The earth is covered by approximately one and a half billion cubic metres of water, 97% of which is salty seawater and the remaining 3% fresh water in the form of lakes, rivers and icebergs and groundwater. Water is usually thought of as an unlimited resource, divided into just two types, fresh and salty.
In reality, water can be distinguished on the basis of other characteristics:
• physical (temperature, colour, turbidity)
• chemical (salt, gas, chemical product content);
• biological (presence of micro organisms)
Polluting water means altering its characteristics in such a way as to make it unsuitable for the purpose it serves.
Types of water pollution
There are different types of water pollution:
• civil: derives from urban waste water that flows into rivers or directly into the sea without any purification treatment;
• industrial: formed by different substances that depend on industrial production;
• agricultural: linked to the excessive or improper use of fertilisers and pesticides, which, being generally water-soluble, penetrate the soil and pollute the groundwater.
Some chemical substances present in the water are particularly hazardous for human health and the survival of many living species, such as some metals (chrome, mercury) or compounds such as chlorinated solvents.
Causes of water pollution
Industrial waste contains a large quantity of pollutants and their composition varies according to the type of production process. Their impact on the environment is complex: toxic substances contained in this waste often mutually reinforce their damaging effects and so the total damage is greater than the sum of each single effect. Chemical fertilisers used in agriculture and sewage produced by animal farms are rich in organic substances which, washed away by the rain, leaches into the groundwater aquifers or into surface bodies of water. These substances are often joined by larger debris, which is deposited on the bottom of pools.
Sea pollution mainly originates on land, and is largely a result of the discharge of wastewater and industrial waste into rivers, which then transport the pollutants out to sea.
The main source of sea pollution is from crude oil, particularly from oil tankers, which sometimes spill large quantities of petroleum into the waters. An example is the ecological disaster caused by the sinking of the oil-laden ship Prestige off the coast of Spain and France, and of the petrol tanker Jessica along the coast of the Galapagos islands. These caused serious environmental problems and much damage to humans and their health due to the pollutants being washed up on the shore.
This includes all pollution off the coast; often caused by the discharge of tank-washing residues or bilge, by naval accidents caused by storms, collisions, explosions, structural collapse or accidents on oil rigs.
This is the most damaging and hazardous form of pollution, as it is very difficult to clean up once it has been washed onshore. Shallow waters mean that the various clean-up units cannot operate, so machines such as skimmers etc are rendered useless.
Here, human intervention and manual cleaning is fundamental, making it the chief field of action for volunteers.
This type of pollution usually occurs following a fire (such as that on the petrol tanker “Haven” in the Gulf of Genoa) when the light component evaporates and the heavy one sinks and settles on the seabed.
Seventeen years have passed since the sinking of the VLCC Haven, the most serious crude oil pollution to ever occur in the Mediterranean. The consequences of that tragedy, though limited by timely and efficient emergency management, still remain. In fact today, small quantities of crude oil occasionally leak from the main shipwreck, and numerous tar deposits are still present over a vast area of the seabed. This has made a decontamination operation necessary on the main wreck of the Haven in order to eliminate the risk of hydrocarbon and oil (fuels and lubricants) leaks caused by the corrosion of material and the collapse of the shipwreck itself. The operation was coordinated by the Department of Civil Protection, carried out by the Dutch company Smit Salvage and led by the COEMM - Centro Operativo Emergenze Marittime (Operations Centre for Maritime Emergencies) of the Department of Civil Protection.