Theoretical analysis for bacteria participating in atmospheric nucleation

Particulate Matter with aerodynamic diameter smaller than 2.5 mu m (PM2.5) especially those with toxic bacteria can heavily damage the human physiological system, and lead to respiratory and cardiovascular disease. Although the biological species is widely observed in aerosol particles, the current knowledge has not clearly clarified why and how that happens. Herein, the ab initio calculation of the interaction between bacteria molecule and inorganic aerosol precursors (i.e., Sulfuric Acid SA, Nitrite Acid NA and Ammonia AM) is conducted, to investigate the potential role of bacteria in atmospheric nucleation. Typical bacteria Gram-positive (G+) bacteria and Gram-negative (G-) bacteria are usually with diameter at similar to 1 mu m, which can initiate heterogeneous nucleation with SA, NA or AM by serving as pre-existing surface. Hydrogen bond (H-bond) is found to be formed and represents the driven force for the heterogeneous nucleation. The enhanced heterogeneous nucleation by bacterium can contribute to secondary aerosol particles. Geometrical analysis shows that the aggregation between bacteria molecule and the SA is the most stable, which bears two H-bond and processes a cyclic structure. Thermochemical analysis indicates no matter the bacteria molecule belongs to G+ or G-, it would prefer to aggregate with the SA, followed by the NA and AM. And the G+ bacteria is relatively more active to aggregate with inorganic precursors compared to G- bacteria.

Automated summary

The study reveals that bacteria molecules can serve as heterogeneous nucleation sources for aerosol particles, aggregating on the surfaces of inorganic aerosol precursors like sulfuric acid, forming hydrogen bonds to drive heterogeneous nucleation and contribute to the formation of secondary aerosol particles.