> State of the environment
> Air
> Deposition of atmospheric
pollutants in Switzerland
Chemical analysis of mosses 1990–2010
Summary of the publication «Deposition von Luftschadstoffen in der Schweiz»
www.bafu.admin.ch/uz-1328-d
Published by the Federal Office for the Environment FOEN
Bern, 2013
> Summary
> Summary
In 2010 (and following similar studies in 1990, 1995, 2000 and 2005), as a Swiss
contribution to the European project, “Monitoring of atmospheric heavy metal and
nitrogen deposition in Europe using bryophytes”, the atmospheric deposition of various
metals, semi-metals (and from 2005 onwards, nitrogen) was estimated in Switzerland
using mosses (Hypnum cupressiforme or Pleurozium schreberi) as accumulative biomonitors. In some European countries, including Switzerland, in the same year estimates were made of levels of sulphur and polycyclic aromatic hydrocarbons in mosses.
With this study the following objectives were achieved: with the aid of moss analyses
it was possible to estimate the regional atmospheric deposition of various elements and
to make national and international comparisons. Changes versus previous measurement
periods were recorded and were used as the basis for assessing the degree of success of
any measures that had been taken with the aim of reducing emissions. Based on the
measurement of nitrogen content it was possible to obtain information regarding
atmospheric deposition of nitrogen. It was also possible to acquire initial practical
experience with the measurement of polycyclic aromatic hydrocarbons in moss. The
study also yielded reference data for the National Soil Monitoring Programme
(NABO), as well as for other studies.
Alongside Switzerland, 26 other European countries participated in the studies in 2010.
In addition to the content of metals, the level of nitrogen was estimated in 13 countries,
and the sulphur content was measured in 8. Polycyclic aromatic hydrocarbons were
included in the analyses in 6 countries. The data recorded in Europe are coordinated by
the “Coordinating Centre of the International Cooperative Programme on Effects of Air
Pollution on Natural Vegetation and Crops” (ICP Vegetation, http://icpvegetation.
ceh.ac.uk/), which is a sub-programme of the “Working Group of Effects” under the
UN/ECE Convention on Long-range Transboundary Air Pollution.
Mosses are a particularly suitable vehicle for this study because they draw water, as
well as all nutrients and pollutants, directly from the atmosphere instead of via their
roots. Samples were collected at a distance of at least 300 metres from roads and
housing developments, since the intention was to record remote pollution levels rather
than local peak levels. In the mountains, collection points located at 400 to 600 metres
above the valley floor were selected. At each location, 5 sub-samples were collected.
The various samples were collected from forest clearings (rejuvenated areas), moors
and Alpine meadows. The moss samples were then processed (removal of pine needles,
etc., selection of portions of growth of the past three years), digested in a microwave
oven and subsequently analysed with the aid of ICP-MS or ICP-AES (Hg with AMA
245, polycyclic aromatic hydrocarbons with HPLC/FLD). For the purpose of quality
assurance, blank values, reference material and retained samples were analysed and
multiple measurements were carried out.
1
2
Deposition of atmospheric pollutants in Switzerland. Chemical analysis of mosses 1990–2010 FOEN 2013
Metals
Fig. 1 > Concentration of heavy metals in μg/g dry matter
Depiction of heavy metal concentrations measured during the five study periods (1990, 1995, 2000, 2005 and 2010). The data
were broken down into three natural regions of Switzerland: NS = northern Switzerland (Jura, central plateau, northern Alps);
CA = central Alps; SA = southern Alps).
µg g-1
Ag
µg g-1
Al
4000
0.20
µg g-1
As
2.0
1.6
0.16
3000
1.2
0.12
2000
0.8
0.08
1000
0.4
0.04
0.00
µg g-1
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
Bi
0.20
0
µg g-1
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
Cd
0.0
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
µg g-1
1.60
5
1.28
4
0.96
3
0.64
2
0.32
1
Ce
0.15
0.10
0.05
0.00
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
0.00
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
0
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
3
> Summary
µg g-1
Co
µg g-1
Cr
8
2.0
Cu
µg g-1
25
1.6
20
6
1.2
15
4
0.8
10
2
0.4
5
0
0.0
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
µg g-1
Fe
3000
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
µg g-1
Hg
0.3
0
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
Ni
µg g-1
12.0
9.6
2400
0.2
7.2
1800
4.8
1200
0.1
2.4
600
0
µg g-1
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
Pb
0.0
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
µg g-1
V
0.0
15
200
88
12
160
66
9
120
44
6
80
22
3
40
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
0
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
Zn
µg g-1
110
0
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
0
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
The studies encompassed the following elements: silver, aluminium, arsenic, bismuth,
cadmium, cerium, cobalt, chromium, copper, iron, mercury, nickel, lead, selenium,
vanadium and zinc. In the case of arsenic, cadmium, copper, nickel, lead and zinc it
was possible to compare the concentrations in moss (medians in central plateau, northern Alps, southern Alps) with the levels of deposits recorded in the NABEL network
(PAY, RIG, MAG), and the degree of consistency was high.
4
Deposition of atmospheric pollutants in Switzerland. Chemical analysis of mosses 1990–2010 FOEN 2013
As was the case in the previous four measurement periods, it was once again apparent
in 2010 that the highest medians for all depicted elements were recorded in the southern Alps region (fig. 1). Here, in addition to local emissions, the main contributing
factors were high levels of precipitation, the regional topography and long-distance
road transport originating from the agglomeration of Milan. The differences between
the Jura, central plateau and northern Alps regions were mostly minor, therefore, they
have been grouped together in this chapter as a single zone (northern Switzerland).
Despite the lower urban density in the northern Alps and Jura regions, the readings are
very similar to those recorded in the central plateau. This is probably attributable to the
higher levels of precipitation in the northern Alps and Jura, which result in high depositions and can have a pronounced influence on heavy metal concentrations similar to
that of urban density in the central plateau. For most elements, the lowest median was
recorded in the central Alps (Fig. 1), which is less exposed to long-distance road
transport because of its more isolated location.
Fig. 2
> Trend in heavy metal concentrations in the period from 1990 to 2010
Depiction of heavy metal concentrations measured during the five study periods (1990, 1995, 2000, 2005 and 2010). The data
were standardised to the concentrations recorded in 1990.
1.0
As
Cd
V
Pb
0.5
Co
Cr
Fe
Hg
Ni
0.0
1990 1995 2000 2005 2010
1990 1995 2000 2005 2010
Cu
Zn
1990 1995 2000 2005 2010
In the period from 1985 to today, numerous industrial facilities both in Switzerland and
abroad have either been closed down or renovated, and the combustion of oil products
has become cleaner. This reduction in emissions is clearly reflected in the concentrations in moss (Fig. 2). The above graphs show the standardised median for the measured heavy metals distributed according to their behaviour over the course of time.
> Left: concentrations of arsenic, cadmium, vanadium and above all lead have fallen
sharply since 1990 (by 71%, 62%, 64% and 86%, respectively).
> Centre: concentrations of cobalt and mercury have also fallen, though not quite as
sharply (by 43% and 39%, respectively). Levels of chromium, iron and nickel were
5
> Summary
also lower in the later periods versus 1990 (down by 42%, 38% and 54%, respectively), but increases have been recorded again in the meantime.
> Right: The mean concentrations of copper remained more or less constant throughout the five measurement periods, and zinc concentrations only began to decline
significantly in the period between 2005 and 2010 (by 32%).
For cadmium, mercury and lead, specific measures to reduce emissions have been
taken in the past few years, including the renovation of waste incineration plants
(above all, Cd) and crematoria (Hg), and the introduction of lead-free petrol, and the
impacts of these measures are clearly reflected in the respective concentrations in moss
(Fig. 3).
Fig. 3 > Comparison between concentrations and emissions, 1990 to 2010
0.20
2
0.15
0.055
0.050
0.045
5
0.040
0.05
1985 1990 1995 2000 2005 2010
Lead
17
13
400
9
0.035
0.10
0
0.060
5
0.030
0.025
0
19851990 1995200020052010
1
0
1985 1990 1995 2000 2005 2010
Source (emissions): 1985: Swiss Federal Statistical Office – Swiss Statistical Encyclopaedia, 1990–2010: FOEN 2102
In a European comparison, somewhat lower levels were recorded in Switzerland for
almost all elements. Similar concentrations were often recorded in Austria, while in
Norway, concentrations of cadmium were significantly lower and those of mercury
were considerably higher. Copper and zinc levels were highest in Germany, while
concentrations of most of the other elements were at their highest in the Czech Republic. Throughout Europe, there has been a reduction in concentrations of almost all
elements in the past 20 years.
In order to obtain an overview of the overall level of pollution with heavy metals, those
elements that are primarily emitted anthropogenically were measured in all five periods
and were depicted in accumulated form on a series of maps (Fig. 4). For this purpose
the levels for As, Cd, Cu, Pb and Zn were standardised to their geometric average for
the five periods, added together for each location and shown in proportion to the spot
size. From the maps we can clearly identify the “problem region” (southern Switzerland), as well as the reduction during the past 20 years, and in particular in the period
between 1990 and 1995 (see also Fig. 5).
Concentrations: µg g-1
0.25
Mercury
21
Emissions: Mg
0.30
Concentrations: µg g-1
Cadmium
800
0.065
10
Emissions: Mg
4
0.35
Concentrations: µg g-1
Emissions: Mg
Depiction of measured Cd, Hg and Pb concentrations in moss and emissions in Switzerland: red circles = emissions /
green bars = moss concentrations.
Deposition of atmospheric pollutants in Switzerland. Chemical analysis of mosses 1990–2010 FOEN 2013
Fig. 4 > Overall pollution with heavy metals in Switzerland
Depiction of overall pollution during the five measurement periods (1990, 1995, 2000, 2005 ad 2010). The levels for
anthropogenically influenced elements (As, Cd, Cu, Pb, Zn) were standardised and added together. The spot sizes are roughly
proportional to the level of pollution.
Fig. 5 > Overall pollution with heavy metals in Switzerland
The levels for anthropogenically influenced elements (As, Cd, Cu, Pb, Zn) were standardised
and summed up. The diagram shows the median levels of overall pollution for the five
measurement periods (1990, 1995, 2000, 2005 and 2010), standardised to 1990.
1.0
0.8
0.6
0.4
0.2
0.0
1990
1995
2000
2005
2010
6
7
> Summary
Nitrogen
In the case of nitrogen a slight increase was recorded between 1995 and 2005, followed
by a slight decrease between 2005 and 2010 (Fig. 6). Higher levels were also recorded
in southern Switzerland, while the lowest median was noted in the northern Alps (Fig.
7). A comparison between concentrations of nitrogen in moss and in depositions from
precipitation shows a strong correlation (Fig. 8).
Fig. 6 > Nitrogen – comparison between three periods
(1990, 2005 and 2010)
Fig. 7 > Nitrogen concentrations in the
five natural regions (2010)
Depiction of median, maximum and minimum levels for
each of the 16 locations. The blue line indicates the
natural nitrogen content in mosses.
Depicted as box plot, divided into the
five natural regions: J = Jura, M =
central plateau, N = northern Alps,
Z = central Alps, SA = southern Alps.
25
mg g-1
N
mg g-1
20
20
15
15
10
10
5
5
0
1995
2000
2005
2010
0
J
M
NA
ZA
SA
2010 2010 2010 2010 2010
Fig. 8 > Comparison with nitrogen depositions from precipitation (2005 and 2010)
Here a comparison was made between nitrogen concentrations in moss and loads of N as
ammonium and nitrate (“bulk”) recorded in the vicinity of the moss collection location.
N concentration in moss, mg g-1
25
2008-2010
2003-2005
20
15
y = 0.54x + 6.67
R² = 0.56
y = 0.54x + 7.09
R² = 0.90
10
5
0
0
5
10
15
20
N deposition, kg ha-1 a-1
Source: Nitrogen in precipitation, calculated by WSL, IAP, FUB
25
8
Deposition of atmospheric pollutants in Switzerland. Chemical analysis of mosses 1990–2010 FOEN 2013
Sulphur
The sulphur concentration in moss was higher in southern Switzerland than in the
central and northern regions, and the same applied to the levels attributable to precipitation. The concentration in moss fell sharply after 1990 (Fig. 9) in southern Switzerland, but not in the other regions, despite significant reductions in sulphur levels in
precipitation since 1990. By contrast with nitrogen, the comparison with sulphur
deposition in precipitation revealed only a very weak correlation (Fig. 10). Following
these measurements it is not clear to what extent the sulphur concentration in moss can
be included in the estimate of sulphur deposition.
Fig. 9 > Sulphur concentration in moss (1990 and 2010)
Fig. 10 > Comparison with sulphur deposition from precipitation
Depiction of heavy metal concentrations measured during the
A comparison was made between sulphur concentration in moss
two periods, 1990 and 2010, in the form of a box plot. The data and the sulphur deposition designated as “bulk” or “wet only”
were broken down into three natural regions of Switzerland: NS (as sulphate) measured in the immediate vicinity.
= northern Switzerland (Jura, central plateau, northern Alps);
ZA = central Alps; SA = southern Alps.
µg g-1
S
1600
S concentration in moss, µg g-1
2000
1500
1000
500
2008–2010
1400
1200
1000
800
600
y = 56x + 728
R² = 0.15
400
200
0
0
NS NS NS NS NS ZA ZA ZA ZA ZA SA SA SA SA SA
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
0
2
4
6
S deposition, kg ha-1 a-1
Source: Sulphur in precipitation, measured by WSL, IAP, FUB
8
> Summary
Polycyclic aromatic hydrocarbons
13 polycyclic aromatic carbons were analysed at 14 locations in the central plateau
(SW-NE transect) and at 6 locations in the Basel region. Figure 11 shows the total of
these 13 components in map form. As we can clearly see, the concentrations in the
western section of the central plateau are lower than in the more densely populated
central and eastern sections, and these are mostly lower than those in the Basel region
where there is a major chemicals industry. The comparison with 9 polycyclic aromatic
hydrocarbons in PM10 at NABEL stations and 13 polycyclic aromatic hydrocarbons in
the soil of NABO locations, in each case within a radius of a few kilometres, shows a
strong correlation (Fig. 12).
Fig. 11 > Total of polycyclic aromatic hydrocarbons in the central plateau and the Basel region
Depiction of the total of 13 polycyclic aromatic hydrocarbon components in the moss samples
collected in 2010. The figures are indicated in μg g-1 TS. The spot sizes are roughly proportional
to the concentration in moss.
9
10
Deposition of atmospheric pollutants in Switzerland. Chemical analysis of mosses 1990–2010 FOEN 2013
Fig. 12 > Total for polycyclic aromatic hydrocarbons: moss compared with PM10 and soil
Total of 13 polycyclic aromatic hydrocarbons:
comparison of levels in moss (2010) with those
in soil (1995–1999) at NABO stations in the
vicinity of the moss collection points.
5
500
4
400
Soil concentration, µg kg-1
Concentration in PM10, ng m-3
Total of 9 polycyclic aromatic hydrocarbons:
comparison of levels in moss with those in
PM10 at NABEL stations in the vicinity of the
moss collection points.
3
2
1
R² = 0.75
300
200
100
R² = 0.55
0
0
0
100
200
300
Moss concentration, ng g-1
0
200
400
Moss concentration, ng g-1
Source of PM10 figures: Gehrig 2011. Source of soil figures, Desaules et al. 2009
Conclusions
This study demonstrates once again that, using the relatively favourable moss analysis
method it is possible to fairly accurately estimate both regional differences as well as
the trend in deposition over the course of time for a broad variety of metals and for
nitrogen. In this way it has been possible to document the impacts of measures aimed
at reducing emissions. The applied method can therefore be used for carrying out
success controls in the area of environmental protection. Mosses are also suitable for
monitoring levels of polycyclic aromatic hydrocarbons.
For a repeat of the study in 2015 less sites would be sufficient for heavy metals. Within
these sites, the calculation of nitrogen concentrations can support the implementation
of a success control concerning measures taken in the future with the aim of reducing
nitrogen oxide and ammoniac emissions, and it is also possible to monitor the trend in
polycyclic aromatic hydrocarbon immissions with the aid of moss analyses.