Emission Characteristic Of Biogenic Volatile Compounds (BVOCs) From Fast-Growing Eucalyptus Foliage

Plants can abundantly produce and emit BVOC. Guangxi province is located in a region of low latitude and strong UV radiation, where BVOCs are more likely to react with NOx (increasingly come from vehicles exhaust) to form secondary pollutants, such as ground-level O3. BVOCs are oxidized by O3 to form secondary organic aerosols (SOA) in daytime. These compounds may potentially contribute to some environmental pollution, such as haze, photochemical smog. Fast-growing Eucalyptus trees are widely cultivated for paper industry in Southern China. Some studies report that eucalypts are among the highest emitter of BVOCs. However, there is relatively little data available from field studies of BVOCs released from large-area Eucalyptus. The investigations in this paper focus on the BVOCs emitted from Eucalyptus urophylla. In this study, the main chemical compounds of BVOCs released from Eucalyptus urophylla are analyzed. Moreover, the BVOCs emission patterns of both attached and detached leaves are investigated and the potential influence of the BVOCs on environment is assessed. The results are as follows:(1) The BVOCs emitted from Eucalyptus urophylla are isoprene, D-limonene, a-pinene, linalool, leaf alcohol, trans-3-Propyalacrolein and so on. The emission rate relationship links EBVOCs and Eisoprene:EBVOC=0.31Eisoprene2+0.37Eisoprene. The emission rates of BVOCs measured by enrichment and dynamic enclosure methods are not significantly different;(2) The emission rates of BVOCs from attached leaves are diurnal and seasonal characteristic. The emission rate of BVOCs at noon reaches to peaking value of 15.03±3.91 μgg-1h-1, and the emission rates at morning and afternoon are 3.37±2.95μgg-1h-1and 4.40±2.94μgg-1h-1, respectively. Seasonal variation of emission rate shows a unimodal pattern, and the peaking value (23.37±5.53μgg-1h-1) is displayed at the end of August. Due to the effect of photonihibition and temperature stress, the emission rate is the highest at 40000 lux and then gradually decreases between 40000 to 70000 lux;(3) The BVOCs emitted by detached leaves are also impacted by light intensity. At high or low level of light intensity, the increasing light intensity does not lead to apparent variation of BVOCs emission. Other effect factors impact significantly the BVOCs emission, such as leaf age, mechanical damage and detaching time. Mature leaves release more BVOCs compared with the other leaves with different ages. The BVOCs emission decreases with the degree of mechanical damage and increasing detaching time;(4) The BVOCs emitted from different species plants are obviously different. The BVOCs emission rate of Encalyptus exserta attached leaves is the highest among all investigated plants, and the value is 12.32±2.04 μgg-1h-1. Moreover, the emission rate of Ficus microcarpa attached leaves is lower than eucalyptus;(5) For 8-year Eucalyptus urophylla trees, the emission of isoprene is 43 t at the adverse environmental and non-environmental conditions and 170 t in summer daytime. The isoprene emitted from Eucalyptus urophylla may form 125 Kg SOA at noon.