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Papers
51 resultsShowing papers from Ehime University
ClearAssessment of the sources and inflow processes of microplastics in the river environments of Japan
Researchers mapped microplastic concentrations across 29 Japanese rivers and found plastic particles present at 31 of 36 sampling sites. The concentrations were strongly linked to urbanization and population density, confirming that human activities in river basins are a major driver of freshwater microplastic pollution. The findings demonstrate that significant plastic fragmentation occurs before debris reaches the ocean, making rivers an important area for pollution monitoring.
Geometric relationship between the projected surface area and mass of a plastic particle
Researchers developed mathematical models to estimate the mass of microplastic particles based on their projected surface area, using over 4,000 particles collected from Japanese rivers. The models provided more accurate mass estimates than previously used methods. This work matters because reliable mass measurements are essential for assessing how much plastic pollution is actually present in waterways and understanding its environmental and health implications.
A review of microplastics pollution in the soil and terrestrial ecosystems: A global and Bangladesh perspective
This review examined microplastic pollution in soils and terrestrial ecosystems from both global and Bangladesh perspectives. Researchers found that while microplastics are well-studied in aquatic environments, their presence in agricultural soils poses a largely unexplored threat to food safety, with evidence suggesting microplastics can transfer from soil through terrestrial agriculture into the human food chain.
Mesoplastics: A Review of Contamination Status, Analytical Methods, Pollution Sources, Potential Risks, and Future Perspectives of an Emerging Global Environmental Pollutant
This review synthesizes existing research on mesoplastics, plastic particles that bridge the size gap between macroplastics and microplastics, examining their contamination status, sources, and ecological risks. Researchers found that most studies have focused on marine and freshwater environments, with a surge in publications from 2014 to 2024 concentrated in East Asia. The study highlights that mesoplastics can disrupt ecosystems, act as vectors for additives and pathogens, and remain understudied in many regions and environments.
Mechanical recycling of plastic waste as a point source of microplastic pollution
Researchers found that mechanical recycling of plastic waste is a significant point source of microplastic pollution, releasing plastic fragments into wastewater during washing, shredding, and processing stages of the recycling chain.
Biofilms: hot spots of horizontal gene transfer (HGT) in aquatic environments, with a focus on a new HGT mechanism
This review covers horizontal gene transfer in aquatic biofilms, with emphasis on antibiotic resistance gene spread, and introduces membrane vesicles as a newly recognized HGT mechanism by which bacteria share genetic material, with implications for understanding resistance spread on microplastic surfaces.
Optimized Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) Production by Moderately Haloalkaliphilic Bacterium <i>Halomonas alkalicola</i> Ext
Researchers isolated a salt- and alkali-tolerant bacterium from a Kenyan lake and optimized its production of the biodegradable polymer PHBV as an alternative to conventional plastics. Through systematic optimization of growth conditions, they achieved a polymer yield of over 45% of the bacterial cell mass. The study demonstrates that extremophilic microorganisms can serve as efficient producers of biodegradable plastics suitable for packaging and biomedical applications.
Beppu Bay, Japan, as a candidate Global boundary Stratotype Section and Point for the Anthropocene series
Researchers evaluated Beppu Bay sediments as a candidate Global boundary Stratotype Section for the Anthropocene, finding unprecedented increases in 99 anthropogenic proxies above a 1953 flood layer, including microplastics, radionuclides, and industrial pollutants.
Comparison of concentration, shape, and polymer composition between microplastics and mesoplastics in Japanese river waters
Researchers conducted field surveys across 147 Japanese rivers to compare the concentration, shape, and polymer composition of microplastics and mesoplastics in river water. They found microplastics at 99% of sampling stations and mesoplastics at 74%, with the gap between the two size categories widening as overall contamination increased. The study argues that monitoring only microplastics or macroplastics while ignoring mesoplastics can lead to significant underestimation of plastic pollution in rivers.
Effect of Protists on Horizontal Transfer of Antimicrobial Resistance Genes in Water Environment
This review examined how protists in aquatic environments facilitate horizontal transfer of antibiotic resistance genes among bacteria, revealing novel mechanisms beyond classical conjugation, transformation, and transduction that contribute to antimicrobial resistance spread.
Discovery of the Marine Biodegradability of Nylon 6 and Nylon 6,6 Copolymer Fishing Lines
Researchers discovered that novel Nylon 6 and Nylon 6,6 copolymer fishing line formulations biodegrade in marine environments, addressing a major challenge since conventional fishing lines persist indefinitely in seawater and entangle marine wildlife.
Distribution characteristics and transport processes of biodegradable microplastics in the Seto Inland Sea, Japan
Researchers modeled the transport of biodegradable microplastics (positively, neutrally, and negatively buoyant) from rivers through the Seto Inland Sea using a 3D hydrodynamic model. Positively buoyant particles showed strong seasonal variation concentrated at the surface, while neutrally buoyant particles distributed through all depths, revealing that buoyancy fundamentally shapes MP fate in coastal seas.
Time-resolved fragmentation pathways of expanded polystyrene microplastics: Intrinsic pathway modulated by sand morphology and degradation state
Researchers used pot-mill experiments to study how expanded polystyrene (EPS) fragments over time (6-240 hours), varying beach vs. river sand morphology and virgin vs. degraded starting material. Two dominant fragment size classes emerged at distinct time points, with sand morphology and prior degradation state strongly influencing fragmentation pathways.
Abundance and size of microplastics in a coastal sea: Comparison among bottom sediment, beach sediment, and surface water
Microplastics were found in surface water, bottom sediment, and beach sediment of Hiroshima Bay, Japan, with higher concentrations in bottom sediment and beach sediment than in surface water. The study documents how foamed polystyrene fragments differently from other plastics and accumulates across multiple environmental compartments in a semi-enclosed coastal bay.
Meta-ecosystem Frameworks Can Enhance Control of the Biotic Transport of Microplastics
Researchers propose applying meta-ecosystem frameworks to better understand and manage the biotic transport of microplastics across landscapes, arguing that current approaches overlook how organisms and trophic transfers move particles between ecosystems. The framework could improve both research design and mitigation strategies.
Microplastics in dumping site soils from six Asian countries as a source of plastic additives
Microplastic abundance and plastic additive concentrations were analyzed in open-dumping site soils from six Asian countries, finding the highest abundance in Cambodia at 218,182 particles/kg and identifying these sites as sources of both primary microplastics and leachable plastic additives.
A 75-year history of microplastic fragment accumulation rates in a semi-enclosed hypoxic basin
A sediment core from a semi-enclosed hypoxic basin revealed a 75-year record of increasing microplastic fragment accumulation rates, with the pace accelerating in line with global plastic production growth. The study also found that biological activity and ocean dynamics influenced microplastic sinking and deposition patterns.
Selective transport of microplastics and mesoplastics by drifting in coastal waters
A combination of field surveys and particle-tracking models in Japan's Seto Inland Sea revealed that tidal currents selectively transport larger mesoplastics toward coastal areas while smaller microplastics remain more widely distributed. The study demonstrates how hydrodynamics shape the size-dependent distribution of plastic debris in coastal waters.
Artificial sweeteners in surface waters from Asian, African and Middle Eastern countries: Utility as molecular markers and water pollution status in 2010–2019
Surface water samples from African, Asian, and Middle Eastern countries collected during 2010-2019 were analyzed for four artificial sweeteners (acesulfame, sucralose, saccharin, cyclamate) as molecular markers of wastewater contamination. The study established a historical baseline of sewage-derived pollution status across regions with varying wastewater treatment infrastructure.
Distribution and accumulation patterns of tire-derived particles in coastal and lake sediments
Tire and road wear particles (TRWP) — tiny fragments shed every time a vehicle brakes or turns — are among the largest sources of microplastics globally, and this study found them in sediments across 32 of 36 sampling sites in Japanese lakes and coastal waters. Critically, at 30 of those 36 sites, concentrations exceeded levels considered safe for aquatic ecosystems, suggesting widespread ecological risk. The research also found that TRWP tend to travel with fine soil particles and organic matter, offering clues about how these pollutants disperse through river systems and settle in aquatic environments.
Removal of polystyrene nanoparticles using MgAl layered double hydroxide membranes synthesized on aluminum plates
Researchers synthesized magnesium-aluminum layered double hydroxide (LDH) membranes on aluminum plates in just 10 minutes and tested them for removing nanoplastic particles from water, finding strong adsorption of both 100 nm and 1 micrometer polystyrene nanoparticles. The easy-to-make, sheet-like membranes offer a simple and scalable approach to filtering nanoplastics from drinking water and other water sources.
Potential sources of microplastic contamination in laboratory analysis and a protocol for minimising contamination
Scientists identified multiple sources of microplastic contamination that can be accidentally introduced during laboratory analysis of biological samples, including from lab water, chemicals, and air. By filtering reagents, pre-treating glass fiber filters, and using a clean working environment, they reduced lab-introduced contamination by 70–100%. These findings are important for accurate microplastic research: without such precautions, studies can significantly overestimate how much plastic is actually present in animal tissues or environmental samples.
An analytical approach to confidence interval estimation of river microplastic sampling
This study proposes a statistical method using the Poisson distribution to calculate confidence intervals for microplastic concentration measurements from single river water samples — addressing a major gap in environmental monitoring where replicate sampling is often impossible. The method is reliable when at least 10 microplastic particles are captured, and achieves sampling errors within ±30% when 50 or more particles are present. Standardizing how uncertainty is reported will make microplastic data from different rivers and studies far more comparable.
Ingestion and translocation of microplastics in tissues of deposit-feeding crabs (Grapsoidea, Ocypodoidea) in Kochi estuary, Japan
More than half of 116 intertidal crabs collected from a Japanese estuary contained microplastics, with PET fragments dominating and particles concentrated primarily in the gut. Smaller deposit-feeding crab species carried a higher microplastic burden relative to body weight than larger omnivorous species, showing that feeding behavior and body size both shape how much plastic wildlife accumulates in contaminated estuaries.