Enrichment and migration of pathogenic microorganisms and antibiotic resistance genes during a severe haze-snowfall pollution in northern China

Atmosphere serves as a significant reservoir and habitat for pathogenic bacteria and antibiotic resistance genes (ARGs). Wet deposition facilitates their entry into terrestrial ecosystems, posing potential health risks. This study investigated the harmful biological components during a winter haze-snowfall event in a northern Chinese city. The findings revealed an elevated PM_2.5 concentration of 309 µg/m³ during severe pollution, which was associated with high concentrations of water-soluble ions and microorganisms. The composition of microbial communities varied in response to the intensification of pollution leading up to snowfall. Prior to snowfall, the dominant phylum was Proteobacteria (83.2 %), with predominant genera including Sphingomonas (16.3 %), Bradyrhizobium (13.6 %), Phyllobacterium (10.6 %), Caulobacter (9.7 %) and Afipia (7.8 %). Following snowfall, the dominant phylum shifted to Bacteroidetes (38.9 %), with key genera being Prevotella (28.3 %), Aliiarcobacter (11.7 %), Staphylococcus (10.7 %), and Pseudomonas (6.9 %). Harmful bioaerosol components were enriched in snow samples, including pathogenic bacteria such as Afipia broomeae, Tsukamurella tyrosinosolvens, Escherichia coli, Aliiarcobacter cryaerophilus, Staphylococcus aureus, and Parabacteroides distasonis along with ARGs like macB, tetA (58), evgS, adeL; these accounted for up to 75 % of pathogenic bacteria present in snow water. A notable enrichment of metabolic pathways related to human diseases following snowfall events observed within clean samples post-snowfall; this increase may be attributed to enrichments occurring during haze pollution that were subsequently transported from the upper atmosphere as analyzed through air mass backward trajectories. This research provides valuable insights into the distribution patterns of pathogenic microorganisms and ARGs within particulate matter and snow samples, meanwhile elucidating preliminary understandings regarding the enrichment and migration mechanisms of high-risk bioaerosol components facilitated by wet deposition during periods of severe air pollution.