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Battulga, B.; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Otosaka, Shigeyoshi*; Koarashi, Jun
Environmental Science and Pollution Research, 31, p.60080 - 60092, 2024/10
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. The radioactivity of plastics was estimated based on the Cs activity concentration of the biofilms and compared seasonally with surrounding environmental samples (i.e., sediment and sand). Cs traces were detected in biofilms with activity concentrations of 21-1300 Bq kg
biofilm (dry weight), corresponding to 0.04-4.5 Bq kg plastic (dry weight). Our results reveal the interaction between Cs and plastics and provide evidence that organic and mineral components in biofilms are essential in Cs retention in environmental plastics.
Battulga, B.; Nakayama, Masataka; Matsuoka, Shunsuke*; Kondo, Toshiaki*; Atarashi-Andoh, Mariko; Koarashi, Jun
Water Research, 264, p.122207_1 - 122207_12, 2024/10
Times Cited Count：5 Percentile：71.94(Engineering, Environmental)Growing attention has been given to microbial attachment and biofilm formation on microplastics (MPs; sizes: 
5 mm) in the environment. Here, we explore the microbial communities in the plastisphere to improve our understanding of microbial ecology as well as their impacts on aquatic ecosystems. Using the amplicon sequence of 16S and ITS genes, we identified bacterial and fungal community composition and diversity on MPs, surface waters, bottom sediments, and coastal sands in two contrasting coastal areas of Japan. Significantly different microbial diversity and taxonomic composition were detected depending on sample types and research sites. This research highlights the microbial metabolic functions in MP-associated biofilm, which could be the key to uncovering the true impact of plastic debris on the global ecosystem.
Battulga, B.; Munkhbat, D.*; Matsueda, Makoto; Atarashi-Andoh, Mariko; Oyuntsetseg, B.*; Koarashi, Jun; Kawahigashi, Masayuki*
Environmental Pollution, 357, p.124427_1 - 124427_10, 2024/09
Times Cited Count：0 Percentile：0.00(Environmental Sciences)The occurrence and characteristics of plastic debris in aquatic and terrestrial environments have been extensively studied. However, there is still limited information 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 from the plastics to uncover the characteristics of the biofilms using analytical, isotopic, and thermogravimetric techniques. Mixtures of organic and mineral particles were detected from extracted biofilms, revealing the plastic as a carrier for exogenous substances including contaminants in the river ecosystem. The present study provides insights into the characteristics and environmental behavior of biofilms which are useful to elucidate the impact of plastic-associated biofilms on organic matter and material cycling in the aquatic ecosystems.
Battulga, B.; Atarashi-Andoh, Mariko; Koarashi, Jun; Bolormaa, O.*; Kawahigashi, Masayuki*
Ecotoxicology and Environmental Safety, 261, p.115100_1 - 115100_10, 2023/08
Times Cited Count：1 Percentile：15.39(Environmental Sciences)The widespread distribution of plastic debris in the 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 accumulation of metal(loid)s on polystyrene foam (PSF) plastics collected from the Tuul River shore of Mongolia. Sorbed metal(loid)s on plastics have been extracted from collected PSF by sonication after peroxide oxidation. Size-dependent association of metal(loid)s indicated that PSFs act as vectors for the pollutants in the urban river environment. In addition, images from scanning electron microscopy (SEM) indicated not only the degraded surface of plastics showing fractures, holes, and pits, but also adhered mineral particles and microorganisms on PSFs. Interaction of metal(loid)s with plastics may be facilitated by altered surface physical and chemical properties of the plastics through photodegradation followed by an increase in surface area by size reduction and/or biofilm development in the aquatic environment. Enrichment ratio (ER) of metals on PSF samples suggested continuous accumulation of heavy metals on plastics. Our results demonstrate that the widespread plastic debris could be one of the carriers for hazardous chemicals in the environment. Since the influences of plastic debris on environmental health are major concerns to be solved, the fate and behavior of hetero-aggregates of plastics in aquatic environments should be continuously studied.
Battulga, B.; Atarashi-Andoh, Mariko; Matsueda, Makoto; Koarashi, Jun
Environmental Science and Pollution Research, 30(31), p.77226 - 77237, 2023/05
Times Cited Count：1 Percentile：12.25(Environmental Sciences)The global survey for the presence of microplastics (MPs) in aquatic environments has attracted widespread scientific attention over the past decade. This study demonstrates a multidimensional analytical approach, including isotopic and thermogravimetric analyses to evaluate characteristics and behavior of MPs in the environment. The MP samples were collected in two contrasting coastal areas of Japan. The 
C values of field-collected polyethylene (PE), polypropylene (PP), and polystyrene (PS) MPs were ranged from -25.6 to -31.4, -23.4 to -30.9, and -27.3 to -28.6 per mil, respectively. The differences in C signature between MPs with the same polymer types (i.e., PE and PP) but different colors. Through thermal analysis, the single-step endothermic process was observed for environmental PE and PS-MPs. The results reveal that degradation may play a significant role in the behavior and characteristics of MP debris in the aquatic environment.
Battulga, B.; Atarashi-Andoh, Mariko; Nakanishi, Takahiro; Koarashi, Jun
Science of the Total Environment, 849, p.157758_1 - 157758_11, 2022/11
Times Cited Count：7 Percentile：44.24(Environmental Sciences)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 (C) and nitrogen (
N) isotope signatures and their interactions with radionuclides especially radiocesium (Cs). After ultrasound-assisted separation from the plastics, biofilm samples were successfully collected via a sequence of syringe treatments. Biofilm-derived organic matter samples (14.5-65.4 mg) from four river mouths in Japan showed Cs activity concentrations of 75 to 820 Bq kg biofilm (dw), providing evidence that environmental plastics, mediated by developed biofilms, serve as a carrier for Cs in the coastal environment. Significant differences in the (C and N signatures were also obtained for the biofilms, indicating the different sources, pathways, and development processes of biofilms on plastics.
Battulga, B.*; Nakayama, Masataka*; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
Takata, Hyoe*; Otsuki, Azusa*; Sato, Shun*; Otosaka, Shigeyoshi*; Toda, Ryoji*; Nishikawa, Jun*; Kenmochi, Hideyuki*; Ishikura, Mei*; Yamada, Momoka*; Shinkai, Yusuke*; et al.
no journal, ,
Research cruises were conducted by the Shinsei Maru from October 7 to October 17, 2021, and from October 2 to 13, 2022, in the coastal waters off Fukushima Prefecture. Those cruises aimed to monitor radionuclide distribution and to clarify the dynamics of radionuclides in the coastal water and the environmental response of ecosystems after the Fukushima Daiichi Nuclear Power Plant accident in March 2011.
Battulga, B.; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
Plastic debris has been widely recognized as emerging pollutants in the global environment. Since plastics are one of the ubiquitous substrates for microbial colonization and biofilm formation in the aquatic environment, characterizing properties of the biofilms (organic coating) is an essential step in uncovering the plastic-mediated material cycling in the "Plastisphere". The current study therefore aimed at (i) developing a new and simple method to extract biofilms from aged plastics using an ultrasonic bath and a syringe and (ii) determining radiocesium (Cs), stable carbon (C), and stable nitrogen (N) isotopes in the biofilms. Plastic samples were collected from coastal river mouths in Ibaraki prefecture, Japan. Although the plastic concentration along the river mouth was not evaluated in the present study, 15.5 to 42.4 mg of biofilm-originated organic substances were obtained by using ultrasonic separation. In addition, preliminary results reveal that plastics act as a carrier of Cs in the coastal river environment, mediated by surface-developed organic coatings and adhered mineral particles. The extraction with a syringe treatment enabled us to obtain homogeneous biofilm samples. The C values for the samples were less negative compared with those obtained without the syringe treatment. A similar trend was also observed for the N values. As a ubiquitous and artificial type of substrates for microbial colonization, it is possible to hypothesize that biofilms developed on environmental plastics might have specific signatures of C and N depending on the source, pathway, and degree of microbial processing of the organic substances. A future study using our method would help understand the status of plastic and microplastics in the environment.
Battulga, B.; Nakayama, Masataka; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
Plastic debris in the aquatic environment has become a growing concern due to their long-term ecological consequences. The current study is focused on microbial community composition on microplastics (MPs; sizes 5 mm) and characteristics of MP-associated biofilms in coastal river environments of Japan in order to understand the impact of MP-associated biofilms on aquatic organic matter cycling. The aims of the current study are i) extraction and characterization of microbial biofilms on MPs and ii) identification of diversity and composition of microbial communities on MP surfaces and in surrounding surface waters and sediments. The samples were collected from two coastal rivers during 2021-2022 on a seasonal basis. In this study, we proposed a new method to extract biofilms from MPs using ultrasound-assisted syringe treatment for isotopic analysis. Morphotypes of MPs and associated specific microbial taxa as well as seasonal differences were also observed.
Battulga, B.; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
Plastic debris has been recognized as an emerging contaminant in the global ecosystem. Although microplastics (MPs) have received special attention from the scientific community owing to their widespread distribution, application of highly sensitive techniques to evaluate the characteristics of MPs is still under consideration. In this study, we demonstrate multiple analytical approaches including microscopic, spectroscopic, and isotopic analyses to track MP characterization obtained from coastal river environment. We selected two sampling sites from coastal areas in Japan and collected visible plastic samples. At the same time, surface water and coastal sand samples were collected to evaluate the seasonal variations in MP occurrence and composition. Seasonal differences in occurrence and morphotypes of MPs were detected in both sampling sites, suggesting variations in geographical patterns and consumption of plastic materials in the studied region. We also found differences in carbon isotopic composition between the MPs composed of the same polymer (i.e., polyethylene and polypropylene) but with different colors. Preliminary results of Cs activity concentrations revealed that plastics serve as carriers for radionuclides mediated by biofilms in the coastal river environment. Furthermore, occurrences and differences in the composition of the MPs in the study areas indicate that point and nonpoint sources of MPs strongly affect their concentration in the aquatic environment.
Battulga, B.; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
Plastic debris has been recognized as one of the carriers of hazardous substances in the aquatic ecosystem due to its ubiquitous distribution and potential interaction with pollutants through developed biofilms. In this study, we aimed to extract biofilms from the environmental plastics using a newly developed extraction method and to determine the concentration of radiocesium (Cs) and stable isotope ratios (C and N) in the extracted biofilm samples. Visible plastics were collected from the mouths of coastal rivers in Ibaraki prefecture, Japan, and applied to the extraction procedures. After plastic and biofilm separation with ultrasonication, biofilm samples were collected by the two ways: freeze-drying (15.5-44.4 mg); and freeze-drying after syringe treatment (14.5-65.4 mg). The XRD diffractograms of biofilm samples confirmed that biofilms obtained by freeze-drying only were still heterogeneous and the agglomerations of organic substances, mineral particles, and small microplastics (MPs, 1 mm). The results also demonstrated that biofilm extraction was achieved by syringe treatment separating the mineral and small MPs particles, resulting in homogenous biofilms from the surface of plastics. Preliminarily results of Cs activity concentrations in heterogenous (ranging from 0.22 to 0.54 Bq g) and homogenous (0.82
0.04 Bq g) biofilm samples revealed that MPs serve as a carrier for Cs in the coastal river environment mediated by developed biofilms.
Munkhbat, D.*; Kawahigashi, Masayuki*; Battulga, B.; Bolormaa, O.*; Sainjargal, B.*
no journal, ,
Battulga, B.; Nakayama, Masataka; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
A growing attention has been addressed on microbial attachment and biofilm formation on plastic debris especially on microplastics (MPs; sizes: 5 mm) in the aquatic environment. The current study is focused on bacterial and fungal community composition, diversity, and structure in MP-associated biofilms to emphasize potential alteration of elemental cycling by the presence of MPs in the coastal aquatic environment. We collected MP, surface water, bottom sediment, and coastal sand samples from two contrasting coastal areas of Japan on a seasonal basis. Surface morphology and attached microorganisms on MPs were visually inspected by scanning electron microscopy (SEM). A high-throughput sequencing using Illumina MiSeq was performed in the collected samples to investigate the microbial community composition and diversity among different samples.
Munkhbat, D.*; Battulga, B.; Oyuntsetseg, B.*; Kawahigashi, Masayuki*
no journal, ,
Battulga, B.; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
Plastic debris in the aquatic environment receives special attention from scientific communities, whereas the radioactivity of environmental plastic and the dynamics of plastic-associated biofilm remain largely unknown. In this study, we addressed plastic-associated biofilms and bottom sediments from two contrasting coastal areas of Japan to elucidate their characteristics and interaction with radionuclides especially radiocesium (Cs) in the environment. We also explored stable isotope (C and N) signatures of the biofilm and sediment samples based on seasonal variations. Trace of Cs was observed in biofilm with an activity concentration of 29219.4 Bq kg biofilm (dw) which correspond to 1.150.08 Bq kg plastic (dw).
Battulga, B.; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
Plastic debris is pervasive and persistent which allows its interaction with a range of organisms and organic and inorganic materials in the environment. Considering that plastics are considered carriers and vectors for pollutants in the aquatic environment, it is of utmost importance to elucidate the interaction between plastic debris and radionuclides. Because the accident at the Fukushima Daiichi Nuclear Power Plant caused by the Great East Japan Earthquake in 2011 led to the release of fission products, in particular radiocesium (Cs), into the environment, we aimed to elucidate the interaction between plastic debris and Cs in the environment. We selected the Kuma, Ukedo, Odaka, and Ohta Rivers of the Fukushima prefecture to collect environmental plastic and sediment samples. In addition, we adopted a newly developed ultrasound-assisted extraction technique to extract biofilm (a thin but robust layer of microbial cells embedded in an extracellular matrix) from plastics. The Cs activity concentrations in plastic-associated biofilms and river bottom sediments were determined by gamma-ray spectrometry. Our results indicate the dominance of common polymer types (i.e., polyethylene, polypropylene, polystyrene) of plastic debris in the river environments. Preliminary results of Cs analysis revealed that plastics serve as carriers for radionuclides mediated by biofilms in the coastal rivers.
