Impact of wildfire on 137Cs and 90Sr wash-off in heavily contaminated forests in the Chernobyl exclusion zone

Igarashi, Yasunori; Onda, Yuichi; Wakiyama, Yoshifumi; Konoplev, A.; Zheleznyak, Mark; Lisovyi, Hlib; Laptev, Gennady; Damiyanovich, Volodyill; Samoilov, Dmitry; Nanba, Kenji; Kirieiev, Serhii

doi:10.1016/j.envpol.2019.113764

Cited by 22 publications

(15 citation statements)

References 43 publications

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“…The surface concentration of 137 Cs was not correlated with that of levoglucosan, which is often used as a marker of biomass burning. These results are distinct from those from Chernobyl, where wildfire plays a key role in the migration of radio-Cs associated with the event (Ager et al, 2019;Igarashi et al, 2020). The contributions of additional 137 Cs emissions from the nuclear reactor buildings of FDNPP to the surface concentrations in Japan were negligibly small compared to the resuspensions from the ground surface (Kajino et al, 2016).…”

Section: Introductionmentioning

confidence: 63%

Eight-year variations in atmospheric radiocesium in Fukushima City

Watanabe

Kajino

Ninomiya

et al. 2021

Preprint

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Abstract. After the Fukushima nuclear accident, atmospheric 134Cs and 137Cs measurements were taken in Fukushima city for eight years, from March 2011 to March 2019. The surface air concentrations and deposition of radio-Cs were high in winter and low in summer; these trends are the opposite of those observed in a contaminated forest area. The half-lives of 137Cs in the concentrations and deposition before 2015 (275 d and 1.11 y) were significantly shorter than those after 2015 (756 d and 4.69 y). The dissolved fractions of precipitation were larger than the particulate fractions before 2015, but the particulate fractions were larger after 2016. The half-lives of 137Cs in the concentrations and deposition were shorter before 2015, probably because the dissolved radio-Cs was discharged from the local terrestrial ecosystems more rapidly than the particulate radio-Cs. X-ray fluorescence analysis suggested that biotite may have played a key role in the environmental behavior of particulate forms of radio-Cs after 2014. However, the causal relationship between the seasonal variations in particle size distributions and the possible sources of particles is not yet fully understood. The current study also proposes a method of evaluating the consistency of a numerical model for radio-Cs resuspension and suggests that improvements to the model are necessary.

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Section: Introductionmentioning

confidence: 63%

Eight-year variations in atmospheric radiocesium in Fukushima City

Watanabe

Kajino

Ninomiya

et al. 2021

Preprint

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“…Wildfires drive radionuclide resuspension via the combustion of upper soil layers and vegetation, and subsequent dispersal via atmospheric processes, as described here and elsewhere. However, another pertinent issue that has only recently started to receive attention in relation to the CEZ (Igarashi et al 2020), is wildfire-driven increases in runoff and soil erosion. Hydrological processes are already considered to be one of the Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Runoff generated within the CEZ flows into the main Prip'yat river, which is a critical component of the Dnieper river reservoir system. The Dnieper system is one of the largest surface water systems in Europe (IAEA 2006), and through this river system, there is potential for radionuclides to be transported into the Kiev metropolitan area (Igarashi et al 2020). Therefore, understanding how surface runoff and soil erosion within the CEZ may impact downstream ecosystems is critical.…”

Section: Discussionmentioning

confidence: 99%

“…Past research within the CEZ has shown that the combustion of the top layer of soil is commonly associated with wildfire events, which results in the destruction of the top elements of soil (Dusha-Gudym 2005), rendering the soil more susceptible to erosion. In a series of plot-scale studies within the CEZ, Igarashi et al (2020) observed dissolved and particulate 137 Cs fluxes of 4.9 and 160.9 Bq m 2 , respectively, on a previously burned site for a 286 mm rainfall event, compared with dissolved and particulate fluxes of 6.22 and 8.63 Bq m 2 at an unburned site for a 182 mm rainfall event. Their results indicate that wildfires do not cause increases in the dissolved 137 Cs fluxes, but do result in a significant increase in the erosion-driven particulate flux.…”

Section: Discussionmentioning

confidence: 99%

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Investigating the drivers of the unprecedented Chernobyl Power Plant Wildfire in April 2020 and its effects on 137Cs dispersal

Newman-Thacker

Turnbull

2021

Nat Hazards

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In this study, we explore the conditions that led to the unprecedented wildfire that occurred in the Chernobyl Exclusion Zone in April 2020 and the effect of this fire on 137Cs dispersal, as wildfires are important drivers of 137Cs resuspension, with potentially harmful consequences for the receiving ecosystems. We characterised the historical wildfire record between 2000 and 2020 using the MCD64A1.006 MODIS Burned Area Monthly Global 500 m dataset and assessed the climatic conditions associated with these wildfire events using ERA5-Land reanalysis data. We also examined fire danger indices at the time of these wildfires. We then explored the widespread effects of the April 2020 wildfire on 137Cs resuspension and subsequent deposition using the NOAA-HYSPLIT model, concluding that the impacts of such resuspension on areas further afield were minimal. Results show that climatic conditions leading to severe wildfires are increasing, especially during March and April. High soil moisture, relative humidity and extreme temperature anomalies are associated with the largest wildfires on record, and fire risk indices at the time of the April 2020 fire were higher than for other large fires on record. We have estimated that 3854 GBq of 137Cs resuspended during the CPPF, with atmospheric transport dominant over Russia, Ukraine, Moldova and Kazakhstan. The observed increase in large wildfires will have implications for wildfire-driven soil erosion processes, which will further exacerbate the effects of atmospheric-driven 137Cs redistribution.

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“…A relatively large contribution from the near-surface layer could then recharge the discharge level, leading to high dissolved-phase 90 Sr concentrations in the snowmelt season. In addition, the effect of N l ( 90 Sr) on the 90 Sr concentration in the river could be limited, because this region is too flat for the wash-off liquid to reach the river 30 . Frequent sampling could reveal a link between heavy rainfall events and 90 Sr wash-off during the summer, therefore, requires further study.…”

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confidence: 99%

Simulating dissolved 90Sr concentrations within a small catchment in the Chernobyl Exclusion Zone using a parametric hydrochemical model

Igarashi

Onda

Smith

et al. 2020

Sci Rep

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Strontium-90 (90 Sr) is the major long-lived radionuclide derived from the chernobyl accident, and is still being detected in the heavily contaminated catchments of the chernobyl exclusion Zone. this study examines the long-term decrease in the dissolved-phase 90 Sr concentration and the concentrationdischarge (90 Sr-Q) relationship in stream water since the accident. We show that the slow decline in 90 Sr follows a double-exponential function, and that there is a clear relationship between 90 Sr and Q. This study is the first to reveal that the log(90 Sr)-log(Q) slope has been gradually decreasing since the accident. this trend persists after decay correction. thus, it is not caused by the physical decay of 90 Sr and environmental diffusion, but implies that the concentration formation processes in stream water have been changing over a long period. We propose a hydrochemical model to explain the timedependency of the 90 Sr-Q relationship. this paper presents a mathematical implementation of the new concept and describes the model assumptions. our model accurately represents both the long-term 90 Sr trend in stream water and the time-dependency of the 90 Sr-Q relationship. Although this paper considers a small catchment in chernobyl, the conceptual model is shown to be applicable to other accidental releases of radionuclides. It has been 34 years since the Chernobyl nuclear power plant (CNPP) accident in Ukraine (Fig. 1), when large amounts of radionuclides were released into the environment. At present, high levels of dissolved-phase strontium-90 (90 Sr) are still being detected in the small catchment streams inside the Chernobyl Exclusion Zone (CEZ) (Fig. 2b). The main long-term source of exchangeable and available 90 Sr in the CEZ soils is micron-sized "fuel particles" (FP) that are gradually dissolving. These are derived from the accidental release from CNPP Unit 4 on 26 April, 1986, and were formed by the mechanical destruction of nuclear fuel. The dissolution rate of FP in CEZ soils varies from several percent to several tens of percent of the activity inventory per year, depending on the degree of oxidation of the particle UO 2 matrix and the ambient geochemical conditions (e.g. soil solution pH and oxygen availability) 1-6. The 90 Sr from small streams in the CEZ is discharged into the main Pripyat river, which is a critical component of the Dnieper river-reservoir system, one of the largest surface water systems in Europe 7. Through this river system, 90 Sr is also transported to the Kiev metropolitan area in Ukraine. Therefore, predicting and evaluating the radionuclide flux within the water system, and using models to evaluate the potential radiological consequences to the downstream population, remain important tasks.

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Impact of wildfire on 137Cs and 90Sr wash-off in heavily contaminated forests in the Chernobyl exclusion zone

Cited by 22 publications

References 43 publications

Eight-year variations in atmospheric radiocesium in Fukushima City

Eight-year variations in atmospheric radiocesium in Fukushima City

Investigating the drivers of the unprecedented Chernobyl Power Plant Wildfire in April 2020 and its effects on 137Cs dispersal

Simulating dissolved 90Sr concentrations within a small catchment in the Chernobyl Exclusion Zone using a parametric hydrochemical model

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