Biofilm-mediated interactions between plastics and radiocesium in coastal environments.

A ubiquitous distribution of plastic debris has been reported in aquatic and terrestrial environments; however, the interactions between plastics and radionuclides and the radioactivity of environmental plastics remain largely unknown. Here, we characterize biofilms developing on the surface of plastic debris to explore the role of plastic-associated biofilms as an interaction medium between plastics and radiocesium (Cs) in the environment. Biofilm samples were extracted from plastics (1-50 mm in size) collected from two contrasting coastal areas in Japan.

Dynamics and functions of microbial communities in the plastisphere in temperate coastal environments.

Microbial attachment and biofilm formation on microplastics (MPs <5 mm in size) in the environment have received growing attention. However, there is limited knowledge of microbial function and their effect on the properties and behavior of MPs in the environment. In this study, microbial communities in the plastisphere were explored to understand microbial ecology as well as their impact on aquatic ecosystems.

Uncovering the characteristics of plastic-associated biofilm from the inland river system of Mongolia.

The occurrence and characteristics of plastic debris in aquatic and terrestrial environments have been extensively studied. However, limited information exists on the properties and dynamic behavior of plastic-associated biofilms in the environment. In this study, we collected plastic samples from an inland river system in Mongolia and extracted biofilms to uncover their characteristics using spectroscopic, isotopic, and thermogravimetric techniques.

Sequential loss-on-ignition as a simple method for evaluating the stability of soil organic matter under actual environmental conditions.

Soil organic matter (SOM) is one of the largest carbon (C) reservoirs on Earth, and therefore its stability attracts a great deal of interest from the perspective of the global C cycle. This study examined the applicability of loss-on-ignition with a stepwise increase in temperature (SIT-LOI) of soil to evaluate the stability of SOM using soil samples having different organic matter (OM) and mineral contents and different mean residence times (MRTs) for SOM. The responses of SOM to the SIT-LOI varied depending on the samples but were all successfully approximated by a liner regression model as a function of the temperature of LOI.

Effect of soil organic matter on the fate of Cs vertical distribution in forest soils.

Understanding the fate of the vertical distribution of radiocesium (Cs) in Japanese forest soils is key to assessing the radioecological consequences of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. The Cs behavior in mineral soil is known to be primarily governed by interaction with clay minerals; however, some observations suggest the role of soil organic matter (SOM) in enhancing the mobility of Cs. Here we hypothesized that soil organic carbon (SOC) concentration profile determines the ultimate vertical pattern of Cs distribution in Japanese forest soils.

Plastic-associated metal(loid)s in the urban river environments of Mongolia.

The widespread distribution of plastic debris in riverine environment is one of the major concerns of environmental pollution because of its potential impact on the aquatic ecosystem. In this study, we investigated the accumulation of metal(loid)s on polystyrene foam (PSF) plastics collected from the floodplain of the Tuul River of Mongolia. The metal(loid)s sorbed on plastics were extracted from the collected PSF via sonication after peroxide oxidation.

Tracking the behavior and characteristics of microplastics using a multi-analytical approach: a case study in two contrasting coastal areas of Japan.

The global survey for the presence of microplastics (MPs) in aquatic environments has attracted widespread scientific attention over the past decade. However, evaluating the composition and characteristics of these anthropogenic debris using highly sensitive techniques is still under consideration. This study demonstrates a multidimensional analytical approach, including isotopic and thermogravimetric analyses to evaluate characteristics and behavior of MPs in the environment.

A new approach to extracting biofilm from environmental plastics using ultrasound-assisted syringe treatment for isotopic analyses.

Plastics are one of the ubiquitous and artificial types of substrates for microbial colonization and biofilm development in the aquatic environment. Characterizing plastic-associated biofilms is key to the better understanding of organic material and mineral cycling in the "Plastisphere"-the thin layer of microbial life on plastics. In this study, we propose a new method to extract biofilms from environmental plastics, in order to evaluate the properties of biofilm-derived organic matter through stable carbon (δC) and nitrogen (δN) isotope signatures and their interactions with radionuclides especially radiocesium (Cs).

Contamination processes of tree components in Japanese forest ecosystems affected by the Fukushima Daiichi Nuclear Power Plant accident Cs fallout.

In forests affected by the Fukushima Daiichi Nuclear Power Plant accident, trees became contaminated with Cs. However, Cs transfer processes determining tree contamination (particularly for stem wood, a prominent commercial resource) remain insufficiently understood. We propose a model for simulating dynamic behavior of Cs in a forest tree-litter-soil system and applied it to contaminated forests of cedar plantation and natural oak stand in Fukushima to elucidate relative impact of distinct Cs transfer processes determining the tree contamination.

Dynamics of radiocaesium within forests in Fukushima-results and analysis of a model inter-comparison.

Forests cover approximately 70% of the area contaminated by the Fukushima Daiichi Nuclear Power Plant accident in 2011. Following this severe contamination event, radiocaesium (Cs) is anticipated to circulate within these forest ecosystems for several decades. Since the accident, a number of models have been constructed to evaluate the past and future dynamics of Cs in these forests.

Spatial variations in radiocesium deposition and litter-soil distribution in a mountainous forest catchment affected by the Fukushima nuclear accident.

The Fukushima Dai-ichi Nuclear Power Plant accident caused serious Cs contamination in mountainous forest areas. To understand the spatial variation in soil Cs inventory in complex mountainous topography and the influencing factors, a whole-area investigation of Cs deposition in a broad-leaved forest catchment of a mountain stream was conducted using grid sampling. Across the catchment, organic and surface mineral soil layers were collected at 42 locations in 2013 and 6 locations in 2015.

Effectiveness of decontamination by litter removal in Japanese forest ecosystems affected by the Fukushima nuclear accident.

The Fukushima Daiichi nuclear power plant accident caused serious radiocesium (Cs) contamination of forest ecosystems over a wide area. The removal of the forest floor litter layer has been considered a potential method for forest decontamination; however, its effectiveness remains largely unknown. We conducted a pilot-scale decontamination study in a deciduous broadleaved forest in Fukushima.

Characterizing vertical migration of Cs in organic layer and mineral soil in Japanese forests: Four-year observation and model analysis.

Because of the Fukushima Dai-ichi Nuclear Power Plant accident, forest ecosystems in wide areas were contaminated with Cs. It is important to characterize the behavior of Cs after its deposition onto forest surface environments for evaluating and preventing long-term radiation risks. In the present study, Cs vertical distributions in the soil profile were observed repeatedly at five forest sites with different vegetation types for 4.

A new perspective on the Cs retention mechanism in surface soils during the early stage after the Fukushima nuclear accident.

The Fukushima Daiichi nuclear power plant accident caused serious radiocesium (Cs) contamination of the soil in multiple terrestrial ecosystems. Soil is a complex system where minerals, organic matter, and microorganisms interact with each other; therefore, an improved understanding of the interactions of Cs with these soil constituents is key to accurately assessing the environmental consequences of the accident. Soil samples were collected from field, orchard, and forest sites in July 2011, separated into three soil fractions with different mineral-organic interaction characteristics using a density fractionation method, and then analyzed for Cs content, mineral composition, and organic matter content.

Radiocesium distribution in aggregate-size fractions of cropland and forest soils affected by the Fukushima nuclear accident.

The Fukushima Daiichi nuclear power plant accident caused serious radiocesium (Cs) contamination in soils in a range of terrestrial ecosystems. It is well documented that the interaction of Cs with soil constituents, particularly clay minerals, in surface soil layers exerts strong control on the behavior of this radionuclide in the environment; however, there is little understanding of how soil aggregation-the binding of soil particles together into aggregates-can affect the mobility and bioavailability of Cs in soils. To explore this, soil samples were collected at seven sites under different land-use conditions in Fukushima and were separated into four aggregate-size fractions: clay-sized (<2 μm); silt-sized (2-20 μm); sand-sized (20-212 μm); and macroaggregates (212-2000 μm).

Forest type effects on the retention of radiocesium in organic layers of forest ecosystems affected by the Fukushima nuclear accident.

The Fukushima Daiichi nuclear power plant disaster caused serious radiocesium (Cs) contamination of forest ecosystems over a wide area. Forest-floor organic layers play a key role in controlling the overall bioavailability of Cs in forest ecosystems; however, there is still an insufficient understanding of how forest types influence the retention capability of Cs in organic layers in Japanese forest ecosystems. Here we conducted plot-scale investigations on the retention of Cs in organic layers at two contrasting forest sites in Fukushima.

Post-deposition early-phase migration and retention behavior of radiocesium in a litter-mineral soil system in a Japanese deciduous forest affected by the Fukushima nuclear accident.

The fate of radiocesium (Cs) derived from the Fukushima nuclear accident and associated radiation risks are largely dependent on its migration and retention behavior in the litter-soil system of Japanese forest ecosystems. However, this behavior has not been well quantified. We established field lysimeters in a Japanese deciduous broad-leaved forest soon after the Fukushima nuclear accident to continuously monitor the downward transfer of Cs at three depths: the litter-mineral soil boundary and depths of 5 cm and 10 cm in the mineral soil.

Modeling dynamics of (137)Cs in forest surface environments: Application to a contaminated forest site near Fukushima and assessment of potential impacts of soil organic matter interactions.

A process-based model for (137)Cs transfer in forest surface environments was developed to assess the dynamic behavior of Fukushima-derived (137)Cs in a Japanese forest. The model simulation successfully reproduced the observed data from 3year migration of (137)Cs in the organic and mineral soil layers at a contaminated forest near Fukushima. The migration of (137)Cs from the organic layer to the mineral soil was explained by the direct deposition pattern on the forest floor and the turnover of litter materials in the organic layer under certain ecological conditions.

Catchment-scale distribution of radiocesium air dose rate in a mountainous deciduous forest and its relation to topography.

A large number of air dose rate measurements were collected by walking through a mountainous area with a small gamma-ray survey system, KURAMA-II. The data were used to map the air dose rate of a mountainous deciduous forest that received radiocesium from the Fukushima Dai-ichi Nuclear Power Plant accident. Measurements were conducted in a small stream catchment (0.

Topographic heterogeneity effect on the accumulation of Fukushima-derived radiocesium on forest floor driven by biologically mediated processes.

The accident at the Fukushima Daiichi nuclear power plant caused serious radiocesium ((137)Cs) contamination of forest ecosystems located in mountainous and hilly regions with steep terrain. To understand topographic effects on the redistribution and accumulation of (137)Cs on forest floor, we investigated the distribution of Fukushima-derived (137)Cs in forest-floor litter layers on a steep hillslope in a Japanese deciduous forest in August 2013 (29 months after the accident). Both leaf-litter materials and litter-associated (137)Cs were accumulated in large amounts at the bottom of the hillslope.

Seasonal and snowmelt-driven changes in the water-extractable organic carbon dynamics in a cool-temperate Japanese forest soil, estimated using the bomb-(14)C tracer.

Water-extractable organic carbon (WEOC) in soil consists of a mobile and bioavailable portion of the dissolved organic carbon (DOC) pool. WEOC plays an important role in dynamics of soil organic carbon (SOC) and transport of radionuclides in forest soils. Although considerable research has been conducted on the importance of recent litter versus older soil organic matter as WEOC sources in forest soil, a more thorough evaluation of the temporal pattern of WEOC is necessary.

137Cs vertical migration in a deciduous forest soil following the Fukushima Dai-ichi Nuclear Power Plant accident.

The large amount of (137)Cs deposited on the forest floor because of the Fukushima Dai-ichi Nuclear Power Plant accident represents a major potential long-term source for mobile (137)Cs. To investigate (137)Cs mobility in forest soils, we investigated the vertical migration of (137)Cs through seepage water, using a lysimetric method. The study was conducted in a deciduous forest soil over a period spanning 2 month to 2 y after the Fukushima nuclear accident.

Comparison of the vertical distributions of Fukushima nuclear accident radiocesium in soil before and after the first rainy season, with physicochemical and mineralogical interpretations.

Effect of intense rainfall on the distribution of Fukushima-accident-derived (137)Cs in soil was examined. Inventories and vertical distributions of (137)Cs in soils were determined at 15 locations (including croplands, grasslands, and forests) in Fukushima city in the post-rainy season, approximately 4.5months after the accident, and were compared with those in the pre-rainy season determined in our former study.

Retention of potentially mobile radiocesium in forest surface soils affected by the Fukushima nuclear accident.

The fate of (137)Cs derived from the Fukushima nuclear accident fallout and associated radiological hazards are largely dependent on its mobility in the surface soils of forest ecosystems. Thus, we quantified microbial and adsorptive retentions of (137)Cs in forest surface (0-3 cm) soils. The K(2)SO(4) extraction process liberated 2.

Factors affecting vertical distribution of Fukushima accident-derived radiocesium in soil under different land-use conditions.

The Fukushima Dai-ichi nuclear power plant accident in Japan, triggered by a big earthquake and the resulting tsunami on 11 March 2011, caused a substantial release of radiocesium ((137)Cs and (134)Cs) and a subsequent contamination of soils in a range of terrestrial ecosystems. Identifying factors and processes affecting radiocesium retention in these soils is essential to predict how the deposited radiocesium will migrate through the soil profile and to other biological components. We investigated vertical distributions of radiocesium and physicochemical properties in soils (to 20 cm depth) at 15 locations under different land-use types (croplands, grasslands, and forests) within a 2 km × 2 km mesh area in Fukushima city.