The effects of amendments on cd and pb under different fertilizer application conditions.

Fertilizer application is a common agricultural practice that enhances soil fertility but can also increase heavy metal mobility in contaminated soils. This study used a pot experiment with four vegetables (water spinach, Chinese cabbage, lettuce, and garland chrysanthemum) to evaluate the impact of BC, ZE, and their combination (CO) on Cd and Pb levels under different fertilization schemes. Results showed that CO treatment significantly enhanced enzyme activities, increasing urease by 2.6-31.6% and catalase by 1.37-14.24% under varying fertilizer conditions. However, sucrase activity increased only with compound fertilizers. The use of compound fertilizers alone raised Cd and Pb levels in vegetable shoots by 0.65 mg·kg⁻¹ and 12.76 mg·kg⁻¹, respectively, while the CO amendment effectively mitigated these increases. BCR sequential extraction indicated that BC and CO shifted Cd and Pb into more stable soil fractions, reducing their bioavailability. Specifically, CO reduced Pb accumulation in shoots by 24.8-49.7%, with BC showing particular efficacy in reducing Cd levels. These findings highlight that BC and ZE, particularly in combination, offer an effective strategy for remediating heavy metal-contaminated soils in agricultural systems, especially when chemical fertilizers are used.