Pollution caused by antibiotics and antibiotic resistance genes (ARGs) has drawn a lot of attention in recent years. They can affect the ecosystem and be transferred to specific soilborne plant pathogens through horizontal gene transfer, thus entering the food chain and endangering human health. A research team from Hong Kong Metropolitan University (HKMU) has developed a unique soil improvement formulation, known as “3-in-1 Soil”, which improves soil quality by significantly reducing the bioavailability of antibiotics and ARGs in the soil to address the risk of antibiotic and ARG contamination in the terrestrial environment.

Antibiotics are biologically active substances that are widely used in the treatment and prevention of diseases for humans and livestock, as well in promoting livestock growth. Antibiotics and their metabolites are discharged into the environment through animal feces and factory wastewater. If they infiltrate farmland, these antibiotics will enter the soil environment and crops grown in the soil, causing further contamination. Given the increased use of antibiotics, there is great concern about the potential environmental contamination caused by antibiotics and their corresponding ARGs. They have the potential to affect plant growth and productivity, and lead to the bioaccumulation and transportation of antibiotics in plants. Soil pathogens may also acquire resistance to antibiotics through gene transfer, thus further contributing to the accumulation of antibiotics in the food chain and adversely influencing human health and the safety of the ecosystem.

Dr Livia Pan and her team at the School of Science and Technology of HKMU developed the “3-in-1 Soil” soil amendment formulation, which is a mixture of three waste-derived materials – sewage sludge, Chinese medicinal herbal residue and biochar – which can be added to the soil to enhance the nutrient content of the soil, significantly reduce antibiotic concentrations in the soil and the bioavailability of ARGs, and promote their degradation, thus improving the soil quality.

Sludge is rich in nitrogen, phosphorus, potassium and other essential elements for soil and crops; Chinese medicinal herbal residue is composed of plant fibre and is thus rich in carbon; and biochar can improve microbial communities in the soil. To determine the golden formula for its “3-in-1 Soil”, Dr Pan and her team conducted multiple trials to test the growth of different crops. The results showed that adding 20% of the formulation to the soil was the most effective, increasing the soil nutrient content and significantly reducing the amount of antibiotics and ARGs in the soil.

Dr Pan said, “In this research project, we mixed various types of environmental waste as soil conditioners and found that the “3-in-1 Soil” formulation can most effectively reduce the bioavailability of antibiotics and ARGs in the soil, while significantly improving the soil quality to provide an ideal growing environment for crops. In the future, the team will continue to optimise the formula to further improve its effectiveness”.

The research was supported by the Research Grants Council's Faculty Development Scheme, and it was granted a short-term patent in Hong Kong. The University looks forward to continuing to publish research results in different areas to give back to the community through scientific research.