2007-9-10

Text:

Definition: Acid rain refers to precipitation in forms of rain, snow and others with pH value lower than 5.6 from the atmosphere. It is a kind of indicators of atmospheric population.

Phenomena: Since 1960s, precipitation and surface water in parts of the earth surface such as Europe, US, east of Canada and China are found higher and higher acidity. (Picture 1: Global SO2 Emission)

Origins of acid rain: emission from the nature: sulfur compounds from volcano eruption, terrestrial heat discharge and ocean wave splash discharged to the atmosphere as well as NOx compounds produced by lightning will have impacts on acid substance content in the atmosphere. Human discharge: majority of sulfur and nitrogen compounds are produced by human activities; however discharge of SO2 and NOx produced from fossil fuel combustions is the root cause of acid rain. (Picture 1: Origins of Acid Rain)

Picture 1:Origins of Acid Rain

Related terms:

Acid deposition-Acid deposition includes'wet deposition'and 'dry deposition'.'Wet deposition' refers to precipitation with pH value lower than 5.6(including various forms of precipitation of rain, snow, frost, hailstone and dew); 'dry deposition'refers to the process of all acid substances in the atmosphere transfer to the ground. Currently, acid rain and acid deposition are understood in the same meaning.

Impacts: Acid rain has a wide range of influences on human living environment:

Acid rain precipitation into rivers and lakes will be harmful to the growth of fish and shrimps even cause them decreased or vanished;

Acid rain also will cause soil acidification, damage soil nutrition, expand poor soil, jeopardize plant growth, result in decreased agriculture crop yield and destroy forest;

Acid rain will also corrode building materials; according to some reliable source, corrosion to historical sites especially to stone carvings, stone inscriptions or cupper sculptures in acid areas exceeds that accumulated for past hundred year even thousand years;

Acid rain changes surface water into acid water and underground water into high metal content water; drinking such kind of water is harmful to human health.

Notes to pictures (see Picture 1-3 for details)

Picture 1:Acid water acidifies freshwater lakes and rivers that greatly decrease fish stocks

Picture 2:Acid rain gives adverse impacts to forestation resulting in forest eco-system degeneration

Picture 3:Acid rain corrupts building materials and metal structures

Countermeasures:

Use low-sulfur fuel and improve combustion equipment

Flue gas desulphurization and denitrification

Control automobile tail gas emission