Tuomo A. Pakkanen
Finnish Meteorological Institute
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Journal of Aerosol Science | 2000
Veli-Matti Kerminen; C.H. Ojanen; Tuomo A. Pakkanen; Risto Hillamo; Minna Aurela; Jouni Meriläinen
Chemistry of oxalic, malonic, and succinic acid was studied at the two sites representing the urban and rural conditions, and at a site intermediate between these two. The investigation was based on the particle collection with a virtual impactor and a Berner low-pressure impactor. Concentrations of the three diacids displayed large seasonal amplitudes with low values in winter. Suggestive of common sources or atmospheric formation processes, the correlation between oxalic and malonic acid concentrations was high. Both the local traffic and secondary production in the long-range transported air masses seemed to be the important sources for these two acids. Contrary to oxalic and malonic acid, no enrichment at the urban site compared with the rural site was observed for succinic acid. The seasonal cycle of this acid resembled that of methanesulfonic acid. The most likely sources for succinic acid in our samples was the secondary production in the long-range transported air, with potentially significant contribution coming from biogenic sources. The three diacids had quite different distributions over the particulate phase. Oxalic acid had a dominant accumulation mode, a clear Aitken mode at sizes below about 0.15 μm of particle diameter, and modes corresponding to the sea-salt and crustal particle size ranges. Most of the malonic acid was associated with sea-salt particles, even though in a few samples an accumulation mode was also present. Succinic acid was distributed between the accumulation and the sea-salt particle modes, in addition to which it frequently had quite a pronounced Aitken mode. Oxalic and succinic acids are among the organics that may contribute to the atmospheric cloud condensation nuclei production. Oxalic and malonic acid, and to a smaller extent succinic acid, participate in reactions occurring in sea-salt particles.
Atmospheric Environment | 1996
Tuomo A. Pakkanen
The results of analyses of six atmospheric aerosol samples collected in Helsinki, Finland, using a Berner low-pressure impactor, are reported. Formation of coarse particle nitrate was studied by evaluating various ion balances of the measured water-soluble ions (NH4+, Na+, K+, Mg2+, Ca2+, Cl−, NO3− and SO42−) and mass size distributions of Na+ Ca 2+, Cl− and NO−3. Atmospheric coarse particle NO−3 was found to be formed in the reaction of nitric acid with sea- and soil-derived coarse particles. The fraction of nitrate found on sea and soil particles followed the measured concentrations and size distributions of these two particle types: the concentration ratio of soil to sea particles increased with increasing particle size as did the fraction of nitrate on soil particles. The reaction with sea-salt particles resulted in the evaporation of Cl− as HCI. The presence of non-sea-salt SO42− indicates that also H2SO4 and/or SO2 reacted with sea salt and contributed to the Cl− loss. Overall, the percentage of evaporated Cl− decreased with increasing particle size, which suggests a surface reaction mechanism. Cl− evaporation was almost complete for the 1–2 um diameter size fraction indicating that all major sea-derived chlorides, NaCl, MgCl2, CaCl2 and KCI, may react with acidic species in the atmosphere. The results showed further some indications of possible reaction of HCI with soil particles.
Atmospheric Environment | 2001
Veli-Matti Kerminen; Risto Hillamo; Kimmo Teinilä; Tuomo A. Pakkanen; Ivo Allegrini; Roberto Sparapani
Abstract A large set of size-resolved aerosol samples was inspected with regard to their ion balance to shed light on how the aerosol acidity changes with particle size in the lower troposphere and what implications this might have for the atmospheric processing of aerosols. Quite different behaviour between the remote and more polluted environments could be observed. At the remote sites, practically the whole accumulation mode had cation-to-anion ratios clearly below unity, indicating that these particles were quite acidic. The supermicron size range was considerably less acidic and may in some cases have been close to neutral or even alkaline. An interesting feature common to the remote sites was a clear jump in the cation-to-anion ratio when going from the accumulation to the Aitken mode. The most likely reason for this was cloud processing which, via in-cloud sulphate production, makes the smallest accumulation-mode particles more acidic than the non-activated Aitken-mode particles. A direct consequence of the less acidic nature of the Aitken mode is that it can take up semi-volatile, water-soluble gases much easier than the accumulation mode. This feature may have significant implications for atmospheric cloud condensation nuclei production in remote environments. In rural and urban locations, the cation-to-anion ratio was close to unity over most of the accumulation mode, but increased significantly when going to either larger or smaller particle sizes. The high cation-to-anion ratios in the supermicron size range were ascribed to carbonate associated with mineral dust. The ubiquitous presence of carbonate in these particles indicates that they were neutral or alkaline, making them good sites for heterogeneous reactions involving acidic trace gases. The high cation-to-anion ratios in the Aitken mode suggest that these particles contained some water-soluble anions not detected by our chemical analysis. This is worth keeping in mind when investigating the hygroscopic properties or potential health effects of ultrafine particles in polluted environments.
Journal of Aerosol Science | 1998
Veli-Matti Kerminen; Kimmo Teinilä; Risto Hillamo; Tuomo A. Pakkanen
Abstract Depletion of chloride in sea-salt particles was studied at a site near the Arctic Ocean. The investigation was based on size-segregated particle sampling using a Berner low-pressure impactor. According to the impactor measurements, average chloride losses were close to 100% for submicron particles. However, this is successively less for increasing particle size in the supermicron size range. The main constituents replacing chloride from supermicron sea-salt particles were sulfate and nitrate followed by MSA- and oxalate, and with malonate and succinate giving a minor contribution. Anions of organic dicarboxylic acids became more important for air spending a longer time over the continent. Our analysis suggests that principal mechanisms accumulating sulfate into sea-salt particles are cloud processing and, to a lesser degree, heterogeneous reactions taking place in deliquescent sea-salt particles. Mechanisms for the chloride replacement by nitrate are less clear. The distributions of MSA- and oxalate over the sea-salt particle size range were similar to each other, whereas other organic anions analyzed here had a peak concentration at a somewhat larger particle size. Better understanding on the chemistry associated with sea-salt particles requires investigating not only reactions in deliquescent sea-salt particles, but also the interactions between these particles and clouds.
Journal of Atmospheric Chemistry | 1996
Tuomo A. Pakkanen; Veli-Matti Kerminen; Risto Hillamo; Minna Màkinen; Timo Mäkelä; Aki Virkkula
A method for determining the distribution of supermicrometer nitrate between size-segregated sea-salt and soil derived particles is presented. The analysis is based on field data from six measurements at a coastal site in southern Finland, and on a theoretical treatment taking into account the transfer of gaseous species onto particle surfaces and their subsequent reaction. Significant amounts of nitrate were found in both the particle types, with the fraction of nitrate associated with soil particles varying from 20–50% in the 1–2 μm size to near 90% in particles larger than 10 μm. Overall, the nitrate accumulation followed closely the relative abundances of these two particle types. Two overlapping modes in supermicron nitrate mass size distributions could be identified. The lower mode, associated with sea-salt, was located between the surface-area and volume distribution of sodium peaking at about 2–3 μm of EAD. The upper mode peaked at 3–5 μm and followed more closely the surface-area distribution of calcium in all samples. At our site, the accumulation of nitrate into both particle types was shown to be limited by an effective ‘surface reaction’ rate rather than by gas-phase diffusion. This rate was estimated to be considerably larger for sea-salt particles. Strong evidence in support of the saturation of nitrate in sea-salt particles were obtained.
Atmospheric Environment | 1997
Veli-Matti Kerminen; Tuomo A. Pakkanen; Risto Hillamo
Abstract Interactions between inorganic trace gases and supermicrometer aerosol particles were studied at a coastal site of Finland. The measurements revealed two supermicron mass modes for both nitrate and non-sea-salt sulfate. The lower-size modes were likely formed when sulfate and nitrate, or their precursor vapors, reacted with sea-salt particles. The upper-size modes were primarily due to accumulation of sulfate and nitrate into particles of continental origin. Chloride displayed only one supermicron mode centered at somewhat larger size than the sea-salt particle mode due to the more efficient evaporation of hydrochloric acid from smaller sea-salt particles. The average chloride losses were calculated to vary from over 95% for 1 μm particles to about 30% for particles greater than 10 μm in diameter. Supermicrometer particles were a net source o f gaseous hydrochloric acid at our site, even though some indications of the reactions between HCl(g) and continental particles could be identified. The estimated chloride loss from sea-salt particles was balanced quite accurately by the additional sulfate and nitrate formed on these particles. It was hypothesized that sea-salt particles collected mostly sulfate in marine air masses, with nitrate collection becoming more important as the particles interact with polluted air. The dry deposition of supermicron particulate nitrate accounted for a significant fraction of total nitrate flux (NO3− + HNO3(g)) into the ground, and dominated the overall particulate nitrate flux. Both sea-salt and continental particles were important contributors to this flux. The role of supermicron particles in overall nitrogen and sulfur budgets was of less importance when one considers the relatively large deposition fluxes of NO2 and SO2 at the site.
Journal of Geophysical Research | 1999
Aki Virkkula; Minna Aurela; Risto Hillamo; Timo Mäkelä; Tuomo A. Pakkanen; Veli-Matti Kerminen; Willy Maenhaut; Filip François; Jan Cafmeyer
An 18-month set of concentration data of various elements in fine (diameter D <2.5 μm) and coarse (2.5 μm<D<15 μm) particles is presented. Measurements were done at Sevettijarvi, ∼60 km WNW of Nikel, a large pollution source on the Kola Peninsula, Russia. The concentrations in aerosol arriving from the Norwegian Sea and the Arctic Ocean are very close to the values observed at more remote Arctic sites. In air from the Kola Peninsula, approximately one third of the samples, concentrations of some trace elements were ∼2 orders of magnitude above the background concentrations. The elements most clearly transported in the pollution plumes from Kola Peninsula were Cd, Ni, Cu, V, Pb, As, Fe, and Co. Penner et al. [1993] presented a method for estimating black carbon (BC) emissions by comparing BC/SO2 (S) close to the sources and used a ratio 0.6 for the former USSR. We found that this ratio was <0.1 in the clearest pollution plumes from Kola peninsula. The ratio of the chemical mass to the gravimetric mass of the aerosol samples was ∼80% both for the fine and coarse particle filters, regardless of the source area. Comparison of the aerosol concentrations with the concentrations of elements in snow showed that the deposition was proportional to the aerosol exposure. The contribution of Kola Peninsula to the deposition is high, ∼80% for Ni, Cu, and Co and somewhat lower for other anthropogenic elements.
Atmospheric Environment. Part A. General Topics | 1990
Esko I. Kauppinen; Tuomo A. Pakkanen
Abstract Mass and elemental size distributions of hospital refuse incineration aerosols were measured in the aerodynamic particle size range 0.02–17 μm with an in-stack compressible flow, low pressure impactor. Oil was used as a supplementary fuel in the refuse combustion process and flue gases were cleaned with a cyclone. Mass size distributions were bimodal. The geometric aerodynamic mean diameter of the fine mode varied between 0.1 and 0.2 μm and the corresponding coarse mode mean between 6 and 10 μm. Mg, Al, Cl, Ti and Fe were found only in coarse mode particles. Elemental size distributions of Na, K, Zn, Cd, Pb and S were bimodal. Over 90% of the particle phase of S, 20–80% of Zn, 62–77% of Cd and 7–74% of Pb, respectively, were found in the fine mode particles. This existence of the fine mode peak in the size distributions of Na, K, Zn, Cd, Pb and S indicates that at least part of these elements vaporizes during the refuse incineration process.
Atmospheric Environment | 1996
Tuomo A. Pakkanen; Risto Hillamo; P. Keronen; Willy Maenhaut; Geert Ducastel; Jozef M. Pacyna
Abstract An intensive aerosol sampling campaign was carried out simultaneously at Birkenes and Nordmoen, southern Norway, from 11 April to 4 May 1988. Two different size segregative sampling instruments were used at each site. Parallel analysis was performed using several methods which allowed the determination of up to 45 components. The atmospheric concentrations were mostly found to be similar at the two sampling sites, which are separated by a distance of about 250 km. During long-range transport episodes, the pollutant concentrations were 20–50 times higher than during background periods. At the Birkenes site detailed information about the elemental and particle mass size distributions was obtained from Berner low-pressure impactor samples. The aerosol fine particle mode clearly shifted to larger particle sizes when the average relative humidity was higher than 80% during sampling. The average fine to total elemental concentration ratios of most elements were found to be similar for the different samplers and for the two sites, although differences between the sites occurred depending on the origin of the air masses sampled. A new approach based on the size distributions measured, the relative size distributions (RSD) method, was developed for the assessment of local and regional aerosol sources. The RSD method and conventional methods revealed local/regional sources of Mn, Zn, Pb, Bi, Br, I, Si and K. The interelemental concentration ratios in air masses of different geographical origin were studied and found to be similar in this study and in southern Sweden (Swietlicki et al., 1989) for air masses originating from the U.K.
Journal of Analytical Atomic Spectrometry | 1993
Tuomo A. Pakkanen; Risto Hillamo; Willy Maenhaut
The aim of this study was to develop a simple dissolution method for atmospheric aerosol samples collected using a Berner impactor. Particular care was taken to ensure that the procedural blank contributions were as low as possible for the elements investigated. The impactor samples were treated for two or three 20 min periods with 0.2 mol l–1 nitric acid in polystyrene test-tubes in an ultrasonic bath at 50 °C. Electrothermal atomic absorption spectrometry (ETAAS) with a graphite furnace was used to determine 14 elements: Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V and Zn. With the exception of Zn, for which a platform was used, all analytes were atomized off the wall of the graphite tube. The blank values for Al, Cd, Cu, Mn, Ni, Pb and V were found to be at or below the detection limits of the method. The blank values for Ca, Fe, K, Mg, Na and Zn varied between 0.5 and 3 µg l–1 but Cr showed an unsuitably high blank of 8 µg l–1. The dissolution method was tested on the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1648 Urban Particulate and the recoveries were found to be 80–93% for Pb, Zn, Cd and Cu. The least recoverable elements in this matrix were Al, Cr, Fe, K and Na, with recoveries between 20 and 44%. A prolonged dissolution time had only a minor effect on the recoveries. Additional tests involved the analysis of ambient aerosol samples, collected with a cascade impactor, by both ETAAS and instrumental neutron activation analysis (INAA), with the latter technique providing the reference values. Six elements (Al, Cu, Mg, Mn, Na and V) were measured by both techniques. Compared with the NIST material, the fine particle (equivalent aerodynamic cut-off diameter<2 µm) impactor samples clearly showed better recoveries for Cu (91%), Mn (90%), Na (102%) and V (96%). Similar or even better recoveries are also expected for fine particle Cd, Zn and Pb, which were not measured in our INAA procedure but exhibited the highest recoveries for the NIST material. For Al, on the other hand, the results from the impactor samples were similar to those for the NIST material and there was a trend that the recoveries were decreasing with increasing particle size, because of incomplete dissolution of the soil dust particles and a lower ability of the coarser particles to form a suspension. Moreover, coarse particle Al was recovered mostly as particulate material. It is assumed that our dissolution method is valid for measuring fine particle Cd, Cu, Mg, Mn, Na, Pb, V and Zn in ambient aerosol samples collected on polycarbonate film by various types of impactors.