Effects of biochar on tire wear particle-derived 6PPD, 6PPD-Q, and antimony levels and microbial community in soil.

Although several studies have documented tire wear particles (TWP)-contaminated soil could increase N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine (6PPD), 6PPD-quinone (6PPD-Q), and antimony (Sb) levels, despite this, effective strategies to address the problem are still lacking. This study focused on mitigating environmental risks from TWPs, a significant but overlooked contaminant. We examined the impact of biochar (BC) on TWP contamination at different soil moisture levels. 6PPD levels in TWP-amended soil peaked at 4.239 µg/g by day 60 in flooded conditions. BC amendments reduced 6PPD and 6PPD-Q concentrations by 85-90 % in both conditions. BC also reduced Sb(III) and Sb(V) levels by 80-83 %, while boosting dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) levels by up to 75 %, improving soil fertility. Our results showed that 6PPD and 6PPD-Q exposure altered bacterial composition, with Desulfobacterota and Planctomycetota thriving in flooded conditions, while Gemmamonadota and Verrucomicrobiota declined in 50 % water holding capacity (WHC). Key results indicated a strong reduction in alpha diversity under 50 % WHC, while treatments with MBc400 maintain higher biodiversity, as indicated by the Shannon index, and higher species richness, shown by the Chao index, especially in 50 % WHC. These results implied that higher-temperature BC effectively reduced 6PPD, 6PPD-Q, and Sb bioavailability while mitigating TWP contamination by enhancing microbial diversity, especially under 50 % WHC.