Aerosol Sources Research Articles

A study on optical properties, classification, and transport of aerosols during the smog period over South Asia using remote sensing.

Over the past few years, South Asian region has experienced frequent and thick smog events because of rapid population growth and enhanced anthropogenic activities, particularly in the Indo-Gangetic Plain (IGP). Therefore, the present study investigates aerosol properties such as aerosol optical depth (AOD) (500nm), Angstrom exponent (AE) (440-870nm), single scattering albedo (SSA), fine-mode fraction (FMF), absorption aerosol optical depth (AAOD), and absorption aerosol exponent (AAE) over selected AERONET sites namely Bhola (2012-2021), Dhaka (2012-2021), Jaipur (2011-2021), Kanpur (2011-2021), Karachi (2011-2021), Lahore (2011-2021), and Pokhara (2011-2021) in the IGP during the smog period (October, November, and December). Additionally, different aerosol types were categorized using AERONET direct sun (AOD, AE) and inversion products (VSD, SSA, RI, FMF, and ASY). The monthly mean AOD, AE, and FMF varied from ⁓0.33 to 1.07, ⁓0.3 to 1.4, and 0.6-0.9µm over all selected AERONET sites during the smog period. Moreover, the outcomes revealed the dominance of biomass-burning and urban/ industrial aerosols over Lahore, Karachi, Dhaka, and Bhola during the smog period. Contrary to this, dust and mixed aerosols were abundant over Jaipur and Karachi, respectively. Furthermore, HYSPLIT cluster analysis is used to trace the transmission paths and potential sources of aerosols over selected sites.

Mitigation of Respirable Aerosol Particles from Speech and Language Therapy Exercises

Phonation and speech are known sources of respirable aerosol in humans. Voice assessment and treatment manipulate all the subsystems of voice production, and previous work (Saccente-Kennedy et al., 2022) has demonstrated such activities can generate >10 times more aerosol than conversational speech and 30 times more aerosol than breathing. Aspects of voice therapy may therefore be considered aerosol generating procedures and pose a greater risk of potential airborne pathogen (eg, SARS-CoV-2) transmission than typical speech. Effective mitigation measures may be required to ensure safe service delivery for therapist and patient. To assess the effectiveness of mitigation measures in reducing detectable respirable aerosol produced by voice assessment/therapy. We recruited 15 healthy participants (8 cis-males, 7 cis-females), 9 of whom were voice-specialist speech-language pathologists. Optical Particle Sizers (OPS) (Model 3330, TSI) were used to measure the number concentration of respirable aerosol particles (0.3 µm-10 µm) generated during a selection of voice assessment/therapy tasks, both with and without mitigation measures in place. Measurements were performed in a laminar flow operating theatre, with near-zero background aerosol concentration, allowing us to quantify the number concentration of respiratory aerosol particles produced. Mitigation measures included the wearing of Type IIR fluid resistant surgical masks, wrapping the same masks around the end of straws, and the use of heat and moisture exchange microbiological filters (HMEFs) for a water resistance therapy (WRT) task. All unmitigated therapy tasks produced more aerosol than unmasked breathing or speaking. Mitigation strategies reduced detectable aerosol from all tasks to a level significantly below, or no different to, that of unmasked breathing. Pooled filtration efficiencies determined that Type IIR surgical masks reduced detectable aerosol by 90%. Surgical masks wrapped around straws reduced detectable aerosol by 96%. HMEF filters were 100% effective in mitigating the aerosol from WRT, the exercise that generated more aerosol than any other task in the unmitigated condition. Voice therapy and assessment causes the release of significant quantities of respirable aerosol. However, simple mitigation strategies can reduce emitted aerosol concentrations to levels comparable to unmasked breathing.

Organic aerosols in the inland Tibetan Plateau: New insights from molecular tracers

Aerosols affect the radiative forcing of the global climate and cloud properties. Organic aerosols are among the most important, yet least understood, components of the sensitive Tibetan Plateau atmosphere. Here, the concentration of and the seasonal and diurnal variations in biomass burning and biogenic aerosols, and their contribution to organic aerosols in the inland Tibetan Plateau were investigated using molecular tracers. Biomass burning tracers including levoglucosan and its isomers, and aromatic acids showed higher concentrations during winter than in summer. Molecular tracers of primary and secondary biogenic organic aerosols were more abundant during summer than those in winter. Meteorological conditions were the main factors influencing diurnal variations in most organic molecular tracers during both seasons. According to the tracer-based method, we found that biogenic secondary organic aerosols (38.5 %) and fungal spores (14.4 %) were the two dominant contributors to organic aerosols during summer, whereas biomass burning (15.4 %) was an important aerosol source during winter at remote continental background site. Results from the positive matrix factor source apportionment also demonstrate the importance of biomass burning and biogenic aerosols in the inland Tibetan Plateau. During winter, the long-range transport of biomass burning from South Asia contributes to organic aerosols. In contrast, the precursors, biogenic secondary organic aerosols, and fungal spores from local emissions/long-range transport are the major sources of organic aerosols during summer. Further investigation is required to distinguish between local emissions and the long-range transport of organic aerosols. In-depth insights into the organic aerosols in the Tibetan Plateau are expected to reduce the uncertainties when evaluating aerosol effects on the climate system in the Tibetan Plateau.

Tandem aerodynamic aerosol classifier – differential mobility analyzer as a single charged aerosol source for diameters up to one micrometer

This work describes a method to generate monodisperse, spherical, single-charged aerosols for instrument calibration in the size range of 32 – 1000 nm using an aerodynamic aerosol classifier (AAC) and differential mobility analyzer (DMA) in series. The AAC is used to input a monodisperse aerosol into the DMA to reduce the fraction of larger multiple charged particles exiting the DMA. The method produces test aerosols over a wide size range with less than 1% multiple charging and in concentrations between 4,000 – 10,000 particles/cm3 at more than 2 liters/minute flow rate, sufficient to be measured with the aerosol electrometer and condensation particle counter (CPC). At diameters between 32 nm and 1000 nm, the multiple charging was less than 0.1%. Operating parameters for the AAC and DMA are provided, along with CPC detection efficiencies up to 1000 nm measured with traceability to the international system of units. Use of the AAC allows for calibrations to be performed over almost the full particle diameter range of the DMA with an easily reproduced experimental setup using commercially available equipment.

Trend relationship between mountain normalized difference vegetation index (NDVI) and aerosol optical depth (AOD) across two decades: implication for water quality within the Lesotho Highlands, Drakensberg, South Africa

There are growing concerns on contribution of vegetation dynamics to atmospheric turbidity and quality of regional water towers. The study sought to determine the trends in the MODIS/TERRA-derived normalized difference vegetation index (NDVI) and aerosol optical depth (AOD) for Lesotho Highland over 2000-2020. The predictive relationship between the two variables was also examined using regression analysis. Irrespective of yearly AOD patterns, the AOD showed biphasic patterns peaking between mid-winter to early spring (July-October) (highest) and autumn (Feb-April) (next highest), and lowest in the summer (Nov-January). The monthly NDVI was largest in January-March (summer-early fall) with smaller values in winter and spring. This seasonality can be related to the peak of anthropogenic biomass combustion during the winter and strong winds during the spring and early summer. The AOD relationship with NDVI showed quadratic patterns peaking and plunging with changes in season. About 30-80% (R2 = 0.3-0.8%) changes in annual AOD from 2000 to 2020 were explainable by the dynamics of NDVI indicating that increased NDVI contributes to about a 50% decrease in AOD in the Lesotho Highlands. However, an outlier trend was observed in 2007 (R2 = 13%). Incidences of high AOD in months of high NDVI may be indicative of traveling aerosols, i.e., aerosols from non-local sources/activity. On the other hand, high AOD in months of low NDVI implicates local aerosol sources. Trend relationship studies on vegetation loss and AOD in mountain areas of other regions could improve knowledge of contaminant dynamics and risk implications for downstream populations.

Efficacy of Surgical Masks Versus N95 Respirators for the Prevention of COVID-19 in Dental Settings: A Systematic Review.

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2. (SARS-CoV-2). It spreads mainly through saliva droplets or nasal discharge. Dentists are among the professionals with the greatestrisk of contracting and transmitting COVID-19. We compared the efficacy of surgical masks versus N95 respirators in preventing COVID-19 infection in dental settings. PubMed, Scopus, Web of Science, and Cochrane Library databases were searched. Search terms corresponded to a predefined PICOS (patient/population, intervention, comparison, and outcomes) question. The risk of bias was evaluated using AMSTAR-2 (A Measurement Tool to Assess Systematic Reviews-2), ROBIS (Risk of Bias in Systematic Reviews), and Health Evidence tools. A total of 191 articles were screened, and nine of them were further evaluated for eligibility, of which five articles (fulfilled the selection criteria) and were included in this study. Two studies concluded that surgical masks could provide equivalent protection to N95 respirators. Another study found that N95 respirators were superior to surgical masks. The fourth study found that better protection can be achieved when using surgical masks by the aerosol source than when the recipient uses an N95 respirator, while the last study concluded that surgical masks or N95 respirators alone do not provide full protection. Thus, according to this systematic review, N95 respirators provide better protection against COVID-19 infection compared to surgical masks.

Technical note: Sublimation of frozen CsCl solutions in an environmental scanning electron microscope (ESEM) – determining the number and size of salt particles relevant to sea salt aerosols

Abstract. We present a novel technique that elucidates the mechanism of the formation of small aerosolizable salt particles from salty frozen samples. We demonstrated that CsCl may be a suitable probe for sea salts due to its similar subzero properties and sublimation outcomes: CsCl substantially increased the visibility of the salt both during and after ice sublimation. Hence, we identified the factors that, during the sublimation of a frozen salty solution, are important in generating fine salt particles as a possible source of salt aerosol. The number, size, and structure of the particles that remain after ice sublimation were investigated with respect to the concentration of the salt in the sample, the freezing method, and the sublimation temperature. The last-named aspect is evidently of primary importance for the preference of fine salt crystals over a large compact piece of salt; we showed that the formation of small salt particles is generally restricted if the brine is liquid during the ice sublimation, i.e. at temperatures higher than the eutectic temperature (Teu). Small salt particles that might be a source of atmospheric aerosols were formed predominantly at temperatures below Teu, and their structures strongly depended on the concentration of the salt. For example, the sublimation of those samples that exhibited a concentration of less than 0.05 M often produced small aerosolizable isolated particles that are readily able to be windblown. Conversely, the sublimation of 0.5 M samples led to the formation of relatively stable and largely interconnected salt structures. Our findings are in good agreement with other laboratory studies which have unsuccessfully sought salt aerosols from, for example, frost flowers at temperatures above Teu. This study offers an explanation of the previously unexplored behaviour.

Marine Fresh Carbon Pool Dominates Summer Carbonaceous Aerosols Over Arctic Ocean

AbstractThe source of marine carbonaceous aerosols is crucial to determine as it provides information about the ocean‐cloud‐climate relationship and the carbon cycle. However, contribution of different marine organic pools to marine primary organic aerosols remains controversial and this will lead to uncertainties in climate models. Here, we report the stable carbon isotopes and carbonaceous fraction of marine aerosols, measured during three summer Arctic cruises (33°N–85°N, July‐September, 2014–2018). By comparing the stable carbon isotopic signatures of seawater and aerosols in the Arctic Ocean, we found that the marine fresh carbon pool had a depleted isotopic signature, contributing 80 ± 12% of the carbonaceous fraction. Both in 2016 and 2018, the aerosol carbon isotopes in the Arctic Ocean were significantly higher than those in 2014. Increased productivity in the Arctic Ocean may dominate the increase of stable carbon isotope in the marine fresh carbon pool on an annual scale. Our research highlights the important contribution of fresh marine carbon pool to marine carbonaceous aerosols in response to marine ecosystem change under Arctic warming.

Ionic Strength Enhances the Multiphase Oxidation Rate of Sulfur Dioxide by Ozone in Aqueous Aerosols: Implications for Sulfate Production in the Marine Atmosphere.

Multiphase oxidation of sulfur dioxide (SO2) by ozone (O3) in alkaline sea salt aerosols is an important source of sulfate aerosols in the marine atmosphere. However, a recently reported low pH of fresh supermicron sea spray aerosols (mainly sea salt) would argue against the importance of this mechanism. Here, we investigated the impact of ionic strength on the kinetics of multiphase oxidation of SO2 by O3 in proxies of aqueous acidified sea salt aerosols with buffered pH of ∼4.0 via well-controlled flow tube experiments. We find that the sulfate formation rate for the O3 oxidation pathway proceeds 7.9 to 233 times faster under high ionic strength conditions of 2-14 mol kg-1 compared to the dilute bulk solutions. The ionic strength effect is likely to sustain the importance of multiphase oxidation of SO2 by O3 in sea salt aerosols in the marine atmosphere. Our results indicate that atmospheric models should consider the ionic strength effects on the multiphase oxidation of SO2 by O3 in sea salt aerosols to improve the predictions of the sulfate formation rate and the sulfate aerosol budget in the marine atmosphere.

Environmental implication of geochemical record in the Arctic Ny-Ålesund glacial sediment, Svalbard (Norway)

Glacial sediments as an important end member of the global dust system, could indicate changes in global climate, aerosols sources, ocean elements, and productivity. With global warming, ice caps shrinking and glaciers retreat at high latitudes have attracted concern. To understand the response of glacier to environment and climate in modern high latitude ice-marginal environments, this paper investigated glacial sediments in the Ny-Ålesund region of the Arctic and clarified the response of polar environmental to global changes through geochemical characteristics of glacial sediments. The results showed that: 1) main factors affecting the elements distribution of the Ny-Ålesund glacial sediments were thought as soil formation, bedrock and weathering, and biological activity; 2) variations of SiO2/Al2O3 and SiO2/Al2O3 + Fe2O3, indicating low weathering of the soil. The ratio of Na2O/K2O indicating a weak chemical weathering, was negatively correlated to the CIA. With the average CIA of Ny-Ålesund glacial sediments for main minerals of quartz, feldspar, and muscovite as well as dolomite and calcite 50.13, which implied glacial sediments at the early stage of chemical weathering and depletion of Ca and Na; 3) the separating effect of stones and soils by stone circle formation due to thermal conductivity and frost heave makes sediments in stone circle have lower chemical weathering with only two main minerals, albite and quartz; 4) changes of carbonate content in sediments with glacier front retreating in different period implied that weathering rate of calcite averagely reached an estimate of 0.0792%wt/year in glacier A. The succession of vegetation made biological weathering become an important driving force for carbonate leaching from glacial sediments. These results and data provide scientifically significant archive for future global change studies.

Size distributions of molecular markers for biogenic secondary organic aerosol in urban Beijing

To understand the source, formation, and seasonality of biogenic secondary organic aerosol (BSOA), a nine-stage cascade impactor was utilized to collect size-segregated particulate samples from April 2017 to January 2018 in Beijing, China. BSOA tracers derived from isoprene, monoterpene, and sesquiterpene were measured with gas chromatography-mass spectrometry. Isoprene and monoterpene SOA tracers exhibited significant seasonal variations, with a summer maximum and a winter minimum. Dominance of 2-methyltetrols (isoprene SOA tracers) with a good correlation with levoglucosan (a biomass burning tracer), which was combined with the detection of methyltartaric acids (possible indicators for aged isoprene) in summer, implies possible biomass burning and long-range transport. In contrast, sesquiterpene SOA tracer (β-caryophyllinic acid) was dominant in winter and was probably associated with the local burning of biomass. Bimodal size distributions were observed for most isoprene SOA tracers, consistent with previous laboratory experiments and field studies showing that they can be formed not only in the aerosol phase but also in the gas phase. Monoterpene SOA tracers cis-pinonic acid and pinic acid showed a coarse-mode peak (5.8–9.0 μm) in four seasons due to their volatile nature. Sesquiterpene SOA tracer β-caryophyllinic acid showed a unimodal pattern with a major fine-mode peak (1.1–2.1 μm), which is linked to local biomass burning. The tracer-yield method was used to quantify the contributions of isoprene, monoterpene, and sesquiterpene to secondary organic carbon (SOC) and SOA. The highest isoprene SOC and SOA concentrations occurred in summer (2.00 μgC m−3 and 4.93 μg m−3, respectively), contributing to 1.61% of OC and 5.22% of PM2.5, respectively. These results suggest that BSOA tracers are promising tracers for understanding the source, formation, and seasonality of BSOA.

Analytical performance of single particle aerosol mass spectrometer for accurate sizing and isotopic analysis of individual particles

The commercial Hexin Single particle aerosol mass spectrometer (SPAMS) has been widely used for environmental aerosol monitoring and source apportionment. However, particle size measurement is easily affected by environment pressure fluctuation and sampling orifice clogging. The capability for quantitative analysis is poor, and few isotope measurement has been reported. This paper aims to evaluate the analytical performance of SPAMS and extend its application. First, the flight time of standard particles having different densities and sizes was measured under various conditions (aerodynamic lens upstream pressure and carrier gas). We proposed a universal method for particle size calibration, measurement and correction, taking into account the effects of lens geometry (acceleration nozzle diameter), particle parameters (density, diameter, and shape factor), and operating conditions (lens upstream pressure and carrier gas). Then, isotope measurement was performed when introducing a solution droplet containing a single element. Metal oxide and metal cluster ions were observed in the mass spectrum, indicating incomplete ionization of the sample droplet. The mass discrimination effect was carefully evaluated to correct the measured isotope ratio. Results show that the achievable accuracy of the corrected isotope ratio for elements investigated was 5%. The instrumental performance was relatively poor for elements having great ionization potential or bond energy. Finally, Ag/Eu2O3 suspension and yellow cake/ethanol suspension were analyzed for size, elemental and isotopic analysis. We confirmed that the mass discrimination effect during suspension introduction could be corrected using the mass discrimination correction factor obtained during solution introduction. The Ag, Eu and U in these suspension particles were all found to be at natural abundance. The uranium in the yellow cake was identified as sodium duranyate (Na2U2O7) with volumetric equivalent diameter of approximately 65 nm. The work presented here is beneficial for instrument improvement and wide application.

Heating and lighting: understanding overlooked energy-consumption activities in the Indian residential sector

Understanding the climate impact of residential emissions starts with determining the fuel consumption of various household activities. While cooking emissions have been widely studied, non-cooking energy-consumption activities in the residential sector such as heating and lighting, have been overlooked owing to the unavailability of data at national levels. The present study uses data from the Carbonaceous Aerosol Emissions, Source Apportionment and Climate Impacts (COALESCE) project, which consists of residential surveys over 6000 households across 49 districts of India, to understand the energy consumed by non-cooking residential activities. Regression models are developed to estimate information in non-surveyed districts using demographic, housing, and meteorological data as predictors. Energy demand is further quantified and distributed nationally at a 4 × 4 km resolution. Results show that the annual energy consumption from non-cooking activities is 1106 [201] PJ, which is equal to one-fourth of the cooking energy demand. Freely available biomass is widely used to heat water on traditional stoves, even in the warmer regions of western and southern India across all seasons. Space heating (51%) and water heating (42%) dominate non-cooking energy consumption. In comparison, nighttime heating for security personnel (5%), partly-residential personal heating by guards, dominant in urban centers and kerosene lighting (2%) utilize minimal energy. Biomass fuels account for over 90% of the non-cooking consumption, while charcoal and kerosene make up the rest. Half of the energy consumption occurs during winter months (DJF), while 10% of the consumption occurs during monsoon, when kerosene lighting is the highest. Firewood is the most heavily used fuel source in western India, charcoal in the northern hilly regions, agricultural residues and dung cake in the Indo-Gangetic plains, and kerosene in eastern India. The study shows that ∼20% of residential energy consumption is on account of biomass-based heating and kerosene lighting activities.

Black Carbon Seasonal Trends and Regional Sources on Bely Island (Arctic)

The impact of aerosol sources on the pollution of the Russian sector of the Arctic is now strongly underestimated. A new polar aerosol station was arranged in August 2019 on Bely Island (Kara Sea), on the pathway of air mass transport from industrial regions of Western Siberia to the Arctic. Continuous aethalometer measurements of a short-lived climate tracer, i.e., black carbon, (from December to April 2019 and from January to November 2020) showed its seasonal variations with high values (60–92 ng/m3) in December–April and low values (18–72 ng/m3) in June–September. Pollution periods are identified. Regional distribution of fossil fuel and biomass combustion sources are obtained using the black carbon concentration weight trajectory model. The impact of gas flaring from oil and gas extraction areas of Western Siberia, the Volga region, the Urals, and the Komi Republic is found to be most pronounced during the cold period, and the impact from wildfire smoke emissions is found to be maximal in the warm season. A marker of biomass burning impact, determined from the difference between the black carbon concentrations measured in a broad wavelength spectrum, indicated the predominant effects from residential wood combustion in the cold period and agricultural and forest fires in the warm season.

Classifying aerosol type using in situ and satellite observations over a semi-arid station, Anantapur, from southern peninsular India

The chemical composition of aerosols is crucial for understanding aerosol radiative characteristics, classifying aerosol sources, and improving atmospheric aerosol satellite retrieval algorithms. In this study, the absorption angström exponent (AAE) and scattering angström exponent (SAE) values are derived from an aethalometer and three wavelength integrating nephelometer. MERRA-2 (Modern-Era Retrospective Study for Research and Applications) speciated aerosol optical depths and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) aerosol subtypes are utilized for the identification of a possible aerosol type over a semi-arid station, Anantapur, in Southern peninsular India from March 2016 to February 2018. Analysis from MERRA-2 for different aerosols illustrates that sulphate aerosol optical depth (SO4 AOD) dominates (>0.16) during winter and post-monsoon, while dust aerosol optical depth (DU AOD), organic carbon optical depth (OCAOD), and sulphate aerosol optical depth (SO4 AOD) mainly contributed (>0.07) to the total AOD during summer. SO4 AOD accounted for over ∼ 50% of total AOD during winter and post-monsoon, whereas DU AOD accounted for<10% of total aerosol optical depth in the respective seasons. The seasonal mean values of SAE (AAE) were found to be 1.95 ± 0.37 (1.03 ± 0.08), 1.65 ± 0.55 (1.03 ± 0.08), 2.53 ± 0.20 (1.03 ± 0.08) and 2.66 ± 0.15 (1.03 ± 0.08) during summer, monsoon, post-monsoon, and winter, respectively. AAE and SAE classification schemes showed that during winter, summer, and post-monsoon, continental polluted aerosols dominated (>56%), while dust and marine pollution aerosols dominated (∼47%) to the total aerosols during the monsoon. Continental aerosols are predominant during all seasons except for monsoon, and result from local anthropogenic activities and the transport of mineral dust particles and smoke aerosols from the north and western India. The observed aerosol types are consistent with the air mass back-trajectory cluster analysis performed with the help of Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT). The various aerosol types (absorbing and non-absorbing) and their change over a region are essential for for reducing the uncertainty in the assessment of aerosol radiative effects.

Sources of Organic Aerosol in China from 2005 to 2019: A Modeling Analysis.

Organic aerosol (OA) is a key component of fine particulate matter (PM2.5) and affects the human health and leads to climate change. With strict control measures for air pollutants during the last decade, the OA concentration in China declined slowly, while its sources remain unclear. In this study, we simulate the primary OA (POA) and secondary OA (SOA) concentrations from 2005 to 2019 with a state-of-the-art air quality model, Community Multiscale Air Quality (CMAQ, version 5.3.2) coupled with a Two-Dimensional Volatility Basis Set (2D-VBS) module, and a long-term emission inventory of full-volatility organic compounds in China and conduct source apportionment and sensitivity analysis. The simulation results show that, from 2005 to 2019, the OA concentration in China decreased from 24.0 to 12.8 μg/m3 with most of the reduction from POA. The OA pollution from residential biomass burning declined 75% from 2005 to 2019, while it is still the major OA source in China. OA pollution from VCP increased by more than 2-fold and became the largest SOA source in China. From 2014 to 2019, the NOx control in China slightly offset the decrease of SOA concentration due to elevated oxidation capacity.

Humic Like Substances (HULIS): Contribution to Global Warming and Stratospheric Ozone Depletion

The authors have previously provided compelling evidence that coal fly ash particles, not chlorofluorocarbons (CFC’s), are the primary cause of stratospheric ozone depletion. Coal burning and coal fly ash aerosols utilized in covert tropospheric geoengineering have already severely damaged the stratospheric ozone layer, leading to deadly ultraviolet radiation UV-B and UV-C penetrating to Earth’s surface. Coal burning and biomass burning are primary sources of a particular organic aerosol, humic-like substances, referred to collectively as HULIS. HULIS, like coal fly ash, plays a key role in climate change due to its ubiquity in biogenic and anthropogenic aerosols, its ability to absorb solar ultraviolet radiation and to transfer that heat to atmospheric gases, which reduces the temperature difference relative to the near-surface air, which reduces atmospheric convection, and which concomitantly reduces heat loss from the surface, causing regional and global warming. HULIS affects human and environmental health by production of reactive oxygen species and environmentally persistent free radicals. Stratospheric ozone was apparently depleted during the Permian Extinction by coal and biomass combustion aerosols produced by massive volcanic activity. A spike in sea and land temperature during World War II, associated with particulate pollution, also is correlated with a spike in HULIS obtained from Alpine ice cores. Recently, large forest fires have also been shown to deplete stratospheric ozone. Since HULIS is common to both coal and biomass burning, and ozone is taken up by submicron HULIS particles, it follows that HULIS aerosols are another cause of stratospheric ozone depletion. Our time is short to end all geoengineering activities and reduce or eliminate anthropogenic coal fly ash and HULIS-type aerosols.

Characterization of free L- and D-amino acids in size-segregated background aerosols over the Ross Sea, Antarctica

The study of airborne chemical markers is crucial for identifying sources of aerosols, and their atmospheric processes of transport and transformation. The investigation of free amino acids and their differentiation between the L- and D- enantiomers are even more important to understand their sources and atmospheric fate. Aerosol samples were collected with a high-volume sampler with cascade impactor at Mario Zucchelli Station (MZS) on the coast of the Ross Sea (Antarctica) for two summer campaigns (2018/19 and 2019/20). The total mean concentration of free amino acids in PM10 was 4 ± 2 pmol m-3 for both campaigns and most of free amino acids were distributed in fine particles. The coarse mode of airborne D-Alanine and dimethylsufoniopropionate in seawater showed a similar trend during both Antarctic campaigns. Thus, the study of D/L Ala ratio in fine, coarse and PM10 fractions indicated the microlayer as the local source. This paper demonstrated that free amino acids follow the trend of DMS and MSA release occurred in the Ross Sea, confirming their applicability as markers for phytoplankton bloom also in paleoclimatic studies.

Influences of meteorology on emission sources and physicochemical properties of particulate matter in Seoul, Korea during the heating period

Chemical properties of particulate matter (PM), organic aerosol (OA) properties, sources and the volatility distribution were investigated during autumn in Seoul, Korea using aerodyne high resolution time of flight aerosol mass spectrometer (HR-ToF-AMS) with a thermodenuder (TD) combined system (TD-AMS). Overall, the average PM1 + black carbon (BC) concentration was 21.49 μg/m3, ranging from 7.85 μg/m3 to 48.36 μg/m3, and the largest proportion of PM1 components was organic (54%), followed by NO3− (17%), SO42− (12%), NH4+ (9%) and BC (6%). During this period, the O/C and H/C ratios were similar to those in other studies (0.45 and 1.70, respectively), but the N/C ratio was slightly higher than that in other studies. Five organic aerosol (OA) sources were identified through positive matrix factorization (PMF) analysis, where four POAs (HOA, COA, SFOA1 and SFOA2) and one SOA (LVOOA) were identified. A distinct feature during this study was that two different combustion-related sources, SFOA1 and SFOA2 were observed. Two different SFOAs showed time-dependent features and different chemical compositions. SFOA2, which was dominant during the higher-temperature period (16.3 °C (5.1–26.6)) showed less O/C (0.41 vs 0.57) and N/C (0.033 vs 0.059) and more volatile feature than the one of SFOA1 during colder period (10.1 °C (−1.8-19.4)). It might be due to different heating activities and more intensive gas to particle parting and oxidizing processing under colder condition. Haze is also influenced by heating activities. When stagnant conditions occur with high heating activities, enhanced emission sources (SFOA1), enhanced gas-to-particle partitioning (nitrate) and the accumulation of primary OA result in severe haze conditions in urban air. This result suggests that controlling emission sources during heating seasons is still required for haze control in urban environments.

Marine aerosols in coastal areas and their impact on cave drip water – A monitoring study from Northern Spain

Marine aerosols affect coastal environments and human infrastructure, hence assessing the marine aerosol deposition in coastal areas is important. Field observations of marine aerosol deposition in coastal regions is commonly limited to a single station at high temporal resolution, which does not provide strong constraints on the spatial changes in the rate of aerosol delivery over the first 10 km distance from the coast, a gradient with the potential to constrain scavenging terms in aerosol models. Here, we provide data of monthly marine aerosol deposition (wet and dry) within the first 10 km from the coast during a 15-month monitoring study. Along a transect, a strong decrease of marine aerosols (Na, Mg, S and K) in the first 3 km from the coast but little decrease between 3 and 10 km is found. Based on fluxes of Na, the most conservative component measured and most completely attributed to marine aerosol sources, overall dry aerosol deposition decreases by nearly 20 to 30-fold from the coast to the station 10 km inland. Wet and dry marine aerosol deposition is significantly increased during the windy season (October until March), which is also the season of higher precipitation. The wind effect on aerosol deposition was greatest at the coast and diminished inland: between October and November 2019, the 3-fold increase in cumulative wind speed above the whitecap threshold caused a nearly 10-fold increase in the most proximal site, a 4-fold increase in 3.2 km sites, but only a 2-fold increase in dry aerosol deposition in the most distal sites. Independent of the season, the aerosol deposition rate >3 km from the coast drops to less than 20% of the most coast proximal station. Comparison of elemental ratios with seawater composition confirms the marine origin of Na and Mg in aerosols, but indicates additional sources and sinks for other elements (S and K) which do not correspond with expected marine sources. Furthermore, we test the time-integrated aerosol deposition in shallow groundwaters intercepted as cave drip waters from 13 caves, which confirm the decreasing contribution with distance from the coast but also reveal additional effects on the natural capture of wet and dry aerosols such as wind shielding effects and vegetation cover. The Na/Mg ratio of drip waters can be used to assess the significance of marine aerosols vs. bedrock to cave waters in the present day.