ASSESSMENT OF GROSS ALPHA AND BETA ACTIVITY IN SURFACE AND UNDERGROUND WATER IN NNEWI NORTH, ANAMBRA STATE

Background of the study

Water as one of the most important natural resources is vital. Water is an essential substance to all living things which include: man, animal and all that surround them. Every living thing is made up of water. The use of water cuts across industrial, agricultural and domestic uses. The two main sources of water are surface and   underground   water.   Underground water is the water present beneath Earth's surface in soil pore spaces and in the fractures of rock formations (boreholes and wells). Groundwater is only a small fraction of the total water in the world - about 0.6% - but it represents the main source of freshwater (Bouwer, 1978). Unfortunately the groundwater below a depth of 0.8 km is saline or is very difficult to extract (Bouwer, 1978). The potential useful water for human consumption is estimated to be about 4 million km3 (Bouwer, 1978). Surface water is water on the surface of the planet such as in stream, lake, river, wetland, or ocean. It can be contrasted with groundwater (Young and Bredehoeft, 1972). About 70% of the Earth’s surface is covered with water, which is estimated at a volume of approximately 1.4 billion km3 (Ashton et al., 2012).

Both surface and underground water can be contaminated by radioactive nuclides which include: Uranium, Radon, Strontium, Radium, Tritium and gross alpha and beta particles emitted from unstable radioactive elements. Certain problems have beset the use of groundwater around the world just as river waters have been over-used and polluted in many parts of the world (El- Mrabet et al., 2002; Guzman et al., 2002). The agricultural use of fertilizers is the main source of groundwater pollution, likewise natural radioactive elements. A portion of the radionuclides contained in fertilizers leaches through the soil and can reach the groundwater table (El-Mrabet et al., 2002; Guzman et al., 2002). However, human beings and natural phenomena are among the major agents that contribute in the deterioration of water sources; thus adversely affecting the quality of water. Water pollution mainly occurs as a result of release of any unwanted substance by human activities into water. Water pollution arises from wastes and sewage disposals into rivers and streams from various locations, such as industrial, hospital and rain wash out from fertilizer used for farming (Helliwell, 1975). Some of these pollutants are radionuclides which could have harmful effect on life. Water sources are equally polluted by naturally occurring radioactive materials (NORMS) of the earth’s crust; which emits alpha (α), beta (β) and gamma (γ) radiations (Helliwell, 1975).These materials which are normally from the potassium, uranium and thorium series are more concentrated in deep ground water than in surface water (Helliwell, 1975).

Radionuclides are radioactive isotopes that can occur naturally (those radionuclides in the earth’s crust and the environment) or result from man-made sources (resulting from nuclear and bomb testing, or power reactors accident, or industries). Typical radionuclides found in drinking water sources are isotopes of radium, uranium, and radon, among others. Fission products from man- made nuclear reactions are also of concern today, particularly radioactive cesium and iodine. Radiation exposure can occur by ingesting, inhaling, injecting, or absorbing radioactive materials (Narasimhan et al., 2005). By ingesting, inhaling, injecting of radioactive materials through water, food or drugs, air, the radiation source is inside the body and this is called internal radiation. On the other hand, when the radiation source is outside the body such as terrestrial radiations from soil, stones, water and X-rays radiation, it is called external radiation.

The amount of radiation exposure is usually expressed in a unit called millirem (mR or mrem), which is a measure of energy deposited in human tissue and its ability to produce biological damage (WHO, 1993). The SI unit of radioactivity is the becquerel (Bq), after Henri Becquerel, where 1Bq = 1 disintegration per second. Guidance levels for drinking-water are given as the activity of the radionuclide per litre, called the specific activity concentration (Bq/litre). The recommended guideline activity concentrations are 0.1 Bq/L for gross alpha activity and 1 Bq/L for gross beta activity (WHO, 1993). The absorbed dose refers to how much energy is deposited in material by the radiation. The SI unit for absorbed dose is the gray (Gy), where 1Gy = 1 J/kg (joule per kilogram).

The terrestrial component of the background is due to various radioactive nuclides that are present in air, soil, water, food and building materials whose abundances vary significantly depending on the geological and geographical features of a region (Bozkurt et al., 2007). Determining the distribution of these radionuclides is necessary for assessing the effects of radiation exposure. The increase in the level of radioactivity [in water] is as a result of possible migration of radionuclides to surface and groundwater from anthropogenic activities: seepage of pollutants into the groundwater bodies, excessive fertilization of agricultural land, abandoned industrial sites, thermonuclear testing or nuclear power plants (WHO, 1993). Post-mining areas, waste dump areas or military areas could also contribute to the radioactivity increase (WHO, 1993).

There is evidence from both human and animal studies that radiation exposure at low to moderate doses may increase the long-term incidence of cancer (WHO, 1993). Animal studies in particular suggest that the rate of genetic malformations may be increased by radiation exposure (WHO, 1993). Acute health effects of radiation, leading to reduced blood cell counts and, in very severe cases, death, occur at very high doses of exposure of the whole body or large part of the body to radiation (IAEA, 1998). No deleterious radiological health effects are however, expected from consumption of drinking-water if the concentrations of radionuclides are below the guidance levels of 0.1mSv/year (WHO, 1993).

Marbaniang (2011), determined the gross activity of the α and β emitting radionuclides present in the naturally occurring water bodies in the Uranium mineralization zone of Domiasiat, Meghalaya, India and found that they are lower compared to the WHO prescribed limit. He estimated that the additional equivalent effective dose derived from annual consumption of water is less than 0.3mSv/yr (2L per day). Gross alpha and beta activities and trace elements levels measured in drinking water of Saudi Arabia showed that trace elements concentrations in water did not exceed WHO, and GSO guidelines, gross alpha values were found to fall below the GSO and WHO recommended MCL of 0.5 Bq/l while the gross beta values in two samples only exceeds the MCL value of 1 Bq/l (Rafat, 2017).

Agbalagba and Avwiri (2012), determined Gross α and β activity concentration and estimated adults and infants dose intake in surface and ground water of ten oil fields environment in western Niger Delta of Nigeria and found that gross β activities were higher than the corresponding gross α activities, adults and infants dose intake obtained were below the WHO recommended reference level of 0.1mSvy-1 except for Uzere river water sample. They concluded that the water sources examined especially from river waters are contaminated radiologically.

Gross alpha and beta radioactivity were determined in ground water from some boreholes and wells in Kaduna North Local Government area using proportional counter. For the counting modes, results showed that the alpha activity in the study area was far below the practical screening level. However, a full sixty percent of the samples showed beta activity levels above the 1Bq/L as recommended by CEC-FAO and WHO (Abdu et al., 2016). Gross beta (β) radioactivity have been also assessed in Nassarawa town and found to be higher in well water than boreholes water (Ahmed et al., 2014), high levels of naturally occurring and carcinogenic radium isotopes have been measured in low saline and oxic groundwater from the Rum Group of the Disi sandstone aquifer in Jordan (Vengosh et al., 2009). The combined 228Ra and 226Ra activities in their study areas were up to 2000% higher than international drinking water standards. Measurement of tritium radioactivity in surface water on the Upper Silesia bordering two regions: Rokitnicki Stream Intervales (area I) and Klodnica and Bierawka Intervales (area II) revealed that tritium contamination has returned to the pre-bomb scale of 4-25 tritium unit TU (Aleksandra et al., 2000).

​​​​​​​Statement of the Problem

Increase in the radionuclide concentration levels has various health effects. Those health effects could be genetic or somatic; the genetic effects could be transferred to offspring while somatic effects could ultimately lead to death depending on the level of exposure (Levi, 2012). One of the exposure pathways is water. Water pollutants from residential, industries, as well as from fertilizers on farmlands; from rainwater and the NORMS affect the quality of water. Man’s ingestion of radioactive material may result from drinking contaminated water in the environment. The most important radionuclides associated with internal radiation exposure and the contaminations of the environment are: 241Am, 241Cm, 238Pu, 239Pu, 222Rn, 226Ra, which are alpha emitters; 45Ca, 14C, 134Cs, 89Sr, 90Sr, and tritium (IAEA, 1989) which are beta emitters. The season of the year determine to a great extent the magnitude of contamination of different water sources (IAEA, 1989; Strand et al., 2002). When alpha particle emitting isotopes are ingested, they are far more dangerous than their half-life or decay rate would suggest, due to the high relative biological effectiveness of alpha radiation to cause biological damages (Little et al., 1985). Alpha radiation is an average of about 20 times more dangerous, and in experiments with inhaled alpha emitter up to 1000 times more dangerous than an equivalent activity of beta emitting or gamma emitting radioisotopes (Little et al., 1985). Anambra state is becoming highly industrialized area: Chicason Group Of Companies offering manufacturing services in cement,

Asia-Afro automobile and plastics, Cutix PLc company manufacturing electric cables and wires, Ibeto Group of Companies offering industrial manufacturing of cement, automotive lead-acid battery and spare parts, Innoson Vehicle Company for motor vehicle assembling services, First Express Aluminum Company Limited manufacturing aluminum roofing sheets, windows and allied products, Uru Industries Limited; an Agro chemical industry with services in the manufacturing of fertilizers and other chemical supplement for agricultural purposes to mention some of them. This study is to ascertain whether the level of radioactivity in the underground water and surface water system that may result from this industrialization could pose any significant health hazard to the population of the area. Some studies made in Nigeria revealed that rivers water and or underground water (Agbalagba and Avwiri, 2012; Nwankwo, 2013; Ahmed et al., 2014; Abdu et al., 2016) are contaminated radiologically in specifics areas. Water has not been investigated for gross radioactivity concentration in Anambra state to the researcher best of knowledge.

​​​​​​​General Objective

To assess the gross alpha and gross beta activity in underground water and surface water in Nnewi North, Anambra state, southeast, Nigeria.

Specific Objectives

1. To determine the gross α level activity of α radiation in surface and underground water in Nnewi, Anambra state.

2. To determine the gross β level activity of β radiation in surface and underground water in Nnewi, Anambra state.

3. To assess the radiation hazard (Annual Effective Dose Equivalent) with the activity of α/β radiation associated with the consumption of water by children and adults in Nnewi, Anambra state.

4. To compare the concentration levels obtained with world standard limits to ascertain whether the level of α/β activity could pose any problem and estimate the radiological implications to Nigerian populace.

5. To compare the results from the present study with findings from different locations in Nigeria and others countries

​​​​​​​Significance of the Study

This study would ascertain whether the level of α/β activity in the underground water and surface water system could pose any problem to the populace. This study would be a guide in the education of the population of Nigeria. This study may provide a guide on a management of radioactive materials and present a data In radioactivity in surface and underground water in Nnewi area which will support Nigeria Nuclear Regulatory Authority (NNRA) in the control of water.

​​​​​​​Scope of Study

This was carried out in Nnewi, Anambra state, southeast, Nigeria. It was focused on samples of water collected from wells, boreholes, taps, rain water, stream and rivers. The samples were analyzed with a proportional counter analyzer to obtain the gross alpha and beta activity and their concentration levels.