300 Years of Acid Deposition in the Arctic from Greenland Ice Cores

Acid rain is one of the primary environmental pollution problems of the last century. Deposition of sulfuric and nitric acid has caused nutrient depletion in forests and acidification and metal toxicity in lakes and streams. The outcome has included decreased forest growth, stressed species populations, and die offs of fish populations. The detailed history of precipitation acidity can now be accurately determined using a novel continuous flow technique for measurement of ice core acidity at monthly resolution. Comparison of the measured acidity with the sum of acid relevant chemical species shows a very high correlation and allows for the clear determination of the contribution of each species to the overall acidity value.

Results from Greenland ice cores show a tripling of annual acidity from the preindustrial to the peak of industrial influence in the 1970s to 1980s. Acidity has since declined, but decreases in H2SO4 have been partially offset by increases in HNO3 and HCl. Comparison between preindustrial and industrial time also reveals a shift from preindustrial acidity driven nearly equally by HNO3 and H2SO4 toward peaks in the industrial period driven primarily by H2SO4. The trends in the ice cores correlate well with aerosol acidity at Alert, Canada, and with acid precipitation trends at sites in the US and Europe, indicating that the ice core values are representative of atmospheric and precipitation acidity trends over a broad region.