Geologic and Hydrologic Factors Controlling Radon‐222 in Ground Water in Maine

Abstract

High Radon‐222 (222Rn) concentrations exist in ground water from most granitic rocks in Maine. Some values exceed the suggested limit of 500 pCi/1 (E.P.A., 1976) by more than 100 times. Although high values (x̄= 22,100 pCi/1) are conclusively linked with the granites, high values are also present in ground water in metasedimentary rocks from sillimanite‐ (x̄= 13,630 pCi/1) and sillimanite‐orthoclase zone metamorphic terrains. Metamorphic (anatectic) pegmatites with hydrothermally introduced uranium are thought to be the source of radon in high grade terrain. At lower grade (chlorite to staurolite), no relationship exists between 222Rn content and metamorphic grade, although each rock formation has a somewhat characteristic 222Rn range from ground water, ranges which overlap. Considerable local 222Rn variations exist within the same rock body, reflecting local geologic and hydrologic conditions. Data on well depth, type of well, well yield, overburden type and thickness, and water chemistry show that 222Rn may increase slightly with well depth up to 50 to 75 m and is essentially constant thereafter. Low yield wells, generally associated with areas of thin overburden, tend to have higher 222Rn values than high yield wells, normally associated with thick sand and gravel overburdens. 222Rn concentrations decrease with increasing sodium concentrations, suggesting that low 222Rn wells are closely linked with surface waters. No other chemical parameter (Na, K, Ca, Mg, Fe, Mn, Zn, and Cu) correlates with 222Rn content within a single rock unit.

Uranium and Radon in Private Bedrock Well Water in Maine: Geospatial Analysis at Two Scales

“…22 However, in greater Augusta, metamorphosed units at lower ranks did not show significantly different distributions of groundwater [Rn] at intermediate spatial scales (SI Table S4). This finding suggests that groundwater [Rn] in meta-sedimentary rocks is not related to the metamorphic grade below the granulite facies.…”

Radon distribution in groundwater of Taiwan

“…In the past 25 years, radon levels were measured in groundwater and spas in various countries such as Taiwan (Lin and Chen 1983;Sabol et al 1995), Finland (Asikainen and Kahlos 1980), Norway (Banks et al 1998a;Banks et al 1998b), Germany (Freyer et al 1997), Spain (Soto et al 1995a;Soto et al 1995b), Kenyan (Otwoma and Mustapha 1998), Saudi Arabia (Alabdula'aly 1996; Alabdula'aly 1999), and the United States (Brutsaert et al 1981;King et al 1982;Sasser and Watson 1978;Loomis 1987;Cech et al 1988;Longtin 1988;Dixon and Lee 1988;Hess et al 1985). Figure 8 summarizes worldwide radon levels in groundwater and spas reported in the literature.…”

“…Asikainen and Kahlos (1979) showed that anomalously high radon-222 concentrations in groundwater in the Helsinki area were caused by high concentrations of uranium and radium-226 deposited in fissures of the bedrock. High radon-222 concentrations exist in groundwater from most granitic rocks in Maine (Brutsaert et al 1981). Brutsaert et al (1981) reported that granites in Maine contain 10 to 100 ppm uranium.…”

“…High radon-222 concentrations exist in groundwater from most granitic rocks in Maine (Brutsaert et al 1981). Brutsaert et al (1981) reported that granites in Maine contain 10 to 100 ppm uranium. Lin et al (1986) reported that conglomerates and sandstones in Taiwan contain 0.87 € 0.63 and 1.53 € 0.59 ppm uranium, respectively.…”

Development and calibration of a portable radon sampling system for groundwater 222Rn activity concentration measurements

“…The 222 Rn activity concentration in groundwater mostly varies in the broad interval between 1 Bq/dm 3 and 1000 Bq/dm 3 Kahlos, 1979, 1980;Bonotto, 2004;Dillon et al, 1991;Zhuo et al, 2001), but local concentrations up to 10 000 Bq/dm 3 or more have been reported in the literature (e.g. Brutsaert et al, 1981).…”