Effects of Elevated CO<sub>2</sub> and O<sub>3</sub> Concentrations on Isoprenoid Emissions from <i>Pinus tabulaeformis</i>

Abstract

Isoprene and monoterpenes have indirect effects on ozone concentration, methane lifetime and aerosol formation. At the same time, the atmospheric composition change (reflected in elevated CO2and O3concentrations) can affect the speciation of monoterpenes / isoprenoids and magnitude of isoprene and monoterpenes fluxes. Ambient concentrations of CO2and O3were 342 μmolmol-1and 40 nmolmol-1, respectively. The effects of elevated CO2(700 μmolmol-1) and O3(80 nmolmol-1) concentrations on isoprenoid emission rates and patterns fromPinustabulaeformiswere studied in open top chambers (OTCs). The released volatiles were quantified by thermal desorption and gas chromatography with flame ionization detector (GC-FID). The study showed that α-pinene was the main compound emitted from Ptabulaeformis, accounting for more 51.5 - 72.6% of the detected volatile compounds. The emissions of isoprene and monoterpenes were reduced in response to elevated CO2concentrations. Exposure to elevated O3for 3 years significantly promoted the isoprene and monoterpenes emissions (p<0.05). Compared with ambient, elevated O3concentration increased isoprene emission from Ptabulaeformisby about 270.5 ± 13.5%. The response of monoterpene emission to elevated O3may vary during the course of exposure to the pollutant. The patterns of monoterpene and isoprene emissions under combined elevated CO2and O3concentrations were similar to those under elevated CO2concentration alone.