Riparian sediment is a hot zone for denitrification that can withhold copper and microplastics (MPs) from outside. It has been proven that MPs affect denitrification and the existing forms of copper in the environment. However, the impact of copper on sediment denitrification under exposure to MPs remains unclear. This study revealed the response of sediment denitrification to copper availability under the adsorption of MPs and the complexation of MP-derived dissolved organic matter (DOM). These results showed that MP accumulation inhibited denitrification. However, aged MPs increased the activity of nitrite reductase (12.64%), nitrogen dioxide reductase (37.68%), and electron transport (28.93%) compared with pristine MPs. The aging behavior of MPs alleviated 28.18% nitrite accumulation and 16.41–118.35% nitrous oxide emissions. Thus, the aging behavior of MPs alleviated the inhibition of denitrification. Notably, we resolved the copper ion adsorption and complexation by MPs, MP-derived DOM contributed to the denitrification process, and we found that the key nitrogen removal factors were affected by K_L, K_M, and K₂. These results fill a gap in our understanding of biochemical synthesis of MPs during denitrification. Furthermore, it can be used to build a predictive understanding of the long-term effects of MPs on the sediment nitrogen cycle.

河岸沉积物是反硝化作用的热区，可以阻止外部的铜和微塑料 (MP)。已经证明，MPs 会影响反硝化作用和环境中铜的存在形式。然而，铜对 MPs 暴露下沉积物反硝化作用的影响仍不清楚。该研究揭示了在 MPs 吸附和 MP 衍生溶解有机物 (DOM) 络合下沉积物反硝化对铜可用性的响应。这些结果表明，MP 积累抑制了反硝化作用。然而，与原始 MPs 相比，老化 MPs 增加了亚硝酸盐还原酶 (12.64%)、二氧化氮还原酶 (37.68%) 和电子传输 (28.93%) 的活性。MPs 的老化行为减少了 28.18% 的亚硝酸盐积累和 16.41-118.35% 的一氧化二氮排放。因此，MPs的老化行为减轻了对反硝化作用的抑制。值得注意的是，我们解决了 MPs 对铜离子的吸附和络合，MP 衍生的 DOM 对反硝化过程有贡献，我们发现关键的脱氮因素受 K 的影响_L、 K _M和 K ₂。这些结果填补了我们对反硝化过程中 MPs 生化合成理解的空白。此外，它可用于建立对 MP 对沉积物氮循环的长期影响的预测性理解。