Activity levels of some radionuclides in Mariout and Brullus lakes, Egypt

Mariout and Brullus are two of the highly fish-productive lakes in the northern coast of Egypt along the Mediterranean Sea. They are widely used to drain industrial wastes, sewage and agriculture drainage. The activities of U-238, Th-232, K-40 and Cs-137 were measured in the uppermost part of the surface sediments of the two lakes, using gamma-ray spectrophotometry. Brullus Lake recorded significantly higher U-238 and Th-232 and lower K-40 (17.222.49, 10.030.56 and 299.7017.78 Bq kg(1)) than Mariout Lake (12.651.53, 7.240.76 and 518.7546.24 Bq kg(1), respectively). Cesium-137 shows nearly equal activities in both lakes (3.330.46 and 3.680.70 Bq kg(1), respectively). Activity distributions of U-238 and Th-232 in the sediments of Mariout Lake show a significant increase to the west, southwest and northeast, K-40 activity increased westwards, while the Cs-137 level was increased to the east and northeast, indicating agriculture drainage, industrial wastes and lands reclamation around the lake. At Brullus Lake, the activity trends of U-238, Th-232, K-40 and(137)Cs were increasing to the west and south towards the agriculture and industrial waste-water-feeding drains.