This cross-sectional study of state-level health data of US children examines the association of lead service lines and blood lead level exceedance rates in a 10-year period that included the Flint water crisis.

Many Americans distrust tap water, leading them to purchase more expensive drinking water sold from water vending machines (e.g., kiosks) that are poorly regulated and sparingly monitored for quality. Here, we analyzed the water quality of 20 kiosks from 4 different manufacturers across 6 states in the first comprehensive comparison of the chemical and microbial characteristics of kiosk water to paired tap samples. Of the 16 kiosks listing specific water treatment processes (others indicated "filtered" or "purified"), only 1 dispensed water with ionic composition (e.g., Na+, Ca2+, Mg2+) inconsistent with the stated treatment. Most kiosks tested used reverse osmosis (RO), which removed fluoride and residual disinfectant, although we found no evidence of microbial contamination. RO also provided the benefit of removing per- and polyfluoroalkyl substances. However, we frequently detected higher lead levels in kiosk water than in nearby tap water. Lead was detected (>0.05 μg/L, our method detection limit) in 15 kiosks; 5 were >1 μg/L (American Academy of Pediatrics recommendation), 2 were >5 μg/L (FDA allowable level for bottled water), and 1 was >10 μg/L (US EPA Action Level). Lead co-occurred with zinc and copper, consistent with corrosion of lead-containing plumbing materials. XRF analysis of plumbing in 2 kiosks from different manufacturers with nationwide distribution confirmed this suspicion although all components in question met the definition of lead free under the Safe Drinking Water Act. Lead release was most evident with the use of RO treatment, which can produce corrosive water low in alkalinity and pH. Going forward, the removal of lead-containing plumbing components downstream of RO treatment and regulation with routine testing of kiosk water quality is imperative to address this unchecked public health risk.

Double carbonates are minerals with a calcite-type structure with alternating cation layers composed of Ca and Mg/Fe coordinated by carbonate groups. While the perfectly ordered AB-stacked crystal is the thermodynamically most stable configuration, natural mineral formation pathways can leave signatures through kinetically trapped disorder, such as AB antisite cation substitutions. This study probes the degree of cation ordering in naturally occurring double-carbonate samples. In particular, the dependence of structural order on the distribution of Fe A and B crystallographic sites (the A site is the Ca layer, and the B site is the Mg/Fe layer) is examined. Mössbauer, X-ray diffraction, X-ray absorption spectroscopies (both the X-ray absorption near edge structure, XANES, and extended X-ray absorption fine structure, EXAFS), and energy-dispersive X-ray spectroscopy were used to collect a comprehensive experimental data set, which we interpret using density functional theory to elucidate the structural effects of cation disorder. Our results show that the A (nominally Ca) site can host a relatively high Fe fraction. We discuss the implications in terms of mineral formation.

Iron oxide minerals regulate the flux of electrons in the environment and are important hosts for trace and minor, yet critical, elements. Here, we present the first evidence of a direct link between the local coordination environments of Ni and Zn and the redox properties of their host phase goethite (α-FeOOH), the most abundant Fe(III) (oxyhydr)oxide at Earth's surface. We used aqueous redox measurements to show that the redox potential EH0, and hence the mineral's stability, follows the order: pure goethite ≥ Zn-goethite > Ni-goethite. Parallel X-ray absorption and scattering measurements demonstrate, using quantum-informed analysis, that the local coordination environment of the smaller impurity, Ni, causes more bulk strain energy than Zn, which nearly accounts for the difference in EH0 between Ni- and Zn-goethite. Our theory-informed, experimental study reveals how two common impurities affect the stability of goethite with implications for the biogeochemical reactivity of Fe(III) (oxyhydr)oxide in mediating elemental and electron fluxes in the environment.

There is an urgent need for rapid, cost-effective approaches to identify residences with lead service lines (LSLs). We evaluated whether analyzing water for corrosion-related metals could accurately identify residences with LSLs without relying on potentially inaccurate property records. We applied principal component analysis logistic regression (PCA-LR) and classification tree models using 28 analytes per bottle (including Pb, Cu, Zn, Fe, Al, and others) measured in 216 water samples collected in Flint, Michigan, in August 2015. The PCA-LR model achieved 87% accuracy (AUROC = 0.93) with 81% sensitivity and 90% specificity, while the classification tree model achieved 80% accuracy (AUROC = 0.77) with 74% sensitivity and 84% specificity. The classification tree provided interpretable decision rules identifying key predictive metals, primarily relying on 1 min flush Pb concentrations with Zn and Al as secondary predictors. It also revealed distinct metal co-occurrence patterns between LSLs and premise plumbing, offering insights into Pb source identification. The tree's interpretable structure makes it particularly valuable for practical implementation by utilities. Although additional work is needed to extend these models to other water systems, our results suggest that metal analysis provides an accurate, cost-effective, and minimally invasive tool that complements existing approaches for predicting the presence of an LSL.

Environmental scientists are increasingly returning to Mössbauer spectroscopy (MBS) to reveal details about iron (Fe)-bearing phases in soils and sediments. MBS is particularly powerful at distinguishing between Fe(II) and Fe(III) and, given appropriate background information, can offer exceptionally precise information on Fe speciation in compositionally complex environmental samples. However, there are relatively few accessible guides for analyzing environmental samples by MBS. In this review, we seek to distill the essential understanding of MBS for earth scientists and provide guidance on analysis, spectral fitting, and interpretation for new practitioners and a consolidation of approaches for experienced users. As a rule, Fe phases in soils and sediments are more disordered and complex than synthetic or geogenic Fe minerals. We cover the most successful ways MBS can be applied to soils, including the determination of Fe(II)/Fe(III) ratios, characterization of Fe (oxyhydr)oxide crystallinity, and the use of 57 Fe isotope spikes, as well as highlighting how to avoid common pitfalls and arrive at Fe phase identification and quantification by leveraging complimentary data and environment context. We outline procedures for sample preparation, analysis, and spectral fitting using decision trees based on the analytical goals and sample conditions. The fitting and interpretation of magnetically ordered ferrous phases at low temperature is lacking in the literature and so we offer an expanded discussion of approaches to these challenging spectra. We provide a discussion and fitting guidance for the most common Fe phases in soils and sediments organized around environmental contexts: young soils (and sediments derived from them) dominated by aluminosilicates, highly weathered soils rich in Fe oxides, organic-rich soils, soils in sulfur-rich environments, and soils exposed to anoxia. For each context, we describe expected Fe phases and their characteristic spectral features while emphasizing the importance of complementary analyses for reliable interpretation. Finally, we identify two critical needs in the field: improved theoretical frameworks for fitting low-temperature ferrous octets and Fe–sulfur phases and a need for standardization of parameter reporting and data sharing within the environmental MBS community. This review aims to both facilitate broader adoption of MBS in the environmental sciences and advance the technique's application to complex natural samples.

This study reveals twice the microbial diversity in well vs. municipal waters, highlighting the need for improved private well monitoring.

Chlorinated ethenes (CEs) are some of the most commonly found groundwater contaminants, and their clean-up still relies heavily on energy intensive clean-up practices such as pump and treat. As a sustainable alternative, abiotic natural attenuation by Fe(II) species would be preferable. While data is available on reduction of some CEs by stable Fe(II) phases, these reactions appear to be slower than reduction by freshly precipitated, transient Fe(II) phases (i.e., reactive mineral intermediates, RMIs). Here, we evaluated cis-1,2-dichloroethene (cDCE) reduction by stable and transient Fe(II)-containing phases, and characterized the transient phases formed. In the absence of aqueous Fe(II) (Fe(II)aq), magnetite, chloride green rust, hematite, mackinawite, and clay minerals did not reduce cDCE. When Fe(II)aq was present with these minerals, reduction usually occurred when conditions favored precipitation of ferrous hydroxide (Fe(OH)2). Additionally, we observed cDCE reduction by Fe(II) precipitates made from FeCl2 and ferrous ammonium sulfate (FAS), but never with FeSO4 present. Under no conditions, with or without Fe(II)aq, was cDCE reduced by goethite, chukanovite, sulfate green rust, or aluminum oxide. Mössbauer spectra of the transient phases indicate that ferrous (oxy)hydroxides such as Fe(OH)2 formed from FeCl2 and FeSO4 and a green rust-like precipitate formed from FAS. These spectra suggest that reduction is faster when the phases are less ordered, possibly because the Fe(II) precipitates are less crystalline or form smaller particles. Our work suggests that although most stable Fe(II) phases do not reduce cDCE sufficiently fast for significant abiotic natural attenuation, Fe(II) RMI phases may contribute to attenuation of cDCE plumes.

Naturally occurring abiotic dechlorination reactions in clayey soils can serve as an important attenuation mechanism for groundwaters impacted by chlorinated solvents such as trichloroethene (TCE). Potential abiotic reactions include both reductive (anoxic) and oxidative (oxic) dechlorination reactions that are facilitated by ferrous minerals. However, tools to provide lines of evidence for such reactions, and ultimately screening‐level estimates of dechlorination rate constants that can be incorporated into site fate and transport models, are yet to be widely accepted for these clayey systems. Herein, coupled bench‐ and field‐scale testing at nine locations within the saturated zone showed that measurement of reduced gases in field‐collected clayey samples was inconclusive for indicating in situ abiotic reductive dechlorination. However, the use of 1% (v/v) HCl extractions and X‐ray diffraction (XRD) for mineral composition provided the information needed to estimate TCE abiotic reductive dechlorination in clays, thereby serving as a potential screening tool for site investigation. While a corresponding screening tool for estimating abiotic oxidative dechlorination in clay was not demonstrated, the rate of hydroxyl radical generation measured for each clay in batch experiments was correlated to in situ hydrogen peroxide concentrations measured in groundwater near the sand‐clay interface. Thus, this observation provides (to our knowledge) a first line of evidence that ongoing reactive oxygen species generation is occurring in situ near the sand–clay (oxic–anoxic) interface, potentially serving as a means to facilitate abiotic oxidative dechlorination and mitigate back‐diffusion of chlorinated solvents from clay.

Clay minerals contain significant amounts of Fe in their alumosilicate framework, and this structural Fe can be reduced and re-oxidized, constituting a potentially renewable source of reduction equivalents in sedimentary environments. However, dissolution and/or clay mineral transformations during microbial Fe reduction contradict this concept. Here, we investigate how Fe reduction and re-oxidation affect the propensity of Fe to be released from the clay mineral structure and use selective sequential extractions in combination with Mössbauer spectroscopy. Negligible amounts of Fe were released in the sequential extraction of high Fe content clay minerals NAu-1 and NAu-2. Once aqueous Fe(II) was added as a reductant, the extraction procedure recovered the initially added Fe amount and up to 30% of the Fe from the clay mineral structure as both Fe(II) and Fe(III). Similar extents of Fe mobilization were found for clay minerals partly reduced (7%–20%) with dithionite, suggesting that mobilization was reduction-induced and independent of the source of reduction equivalents (Fe(II), dithionite). Although higher Fe reduction extents mobilized more structural Fe, i.e., >90% in fully reduced clay minerals, re-oxidation largely reverted the reduction-induced Fe mobilization in clay minerals. Our finding of reduction-driven Fe mobilization provides a plausible explanation for conflicting reports on Fe release from clay minerals and how extensive Fe atom exchange between aqueous and clay mineral Fe occurs.

Here, we investigate how the oxidation state of Cr adsorbed to solid surfaces can change during XPS analysis. Experiments are performed to test how Fe(III) solid surfaces, aqueous chemistry, and XPS vacuum conditions affected the measured Cr oxidation state. While oxidized Cr(VI) adsorbs onto nonreducing solid surfaces in the experiments, reduced Cr(III) is primarily measured by XPS. The reduction of adsorbed Cr(VI) occurs under the vacuum conditions of the XPS as CO2, O-2, and H2O are removed from the sample surface. These results suggest that Fe(III) solid surfaces exposed to high-vacuum conditions and/or X-rays can cause the reduction of Cr or other elements with a high redox potential contained on that surface.

Storage conditions affect the initial tetrahedral iron and hydroxyl populations of ferrihydrite, both are correlated and decrease over time as function of ageing.

Locating and developing ideal sites for large-scale capture and storage of carbon dioxide has become increasingly necessary due to increasing global emissions and warming. Mafic-ultramafic rocks present a unique geologic setting as they can trap injected CO2 in pore space, mineralize that CO2 to permanently store it as carbonate minerals, and simultaneously release critical minerals. However, these reservoirs are undercharacterized relative to sedimentary carbon storage settings. In this study, we execute a methodology for determining carbonation and critical mineral recovery potential in mafic-ultramafic reservoirs. Using an olivine-rich basalt from the island of Hawai'i, we performed petrologic and geochemical analyses to determine its chemistry, mineralogy, and pore network architecture. We use this data to first quantify the nonreactive storage resource potential and determine the bulk storage of 50 MMT of CO2 in the pore space of a basalt volume test case, along with realistic P10, P50, and P90 scenarios for that same volume. Then, using the chemistry and mineralogy, we both estimate the total mineralization and critical mineral recovery potential, as well as more realistic values based on dissolution-precipitation reactions at the surface areas of pores. This storage resource estimate methodology can assist in accelerating the global commercialization of geologic carbon storage and critical mineral recovery.

Background: Iron is crucial for growth and development, but excess iron is harmful. Neonatal mice have elevated concentrations of circulating iron, but the source of this iron is unclear. This lack of understanding makes it dif fi cult to optimize early life iron balance. Objectives: Identify the origins of neonatal tissue-speci fi c iron pools using dietary manipulation and cross-fostering murine models. Methods: To determine whether tissue-speci fi c neonatal iron was primarily acquired during gestation or after birth, pups born to ironsuf fi cient or iron-de fi cient dams were cross-fostered, and tissues were harvested at postnatal days 3 - 5 to measure iron content. A separate set of female mice were fed a diet enriched with the stable iron isotope 57 ( 57 Fe) for 4 generations to replace naturally abundant liver iron isotope 56 ( 56 Fe) stores with 57 Fe. To quantify the proportions of neonatal iron acquired during gestation, pups born to dams with 56 Fe or 57 Fe stores were cross-fostered, and tissues were harvested at postnatal day 3 - 5 to determine 56 Fe: 57 Fe ratios by inductively coupled plasma mass spectrometry. Finally, to quantify the proportion of neonatal iron acquired from the maternal diet, female mice with 56 Fe or 57 Fe stores switched diets upon mating, and pup tissues were harvested on P0 to determine 56 Fe: 57 Fe ratios by inductively coupled plasma mass spectrometry. Results: Perinatal iron de fi ciency resulted in smaller pups, and gestational iron de fi ciency resulted in lower neonatal serum and liver iron. Cross-fostering between dams with 56 Fe and 57 Fe stores demonstrated that < 70% of neonatal serum, liver, and brain iron were acquired during gestation. Dietary manipulation experiments using dams with 56 Fe and 57 Fe stores showed that over half of neonatal serum, liver, and brain iron were from the dam ' s gestational diet rather than preconception iron stores. Conclusions: This study provides quantitative values for the sources of neonatal iron, which may inform approaches to optimize neonatal iron status.

Transformation of nanocrystalline ferrihydrite to more stable microcrystalline Fe(III) oxides is rapidly accelerated under reducing conditions with aqueous Fe(II) present. While the major steps of Fe(II)-catalyzed ferrihydrite transformation are known, processes in the initial phase that lead to nucleation and the growth of product minerals remain unclear. To track ferrihydrite–Fe(II) interactions during this initial phase, we used Fe isotopes, Mössbauer spectroscopy, and extractions to monitor the structural, magnetic, and isotope composition changes of ferrihydrite within ∼30 min of Fe(II) exposure. We observed rapid isotope mixing between aqueous Fe(II) and ferrihydrite during this initial lag phase. Our findings from Mössbauer spectroscopy indicate that a more magnetically ordered Fe(III) phase initially forms that is distinct from ferrihydrite and bulk crystalline transformation products. The signature of this phase is consistent with the early stage emergence of lepidocrocite-like lamellae observed in previous transmission electron microscopy studies. Its signature is furthermore removed by xylenol extraction of Fe(III), the same approach used to identify a chemically labile form of Fe(III) resulting from Fe(II) contact that is correlated to the ultimate emergence of crystalline product phases detectable by X-ray diffraction. Our work indicates that the mineralogical changes in the initial lag phase of Fh transformation initiated by Fe(II)–Fh electron transfer are critical to understanding ferrihydrite behavior in soils and sediments, particularly with regard to metal uptake and release.