Significance: A massive atmospheric release of radioactive ¹⁰⁶ Ru occurred in Eurasia in 2017, which must have been caused by a sizeable, yet undeclared nuclear accident. This work presents the most compelling monitoring dataset of this release, comprising 1,100 atmospheric and 200 deposition data points from the Eurasian region. The data suggest a release from a nuclear reprocessing facility located in the Southern Urals, possibly from the Mayak nuclear complex. A release from a crashed satellite as well as a release on Romanian territory (despite high activity concentrations) can be excluded. The model age of the radioruthenium supports the hypothesis that fuel was reprocessed ≤2 years after discharge, possibly for the production of a high-specific activity ¹⁴⁴ Ce source for a neutrino experiment in Italy.

Two methods – in situ sediment trap experiments and an isotopic method based on measurements of 210Pb activities in the sediment cores taken near the traps – were applied for determining sediment deposition and sediment accumulation rates in the eastern part of Puck Bay. The sediment deposition rate (1.67mmyear−1) based on the in situ measurement was comparable with the sediment accumulation rate calculated using the Constant Flux:Constant Sedimentation Rate model for the isotopic method. The age of the sediment layers was determined with the Constant Rate of Supply model; the deepest layers had accumulated around 1900

Numerous species of wild-grown mushrooms are among the most vulnerable organisms for contamination with radiocesium released from a radioactive fallout. A comparison was made on radiocesium as well as the natural gamma ray-emitting radionuclide (⁴⁰K) activity concentrations in the fruiting bodies of several valued edible Boletus mushrooms collected from the region of Europe and Yunnan Province in China. Data available for the first time for Boletus edulis collected in Yunnan, China, showed a very weak contamination with ¹³⁷Cs. Radiocesium concentration activity of B. edulis samples that were collected between 2011 and 2014 in Yunnan ranged from 5.2 ± 1.7 to 10 ± 1 Bq kg⁻¹ dry matter for caps and from 4.7 ± 1.3 to 5.5 ± 1.0 Bq kg⁻¹ dry matter for stipes. The mushrooms Boletus badius, B. edulis, Boletus impolitus, Boletus luridus, Boletus pinophilus, and Boletus reticulatus collected from the European locations between 1995 and 2010 showed two to four orders of magnitude greater radioactivity from ¹³⁷Cs compared to B. edulis from Yunnan. The nuclide ⁴⁰K in B. badius was equally distributed between the caps and stipes, while for B. edulis, B. impolitus, B. luridus, B. pinophilus, and B. reticulatus, the caps were richer, and for each mushroom, activity concentration seemed to be more or less species-specific.

SummaryThe article presents data on heavy metal – Hg, Pb, Cd and Zn – distribution in the layers of marine sediments from the off-shore areas of the southern Baltic Sea: Gdańsk Deep, SE Gotland Basin and Bornholm Deep. Depth profiles of metal concentrations were converted to time-based profiles using the 210Pb dating method and verified by 137Cs distribution in the vertical profile. The linear sedimentation rates in the Gdańsk Deep and SE Gotland Basin are similar, 0.18cmyr−1 and 0.14cmyr−1, respectively, while the region of the Bornholm Deep is characterized by a greater sedimentation rate: 0.31cmyr−1. Regarding anthropogenic pressure, Gdańsk Deep receives the largest share among the analyzed regions. The maximal metal concentrations detected in this area were Zn – 230mgkg−1, Pb – 77mgkg−1, Cd – 2.04mgkg−1 and Hg – 0.27mgkg−1. The least impact of anthropogenic pressure was noticeable in SE Gotland Basin. The combination of sediment dating with the analysis of vertical distribution of heavy metals in sediments benefited in the determination of target metal concentrations used in environmental status assessments. Reference values of heavy metal concentrations in marine sediments were determined as: Zn – 110mgkg−1, Pb – 30mgkg−1, Cd – 0.3mgkg−1 and Hg – 0.05mgkg−1 from the period of minor anthropogenic pressure. Basing on the determined indices: enrichment factor (EF), geoaccumulation indicator (Igeo) and contamination factor (CF) the status of marine environment was assessed regarding the pollution with heavy metals

The radioisotopes of caesium (137Cs) and strontium (90Sr) make the greatest contribution to the radioactivity level due to artificial radionuclides in the Baltic Sea, where the level of 137Cs contamination is higher than in any other part of the world ocean. The main sources of man-made radionuclides are the Chernobyl accident in 1986 and the nuclear weapons tests carried out in the 1950s and 1960s. This study discusses the distribution patterns and trends in activity concentrations of 137Cs and 90Sr recorded in various compartments of the marine environment of the southern Baltic Sea. It is based on an investigation of radioactive substances as part of the Polish National Environmental Monitoring Programme. In 2010 the average concentration of 137Cs in the southern Baltic was 35Bqm−3, while the level of 90Sr in these waters has remained at much the same level in recent years (ca 8Bqm−3). The distribution of isotopes in the bottom sediments reflect historical events that can be identified in sediment profiles. The activity concentrations of the caesium isotope are the highest in sediments from the Gulf of Gdańsk, whereas the least polluted sediments are found in the Bornholm Basin, in the western part of the southern Baltic. The highest concentrations of 137Cs in benthic plants were measured in the red alga Polysiphonia fucoides: 22.3Bqkg−1 d.w. in June and 40.4Bqkg−1 in September. These levels were much higher than those found in the bivalve Mytilus trossulus (7.3Bqkg−1 d.w.). 137Cs concentrations in fish have decreased in time, reflecting the trends recorded in seawater. In 2010 the respective 137Cs activities in Clupea harengus, Platichthys flesus and Gadus morhua were 4.7, 4.9 and 6.6Bqkg−1 w.w