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1. Reductive transformations of dichloroacetamide safeners: effects of agrochemical co-formulants and iron oxide + manganese oxide binary-mineral systems

   https://doi.org/10.1039/D0EM00331J  

   Ricko, Allison N.; Psoras, Andrew W.; Sivey, John D. (October 2020, Environmental Science: Processes & Impacts)

   null (Ed.)

   The toxic effects of herbicides are often incompletely selective and can harm crops. Safeners are “inert” ingredients commonly added to herbicide formulations to protect crops from herbicide-induced injury. Dichloroacetamide safeners have been previously shown to undergo reductive dechlorination in anaerobic abiotic systems containing an iron (hydr)oxide mineral (goethite or hematite) amended with Fe( ii ). Manganese oxides ( e.g. , birnessite) are important redox-active species that frequently co-occur with iron (hydr)oxides, yet studies examining the effects of more than one mineral on transformations of environmental contaminants are rare. Herein, we investigate the reactivity of dichloroacetamide safeners benoxacor, furilazole, and dichlormid in binary-mineral, anaerobic systems containing Fe( ii )-amended hematite and birnessite. As the molar ratio of Fe( ii )-to-Mn( iv ) oxide increased, the transformation rate of benoxacor and furilazole increased. The safener dichlormid did not transform appreciably over the sampling period (6 hours). The concentration of pH buffer ([MOPS] = 10–50 mM), ionic strength ([NaCl] = 10–200 mM), and order of solute addition ( e.g. , safener followed by Fe( ii ) or vice versa ) do not appreciably affect transformation rates of the examined dichloroacetamide safeners in Fe( ii ) + hematite slurries. The presence of agrochemical co-formulants, including the herbicide S -metolachlor and three surfactants, in solutions containing Cr(H 2 O) 6 2+ (as a model homogeneous reductant) also did not substantially influence rates of safener transformation. This study is among the first to examine laboratory systems of intermediate complexity ( e.g. , systems containing mixtures of agrochemical co-formulants or mineral phases) when assessing the environmental fate of emerging contaminants such as dichloroacetamide safeners. 

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2. Origins of Fermi Level Pinning for Ni and Ag Metal Contacts on Tungsten Dichalcogenides

   https://doi.org/10.1021/acsnano.3c06494  

   Wang, Xinglu; Hu, Yaoqiao; Kim, Seong Yeoul; Addou, Rafik; Cho, Kyeongjae; Wallace, Robert M (October 2023, ACS Nano)

   Tungsten transition metal dichalcogenides (W-TMDs) are intriguing due to their properties and potential for application in next-generation electronic devices. However, strong Fermi level (EF) pinning manifests at the metal/W-TMD interfaces, which could tremendously restrain the carrier injection into the channel. In this work, we illustrate the origins of EF pinning for Ni and Ag contacts on W-TMDs by considering interface chemistry, band alignment, impurities, and imperfections of W-TMDs, contact metal adsorption mechanism, and the resultant electronic structure. We conclude that the origins of EF pinning at a covalent contact metal/W-TMD interface, such as Ni/W-TMDs, can be attributed to defects, impurities, and interface reaction products. In contrast, for a van der Waals contact metal/TMD system such as Ag/W-TMDs, the primary factor responsible for EF pinning is the electronic modification of the TMDs resulting from the defects and impurities with the minor impact of metal-induced gap states. The potential strategies for carefully engineering the metal deposition approach are also discussed. This work unveils the origins of EF pinning at metal/TMD interfaces experimentally and theoretically and provides guidance on further enhancing and improving the device performance. 

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3. Dissolution of Mn-bearing dolomite drives elevated Cr( vi ) occurrence in a Permian redbed aquifer

   https://doi.org/10.1039/D2EM00395C  

   Westrop, Jeffrey P.; Tomlinson, Zachary D.; Maples, Brandon M.; Dee, Kato T.; Swindle, Andrew L.; Elwood Madden, Megan E.; Hu, Qinhong; Elwood Madden, Andrew S. (December 2022, Environmental Science: Processes & Impacts)

   Municipalities in central Oklahoma, U.S.A. increasingly rely on water drawn from the Central Oklahoma Aquifer (COA) as surface water resources have not grown in proportion to population and current water demands. However, water drawn from certain regions of the COA frequently contains elevated levels of naturally occurring hexavalent chromium. Rock samples from the Norman Arsenic Test Hole Core (NATHC) were investigated to identify the mineralogic host(s) of Cr and mechanisms of Cr( vi ) release via bulk mineralogy and chemistry measurements, selective chemical extractions, and microscale elemental analyses. Results demonstrate most COA Cr is contained in Fe oxides and clays as isomorphic substitutions for Fe( iii ). Analyses of regional groundwater data, including hierarchical clustering methods and GIS, demonstrate the most intense Cr( vi ) occurrence is linked to cation exchange with Na-clays at depth. Cation exchange allows dissolution of Mn-bearing dolomite, which in turn produces Mn oxides in otherwise dolomite-saturated groundwaters. Mn oxides in turn are known to oxidize Cr( iii ) to Cr( vi ). In general, co-occurrence of Mn-bearing carbonates and exchangeable clays in any aquifer, particularly those with Cr( iii ) present in iron oxide cements, serve as ingredients for groundwater occurrences of oxidizable trace metals. 

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4. Influence of environment and mineralogy on euendolithic microboring patterns

   https://doi.org/10.1002/dep2.70029  

   Lincoln, Tyler; Lingappa, Usha; Hibner, Brianna; Trower, Elizabeth J (November 2025, The Depositional Record)

   Abstract Euendolithic microorganisms, capable of bioerosion in carbonate substrates, play an important role in modern marine ecosystems and have a fossil record extending into deep time. Understanding the factors driving microboring behaviour is essential for interpreting their ecological impact and reconstructing ancient environmental conditions. In this study, we conducted field incubation experiments across multiple sites at Little Ambergris Cay in the Turks and Caicos Islands, examining microboring density in abiotic optical calcite and aragonite under varying conditions of light, subaerial exposure, current energy, substrate mineralogy and trace metal content. We observed sinuous tunnels within 1 week of incubation in transparent calcite, with longer deployment times (2.5–5 months) resulting in meaningful increases in boring density. We also documented boring activity in dark conditions, suggesting potential for enhanced mineral dissolution at night when geochemical conditions are more optimal. Trace metal analysis of our experimental substrates revealed Fe/Ca and Mn/Ca ratios exceeding western Atlantic sea water estimates by 1–3 orders, with calcites more enriched in Mn than aragonites, offering preliminary support for the novel hypothesis that dissolution of CaCO₃minerals might be a useful source of trace metals for euendoliths. Sea water chemistry varied across sites, particularly between restricted interior and open platform sites. A comparison of boring densities suggests that trace metal abundance, mineralogy, local sea water CaCO₃mineral saturation state (Ω) and subaerial exposure (e.g. intertidal vs. shallow subtidal) may all influence microboring. These findings offer new perspectives on the euendolithic lifestyle, showing how substrate selection and temporal partitioning of dissolution activity balance metabolic costs with environmental constraints. They also enhance our ability to interpret the fossil record and bioerosion dynamics under changing conditions. 

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5. Cobalt mineralogy at the Iron Creek deposit, Idaho cobalt belt, USA: Implications for domestic critical mineral production

   https://doi.org/10.1130/G51160.1  

   Holley, E.A.; Zaronikola, N.; Trouba, J.; Pfaff, K.; Thompson, J.; Spiller, E.; Anderson, C.; Eggert, R. (June 2023, Geology)

   Abstract Current U.S. policies aim to establish domestic supply chains of critical minerals for the energy transition. The Iron Creek deposit in the Idaho cobalt belt (ICB) is one of the most promising cobalt (Co) targets. Our case study illustrates the importance of mineralogy in strategic evaluations of critical mineral potential. Most of the Co at Iron Creek occurs as Fe substitution in pyrite, with lattice-bound and inclusion-hosted Ag, As, Bi, Ni, Pb, Se, Te ± trace Au and Sb. Cobalt also occurs in minor cattierite-vaesite. The Co minerals are intergrown with Co-poor chalcopyrite hosting Cu ± minor In and Zn. Worldwide, most Co is recovered from deposits mineralogically distinct from the ICB, and the United States currently lacks infrastructure to recover this Co and its associated metals. ICB ore minerals could be processed by autoclave, roaster, smelter, bioleach, or heap leach. Recovery of the Ag, As, Au, Bi, In, Pb, Se, Te, and Zn would be costly by autoclave, and construction of a custom smelter for ICB ores is likely uneconomic, so these elements would become waste irrespective of criticality. The Co-Fe and Co-As sulfide minerals are most suitable for Co and Ni recovery by a hydrometallurgical autoclave process, with potential pretreatment of cobaltiferous pyrite/arsenopyrite in an inert-atmosphere roaster, in new domestic or anticipated international facilities. The ICB is the second largest known Co resource in the United States. Consideration of ore mineralogy in the ICB is essential in strategies for domestic production. 

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