Radon in groundwater from India- a brief report.

There have also been a number of reports of the presence of dissolved radon in groundwater from India.
by
Dr. Nitish Priyadarshi

Presence of high levels of Radon (222 Rn) has been reported from groundwater in Bangalore city, Keolari-Nainpur area, Seoni-Mandla district in Madhya Pradesh, Bathinda , Gurdaspur, Garhwal, Himachal Pradesh and Siwalik Himalayas and underground waters of the Doon valley in India.

To ascertain the ground reality and the nature of the hazards, if any, a study was conducted by the Central Ground Water Board, Bangalore in and around Bangalore city. The analytical results of all the groundwater samples collected from the gneissic and granitic rocks shows Radon concentration is above the permissible limit of 11.83 Bq/l and at places the concentration is as high as hundred times. The radon gas is occurring in the groundwater of the area ranging from 55.96 Bq/l to 1189.30 Bq/l plus or minus error values.

There is no relation between the radon concentration and the depth of bore wells. However it is observed that the formation waters from very shallow aquifers are having the least concentration of radon due to its easy loss to the atmosphere. Surface water samples are having negligible quantity of radon, which is well within the safe limits. It is observed that there is a good correlation between the presence of high radon content and the presence of granitic rocks.

Higher concentration of uranium and radon in groundwater of Keolari-Nainpur area have been observed during an exploration programmes for uranium. The average value of dissolved uranium in bore well waters is 13 ppb (parts per billion). Considering 200 ppb as a safe limit, it has been possible to delineate several pockets, where groundwater is contaminated by very high uranium ( 217- 4,500 ppb in 13 villages) and radon (34,151 Bq/m3 to 1,146,075 Bq/m3 in 6 villages). These pockets, therefore, have been classified as high background radiation area on the basis of (a) long lived alpha radioactivity through ingestion of more than 2 Bq/day (b) 222Rn concentration on potable water exceeding 200 Bq/m3.

High radon concentration has been reported in river waters of Garhwal and Siwalik
Himalayas and underground waters of the Doon valley. Extremely high uranium content was reported in groundwater of Bathinda district in the Punjab state. The radon concentrations have been measured in all those areas where high uranium content was
reported in groundwater. The average radon concentration in hand-pump drawn water is 3.8 Bq /l and in tube-well drawn water, its value is 3.6 Bq /l. Radon values for Bathinda district are lower than the corresponding values for Gurdaspur district. The occurrence of radon in groundwater is reasonably related to the uranium content of the bedrocks and it can easily enter into the interacting groundwater by the effect of lithostatic pressure. Relatively high concentrations of radon (25–92 Bq/l) were reported for groundwater from Quaternary alluvial gravels associated with uranium-rich sediments in the Doon Valley of the Outer Himalaya.


Radon activities in groundwater samples in different districts of Himachal Pradesh varies from 0.3 ± 0.2 to 792 ± 9 Bq /l. The maximum value of radon concentration is found in groundwater of thermal springs and the minimum value in a water tank. The highest value of radon concentration is recorded in thermal spring (no. III) at Kasol,
792 ± 9 Bq/ l which is in the Kullu district of Himachal Pradesh. The uranium content of water in the Kasol thermal springs was found to be 37.40 ± 0.41 ppb. The radon
anomalies are related to Shat-Chinnjra and Kasol mineralisation. The radon concentration at Chinnjra also shows a high value of 144 ± 4 Bq/ l in natural spring (bauli) as compared to other natural springs at Takrer and Bradha in the same area.

The study was also carried out in Varahi and Markandeya river basins, Karnataka State, India. The measured 222Rn activities in 16 groundwater samples of Varahi command area ranged between 0.2 ± 0.4 and 10.1 ± 1.7 Bq/ l with an average value of 2.07 ± 0.84 Bq /l. In contrast, the recorded 222Rn activities in 14 groundwater samples of Markandeya command area found to vary from 2.21 ± 1.66 to 27.3 ± 0.787 Bq/ l with an average value of 9.30 ± 1.45 Bq /l.

Despite its known health effects, no WHO guideline value exists for radon in drinking water because of the difficulties in defining a regionally-applicable value given the relative importance of inhalation compared to ingestion from drinking water. Radon concentrations in groundwater also change significantly on abstraction, aeration, storage and boiling.

Radon is essentially chemically inert, but radioactive (www. chemistrydaily.com). It is the heaviest noble gas at room temperature. At standard temperature and pressure radon is colorless. Natural radon concentrations in the Earth’s atmosphere are very low, the water in contact with the atmosphere will continually lose radon by volatilization, while groundwater has a higher concentration of 222 Rn than surface water. Likewise, the saturated zone of soil frequently has higher radon content than the unsaturated zone due to the diffusional losses to the atmosphere.

Radioactive substances in ground water, such as radium, uranium and thorium, occur naturally. They are present at least to some extent in almost all rocks and radium, in particular, dissolves more readily into ground water in contact with sands or soils. The acidity of the water, which may be increased by the presence of elevated levels of nitrates associated with agricultural land use, is believed to increase the amount of radium that dissolves into ground water from contact with sands and soils.

There are twenty known isotopes of radon. The most stable isotope is radon-222 which is decay product ( daughter product) of radium-226, has a half life of 3.823 days and emits radioactive alpha particles. Radon-220 is a natural decay product of thorium and is called thoron. It has a half life of 55.6 seconds and also emits alpha rays. Radon-219 as derived from actinium, is called action and is an alpha emitter having a half life of 3.96 seconds.

Radon being the daughter product of the uranium is expected in higher levels in rocks containing uranium. The studies indicate the granits, pegmatites and other acidic rocks are generally rich in uranium compared to other rocks types. When groundwater percolates through rocks rich in uranium, it is expected to contain high level of radon gas in groundwater.

Radon is a carcinogenic gas and is radioactive. It is hazardous to inhale this element, since it emits alpha particles. Radon in water may therefore present dual pathways of exposure for individuals through drinking water and inhalation of air containing radon released from groundwater.

Its solid decay products, and their respective daughter products, tend to form fine dust, which can easily enter the air passage and become permanently stuck to lung tissue, causing heavy localized exposure. Build-up of radon in homes has also been a more recent health concerns and many lung cancer cases are attributed to radon exposure each year. Radon escalates health hazard to smokers.

Reference:

Hunse, T.M., Najeeb, K.Md., Rajarajan, K. and Muthukkannan, M., 2010. Presence of Radon in groundwater in parts of Bangalore. Jour. Geol. Soc. of India, v.75, pp. 704-708.

Sinha, D.K., Shrivastava, P.K., Hansoti, S.K. and Sharma, P.K., 1997. Uranium and radon concentration in groundwater of Deccan Trap country and environmental hazard in Keolari-Nainpur area, Seoni-Mandla district, Madhya Pradesh. Geol. Surv. Ind. Spl. Pub. v.2, no.48, pp. 115-121.

http://www.nj.gov/dep/rpp/download/radwater.pdf
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Think twice before using radioactive granite for decorative purpose in your house- radiation may affect you.

Granite rocks in some parts of Jharkhand State of India is highly radioactive- says research.

By

Dr. Nitish Priyadarshi

A physics professor at Rice University is warning of a radioactive threat found in some kitchen countertops.
Some granite countertops contain levels of uranium high enough to be dangerous to humans, said Rice professor W.J. Llope.

Using a spectrometer, Llope tested 25 varieties of granite bought from Houston-area dealers. In some cases, he said, he found countertops that could expose homeowners to 100 millirems of radiation in just a few months — the annual exposure limit set by the Department of Energy for visitors to nuclear labs.

Scientists at the national geophysical research institute (NGRI) of India have disturbing news for residents of Hyderabad city especially those living in rocky Banjara and Jubilee hills area. They have found that the granite rocks of Hyderabad have abnormally high concentrations of radioactive uranium and thorium compared to elsewhere in southern India. Team has measured the radioactivity of rocks from nearly 2,000 locations in the states of Karnataka, Tamil Nadu and Andhra Pradesh and nowhere did they find it to be as high as in Hyderabad.

Rocks in the western part of Hyderabad are more radioactive compared to those in the east. Rocks in the posh areas of jubilee and Banjara hills have twice as much uranium as found in Uppal in the southeastern part of the city.

The uranium content of Hyderabad granites varied from 10 parts per million (ppm) to 25 ppm in contrast to 0.23 ppm for Chennai and 1.7 ppm to 7.5 ppm for Bangalore. The thorium content of Hyderabad granites was also found to be four to five times higher than that of Bangalore. These high values of radioactive elements could pose a health hazard.

According to A. M. El Arabi, N. K. Ahmed and K. Salahel Din of Physics Department, South Valley University, Qena, Egypt, the average dose rates values for outdoor and indoor air for Elba granites of Egypt are found to be three times higher than the world average. Whereas, the corresponding average values for Qash Amir and Hamra Dome granites are five and six times higher than the world average, respectively. Thus, this information is an important alert for the local people to avoid the use of these granites in the construction of dwelling without radioactivity control.

While most experts agree that only a small percentage of granite in homes today poses any health risk, the current debate centers on identifying granite that might emit radiation and determining under what circumstances a danger occurs.

All rocks have a small amount of radioactivity in them due to the presence of minerals that contain radioactive elements uranium (U), thorium (Th) and potassium-40 (40K). Because granite typically contains more of these elements than most other rocks, it will be more radioactive than a slate or marble. All of the minerals in granite contain some radioelements; the white or pink feldspars contain 40K, the black biotites and horn-blendes contain 40K, U and Th, and the small inclusions of minerals such as zircon, apatite, sphene, etc. contain the most U and Th.

People living in granite areas or on mineralized sands receive more terrestrial radiation than others, while people living or working at high altitudes receive more cosmic radiation. A lot of our natural exposure is due to radon, a gas which seeps from the earth's crust and is present in the air we breathe.

It has been established that human exposure to radioactivity comes mainly from natural sources. The natural radiation to which the general public is exposed consists of two components, namely, internal exposure and external exposure. Internal exposure is due to the inhalation of radon gas in the air and the intake of traces of radio nuclides in food and drinking water. External exposure arises from terrestrial gamma rays and cosmic radiation incident on the earth’s surface. In fact, only about 15% of the total effective dose is derived from cosmic radiation and about 0.6% is attributable to cosmogenic radio nuclides. The members of the radioactive decay chains of 232Th (14%), 235U and 238U (55.8%), along with 40K (13.8%) are responsible for the main contributions to the dose from natural radiation, while a more than 0.3% is due to the effect of 87Rb.

Many natural rocks contain radioactive elements such as 238U, 226Ra, 232Th and 40K. Although these radio nuclides are widely distributed, their concentrations depend on geological and geographical conditions and as such they vary from place to place.

In geology, rock is a naturally occurring aggregate of minerals. Rocks have had a huge impact on the cultural and technological advancement of the human race. Rocks especially granite have been used by Homo sapiens and other hominids for more than 2 million years. The prehistory and history of civilization is classified into the Stone Age, Bronze Age, and Iron Age. Although the stone age has ended virtually everywhere, rocks continue to be used to construct buildings and infrastructure.

But now a days rock (granite) are now seen as source of dangerous radioactivity. It is in the form of natural background radiation which affects the humans. Humans have always been exposed throughout their period of existence to naturally occurring ionizing radiation.

Geologically the term granite is placed under felsic or acidic divisions. It refers to a rock composed mainly of quartz and feldspar as essential minerals. The dark minerals like biotite, tourmaline and few of amphiboles groups, etc. occur as minor constituents of granite. Granite is the typical example of relatively coarse- grained plutonic rocks that crystallized slowly in large masses within the crust.

Granite is actually rather radioactive and has 5 to 20 times the concentration of uranium compared to other common rock types. Some health concern exists in areas that are rich in granitic terrain, as background radiation is enhanced by the presence of large granite bodies. Although the uranium is generally not concentrated enough to make granite a uranium ore, the leaching and erosion of granite has helped produce most of the uranium ore deposits around the world.

Some granites contain around 10 to 20 parts per million of uranium. By contrast, more mafic rocks such as tonalite, gabbro or diorite have 1 to 5 ppm uranium, and limestones and sedimentary rocks usually have equally low amounts. Granite could be considered a potential natural radiological hazard as, for instance, villages located over granite may be susceptible to higher doses of radiation than other communities.

Granite has been extensively used as a dimension stones and as flooring tiles in public and commercial buildings and monuments. Because of its abundance, granite was commonly used to build foundations for homes in New England. With increasing amounts of acid rain in parts of the world, granite has begun to supplant marble as a monument material, since it is much more durable. Polished granite is also a popular choice for kitchen countertops due to its high durability and aesthetic qualities.

People using granites, containing high uranium, for decorative purpose inside house may be affected with radiation.

People of Ranchi and other parts of Jharkhand state of India are frequently using polished granites for different decorative purpose without knowing how much uranium is present in the stone. Author has earlier warned the people of Ranchi about the possibility of radioactivity in Ranchi rocks. People using local granites or brought from Hyderabad, for decorative purpose, should be more cautious.

Even the granites of the Daltonganj area of Jharkhand state contain anomalous uranium values. Uranium mineralization has also been observed in the granitic rocks comprising the southern periphery of the Hutar basin of Daltonganj area. The Proterozoic granitoids, forming the provenance for the Hutar and Auranga subbasin, have been analyzed which revealed uranium content up to 520 ppm. ( Virnave, 1999).

As demand for granite has increased, exotic stones are being imported from remote corners of the world and greater scrutiny is needed. Lots of varieties of granite are sold for household use in the Jharkhand State. None of them is routinely tested for radioactivity. Even the businessman selling granites are in regular contact with the radiation.

People must go for alternative decorative stones like sandstone or marble, having low uranium, other than using radioactive granites. Even if they are using granites, their houses should be proper ventilated so that the poisonous gases can be flushed out.

Sources:

A. M. El Arabi, N. K. Ahmed and K. Salahel Din. ASSESSMENT OF TERRESTRIAL GAMMA RADIATION DOSES FOR SOME EGYPTIAN GRANITE SAMPLES. Radiation Protection Dosimetry 1-4 (2007).

Bruzzi, L., Baroni, M., Mele, R. and Nanni, E. Proposal for a method of certification of natural radioactivity in building materials. Radiolo. Protec. 17(2), 85–94 (1997).

Iqbal, M., Tufail, M. and Mirza, S. M. Measurement of natural radioactivity in marble found in Pakistan using a NaI(Tl) gamma-ray spectrometer. Environ. Radioact. 51, 255–265 (2000).

Virnave, S.N. Nuclear Geology and Atomic Mineral Resources. Bharati Bhawan, Patna. 169.

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