Direct measurements of radon activity in water from various natural sources using nuclear track detectors.

Radon activities measured in several types of natural waters from the Santos region in Brazil are presented. Makrofol E polycarbonate plastic detector was used. The detector foils were exposed to radon emanating from the water samples for 30 days in a system of two tightly coupled cups, one of which contained the detector foil and the other hosted the analyzed water sample. After irradiation and chemical etching of the plastic foils, the tracks produced by the alpha particles emitted by radon and its progeny were counted with a system consisting of an optical microscope and a video camera. The measured radon radioactivities ranged from 0.95 to 36.00 Bq/l for ground waters, from 0.30 to 0.54 Bq/l for sea waters, from 0.39 to 0.47 Bq/l for tap waters, from 0.43 to 2.40 Bq/l for river waters, and amounted to 2.35 Bq/l for water from the Santos/São Vicente public water supply.