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Clouds developing in a polluted environment have more numerous, smaller cloud droplets that can increase the cloud lifetime and liquid water content. Such changes in the cloud droplet properties may suppress low precipitation allowing... more
Clouds developing in a polluted environment have more numerous, smaller cloud droplets that can increase the cloud lifetime and liquid water content. Such changes in the cloud droplet properties may suppress low precipitation allowing development of a stronger convection and higher freezing level. Delaying the washout of the cloud water (and aerosol), and the stronger convection will result in higher clouds with longer life time and larger anvils. We show these effects by using large statistics of the new, 1km resolution data from MODIS on the Terra satellite. We isolate the aerosol effects from meteorology by regression and showing that aerosol microphysical effects increases cloud fraction by average of 30 presents for all cloud types and increases convective cloud top pressure by average of 35mb. We analyze the aerosol cloud interaction separately for high pressure trade wind cloud systems and separately for deep convective cloud systems. The resultant aerosol radiative effect on...
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Air particulate matter contains a wide range of substances which influence the physicochemical properties of aerosol particles and thus their effects on atmospheric chemistry and physics, climate, and public health. Chemical reactions... more
Air particulate matter contains a wide range of substances which influence the physicochemical properties of aerosol particles and thus their effects on atmospheric chemistry and physics, climate, and public health. Chemical reactions occurring on aerosol particles can transform these components and change their atmospheric and health effects. Gas-particle interactions generally involve multiple steps of mass transport and chemical reaction, and measurement data on the kinetics and products of these processes are sparse. Moreover, the terminology and formalisms applied for the interpretation and extrapolation of experimental results in different studies and aerosol systems are often incompatible. To provide a better basis for the analysis and comparison of laboratory measurement results and for their extrapolation and use in atmospheric models, a consistent and universally applicable terminology and mathematical framework for atmospheric aerosol surface chemistry and gas-particle in...
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Reactions of organic aerosols can lead to changes in their hygroscopicity and their CCN activity. As a result, these processes may change organic aerosols' roles in local, regional and global air quality and climate. While most... more
Reactions of organic aerosols can lead to changes in their hygroscopicity and their CCN activity. As a result, these processes may change organic aerosols' roles in local, regional and global air quality and climate. While most organic aerosols are secondary and hence already at least slightly processed in the atmosphere, it is quite possible that during their atmospheric lifetime they will continue to change. While several previous studies suggested increase of hygroscopicity, other studies have shown that reactions of the organic matter either do not affect hygroscopicity or even decrease it. We will present recent laboratory studies demonstrating how reactions of ozone and ammonia with aerosol particles containing model organic compounds (organic acids, alkenes) and complex organic matter (HULIS and fulvic acids) affect their hygroscopicity. Specifically, we will discuss under which conditions these reactions occur most efficiently (concentration ranges, exposure times, and h...
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The heterogeneous reactions between ammonium sulfate (AS), a proxy for inorganic ambient aerosol, and glycine, the most abundant amino acid in atmospheric aerosols with gas phase glyoxal were studied in terms of their optical, physical... more
The heterogeneous reactions between ammonium sulfate (AS), a proxy for inorganic ambient aerosol, and glycine, the most abundant amino acid in atmospheric aerosols with gas phase glyoxal were studied in terms of their optical, physical and chemical properties. The reactions were studied under different relative humidity (RH) conditions, varying from dry conditions, representative of arid regions (~19% RH) and up to 90% RH, typical for tropical conditions or in the vicinity of clouds. The product aerosols demonstrate a substantial growth in both geometric and optical extinction cross sections at λ=355nm under hydrated conditions, at a broad range of RH values of 35-90%. All reactions with gas phase glyoxal show a trend of increasing physical and optical growth relative to their initial size with decreasing seed aerosol size, from 100nm to 300nm, as well as with decreasing RH values from 90% to ~40%. This reaction occurs before deliquescence and may indicate the absorption of a few mo...
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One of the major uncertainties in the understanding of Earth's climate system is the interaction between solar radiation and aerosols in the atmosphere. This interaction is dependent on the physical and chemical properties of the... more
One of the major uncertainties in the understanding of Earth's climate system is the interaction between solar radiation and aerosols in the atmosphere. This interaction is dependent on the physical and chemical properties of the aerosols and on the wavelength of the incident light. Aerosols exposed to high humidity areas will change their chemical, physical, and optical properties. To model hydrated aerosols, atmospheric chemistry models use the volume weighted mixing rule to predict the complex refractive index (RI) of aerosols when they interact with high relative humidity areas, and, in general, assume homogeneous mixing. The validity of these assumptions is explored. The extinction coefficient and growth factor of humidified aerosols, at 80% and 90% RH, and at 532 nm and 355 nm wavelengths was measured for size-selected aerosols of ammonium sulfate, peat (a lightly absorbing humic-like substance proxy), nigrosine (a black dye to model highly absorbing substances), and a mix...
Airborne fungi can cause a wide array of adverse responses in humans depending on the type and quantity present. Since dose and human response is highly individual, the sensitivity of a person exposed is also an important consideration.... more
Airborne fungi can cause a wide array of adverse responses in humans depending on the type and quantity present. Since dose and human response is highly individual, the sensitivity of a person exposed is also an important consideration. The abundance of bioaerosols in the ambient air and their health impacts depend on the season and on the environmental conditions. In order to quantify and identify fungi bioaerosols' contribution to atmospheric aerosols and the impact to public health, it has been suggested to use chemicals that are typical of bioaerosols as biomarkers in chemical analysis of collected aerosols. An often used biomarker for determining the fungal biomass is ergosterol. Recently, Bauer et al. (2008) found that mannitol and arabitol concentrations are correlated with the fungal spore counts in atmospheric PM10. In this study, ergosterol, arabitol and mannitol were quantified in ambient aerosols collected in the Eastern Mediterranean region for 12 months in order to...
The optical properties of complex aerosols, important in determining their radiative forcing in the atmosphere and, subsequently, their impact on climate, are extensively examined. There is an abundance of natural and anthropogenic... more
The optical properties of complex aerosols, important in determining their radiative forcing in the atmosphere and, subsequently, their impact on climate, are extensively examined. There is an abundance of natural and anthropogenic organic compounds in the atmosphere that can be released as primary aerosols or form secondary organic aerosols (SOAs) via photocchemical reactions with OH, NO3, and O3. SOAs can undergo further processing in the atmosphere with oxidative species, changing the chemical, physical, and optical properties of the particles. Absorbing aerosol components include nitrated aromatics, aromatic polycarboxylic acids, phenols, polycyclic aromatic hydrocarbons, and nitrated inorganics. Many of these species have been found in atmospheric particles. Some of them are strong absorbers at long UV wavelengths. Such aerosols may affect downward UV irradiances in urban location and may be important for predicting smog evolution in urban areas. It is possible that such specie...
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Inhalation of traffic-associated atmospheric particulate matter (PM2.5) is recognized as a significant health risk. In this study we focused on a single ("sub-clinical response") exposure to water-soluble extracts from PM... more
Inhalation of traffic-associated atmospheric particulate matter (PM2.5) is recognized as a significant health risk. In this study we focused on a single ("sub-clinical response") exposure to water-soluble extracts from PM collected at a roadside site in a major European city, to elucidate potential components that drive pulmonary inflammatory, oxidative and defense mechanisms, and their systemic impacts. Intra-tracheal instillation (IT) of the aqueous extracts induced a 24h inflammatory response characterized by increased broncho-alveolar lavage fluid (BALF) cells and cytokines (IL-6 and TNF-α), increased reactive oxygen species production, but insignificant lipids and proteins oxidation adducts in mice' lungs. This local response was largely self-resolved by 48h, suggesting that it could represent a sub-clinical response to everyday-level exposure. Removal of soluble metals by chelation markedly diminished the pulmonary PM-mediated response. An artificial metal soluti...
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Heterogeneous reactions of oleic acid aerosol particles with ozone are studied below 1% relative humidity. The particles have inert polystyrene latex cores (101-nm diameter) coated by oleic acid layers of 2 to 30 nm. The chemical content... more
Heterogeneous reactions of oleic acid aerosol particles with ozone are studied below 1% relative humidity. The particles have inert polystyrene latex cores (101-nm diameter) coated by oleic acid layers of 2 to 30 nm. The chemical content of the organic layer is monitored with ...
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Research Interests:
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ABSTRACT The Amazon basin is a hot spot of anthropogenically-driven biomass burning, accounting for approximately 15% of total global fire emissions. It is essential to accurately measure these fires for robust regional and global... more
ABSTRACT The Amazon basin is a hot spot of anthropogenically-driven biomass burning, accounting for approximately 15% of total global fire emissions. It is essential to accurately measure these fires for robust regional and global modeling of key environmental processes. Here we have explored the link between spatio-temporal variability patterns in the Amazon basin's fires and the resulting smoke loading using 11 years (2002-2012) of data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Aerosol Robotic Network (AERONET) observations. Focusing on the peak burning season (July-October), our analysis shows strong inter-annual correlation between aerosol optical depth (AOD) and two MODIS fire products: fire radiative power (FRP) and fire pixel counts (FC). Among these two fire products, the FC better indicates the amount of smoke in the basin, as represented in remotely sensed AOD data. This fire product is significantly correlated both with regional AOD retrievals from MODIS and with point AOD measurements from the AERONET stations, pointing to spatial homogenization of the smoke over the basin on a seasonal time scale. However, MODIS AODs are found better than AERONET AODs observation for linking between smoke and fire. Furthermore, MODIS AOD measurements are strongly correlated with number of fires ∼1-2 degrees to the east, most likely due to westward advection of smoke by the wind. These results can be rationalized by the regional topography and the wind regimes. Our analysis can improve data assimilation of satellite and ground-based observations into regional and global model studies, thus improving the assessment of the environmental and climatic impacts of frequency and distribution variability of the Amazon basin's fires. We also provide the optimal spatial and temporal scales for ground-based observations, which could be used for such applications.
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Heterogeneous neutralization reactions of ammonia and alkylamines with sulfuric acid play an important role in aerosol formation and particle growth. However, little is known about the physical and chemical properties of alkylaminium... more
Heterogeneous neutralization reactions of ammonia and alkylamines with sulfuric acid play an important role in aerosol formation and particle growth. However, little is known about the physical and chemical properties of alkylaminium salts of organic acids. In this work we studied the thermal stability and volatility of alkylaminium carboxylate salts of short aliphatic alkylamines with monocarboxylic and dicarboxylic acids. The enthalpy of vaporization and saturation vapor pressure at 298 K were derived using the kinetic model of evaporation and the Clausius-Clapeyron relation. The vapor pressure of alkylaminium dicarboxylate salts is ∼10(-6) Pa, and the vaporization enthalpy ranges from 73 to 134 kJ mol(-1). Alkylaminium monocarboxylate salts show high thermal stability, and their thermograms do not follow our evaporation model. Hence, we inferred their vapor pressure from their thermograms as comparable to that of ammonium sulfate (∼10(-9) Pa). Further characterization showed that...
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ABSTRACT The first stage of retrieving the aerosol properties from space is masking out the cloudy pixels. The measured reflectance is inverted then to aerosol loading and properties. We show that a large portion of the cloud free... more
ABSTRACT The first stage of retrieving the aerosol properties from space is masking out the cloudy pixels. The measured reflectance is inverted then to aerosol loading and properties. We show that a large portion of the cloud free atmosphere, defined here as the twilight zone, has unique optical properties due to possible contributions from undetectable clouds and humidified aerosol. The contribution consists of coarse mode particles extending tens of kilometers from the nearest detectable cloud. we show that the magnitude and the decay rate, from a cloudy dominant optical signature to a dry aerosol signature, depends heavily on the background aerosol loading and therefore can be considered an aerosol effect in the vicinity of clouds rather than cloud contamination.
ABSTRACT The role of the Amazon rainforest on earth climatic system is well recognized. To keep forest wellbeing and the fragile balance between the rainforest and the atmosphere, the Amazon must contain a satisfactory amount of nutrients... more
ABSTRACT The role of the Amazon rainforest on earth climatic system is well recognized. To keep forest wellbeing and the fragile balance between the rainforest and the atmosphere, the Amazon must contain a satisfactory amount of nutrients to support the plants. The extensive rain and floods wash most of the soluble nutrients from the rainforest soil, leaving behind acidic kaolinite clay or sandy soil, with limited minerals for plant growth. It was suggested that lack of mineral in the soil may be replenished by deposition of Saharan mineral dust. Using remote sensing data (from the A-train satellites constellation) following with in-situ measurements (as part of the AMazonian Aerosol CharacteriZation Experiment (AMZE) campaign), ground-based data (from AErosol RObotic NETwork (AERONET)) and back trajectory calculations, we analyzed Saharan dust transport toward the Amazon basin during the AMZE period (Feb 7 to Mar 14, 2008). Dust mass, sink, vertical distribution and surface wind speeds were analyzed over the Bodele depression (located in Chad), where most of the dust is emitted, along the Atlantic Ocean and near the Brazilian coastline. Using an integrated data analysis approach we followed dust packages from their emission in the Sahara to their sink in the Amazon forest.
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ABSTRACT Humic-like substances (HULIS), often found in biogenic and secondary organic aerosols, are hypothesized to affect cloud droplet activation because of their possible effect on droplet surface tension. We will present measurements... more
ABSTRACT Humic-like substances (HULIS), often found in biogenic and secondary organic aerosols, are hypothesized to affect cloud droplet activation because of their possible effect on droplet surface tension. We will present measurements of surface tension changes due to the presence of model aquatic compounds (Suwannee River Fulvic Acid) and HULIS extracted from aged and fresh wood burning and pollution aerosols. While most previous measurements were conducted on macroscopic droplets at equilibrium, it is not clear what value of surface tension should be used to describe a water droplet growing on HULIS surfactants? Depending on the diffusion rate of the surfactants, it is possible that the advancing surface of the growing droplet gets ahead of the solution or fully incorporates the solution. In the slow diffusion case, surface tension of pure water should be used while in the fast diffusion case, a lower concentration-dependent surface tension is appropriate. Two questions naturally arise: 1) what is fast and slow; 2) is the magnitude of the effect significant. We shall briefly address these questions and then proceed to report new surface tension measurements of HULIS surfactants and interpret their time-dependence and characteristic scales. We will also present density measurements of these species and discuss how aging processes affect these physical properties.
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Research Interests:
Recent studies have emphasized the role of organic atmospheric particles in cloud formation, radiative forcing, and health effects. Quantification of these effects is limited because the compositions, morphologies, and chemical... more
Recent studies have emphasized the role of organic atmospheric particles in cloud formation, radiative forcing, and health effects. Quantification of these effects is limited because the compositions, morphologies, and chemical reactivities of organic particles are poorly understood. Laboratory studies are motivated to understand and quantify complex particles and their processes. A critical unknown is the heterogeneous chemistry that depends upon
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ABSTRACT
ABSTRACT Alkyl aminium sulfates have been postulated to constitute important components of nucleation and accumulation mode atmospheric aerosols. In this study we present laboratory data on the thermochemical, cloud condensation nuclei... more
ABSTRACT Alkyl aminium sulfates have been postulated to constitute important components of nucleation and accumulation mode atmospheric aerosols. In this study we present laboratory data on the thermochemical, cloud condensation nuclei (CCN) activity, and optical properties of selected aminium sulfate compounds of atmospheric relevance (monomethyl aminium sulfate (MMAS), dimethyaminium sulfate (DMAS), trimethylaminium sulfate, monoethylaminium sulfate (MEAS), diethylaminium sulfate (DEAS), and triethylaminium sulfate (TEAS)). We found that the vapor pressure of these aminium salts is 1–3 orders of magnitude lower than that of ammonium sulfate and as such they can contribute to new aerosols and secondary aerosols formation. We infer that these species have very high CCN activity, with hygroscopicity parameter that is similar to that ammonium sulfate. Finally, between 360 and 420 nm, these aminium sulfate salts scatter light less efficiently than ammonium sulfate, and do not absorb light. These derived parameters can contribute to the better understanding and characterization of the role that these compounds play in atmospheric chemical reactions, gas–solid partitioning and their possible contribution to the microphysical and radiative effects of atmospheric aerosols.
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Heterogeneous reactions of oleic acid aerosol particles with ozone are studied below 1% relative humidity. The particles have inert polystyrene latex cores (101-nm diameter) coated by oleic acid layers of 2 to 30 nm. The chemical content... more
Heterogeneous reactions of oleic acid aerosol particles with ozone are studied below 1% relative humidity. The particles have inert polystyrene latex cores (101-nm diameter) coated by oleic acid layers of 2 to 30 nm. The chemical content of the organic layer is monitored with ...
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Research Interests:
This study focuses on the heterogeneous reactions of gas phase glyoxal with aerosols of glycine, the most abundant amino acid in atmospheric aerosols, as well as with a mixture of glycine and ammonium sulfate (AS) at a molar ratio of... more
This study focuses on the heterogeneous reactions of gas phase glyoxal with aerosols of glycine, the most abundant amino acid in atmospheric aerosols, as well as with a mixture of glycine and ammonium sulfate (AS) at a molar ratio of 1:100 (glycine-AS 1:100). Aerosols were exposed to varying relative humidity (RH) conditions in the presence of gas phase glyoxal for ∼1 h, followed by drying and efflorescence. The changes in size, chemical composition, and optical properties were consequently measured. The reactions occur over a wide range of relative humidities, from ∼30% up to 90% RH, covering values that are substantially lower as well as above the deliquescence point of the investigated aerosols. The product aerosols exhibit a trend of increasing growth in size, in optical extinction cross sections, and in extinction efficiencies (at λ = 355 nm) with decreasing seed aerosol size, and with decreasing RH values from 90% to ∼50%. For glycine-AS 1:100 particles, the ratio of the geometric cross section of the product aerosol to the original seed aerosol reached a value of ∼3, the optical extinction cross section ratio was up to ∼25, and the Q(ext) ratio was up to ∼8, exceeding those of both AS and glycine separately, suggesting a synergistic effect. Aerosol mass spectrometer analyses show that the main products of all the studied reactions are glyoxal oligomers (light scattering compounds), with a minor contribution from imidazoles (absorbing compounds at λ = 355 nm). These findings imply that the changes in the optical properties are likely due to enhanced scattering by the reaction products. The fraction of absorbing substances in the reacted aerosol increases with increasing RH, suggesting that the absorption component may become more substantial after longer reaction times, possibly in cloud or fog droplets. The results suggest that these reactions are possibly important in low RH regions, plausibly due to the reaction occurring in a few interfacial monolayers of water well before deliquescence.
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... Tamar Moise and Yinon Rudich*. Department of Environmental Sciences, Weizmann Institute, Rehovot 76100, Israel. J. Phys. ... 1999134) and by the Minerva Science Foundation. Yinon Rudich is the incumbent of the William Z. and Eda Bess... more
... Tamar Moise and Yinon Rudich*. Department of Environmental Sciences, Weizmann Institute, Rehovot 76100, Israel. J. Phys. ... 1999134) and by the Minerva Science Foundation. Yinon Rudich is the incumbent of the William Z. and Eda Bess Novick career development chair. ...