|作者：||Lejish Vettikkat, Vinayak Sinha, Savita Datta, Ashish Kumar, Haseeb Hakkim, Priya Yadav, Baerbel Sinha|
1Department of Earth and Environmental Sciences, Indian Institute ofScience Education and Research Mohali, Sector 81, S. A. S. Nagar, ManauliPO, Punjab, 140306, India
2Invited contribution by Lejish Vettikkat, recipient of the EGU Atmospheric Sciences Outstanding Student Poster and PICO Award 2019.
|刊名：||Atmospheric Chemistry and Physics, 2020, Vol.20 (1), pp.375-389|
|原始语种摘要：||Biogenic volatile organic compounds exert a stronginfluence on regional air quality and climate through their roles in thechemical formation of ozone and fine-mode aerosol. Dimethyl sulfide (DMS),in particular, can also impact cloud formation and the radiative budget asit produces sulfate aerosols upon atmospheric oxidation. Recent studies havereported DMS emissions from terrestrial sources; however, their magnitudeshave been too low to account for the observed ecosystem-scale DMS emissionfluxes. Big-leaf mahogany ( Swietenia macrophylla King) is an agroforestry and natural forest tree knownfor its high-quality timber and listed under the Convention on InternationalTrade in Endangered Species (CITES). It is widely grown in the American andAsian environments ( >2.4... million km 2 collectively). Here,we investigated emissions of monoterpenes, isoprene and DMS as well asseasonal carbon assimilation from four big-leaf mahogany trees in theirnatural outdoor environment using a dynamic branch cuvette system, high-sensitivity proton transfer reaction mass spectrometer and cavity ring-downspectrometer. The emissions were characterized in terms of environmentalresponse functions such as temperature, radiation and physiological growthphases including leaf area over the course of four seasons (summer, monsoon,post-monsoon, winter) in 2018–2019. We discovered remarkably high emissions ofDMS (average in post-monsoon: ∼19 ng g −1 leaf dry weight h −1 ) relative to previous known tree DMS emissions, high monoterpenes(average in monsoon: ∼15 µ g g −1 leaf dry weight h −1 , which is comparable to oak trees) and low emissions ofisoprene. Distinct linear relationships existed in the emissions of allthree BVOCs with higher emissions during the reproductive phase (monsoon andpost-monsoon seasons) and lower emissions in the vegetative phase (summerand winter seasons) for the same amount of cumulative assimilated carbon.Temperature and PAR dependency of the BVOC emissions enabled formulation ofa new parameterization for use in global BVOC emission models. Using themeasured seasonal emission fluxes, we provide the first estimates for theglobal emissions from mahogany trees which amount to circa 210–320 Gg yr −1 for monoterpenes, 370–550 Mg yr −1 for DMS and 1700–2600 Mg yr −1 for isoprene. Finally, through the results obtained in this study,we have been able to discover and identify mahogany as one of the missingnatural sources of ambient DMS over the Amazon rainforest as well. These newemission findings, indication of seasonal patterns and estimates will beuseful for initiating new studies to further improve the global BVOCterrestrial budget.|