ACID RAIN

What is acid rain?

• Acid rain is created when gases (such as nitrogen oxide -Nox- and sulfur oxide -SOx-) produced by the burning of fossil fuels (such as coal and oil), react in the atmosphere with sunlight to produce acids such as nitric and sulfuric acid. These acids dissolve in rain to become acid rain.

At what acidity level is rain considered acid rain?

• In Japan, rain which registers pH 5.6 or less is considered acid rain; some 80-90% of the rain that falls in Japan in a year is acid rain.

Effects of acid rain in monuments, buildings...

• In Japan, acid rain with acidity akin to lemon juice has been observed at Mount Tsukuba in 1984 (pH 2.5) and at Kagoshima in 1987 (pH 2.45). The problem is even more serious in North America and Europe. In those regions, forests are withering and lakes becoming uninhabitable to fish, and stone structures such as buildings and bronze statues are being damaged by corrosion.

Other Situations

The deterioration of two kinds of sandstone is discussed for two 18th century buildings in central Stockholm: the Royal Palace, and the Royal Carolean Burial Chapel (Karolinska gravkoret) annexed to the mediaeval Riddarholm church. The facades of calcitic Gotland sandstone show many signs of serious decay.

The socles are built of the more resistant quartzitic Roslagen sandstone, displaying some discolouration, cracks, and slight exfoliation. In total about 300 samples have been analysed. The surface concentration of sulphur is highest at ground level and at rain-sheltered positions.

Effects of Acid Rain in Forests, Plants...After much analysis, researchers now know that acid rain causes slower growth, injury,

or death of forests. Acid rain has been implicated in forest and soil degradation in many areas of the eastern U.S., particularly high elevation forests of the Appalachian Mountains from Maine to Georgia that

include areas such as the Shenandoah and Great Smoky Mountain National Parks. Of course, acid rain is not the only cause of

such conditions. Other factors contribute to the overall stress of these areas, including air pollutants, insects, disease, drought, or very cold weather. In most cases, in fact,

the impacts of acid rain on trees are due to the combined effects of acid rain and these other environmental stressors. After many

years of collecting information on the chemistry and biology of forests,

researchers are beginning to understand how acid rain works on the forest soil,

trees, and other plants.

Other situations…• Acid rain has been implicated in

contributing to forest degradation, especially in high-elevation spruce trees that populate the ridges of the Appalachian Mountains from Maine to Georgia, including national park areas such as the Shenandoah and Great Smoky Mountain national parks. Acidic deposition seems to impair the trees' growth in several ways; for example, acidic cloud water at high elevations may increase the susceptibility of the red spruce to winter injury.