Abstract:

Riverine transport has a significant impact on marine microplastic pollution, and the Pearl River stands out for its high level of microplastic flux compared to other global rivers, primarily due to land-based microplastics from tributaries in Guangzhou City. To better understand the contamination pattern and potential ecological risk of microplastics in river waters of Guangzhou, we conducted two field surveys in autumn and winter, collecting microplastic samples from 19 sampling sites using a Manta trawl. Our results showed that the abundance of riverine microplastics in the Guangzhou section of the Pearl River ranged from 0.092 to 26.4 pieces•m⁻³ in autumn and 0.044 to 2.07 pieces•m⁻³ in winter, which is considered average in China and globally. Microplastic abundance was highest in the central city area, surrounded by residential areas with high population density. The main polymer types identified were polyamide, polypropylene, and polyethylene, accounting for over 80% of the microplastics. Transparent and white microplastics were the most common, while color distribution showed no clear pattern. Small microplastics under 2 mm in size were more abundant than large-size microplastics, with fragments and fibers being the most frequently detected shapes. Changes in color, size, and shape may be associated with the aging of microplastics in the environment. By evaluating both the polymer types and abundance, we assessed the ecological risk of riverine microplastics in the Guangzhou section of the Pearl River using the ecological risk index (H) and pollution load index (P_L). The H index ranged from 0.72 to 63.1, and the PLI ranged from 1.31 to 16.9, indicating a moderate ecological risk. Most sampling sites were classified as level I risk, but a few were classified as level II, likely due to anthropogenic activities. Urgent action is needed to reduce plastic waste entering the river.

Key words: microplastics, ecological risk assessment, Pearl River, water, contamination pattern, estuary

摘要：

珠江河流微塑料入海通量在世界河流中处于中上水平，流经广州市区的珠江各支流带来的陆基微塑料是珠江入海微塑料的主要来源，其微塑料污染特征和潜在生态风险值得进一步研究。分别在秋季和冬季在珠江广州段的19个监测点的微塑料污染现状开展了调查，采用Manta拖网过滤法采集水体表面0－0.5 m深的微塑料样品。结果显示，珠江广州段河流水体微塑料丰度在秋季和冬季分别为0.092－26.4 pieces•m⁻³和0.044－2.07 pieces•m⁻³，在全国乃至全世界范围内处于中等水平。处于广州市中心区的采样点微塑料丰度远高于入海口，水体微塑料丰度的最高点（26.4 pieces•m⁻³）出现在位于市内区域的采样点，该点位于广州市老城区，主要以生活区为主，人口密集，证实了人为活动对水体微塑料分布的影响。聚酰胺/尼龙、聚丙烯和聚乙烯这三类聚合物是检出的主要聚合物类型，占据所有微塑料样品的80%以上。在所有微塑料中，透明色和白色居多，其他颜色未发现明显的规律特征，粒径小于2 mm的小尺寸微塑料丰度占比高于大尺寸微塑料，碎片类和纤维类的微塑料在所有样品中均频繁检出，微塑料在颜色、尺寸和形态上的变化可能与微塑料在环境中的不断老化有关。综合考虑各采样点微塑料的类型和丰度评估珠江广州段水体微塑料的生态风险，其生态风险指数（H）和污染负荷指数（P_L）分别为0.72－63.1和1.31－16.9。绝大多数采样点位的风险等级为I级，仅少数采样位点的风险等级为II级，且明显受到采样区域内人为活动的影响，亟需采取适当的微塑料管控措施来控制重点区域塑料垃圾的入河量。

关键词: 微塑料, 生态风险评价, 珠江, 水体, 污染特征, 入海口