Molecular insights into microbial transformation of bioaerosol-derived dissolved organic matter discharged from wastewater treatment plant

Wastewater treatment plants (WWTP) are important sources of aerosol-derived dissolved organic matter (ADOM) which may threaten human health via the respiratory system. In this study, aerosols were sampled from a typical WWTP to explore the chemical molecular diversity, molecular ecological network, and potential toxicities of the ADOM in the aerosols. The high fluorescence index (>1.9) and biological index (0.66-1.17) indicated the strong autogenous microbial source characteristics of the ADOM in the WWTP. DOM and microbes in the wastewater were aerosolized due to strong agitation and bubbling in the treatment processes, and contributed to 74 % and 75 %, respectively, of the ADOM and microbes in the aerosols. The ADOM was mainly composed of CHO and CHOS accounting for 35 % and 29 % of the total number of molecules, respectively, with lignin-like (69 %) as the major constituent. 49 % of the ADOM transformations were thermodynamically limited, and intragroup transformations were easier than intergroup transformations. Bacteria in the aerosols involved in ADOM transformations exhibited both cooperative and divergent behaviors and tended to transform carbohydrate-like and amino sugar/protein-like into recalcitrant lignin-like. The microbial compositions were affected by atmosphere temperature and humidity indirectly by modulating the properties of ADOM. Tannin-like, lignin-like, and unsaturated hydrocarbon-like molecules in the ADOM were primary toxicity contributors, facilitating the expression of inflammatory factors IL-beta (2.2-5.4 folds), TNF-alpha (3.5-7.0 folds), and IL-6 (3.5-11.2 folds), respectively.