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Predicting Risk from Radon in Source Waters from Water Quality Parameters
Citation:
Paolucci, A., J. SAXE, AND CHRISTOPHER IMPELLITTERI. Predicting Risk from Radon in Source Waters from Water Quality Parameters . Presented at Geological Society of America 2009 Annual Conference, Portland, OR, October 18 - 21, 2009.
Impact/Purpose:
To inform the public.
Description:
Overall, 47 groundwater samples were collected from 45 small community water systems (CWSs) and analyzed for radon and other water quality constituents. In general, groundwater from unconsolidated deposits and sedimentary rocks had lower average radon levels (ranging from 223 to 284 pCi/L) than metamorphic and igneous rocks (ranging from 268 to 5,820 pCi/L), which is consistent with similar investigations that have found that the highest radon levels in groundwater originated from crystalline-rock aquifers which typically contain relatively high amounts of uranium (PA DEP, 2008; DeSimone, 2009). The proposed maximum contaminant level (MCL) of 300 pCi/L and proposed alternative MCL of 4,000 pCi/L for states or water systems that implement a multimedia mitigation plan for radon are used as guidelines to evaluate human health risks of radon in source water supplies. The majority of groundwater samples with radon levels below 300 pCi/L were primarily from unconsolidated deposits (57%). Samples exceeding 300 pCi/L were found in each of the nine lithology groups, with the exception of low/med/high grade metamorphic rock basalt. Of the 47 groundwater samples, only four samples exceeded 4,000 pCi/L, all originating from igneous and metamorphic rocks. Overall, the statistical analysis indicated that the final predictive model correlates with radon levels greater than 900 pCi/L with a R2 value of 98.0%. At lower radon levels, there is greater scattering about the reference line indicating a decreased predictability of radon in groundwater supplies used for drinking water. Based on these findings, the stepwise regression model inadequately predicts radon levels in groundwater and appears to be biased toward fitting higher radon levels. In general, there is only limited spatial correlation within EPA Region III indicating insufficient data to accurately contour radon levels across the region, most likely due to the limited number of sites and relatively large scale. However, GIS mapping indicated that there is a relationship between predicted indoor air screening levels and radon levels in groundwater. More specifically, radon levels in source water =4,000 pCi/L are strongly related to predicted indoor air screening levels >4 pCi/L and subsequently geologic faulting in the region.
URLs/Downloads:
Final Program Abstract
FOR FURTHER INFORMATION_PRINCIPAL INVESTIGATOR.PDF (PDF, NA pp, 5 KB, about PDF)
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