Environment

Atmospheric acidity almost back down to preindustrial levels

After increased industrialization in the 1930s, atmospheric acidity levels rose up sharply to a peak in the 1970s, but 40 years after the US and Europe introduced legislation to combat air pollution, acidity in the air has now dropped back down to pre-1930 levels. These figures come out of research by the University of Copenhagen, which used a new technique to measure the pH balance of ice core samples from the Greenland ice sheet, and how it's changed year to year.

In an area as cold as Greenland, the snow that falls never has a chance to melt. Instead, every year a new layer forms over the top of the previous one, which eventually packs into a tightly compressed layer of ice. With each layer preserving a record of the climate and atmospheric conditions of the time, the Greenland ice sheet provides scientists with a time capsule dating back over 100,000 years.

The problem with looking at samples of the layers in the top 60 m (200 ft), representing the last 100 years, is that they are still relatively fresh and porous. Since it hasn't yet compressed into hard ice, it's more difficult to analyze, which is unfortunate because this past century is of particular interest to researchers looking into the human impact on the climate.

Building on a technique called Continuous Flow Analysis – where water from a piece of melting ice core is analyzed for chemical impurities – the research team at the University of Copenhagen's Niels Bohr Institute (NBI) has developed a new way to study the acid concentration of that upper portion using a spectrometer, providing near-instant analysis of the melting ice.

"We have an ice rod that is cut along the length of the ice core," says Helle Astrid Kjær, lead author of the study. "This ice core rod is slowly melted and the meltwater runs into a laboratory where they take a lot of chemical measurements. With our new method you can also measure the acidity, that is to say, we measure the pH value and this is seen when the water changes color after the addition of a pH dye. We can directly see the fluctuations from year to year."

The team's graph shows acid content fluctuations over the years, with a clear downward trend over the last few decades
Helle Astrid Kjær, NBI

These annual figures can be influenced by natural emission spikes, from sources such as volcanic eruptions and large forest fires, but the system is able to distinguish between these and industrial pollution. The resulting data paints an optimistic portrait of environmental regulation.

"In the 1970s, both Europe and the United States adopted the Clean Air Act Amendments, which required filters in factories, thus reducing acid emissions and this is what we can now see the results of," says Kjær. "The pollution of acid in the atmosphere is now almost down to the level it was before the pollution really took off in the 1930s."

Teams from the US, New Zealand and Denmark have already put the method into practice on ice cores from other sites in Greenland and Antarctica.

The NBI research was published in the journal Environmental Science and Technology.

Source: University of Copenhagen

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4 comments
Bob
I have serious doubts about the Clean Air Act having much effect. The air was much clearer in the 1950-1975 time period. I did a lot of flying during that time. Over most of the country you could see the buildings of large cities from up to 100 miles away. One of the most beautiful sights on earth was to see the big island of Hawaii where you could see all the shades of green for miles up the side of the volcano and then look at all the shades of blue looking out over 50 miles of the ocean. Now the visibility in the US is typically down to 10 miles and often even less in Hawaii. Thanks to US manufacturing moving to China to avoid those pesky environmental regulations and air quality standards, air and water pollution are worse than ever. Much worse.
ljaques
That's good news, UOC! Thanks. This is exactly the kind of data which tweaks me about the radical environmentalist movement. Humanity saw its enviro mistakes and started correcting them. There are pollution controls on everything now and every point is receding, as just proven by UOC. As old tech dies, new, -much- cleaner tech takes over. Man is lightening his footprint at every level, yet the Greens are still screaming about everything and we'reallgonnadie! I could see a distinct difference (improvement) during the drive from San Diego to Los Angeles CA back in 2000. In the '80s, you'd come over the hill in Anaheim and there was a thick brown cloud all over L.A. Now I doubt it's even visible, despite the population density and number of commuters.
JoeFrederick
Don't tell Obama! Or Gore! Or the UN! And as for the air being "much clearer in the 1950-1975 time period," Bob, you just must have missed LA in the 60's. In 1966 the sky every day was purplish brown and yellow. And if you parked you car at work at 9am with a clean windshield, at 5pm you found it completely covered with black soot. Catalytic convertors fixed this problem pretty well, and by the 90's, the sky in LA was actually blue.
highlandboy
White catalytic converters and diesel particulate filters have done much to clean the air of suspended solids this article is about acidity - not visible pollution. In fact catalytic converters resulted in an increase in nitrous oxide and hydrogen sulfide. These with the addition of atmospheric water created nitric and sulphuric acid. Europe then started pushing for low sulphur fuels. While most Middle eastern crudes are low in sulphur, Asian crudes are mostly high in sulphur and have required greater refining. Catalytic converters work best at higher engine revs, and increase file consumption and may increase pollution when a motor is idling, thereby increasing overall pollution. Modern engines are tuned to reduce a range of pollutants. Changing tune or adding catalysts to reduce one usually results in an increase in another. As a result the move from fossel fuels to sustainable technology is likely to have a greater effect on overall pollution than a large number of additive technologies.