Biochar amendment affects the fate of phthalic acid esters in the soil-vegetable system

Phthalates, e.g., esters of phthalic acid (PAEs), when used as plasticizers due to weak physical bonding with polymer matrix favoring leaching, are widely noted in the environment. Their confirmed toxicity to plants and animals implies that their fate should be monitored in the environment, especially when considering the interaction between soil and vegetables. Removal of PAEs from the environment or limiting their bioavailability is a key point in reducing their harmful effects. In the present paper, the fate of six PAEs in the biochar-amended soil during the cultivation of two popular vegetables, lettuce, and radish, was estimated. High bioaccumulation in the soil was noted with the biochar obtained from residues from biogas production being up to 15% higher than in the case of the other biochar and up to 10 times higher than in plants due to increased basic character of biochar. This biochar reduced the bioavailability of DEP (diethyl phthalate), DBP (dibutyl phthalate), BBP (butyl benzyl phthalate), and DNOP (di-n-octyl phthalate) in radish roots and DBP in lettuce leaves. However, PAEs significantly increased the fresh mass of radish and slightly increased the mass of lettuce. All six tested PAEs in both plants reached higher concentrations in the leaves (up to two orders of magnitude) than in the roots. Additionally, PAEs were present in two times higher concentrations in the lettuce than in the radish. The biochar aromaticity, porosity, and the presence of organic carbon and inorganics (ash) affect the fate of tested pollutants depending on the tested plant and compound.