Tuesday, December 9, 2014

A Game Changing Look at Pollution in the Salt Lake Valley

Regular readers of this blog know that I believe we desperately need more real-time air quality monitors in the Salt Lake Valley (see Inversion Snippets from 23 Jan 2013 for example).

I'm pleased to report that some of my colleagues have taken the bull by the horns and have placed weather and air quality instruments on a Utah Transportation Authority (UTA) TRAX train system.  This will provide an unprecedented look at PM2.5 concentrations in the Salt Lake Valley and along transects running up the west and east benches.

Here's a look at the data coming in this morning.  PM2.5 concentrations this morning are lowest on the west bench (light green circles) and highest from roughly 4500 South to 2100 South (yellow circles).

Source: http://meso1.chpc.utah.edu/mesotrax/
Another perspective is provided by the time series below showing measurements over a 3-hour period.  The cyan line is pressure.  When it's high, the train is along the valley floor and when it is low it is on a bench (probably the west bench in this instance).  The violet line is PM2.5.  Note how the PM levels are more elevated when the train is on the valley floor than on the west bench.

Source: http://meso1.chpc.utah.edu/mesotrax/
It will be very interesting to look at this data during inversion events this winter.  I suspect we will see many cases where the benches have better air than the valley floor, but perhaps some periods when that's not the case.  In addition, it will be interesting to see how the air quality varies along the valley floor.  The Utah Division of Air Quality provides real-time trends only for a station at Hawthorne Elementary School.  We may find that there are areas with worse air quality (it's too bad the train doesn't run right past Hawthorne for a better comparison).

For a look at the Trax PM2.5 data, see http://meso1.chpc.utah.edu/mesotrax/.  This is an experimental product, so there will be periods when data is not available.


  1. This is fantastic! Thank you and kudos to UTA for allowing this equipment to be on board TRAX.

  2. Agreed, very cool.

    I'm intrigued by the pointy bits on the graph above (noise in the data?). Is the sensor sensitive enough (and fast enough) to pick up the clouds of pollution that form when clusters of cars stop for the train?

    1. I think those are probably real (they are also fairly small and ~2ug/m3 in amplitude). PM2.5 tends to be fairly spiky.

  3. Great idea, we need a second opinion.