Atmospheric sulfur hexafluoride in-situ measurements at the Shangdianzi regional background station in China

We present in-situ measurements of atmospheric sulfur hexafluoride (SF₆) conducted by an automated gas chromatograph-electron capture detector system and a gas chromatography/mass spectrometry system at a regional background site, Shangdianzi, in China, from June 2009 to May 2011, using the System for Observation of Greenhouse gases in Europe and Asia and Advanced Global Atmospheric Gases Experiment (AGAGE) techniques. The mean background and polluted mixing ratios for SF₆ during the study period were 7.22 × 10^-12 (mol/mol, hereinafter) and 8.66 × 10^-12, respectively. The averaged SF₆ background mixing ratios at Shangdianzi were consistent with those obtained at other AGAGE stations located at similar latitudes (Trinidad Head and Mace Head), but larger than AGAGE stations in the Southern Hemisphere (Cape Grim and Cape Matatula). SF₆ background mixing ratios increased rapidly during our study period, with a positive growth rate at 0.30 × 10^-12 year^-1. The peak to peak amplitude of the seasonal cycle for SF₆ background conditions was 0.07 × 10^-12, while the seasonal fluctuation of polluted conditions was 2.16 × 10^-12. During the study period, peak values of SF₆ mixing ratios occurred in autumn when local surface horizontal winds originated from W/WSW/SW/SWS/S sectors, while lower levels of SF₆ mixing ratios appeared as winds originated from N/ NNE/NE/ENE/E sectors.