Secondary Hydrogeologic Regions of the Conterminous United States

Self Cite

111

Chemical data from 43 334 wells were used to examine the role of land surface−soil−aquifer connections in producing elevated manganese concentrations (>300 μg/L) in United States (U.S.) groundwater. Elevated concentrations of manganese and dissolved organic carbon (DOC) in groundwater are associated with shallow, anoxic water tables and soils enriched in organic carbon, suggesting soil-derived DOC supports manganese reduction and mobilization in shallow groundwater. Manganese and DOC concentrations are higher near rivers than farther from rivers, suggesting river-derived DOC also supports manganese mobilization. Anthropogenic nitrogen may also affect manganese concentrations in groundwater. In parts of the northeastern U.S. containing poorly buffered soils, ∼40% of the samples with elevated manganese concentrations have pH values < 6 and elevated concentrations of nitrate relative to samples with pH ≥ 6, suggesting acidic recharge produced by the oxidation of ammonium in fertilizer helps mobilize manganese. An estimated 2.6 million people potentially consume groundwater with elevated manganese concentrations, the highest densities of which occur near rivers and in areas with organic carbon rich soil. Results from this study indicate land surface−soil−aquifer connections play an important role in producing elevated manganese concentrations in groundwater used for human consumption.

Section: ■ Introductionmentioning

confidence: 70%

Elevated Manganese Concentrations in United States Groundwater, Role of Land Surface–Soil–Aquifer Connections

McMahon

Belitz

Reddy

et al. 2018

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111

“…It is also not known if a similar frequency of occurrence of high 210 Pb or 210 Po is found in similar felsic crystalline (granitic) rock or semiconsolidated sediment Coastal Plain terranes, respectively, in the USA, or globally (known occurrence in granitic rock in Finland being an exception) . Settings could be targeted for monitoring, including granitic mountain ranges or terranes, which are widespread in the western USA and underlie or crop out in parts of the populous northern glaciated regions, and contain public and private supply wells . Additional research on the potential efficiency of available water treatment technologies on concentrations of 210 Pb and 210 Po in finished drinking waters is warranted to help minimize exposure risk.…”

Section: Resultsmentioning

confidence: 99%

“…62 Settings could be targeted for monitoring, including granitic mountain ranges or terranes, which are widespread in the western USA and underlie or crop out in parts of the populous northern glaciated regions, and contain public and private supply wells. 110 Additional research on the potential efficiency of available water treatment technologies on concentrations of 210 Pb and 210 Po in finished drinking waters is warranted to help minimize exposure risk.…”

mentioning

confidence: 99%

Occurrence and Geochemistry of Lead-210 and Polonium-210 Radionuclides in Public-Drinking-Water Supplies from Principal Aquifers of the United States

Szabó

Stackelberg

Cravotta

2020

On the basis of lifetime cancer risks, lead-210 (210Pb) and polonium-210 (210Po) ≥ 1.0 and 0.7 pCi/L (picocuries per liter), respectively, in drinking-water supplies may pose human-health concerns. 210Pb and 210Po were detected at concentrations greater than these thresholds at 3.7 and 1.5%, respectively, of filtered untreated groundwater samples from 1263 public-supply wells in 19 principal aquifers across the United States. Nationally, 72% of samples with radon-222 (222Rn) concentrations > 4000 pCi/L had 210Pb ≥ 1.0 pCi/L. 210Pb is mobilized by alpha recoil associated with the decay of 222Rn and short-lived progeny. 210Pb concentrations ≥ 1.0 pCi/L occurred most frequently where acidic groundwaters inhibited 210Pb readsorption (felsic-crystalline rocks) and where reducing alkaline conditions favored dissolution of iron–manganese- (Fe–Mn-) oxyhydroxides (which adsorb 210Pb) and formation of lead–carbonate complexes (enhancing lead (Pb) mobility). 210Po concentrations ≥ 0.7 pCi/L occurred almost exclusively in confined Coastal Plain aquifers where old (low percent-modern carbon-14) groundwaters were reducing, with high pH (>7.5) and high sodium/chloride (Na/Cl) ratios resulting from cation exchange. In high-pH environments, aqueous polonium (Po) is poorly sorbed, occurring as dihydrogen polonate (H2PoO3(aq)) or, under strongly reducing conditions, as a hydrogen-polonide anion (HPo–). Fe–Mn- and sulfate-reduction and cation-exchange processes may mobilize polonium from mineral surfaces. Po2+ occurrence in low-to-neutral-pH waters is attenuated by adsorption.

“…Sites were part of a Principal Aquifer Survey (PAS) or Major Aquifer Study (MAS). The Floridan aquifer system and Mississippi Embayment aquifer system are each shown with two lithologies 69.…”

mentioning

confidence: 99%

Hormones and Pharmaceuticals in Groundwater Used As a Source of Drinking Water Across the United States

Bexfield

Toccalino

Belitz

et al. 2019

Self Cite

177

This is the first large-scale, systematic assessment of hormone and pharmaceutical occurrence in groundwater used for drinking across the United States. Samples from 1091 sites in Principal Aquifers representing 60% of the volume pumped for drinking-water supply had final data for 21 hormones and 103 pharmaceuticals. At least one compound was detected at 5.9% of 844 sites representing the resource used for public supply across the entirety of 15 Principal Aquifers, and at 11.3% of 247 sites representing the resource used for domestic supply over subareas of nine Principal Aquifers. Of 34 compounds detected, one plastics component (bisphenol A), three pharmaceuticals (carbamazepine, sulfamethoxazole, and meprobamate), and the caffeine degradate 1,7-dimethylxanthine were detected in more than 0.5% of samples. Hydrocortisone had a concentration greater than a human-health benchmark at 1 site. Compounds with high solubility and low K oc were most likely to be detected. Detections were most common in shallow wells with a component of recent recharge, particularly in crystalline-rock and mixed land-use settings. Results indicate vulnerability of groundwater used for drinking water in the U.S. to contamination by these compounds is generally limited, and exposure to these compounds at detected concentrations is unlikely to have adverse effects on human health.