Unexpected High Loading of Active Carbonyls and Terpenoids in Alpine Forest on Tibetan Plateau: Implication of Secondary Organic Aerosols and Ozone Formation

The reaction of volatile organic compounds (VOCs) can enhance the formation of secondary organic aerosols (SOA) and ozone, and further cause climate forcing on Tibetan Plateau (TP), while their origins are lack of clearly understanding. An atmospheric VOC monitoring campaign was performed for different altitudes in TP in this study. High concentrations of active carbonyls (up to 17.00 ppbv, 79% of the sum of VOCs measured) and terpenoids (up to 2.87 ppbv, 17% of the sum of VOCs measured) were observed in the alpine forest. Compositions of carbonyls and terpenoids varied synchronously among different tree species across the altitude gradient, and the potential sources of carbonyls and terpenoids in southeast Tibet were mainly distributed on the pathway of Asia monsoon in alpine forest, which imply that local air-ground exchange is the major contributing factor for the ambient VOCs. The carbonyls and terpenoids were estimated for the formation of SOA at approximately 1.78 μg m⁻³ and 0.54 μg m⁻³, respectively. The results confirmed the high impacts of air-ground exchange of active VOCs on formation of secondary organic aerosols and regional climate.