Questions & Answers: Air Pollution
The following are questions asked of ACMP scientists and the answers they provided. Click on the question at the top to jump to the answer below.
- How did you discover that our air in the springtime comes from the Gobi dessert?
- What is Arctic Haze?
- How much pollution do we get from Russia and Asia?
- Is the air pollution transported from Russia and Asia something we should be concerned about, specifically when it comes to subsistence food?
- How big is the unmanned aerial vehicle (UAV) that the air sniffers will be on?
- Why are scientists seeing more pollutants in Canada than here in Alaska?
Different soils have different fingerprints; they each have different amounts of different types of elements in them, so their characteristics are like individual people's fingerprints. The Gobi Desert in Mongolia has a different fingerprint than the Taklamaken Desert in China, which has a different fingerprint than the Sahara Dessert in Africa.
In Alaska, we were seeing this dust come in every spring on the satellite images. In the satellite images, you can see a cloud of yellowish-brown dust coming across the Bering Sea and into Alaska. At that point in the year, Alaska is still snow covered. On the image, you can see beautiful white Alaska and this brown cloud coming in.
If you use an air sampler and collect a sample of that brown cloud and look at it chemically, you can see that fingerprint. The fingerprinting matches the fingerprint of the Gobi desert, so chemically this dust is the same as the Gobi desert. So the question is how did it get from the Gobi desert to here in Alaska. And the answer is the wind. We do what's called meteorological back trajectory modeling, which is a fancy way of saying you find out where the air has come from. I use a model called Hysplit. Hysplit lets me determine where the air from a particular region was 6 hours ago, and 6 hours before that, and so on. With that model, I can see that the same that air passes over the Gobi dessert, passes over Alaska.
Now, I know that the fingerprint of the dust is the same as the Gobi Desert, I can see from the satellite image that dust is traveling over Alaska from the general direction of the Gobi Desert, and the model shows me that the winds are coming from the Gobi Desert. From all three of those things, I can say, yes, this is Gobi Desert dust and it has been blown here to Alaska. That dust usually reaches us in the spring, between March and June. - Cathy Cahill
Arctic Haze is a different kind of pollution that dust. Dust pollution is natural. Arctic Haze is a layered black haze you tend to see in the Arctic. It's mainly produced from industrial emissions such as power plant emissions and metal smith emissions, typically from Northern Russian and Northern Europe. The power plants produce clouds of pollution that is transported around the pole by the wind. You can see it come across as a black set of layered hazes coming over the fairly clean Arctic environment. The clouds of pollution contain metals and other materials that act as fingerprints in the same way that dust has a fingerprint. By looking at the composition of the pollution, one can determine where it came from.
In Alaska, we see Arctic Haze every winter. The power plants emit directly into what we call the polar air mass. During the winter, there's a great big cold mass of air that sits right over the pole. It often comes down as far south as the Aleutians. This cool air mass is very stable, so it tends to just go around the pole. It generally goes from West to East, so stuff that is emitted West of us, in places like Russia, go around the pole and cross over Alaska, then hits Canada, and then Greenland, before going back over Europe.
Arctic Haze was one of the first pieces of evidence scientists had for the fact that something in the air could be transported a very long distance. Things 1,000 miles upwind can still influence an area. Arctic Haze occurs in the winter, from November through March. - Cathy Cahill
Alaska is downwind of Russia and Asia, so whatever they put up into the air, we end up breathing. Arctic Haze is Russian pollution coming to us. From Asia, we get dust storms, but the dust storms aren't all of it. The dust in Asia travels over the cities in China, and as it does, it picks up a lot of junk and transports it to Alaska. The compounds in the dust tell us where it originates from, but we also see a lot of pollution. We see pollution from China, Japan, Korea, India and Southern Russia. We can tell where the pollution originates from based on what type it is. For example, we see things like pesticides that we don't use here, and the only place that uses them is India, so we know that air is coming across India. - Cathy Cahill
Is the air pollution transported from Russia and Asia something we should be concerned about, specifically when it comes to subsistence food?
We are actually very concerned about long-range transported pollutants, because the stuff coming in from Russia has heavy metals including mercury and lead that we know are hazardous to human health. As the air is transported in, some of it falls out onto the ground. Once it falls out, it gets on plants, and animals eat the plants, and we eat the animals, and so we end up eating some stuff that we really don't want to be eating.
Subsistence foods, which usually are very good for you, are getting these heavy metals in them, and these are things we don't want people exposed to. However, it's difficult to just stop the pollution because it is coming from Russia, not within the United States. The United States can't force Russia to follow its regulations. A lot of scientists and politicians are working internationally to convince other countries to reduce their emission so that we can have healthier air and healthier subsistence foods, but it's a difficult process. - Cathy Cahill
The UAV that is built by the University of Alaska Fairbanks, which carries the air sniffers, has a wingspan of 10 feet and can carry approximately 5 pounds. There are other UAVs; the military makes a UAV called a predator that can carry several hundred pounds. When I'm building a instrument, it is important for me to know what size UAV I'm going to be using so that I can make sure the instrument is the appropriate size. - Cathy Cahill
There are two reasons that the air pollutants are worse in Canada than Alaska. The first reason has to do with the air transportation. The Bering Sea protects Alaska somewhat by warming it. The warmth of the air forces the air mass North during the winter. In Canada, they do not have anything forcing the air North, so they get more pollution from the air.
There is also a thing called the grasshopper effect. A pollutant cools and condenses and deposits on the ground. When it warms up, it will go back into the atmosphere, transport until it gets further north and cold again, deposit again, and so on. If you happen to be fairly far north, once it deposits, it never comes back up and it enters the food chain. Here in Alaska, where it is a little bit warmer, some of those pollutants are put back into the atmosphere. - Cathy Cahill