1J: Bio-aerosols and UV radiation

Bio-aerosols – biological particles suspended in the atmosphere that include pollen, fungi, and bacteria – are of interest to atmospheric sciences because of their recently recognized role as cloud condensation nuclei (esp. for ice clouds). Long-range transport of bio-aerosols has played a major role in the geographic redistribution of genetic material on evolutionary time scales, and continues to be a concern in the context of unwanted cross-pollination (esp. genetically modified crops). An important issue is whether such bio-aerosols can remain viable under exposure to ultraviolet (UV) radiation in the atmosphere. DNA molecules readily absorb UV photons and are damaged by them, leading to inactivation or cell death.  We have combined knowledge of the DNA absorption spectrum with our calculations of UV radiation to estimate the rates of DNA inactivation at various height in the atmosphere (see Figure 1). These rates compete with wind-driven transport to limit the atmospheric lifetimes and distances traveled from source regions. The modeling framework developed here parallels the computation of photochemical dissociation coefficients, and can be implemented easily in 3D regional and global chemistry-transport models.

The vertical structure of DNA-damaging fluence.
Figure 1. in the presence of clouds, at two locations (polar circle and equator) for several cloud optical depths given in legend. Dashed curves are for cloud-free conditions. Calculated with the TUV model. Click for larger image.

Reference:

Madronich, S., L. O. Björn, and R. L. McKenzie, Solar UV radiation and microbial life in the atmosphere Photochem. Photobiol. Sci., 2018. doi:10.1039/C7PP00407A