Papers

61,005 results
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Article Tier 2

Microplastics Survey in Osaka Bay

Researchers measured microplastic density at two locations in Osaka Bay in September and December 2019, finding peak concentrations of 4.1 particles per cubic meter after heavy rainfall — far exceeding 2015 reference levels — with seasonal variation in particle types including artificial turf and fertilizer capsules.

2024 Journal of Japan Society on Water Environment
Article Tier 2

Microplastic volumes in Tokyo Bay

Researchers quantified microplastic volumes across multiple sites in Tokyo Bay, Japan, finding spatial variation linked to urban runoff and river inputs, with surface waters and sediments showing distinct accumulation patterns.

2024 Marine Pollution Bulletin 8 citations
Article Tier 2

A Field Investigate on Curent Status of Microplastic Pollution on Sandy Beaches of Osaka Bay, Japan

Researchers investigated microplastic pollution on sandy beaches across Osaka Bay, Japan, sampling 13 coastal sites and finding concentrations ranging from 50 to 9,500 particles per square meter with most accumulation above the maximum monthly high-tide line. The study found that the innermost areas of the bay had markedly higher contamination, averaging 253-313 particles per square meter compared to a bay-wide mean of 52 particles per square meter.

2024 Japanese Journal of JSCE
Article Tier 2

An integrated assessment of microplastic pollution in coastal surface water and sediment of Japan

Researchers conducted a comprehensive survey of microplastic pollution across 14 coastal locations around Japan from Hokkaido to Okinawa, measuring concentrations of 288.7 g/km2 in surface water and 1,185 kg/km2 in sediment and characterizing polymer types, shapes, and size distributions.

2025
Article Tier 2

Comprehensive Understanding of Microplastics Inflow Off the Coast of Funabashi

Researchers conducted continuous monitoring of microplastic (MP) contamination in rivers, sewage, and coastal waters around Funabashi in Tokyo Bay, finding that MP number densities showed high temporal variability and a gradual decreasing trend, with upstream river sources driving contamination that diminished toward the sea as particles settled into bottom sediments, while sewage was also implicated as a contributor to marine MP pollution.

2025 Japanese Journal of JSCE
Article Tier 2

Contamination of sea surface water offshore the Tokai region and Tokyo Bay in Japan by small microplastics

Surface water off the Tokai region and within Tokyo Bay, Japan, was sampled with a nested net system distinguishing small microplastics (under 350 micrometers) from larger microplastics. Small microplastic concentrations were 20 to 60 times higher than larger ones, with concentrations up to 5,900 pieces per cubic meter in Tokyo Bay's inner waters.

2022 Marine Pollution Bulletin 61 citations
Article Tier 2

Microplastics contamination in tidelands of the Osaka Bay area in western Japan

Researchers surveyed microplastic contamination in the mudflats of four Osaka Bay tidelands in Japan, finding that concentrations in sediment increased with proximity to urban areas, and detected microplastics in 10% of bivalves, 6.7% of crabs, and in the stomach of a tufted duck. The results suggest biomagnification potential in the food web, with higher-order predators potentially accumulating greater microplastic loads in tideland ecosystems near cities.

2019 Water and Environment Journal 27 citations
Article Tier 2

An Integrated Assessmentof Microplastic Pollutionin Coastal Surface Water and Sediment of Japan

Researchers conducted an integrated assessment of microplastic pollution in coastal surface water and sediment around Japan, providing a comprehensive dataset that clarifies the extent of contamination in Japanese coastal areas previously lacking systematic monitoring data.

2025 Figshare
Article Tier 2

Microplastics on the sea surface of the semi-closed Tokyo Bay

Researchers surveyed microplastic pollution in Tokyo Bay using neuston nets in May 2019 and January 2020, finding average abundances of 3.98 pieces per square metre with polyethylene fragments dominating, and identifying river inputs as the primary source based on matching seasonal abundance patterns between riverine and inner bay samples.

2020 Marine Pollution Bulletin 81 citations
Article Tier 2

Microplastics Occurrence in Surface Waters and Sediments in Five River Mouths of Manila Bay

Researchers documented microplastic contamination in water and sediments at five river mouths of Manila Bay in the Philippines, finding fragments and fibers as the dominant types, with polyethylene and polypropylene the most common polymers.

2021 Frontiers in Environmental Science 116 citations
Article Tier 2

Survey on Microplastics and Macroscopic Floating Garbage in River, Coasts, and Estuary in the Eastern Part of Takamatsu City, Japan

Researchers surveyed microplastics and macroscopic floating litter in rivers, coasts, and estuaries in eastern Takamatsu City, Japan, finding PE and PP dominated microplastics in both river and coastal environments, and that plastic fragments, bags, and cigarette butts were the most common macro-litter items with distribution influenced by wind and wave conditions.

2025 Japanese Journal of JSCE
Article Tier 2

High-Resolution Mapping of Japanese Microplastic and Macroplastic Emissions from the Land into the Sea

Researchers developed a high-resolution method to map microplastic and macroplastic emissions from Japanese river catchments into the sea, using correlations between observed river concentrations and basin characteristics such as urban area ratio and population density to generate nationwide plastic emission estimates.

2020 Water 85 citations
Article Tier 2

Microplastics in the tropical Northwestern Pacific Ocean and the Indonesian seas

Researchers measured microplastic abundance in the tropical Northwestern Pacific and Indonesian seas, finding very low concentrations in open-ocean currents but an order of magnitude higher levels in the Indonesian straits due to river runoff and current convergence patterns.

2023 Journal of Sea Research 50 citations
Article Tier 2

Current Status and Issues of Microplastic Pollution Research

This Japanese review summarized microplastic research in river and ocean environments, including national estimates of plastic discharged from Japan's rivers to the sea and microplastic distribution in Tokyo Bay. The paper also reviewed current analytical methods and their limitations for measuring small microplastic particles.

2021 Journal of Japan Society on Water Environment 13 citations
Article Tier 2

Microplastics in the sediments of small-scale Japanese rivers: Abundance and distribution, characterization, sources-to-sink, and ecological risks

Researchers characterized microplastic pollution in sediments of four small-scale Japanese rivers, finding widespread contamination and identifying polymer types and potential sources, highlighting that even small river systems serve as microplastic transport pathways.

2021 The Science of The Total Environment 109 citations
Article Tier 2

Occurrence, distribution, and possible sources of microplastics in the surface river water in the Arakawa River watershed

Researchers investigated the occurrence, distribution, and potential sources of microplastics in surface river water along the Arakawa River watershed running through the Tokyo Metropolitan area, contributing to data on microplastic contamination in populated urban freshwater systems.

2021 Environmental Science and Pollution Research 38 citations
Article Tier 2

Microplastics in urban wastewater and estuarine water: Importance of street runoff

Microplastics ranging from 10 micrometers to 5 mm were measured in untreated sewage, treated sewage, highway runoff, and estuarine water in Tokyo during dry and wet weather. Particles smaller than 200 micrometers made up more than 60% of total microplastic counts across all sample types, with highway runoff identified as a significant contributor.

2021 Environmental Monitoring and Contaminants Research 69 citations
Article Tier 2

Characteristics of Microplastics and Macro-sized Coastal Debris on the Beaches of the Eastern Takamatsu City, Japan

A beach survey in eastern Takamatsu, Japan found that the beach near a large urban river mouth had higher concentrations of both microplastics and macro-litter than a more remote beach, with polyethylene dominating at one site and polystyrene at the other. Most litter items were less than six months old, suggesting rapid accumulation from nearby sources rather than long-range ocean transport.

2026 Japanese Journal of JSCE
Article Tier 2

Occurrence and distribution of plastic particles (10–25,000 μm) and microfibers in the surface water of an urban river network in Japan

This study assessed the occurrence and distribution of plastic particles (10-25,000 micrometers) and microfibers in the surface water of an urban river network in Japan, finding that plastic abundance was closely tied to urban land use and proximity to discharge points.

2023 Environmental Monitoring and Assessment 16 citations
Article Tier 2

Microplastic in three urban estuaries, China

Researchers surveyed three urban estuaries in China and found microplastics throughout, with concentrations and types reflecting the combined influence of surrounding city density, stormwater runoff, and tidal mixing.

2015 Environmental Pollution 696 citations
Article Tier 2

Spatiotemporal variations of surface water microplastics near Kyushu, Japan: A quali-quantitative analysis

Researchers conducted six surveys over 14 months at nine stations near Kyushu, Japan, identifying 6,131 microplastic items with an average abundance of 0.49 items per square meter and average size of 1.71 mm. Spatiotemporal variability was high, with the greatest differences between sampling locations exceeding differences between seasons.

2021 Marine Pollution Bulletin 46 citations
Article Tier 2

A Microplastic Pollution Hotspot: Elevated Levels in Sediments from the San Francisco Bay Area

Sediment samples from San Francisco Bay revealed elevated microplastic concentrations across sites, with polymer types and morphologies consistent with local urban runoff and atmospheric deposition sources.

2024 Environments 6 citations
Article Tier 2

Measurement, quantification, and potential risk of microplastics in the mainstream of the Pearl River (Xijiang River) and its estuary, Southern China

Microplastic distribution was surveyed across the mainstream and estuary of China's Pearl River, finding higher concentrations near urban centers and establishing a detailed inventory of microplastic abundance, polymer types, and potential sources in this major waterway.

2021 Environmental Science and Pollution Research 60 citations
Article Tier 2

Assessment 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.

2018 Environmental Pollution 514 citations