Biogenic emissions from <italic>Citrus</italic> species in California: Fid-Bau Portal

Biogenic emissions from Citrus species in California

Fares, Silvano / Gentner, Drew R. / Park, Jeong-Hoo / Ormeno, Elena / Karlik, John / Goldstein, Allen H.

Abstract Biogenic Volatile Organic Compounds (BVOC) emitted from plants are the dominant source of reduced carbon chemicals to the atmosphere and are important precursors to the photochemical production of ozone and secondary organic aerosols. Considering the extensive land used for agriculture, cultivated Citrus plantations may play an important role in the chemistry of the atmosphere especially in regions such as the Central Valley of California. Moreover, the BVOC emissions from Citrus species have not been characterized in detail and more species-specific inputs for regional models of BVOC emissions are needed. In this study, we measured the physiological parameters and emissions of the most relevant BVOC (oxygenated compounds, monoterpenes, and sesquiterpenes) for four predominant Citrus species planted in California (Citrus sinensis var. ‘Parent Navel’, Citrus limon var. ‘Meyer’, Citrus reticulata var. ‘W. Murcott’ and ‘Clementine’). We used two analytical techniques to measure a full range of BVOC emitted: Proton Transfer Reaction Mass Spectrometry (PTR-MS) and gas chromatography with mass spectrometry. Methanol, followed by acetone and acetaldehyde, were the dominant BVOC emitted from lemon and mandarin trees (basal emission rates up to 300 ng(C) g(DW)⁻¹ h⁻¹), while oxygenated monoterpenes, monoterpenes, and sesquiterpenes were the main BVOC emitted from orange trees (basal emission rates up to = 2500 ng(C) g(DW)⁻¹ h⁻¹). Light and temperature-dependent algorithms were better predictors of methanol, acetaldehyde, acetone, isoprene and monoterpenes for all the Citrus species. Whereas, temperature-dependent algorithms were better predictors of oxygenated monoterpenes, and sesquiterpenes. We observed that flowering increased emissions from orange trees by an order of magnitude with the bulk of BVOC emissions being comprised of monoterpenes, sesquiterpenes, and oxygenated monoterpenes. Chemical speciation of BVOC emissions show that the various classes of terpene emissions among all Citrus species are dominated by ocimenes, β-caryophyllene, and linalool, respectively. In addition to utilizing our reported emission factors in BVOC emission models, we recommend that future BVOC emission models consider additional emissions from flowering and harvest, which occur seasonally and may have a significant impact on regional atmospheric chemistry.

Highlights ► We measured physiological parameters and emissions of BVOC for four Citrus species. ► Methanol, acetone and acetaldehyde, were the dominant BVOC emitted from lemons and mandarins. ► Oranges emitted mainly oxygenated monoterpenes, monoterpenes, and sesquiterpenes. ► Flowering increased emissions from orange trees by an order of magnitude. ► Ocimenes, β-caryophyllene, and linalool were the main terpenes emitted from Citrus.