Cesium 137 contamination of Elaphomyces – Radiocesium readings of “deer truffle”

Elaphomyces granulatus is prepared in the laboratory for radioactive measurement
Fig. 1: The fruiting body of Elaphomyces granulatus is prepared for radioactive measurement

The Chernobyl nuclear disaster occurred on April 26, 1986. In the following days, radioactivity was also spread over Germany by the Chernobyl fallout. Today, cesium-137 is still found in the environment due to its half-life of about 30 years. Due to the special ecology of forest soils compared to arable soils, elevated levels of Cs-137 contamination can still be found in some forest biomedia, especially in deer truffles and wild boar.

We at Umweltanalysen have been investigating the radiocesium contamination of deer truffles in selected areas in Germany for 20 years, both within the framework of contract research and on our own behalf. The object of investigation is by far the most common species Elaphomyces granulatus.

Figure 1 shows a warty deer truffle still enclosed in the root sheath. The protruding light threads are mycelium of the fungus.

Caesium-137 readings from deer truffles from 2018, 2019 and 2020

Current 2020 measurements
On 23.02.2020, fruiting bodies of deer truffles were found in Hambühren, Lower Saxony. A composite sample was formed from each collection and this was measured by gamma spectrometry at Laboratory for Radioisotopes of the Georg-August-University Göttingen. (LARI). The caesium-137 activity of the 4 samples was, based on fresh weight:

Cesium 137
847 Bq/kg
1,017 Bq/kg
1,555 Bq/kg
1,138 Bq/kg

We last analyzed deer truffles from an area particularly affected by the Chernobyl fallout in the Bavarian Forest National Park (see also map Cs-137 soil contamination) for cesium-137 activity in 2018 and 2019. The gamma spectrometric measurements were performed at the LARI. The measurement error was <10%. The results are given in Table 1 and Table 2.

Tab. 1: Cesium-137 activity of deer truffle spores and peridium. Place of discovery Zwieseler Waldhaus (Bavarian Forest National Park). Collection date 08.08.2019. FW=Fresh Weight, DW= Dry Weight.

Cs-137 [Bq/kg FW] Cs-137 [Bq/kg DW]
11777 29370
8600 22280
5593 12540
5825 14860

Tab. 2: Cesium-137 activity of Elaphomyces granulatus from the Bavarian Forest National Park. Date of discovery 18.09.2018

Cs-137 [Bq/kg FW] Cs-137 [Bq/kg DW]
45497 101200
38754 83930
23714 52020
19909 43070
15918 38070
14997 33430
14874 30120
14233 28290
12505 26050
7934 17750

Cs-137 activity ranged from 7,934 Bq/kg to 45,497 Bq/kg based on fresh weight.
Time series show as trend a decrease of radiocesium contamination (example in Figure 2). Apparently, the half-life of 30.17 years makes itself felt. If the Cs-137 contamination of deer truffles in the first 2 decades after the reactor accident was probably determined especially by chemical-physical relocation and biotic transport processes, radioactive decay could dominate now.

Cesium 137 contamination of Elaphomyces granulatus from 1998 - 2020

Fig. 2: Development of the caesium-137 activity of deer truffles on permanent sample plot B1, Bodenmais (Bavaria) with linear regression line.

Measurement data from research projects from 2000 – 2010

In several research projects the radiocesium contamination of deer truffles was determined. In tables 3 – 6 measured data from different research areas are given.

Tab. 3: Cs-137 measured values of deer truffles and soil, study area Arnsberg (North Rhine-Westphalia), sampling 2009 – 2010. Source: Fielitz and Richter 2013. TF = Transfer factor

Elapomyces species Fruiting body Soil      TF
C-137 C-137
[Bq/kg FW] [Bq/kg FW]
E. granulatus 108
E. g. 127
E. g. 225
E. g. 260
E. g. 286
E. g. 314
E. g. 325
E. g. 339
E. g. 364
E. g. 394
E. g. 490
E. g. 526
E. g. 680
E. g. 694 91.4 7.6
E. g. 719
E. g. 826 84.8 9.7
E. g. 865
E. g. 983
E. g. 1314 88.5 14.8
E. g. 1582
E. muricatus 98,7
E. muricatus 219
E. muricatus 877 111 7.9
E. muricatus 991 120 8.3
E. muricatus 1307 110 11.9

Tab. 4: Cs-137 measured values of deer truffles and soil, study area Göhrde (Lower Saxony), sampling 2009 – 2010. Source: Fielitz and Richter 2013.

Elapomyces species Fruiting body Soil      TF
C-137 C-137
[Bq/kg FW] [Bq/kg FW]
E. granulatus 80,9
E. g. 213
E. g. 395 130 3
E. g. 398 63.7 6.3
E. g. 478
E. g. 610
E. g. 638
E. g. 669
E. g. 841
E. g. 1160 94.5 12.3
E. g. 1194 75.4 15.8
E. g. 1446
E. g. 1527
E. g. 1626
E. g. 1648 57.3 28.8
E. g. 1780
E. g. 1806 18.2 99.2
E. g. 1865
E. g. 1919
E. g. 2093
E. g. 2575
E. g. 2584
E. g. 2647 76.2 34.7
E. g. 2841
E. g. 2863
E. muricatus 228
E. m. 712
E. m. 887 75.4 11.8
E. m. 2384 94,5 25.2
E. m. 3099 76.2 40.7

Tab. 5: Cs-137 measured values of deer truffles and soil, study area Harz (Lower Saxony), sampling 2009 – 2010. Source: Fielitz and Richter 2013.

Elapomyces species Fruiting body Soil      TF
C-137 C-137
[Bq/kg FW] [Bq/kg FW]
E. granulatus 31
E. g. 353
E. g. 585
E. g. 593
E. g. 614
E. g. 632
E. g. 702
E. g. 780 167 4,7
E. g. 972
E. g. 1038
E. g. 1283 338 3,8
E. g. 1536
E. g. 1832
E. g. 1847 230 8
E. g. 1863 40,5 46
E. g. 1957
E. g. 1983
E. g. 2830
E. g. 3995
E. g. 4838
E. g. 5520
E. g. 6655
E. muricatus 217
E. m. 1323 143 9,3
E. m. 1585 131 12,1
E. m. 2041
E. m. 2424 227 10.7
E. m. 2353
E. m. 2553 97.3 26.2

Tab. 6: Cs-137 measured values of deer truffles and soil, study area Ohrdruf (Thuringia), sampling 2009 – 2010. Source: Fielitz and Richter 2013.

Elapomyces species Fruiting body Soil      TF
C-137 C-137
[Bq/kg FW] [Bq/kg FW]
E. granulatus 96
E. granulatus 183
E. granulatus 381 116 3.3
E. granulatus 873 188 4.6
E. granulatus 370
E. granulatus 570
E. muricatus 588 222 2.7
E. granulatus 595
E. granulatus 644
E. granulatus 661
E. granulatus 677
E. granulatus 734
E. granulatus 758
E. granulatus 765
E. granulatus 847
E. granulatus 888
E. granulatus 903
E. granulatus 946 118 8
E. granulatus 1202
E. granulatus 1597
E. muricatus 301
E. muricatus 558
E. muricatus 678 156 4.3
E. muricatus 745 244 3.2
E. granulatus 1513 401 3.8

Distribution of Cs-137 activity in a deer truffle fruiting body

The distribution of Cs-137 activity in the fruiting body of a deer truffle was determined using a phosphor imager (Raytest company). In this process, the activity distribution is converted into a color-intensive image. For this purpose, a 2 mm thick slice was cut from the center of a deer truffle and exposed to a phosphor imager for 24 hours (Figure 3).

Cesium 137 activity in a deer truffle fruiting body
Fig. 3: “photostimulated luminescence” image of the Cs-137 distribution of a 2 mm thick slice of a deer truffle (left image) and the pure spore mass (right image) by a phosphor imager (see text for explanations).

The measuring principle is based on the excitation of phosphorus atoms (P-32) by radioactive radiation, in this case predominantly Cs-137 (“photostimulated luminescence” PSL).
The left picture shows the “photostimulated luminescence” image of the whole slice of deer truffle. The area between the lines marked 1 and 2 corresponds to the bark. The right image shows a slice of the same deer truffle, without the bark. It can be clearly seen that the highest activity is in the bark (orange color occupation), the spore mass inside contains much less Cs-137 (right figure). The color pattern outside the bark is due to scattered radiation. The Cs-137 activity of this deer truffle (weight 11 g) was additionally determined in the borehole detector. The bark contained 17,560 Bq Cs-137/kg (fresh weight), the spore mass 2,050 Bq/kg.

Literature

Boudier E. 1876. Du parasitisme probable de quelques espèces du genre Elaphomyces et de la recherche de ces Tubéracés. Bulletin de la Société botanique de France 23: 115–119. Link
Fielitz U., 2005: Untersuchungen zum Verhalten von Radiocäsium in Wildschweinen und anderen Biomedien des Waldes.
Abschlussbericht zum Forschungsvorhaben StSch4324 im Auftrag des Bundesministeriums für Umwelt, Naturschutz und
Reaktorsicherheit

Fielitz U., Richter K., 2013: Bundesweiter Überblick über die Radiocäsiumkontamination von Wildschweinen. Ressortforschungsberichte zur kerntechnischen Sicherheit und zum Strahlenschutz. Vorhaben 3607S0456

Hohmann U., Huckschlag D. 2004: Forschungsbericht – Grenzwertüberschreitende Radiocäsiumkontamination von Wildschweinfleisch in Rheinland-Pfalz – Eine Mageninhaltsanalyse erlegter Wildschweine aus dem westlichen Pfälzerwald.
Ławrynowicz, M., Faliński, J.B., Bober, J., 2006: Interactions among hypogeous fungi and wild boars in the subcontinental pine forest. Biodiv. Res. Conserv. 1-2: 102-106. PDF

Steiner M., Fielitz U., 2009: Deer truffles – the dominant source of radiocaesium contamination of wild boar. Radioprotection,vol.44,n◦5 (2009) 585–588

The measuring principle is based on the excitation of phosphorus atoms (P-32) by radioactive radiation, in this case predominantly Cs-137 (“photostimulated luminescence” PSL).
The left picture shows the “photostimulated luminescence” image of the whole slice of deer truffle. The area between the lines marked 1 and 2 corresponds to the bark. The right image shows a slice of the same deer truffle, without the bark. It can be clearly seen that the highest activity is in the bark (orange color occupation), the spore mass inside contains much less Cs-137 (right figure). The color pattern outside the bark is due to scattered radiation. The Cs-137 activity of this deer truffle (weight 11 g) was additionally determined in the borehole detector. The bark contained 17,560 Bq Cs-137/kg (fresh weight), the spore mass 2,050 Bq/kg.

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