Looking at the layer "Air Quality" on my iOS weather app there seem to be large circular areas of air pollution outside of large cities.

What could be the cause for such phenomena?

2021-11-02 04:00 PT


I looked at the same region after one day. The blob near Reno seems to persist. The blob in Montana nearly disappeared.

2021-11-03 02:00 PT

I could not find any incident in Montana to explain the temporary blob.

The blob near Reno has a diameter of min. 50km and is located directly over Yerington. The only incident I found in this area was on October 27. There was a car crash which could/should not be the cause for this.


The source of the weather app is linked to this: https://air.plumelabs.com/en/

Here the Plume Index is shown and the blob near Reno is clearly visible.

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    $\begingroup$ The blob near Reno could correspond to this mine although it seems to be pollutant to ground and water rather than air. $\endgroup$ Nov 2, 2021 at 13:22
  • $\begingroup$ @Jean-MariePrival thank you for the information! It seems to be linked to this region near Reno. I could find the same blob on air.plumelabs.com/en . Yet, I could not find the blob at SE of MT. $\endgroup$
    – Andy
    Nov 2, 2021 at 14:40
  • $\begingroup$ An idea of how the map is changing (if some of the blobs are persistent) might be helpful. Though I'd guess they're using some poorly produced proxy\model map and throwing up as "useful". There was a very similar question in many ways last week about high pressure blobs which showed similar issues and leaned towards similar conclusions... these "snazzy" weather apps often take quick and poor liberties on some of their "secondary" plots $\endgroup$ Nov 2, 2021 at 23:45
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    $\begingroup$ According to the archive at gispub.epa.gov/airnow, the blob started on October 27, there was nothing there before. Still can't figure out what could have triggered it... $\endgroup$ Nov 3, 2021 at 8:12

1 Answer 1


The blob near Reno Nevada is not the Anaconda copper mine, which ceased processing activities in 2000 and is currently being rehabilitated.

The blob of airborne pollution is most likely due to the gas fired power station, Frank A. Tracy, in Storey County. The Anaconda mine has co-ordinates of 38° 59' N, 119° 12'W (38.983° N, 119.2°). The co-ordinates of the power station are 39.5625°N 119.5250°W.

Regarding the blob in Montana, that coincides with the Powder River Basin, a large coal mining region. Broadus, Montana is in the southeastern corner of the State. Its co-ordinates are 45° 26' 34" N, 105° 24' 33" W (45.576° N, 105.409° W). It is located near a number of power stations in Montana, such as Colstrip Steam Electric Station with co-ordinates 45.8831°N 106.614°W.

The blob in Washington is near the town of Colville (48 N, 117 W) which is near the Boulder Park Generation Station (47 N, 117 W).

So those, significant sized, blobs were associated with power stations. The other blobs may also be due to fossil fueled power stations.

  • $\begingroup$ Your assertions seem feasible. Though it is an interesting question how such plots (presumedly daily updating since its in app) are made... are they going to the trouble to use that as input data into their plot, just tracking air stagnation in models (as it has seemed is often been done in the past to hint at pollution\smoke\CO2\etc levels)... or are they using some type of remote sensing. Something tells me such a plot didn't receive a great deal of attention in the programming\development, so I'm wondering how well it's really displaying reality. $\endgroup$ Nov 2, 2021 at 23:35
  • $\begingroup$ en.wikipedia.org/wiki/… would seem to offer a bit of doubt to your answer... as each blob is displaced a fair bit from their locations (even with wind, would think peak would be near the plant)... and other similar sized plants in Utah, Wyoming, and near the AZ\NM border aren't on the pollution image (unless they're not operating currently)? $\endgroup$ Nov 2, 2021 at 23:35
  • $\begingroup$ A cursory look at mining metals (and its history) or coal don't seem too likely either, though not conclusive. $\endgroup$ Nov 2, 2021 at 23:43
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    $\begingroup$ The blob southeast of Reno & Carson City is unlikely to be from the Tracy plant, as that's ~20 miles east of Reno. (Find the Patrick exit from I-80 on a road map.) It's in the Truckee River canyon, separated from the blob by a couple of significant mountain ranges. Might be the Ft. Churchill power plant, but otherwise there's really not much of anything near where the center of the blob is. Need to know when the map was made, and what exactly is being measured. Could be particulates off a dry lake, or smoke from a wildfire. $\endgroup$
    – jamesqf
    Nov 3, 2021 at 4:30
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    $\begingroup$ The Mason Valley Wildlife Management area also occasionally does controlled burns of undergrowth $\endgroup$
    – justCal
    Nov 7, 2021 at 5:48

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