Aerosols are liquid or solid particles suspended in the atmosphere, typically with diameters on the order of nanometers to microns. These particles impact air quality and the radiative balance of the ...planet. Dry deposition is a key process for the removal of aerosols from the atmosphere and plays an important role in controlling the lifetime of atmospheric aerosols. Dry deposition is driven by turbulence and shows a strong dependence on particle size. This review summarizes the mechanisms behind aerosol dry deposition, including measurement approaches, field observations, and modeling studies. We identify several gaps in the literature, including deposition over the cryosphere (i.e., snow and ice surfaces) and the ocean; in addition, we highlight new techniques to measure black carbon fluxes. While recent advances in aerosol instrumentation have enhanced our understanding of aerosol sources and chemistry, dry deposition and other loss processes remain poorly investigated.
Particulate matter (PM) from automobile exhaust has drastic effects on human health. The enforcement of environmental laws has controlled vehicle emissions and reduced the total PM. However, another ...significant source of PM is debris from tire wear, break wear, and road wear. In particular, tire-wear particles (TWPs) are further fragmented into nanoparticles, similar to the PMx or black carbon (BC) sources. As approximately 30 wt% of carbon black (CB) is used as filler in tires, TWPs can fragment into free-bound nano-CB. This study evaluates the emission factors of BC from the ternary plots of PMx and BC to estimate the concentration of nano-CB in TWPs. Based on the emission factors of BC for TWP, approximately 500 monitoring data points were acquired at four different sites. Semi-closed sites in a field measurement test have 2.9–4.0 times larger BC concentration than open sites. The mass concentration of nano-CB evaluated with the BC data and emission factors at the open sites is 22.47–23.96 ng/m3, whereas that at the semi-closed sites is 66.32–90.33 ng/m3. Transmission electron microscopy analysis with scanning mobility particle sizer and selected-area electron diffraction reveals grape-like aggregated nanoparticles, which is considered as CB. To compare the effect of the washing out of airborne particulates by rain, further analysis is conducted on the interior and exterior of the tunnel on a rainy day. While the concentration of PMs was effectively reduced by rainfall, the amount of BC and CB in the interior of a tunnel was not changed. Namely, even under rainfall, nano-CB still exists in the tunnels and thus free-bound CB and nanoparticles released from TWP will be effected on the human health.
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•Correlation between PM10, PM2.5, and black carbon (BC) was identified in situ.•New approach distinguishes between BC and carbon black (CB).•Open and semi-closed sites have 22.47–23.96 and 66.32–90.33 ng/m3 of nano-CB.•Rain cannot deposit nano-CB on the ground even in semi-closed sites.
Flow-electrode electrochemical desalination (FEED) processes (e.g., flow-electrode capacitive deionization), which use flowable carbon particles as the electrodes, have attracted increasing ...attention, holding the promise for continuous desalination and high desalting efficiency. While it is generally believed that carbon particles with abundant microporous and large specific capacitances (e.g., activated carbon, AC) should be ideal candidates for FEED electrodes, we provide evidence to the contrary, showing that highly conductive electrodes with low specific surface area can outperform microporous AC-based electrodes. This study revealed that FEED using solely high surface area AC particles (∼2000 m2 g–1, specific capacitance of ∼44 F g–1, average salt adsorption rate of ∼0.15 μmol cm–2 min–1) was vastly outperformed by electrodes based solely on low-surface area carbon black (CB, ∼70 m2 g–1, ∼0.5 F g–1, ∼0.75 μmol cm–2 min–1). Electrochemical impedance spectroscopy results suggest that the electrode formed by CB particles led to more effective electronic charge percolation, likely contributing to the improved desalination performance. In addition, we propose and demonstrate a novel operation mode, termed single cycle (SC), which greatly simplified the FEED cell configuration and enabled simultaneous charging and discharging. Using SC mode with CB flow electrodes delivered an increased average salt removal rate relative to the more traditional short-circuited closed cycle (SCC) mode, achieving up to 1.13 μmol cm–2 min–1. Further investigations demonstrate that up to 50% of energy input would be avoided when using CB flow electrodes operated under SC mode as compared to that of AC flow electrodes operated under SCC mode. In summary, the FEED process presented in this study provided an innovative and promising approach toward high-efficient and low-cost brackish water desalination.
During the last years the atmosphere of the Great Athens Area (GAA) and other Greek cities is burdened from extended residential biomass burning for heating purposes. In this work, a series of near ...real-time and off-line biomass burning tracers are analyzed during intense wood burning events in Athens. The measurements were conducted at an urban background site located in the center of Athens, and in the heart of wood burning activities (winter 2013–2014). The measured tracers include high resolution measurements of non-sea salt potassium (nss-K+), wood burning black carbon (BCwb), the m/z 60 fragment associated with levoglucosan and monosaccharide anhydrides (levoglucosan, mannosan and galactosan) determined on selected filter samples. The suitability of these tracers was evaluated when the prevailing meteorological conditions with low dispersion and deposition mechanisms (low wind speed, absence of precipitation) were associated with high biomass burning emissions at nighttime. During the severe smog periods, the levels of K+, BCwb, m/z 60 and levoglucosan were up to 2.2 μg m−3, 12.5 μg m−3, 3.4 μg m−3 and 8.6 μg m−3, respectively, higher by a factor of at least two, relatively to the non smog periods due to biomass burning. Correlations between biomass burning tracers as well as between monosaccharide anhydrides provided information about the type of material and wood being burned.
•High temporal resolution measurements were deployed during wintertime in Athens to track and identify a number of different biomass burning tracers.•Biomass burning tracers such as non sea salt potassium (nss-K+), black carbon (BCwb), the organic fraction m/z 60 and levoglucosan were monitored.•The enhanced levels of chloride (Cl−) could provide evidence of combustion of inappropriate materials being used as fuel.•Sodium (Na+) was also shown to be an alternative combustion tracer.•The significant correlation between PM2.5 and levoglucosan, indicated that wood burning could be responsible for PM2.5 higher than 45 μg m−3.
Sea breeze onset studies are very important to understand the effects of local air pollution and its environmental impacts. In the present work, we obtained and studied the sea breeze onset time ...(SBOT) over a semi-urban environment (12.81°N, 80.03°E) located on a tropical east coast of India. Weather data measurements were carried out in the university campus of SRM Institute of Science and Technology from June 2019 to January 2020, except for the month of December 2019. The sea breeze component (SBC) was calculated on an hourly scale, and the SBOTs for different days were obtained and are discussed in detail. Measurements of surface black carbon mass concentration (SBCMC) from an aethalometer (AE-31) and aerosol optical depth (AOD) from a Microtops II Sunphotometer were obtained and used to assess the impact of sea breeze onset on SBCMC. The results of the study indicate that (i) the study site experienced the sea breeze on 33% of the 163 days of the study period, and the maximum days with SBOT occurred from 10:00 to 12:00 IST, (ii) an average decrease of 0.236 µg/m
3
in SBCMC was observed on most of the days (72.2%) after the onset of the sea breeze, and (iii) an increase in AOD associated with a decrease in the Angstrom exponent (AE) was observed after the sea breeze onset, which suggests that the natural sea aerosols replaced the anthropogenic black carbon aerosols over the study location.
Black carbon (BC) aerosols in the atmosphere strongly affect direct radiative forcing and climate, not only while suspended in the atmosphere but also after deposition onto high albedo surfaces. Snow ...surfaces are especially sensitive to BC deposition, because of their high surface albedo and additional positive feedbacks further enhance faster snowpack melting caused by BC deposition, resulting in modifications in water resources and recession of glaciers. For the analysis of BC deposition on snow, a precise quantification of BC mass is needed. Instead, optical methods have the potential of quantifying only BC, based on its characteristic spectral absorption. Commercial optical transmissometers commonly use quartz filters to filter BC and measure its optical attenuation. They are calibrated for the determination of BC mass concentrations in air, but not adapted or calibrated for their determination in water or snowmelt samples. Additionally, they are generally calibrated using BC-simulating materials that are not representative of ambient BC particles.
Here, a new analytical method is demonstrated for the quantitative determination of BC mass concentration in snow samples that considers filtering of melted snow with polycarbonate filters in a new device, and optical filter attenuation BC mass concentration measurement (880 nm). The attenuation can be obtained with any optical equipment that can measure the 880-nm attenuation of filters impacted with BC/snow impurities.
This method has been calibrated using real diesel vehicle exhaust soot with well-known optical properties as reference material, yielding a multipoint calibration curve for common BC concentration levels in snow. The limits of detection (0.011 mg of BC), quantification (0.036 mg of BC) and reproducibility (96.39%) of this new analytical method have been determined. Real surface snow samples collected at different locations in “Los Andes” mountains of Chile were measured with this method given a BC concentrations ranged from 151 to 5987 μg kg−1.
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•Black Carbon quantification in snow using diesel vehicle exhaust soot calibration curve.•The underestimating of BC mass in snow samples was 80–97% without using calibration curve.•Diesel vehicle exhaust soot calibration curve is a good material reference for external calibration.•In Andes Mountain the BC concentration varied 151–5987 μg of BC/kg of snow.
The mixing state of black carbon aerosols (BC) has the largest uncertainty for climate forcing evaluation. In this study, a tandem observation, combining a centrifugal particle mass analyzer (CPMA) ...and a single particle soot photometer (SP2), was conducted to investigate the mixing state of BC in a coastal city in eastern China. First, particles with specific masses (1.0 fg, 2.1 fg, 4.5 fg, 9.7 fg, and 20.1 fg) were selected using CPMA and consecutively measured by SP2 to determine the corresponding BC mass (MBC) of the particle. The mass ratio (MR) of the coating matter to the BC core was used to indicate the coating thickness and aging degree of BC. The results showed that the MR value obtained from the CPMA-SP2 system was well correlated with the mixing state condition derived from the traditional lag-time method. However, the lag-time method tends to misclassify thickly to thinly coated BC as particles with larger masses. The MR generally increased as the mass of BC-containing particles increased. MR showed a clear diurnal pattern with a minimum at 8:00 and a maximum at 13:00 due to photochemical process during the daytime. The larger BC-containing particles had a much weaker diurnal pattern because other secondary processes may contribute more to the coatings for large BC-containing particles. The MR maintained a high value when the air mass was stagnant in the local area with high pollutant concentrations and high relative humidity (RH), while the MR was at its lowest value when the air mass was derived from the marine area with high RH and low pollutant concentrations. These observations suggest that the increase in MR is the result of the combined effect of high RH and high pollutant concentrations.
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•Traditional lag-time method tends to misclassify thickly to thinly coated BC as particles with larger masses.•The increase of BC's coating needs the joint action of pollutants precursors, aging time and humidity.•The coating thickness of BC with larger masses had weaker diurnal pattern.
This paper reports the chemistry of fine (PM
2.5
) and coarse (PM
10
) aerosols sampled over a period of three years during 2018–2021 at a semi -arid tropical location in the rain shadow region of ...the peninsular India. The data is classified in to dry (December to May) and wet (June to November) periods. Scavenging effect due to rains have culminated in to less concentrations of both fine and coarse aerosols and their ionic components in the wet period. Significantly high concentrations of the crustal components such as Ca, Na, K and Mg from the local dust resulted in the alkaline pH in both dry and wet periods with Ca and Mg emerging as major neutralizing components. Overall, < 20% samples of both fine and coarse aerosols depicted acidic pH. Concentration of SO
4
was comparatively more than NO
3
indicating towards more presence of stationary sources (industrial/domestic emissions) than mobile (vehicular emissions) sources. Combustion generated and highly absorbing black carbon aerosols showed high concentration during the dry period. Local activities comprising residential, agricultural, vehicular and industrial emissions were the major sources of aerosols at Solapur however, the contribution from the distant sources were also found to contribute as inferred from the cluster analysis and concentration weighted trajectories (CWT). The observed abundances of the alkaline dust aerosols that could act as cloud condensation nuclei or ice nuclei will have important implications on the studies related to cloud aerosol precipitation interaction over this region.
The ground and vertical profiles of particulate matter (PM) were mapped as part of a pilot study using a Tethered balloon within the lower troposphere (1000m) during the foggy episodes in the winter ...season of 2015–16 in New Delhi, India. Measurements of black carbon (BC) aerosol and PM <2.5 and 10μm (PM2.5 & PM10 respectively) concentrations and their associated particulate optical properties along with meteorological parameters were made. The mean concentrations of PM2.5, PM10, BC370nm, and BC880nm were observed to be 146.8±42.1, 245.4±65.4, 30.3±12.2, and 24.1±10.3μgm−3, respectively. The mean value of PM2.5 was ~12 times higher than the annual US-EPA air quality standard. The fraction of BC in PM2.5 that contributed to absorption in the shorter visible wavelengths (BC370nm) was ~21%. Compared to clear days, the ground level mass concentrations of PM2.5 and BC370nm particles were substantially increased (59% and 24%, respectively) during the foggy episode. The aerosol light extinction coefficient (σext) value was much higher (mean: 610Mm−1) during the lower visibility (foggy) condition. Higher concentrations of PM2.5 (89μgm−3) and longer visible wavelength absorbing BC880nm (25.7μgm−3) particles were observed up to 200m. The BC880nm and PM2.5 aerosol concentrations near boundary layer (1km) were significantly higher (~1.9 and 12μgm−3), respectively. The BC (i.e BCtot) aerosol direct radiative forcing (DRF) values were estimated at the top of the atmosphere (TOA), surface (SFC), and atmosphere (ATM) and its resultant forcing were - 75.5Wm−2 at SFC indicating the cooling effect at the surface. A positive value (20.9Wm−2) of BC aerosol DRF at TOA indicated the warming effect at the top of the atmosphere over the study region. The net DRF value due to BC aerosol was positive (96.4Wm−2) indicating a net warming effect in the atmosphere. The contribution of fossil and biomass fuels to the observed BC aerosol DRF values was ~78% and ~22%, respectively. The higher mean atmospheric heating rate (2.71Kday−1) by BC aerosol in the winter season would probably strengthen the temperature inversion leading to poor dispersion and affecting the formation of clouds. Serious detrimental impacts on regional climate due to the high concentrations of BC and PM (especially PM2.5) aerosol are likely based on this study and suggest the need for immediate, stringent measures to improve the regional air quality in the northern India.
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•First time - a tethered balloon-based soot measurement in a megacity “Delhi”.•Sign. higher BC conc.(~1.9μg/m3) near the boundary layer (BL) during the foggy period•~20% contribution of BC to near ultra-fine particles (PM1.0) at surface and BL•Cons. of BC370nm and PM10 increased ~85% & 46% during dense foggy period.•Higher heating (2.71Kday−1) due to BC, influences regional climate.
Airborne particles containing elemental carbon (EC) are currently at the forefront of scientific and regulatory scrutiny, including black carbon, carbon black, and engineered carbon-based ...nanomaterials, e.g., carbon nanotubes, fullerenes, and graphene. Scientists and regulators sometimes group these EC-containing particles together, for example, interchangeably using the terms carbon black and black carbon despite one being a manufactured product with well-controlled properties and the other being an undesired, incomplete-combustion byproduct with diverse properties. In this critical review, we synthesize information on the contrasting properties of EC-containing particles in order to highlight significant differences that can affect hazard potential. We demonstrate why carbon black should not be considered a model particle representative of either combustion soots or engineered carbon-based nanomaterials. Overall, scientific studies need to distinguish these highly different EC-containing particles with care and precision so as to forestall unwarranted extrapolation of properties, hazard potential, and study conclusions from one material to another.
•Major classes of elemental carbon-containing particles have distinct properties.•Despite similar names, carbon black should not be confused with black carbon.•Carbon black is distinguished by a high EC content and well-controlled properties.•Black carbon particles are characterized by their heterogenous properties.•Carbon black is not a model particle representative of engineered nanomaterials.
This review demonstrates the significant physical and chemical distinctions between elemental carbon-containing particles e.g., carbon black, black carbon, and engineered nanomaterials.
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