Isoprene and monoterpenes are very reactive biogenic volatile organic compounds and have indirect effects on urban air quality. In this study, eight major planting tree species (six arbores and two shrubs) in Shenyang area were examined for the emission of isoprene and monoterpenes using thermal desorption instruments and gas chromatography. The results showed that there were strong seasonal variations in isoprene and monoterpenes emissions from these urban trees. The highest emission rates for Populus alba x berolinensis and Salix babylonica were observed in June with values of about 426.4 mu g.g(-1)h(-1) and 100.5 mu g.g(-1)h(-1), respectively. The emission flux from Salix babylonica, Populus alba x berolinensis, Pinus tabulaeformis, Gingo Bilobo, Ulmus pumila, Gleditsia japonica, Syringa oblate and Ligustrum obtusifolium in Shenyang were 168.66tC.y(-1), 104.86tC-y(-1), 14.48 tC. y(-1), 12.16 tC. y(-1), 3.56tC.y(-1), 1.27tC.y(-1), 4.07tC.y(-1) and 1.33tC.y(-1), respectively. Isoprene and monoterpenes emissions pattern were depended on tree species. Populus alba x berolinensis, Salix babylonica, Syringa oblate and Ligustrum obtusifolium mainly emitted isoprene (64.5-99.7%). Other 4 tree species mainly emitted monoterpenes, amounted to 66.0-94.1% of total emission. Pinus tabulaeformis mainly emitted a-pinene. Ulmus pumila and Gleditsia japonica mainly emitted limonene. Gingo Biloba emitted isoprene and limonene, accounted for 33.99% and 39.53%, respectively. The grade of emission rates of isoprene and monoterpenes from 8 tree species was classified. Populus alba xberolinensis was a high isoprene and monoterpenes emission tree species in summer. Salix babylonica was a medium isoprene and high monoterpenes emission tree species over growth season. These data demonstrate that rate and flux of the isoprene and monoterpenes emission from planting tree species in urban must be considered on selection of planting tree species for urban atmospheres environment.
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