Browsing by Author "Helmig, Detlev"
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- Aerosol Measurements in the Free Troposphere at the North Atlantic Pico Mountain Observatory in the Azores.Publication . Mazzoleni, Claudio; Fialho, Paulo; Gorkowski, Kyle; Owen, Robert; Dziobak, Michael P.; Hueber, Jacques; Dzepina, Katja; Kramer, Louisa; Olsen, Seth C.; Kumar, Sumit; Helmig, DetlevPico is a small island (447 km2) in the archipelago of the Azores, Portugal, in the North Atlantic Ocean. The island has a very steep inactive volcano. An atmospheric monitoring station (Pico Mountain Observatory) was established close to the summit of the volcano by the late Dr. Richard Honrath and colleagues in 2001. The station, far from persistent local sources, is located near the northern cliff of the summit caldera at an altitude of 2225 meters. The station altitude is typically well above the boundary layer during summertime, when average marine boundary-layer heights are below 1200 meters and rarely exceed 1300 meters. Air masses reaching the station are often transported from North America and seldom from Europe or North Africa. The station’s uniqueness and significance lie in its location that allows study of the transport and evolution of gases and aerosols from North America in the free troposphere. Until recently, the focus was on the measurement and analysis of trace gases (ozone, carbon monoxide, non-methane hydrocarbons, nitrogen oxides) and light-absorbing aerosol (black carbon and iron oxide). Aerosol light attenuation has been measured at the site since 2001 using a seven-wavelengths aethalometer. An optical particle sizer was installed at the site in 2010 and has been running in parallel to the aethalometer for two seasons. A three-wavelength nephelometer, to measure the aerosol total- and back-scattering, and aerosol samplers for morphological and chemical analysis will be installed at the site in 2012. Our goal is to enhance the observatory monitoring capabilities for aerosol research. The objectives of this new research program are to: (a) assess background as well as specific event tropospheric aerosol properties, (b) compare aerosol and gases measurements with model outputs, and (c) use the data collected to provide satellite validation. This research is anticipated to enhance our understanding of the interactions between tropospheric aerosols, clouds, and climate by allowing, for example, the analysis of North American outflows and seasonal changes, the assessment of different source regions, the estimation of aerosol radiative forcing above marine clouds and in clear sky, and the study of the relative contribution of anthropogenic versus biomass burning emissions. In this poster we present a preliminary analysis of the black carbon and aerosol size data in conjunction with retroplume model analysis.
- Climatology and Atmospheric Chemistry of Non-Methane Hydrocarbon Emissions over the North Atlantic.Publication . Muñoz, Mauricio; Helmig, Detlev; Hueber, Jacques; Mazzoleni, Claudio; Mazzoleni, Lynn R.; Owen, Robert; Val Martin, Maria; Fialho, Paulo; Plass-Duelmer, ChristianNon-methane hydrocarbons (NMHC) covering the C2 to C7 volatility range have been monitored at the Pico Mountain Observatory, Pico Island, Azores, Portugal, since 2004. The Observatory is located at 2225 m a.s.l. in the caldera of the Pico Mountain volcano, and during most times receives lower free tropospheric air that has been transported across the North Atlantic. The 7-year NMHC record has been analyzed for seasonal behavior of photochemical processing, atmospheric transport time, and source region using ratios of NMHC species as indicators of photochemical aging and HYSPLIT model outputs. Transport conditions resulting in elevated and low NMHC conditions were specifically studied to investigate seasonal pollution transport in the North Atlantic region.
- Climatology and atmospheric chemistry of the non-methane hydrocarbons ethane and propane over the North AtlanticPublication . Helmig, Detlev; Muñoz, Mauricio; Hueber, Jacques; Mazzoleni, Claudio; Mazzoleni, Lynn R.; Owen, Richard C.; Val-Martin, Maria; Fialho, Paulo; Plass-Duelmer, Christian; Palmer, Paul I.; Lewis, Alastair C.; Pfister, GabrieleA record spanning ten years of non-methane hydrocarbon (NMHC) data from the Pico Mountain Observatory (PMO), Pico Island, Azores, Portugal, was analyzed for seasonal NMHC behavior, atmospheric processing, and trends, focusing on ethane and propane. The location of this site in the central North Atlantic, at an elevation of 2225 m asl, allows these data to be used to investigate the background conditions and pollution transport events occurring in the lower free North Atlantic troposphere. The quantity ln([propane]/[ethane]) was used as an indicator of both photochemical processing and a marker for the occurrence of pollution transport events detected at the station. The Pico data were compared with three other continuous NMHC data sets from sites bordering the North Atlantic, i.e. the Global Atmospheric Watch (GAW) stations at Summit, Greenland, Hohenpeisssenberg, Germany, and Cape Verde, using ln([propane]/[ethane]) results as an indicator for the degree of photochemical processing (‘aging’) seen in the data. Comparisons of these three data sets showed some significant differences in the seasonal background and range of observed values. The statistical distribution of binned monthly data was determined, and individual sample events were then scaled to the monthly median observed value. Back trajectories, determined by the HYSPLIT model were used to investigate the geographic origin of the observed trace gases as a function of the degree of photochemical processing. Results show that PMO samples have been subjected to a diversity of air transport and aging, from highly processed air to freshly emitted air throughout the year, and in particular during summer months. The predominant air transport is from North America, with only occasional influence from continental areas located east and southeast (Europe and Africa). The available record was found to be too variable and still too short to allow deciphering NMHC trends from the data. Ethane and propane measurements at the PMO were compared with the MOZART-4 atmospheric chemistry and transport model at the appropriate time and location. The model was found to yield good agreement in the description of the lower range of atmospheric mole fractions observed, of the seasonal cycle, and the regional oxidation chemistry. However, ethane and propane enhancements in transport events were underestimated, indicating that after the ≥ 3 days of synoptic transport to PMO the spatial extent of plumes frequently is smaller than the 2.8° × 2.8° (∼300 km) model grid resolution.
- 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.
- Impacts of anthropogenic and boreal fire emissions in the central North Atlantic lower free troposphere: summertime observations at the PICO-NARE observatory.Publication . Val Martin, Maria; Honrath, Richard; Kleissl, J.; Owen, Robert; Lapina, K.; Fialho, Paulo; Helmig, Detlev; Tanner, D. M.We present measurements of CO, O3, aerosol Black Carbon (BC) made over the central North Atlantic lower Free Troposphere (FT) during the summers of 2001-2004 along with measurements of nitrogen oxides (NOx and NOy) made during the summer of 2004 (ICARTT period) and non-methane hydrocarbons (NMHCs) made during the winter 2004-spring 2005.
- Large-scale impacts of anthropogenic and boreal fire emissions apparent in multi-year free tropospheric observations in the Azores.Publication . Honrath, Richard; Val Martin, Maria; Kleissl, J.; Owen, Robert; Lapina, K.; Fialho, Paulo; Helmig, Detlev; Tanner, D. M.Pico Mountain in the Azores Islands provides an ideal location for studies of the central N. Atlantic lower free troposphere. The PICO-NARE station has operated there since summer 2001. Here, we present key findings from summertime measurements, during 2001-2004. Main Findings: Anthropogenic and boreal wildfire emissions dominate variations in CO and have major impacts on O3, nitrogen oxides, non-methane hydrocarbons (NMHCs) and black carbon.
- Measurement of Aerosols and Trace Gases in the Free Troposphere at the Pico Mountain Observatory in the Azores.Publication . Kramer, Louisa; Mazzoleni, Claudio; Mazzoleni, Lynn R.; Fialho, Paulo; Helmig, Detlev; Olsen, Seth C.; Owen, R. Chris; Dziobak, Michael P.; Hueber, Jacques; Dzepina, Katja; Kumar, SumitHere, we present an overview of gas and aerosol data measured at the Pico Mountain Station. The primary objective of these measurements are to enhance our knowledge of anthropogenic and biomass burning emissions from North America and their relative impact on atmospheric composition and radiative forcing in the free troposphere of the North Atlantic.
- Measurement of Free Tropospheric Aerosols in the North Atlantic at the Pico Mountain Observatory.Publication . Dzepina, Katja; Kumar, Sumit; Mazzoleni, Claudio; Fialho, Paulo; Dziobak, Michael P.; Hueber, Jacques; Helmig, Detlev; Kramer, Louisa; Olsen, Seth C.; Mazzoleni, Lynn R.The Pico Mountain Observatory is located at 2225 m amsl on an inactive volcano at Pico Island in the Azores archipelago in the North Atlantic ~3900 km east and downwind of North America (38º28'15''N; 28º24’'14''W). The unique location of the Observatory enables sampling of free tropospheric air transported over long, intercontinental distances and is rarely affected by local emissions. The Observatory is affected mainly by North American outflow after its trans-Atlantic transport. Therefore, its location is ideal for observations of long-range transported pollutants emitted from anthropogenic and biogenic continental sources. The composition of continental pollution outflow is altered during transport by mixing, chemical reactions, phase changes, and removal processes. Thus, the properties of aerosol and trace gases in downwind regions are impacted by the outflow of pollutants, their chemical transformation, and sinks. In previous work, the sampled air-mass measurements (including CO, O3, NOx, NOy, NMHC, black carbon and aerosol optical size) and the simulations of their dispersion indicated outflow of North American tropospheric ozone and its precursors. Although the measurements have been crucial in explaining the evolution of North American gaseous pollution, little is known regarding the nature of the aged aerosol. New work is currently underway at the Observatory to provide chemical characterization of the intercepted free tropospheric aerosols. Here, we show the preliminary results of the free tropospheric aerosol composition and its physical properties. Samples were collected using high-volume filter samplers with quartz filters and analyzed for organic and elemental carbon (OC and EC, respectively). We compare the observed OC and EC values to the collocated measurements of gas- and particle-phase species, meteorological parameters and to the values found in current literature. We highlight the future work in which we will select filter samples based on the arrival of highly polluted air masses from anthropological or biomass burning emissions for further detailed analysis.
- 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.