Co-Application of Sewage Sludge, Chinese Medicinal Herbal Residue and Biochar Attenuated Accumulation and Translocation of Antibiotics in Soils and Crops

Sewage sludge (SL), Chinese medicinal herbal residues (CMHRs) and the raw materials of biochar (BC) are normally treated as wastes. However, SL, CMHRs and BC are potential candidates for soil amendments. The performances of soils amended with three different proportions (5%, 10% and 20% on a dry-weight basis) of SL-BC and SL-CMHR-BC in terms of ameliorating soil properties and attenuating antibiotics in soil–plant systems were investigated with two common crop species: carrot and lettuce. The amended soils in general showed higher nutrient levels than the control soils, and particularly for the 20% SL-CMHR-BC. The soils with 10% or 20% SL-BC or SL-CMHR-BC apparently retarded the germination performances of the two crop species, but the negative effects were not noticeable after a growing period. Six target antibiotics, amoxicillin (AMX), tetracycline (TC), sulfamethazine (SMX), norfloxacin (NOR), erythromycin (ERY) and chloramphenicol (CAP), were applied for growing the crops by using irrigation water with 3 μg L⁻¹ (IW3) and 30 μg L⁻¹ (IW30) of each antibiotic. The amended soils led to lower levels of antibiotics in the soils and crop tissues as compared with the control, with the 20% SL-CMHR-BC soils showing the most pronounced effect. The effects of the soil amendments on the bioconcentration factor (BCF) varied, but generally with lower values in the amended soils. Both SL-BC and SL-CMHR-BC were proven in the study as potential soil amendments for alleviating the environmental dispersal and human exposure risks of different antibiotics, and specifically 20% SL-CMHR-BC.