ABSTRACT

An investigation of the ²²²Rn levels in ground water, soils, and indoor air has disclosed two ²²²Rn ground-water anomalies in the Kingsville, Texas, area from uranium-enriched sandstones of the Evangeline aquifer. Indoor air ²²²Rn levels were measured in summer 1991 (from undetectable to 3.2 pCi/l) and winter 1991-1992 (0.01 to 3.98 pCi/l) to determine seasonal extremes and risk to the public. Soil ²²²Rn concentration maps ranging from undetectable to 75.4 pCi/l correlate to the low levels found in homes. Results of this study are based on analyses of 218 water samples, 52 in situ soil samples, and 104 indoor air samples. Water samples were injected into a scintillation mix (EPA/EERF-Manual-78-1) and analyzed by liquid scintillation techniques. Indoor air and soil samples were collected using passive charcoal canisters and analyzed by gamma-ray detection techniques (EPA 520/5-87-005).

One ground-water ²²²Rn anomaly lies near the permitted boundary of a large uranium deposit that is being mined. Private wells near the ore body yielded 1,023 to 23,256 pCi/l at the well head. A second anomaly is located 2.5 mi (4 km) north of the uranium ore body near Naval Air Station, Kingsville. Private water wells in this area yielded 442 to 1,950 pCi/l ²²²Rn at the well head. The radon anomalies are related to subsurface mineralization, which is one of the known natural geologic hazards of this area.

Indoor air ²²²Rn levels are well below the U.S. Environmental Protection Agency (US/EPA) action limit of 4 pCi/l. However, the high levels of ²²²Rn in ground water should be mitigated before entry into the home environment. High ²²²Rn levels in ground water were reduced to background levels in household waters by use of a pre-introduction large-capacity holding tank.