The number of plastic particles found in estuarine sediment and water samples of five estuaries, Durban, KwaZulu-Natal, South Africa

Widespread disposal of plastics negatively affects biotic and abiotic components of marine systems. Monitoring plastics transitioning through estuaries is vital in assessing terrestrial inputs to oceanic environments. Data on microplastics (particles <= 5mm) in estuaries are scant. This study determined microplastic levels within five estuaries along the Durban coastline and on intervening beaches. Plastics were isolated from estuarine sediment, beach sediment and the surface water of each estuary and characterised. Sediment at the Bayhead area of Durban Harbour was found to contain the highest average plastic concentrations (745.40 ± 129.72 particles per 500ml). Overall an attenuating concentration trend away from the city center was found. Fragments composed the largest percent of plastics (59 %) found in Bayhead, whereas fibers dominated other estuaries (Mdloti - 66 %, uMgeni - 38 %, Isipingo - 45 % and iLovu - 53 %). Plastic particle concentration in estuarine sediment generally increased from larger to smaller size classes. If high input and high retention in the harbour is coupled with high organic and metal pollutant loads, this area can become (if not already) a major environmental hazard.塑料的广泛无序丢弃会对海洋生态系统的生物与非生物组分造成显著负面影响。对塑料在河口系统中迁移过程的监测，是评估陆地源污染物向海洋环境输入量的关键手段。目前关于河口内微塑料（microplastics，粒径≤5mm的颗粒）的实测数据仍较为匮乏。本研究针对德班沿岸的五个河口及毗邻海滩中的微塑料含量展开了系统性测定。研究人员从各河口的沉积物、海滩沉积物以及河口水体中分离提取塑料颗粒，并完成了组分与形态表征分析。检测结果显示，德班港贝黑德区域的沉积物中平均塑料颗粒浓度最高，达(745.40 ± 129.72)颗/500ml。整体而言，塑料颗粒浓度呈现出随距市中心距离增加而逐渐衰减的空间分布趋势。贝黑德区域的塑料颗粒以碎片类为主，占比达59%；而其余四个河口则均以纤维类塑料颗粒占比最高：姆德洛蒂河口（Mdloti）为66%、乌姆格尼河口（uMgeni）为38%、伊西平戈河口（Isipingo）为45%以及伊洛武河口（iLovu）为53%。河口水体沉积物中的塑料颗粒浓度总体呈现出随粒径减小而递增的分布规律。若该港口区域同时存在高强度的塑料输入与滞留效应，且伴随高负荷的有机污染物与金属污染物，则该区域即便尚未成为，也极有可能演变为重大环境隐患。