There are also electronic instruments for measuring pH. The pH of rain should be monitored carefully to detect acid rain. It is any precipitation, rain, fog, mist, or snow that is more acidic than a normal pH value of 5.6. Some factories believed that they could solve the problem of acid rain by raising the heights of their smoke stacks. A nickel smelting plant is Sudbury, Ontario, has a chimney nearly a quarter of a mile into the sky. The acid rain can cause acid levels in rivers and lakes to rise.
Streams are usually acidic for two reasons.
The pollutants, which cause the problems, are both natural and man-made. Lakes are also in danger. Seventy percent of the lakes in Norway and eighty percent of the lakes of the Adirondack Mountains in New York have no fish because of acidic levels. One fourth of the lakes in Minnesota's famed Boundary Waters Canoe Area are affected by some degree of acidity. Streams and lakes in areas of basic bedrock and soil, such as limestone bedrock and calcareous soils, are naturally buffered against acid precipitation.