Characterization of atmospheric aerosols in the city of So Paulo, Brazil: comparisons between polluted and unpolluted periods

The objective of this study was to determine the size and composition of atmospheric aerosols in the downtown area of the city of So Paulo, Brazil, for a polluted and an unpolluted period. Aerosols were sampled with a portable air sampler (PAS), Micro-Orifice Uniform Deposit Impactor (MOUDI), and Scanning Mobility Particle Sizer. At the study site, air quality is poor, especially during the winter, high concentrations of pollutants being emitted primarily by the light- and heavy-duty vehicle fleet. We analyzed mass, black carbon (BC), Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sn, Zr, and Pb. During the polluted period, diurnal PM(10) was higher than nocturnal PM(10), whereas the inverse was true during the unpolluted period. The FPM was rich in BC, S, and Pb, whereas CPM was rich in Al, Si, Ca, Ti, and Fe. Mass balance was performed by category: ammonium sulfate, sodium chloride, crustal material, BC, and other. The PAS-determined FPM was mainly BC. The MOUDI-determined FPM crustal material explained more mass than did ammonium sulfate and BC during the polluted period, whereas ammonium sulfate had the largest mass during the unpolluted period. Crustal material was the major CPM component, followed by ammonium sulfate and BC. During the unpolluted period, FPM concentrations were lower, whereas those of ammonium sulfate were relatively higher, especially at night, and particle number was inversely proportional to particle size. Aerosol growth was more intense during the polluted period.

Development of analytical methodologies for iodine species in gaseous and particulate phases of the coastal atmosphere

It has been demonstrated that iodine does have an important influence on atmospheric chemistry, especially the formation of new particles and the enrichment of iodine in marine aerosols. It was pointed out that the most probable chemical species involved in the production or growth of these particles are iodine oxides, produced photochemically from biogenic halocarbon emissions and/or iodine emission from the sea surface. However, the iodine chemistry from gaseous to particulate phase in the coastal atmosphere and the chemical nature of the condensing iodine species are still not understood. A Tenax / Carbotrap adsorption sampling technique and a thermo-desorption / cryo-trap / GC-MS system has been further developed and improved for the volatile organic iodine species in the gas phase. Several iodo-hydrocarbons such as CH3I, C2H5I, CH2ICl, CH2IBr and CH2I2 etc., have been measured in samples from a calibration test gas source (standards), real air samples and samples from seaweeds / macro-algae emission experiments. A denuder sampling technique has been developed to characterise potential precursor compounds of coastal particle formation processes, such as molecular iodine in the gas phase. Starch, TMAH (TetraMethylAmmonium Hydroxide) and TBAH (TetraButylAmmonium Hydroxide) coated denuders were tested for their efficiencies to collect I2 at the inner surface, followed by a TMAH extraction and ICP/MS determination, adding tellurium as an internal standard. The developed method has been proved to be an effective, accurate and suitable process for I2 measurement in the field, with the estimated detection limit of ~0.10 ng∙L-1 for a sampling volume of 15 L. An H2O/TMAH-Extraction-ICP/MS method has been developed for the accurate and sensitive determination of iodine species in tropospheric aerosol particles. The particle samples were collected on cellulose-nitrate filters using conventional filter holders or on cellulose nitrate/tedlar-foils using a 5-stage Berner impactor for size-segregated particle analysis. The water soluble species as IO3- and I- were separated by anion exchanging process after water extraction. Non-water soluble species including iodine oxide and organic iodine were digested and extracted by TMAH. Afterwards the triple samples were analysed by ICP/MS. The detection limit for particulate iodine was determined to be 0.10~0.20 ng•m-3 for sampling volumes of 40~100 m3. The developed methods have been used in two field measurements in May 2002 and September 2003, at and around the Mace Head Atmospheric Research Station (MHARS) located at the west coast of Ireland. Elemental iodine as a precursor of the iodine chemistry in the coastal atmosphere, was determined in the gas phase at a seaweed hot-spot around the MHARS, showing I2 concentrations were in the range of 0~1.6 ng∙L-1 and indicating a positive correlation with the ozone concentration. A seaweed-chamber experiment performed at the field measurement station showed that the I2 emission rate from macro-algae was in the range of 0.019~0.022 ng•min-1•kg-1. During these experiments, nanometer-particle concentrations were obtained from the Scanning Mobility Particle Sizer (SMPS) measurements. Particle number concentrations were found to have a linear correlation with elemental iodine in the gas phase of the seaweeds chamber, showing that gaseous I2 is one of the important precursors of the new particle formation in the coastal atmosphere. Iodine contents in the particle phase were measured in both field campaigns at and around the field measurement station. Total iodine concentrations were found to be in the range of 1.0 ~ 21.0 ng∙m-3 in the PM2.5 samples. A significant correlation between the total iodine concentrations and the nanometer-particle number concentrations was observed. The particulate iodine species analysis indicated that iodide contents are usually higher than those of iodate in all samples, with ratios in the range of 2~5:1. It is possible that those water soluble iodine species are transferred through the sea-air interface into the particle phase. The ratio of water soluble (iodate + iodide) and non-water soluble species (probably iodine oxide and organic iodine compounds) was observed to be in the range of 1:1 to 1:2. It appears that higher concentrated non-water soluble species, as the products of the photolysis from the gas phase into the particle phase, can be obtained in those samples while the nucleation events occur. That supports the idea that iodine chemistry in the coastal boundary layer is linked with new particle formation events. Furthermore, artificial aerosol particles were formed from gaseous iodine sources (e.g. CH2I2) using a laboratory reaction-chamber experiment, in which the reaction constant of the CH2I2 photolysis was calculated to be based upon the first order reaction kinetic. The end products of iodine chemistry in the particle phase were identified and quantified.

Characterisation and field deployment of a novel quantitative Time-of-Flight Aerosol Mass Spectrometer (ToF-AMS)

Das Time-of-Flight Aerosol Mass Spectrometer (ToF-AMS) der Firma Aerodyne ist eine Weiterentwicklung des Aerodyne Aerosolmassenspektrometers (Q-AMS). Dieses ist gut charakterisiert und kommt weltweit zum Einsatz. Beide Instrumente nutzen eine aerodynamische Linse, aerodynamische Partikelgrößenbestimmung, thermische Verdampfung und Elektronenstoß-Ionisation. Im Gegensatz zum Q-AMS, wo ein Quadrupolmassenspektrometer zur Analyse der Ionen verwendet wird, kommt beim ToF-AMS ein Flugzeit-Massenspektrometer zum Einsatz. In der vorliegenden Arbeit wird anhand von Laborexperimenten und Feldmesskampagnen gezeigt, dass das ToF-AMS zur quantitativen Messung der chemischen Zusammensetzung von Aerosolpartikeln mit hoher Zeit- und Größenauflösung geeignet ist. Zusätzlich wird ein vollständiges Schema zur ToF-AMS Datenanalyse vorgestellt, dass entwickelt wurde, um quantitative und sinnvolle Ergebnisse aus den aufgenommenen Rohdaten, sowohl von Messkampagnen als auch von Laborexperimenten, zu erhalten. Dieses Schema basiert auf den Charakterisierungsexperimenten, die im Rahmen dieser Arbeit durchgeführt wurden. Es beinhaltet Korrekturen, die angebracht werden müssen, und Kalibrationen, die durchgeführt werden müssen, um zuverlässige Ergebnisse aus den Rohdaten zu extrahieren. Beträchtliche Arbeit wurde außerdem in die Entwicklung eines zuverlässigen und benutzerfreundlichen Datenanalyseprogramms investiert. Dieses Programm kann zur automatischen und systematischen ToF-AMS Datenanalyse und –korrektur genutzt werden.

Characterization of Halyomorpha halys (brown marmorated stink bug) biogenic volatile organic compound emissions and their role in secondary organic aerosol formation.

The formation of aerosols is a key component in understanding cloud formation in the context of radiative forcings and global climate modeling. Biogenic volatile organic compounds (BVOCs) are a significant source of aerosols, yet there is still much to be learned about their structures, sources, and interactions. The aims of this project were to identify the BVOCs found in the defense chemicals of the brown marmorated stink bug Halymorpha halys and quantify them using gas chromatography-mass spectrometry (GC/MS) and test whether oxidation of these compounds by ozone-promoted aerosol and cloud seed formation. The bugs were tested under two conditions: agitation by asphyxiation and direct glandular exposure. Tridecane, 2(5H)-furanone 5-ethyl, and (E)-2-decenal were identified as the three most abundant compounds. H. halys were also tested in the agitated condition in a smog chamber. It was found that in the presence of 100-180 ppm ozone, secondary aerosols do form. A scanning mobility particle sizer (SMPS) and a cloud condensation nuclei counter (CCNC) were used to characterize the secondary aerosols that formed. This reaction resulted in 0.23 microg/ bug of particulate mass. It was also found that these secondary organic aerosol particles could act as cloud condensation nuclei. At a supersaturation of 1%, we found a kappa value of 0.09. Once regional populations of these stink bugs stabilize and the populations estimates can be made, the additional impacts of their contribution to regional air quality can be calculated.

Sedimentological, physical, bulk geochemical, elemental and rock magnetic properties of the Middle to Late Pleistocene Rodderberg (Eifel/Germany)

The sediment record from Rodderberg potentially provides a climate and environmental record spanning at least the last ca 130 ka. Results from a low resolution pilot study reveal characteristic fluctuations that can be related to global climate variability as reflected in marine isotope stages and document the potential of this site for continuous and high-resolution investigations of the Middle to Late Pleistocene. Here we document the tentative lithology drilled, and show how the elemental composition can be interpreted with regard to lake level fluctuations, related redox conditions, but also to grain-size distribution and changes in lacustrine productivity. Finally, based on major lithological changes, a preliminary depth/age model is suggested that allows reassessing published luminescence ages from the same site.

Geochemical composition and granulometry of ODP Hole 167-1017E sediments

Intensification of North Pacific Intermediate Water during the Younger Dryas and stadials of the last glacial episode has been advocated by Kennett and his colleagues based on studies of ventilation history in Santa Barbara Basin. Because Santa Barbara Basin is a semi-isolated marginal basin, this hypothesis requires testing in sequences on the upper continental margin facing the open-ocean of the Pacific. Ocean Drilling Program Site 1017 is located on the upper slope of southern California off Point Conception close to the entrance of Santa Barbara Basin, an ideal location to test the hypothesis of late Quaternary switching in intermediate waters. We examined chemical and mineral composition, sedimentary structures, and grain size of hemipelagic sediments representing the last 80 k.y. at this site to detect changes in behavior of intermediate waters. We describe distinct compositional and textual variations that appear to reflect changes in grain size in response to flow velocity fluctuations of bottom waters. Qualitative estimates of changes in degree of pyritization indicate better ventilation of bottom water during intervals of stronger bottom-water flow. Comparison between variations in the sediment parameters and the planktonic d18O record indicates intensified bottom-current activity during the Younger Dryas and stadials of marine isotope Stage 3. This result strongly supports the hypothesis of Kennett and his colleagues. Our investigation also suggests strong grain-size control on organic carbon content (and to less extent carbonate carbon content). This, in turn, suggests the possibility that organic carbon content of sediments, which is commonly used as an indicator of surface productivity, can be influenced by bottom currents.

Grain size analyses of ODP Leg 116 holes

Ocean Drilling Program (ODP) Leg 116 cored the distal part of the Bengal Fan at three closely spaced sites (717-719). The recovered sediments consisted dominantly of turbidites that varied in thickness between a few centimeters and 2 m or more. A number of different facies have been identified in the sequence and are described by Stow et al. (1990, doi:10.2973/odp.proc.sr.116.110.1990). Representative examples of these facies types were selected and sampled for grain-size analysis. The results of these analyses are tabulated in this data report.

Concentration and composition of aerosols over the North Atlantic in August 1995

Data on composition of aerosols are considered. Investigations include electron microscopy, grain size, mineralogical and chemical analyses. Samples of aerosols were collected Cruise 37 of R/V Akademik Mstislav Keldysh along a transatlantic section along 40°-50°N. Variability of concentrations and composition of aerosols with distance from continents is shown: concentrations of aerosols decrease by factor of ten and more. Significant portion of mineral components in aerosols collected over the continent is replaced by organic matter due to mechanical differentiation during transportation. Such anthropogenic components as soot, ash, and combustion spheres were detected in all samples. North African dust was found in one sample in the western part of the section.

Grain size composition and age of ODP Hole 167-1017E sediments

Siliciclastic sedimentation at Ocean Drilling Program Site 1017 on the southern slope of the Santa Lucia Bank, central California margin, responded closely to oceanographic and climatic change over the past ~130 ka. Variation in mean grain-size and sediment sorting within the ~25-m-thick succession from Hole 1017E show Milankovitch-band to submillenial-scale variation. Mean grain size of the "sortable silt" fraction (10-63 µm) ranges from 17.6 to 33.9 µm (average 24.8 µm) and is inversely correlated with the degree of sorting. Much of the sediment has a bimodal or trimodal grain-size distribution that is composed of distinct fine silt, coarse silt to fine sand, and clay-size components. The position of the mode and the sorting of each component changes through the succession, but the primary variation is in the presence or abundance of the coarse silt fraction that controls the overall mean grain size and sorting of the sample. The occurrence of the best-sorted, finest grained sediment at high stands of sea level (Holocene, marine isotope Substages 5c and 5e) reflect the linkage between global climate and the sedimentary record at Site 1017 and suggest that the efficiency of off-shelf transport is a key control of sedimentation on the Santa Lucia Slope. It is not clear what proportion of the variation in grain size and sorting may also be caused by variations in bottom current strength and in situ hydrodynamic sorting.

Grain size and XRD analysis on Site 162-983

The grain size of deep-sea sediments provides an apparently simple proxy for current speed. However, grain size-based proxies may be ambiguous when the size distribution reflects a combination of processes, with current sorting only one of them. In particular, such sediment mixing hinders reconstruction of deep circulation changes associated with ice-rafting events in the glacial North Atlantic because variable ice-rafted detritus (IRD) input may falsely suggest current speed changes. Inverse modeling has been suggested as a way to overcome this problem. However, this approach requires high-precision size measurements that register small changes in the size distribution. Here we show that such data can be obtained using electrosensing and laser diffraction techniques, despite issues previously raised on the low precision of electrosensing methods and potential grain shape effects on laser diffraction. Down-core size patterns obtained from a sediment core from the North Atlantic are similar for both techniques, reinforcing the conclusion that both techniques yield comparable results. However, IRD input leads to a coarsening that spuriously suggests faster current speed. We show that this IRD influence can be accounted for using inverse modeling as long as wide size spectra are taken into account. This yields current speed variations that are in agreement with other proxies. Our experiments thus show that for current speed reconstruction, the choice of instrument is subordinate to a proper recognition of the various processes that determine the size distribution and that by using inverse modeling meaningful current speed reconstructions can be obtained from mixed sediments.