| Volatile Organic Compounds(VOCs)are important precursors in atmospheric chemistry and photochemical processes,which can produce environmentally harmful substances such as ozone(O3)and secondary organic aerosols(SOA).In summer,the atmosphere in Shanghai is seriously polluted with ozone,and biogenic Volatile Organic Compounds(BVOCs)play an important role in the formation of ozone pollution.In this paper,the emission rate of BVOCs of 15 plants in different growing seasons was determined in situ by dynamic headspace bagging method,the seasonal variation characteristics of emission components and rates were analyzed,and the emission rate of BVOCs in Shanghai in 2022 was established by the "G95”model based on the measured emission rate and emission factors of relevant literature,which provided a theoretical basis for the selection of green tree species,regional emission reduction and urban air pollution control in Shanghai.The main results are as follows:(1)Among the 15 plants surveyed,except for crops and fruit trees,the emission of BVOCs of other plants showed strong seasonal variation,and the emission rate was basically the highest in summer and the lowest in winter.There were significant differences in emission composition and rate of crops and fruit trees at different phenological periods(P<0.05).Among the 15 plant species,poplar had the highest emission level of isoprene,with an emission rate of 72.94 ±4.74 μg·g-1·h-1.The emission levels of BVOCs in camphor,magnolia,osmanthus and boxwood were relatively low,and the emission rates were all<1 μg·g-1·h-1.Isoprene and monoterpenes were the two main components of plant BVOCs emissions.In terms of monoterpene components,a total of 11 monoterpene components were detected in 15 plants investigated,including α-pinene,campene,3-pinene,β-pinene and D-limonene.(2)Based on the emissions of isoprene and monoterpenes in Shanghai,the total OFP of isoprene and monoterpene in major agricultural and natural source vegetation in Shanghai in 2022 was estimated to be 66940.0 t and 12666.6 t,respectively,using the MIR of isoprene and monoterpene.The plant that contributes the most to the isoprene OFP in Shanghai is poplar.The largest contribution of monoterpene OFP is Metasequoia.Due to the large planting area,rice contributed the most to the OFP of isoprene and monoterpenes in cultivated land in Shanghai.The monthly changes of BVOCs emissions in Shanghai in 2022 were in line with the changes in the trend of ozone pollution concentration in Shanghai,and both showed a unimodal distribution.(3)Based on the emissions of isoprene and monoterpenes in Shanghai,the total OFP of isoprene and monoterpene in major agricultural and natural source vegetation in Shanghai in 2022 was estimated to be 66940.0 t and 12666.6 t,respectively,using the MIR of isoprene and monoterpene.The plant that contributes the most to the isoprene OFP in Shanghai is poplar.The largest contribution of monoterpene OFP is Metasequoia.Due to the large planting area,rice contributed the most to the OFP of isoprene and monoterpenes in cultivated land in Shanghai.The monthly variation of BVOCs emissions in Shanghai in 2022 was consistent with the change of ozone pollution concentration in summer in Shanghai,and both showed a unimodal distribution.Among them,summer BVOCs emitted the highest emissions,and ozone pollution is also the most serious. |
