A3.4.2 Adverse Effects of Pollution on Land


Pollution to land can be industrial releases directly into the ground, through discharge or accidental spillages. This of course could consist of any polluting material, including oil.

A principle cause of pollution on land is acid deposition. The acidity of the rain causes changes to the chemistry of the soil.

Increasing soil acidity can affect micro-organisms which break down organic matter into nutrient form for plants to take up. It can also allows aluminium (a common constituent of soil minerals) to be present as a solution. In its free organic form, aluminium is toxic to plant roots and can lock up phosphate, thereby reducing the concentrations of this important plant nutrient.

The impact upon soil in any area is partly dependant on the original composition of the soil. For example, soils containing calcium and limestone are more able to neutralise sulphuric and nitric acid depositions than a thin layer of sand or gravel with a granite base. If the soil is rich in limestone, or if the underlying bedrock is either composed of limestone or marble, then the acid rain may be neutralised. This is because limestone and marble are more alkaline (basic) and produce a higher pH when dissolved in water. The higher pH of these materials dissolved in water offsets or buffers the acidity of the rainwater producing a more neutral pH.

Where the composition of the soil is such that no natural neutralisation occurs, the acid rainwater can accumulate in the bodies of water in the area. Trees and plants can be adversely affected because acid rain can leach many nutrients out of the soil. The number of micro-organisms in the soil may be decreased, which will in turn affect the level of nutrient because micro-organisms assist the decaying processes, which transfers nutrients from decaying matter into the soil. Polluted soil can make plants more susceptible to diseases and pests, as well as weakening the plant to the point that it is more susceptible to the weather (e.g. cold winters or high winds).