Radiocaesium in Tricholoma spp. from the Northern Hemisphere in 1971-2016.

A considerable amount of data has been published on the accumulation of radiocaesium (134Cs and particularly, 137Cs) in wild fungi since the first anthropogenically influenced releases into the environment due to nuclear weapon testing, usage and subsequently from major accidents at nuclear power plants in Chernobyl (1986) and Fukushima (2011). Wild fungi are particularly susceptible to accumulation of radiocaesium and contamination persists for decades after pollution events. Macromycetes (fruiting bodies, popularly called mushrooms) of the edible fungal species are an important part of the human and forest animal food-webs in many global locations. This review discusses published occurrences of 134Cs and 137Cs in twenty four species of Tricholoma mushrooms sourced from the Northern Hemisphere over the last five decades, but also includes some recent data from Italy and Poland. Tricholoma are an ectomycorrhizal species and the interval for contamination to permeate to lower soils layers which host their mycelial networks, results in a delayed manifestation of radioactivity. Available data from Poland, over similar periods, may suggest species selective differences in accumulation, with some fruiting bodies, e.g. T. portentosum, showing lower activity levels relative to others, e.g. T. equestre. Species like T. album, T. sulphurescens and T. terreum also show higher accumulation of radiocaesium, but reported observations are few. The uneven spatial distribution of the data combined with a limited number of observations make it difficult to decipher any temporal contamination patterns from the observations in Polish regions. When data from other European sites is included, a similar variability of 137Cs activity is apparent but the more recent Ukrainian data appears to show relatively lower activities. 40K activity in mushrooms which is associated with essential potassium, remains relatively constant. Further monitoring of 137Cs activity in wild mushrooms would help to consolidate these observations.

Radioactive caesium (134Cs and 137Cs) in mushrooms of the genus Boletus from the Reggio Emilia in Italy and Pomerania in Poland.

Activity concentrations of 134Cs and 137Cs were determined in mushrooms of the Boletus species B. aereus, B. reticulatus, B. appendiculatus, B. calopus, B. edulis, B. erythropus, B. fechtneri, B. pinophilus, B. pseudoregius, B. rhodopurpureus, B. rhodoxanthus collected in the Reggio Emilia, Italy, in 1993 and 1994 and in B. edulis collected in Pomerania in northern Poland in the period from 1995-2015. Boletus edulis from the Reggio Emilia showed presence of 137Cs at 330 ± 220 Bq kg-1 dry biomass in 1993 and at 370 ± 180 Bq kg-1 dry biomass in 1994. In B. edulis sampled in the Reggio Emilia in 1993 and 1994, the pre-Chernobyl 137Cs from global fallout amounted to 39-46 % of the total activity concentrations of isotope 137Cs. B. edulis from Pomerania contained 137Cs in caps at 270 ± 15 Bq kg-1 dry biomass in 1995, and in whole fruiting bodies it was found to be 470 ± 9 Bq kg-1 dry biomass in 2015. The activity concentrations of 137Cs determined in fruiting bodies of B. edulis from Pomerania fluctuated but persisted over the period from 1995 to 2015, while the maximum activity concentrations were well below the tolerance limit of 600 Bq kg-1 fresh product.

Radiocaesium in Cortinarius spp. mushrooms in the regions of the Reggio Emilia in Italy and Pomerania in Poland.

Activity concentrations of 134Cs and 137Cs have been determined in 23 species of mushrooms of the genus Cortinarius (59 individual samples) collected from the Reggio Emilia in Italy 1992-1999 and in 4 species (16 composite samples and 413 individuals) from the Pomerania region in Poland from 1996 to 2015. Across all the Cortinarius species from the Reggio Emilia, the activity concentrations were relatively high in Cortinarius alboviolaceus, Cortinarius duracinus, Cortinarius orellanus, Cortinarius rapaceus, and Cortinarius subannulatus, in which 137Cs was at 10,000 ~ 100,000 Bq kg-1 dry biomass (db) in 1994. Smaller activity concentrations were found in Cortinarius bivelus, Cortinarius bulliardii, Cortinarius cotoneus, Cortinarius largus, Cortinarius lividoviolaceus, Cortinarius purpureus, Cortinarius rufo-olivaceus, Cortinarius torvus, and Cortinarius venetus with levels at 1000 ~ 6000 Bq kg-1 db from 1992 to 1994, and further in Cortinarius anserinus, Cortinarius auroturbinatus, C. largus, Cortinarius praestans, Cortinarius purpurascens, Cortinarius scaurus, Cortinarius sebaceous, Cortinarius talus, and Cortinarius variecolor with activity concentrations at 100 ~ 600 Bq kg-1 db in 1994. All the data were calculated for dehydrated fungal material corrected back to the exact date samples of collection. The greatest activity concentrations of 137Cs both in Italy (1992-1999) and Poland (1996-2010) were found in the popular Cortinarius caperatus, confirming its very high capacity of radiocaesium accumulation. Besides 137Cs, the isotope 134Cs was detected in some species from the Reggio Emilia. An average calculated ratio of activities of 134Cs to 137Cs referenced to 1986 was equal to 0.38 in mushrooms from the Reggio Emilia, and this value slightly differ from that specific for Chernobyl fallout, which was 0.54. It was calculated that 137Cs originating from Chernobyl accident constituted about 68 % of the total activity concentration of the isotope in Reggio Emilia in 1986, while as much as 32 % of 137Cs in mushrooms were from the global fallout from nuclear bomb testing.