. Understanding sources and atmospheric processes that can influence
the physiochemical properties of carbonaceous aerosols is essential to
evaluate their impacts on air quality and climate. However, resolving the
sources, emission characteristics, and aging processes of carbonaceous
aerosols in complex urban environments remains challenging. In this work, a
soot particle aerosol mass spectrometer (SP-AMS) was deployed to
characterize organic aerosols (OAs), refractory black carbon (rBC), and trace metals in
Singapore, a highly urbanized city with multiple local and regional air
pollution sources in the tropical region. rBC ( C 1 + – C 9 + )
fragments and trace metal ions ( K+ , Na+ , Ni+ , V+ , and
 Rb+ ) were integrated into our positive matrix factorization of OA. Two
types of fossil fuel combustion-related OAs with different degrees of
oxygenation were identified. This work provides evidence that over 90 % of
rBC originated from local combustion sources with a major part related
to traffic and ∼30  % associated with fresh
secondary organic aerosol (SOA) produced under the influence of shipping
and industrial emission activities (e.g., refineries and petrochemical
plants) during daytime. The results also show that ∼43  % of
the total rBC was emitted from local traffic, while the rest of the rBC fraction
stemmed from multiple sources including vehicular sources, shipping, and industrial
emissions, but was not fully resolved. There was only a weak association
of the cooking-related OA component with rBC. Although there was no
observable biomass burning episode during the sampling period, K+ and
 Rb+ were mainly associated with the more oxidized oxygenated OA
component, indicating the potential contribution of regional biomass burning
and/or coal combustion emissions to this aged OA component. Furthermore, the
aerosol pollutants transported from the industrial area and shipping ports
presented higher C 1 + / C 3 + and V + / Ni + ratios than
those associated with traffic. The observed association between Na+ and
rBC suggests that the contribution of anthropogenic emissions to total
particulate sodium should not be ignored in coastal urban environments.
Overall, this work demonstrates that rBC fragments and trace metal ions can
improve our understanding of the sources, emission characteristics, and
aging history of carbonaceous aerosol (OA and rBC) in this type of complex
urban environment.

/pdf/characterization-of-carbonaceous-aerosols-in-singapore-11uym7i4gs.pdf

Characterization of carbonaceous aerosols in Singapore: insight from black carbon fragments and trace metal ions detected by a soot particle aerosol mass spectrometer

This study developed a data-driven model for the prediction of fluid-particle dynamics by coupling a flow surrogate model based on the deep convolutional neural network (CNN) and a Lagrangian particle tracking model based on the discrete phase model (DPM). The applicability of the model for the prediction of the single fiber filtration efficiency (SFFE) for elliptical- and trilobal-shaped fibers was investigated. The ground-truth training data for the CNN flow surrogate model was obtained from a validated computational fluid dynamics (CFD) model for laminar incompressible flow. Details of fluid-particle dynamics parameters, including fluid and particle velocity vectors and contribution of Brownian and hydrodynamic forces, were examined to qualitatively and quantitatively evaluate the developed data-driven model. The CNN model with the U-net architecture provided highly accurate per-pixel predictions of velocity vectors and static pressure around the fibers with a speed-up of more than three orders of magnitude compared with CFD simulations. Although SFFE was accurately predicted by the data-driven model, the uncertainties in the velocity predictions by the CNN flow surrogate model in low-velocity regions near the fibers resulted in deviations in the particle dynamics predictions. These flow uncertainties contributed to the random motion of particles due to Brownian diffusion and increased the probability of particles being captured by the fiber. The findings provide guidelines for the development of data-science-based models for multiphysics fluid mechanics problems encountered in fibrous systems.

Prediction of Submicron Particle Dynamics in Fibrous Filter Using Deep Convolutional Neural Networks

An evaluation of the photochemical air quality modeling using CMAQ in the industrial area of Quintero-Puchuncavi-Concon, Chile

Real-time non-refractory PM1 chemical composition, size distribution and source apportionment at a coastal industrial park in the Yangtze River Delta region, China.

Pellet combustion in residential heating stoves has increased globally during the last decade. Despite their high combustion efficiency, the widespread use of pellet stoves is expected to adversely impact air quality. The atmospheric aging of pellet emissions has received even less attention, focusing mainly on daytime conditions, while the degree to which pellet emissions undergo night-time aging as well as the role of relative humidity remain poorly understood. In this study, environmental simulation chamber experiments were performed to characterize the fresh and aged organic aerosol (OA) emitted by a pellet stove. The fresh pellet stove PM1 (particulate matter with an aerodynamic diameter less than 1 μm) emissions consisted mainly of OA (93 ± 4%, mean ± standard deviation) and black carbon (5 ± 3%). The primary OA (POA) oxygen-to-carbon ratio (O : C) was 0.58 ± 0.04, higher than that of fresh logwood emissions. The fresh OA at a concentration of 70 μg m−3 (after dilution and equilibration in the chamber) consisted of semi-volatile (68%), low and extremely low volatility (16%) and intermediate-volatility (16%) compounds. The oxidation of pellet emissions under dark conditions was investigated by injecting nitrogen dioxide (NO2) and ozone (O3) into the chamber, at different (10–80%) relative humidity (RH) levels. In all dark aging experiments secondary organic aerosol (SOA) formation was observed, increasing the OA levels after a few hours of exposure to NO3 radicals. The change in the aerosol composition and the extent of oxidation depended on RH. For low RH, the SOA mass formed was up to 30% of the initial OA, accompanied by a moderate change in both O : C levels (7–8% increase) and the OA spectrum. Aging under higher RH conditions (60–80%) led to a more oxygenated aerosol (increase in O : C of 11–18%), but only a minor (1–10%) increase in OA mass. The increase in O : C at high RH indicates the importance of heterogeneous aqueous reactions in this system, that oxidize the original OA with a relatively small net change in the OA mass. These results show that the OA in pellet emissions can chemically evolve under low photochemical activity (e.g. the wintertime period) with important enhancement in SOA mass under certain conditions.

Characterization and dark oxidation of the emissions of a pellet stove

Characterization of submicron aerosol chemical composition and sources in the coastal area of Central Chile

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Characterization of submicron aerosol chemical composition and sources in the coastal area of Central Chile