scholarly journals Submicron aerosol composition in the world's most polluted megacity: The Delhi Aerosol Supersite campaign

2018 ◽  
Author(s):  
Shahzad Gani ◽  
Sahil Bhandari ◽  
Sarah Seraj ◽  
Dongyu S. Wang ◽  
Kanan Patel ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Atmospheric Chemistry ◽  
Local Context ◽  
Aerosol Composition ◽  
Time Resolved ◽  
Diurnal Variability ◽  
Submicron Aerosol ◽  
Secondary Species ◽  
Primary Emissions ◽  
Chloride Concentrations

Abstract. Delhi, India routinely experiences some of the world's highest urban particulate matter concentrations. We established the Delhi Aerosol Supersite campaign to provide long-term characterization of the ambient submicron aerosol composition in Delhi. Here we report on 1.25 years of highly time resolved speciated submicron particulate matter (PM1) data, including black carbon (BC) and non-refractory PM1 (NR-PM1), which we combine to develop a composition-based estimate of PM1 (“C-PM1” = BC + NR-PM1) concentrations. We observed marked seasonal and diurnal variability in the concentration and composition of PM1 owing to the interactions of sources and atmospheric processes. Winter was the most polluted period of the year with average C-PM1 mass concentrations of ~210 μg m−3. Monsoon was hot and rainy, consequently making it the least polluted (C-PM1 ~50 μg m−3) period. Organics constituted more than half of the C-PM1 for all seasons and times of day. While ammonium, chloride and nitrate each were ~10% of the C-PM1 for the cooler months, BC and sulfate contributed ~5% each. For the warmer periods, the fractional contribution of BC and sulfate to C-PM1 increased and the chloride contribution decreased to less than 2%. The seasonal and diurnal variation in absolute mass loadings were generally consistent with changes in ventilation coefficients, with higher concentrations for periods with unfavorable meteorology—low planetary boundary layer height and low wind speeds. However, the variation in C-PM1 composition was influenced by temporally varying sources, photochemistry and gas-particle partitioning. During cool periods when wind was from the northwest, episodic hourly averaged chloride concentrations reached 50–100 μg m−3, ranking among the highest chloride concentrations reported anywhere in the world. We estimated the contribution of primary emissions and secondary processes to Delhi's submicron aerosol. Secondary species contributed almost 50–70% of Delhi's C-PM1 mass for the winter and spring months, and up to 60–80% for the warmer summer and monsoon months. For the cooler months that had the highest C-PM1 concentrations, the nighttime sources were skewed towards primary sources, while the daytime C-PM1 was dominated by secondary species. Overall, these findings point to the important effects of both primary emissions and more regional atmospheric chemistry on influencing the extreme particle concentrations that impact the Delhi megacity region. Future air quality strategies considering Delhi's situation in both a regional and local context will be more effective than policies targeting only local, primary air pollutants.

scholarly journals Submicron aerosol composition in the world's most polluted megacity: the Delhi Aerosol Supersite study

2019 ◽  
Vol 19 (10) ◽  
pp. 6843-6859 ◽  
Author(s):  
Shahzad Gani ◽  
Sahil Bhandari ◽  
Sarah Seraj ◽  
Dongyu S. Wang ◽  
Kanan Patel ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Atmospheric Chemistry ◽  
Local Context ◽  
Aerosol Composition ◽  
Time Resolved ◽  
Diurnal Variability ◽  
Submicron Aerosol ◽  
Secondary Species ◽  
Primary Emissions ◽  
Chloride Concentrations

Abstract. Delhi, India, routinely experiences some of the world's highest urban particulate matter concentrations. We established the Delhi Aerosol Supersite study to provide long-term characterization of the ambient submicron aerosol composition in Delhi. Here we report on 1.25 years of highly time-resolved speciated submicron particulate matter (PM1) data, including black carbon (BC) and nonrefractory PM1 (NR-PM1), which we combine to develop a composition-based estimate of PM1 (“C-PM1” = BC + NR-PM1) concentrations. We observed marked seasonal and diurnal variability in the concentration and composition of PM1 owing to the interactions of sources and atmospheric processes. Winter was the most polluted period of the year, with average C-PM1 mass concentrations of ∼210 µg m−3. The monsoon was hot and rainy, consequently making it the least polluted (C-PM1 ∼50 µg m−3) period. Organics constituted more than half of the C-PM1 for all seasons and times of day. While ammonium, chloride, and nitrate each were ∼10 % of the C-PM1 for the cooler months, BC and sulfate contributed ∼5 % each. For the warmer periods, the fractional contribution of BC and sulfate to C-PM1 increased, and the chloride contribution decreased to less than 2 %. The seasonal and diurnal variation in absolute mass loadings were generally consistent with changes in ventilation coefficients, with higher concentrations for periods with unfavorable meteorology – low planetary boundary layer height and low wind speeds. However, the variation in C-PM1 composition was influenced by temporally varying sources, photochemistry, and gas–particle partitioning. During cool periods when wind was from the northwest, episodic hourly averaged chloride concentrations reached 50–100 µg m−3, ranking among the highest chloride concentrations reported anywhere in the world. We estimated the contribution of primary emissions and secondary processes to Delhi's submicron aerosol. Secondary species contributed almost 50 %–70 % of Delhi's C-PM1 mass for the winter and spring months and up to 60 %–80 % for the warmer summer and monsoon months. For the cooler months that had the highest C-PM1 concentrations, the nighttime sources were skewed towards primary sources, while the daytime C-PM1 was dominated by secondary species. Overall, these findings point to the important effects of both primary emissions and more regional atmospheric chemistry on influencing the extreme particle concentrations that impact the Delhi megacity region. Future air quality strategies considering Delhi's situation in both a regional and local context will be more effective than policies targeting only local, primary air pollutants.

A study of summer and winter highly time-resolved submicron aerosol composition measured at a suburban site in Prague

2015 ◽  
Vol 118 ◽  
pp. 45-57 ◽  
Author(s):  
Lucie Kubelová ◽  
Petr Vodička ◽  
Jaroslav Schwarz ◽  
Michael Cusack ◽  
Otakar Makeš ◽  
...  
Keyword(s):  
Aerosol Composition ◽  
Time Resolved ◽  
Submicron Aerosol ◽  
Suburban Site

Back to the Future: Reducing Atmospheric Particulate Matter Levels to Improve Human Health

2021 ◽  
Author(s):  
Spyros Pandis
Keyword(s):  
Particulate Matter ◽  
Atmospheric Aerosols ◽  
Atmospheric Chemistry ◽  
Control Strategy ◽  
Atmospheric Particulate Matter ◽  
Anthropogenic Emissions ◽  
The Us ◽  
Negative Impacts ◽  
Predictive Understanding ◽  
Physical And Chemical

<p>The human development of our planet has a variety of negative impacts on the composition of its atmosphere at every scale – locally, regionally, and even globally. One of these dramatic changes has been the increase in the mass concentrations of sub-micrometer particles by one to sometimes two orders of magnitude over populated areas in the Northern Hemisphere. These atmospheric aerosols can cause serious health problems, reduce visibility, contribute to acidic deposition and material damage, but are also cooling the planet by reflecting sunlight back to space. Atmospheric chemistry occurs within a fabric of complicated atmospheric dynamics and physics. This interplay often results in nonlinear and often counterintuitive changes of the system when anthropogenic emissions change. A major goal of our research has been to gain a predictive understanding of the physical and chemical processes that govern the dynamics, size, and chemical composition of atmospheric aerosols.</p><p>To illustrate the advances in the experimental techniques and theoretical tools in atmospheric aerosol science, we will go back to the beginning of the 21<sup>st</sup> century and we will revisit the design a particulate matter control strategy for the Eastern US based on the data, knowledge, and tools available at that time. We will then look at the effects of the parts of this control strategy that have been materialized and their effects on public health using the current understanding. Finally, we will look forward in ways of further improving air quality in the US and Europe.</p>

Experimental and theoretical study of particulate re-entrainment from the combustion chamber walls of a diesel engine

1997 ◽  
Vol 211 (1) ◽  
pp. 49-57 ◽  
Author(s):  
M Abu-Qudais ◽  
D. B. Kittelson
Keyword(s):  
Particulate Matter ◽  
Diesel Engine ◽  
Combustion Chamber ◽  
Mass Concentration ◽  
High Surface ◽  
Combustion Process ◽  
Surface Shear ◽  
Time Resolved ◽  
Soot Deposition ◽  
Engine Cycle

The purpose of this research was to investigate the influence of the in-cylinder surfaces on the net emission of the particulate matter in the exhaust of a single cylinder, diesel engine. In order to obtain this information, time-resolved sampling was done to characterize the particulate matter emitted in the engine exhaust. A rotating probe sampled the free exhaust plume once each engine cycle. The rotation of the probe was synchronized with the engine cycle in such a way that the samples could be taken at any predetermined crank angle degree window. The sampling probe was designed for isokinetic sampling in order to obtain reliable results. To characterize the exhaust particulate in real time, a filter for mass concentration measurements was used. The results showed about 45 per cent higher mass concentrations as well as particles of larger diameter emitted during blowdown than late in the displacement phase of the exhaust stroke. This suggests that high in-cylinder shear rates and velocities which are associated with the blowdown process, cause the deposited soot to be re-entrained from the surfaces of the combustion chamber, where re-entrainment is favoured by conditions of high surface shear. A mathematical model to predict the amount of soot re-entrained from the cylinder walls is presented. This model is based on information presented in the literature along with the results of the time-resolved measurements of mass concentration. This model supported the hypothesis of soot deposition during the combustion process, with subsequent re-entrainment during the blowdown process of the exhaust stroke.

scholarly journals Weaker cooling by aerosols due to dust–pollution interactions

2020 ◽  
Vol 20 (23) ◽  
pp. 15285-15295
Author(s):  
Klaus Klingmüller ◽  
Vlassis A. Karydis ◽  
Sara Bacer ◽  
Georgiy L. Stenchikov ◽  
Jos Lelieveld
Keyword(s):  
Atmospheric Chemistry ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Radiative Effect ◽  
Dust Pollution ◽  
Aerosol Composition ◽  
Anthropogenic Aerosol ◽  
Aerosol Forcing ◽  
Condensed Water ◽  
Chemical Ageing

Abstract. The interactions between aeolian dust and anthropogenic air pollution, notably chemical ageing of mineral dust and coagulation of dust and pollution particles, modify the atmospheric aerosol composition and burden. Since the aerosol particles can act as cloud condensation nuclei, this affects the radiative transfer not only directly via aerosol–radiation interactions, but also indirectly through cloud adjustments. We study both radiative effects using the global ECHAM/MESSy atmospheric chemistry-climate model (EMAC) which combines the Modular Earth Submodel System (MESSy) with the European Centre/Hamburg (ECHAM) climate model. Our simulations show that dust–pollution–cloud interactions reduce the condensed water path and hence the reflection of solar radiation. The associated climate warming outweighs the cooling that the dust–pollution interactions exert through the direct radiative effect. In total, this results in a net warming by dust–pollution interactions which moderates the negative global anthropogenic aerosol forcing at the top of the atmosphere by (0.2 ± 0.1) W m−2.

scholarly journals High spatial resolution mapping of aerosol composition and sources in Oakland, California using mobile aerosol mass spectrometry

2018 ◽  
Author(s):  
Rishabh U. Shah ◽  
Ellis S. Robinson ◽  
Peishi Gu ◽  
Allen Robinson ◽  
Joshua S. Apte ◽  
...  
Keyword(s):  
Urban Areas ◽  
Central Business District ◽  
Photochemical Activity ◽  
Spatial And Temporal Patterns ◽  
Aerosol Composition ◽  
Elemental Ratios ◽  
Air Masses ◽  
Aerosol Mass ◽  
Secondary Origin ◽  
Primary Emissions

Abstract. We investigated spatial and temporal patterns in concentration and composition of sub-micron particulate matter (PM1) in Oakland, California in the summer of 2017 using an aerosol mass spectrometer mounted in a mobile laboratory. We performed ∼ 160 hours of mobile sampling in the city over a 20-day period. Measurements are compared for three adjacent neighborhoods with distinct land uses: a central business district (downtown), a residential district (West Oakland), and a major shipping port. The average organic aerosol (OA) concentration is 5.3 μgm−3 and contributes ∼ 50 % of the PM1 mass. OA concentrations in downtown are, on average, 1.5 μgm−3 higher than in West Oakland and Port. We decomposed OA into three factors using positive matrix factorization: hydrocarbon-like OA (HOA; 20 % average contribution), cooking OA (COA; 25 %) and semi-volatile oxidized OA (SV-OOA; 55 %). The collective 45 % contribution from primary OA (HOA + COA) emphasizes the importance of primary emissions in Oakland. The dominant source of primary OA shifts from HOA-rich in the morning to COA-rich after lunch time. COA in downtown is consistently higher than West Oakland and Port due to a large number of restaurants. HOA exhibits variability in space and time. Morning-time HOA concentration in downtown is twice that in Port, but Port HOA increases more than two-fold during mid-day, likely because trucking activity at the Port peaks at that time. Despite the expectation of being spatially uniform, SV-OOA also exhibits spatial differences. Morning-time SV-OOA in downtown is roughly 25 % (∼ 0.6 μgm−3) higher than the rest of Oakland. Even as the entire domain approaches a more uniform photo-chemical state in the afternoon, downtown SV-OOA remains statistically higher than West Oakland and Port, suggesting that downtown is a microenvironment with higher photochemical activity. Higher concentrations of particulate sulfate (also of secondary origin) with no direct sources in Oakland further reflect higher photochemical activity in downtown. A combination of several factors (poor ventilation of air masses in street canyons, higher concentrations of precursor gases, higher concentrations of the hydroxyl radical) likely result in the proposed high photochemical activity in downtown. Lastly, through Van Krevelen analysis of elemental ratios (H/C, O/C) of the OA, we show that OA in Oakland is more chemically reduced than several other urban areas. This underscores the importance of primary emissions in Oakland. We also show that mixing of oceanic air masses with these primary emissions in Oakland is an important processing mechanism that governs the overall OA composition in Oakland. The findings of this study are important because the pollutants we find contributing the most to OA variability, both of primary and secondary origin, are ubiquitous in other urban locations.

scholarly journals The Finokalia Aerosol Measurement Experiment – 2008 (FAME-08): an overview

2010 ◽  
Vol 10 (3) ◽  
pp. 6641-6679 ◽  
Author(s):  
M. Pikridas ◽  
A. Bougiatioti ◽  
L. Hildebrandt ◽  
G. J. Engelhart ◽  
E. Kostenidou ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Back Trajectory ◽  
Aerosol Composition ◽  
Air Masses ◽  
The Balkans ◽  
Aerosol Measurement ◽  
Aerosol Mass Concentration ◽  
Measurement Experiment

Abstract. A month (4 May to 8 June 2008) of ambient aerosol, air ion and gas phase sampling (Finokalia Aerosol Measurement Experiment 2008, FAME-08) was conducted at Finokalia, on the island of Crete, Greece. The purpose of the study was to characterize the physical and chemical properties of aged aerosol and to investigate new particle formation. Measurements included aerosol and air ion size distributions, size-resolved chemical composition, organic aerosol thermal volatility, water uptake and particle optical properties (light scattering and absorption). Statistical analysis of the aerosol mass concentration variations revealed the absence of diurnal patterns suggesting the lack of strong local sources. Sulfates accounted for approximately half of the particulate matter less than 1 micrometer in diameter (PM1) and organics for 26%. The PM1 organic aerosol fraction was highly oxidized with 80% water soluble. The supermicrometer particles were dominated by crustal components (50%), sea salt (24%) and nitrates (16%). The organic carbon to elemental carbon (OC/EC) ratio correlated with ozone measurements but with a one-day lag. The average OC/EC ratio for the study period was equal to 5.4. For three days air masses from North Africa resulted in a 6-fold increase of particulate matter less than 10 micrometers in diameter (PM10) and a decrease of the OC/EC ratio by a factor of 2. Back trajectory analysis, based on FLEXPART footprint plots, identified five source regions (Athens, Greece, Africa, other continental and marine), each of which influenced the PM1 aerosol composition and properties. Marine air masses had the lowest PM1 concentrations and air masses from the Balkans, Turkey and Eastern Europe the highest.

scholarly journals Determination of the absorption cross-sections of higher order iodine oxides at 355 nm and 532 nm

2020 ◽  
Author(s):  
Thomas R. Lewis ◽  
Juan Carlos Gómez Martin ◽  
Mark A. Blitz ◽  
Carlos A. Cuevas ◽  
John M. C. Plane ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Atmospheric Chemistry ◽  
Absorption Cross Section ◽  
Absorption Cross ◽  
Time Resolved ◽  
Flight Mass Spectrometry ◽  
Iodine Oxides ◽  
Photo Ionization

Abstract. Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layer and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules has not been studied in detail previously. Here, we report the first determination of the absorption cross sections of IxOy, x = 2, 3, 5, y = 1–12 at λ = 355 nm by combining pulsed laser photolysis of I2/O3 gas mixtures in air with time-resolved photo-ionization time-of-flight mass spectrometry, using NO2 actinometry for signal calibration. The oxides selected for absorption cross section determinations are those presenting the strongest signals in the mass spectra, where signals containing 4 iodine atoms are absent. The method is validated by measuring the absorption cross section of IO at 355 nm, σ355 nm, IO = (1.2 ± 0.1) ×  10–18 cm2, which is found to be in good agreement with the most recent literature. The results obtained are: σ355 nm, I2O3 

A Future Multi-Platform Atmospheric Chemistry Measurement Campaign to Study Oxidation in Mixed Anthropogenic-Biogenic Air Masses

2021 ◽  
Author(s):  
Christopher Cantrell ◽  
Vincent Michoud ◽  
Paola Formenti ◽  
Jean-Francois Doussin ◽  
Stephanie Alhajj Moussa ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Los Angeles ◽  
Organic Compounds ◽  
Atmospheric Chemistry ◽  
Vapor Pressures ◽  
Air Masses ◽  
Measurement Campaign ◽  
Secondary Species ◽  
Volatile Organic ◽  
Urban Plumes

<p>It is well known that the high population density of urban regions leads to significant degradation of the quality of the air because of the emissions of pollutants that are by-products of energy production, transportation, and industry. The composition and chemistry of urban air has been studied for many decades and these studies have led to detailed understanding of the factors controlling, for example, the formation of ozone, peroxyacetyl nitrate and other secondary species. In the last 20 to 30 years, significant progress has been made in reducing emissions of volatile organic compounds (VOCs) and oxides of nitrogen (NO<sub>x</sub>) in urban atmospheres. Substantial reductions in the abundance of secondary compounds, though, have been more elusive.</p><p>Research has continued to reveal more and more details of the complex processes involved in the atmospheric degradation of wide varieties of volatile organic compounds (VOCs) of anthropogenic and biospheric (BVOCs) origins. BVOCs include isoprene, monoterpenes and sesquiterpenes, and oxygenated VOCs (OVOCs, such as small alcohols). Emissions of BVOCs depend on several factors such as plant or tree species, temperature, and photosynthetically active radiation. They consist almost exclusively of unsaturated compounds with chemistry somewhat different from those of typical urban organic compound emissions. Oxidation of VOCs can lead to molecules of low volatility that are prone to uptake into the aerosol phase.</p><p>Recent studies conducted in megacities such as Paris, Mexico City, Los Angeles and those in China have led to significant advances in our understanding of the chemical evolution of urban plumes. However, important scientific questions remain on how mixing of anthropogenic and biogenic air masses modifies the composition of urban plumes and hence their impacts. Indeed, the proximity of cites to areas of strong biogenic emissions is not unusual. Many major cities at mid-latitudes are surrounded by forested areas.</p><p>ACROSS (Atmospheric ChemistRy Of the Suburban foreSt) is an integrative, innovative, multi-scale project awarded under the “Make Our Planet Great Again” (MOPGA) framework that seeks to definitively improve understanding of the impacts of mixing urban and biogenic air masses on the oxidation of atmospheric VOCs. The ACROSS working hypothesis is that this leads to changes in the production of oxygenated VOCs whose properties (e.g. vapor pressures) alter their importance in incorporation into SOA and their roles in production of ozone and other secondary species. Changes are also expected in the efficiency of radical recycling affecting the atmospheric oxidative capacity. Particularly important is NO<sub>x</sub> transport to suburban biogenic environments and the resulting modification of key chemical processes.</p><p>A key highlight of ACROSS is an intensive, multi-platform measurement campaign in the summer of 2022. It will use instruments staged on an airborne platform, a tower in the Rambouillet Forest near Paris, and other ground sites. The data collected from this campaign will be analyzed and studied to extract information about tropospheric oxidation chemistry generally, but also changes observed in the situation of mixed urban and biogenic air masses.</p><p>This presentation will summarize plans for the ACROSS campaign.</p>

Sign in / Sign up

Export Citation Format

Share Document