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

Abstract

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.

WITHDRAWN: Natural Sources of Iron and Manganese in Groundwater of the Lower Kelantan Basin, North-eastern Coast of Peninsula Malaysia: Water Quality Assessment and an Adsorption-based Method for Remediation

“…Higher concentrations of manganese generally occur in acidic groundwater under reducing conditions (McMahon et al, 2018;Homoncik et al, 2010). Manganese is dominantly present as the more soluble divalent form at lower Eh and pH conditions.…”

Machine Learning Predictions of pH in the Glacial Aquifer System, Northern USA

“…In these areas NO 3 concentrations are inversely related to pH (Spearman's rho = −0.45; p < 0.001). These findings corroborate the findings of (McMahon et al 2019) and indicate that poorly buffered areas of the GLAC with pH <6 may be susceptible to elevated Mn concentrations regardless of redox condition. At depths typical of domestic and public supplies, predicted values of pH <6 occur primarily in the southeastern portion of terrane 1A where poorly buffered sediments support low pH conditions (Figure 6).…”

“…High concentrations of Mn were found to occur more commonly under reducing conditions across the GLAC, except in terrane 4A where elevated Mn was driven by pH < 7.0. A recent study of elevated Mn concentrations in groundwater across the United States found that in shallow or poorly buffered aquifers with pH < 6, the oxidation of ammonium in agricultural areas can lower pH and enhance Mn mobility (McMahon et al 2019).…”

The Energetic Potential for Undiscovered Manganese Metabolisms in Nature

“…Mn oxides are found in ocean and lake sediments, ore deposits, soils, hydrothermal vents ( Villalobos et al, 2003 ; Yang et al, 2018 ), interlayered with Fe-oxides that have recently become aerobic ( Tazaki, 2000 ), caves ( Northup et al, 2003 ) streams, and desert varnish ( Tebo et al, 2004 ). Aqueous Mn(II), Mn 2+ , is common in suboxic and anoxic settings such as sediment pore water ( Madison et al, 2013 ; Oldham et al, 2017b ), stratified water bodies ( Trouwborst et al, 2006 ; Yakushev et al, 2007 , 2009 ; Dellwig et al, 2012 ; Oldham et al, 2015 ), ground water ( Wasserman et al, 2006 ; de Meyer et al, 2017 ; McMahon et al, 2019 ) and drinking water systems ( Cerrato et al, 2010 ). Mn(II) often coexists with birnessite (δ-MnO 2 ) where redox conditions fluctuate, such as in ocean and lake sediments ( Yang et al, 2018 ).…”