EFFECT OF SOME PHYSICAL PROPERTIES OF THE BLACK SANDS ON THE RADIATION EXPOSURES AT MASTAROUH, NORTH NILE DELTA, EGYPT

The average apparent density of studied sediment is 1599kg/m3 and its effective porosity is 0.22. The
total heavy mineral contents in the black sands at Mastarouh area was found to vary from 10.56 % to 39.66%
with an average of 26.60%. Its variation affects the activity concentrations of the four radio-nuclides, 238U,
232Th, 226Ra, and 40K, as well as the absorbed dose rate, radon flux and the total radioactivity. The mentioned
variables display the same behavior like the total heavy minerals except 232Th. The averages of the activity
concentration, in Bq/kg, for the four profiles due to the four radio-nuclides are: It is 61.75, 47.64, 34.99 and
44.11 for 238U; 63.22, 49.88, 35.19 and 33.06 for 232Th, and 42.28, 37.6, 18.5 and 25.36 for 226Ra. The
measured activity concentration emitted from 40K was found to vary from not detected in the four profiles
to maximum values of 187.70, 97.03, 63.73 and 106.40 with the averages 63.50, 55.40, 37.56 and 56.79,
respectively. The minimum values for the total radioactivity in Bq/kg for the four profiles are 118.00, 61.41,
49.06 and 85.94 while the adjacent maximum values are 340.20, 24.40, 153.70 and 109.70. The radon gas
concentration in Bq/kg was found to vary from 111 to 2057 with an average of 1211.
The measured dose values, in nGy/h, are generally less than the calculated values. The calculated ones
vary from a minimum value of 20.50 to a maximum value of 111.00. About three quarters of the averages
absorbed dose rate (D) are beyond the worldwide average absorbed dose rate. The average of the absorbed
dose rate on the first profile, neighbor the shore line, is higher than the worldwide average then it decreases
for the next three profiles to be less than the worldwide average. The radon flux at Mastarouh area has an
average of 2.48X10-3 (Bq m-2s-1) being much lower than the worldwide average. However, the radiation
exposures at Mastarouh area are below the worldwide public exposures. The activity concentrations of
all the studied radio-nuclides in the black sands due north from the North Africa International Highway at
Mastarouh area are comparable to the typical worldwide concentrations.