Browsing by Author "Harb, Charbel"

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    Drone-based water sampling and characterization of three freshwater harmful algal blooms in the United States
    Hanlon, Regina; Jacquemin, Stephen J.; Birbeck, Johnna A.; Westrick, Judy A.; Harb, Charbel; Gruszewski, Hope; Ault, Andrew P.; Scott, Durelle T.; Foroutan, Hosein; Ross, Shane D.; González-Rocha, Javier; Powers, Craig; Pratt, Lowell; Looney, Harry; Baker, Greg; Schmale, David G. III (Frontiers, 2022-08-24)
    Freshwater harmful algal blooms (HABs), caused mostly by toxic cyanobacteria, produce a range of cyanotoxins that threaten the health of humans and domestic animals. Climate conditions and anthropogenic influences such as agricultural run-off can alter the onset and intensity of HABs. Little is known about the distribution and spread of freshwater HABs. Current sampling protocols in some lakes involve teams of researchers that collect samples by hand from a boat and/or from the shoreline. Water samples can be collected from the surface, from discrete-depth collections, and/or from depth-integrated intervals. These collections are often restricted to certain months of the year, and generally are only performed at a limited number of collection sites. In lakes with active HABs, surface samples are generally sufficient for HAB water quality assessments. We used a unique DrOne Water Sampling SystEm (DOWSE) to collect water samples from the surface of three different HABs in Ohio (Grand Lake St Marys, GLSM and Lake Erie) and Virginia (Lake Anna), United States in 2019. The DOWSE consisted of a 3D-printed sampling device tethered to a drone (uncrewed aerial system, or UAS), and was used to collect surface water samples at different distances (10–100 m) from the shore or from an anchored boat. One hundred and eighty water samples (40 at GLSM, 20 at Lake Erie, and 120 at Lake Anna) were collected and analyzed from 18 drone flights. Our methods included testing for cyanotoxins, phycocyanin, and nutrients from surface water samples. Mean concentrations of microcystins (MCs) in drone water samples were 15.00, 1.92, and 0.02 ppb for GLSM, Lake Erie, and Lake Anna, respectively. Lake Anna had low levels of anatoxin in nearly all (111/120) of the drone water samples. Mean concentrations of phycocyanin in drone water samples were 687, 38, and 62 ppb for GLSM, Lake Erie, and Lake Anna, respectively. High levels of total phosphorus were observed in the drone water samples from GLSM (mean of 0.34 mg/L) and Lake Erie (mean of 0.12 mg/L). Lake Anna had the highest variability of total phosphorus with concentrations that ranged from 0.01 mg/L to 0.21 mg/L, with a mean of 0.06 mg/L. Nitrate levels varied greatly across sites, inverse with bloom biomass, ranging from below detection to 3.64 mg/L, with highest mean values in Lake Erie followed by GLSM and Lake Anna, respectively. Drones offer a rapid, targeted collection of water samples from virtually anywhere on a lake with an active HAB without the need for a boat which can disturb the surrounding water. Drones are, however, limited in their ability to operate during inclement weather such as rain and heavy winds. Collectively, our results highlight numerous opportunities for drone-based water sampling technologies to track, predict, and respond to HABs in the future.
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    Experimental development of a lake spray source function and its model implementation for Great Lakes surface emissions
    Harb, Charbel; Foroutan, Hosein (European Geosciences Union, 2022-09-12)
    Lake spray aerosols (LSAs) are generated from freshwater breaking waves in a mechanism similar to their saltwater counterparts, sea spray aerosols (SSAs). Unlike the well-established research field pertaining to SSAs, studying LSAs is an emerging research topic due to their potential impacts on regional cloud processes and their association with the aerosolization of freshwater pathogens. A better understanding of these climatic and public health impacts requires the inclusion of LSA emission in atmospheric models, yet a major hurdle to this inclusion is the lack of a lake spray source function (LSSF), namely an LSA emission parameterization. Here, we develop an LSSF based on measurements of foam area and the corresponding LSA emission flux in a marine aerosol reference tank (MART). A sea spray source function (SSSF) is also developed for comparison. The developed LSSF and SSSF are then implemented in the Community Multiscale Air Quality (CMAQ) model to simulate particle emissions from the Great Lakes surface from 10 to 30 November 2016. Measurements in the MART revealed that the average SSA total number concentration was 8 times higher than that of LSA. Over the 0.01–10 µm aerosol diameter size range, the developed LSSF was around 1 order of magnitude lower than the SSSF and around 2 orders of magnitude lower for aerosols with diameters between 1 and 3 µm. Model results revealed that LSA emission flux from the Great Lakes surface can reach ∼105 m−2 s−1 during an episodic event of high wind speeds. These emissions only increased the average total aerosol number concentrations in the region by up to 1.65 %, yet their impact on coarse-mode aerosols was much more significant, with up to a 19-fold increase in some areas. The increase in aerosol loading was mostly near the source region, yet LSA particles were transported up to 1000 km inland. Above the lakes, LSA particles reached the cloud layer, where the total and coarse-mode particle concentrations increased by up to 3 % and 98 %, respectively. Overall, this study helps quantify LSA emission and its impact on regional aerosol loading and the cloud layer.
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    Filtration evaluation and clinical use of expired elastomeric P-100 filter cartridges during the COVID-19 pandemic
    Patolia, Harsh H.; Pan, Jin; Harb, Charbel; Marr, Linsey C.; Baffoe-Bonnie, Anthony W. (Cambridge University Press, 2020-05-27)
    To the Editor—The limited supply of more conventional disposable personal protective equipment (PPE), namely single-use N95 filtering facepiece respirators (FFRs), among hospital systems in the United States during the COVID-19 pandemic has been alleviated with the adoption of extended use and reuse policies by the Centers for Disease Control and Prevention (CDC).1 These measures, along with a variety of implemented decontamination methodologies (eg, ultraviolet germicidal irradiation, vaporized hydrogen peroxide, etc), have prolonged PPE supplies during pressing times. Another strategy adopted by the CDC and health systems to protect healthcare providers caring for COVID-19 patients and patients under investigation in limited resource settings includes the use of elastomeric FFRs with reusable cartridges. Although elastomeric respirators have not been approved by the Food and Drug Administration for fluid resistance, they have been endorsed by the CDC as reasonable alternatives for N95 FFRs during the COVID-19 pandemic due to their filtration approval by the National Institutes for Occupational and Safety Health (NIOSH).2 Subsequently, elastomeric respirators have formed a major arm of the COVID-19 pandemic response strategy in many hospital systems...
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    Inward and outward effectiveness of cloth masks, a surgical mask, and a face shield
    Pan, Jin; Harb, Charbel; Leng, Weinan; Marr, Linsey C. (Virginia Tech, 2020-11-20)
    We evaluated the effectiveness of 11 face coverings for material filtration efficiency, inward protection efficiency on a manikin, and outward protection efficiency on a manikin. At the most penetrating particle size, the vacuum bag, microfiber cloth, and surgical mask had material filtration efficiencies >50%, while the other materials had much lower filtration efficiencies. However, these efficiencies increased rapidly with particle size, and many materials had efficiencies >50% at 2 μm and >75% at 5 μm. The vacuum bag performed best, with efficiencies of 54-96% for all three metrics, depending on particle size. The thin acrylic and face shield performed worst. Inward protection efficiency and outward protection efficiency were similar for many masks; the two efficiencies diverged for stiffer materials and those worn more loosely (e.g., bandana) or more tightly (e.g., wrapped around the head) compared to a standard earloop mask. Discrepancies between material filtration efficiency and inward/outward protection efficiency indicated that the fit of the mask was important. We calculated that the particle size most likely to deposit in the respiratory tract when wearing a mask is ∼2 μm. Based on these findings, we recommend a three-layer mask consisting of outer layers of a flexible, tightly woven fabric and an inner layer consisting of a material designed to filter out particles. This combination should produce an overall efficiency of >70% at the most penetrating particle size and >90% for particles 1 μm and larger if the mask fits well.
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    Spray Aerosols From Saltwater to Freshwater Breaking Waves
    Harb, Charbel (Virginia Tech, 2022-08-24)
    While sea spray aerosols (SSAs) generation by oceanic breaking waves continues to be an active research area, lake spray aerosols (LSAs) production by freshwater breaking waves is an emerging research field. Recent studies have linked LSAs to regional cloud processes and the aerosolization of freshwater pathogens and pollutants. Yet, differences in spray aerosol ejection between freshwater and saltwater and their impact on the water-to-air dispersal of microorganisms and pollutants are poorly understood. The goals of this dissertation work were to understand mechanistic differences between spray aerosol generation in freshwater and saltwater, develop a representation of LSA emissions in atmospheric models and evaluate their impact on regional aerosol loading, and compare the aerosolization of bacteria and microplastics by SSAs and LSAs. Experiments in a breaking-waves analogue tank revealed that the subsurface bubble plume in saltwater is characterized by more submillimeter bubbles than that in freshwater, and hence, saltwater surface foams were more persistent and were comprised of more submillimeter surface bubbles. Consequently, the average number concentration of generated SSAs was eight times higher than that of LSAs. Using these measurements, the developed LSA emission parametrization revealed that freshwater emissions were, at least, an order of magnitude lower than saltwater emissions for the same wave-breaking conditions. When implementing this emission parameterization to simulate LSA emissions from the Laurentian Great Lakes, LSAs did not contribute significantly to regional aerosol loading (< 2%), yet their impact on coarse-mode aerosols was more significant with up to a 19-fold increase in some areas. Furthermore, modeled LSAs reached up to 1000 km inland and were incorporated in the lakes' cloud layer. Despite the generation of more spray aerosols in saltier waters, cumulative salt additions in the freshwater–saltwater continuum (0-35 g/kg) led to a nonmonotonic increase in freshwater bacterial aerosolization abundance, which exhibited a peak at lower oligohaline conditions (0.5-1 g/kg). However, the aerosolization of microplastics by SSAs was one order of magnitude higher than that by LSAs. Overall, this dissertation work showed that LSA emissions are intrinsically different from SSA emissions, which influences their role in transferring microorganisms and pollutants at the air-water interface.