Water-based Condensation Particle Counter Research Articles

Novel method for the continuous mass concentration measurement of ultrafine particles (PM 0.1 ) with a water-based condensation particle counter (CPC)

Novel method for the continuous mass concentration measurement of ultrafine particles (PM _0.1 ) with a water-based condensation particle counter (CPC)

Mapping the performance of a versatile water-based condensation particle counter (vWCPC) with numerical simulation and experimental study

Abstract. Accurate airborne aerosol instrumentation is required to determine the spatial distribution of ambient aerosol particles, particularly when dealing with the complex vertical profiles and horizontal variations of atmospheric aerosols. A versatile water-based condensation particle counter (vWCPC) has been developed to provide aerosol concentration measurements under various environments with the advantage of reducing the health and safety concerns associated with using butanol or other chemicals as the working fluid. However, the airborne deployment of vWCPCs is relatively limited due to the lack of characterization of vWCPC performance at reduced pressures. Given the complex combinations of operating parameters in vWCPCs, modeling studies have advantages in mapping vWCPC performance. In this work, we thoroughly investigated the performance of a laminar-flow vWCPC using COMSOL Multiphysics® simulation coupled with MATLAB™. We compared it against a modified vWCPC (vWCPC model 3789, TSI, Shoreview, MN, USA). Our simulation determined the performance of particle activation and droplet growth in the vWCPC growth tube, including the supersaturation, Dp,kel,0 (smallest size of particle that can be activated), Dp,kel,50 (particle size activated with 50 % efficiency) profile, and final growth particle size Dd under wide operating temperatures, inlet pressures P (30–101 kPa), and growth tube geometry (diameter D and initiator length Lini). The effect of inlet pressure and conditioner temperature on vWCPC 3789 performance was also examined and compared with laboratory experiments. The COMSOL simulation result showed that increasing the temperature difference (ΔT) between conditioner temperature Tcon and initiator Tini will reduce Dp,kel,0 and the cut-off size Dp,kel,50 of the vWCPC. In addition, lowering the temperature midpoint (Tmid=Tcon+Tini2) increases the supersaturation and slightly decreases the Dp,kel. The droplet size at the end of the growth tube is not significantly dependent on raising or lowering the temperature midpoint but significantly decreases at reduced inlet pressure, which indirectly alters the vWCPC empirical cut-off size. Our study shows that the current simulated growth tube geometry (D=6.3 mm and Lini=30 mm) is an optimized choice for current vWCPC flow and temperature settings. The current simulation can more realistically represent the Dp,kel for 7 nm vWCPC and also achieved good agreement with the 2 nm setting. Using the new simulation approach, we provide an optimized operation setting for the 7 nm setting. This study will guide further vWCPC performance optimization for applications requiring precise particle detection and atmospheric aerosol monitoring.

Characterisation of a self-sustained, water-based condensation particle counter for aircraft cruising pressure level operation

Abstract. Aerosol particle number concentration measurements are a crucial part of aerosol research. Vertical profile measurements and high-altitude/low-pressure performance of the respective instruments become more important for remote sensing validation and a vital tool for the observation of climate variables. This study tests the new, commercially available water condensation particle counter (MAGIC 210-LP) for the deployment at aircraft cruising pressure levels that the European research infrastructure IAGOS (In-service Aircraft for a Global Observing System; http://www.iagos.org, last access: 2 May 2023) is aiming for by operating measurement instrumentation onboard passenger aircraft. We conducted laboratory experiments for conditions to simulate passenger aircraft flight altitude at operation pressure. We demonstrate that this type of water condensation particle counter shows excellent agreement with a butanol-based instrument used in parallel. A Faraday cup aerosol electrometer serves as the reference instrument. Experiments are performed with test aerosol ammonium sulfate and fresh combustion soot at pressure levels ranging from 700 to 200 hPa. For soluble particles like ammonium sulfate, the 50 % detection efficiency cut-off diameter (D50) is around 5 nm and does not differ significantly for all performed experiments. For non-soluble fresh soot particles, the D50 cut-off diameter of approximately 10 nm does not vary substantially as a function of pressure, whereas the 90 % detection efficiency cut-off diameter D90 increases from 19 nm at 700 hPa to 37 nm at 200 hPa. The overall counting efficiency for particles larger than 40 nm reaches 100 % for working pressures of 200 hPa and higher.

Simulation-aided characterization of a versatile water-based condensation particle counter for atmospheric airborne research

Abstract. Capturing the vertical profiles and horizontal variations of atmospheric aerosols often requires accurate airborne measurements. With the advantage of avoiding health and safety concerns related to the use of butanol or other chemicals, water-based condensation particle counters have emerged to provide measurements under various environments. However, airborne deployments are relatively rare due to the lack of instrument characterization under reduced pressure at flight altitudes. This study investigates the performance of a commercial “versatile” water-based condensation particle counter (vWCPC, model 3789, TSI, Shoreview, MN, USA) under various ambient pressure conditions (500–920 hPa) with a wide range of particle total number concentrations (1500–70 000 cm−3). The effect of conditioner temperature on vWCPC 3789 performance at low pressure is examined through numerical simulation and laboratory experiments. We show that the default instrument temperature setting of 30 ∘C for the conditioner is not suitable for airborne measurement and that the optimal conditioner temperature for low-pressure operation is 27∘. Under the optimal conditioner temperature (27∘), the 7 nm cut-off size is also maintained. Additionally, we show that insufficient droplet growth becomes more significant under the low-pressure operation. The counting efficiency of the vWCPC 3789 can vary up to 20 % for particles of different chemical compositions (e.g., ammonium sulfate and sucrose particles). However, such variation is independent of pressure.

The nano-scanning electrical mobility spectrometer (nSEMS) and its application to size distribution measurements of 1.5–25 nm particles

Abstract. Particle size measurement in the low nanometer regime is of great importance to the study of cloud condensation nuclei formation and to better understand aerosol–cloud interactions. Here we present the design, modeling, and experimental characterization of the nano-scanning electrical mobility spectrometer (nSEMS), a recently developed instrument that probes particle physical properties in the 1.5–25 nm range. The nSEMS consists of a novel differential mobility analyzer and a two-stage condensation particle counter (CPC). The mobility analyzer, a radial opposed-migration ion and aerosol classifier (ROMIAC), can classify nanometer-sized particles with minimal degradation of its resolution and diffusional losses. The ROMIAC operates on a dual high-voltage supply with fast polarity-switching capability to minimize sensitivity to variations in the chemical nature of the ions used to charge the aerosol. Particles transmitted through the mobility analyzer are measured using a two-stage CPC. They are first activated in a fast-mixing diethylene glycol (DEG) stage before being counted by a second detection stage, an ADI MAGIC™ water-based CPC. The transfer function of the integrated instrument is derived from both finite-element modeling and experimental characterization. The nSEMS performance has been evaluated during measurement of transient nucleation and growth events in the CLOUD atmospheric chamber at CERN. We show that the nSEMS can provide high-time- and size-resolution measurement of nanoparticles and can capture the critical aerosol dynamics of newly formed atmospheric particles. Using a soft x-ray bipolar ion source in a compact housing designed to optimize both nanoparticle charging and transmission efficiency as a charge conditioner, the nSEMS has enabled measurement of the contributions of both neutral and ion-mediated nucleation to new particle formation.

Intercomparison in the laboratory of various Condensation Particle Counters challenged by nanoaerosols in the range 6 – 460 nm

This study aim is to compare the number concentration of airborne nanoparticles reported by 13 different Condensation Particle Counters (CPC) with regards to a reference CPC, for a set of aerosols of interest. Among the models investigated, 5 are handheld CPC, while the 8 others are stationary CPC. The latter include butanol-based CPC as well as water-based CPC. Polydisperse test aerosols with modal diameters between 6 and 460 nm were produced in the CAIMAN experimental facility. Non-hydrophobic aerosols consisted of metal-based particles (Ti, C, Al, Cu, Ag), as well as nebulized suspensions (SiO2). Hydrophobic particles consisted of DEHS as well as alkanes (n-C13 to n-C20). Overall, about 400 different conditions were investigated to represent a wide range of aerosols potentially encountered in workplaces. The range of number concentrations provided by the reference CPC was 500 – 400 000 cm−3. To highlight the possible effect of particle counting efficiency on the total concentration reported by the different CPCs, 40% of the test aerosols presented a modal diameter below 40 nm. The influence of particle material for water-based CPCs was investigated through the generation of about 100 hydrophobic test aerosols. CPC response was found to be sensitive to the mode of the aerosols measured, depending on the counting efficiency curve of the CPC investigated. An effect of particle hydrophobicity on the response of some water-based CPC models was demonstrated, while one water-based CPC did not show any material dependence.

A MAGIC concept for self-sustained, water-based, ultrafine particle counting

A self-sustaining, motion-tolerant, water-based condensation particle counter (CPC) has been designed, fabricated, and tested. Referred to as “MAGIC” for moderated aerosol growth with internal water cycling, the particle size response is similar to the 5-nm cut-point commercial CPCs. MAGIC is a laminar-flow instrument with three temperature stages: cool, warm, and cool. The middle warm-walled stage initiates the condensational growth and the final cool-walled stage maintains supersaturated conditions while recovering water vapor. By using a continuous wick throughout all three stages, the system recharges itself through a combination of water condensate from the sampled airstream and recovery of water vapor from the peak supersaturation region. A reservoir-less prototype system based on this concept was built and tested. Experiments show equal performance in any orientation, upright or inverted, and tolerance to tipping, shaking and vibrational shocks up to 5 g. Under mild ambient conditions, it provided multi-week operation without replenishing the wick.Copyright © 2018 American Association for Aerosol Research

Performance evaluation of conventional type conductive cooling continuous flow compact water-based CPC (Hy-WCPC)

In this study, a water-based compact handheld condensation particle counter (Hy-WCPC) is developed and its performance is evaluated. The Hy-WCPC is a small and light water-based CPC and the operating principle is the same as the conventional continuous flow conductive cooling alcohol-based condensation particle counters (CPC). This study presents the particle material dependent Hy-WCPC cut-off sizes and the particle concentration counting linearity between the Hy-WCPC and electrometer by generating silver, sodium chloride, zinc and paraffin particles. Moreover, the comparison between the Hy-WCPC and commercially available ultrafine CPC (TSI 3776) for ambient airborne particles is presented. The cut-off sizes of the Hy-WCPC for silver and paraffin particles are 3.61nm and 5.30nm, respectively. For sodium chloride and zinc particles, the Hy-WCPC lower detection limit is achieved less than 4nm. Moreover, the particle concentration counting linearity between the Hy-WCPC and electrometer is presented. The excellent particle number concentration counting linearity agreement between the Hy-WCPC and electrometer is shown for the laboratory generated particles. Also, the particle concentration counting linearity between the Hy-WCPC and the TSI 3776 for outdoor ambient airborne particles is shown. The reasonable agreement between the Hy-WCPC and the TSI 3776 was obtained. In the long-term measurement of outdoor ambient airborne particles for 7 days, this agreement had been maintained, however, after 7 days, the TSI 3776 did not operate properly due to the high humidity, while the Hy-WCPC was operating without the problem.

A DMA-train for precision measurement of sub-10 nm aerosol dynamics

Abstract. Measurements of aerosol dynamics in the sub-10 nm size range are crucially important for quantifying the impact of new particle formation onto the global budget of cloud condensation nuclei. Here we present the development and characterization of a differential mobility analyzer train (DMA-train), operating six DMAs in parallel for high-time-resolution particle-size-distribution measurements below 10 nm. The DMAs are operated at six different but fixed voltages and hence sizes, together with six state-of-the-art condensation particle counters (CPCs). Two Airmodus A10 particle size magnifiers (PSM) are used for channels below 2.5 nm while sizes above 2.5 nm are detected by TSI 3776 butanol-based or TSI 3788 water-based CPCs. We report the transfer functions and characteristics of six identical Grimm S-DMAs as well as the calibration of a butanol-based TSI model 3776 CPC, a water-based TSI model 3788 CPC and an Airmodus A10 PSM. We find cutoff diameters similar to those reported in the literature. The performance of the DMA-train is tested with a rapidly changing aerosol of a tungsten oxide particle generator during warmup. Additionally we report a measurement of new particle formation taken during a nucleation event in the CLOUD chamber experiment at CERN. We find that the DMA-train is able to bridge the gap between currently well-established measurement techniques in the cluster–particle transition regime, providing high time resolution and accurate size information of neutral and charged particles even at atmospheric particle concentrations.

Detection near 1-nm with a laminar-flow, water-based condensation particle counter

ABSTRACTPresented is a laminar-flow, water-based condensation particle counter capable of particle detection near 1 nm. This instrument employs a three-stage, laminar-flow growth tube with a “moderator” stage that reduces the temperature and water content of the output flow without reducing the peak supersaturation, and makes feasible operation at the large temperature differences necessary for achieving high supersaturations. The instrument has an aerosol flow of 0.3 L/min, and does not use a filtered sheath flow. It is referred to as a “versatile” water condensation particle counter, or vWCPC, as operating temperatures can be adjusted in accordance with the cut-point desired. When operated with wall temperatures of ∼2°C, >90°C, and ∼22°C for the three stages, respectively, the vWCPC detects particles generated from a heated nichrome wire with a 50% efficiency cut-point near 1.6 nm mobility diameter. At these operating temperatures, it also detects 10–20% of large molecular ions formed from passing filte...

Water-based single-flow mixing condensation particle counter

ABSTRACTA novel water-based condensation particle counter has been developed using a patented, single-flow mixing (SFM) condenser that permits a conventional thermal approach of using a hot saturator followed by a cold condenser to activate and grow particles for counting with an optical detector. A computational fluid dynamics (CFD) model of the internal flow, temperature, and vapor profiles was used to predict the effectiveness of the SFM condenser. Using the results from the CFD model, the counting efficiency was numerically calculated for pure water droplets, and the CPC cut-point (i.e., 50% counting efficiency) was predicted to be 8.3 nm. The experimental performance of the new CPC was measured with differential mobility analyzer-classified, monodisperse particles. The measured cut-points were 8.2 nm for Ag particles and 3.9 nm for NaCl particles. The reduction in the cut-point for NaCl is the result of a compound effect: water uptake by NaCl particles, which increases their size before entering into...

Scanning supersaturation condensation particle counter applied as a nano-CCN counter for size-resolved analysis of the hygroscopicity and chemical composition of nanoparticles

Abstract. Knowledge about the chemical composition of aerosol particles is essential to understand their formation and evolution in the atmosphere. Due to analytical limitations, however, relatively little information is available for sub-10 nm particles. We present the design of a nano-cloud condensation nuclei counter (nano-CCNC) for measuring size-resolved hygroscopicity and inferring chemical composition of sub-10 nm aerosol particles. We extend the use of counting efficiency spectra from a water-based condensation particle counter (CPC) and link it to the analysis of CCN activation spectra, which provides a theoretical basis for the application of a scanning supersaturation CPC (SS-CPC) as a nano-CCNC. Measurement procedures and data analysis methods are demonstrated through laboratory experiments with monodisperse particles of diameter down to 2.5 nm, where sodium chloride, ammonium sulfate, sucrose and tungsten oxide can be easily discriminated by different characteristic supersaturations of water droplet formation. A near-linear relationship between hygroscopicity parameter κ and organic mass fraction is also found for sucrose-ammonium sulfate mixtures. The design is not limited to the water CPC, but also applies to CPCs with other working fluids (e.g. butanol, perfluorotributylamine). We suggest that a combination of SS-CPCs with multiple working fluids may provide further insight into the chemical composition of nanoparticles and the role of organic and inorganic compounds in the initial steps of atmospheric new particle formation and growth.

A source-independent empirical correction procedure for the fast mobility and engine exhaust particle sizers

The TSI Fast Mobility Particle Sizer (FMPS) and Engine Exhaust Particle Sizer (EEPS) provide size distributions for 6–560 nm particles with a time resolution suitable for characterizing transient particle sources; however, the accuracy of these instruments can be source dependent, due to influences of particle morphology. The aim of this study was to develop a source-independent correction protocol for the FMPS and EEPS. The correction protocol consists of: (1) broadening the >80 nm size range of the distribution to account for under-sizing by the FMPS and EEPS; (2) applying an existing correction protocol in the 8–93 nm size range; and (3) dividing each size bin by the ratio of total concentration measured by the FMPS or EEPS and a water-based Condensation Particle Counter (CPC) as a surrogate scaling factor to account for particle morphology. Efficacy of the correction protocol was assessed for three sources: urban ambient air, diluted gasoline direct injection engine exhaust, and diluted diesel engine exhaust. Linear regression against a reference instrument, the Scanning Mobility Particle Sizer (SMPS), before and after applying the correction protocol demonstrated that the correction ensured agreement within 20%.

Analysis of particulate size distribution and concentrations from simulated jet engine bleed air incidents

Engine oil migrating into the bleed air stream of aircraft environmental control systems occurs with enough frequency and deleterious effects to generate significant public interest. While previous work has explored the chemical makeup of the contaminants in the aircraft cabin during these events, little is known about the characteristics of the aerosol resulting from oil contamination of bleed air. This article presents particle counter data (giving both size distributions and concentration information) of the oil droplets from simulated jet engine bleed air. Four particle counters—a scanning mobility analyzer, an aerodynamic particle-sizer, an optical particle counter, and a water-based condensation particle counter—were used in the study encompassing a size range from 13 nm to 20 μm. The aerosol characterization is given for different bleed air temperatures and pressures. The data show a substantial increase of ultrafine particles as the temperature is increased to the maximum temperatures expected during normal aircraft operation. This increase in ultrafine particles is consistent with smoke generated from the oil. The pressure of the bleed air had little discernible effect on the particle size and concentration.

A Unique Online Method to Infer Water-Insoluble Particle Contributions

Particle number, size, and composition information is important for constraining aerosol effects on air quality, climate, and health. The composition of particles, especially from vehicular sources, may contain insoluble black carbon (BC) materials that modify particle nucleating properties. In this study, we develop a method to provide quantitative and real-time information on the water-insoluble components found in near-road aerosol sources. A water-based condensation particle counter (W-CPC) and a butanol-based CPC (B-CPC) were used to measure the particle number concentration. Both instruments were coupled with a scanning mobility particle sizer (SMPS) to record the particle number and size data. Real time water-insoluble particle mass was estimated from the difference in particle number concentration between the two CPCs; theoretical water-insoluble mass was calculated from the ideal hygro- scopicity single parameter κ-values. This online method was calibrated with test compounds and then applied to ...

Counting Efficiency of a TSI Environmental Particle Counter Monitor Model 3783

In this study, we present our investigations on the counting efficiency of a TSI Environmental Particle Counter (EPC) Monitor Model 3783. The operation of the instrument is based on activation of sampled particles by water condensation, thus making it essentially a water-based condensation particle counter (WCPC). The counting efficiency was measured and simulated using different temperature settings on the conditioner and the growth tube, as well as using hygroscopic and water-soluble ammonium sulfate and sodium chloride particles, and insoluble and hydrophobic silver particles. The parameter that best describes the performance of the instrument is the cut-off diameter, or the diameter where 50% of sampled particles are activated and detected. In this study, the cut-off diameter for silver particles varied from 5.2 nm to 7.4 nm as a function of the temperature difference between the conditioner and the growth tube. The chemical composition and, specifically, the water solubility of particle components, h...

Minimizing Concentration Effects in Water-Based, Laminar-Flow Condensation Particle Counters

Concentration effects in water condensation systems, such as used in the water-based condensation particle counter, are explored through numeric modeling and direct measurements. Modeling shows that the condensation heat release and vapor depletion associated with particle activation and growth lowers the peak supersaturation. At higher number concentrations, the diameter of the droplets formed is smaller, and the threshold particle size for activation is higher. This occurs in both cylindrical and parallel plate geometries. For water-based systems we find that condensational heat release is more important than is vapor depletion. We also find that concentration effects can be minimized through use of smaller tube diameters, or more closely spaced parallel plates. Experimental measurements of droplet diameter confirm modeling results.

Performance of water-based CPC 3788 for particles from a propane-flame soot-generator operated with rich fuel/air mixtures

The new TSI Inc. Nano Water-based Condensation Particle Counter 3788 (N-WCPC Model 3788) is designed for counting particles down to a mobility diameter of dp=2.5nm. Published studies have shown that the use of water as a working fluid does not have a significant effect on the instrument performance. With the exception of a few specific substances, like emery oil or dioctyl sebacate which present a somewhat larger cut-point diameter, data in peer-reviewed literature suggests that the composition of the particles is not an issue as long as the particle diameter falls within the working range of the device. However, we have observed a very reduced counting efficiency from this water condensation particle counter for particles from a propane-rich fuel mixture (i.e. high carbon-to-oxygen ratio) generated by means of a Combustion Aerosol STandard burner (CAST). The percentage of detected particles decreases for an increasingly richer fuel mixture. The reduced efficiency is still present for particles well above the cut-point of the instrument. The 3788 N-WCPC counted only half as many dp=70nm particles when compared to two butanol based Condensation Particle Counters (CPC, models 3025A and 3022A, TSI Inc.), and the efficiency was even lower for smaller particles: only 0.14±0.001 and 0.002±0.0001 for monodisperse particles with a mobility diameter of dp=30nm and dp=15nm, respectively. Preconditioning the polydisperse sample using a thermodenuder at 100 or even 250°C slightly increased the counting efficiency of the N-WCPC, but this still remained below the counts of the butanol CPC. No reduction in counting efficiency was detected for CAST particles from propane-lean fuel-mixtures (otherwise known as black soot) or for organic particles produced by the photo-oxidation of α-pinene. For this reason, we believe that the effect is caused by the combination of the hydrocarbon rich composition of the particles and their low oxidation state.

Water-based condensation particle counters comparison near a major freeway with significant heavy-duty diesel traffic

This study compares the instrumental performance of three TSI water-based condensation particle counter (WCPC) models measuring particle number concentrations in close proximity (15 m) to a major freeway that has a significant level of heavy-duty diesel traffic. The study focuses on examining instrument biases and performance differences by different WCPC models under realistic field operational conditions. Three TSI models (3781, 3783, and 3785) were operated for one month in triplicate (nine units in total) in parallel with two sets of Scanning Mobility Particle Sizer (SMPS) spectrometers for the concurrent measurement of particle size distributions. Inter-model bias under different wind directions were first evaluated using 1-min raw data. Although all three WCPC models agreed well in upwind conditions (lower particle number concentrations, in the range of 103–104 particles cm−3), the three models' responses were significantly different under downwind conditions (higher particle number concentrations, above 104 particles cm−3). In an effort to increase inter-model linear correlations, we evaluated the results of using longer averaging time intervals. An averaging time of at least 15 min was found to achieve R2 values of 0.96 or higher when comparing all three models. Similar results were observed for intra-model comparisons for each of the three models. This strong linear relationship helped identify instrument bias related to particle number concentrations and particle size distributions. The TSI 3783 produced the highest particle counts, followed by TSI 3785, which reported 11% lower during downwind conditions than TSI 3783. TSI 3781 recorded particle number concentrations that were 24% lower than those observed by TSI 3783 during downwind condition. We found that TSI 3781 underestimated particles with a count median diameter less than 45 nm. Although the particle size dependency of instrument performance was found the most significant in TSI 3781, both models 3783 and 3785 showed somewhat size dependency. In addition, within each tested WCPC model, one unit was found to count significantly different and be more sensitive to particle size than the other two. Finally, exponential regression analysis was used to numerically quantify instrumental inter-model bias. Correction equations are proposed to adjust the TSI 3781 and 3785 data to the most recent model TSI 3783.

Optimisation of the operation regimes for the water-based condensation particle counter

A water-based condensation particle counter (CPC) TSI 3785 is a new step for the ultrafine particle measurement technique. A new instrument was examined in this study. Detection efficiency was investigated experimentally using different temperatures of the saturator and of the growth tube. The experiments showed that detection efficiency can be improved by increasing the temperature of the growth tube and decreasing the saturator temperature. Fitting a two-free parameter equation to the experimental data, the cut-sizes D50% were determined. The determined cut-sizes were comparable with the other three widely used fitting equations. The cut-sizes were studied by changing the growth tube temperature from 40 to 65 °C and varying the saturator temperature from 10 to 30 °C. For the purpose of the study, the instrument operation regime (saturator and growth tube temperatures) can be optimised by selecting the needed cut-size. The cut-sizes can be changed in a wide range. The smallest detected cut-size D50% was 4.2 nm, and the largest 14.6 nm. In the default operation regime, the instrument cut-size was 5.9 nm. The detection efficiency of the studied TSI CPC 3785 was compared with the ultrafine TSI CPC 3786. The results showed that the studied CPC can be optimised to the regime having a smaller cut-size than the cut-size of the ultrafine CPC in the default regime. Thus, the tested TSI CPC 3785 had the lowest detection limit (D50%) of 4.2 nm, and the TSI CPC 3786 had 4.6 nm for the silver particles.