What does a paper on air pollution have to do with pollen movement?

Air pollution reduces visibility in Benxi, China. Photo by Susannah Tysor.

Recently, some mathematicians at Arizona State and Notre Dame modeled how wind moves pollutants around in a city. Liat Clark summarizes their findings nicely. Basically, if you look at air movement over a long period of time, you find that most of the pollution ends up in a few predictable places. This is important for city planning – if you can figure out how the physical structure of your city interacts with the wind to distribute pollution in the city, you can prevent or fix pollution ‘hotspots.’

I’m studying pollen, not air pollution. But the technique this paper uses could be very useful for me. Like air pollutants, pollen are tiny particles carried along by the wind. I’m trying to figure out how similar patterns of pollen travel are every year – does population A send pollen to population B every year, every 10 years, every 50 years, never? This paper suggests that at least at small scales (the size of a city), pollen movement will be highly structured and similar year to year.

The geometry of inertial particle mixing in urban flows, from deterministic and random displacement modelsPhys. Fluids 24, 063302 (2012)http://dx.doi.org/10.1063/1.4729453