Radioactivity in the Environment

*Radioactivity is the spontaneous decay of unstable nuclei, accompanied by the emission of radiation.
There are three types of radiation emitted by radioactive isotopes.

1. Alpha particles (α)
2. Beta particles (β)
3. Gamma rays (γ)

Alpha (α)

*Alpha particles are helium nuclei, with a positive charge and little penetrating ability.

Alpha particles consist of two protons and two neutrons. They can be stopped easily, human skin or a few sheets of paper. If alpha particles enter the body(ingestion) it can be hazardous. An example is americium-241, used in smoke detectors.

Beta (β)

*Beta particles are electrons, with a negative charge and greater penetrating ability than alpha particles.

In some radioactive elements, neutrons disintegrate into protons and electrons. The electrons -β particles are emitted from the atom fast. They can be stopped by 2-3 mm thickness of aluminium. An example is Carbon-14 which is used in dating of artefacts. 

Gamma (γ)

*Gamma rays are high energy electromagnetic radiation, with greater penetrating ability than beta and alpha. 

This type of radioactivity is emitted  by isotopes in a form of rays. They have no mass or charge. They move very quickly and have a strong penetrating ability. A thick shield of concrete or lead can stop them. An example is cobalt-60 which is used in cancer treatment and food irradiation. 

Half-life t_½

*The half-life of a radioactive isotope is the time taken for half of the atoms in a sample of the isotope to decay.

Different elements have different half lives. For example: Carbon-14 has a half-life of 5,730 years. Uranium-238 has a half-life of 4.5 billion years! For a radioactive atom to fully disintegrate it must go though 10 and a half half-life's 

Background Radiation

We are all exposed all the time to some radiation, called background radiation. It is natural and fund from:

• Cosmic Radiation
• Rocks-containing traces of uranium and its decay product Radon. Granite rock releases Radon. It can accumulate in houses to levels that increase of lung cancer.
• Man made radioactive materials.

Natural Radiation

• 87% of background radiation.
• Produce natural radiation.
• Many radioactive atoms that once existed have now emitted radiation and have now become non-reactive.
• Examples, Uranium, Radon and Thorium.

Radon

Atomic number 86, symbol Rn, noble gas. Radon is responsible for the majority of public exposure ionizing radiation. It is the largest contribution to an individual's background radiation dose and varies from location. Radon is a gas and can accumulate in a building especially in a confined room such as attics. Epidemiological studies have shown a link between breathing high  concentrations or radon gas and lung cancer. You can measure radon in your home by placing two small detectors in your home for three months. One is placed  in the main bedroom and the other in the living room. After three months the detectors are returned to the lab. A report will be issued indicating the average level of radon and advice on what to do if the level is high. 

Links:

http://www.rpii.ie/ 

http://www.rpii.ie/Measurement-Services/Radon-Measurement/Services/Apply-For-Measurement-Online.aspx 

http://www.rsc.org/images/number6_tcm18-17768.pdf

Asteroid to pass over the Earth

An asteroid bigger than an aircraft carrier will brush past the Earth within the next few hours.

The 400-metre (437-yard) wide asteroid, called 2005 YU55, will speed past the planet at a distance of 201,700 miles - closer than the moon.

It Is our closest encounter with such a large space rock in three decades.

But Marina Brozovic of Nasa said there is no cause for alarm.

"It is not going to hit us," she said.

"We have a good idea of its orbit for the next 100 years and the is no chance of impact."

The asteroid was discovered in April 2010, when observations with the Arecibo radar telescope revealed a fuzzy image of the rock tumbling through space.

Nasa is hoping to take much higher resolution photographs of its dark surface as it passes by at 23.28 GMT time on November 8.

Amateur astronomers will need a six-inch telescope to stand a chance of seeing the asteroid, but have been warned that it is moving so fast that it will be difficult to track.

Nasa has set up a near earth object programme known as Spaceguard to locate the estimated 1,000 asteroids and comets larger than 1km (1,093 yards) in diameter - large enough to cause mass extinction of most life on Earth.

Murmuration of Starlings on the River Shannon