 |
| Titel |
Changes in background aerosol composition in Finland during polluted and clean periods studied by TEM/EDX individual particle analysis |
| VerfasserIn |
J. V. Niemi, S. Saarikoski, H. Tervahattu, T. Mäkelä, R. Hillamo, H. Vehkamäki, L. Sogacheva, M. Kulmala  |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 6, no. 12 ; Nr. 6, no. 12 (2006-11-03), S.5049-5066 |
| Datensatznummer |
250004170
|
| Publikation (Nr.) |
 copernicus.org/acp-6-5049-2006.pdf |
|
|
|
|
|
| Zusammenfassung |
| Aerosol samples were collected at a rural background site in southern
Finland in May 2004 during pollution episode (PM1~16 µg m−3,
backward air mass trajectories from south-east), intermediate
period (PM1~5 µg m−3, backtrajectories from
north-east) and clean period (PM1~2 µg m−3,
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 PM0.2–1
and PM1–3.3 size fractions were strongly internally mixed with S, C
and/or N. The major particle types in PM0.2–1 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 PM0.2–1 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 PM1–3.3 and PM3.3–11 samples, while the
PM0.2–1 and PM1–3.3 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, PM1–3.3 samples contained mainly sea salt particles (67–89%)
with a variable rate of Cl substitution (mainly by NO3−). During
the intermediate period, the PM1–3.3 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 PM3.3–11 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. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|