Tuesday, 22 May 2012

On April 25, 1998 the dam of the mining residual tank of a pyrite mine in Aznalcollar, Spain suffered a rupture, releasing sludge and contaminated wastewater. The wastewater entered the Guadiamar River, polluting the river with heavy metals such as cadmium, lead, zinc and copper. It affected an area of 4.634 hectares, contaminating 2.703 hectares with sludge and 1.931 with acidic water.
The river pollution caused cultivation lands and forests to be affected. Harvests were no longer fit for consumption, causing financial problems for farmers in the area. Major fish mortality occurred and birds died as a result of consumption of polluted fish. It took one whole month for the river water to recover to its original state.
After the wastewater flow had entered the river a major cleanup operation started, including the installation of walls to prevent further spreading of contaminants and the removal of contaminated sludge. The pH values of the soil were restored by liming and arsenic was removed by adding iron oxyhydroxides, causing a precipitation reaction.
Company technicians stated that the rupture of the residual tank was caused by a deep landslide, which provoked the movement of a certain section of the wall. Authorities also researched the cause of the disaster. Apparently the dam was a weak construction and warnings of possible breakthrough were neglected. The Canadian/ Swedish corporation Boliden was held responsible for the wastewater spill. The company was sentenced to financing the cleanup operation and paying compensation to victims.
At approximately 4:00 a.m. on March 28, 1979 the main feed water pumps in the non-nuclear cooling system of reactor 2 of the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania failed. This caused cooling water to drain away from the reactor resulting in partial melting of the reactor core. Operator errors, a stuck valve, faulty sensors and design errors together resulted in a release of approximately one thousandth as much radiation as during the Chernobyl explosion.

Fortunately about 18 billion curies of radiation that could have been released were held by the containment structure around the reactor. This caused some advocates to think that serious nuclear accidents will not occur in the United States. However, many experts have claimed that only luck kept the accident from being worse. The reactor core, according to them, was only just short of becoming hot enough to totally melt down. Complete melt-down was only prevented by immediate implementation of safety measures.

It is very uncertain how much radiation was exactly released at the nuclear accident. It is estimated that this was about 2,5 million curies. A few days after the accident had occurred all children and pregnant women were evacuated from an 8 km radius of Three Mile Island as a safety precaution.
Radiation from the Three Mile Island reactor has contributed to the premature deaths of some elderly people that lived in the region. Dairy farmers reported that many animals have died consequential to the accident and local residents have developed cancers. Some studies suggested that premature deaths and birth defects also resulted from the nuclear melt-down.

The reactor cleanup started in August 1979 and officially ended in December 1993 at a cost of around 975 million dollars. From 1985 to 1990 almost 100 tonnes of radioactive fuel were removed from the site. Reactor 2 had been online only three months, but now had a ruined reactor vessel and was unsafe to walk in, therefore it has been permanently closed. Reactor 1 was restarted in 1985, but many plans for building new reactors of the same type were dismissed later.
Sources
- Lomborg, B., The Skeptical Environmentalist - Measuring the Real State of the World. Cambridge University Press 1998, United Kingdom
- McKinney, M.L., Schoch, R.M., Environmental Science: Systems and Solutions, Third Edition Jones and Bartlett Publishers, Sudbury Massachusetts 2003
- Encyclopaedia: http://www.wikipedia.org
- Encyclopaedia: http://www.britannica.com
- Chernobyl: http://www.chernobyl.co.uk/ and the Chernobyl Children's Project International: http://www.chernobyl-international.com/aboutchernobyl/disaster.asp
- London Smog: BBC news, London University
- NOAA Oil spill review, published in 2003 - http://response.restoration.noaa.gov/oilaids/spilldb.pdf
- BSE crisis: BBC, Asian Food Information Center
- Spain wastewater spill: Oceanographic Institute of Paris, Environmental Restoration of the Guadiamar River Basin Affected by the Accident at the mine in Aznalcollar, Spain. Paris, October 2002 -> http://www.le-cedre.fr/uk/publication/jourinfo02/esp.pdf

Natural environmental disasters


Read more: http://www.lenntech.com/environmental-disasters.htm#ixzz1vdAjqF22
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