The effects of riverside cities on microplastics in river water: A case study on the Southern Jiangsu Canal, China

Microplastics, which are usually recognized as artificial polymer particles with a particle size <5 mm, have attracted much attention as new pollutants in recent years. Urban areas are a major contributor of microplastics to the environment, but their microplastic emission intensity and characteristics are not clear. In this paper, the microplastic abundances and characteristics in the Southern Jiangsu Canal were studied to reveal the effect of riverside cities on microplastics in river water. The results show that the microplastic abundance in the water body of the South Jiangsu Canal ranges from 3.41 to 19.07 particles L^-1, with an average of 9.59 ± 3.95 particles L^-1, which is at the same level as major urban agglomerations in the world. The top five polymers were polyethylene terephthalate (PET), polycarbonate (PC), polyethylene (PE), chlorinated polyethylene (CPE) and polyurethane (PU). Fragments accounted for the largest proportion (68.47 %), followed by beads and fibers. Most microplastics were <100 μm (83.87 %). Human life and industry in riverside cities contribute significantly to microplastics in the Southern Jiangsu Canal water. After flowing through the cities, the microplastic abundance in the canal water increased by 26 % ~ 211 %. The overall economic and social development of the city affects the occurrence characteristics of the canal water microplastics. The average abundance of microplastics was positively correlated with Regional Gross Domestic Product (GDP) per capita. Wastewater treatment plant effluent is an important point source of microplastics in canal water. The microplastic abundances downstream of WWTPs increased by 21.8 % ~ 64.6 % compared with those upstream.