Aging Dynamics of\nPolyvinyl Chloride Microplastics\nin Three Soils with Different Properties

Microplastic (MP) contamination in soil has been of great\nconcern,\nbut the dynamic aging process and potential pathways of MPs in natural\nsoil systems remain poorly understood. Herein, poly(vinyl chloride)\nmicroplastics (5% w/w) were weathered for 12 months in sandy soil,\nsilty clay, and silt loam. The results showed that the continuous\nincrease of CO and O–H groups (rate constant, <i>k</i> = 0.080–0.424 m<sup>–1</sup>) with time\nwas observed on the surface of MPs aging in sandy soil due to the\nleading role of <sup>•</sup>OH induced by light irradiation.\nIn the loam soil, the abundant coating of aluminosilicates and iron\noxides on the MP surface by the formation of mineral-hydroxyl groups\ninhibited the generation of the CO group (<i>k</i> < 0.165 m<sup>–1</sup>). The <i>k</i> of the\ncharacteristic bond C–Cl during the first 9 months was 9.51\nand 1.93 times higher in clay compared to that in sandy and loam soil,\nrespectively, revealing that dechlorination triggered the first step\nof the aging process for MPs in clay owing to the participation of\ndegrading bacteria (Phenylobacterium and Caulobacteraceae). The results\nprovide important insights into the aging dynamics of MPs in environmentally\nrealistic circumstance, which account for understanding the different\naging processes of MPs in different soils.