Radon

Radon Gas: Threats & Benefits Navpreet Kaur* and SS Verma Department of Physics, SLIET, Longowal, Distt.-Sangrur (Punjab)-148106 Radon is chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, tasteless noble gas occurring naturally as an indirect decay product of uranium and thorium. It is monatomic gas.

Its most stable isotope is 222Rn, has a half life of 3.8days. Radon is one of the densest substances that remain a gas under normal conditions. It is also the only gas under normal condition that has radioactive isotope and is considered as health hazard due to radioactivity. Radon itself decay, it produces new radioactive element called radon daughter or decay product.

Fig: Decay process of radon

Some properties of Radon are: Physical properties: Phase gas Melting point 202 K (−71 °C, − 96 °F) Boiling point 211.5 K (−61.7 °C, −79.1 °F) Density9.73 g/L (at 0 °C , 101.325 kPa) Liquid density at b.p.: 4.4 g·cm−3 Critical point377 K, 6.28[1] MPa Heat of fusion3.247 kJ·mol−1 Heat of vaporization18.10 kJ·mol−1 Molar heat capacity 5R/2 = 20.786 J·mol−1·K−1 Atomic properties: Atomic number 86 Standard atomic weight(222) Categorynoble gases Electron configuration[Xe] 4f14 5d10 6s2 6p6 Per shell2, 8, 18, 32, 18, 8 Oxidation states6, 2, 0 Electro negativity2.2 (Pauling scale) Ionization energies1st: 1037 kJ·mol−1 Covalent radius150 pm Van der Waals radius 220 pm * M.Sc. (Physics) final year student & Corresponding author

Miscellanea properties of Radon: Crystal structure face-centered cubic (fcc) Thermal conductivity 3.61×10−3 W·m−1·K−1 Magnetic ordering non-magnetic Number of isotopes36 (ranging from atomic No. 193 to 228) Most stable isotope222 Rn Unit for measuring concentration pCi/L (pico curies per liter)

of

radon-

Bq/m3(Becquerel

per

cubic

meter),

Production: Radon is not produced as a commercial product. Radon is naturally occurring radioactive gas and come from the natural breakdown (radioactive decay) of uranium. It is a usually found rock and soil but in some cases well water may also be source of Radon.

How much Radon is too much?

Radon levels in outdoor air, indoor air, soil air, and ground water can be very different.

Radon in indoor air The U.S. Environmental Protection Agency has set an advisory "action level" of 4 pCi/L for radon gas in indoor air. While not a mandated health standard, this level is a guideline for people to use in assessing the seriousness of their exposure to airborne Radon. Concentrations noticeably lower than 4 pCi/L are desirable. The standard deviation of radon concentration is 11.23 Bq/m3.

Radon in outdoor air Outdoor air ranges from less than 0.1 pCi/L to about 30 pCi/L, but it probably averages about 0.2 pCi/L. Radon in indoor air ranges from less that 1 pCi/l to about 3,000 pCi/L, but it probably averages between 1 and 2 pCi/L. The amount of Radon dissolved in ground water ranges from about 100 to nearly 3 million pCi/L. Harmful effects of Radon:

*

M.Sc. (Physics) final year student & Corresponding author

Radon and its daughters present in the environment results in the largest contribution to the average effective dose received by human beings .Radon is a gas but its daughters are solid and stick to surface such as dust particles in air. If such contaminant dust is inhaled, these particles can stick to the airways of lung .These radon decay products trapped in lungs can radiate and penetrate the cells of mucous membranes, bronchi and other pulmonary tissues. The ionizing radiation energy affecting the bronchial epithelial cells is believed to initiate the process of cancer causing process.

Radon Pathways into Your Home: Although there are some exceptions, in general, the migration of Radon up from the soil contributes the largest percent of Radon found in the average home. Radon from a groundwater supply source, particularly a bedrock well (also known as drilled well), contributes the next largest percentage of Radon in the home. The radon contributed from building materials is typically very small.

Although there are some exceptions, in general, the migration of Radon up from the soil contributes the largest percent of Radon found in the average home. Radon from a groundwater supply source, particularly a bedrock well (also known as drilled well), contributes the next largest percentage of Radon in the home. The radon contributed from building materials is typically very small. Radon can enter a home via at least three common pathways: • Migration (up from the soil) into the basement through cracks and/or other openings in the foundation. • Release of dissolved radon gas from the household on-site water supply. • Release from building materials such as a granite block foundation, some fireplace materials, and floor or wall tiles.

Methods to reduce radon in homes: There are so many methods to reduce the radon in homes few are discussed below*

M.Sc. (Physics) final year student & Corresponding author

Depressurization and associated techniques basically involve removing air from the area beneath the house slab, basement, or crawlspace and exhausting it and any accumulated radon gas to an area where it is dispersed and diluted so as not to be a serious health hazard.

Sealing cracks and other openings in the foundation is a basic part of most approaches to radon reduction. Sealing the cracks limits the flow of radon into your home thereby making other radon reduction techniques more effective and cost-efficient.

House/room pressurization uses a fan to blow air into the basement or living area from either upstairs or outdoors. It attempts to create enough pressure at the lowest level indoors (in a basement for example) to prevent radon from entering into the house.

Natural ventilation occurs in all houses. By opening windows, doors, and vents on the lower floors you increase the ventilation in your house. This increase in ventilation mixes outdoor air with the indoor air containing radon, and can result in reduced radon levels.

Uses of Radon: Health Uses * Since the early 1950's, unused gold and uranium mines have been used as health mines and spas. When the health mines and spas first opened, the risks associated with radon were not known, but still today hundreds of people visit these radon spas every summer.

Many of the visitors are Amish and Mennonites and they come to the mines and spas to live surrounded by radioactive radon gas, bath in radioactive water and drink radioactive water to improve their health. Radiation levels in the mines and spas can reach 175 times the federal base level, but the visitors claim that the radon mines and spas offer a cure for rheumatoid arthritis, multiple sclerosis, depression and cataracts. Some physicians even recommend these mines and spas for their patients.

Other Uses * Besides health mines and spas, radon is used to study atmospheric transport and to explore petroleum and uranium. Because radon decays rapidly and disappears quickly in the air, radon gas is used in hydrologic research to study interactions between ground water and streams. This finding has led to studies of concentration of radon gas in streams that indicate there is an outlet for groundwater in the stream. Scientists have also found that radon concentrations are increased or are quickly changing around faults and possible earthquake locations, so radon gas can be used to predict earthquakes. In addition, radon can initiate and influence chemical reactions, as well as be used to study surface reactions and detect leaks.

*

M.Sc. (Physics) final year student & Corresponding author

*

M.Sc. (Physics) final year student & Corresponding author