Escola Secundária de Loulé
Beside the problem of the asymmetries of water distribution, the quality of water is one of the main issues of modern societies. Even in the more developed countries where there is more and more restrict legislation about the quality of water and the treatment of water is very careful the problem of water pollution cannot be neglected.
Even the water of the aquifers has, here and there, some problems with water pollution. In general, the amount of water that is available per habitant has decreased about 40% since 1970. Water, usually considered as an inexhaustible resource, has become a rare and precious resource.
Even rain water that has been distillated by nature has lost its purity. This gift from above that returns to Earth as part of the water cycle, has become “acid” due to atmospheric pollution.
Rain is normally acid due to the dissolution of carbon dioxide is something natural. The rain’s normal pH of rain water due to the reaction
can be as low as 5.5 (in fact 5.6) at the temperature of 25ºC.
Nonetheless, due to atmospheric pollution rain water presents different pH values.
Taking this value as a reference, one may define:
• “Normal” rain has pH between 5.6 and 7 (at 25ºC).
• Acid rain that has pH bellow 5.5.
Even the water of the aquifers has, here and there, some problems with water pollution. In general, the amount of water that is available per habitant has decreased about 40% since 1970. Water, usually considered as an inexhaustible resource, has become a rare and precious resource.
Even rain water that has been distillated by nature has lost its purity. This gift from above that returns to Earth as part of the water cycle, has become “acid” due to atmospheric pollution.
Rain is normally acid due to the dissolution of carbon dioxide is something natural. The rain’s normal pH of rain water due to the reaction
can be as low as 5.5 (in fact 5.6) at the temperature of 25ºC.
Nonetheless, due to atmospheric pollution rain water presents different pH values.
Taking this value as a reference, one may define:
• “Normal” rain has pH between 5.6 and 7 (at 25ºC).
• Acid rain that has pH bellow 5.5.
