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J.Radioanal.Nucl. Chem.,Letters 200 (2) 147-158 (1995)

DEPOSITION OF FISSION PRODUCT RADIONUCLIDES IN LICHENS AND CONIFEROUS PLANTS IN TURKEY

H. Akgay

Department of Chemistry, Dokuz Eyl~l University of Izmir,

TR-35150 Buca-Izmir, Turkey

Received 20 January 1995 Accepted 31 January 1995

The effects of the Chernobyl disaster on lichens and pines, which are widely distrib- uted in northern and western Turkey, have been examined within the four years between 1986-1990. Analyses of the plants studied by y-spectrometry and spectrophotometric tech- niques have shown that the highest radioactive pollution was observed in the Pseud- evernia furfuracea. The effects of Chernobyl on the ecosystem have been examined by com- paring different plant species from the point of view of their reception and accu- mulation of fallout radionuclides.

INTRODUCTION

The existence of radioactive fallout in plants has

recently become the center of special interest for en-

vironmentalists because of their particularity in inter-

ception and retention of radioactive isotopes, and studies

on the transfer of these elements to people through food chains1,9,12,14,15,18,19

0236-5731/951US $ 9.50 Copyright �9 1995 Akad(rniai Kiad6,BlMapest All rights reserved

147

AKCAY: DEPOSITION OF RADIONUCLIDES IN LICHENS

The data and findings related to one of the major nu-

clear accidents in the history of nuclear energy, which

occurred in Chernobyl, Ukraine, are still considered to

be current issues with a great number Of indefinite as-

pects in the Ukraine and other countries in eastern

Europe. The majority of fission product radionuclides

released into the atmosphere as a result of this nu-

clear accident remained in the region near Chernobyl.

The main fission product radionuclides in Turkey and

other countries contaminated by the radioactive pollu-

tion were 131I, 137Cs and 134Cs. The radioactive ele-

ments which reached Turkey via radioactive clouds did

not remain for a long time over Turkey, so that the

doses of radiation through air did not cause significant

effects.

In the first days after the accident, the measure-

ments showed that 90% of the radioactivity accumulated 131

in the soil was I, and after the sixth and seventh

weeks it was proved that this amount decreased by half

for cesium and the other radioactive elements.

It has been determined that the radioactive pollu-

tion varies by a factor of 10 over different localities,

depending on the radioactive fallout. According to eco-

logical characteristics, especially lichens and pine

trees are indicate most definitely the radioactive pol-

lution. It was proved a long time ago that these plants

play an important role in the transfer of radioactive

elements to people.

In this work, coniferous plants and lichens which form

vast green areas especially in the northern and western

regions of Turkey, have been examined to determine the

level of contamination from the Chernobyl accident.

148

AK~AY: DEPOSITION OF RADIONUCLIDES IN LICHENS

"~' Jl

~'~C.,% " , . . . . . - x . J Z �9

</ Fig. I. The collecting areas of the samples (I. Trabzon,

II. Zonguldak, III. Izmir)

EXPERIMENTAL

Among higher plants, lichens and pine trees have been

used as experimental materials. For this aim Turkey was

divided into three sample collecting areas in the light

of the results of survey about the Chernobyl disaster

(Fig. I) I-3

The various lichen (Pseudevernia furfuracea, Parmelia

capetera, Lecanora muralis, Parmelia tractica, Cladonia

rangiformis, Squamarina cartilaginea) and pine species

(Picea orientalis, Pinus nigra, Pinus brutia, Pinus mari-

tima) were collected from the three areas between 1986-

1990 (Fig. I).

The lichens were collected by scraping from their

substrate rock surfaces and trees in the reguired quan-

tity. These samples collected from different localities

were classified according to their species and then dif-

ferent plant populations of the same species were mixed.

100-500 g species of the same kind of lichens and I-2 kg

149


species of the same kind of needle shoots of pine were

collected.

The samples were milled and dried for 8 h at 110 ~

Considering the low boiling point of cesium, samples with

low activities were turned into ash form at 500 ~ and

samples of 1.0-10.0 g taken from this ash were measured

by a planar X-ray detector. The detection limit was re-

duced to 10 Bq by this detector.

Each sample dried and weighed was placed into a Mari-

nelli beaker or a transparent container of 125 ml and

was counted using a HPGe technique.

The y-spectra of the samples were taken at the Radio-

chemistry Laboratory of Nice University, and the Nuclear

Research Center of 9ekmece, Istanbul. The analyses were

made by using two different germanium detectors. The

first one was a coaxial HPGe detector (EG-G ORTEC) with

a relative efficiency of 17% and a resolution of 1.9 keV

(FWHM) at 1.33 MeV. The second one was a 2 ml planar de-

tector with a low energy photon spectrophotometer X-ray

detector.

RESULTS AND DISCUSSION

The radioisotopes and the activity values of the

lichens collected from the East and West Black Sea region

and from the Aegean region are shown in Table I.

The isotope values that have been measured in the vi-

cinity of Izmir show a concordance with the findings

during studies in Southern France, South-Western Poland

and Austria (Table I).

On the hypothesis that activities measured in Septem-

ber 1986 have decreased only due to radioactive decay,

these activities have been compared with the values meas-

150

A K ~ A Y : D E P O S I T I O N O F R A D I O N U C L I D E S IN L I C H E N S

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0 0 0 0 0 ~ ~ ~ 0 ~ 0 ~

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~ r ~ o ~ o c o o

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oo O~ v -

t t ~ ! t 1 I v--

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151


3ooo- {13,c, ~_ 2700

2400 2100

1800

1500 - 13

1200 ~~1~, 900 - Ce/144pr

600-'~ u % ~ '06Ru I 106Rh

300-125Sb i ~ , ~ ~ ~ ~ 0 1 1986 1987 1988 1989 1990

Year Fig. 2. Variation of activity for a lichen collected

from Trabzon

,~ 2700 " '37cs~

2400

< 2100

1800 -

1500

1200i- ~4C s 900 o

600 106Ru

300 q 0 3 R u ~ ~ . . ~

198.6 1987 1988 1989 1990 Year

Fig. 3. Variation of activity for Parmelia tractica col lected from Trabzon

152


ured in the subsequent years (Figs 2 and 3). The Am/A d

values for Lecanora muralis (A m activity measured and

A d activity calculated for decay) show a rapid in-

crease.

In the following year the 134Cs adsorbed by the

lichens has rapidly increased due to erosion, other at-

mospheric phenomena and due to wash-out by rain. However,

in the beginning of 1988, this fast decrease has compara-

tively slowed down and in 1988-1990 it has become ap-

proximately stable. This conclusion shows a similarity

with the result obtained for 137Cs.

On the other hand, the decrease in the amount of 106Ru

is approximately half of the decrease obtained for Cs.

This result shows that the absorption mechanism of' Ru is

different.

Among the lichen species which have been systemati-

cally studied, Parmelia furfuracea exhibits the highest -I

activity (6727 Bq kg ) and Parmelia tractica shows the -I

lowest activity (3882 Bq kg ) due to the fact that

these plants generally exist on the surface of rock

(epilithic lichens) and this situation is quite incon-

venient for isotope absorption (Tables 2 and 3). The

fact that Parmelia furfuracea contains approximately

twice as much activity in comparison with Parmelia

tractica can be related to two different reasons: the

first one is that Parmelia furfuracea has a very porous

structure and the other one is that this particular lichen

lives on the branches of trees (epiphytic lichen) and

therefore absorbs quite a large amount of radioelements

found in rain.

The cesium activities measured in the pine species in

the areas of Trabzon, Zonguldak and Izmir studied since

1986, are shown in Table 4. It was found that, according

to analyses carried out in pine trees in Northern Italy,

153

AK~AY: DEPOSITION OF RADIONUCLIDES IN LICHENS

TABLE 2

The Am/A d values for Pseudevernia furfuracea, Ao, activities measured in September 1986; A m , activities

measured in years following 1986; A d, activities calculated according to radioactive decay

Isotope T, year X A (1986) o

~/%

1987 1989 1990

103Ru 0.1078 6.4290 630

106Ru 1.0082 0.6874 650

125Sb 2.77 0.2502

134Cs 30.1 0.023

(180/327) (122/164) (20/42) 0.55 0.63 0.48

1320 (310/941) (280/673) (153/344) 0.33 0.42 0.46

144Ce 0.7803 0.8881 1000 (200/411) 0.49

TABLE 3

Time dependent radioactive concentrations, in Bq kg -I and activity ratios of P. furfuracea collected from

Trabzon (nd: non-detected)

Year 103Ru 106Ru/106Rh 125Sb 134Cs 137Cs 144Ce/144pr 235 U

1986 630 650 177 1320 2950 1000 nd

1987 195 250 32 370 1170 320 nd

1988 60 122 - 280 956 156 nd

1989 - 52 - 218 808 - -

1990 20 - 159 740

154

AK(2AY: DEPOSITION OF RADIONUCLIDES IN LICHENS

TABLE 4

Cesium inventory in Bq kg -I according to localities and years

Year Locality Plants species 134Cs 137Cs

1986 Trabzon Pinus brutia 49 181 Izmir Pinus brutia 45 169 Trabzon Pinus nigra 52 186 Izmir Pinus nigra 44 167 Trabzon Picea orientalis 86 307

1987 Trabzon Pinus brutia 44 165 Izmir Pinus brutia 37 150 Trabzon Pinus nigra 46 171 Izmir Pinus nigra 34 150 Trabzon Picea orientalis 77 285

1988 Trabzon Pinus nigra 38 153 Zonguldak Pinus nigra 7 32 Izmir Pinus nigra 25 94 Trabzon Picea orientalis 68 249

1989 Zonguldak Pinus maritima 4 12

Middle France and Belgium, these show 4-6 times greater

pollution than those in the Eastern Black Sea region of Turkey4,5, 15-17

The activity ratios for different isotopes of the same

element greatly resemble the ratio of the 137Cs activity

of any isotope in different areas. When Table 5 is exam-

ined, it can easily be seen that the activity ratios for

different isotopes of the same element strongly resemble

the ratio of the same isotopes to 134Cs. These values

also show a similarity to Baldini's findings for pine 4 needles of Northern Italy

Experimental results show that the species studied have

a high absorption rate for 134Cs, 137Cs and 40K isotopes.

155


TABLE 5

Activity ratios for different isotopes measured in lichens and pines (nd: non-detected)

Lichen Pine Ratio . . . . .

Trabzon Izmir Trabzon Zonguldak Izmir area area area area area

137Cs/134Cs 3.2 3.3 3.7 3.7 3.6

103Ru/106Ru 2.2 2.2 nd nd nd

141Ce/144Ce 2.4 2.4 nd nd nd

On the other hand, it was observed that the pine species

covering most of the area collected a lot of Cs isotopes

especially in the year following the Chernobyl accident.

It has been found that although there are differences

between lichen species, their 137Cs uptake capacity is

approximately 10 times larger than that of pine species.

The radioactive pollution of pine trees by rain is mostly

caused by pine needles.

Measurements carried out in different periods show

that the cesium activity is found especially in parti-

cles with radii below a few micrometers I'7'17

Lichens have the characteristics of collecting dust,

aerosol particles, radioelements and most of the heavy

metals5, 6'13'15'20, due to the slow growth and the long

life span of these plants and the fact that the plant

surface area to biomass ratio is very small and that each

unit of the surface has a lot of stomata.

The capacity of the plants to collect and deposit ra-

dioactive isotopes depends on their morphological struc-

ture. The uptake of radioisotopes into the leaf mesophyl

and their transportation to the root of the plant by

156

AK(~AY: DEPOSITION OF RADIONUCLIDES IN LICHENS

other organs of the tree is a complex phenomenon, which

is related to some physiological factors and to chemical

interactions between plant tissue and the radioisotopes.

The author expresses his thanks to the Turkish Scien-

tific and Technical Board, which supported the main pro-

ject financially (DEBgA~, 39) and to Dr. T. Kesercio~lu

(Dokuz Eyl01 University), Dr. Volker John (Pfalzmuseum

for Naturkunde Bad DHrkheim, Germany), Dr. Ulvi Zeybek

(Ege University), Adnan Erdag (Ege University) who helped

to identify the plants.

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