Dataset for "Halocline-associated microplastic accumulation in a weakly mixed estuary: Insights from the Oyabe River, Japan"

The dataset includes microplastic particle count data obtained from 1 m³ vertical water sampling at 1 m intervals from 1.0 to 5.0 m depth together with the halocline layer (for all survey dates), FTIR spectra for all detected microplastics in CSV, SPA, and JDV formats, scaled photographs of each particle, and multi-parameter water quality data measured at 10 cm vertical intervals.