Microplastic pollution in the offshore sea, rivers and wastewater treatment plants in Jiangsu coastal area in China

Offshore areas are particularly important in recognizing microplastics pollution because they are sinks of land imports and sources of ocean microplastics. This study investigated the pollution and distribution of microplastics in the offshore Sea, rivers and wastewater treatment plants (WWTPs) in Jiangsu coastal area in China. Results showed that microplastics were widely present in the offshore area, with an average abundance of 3.1-3.5 items/m3. Significantly higher abundance was present in rivers (3.7-5.9 item/m3), municipal WWTPs (13.7 ± 0.5 item/m3), and industrial WWTPs (19.7 ± 1.2 item/m3). The proportion of small-sized microplastics (1-3 mm) increased from WWTPs (53%) to rivers (64%) and the offshore area (53%). Polyamide (PA), polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), and rayon (RA) were dominant types of microplastics. Both living and industrial sources contributed to the prevalent microplastics in the offshore Sea. Redundancy analysis showed that small-sized microplastics (1-3 mm) were positively correlated to total phosphorus (TP), while large-sized microplastics (3-5 mm) were positively correlated to TP and NH3-N. The abundance of PE, PP and PVC microplastics were positively correlated to TP and total nitrogen (TN), thus nutrients could be indicators of microplastics pollution in the offshore area.