Evaluating the role of biochar aging in pesticide dynamics in a continuous cropping soil-celery system

Pesticide residues in agricultural soils present a potential risk to the safe production of celery. Biochar (BC), is a promising soil amendment with the potential to mitigate these risks. However, its long-term environmental effects, particularly in continuous cropping systems, require further examination. This study investigates the effects of BC aging on the dissipation and translocation of chlorpyrifos and pendimethalin in soil and celery (root, shoot, and leaf) based on continuous three-crop field trials (a total of 144 days). BC application consistently delayed the dissipation of both pesticide in three crops soil, increasing their average concentrations by 7.19-35.1 % compared to unamended controls. For the first crop (short-term effect), fresh BC application reduced both pesticides residues in roots and edible parts (stems and leaves) by 19.6-25.6 % and 9.02-20.9 %, respectively. However, for the second and third crops (long-term effect), aged BC promoted translocation of both pesticide from soil to edible parts, resulting in 9.72 %-32.1 % higher residues than the control. Risk assessment results demonstrate that long-term exposure of BC increased the risk quotient in edible parts. These findings highlight the ecological risks associated with aged BC and provide a basis for optimizing BC application strategies in agricultural fields.