The concentration of naturally occurring radioactive materials (NORM) in surface water and irrigation wells is measured using gamma ray spectrometry by HPGe detector. Measurement was carried out for samples that were collected over seventeen points in Tehran city and its suburbs. The samples were prepared in compliance with the principles from irrigation wells of city. The specific radioactivity of Ra-226, Th-232 and K-40 were measured and the results from different locations covered a range with the minimum being below "minimum detectable activity" up to maximum of 4.04, and 6.85 and 4.7 Bq per liter of water, respectively. The accumulation of radioactive materials in the samples from southern areas of Tehran was more than that of central areas. Also, concentration of Ra-226 in all the samples was less than the Derived Release Limit of Canada and Environmental Protection Agency standard threshold.
- Natural radioactivity of water resources in city of Tehran is measured.
- A precisly calibrated HPGe detector has been employed.
- Radioactivity concentration is higher at south part of Tehran.
- Activity is mostly due to Th-232 and K-40 but little from Ra-226.
- Results show that the whole activity is more than many countries but comparable with standards.