Characteristics Of Terpenes Compounds From Typical Biomass Burning In South China

Broadleaf,coniferous and herbaceous plants distribute widely and diversely in South China,where forest fires are frequent occurred and may result in large number of terpene emissions.Terpenes are precursors of secondary organic aerosols and ozone because of their significant structural dependence and strong reactivity.In this study,simulated burning experiments were conducted and the emission factors of terpenoids were estimated for the open burning of Eucalyptus（a representative species of broadleaf）,Horsetail Pine（a representative species of coniferous forest）,and Miscanthus（a representative species of herbaceous）.Combining the emission factors from this paper and the literature and satellite ignition activity data,the emissions of terpenoids from biomass open burning were estimated in Guangdong Province in the past five years.The main results are as following:（1）Simulated open burning experiments were conducted for Eucalyptus,Horsetail Pine and Miscanthus.Eight terpenes were detected and the emission factors were estimated,including Isoprene,α-pinene,β-pinene,Camphene,Sabinene,3-carene,Limonene and Ocimene.The highest terpenes were emitted from the burning of Horsetail Pine（0.43±0.11g/kg）,followed by Eucalyptus（0.11±0.01g/kg）and Miscanthus（0.12±0.02g/kg）.Isoprene was the species with the highest emission,followed byα-pinene,β-pinene and Limonene.（2）The thermal behavior process of the biomass burning can be divided into five phases,i.e.,dehydration phase,distill phase,holocellulose decomposition phase,lignin decomposition phase,and ash formation phase.In N₂ enviroment,Eucalyptus and Horsetail Pine emitted the highest monoterpenes in the dehydration phase,and Miscanthus was in the evaporation phase.For the burning of Eucalyptus and Horsetail Pine,the order of monoterpenes emission was leaves>bark>twigs.The monoterpene emission factors for the burning of fresh plants were higher than that of litters in all burning phases.In air,all the burnings emitted the highest monoterpene during the distill phase.The ranking of monoterpene emissions from Eucalyptus and Horsetail Pine was leaf>bark>twig.The monoterpene emission from all the burnings of litters were higher than that of fresh plants in all burning phases.Comparing the thermogravimetric results in both N₂ and air enviroments,the terpenoids emission patterns for the five burning phases are nearly consistent.However,the emission factors of terpenoids in air enviroment are higher than N₂ enviroment.（3）In Guangdong Province,the average annual terpenes emission is 480.80±162.20t/a and shows a gradual decreasing trend during 2016 to 2020.The annual average emission of terpenes from forest fires is 394.05±141.07t/a,grassland fires is 39.33±7.51t/a,shrub fires is 39.77±11.96t/a,and straw burning is 7.64±2.65t/a.The contribution of terpenes from biomass burning to the total terpenes emission in Guangdong Province is about 0.49-0.99%.The monthly emission contribution from December to March when biomass burning is frequent is2.01-3.55%.