Urban drainage channels as a pathway for microplastics in riverine systems: A case study of Delhi, India

Abstract

Urban drainage channels act as significant routers of microplastics (MPs) originating from terrestrial to aquatic systems. In the present study, contamination of MPs (250–5,000 μm size) has been investigated in an interlinked urban aquatic system comprising Najafgarh drain, corresponding secondary drains, and Yamuna River in Delhi, India. A range of 100–4,300 MPs/m3 (pre-monsoon) and 100–6,700 MPs/m3 (post-monsoon) were detected in secondary drains, which meet the Najafgarh drain through its course in the city. Najafgarh drain showed an average abundance of 771 and 343 MPs/m3 during pre- and post-monsoon season, respectively. The discharge of MP-laden wastewater from the Najafgarh drain into the Yamuna River created a rise in MP abundance in the river at the drain’s downstream location. Thus, revealing that secondary drains play a significant role in MP channelization to the Najafgarh drain and subsequently Yamuna River. White MP fragments were dominating in the study area. Chemical characterization revealed 11 types of MP polymers, with a predominance of polyethylene. Considering the knowledge gap in MP database of interconnected urban aquatic systems in India, this study might help in providing baseline information and encourage more studies addressing the magnitude of this problem for predicting long-term environmental risks. HIGHLIGHTS Najafgarh and its corresponding secondary drains transport microplastic (MP) contaminants to Yamuna River, Delhi.; Fragment-type MPs were most abundant across the study area.; Dominant MP colors were white followed by blue.; Blue-colored HDPE pellets were characteristic MPs found in Supplementary drain, NG drain, and Yamuna River.; The study would help in developing a baseline MP database for this interlinked urban aquatic system.;

Keywords

• abundance
• characterization
• microplastics
• najafgarh drain
• urban drainage
• yamuna river