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Ocean aerobiology is defined here as the study of biological particles of marine origin, including living organisms, present in the atmosphere and their role in ecological, biogeochemical, and climate processes. Hundreds of trillions of microorganisms are exchanged between ocean and atmosphere daily. Within a few days, tropospheric transport potentially disperses microorganisms over continents and between oceans. There is a need to better identify and quantify marine aerobiota, characterize the time spans and distances of marine microorganisms' atmospheric transport, and determine whether microorganisms acclimate to atmospheric conditions and remain viable, or even grow. Exploring the atmosphere as a microbial habitat is fundamental for understanding the consequences of dispersal and will expand our knowledge of biodiversity, biogeography, and ecosystem connectivity across different marine environments. Marine organic matter is chemically transformed in the atmosphere, including remineralization back to CO2. The magnitude of these transformations is insignificant in the context of the annual marine carbon cycle, but may be a significant sink for marine recalcitrant organic matter over long (∼104 years) timescales. In addition, organic matter in sea spray aerosol plays a significant role in the Earth's radiative budget by scattering solar radiation, and indirectly by affecting cloud properties. Marine organic matter is generally a poor source of cloud condensation nuclei (CCN), but a significant source of ice nucleating particles (INPs), affecting the formation of mixed-phase and ice clouds. This review will show that marine biogenic aerosol plays an impactful, but poorly constrained, role in marine ecosystems, biogeochemical processes, and the Earth's climate system. Further work is needed to characterize the connectivity and feedbacks between the atmosphere and ocean ecosystems in order to integrate this complexity into Earth System models, facilitating future climate and biogeochemical predictions. [ABSTRACT FROM AUTHOR]

Ocean aerobiology is defined here as the study of biological particles of marine origin, including living organisms, present in the atmosphere and their role in ecological, biogeochemical, and climate processes. Hundreds of trillions of microorganisms are exchanged between ocean and atmosphere daily. Within a few days, tropospheric transport potentially disperses microorganisms over continents and between oceans. There is a need to better identify and quantify marine aerobiota, characterize the time spans and distances of marine microorganisms’ atmospheric transport, and determine whether microorganisms acclimate to atmospheric conditions and remain viable, or even grow. Exploring the atmosphere as a microbial habitat is fundamental for understanding the consequences of dispersal and will expand our knowledge of biodiversity, biogeography, and ecosystem connectivity across different marine environments. Marine organic matter is chemically transformed in the atmosphere, including remineralization back to CO2. The magnitude of these transformations is insignificant in the context of the annual marine carbon cycle, but may be a significant sink for marine recalcitrant organic matter over long (∼104 years) timescales. In addition, organic matter in sea spray aerosol plays a significant role in the Earth’s radiative budget by scattering solar radiation, and indirectly by affecting cloud properties. Marine organic matter is generally a poor source of cloud condensation nuclei (CCN), but a significant source of ice nucleating particles (INPs), affecting the formation of mixed-phase and ice clouds. This review will show that marine biogenic aerosol plays an impactful, but poorly constrained, role in marine ecosystems, biogeochemical processes, and the Earth’s climate system. Further work is needed to characterize the connectivity and feedbacks between the atmosphere and ocean ecosystems in order to integrate this complexity into Earth System models, facilitating future climate and biogeochemical predictions.

We review the evidence for bio-regulation by coral reefs of local climate through stress-induced emissions of aerosol precursors, such as dimethylsulfide. This is an issue that goes to the core of the coral ecosystem’s ability to maintain homeostasis in the face of increasing climate change impacts and other anthropogenic pressures. We examine this through an analysis of data on aerosol emissions by corals of the Great Barrier Reef, Australia. We focus on the relationship with local stressors, such as surface irradiance levels and sea surface temperature, both before and after notable coral bleaching events. We conclude that coral reefs may be able to regulate their exposure to environmental stressors through modification of the optical properties of the atmosphere, however this ability may be impaired as climate change intensifies.

We review the evidence for bio-regulation by coral reefs of local climate through stress-induced emissions of aerosol precursors, such as dimethylsulfide. This is an issue that goes to the core of the coral ecosystem's ability to maintain homeostasis in the face of increasing climate change impacts and other anthropogenic pressures. We examine this through an analysis of data on aerosol emissions by corals of the Great Barrier Reef, Australia. We focus on the relationship with local stressors, such as surface irradiance levels and sea surface temperature, both before and after notable coral bleaching events. We conclude that coral reefs may be able to regulate their exposure to environmental stressors through modification of the optical properties of the atmosphere, however this ability may be impaired as climate change intensifies. [ABSTRACT FROM AUTHOR]

The model estimation is presented for the impact of interaction between anthropogenic and biogenic emissions of trace gases and aerosols on the mass concentration of the fine fraction of particulate matter (PM2.5) in the central region of the European part of Russia. The numerical study is performed with the CHIMERE chemistry transport model taking into account the formation of secondary organic aerosol from the oxidation of semivolatile organic compounds. The simulation results are in agreement with data of PM2.5 measurements at the Mosekomonitoring stations in Moscow. It is shown that the anthropogenic-biogenic interaction results in the growth of PM2.5 concentration. Its relative value varies within the analyzed region from several percent to several tens of percent and leads to the considerable (by 1.5 times) increase in the number of episodes in which average daily PM2.5 concentration exceeds the maximum permissible concentration accepted in Russia. It is found that the revealed increase in the number of such episodes is mainly caused by the accelerated formation of biogenic secondary organic aerosol in the presence of anthropogenic air pollution which accounts (on average over the region and season) for ∼60% of its surface mass concentration. [ABSTRACT FROM AUTHOR]

Monoterpenes react with nitrate radicals (NO 3 ), contributing substantially to nighttime organic aerosol (OA) production. In this study, the role of reactions of monoterpenes + NO 3 in forming biogenic secondary organic aerosol (BSOA) was examined using the Community Multiscale Air Quality (CMAQ) model, with extended emission profiles of biogenic volatile organic compounds (BVOCs), species-specific representations of BSOA production from individual monoterpenes and updated aerosol yields for monoterpene + NO 3 . The model results were compared to detailed measurements from the Southern Oxidants and Aerosol Study (SOAS) at Centreville, Alabama. With the more detailed model, monoterpene-derived BSOA increased by ∼1 μg m −3  at night, accounting for one-third of observed less-oxidized oxygenated OA (LO-OOA), more closely agreeing with observations (lower error, stronger correlation). Implementation of a multigenerational oxidation approach resulted in the model capturing elevated OA episodes. With the aging model, aged semi-volatile organic compounds (ASVOCs) contributed over 60% of the monoterpene-derived BSOA, followed by SOA formation via nitrate radical chemistry, making up to 34% of that formed at night. Among individual monoterpenes, β-pinene and limonene contributed most to the monoterpene-derived BSOA from nighttime reactions. [ABSTRACT FROM AUTHOR]

In this work we use cluster analysis of long term particle size distribution data to expand an array of different shorter term atmospheric measurements, thereby gaining insights into longer term patterns and properties of Arctic aerosol. Measurements of aerosol number size distributions (9–915 nm) were conducted at Villum Research Station (VRS), Station Nord in North Greenland during a 5 year record (2012–2016). Alongside this, measurements of aerosol composition, meteorological parameters, gaseous compounds and cloud condensation nuclei (CCN) activity were performed during different shorter occasions. K-means clustering analysis of particle number size distributions on daily basis identified several clusters. Clusters of accumulation mode aerosols (main size modes > 100 nm) accounted for 56% of the total aerosol during the sampling period (89–91% during February–April, 1–3% during June–August). By association to chemical composition, cloud condensation nuclei properties, and meteorological variables, three typical accumulation mode aerosol clusters were identified: Haze (32% of the time), Bimodal (14%) and Aged (6%). In brief: (1) Haze accumulation mode aerosol shows a single mode at 150 nm, peaking in February–April, with highest loadings of sulfate and black carbon concentrations. (2) Accumulation mode Bimodal aerosol shows two modes, at 38 nm and 150 nm, peaking in June–August, with the highest ratio of organics to sulfate concentrations. (3) Aged accumulation mode aerosol shows a single mode at 213 nm, peaking in September–October and is associated with cloudy and humid weather conditions during autumn. The three aerosol clusters were considered alongside CCN concentrations. We suggest that organic compounds, that are likely marine biogenic in nature, greatly influence the Bimodal cluster and contribute significantly to its CCN activity. This stresses the importance of better characterizing the marine ecosystem and the aerosol-mediated climate effects in the Arctic. [ABSTRACT FROM AUTHOR]

In remote marine areas, biogenic productivity and atmospheric particulate are coupled through dimethylsulfide (DMS) emission by phytoplankton. Once in the atmosphere, the gaseous DMS is oxidized to produce H2SO4 and methanesulfonic acid (MSA); both species can affect the formation of cloud condensation nuclei. This study analyses eight years of biogenic aerosol evolution and variability at two Arctic sites: Thule (76.5° N, 68.8° W) and Ny Ålesund (78.9° N, 11.9° E). Sea ice plays a key role in determining the MSA concentration in polar regions. At the beginning of the melting season, in April, up to June, the biogenic aerosol concentration appears inversely correlated with sea ice extent and area, and positively correlated with the extent of the ice-free area in the marginal ice zone (IF-MIZ). The upper ocean stratification induced by sea ice melting might have a role in these correlations, since the springtime formation of this surface layer regulates the accumulation of phytoplankton and nutrients, allowing the DMS to escape from the sea to the atmosphere. The multiyear analysis reveals a progressive decrease in MSA concentration in May at Thule and an increase in July August at Ny Ålesund. Therefore, while the MSA seasonal evolution is mainly related with the sea ice retreat in April, May, and June, the IF-MIZ extent appears as the main factor affecting the longer-term behavior of MSA.

A field campaign combined with numerical simulations was designed to better understand the emission sources and formation processes of organic aerosols (OA) in a subtropical environment. The field campaign measured total and water soluble organic carbon (OC) in aerosol, as well as its precursor gases in the Taipei metropolis and a nearby rural forest during the summer of 2011. A regional air-quality model modified with an additional secondary organic aerosol (SOA) formation pathway was used to decipher the observed variations in OA, with focus on various formation pathways and the relative contributions from anthropogenic and biogenic sources. According to the simulations, biogenic sources contributed to 60% and 72% of total OA production at the NTU (urban) and HL (rural) sites. The simulated fractions of SOA in total OA were 67% and 79% near the surface of NTU and HL, respectively, and these fractions increased with height and reach over 90% at the 1-km altitude. Estimated from the simulation results, aqueous-phase dicarbonyl uptake was responsible of 51% of OA production in the urban area, while the primary emissions, reversible partitioning of semi-volatile oxidation products, oligomerization of semi-volatile SOA in the particulate phase and acid-enhanced oxidation contributed to 33%, 10%, 5% and 1% respectively; in the rural area, the percentages were 59%, 21%, 13%, 7% and 1%, respectively. Meteorological factors, including large-scale wind direction, local circulation and planetary boundary layer height, all have strong influences on the source contributions and diurnal variations of OA concentration. [ABSTRACT FROM AUTHOR]

The characteristics of atmospheric ultrafine particles (i.e. <100 nm, nanoparticles or PM0.1), PM2.5 and PM10 were studied at the Lulin Atmospheric Background Station (LABS, 2862 m a.s.l., Taiwan) as part of the 7SEAS/Dongsha campaign. Sampling was conducted in July and August of 2009 and September to November of 2010, during which two 96-h and four 72-h PM samples were taken. Real-time particle size distributions were measured continuously from July to August of 2009 and July to November of 2010. PM0.1, PM2.5 and PM10 were collected by using two MOUDIs (micro-orifice uniform deposit impactor, MSP 110) and a Dichotomous PM10 sampler (Andersen SA-241) while real-time size distributions of particles of 5.5–350 nm in diameter were measured by an SMPS (scanning mobility particle sizer, TSI 3936). Filter samples were analyzed for gravimetric mass and chemical compositions, including organic carbon (OC), element carbon (EC), water-soluble ions and trace elements. Meteorology parameters and gaseous O3 and CO concentrations were also monitored along with the SMPS data for studying particle nucleation, condensation, SOA (secondary organic aerosol) formation and long-range air pollutant transport at the LABS. SMPS data showed that nanoparticle concentrations at the LABS remained relatively stable at low level (∼300–500 #/cm3) during the nighttime (22:00–04:00), increased during daytime, and reached a maximum (∼2000–4000 #/cm3) in the afternoon (12:00–16:00). The NMD (number median diameter) showed an opposite trend with the peak number concentrations observed in the afternoon corresponding to the smallest NMD (20–40 nm). These results indicate the dominance of local sources rather than the transport from other atmospheric air because that the lifetime of nanoparticles was only few minutes. Chemical analysis of filter samples showed that the concentrations of trace elements K and Mn, which serve as biomass burning markers, were elevated in the fine particle fractions during November 9–12th when the air mass passed through South and Southeast Asia prior to reaching the LABS. The concentrations of K and Mn would have been low if the aerosols had local origins The biomass burning derived K was found in all fine particle samples at the LABS suggesting that the free troposphere around Taiwan is frequently impacted by the long-range transport of biomass burning plumes via the westerly winds. [ABSTRACT FROM AUTHOR]

Abstract: The number size distributions of aerosol particles were measured using a scanning mobility particle sizer (SMPS) at a mid-latitude forest in Japan during 20–30 August 2010. Four days during the observation period experienced new particle formation (NPF) under the conditions of low condensation and coagulation sinks. The formation rate of new particles was calculated to be in the range between 0.2 and 1.0 cm−3 s−1 for the NPF events. The growth rates of the newly formed mode of aerosol particles ranged between 5.0 and 15.7 nm h−1. The backward air mass trajectories revealed that the NPF occurred in clean maritime air masses originated from the North Pacific, which is characterized with the low mass concentrations of aerosol components. The results from the classification analysis of backward air mass trajectories indicate that the maritime air mass conditions are frequent at this forest site and are primarily in summer season. Large increases in the number concentrations of accumulation mode particles (above 90 nm) were followed by the increased precipitation rates in the afternoon hours on the NPF event days. Therefore, the newly-formed particles would be involved in the convective cloud formation and precipitation over the studied region. [Copyright &y& Elsevier]

Abstract: Source apportionment of 13 organic compounds, elemental carbon and organic carbon of ambient PM10 and PM1 was performed with positive matrix factorization (PMF). Samples were collected at three sites characterized by different vegetation influences in Berlin, Germany in 2010. The aim was to determine organic, mainly biogenic sources and their impact on urban aerosol collected in a densely populated region. A 6-factor solution provided the best data fit for both PM-fractions, allowing the sources isoprene- and α-pinene-derived secondary organic aerosol (SOA), bio primary, primarily attributable to fungal spores, bio/urban primary including plant fragments in PM10 and cooking and traffic emissions in PM1, biomass burning and combustion fossil to be identified. With mean concentrations up to 2.6μgCm−3, biomass burning dominated the organic fraction in cooler months. Concentrations for α-pinene-derived SOA exceeded isoprene-derived concentrations. Estimated secondary organic carbon contributions to total organic carbon (OC) were between 7% and 42% in PM10 and between 11% and 60% in PM1, which is slightly lower than observed for US- or Asian cities. Primary biogenic emissions reached up to 33% of OC in the PM10-fraction in the late summer and autumn months. Temperature-dependence was found for both SOA-factors, correlations with ozone and mix depth only for the α-pinene-derived SOA-factor. Latter indicated input of α-pinene from the borders, highlighting differences in the origin of the precursors of both factors. Most factors were regionally distributed. High regional distribution was found to be associated with stronger influence of ambient parameters and higher concentrations at the background station. A significant contribution of biogenic emissions and biomass burning to urban organic aerosol could be stated. This indicates a considerable impact on PM concentrations also in cities in a densely populated area, and should draw the attention concerning health aspects not only to cardio-vascular diseases but also to allergy issues. [Copyright &y& Elsevier]

Abstract: A year-round study, which was conducted from November 2004 to November 2007, of atmospheric oxidised sulphur compounds (methanesulphonic acid (MSA) and sulphate) was carried out in the east Antarctic Plateau at Dome C (75° 06′ S, 123° 20′ E, 3220m a.s.l. and 1100km away from the nearest coast). The two sulphur-derived species exhibit a seasonal cycle characterised by maxima in the summer from November to March. Size-segregated sampling performed with Andersen 8-stage impactors revealed that SO4 2− and MSA have different size distributions in early summer (November) in comparison with mid-late summer (February). In November, the size distribution exhibited two distinct modes, the accumulation (0.4–0.7μm) and the micrometric mode (1.1–2.1μm), which is in contrast to February when only the accumulation mode was observed. The two modes exhibited different speciation; in the finest mode, sulphate and methanesulphonate were present primarily in the acidic form, whereas they were present primarily as sodium or ammonium salts in the micrometric mode. The different size distributions and speciation patterns in the two months are related to different transport pathways from oceanic areas to the central Antarctic Plateau. In the early summer months, air masses came primarily from the Indian Ocean and lingered for a long time over the Antarctic continent. The transport of sulphur compounds is related to sea spray aerosols and the resulting condensation of H2SO4 and MSA over sea salt particles to form sodium salts. In contrast, a rapid transport of H2SO4 and MSA formed above the boundary layer over oceanic areas leads to higher concentrations of the acidic species in the fine fraction of aerosols reaching Dome C in February relative to other summer months. [Copyright &y& Elsevier]

Abstract: Organosulfates have recently been observed in ambient atmospheres as a component of aerosol organic matter. This study presents the first characterization of organosulfates in Asia and demonstrates their ubiquity and chemical diversity, yet minor contribution to fine particulate mass. Organosulfates were characterized in ambient aerosol by ultra-performance liquid chromatography and high-resolution mass spectrometry, which allowed for experimental determination of molecular formulas and estimation of atmospheric abundance. Aerosols were analyzed from four sites spanning urban and remote locations, including Hanimaadhoo, Maldives, Gosan, Korea, Singapore, and Lahore, Pakistan. Semi-quantitative analysis yielded average estimates of OS accounting for less than 1% of PM2.5 mass, 2.3% of organic carbon, and 3.8% of total sulfate. The majority of the observed compounds were attributed to biogenic secondary organic aerosol from isoprene or monoterpenes. New organosulfates are also reported. [Copyright &y& Elsevier]

Abstract: PM10 and PM1 aerosol samples were collected between February and October, 2010 at three sites in Berlin that were characterized by different vegetation influences. The aim of the study was to determine the spatial and seasonal variations of several, mainly biogenic secondary and primary tracers in an urban area. Selected tracers including isoprene and α-pinene markers, fatty acids and levoglucosan were detected with GC-MS. The highest median concentrations, up to 45.1ngm−3, were found for the combustion product levoglucosan. The concentration range of the secondary compounds was 0.3ngm−3 for the isoprene markers 2-methyltetrols up to 35.7ngm−3 for malic acid. The occurrence of these compounds was mainly affected by the seasons, which could be described by three patterns. Whereas secondary compounds were mainly characterized by significantly higher concentrations during the warmer months, levoglucosan showed significantly higher concentrations during the colder months. No significant concentration differences between the two periods were rather observed for the primary compounds but also for the α-pinene degradation product pinonic acid. The secondary compounds and levoglucosan could be associated with the fine mode (particles with an aerodynamic diameter (AD)<1μm), while primary compounds are rather associated with the coarse mode (AD>1μm). Spatial variations were emphasized with a tendency toward higher concentrations for most compounds at sites that were influenced by vegetation, especially evident for the PM10 fraction. Besides concentration differences, spatial variations could also be described by differences in seasonal behavior and the size distribution, indicating major complexity in the composition of biogenic PM within the city of Berlin. [Copyright &y& Elsevier]

Abstract: The volatility of secondary organic aerosol (SOA) produced from the ozonolysis of α-pinene, β-pinene, and limonene, at low and intermediate RH, and at low and high NOx conditions was investigated using a thermodenuder (TD). More than 90% of the α-pinene and β-pinene SOA volume (for 200nm particles) and approximately 75% of the limonene SOA evaporated at 70°C for a centerline residence time of approximately 16s in the heated zone. Practically all the SOA in all systems evaporated at approximately 90°C. The relative humidity during the formation of SOA had a small effect on its volatility (changes in the evaporated fraction were less than 10%). NOx concentrations had a significant impact on the volatility of α-pinene and β-pinene SOA (reductions of the evaporated fraction by approximately 30%), but a negligible effect on the volatility of limonene SOA. High NOx levels resulted in more volatile SOA than low NOx conditions due to the presence of relatively volatile nitrate containing species at high NOx. The behavior of the SOA in the thermodenuder can be reproduced using an aerosol dynamics model based on the volatility basis-set approach and SOA yield parameters derived in previous smog chamber studies if appropriate values of the mass accommodation coefficient and heat of vaporization (ΔH vap) are chosen. Use of either a very low effective accommodation coefficient (0.002–0.01) and a heat of vaporization depending on the saturation concentration, or an effective accommodation coefficient of 0.05 for the initial stages of the evaporation and 1 afterward, with a low volatility-independent value of the ΔH vap, is needed for the simulation of the SOA evaporation. [Copyright &y& Elsevier]

Abstract: The chemical composition of secondary organic aerosol (SOA) generated from the ozonolysis of isoprene (C5H8) in the presence of an OH scavenger was examined using high-resolution electrospray ionization mass spectrometry (ESI-MS) in the mass range m/z = 50–1000. The chemical composition of SOA is complex, with more than 1000 assigned peaks observed in the positive and negative ion mode spectra. Only a small fraction of peaks correspond to known products of isoprene oxidation, such as pyruvic acid, glycolic acid, methylglyoxal, etc. The absolute majority of the detected peaks correspond to highly oxidized oligomeric constituents of SOA, with an average O:C molar ratio of 0.6. The corresponding organic mass (OM) to organic oxygen (OO) ratio is 2.4. Approximately 8% of oxygen atoms in SOA are in the form of peroxides, as quantified with an iodide test. Double bond equivalency (DBE) factors, representing the sum of all double bonds and rings, increase by 1 for every 1–2 additional carbon atoms in the molecule. The number of unoxidized Cbonds is estimated to be less than 10%; the remaining DBE is due to Cl groups. Kendrick analysis suggests that the prevalent oligomer building blocks are small carbonyls with a C1–C2 skeleton. Formaldehyde (CH2O) is identified as the most common repetitive building block in the observed oligomeric compounds. [Copyright &y& Elsevier]

Fungal spores constitute a sizeable fraction of coarse organic carbon (OC) in the atmospheric aerosol. In order to avoid tedious spore count methods, tracers for quantifying the spore-OC in atmospheric aerosol are sought. Arabitol and mannitol have been proposed as such tracers, since no other emission sources for these compounds have been reported. By parallel investigations of spore counts and tracer determinations from PM10 filter samples we could derive quantitative relationships between the amounts of tracer compounds and the numbers of spores in the atmosphere for different sites in the area of Vienna. We obtained over all average relationships of 1.2pgarabitolspore−1, with a range of 0.8–1.8, and 1.7pgmannitolspore−1, with a range of 1.2–2.4, with a clear site dependence. Thus, using these conversion factors from spore counts to spore-OC and spore-mass, along with analytical data for arabitol or mannitol in filter samples, the contribution of fungal spores to the OC and to the mass balance of atmospheric aerosol particles can be estimated. [Copyright &y& Elsevier]

Measurements of a number of aerosol properties and trace gases were conducted at Golden Ears Provincial Park (GE park), near the town of Maple Ridge, B.C., Canada from 6th to 11th of August 2001, just prior to the beginning of the main Pacific 2001 study. The measurements were intended to help with the characterization of the particulate matter (PM) in the forest that borders the northern side of the Lower Fraser Valley (LFV). The concentrations of inorganic ions in the particles decreased after 8th August, while the organic mass concentrations in the particles increased after 8th August. Throughout the study, organic carbon (OC) was the single highest component of the aerosol, and after 8th August, OC comprised about 90% of the particle composition. During the daytime, there was a clear anthropogenic influence from upslope flow driven by the sea breeze. The mixing ratio of monoterpenes increased overnight, when the winds were from the forests to the north but the cis-pinonic acid increased during the day, along with the anthropogenic tracers, suggesting that the oxidation of monoterpenes occurred with the help of anthropogenic oxidants. The particle volume data showed increases often corresponding with decreases in monoterpenes. A steady increase in particle volumes resulted from condensation of OC on the particles, and despite an increase in water soluble organic carbon (WSOC) the effectiveness of the OC at absorbing water for relative humidity (RH) values 90% was low relative to sulphate. [Copyright &y& Elsevier]

Capturing the effects of the complex processes of chemical aging of biogenic secondary organic aerosol (SOA) in chemical transport models (CTMs) has been challenging. Recent laboratory results from atmospheric simulation chambers are used in this study to develop a parameterization for biogenic SOA formation as a result of aging for use in CTMs using the Volatility Basis Set framework. This parameterization was implemented in PMCAMx which was then applied over the eastern United States to simulate summertime conditions. Using the base case parameterization of monoterpene SOA chemical aging resulted in modest increases (17–21%) in predicted domain average biogenic SOA. An alternative parameterization was developed fitting the same laboratory results, but assuming higher volatility products of chemical aging reactions. Use of this parameterization resulted in small increases (1–4%) of the predicted biogenic SOA. The PMCAMx predictions in sites where most of the SOA was biogenic were evaluated against measurements from the EPA IMPROVE network in July 2001 and during the Southern Oxidant and Aerosol Study in June 2013. The differences in the model performance were modest and mixed, a result consistent with the relatively small effect of the proposed parameterization on total organic aerosol levels. • Developed parameterization for monoterpene aging chemistry in VBS. • Modest increases (17–21%) predicted for biogenic SOA during summer in Eastern US. • Sensitivity tests suggest that the effect may be even smaller. • Modest effect on the performance of PMCAMx during 2001 and 2013 (SOAS). [ABSTRACT FROM AUTHOR]