الفهرس 
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Abstract
Oil and gas industry is potential and considerable source of radiation since the extraction process enhances the presence of certain radioisotopes through further processes such as refining, ending with the disposal of the wastewater to its final destination. This radiation source should be monitored and taken in account while calculating the accumulated doses to oil and gas workers, the waterbodies into which the wastewater is disposed and the other environmental elements such as fauna and flora (Ali M. et. al., 2019).
To determine the radioactivity levels in wastewater streams produced from two oil refineries located in Alexandria, Egypt. And to assess the possible environmental impact of disposing this wastewater to adjacent water bodies.
Three groups of samples were collected and studied from two oil refining companies located in Egypt. These samples were studied by measuring the radioactivity for samples taken from the water body in which the disposal of wastewater takes place and compared with the guidance levels set by WHO.
First site (COMPANY1): the radioisotopes measured in the samples of different origins (before and after refining and from water body in which the disposal of wastewater takes place) were 7Be, 40K, 137Cs, 208TI, 210Pb, 212Bi, 212Pb, 214Bi, 214Pb, 226Ra, 228Ac (228Ra), 234Th, 235U, 238U.
The total gamma radiation was non-significantly increased in water samples after refining (12.98±1.830 Bq/L) compared with its level in water samples before refining (10.85±0.990 Bq/L).
For 210Pb, 214Bi, 226Ra, 234Th, 235U and 238U, there were significant increases in radioactivities in water samples of COMPANY1 after being involved in refining compared with their radioactivities before refining (P<0.05).
For 7Be, 40K, 214Pb and 228Ac (228Ra), there were non-significant increases in radioactivities in water samples of COMPANY1 after being involved in refining compared with before refining (P>0.05).
For 212Pb, 226Ra, 235U and 238U, there were significant increases in radioactivities in water samples from adjacent water bodies in which disposal took place in COMPANY1 compared with their radioactivities after refining (P<0.05), while there were non-significant increases in radioactivities for 137Cs, 210Pb, 214Bi, 228Ac (228Ra) and 234Th (P>0.05).
The total gamma radiation calculated in water samples from adjacent water bodies in which disposal took place showed a non-significant elevations compared with after and before refining (14.45±0.690 Bq/L vs 12.98±1.830 Bq/L and 10.85±0.990 Bq/L; respectively).
Specific radionuclides from samples from water body in which the disposal of wastewater takes place were selected to be compared with WHO guidance for drinking water quality. These isotopes were 137Cs, 210Pb, 226Ra, 228Ac (228Ra) and 238U. The activity (Bq/L) in samples were 0.02±0.013, 2.91±1.727, 5.05±0.951, 0.22±0.091 and 1.37±0.401respectively. 137Cs and 238U radioactivities were found to be acceptable with respect to WHO limits while 210Pb, 226Ra, 228Ac (228Ra) exceeded the limits set by WHO.
Second site (COMPANY2): the radioisotopes measured in the samples of different origins (before and after refining and from water body in which the disposal of wastewater takes place) were 7Be, 40K, 137Cs, 208TI, 210Pb, 212Bi, 212Pb, 214Bi, 214Pb, 226Ra, 228Ac (228Ra), 234Th, 235U, 238U.
The total gamma radiation was non-significantly increased in water samples after refining (10.43±1.314 Bq/L) compared with its level in water samples before refining (9.49±1.960 Bq/L).
For 40K, 210Pb, 212Pb, 214Pb, 226Ra, 228Ac (228Ra), 234Th, 235U and 238U, there were non-significant increases in radioactivities in water samples of COMPANY2 after being involved in refining compared with before refining (P>0.05).
For 40K, there was significant increase in radioactivity in water samples from adjacent water bodies in which disposal took place in COMPANY2 compared with its radioactivity after refining (P<0.05), while there were non-significant increases in radioactivities for 208Tl, 210Pb, 212Bi, 212Pb, 214Bi, 226Ra, 228Ac (228Ra), 234Th, 235U and 238U (P>0.05).
The total gamma radiation calculated in water samples from adjacent water bodies in which disposal took place showed a non-significant elevations compared with after and before refining (14.27±1.907 Bq/L vs 10.43±1.314 Bq/L and 9.49±1.960 Bq/L; respectively).
Specific radionuclides from samples taken from water body in which the disposal of wastewater takes place were selected to be compared with WHO guidance for drinking water quality. These radionuclides were 137Cs, 210Pb, 226Ra, 228Ac (228Ra) and 238U. The activity (Bq/L) in samples were 0.00±0.000, 1.31±0.463, 3.39±0.796, 0.35±0.152 and 1.33±0.337 respectively. 210Pb, 226Ra, 228Ac (228Ra) exceeded the limits set by WHO, while 137Cs and 238U didn’t.