Biochar reduces the bioavailability of di-(2-ethylhexyl) phthalate in soil

• Biochar increases the retention of di-(2-ethylhexyl) phthalate (DEHP) in soils.
• High soil organic carbon content can decrease the bioavailability of DEHP.
• Biochar significantly decreases the potential risk of human uptake of DEHP.
• Effect of biochar on DEHP fate depends on soil organic carbon content and biochar types.

A pot experiment was conducted to evaluate the effect of biochars on the bioavailability of di-(2-ethylhexyl) phthalate (DEHP) in two soils using Brassica chinensis L. as an indicator plant. The residual concentrations of DEHP tended to be higher in the biochar-amended soils than in the control soils. They were lower (p < 0.05) in the high organic carbon content soil (HOC; 2.2%C) than in the low organic carbon content soil (LOC; 0.35%C). The DEHP concentrations in plant shoots grown in the HOC soils were lower than those in the LOC soils (p < 0.05). Compared to the control, the biochar addition decreased the DEHP concentrations in shoots grown in the LOC soils; whereas there was no significant difference in the HOC soils. Our results showed that soil OC content as well as biochar properties are the key factors influencing the bioavailability of DEHP in soils.