Abstract
High concentrations of Rn-222 in potable water, as from some wells, is a potential health hazard. Well water sometimes undergoes temporary storage in reservoirs before distribution. Rn-222 concentration in the effluent water from these reservoirs was assayed using standard liquid scintillation counting. In most cases five samples were taken from each reservoir under conditions that minimize loss of Rn-222 gas. In most of the tested reservoirs, except one providing water mostly for domestic uses, the 222Rn concentrations were found to be about equal to that of the water fed to the reservoir or less by different amounts depending upon length of the storage period. However for a certain reservoir the results were different. The water fed to that reservoir was a mixture of water from private well and from municipality supplied well water with Rn-222 concentrations equal to 743 +/- 47 pCi L-1 (27.49 +/-1.7 Bq L-1) and 393 +/- 55 pCi L-1 (14.54 +/-2.0 Bq L-1), respectively. The effluent water had a Rn-222 concentration of 3,131 +/- 98 pCi L-1 (115.85 +/-3.63 Bq L-1). Over a period of 1 y there was little change in effluent Rn-222 concentrations. Although Ra-226 concentration in feed water was below detection limit, yet it is known that the positively charged Ra-226 ions easily absorb and accumulate on surfaces. Since that reservoir was in a rural area supplying a small community, it is likely that the residence time of the fed water was longer than usual allowing increased adsorption and accumulation of Ra-226, which must have been present in the fed water although below detection limit. The decay of Ra-226 enriches the stored water Rn-222 concentration. That particular reservoir had been in use for several years and had thus accumulated much Ra-226 and was remediated.