Volatile organic compounds (VOCs) emitted by plant foliage play an important role in ozone (O3) and secondary organic aerosol (SOA) formation. Their emissions can be influenced by the leaf age. We explored the VOCs emissions and their effects on the formation of O3 and SOA from plant foliage in different ages. VOCs emissions from the young, mature, and senescent leaves of Ginkgo biloba, Ligustrum lucidum, and Forsythia suspensa were measured using the dynamic enclosure system and the TD-GC-MS technique. Based on the emission rates of quantified compounds, their potential to form O3 and SOA was estimated. Results showed that there were significant differences in the VOCs emission rate and their composition among leaves in different ages. The emission rate of the total VOCs by young leaves was the highest, while the lowest by senescent leaves. Monoterpenes were the dominant VOCs category, and isoprene emission had the lowest contribution for the leaves at each age. With increasing leaf age, the proportion of monoterpenes emission increased, and the proportion of sesquiterpenes decreased. The variations of isoprene and other VOCs were different. The potentials of total VOCs, isoprene, monoterpenes, sesquiterpenes, and other VOCs to form O3 (OFP) and SOA (SOAP) varied significantly among leaves at different ages. The total OFP and SOAP were the highest by young leaves, while the lowest by senescent leaves. With increasing leaf age, the contribution of monoterpenes to OFP and SOAP also increased, while that of sesquiterpenes decreased. Our study will provide support for the more accurate parameterization of the emission model and help to understand the VOCs emissions and study the precise prevention and control of complex air pollution at different times.
Keywords: biogenic volatile organic compound; leaf age; ozone; secondary organic aerosol.