Abstract
AbstractSesquiterpenes 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.
Highlights
Organic aerosols (OA) have a large impact on air quality, biogeochemistry, and the climate through interactions with reactive trace gases, water vapor, clouds, precipitation, and radiation [Intergovernmental Panel on Climate Change (IPCC), 2013]
secondary organic aerosol (SOA) is defined as products of gas-phase oxidation or as emitted volatile organic compounds (VOC) from biogenic or anthropogenic sources, such as vegetation and combustion emissions, which have partitioned from the gas to the aerosol phase [Kroll and Seinfeld, 2008; Hallquist et al, 2009]
The degradation mechanisms of sesquiterpenes have been added to the aerosol module of Common Representative Intermediates mechanism version 2 (CRI v2)-R5 chemical mechanism and employed in a global chemistry transport model, STOCHEM to investigate the formation of SOA from sesquiterpenes using β-caryophyllene as a representative species
Summary
Organic aerosols (OA) have a large impact on air quality, biogeochemistry, and the climate through interactions with reactive trace gases, water vapor, clouds, precipitation, and radiation [Intergovernmental Panel on Climate Change (IPCC), 2013]. In which the oxidation of β-caryophyllene (and/or other sesquiterpenes) has been treated, have used highly simplified or parameterized representations of the chemistry [Lane et al, 2008; Sakulyanontvittaya et al, 2008; Carlton et al, 2010; Zhang and Ying, 2011], with SOA formation represented by assigning empirically derived yields and partitioning coefficients to notional products, based on the results of chamber studies. We show a comparison between model results and a wide range of measurements of SOA from flight data sets and individual field measurements
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