Forest-stream ecosystems are widespread and biodiverse terrestrial landscapes with physical and social connections to downstream human activities. After radiocesium is introduced into these ecosystems, various material flows cause its accumulation or dispersal. We review studies conducted in the decade after the Fukushima nuclear accident to clarify the mechanisms of radiocesium transfer within ecosystems and to downstream areas through biological, hydrological, and geomorphological processes. After its introduction, radiocesium is heavily deposited in the organic soil layer, leading to persistent circulation due to biological activities in soils. Some radiocesium in soils, litter, and organisms is transported to stream ecosystems, forming contamination spots in depositional habitats. While reservoir dams function as effective traps, radiocesium leaching from sediments is a continual phenomenon causing re-contamination downstream. Integration of data regarding radiocesium dynamics and contamination sites, as proposed here, is essential for contamination management in societies depending on nuclear power to address the climate crisis.

Vast areas of Europe were contaminated by the fallout of ¹³⁷Cs and other radionuclides, as a result of the Chernobyl accident in 1986. The post-fallout redistribution of Chernobyl-derived ¹³⁷Cs was associated with erosion and sediment transport processes within the fluvial system. Bottom sediments from lakes and reservoirs can provide a valuable source of information regarding the post-fallout redistribution and fate of ¹³⁷Cs released by the Chernobyl accident. A detailed investigation of sediment-associated ¹³⁷Cs in the bottom sediments of a reservoir in a Chernobyl-affected area in Central Russia has been undertaken. A new approach, based on the vertical distribution of ¹³⁷Cs activity concentrations in the reservoir bottom sediment makes it possible to separate the initially deposited bottom sediment, where the ¹³⁷Cs activity reflects the direct fallout of Chernobyl-derived ¹³⁷Cs to the reservoir surface and its subsequent incorporation into sediment deposited immediately after the accident, from the sediment mobilized from the catchment deposited subsequently. The deposits representing direct fallout from the atmosphere was termed the “Chernobyl peak”. Its shape can be described by a diffusion equation and it can be distinguished from the remaining catchment-derived ¹³⁷Cs associated with sediment accumulated with sediments during the post-Chernobyl period. The ¹³⁷Cs depth distribution above the "Chernobyl peak" was used to provide a record of changes in the concentration of sediment-associated ¹³⁷Cs transported from the upstream catchment during the post-Chernobyl period. It was found that the ¹³⁷Cs activity concentration in the sediment deposited in the reservoir progressively decreased during the 30-year period after the accident due to a reduction in the contribution of sediment eroded from the arable land in the catchment. This reflects a reduction in both the area of cultivated land area and the reduced incidence of surface runoff from the slopes during spring snowmelt due to climate warming.

A long-term case of residual pollution is studied after 20 years since the largest mining accident in Spain (the Aznalcóllar spill) happened. This pollution is manifested through a surface zoning consisting of bare soils (B0), sparsely vegetated soils (B1), and densely vegetated and recovered soils (B2). A biopiles treatment with a mixture of contaminated soils (B0 and B1) with recovered soils (B2) at 50% (w/w), and vermicompost addition (50 tons ha-1) was evaluated. To assess the effectiveness of treatments, total, water-soluble, and bioavailable fractions of the most polluting elements in the zone (Cu, Zn, As, Pb, Cd, and Sb) was analyzed. To evaluate the potential risk of contamination for the ecosystem, a bioassay with earthworm Eisenia andrei was carried out. Twenty years after the accident, there are still soils where total As and Pb exceed the regulatory levels and water-soluble Zn and As exceed the toxicity guidelines. According to toxicity bioassay, weight variation and juvenile production of earthworms showed an improvement after biopiles treatment, with values that trend to be similar to those of recovered soils. The only bioaccumulated element in earthworms was Cd (BAF>1), both in polluted as in treated soils, which indicates the possible existence of exclusion mechanisms of the other pollutants by earthworms. The comparison between biopiles and polluted soils showed no significant differences for the bioaccumulation factor of trace elements, with the exception of Zn and Cu, which slightly increased after treatment. According to our results, biopiles treatment combined with vermicompost addition is a good technique for the recovery of residual contaminated areas, by the improvement of soil properties and the reduction of the potential toxicity; anyway, monitoring of soils and organisms is needed to prevent the increase of bioavailability of some potentially pollutant elements over time.

In this paper, we briefly described the ecological consequences of six space rocket accidents launched from the Baikonur Cosmodrome between 1999 and 2018 and focused on an assessment of efficiency of soil remediation following the accidental crash of launch vehicle Proton-M on July 2, 2013, which resulted in the severest environmental impact in the modern Russian space industry. On the day after the accident, the content of carcinogenic unsymmetrical dimethylhydrazine and nitrosodimethylamine, as well as nitrate in soils of the crash site exceeded their maximal permissible concentrations by 8900, 6100 and 85 times, respectively. Mitigation measures included soil detoxication by a solution of 10% H₂O₂ and 1% iron complexonate, soil excavation and ploughing. Two years later (in April 2015), both unsymmetrical dimethylhydrazine and nitrosodimethylamine concentrations were below 0.05 mg/kg and nitrate concentration did not exceed 3.9 g/kg. As compared to background sites, soils of the crash site had significantly (P-value<0.05) lower values of pH and the content of total organic carbon, basicity from soda and carbonates and higher total nitrogen and soluble salt contents. Soil microbial communities were the most vulnerable component of the disturbed arid ecosystems, as their suppressed condition was indicated by a low biochemical oxygen demand and a very low cellulase activity.

The growing use of coastal areas for different economic purposes is responsible for increasing pollution by hydrocarbons in marine environments. As a consequence of these activities, accidents during fuel extraction, transport, and storage can occur, causing intense environmental degradation. Numerical modeling of the trajectory of oil stains becomes an important tool with low operational costs, providing powerful support to the government agencies in charge of risk management associated with possible oil accidents, by helping to generate scenarios and strategies for containment and cleaning of affected environments. In this sense, the aim of this study is to estimate environmental vulnerability to oil at beaches located in the Itapuã State Park (PEI), a Protection Conservation Unit. This work focused on describing a methodology to estimate the vulnerability of coastal areas, with emphasis on the fact that the study was carried out in a closed environment. For that, an approach was used based on the integration of: (1) an intrinsic variable to the environment; (2) a dynamic variable determined through diesel oil surface dispersion scenarios. Four hypothetical accident scenarios with 20 m³ of diesel oil were simulated in 2018, during five days of simulations with instant dumping in the navigation channel of the local waterway near the PEI. The results suggest the forcing of the field of intensity and direction of the local winds as preponderant for the dynamics of movement and structure of the spots, with the zonal and meridional components of the fields of superficial currents acting in this process as a secondary factor. The study showed that all beaches in the park are susceptible to contact with oil throughout the simulated year, with Pombas Beach, Pedreira Beach, and Onça Beach being affected in all simulated scenarios, which classifies them as very high vulnerability and defines them as priority protection areas.

The accidental leakage of industrial wastewater containing heavy metals from enterprises poses great risks to resident health, social instability, and ecological safety. During 2005–2018, heavy metal mixed pollution accidents comprised approximately 33% of the major environmental ones in China. A Bayesian Networks-based probabilistic approach is developed to quantitatively predict ecological and human health risks for heavy metal mixed pollution accidents at the watershed scale. To estimate the probability distributions of joint ecological exposure once a heavy metal mixed pollution accident occurs, a Copula-based joint exposure calculation method, comprised of a hydro-dynamic model, emergent heavy metal pollution transport model, and the Copula functions, is embedded. This approach was applied to the risk assessment of acute Cr⁶⁺-Hg²⁺ mixed pollution accidents at 76 electroplating enterprises in 24 risk sub-watersheds of the Dongjiang River downstream watershed. The results indicated that nine sub-watersheds created high ecological risks, while only five created high human health risks. In addition, the ecological and human health risk levels were highest in the tributary (the Xizhijiang River), while the ecological risk was more critical in the river network, and the human health risk was more serious in the mainstream of the Dongjiang River. The quantitative risk assessment provides a substantial support to incident prevention and control, risk management, as well as regulatory decision making for electroplating enterprises.

In this paper, a marine environmental sensitivity index system was constructed based on three factors: the marine biological species sensitivity, the marine ecological value sensitivity and the social and economic sensitivity. Combined with numerical simulations of ¹³⁷Cs in the Beibu Gulf under the condition of a level-7 nuclear accident, a comprehensive risk assessment of marine radioactivity under the simulated accident in the Beibu Gulf was carried out. The results show that the areas at high risk and medium-to-high risk to marine radioactivity are mainly concentrated within 30 km of the Fangchenggang Nuclear Power Plant. The medium-risk areas are mainly distributed in sea areas within 30–50 km of the nuclear power plant, and the other sea areas are low-risk areas. The distribution of the risk sources and the characteristics of the regional tidal currents are the main factors affecting the magnitude and distribution of the comprehensive risk of regional marine radioactivity.

Anthropogenic radionuclides are among those human impacts, which can be seen widely in the marine and terrestrial ecosystems. Fallout from the 1986 Chernobyl nuclear power plant accident has rendered the Baltic Sea as the most polluted marine body in the world with respect to ¹³⁷Cs. This research investigated sediment cores from 56 sites around the Gulf of Bothnia, Baltic Sea. Radioactivity from ¹³⁷Cs in sediments has generally declined due to natural/radioactive decay of ¹³⁷Cs over the last decades. However, ¹³⁷Cs contents in subsurface sediments remain at elevated levels compared to pre-Chernobyl levels. The highest ¹³⁷Cs activity contents in subsurface sediments (>4000 Bg kg⁻¹) occur in coastal areas including estuaries. These areas often experience severe anthropogenic pressure. The southern Bothnian Sea, Kvarken archipelago, and southern Bothnian Bay all show elevated ¹³⁷Cs values in subsurface sediments. Sedimentary ¹³⁷Cs can also help constrain recent rates of sedimentation. Post-Chernobyl sedimentation rates in the Gulf of Bothnia varied from 0.1 to 4.8 cm/year with an average sedimentation rate of 0.54 cm/year.

Marine protection is one of the main Sustainable Development Goals designed by the United Nations. Specifically, Goal 6.3 – Clean Water and Sanitation – defends that the spill of dangerous and pollutant substances must be eliminated. This principle is inherent in Maritime law since maritime salvage concerns not only vessels and cargo but also the marine environment. Since the Torrey Canyon accident in 1967, spilt crude has become the centre of attention of the International Maritime Organization (IMO). Nowadays, IMO has extended its scope of application to new threats, such as pollutant gas emissions. Its last approved strategy is IMO 2020, focused on the reduction of sulphur emissions by vessels. It came into force on the 1st of January 2020, becoming one effective measure to minimize the sulphur emissions to the atmosphere and to improve the environmental conditions, not only at the sea but also in the coastal and inland areas.

Through the application of the Water Pollution Emergency Response System (WPERS) in the Changjiang Estuary, it was found that tidal flats significantly affect the trajectory of an oil film, and the deposition of the oil film on tidal flats is remarkable. In this study, the Estuarine Oil Spill Model (EOSM) was developed to simulate the process of the oil film landing on tidal flats. The Lagrangian particle algorithm and oil fate experience algorithms were adopted. An algorithm for generating dynamic shorelines was also involved. Compared to the oil spill algorithm without wet-dry functionality, the spatial distribution of the oil film deposition simulated in the EOSM better matched the reanalysis data of the satellite remote sensing image. This indicated that the dynamic wet-dry switch phenomenon of tidal flats could be involved in the simulation of offshore oil spills to improve the accuracy of accident prediction and ecological loss assessment.On December 30th, 2012, a vessel carrying 400 tons of heavy oil sank in the Changjiang Estuary, China. The heavy oil leaked at around 4 am the next day. In this study, a new oil spill model was developed to simulate the process of an oil film landing on land and tidal flats. An algorithm for generating the dynamic shorelines in an oil spill simulation was adapted for the wet-dry switch of tidal flats. The landing distribution of the oil film in this new model was well matched to the satellite image for this accident. This indicated that the dynamic wet-dry switch phenomenon of tidal flats could be involved in the simulation of oil spills offshore, to improve the accuracy of accident prediction and ecological loss assessment. The research results could provide some new ideas for the development of offshore oil spill simulation technology.