Chemical composition (precipitation quality) and atmospheric deposition have
been monitored in the long term at relatively large number of stations in the
Czech Republic. Precipitation quality station networks operated by CHMI, ČGS,
VÚV TGM, VÚLHM and HBÚ AV ČR from which data on precipitation quality and
atmospheric deposition were processed in 2005, are plotted in
Fig. III.1. Most of the CHMI stations
measure wet-only samples in weekly interval (monthly interval was switched over
to weekly interval in 1996 in line with the EMEP methodology). In 1997 the
special weekly precipitation sampling with dustfall (bulk) for heavy metals
analysis was introduced at these stations. In localities of other organizations
monthly sampling (or irregular sampling) is used for measuring concentrations in
precipitation with dustfall in open area (or throughfall). Detailed information
on individual localities and sampling types is presented in
Table III.4.
Tables III.5 and III.6
contain average values of the chemical composition of atmospheric precipitation
and the values of the 2005 annual wet deposition.
Wet deposition charts were compiled for selected ions on the basis of all-round
chemical analyses of precipitation samples, specifically for SO42--
S, NO3-- N, NH4+ - N, H+
(pH), F , Cl-, Pb2+, Cd2+ and Ni2+.
The above ions were selected to represent deposition fields with regard to their
considerable impact on the various spheres of the environment. Wet deposition
charts for each of the ions were derived from the field of ion concentrations in
precipitation (based on annual mean concentrations weighted by precipitation
totals calculated from the data observed), and from the field of annual
precipitation totals which was generated on data from 750 precipitation gauging
stations, taking into account the altitudes effect on precipitation amount.
When constructing wet deposition fields, results of wet-only samples analysis
are preferred to bulk samples with dustfall, and weekly samples are preferred
to monthly samples. Data from the stations operated by ČGS, VÚV TGM and VÚLHM
which are based on monthly bulk sampling with dustfall (see
Table III.4) are modified by empirical coefficients
expressing the individual ions ratios in bulk and wet-only samples (values for
each of the ions from 0.94 to 1.35) for the purpose of the development of the
wet deposition charts.
In addition to wet deposition, also dry and total deposition charts are included
for sulphur, nitrogen and hydrogen ions. Dry sulphur and nitrogen deposition was
calculated using fields of annual mean SO2 and NOx
concentrations for the Czech Republic, and the deposition rates found in [21]
for SO2 0.7 cm.s-1/0.35 cm.s-1, and NOx
0.4 cm.s-1 / 0.1 cm.s-1, in case of forested/unforested
area. Total deposition charts were produced by adding S and N wet and dry
deposition charts. The wet hydrogen ion deposition chart was compiled on the
base of pH values measured in precipitation. Dry hydrogen ion deposition
reflects SO2 and NOx deposition based on stechiometry,
assuming their acid reaction in the environment. The total hydrogen ion
deposition chart was developed by summation of wet and dry deposition charts.
The average deposition fluxes of S, N and H are presented in the following
table:
Tab. III.1 Average deposition fluxes S, N and H in
the Czech Republic, 2005
Throughfall sulphur deposition chart was generated for forested areas from
the field of sulphur concentrations in throughfall and a verified field of
precipitation, which was modified by a percentage of precipitation amounts
measured under canopy at each station (52–97 % of precipitation totals in 2005).
Throughfall deposition generally includes wet vertical and horizontal deposition
and dry deposition of particles and gases in forests; in case of sulphur, its
circulation within the forests is negligible; throughfall deposition is thus
considered to provide a good estimate of total deposition.
Heavy metal wet deposition charts for Pb, Cd and Ni were derived from
concentrations of these metals in bulk precipitation samples with dustfall at
individual stations. The field of deposition flows of Pb and Cd contained in PM10
(dry Pb and Cd deposition) were derived from the fields of these metals
concentrations in the ambient air. The deposition rate of Cd contained in SPM
was taken as 0.27 cm.s-1 for a forest and 0.1 cm.s-1 for
unforested terrain; the figures for Pb are 0.25 cm.s-1 for a forest and 0.08
cm.s-1 for unforested terrain [21].
The data on precipitation quality are controlled routinely using the method of
ion balance calculation (the difference between the sum of cations and the sum
of anions in the sample should meet the allowable criteria which differ slightly
in various organizations).
Another control is carried out by comparing the calculated conductivity and the
measured conductivity which both should meet the allowable criteria.
Analysis of the blank laboratory samples is also used and blank field samples
are monitored and assessed continuously. This enables the control of work during
sampling and the control of changes occurring due to transport, manipulation,
storage and preparation of the samples prior to the chemical analysis.
Results
- The average value of total precipitation in the year 2005 for the
territory of the Czech Republic was slightly above the of the long-term
normal for the years 1961–1990; it reached 109 % of the long-term normal.
- Wet sulphur deposition decreased after 1997 below 50,000 t and this
trend continued up to 1999. Since 2000 the profound decrease had not
continued and the values remained more or less at the level of 1999 with the
exception of lower depositions in 2003, where the precipitation total was
markedly subnormal. The comparison of concentrations show that in 2005
similar values as in 2004 were reached. The highest values of sulphur wet
deposition were recorded in the Orlické hory Mts., in the Jizerské hory Mts.,
in the Krkonoše Mts. and in the Moravskoslezské Beskydy Mts.
- Dry sulphur deposition the most significant decline of which was
recorded in the year 1998 (the value decreased by 45 % in comparison with
the average value for the period 1995–1997), continued to decline in
1999–2000. In 2000–2005 the deposition field remained at the same level,
which is coherent with SO2 concentrations in the ground-level
ambient air. The field of total sulphur deposition is the sum of wet and dry
depositions and it shows the total sulphur deposition amounting to 69,183 t
for the Czech Republic's territory for the year 2005 see (Table III.2). After the previous decrease from the values markedly above
100,000 t, in the period 2000–2005 the sulphur deposition remained within
the range from 69,000 to 75,000 t per year with the exception of the year
2003 which was markedly below normal as for the precipitation (see
Fig. III.21). The total sulphur deposition reached the maximum values in the
Krušné hory Mts., the Orlické hory Mts. and the Jizerské hory Mts.
- The throughfall sulphur deposition field in several mountainous areas (the
Krušné hory Mts., the Orlické hory Mts.) reaches, in the long-term, higher
values than the total deposition calculated as the sum of wet (only vertical)
and dry deposition. The increased contribution can be attributed to
deposition from fog and low clouds which is not included in total summary
deposition because of uncertainties. Hoarfrost and fog are normally highly
concentrated and may significantly contribute to sulphur and other elements
deposition in mountainous areas and areas with frequent fogs (valley fogs,
fogs near water courses and lakes). The problem is in a very erratic
character of this type of deposition from place to place where some
uncertainties may occur when extrapolating to a wider area. In such case,
the field of throughfall deposition can be considered as illustrative for
what values the total sulphur deposition (including horizontal deposition)
might reach, because sulphur circulation within vegetation is, unlike other
pollutants, negligible. Table III.3 shows the values of total and
throughfall deposition for the forested areas of the Czech Republic since
1997. The higher values of throughfall deposition (containing also fog and
low clouds deposition) confirm its significance for the determination of
total sulphur deposition.
- The map of wet deposition of nitrates is similar to that presented in
the previous year. The wet deposition of ammonia ions slight increase was
recorded in the area of the Jizerské hory Mts. and Orlické hory Mts., which
resulted in the increase of total wet annual deposition of nitrogen in these
areas up to the level of 1.5–2 g.m-2.year-1. This increase caused also the
increase in total wet deposition in these areas up to the level of 2–3
g.m-2.year-1 The total wet deposition of oxidized forms of nitrogen in the
territory of the Czech Republic slightly decreased in comparison with the
previous year (see Fig. III.22). The map of dry nitrogen deposition is of
similar character as in the previous years. Dry deposition of oxidized forms
of nitrogen was declining up to the year 2002 (when the value reached 48 %
of the value of the average for the years 1995–1997). The trend of slight
increase in the years 2003–2004 was not confirmed, in 2005 a slight decline
occurred (see Fig. III.21).
- In 2005 the total nitrogen deposition reached 78,317 t of N (ox+red).
year-1 for the area of the Czech Republic (see
Table III.2), which is
comparable with the values reached in the period 1999–2004 when the total
deposition ranged between 77,000 and 85,000 t of N. year-1 (with the
exception of the year 2003 which was significantly below normal). The
highest values of total nitrogen deposition were reached in the Jizerské
hory Mts., Krkonoše Mts., Orlické hory Mts. and the Krušné hory Mts. The
increase in these areas is related with the increase of wet deposition of
ammonia ions.
- The charts of both wet and dry deposition of hydrogen ions have shown
relative minimal differences in the period of 2000–2005. The slight increase
of wet deposition from 2004 did not continue, and on the contrary slight
decrease in the territory of the Czech Republic occurred. The maximum values
of wet deposition were reached in the Moravskoslezské Beskydy Mts, the
Jizerské hory Mts., the Krušné hory Mts., the Slavkovský les Mts. and in the
Šumava. Mts. The map of total deposition of hydrogen ions is similar as in
the previous year (Fig. III.13). In the second half of the 90s of the last
century both wet and dry depositions of hydrogen ions decreased by 50 % per
the whole area of the Czech Republic, the decrease of dry deposition of
hydrogen ions values was in coherence with the already mentioned decrease of
dry deposition of SO2–S and NOx–N.
- After the year 2000 when the distribution of leaded petrol was finished
the field of wet deposition of lead ions remains at a markedly lower level.
The field of wet deposition for the year 2005 is similar as in the previous
years 2001–2004. Slightly increase values of depositions were recorded,
similarly as in previous years, in the Krkonoše Mts. and in the area of the
Moravskoslezské Beskydy Mts. The map of dry lead deposition is similar as in
the previous years.
- Similarly as in the previous years the markedly highest values of dry
and wet deposition of cadmium ions were recorded in the area of the Jizerské
hory Mts. This is probably local pollution as this is the area with long-term
increased cadmium concentrations in the ambient air. Significant emission
source from the glassworks is one of the probable reasons of this situation.
In comparison with the previous year, the highest values of dry deposition
increased above the level of 1mg.m-2.year-1.
- The map of wet annual deposition of nickel ions shows the increase of
precipitation pollution in comparison with the previous years. The most
significant increase was recorded in the Ostrava Region, in the
Moravskoslezské Beskydy Mts., in the Hrubý Jeseník Mts., in the Jizerské
hory Mts., in the Šumava Mts. and in the Středočeská pahorkatina (Central
Bohemian Upland). At present the potential reasons of the increased
concentrations are under review.
- In 2005 the increase of fluoride ions deposition was recorded in the
locality Lužnice, as compared with the previous year.
- After the decrease of wet deposition of several components (mainly
sulphates, hydrogen ions and lead ions) in the second half of the 90s, the
development of annual wet deposition of the main elements as measured at
selected stations in the Czech Republic (Fig. III.21) shows stagnation
instead. The decrease of sulphate deposition was substantial not only at the
exposed stations as Ústí nad Labem, Prague-Libuš or Hradec Králové but it
was also obvious at the background stations Košetice and Svratouch. The
marked decrease of sulphur deposition is directly linked with the change of
the proportion of sulphur and nitrogen at the stations. The deposition of
both elements has been balanced since the second half of the 90s, at the
background stations the nitrogen deposition is slightly higher (Košetice).
The decrease was substantial at the station Ústí nad Labem where the wet
sulphate deposition decreased by 60 % after 1995 and where the decrease of
other substances (NO3-, NH4+, Pb2+) was also obvious. During the recent
three years this locality recorded slight increase again (NO3-, SO42-,
Pb2+). With the development of sulphur and nitrogen deposition the
development of the proportion of both elements can be observed in
atmospheric precipitation. Since the second half of the 90s a slight
increase of nitrogen and sulphur proportion has been observed.
Tab. III.1 Average deposition fluxes S, N and H in
the Czech Republic, 2005
Tab. III.2 Estimate of the total annual deposition
in the Czech Republic (78,841 sq. km) in tonnes, 2005
Tab. III.3 Estimate of the total annual deposition
of sulphur on the forested part of the Czech Republic (16,990 sq. km) in tonnes,
1997–2005
Tab. III.4 Station networks monitoring
precipitation quality and atmospheric deposition, 2005
Tab. III.5 Average annual concentrations of
principal pollutants in precipitation at stations in the Czech Republic, 2005
Tab. III.6 Annual wet atmospheric deposition at
stations in the Czech Republic, 2005
Fig. III.1 Station networks monitoring precipitation quality and atmospheric
deposition, 2005
Fig. III.2 Fields of annual wet deposition of sulphur (SO42-–S),
2005
Fig. III.3 Fields of annual dry deposition of sulphur (SO2–S),
2005
Fig. III.4 Fields of annual total deposition of sulphur, 2005
Fig. III.5 Fields of annual throughfall deposition of sulphur, 2005
Fig. III.6 Fields of annual wet deposition of nitrogen (NO3-–N),
2005
Fig. III.7 Fields of annual wet deposition of nitrogen (NH4+–N),
2005
Fig. III.8 Fields of annual total wet deposition of nitrogen, 2005
Fig. III.9 Fields of annual dry deposition of nitrogen (NOx–N),
2005
Fig. III.10 Fields of annual total deposition of nitrogen, 2005
Fig. III.11 Fields of annual wet deposition of hydrogen ions, 2005
Fig. III.12 Fields of annual dry deposition of hydrogen ions corresponding to
SO2 and NOx deposition, 2005
Fig. III.13 Fields of annual total deposition of hydrogen ions, 2005
Fig. III.14 Fields of annual wet deposition of fluoride ions, 2005
Fig. III.15 Fields of annual wet deposition of chloride ions, 2005
Fig. III.16 Fields of annual wet deposition of lead ions, 2005
Fig. III.17 Fields of annual dry deposition of lead, 2005
Fig. III.18 Fields of annual wet deposition of cadmium ions, 2005
Fig. III.19 Fields of annual dry deposition of cadmium, 2005
Fig. III.20 Fields of annual wet deposition of nickel ions, 2005
Fig. III.21 Annual wet deposition at selected stations between 1991 and 2005,
the Czech Republic
Fig. III.22 Annual deposition of sulphur (SO42-–S, SO2–S)
and oxidated forms of nitrogen (NO3-–N, NOx–N)
and hydrogen in the Czech Republic, 1995–2005
