Determination of the stable carbon isotopic compositions of 2-methyltetrols in ambient aerosols from the Changbai Mountains

Abstract

Isoprene is one of the most important non-methane hydrocarbons (NMHCs) in the troposphere: it is a significant precursor of O3 and it affects the oxidative state of the atmosphere. The diastereoisomeric 2-methyltetrols, 2-methylthreitol and 2-methylerythritol, are marker compounds of the photooxidation products of atmospheric isoprene. In order to obtain valuable information on the δ13C value of isoprene in the atmosphere, the stable carbon isotopic compositions of the 2-methyltetrols in ambient aerosols were investigated. The 2-methyltetrols were extracted from filter samples and derivatized with methylboronic acid, and the δ13C values of the methylboronate derivatives were determined by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The δ13C values of the 2-methyltetrols were then calculated through a simple mass balance Equation between the 2-methyltetrols, methylboronic acid and the methylboronates. The δ13C values of the 2-methyltetrols in aerosol samples collected at the Changbai Mountain Nature Reserves in eastern China were found to be -24.66±0.90% and -24.53±1.08% for 2-methylerythritol and 2-methylthreitol, respectively. Based on the measured isotopic composition of the 2-methyltetrols, the average δ13C value of atmospheric isoprene is inferred to be close to or slightly heavier than -24.66% at the collection site during the sampling period. © 2010 John Wiley & Sons, Ltd.