Effects of acidification

Acidification of water

Back in the 1950s it was discovered that fish were disappearing from lakes and waterways in southern Scandinavia. Over the years, many thousands of lakes, streams and rivers have been affected by acidification, with widespread damage to plant and animal life as a consequence. The damage is extensive in large parts of Scandinavia, but also occurs in other parts of Europe and in North America.

Soil depletion

Sensitivity to acidification is greatest in areas where the minerals in the soil weather slowly. When the soil becomes acidified its essential nutrients are leached out, which reduces the fertility of the soil. The acidification process also releases metals that can harm the micro-organisms in the soil that are responsible for decomposition, as well as birds and mammals higher up the food chain, including man.

Plants and animals disappear

The sensitivity of individual species to air pollutants and acidification varies. The most sensitive groups include fish, lichens, mosses, certain fungi and small aquatic organisms.

Forest damage

European surveys have shown that a significant share of the trees examined can be classified as damaged (the loss of leaves or needles exceed 25 per cent). This damage to the forest has many causes, but most researchers agree that acidification and/or eutrophication of the soil and high concentrations of ground-level ozone are important contributing factors.

Corrosion

Corrosion of some important materials can be greatly accelerated by sulphur dioxide and nitrogen oxides.These are converted into strong acids which attack new and old buildings, bridges, monuments, rock carvings, etc. Worst affected are objects and structures of easily weathered materials, such as limestone and sandstone.

Health

The mobility of many metals increases in acid environments. The average levels of cadmium in groundwater have, for example, been shown to be three times higher in water with a pH value under 5, compared with water that has a pH above 6. The cadmium uptake of crops also rises when the pH of the soil drops. The concentrations of cadmium that parts of the population are exposed to are already close to the levels at which kidney damage can occur. Cadmium is also suspected of giving rise to bone embrittlement at relatively low exposures. Human exposure to other potentially toxic metals, such as aluminium and mercury, also increases in acidic environments.