Radon concentration Measurements in Qaysare of Erbil City

In this study the assessment of indoor radon concentration in the air of Qaysare in Erbil city have been studied by using CR-39 Solid–State Nuclear Track Detector Technique. A total of 18 selected zones inside the suq have been selected to place the dosimeters. The average radon concentration was found to be 21.54 ± 8.017 Bq/m 3 ,which is fortunately lower than the standard international limit from 200-600 Bq/m 3 as recommended by ICRP, IAEA. The potential alpha energy concentration and annual effective dose have been calculated. A proportional relationship between the annual effective dose and radon concentration within the studied region has been certified.


1.INTRODUCTION
Solid State Nuclear Track Detectors (SSNTDs) are insulating solids both naturally occurring and man-made. There are several types of these detectors including inorganic crystals, glasses and plastics. International studies of radon indoors and in the workplace have shown that the dose contribution due to the inhalation of 220Rn and its short-lived decay products have been detected as a significant component of the total radon contribution. To measure both 222Rn and 220Rn gas concentrations in the environment, solid state nuclear track dosimeters are commonly used in dual chambered passive diffusion monitors. It is possible to differentiate between 222Rn and 220Rn gas due to the relative differences in their It is estimated that the annual effective dose by radon and its progeny from the inhalation of air is about 50% of natural public exposure to high levels of radon can cause lung cancer [4]. Radon can enter buildings through the floor, and in cases where ventilation is poor, the radon concentration can build up to high levels, exposing the occupants via inhalation. [6].
Alpha particles are high linear energy transfer (LET) radiation and carry sufficient energy to cause permanent dames to DNA [7]. In addition, a number of in vitro studies using radon gas were defined for understanding the early changes induced at cellular and molecular level and DNA repair of these events. The studies proved that radon is capable of inducing significant chromosome damage event at very low doses and low dose-rate [8]. The studies proved that radon is capable of inducing significant chromosome even at very low doses and low dose-rate [9]. As well as, high ratio of indoor radon has impact of the male fertility [10], this more effects on the infertility of the male children.
Radon is responsible for the majority of the public exposure to naturally occurring radiation. The United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reported that radon and its progenies cause on average a radiation dose of 1.3 mSv per year and 79% of the radiation dose is due to the indoor radon inhalation. Therefore, each country makes national surveys of the actual radon concentration and implements radon management measures to protect its citizens [11].
The main source of radon in the air of a dwelling is the ground under buildings, which is responsible for 80% of the whole radon concentration inside a typical house [12].
Radon concentration in a dwelling mainly depends on the concentration of this gas in ground air, permeability of soil on which the building is erected and tightness of a house construction. Radon concentration in the air of dwellings is subject to seasonal and twentyfour hour variations. Moreover, radon contributes most to the effective annual dose received by people living in the area of normal gamma radiation background [13]. In Erbil city (the Capital of Iraqi Kurdistan Region), and despite of its historical background as the oldest city still being populated, there is a few number of works concerning the radon concentration measurements in closed areas [14]. For this the idea of radon concentration measurements in the semi-closed and ancient bazar (Qaisare) has been adopted to assess the radon levels inside and making comparison with the standard permissible values.
In solid state track detectors as CR-39 and other polycarbonate compounds, the path of an ionizing particle along the damaged trail is revealed by a conical pitch which is visible to microscopic analysis after a chemical etching. The pitch characteristics depend on properties of the etching solution and on travelling ion, so to allow determination of ion properties.
So nuclear track detectors (NTDs) register alpha particles emitted by radon gas and its progeny in the form of tracks, which will become visible under the optical microscope upon suitable chemical etching of the NTDs [15]. Interesting of radon dosimeters depended on the calibration factor, this factor has a wide range depends not only on the geometry of the used configuration but also on many parameters such as; type of the sued detector via their etching conditions, detector efficiency and the dosimeter dimensions [16][17].

2.MEASUREMENT METHODS
Diffusive chambers with CR-39 type track detectors with 500 µm thickness and dimensions of 1.5 cm x 1.5 cm were used in the present study. Dosimeters, such as shown in

3.CALCULATIONS AND EVALUATIONS
The CR-39 detectors exposed to the air inside the shops will be affected by radon and its daughters in the volume of air around them. In relating the observed track densities to the radon and its daughter activities per unit volume of air, the following equation has been used [19]: Where:  : is the number of tracks per cm 3 per unit volume.
x: is a constant with dimension of length (cm) A: is the alpha activity per unit volume (disintegrations per unit time per cm 3 ) The detailed calculation related to the equation has been published earlier [19]. The value of the constant x is the sum of separate constants calculated for all isotopes ( 222 Rn, 213 Po, 214 Po).In order to estimate the radon concentration, experimental method for radon detection and measurement are based on alpha-counting of radon and its daughters.  which is given by [22]: where: F is the equilibrium factor and recommended as F Rn = 0.4 [23]. Furthermore Qureshi. A et.al. [24] proposed a method to calculate the annual effective dose using the Working Level Month (WLM) units, and is given by Eq. (4): Therefore, the relation between the effective dose and Radon concentration is given by: where: G is constant.
In this study measurement of indoor radon concentration (C Rn ), potential alpha energy concentration (PAEC) and annual effective dose (H E ) have been performed.
The potential alpha energy concentration (WL) was calculated using Eq. (3), annual effective dose equivalent (WLM/year) and effective dose also has been calculated using Eqs.

4.RESULTS AND DISCUSSION
The recorded values of radon concentration (Bq/m 3 ) in different zones inside Erbil-Qaysare, Annual effective dose using the Working Level Month (WLM) units are presented in Table (1). The histogram schemes of these data are then shown in Figures (3) through (5) in which the results of different zones were declared obviously. The calculated average Radon concentration was (21.54 ± 8.017) Bq/m3. This value is lower than the radon references level which ranges from 200-600 Bqm-3 as recommended by ICRP, IAEA. [25,26] . On the other hand, radon concentration was varying from region to another, for example the activity of radon concentration in (Gold Smith) zone (5, 7, 10, and 15) is more than the other zones, while the minimum value was in (Shops selling textiles and clothing) Zone (11 and 13).
The comparison between the maximum and minimum values of radon activity concentration obtained at the different zones is given in Table 2

5.CONCLUSIONS
The radon concentration values obtained was varied within the studied zones depending on the height, wide, and ventilation opportunities of qaysare tracks. The recorded values of radon concentration were lower than the standard limits. A linear relationship has been traced between the annual effective dose and the measured radon concentrations.