A modeling study of secondary organic aerosol formation from sesquiterpenes using the STOCHEM global chemistry and transport model

Abstract

Sesquiterpenes are one of the precursors of secondary organic aerosol (SOA) which can be an important global sources of organic aerosol (OA). Updating the chemistry scheme in the global chemistry transport model by incorporating an oxidation mechanism for β‐caryophyllene (representing all sesquiterpenes), adding global sesquiterpene emissions of 29 Tg/yr, and revising global monoterpene emissions up to 162 Tg/yr [Guenther et al., 2012] led to an increase of SOA burden by 95% and SOA production rate by 106% relative to the base case described in Utembe et al. [2011]. Including the emissions of sesquiterpenes resulted in increase of SOA burden of 0.11 Tg and SOA production rate of 12.9 Tg/yr relative to the base case. The highest concentrations of sesquiterpene‐derived SOA (by up to 1.2 μg/m3) were found over central Africa and South America, the regions having high levels of biogenic emissions with significant biomass burning. In the updated model simulation, the multigeneration oxidation products from sesquiterpenes and monoterpenes transported above the boundary layer and condensed to the aerosol phase at higher altitude led to an increase of OA by up to 30% over the tropics and northern midlatitude to higher altitude. The model evaluation showed an underestimation of model OA mostly for the campaigns dominated by regional anthropogenic pollution. The increase of SOA production from sesquiterpenes reduced the discrepancies between modeled and observed OA concentrations over the remote and rural areas. The increase of SOA concentrations by up to 200% from preindustrial to present scenarios was found over the tropical oceans.

Investigating the Tropospheric Chemistry of Acetic Acid Using the Global 3‐D Chemistry Transport Model, STOCHEM‐CRI

“…The coarse model resolution (5° × 5°) is responsible for poorer model performance over polluted regions because they cannot represent typical biomass burning plumes or regional pollution correctly. More details about the uncertainty of the model can be found in Khan et al (), Khan, Cooke, Utembe, Archibald, Derwent, et al (), Khan, Cooke, Utembe, Archibald, Maxwell, et al (), Khan, Cooke, et al (), and Khan, Jenkin, et al ().…”

“…The detail of the CRI v2‐R5 mechanism is given by Jenkin et al (), Watson et al (), and Utembe et al (). Further amendments to the chemical mechanism and a description of the addition of an organic aerosol module are reported by Khan, Jenkin, et al (). The chemical scheme comprises 244 chemical species that take part in 564 chemical reactions and 98 photolysis reactions.…”

Observations of sesquiterpenes and their oxidation products in central Amazonia during the wet and dry seasons

“…S2, 4b, and 5b). In addition, while it is typical practice to take total sesquiterpene concentration and use k O 3 +β-caryophyllene for all sesquiterpenes (Jardine et al, 2011;Khan et al, 2017), this would result in an overestimate of sesquiterpene reactivity with O 3 by an order of magnitude at T3. Thus, with the majority of sesquiterpene ozonolysis occurring within or just outside the canopy, we expect to observe fewer sesquiterpenes at our measurement site but that their oxidation products may be observed even when the primary sesquiterpenes are not.…”

“…Chen et al, 2015), of which a large portion is attributed to the uptake of isoprene-epoxydiols (Hu et al, 2015;de Sá et al, 2017), the remaining contribution to OA from other BVOC precursors such as monoterpenes and sesquiterpenes remains largely unconstrained. Khan et al (2017) report that including updated sesquiterpene emissions and SOA pathways (all represented by the β-caryophyllene mechanism) in the STOCHEM global chemical transport model led to a 48 % increase in global SOA burden and 57 % increase in SOA production rate. In addition, the highest concentrations of sesquiterpene-derived SOA were modeled to be present over central Africa and South America.…”

Reduction of Atmospheric PM2.5 Level by Restricting the Idling Operation of Buses in a Busy Station

“…OC also had the secondary origin from gas-to-particle conversion of volatile organic compounds in the atmosphere, either as result of the condensation of low pressure volatile organic compounds, or from physical and chemical adsorption of gaseous species on aerosol particle surfaces. The purpose of quantify the secondary organic carbon is to understand how well the method could be reduce the aim object since reduction of direct emission only effects primary particulate carbon constituents (Ligocki and Pankow, 1989;Pandis et al, 1992;Khan et al, 2017).…”