Abstract:

Plastics are commonly utilized in daily life and manufacturing processes, owing to their remarkable properties. However, they are not easily degraded in the environment, leading to many microplastics that may pose potential ecological and environmental risks. Therefore, identifying the abundance and conducting risk assessment of microplastics in water bodies are crucial to reduce the safety concerns posed by microplastics. However, previous studies on the abundance of microplastics in the watershed mostly focused on the surface water of rivers, ignoring the influence of horizontal sampling points and sampling depth on the distribution of microplastics, and the conclusions obtained are not representative enough. The Ganjiang River is a major tributary in the middle reaches of the Yangtze River. In this study, samples were collected and analyzed at a representative section of the Ganzhou urban section, and changes in the abundance, color morphology, particle size, and polymer status of microplastics were analyzed horizontally and vertically. The risk levels of microplastics were calculated using the ecological risk index method. The results showed that the microplastic abundance of the representative section was 0.25-0.35 n·L^-1, and the average microplastic abundances in the surface, middle, and bottom waters were 2.65, 2.03, and 0.91 n·L^-1, respectively. The horizontal microplastic abundance increased in the area near the riverbank, and the vertical microplastic abundance decreased with increasing sampling depth. The main shapes of microplastics were fiber and debris, mainly black, with a particle size range of 0.125-3.000 mm, accounting for more than 94%, and the aggregate types were polyethylene, polypropylene, polystyrene, polyamide, ethylene-vinyl acetate copolymer, polycarbonate, polyethylene terephthalate, and polyvinyl chloride. The potential risk level of microplastics in the study area was Class II. In general, the horizontal and vertical distributions of river microplastics in the Ganzhou urban section of the Ganjiang River were uneven, and the degree of pollution was relatively low. This study will promote the understanding of the distribution characteristics of vertical microplastics in urban water bodies, and has guiding significance for the investigation of microplastics in other water basins.

Key words: microplastics, city, distribution characteristics, pollution situation, risk assessment, Ganjiang river

摘要：

塑料由于其优异的性能被广泛的应用于生产生活，然而其在环境中不易降解，这导致环境当中存在着许多微塑料，可能造成潜在的生态环境风险。因此，明确水体当中微塑料的丰度并对其进行风险评估对于降低微塑料带来的安全问题有着至关重要的作用。然而，此前关于流域内微塑料丰度的研究多停留于河流表层水体的研究，忽略了水平方向取样点位以及取样深度对微塑料分布造成的影响，所得出的结论代表性不足。赣江是长江中游的主要支流，在赣州城市区段的代表断面处取样分析，横向与纵向相结合分析了该断面处微塑料的丰度、颜色形态、粒径、聚合物情况的变化情况，并通过生态风险指数法计算了微塑料风险等级。结果表明：该代表断面微塑料丰度为0.25－0.35 pieces·L^-1，表层水、中层水和底层水的平均微塑料丰度分别为2.65、2.03和0.91 pieces·L^-1，微塑料丰度横向范围表现处越靠近河岸处越大，纵向范围随着取样深度的增大而减小；微塑料主要形状为纤维和碎片，以黑色为主，粒径范围在0.125－3.000 mm的微塑料的占比超过94%；集合种类为聚乙烯、聚丙烯、聚苯乙烯、聚酰胺、乙烯-醋酸乙烯共聚物、聚碳酸酯、聚对苯二甲酸乙二脂和聚氯乙烯；研究区域微塑料潜在风险等级为Ⅱ级。总体而言，赣江赣州城市段河流微塑料丰度在横向和纵向分布上是不均匀的，污染程度总体而言相对较轻。该研究将促进对城市水体当中垂直领域微塑料分布特征的理解，对其他水体流域开展微塑料的相关调研具有指导意义。

关键词: 微塑料, 城市水体, 分布特征, 污染现状, 风险评估, 赣江