Healing the acid wound.

Healing the acid wound

Acidic pollution has seared its mark on lakes and forests across Europe and eastern North America. For those combating the problem, it is important to know whether pollution control can reverse the effects of the acidic rain, snow and particles that settle out of the atmosphere. Now the results of a unique project in Norway provide the first experimental evidence that acidified areas can begin to recover.

The four-year-old RAIN project (Reversing Acidification in Norway) has focused on a small drainage basin -- called a catchment -- in the southernmost region of Norway, a sensitive area that receives a significant amount of acidic precipitation. Norwegian and Swedish researchers covered the 8000-square-meter catchment with a large transparent roof that protects the area from natural precipitation. Rain collected from the roof is cleansed with an ion exchanger and then sprinkled over the covered land. Commercial snow-making equipment supplies artificial "clean" snow to the catchment during the winters. By analyzing runoff within the catchment, project members have tracking the protected plot and compared its evolution with that of control catchments. One control is covered and receives "normal" acidic precipitation, while another control remains uncovered.

Results indicate the protected catchment has started on its way to recovery. Richard Wright from the Norwegian Institute for Water Research in Oslo and his colleagues in the Aug. 25 NATURE. The acidity of runoff has dropped and so have the concentration of sulfate and nitrate ions, which are principal components of the sulfuric acid and nitric acid in acidic precipitation.

While the project provides some answers about an area's ability to recover from acidification, other questions remain. The protected catchment was less than half the size of a football field -- too small to hold any lakes or real streams -- so researchers may have difficulty relating these results to larger areas. It also remains unclear whether the catchment will recover completely. Yet James Galloway of the University of Virginia in Charlottesville, who studies acid rain in the United States, says the results of the RAIN project have confirmed predictions from computer simulations -- a finding that tells modelers they are on the right track.