Whatever happened to acid rain?

Slate : Acid rain has been a major problem since the Industrial Revolution. Acidification can cause imbalances in soil chemistry, exacerbating problems for watersheds and plant life, and threaten sensitive tree populations like the Red Spruce in the Northeast mountains.The 1990 amendments to the Clean Air Act require power plants make significant cuts on sulfur dioxide and nitrogen oxides emissions—which cause acid rain—by installing " scrubbers ” in their smokestacks and switching to low-sulfur coal . Cap-and-trade programs came online in 1995 for sulfur dioxide and 2003 for nitrogen oxides. Vehicles, which emit large amounts of nitrogen oxides, became cleaner thanks to the catalytic converters.According to the National Emissions Inventory , sulfur dioxide emissions from all sources fell from nearly 26 million tons in 1980 to 11.4 million tons in 2008. Nitrogen oxides decreased from 27 million tons to 16.3 million tons in the same time frame.However, despite these improvements, much of the rainwater in the East is between 2.5 and 8 times more acidic than it should be.