Natural radioactivity in drinking water from 328 drilled wells was studied in correlation to source parameters. Poor correlation to both aquifer geology and bedrock radioactivity was observed. Concentrations of ²³⁸U, ²²⁶Ra, ²²²Ra, ²²²Rn and ²¹⁰Po in groundwater samples was in the ranges <0.027-5.3, <0.016-4.9, <0.014-1.24, 5-8105 and <0.05-0.947 Bq.l^-1 respectively. In about 80% of the sites the radon concentration exceeds the Nordic recommended exemption level for radon in drinking water and 15% of the sites exceed the action limit. The effective doses from ingestion were calculated and presented in association with geology. Doses due to ingestion ranged between 0.05 and 20.4 mSv.y^-1, where the average contribution from ²²²Rn amounted to 75%. In comparison, the effective doses from inhalation of indoor ²²²Rn ranged between 0.2 and 20 mSv.y^-1. The average contribution from inhalation of ²²²Rn in air to the total effective dose (ingestion+inhalation) was 58 ± 22%, 73 ± 18% and 77 ± 16% (1 SD) for the age categories 1 y, 10 y and adults respectively.

The current work aims at determining and assessing the total and bioavailable concentrations of some heavy metals, besides some properties, in soil samples from agricultural, industrial, and residential areas in Sudan. The GIS maps show similar trend of all examined metals in Marawi (the Northern state) area and different trends in other areas. Cluster analysis of the total contents of heavy metals shows the classification of 18 locations in Alhasahisa area in one group while the rest of locations from the three examined areas scattered in other nine groups with high variations.