Pollutants found to be making sea more acidic

Hawaii’s tradewinds blow away much of the pollution caused by sulfur and nitrogen released into the atmosphere from human activities, says a University of Hawaii scientist.

That’s good news for Honolulu, but how about for the ocean?

The magnitude of nitrogen and sulfur-bearing acids falling into coastal waters is not really known, says Fred Mackenzie, professor emeritus of sedimentary and global geochemistry.

“We get a little smog downtown from combustion activities and see it at times, particularly when we get Kona winds, but most of the stuff really blows out to sea, past the coastal region,” he said.

Mackenzie participated in a study led by Scott Doney of the Woods Hole Oceanographic Institution that looked at the role of nitrogen and acid rain.

They found the release of sulfur and nitrogen into the atmosphere by power plants and other human activity has a minor role in making the ocean more acidic globally. But the impact is greatly intensified in shallower waters of the coastal ocean, the researchers found.

Ocean acidity affects the ability of sea urchins, corals, certain types of plankton and other marine organisms to build hard outer shells, or exoskeletons, of calcium carbonate, they said.

The decline of such organisms could affect entire ocean ecosystems because they provide essential food and habitat to other species, the scientists said.

Mackenzie, in an interview, said the oceans are becoming more acidic because of the uptake of carbon dioxide from the atmosphere and the fallout of nitrogen and sulfur.

Nitrogen and sulfur make up only about 2 percent of the total acidification of the ocean due to carbon dioxide, he said.

However, as much as 30 to 50 percent of acidification of surface waters could be due to elements other than carbon dioxide in small coastal regions with significant atmospheric inputs, particularly of nitrogen from combustion, Mackenzie said.

Doney, in a report from Woods Hole, said the effect of acid rain “is most pronounced near the coasts, which are already some of the most heavily affected and vulnerable parts of the ocean due to pollution, overfishing and climate change.”

Mackenzie said he would be surprised if Hawaii had a big problem from acid rain in near-coastal waters, “but it definitely would be worth doing some work on, just to make sure that’s the outcome,” he added.

Helen Altonn, Star Bulletin, Honolulu, 24 September 2007. Article.

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