Aerosol Collection Research Articles

Collecting e-cigarette aerosols for in vitro applications: A survey of the biomedical literature and opportunities to increase the value of submerged cell culture-based assessments.

Electronic nicotine delivery systems (ENDS) are being developed as potentially reduced‐risk alternatives to the continued use of combustible tobacco products. Because of the widespread uptake of ENDS—in particular, e‐cigarettes—the biological effects, including the toxic potential, of their aerosols are under investigation. Preclinically, collection of such aerosols is a prerequisite for testing in submerged cell culture‐based in vitro assays; however, despite the growth in this research area, there is no apparent standardized collection method for this application. To this end, through an Institute for in vitro Sciences, Inc. workshop initiative, we surveyed the biomedical literature catalogued in PubMed® to map the types of methods hitherto used and reported publicly. From the 47 relevant publications retrieved, we identified seven distinct collection methods. Bubble‐through (with aqueous solvents) and Cambridge filter pad (CFP) (with polar solvents) collection were the most frequently cited methods (57% and 18%, respectively), while the five others (CFP + bubble‐through; condensation; cotton filters; settle‐upon; settle‐upon + dry) were cited less often (2–10%). Critically, the collected aerosol fractions were generally found to be only minimally characterized chemically, if at all. Furthermore, there was large heterogeneity among other experimental parameters (e.g., vaping regimen). Consequently, we recommend that more comprehensive research be conducted to identify the method(s) that produce the fraction(s) most representative of the native aerosol. We also endorse standardization of the aerosol generation process. These should be regarded as opportunities for increasing the value of in vitro assessments in relation to predicting effects on human health.

Use of a Biological Tracer to Investigate Microbial Aerosols Generated by Heater-Cooler Units

Background: A multinational outbreak of Mycobacterium chimaera endocarditis following cardiac surgery has been attributed to the use of heater-cooler units (HCUs) during cardiopulmonary bypass. It is hypothesized that mycobacteria can be transmitted to the surgical site via the aerosolization of contaminated water from within the unit. In the United Kingdom, M. chimaera infections have been linked to 1 specific make and model of HCU, which was shown to generate microbial aerosols when circulating water. The manufacturer has since modified this HCU and claims that the dispersal of aerosols has now been prevented. M. chimaera is a common contaminant of HCUs, regardless of make, model, and manufacturer. To help inform local decision making, hospitals require evidence that this modified HCU and/or alternative heater-cooler systems can reduce the risk of mycobacterial infection by incorporating design features that prevent the generation of microbial aerosols external to the device. The time required to culture M. chimaera means investigations focusing on naturally or artificially contaminated HCUs are problematic. Instead, specialist aerobiological techniques incorporating a nonpathogenic, aerostable, biological tracer (Bacillus atrophaeus) were used to investigate microbial aerosols generated and released from brand-new and ‘upgraded’ HCUs. Methods: 4 HCUs (A–D), supplied directly by the manufacturers, were filled with filtered tap water, and high numbers of B. atrophaeus (109 CFU/L) were added to the tanks. High-volume cyclone samplers were used to sample the air when each HCU was switched off and during different operational phases. Samplers were operated for 5 minutes and the collecting fluid cultured for B. atrophaeus. The number of colonies was converted to CFU per cubic meter of air. Results: Under controlled experimental conditions, HCU-A released a small but significant level of aerosol during operational phases (eg, cooling) that resulted in increased pressure within the tank. The filler flap was identified as the principal area of aerosol release. The circulation of water within HCU-B and HCU-C was shown to generate an aerosol but, when connected to an ‘aerosol collection set,’ this aerosol was not released. However, it is essential that effective and sufficient vacuum is maintained. There was no aerosol release from HCU-D. Conclusions: A specialist in aerobiology using a biological tracer can determine the level of aerosol released from an HCU and its location. However, transmission of M. chimaera could occur via aerosolization of contaminated water, but it is not the only possible route of infection. The efficacy of recommended decontamination procedures must also be assured.Funding: NoneDisclosures: None

Aerosol analysis using quantum cascade laser infrared spectroscopy: Application to crystalline silica measurement

A method for trace analysis of aerosol mineral components using quantum cascade laser (QCL) based infrared absorption spectroscopy is described. The measurement approach involves: (a) collection of aerosol on a particulate filter; (b) sample treatment using low-temperature oxygenated plasma to minimize the matrix interferences; (c) redeposition of the treated sample as a dried spot for direct-on-filter analysis; and (d) infrared transmittance measurement of the dried spot using the QCL and mercury-cadmium-telluride detector. The method was applied to quantification of trace α-quartz in workplace aerosols. Infrared absorbance spectra in the range 750–1030 cm−1 were obtained using the QCL instrument; the characteristic peak of α-quartz at 798 cm−1 was used to measure its content. A correction scheme was applied to account for spectral interference from kaolinite mineral for coal dust samples. The detection limit for α-quartz was estimated to be 0.12 μg for a dried spot diameter of 1 mm. This detection limit is an order-of-magnitude lower than those attainable by the current standard X-ray diffraction (XRD) or Fourier transform infrared spectroscopy (FTIR) methods involving similar sample preparation and treatment. The QCL method was extended to the measurement of respirable α-quartz concentrations in workplace aerosols released during cutting of fiber-reinforced cement and engineered stone products (used in building construction), as well as those from various coal mine dusts. The measurements compared well with those from the standard XRD method, even for samples with matrix and mineral interferences. The results show that QCL-based IR transmission spectroscopy can offer sensitive, trace-level measurement of aerosol mineral components.

A PM2.5 Sensor Module Based on a TPoS MEMS Oscillator and an Aerosol Impactor

In this work, a real-time PM2.5 sensor module with high mass resolution and wide detection range is successfully demonstrated while the module consists of a two-stage aerosol impactor, a Thin-film Piezoelectric-on-Silicon (TPoS) MEMS oscillator, and a micro-pump. The aerosol impactor's collection efficiency of 51% for $2.54~\mu \text{m}$ and 50% for $1.03~\mu \text{m}$ is verified for stage 1 and stage 2, respectively. A length-extensional mode TPoS MEMS resonator is implemented, featuring a resonant frequency of 4.05 MHz and a quality factor (${Q}$ ) of 438 in air. To achieve a portable sensor module, a board-level sustaining circuit, which includes a transimpedance amplifier (TIA), a phase shifter, a band-pass filter, and a buffer circuit are integrated to fulfill the condition of Barkhausen criteria for oscillation. Phase noise of -111.92 dBc/Hz at 1 kHz offset was recorded under ambient pressure and room temperature for a carrier frequency of 4.05 MHz. The mass resolution for the PM2.5 sensor implemented in this work is 0.71 pg. Finally, an incense was used to produce the liquid type particles continuously for the aerosol measurement. The coefficient of determination (${R} ^{2}$ ) of 0.81 between the frequency slope of the proposed sensor and the aerosol concentration of the commercial optical aerosol sensor within a range of $10~\mu $ g/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> to $1000~\mu $ g/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . This work successfully integrated MEMS, circuit, and air flow technologies to realize a complete mass sensing module, and has the potential to be implemented in the particulate matter concentration monitoring applications of air.

Pollution Characteristics of Water-soluble Inorganic Ions in Chengdu in Summer and Winter

The water-soluble inorganic ions (WSIIs) in PM2.5 and gaseous precursors of Chengdu were continuously observed by a gas and aerosol collector combined with ion chromatography (GAC-IC) in the summer and winter of 2017, and both their pollution characteristics and a typical pollution process in winter were analyzed. It was found that the concentration of PM2.5 in winter (100.2 μg·m-3) was significantly higher than that in summer (34.0 μg·m-3). WSIIs were important components of PM2.5 and their total contributions to PM2.5 were 52.9% and 53.3% in summer and winter, respectively. Secondary ions (SNA) accounted for 73.2% and 87.6% of WSIIs in summer and winter, respectively. SO42- and NO3- dominated the SNA in summer and winter, and the contributions to SNA were 37.7% and 59.7%, respectively. The NO3-/SO42- ratio (2.7) in winter was significantly higher than that in summer (0.8), reflecting the important contribution of mobile sources (especially motor vehicles) to PM2.5 in this season. The diurnal variation of SNA in the two seasons was obviously different due to the differences in sources and meteorological conditions. In winter, with the aggravation of pollution, the concentrations of WSIIs and gaseous precursors increased significantly, and NO3- was the key component in causing heavy pollution. Backward trajectory analysis revealed that the air masses in the two seasons in Chengdu differed significantly from each other. The WSIIs in summer and winter were dominated by SO42- and NO3-, respectively. The short-distance and low-altitude transmission from the east and south of Chengdu contributed significantly to PM2.5 pollution in Chengdu.

Standardized protocols for microplastics determinations in environmental samples from the Gulf and marginal seas

Microplastics are a group of ubiquitous persistent pollutants that have rapidly attracted much attention from the scientific community as well as the general public due to the growing awareness of the environmental risks they pose. However, due to limitations and variations in sampling, analytical measurement methods, and the different units used for reporting data, reliable comparisons between studies in the Gulf region and internationally are not straightforward. This study proposes standardized protocols for marine sediment, seawater, marine biota and aerosol (1) sampling, (2) sample processing, (3) sample identification and (4) reporting units to be used. An attempt has been made to highlight the limitations of the widely employed strategies for sampling microplastics in seawater, where a large portion of the microplastics is not sampled due to the mesh sizes used. The issues with the processing of biota samples and aerosols are likewise addressed, and recommendations are also made for standardization of units for reporting microplastic quantification. Protocols for collection of bottom sediments and aerosols are also proposed. These are the environmental matrixes for which there are no harmonized protocols in the Gulf region; hence if a standardized approach is adopted, it will enable and improve comparisons between the studies within this region and can be useful for similar studies in other marine areas as well.

Comparative Evaluation of Efficacy of Chlorhexidine and Herbal Mouthwash as a Preprocedural Rinse in Reducing Dental Aerosols: A Microbiological Study

Objective. The risk to dentists, assistants, and patients of infectious diseases through aerosols has long been recognized. The aim of this study was to evaluate and compare the efficacy of commercially available preprocedural mouth rinses containing 0.2% chlorhexidine (CHX) gluconate, Befresh™ herbal mouthwash, and water in reducing the levels of viable bacteria in aerosols. Materials &amp; Methods. This was a single-center, double-masked, placebo-controlled, randomized, three-group parallel design study. 30 patients (10 patients in each group) were recruited in the study. Patient rinsed mouth with 10 ml of CHX, 10 ml Befresh™, or 10 ml water. All the patients underwent supragingival ultrasonic scaling for a minimum of 30 min. The aerosol collection was done using a blood agar plate. The blood agar plates were kept approximately 12 inches from the patient’s mouth. The microbial culture was analyzed. The colony-forming unit (CFU) counting in all three groups was assessed using one-way ANOVA test to compare among the groups (p value &lt;0.001). The intergroup comparison was done using the post hoc Tukey test. Result. There was a marked reduction in the CFU in the CHX group in all three areas. This was followed by Befresh™ (Sagar Pharmaceuticals) mouthwash. There was no reduction in the CFU of the water group. Conclusion. This study proves that a regular preprocedural mouth rinse could significantly reduce the majority bacteria present in aerosols generated by the use of an ultrasonic unit, and Befresh™ mouth rinse was found to be equally effective in reducing the aerosol contamination to 0.2% CHX gluconate.

Performance of two shrouded probes for the collection of liquid aerosols in a wind tunnel optimized for high air speeds

A combination of type A (high flow model) or B (low flow model) shrouded probe and appropriate isokinetic air-sampler (IAS) was tested in a wind tunnel that was optimized for high air speed testing...

Comparison and evaluation of a high volume air sampling system for the collection of Clostridioides difficile endospore aerosol in health care environments

Environmental contamination of patient rooms and adjacent areas with C. difficile spores is a recognized transmission risk. Previous studies have shown that spores are aerosolized during patient care. These spores can remain airborne for extended periods and may contaminate distant surfaces. High-volume air sampling equipment allows for the collection of a large volume of air and was evaluated in the collection of C. difficile aerosol. Air samplers evaluated in this research included the DFU-1000, XMX/2L-MIL, Biocapture-650, and a MB2. Aerosols of C. difficile were generated in a 5-m3 chamber and each air sampler sampled in the aerosol test chamber simultaneously with referee air samplers. The DFU-1000 achieved the highest efficiency of the 4 air samplers (P = .0145) with a mean efficiency of 38.60%. The relative efficiencies of the Biocapture-650, XMX/2L-MIL, and MB2 were 28.16%, 10.51%, and 3.05%, respectively. This study demonstrated high variation based on the sampling method employed. Based on the results of these studies, high-volume air samplers may be effectively applied to sample for airborne C. difficile in health care environments. The high sampling flow rate of the DFU-1000 would allow for the complete sampling of a patient room-sized volume in less than 1 hour.

Protein stability during nebulization: Mind the collection step!

Inhaled protein therapeutics meet a growing interest for the treatment of respiratory diseases. In liquid aerosols, proteins face stresses that may generate instabilities, such as physicochemical denaturations, aggregation and loss of activity. Monitoring protein stability is thus crucial but implies collection of aerosol droplets before analysis. Many aerosol collection methods may be used, still their interference on protein stability is unknown. In this study, we compared the impact of six aerosol samplers on the stability of a model monoclonal antibody (Ig1), aerosolized with a mesh nebulizer. Ig1 stability was assessed for aggregation and biological activity. The six aerosol samplers generated distinct aggregation profiles for Ig1 at all size scales; counts of micron-sized particles varied by a factor of 100. The heterogeneity did not impact Ig1 activity, which was not significantly changed after nebulization. To extrapolate these results, we evaluated the impact of two samplers on three other proteins. Depending on the protein, samplers gave discordant aggregation and/or activity profiles, sometimes in the reverse trend as compared to Ig1. In conclusion, aerosol samplers interfere with protein stability; this impact depends both on the samplers and the protein, highlighting the importance of using the same collection device throughout the aerosol development process.

Digital Microfluidics for the Detection of Selected Inorganic Ions in Aerosols.

A prototype aerosol detection system is presented that is designed to accurately and quickly measure the concentration of selected inorganic ions in the atmosphere. The aerosol detection system combines digital microfluidics technology, aerosol impaction and chemical detection integrated on the same chip. Target compounds are the major inorganic aerosol constituents: sulfate, nitrate and ammonium. The digital microfluidic system consists of top and bottom plates that sandwich a fluid layer. Nozzles for an inertial impactor are built into the top plate according to known, scaling principles. The deposited air particles are densely concentrated in well-defined deposits on the bottom plate containing droplet actuation electrodes of the chip in fixed areas. The aerosol collection efficiency for particles larger than 100 nm in diameter was higher than 95%. After a collection phase, deposits are dissolved into a scanning droplet. Due to a sub-microliter droplet size, the obtained extract is highly concentrated. Droplets then pass through an air/oil interface on chip for colorimetric analysis by spectrophotometry using optical fibers placed between the two plates of the chip. To create a standard curve for each analyte, six different concentrations of liquid standards were chosen for each assay and dispensed from on-chip reservoirs. The droplet mixing was completed in a few seconds and the final droplet was transported to the detection position as soon as the mixing was finished. Limits of detection (LOD) in the final droplet were determined to be 11 ppm for sulfate and 0.26 ppm for ammonium. For nitrate, it was impossible to get stable measurements. The LOD of the on-chip measurements for sulfate was close to that obtained by an off-chip method using a Tecan spectrometer. LOD of the on-chip method for ammonium was about five times larger than what was obtained with the off-chip method. For the current impactor collection air flow (1 L/min) and 1 h collection time, the converted LODs in air were: 0.275 μg/m3 for sulfate, 6.5 ng/m3 for ammonium, sufficient for most ambient air monitoring applications.

Development of an Aerosol Dose Collection Apparatus for In Vitro Dissolution Measurements of Orally Inhaled Drug Products

The aim of the study was to develop a robust and standardized in vitro dissolution methodology for orally inhaled drug products (OIDPs). An aerosol dose collection (ADC) system was designed to uniformly deposit the whole impactor stage mass (ISM) over a large filter area for dissolution testing. All dissolution tests were performed under sink conditions in a sodium phosphate buffered saline solution containing 0.2%w/w sodium dodecyl sulphate. An adapted USP Apparatus V, Paddle over Disk (POD), was used throughout the study. The dissolution characteristics of the ISM dose of a commercial metered-dose inhaler (MDI) and a range of dry powder inhaler (DPI) formulations containing inhaled corticosteroids were tested. The uniform distribution of the validated ISM dose considerably reduced drug loading effects on the dissolution profiles for both MDI and DPI formulations. The improvement in the robustness and discriminatory capability of the technique enabled characterization of dissolution rate differences between inhaler platforms and between different DPI product strengths containing fluticasone propionate. A good correlation between in vivo mean absorption time and in vitro dissolution half-life was found for a range of the inhaled corticosteroids. The ADC system and the reproducible in vitro POD dissolution measurements provided a quantitative-based approach for measuring the relationship between the influence of device and the dispersion characteristics on the aerosol dissolution of low solubility compounds. The in vitro dissolution method could potentially be applied as a dissolution methodology for compendial, quality control release testing, and during development of both branded orally inhaled drug products and their generic counterparts.

State-of-the-art methods and devices for the generation, exposure, and collection of aerosols from heat-not-burn tobacco products

Tobacco harm reduction is increasingly recognized as a promising approach to accelerate the decline in smoking prevalence and smoking-related population harm. Potential modified risk tobacco products (MRTPs) must undergo a rigorous premarket toxicological risk assessment. The ability to reproducibly generate, collect, and use aerosols is critical for the characterization, and preclinical assessment of aerosol-based candidate MRTPs (cMRTPs), such as noncombusted cigarettes, also referred to as heated tobacco products, tobacco heating products, or heat-not-burn (HNB) tobacco products. HNB tobacco products generate a nicotine-containing aerosol by heating tobacco instead of burning it. The aerosols generated by HNB products are qualitatively and quantitatively highly different from cigarette smoke (CS). This constitutes technical and experimental challenges comparing the toxicity of HNB aerosols with CS. The methods and experimental setups that have been developed for the study of CS cannot be directly transposed to the study of HNB aerosols. Significant research efforts are dedicated to the development, characterization, and validation of experimental setups and methods suitable for HNB aerosols. They are described in this review, with a particular focus on the Tobacco Heating System version 2.2. This is intended to support further studies, the objective evaluation and verification of existing evidence, and the development of scientifically substantiated HNB MRTPs.

State-of-the-art methods and devices for generation, exposure, and collection of aerosols from e-vapor products

E-vapor products (EVP) have become popular alternatives for cigarette smokers who would otherwise continue to smoke. EVP research is challenging and complex, mostly because of the numerous and rapidly evolving technologies and designs as well as the multiplicity of e-liquid flavors and solvents available on the market. There is an urgent need to standardize all stages of EVP assessment, from the production of a reference product to e-vapor generation methods and from physicochemical characterization methods to nonclinical and clinical exposure studies. The objective of this review is to provide a detailed description of selected experimental setups and methods for EVP aerosol generation and collection and exposure systems for their in vitro and in vivo assessment. The focus is on the specificities of the product that constitute challenges and require development of ad hoc assessment frameworks, equipment, and methods. In so doing, this review aims to support further studies, objective evaluation, comparison, and verification of existing evidence, and, ultimately, formulation of standardized methods for testing EVPs.

Aerosols and Clouds Interactions in an Urban Atmosphere

Aerosols create great uncertainties in studying climate change under global warming and atmospheric dynamics. To understand the impacts of aerosols on cloud properties in Madurai, we have analyzed an extensive collection of aerosol and cloud properties, obtained from the Moderate resolution Imaging Spectroradiometer (MODIS) data, over the study site during 2012-2013. Monthly, seasonal and annual variations of aerosols and clouds studied along their interactions and impacts on climate. Considering annual averages for all these parameters, most often the year 2012 was dominated with a higher presence of AOD, COD, CER, CTT, CTP whereas rainfall and CF were found to be dominated in 2013. The presence of higher CF in 2013 may be a cause for the higher rainfall and the lower level of CF in 2012 may be a cause for less rainfall. High aerosol loading in this area is due to biomass burning and urban air pollution which may significantly suppress precipitation. Increased aerosols and the local aerosol emissions may reduce the precipitation efficiency, which is responsible for the precipitation reduction and vice-versa.

A Screening Method by Gas Chromatography-Mass Spectrometry for the Quantification of 24 Aerosol Constituents from Heat-Not-Burn Tobacco Products

Summary A screening method allowing the quantification of 24 aerosol constituents using gas chromatography-mass spectrometry has been developed to assess the aerosol chemistry of heat-not-burn tobacco products. The aim of this method was to quantify phenol, o-cresol, m-cresol, p-cresol, catechol, resorcinol, hydroquinone, 1,3-butadiene, isoprene, benzene, acrylonitrile, toluene, pyridine, styrene, 1,2-propylene glycol, menthol, 2-furanmethanol, acrylamide, naphthalene, nicotine, acetamide, quinoline, triacetin, and glycerine in the aerosol emitted by heated tobacco products. The aerosol was generated by an electrically heated tobacco system (PMI’s Heated Tobacco System (THS 2.4)) with one single aerosol collection method, using the Health Canada smoking regimen and analyzed with two analytical methods. The method was validated according to the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use and the Association of Official Analytical Chemists guidelines. A regression model based on a linear relationship between concentration and response ratio with a 1/x weighting factor was selected for phenol, o-cresol, m-cresol, p-cresol, 1,3-butadiene, isoprene, benzene, acrylonitrile, toluene, pyridine, styrene, 2-furanmethanol, acrylamide, naphthalene and acetamide. A quadratic regression model with a 1/x weighting factor was chosen for catechol, resorcinol, hydroquinone, 1,2-propylene glycol, menthol, nicotine, quinoline, triacetin and glycerine. Coefficients of variation for repeatability were determined between 7.9% and 17.8% and for intermediate precision between 8.1% and 19.9%. The matrix effect of the heated tobacco aerosol extract was assessed by performing a recovery study, where the aerosol extracts were spiked at different concentrations for the compounds to be analyzed. In addition, the mainstream smoke from 3R4F reference cigarettes was analyzed, and results were compared with previously published studies. The method was successfully validated, providing data consistent with published data and it was shown to be selective, precise and accurate.

Scavenging efficiency of water soluble inorganic and organic aerosols by fog droplets in the Indo Gangetic Plain

Abstract The interaction of aerosols with fog droplets impacts the processing and scavenging of ambient particles. It is essential to know about such interaction for refining the regional model description of particles lifetime. Towards this, we performed simultaneous collection of aerosol and fog water samples during winter period at a rural location of Indo Gangetic Plain. These samples were analyzed for water soluble inorganics ions and organic carbon (WSOC) and heavy metals. The results showed that aerosol and its water soluble constituent's concentration get reduced during foggy nights compared to non-foggy nights, due to the scavenging of aerosols by fog droplets. Nitrate was found to be the dominant inorganic species during foggy nights whereas sulfate during non-foggy nights. The aerosol neutralization ratio for fog water and interstitial aerosol samples were found to be around unity during the foggy nights which indicated that fog condensation nuclei formed upon the neutralized state of aerosol. Combined vehicular emission and road dust, biomass burning and secondary transformation were found to be main sources for the water soluble species loading of aerosol with the latter two sources were higher during foggy nights. Based on the ratio of fog water to aerosol enrichment factor, Cu, Mn and Ba found to be highly soluble. Mass scavenging efficiency (MSE) results showed that crustal oriented components scavenged rate was higher followed by the secondary components and biomass burning species. MSE for secondary species were found to be dependent directly on liquid water content and inversely on aerosol concentration. The MSE of WSOC was found to be comparable to secondary inorganics which displayed its equally important role in nucleation scavenging. The aqueous production of sulfate in the fog droplets contributed more than scavenged sulfate which can lead to enrichment in aerosol concentration after the evaporation of fog droplets.

Characterisation of the filter inlet system on the FAAM BAe-146 research aircraft and its use for size-resolved aerosol composition measurements

Abstract. Atmospheric aerosol particles are important for our planet's climate because they interact with radiation and clouds. Hence, having characterised methods to collect aerosol from aircraft for detailed offline analysis are valuable. However, collecting aerosol, particularly coarse-mode aerosol, onto substrates from a fast-moving aircraft is challenging and can result in both losses and enhancement in particles. Here we present the characterisation of an inlet system designed for collection of aerosol onto filters on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146-301 Atmospheric Research Aircraft. We also present an offline scanning electron microscopy (SEM) technique for quantifying both the size distribution and size-resolved composition of the collected aerosol. We use this SEM technique in parallel with online underwing optical probes in order to experimentally characterise the efficiency of the inlet system. We find that the coarse-mode aerosol is sub-isokinetically enhanced, with a peak enhancement at around 10 µm up to a factor of 2 under recommended operating conditions. Calculations show that the efficiency of collection then decreases rapidly at larger sizes. In order to minimise the isokinetic enhancement of coarse-mode aerosol, we recommend sampling with total flow rates above 50 L min−1; operating the inlet with the bypass fully open helps achieve this by increasing the flow rate through the inlet nozzle. With the inlet characterised, we also present single-particle chemical information obtained from X-ray spectroscopy analysis, which allows us to group the particles into composition categories.

Piperazine aerosol mitigation for post-combustion carbon capture

Amine loss as aerosol is still a challenge for reliable long-term operations in amine scrubbing units. While attempts have been made to understand, predict, and mitigate amine aerosol growth in the absorber, demonstration of the mitigation of piperazine (PZ) aerosol has not been published. This paper presents results from a comprehensive emission study using 5 m PZ. The focus of this work is not to validate growth mechanisms, but to provide data from which existing hypotheses can be analyzed. PZ aerosol at the water wash outlet was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and an Electrical Low-Pressure Impactor (ELPI+). Two mitigation strategies were successfully implemented during episodes of PZ aerosol emission. These episodes resulted from the presence of SO3 in the flue gas due to periods of sub-optimal SO3 removal upstream of the CO2 capture facility. Four weeks of aerosol tests were also run with 0–6 ppm of SO3 generated and injected into the flue gas to evaluate the resilience of the mitigation strategies. The first approach to aerosol emission mitigation was to remove aerosol nuclei present in the flue gas. The second approach was to run the absorber with flue gas containing varying SO3 at conditions that accelerate aerosol nuclei growth and collection within the packing. SO3 control via hydrated lime addition upstream of the absorber eliminated aerosol while higher lean solvent temperature in the absorber and a two-stage water wash configuration were tested to accelerate aerosol nuclei growth and collection. Increasing the lean solvent temperature by 11 °C and using a two-stage water wash resulted in 98% reduction of PZ emissions. Absorber performance at the elevated lean solvent temperature was sustained in the existing packing with solvent intercooling. PZ emissions were managed to less than 1 ppm for extended periods during the pilot plant campaign.

Development of a Physiologically Relevant Online Chemical Assay To Quantify Aerosol Oxidative Potential.

Large-scale epidemiological studies have shown a close correlation between adverse human health effects and exposure to ambient particulate matter (PM). The oxidative potential (OP) of ambient PM has been implicated in inducing toxic effects associated with PM exposure. In particular, reactive oxygen species (ROS), either bound to PM or generated by particulate components in vivo, substantially contribute to the OP and therefore toxicity of PM by lowering antioxidant concentrations in the lung, which can subsequently lead to oxidative stress, inflammation, and disease. Traditional methods for measuring aerosol OP are labor intensive and have poor time resolution, with significant delays between aerosol collection and ROS analysis. These methods may underestimate ROS concentrations in PM because of the potentially short lifetime of some ROS species; therefore, continuous online, highly time-resolved measurement of ROS components in PM is highly advantageous. In this work, we develop a novel online method for measuring aerosol OP based on ascorbic acid chemistry, an antioxidant prevalent in the lung, thus combining the advantages of continuous online measurement with a physiologically relevant assay. The method limit of detection is estimated for a range of atmospherically important chemical components such as Cu(II) 0.22 ± 0.03 μg m-3, Fe(II) 47.8 ± 5.5 μg m-3, Fe(III) 0.63 ± 0.05 μg m-3, and secondary organic aerosol 41.2 ± 6.9 μg m-3, demonstrating that even at this early stage of development, the online method is capable of measuring the OP of PM in polluted urban environments and smog chamber studies.