the troposphere, seem to be explained by large bomb-produced 14 C inventories and/or high 14 C production by cosmic rays, as well as weak vertical mixing of air masses in the stratosphere.