odd CO2 in Salt lake city

While i was doing some research on CO2 concentrations i came upon something rather odd.
NOAA CO2 Maps

when looking at a map of north america there where higher concentrations in unexpected places. places like Phoenix, Orlando area , and Las Vegas with extreme population and traffic and large industrial zones would show up much like LA and Houston. but that isn't the case

There are also strange areas around Salt Lake and Amarillo that show unusually higher CO2 concentrations then the surrounding area, and more then one would expect from that area.

While the maps are good there variance is only ~4ppm so most graphs have max's and Min's that go past the extreme of the chart.

any ideas?