Distribution Characteristics of Typical Antibiotics in Reclaimed Water Infiltration Area and Influencing Factors of Groundwater Microbial Community

Antibiotic pollution carried by reclaimed water infiltration is one of the sources of groundwater pollution, which has become a problem that cannot be ignored in the safety of urban groundwater resources. The effects of antibiotics on microbial communities and their functions in complex and fragile groundwater environments deserve attention.

To explore the differences of groundwater environmental factors in different seasons and the distribution characteristics of antibiotic pollution, and to explore the influence mechanism of antibiotics on a microbial community.

Based on the high-throughput sequencing method of 16S rRNA gene, the microbial community structure in urban groundwater in the infiltration area of reclaimed water in March and September was studied. Combined with field investigation and indoor analysis, the ion (K⁺, Na⁺, Ca²⁺, Mg²⁺, NH₄⁺, F^-, Cl^-, SO₄^2-, NO₃^-, NO₂^-, HCO₃^-, CO₃^2-) concentration in the sample was measured, and the main antibiotic (ciprofloxacin, norfloxacin, ofloxacin, moxifloxacin, sulfapyridine, sulfacetamide) concentration was measured by ultra-high performance liquid chromatography-tandem mass spectrometry.

(1) In the study area, the concentration of antibiotics in groundwater in March was higher than that in September, mainly sulfacetamide and ciprofloxacin. In addition to seasonal factors, human activities may be another factor affecting the distribution of antibiotics. (2) The microbial community was mainly composed of Proteobacteria (81.04%), Bacteroidota (7.60%), and Firmicutes (4.21%). 3-nitrogen (NH₄⁺, NO₃^-, NO₂^-) and antibiotics were important factors affecting the microbial community structure in the study area. Different antibiotics had different effects on the microbial community. Among them, sulfapyridine, norfloxacin, ofloxacin and moxifloxacin had the greatest impact on microorganisms, while ciprofloxacin and sulfacetamide had less impact. (3) Co-occurrence network analysis found that the two dominant functional groups had a high degree of connection with antibiotics, namely, antibiotics had a potential impact on the main microbial functional groups and their functions in the study area.

The study provides support for understanding the impact mechanism of antibiotics on a groundwater microbial community and the ecological risk.