تحديد تراكيز الرادون و اليورانيوم و نظائر مشعة أخرى في أنواع مختلفة من المياه الطبيعية في محافظة نينوى

Abstract EN

Radon (222Rn) is a naturally occurring radioactive gas with a half-life of 3.82 days, released from the normal decay of the elements uranium, thorium and radium in rocks and soil.

It is an invisible, colourless, odourless and chemically inert gas and has no taste.

Radon is fairly soluble in water and organic solvents and seeps up through the ground and diffuses into the air.

It dissolves into ground water and surface water and can be released into the air when water is used.

Radon is also present outdoors and indoors, but it is normally found at very low levels in outdoor air and in water from rivers and lakes.

Water represents the most important source for life and forms up (70–75)% of the total body weight.

While 70% of the world's surface is covered by water, only 0.3 % of the total water resources on earth is drinkable and suitable for daily use.

Human race provides its water from surface water and ground water.

Ground water is more radioactive than surface water, since it passes through rock and soil formations, dissolving many compounds, minerals and radioactive substances.

Naturally occurring radioactive material in groundwater (springs and wells) mainly comes from the uranium decay series with major members of concern for human health being 238U and 234U, 226Ra, 222Rn and 210Pb.

The concentrations of the radionuclides may vary over a wide range, depending on the bedrock in which the aquifer is located as well as the water parameters such as pH, Eh and alkalinity.

Radon decays into solid radioactive elements called radon daughters or radon progeny, such as 218Po, 214Po, 214Bi and 214Pb.

These daughters can attach to dust and other particles and can be breathed into the lungs.

As radon and radon progeny in the air decay, they give off alpha particles, a form of high-energy radiation.

When inhaled, these radioactive particles can damage the DNA inside the body's cells and also damage the cells that line the lung.

Long-term exposure to radon can lead to lung cancer, the only cancer proven to be associated with inhaling radon.

There has been a suggestion of increased risk of leukemia associated with radon exposure in adults and children.

The contribution to the mean effective dose equivalent from inhalation of 222Rn and its shortlived decay products 218Po, 214Po, 214Bi and 214Pb is estimated to be about 50% of the total effective dose equivalent from natural radiation sources.

The presence of 222Rn in the environment and ground waters is associated mainly with trace amounts of uranium and its immediate parent, radium (226Ra), in rocks and soil.

Radon can easily lose from water when it is agitated; for example, when river or other water sources flow over rocks or are moved by wind.

Natural water and drinking water may contain varying levels of radioactivity.

It is therefore important to determine the radon and the radium levels as well as other radionuclides’ levels in water for public health and radiation protection.

This paper presents results of radon (222Rn), radium (226Ra), uranium (238U), Bismuth (214Bi) and potassium (40K) concentrations in underground water (springs and wells), surface water (from rivers and lakes), drinking water from different sources as well as rain water in Nenava governorate in Iraq.

Thirty four (34) samples of natural waters were brought from different sources: projects of tapwater, underground wells, pure and mineral springs, as well as rain water in Nenava governerate.

Long-term technique for alpha particles emission with solid state nuclear track detector (SSNTD) CR-39 and short-term technique for gamma spectroscopy with high purity germanium detectors (HPGe) have been used to determine the concentrations of radon (222Rn), uranium (238U) and other radioactive isotopes, such as radium (226Ra), bismuth (214Bi) and potassium (40K) in the water samples.

The solid state detector CR-39 was exposed to water samples for 95 days within the period from 23/12/2003 to 5/4/2004, except that for rain water sample the period of exposure was from 25/1 to 30/4/2004, to measure the concentrations of radon, radium and uranium in the water samples through alpha particles’ emission, while multi-channel analyzer was used to determine the concentrations of potassium and uranium through gamma-ray emission from these samples.

The results showed concentrations between (0.838-1.758) Bq.L-1 for radon (222Rn) with high value in rain water.

Uranium (234U) concentration has ranged between (67-142) ppb and (73.2-138.3) ppb using SSNTD and HPGe techniques, respectively, and these values are lower than the maximum allowed concentration of dissolved uranium in drinking water which is about 9000 ppm.

Concerning radium (226Ra), its level ranged between (2.29-4.8)*10-5 ppb, while the concentration of potassium (40K) was (6.525-10.125) Bq.L-1 and that of bismuth (214Bi) was (5.179 - 9.446) Bq.L-1.

The annual effective dose of radon was calculated, and it ranged between (4.40-9.24) sv.y-1 in case of ingestion and (2.30-4.82) sv.y-1 in case of inhalation.

These values are regarded less in comparison with the allowed normal limit which is about 0.1 msv.y-1 for drinking water.

In general, the concentrations of radon in natural waters are less than the maximum allowed limit which is about 18 Bq.L-1, and there will be no risk on the human being life.