14-Klos - Use.vp:CorelVentura 7.0

ECOLOGICAL CHEMISTRY AND ENGINEERING
Vol. 13, No. 8
2006
Andrzej K£OS*, Ma³gorzata RAJFUR*,
Maria WAC£AWEK* and Witold WAC£AWEK**
USE OF LICHENS TO ASSESS
LOCAL SOIL AEROSOL POLLUTION
WITH RADIOCESIUM-137
WYKORZYSTANIE POROSTÓW DO OZNACZENIA RADIOCEZU-137
W LOKALNYM AEROZOLU GLEBOWYM
Summary: The experimental results presented concern the possibility of lichen utilization in the environmental pollution estimation by metals. The investigations were carried out in the region of Bory Stobrawskie.
This area is situated 20–50 km north-east from Opole, PL. Cesium-137 of Chernobyl origin, is still present in
the forest areas and its radioactivity in the investigated region (partly overlapping the region of the so-called
Opole Anomaly) is several tens time bigger than the average for Poland. Taking into account the 137Cs
activities in lichen and in soil the dependence Alichen = f(DAsoil) was determined. This relationship could be also
utilized for interpretation of measurement results of other metals concentration in the environment.
Keywords: lichens, cesium-137, heavy metals, environmental pollution
Nowadays in the environment pollution estimation more and more frequently
biomonitors were used. They use organisms, which react on changes of the chemical
composition of environment [1]. Lichens are perceived as one of the best bioindicators
of different air pollutants (e.g. [2]). The data on trace element concentration cumulated
in lichen thallus are a source of interesting information e.g. on pollutants emitted to the
environment, on changes in environment quality and it makes possible to estimate the
directions of pollutants’ spreading. The basic problem of the quantitative assessment of
environment pollution by trace elements accumulated in lichens is multidimensionality
of the lichen interaction with surrounding [3]. To the abiotic factors influencing the
sorption intensity of trace elements one can count inter alia climatic conditions as well
as the chemical composition of substrata, on which the lichens grow.
** Chair of Biotechnology and Molecular Biology, Opole University, ul. Kard. B. Kominka 4, 45–032
Opole, email: [email protected],
** Chair of Chemical Physics, Opole University, ul. Oleska 48, 45–052 Opole, email: [email protected]
834
Andrzej K³os et al.
The aim of this investigation is the assessment of the possibilities of using lichens to
evaluate the pollution level in the Bory Stobrawskie area (Southern Poland). The mutual
correlations between 137Cs radionuclide content in soil and in lichens was also the aim
of the research. Radioactive cesium of Chernobyl origin is still present in the
investigated areas. Its concentrations are higher of several tens times than the average
for Poland. Earlier studies have shown, that the main mechanism of cation sorption in
lichens is ion exchange occuring between lichen cationoactive layer (extracellular
structure) and water solution wetted lichens [4–7]. Heavy metals and 137Cs compounds
dissociating in water, they could be gathered onto lichen surface due to dry and wet
depositons from atmosheric aerosol (inflowing contamination) or to be precipitated onto
lichen surface due to secondary dry deposition of the local soil aerosol. It was shown,
that the extreme pH value for solutions, with which lichens have been in contact in
natural conditions equals to 3.9. Long-term lichens contact with solution having smaller
pH values leads to lichen thallus destruction [4]. The following thesis was put: under
natural conditions, because of secondary dry deposition of soil aerosol to lichens,
metals from soil can be transferred onto lichen surface. Such approach was used for
searching a correlation between 137Cs concentration bound in lichens and mobile 137Cs
concentration in soil. Various concentrations of 137Cs in forest soils in the investigated
area and the fact, that at present 137Cs is not inflowing to Poland (its mean activity in air
is only 1.4 mBq × m–3) [8] makes it possible to assess the mutual correlations of 137Cs
concentration in lichens and in soil.
Materials and methods
Specimens of lichens Hypogymnia physodes growing on spruces and larchs in the
forest area, mainly in Bory Stobrawskie were sampled for laboratory investigation. Bory
Stobrawskie is forest situated 20–50 km north-east from the provincial city of Opole.
The investigated region has an area of ca 3000 km2. Lichen sampling was carried out
from May 2005 to the end of August 2006. Localisation of 17 sampling place are shown
in Fig. 1.
Fig. 1. The
137
Cs radioactivities measured for soil in 1994
Use of Lichens to Assess Local Soil Aerosol Pollution with Radiocesium-137
835
A part of the so-called Opole Anomaly area (of the heavy Chernobyl fallout) belongs
to the Bory Stobrawskie territory. In some places of this region 137Cs activity in soils
registered in 1994 were several tens times higher than the average for Poland [9]. The
20 years after Chernobyl disaster 137Cs is still present in the forests and wastelands. Its
translocation in soil is an interesting subject of research (e.g. [10, 11]).
Sampling and measurement methods
Lichens were taken with withered branches of spruce or larch lying horizontally at
the height of 1.0 to 1.5 m above the ground. The samples were purified from
mechanical impurities and dried at 303 K. In the same places samples of soil and
ectohumus were taken. The samples were homogenised and dried at 353 K. Then 137Cs
activity concentrations were measured.
The 137Cs activity was also measured for homogenised soil samples (ca 200 g d.m.).
Then the sample was leached with a solution of hydrochloric acid (pH = 3.9). For the
extracted soil samples, after washing with demineralised water 137Cs activity is again
measured.
Equipment
The measurement of radiocesium activity for samples of lichens and forest soil
was carried out using a gamma-spectrometer with a germanium detector HPGe
(CANBERRA).
Results
The examined samples of soil and lichens were collected in the Bory Stobrawske
area at locations numbered 1–17 on the map (Fig. 1). The measured date of 137Cs
activity are presented in Table 1. The measurement uncertainty did not exceed 3 %.
Table 1
The
No.
1
2
3
4
5
6
7
8
9
137
Cs radioactivity [Bq(kg d. m.)
Nearest place
Rzêdów I
Rzêdów II
Kosowce
Szumirad (Smolnik)
Chudoba
Boroszów
Trzebiszyn
ZagwiŸdzie
Knieja
–1
in lichen and soil samples]
Lichens
Soil before
extraction
Soil after
extraction
1386 ± 28
1147 ± 23
922 ± 22
920 ± 53
681 ± 17
455 ± 11
420 ± 18
313 ± 7.8
166 ± 5.3
1425 ± 36
628 ± 12
363 ± 8.3
2278 ± 73
276 ± 4.2
190 ± 3.5
801 ± 15
362 ± 8.2
168 ± 3.3
1238 ± 33
485 ± 9.1
329 ± 6.5
1904 ± 48
249 ± 4.4
171 ± 3.2
777 ± 11
350 ± 5.9
156 ± 3.2
137
Cs loss during
extraction
187
143
34
374
27
19
24
12
12
836
Andrzej K³os et al.
Table 1 contd.
No.
10
11
12
13
14
15
16
17
Nearest place
Szczedrzyk
Krupski M³yn
Pokój
Klekotna
Zawadzkie
Kolonowskie
Blachownia
Staniszcze Wielkie
Lichens
Soil before
extraction
Soil after
extraction
116 ± 11
37.3 ± 2.5
35.0 ± 1.9
34.5 ± 2.7
25.5 ± 2.4
17.4 ± 1.4
14.1 ± 1.6
13.0 ± 1.6
318 ± 6.0
13.9 ± 0.4
72.2 ± 1.9
52.6 ± 1.5
19.4 ± 0.3
28.7 ± 0.9
12.8 ± 1.1
155 ± 4.6
308 ± 5.5
6.9 ± 0.5
68.1 ± 1.8
44.8 ± 1.0
11.9 ± 0.4
20.6 ± 0.8
3.9 ± 0.2
149 ± 2.8
137
Cs loss during
extraction
10
7.0
4.1
7.8
7.5
8.1
8.9
6
In Fig. 2 a comparison of 137Cs activities in lichens and radiocesium extracted from soil
to HCl solution with pH = 3.9 (DAsoil = Asoil1 – Asoil2) was shown.
Alichen [Bq (kg d.m.)–1]
1600
1
1400
1200
2
1000
4
3
800
5
600
6
7
400
8
200
9, 10
11–17
0
0
50
100
150
200
250
300
350
400
DAsoil [Bq (kg d.m.)–1]
Fig. 2. Comparison of
pH = 3.9
137
Cs activities in lichen and radiocesium extracted from soil to HCl solution with
The Alichen = f(DAsoil) dependences could be described by logarithmic function
Alichen = a + b ln(DAsoil)
(1)
A striking deviation from the dependence observed for location 8 was probably
caused by physicochemical properties of the soil sample. For this sample the biggest
137
Cs activity (2278 Bq/kg d.m.) was found. The soil sample was taken from
swampland. In natural environment a big soil moisture hindered secondary contaminant
Use of Lichens to Assess Local Soil Aerosol Pollution with Radiocesium-137
837
deposition from soil to lichen. Table 2 shows the parameters of logarithmic function
describing relationship observed.
Table 2
The a and b parameters and their standard deviations sa and sb of equation (1)
and correlation coefficient r describing the relationship between 137Cs activities in lichens and in soil
a
sa
b
sb
R2
–806
71
419
24
0.96
Discussion
Figure 2 showed the relationship between 137Cs concentration in lichens and
concentration of leacheable 137Cs in soil. This relationship was described by the
function cCs,lichen = a + b ln(DcCs soil). It should be reminded that concentration of
leacheable cations was set up as cations concentration released from soil into HCl
solution of pH = 3.9. Earlier investigations showed that water of the same pH might wet
lichens in their natural environment. In this conditions radiocesium cations released
from the dust covering lichen (from secondary deposition) were transported in the way
of ion exchange inside thallus. Ion exchange was acknowledged to be the mechanism of
cation absorption in lichens [12–14].
Because of similarities in absorption mechanism of radiocesium and heavy metals in
lichen it could be supposed that the relationships between heavy metals concentration in
lichen and their mobile forms in soil would be also described by the relationship
cM,lichen = a + b ln (DcM,soil). The values of a and b constants should be characteristic for
each cation. But in this case rather more general formula should be used, which takes
also into account heavy metals deposition from non-local atmospheric aerosol on their
total load in lichen. Therefore, into Eq. 1 a term f(cM,air) should be added, which
describes the effect. Hence one obtains the following formula:
c’M,lichen = a + b ln(DcM,soil) + f(cM,air)
(2)
where the a and b constants are characteristic for the cation investigated.
In the case of Cs-137 for the investigated area of Bory Stobrawskie cM,air =
= 1.4 mBq × m–3, i.e. the term can be neglected.
Eq. 2 could be transformed into a linear form:
c’M,lichen · (ln(DcM,soil))–1 = (a + f(cM,air)) · (ln(DcM,soil))–1 + b
(3)
In Eq. 3 the coefficient (a + f(cM,air) is determined by local soil suspended dust as
well as by long-distance metals depositions from atmospheric aerosol.
Conclusions
A method of the environmental pollution estimation on the basis of heavy metals
concentrations determination in lichen and soil was described. This method allowed to
838
Andrzej K³os et al.
distinguish between the air chemical (mainly metallic) pollution due to local and
non-local origins. The research will be continued.
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Schwartzman K.: An ion-exchange model of lead-210 and lead uptake in a foliose lichen; application to
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WYKORZYSTANIE POROSTÓW DO OZNACZENIA RADIOCEZU-137
W LOKALNYM AEROZOLU GLEBOWYM
S t re s z c z e ni e
Przedstawiono wyniki badañ doœwiadczalnych dotycz¹cych wykorzystania porostów do oceny stanu
zanieczyszczenia œrodowiska przez metale. Badania wykonano dla obszaru Borów Stobrawskich, po³o¿onych
20–50 km na po³udniowy wschód od Opola. Cez-137 pochodz¹cych z awarii elektrowni nuklearnej
w Czarnobylu jest nadal obecny na badanych obszarach leœnych. Teren ten czêœciowo pokrywa siê, z tzw.
anomali¹ opolsk¹, dla której aktywnoœæ promieniotwórcza jest o kilka rzêdów wielkoœci wiêksza ni¿ jej
œrednia wartoœæ dla ca³ego obszaru Polski. Poprzez pomiar wartoœci aktywnoœci A cezu-137 w porostach
i glebie wyznaczono zale¿noœæ Aporost = f(DAgleba). Ta zale¿noœæ mo¿e byæ równie¿ wykorzystana dla
interpretacji wyników pomiarów stê¿enia innych metali znajduj¹cych siê w œrodowisku.
S³owa kluczowe: porosty, cez-137, metale ciê¿kie, zanieczyszczenia œrodowiska