Search

Aircraft gas turbine engines produce Particulate Matter (PM) emissions that have been linked to human health and climate issues, leading to the introduction of regulatory sampling and measurement standards for nonvolatile PM (nvPM) by the International Civil Aviation Organization (ICAO). Due to the significant nvPM losses within the prescribed sampling systems, loss corrections are used. Currently, based on sampling assumptions, electrostatic losses are not included in the standardized loss tool, as it is estimated to account for less than 3% of the total nvPM loss. This study experimentally investigated electrostatic loss of unipolar, bipolar, and naturally charged salt, silver, and carbon black particles at sizes (4–150 nm) and through sampling tubes representative of aircraft nvPM sampling. A unipolar and bipolar charger, along with a tandem SMPS-CPC measurement methodology, were employed to explore the impacts of tube material, Reynolds Number, tube diameter, residence time, and particle charge state on electrostatic loss. Minimal electrostatic loss was measured for conductive stainless steel and extensively bedded-in (above 300 h) carbon-loaded PTFE. However, an additional loss of up to 50% was observed within new cPTFE (with approximately 30 min of bedding-in), attributed to precipitation in an electric field. Furthermore, it was found that electrostatic dispersion could cause significant additional losses at high concentrations of unipolar or bipolar asymmetrically charged particles. Therefore, further research is required to determine the charge state of aircraft nvPM across different aircraft engine conditions to determine if unquantified electrostatic loss could occur within the probe section of the sampling system. [ABSTRACT FROM AUTHOR]

Madrid–Barajas Airport (MAD) is the fourth-busiest airport in Europe. The aerosol chemical composition and the concentrations of other key pollutants were measured at the airport perimeter during October 2021 to assess the impact of airport emissions on local air quality. A high-fidelity ambient instrumentation system was deployed at Madrid–Barajas Airport to measure the following: concentrations of organic aerosols (with their composition), black carbon (eBC), carbon dioxide (CO2), carbon monoxide (CO), nitrogen dioxide (NOx), sulfur dioxide (SO2), particulate matter (PM 2.5 , PM 10), total hydrocarbon (THC), and total particle number. The average concentrations of eBC, NOx , SO2 , PM 2.5 , PM 10 , CO, and THC at the airport for the entire campaign were 1.07 µgm-3 , 22.7 µgm-3 , 4.10 µgm-3 , 9.35 µgm-3 , 16.43 µgm-3 , 0.23 mgm-3 , and 2.30 mgm-3 , respectively. The source apportionment analysis of the non-refractory organic aerosol (OA) using positive matrix factorisation (PMF) allowed us to discriminate between different sources of pollution, namely less oxidised oxygenated organic aerosol (LO-OOA), alkane organic aerosol (AlkOA), and more oxidised oxygenated organic aerosol (MO-OOA). The results showed that LO-OOA and MO-OOA account for more than 80 % of the total organic particle mass measured near the runway. Trace gases correlate better with the AlkOA factor than LO-OOA and MO-OOA, indicating that AlkOA is mainly related to primary combustion emissions. Bivariate polar plots were used for pollutant source identification. Significantly higher concentrations of the obtained factors were observed at low wind speeds (<3 ms-1) from the southwest, where two of the runways and all terminals are located. Higher SO2/NOx and CO/eBC ratios were observed when the winds originated from the northeast, where the two northern runways are located. These elevated ratios are attributed to the aircraft activity being the major pollutant source in the northeast area. [ABSTRACT FROM AUTHOR]

Madrid-Barajas International Airport (MAD), located in Spanish Capital Madrid, is the fourth-busiest airport in Europe. As part of the AVIATOR campaign, chemical composition of particulate matter and other key pollutants were measured at the airport perimeter during October 2021, to assess the impact of airport emissions on local air quality. A high-fidelity ambient instrumentation system was deployed at Madrid Airport to measure: composition of ambient aerosol and concentrations of black carbon (eBC), carbon dioxide (CO2) carbon monoxide (CO), nitrogen dioxide (NOx), sulphur dioxide (SO2), particulate matter (PM2.5, PM10), total hydrocarbon (THC), and total particle number. The average concentration for the entire campaign of eBC, NOx, SO2, PM2.5, PM10, CO and THC at the airport were, 1.07 (μg/m³), 22.7 (μg/m³), 4.10 (μg/m³), 9.35 (μg/m³), 16.43 (μg/m³), 0.23 (mg/m³) and 2.30 (mg/m³) respectively. The source apportionment analysis of the non-refractory organic aerosol (OA) using positive matrix factorisation (PMF) allowed us to discriminate between different sources of pollution, namely: Semi Volatile Oxygenated Organic Aerosol (SV-OOA), Alkane Organic Aerosol (AlkOA), and More Oxidised Oxygenated Organic Aerosol (MO-OOA) source. The results showed that SVOOA and MO-OOA accounts for more than 80% of the total organic particle mass that was measured near runway at the airport. Trace gases correlate better with AlkOA factor more than SVOOA and MO-OOA which indicate that AlkOA is mainly related to the primary emissions of combustion. Bivariate polar plots were used for the source identification. Significantly higher concentrations of the obtained factors were observed at low wind speeds < 3m/s from the southwest where two of runways, as well as all terminals are located. Higher SO2/NOx and CO/eBC ratios were observed when the winds originating from the northeast where the 18L/36R runways are located. This is attributed to the aircraft influence and the lack of a local road source in the northeast area. [ABSTRACT FROM AUTHOR]

Dynamic domain observations have been made using a high-magnification Kerr microscope in combination with a high-speed light-intensified CMOS camera. Results have demonstrated nonrepeatable domain wall motion in electrical steel and amorphous ribbon at 1 and 50-Hz magnetizing frequencies. Index Terms--Amorphous ribbon, electrical steel, magnetic domains, magneto-optic Kerr microscopy.

Seasonal biomass burning (BB) over West Africa is a globally significant source of carbonaceous particles in the atmosphere, which have important climate impacts but are poorly constrained. Here, the evolution of smoke aerosols emitted from flaming-controlled burning of agricultural waste and wooded savannah in the Senegal region was characterized over a timescale of half-day advection from source during the MOYA-2017 (Methane Observation Yearly Assessment-2017) aircraft campaign. Plumes from such fire types are rich in black carbon (BC) emissions. Concurrent measurements of chemical composition, organic aerosol (OA) oxidation state, bulk aerosol size and BC mixing state reveal that emitted BB submicron aerosols changed dramatically with time. Various aerosol optical properties (e.g., absorption Ångström exponent (AAE), and mass absorption coefficients (MAC)) also evolved with ageing. In this study, brown carbon (BrC) was a minor fractional component of the freshly emitted BB aerosols (< 0.5 h), but the increasing AAE with particle age indicates that BrC formation dominated over any loss process over the first ~12 hours of plume transport. Using different methods, the fractional contribution of BrC to total aerosol absorption showed an increasing trend with time and was ~18-31 % at the optical wavelength of 405 nm after half-day transport. The generated BrC was found to be positively correlated with oxygenated and low-volatility OA, likely from the oxidation of evaporated primary OA and secondary OA formation. We found that the evolution of BrC with particle age was different in this region compared with previous BB field studies that mainly focused on emissions from smouldering fires, which have shown a high contribution from BrC at source and BrC net loss upon ageing. This study suggests an initial stage of BrC absorption enhancement during the evolution of BB smoke. Secondary processing is the dominant contributor to BrC production in this BB region, in contrast to the primary emission of BrC previously reported in other BB studies. The total aerosol absorption normalized to BC mass (MACmeas-BC) was also enhanced with ageing, due to the lensing effect of increasingly thick coatings on BC and the absorption by BrC. The effect of ageing on aerosol absorption, represented by the absorption enhancement (EAbs-MAC), was estimated over timescales of hours. MOYA-2017 provides novel field results. The comparisons between MOYA-2017 and previous field studies imply that the evolution of absorbing aerosols (BC and BrC) after emission vary with source combustion conditions. Different treatments of absorbing aerosol properties and their evolution in different types of fires should be considered when modelling regional radiative forcing. These observational results will be very important for predicting climate effects of BB aerosol in regions controlled by flaming burning of agricultural waste and savannah-like biomass fuels. [ABSTRACT FROM AUTHOR]

Atmospheric aerosol particles are known to have detrimental effects on human health and climate. Black carbon is an important constituent of atmospheric aerosol particulate matter (PM), emitted from the incomplete combustion process and cause significant effects on the air quality and human health. Source apportionment of BC is very important, to identify the fraction of BC that has an anthropogenic origin and to evaluate the influence of different sources. The High-Resolution Soot Particle Aerosol Mass Spectrometer (HR-SP-AMS) instrument uses a laser vaporizer, which allows the real-time detection and characterization of refractory BC and its internally mixed particles such as metals, coating species and rBC subcomponent in the form of fullerene. In this case study, the soot data was collected by using HR-SP-AMS during Guy Fawkes Night on 5th of November 2014. Positive matrix factorization (PMF) was applied in order to positively discriminate between different wood-burning sources for the first time, in this case, BC from domestic wood-burning and bonfires, which no existing black carbon source apportionment technique is currently able to do. Along with this, the use of the fullerene signals in differentiating between soot sources and the use of metals as a tracer for fireworks has also been investigated, which has not significantly contributed to the BC concentrations. The addition of fullerenes signals and successful application of PMF on SP-AMS data apportioned BC into more than two sources. These bonfire sources are hydrocarbon-like Fullerenes, biomass burning organic aerosol, HULIS (humic-like substance) and non-bonfire sources such as hydrocarbon-like OA and domestic burning. The result of correlation analysis between HR-SP-AMS data with previously published Aethalometer, MAAP and CIMS data provides an effective way of quickly gaining insights in relations between the variables and also provide a quantitative estimate of the source contributions to the BC budget during this period. This research study is an important demonstration of using HR-SP-AMS for the purpose of BC source apportionment. [ABSTRACT FROM AUTHOR]

Seasonal biomass burning (BB) from June to October in central and southern Africa leads to absorbing aerosols being transported over the south Atlantic Ocean every year, and contributes significantly to the regional climate forcing. The vertical distribution of submicron aerosols and their properties were characterized over the remote southeast Atlantic for the first time, using airborne in-situ measurements made during the CLoud-Aerosol-Radiation Interactions and Forcing for Year 2017 (CLARIFY-2017) campaign. BB aerosols were intensively observed in the region surrounding Ascension Island, in the marine boundary layer (MBL) and free troposphere (FT) up to 5 km. We show that the aerosols had undergone a significant aging process during > 7 days transit from source, as indicated by highly oxidized organic aerosol and thickly coated black carbon (BC). The highly aged BB aerosols in the CLARIFY region were also especially rich in BC compared with those from other regions. We also found significant vertical variation in the single scattering albedos (SSA) of these aerosols, as a function of relative chemical composition and size. The lowest SSA was generally in the low FT layer around 2000 m altitude (medians: 0.83 at 405 nm and 0.80 at 658 nm). This finding is important since it means that BB aerosols across the east Atlantic region are more absorbing than is currently represented in climate models. Furthermore, in the FT, we show that SSA increased with altitude and this was associated with an enhanced inorganic nitrate mass fraction and aerosol size. This likely results from increased partitioning to the existing particles at higher altitude with lower temperature and higher relative humidity. After entrainment into the BL, aerosols were generally smaller in size than were observed in the FT, and had a larger fraction of scattering material with resultant higher average dry SSA, mostly due to marine emissions and aerosol removal by drizzle. Our results provide unique observational constraints on aerosol parameterizations used in modelling regional radiation interactions over this important region. We recommend that future work should consider the impact of this vertical variability on climate models. [ABSTRACT FROM AUTHOR]

Methane emission fluxes from facility-scale sources may be poorly quantified, leading to uncertainties in the global methane budget. Accurate atmospheric measurement based flux quantification is urgently required to address this. This paper describes the test of a new near-field Gaussian plume inversion (NGI) technique, suitable for facility-scale flux quantification, using a controlled release of methane gas. Two unmanned aerial vehicle (UAV) platforms were used to perform 22 flight surveys downwind of a point-source release of methane gas from a regulated and flow-metered cylinder. One UAV was tethered to an instrument on the ground, while the other UAV carried an on-board high-precision prototype instrument, both of which used the same near-infrared laser technology. The performance of these instruments from UAV sampling is described. Both instruments were calibrated using certified standards, to account for variability in the instrumental gain factor. Furthermore, a modified approach to correcting for the effect of water vapour applied and is described here in detail. The NGI technique was used to derive emission fluxes for each UAV flight survey. We found good agreement of most NGI fluxes with the known controlled emission flux, within uncertainty, verifying the flux quantification methodology. The lower NGI flux uncertainty bound was, on average, 17 % ± 10(1σ) % of the controlled emission flux and the upper NGI flux uncertainty bound was, on average, 218 % ± 100(1σ) % of the controlled emission flux. These highly conservative uncertainty ranges incorporate factors including the variability in the position of the plume and the potential for under-sampling. While these average uncertainties are large compared to methods such as tracer dispersion, we suggest that UAV sampling can be highly complementary to a toolkit of flux approaches and may perform well in situations where site access for tracer release is problematic. We see tracer release applied to UAV sampling as an effective combination in future flux quantification studies. Successful flux quantification using this UAV sampling methodology demonstrates its future utility in identifying and quantifying emissions from methane sources such as oil and gas infrastructure facilities, livestock agriculture and landfill sites, where site access may be difficult. [ABSTRACT FROM AUTHOR]