pH OF PRECIPITATION ACROSS THE UNITED STATES IN 1994 AND 2009
FIGURE 13.31 (a) In 1994 precipitation was highly acidified (pH <5.3) in the eastern half of the country, especially in the upper Midwest and Northeast. (b) By 2009, however, acid rain control programs resulted in substantial reductions in the acidity of rain across the country. (MAPs from National Atmospheric Deposition Program, http:/