About

Akua Asa-Awuku is a Professor in the Department of Civil and Environmental Engineering at the University of Maryland, with additional roles as Associate Dean and affiliation with the Robert E. Fischell Institute for Biomedical Devices. She holds a Ph.D. in Chemical Engineering from Georgia Institute of Technology, earned in 2008. Her research focuses on water uptake of particles, characterizing thermodynamic properties governing droplet formation for air quality, health, and climate impacts. She investigates the novel characterization of primary and secondary organic aerosols, black carbon, and their chemical composition and effects on health and the hydrological cycle. Her experimental investigations include cloud droplet formation, the activation of organic Cloud Condensation Nuclei (CCN), and their subsequent effects on climate. Asa-Awuku has contributed significantly to understanding the formation, composition, and measurement of anthropogenic and biogenic aerosols to explore their impacts on climate and health. Her work is recognized through numerous awards, including the NSF CAREER award in 2012 and the EPA STAR grant in 2011. She is an active member of professional organizations such as the American Association for Aerosol Research, American Chemical Society, and American Geophysical Union.

Research topics

• Chemistry
• Meteorology
• Political Science
• Chromatography
• Thermodynamics
• Sociology
• Business
• Archaeology
• Earth science
• Computational physics
• Organic chemistry
• Mechanics
• Physics
• Medicine
• Environmental chemistry
• Pedagogy
• Mathematics education
• Geology
• Psychology
• Geography

Selected publications

• Reply on RC2

  2025-08-15

  peer-reviewOpen access1st authorCorresponding

  <strong class="journal-contentHeaderColor">Abstract.</strong> Isoprene-derived secondary organic aerosol (SOA) components, such as the 2-methyltetrols (2-MT) and 2-methyltetrol sulfates (2-MTS), have been readily detected in atmospheric aerosols. SOA commonly exist in aerosol mixtures containing inorganic salts, such as ammonium sulfate (AS). Despite its prevalence in the atmosphere, the water uptake of 2-MT, 2-MTS, and their mixtures are not well understood. In this study, we determine the physicochemical properties of 2-MT, 2-MTS, and their mixtures with AS. 2-MT and 2-MTS are viscous and dynamic surface tension measurements were taken to determine organic diffusion coefficients. The droplet growth was measured and both subsaturated and supersaturated hygroscopicity are parameterized by the single hygroscopicity parameter &kappa;. &nbsp;Furthermore, aerosol phase state and morphology were analysed using atomic force microscopy. Results show that solute diffusion and salting-in influence the water uptake of 2-MT and 2-MTS with AS. The diffusion for 2-MTS/AS becomes an order of magnitude greater than for the organic alone but 2-MT diffusivity remains unchanged in the presence of AS. 2-MT/AS aerosols present a plateau in sub- and supersaturated &kappa;-values close to pure AS. 2-MTS/AS aerosols exhibit a similar behavior under subsaturated conditions. However, under supersaturated conditions, 2-MTS/AS behaves as an ideal well-mixed aerosol that can be described by traditional &kappa;-K&ouml;hler theory. 2-MT and 2-MTS are abundant globally, and thus the impact from biogenic sources and non-ideal droplet activation properties must be considered in aerosol-cloud interactions.

  PublisherDOI

• 3d Printed Microcyclones for Enhanced Collection, Separation, and Recovery of Sub-Micrometer Bioaerosols

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

• 3D printed microcyclones for enhanced collection, separation, and recovery of sub-micrometer bioaerosols

  Sensors and Actuators B Chemical · 2025-07-16 · 2 citations

  articleOpen access

  The collection and separation of aerosols is necessary to support the capture and analysis of particulate matter that can impact human health, enabling effective monitoring and prediction of exposure risk, and supporting fundamental studies of aerosol generation, transport, and distribution. Of particular concern are sub-micrometer particles which can deeply infiltrate the lungs, but efficient separation and capture of these smaller particles is challenging. In the case of bioaerosols, effective recovery of biological particles following capture often involves significant dilution of the collected sample, hindering downstream analysis. Here we report a miniature 3D printed cyclone-based platform capable of highly effective separation and recovery of submicron bioaerosols with well-defined cut-off sizes. Using a set of geometrically similar microcyclones fabricated at different size scales, with minimum channel dimensions of 0.75 mm, cut diameters as low as 0.05 µm are achieved at aerosol flow rates up to 5 L/min, with sharp cut-offs yielding nearly 100% capture efficiency for larger particulates. Furthermore, captured influenza virus is recovered from the devices with up to 85% efficiency and minimal dilution via a rapid elution process that takes advantage of the low internal microcyclone volume. The high capture efficiency for submicron particles enabled by the microcyclone platform, together with its compact form factor, effective sample recovery, tunable cut size, and cost-effective manufacture, makes the technology a promising tool for broad applications in aerosol and bioaerosol monitoring. Stereolithographic 3D printing enables flexible design and fabrication of miniature cyclones Microcyclones operating at 5 L/min with particle cutoff size of 50 nm are achieved Efficient recovery of captured influenza virus is achieved by direct elution process Modified cyclone geometries enabled by 3D printing enable optimized performance

  PublisherDOI

• Supplementary material to "Hygroscopicity of Isoprene-Derived Secondary Organic Aerosol Mixture Proxies: The Importance of Solute Diffusion and Salting-In Effects"

  2025-06-10

  preprintOpen accessSenior author
  PublisherDOI

• Hygroscopicity Depends on Aerosol Acidity and Sulfate Content during the Reactive Uptake of Isoprene Epoxydiols

  ACS Earth and Space Chemistry · 2025-08-13 · 2 citations

  article

  Aerosol liquid water content has a significant but highly uncertain effect on atmospheric radiative forcing. Hygroscopicity of organic–inorganic mixed aerosols is complex, especially when they are also phase-separated, and little is understood about their dependence on acidity. We conducted cloud condensation nuclei (CCN) measurements during smog chamber studies, where secondary organic aerosol (SOA) was generated from the acid-driven reactive uptake of isoprene epoxydiols (IEPOX) onto sulfate seed aerosols at pH 0.9 (pure H2SO4), 1.1, and 2 [mixtures of H2SO4 and (NH4)2SO4]. Direct CCN measurements were compared to predictions of the hygroscopicity parameter κ using a weighted-sum model with measured κ values of authentic standards for the three major particle constituents, including inorganic sulfate (Sulfinorg), 2-methyltetrols (2-MT), and methyltetrol sulfates (MTS). Sulfinorg was quantified using ion chromatography (IC), while 2-MT and MTS were quantified using hydrophilic interaction liquid chromatography interfaced to high-resolution quadrupole time-of-flight mass spectrometry and equipped with electrospray ionization (HILIC/ESI–HR-QTOFMS). SOA κ values ranged from 0.2 to 0.6, while single-component aerosols generated from authentic standards of 2-MT and MTS had κ values of 0.11 and 0.15, respectively. We found that predicted and measured κ values matched well at high IEPOX/Sulfinorg, but the discrepancy varied with initial IEPOX/Sulfinorg and seed solution pH and changed over the course of an experiment. The density of 2-MT and MTS was measured using an aerodynamic aerosol classifier and used to calculate total mass loadings from the measured volume concentration, revealing that, although 2-MT and MTS make up the bulk of IEPOX-derived SOA, other constituents may be significantly denser.

  PublisherDOI

• Salting out and nitrogen effects on cloud-nucleating ability of amino acid aerosol mixtures

  Environmental Science Atmospheres · 2025-01-01 · 4 citations

  articleOpen accessSenior authorCorresponding

  We investigate the water uptake ability of amino acid ternary mixtures.

  PublisherOA PDFDOI

• Influence of Salting Out and Organic Nitrogen on Mixed Amino Acid Aerosol Cloud-Nucleating Ability

  2025-03-14

  preprintOpen accessSenior authorCorresponding

  Aerosols are present as complex organic-inorganic mixtures within our atmosphere, resulting in particles presenting phase separated morphology. Mixed organic-inorganic aerosols can be predominantly found in nascent sea spray aerosols (SSA). When these aerosols are exposed to supersaturated conditions (&gt;100% RH), the water uptake ability of the aerosols vary based on the composition of the mixture. Previous studies have characterized phase separated systems through the determination of an average oxygen to carbon (O/C) ratio where liquid-liquid phase separation (LLPS) reaches its limit. The hygroscopicity of complex mixtures presenting LLPS was previously studied through the measurement of CCN activity within a 2-methylglutaric (2-MGA)/ammonium sulfate (AS) binary system and a 2-MGA/AS/sucrose ternary system; both studies correlated water-uptake abilities to O/C and surface tension. However, little is known about the influence of solubility of the third component on phase separation of a ternary mixture containing 2-MGA/AS. Additionally, the water-uptake properties of mixtures containing nitrogen containing compounds, such as amino acids, are not well defined. Amino acids are a major component of SSA and can contribute to aerosol hygroscopicity. Therefore, it is undetermined if O/C alone is an acceptable parameter for the estimation of solubility and hygroscopicity of complex amino acid mixtures. To improve our understanding of LLPS within aerosol mixtures and factors influencing its presence, three ternary systems were studied &amp;#8211; a leucine system (2-MGA/AS/leucine), valine system (2-MGA/AS/valine), and proline system (2-MGA/AS/proline). For each system, the CCN activity of mixture compositions with varying O/C ratios and compositions was measured using a Cloud Condensation Nuclei Counter (CCNC) at 0.375% to 1.667% SS. For all mixtures, the single hygroscopic parameter &amp;#954; was calculated. Experimental &amp;#954;-results demonstrated increased hygroscopic activity as the amino acid became more soluble in the order of leucine

  PublisherDOI

• Chemical signatures of water-soluble organic carbon (WSOC) fraction of long-range transported wildfire PM _2.5 from Canada to the United States Mid-Atlantic region

  Environmental Science Atmospheres · 2025-11-25 · 1 citations

  articleOpen accessSenior author

  Long range transport of Canadian wildfire emissions to College Park, Maryland.

  PublisherOA PDFDOI

• Hygroscopicity of Isoprene-Derived Secondary Organic Aerosol Mixture Proxies: The Importance of Solute Diffusion and Salting-In Effects

  2025-06-10 · 2 citations

  preprintOpen accessSenior authorCorresponding

  Abstract. Isoprene-derived secondary organic aerosol (SOA) components, such as the 2-methyltetrols (2-MT) and 2-methyltetrol sulfates (2-MTS), have been readily detected in atmospheric aerosols. SOA commonly exist in aerosol mixtures containing inorganic salts, such as ammonium sulfate (AS). Despite its prevalence in the atmosphere, the water uptake of 2-MT, 2-MTS, and their mixtures are not well understood. In this study, we determine the physicochemical properties of 2-MT, 2-MTS, and their mixtures with AS. 2-MT and 2-MTS are viscous and dynamic surface tension measurements were taken to determine organic diffusion coefficients. The droplet growth was measured and both subsaturated and supersaturated hygroscopicity are parameterized by the single hygroscopicity parameter κ. Furthermore, aerosol phase state and morphology were analysed using atomic force microscopy. Results show that solute diffusion and salting-in influence the water uptake of 2-MT and 2-MTS with AS. The diffusion for 2-MTS/AS becomes an order of magnitude greater than for the organic alone but 2-MT diffusivity remains unchanged in the presence of AS. 2-MT/AS aerosols present a plateau in sub- and supersaturated κ-values close to pure AS. 2-MTS/AS aerosols exhibit a similar behavior under subsaturated conditions. However, under supersaturated conditions, 2-MTS/AS behaves as an ideal well-mixed aerosol that can be described by traditional κ-Köhler theory. 2-MT and 2-MTS are abundant globally, and thus the impact from biogenic sources and non-ideal droplet activation properties must be considered in aerosol-cloud interactions.

  PublisherOA PDFDOI

• Hygroscopicity of isoprene-derived secondary organic aerosol mixture proxies: importance of diffusion and salting-in effects

  Atmospheric chemistry and physics · 2025-11-13 · 1 citations

  articleOpen accessSenior authorCorresponding

  Abstract. Isoprene-derived secondary organic aerosol (SOA) constituents, such as the 2-methyltetrols (2-MT) and 2-methyltetrol sulfates (2-MTS), have been readily detected in atmospheric aerosols (PM2.5) and within mixtures containing ammonium sulfate (AS). Despite its prevalence, the water uptake of 2-MT, 2-MTS, and their mixtures is not well understood. In this study, we determine the physicochemical properties (e.g., surface activity, diffusivity, phase morphology) of synthesized 2-MT and 2-MTS samples and their mixtures with AS. 2-MT and 2-MTS have been identified as surface active and viscous. Thus, dynamic surface tension (σs/a) measurements were taken to determine organic diffusion coefficients (Ds). The droplet growth of organic / AS mixtures was measured under subsaturated conditions using a humidified tandem differential mobility analyzer (H-TDMA) at 88.2 % RH ±1.5 %. Droplet activation was measured under supersaturated (&gt;100 % RH) conditions using a cloud condensation nuclei counter (CCNC); supersaturation (SS) ranged from 0.3 %–1.4 %. Hygroscopicity in both regimes was parameterized by the single hygroscopicity parameter κ. This study demonstrates how diffusion and salting-in effects influence the water uptake of synthesized, isoprene-derived SOA mixtures. Results show that when mixed with AS, organic diffusion for 2-MTS / AS becomes an order of magnitude faster, while 2-MT diffusivity remains unchanged. Both 2-MT / AS and 2-MTS aerosols present a plateau in subsaturated κ values close to pure AS. However, under supersaturated conditions, 2-MTS / AS behaves ideally and well mixed and can be characterized by κ-Köhler theory. Isoprene-derived SOAs like 2-MT and 2-MTS samples are ubiquitous, and thus, the impact from biogenic sources and its non-ideal thermodynamic properties must be considered in aerosol–cloud interactions.

  PublisherOA PDFDOI

Recent grants

• Collaborative Research: The role of interactions between organic components on aerosol hygroscopicity

  NSF · $383k · 2021–2026

• CAREER: Toward an Understanding of Secondary Aerosol Formation, Particle Ageing in Droplets, and Cloud Processing

  NSF · $308k · 2017–2019

• BRIGE: Development of a Novel Organic-Water Thermodynamic Measurement and Modeling Technique for Health and Climate Applications

  NSF · $175k · 2010–2013

• Collaborative Research: Effects of Aerosol Phase, Morphology, and Mixing State on Droplet Formation

  NSF · $344k · 2017–2022

• Nanoscale Visualization and Understanding of Atmospheric Aerosol Dissolution Kinetics in Aqueous Organic Droplets

  NSF · $589k · 2020–2025

Frequent coauthors

• Thomas D. Durbin

  University of California, Riverside

  35 shared

• Georgios Karavalakis

  University of Washington

  28 shared

• David R. Cocker

  University of California, Riverside

  24 shared

• Diep Vu

  23 shared

• Daniel Short

  University of California, Riverside

  23 shared

• Athanasios Nenes

  École Polytechnique Fédérale de Lausanne

  22 shared

• Mingjin Tang

  21 shared

• Kotiba A. Malek

  University of Maryland, College Park

  21 shared

Education

• PhD, Chemical and Biomolecular Engineering

  Georgia Institute of Technology

Awards & honors

• NSF CAREER (2012)
• EPA Science to Achieve Results (STAR) (2011)
• NSF-Georgia Tech FACES Career Initiation Grant Recipient (20…
• Atmospheric Chemistry Colloquium for Emerging Senior Scienti…
• NSF-Georgia Tech FACES Postdoctoral Fellowship (2008)