Total Particle Mass Concentration Research Articles

Experimental studies on the particulate matter emission characteristics of a lateral swirl combustion system for direct injection diesel engines

To analyze the particulate emission characteristics of a lateral swirl combustion system (LSCS), experimental research on a single-cylinder diesel engine was done and compared against the Turbocharger-Charge Air Cooling-Diesel Particle Filter Series combustion system (TCDCS) at different conditions. Compared to the TCDCS, the LSCS presents better combustion performance and lower total particle emission characteristics: As for the LSCS, the vast majority of the particle number size distributions shifted downward, indicating a decrease in the particle number concentration. The total particle number and mass concentrations of the LSCS decreased by 8.7–62.4% and 15.2–55.6% at various loads. The number concentration of particles smaller than approximately 8 nm increased for the LSCS, which can be attributed to the higher temperature and more thorough fuel/air mixture, facilitating the oxidation of large particles into small particles. Combined with the simulation, the LSCS perfectly exerts the wall-flow-guided effect, remarkably improving the fuel/air mixing quality and reducing the local over-concentration regions, which can inhibit the formation of particles. Hence, the LSCS effectively reduces the particle number and mass concentrations, exhibiting excellent particulate emission characteristics.

Mobile measurements of atmospheric pollutant concentrations in the pollutant plume of BER airport

Recent research has demonstrated that airports are important emission sources for ultrafine particles (UFP) which may largely contribute to regional UFP number concentrations. However, in areas where multiple particle sources are present, the differentiation and the quantification of the contribution of aircraft emissions to ambient UFP is challenging. We present the results from a car-based mobile measurement campaign in the vicinity of the recently opened Berlin-Brandenburg airport (BER) in Germany. Total particle number concentrations (TNC), CO2, particle mass (PM) and equivalent black carbon (eBC) concentrations were measured downwind from the airport. TNC roughly followed an exponential decline with increasing distance to the airport, which was more pronounced during the measurement campaign in the fall than in the subsequent summer. Cluster analysis showed that airport emissions are dominated by elevated TNC concentrations (median elevation by 59%), while particle emissions from vehicle traffic coincided with increased CO2 and eBC concentrations. The airport emission cluster could be found up to approx. 7000 m distance to the central terminal building of the airport during the fall campaign. The real-world emission factors derived from the measurements indicate that aircrafts emit roughly eight times the number of particles per kg fuel than vehicle traffic. Overall, our study presents the effects of airport-related emissions onto the regional air quality downwind from the airport. To get further insights into the contribution percentage of airports to ambient UFP, studies on aerosol dispersion and dynamics modelling are needed.

Development of a job-exposure matrix (JEM) for exposure to smoke particle mass among firefighters of the Fire Department of the City of New York (FDNY)

ObjectivesA refined job exposure matrix (JEM) based on incident types and severities and response characteristics was developed for firefighters to estimate quantities of smoke particles emitted during structural and non-structural...

Aerosol concentrations and size distributions during clinical dental procedures

BackgroundSuspected aerosol-generating dental instruments may cause risks for operators by transmitting pathogens, such as the SARS-CoV-2 virus. The aim of our study was to measure aerosol generation in various dental procedures in clinical settings. MethodsThe study population comprised of 84 patients who underwent 253 different dental procedures measured with Optical Particle Sizer in a dental office setting. Aerosol particles from 0.3 to 10 μm in diameter were measured. Dental procedures included oral examinations (N = 52), restorative procedures with air turbine handpiece (N = 8), high-speed (N = 6) and low-speed (N = 30) handpieces, ultrasonic scaling (N = 31), periodontal treatment using hand instruments (N = 60), endodontic treatment (N = 12), intraoral radiographs (N = 24), and dental local anesthesia (N = 31). ResultsAir turbine handpieces significantly elevated <1 μm particle median (p = 0.013) and maximum (p = 0.016) aerosol number concentrations as well as aerosol particle mass concentrations (p = 0.046 and p = 0.006) compared to the background aerosol levels preceding the operation. Low-speed dental handpieces elevated >5 μm median (p = 0.023), maximum (p = 0.013) particle number concentrations,> 5 μm particle mass concentrations (p = 0.021) and maximum total particle mass concentrations (p = 0.022). High-speed dental handpieces elevated aerosol concentration levels compared to the levels produced during oral examination. ConclusionsAir turbine handpieces produced the highest levels of <1 μm aerosols and total particle number concentrations when compared to the other commonly used instruments. In addition, high- and low-speed dental handpieces and ultrasonic scalers elevated the aerosol concentration levels compared to the aerosol levels measured during oral examination. These aerosol-generating procedures, involving air turbine, high- and low-speed handpiece, and ultrasonic scaler, should be performed with caution. Clinical significanceAerosol generating dental instruments, especially air turbine, should be used with adequate precautions (rubber dam, high-volume evacuation, FFP-respirators), because aerosols can cause a potential risk for operators and substitution of air turbine for high-speed dental handpiece in poor epidemic situations should be considered to reduce the risk of aerosol transmission.

The effect of COVID-19 lockdown on atmospheric total particle numbers, nanoparticle numbers and mass concentrations in the UK

The main aim of the COVID-19 lockdown was to curtail the person-to-person transmission of COVID-19. However, it also acted as an air quality intervention. The effect of the lockdown has been extensively analysed on NO2, O3, PM10 and PM2.5, however, little has been done on how total (TPN) and nanoparticle numbers (NPN) have been affected by the lockdown. This paper quantifies the effect of the lockdown on TPN and NPN in the UK, and compares how the effect varies between rural, urban background and traffic sites. Furthermore, the effect on particle numbers is compared with particle mass concentrations, mainly PM10 and PM2.5. Two approaches are used: (a) comparing measured levels of the pollutants in 2019 with 2020 during the lockdown periods; and (b) comparing the predictions of machine learning with measured concentrations using business as usual (BAU) scenario during the lockdown period. P100 (particle size ≤100 nm) increased by 39% at Chilbolton Observatory (CHO) and decreased by 13% and 14% at London Honor Oak Park (LHO) and London Marylebone Road (LMR), respectively. Particles from 101 to 200 nm (P200) showed a similar trend to P100, however, average levels of particles 201–605 nm (P605) decreased at all sites. TPN, PM10 and PM2.5 concentrations decreased at LMR and LHO sites. Estimated PM10, PM2.5 and TPN decreased at all three sites, however, the amount of change varied from site to site. Pollutant concentrations increased back the to pre-pandemic levels, suggesting more sustainable interventions for permanent air quality improvement.

Impact of engine oil volatility and viscosity on blow-by aerosol formation

AbstractParticulate emissions from diesel engines are a matter of public concern and continued industrial development. For an internal combustion engine, particles may originate either from the after treatment box or from the crankcase ventilation system. This paper quantifies and discusses particle sources within the crankcase ventilation system of a medium-duty 4-cylinder and a heavy-duty 6-cylinder engine and their dependence on the engine oil parameters viscosity (expressed as Noack number) and HTHS volatility. Crankcase aerosol spectra were measured by an optical particle counter in the size range of 0.3–5 µm. For a few cases data of filter samples downstream the separator unit are discussed for the total blow-by aerosol. Engines were found to behave very similarly with regard to changes in either oil parameter, with volatility generally being the far stronger factor of influence. Total particle mass concentration increased by a factor of up to 5 for a rise in Noack volatility of about 13–25%. The mass concentration downstream of the separator also increases with oil volatility. A variation of HTHS viscosity from 3.5 to 2.6 mPas generated a marginal change in aerosol output by a factor of about 1.2. However, and unexpectedly, the most viscose oil generated the relatively highest particle mass concentrations for both engines.

Assessing the value of complex refractive index and particle density for calibration of low-cost particle matter sensor for size-resolved particle count and PM2.5 measurements.

Low-cost optical scattering particulate matter (PM) sensors report total or size-specific particle counts and mass concentrations. The PM concentration and size are estimated by the original equipment manufacturer (OEM) proprietary algorithms, which have inherent limitations since particle scattering depends on particles' properties such as size, shape, and complex index of refraction (CRI) as well as environmental parameters such as temperature and relative humidity (RH). As low-cost PM sensors are not able to resolve individual particles, there is a need to characterize and calibrate sensors' performance under a controlled environment. Here, we present improved calibration algorithms for Plantower PMS A003 sensor for mass indices and size-resolved number concentration. An aerosol chamber experimental protocol was used to evaluate sensor-to-sensor data reproducibility. The calibration was performed using four polydisperse test aerosols. The particle size distribution OEM calibration for PMS A003 sensor did not agree with the reference single particle sizer measurements. For the number concentration calibration, the linear model without adjusting for the aerosol properties and environmental conditions yields an absolute error (NMAE) of ~ 4.0% compared to the reference instrument. The calibration models adjusted for particle CRI and density account for non-linearity in the OEM's mass concentrations estimates with NMAE within 5.0%. The calibration algorithms developed in this study can be used in indoor air quality monitoring, occupational/industrial exposure assessments, or near-source monitoring scenarios where field calibration might be challenging.

Regeneration performance and particulate emission characteristics during active regeneration process of GPF with ash loading

The deposited ash has an important effect on the regeneration of GPF, this paper aims to study the effects of ash particle size and loading on particle emission characteristics. The results indicates that the deposited carbon black particles are easy to be blown out during heating stage and local high temperature leads to 3 orders of magnitude of emitted particles during regeneration stage. The pure Al2O3 ash#1 (2 μm) inhibit the release of particles during heating stage and also promotes regeneration efficiency, resuliting in high total emitted particle mass concentration during regeneration stage. While the impacts of the pure Al2O3 ash#2 (15 μm) is opposite to ash#1. As the loading of mixed particle Al2O3 + SiO2 ash#3 (low thermal conductivity) increases from 5 g/L to 15 g/L, particles are more likely to be blown out because of the coupling of the ash layer and filter wall, and the exhaust particles at GPF outlet also decrease, mainly distributing in large-size aggregated particles (50–100 nm) during the regeneration stage.

Smoke Particle, Polycyclic Aromatic Hydrocarbons and Total Benzo[a]pyrene Toxic Equivalence Emitted by Palm Oil Sewage Sludge Bio-Char Combustion

The size distribution, total particle mass concentration (TPMC), polycyclic aromatic hydrocarbons (PAHs) value, and total Benzo[a]pyrene Toxic Equivalence (BaPTE) concentration of smoke particles from palm oil sewage sludge (POSS) bio-char combustion were studied. In this experiment, temperature data of the POSS bio-char combustion were recorded in two parts: particle temperature (Tp) by using a two-color pyrometer and temperature at 300, 500 and 800 mm, respectively, above the fire base by using K-type thermocouples. The POSS bio-char moisture content, clean air speed values, and burning period affected the change of temperature above the fire base. The mass median aerodynamic diameter (MMAD) values of the POSS bio-char combustion were found to be 0.44 to 1.05 micron at various moisture contents and burning periods. The MMAD, TPMC, and PAHs values increased with increasing moisture content and decreased the POSS bio-char combustion period. For the total BaPTE values, the results showed that the decrease in moisture content of the POSS bio-char samples had a prime influence in decreasing the total BaPTE values. Meanwhile, with decreases in the clean air speed values, the total BaPTE values were increased. Comparing the total BaPTE data between the experimental results and predicted values, the first-degree model had a better fit in predicting than the zero-degree model; this result was confirmed by the higher mean of the coefficient of determination.

Development of a real-time total suspended particle mass concentration measurement system based on light scattering for monitoring fugitive dust in construction sites

In this paper, to monitor fugitive dust in construction sites, we propose a portable and inexpensive measurement system that can accurately measure the mass concentration of the total suspended particles (TSPs, that is, particles smaller than 50 μ m) in real time. The proposed system can measure the real-time mass concentration of the TSPs, which cannot be measured by conventional mass concentration measurement devices. It has four components: (1) particle collection section, (2) temperature and humidity measurement section, (3) particle measurement section, and (4) signal-processing circuit. When particles of different sizes reach the proposed system, they are selectively collected based on their size in the collection section. Thereafter, the collected particles reach the particle measurement section via the temperature and humidity measurement section. The particles are detected in the particle measurement section, and the mass concentration is calculated in the signal-processing circuit. Further, we analyzed the characteristics of each section, and the measurement results of the proposed system were compared using a filter-based gravity method. The calculated mass concentration of the TSPs corresponds to the results measured obtaining using the filter-based gravity method. Moreover, field test results indicate that the proposed system was successfully applied in construction sites.

Prediction of Size Distribution and Mass Concentration of Smoke Particles on Moisture Content and Combustion Period from Para Rubber Wood Burning

The size distribution and total particle mass concentration (TPMC) of smoke particles from para rubber wood (Hevea brasiliensis) combustion in the ribbed smoked sheet (RSS) process were studied. In this experiment, temperature data values of para rubber wood combustion were recorded at 500 mm above the base of the fire by K-type thermocouples. The wood moisture content and wood combustion period were used to find and improve an equation of smoke particle size distribution (SPSD) and TPMC by the response surface method (RSM). An eight-stage Andersen air sampler and a high-volume sampler were used to measure and calculate SPSD and TPMC, respectively. Resulting data in this experiment showed that TPMC ranged from 3.12 to 77.42 mg/m3. SPSD was single mode in which MMAD, mass median aerodynamic diameter, ranged from 0.64 to 1.27 microns for para wood with moisture content ranging from 31.5 to 89.7% dry weight basis. The combustion period and moisture content of para wood have a direct effect on the change of temperature data above the base of the fire and the TPMC and MMAD values. For predicting TPMC and MMAD values by the para wood moisture contents in each combustion period, the results found that the second-degree model was a better plot than the first-degree model, confirmed by higher values of the coefficient of determination (R2).

Measurement report: Firework impacts on air quality in Metro Manila, Philippines, during the 2019 New Year revelry

Abstract. Fireworks degrade air quality, reduce visibility, alter atmospheric chemistry, and cause short-term adverse health effects. However, there have not been any comprehensive physicochemical and optical measurements of fireworks and their associated impacts in a Southeast Asia megacity, where fireworks are a regular part of the culture. Size-resolved particulate matter (PM) measurements were made before, during, and after New Year 2019 at the Manila Observatory in Quezon City, Philippines, as part of the Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex). A high-spectral-resolution lidar (HSRL) recorded a substantial increase in backscattered signal associated with high aerosol loading ∼440 m above the surface during the peak of firework activities around 00:00 (local time). This was accompanied by PM2.5 concentrations peaking at 383.9 µg m−3. During the firework event, water-soluble ions and elements, which affect particle formation, growth, and fate, were mostly in the submicrometer diameter range. Total (&gt;0.056 µm) water-soluble bulk particle mass concentrations were enriched by 5.7 times during the fireworks relative to the background (i.e., average of before and after the firework). The water-soluble mass fraction of PM2.5 increased by 18.5 % above that of background values. This corresponded to increased volume fractions of inorganics which increased bulk particle hygroscopicity, kappa (κ), from 0.11 (background) to 0.18 (fireworks). Potassium and non-sea-salt (nss) SO42- contributed the most (70.9 %) to the water-soluble mass, with their mass size distributions shifting from a smaller to a larger submicrometer mode during the firework event. On the other hand, mass size distributions for NO3-, Cl−, and Mg2+ (21.1 % mass contribution) shifted from a supermicrometer mode to a submicrometer mode. Being both uninfluenced by secondary aerosol formation and constituents of firework materials, a subset of species were identified as the best firework tracer species (Cu, Ba, Sr, K+, Al, and Pb). Although these species (excluding K+) only contributed 2.1 % of the total mass concentration of water-soluble ions and elements, they exhibited the highest enrichments (6.1 to 65.2) during the fireworks. Surface microscopy analysis confirmed the presence of potassium/chloride-rich cubic particles along with capsule-shaped particles in firework samples. The results of this study highlight how firework emissions change the physicochemical and optical properties of water-soluble particles (e.g., mass size distribution, composition, hygroscopicity, and aerosol backscatter), which subsequently alters the background aerosol's respirability, influence on surroundings, ability to uptake gases, and viability as cloud condensation nuclei (CCN).

Experimental and numerical study on flow, combustion and emission characteristics of CI engine fueled with n-butanol/diesel blends under post-injection strategy

Since the technology of n-butanol/diesel blending fuel coupled with post-injection (PI) strategy increases the complexity of engine combustion process, the disputes that the interpretation of the formation mechanism of pollutants are still existed. Moreover, studies on the effects of this coupling-strategy on fine-particles (DP < 25 nm) have not been carried out. Therefore, this paper first adopts an experimental approach to study the macroscopic effects of the coupling-strategy on commercial engines, especially the change of fine-particles is analyzed. Then, the influence mechanism of coupling-strategy on atomization, combustion and pollutant generation is clarified by revealing the difference between intermediate products and combustion variables by using simulation method. The results show that the mixture has the higher evaporation rate and smaller SMD, and the PI strategy significantly increases the velocity and turbulent kinetic energy of gas in terms of atomization and flow. In terms of combustion, the brake thermal efficiency of D100 reaches 36.9% when the PI rate is 25%. About conventional emissions, the coupling-strategy reduces CO emissions by enhancing the CO + OH = CO2 + H reaction process. In addition, both blending fuel and PI strategy reduce soot precursors A1 and A4. Especially, the PI strategy increases the oxidation of soot by enhancing air entrainment. In terms of particulate emissions, the coupling-strategy reduces aggregation mode particles and total particulate mass concentration, but result in a higher proportion of fine-particles.

Vaporization characteristics and aerosol optical properties of electronic cigarettes.

The aerosols generated from electronic cigarettes have a significant impact on the human respiratory system. Understanding the vaporization characteristics and aerosol optical properties of electronic cigarettes is important for assessing human exposure to aerosols. An experimental platform was designed and built to simulate the atomization process of electronic cigarette and detect the laser transmissivity of aerosols. The optical properties of single particles and polydispersed particle system for aerosols in the visible wavelength ranges of 400-780nm were analyzed based on Mie theory. The results show that a higher heating power supplied by coil results in a larger average vaporization rate of e-liquid. Meanwhile, the steady-state transmissivity of the laser beam for aerosols reduces as the heating power increases. Under the same heating power and puffing topography, the total particulate mass (TPM) of aerosols generated by the e-liquid composed of higher vegetable glycerin (VG) content decreases. The scattering efficiency factor of aerosol particle of electronic cigarette increases with an increase in particle size. The volume scattering coefficients of a polydispersed particle system of aerosols decrease as the incident visible wavelengths increase. A higher VG content in e-liquid results in decreased TPM and particle number concentration of aerosols and increased the volume scattering coefficient in the visible wavelength range. It can explain an interesting phenomenon that a lower TPM and a better visual effect brought by the aerosols generated by the e-liquid with a higher VG content could be observed concurrently. The mass indexes (e.g., TPM, average vaporization rate, average mass concentration) and optical indexes (e.g., volume scattering coefficient, laser transmissivity) are suggested to be used for the comprehensive evaluation of relative amounts of aerosols. The results have potential significances for the objective and quantitative assessments of aerosols generated from electronic cigarettes.

Ambient nitro-aromatic compounds – biomass burning versus secondary formation in rural China

Abstract. Nitro-aromatic compounds (NACs) were measured hourly at a rural site in China during wintertime to monitor the changes due to local and regional impacts of biomass burning (BB). Concurrent and continuous measurements of the concentrations of 16 NACs in the gas and particle phases were performed with a time-of-flight chemical ionization mass spectrometer (CIMS) equipped with a Filter Inlet for Gases and AEROsols (FIGAERO) unit using iodide as the reagent ion. NACs accounted for &lt;2 % of the mass concentration of organic matter (OM) and total particulate matter (PM), but the total particle mass concentrations of these compounds can reach as high as 1000 ng m−3 (299 ng m−3 avg), suggesting that they may contribute significantly to the radiative forcing effects of atmospheric particles. Levels of gas-phase NACs were highest during the daytime (15:00–16:00 local time, LT), with a smaller night-time peak around 20:00 LT. Box-model simulations showed that this occurred because the rate of NAC production from gas-phase sources exceeded the rate of loss, which occurred mainly via the OH reaction and to a lesser degree via photolysis. Data gathered during extended periods with high contributions from primary BB sources (resulting in 40 %–60 % increases in NAC concentrations) were used to characterize individual NACs with respect to gas–particle partitioning and the contributions of regional secondary processes (i.e. photochemical smog). On days without extensive BB, secondary formation was the dominant source of NACs, and NAC levels correlated strongly with the ambient ozone concentration. Analyses of individual NACs in the regionally aged plumes sampled on these days allowed precursors such as phenol and catechol to be linked to their NAC derivatives (i.e. nitrophenol and nitrocatechol). Correlation analysis using the high time resolution data and box-model simulation results constrained the relationships between these compounds and demonstrated the contribution of secondary formation processes. Furthermore, 13 of 16 NACS were classified according to primary or secondary formation process. Primary emission was the dominant source (accounting for 60 %–70 % of the measured concentrations) of 5 of the 16 studied NACs, but secondary formation was also a significant source. Photochemical smog thus has important effects on brown carbon levels even during wintertime periods dominated by primary air pollution in rural China.

Experimental and numerical study on the effect of single-hydroxybenzene/n-heptane blends on engine combustion and particulate emissions

Understanding the influence of the primary components of diesel on engine combustion and emissions is essential to the construction of a model diesel fuel. In this study, straight-chain alkanes in diesel are represented by n-heptane, and aromatic hydrocarbons are represented by toluene, n-butylbenzene, and 1,2,4-trimethylbenzene. The effect of single-hydroxybenzene/n-heptane blended fuel on engine performance and particle emission characteristics is studied experimentally and by simulation to identify an optimal composition for a model diesel fuel. The test fuels were pure diesel (D100) and single-hydroxybenzene/n-heptane blends (toluene, n-butylbenzene and 1,2,4-trimethylbenzene each of which was added to n-heptane at a volume ratio of 20% (T20, BBZ20, TMB20) or 30% (T30, BBZ30, TMB30)). The results show that as the EGR rate increases, the total particle number concentration (TPNC), particle size distribution concentration (PSDC), total particle mass concentration (TPMC), and particle geometric mean diameter (PGMD) increase. The peak heat release rate (HRR) and peak in-cylinder pressure (IP) of single-hydroxybenzene/n-heptane are higher than those of D100; however, the values of PSDC, TPNC, TPMC, and PGMD are lower than those of D100. Among the tested fuels, the effects of n-butylbenzene/n-heptane blend on engine performance and particle emission characteristics are closest to D100. The spatial distribution of temperature field, equivalent ratio, OH-groups and NO of BBZ20 are close to that of D100. The n-butylbenzene/n-heptane fuel is suitable for modeling diesel, particularly when the addition ratio of n-butylbenzene is 20%, the combustion and emission characteristics are the closest to those of D100.

Characterization of User PM Exposure During the Application of Aerosol Mineral-Based Sunscreens Shows Minimal Risk

This study characterizes particles emitted from three commercial sunscreen sprays with a sun protection factor (SPF) of 30. Sample collection and measurement were made at 20 cm longitudinally and 36 cm laterally from the emission point to simulate the point of inhalation for an application on one’s arm. Over 85% of all particles by count had a diameter of less than 100 nm. The three products had a mass median diameter of 0.65 µm, 1.40 µm, and 1.70 µm, respectively. The collected aerosols in the breathing zone from application of the sunscreen sprays with TiO2 and ZnO contained less than advertised. The product containing only TiO2 as active ingredient generated aerosols with a higher mass fraction of TiO2. The total particle mass concentrations of the sunscreens were 0.77 µg/m3, 0.57 µg/m3, and 0.80 µg/m3, respectively. The PM2.5 mass concentrations were 0.45 µg/m3, 0.30 µg/m3, and 0.37 µg/m3, respectively. The estimated mass concentrations for total particles, PM2.5, TiO2, ZnO, and SiO2 did not exceed the regulatory limits by the Occupational Health and Safety Administration (OSHA) or the recommended limits by the National Institute for Occupational Safety and Health (NIOSH), meaning 8-h daily average exposures at these levels throughout a typical career would comply with current regulations. Consequently, applying the three sunscreen sprays does not pose a significant hazard via respiratory exposure under these conditions, and considering the transient and relatively infrequent use by most consumers, a substantial factor of safety exists.

Effect of dimethoxymethane (DMM) additive on combustion and emission characteristics under different working conditions in CI engines

Dimethoxymethane (DMM) is considered a potential oxygenated fuel due to its high oxygen content (42.1%) and considerable heat value. However, little research emphasizes the impact of oxygenated fuels on small-particles (DP < 25 nm), which is harmful for human beings. In this investigation, the effect of DMM-diesel mixture on combustion and emission characteristics of a four-cylinder commercial CI engine is studied under normal working speeds and loads. Especially, the influence of DMM-diesel fuels on PMs included small-particles is analyzed comprehensively. The results show that the brake thermal efficiency (BTE) of DMM13 and DMM6.4 fuels increases by 1.06% and 0.4%, respectively, compared with that of D100 at the condition of 1400 rpm and 1.0 MPa. In terms of emission, the soot emission of DMM13 is reduced by 46% with respect to that of D100 at the condition of 0.6 MPa and 1400 rpm. Meanwhile, with the addition of DMM13, the peak particle number concentration (PNC) drops significantly, but increasing the proportion of small-particles. Moreover, the lowest total particle mass concentration (TPMC) is obtained as well. Substantially, DMM-diesel blends can realize the balance between low total particle number concentration (TPNC) and small geometric mean diameter (GMD).

Multi-year ACSM measurements at the central European research station Melpitz (Germany) – Part 1: Instrument robustness, quality assurance, and impact of upper size cutoff diameter

Abstract. The aerosol chemical speciation monitor (ACSM) is nowadays widely used to identify and quantify the main components of fine particles in ambient air. As such, its deployment at observatory platforms is fully incorporated within the European Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS). Regular intercomparisons are organized at the Aerosol Chemical Monitoring Calibration Center (ACMCC; part of the European Center for Aerosol Calibration, Paris, France) to ensure the consistency of the dataset, as well as instrumental performance and variability. However, in situ quality assurance remains a fundamental aspect of the instrument's stability. Here, we present and discuss the main outputs of long-term quality assurance efforts achieved for ACSM measurements at the research station Melpitz (Germany) since 2012 onwards. In order to validate the ACSM measurements over the years and to characterize seasonal variations, nitrate, sulfate, ammonium, organic, and particle mass concentrations were systematically compared against the collocated measurements of daily offline high-volume PM1 and PM2.5 filter samples and particle number size distribution (PNSD) measurements. Mass closure analysis was made by comparing the total particle mass (PM) concentration obtained by adding the mass concentration of equivalent black carbon (eBC) from the multi-angle absorption photometer (MAAP) to the ACSM chemical composition, to that of PM1 and PM2.5 during filter weighing, as well as to the derived mass concentration of PNSD. A combination of PM1 and PM2.5 filter samples helped identifying the critical importance of the upper size cutoff of the ACSM during such exercises. The ACSM–MAAP-derived mass concentrations systematically deviated from the PM1 mass when the mass concentration of the latter represented less than 60 % of PM2.5, which was linked to the transmission efficiency of the aerodynamic lenses of the ACSM. The best correlations are obtained for sulfate (slope =0.96; R2=0.77) and total PM (slope =1.02; R2=0.90). Although, sulfate did not exhibit a seasonal dependency, total PM mass concentration revealed a small seasonal variability linked to the increase in non-water-soluble fractions. The nitrate suffers from a loss of ammonium nitrate during filter collection, and the contribution of organo-nitrate compounds to the ACSM nitrate signal make it difficult to directly compare the two methods. The contribution of m∕z 44 (f44) to the total organic mass concentration was used to convert the ACSM organic mass (OM) to organic carbon (OC) by using a similar approach as for the aerosol mass spectrometer (AMS). The resulting estimated OCACSM was compared with the measured OCPM1 (slope =0.74; R2=0.77), indicating that the f44 signal was relatively free of interferences during this period. The PM2.5 filter samples use for the ACSM data quality might suffer from a systematic bias due to a size truncation effect as well as to the presence of chemical species that cannot be detected by the ACSM in coarse mode (e.g., sodium nitrate and sodium sulfate). This may lead to a systematic underestimation of the ACSM particle mass concentration and/or a positive artifact that artificially decreases the discrepancies between the two methods. Consequently, ACSM data validation using PM2.5 filters has to be interpreted with extreme care. The particle mass closure with the PNSD was satisfying (slope =0.77; R2=0.90 over the entire period), with a slight overestimation of the mobility particle size spectrometer (MPSS)-derived mass concentration in winter. This seasonal variability was related to a change on the PNSD and a larger contribution of the supermicrometer particles in winter. This long-term analysis between the ACSM and other collocated instruments confirms the robustness of the ACSM and its suitability for long-term measurements. Particle mass closure with the PNSD is strongly recommended to ensure the stability of the ACSM. A near-real-time mass closure procedure within the entire ACTRIS–ACSM network certainly represents an optimal quality control and assurance of both warranting the quality assurance of the ACSM measurements as well as identifying cross-instrumental biases.

Composite In Situ Microphysical Analysis of All Spiral Vertical Profiles Executed within BAMEX and PECAN Mesoscale Convective Systems

AbstractVertical profiles of temperature, relative humidity, cloud particle concentration, median mass dimension, and mass content were derived using instruments on the NOAA P-3 aircraft for 37 spiral ascents/descents flown within five mesoscale convective systems (MCSs) during the 2015 Plains Elevated Convection at Night (PECAN) project, and 16 spiral descents of the NOAA P-3 within 10 MCSs during the 2003 Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX). The statistical distribution of thermodynamic and microphysical properties within these spirals is presented in context of three primary MCS regions—the transition zone (TZ), enhanced stratiform rain region (ESR), and the anvil region (AR)—allowing deductions concerning the relative importance and nature of microphysical processes in each region. Aggregation was ubiquitous across all MCS zones at subfreezing temperatures, where the degree of ambient subsaturation, if present, moderated the effectiveness of this process via sublimation. The predominately ice-supersaturated ESR experienced the least impact of sublimation on microphysical characteristics relative to the TZ and AR. Aggregation was most limited by sublimation in the ice-subsaturated AR, where total particle number and mass concentrations decreased most rapidly with increasing temperature. Sublimation cooling at the surface of ice particles in the TZ, the driest of the three regions, allowed ice to survive to temperatures as high as +6.8°C. Two spirals executed behind a frontal squall line exhibited a high incidence of pristine ice crystals, and notably different characteristics from most other spirals. Gradual meso- to synoptic-scale ascent in this region likely contributed to the observed differences.