Correction: FeS colloids - formation and mobilization pathways in natural waters.

[This corrects the article DOI: 10.1039/C9EN01427F.].

Metal toxin threat in wildland fires determined by geology and fire severity.

Accentuated by climate change, catastrophic wildfires are a growing, distributed global public health risk from inhalation of smoke and dust. Underrecognized, however, are the health threats arising from fire-altered toxic metals natural to soils and plants. Here, we demonstrate that high temperatures during California wildfires catalyzed widespread transformation of chromium to its carcinogenic form in soil and ash, as hexavalent chromium, particularly in areas with metal-rich geologies (e.

Uranium surface processes with sandstone and volcanic rocks in acidic and alkaline solutions.

Understanding the behaviour of uranium waste, for disposal purposes, is crucial due to the correlation between pH values and the disposal of distinct types of waste, with low level waste typically associated with acidic pH values, and higher and intermediate level waste commonly related to alkaline pH values. We studied the adsorption of U(VI) on sandstone and volcanic rock surfaces at pH 5.5 and 11.

Effects of Transition Metals on Metal-Octaaminophthalocyanine-Based 2D Metal-Organic Frameworks.

Metal-octaaminophthalocyanine (MOAPc)-based 2D conductive metal-organic frameworks (cMOFs) have shown great potential in several applications, including sensing, energy storage, and electrocatalysis, due to their bimetallic characteristics. Here, we report a detailed metal substitution study on a family of isostructural cMOFs with Co, Ni, and Cu as both the metal nodes and the metal centers in the MOAPc ligands. We observed that different metal nodes had variations in the reaction kinetics, particle sizes, and crystallinities.

Iron Reduction in Profundal Sediments of Ultraoligotrophic Lake Tahoe under Oxygen-Limited Conditions.

Increased periods of bottom water anoxia in deep temperate lakes due to decreasing frequency and depth of water column mixing in a warming climate may result in the reductive dissolution of iron minerals and increased flux of nutrients from the sediment into the water column. Here, we assessed the sediment properties and reactivities under depleted oxygen concentrations of Lake Tahoe, a deep ultraoligotrophic lake in the Sierra Nevada mountain range. Using whole-core incubation experiments, we found that a decrease in dissolved oxygen concentration in the top 2 cm of the sediment resulted in an extension of the microbial iron reduction zone from below 4.

Environmental Risk of Arsenic Mobilization from Disposed Sand Filter Materials.

Arsenic (As)-bearing water treatment residuals (WTRs) from household sand filters are usually disposed on top of floodplain soils and may act as a secondary As contamination source. We hypothesized that open disposal of these filter-sands to soils will facilitate As release under reducing conditions. To quantify the mobilization risk of As, we incubated the filter-sand, the soil, and a mixture of the filter-sand and soil in anoxic artificial rainwater and followed the dynamics of reactive Fe and As in aqueous, solid, and colloidal phases.

Templated encapsulation of platinum-based catalysts promotes high-temperature stability to 1,100 °C.

Stable catalysts are essential to address energy and environmental challenges, especially for applications in harsh environments (for example, high temperature, oxidizing atmosphere and steam). In such conditions, supported metal catalysts deactivate due to sintering-a process where initially small nanoparticles grow into larger ones with reduced active surface area-but strategies to stabilize them can lead to decreased performance. Here we report stable catalysts prepared through the encapsulation of platinum nanoparticles inside an alumina framework, which was formed by depositing an alumina precursor within a separately prepared porous organic framework impregnated with platinum nanoparticles.

Mobilization of As, Fe, and Mn from Contaminated Sediment in Aerobic and Anaerobic Conditions: Chemical or Microbiological Triggers?

We integrated aqueous chemistry, spectroscopy, and microbiology techniques to identify chemical and microbial processes affecting the release of arsenic (As), iron (Fe), and manganese (Mn) from contaminated sediments exposed to aerobic and anaerobic conditions. The sediments were collected from Cheyenne River Sioux Tribal lands in South Dakota, which has dealt with mining legacy for several decades. The range of concentrations of total As measured from contaminated sediments was 96 to 259 mg kg, which co-occurs with Fe (21 000-22 005 mg kg) and Mn (682-703 mg kg).

U(VI) binding onto electrospun polymers functionalized with phosphonate surfactants.

We previously observed that phosphonate functionalized electrospun nanofibers can uptake U(VI), making them promising materials for sensing and water treatment applications. Here, we investigate the optimal fabrication of these materials and their mechanism of U(VI) binding under the influence of environmentally relevant ions (e.g.

From Adsorption to Precipitation of U(VI): What is the Role of pH and Natural Organic Matter?

We investigated interfacial reactions of U(VI) in the presence of Suwannee River natural organic matter (NOM) at acidic and neutral pH. Laboratory batch experiments show that the adsorption and precipitation of U(VI) in the presence of NOM occur at pH 2 and pH 4, while the aqueous complexation of U by dissolved organic matter is favored at pH 7, preventing its precipitation. Spectroscopic analyses indicate that U(VI) is mainly adsorbed to the particulate organic matter at pH 4.

Direct Integration of Strained-Pt Catalysts into Proton-Exchange-Membrane Fuel Cells with Atomic Layer Deposition.

The design and fabrication of lattice-strained platinum catalysts achieved by removing a soluble core from a platinum shell synthesized via atomic layer deposition, is reported. The remarkable catalytic performance for the oxygen reduction reaction (ORR), measured in both half-cell and full-cell configurations, is attributed to the observed lattice strain. By further optimizing the nanoparticle geometry and ionomer/carbon interactions, mass activity close to 0.

Emerging investigator series: entrapment of uranium-phosphorus nanocrystals inside root cells of plants from a mine waste site.

We investigated the mechanisms of uranium (U) uptake by Tamarix (salt cedars) growing along the Rio Paguate, which flows throughout the Jackpile mine near Pueblo de Laguna, New Mexico. Tamarix were selected for this study due to the detection of U in the roots and shoots of field collected plants (0.6-58.

Valence-Dependent Electrical Conductivity in a 3D Tetrahydroxyquinone-Based Metal-Organic Framework.

Electrically conductive metal-organic frameworks (cMOFs) have become a topic of intense interest in recent years because of their great potential in electrochemical energy storage, electrocatalysis, and sensing applications. Most of the cMOFs reported hitherto are 2D structures, and 3D cMOFs remain rare. Herein we report FeTHQ, a 3D cMOF synthesized from tetrahydroxy-1,4-quinone (THQ) and iron(II) sulfate salt.

Organic compounds alter the preference and rates of heavy metal adsorption on ferrihydrite.

The availability of heavy metals in terrestrial environments is largely controlled by their interactions with minerals and organic matter, with iron minerals having a particularly strong role in heavy metal fate. Because soil organic matter contains a variety of compounds that differ in their chemical properties, the underlying impact organic matter-soil mineral associations bestow on heavy metal binding is still unresolved. Here, we systematically examine the binding of Cd, Zn and Ni by a suite of organic-ferrihydrite assemblages, chosen to account for various compound chemistries within soil organic matter.

Effect of Natural Organic Matter on the Fate of Cadmium During Microbial Ferrihydrite Reduction.

Natural organic matter (NOM) is known to affect the microbial reduction and transformation of ferrihydrite, but its implication toward cadmium (Cd) associated with ferrihydrite is not well-known. Here, we investigated how Cd is redistributed when ferrihydrite undergoes microbial reduction in the presence of NOM. Incubation with showed that both the rate and the extent of reduction of Cd-loaded ferrihydrite were enhanced by increasing concentrations of NOM (i.

Arsenic Fate in Peat Controlled by the pH-Dependent Role of Reduced Sulfur.

Reduced sulfur (S) has a contrasting role in the fate of arsenic (As) in peatlands. Sulfur bridges provide efficient binding of As to organic carbon (C), but the formation of aqueous As-S species, so-called thioarsenates, leads to a low to no sorption tendency to organic C functional groups. Here, we studied how pH changes the role of reduced S in desorption and retention of presorbed As in model peat.

Effect of Bicarbonate, Calcium, and pH on the Reactivity of As(V) and U(VI) Mixtures.

Natural or anthropogenic processes can increase the concentration of uranium (U) and arsenic (As) above the maximum contaminant levels in water sources. Bicarbonate and calcium (Ca) can have major impacts on U speciation and can affect the reactivity between U and As. We therefore investigated the reactivity of aqueous U and As mixtures with bicarbonate and Ca for acidic and neutral pH conditions.

Redox Heterogeneities Promote Thioarsenate Formation and Release into Groundwater from Low Arsenic Sediments.

Groundwater contamination by As from natural and anthropogenic sources is a worldwide concern. Redox heterogeneities over space and time are common and can influence the molecular-level speciation of As, and thus, As release/retention but are largely unexplored. Here, we present results from a dual-domain column experiment, with natural organic-rich, fine-grained, and sulfidic sediments embedded as lenses (referred to as "reducing lenses") within natural aquifer sand.

Advancing Chelation Chemistry for Actinium and Other +3 f-Elements, Am, Cm, and La.

A major chemical challenge facing implementation of Ac in targeted alpha therapy-an emerging technology that has potential for treatment of disease-is identifying an Ac chelator that is compatible with applications. It is unclear how to tailor a chelator for Ac binding because Ac coordination chemistry is poorly defined. Most Ac chemistry is inferred from radiochemical experiments carried out on microscopic scales.

Antimonite Binding to Natural Organic Matter: Spectroscopic Evidence from a Mine Water Impacted Peatland.

Peatlands and other wetlands are sinks for antimony (Sb), and solid natural organic matter (NOM) may play an important role in controlling Sb binding. However, direct evidence of Sb sequestration in natural peat samples is lacking. Here, we analyzed solid phase Sb, iron (Fe), and sulfur (S) as well as aqueous Sb speciation in three profiles up to a depth of 80 cm in a mine water impacted peatland in northern Finland.

Effect of Bicarbonate and Oxidizing Conditions on U(IV) and U(VI) Reactivity in Mineralized Deposits of New Mexico.

We investigated the effect of bicarbonate and oxidizing agents on uranium (U) reactivity and subsequent dissolution of U(IV) and U(VI) mineral phases in the mineralized deposits from Jackpile mine, Laguna Pueblo, New Mexico, by integrating laboratory experiments with spectroscopy, microscopy and diffraction techniques. Uranium concentration in solid samples from mineralized deposit obtained for this study exceeded 7000 mg kg, as determined by X-ray fluorescence (XRF). Results from X-ray photoelectron spectroscopy (XPS) suggest the coexistence of U(VI) and U(IV) at a ratio of 19:1 at the near surface region of unreacted solid samples.

Reactivity of As and U co-occurring in Mine Wastes in northeastern Arizona.

The reactivity of co-occurring arsenic (As) and uranium (U) in mine wastes was investigated using batch reactors, microscopy, spectroscopy, and aqueous chemistry. Analyses of field samples collected in proximity to mine wastes in northeastern Arizona confirm the presence of As and U in soils and surrounding waters, as reported in a previous study from our research group. In this study, we measured As (< 0.

Organic Functional Group Chemistry in Mineralized Deposits Containing U(IV) and U(VI) from the Jackpile Mine in New Mexico.

We investigated the functional group chemistry of natural organic matter (NOM) associated with both U(IV) and U(VI) in solids from mineralized deposits exposed to oxidizing conditions from the Jackpile Mine, Laguna Pueblo, NM. The uranium (U) content in unreacted samples was 0.44-2.

Antimonite Complexation with Thiol and Carboxyl/Phenol Groups of Peat Organic Matter.

Peatlands and other wetlands with abundant natural organic matter (NOM) are important sinks for antimony (Sb). While formation of Sb(III) sulfide phases or Sb(III) binding to NOM are discussed to decrease Sb mobility, the exact binding mechanisms remain elusive. Here, we reacted increasing sulfide concentrations with purified model peat at pH 6, forming reduced organic sulfur species, and subsequently equilibrated the reaction products with 50 μM of antimonite under anoxic conditions.

The coordination chemistry of Cm, Am, and Ac in nitrate solutions: an actinide L-edge EXAFS study.

Understanding actinide(iii) (An = Cm, Am, Ac) solution-phase speciation is critical for controlling many actinide processing schemes, ranging from medical applications to reprocessing of spent nuclear fuel. Unfortunately, in comparison to most elements in the periodic table, An speciation is often poorly defined in complexing aqueous solutions and in organic media. This neglect - in large part - is a direct result of the radioactive properties of these elements, which make them difficult to handle and acquire.