Radiation Detection in Vegetable Leaves - a Comparative Case Study in Coastal and Hinterland Regions of Akwa Ibom State

RADIATION DETECTION IN VEGETABLE LEAVES:

A COMPARATIVE CASE STUDY IN COASTAL AND HINTERLAND REGIONS OF AKWA IBOM STATE

BY

Godfrey T. Akpabio,

Ime E. Essien

And

Bassey E. Bassey.

Department of Physics,

University of Uyo,

Uyo.

ABSTRACT

Radioactive radiation level was detected for five samples of vegetable leaves namely: Water leaf, Fluted Pumpkin, Editan - Lasientera africana and Afang - Gnetum africanum. These vegetable leaves were collected from Uyo (interland region) and Ibeno (coastal region) in Akwa Ibom. Radioactivity level in each of these samples were measured and recorded. In Uyo waterleaf has the least radioactive level of 0.00079Bq/g while Editan has the highest level of 0.0019Bq/g. In Ibeno, fluted pumpkin has the least level of 0.0037Bq/g while waterleaf records the highest radioactive level 0.0070Bq/g. The higher radioactive level observed in Ibeno is attributed to the presence of radioactive materials in the environment due to oil drilling activities in the area.

Keywords: Radioactivity, Radiation, Vegetable leaves, NORM

INTRODUCTION

Radiation is energy that comes from a source and travels through some material or through space. The term radiation refers to the emission of particles, such as electrons, neutrons, or alpha particles as well as to electromagnetic radiation. Nuclei that are not stable are radioactive (Tippler, 1991). Radioactivity can be dangerous to human health. Natural occurring radioactive materials (NORM), produced along with oil and gas production, are often concentrated at some point in the hydrocarbon production process. Concentrations of NORM are found in oil and gas production equipment and waste. The radioactive component is, of course the major environmental concern especially a place like Akwa Ibom State. Many processes occur in a leaf, but the distinctive and most important is food manufacture. Green plants posses the ability to manufacture food from raw materials derived from the soil and the air, and upon this activity depends not only the life of plants but also the life all animals, including man (Wilson et. al., 1971). All leaves are metabolic factories equipped with photosynthetic cells, but they vary enormously in size, shape and texture (Starr and Targgart, 1995). Vegetable leaves are plant or part of plant (leaves) that is eaten as food (Hornby, 2001)

There are a number of devices that can be used to detect the particles and photons emitted when a radioactive nucleus decays, such devices detect the ionization that these particles and photon cause as they pass through matter, (Cutnell and Johnson, 1998). The presence of radioactive substance is easily detected with a Geiger Muller counter, based on the ionization produced by the radioactive emanations, (Eno, 1998). One of the most common radiation detectors is the Geiger counter. These radiation detectors are based on the ionization or excitation of atoms by the passage of energetic particles through matter, (Wilson and Buffer, 2000). The GM counter is non-energy dissipative, hence effectively useful for environmental radiation measurements, (Sigalo and Briggs- Kamara, 2004)

The rate at which radioactive materials disintegrates or decay is almost independent of all physical and chemical conditions. The activity of a radioactive sample can be expressed in terms of the rate of decay, that is, the number of disintegration per second in the sample (Holwill and Silvester, 1976). Unstable nuclei are radioactive and decay by emitting  particles (4He nuclei),  particles (electrons or positrons), or  rays (photons). (Tipler, 1991). Radioactivity, or the emission of  - or  - particles and  rays, is due to the disintegrating nuclei of atoms. All radioactivity is statistical in nature and follows an exponential decay law, equation 4.

The number of atoms disintegrating per seconds, dN/dt, is directly proportional to the number of atoms, N, present at the instant. (Nelkon and Parker, 1977).

Hence

= -N (1)

where  is a constant characteristic of the atom concerned called the radioactivity decay constant.

Thus, if N0 is the number of radioactive atoms present at a time t = 0, and N is the number at the end of a time t, we have by integration

= -  dt (2)

[ ln N] = - t (3)

 N = N0e-t (4)

Thus the number N of radioactive atoms left decreases exponentially with time t.

The rate of decay is given by

R = N = R0e-t (5)

The time it takes for the number of nuclei or the decay rate to decrease by half is called the half life TÐ..., that is, in a time TÐ... the radioactivity of the element diminishes to half its value.

Hence from (5)

= N0e-t (6)

 TÐ... = ln 2 = (7)

TÐ... = (8)

This work is to determine how safe our vegetable leaves are in an oil producing area of Akwa Ibom State.

Table 1: Experimental Results for Samples obtained from Ibeno LGA

Samples Mass (g) Background

Count for 10 mins. Background + Sample count

for 10 mins. Sample

Count for

10 mins Corrected

count for

1 sec. Counts per

Grammes

(Bq/g)