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The Science of the Total Environment Nov 2022Atmospheric black carbon (BC), primary and secondary brown carbon (BrC and BrC) are the light-absorbing carbonaceous aerosol components. The vertical changes in the BC...
Atmospheric black carbon (BC), primary and secondary brown carbon (BrC and BrC) are the light-absorbing carbonaceous aerosol components. The vertical changes in the BC and BrC distributions are not generally known. Here, we presented a study of the spectral light absorption properties, direct solar absorption, and potential source areas of BC and BrC at the foothill (375 m a.s.l.) and summit (2060 m a.s.l.) of Mt. Hua, China. More than tripled BC and BrC light absorption coefficient were observed at the foothill compared to the summit. The dominant carbonaceous light-absorbing was attributed to BC with the percentages of 77 % (foothill) and 79 % (summit), respectively. The light absorption coefficient and direct solar absorption of BrC were much higher than those of BrC at foothill, especially in winter. The enhancing contributions of BrC light absorption coefficient and direct solar absorption were observed with high RH and visibility at the summit. The light absorption properties of BC, BrC, and BrC may be attributed to the emissions, meteorological conditions, and photochemical oxidation. The inferred potential source spatial distributions of BC and BrC showed different patterns at the foothill and summit. The results underlined the primary emission effects (including BC and BrC) at the foothill and the importance of BrC at the summit, respectively.
Topics: Aerosols; Air Pollutants; Carbon; China; Environmental Monitoring; Soot
PubMed: 35931170
DOI: 10.1016/j.scitotenv.2022.157814 -
Journal of Exposure Science &... May 2023Little is known about sources of residential exposure to carbonaceous aerosols, which include black carbon (BC), the elemental carbon core of combustion particles, and...
BACKGROUND
Little is known about sources of residential exposure to carbonaceous aerosols, which include black carbon (BC), the elemental carbon core of combustion particles, and organic compounds from biomass combustion (delta carbon).
OBJECTIVE
Assess the impact of residential characteristics on indoor BC and delta carbon when known sources of combustion (e.g., smoking) are minimized.
METHODS
Between November 2012-December 2014, 125 subjects (129 homes) in Northeast USA were recruited and completed a residential characteristics questionnaire. Every 3 months, participants received an automated sampler to measure fine particulate matter (PM) in their home during a weeklong period (N = 371 indoor air samples) and were also questioned about indoor exposures. The samples were analyzed using a transmissometer at 880 nm (reflecting BC) and at 370 nm. The difference between the two wavelengths estimates delta carbon. Outdoor BC and delta carbon were measured using a central site aethalometer.
RESULTS
Geometric mean indoor concentrations of BC and delta carbon (0.65 µg/m³ and 0.19 µg/m³, respectively), were greater than central site concentrations (0.53 µg/m³ and 0.02 µg/m³, respectively). Multivariable analysis showed that greater indoor concentrations of BC were associated with infrequent candle use, multi-family homes, winter season, lack of air conditioning, and central site BC. For delta carbon, greater indoor concentrations were associated with apartments, spring season, and central site concentrations.
SIGNIFICANCE
In addition to outdoor central site concentrations, factors related to the type of housing, season, and home exposures are associated with indoor exposure to carbonaceous aerosols. Recognition of these characteristics should enable greater understanding of indoor exposures and their sources.
Topics: Humans; Air Pollutants; Air Pollution, Indoor; Environmental Monitoring; Particulate Matter; New England; Surveys and Questionnaires; Aerosols; Carbon; Soot
PubMed: 35079108
DOI: 10.1038/s41370-021-00405-6 -
Nature Dec 2022
Topics: Soot; Carbon
PubMed: 36543950
DOI: 10.1038/s41586-022-05519-x -
Environmental Science and Pollution... Sep 2023Impact of COrona VIrus Diseases 2019 (COVID-19) restrictive measures on aerosol optical depth (AOD) and black carbon (BC) concentration is investigated for the western,...
Impact of COrona VIrus Diseases 2019 (COVID-19) restrictive measures on aerosol optical depth (AOD) and black carbon (BC) concentration is investigated for the western, central, and eastern Indo-Gangetic Plain (IGP) using satellite-based observations. Due to COVID-19-induced lockdown measures, a noticeable decline in AOD and BC concentrations was observed across the IGP when compared to pre-lockdown period of 2020 and the lockdown concurrent period of 2015-2019. During the total lockdown period, a maximum drop in AOD and BC was observed in the central IGP (26.5 % and 10.1 %), followed by western IGP (24.9% and 5.2%) and eastern IGP (23.2 % and 4.9 %) with respect to the same period of 2015-2019. We have removed seasonal influences on aerosol properties during the COVID-19 lockdown, by taking average seasonal variations during the period of 2015-2019 as reference and projecting the hypothetical AOD and BC for the lockdown period under normal scenario. The difference between the hypothetical AOD and BC (under normal scenario) and the retrieved AOD and BC for the lockdown period is the absolute percentage change in AOD and BC concentration due to the lockdown alone. This elimination of seasonal influence is a novel approach. Central IGP showed an absolute decrease in AOD and BC of 38.5% and 18.2% during the lockdown period followed by western IGP (34.6% and 7.7%) and eastern IGP (25.9% and 11.5%). The observed absolute reduction in AOD, 26-39 %, is significantly higher than the global average reduction in AOD of 2-5%. CALIPSO-derived aerosol sub-types over major location of the western, central, and eastern IGP suggests prevalence of anthropogenic activities during pre- and post-lockdown periods. During the lockdown, IGP was influenced by aerosols from natural sources, with mineral dust and polluted dust in the western and central IGP, and aerosols from marine regions in the eastern IGP. Replenishment of aerosols within the boundary layer were far quicker when compared to total column during post-lockdown. Overall, the study reveals a reduction in anthropogenic emissions during the COVID-19-induced lockdowns, leading to temporary improvements in air quality over the IGP. Our study presents a comprehensive analysis of COVID-19 lockdown impact on aerosols properties over the IGP and highlights unprecedented reductions in AOD (~ 40 %) and BC (~ 20 %), due to imposition of lockdown and subsequent cessation of aerosol sources, by removing seasonal influences.
Topics: Humans; Air Pollutants; Environmental Monitoring; COVID-19; Communicable Disease Control; Respiratory Aerosols and Droplets; Dust; Soot; India
PubMed: 37632617
DOI: 10.1007/s11356-023-29449-x -
Environmental Research Sep 2022Black carbon (BC) is a product of incomplete combustion, present in urban aerosols and sourcing mainly from road traffic. Epidemiological evidence reports positive...
Black carbon (BC) is a product of incomplete combustion, present in urban aerosols and sourcing mainly from road traffic. Epidemiological evidence reports positive associations between BC and cardiovascular and respiratory disease. Despite this, BC is currently not regulated by the EU Air Quality Directive, and as a result BC data are not available in urban areas from reference air quality monitoring networks in many countries. To fill this gap, a machine learning approach is proposed to develop a BC proxy using air pollution datasets as an input. The proposed BC proxy is based on two machine learning models, support vector regression (SVR) and random forest (RF), using observations of particle mass and number concentrations (N), gaseous pollutants and meteorological variables as the input. Experimental data were collected from a reference station in Barcelona (Spain) over a 2-year period (2018-2019). Two months of additional data were available from a second urban site in Barcelona, for model validation. BC concentrations estimated by SVR showed a high degree of correlation with the measured BC concentrations (R = 0.828) with a relatively low error (RMSE = 0.48 μg/m). Model performance was dependent on seasonality and time of the day, due to the influence of new particle formation events. When validated at the second station, performance indicators decreased (R = 0.633; RMSE = 1.19 μg/m) due to the lack of N data and PM and the smaller size of the dataset (2 months). New particle formation events critically impacted model performance, suggesting that its application would be optimal in environments where traffic is the main source of ultrafine particles. Due to its flexibility, it is concluded that the model can act as a BC proxy, even based on EU-regulatory air quality parameters only, to complement experimental measurements for exposure assessment in urban areas.
Topics: Air Pollutants; Air Pollution; Carbon; Environmental Monitoring; Nonlinear Dynamics; Particulate Matter; Soot
PubMed: 35427594
DOI: 10.1016/j.envres.2022.113269 -
Environmental Science & Technology Oct 2023Residential biomass combustion in developing countries produces significant primary particulate matter (PM) emissions. Highly time-resolved aerosol mass spectrometry and...
Residential biomass combustion in developing countries produces significant primary particulate matter (PM) emissions. Highly time-resolved aerosol mass spectrometry and aethalometer measurements were used to investigate the dynamic changes of emitted PM chemical composition from a typical improved stove burning with wood and crop straw in China. Combustion temperature and organic aerosol (OA) concentration increased quickly during the ignition stage. The flaming stage was characterized by high combustion temperature and high pollutant [including OA, black carbon (BC), inorganic salts, and polycyclic aromatic hydrocarbons (PAHs)] emissions, while the burnout stage is characterized by low combustion temperature and lower pollutant emissions. OA was the primary emitted species; emission factors of OA in the flaming stage were generally higher (24.5-792%) than those in the burnout stage. Mass spectral signatures of OA were obtained. The ratio of Cl/OA for wood combustion (0.05 ± 0.01) is much lower than that from burning crop straw (0.32 ± 0.19). Hydrocarbon OA emissions dominated during the ignition and flaming stages. A high percentage of oxidized OA was emitted during the burnout stage. The relationship between PAHs and BC/OA emissions under different burning conditions was investigated, and PAHs may act as intermediate products in the conversion of OA to BC.
Topics: Particulate Matter; Air Pollutants; Biomass; Environmental Pollutants; Polycyclic Aromatic Hydrocarbons; Aerosols; Soot
PubMed: 37747327
DOI: 10.1021/acs.est.3c05412 -
Journal of the Air & Waste Management... Sep 2017Off-road vehicles used in construction and agricultural activities can contribute substantially to emissions of gaseous pollutants and can be a major source of...
UNLABELLED
Off-road vehicles used in construction and agricultural activities can contribute substantially to emissions of gaseous pollutants and can be a major source of submicrometer carbonaceous particles in many parts of the world. However, there have been relatively few efforts in quantifying the emission factors (EFs) and for estimating the potential emission reduction benefits using emission control technologies for these vehicles. This study characterized the black carbon (BC) component of particulate matter and NOx, CO, and CO EFs of selected diesel-powered off-road mobile sources in Mexico under real-world operating conditions using on-board portable emissions measurements systems (PEMS). The vehicles sampled included two backhoes, one tractor, a crane, an excavator, two front loaders, two bulldozers, an air compressor, and a power generator used in the construction and agricultural activities. For a selected number of these vehicles the emissions were further characterized with wall-flow diesel particle filters (DPFs) and partial-flow DPFs (p-DPFs) installed. Fuel-based EFs presented less variability than time-based emission rates, particularly for the BC. Average baseline EFs in working conditions for BC, NOx, and CO ranged from 0.04 to 5.7, from 12.6 to 81.8, and from 7.9 to 285.7 g/kg-fuel, respectively, and a high dependency by operation mode and by vehicle type was observed. Measurement-base frequency distributions of EFs by operation mode are proposed as an alternative method for characterizing the variability of off-road vehicles emissions under real-world conditions. Mass-based reductions for black carbon EFs were substantially large (above 99%) when DPFs were installed and the vehicles were idling, and the reductions were moderate (in the 20-60% range) for p-DPFs in working operating conditions. The observed high variability in measured EFs also indicates the need for detailed vehicle operation data for accurately estimating emissions from off-road vehicles in emissions inventories.
IMPLICATIONS
Measurements of off-road vehicles used in construction and agricultural activities in Mexico using on-board portable emissions measurements systems (PEMS) showed that these vehicles can be major sources of black carbon and NO. Emission factors varied significantly under real-world operating conditions, suggesting the need for detailed vehicle operation data for accurately estimating emissions inventories. Tests conducted in a selected number of sampled vehicles indicated that diesel particle filters (DPFs) are an effective technology for control of diesel particulate emissions and can provide potentially large emissions reduction in Mexico if widely implemented.
Topics: Air Pollutants; Carbon Dioxide; Carbon Monoxide; Environmental Monitoring; Mexico; Nitrogen Oxides; Off-Road Motor Vehicles; Soot; Vehicle Emissions
PubMed: 28379119
DOI: 10.1080/10962247.2017.1310677 -
Critical Reviews in Toxicology Feb 2018Carbon black is produced industrially by the partial combustion or thermal decomposition of gaseous or liquid hydrocarbons under controlled conditions. It is considered... (Review)
Review
Carbon black is produced industrially by the partial combustion or thermal decomposition of gaseous or liquid hydrocarbons under controlled conditions. It is considered a poorly soluble, low toxicity (PSLT) particle. Recently, results from a number of published studies have suggested that carbon black may be directly genotoxic, and that it may also cause reproductive toxicity. Here, we review the evidence from these studies to determine whether carbon black is likely to act as a primary genotoxicant or reproductive toxicant in humans. For the genotoxicity endpoint, the available evidence clearly shows that carbon black does not directly interact with DNA. However, the study results are consistent with the mechanism that, at high enough concentrations, carbon black causes inflammation and oxidative stress in the lung leading to mutations, which is a secondary genotoxic mechanism. For the reproductive toxicity endpoint for carbon black, to date, there are various lung instillation studies and one short-term inhalation study that evaluated a selected number of reproduction endpoints (e.g. gestational and litter parameters) as well as other general endpoints (e.g. gene expression, neurofunction, DNA damage); usually at one time point or using a single dose. It is possible that some of the adverse effects observed in these studies may be the result of non-specific inflammatory effects caused by high exposure doses. An oral gavage study reported no adverse reproductive or developmental effects at the highest dose tested. The overall weight of evidence indicates that carbon black should not be considered a direct genotoxicant or reproductive toxicant.
Topics: Animals; DNA Damage; Developmental Disabilities; Environmental Exposure; Female; Graphite; Humans; Male; Mice; Mutagenicity Tests; Pregnancy; Reproduction; Soot; Toxicity Tests
PubMed: 29095661
DOI: 10.1080/10408444.2017.1391746 -
Redox Biology Nov 2021Oxidation of engineered nanomaterials during application in various industrial sectors can alter their toxicity. Oxidized nanomaterials also have widespread industrial...
Oxidation of engineered nanomaterials during application in various industrial sectors can alter their toxicity. Oxidized nanomaterials also have widespread industrial and biomedical applications. In this study, we evaluated the cardiopulmonary hazard posed by these nanomaterials using oxidized carbon black (CB) nanoparticles (CB) as a model particle. Particle surface chemistry was characterized by X-ray photo electron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). Colloidal characterization and in vitro dosimetry modeling (particle kinetics, fate and transport modeling) were performed. Lung inflammation was assessed following oropharyngeal aspiration of CB or oxidized CB particles (20 μg per mouse) in C57BL/6J mice. Toxicity and functional assays were also performed on murine macrophage (RAW 264.7) and endothelial cell lines (C166) with and without pharmacological inhibitors. Oxidant generation was assessed by electron paramagnetic resonance spectroscopy (EPR) and via flow cytometry. Endothelial toxicity was evaluated by quantifying pro-inflammatory mRNA expression, monolayer permeability, and wound closure. XPS and FTIR spectra indicated surface modifications, the appearance of new functionalities, and greater oxidative potential (both acellular and in vitro) of CB particles. Treatment with CB demonstrated greater in vivo inflammatory potentials (lavage neutrophil counts, secreted cytokine, and lung tissue mRNA expression) and air-blood barrier disruption (lavage proteins). Oxidant-dependent pro-inflammatory signaling in macrophages led to the production of CXCR3 ligands (CXCL9,10,11). Conditioned medium from CB-treated macrophages induced significant elevation in endothelial cell pro-inflammatory mRNA expression, enhanced monolayer permeability and impairment of scratch healing in CXCR3 dependent manner. In summary, this study mechanistically demonstrated an increased biological potency of CB particles and established the role of macrophage-released chemical mediators in endothelial damage.
Topics: Animals; Lung; Mice; Mice, Inbred C57BL; Nanoparticles; Receptors, Chemokine; Soot
PubMed: 34624601
DOI: 10.1016/j.redox.2021.102161 -
International Journal of Molecular... Nov 2022Soot molecules are hazardous compounds threatening human health. Computational chemistry provides efficient tools for studying them. However, accurate quantum chemistry...
Soot molecules are hazardous compounds threatening human health. Computational chemistry provides efficient tools for studying them. However, accurate quantum chemistry calculation is costly for the simulation of large-size soot molecules and high-throughput calculations. Semi-empirical (SE) quantum chemistry methods are optional choices for balancing computational costs. In this work, we validated the performances of several widely used SE methods in the description of soot formation. Our benchmark study focuses on, but is not limited to, the validation of the performances of SE methods on reactive and non-reactive MD trajectory calculations. We also examined the accuracy of SE methods of predicting soot precursor structures and energy profiles along intrinsic reaction coordinate(s) (IRC). Finally, we discussed the spin density predicted by SE methods. The SE methods validated include AM1, PM6, PM7, GFN2-xTB, DFTB2, with or without spin-polarization, and DFTB3. We found that the shape of MD trajectory profiles, the relative energy, and molecular structures predicted by SE methods are qualitatively correct. We suggest that SE methods can be used in massive reaction soot formation event sampling and primary reaction mechanism generation. Yet, they cannot be used to provide quantitatively accurate data, such as thermodynamic and reaction kinetics ones.
Topics: Humans; Soot; Quantum Theory; Thermodynamics; Computer Simulation; Molecular Structure
PubMed: 36362159
DOI: 10.3390/ijms232113371