Long-term Effects of Biochar Application on Physicochemical Properties and Microplastic Accumulation in Aeolian Sandy Soils

• • Biochar application at 126.00 t·hm−2 significantly increased soil porosity and available nitrogen, phosphorus, and potassium, while reducing bulk density, enhancing soil fertility in aeolian sandy soils. • • Microplastic abundance in the 0–30 cm soil layer averaged 3459.57 pieces·kg−1, with the highest at 126.00 t·hm−2 biochar, indicating a dose-dependent accumulation effect. • • In the 30–60 cm layer, microplastic abundance averaged 3163.50 pieces·kg−1, peaking at 63.00 t·hm−2 biochar, suggesting depth-dependent transport and retention. • • Biochar application did not alter microplastic morphology; transparent, film-shaped, 0–0.5 mm particles dominated, implying biochar may facilitate microplastic retention without changing their physical characteristics.