Chemistry Reference
In-Depth Information
The duration of the smoke episode observed in April to May 2006 was extraor-
dinarily long. For example in Helsinki, elevated PM
2.5
concentrations lasted almost
a period of 2 weeks [
19
]. There was a long-lasting anticyclonic system over
Western Russia which caused the smoke particles to be transported northward of
the burning region. During the episode the visibility decreased remarkably and the
air was dry. In Helsinki the highest 30-min average PM
2.5
concentration was
69
gm
3
[
19
]. Coarse particle concentration (PM
2.5-10
) increased as well but
less than PM
2.5
. Besides in Helsinki, the smokes from biomass burning were
observed in Southern Finland in Kotka [
21
] and in Virolahti [
22
]. In Northern
Finland elevated concentrations were reported from Pallas [
25
].
In Sweden the spring 2006 wildfire episode was detected in two parts: first from
24 April to 3 May and later on 5-9 May [
25
]. The first part was observed only in the
eastern and northern parts of Sweden whereas the second part of the episode was
also noticed in Western and Southern Sweden. PM concentrations rose remarkably
in Sweden, at stations around Stockholm the PM
10
concentrations reached the
values equal to 70
m
gm
3
being 5-9 times higher than in the reference period.
PM
10
was also elevated in Denmark from 3 to 8 May with the maximum PM
10
concentrations of 70-90
m
gm
3
[
11
]. In Norway PM
10
levels showed a slight
increase above the baseline from 2 to 12 May but there were no obvious peaks and
the concentrations generally remained below 60
m
gm
3
. However, as aerosols were
not removed from the atmosphere to a significant extent by precipitation, a severe
air pollution episode was observed in the Norwegian Arctic at Spitsbergen on
27 April and early May 2006 [
10
]. In addition to Northern Europe, high particle
concentrations were also observed in other areas in Europe, e.g., in Lithuania [
36
],
UK, and Germany [
11
]. At the same time with the smoke episodes, there was also a
sudden release of pollen in European countries, mainly from birch and pine trees
[
11
]. Pollen was observed in the smoke plume at Spitsbergen as it was transported
across Scandinavian [
10
].
In contrast to the nearly constantly elevated PM concentrations in spring 2006, in
August 2006 there was a series of short-term smoke plumes. In August 2006 the
fires were close to Helsinki (~200-300 km from Helsinki; [
18
]), whereas in spring
the smoke particles had been in the atmosphere probably for days. Besides different
source areas and transport times, the burning material was assumed to be different
in August from spring: in spring the burning material was dry hay and agricultural
biomass from previous season, whereas in August mainly bog peat and fresh forest
were burning. The average PM
2.5
mass concentration during the smoke plumes was
equal to 45
m
gm
3
in Helsinki with the highest 1-h average concentration peak
m
gm
3
on 21 August.
In 2010 smokes from the extensive wildfires in the western part of Russia, near
Moscow, were observed in Eastern Finland, Kuopio [
32
,
33
]. Kuopio is around
1,000 km northwest of Moscow and the transport time from the fire area was
estimated to be around 1-2 days. Especially on 2 days, on 29 July and 8 August,
the influence of wildfire smokes was clear with the highest PM
2.5
and PM
10
concentrations around 50 and 60-70
being 180
m
gm
3
, respectively. There was a difference
in the vertical location of the plume between the 2 days. In July the plume was
m
