Saturday, December 6, 2008

Rocks of Ranchi city in India is radioactive.

Are the rocks of Ranchi city in India is Radioactive?
by
Dr. Nitish Priyadarshi







Ranchi is the capital city of the Indian state of Jharkhand.  / The total area covered by Ranchi - Municipal Area is about 110 square kilometers and the average elevation of the city is 2,140 feet above sea level.
Geographically, Ranchi is located on southern part of the Chota Nagpur plateau which forms the eastern edge of the Deccan plateau system. The area surrounding Ranchi has been endowed with natural attractions and it is referred to as the “City of Waterfalls”.
As of 2001 India census, Ranchi had a population of 846,454. Males constitute 53% of the population and females 47%.

Rocks around Ranchi:

The oldest geological formation of this district is represented by Dharwar sediments with the basic intrusive. These, being later intruded by the batholithic mass of Chota Nagpur granite, were metamorphosed into various types of schistose and gneissic rocks. The remnants of the earlier sedimentary and igneous rocks are known from the inclusions of phyllites and schists of varying dimensions in the granite mass and the extensive areas of Khondalites. Phyllites are by far the predominant rock type in the south-east portion of this district. Chota Nagpur granite gneiss forms the country rocks of the district and is a part of the enormous intrusive mass.

Within the main body, the granite gneiss varies from a normal medium- grained rock to a porphyritic material with large crystals of potash feldspar. Quartz, biotite or hornblende are the other essential minerals. Apatite, zircon, sphene are rutile are the accessories. The amphibolites occur as minor intrusive in the Khondalite series. Amphibolite also occur as minor enclaves in the granite gneisses in and around Ranchi city.

Radioactivity in the Environment:

Humans have always been exposed throughout their period of existence to naturally occurring ionising radiation. Specifically, naturally occurring radionuclides are present in variable amounts in our environment. To assess radiological health hazards, naturally occurring radionuclides are being measured in soil, sand, marble, bricks etc throughout the world.

Terrestrial radiation comes from radioactive elements that were present at the time the earth was formed. They continue to decay and form additional radioactive materials.
Unusual soil composition has increased background radiation twenty-five fold or more in a few areas in the world. Locations with high background radiation in the soil, mainly from uranium, include the Rocky Mountains, Kerala India, coastal regions of Brazil, granite rock areas of France, and the northern Nile Delta.
In the United States, lower background radiation is seen in the sandy soils of the Atlantic and Gulf coastal plains.


The distribution of naturally-occurring uranium, radon, and other radioactive elements, radionuclides, depends on the distribution of rocks from which they originate and the processes which concentrate them. The key therefore is to know the distribution of source-rock materials containing elevated levels of radionuclides and to understand the physical and geochemical processes that concentrate radionuclides."

Gamma and alpha radiation emitted by radioactive elements in rocks and soils, especially those that decay quickly (such as radon), pose a health risk. This radiation is implicated in cancers of the lung, bone, and of other organs.

Radioactivity generated by those radioactive elements that exist in the Earth's crust. All the elements from polonium (atomic number 84) to uranium (atomic number 92) are radioactive. Radioisotopes of some lighter elements are also found in nature (for example potassium-40).

Radioactive gases such as radon are found in soil and may seep upwards into buildings.

Radioactivity in Ranchi soil:

Seeing the rock types and its mineral composition background or radioactive radiation cannot be ruled out in Ranchi. This fact was justified by a published report of Research Reactor Institute, Kyoto University. According to the report Air-gamma dose rate was 0.30 μSv/h on the surface in the densely populated area in the city. In Ranchi the concentration of K-40 (potassium-40) and thorium is high. Concentration of Radium-226 was 75 Bq/Kg in the soils.

Very interesting thing in the Ranchi city is that name of one of its major road is RADIUM ROAD. Till today no body knows from where did this name came from. Name of this road exists from the British rule in India i.e. before 1947.

Potassium 40 is found in potassium feldspar (orthoclase), muscovite, and amphibole.
Uranium may be found in zircon ,urananite ,monazite ,apatite and sphene . Seeing the presence of apatite, sphene and zircon in the Ranchi rocks, presence of Uranium cannot be ruled out. According to the report Uranium concentration is also high in Ranchi. All these concentrations are of natural origin. Radioactivity in the bricks made by the local soil may pose threat to the people living in the houses made by these bricks.

When Uranium is there, presence of Radon cannot be ruled out. It is radioactive gas that comes up from the soil and collects in basements and ground floors, sometimes in well water. Radon is a prominent villain in the United States, blamed for tens of thousands of deaths from lung cancer.

Radon is relatively high in uranium-rich rocks such as ancient granites, like Ranchi, high-organic shales and coal beds.

There are areas in the world where the content of the uranium or thorium in soil are high, and the people are receiving exposure of 10 or more times in such a place compared with other areas. There is no other way but to accept. Ranchi, the capital of Jharkhand, is one of such the places.

Health effects:

Potassium-40 can present both an external and internal health hazard. In the body, potassium-40 poses a health hazard from the both the beta particles and gamma rays. . The health hazard of potassium-40 is associated with cell damage caused by the ionizing radiation that results from radioactive decay.

There is no evidence that exposure to naturally present levels of radium has harmful effects on human health. However, exposure to higher levels of radium may result in health effects, such as teeth fracture, anaemia and cataract.

Radium is constantly produced by the radioactive decay of uranium and thorium. Radium is present at very low levels in rocks and soil and strongly attaches to those materials. It is also found in air. High concentrations of radium exist in water on some locations.Uranium mining results in higher levels of radium in water near uranium mines. Plants absorb radium from the soil. Animals that eat these plants will accumulate radium.Finally, radium may concentrate in fish and other aquatic organisms and bio magnify up the food chain.
People will always be exposed to small amounts of thorium through air, food and water, because it is found nearly everywhere on earth.All people absorb some thorium through food or drinking water, and the amounts in air are so small, that the uptake through air can usually be ignored. Breathing in thorium in the workplace may increase the chances of development of lung diseases and lung and pancreas cancer many years after people have been exposed. Thorium has the ability to change genetic materials.
Seeing the high concentration of thorium (210 Bq/kg) people of Ranchi may face some thorium exposures.

Conclusion:
Even the exposure in Ranchi city may be of very low dose, exposure to radiation accompanies risk. However, since the natural activity exists on the earth and there is a radiation such as a cosmic ray, we cannot escape the exposure completely. Seeing the possibilities of Radon gas, houses built in Ranchi should be proper ventilated and making of basements should be avoided.

Reference:

Priyadarshi, N. 1998. A handbook geology of Chotanagpur, Aoyushi Publications, Ranchi, India.

http://encyclopedia.farlex.com/natural+radioactivity

http://encyclopedia.farlex.com/background+radiation

Post a Comment