On the horizon

Winter de-icers are soiling the soil

The Northeast may be taking its winters with too many grains of salt. And that could spell trouble for the region's freshwater ecosystems, according to a team of government and university researchers in the United States.

The team finds that during the past 30 years, road salt and other de-icers have boosted chloride levels in groundwater and aquifers, even in areas where the salt use has remained constant. And concentrations remain high during the summer. These trends suggest that salts are accumulating in the environment faster than natural processes can get rid of them, says Peter Groffman, a University of Maryland ecologist and member of the group studying the issue.

The team looked at freshwater systems from Baltimore through the Hudson River Valley and into New Hampshire's White Mountains. In some places, chloride levels exceed the level deemed harmful to fish and aquatic plants. In Baltimore, in winter, urban waterways can reach as much as 25 percent of the ocean's salinity.

The scientists suggest that if current trends continue, water in many of the region's ponds, lakes, rivers, and streams could become toxic to aquatic life by the end of the century. The results of the study appear in the current edition of the Proceedings of the National Academy of Sciences.

Brakes put on ozone depletion?

The overall decline in Earth's protective ozone layer appears to have leveled off, according to a recent study in the Journal of Geophysical Research. In some regions of the world, the layer is registering small increases in the gas, which blocks ultraviolet radiation beaming in from the sun.

The team reporting the results urges caution in declaring victory over human-induced ozone depletion. "We will have to continue to monitor ozone levels for years to come before we can be confident," says Elizabeth Weatherhead, a researcher with the National Oceanic and Atmospheric Administration and one of the study's authors.

Researchers say it will take decades for the ozone layer to recover, and it probably never will stabilize at pre-1970s levels, when scientists first learned that industrial chemicals could erode the layer. Still, the results suggest that an international ban on the main culprit, a group of gases known as chlorofluorocarbons, is having a beneficial effect.

From 1996 to 2002, the team measured the total concentration of ozone between Earth's surface and the upper atmosphere at ground stations on three continents and via satellites. The results build on studies in 2003 that point to a slowing rate of ozone destruction.

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