Humic acid accelerates polyurethane microplastic degradation via light-dark synergy, shortening degradation cycle...

In agricultural ecosystems, the accumulation of polyurethane microplastics (PuM) resulting from the long-term application of controlled-release fertilizer (CRF) constitutes an irreversible pollution-each kilogram of CRF introduces approximately 32,000 particles-and these particles are difficult to recover. This study proposes a synergistic approach: the combined use of CRF and humic acid (HA) not only increases crop yields by 12.3 %-22.4 % but also accelerates the degradation of polyurethane microplastics by 34.3 %-43.9 %, which is of great significance for addressing the dual challenges of ensuring food security and remediating soil microplastic contamination. This study also explores the interaction between HA and PuM: under dark conditions, HA facilitates radical formation through the cleavage and isomerization of C-H bonds in PuM macromolecules; under light conditions, the phenolic hydroxyl and carboxyl groups in HA moieties mediate the generation of reactive oxygen species via photoexcitation, thereby initiating the oxidative scission of PuM's carbon backbone. This research provides new ideas on how to solve the pollution of polyurethane microplastics in farmland and for the in-situ treatment of microplastics in farmland.