Key Takeaways & Executive Findings
- •• • Seawater MP abundance ranged from 316.67 to 1300 n·m−3, while river water ranged from 400 to 5416.67 n·m−3, indicating rivers as a significant conduit for terrestrial MPs; this differential informs source mitigation priorities. • • Dominant polymer in seawater was polyethylene terephthalate (PET), whereas river water was dominated by polypropylene-ethylene copolymer (PP-PE); this polymer-specific signature aids in tracing sources and selecting targeted waste management. • • Seawater MP abundance correlated significantly with tourist numbers, with distribution pattern tourism areas > natural areas > aquaculture areas > residential areas; this quantifies tourism's impact, guiding policy for coastal tourism management. • • Ecological risk assessment showed moderate risk in seawater and medium-low in river water, but 15% of seawater sites reached polymer risk level Ⅳ due to polyacrylonitrile's high toxicity; this identifies hotspots requiring urgent intervention.
Abstract
Coastal areas serve as critical ecological interfaces for the migration of terrestrial microplastics (MPs) into the ocean, and characterizing their pollution is essential for integrated coastal management. This study investigated the occurrence, sources, and ecological risks of MPs in surface waters of nearshore areas and river estuaries around Hainan Island, a typical tropical tourist island. MPs abundance ranged from 316.67 to 1300 n·m−3 in seawater and from 400 to 5416.67 n·m−3 in river water. In seawater, the dominant polymer was polyethylene terephthalate, with fibers being the predominant shape, size class 500–1000 μm, and white/transparent color. In river water, polypropylene-ethylene copolymer dominated, also as fibers, but with size class 100–500 μm and white/transparent color. Seawater MP abundance showed a significant positive correlation with tourist numbers, and distribution across functional areas followed: tourism areas > natural areas > aquaculture areas > residential areas. Multiple correspondence analysis identified household plastic waste, laundry wastewater, aquaculture, and fishery products as primary sources of seawater MPs. Principal component analysis indicated homologous characteristics between seawater and river MPs, suggesting rivers are a major pathway for terrestrial MP transport to coastal zones. Ecological risk assessment revealed low pollution loads, with potential ecological risks moderate for seawater and medium-low for river water. Notably, 15% of seawater sampling sites exhibited polymer risk level Ⅳ, primarily driven by polyacrylonitrile's high biological toxicity. These findings provide a scientific basis for developing MP pollution control strategies in Hainan Island.
1. Introduction
Microplastic pollution in coastal environments has emerged as a pressing global concern, yet comprehensive assessments in tropical tourist islands remain scarce. Existing studies often focus on temperate or continental coastlines, overlooking the unique dynamics of island ecosystems where tourism, aquaculture, and riverine inputs intersect. The lack of baseline data on MP abundance, polymer composition, and ecological risk in such regions hampers the development of effective management strategies. Hainan Island, a major tropical tourist destination in China, exemplifies this gap, with its coastal waters and rivers facing increasing plastic pressure from anthropogenic activities.
This study addresses the bottleneck by systematically characterizing MPs in surface waters of Hainan's nearshore areas and inflowing rivers. By employing abundance quantification, polymer identification, and multivariate statistical analyses, we elucidate the spatial distribution, potential sources, and source-sink relationships between riverine and marine MPs. Furthermore, we apply a comprehensive ecological risk assessment framework to evaluate pollution load and polymer-specific hazards. The findings not only fill a critical data void but also provide actionable insights for targeted pollution control in tropical island coastal zones, balancing economic development with environmental sustainability.
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ZHANG Xiaoyan, HUANG Weiyu, DENG Hanqiang, SUN Kaifeng, CHEN Wenwen, LIU Bingjie (2026). Pollution Characteristics and Ecological Risks of Microplastics in Surface Waters of Coastal Area and Rivers Entering the Sea on Hainan Island. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025030501
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Frequently Asked Questions
What is the abundance range of microplastics in seawater and river water, and how do these compare to other regions?
Seawater microplastic abundance ranged from 316.67 to 1300 n·m−3, while river water ranged from 400 to 5416.67 n·m−3. These values are within the range reported for other coastal and riverine systems globally, but the riverine levels are notably higher, indicating significant terrestrial input.
Which polymer types dominate in seawater and river water, and what are their potential sources?
In seawater, polyethylene terephthalate (PET) was dominant, likely from beverage bottles and textile fibers. In river water, polypropylene-ethylene copolymer (PP-PE) dominated, possibly from packaging and fishing gear. Source analysis suggests contributions from household waste, laundry wastewater, aquaculture, and fisheries.
How does tourism affect microplastic pollution in coastal waters?
Seawater microplastic abundance showed a significant positive correlation with tourist numbers. Distribution across functional areas followed tourism areas > natural areas > aquaculture areas > residential areas, indicating that tourism-related activities are a major contributor to microplastic pollution.
What is the ecological risk level of microplastics in the study area, and which polymers pose the highest risk?
The pollution load was low, with potential ecological risk moderate for seawater and medium-low for river water. However, 15% of seawater sites reached polymer risk level Ⅳ, primarily due to polyacrylonitrile's high biological toxicity, indicating localized high-risk zones.
Are the microplastics in seawater and river water from the same sources?
Principal component analysis indicated homologous characteristics between seawater and river microplastics, suggesting that rivers are a major pathway for terrestrial microplastics to coastal areas. This implies that controlling riverine inputs could effectively reduce coastal microplastic pollution.
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