Saturday, February 10, 2007

Shreveport Louisiana Update: Very "Sooty" at 6pm

Click on photo to enlarge.

As the sun sets, you can really make out the rush hour traffic haze in this area of town not far from the interstate. The surface winds are from the NE and therefore everything from Bossier City 3-4 miles away is headed towards us here in the middle of Shreveport. We unfortuneately moved to almost dead center of town....the worst possible place to be generally, unless your city has a good strong prevailing wind pattern, in which case you'd want to be upwind of course. In general, surface winds may vary throughout the year from all directions (google: "Wind Roses" for your city's prevailing winds), but the higher level winds play a larger role in your exposure since for most of us here in the Northern hemisphere, the upper-level (or Jet Stream) winds almost always blow from the West, and therefore we here in Louisiana often get our auto/coal plant exhaust soot from Texas (population 22 million vs our meager 4.5million in LA). Throughout the US, the background or regional contribution to your soot/particulate matter (pm2.5) seems to be about 30%, from what I've read.

We felt pretty good most of the day with local pm2.5 levels about 5-8ug's I'd estimate, but after the rush hour at about 6pm the headaches started and did not get better till about 9 or 10pm. We both get pretty cranky when these peaks occur..sort of like how you'd feel after smoking a fat nasty cigar...if you've ever had the pleasure.

The rush hour peaks like the one i'm in now here near the center of a city can hit 20-30ug's quickly and usually drop back down by 7 or 8pm, but not allways. If the winds die down, then here in the river flats encompasing most of Shreveport, we can get a settling of haze forming Smog overnight similar to what you'd see in valleys of mounainous areas with the surrounding highlands having cleaner air quality and lack of smog. Now in Karnack Texas (about 15 miles NW of Shreveport) we are up to 8 ug's from a low of 5 today at noon. A while back I looked at the raw hourly pm2.5 data for Shreveport and compared it to Karnack, and found an average 3 ug increase for Shreveport proper. This is helpful since our monitor here in Shreveport sadly does not report the actual numeric value of pm2.5 levels...only a color coded system that only alerts you to levels over 20ug's/m3. The Karnack monitor location, historic and hourly data is here.

Being 3 miles from Interstate 20, I found this list of articles on the Health Effects of Deisel exhaust quite alarming!


At 2/10/2007 9:27 PM, Anonymous Evonne Turner said...

The additional car exhaust around 5 & 6 o'clock probably explains why I have headaches after driving home from work.


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