SL-CMHR-BC soil amendment
Antibiotics are frequently used in livestock and human medicine for growth promotion, illness, and disease treatment. These compounds undergo metabolic reactions, such as hydroxylation, cleavage, and glucuronidation, in animal and human bodies. Significant fractions of antibiotics are excreted in their original form, along with the metabolised products, via urine and manure. The fate and determination of antibiotics and antibiotic resistance genes (ARGs) in the soil-plant system have become important issues for environmental and public health protection. ARGs are considered new contaminants due to their ease of retention in the soil-plant system and their potential transfer to specific soilborne phytopathogens through horizontal gene transfer in terrestrial environments. Moreover, the bioaccumulation and translocation of different types of antibiotics have been recognised as the main sources for ARG generation and propagation.
A potential solution to address antibiotic pollution in terrestrial environments involves the use of three waste-derived materials: sewage sludge (SL), Chinese medicinal herbal residues (CMHR), and biochar (BC). SL is characterised by its high organic matter content, nitrogen, phosphorus, potassium and other microelements, and the co-application of SL and BC can minimise the environmental risk as they can reduce the bioavailability of antibiotics and ARGs and promote their dissipation and degradation in the soil. CMHR primarily consists of fibrous plant materials and is carbon-rich, which aids in altering microbial communities and inhibiting the spread of antibiotics and ARGs. However, there is currently no information on the effects of co-applying SL, CMHR, and BC on antibiotics and ARGs in the soil-plant system.
Plant cultivation experiment
To explore the effectiveness of the co-application of SL-CMHR-BC, Dr Livia Pan, Lecturer in the School of Science and Technology at Hong Kong Metropolitan University, conducted a research project to determine the optimal nutrient levels and the best proportion of SL-CMHR-BC to be used as a novel soil amendment. This project also aimed to test the hypothesis that the SL-CMHR-BC amendment has an inhibitory effect on antibiotic bioaccumulation and the bioavailability of antibiotic-resistant bacteria and ARGs in soil, as well as whether it improves the physico-chemical properties of soil.
The findings revealed that the amended soils with SL-CMHR-BC had a lower level of antibiotics and corresponding ARGs in soils and crop tissues compared with the control soils without adding the soil amendment. The 20% SL-CMHR-BC soils showed the most significant effect.
Dr Pan's study is the first to evaluate the effectiveness of the co-application of SL-CMHR-BC as a new type of soil amendment. The research outcomes indicated that this soil amendment effectively addresses the antibiotic and ARGs pollution problem and improved the soil fertility in terrestrial environments. This method can help reduce the ecological risks of antibiotics and ARGs and mitigate their potential adverse effects on human health through the food chain.
This research project was supported by the Faculty Development Scheme of the Hong Kong Research Grants Council.[1] The soil-plant system amendment method and composition generated from this research was granted a Hong Kong short-term patent (no. HK30091803) in 2023.
For more details, please refer to the following publications generated from the research project:
[1] Reference No.: UGC/FDS25(16)/M02/19
