Insights into the horizontal and vertical profiles of microplastics in a river emptying into the sea affected by intensive anthropogenic activities in Northern China

Studies focused only on surface water may underestimate microplastic abundance in aquatic environments. This was the first survey to investigate the vertical (surface, intermediate, and bottom waters) distribution and composition of microplastics (MPs) in the water columns and surface sediments collected from an urban seagoing river in northern China. Microplastic abundance in the water columns ranged from 5.6 to 31.4 items∙L−1 and from 2141 to 10,035 items∙kg−1 dry weight (dw) in the surface sediments. Polyethylene dominated throughout the water columns to the surface sediments, in which low- and high-density polyethylene (LDPE and HDPE) were dominant in the water columns and surface sediments, respectively. The dominant shape of MPs was fibers/lines in both the water column and the surface sediment samples. Different from the estimations, the average abundance of MPs in the surface and intermediate waters was significantly lower (p