|
| << vorige | volgende >> |
Tijdschrift beschrijving
Alle jaargangen van het bijbehorende tijdschrift
Alle afleveringen van het bijbehorende jaargang
Alle artikelen van de bijbehorende aflevering
Details van artikel 15 van 106 gevonden artikelen
| Titel: |
Changes in background aerosol composition in Finland during polluted and clean periods studied by TEM/EDX individual particle analysis |
| Auteur: |
J. V. Niemi S. Saarikoski H. Tervahattu T. Mäkelä R. Hillamo H. Vehkamäki L. Sogacheva M. Kulmala |
| Verschenen in: |
Atmospheric chemistry and physics |
| Paginering: | Jaargang 6 (2006) nr. 12 pagina's 5049-5066 |
| Jaar: |
2006 |
| Inhoud: |
Aerosol samples were collected at a rural background site in southern Finland in May 2004 during pollution episode (PM<sub>1</sub>~16 µg m<sup>−3</sup>, backward air mass trajectories from south-east), intermediate period (PM<sub>1</sub>~5 µg m<sup>−3</sup>, backtrajectories from north-east) and clean period (PM<sub>1</sub>~2 µg m<sup>−3</sup>, backtrajectories from north-west/north). The elemental composition, morphology and mixing state of individual aerosol particles in three size fractions were studied using transmission electron microscopy (TEM) coupled with energy dispersive X-ray (EDX) microanalyses. The TEM/EDX results were complemented with the size-segregated bulk chemical measurements of selected ions and organic and elemental carbon. Many of the particles in PM<sub>0.2–1</sub> and PM<sub>1–3.3</sub> size fractions were strongly internally mixed with S, C and/or N. The major particle types in PM<sub>0.2–1</sub> samples were 1) soot and 2) (ammonium)sulphates and their mixtures with variable amounts of C, K, soot and/or other inclusions. Number proportions of those two particle groups in PM<sub>0.2–1</sub> samples were 0–12% and 83–97%, respectively. During the pollution episode, the proportion of Ca-rich particles was very high (26–48%) in the PM<sub>1–3.3</sub> and PM<sub>3.3–11</sub> samples, while the PM<sub>0.2–1</sub> and PM<sub>1–3.3</sub> samples contained elevated proportions of silicates (22–33%), metal oxides/hydroxides (1–9%) and tar balls (1–4%). These aerosols originated mainly from polluted areas of Eastern Europe, and some open biomass burning smoke was also brought by long-range transport. During the clean period, when air masses arrived from the Arctic Ocean, PM<sub>1–3.3</sub> samples contained mainly sea salt particles (67–89%) with a variable rate of Cl substitution (mainly by NO<sub>3</sub><sup>−</sup>). During the intermediate period, the PM<sub>1–3.3</sub> sample contained porous (sponge-like) Na-rich particles (35%) with abundant S, K and O. They might originate from the burning of wood pulp wastes of paper industry. The proportion of biological particles and C-rich fragments (probably also biological origin) were highest in the PM<sub>3.3–11</sub> samples (0–81% and 0–22%, respectively). The origin of different particle types and the effect of aging processes on particle composition and their hygroscopic and optical properties are discussed. |
| Uitgever: |
Copernicus GmbH (provided by DOAJ) |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 15 van 106 gevonden artikelen
| << vorige | volgende >> |