Introduction

Humans have always been subjected to natural radiation. We are exposed to radiation from the sun and outer space. Naturally occuring radioactive materials are present in the earth, from the structures we inhabit, and from the food and water we consume.

As a result of the radioactive gases in the atmosphere, our bodies absorb radioactivity. The levels of this natural (or background) radiation vary greatly from location to location.

The U²³⁸ , Th²³² and U²³⁵ series naturally occur in the earth’s crust. Therefore it is also present in our drinking water. Each of the series has a long-lived main nuclide and a number of short-lived daughters. In this paper, we analyze the concentrations of radioactivity in well water in the Wadi Al_Arab area of Jordan.

In the context of drinking water, “short-lived” radionuclides develop during underground transport, or during processing and storage prior to consumption. On the contrary, “long-lived” radionuclides dissolved in water at the rock-water interface and are still detectable at the point of sampling from wells, springs or drain outputs (Surbeck, 1994).

According to our literature survey, only a few studies have been made to measure the natural radioactivity in northern Jordan, especially in the Wadi Al-Arab area. The studies done on the Wadi Al-Arab dam and surrounding areas have focused on the quality of water, and the concentration and distribution of heavy elements. These found that heavy metal concentrations nearly reflect the natural background radiation value given by Turekian and Wedepole (1961). Therefore, we have made a systematic measurement of natural radiation in water in the Wadi Al-Arab area.

Experimental Method

Using a water sampler, 1.00 L samples were taken from both surface and ground water at different locations and depths in the reservoir.

To prevent contamination, Merineelli (polyethylene) beakers were pre-washed with sampled water. The samples were then transferred to these beakers, which were immediately sealed to prevent the volatile radon gas from escaping.

In the laboratory, the water samples were analysed by a Gamma spectrometer. Gamma spectroscopy measurements were carried out using a germanium detector (EG&G ORTEC’s GammaVision). This allowed us to determine the activity of many elements. However, some elements do not produce a significant gamma ray and in other cases, different elements may interfere with each other.

Specifically, we measure the following radionuclides by their characteristic signals:

a) ²²²Rn concentration was determined by measuring the 295.1 (19.2%) and 352 (37.1%) keV -rays from Pb²¹⁴ and the 609.3 (46.1%) and 1120.3 (15%) keV γSrays from Bi²¹⁴.

The Ra²²⁶ concentration was calculated by averaging over the measured concentrations for Pb²¹⁴ and Bi²¹⁴.

b) Ra²²⁶ concentration was determined by measuring the 186 (5.4%) keV γSray.