Black Carbon in the Arctic

The news mention it once in a while: Black Carbon in the Arctic. This article addresses what it is, where it comes from and how it gets into the Arctic.

Air pollution does not know boarders

Some time ago, I wrote a post on ship emissions in the Arctic and their impact on air quality. Among the various gases and particles In released is also black carbon. In today’s post, I want to introduce you to black carbon in the Arctic and its potential impacts on climate, air quality and health.

What is black carbon?

Black carbon (BC) is a component of fine particulate matter with diameters of less than 2.5 micrometer often called PM_2.5. It is about 70 times smaller than the diameter of a human hair! The term black carbon refers to the strongly absorption of light in the visible spectral range. It serves as a synonym for elemental and graphitic soot. Therefore, scientists often use the term elemental carbon when discussing BC in conjunction with thermal and wet chemical determinations. The term graphitic carbon refers to graphite-like micro-crystalline structures being present that can be detected by Raman spectroscopy.

For further explanation of the terms given in bold see the High Latitude Style Glossary which opens in a new tab for your convenience.

BC has natural and anthropogenic sources

Black carbon is emitted by burning of biomass, biofuel or fossil fuels. In Alaska, BC from natural sources stems from wildfires in Alaska and Siberia. Major anthropogenic sources of BC emitted in Alaska are wood burning for heating and power generation in winter, burning of diesel by heavy equipment, diesel locomotives, diesel vehicles, and power plants, burning of coal for energy generation. Add on-shore and offshore emissions of BC from oil drilling and oil production to the mix.

Screenshot of ships in Alaska’s waters in October last year. Live Ships Map – AIS – Vessel Traffic and Positions – AIS Marine

Areas burned by wildfires in Interior Alaska since 1939

Trans-border transport of BC

Air does not know any borders. Thus, under certain weather situations, pollutants emitted by ships in the international shipping lane between Asia and North America reach Southwest or Southeast Alaska. Other weather situations bring BC emitted in northern Europe and Siberia to Alaska. For long-range transport, the BC must be lifted into the upper troposphere (higher than 5 km above ground) by the updrafts of pyro-clouds (clouds caused by wildfires) or high reaching clouds like thunderstorms. Here wind speed is very high which permits BC to travel far away from its sources despite the BC tends to fall out of the atmosphere. Think of this process like the dust that your furniture collects 😉 .

Why do we care about BC in the Arctic (and elsewhere)?

BC may affect weather, air quality and climate

Since BC strongly absorbs in the visible spectrum, it affects the energy budget of the atmosphere. Once it reaches othe ground, it also may alter the surface energy budget as it darkens light surfaces. Consequently, it has a potential impact on climate on the long term, when its concentration changes. Note that changes can be increases meaning more BC is present or decreases meaning less BC is present due to emission control measures.

BC is health adverse

Unfortunately, the hairs in our noses fail to scavenge out PM_2.5. Thus, any particles of this size or smaller can reach deep into our lungs. According to medical studies, black carbon, which is one of the components of particulate matter, itself is not toxic or health-adverse. However, during the emission process carcinogen gases or components can adhere on the carbon-particles. Thus, such contaminated  BC may lead to premature deaths according to medical studies. Medical studies also showed that long-term exposure to BC can inflame the respiratory system of children.

Black carbon in the Arctic is not just bad

The satellite image composite below shows smoke from summer wildfires. The smoke transports black carbon among other pollutants. When black carbon sediments out of the atmosphere and gets incorporated into soils. Here it acts as a fertilizer. It namely enables plants to absorb important nutrients. When I was a kid, farmers in Europe often burned their fields after the harvest for cheap fertilization.

How are Alaskans exposed

As said before, in Alaska, the exposure to BC varies by regions. The largest impacts from local sources are commercial shipping and cruise ships in the port cities, and ship emissions in the international shipping lane for coastal communities. On the North Slope, emissions related to exploration and oil production are major local sources. In the Interior, wildfires and the “let burn policy” are the major local sources in summer. Thus,

Alaska summer smell like putting your head into a fire place.

Diesel engines from various industrial sectors, energy production and residential heating are the major sources in winter. Since these sources are very localized and the impact of BC decreases strongly with the distance from the sources, Alaska’s air is still pristine in remote areas away from these major sources.

What are the major sources of BC where you live? Just curious.

When you found this post interesting invited your friends to Read this interesting post I found on black carbon in Alaska. #FocusAlaska #airquality Click To Tweet

LOTD

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References

Mölders, N. and Edwin, S. (2018) Review of Black Carbon in the Arctic—Origin, Measurement Methods, and Observations, Open Journal of Air Pollution, 7, 181-213.

When you are interested in Alaska air quality you may like to read about Fairbanks’ winter air pollution problem, or poor air quality due to wildfires that release hazardous smoke every summer.

Photos: G. Kramm

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