There was an overall trend towards higher abundance of MPs in sampling sites in the lower and tidal-influenced reaches of the River Barrow, with the four highest MP numbers occurring within the five sampling locations in the lower catchment areas.
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The sentences
Wastewater discharges are well established as sources of MPs ( Tibbetts et al., 2018 ), and the abundance of fibre morphology across all sampling locations, as represented in Figure 2 , suggests that secondary MPs from clothing wear via laundry water discharges are likely to be significant contributors to the overall MP abundance in many locations.