Deja vu: acid rain in China.

Deja vu: Acid rain in China

If you can picture what it was like inTennessee about 65 years ago, you get a sense of the present air-pullution situation in parts of China. Recent measurements show that precipitation in China tends to have high concentrations of sulfate and calcium ions but relatively low acidity. These levels are similar to those observed around Knoxville, Tenn., in the early 1920S.

This conclusion emerges from a recentcomparison of precipitation composition in China, the eastern United States and a remote area in Australia. The report, published in the June 19 SCIENCE, also notes that the sulfate levels in China's rainwater may be high enough to cause "significant and severe ecological changes.c The study was conducted by James N. Galloway of the University of Virginia in Charlottesville, Zhao Dianwu of the Institute of Environmental Chemistry at the Academia Sinica in Beijing, and their colleagues.

Rainfall composition in China reflectsthe country's reliance on coal combustion for electricity generation, home heating and cooking. The available coal generally has a high sulfur content, and it is usually burned in small furnaces or stoves with no pollution controls. With so many low-to-the-ground sources, pollution is kept close to its origin. Sulfate concentrations in Guiyang City, China, for instance, are about six times higher than present levels in New York City. In contrast, the small number of motor vehicles keeps nitrate levels lower than in comparable U.S. areas.

In rural and suburban areas, calcium-richsoils, the extensive use of lime-stone for building and the emission of alkaline materials by furnaces helps lower rainfall acidity. Precipitation in rural China also has a high concentration of ammonium ions, generated by excretory wastes used as fertilizer. As a result, pH values in China are generally higher than those in the eastern United States.

"The reduction of the acidity, however,does not necessarily reduce the potential for acidification of aquatic and terrestrial ecosystems," the researchers say. The hazard depends more on sulfate concentration than on the acidity of the rainfall itself. Although the potential for ecological deterioration in China is unknown, they say, other areas of the world have suffered damage "at levels of atmospheric deposition of sulfur- and nitrogen-containing compounds that are less than those currently existing in China."