Browsing by Author "China, Swarup"
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- Free Tropospheric Aerosol Measurements at the Pico Mountain Observatory, Azores (2225m asl).Publication . Mazzoleni, Claudio; Mazzoleni, Lynn R.; Fialho, Paulo; Kumar, Sumit; Dzepina, Katja; Dziobak, Michael P.; Kramer, Louisa; Olsen, Seth C.; Owen, Robert; Helmig, Detlev; Hueber, Jacques; China, SwarupIn this poster we discuss a limited subset of the aerosol measurements performed at the Pico Mountain Observatory. The Black Carbon (BC) mass shows a clear seasonal pattern over a ten-years period. The 2012 scattering measurements show highly variable signals with events with high scattering and periods of very low aerosol loading. Dust events are clearly captured by the aethalometer, as well the nephelometer Ångström exponents. Particles have various shapes, and mixing states, and soot particles typically are very compacted.
- Molecular characterization of free tropospheric aerosol collected at the Pico Mountain Observatory : a case study with a long-range transported biomass burning plumePublication . Dzepina, Katja; Mazzoleni, Claudio; Fialho, Paulo; China, Swarup; Zhang, Bo; Owen, R. Chris; Helmig, Detlev; Hueber, Jacques; Kumar, Sumit; Perlinger, Judith A.; Kramer, Louisa; Dziobak, Michael P.; Ampadu, Marian T.; Olsen, Seth C.; Wuebbles, Donald J.; Mazzoleni, Lynn R.Free tropospheric aerosol was sampled at the Pico Mountain Observatory located at 2225 m above mean sea level on Pico Island of the Azores archipelago in the North Atlantic. The observatory is located ~ 3900 km east and downwind of North America, which enables studies of free tropospheric air transported over long distances. Aerosol samples collected on filters from June to October 2012 were analyzed to characterize organic carbon, elemental carbon, and inorganic ions. The average ambient concentration of aerosol was 0.9 ± 0.7 μg m−3. On average, organic aerosol components represent the largest mass fraction of the total measured aerosol (60 ± 51%), followed by sulfate (23 ± 28%), nitrate (13 ± 10%), chloride (2 ± 3%), and elemental carbon (2 ± 2%). Water-soluble organic matter (WSOM) extracted from two aerosol samples (9/24 and 9/25) collected consecutively during a pollution event were analyzed using ultrahigh-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Approximately 4000 molecular formulas were assigned to each of the mass spectra in the range of m/z 100–1000. The majority of the assigned molecular formulas had unsaturated structures with CHO and CHNO elemental compositions. FLEXPART retroplume analyses showed the sampled air masses were very aged (average plume age > 12 days). These aged aerosol WSOM compounds had an average O/C ratio of ~ 0.45, which is relatively low compared to O/C ratios of other aged aerosol. The increase in aerosol loading during the measurement period of 9/24 was linked to biomass burning emissions from North America by FLEXPART retroplume analysis and Moderate Resolution Imaging Spectroradiometer (MODIS) fire counts. This was confirmed with biomass burning markers detected in the WSOM and with the morphology and mixing state of particles as determined by scanning electron microscopy. The presence of markers characteristic of aqueous-phase reactions of phenolic species suggests that the aerosol collected at the Pico Mountain Observatory had undergone cloud processing before reaching the site. Finally, the air masses of 9/25 were more aged and influenced by marine emissions, as indicated by the presence of organosulfates and other species characteristic of marine aerosol. The change in the air masses for the two samples was corroborated by the changes in ethane, propane, and ozone, morphology of particles, as well as by the FLEXPART retroplume simulations. This paper presents the first detailed molecular characterization of free tropospheric aged aerosol intercepted at a lower free troposphere remote location and provides evidence of low oxygenation after long-range transport. We hypothesize this is a result of the selective removal of highly aged and polar species during long-range transport, because the aerosol underwent a combination of atmospheric processes during transport facilitating aqueous-phase removal (e.g., clouds processing) and fragmentation (e.g., photolysis) of components.
- Molecular characterization of free tropospheric aerosol collected at the Pico Mountain Observatory : a case study with long range transported biomass burning plumesPublication . Dzepina, Katja; Mazzoleni, Claudio; Fialho, Paulo; China, Swarup; Zhang, Bo; Owen, R. Chris; Helmig, Detlev; Hueber, Jacques; Kumar, Sumit; Perlinger, Judith A.; Kramer, Louisa; Dziobak, Michael P.; Ampadu, Marian T.; Olsen, Seth C.; Wuebbles, Donald J.; Mazzoleni, Lynn R.Free tropospheric aerosol was sampled at the Pico Mountain Observatory located at 2225 m above mean sea level on Pico Island of the Azores archipelago in the North Atlantic. The observatory is located ~ 3900 km east and downwind of North America, which enables studies of free tropospheric air transported over long distances. Aerosol samples collected on filters from June to October 2012 were analyzed to characterize organic carbon, elemental carbon, and inorganic ions. The average ambient concentration of aerosol was 0.9 ± 0.7 μg m−3. On average, organic aerosol components represent the largest mass fraction of the total measured aerosol (60 ± 51%), followed by sulfate (23 ± 28%), nitrate (13 ± 10%), chloride (2 ± 3%), and elemental carbon (2 ± 2%). Water-soluble organic matter (WSOM) extracted from two aerosol samples (9/24 and 9/25) collected consecutively during a pollution event were analyzed using ultrahigh-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Approximately 4000 molecular formulas were assigned to each of the mass spectra in the range of m/z 100–1000. The majority of the assigned molecular formulas had unsaturated structures with CHO and CHNO elemental compositions. FLEXPART retroplume analyses showed the sampled air masses were very aged (average plume age > 12 days). These aged aerosol WSOM compounds had an average O/C ratio of ~ 0.45, which is relatively low compared to O/C ratios of other aged aerosol. The increase in aerosol loading during the measurement period of 9/24 was linked to biomass burning emissions from North America by FLEXPART retroplume analysis and Moderate Resolution Imaging Spectroradiometer (MODIS) fire counts. This was confirmed with biomass burning markers detected in the WSOM and with the morphology and mixing state of particles as determined by scanning electron microscopy. The presence of markers characteristic of aqueous-phase reactions of phenolic species suggests that the aerosol collected at the Pico Mountain Observatory had undergone cloud processing before reaching the site. Finally, the air masses of 9/25 were more aged and influenced by marine emissions, as indicated by the presence of organosulfates and other species characteristic of marine aerosol. The change in the air masses for the two samples was corroborated by the changes in ethane, propane, and ozone, morphology of particles, as well as by the FLEXPART retroplume simulations. This paper presents the first detailed molecular characterization of free tropospheric aged aerosol intercepted at a lower free troposphere remote location and provides evidence of low oxygenation after long-range transport. We hypothesize this is a result of the selective removal of highly aged and polar species during long-range transport, because the aerosol underwent a combination of atmospheric processes during transport facilitating aqueous-phase removal (e.g., clouds processing) and fragmentation (e.g., photolysis) of components.
- Morphology and Mixing State of Aged Soot Particles at a Remote Marine Free Troposphere Site : Implications for Optical PropertiesPublication . China, Swarup; Scarnato, Barbara; Owen, Robert C.; Zhang, Bo; Ampadu, Marian T.; Kumar, Sumit; Dzepina, Katja; Dziobak, Michael P.; Fialho, Paulo; Perlinger, Judith A.; Hueber, Jacques; Helmig, Detlev; Mazzoleni, Lynn R.; Mazzoleni, ClaudioThe radiative properties of soot particles depend on their morphology and mixing state, but their evolution during transport is still elusive. Here we report observations from an electron microscopy analysis of individual particles transported in the free troposphere over long distances to the remote Pico Mountain Observatory in the Azores in the North Atlantic. Approximately 70% of the soot particles were highly compact and of those 26% were thinly coated. Discrete dipole approximation simulations indicate that this compaction results in an increase in soot single scattering albedo by a factor of ≤2.17. The top of the atmosphere direct radiative forcing is typically smaller for highly compact than mass-equivalent lacy soot. The forcing estimated using Mie theory is within 12% of the forcing estimated using the discrete dipole approximation for a high surface albedo, implying that Mie calculations may provide a reasonable approximation for compact soot above remote marine clouds.
- Properties of Aerosol in the North Atlantic Free Troposphere at the Pico Mountain Observatory, Azores.Publication . Mazzoleni, Claudio; Mazzoleni, Lynn R.; Fialho, Paulo; Kumar, Sumit; Dzepina, Katja; Dziobak, Michael P.; Kramer, Louisa; Olsen, Seth C.; Owen, Robert; Helmig, Detlev; Hueber, Jacques; Wrigth, Kendra; Zhang, Bo; China, SwarupThe Pico Mountain Observatory is located at an altitude of 2225 meters above sea level in the summit caldera of the Pico volcano in the Azores, Portugal (38.47°N, 28.40°W). The scientific value of the station stems from the fact that this is the only permanent free-tropospheric monitoring station in the central North Atlantic, with negligible influence from local sources and that frequently samples air from the North American continent. Thus, it is an ideal site for studying long-range transported pollution. The station started operating in 2001 with a focus on gaseous species (e.g., ozone, carbon monoxide, nitrogen oxides, and non-methane hydrocarbons) and aerosol particles that absorb light (black carbon [BC] and aerosol dust). The absorbing aerosol mass concentrations, in units of equivalent black carbon mass concentrations, have been monitored using a seven-wavelength aethalometer (Magee scientific model AE31). Ancillary measurements at the station include meteorological parameters such as temperature, relative humidity, pressure, wind direction, and speed. Due to the harsh environmental conditions at the site, most measurements have been performed during the summer seasons. In the summer of 2012, new aerosol instrumentation and samplers were installed at the station. The new equipment includes a three-wavelength nephelometer (Ecotech model Aurora 3000) that measure aerosol scattering and backscattering fraction, a set of four high-volume samplers for the collection and chemical analysis of aerosol, a sequential sampler to collect aerosols on membranes and grids, and an optical particle counter. Membranes and grids are analysed offline with scanning and transmission electron microscopy to study morphological properties and elemental composition of the aged aerosols. In this poster we will discuss some of the analysis of the decadal BC mass concentration data, as well as some analysis of the new aerosol data with a focus on aerosol optical properties and morphology. Analysis of these properties is important for a better understanding of aerosol’s life cycle and ageing during their transport over the Atlantic, with implications on aerosol radiative properties and climate science.