Behavior of potentially toxic elements from stoker-boiler fly ash in Interior Alaska: paired batch leaching and solid-phase characterization.

Despite significant investigation of fly ash spills and mineralogical controls on the release of potentially toxic elements (PTEs) from fly ash, interactions with the surficial environment remain relatively poorly understood. We conducted 90-day batch leaching studies with paired analysis of supernatant and solid-phase mineralogy to assess the elemental release and transformation of fly ash upon reaction with aquatic media (18 MΩ cm-1 water and simulated rainwater). The fly ash in this study, collected from the University of Alaska Fairbanks stoker-boiler power plant, is high in unburned carbon (~20% LOI) and highly enriched in several PTEs relative to the upper continental crust. Supernatant concentrations of oxyanion-forming elements (e.g., As, Se, Mo, Sb) remained relatively low and constant, suggesting equilibrium with the solid phase, possibly ettringite [Ca6Al2(SO4)3(OH)12•26H2O], which is known to incorporate and sorb oxyanion-forming PTEs and was identified by X-ray diffraction. Synthetic precipitation leaching procedure (SPLP) results failed to capture important temporal trends. Lead and Ba supernatant concentrations consistently exceeded drinking water standards, as well as others upon exposure to simulated physiological solutions. Seven-day experiments with dissolved organic matter-isolate solutions indicated that for certain elements, liberation was influenced by carbon concentration and/or the identity of the isolate. Overall, this paired approach can serve as a model for future studies, bridging existing gaps between batch leaching and single-element mineralogical, sorption, or speciation studies.

The Role of Hydrates, Competing Chemical Constituents, and Surface Composition on ClNO2 Formation.

Atomic chlorine (Cl•) affects air quality and atmospheric oxidizing capacity. Nitryl chloride (ClNO2) - a common Cl• source-forms when chloride-containing aerosols react with dinitrogen pentoxide (N2O5). A recent study showed that saline lakebed (playa) dust is an inland source of particulate chloride (Cl-) that generates high ClNO2. However, the underlying physiochemical factors responsible for observed yields are poorly understood. To elucidate these controlling factors, we utilized single particle and bulk techniques to determine the chemical composition and mineralogy of playa sediment and dust samples from the southwest United States. Single particle analysis shows trace highly hygroscopic magnesium and calcium Cl-containing minerals are present and likely facilitate ClNO2 formation at low humidity. Single particle and mineralogical analysis detected playa sediment organic matter that hinders N2O5 uptake as well as 10 Å-clay minerals (e.g., Illite) that compete with water and chloride for N2O5. Finally, we show that the composition of the aerosol surface, rather than the bulk, is critical in ClNO2 formation. These findings underscore the importance of mixing state, competing reactions, and surface chemistry on N2O5 uptake and ClNO2 yield for playa dusts and, likely, other aerosol systems. Therefore, consideration of particle surface composition is necessary to improve ClNO2 and air quality modeling.

Geographic Variability of Active Ingredients in Spice as an Indicator of Mechanisms of Distribution and Manufacture Within Alaska.

Designer drugs, like Spice, are synthetic psychoactive analogs of illegal substances with understudied health effects since they have traditionally been sold in packages labeled "not for human consumption" and the molecular structures can be specifically altered to circumvent legislation. Recent legislation has focused on regulating packaging and has reduced, but not eliminated, the distribution of Spice in Alaska. Legally obtained Spice samples from three geographic regions in Alaska were analyzed using liquid injection gas chromatography-mass spectrometry (GC-MS). Most (70%) of the samples contained illegal cannabinoids that have been regulated by the Drug Enforcement Agency and 47% contained multiple active ingredients. We hypothesized that the heterogeneity of the active ingredients between brands and across regions could be used to indicate small- or larger-scale manufacturing, and the results indicate multiple manufacturing scales. Evidence for small-scale manufacturing included inconsistent packaging, several of which contained similar active ingredient profiles in different brands purchased from a single store. Evidence for large-scale production was also found with some brands having consistent active ingredient profiles across regions. This study provides preliminary data for the geographic variability of active ingredients in Spice as an indicator of mechanisms of manufacture and distribution to inform legislators and law enforcement and help prioritizing resource allocation in an effort to quell Spice use in Alaska.

Engaging Early-Career Students in Research Using a Tiered Mentoring Model.

Incorporating research into undergraduate curricula, especially at an early stage, has been linked to improved critical thinking, intellectual independence, and student retention. This results in a graduating population more ready to enter the workforce or graduate school. Similarly, mentoring has been linked to enhanced self-efficacy, persistence, and desire to pursue graduate studies. We have designed two linked courses that engage second-year undergraduate students in developing self-directed research projects, proposal writing. These courses also serve to nucleate relationships with graduate student mentors enrolled in the companion course. Early-career undergraduate students, with no previous research experience, receive formal training in the process of scientific research from a faculty process mentor while working with a graduate student content mentor to develop an independent research project and write a proposal and embed themselves in an active research group. Undergraduate students may elect to submit their proposals for funding to continue the project, either as part of the upper division research course required for graduation or independently. Graduate students enrolled in the companion course gain experience in mentoring through formal training and actively mentoring early-career undergraduates. This chapter presents both the model and early assessment of our integrated approach to engaging early career undergraduates in developing and funding independent research projects with the support of empowering mentoring relationships.

Introduction to Environmental Chemistry of the Arctic: An Introductory, Lab-Based Course Offered Both Face-to-Face and by Distance.

In this chapter, we present a model for an entry-level lab-based undergraduate environmental chemistry course delivered simultaneously by face-to-face and distance modalities. This course frames conceptual chemistry using the theme of Alaskan Arctic environmental issues in order to increase engagement and perceived relevance of chemical principles. Synchronously delivered lectures and guided discussions along with the incorporation of peer-mentored research projects encourage the development of a learning community among students in the course. Distance students participate in the same virtual and "kitchen" lab experiments as on-campus students, thus providing an educationally equivalent curriculum to all. In mixed teams of on-campus and distance students, all students participate in research projects to allow entry-level students to explore their interests in STEM fields. Students thereby begin to build an identity as a scientist and hopefully this course will serve as a mechanism to improve recruitment and retention of students, especially from traditionally underrepresented groups, in the chemical sciences and other STEM fields of study. Responses from the first course offering communicated positive attitudes toward the course content and methods.

Safety and Acceptability of Patient-Administered Sedatives During Mechanical Ventilation.

BACKGROUND: Safety and acceptability of sedative self-administration by patients receiving mechanical ventilation is unknown. OBJECTIVES: To determine if self-administration of dexmedetomidine by patients is safe and acceptable for self-management of anxiety during ventilatory support. METHODS: In a pilot trial in 3 intensive care units, 17 intubated patients were randomly assigned to dexmedetomidine and 20 to usual care. Dexmedetomidine was administered via standard pumps for patient-controlled analgesia, with a basal infusion (0.1-0.7 µg/kg per hour) titrated by the number of patient-triggered doses (0.25 µg/kg per dose). Safety goals were heart rate greater than 40/min, systolic blood pressure greater than 80 mm Hg, and diastolic blood pressure greater than 50 mm Hg. Acceptability was based on patients' self-reported satisfaction and ability to administer the sedative. A 100-mm visual analog scale was used daily to assess patients' anxiety. RESULTS: The sample was 59% male and 89% white. Mean values were age, 50.6 years; score on the Acute Physiology and Chronic Health Evaluation, 60.1; and protocol duration, 3.4 days. Five dexmedetomidine patients had blood pressure and/or heart rate lower than safety parameters, necessitating short-term treatment. Nurses' adherence to reporting of safety parameters was 100%; adherence to the dexmedetomidine titration algorithm was 73%. Overall baseline anxiety score was 38.4 and did not change significantly (ßday = 2.1; SE, 2.5; P = .40). Most dexmedetomidine patients (92%) were satisfied or very satisfied with their ability to self-administer medication. CONCLUSIONS: For select patients, self-administration of dexmedetomidine is safe and acceptable.

Clofarabine desensitization: A case report: Leukemia research reports.

We describe a relapsed AML patient who had two prior severe reactions to clofarabine involving rigors, emesis, tachycardia, hypotension, and acute kidney injury. Given previous prolonged remission achieved with clofarabine and cytarabine therapy years prior, rechallenge was undertaken upon discovery of AML relapse. We designed a desensitization protocol performed with the first dose of clofarabine, leading to successful administration of the entire clofarabine/cytarabine treatment course. From this case we show promise for clofarabine rechallenge after prior hypersensitivity reactions in patients with few treatment options for relapsed AML.

Is Unpaved Road Dust Near Fairbanks, Alaska a Health Concern? Examination of the Total and Bioaccessible Metal(loid)s.

Recent studies highlight the health risks associated with toxic metal(loid)s [e.g., arsenic (As), zinc (Zn), and lead (Pb)] in dust from mining operations, urban settings, and rural roads. To have a deleterious health effect, inhaled or ingested metal(loid)s must dissolve under conditions in the lung or gastrointestinal tract. In this study, we determined total and physiologically-soluble fractions of metal(loid)s in road dust from four sites in east-central interior Alaska. Total As and antimony (Sb) were enriched up to 26.2 and 53.7, respectively in dusts relative to average crustal abundance. Several elements such as nickel (Ni), As, and Sb were highly to moderately soluble in simulated lung fluids (7-80%, 15-51%, and 5-42%, respectively). Nickel and As exceeded the EPA inhalation risk unit, which is an exposure level of minimal risk. Despite several elements being highly soluble in simulated gastric fluids, including Ni, Cu, As, and Pb, only As samples exceeded the oral reference dose for children (based on total elemental concentrations) in some samples. The highest exposure risks identified in this study are inhalation of As and Ni present in road dust and ingestion of As-containing dust, especially by children. Additional studies would be needed to further quantify the health risk posed by road dust in this region.

Systematic Review and Meta-Analysis of Acute Kidney Injury Associated with Concomitant Vancomycin and Piperacillin/tazobactam.

Concomitant vancomycin and piperacillin/tazobactam may be associated with increased acute kidney injury (AKI) compared to vancomycin without piperacillin/tazobactam. A systematic search of Medline, Cochrane Library, and Scopus through October 2016 using ["vancomycin" and "piperacillin" and "tazobactam"] and ["AKI" or "acute renal failure" or "nephrotoxicity"] and registered meta-analysis (PROSPERO: CRD42016041646) with relevant scenarios was performed. From 307 results, fourteen observational studies totaling 3549 patients were analyzed. Concomitant vancomycin and piperacillin/tazobactam was associated with AKI in unadjusted (odds ratio (OR) 3.12, 95% confidence interval (CI) 2.04-4.78) and adjusted (aOR 3.11, 95% CI 1.77-5.47) analyses. Similar findings were seen assessing studies in adults (aOR 3.15, 95% CI 1.72-5.76), children (OR 4.55, 95% CI 2.71-10.21), and when <50% of patients received care in an intensive care unit (aOR 3.04, 95% CI 1.49-6.22) but not ≥50% (aOR 2.83, 95% CI 0.74-10.85). Increased AKI with concomitant vancomycin and piperacillin/tazobactam should be considered when determining beta-lactam therapy.

Toxic metal(loid) speciation during weathering of iron sulfide mine tailings under semi-arid climate.

Toxic metalliferous mine-tailings pose a significant health risk to ecosystems and neighboring communities from wind and water dispersion of particulates containing high concentrations of toxic metal(loid)s (e.g., Pb, As, Zn). Tailings are particularly vulnerable to erosion before vegetative cover can be reestablished, i.e., decades or longer in semi-arid environments without intervention. Metal(loid) speciation, linked directly to bioaccessibility and lability, is controlled by mineral weathering and is a key consideration when assessing human and environmental health risks associated with mine sites. At the semi-arid Iron King Mine and Humboldt Smelter Superfund site in central Arizona, the mineral assemblage of the top 2 m of tailings has been previously characterized. A distinct redox gradient was observed in the top 0.5 m of the tailings and the mineral assemblage indicates progressive transformation of ferrous iron sulfides to ferrihydrite and gypsum, which, in turn weather to form schwertmannite and then jarosite accompanied by a progressive decrease in pH (7.3 to 2.3). Within the geochemical context of this reaction front, we examined enriched toxic metal(loid)s As, Pb, and Zn with surficial concentrations 41.1, 10.7, 39.3 mM kg-1 (3080, 2200, and 2570 mg kg-1), respectively. The highest bulk concentrations of As and Zn occur at the redox boundary representing a 1.7 and 4.2 fold enrichment relative to surficial concentrations, respectively, indicating the translocation of toxic elements from the gossan zone to either the underlying redox boundary or the surface crust. Metal speciation was also examined as a function of depth using X-ray absorption spectroscopy (XAS). The deepest sample (180 cm) contains sulfides (e.g., pyrite, arsenopyrite, galena, and sphalerite). Samples from the redox transition zone (25-54 cm) contain a mixture of sulfides, carbonates (siderite, ankerite, cerrusite, and smithsonite) and metal(loid)s sorbed to neoformed secondary Fe phases, principally ferrihydrite. In surface samples (0-35 cm), metal(loid)s are found as sorbed species or incorporated into secondary Fe hydroxysulfate phases, such as schwertmannite and jarosites. Metal-bearing efflorescent salts (e.g., ZnSO4·nH2O) were detected in the surficial sample. Taken together, these data suggest the bioaccessibility and lability of metal(loid)s are altered by mineral weathering, which results in both the downward migration of metal(loid)s to the redox boundary, as well as the precipitation of metal salts at the surface.

Surficial weathering of iron sulfide mine tailings under semi-arid climate.

Mine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering under semi-arid climate at an EPA Superfund Site in semi-arid central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2 m of tailings. Despite nearly invariant Fe and S concentration with depth (130-140 and 100-120 g kg-1, respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5 m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even in the lowest pH samples, indicating its metastable persistence in these semiarid tailings. The resulting sharp geochemical speciation gradients in close proximity to the tailings surface have important implications for plant colonization, as well as mobility and bioavailability of co-associated toxic metal(loid)s.

Geochemical weathering increases lead bioaccessibility in semi-arid mine tailings.

Mine tailings can host elevated concentrations of toxic metal(loid)s that represent a significant hazard to surrounding communities and ecosystems. Eolian transport, capable of translocating small (micrometer-sized) particles, can be the dominant mechanism of toxic metal dispersion in arid or semiarid landscapes. Human exposure to metals can then occur via direct inhalation or ingestion of particulates. The fact that measured doses of total lead (Pb) in geomedia correlate poorly with blood Pb levels highlights a need to better resolve the precise distribution of molecularly speciated metal-bearing phases in the complex particle mixtures. Species distribution controls bioaccessibility, thereby directly impacting health risk. This study seeks to correlate Pb-containing particle size and mineral composition with lability and bioaccessibility in mine tailings subjected to weathering in a semiarid environment. We employed X-ray absorption spectroscopy (XAS) and X-ray fluorescence (XRF), coupled with sequential chemical extractions, to study Pb speciation in tailings from the semiarid Arizona Klondyke State Superfund Site. Representative samples ranging in pH from 2.6 to 5.4 were selected for in-depth study of Pb solid-phase speciation. The principle lead-bearing phase was plumbojarosite (PbFe(6)(SO(4))(4)(OH)(12)), but anglesite (PbSO(4)) and iron oxide-sorbed Pb were also observed. Anglesite, the most bioavailable mineral species of lead identified in this study, was enriched in surficial tailings samples, where Pb concentrations in the clay size fraction were 2-3 times higher by mass relative to bulk. A mobile and bioaccessible Pb phase accumulates in surficial tailings, with a corresponding increase in risk of human exposure to atmospheric particles.

Changes in zinc speciation with mine tailings acidification in a semiarid weathering environment.

High concentrations of residual metal contaminants in mine tailings can be transported easily by wind and water, particularly when tailings remain unvegetated for decades following mining cessation, as is the case in semiarid landscapes. Understanding the speciation and mobility of contaminant metal(loid)s, particularly in surficial tailings, is essential to controlling their phytotoxicities and to revegetating impacted sites. In prior work, we showed that surficial tailings samples from the Klondyke State Superfund Site (AZ, USA), ranging in pH from 5.4 to 2.6, represent a weathering series, with acidification resulting from sulfide mineral oxidation, long-term Fe hydrolysis, and a concurrent decrease in total (6000 to 450 mg kg(-1)) and plant-available (590 to 75 mg kg(-1)) Zn due to leaching losses and changes in Zn speciation. Here, we used bulk and microfocused Zn K-edge X-ray absorption spectroscopy (XAS) data and a six-step sequential extraction procedure to determine tailings solid phase Zn speciation. Bulk sample spectra were fit by linear combination using three references: Zn-rich phyllosilicate (Zn(0.8)talc), Zn sorbed to ferrihydrite (Zn(adsFeOx)), and zinc sulfate (ZnSO(4) · 7H(2)O). Analyses indicate that Zn sorbed in tetrahedral coordination to poorly crystalline Fe and Mn (oxyhydr)oxides decreases with acidification in the weathering sequence, whereas octahedral zinc in sulfate minerals and crystalline Fe oxides undergoes a relative accumulation. Microscale analyses identified hetaerolite (ZnMn(2)O(4)), hemimorphite (Zn(4)Si(2)O(7)(OH)(2) · H(2)O) and sphalerite (ZnS) as minor phases. Bulk and microfocused spectroscopy complement the chemical extraction results and highlight the importance of using a multimethod approach to interrogate complex tailings systems.

Changes in lead and zinc lability during weathering-induced acidification of desert mine tailings: Coupling chemical and micro-scale analyses.

Desert mine tailings may accumulate toxic metals in the near surface centimeters because of low water through-flux rates. Along with other constraints, metal toxicity precludes natural plant colonization even over decadal time scales. Since unconsolidated particles can be subjected to transport by wind and water erosion, potentially resulting in direct human and ecosystem exposure, there is a need to know how the lability and form of metals change in the tailings weathering environment. A combination of chemical extractions, X-ray diffraction, micro-X-ray fluorescence spectroscopy, and micro-Raman spectroscopy were employed to study Pb and Zn contamination in surficial arid mine tailings from the Arizona Klondyke State Superfund Site. Initial site characterization indicated a wide range in pH (2.5 to 8.0) in the surficial tailings pile. Ligand-promoted (DTPA) extractions, used to assess plant-available metal pools, showed decreasing available Zn and Mn with progressive tailings acidification. Aluminum shows the inverse trend, and Pb and Fe show more complex pH dependence. Since the tailings derive from a common source and parent mineralogy, it is presumed that variations in pH and "bioavailable" metal concentrations result from associated variation in particle-scale geochemistry. Four sub-samples, ranging in pH from 2.6 to 5.4, were subjected to further characterization to elucidate micro-scale controls on metal mobility. With acidification, total Pb (ranging from 5 - 13 g kg(-1)) was increasingly associated with Fe and S in plumbojarosite aggregates. For Zn, both total (0.4 - 6 g kg(-1)) and labile fractions decreased with decreasing pH. Zinc was found to be primarily associated with the secondary Mn phases manjiroite and chalcophanite. The results suggest that progressive tailings acidification diminishes the overall lability of the total Pb and Zn pools.