Pollution Characteristics And Spread Mechanism Of ARB And ARGs Carried By PM_2.5 In Handan

As a new environmental pollutant,antibiotic resistance genes（ARGs）pose a potential threat to public health.In particular,multiple resistant pathogens caused by excessive use or abuse of antibiotics pose serious challenges to clinical treatment.Due to the mobility of atmospheric reservoir for ARGs,antibiotic resistance bacteria（ARB）carrying ARGs can produce dormant bodies to keep alive for a long time and spread globally.However,the role of PM_2.5 in the spread of ARGs remains unclear.In this paper,investigates the source,spread and fate of ARB and ARGs loaded by PM_2.5 in the atmospheric environment of Handan City,a Province of Hebei,and the transmission characteristics and diffusion mechanism of airborne ARGs were discussed.First of all,the abundance of ARGs carried in PM_2.5 collected by a rainfall event was quantified,and microcosmic experiments were carried out in the laboratory to reveal the propagation and diffusion mechanism of ARB and ARGs from atmosphere to the soil using rainwater as the carrier.The results show that ARGs and Mobile Genetic Elements（MGEs）detected in PM_2.5 and rainwater during rainfall were significantly higher compared with before and after rainfall（up to 32 times）.The abundance of airborne ARGs during the rainfall event was positively correlated with the frequency of wind speed and direction changes.In addition,studies on soil after rain treatment showed that the abundance of ARGs and MGEs increased with time and the soil containing heavy metals was more effective.Meanwhile,after 20 days of experiment,the indigenous microorganism in rainwater treatment group had stronger antibiotic resistance than the soil treatmented by sterile water,which confirmed that ARGs and MGEs were horizontally transferred from rainwater to soil.This research provides a way of source of ARGs in remote areas with few human activities.Furthermore,the abundance of airborne ARGs in four seasons were detected in Handan,a city in southern Hebei Province.Correspondingly,the air mass trajectory of the four seasons was simulated based on the HYSPLIT software,and the results were statistically analyzed by the Potential Source Contribution Function（PSCF）and the Concentration Weighted Trajectory（CWT）to reveal the seasonal distribution characteristics and potential contribution sources of ARGs.Based on the positive correlation between ARGs and PM_2.5 concentration,the measurement methods of ARGs _releaseelease and airborne ARGs _delivery were proposed.Research showed that 90%of ARGs had the highest abundance in winter（25.2-818.9 copies/m³）and the lowest in summer（7.1-507.3 copies/m³）.The analysis combined with backward trajectory shows that the difference in air mass source in the study area is the main factor leading to the variable air pollutants at the sampling point.In the winter,the high concentration of PM_2.5 from North China provides the nutrients needed for microbial growth,as well as the residual antibiotics in the area covered by air mass synergizes with heavy metals that make up the air pollutants produce selective pressure for horizontal transfer of ARGs,so that high levels of ARGs were detected in winter.In the summer,the clean ocean air mass dominates the atmosphere of the sampling point.As a result of the variable ocean weather,the air pollutants rapidly diffuse.Low contribution of ARGs in the potential sources to the sampling points,resulting in the overall abundance of ARGs maintain a low level in summer.The changes in the ARGs abundance and antibiotic resistance of indigenous microbial in the soil after invaded by microorganisms in rainwater were described in this paper,and trace the source of ARB and ARGs in the atmosphere.The study has significant significance for a comprehensive understanding of the long distance transmission and fate of ARGs in the atmospheric environment,and is helpful to provide a theoretical basis for the prevention and control of ARGs in the atmospheric environment.