|Znečištění ovzduší a atmosférická depozice v Krkonoších|
|Ambient air pollution and atmospheric deposition in the Giant Mts|
|Iva Hůnová; Lea Paličková|
|časový trend, depozice, dusík, přízemní ozon, prostorové rozložení|
|time trend, deposition, nitrogen, ambient ozone, spatial distribution|
Práce uvádí vybrané výsledky dlouhodobého sledování stavu ovzduší Českým hydrometeorologickým ústavem a prezentuje časové trendy a prostorové rozložení hlavních znečišťujících látek včetně atmosférické depozice. Kvalita ovzduší v Krkonoších je znázorněna v kontextu situace celé ČR. Pozornost je věnována zejména přízemnímu ozonu a depozici dusíku, faktorům, které mohou vzhledem k aktuálně měřeným úrovním potenciálně negativně ovlivnit citlivé horské ekosystémy. V současné době je více než polovina území KRNAP zatížena depozicí dusíku vyšší než 1 g.m-2, což je kritická zátěž pro středoevropské lesy. Po významném snížení emisí prekursorů se koncentrace přízemního ozonu významně mění podle meteorologické situace příslušného roku, maximálních koncentrací bylo dosaženo v r. 2003 a 2006.
We summarize results of long-term monitoring of ambient air quality run by the Czech Hydrometeorological Institute. The time trends and spatial patterns of principal ambient air pollutants, including atmospheric
deposition fl uxes are presented. Ambient air pollution in the Giant Mts. is visualized within the context of the Czech Republic. We focus on ambient ozone and nitrogen deposition as the major stress factors, which may potentially result, with regard to their measured levels, in negative impacts on sensitive mountain ecosystems. Currently, about 60% of the KRNAP area records nitrogen deposition higher than 1 g.m-2 which is considered to be a critical load for Central European forests. After the decrease of precursor emissions in the 1990s, the ambient ozone levels are driven by meteorological conditions of individual years; the peak concentrations were recorded in 2003 and 2006.
|Introduction Ambient air pollution is a factor that|
might substantially infl uence sensitive mountain
ecosystems. In the Giant Mts. this was striking during
the 1970´s and 1980´s due to the heavy SO2
emissions, which apparently triggered the forest
dieback. After a profound SO2 decrease, other air pollutants
remain to threat the local ecosystems. Czech
Hydrometeorological Institute runs a nation-wide
ambient air quality monitoring and is responsible
for air pollution assessment. Regularly the annual
ambient air quality report in the Czech Republic
is published and is freely accessible at www.chmi.
cz. The aim of this paper is to present the long term
trends and spatial patterns of major air pollutants
including atmospheric deposition in the Giant Mts.
in context of the Czech Republic.
Methods Krkonoše-Rýchory site (1001 m a.s.l.),
monitoring the ambient air pollution since 1994,
is a representative station for the Giant Mts. It observes
the real-time concentrations of the major air
pollutants: SO2 (UV-fl uorescence), NO2 (chemiluminiscence),
PM10 (absorption of beta radiation), and
surface O3 (UV-absorbance). Measured records are
stored in a nation-wide ambient air quality databasis
ISKO run by the CHMI.
Exposure index AOT40 F is a tool for estimation
of O3 potential risk for forest. It is defi ned as a cumulative
exposure above 40 ppb over the vegetation
season (April–September) for daylight hours. The
critical threshold for forests is 5 ppm h.
For time trends we used Mann-Kendall test recommended
by the WMO for this type of data (Määttä
et al. 2002).The air pollution maps were prepared
using the standard methods applied for mapping
in “Graphical Yearbooks” published by the CHMI
Results Annual mean SO2 concentrations markedly
decreased from 18 μg.m-3 in 1995 to 5–6 μg.m-3
after 1998, due to newly applied emission limits, to
current concentrations around 3 μg.m-3. Annual
mean NO2 levels are steady ranging between 7 and
10 μg.m-3. SO2 and NOx ambient air quality limits for
vegetation and ecosystem protection are not exceeded.
Annual mean PM10 levels somewhat decreased from
19 μg.m-3 in 1996 to 12 μg.m-3 in 2012. Ambient
O3 concentrations, in contrast are relatively high,
as these usually increase with increasing altitude.
The inter-annual variations of O3 concentrations
are remarkably refl ecting the meteorological conditions
of individual years. The distinct O3 peaks were
recorded in 2003 (annual mean concentration of 90
μg.m-3), and 2006 (annual mean concentration of 86
μg.m-3) due to extremely hot, sunny summer periods,
conducive for O3 formation. AOT40F inter-annual
variations were even more profound ranging between
10 ppm.h (in 2001 and 2005), and 37 ppm.h
(in 2003), exceeding more than 7times the critical
threshold. The AOT40F spatial pattern shows that
the critical threshold was exceeded over the entire
territory of the Czech Republic and ranged between
15 and 20 ppm.h in the Giant Mts. in 2015. Current
sulphur atmospheric deposition is low. In contrast,
current nitrogen deposition is fairly high, exceeding
the critical threshold for Central European forest
(1 g.m-2.y-1) over 60% of the Giant Mts. territory.
Discussion Our results clearly indicated that with
regard to the ambient air pollution, ambient O3 and
nitrogen deposition fl ux might impact negatively the
ecosystems in the Giant Mts. Elevated O3 exposure
does not mean automatically the injury, however. For
example, though we measured similar high exposures
in adjacent Jizerske hory Mts., the O3 – induced symptoms
were minute, though stomatal fl ux was high.
It is well known that nitrogen overloading might
result in acidifi cation, eutrofi cation, and loss of biodiversity.
The nitrogen deposition measured in the
Giant Mts. exceeded the critical threshold over 60% of
the area. Moreover, it is likely that sensitive mountain
ecosystems on acidic bedrock might be negatively
impacted even by lower deposition. Furthermore,
some nitrogen containing compounds in air (such
as NH3, HNO3 (g)) are not routinely measured. The
same applies for fog. Thus the “total” deposition we
presented is likely to be substantially underestimated,
and not refl ecting the real atmospheric deposition.
Additionally, recently published papers argue that
ecosystems might be negatively affected by even lower
nitrogen loads than has been assumed so far, and the
regions exposed currently to low nitrogen deposition
are likely to be the most vulnerable to its increase.
Interestingly, statistically signifi cant increase of the
N-NH4+/NO3- ratio, both in precipitation and wet
deposition over the Czech Republic in 2004–2014,
was recorded. This change is attributable to changes
in NH3 and NOx emission sources. Recently published
papers have indicated that increasing N-NH4+/NO3-
ratio is likely to negatively affect ecosystems.
In the view of elevated ambient O3 levels and
nitrogen loads in the Giant Mts., it would be not
only interesting, but extremely useful, to study their
realistic impacts on local ecosystems in more detail,
taking into account the relevant indicators of change.