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A survey was conducted on the surface water samples of Ningyuan River in Hainan Province. The samples were collected through on-site filtration and concentration methods, and pretreated through oxidation digestion and density separation. The microplastics were statistically analyzed by confocal micro-Raman spectrometer, elucidating the abundance, type, particle size, and shape characteristics of the microplastics in the water samples. Seasonal differences were analyzed, and the main conclusions were as follows: microplastics were detected at all sampling points, with the abundance range of 66.67 items/m3 to 1106.67 items/m3; polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), and polystyrene (PS) are the main types of microplastics; 100-1000 μm is the main particle size distribution range; the proportion order of microplastics with different shapes is fiber> fragment> film> particle. In terms of spatial distribution, there are significant differences due to the influence of functional zones along the river banks, while in terms of seasonal distribution, there is no significant difference between dry and rainy seasons; The overall level of microplastic pollution belongs to a medium to low risk.

Hainan Island, China’s second largest island, is located in the tropics and its rivers are significantly affected by precipitation. With the construction of free trade port with Chinese characteristics, Hainan Island’s industry, agriculture, tourism and urbanization have developed in an all-round way. With the rapid development of economy, water environment ecology has been destroyed. Based on the two seasons of drought and rain, this paper took Ningyuan River and Wanquan River as the research object to study the spatial and temporal distribution of nitrogen and phosphorus nutrients in the rivers entering the sea in Hainan, and found that the concentration of nutrients in Ningyuan River was higher than that in Wanquan River. The total nitrogen pollution in dry season was higher than that in rainy season, and that in tributaries was higher than that in main stream. The maximum nitrogen content in Ningyuan River reached 2.99 mg/L and 2.37 mg/L in the dry season and rainy season, and human activities were the main reason for the increase of nutrient concentration.

Heavy metals are of wide concern due to their high toxicity, bioaccumulation and non-degradability. In this study, eight heavy metals (Cr, Mn, Ni, Cu, Zn, As, Cd, Pb) in the surface sediments of Ningyuan River were studied to investigate the distribution pattern, pollution status and potential pollution sources, and it was concluded that the concentration distribution of heavy metals in sediments is highly consistent with the population distribution pattern in space and there is a certain degree of risk of Cd pollution, and the heavy metals mainly come from mineral weathering, agricultural and shipping wastes.