• Arid Ecosystem Vegetation Canopy-Gap Dichotomy: Influence on Soil Microbial Composition and Nutrient Cycling Functional Potential

      Kushwaha, Priyanka; Neilson, Julia W.; Barberán, Albert; Chen, Yongjian; Fontana, Catherine G.; Butterfield, Bradley J.; Maier, Raina M.; Department of Environmental Science, University of Arizona (American Society for Microbiology, 2021-12-11)
      Increasing temperatures and drought in desert ecosystems are predicted to cause decreased vegetation density combined with barren ground expansion. It remains unclear how nutrient availability, microbial diversity, and the associated functional capacity vary between the vegetated canopy and gap soils. The specific aim of this study was to characterize canopy versus gap microsite effect on soil microbial diversity, the capacity of gap soils to serve as a canopy soil microbial reservoir, nitrogen (N)-mineralization genetic potential (ureC gene abundance) and urease enzyme activity, and microbial-nutrient pool associations in four arid-hyperarid geolocations of the western Sonoran Desert, Arizona, United States. Microsite combined with geolocation explained 57% and 45.8% of the observed variation in bacterial/archaeal and fungal community composition, respectively. A core microbiome of amplicon sequence variants was shared between the canopy and gap soil communities; however, canopy soils included abundant taxa that were not present in associated gap communities, thereby suggesting that these taxa cannot be sourced from the associated gap soils. Linear mixed-effects models showed that canopy soils have significantly higher microbial richness, nutrient content, and organic N-mineralization genetic and functional capacity. Furthermore, ureC gene abundance was detected in all samples, suggesting that ureC is a relevant indicator of N mineralization in deserts. Additionally, novel phylogenetic associations were observed for ureC, with the majority belonging to Actinobacteria and uncharacterized bacteria. Thus, key N-mineralization functional capacity is associated with a dominant desert phylum. Overall, these results suggest that lower microbial diversity and functional capacity in gap soils may impact ecosystem sustainability as aridity drives openspace expansion in deserts.
    • Phytoextraction efficiency of Arabidopsis halleri is driven by the plant and not by soil metal concentration

      Dietrich, Charlotte C.; Tandy, Susan; Murawska-Wlodarczyk, Kamila; Banaś, Angelika; Korzeniak, Urszula; Seget, Barbara; Babst-Kostecka, Alicja; Department of Environmental Science, The University of Arizona (Elsevier BV, 2021-12)
      The hyperaccumulation trait allows some plant species to allocate remarkable amounts of trace metal elements (TME) to their foliage without suffering from toxicity. Utilizing hyperaccumulating plants to remediate TME contaminated sites could provide a sustainable alternative to industrial approaches. A major hurdle that currently hampers this approach is the complexity of the plant-soil relationship. To better anticipate the outcome of future phytoremediation efforts, we evaluated the potential for soil metal-bioavailability to predict TME accumulation in two non-metallicolous and two metallicolous populations of the Zn/Cd hyperaccumulator Arabidopsis halleri. We also examined the relationship between a population's habitat and its phytoextraction efficiency. Total Zn and Cd concentrations were quantified in soil and plant material, and bioavailable fractions in soil were quantified via Diffusive Gradients in Thin-films (DGT). We found that shoot TME accumulation varied independent from both total and bioavailable soil TME concentrations in metallicolous individuals. In fact, hyperaccumulation patterns appear more plant- and less soil-driven: one non-metallicolous population proved to be as efficient in accumulating Zn on non-polluted soil as the metallicolous populations in their highly contaminated environment. Our findings demonstrate that in-situ information on plant phytoextraction efficiency is indispensable to optimize site-specific phytoremediation measures. If successful, hyperaccumulating plant biomass may provide valuable source material for application in the emerging field of green chemistry. © 2021 Elsevier Ltd
    • Iron-activated persulfate oxidation degrades aqueous Perfluorooctanoic acid (PFOA) at ambient temperature

      Tran, Thien; Abrell, Leif; Brusseau, Mark L.; Chorover, Jon; Arizona Laboratory for Emerging Contaminants, The University of Arizona; Department of Environmental Science, The University of Arizona (Elsevier BV, 2021-10)
      Perfluorooctanoic acid (PFOA, C8HF15O2) is an industrial surfactant that is highly resistant to natural breakdown processes such as those mediated by heat, hydrolysis, photolysis, and biodegradation. Many efforts have been developed to breakdown PFOA to less harmful species due to its widespread human exposure and potential toxicity. However, these methods require high temperature or specialized equipment with serious disadvantages of high energy cost for long-term use. We investigated the effectiveness of PFOA degradation by ferrous iron-activated persulfate oxidation (IAPO) under various aqueous geochemical conditions. Approximately 64% of PFOA (initial concentration = 1.64 μmol L−1) was degraded after 4 h under illuminated anoxic conditions at ambient temperature. This degradation rate and magnitude support the potential use of IAPO as a novel inexpensive and environmentally friendly method to remediate PFOA in soil and groundwater. © 2021 Elsevier Ltd
    • Norm inflation for the Boussinesq system

      Li, Zongyuan; Wang, Weinan; Department of Mathematics, University of Arizona (American Institute of Mathematical Sciences (AIMS), 2021-10)
      We prove the norm inflation phenomena for the Boussinesq system on T3. For arbitrarily small initial data (u0,ρ0) in the negative-order Besov spaces B˙−1∞,∞×B˙−1∞,∞, the solution can become arbitrarily large in a short time. Such largeness can be detected in ρ in Besov spaces of any negative order: B˙−s∞,∞ for any s>0.
    • Racial resentment predicts eugenics support more robustly than genetic attributions

      Schneider, Stephen P.; Gonzalez, Frank J.; School of Government and Public Policy, University of Arizona (Elsevier BV, 2021-10)
      Recent interest in human genetics has raised concerns about a revival in support for eugenic policies. However, historically, eugenic policies have been closely tied to racism, and the question remains how much support for eugenics is due to beliefs about heritability rather than racial prejudice. Using a survey administered by YouGov to a representative sample of Americans (n = 446) in the fall of 2015, we find that racial resentment is a robust and at times stronger predictor of support for eugenics, particularly negative eugenics (policies discouraging or preventing reproduction), than beliefs about heritability, and that when beliefs about heritability matter, it is mainly in racial domains. These findings offer insight into the connection between racism and eugenics, and how the role of beliefs about heritability may be exaggerated.
    • Designing additively manufactured lattice structures based on deformation mechanisms

      Babamiri, Behzad Bahrami; Barnes, Baxter; Soltani-Tehrani, Arash; Shamsaei, Nima; Hazeli, Kavan; Aerospace and Mechanical Engineering Department, The University of Arizona (Elsevier BV, 2021-10)
      The post-yield mechanical behavior of additively manufactured lattice structures (AMLS) is governed by the interplay between intrinsic (microstructural) and extrinsic (structural topology) properties at different length scales. Herein, we introduce a novel design optimization approach that accounts for scale separation and size effects, which control deformation mechanisms, to achieve a certain targeted macroscopic mechanical response. The new topological designs are guided by finding a direct correlation between the distribution of local stresses within struts and the underlying microstructures. The local stresses are computed using a strut-level yield criterion that has been calibrated to strut-level tensile, compressive, and shear loading experiments. Therefore, the local response of the struts, including tension-compression asymmetry, build direction dependence, and size effects, are accounted for in the yield surface, enabling a more accurate representation of the local stress state. Accurate calculation of the stress state for a given microstructure and topology combination allows for optimizing the topology for the given strut-level microstructure. The interplay between the topology and microstructure is assessed by investigating the unit cell-level deformation mechanisms and quantifying their influence on the global stress-strain relationship via finite element simulations. Using these relationships, a new set of topologies is designed, built, and validated with experiments. On average, the new topologies demonstrate 40% and 72% improvement in energy absorption capacity and flow stress, respectively, compared to topologies that had been previously optimized using constitutive models, which are homogeneous throughout the unit cell. The goal of the presented article is to demonstrate that simultaneously considering the effects of topology and microstructure on the mechanical behavior of AMLS has the potential to substantially improve key performance metrics, including ultimate strength and energy dissipation. The distinguishing and novel feature of our approach is that the topological optimization is performed while accounting for the heterogeneous distribution of strut-level microstructural features and concomitant mechanical behavior, which leads to new insights relative to peak AMLS structural performance.
    • Hyperspectral remote sensing for detecting geotechnical problems at ray mine

      He, Jingping; Barton, Isabel; Department of Mining and Geological Engineering, University of Arizona (Elsevier BV, 2021-10)
      While many or most geotechnical problems at open-pit mines are related to geological structures or discontinuities, highwall movement and failure can also occur as a consequence of nonstructural geological factors. Nonstructural causes of movement are not amenable to detection by conventional geotechnical sensing techniques such as LiDAR. In this case study, we applied hyperspectral remote sensing for large-scale mapping and detection of minerals at a non-structure-related ground instability in the highwalls of the Ray mine near Tucson, Arizona. The spectral images, obtained and integrated with radar images and the geological map, show that the dominant spectrally active mineral underlying the unstable area is the swelling clay montmorillonite, whereas kaolinite and white mica are more common in more stable parts of the highwall. The montmorillonite is concentrated in an outcropping altered diabase and conglomerate that underlie more competent rocks, providing a potential lift and slip surface. This study shows that hyperspectral remote sensing can aid in geotechnical slope characterization, particularly for nonstructural causes of failure. We provide a brief overview of best practices for hyperspectral remote sensing in geotechnical applications (combining drone- and tripod-mounted sensors, integrating hyperspectral with LiDAR and radar data, and using an iteratively refined spectral library based on site-specific sampling supported by ground truth).
    • Highly Dy2O3 and Er2O3 doped boron-aluminosilicate glasses for magneto-optical devices operating at 2 µm

      Dubrovin, V.D.; Zhu, X.; Mollaee, M.; Zong, J.; Peyghambarian, N.; James C. Wyant College of Optical Sciences, The University of Arizona (Elsevier BV, 2021-10)
      Magneto-optical glass materials with large Verdet constants at 2 μm have attracted increasing attention due to the significant advances of novel lasers operating at this wavelength region. In this paper, 13Al2O3-21B2O3-35.4SiO2-(30.6-X)Er2O3-XDy2O3 glasses have been synthesized, and their physical, optical, and magneto-optical properties were studied for making Faraday devices at 2 μm. A Verdet constant of as high as −5.9 rad/(T*m) at 1950 nm was measured with a 13Al2O3-21B2O3-35.4SiO2-30.6Dy2O3 glass. The temperature difference between crystallization and glass transition of 150 °C and the synthesis temperature of below 1500 °С make this glass very promising for making magneto-optical devices for 2 μm applications.
    • Source identification of PM2.5 carbonaceous aerosol using combined carbon fraction, radiocarbon and stable carbon isotope analyses in Debrecen, Hungary

      Major, István; Furu, Enikő; Varga, Tamás; Horváth, Anikó; Futó, István; Gyökös, Brigitta; Somodi, Gábor; Lisztes-Szabó, Zsuzsa; Jull, A.J. Timothy; Kertész, Zsófia; et al. (Elsevier BV, 2021-08)
      In this study, PM2.5 aerosol samples collected continuously in Debrecen, Hungary from December 2011 to July 2014 were processed and analysed. Mass concentration and ratios of PM2.5 aerosol, organic and elemental carbon fractions, in addition, radio and stable carbon isotopes were evaluated together to obtain a better sight into the possible local and regional sources. For the studied period, the mean mass concentration of PM2.5 aerosol and the constituting total, organic and elemental carbon were 23.6, 5.8, 5.0 and 0.8 μg m−3, respectively. In all cases, the mean for the heating periods were on average 2–3 times that of the vegetation (i.e. heating-free) periods. The relatively high mean secondary organic carbon concentration of 4.1 μg m−3 and OC/EC ratio of 6.9 suggested the dominance of combustion processes in winter and, based on the higher contemporary carbon fraction of 0.77, wood fuels prevailed over coal or oil. The average δ13C of the tested wood fuels implies that combustion of black locust, oak and beech was a significant factor in forming the mean δ13C of PM2.5 of −25.6‰ during the heating months. The mean δ13C of −26.7‰ in summer was more influenced by emissions from transportation and the surrounding vegetation. In addition, using coupled backward trajectory modeling (HYSPLIT) and visualization of open fire events (FIRMS), we presume that the conspicuously enriched δ13C values of PM2.5 collected in October of the observation years were probably caused by long-range transport of particles derived from agricultural combustion of C4 plants close to the southern and eastern Hungarian borders. © 2021 Elsevier B.V.
    • Climate sensitivity and drought seasonality determine post-drought growth recovery of Quercus petraea and Quercus robur in Europe

      Bose, Arun K.; Scherrer, Daniel; Camarero, J. Julio; Ziche, Daniel; Babst, Flurin; Bigler, Christof; Bolte, Andreas; Dorado-Liñán, Isabel; Etzold, Sophia; Fonti, Patrick; et al. (Elsevier BV, 2021-08)
      Recent studies have identified strong relationships between delayed recovery of tree growth after drought and tree mortality caused by subsequent droughts. These observations raise concerns about forest ecosystem services and post-drought growth recovery given the projected increase in drought frequency and extremes. For quantifying the impact of extreme droughts on tree radial growth, we used a network of tree-ring width data of 1689 trees from 100 sites representing most of the distribution of two drought tolerant, deciduous oak species (Quercus petraea and Quercus robur). We first examined which climatic factors and seasons control growth of the two species and if there is any latitudinal, longitudinal or elevational trend. We then quantified the relative departure from pre-drought growth during droughts, and how fast trees were able to recover the pre-drought growth level. Our results showed that growth was more related to precipitation and climatic water balance (precipitation minus potential evapotranspiration) than to temperature. However, we did not detect any clear latitudinal, longitudinal or elevational trends except a decreasing influence of summer water balance on growth of Q. petraea with latitude. Neither species was able to maintain the pre-drought growth level during droughts. However, both species showed rapid recovery or even growth compensation after summer droughts but displayed slow recovery in response to spring droughts where none of the two species was able to fully recover the pre-drought growth-level over the three post-drought years. Collectively, our results indicate that oaks which are considered resilient to extreme droughts have also shown vulnerability when droughts occurred in spring especially at sites where long-term growth is not significantly correlated with climatic factors. This improved understanding of the role of drought seasonality and climate sensitivity of sites is key to better predict trajectories of post-drought growth recovery in response to the drier climate projected for Europe.
    • Thunderstorm and fair-weather quasi-static electric fields over land and ocean

      Wilson, Jennifer G.; Cummins, Kenneth L.; Department of Hydrology and Atmospheric Sciences, University of Arizona (Elsevier BV, 2021-08)
      Natural lightning and the associated clouds are known to behave differently over land and ocean, but many questions remain. We expand the related observational datasets by obtaining simultaneous quasi-static electric field observations over coastal land, near-shore water, and deep ocean regions during both fair-weather and thunderstorm periods. Oceanic observations were obtained using two 3-m NOAA buoys that were instrumented with Campbell Scientific electric field mills to measure the quasi-static electric fields. These data were compared to selected electric field records from the existing on-shore electric field mill suite of 31 sensors at Kennedy Space Center (KSC). Lightning occurrence times, locations and peak current estimates for both onshore and ocean were provided by the U.S. National Lightning Detection Network. The buoy instruments were first evaluated on-shore at the Florida coast, and the first system was calibrated for field enhancements and to confirm proper behavior of the system in elevated-field environments. The buoys were then moored 20 mi and 120 mi off the coast of KSC in February (20 mi) and August (120 mi) 2014. Diurnal fair-weather fields at both ocean sites matched will with each other and with those found during the Carnegie cruise, but mean values were 33% smaller, due at least in-part to constraints on the calibration procedure. Diurnal fair-weather fields variations at coastal and inland sites were a poorer match than offshore, likely because the offshore environment is “cleaner” with limited variations in local space charge, lower surface aerosol densities, little surface heating to disturb the surface charge layer during fair weather, and fewer local radioactive sources to modulate the near-surface electrical conductivity. Storm-related static fields were 4-5× larger at both oceanic sites than over land, likely due to decreased screening by near-surface space charge produced by corona current. The time-evolution of the electric field and field changes during storm approach are sufficiently different over land and ocean to warrant further study. This work shows the quality, accuracy, and reliability of these data, and has demonstrated the practicality of off-shore electric field measurements for safety- and launch-related decision making at KSC.
    • Rapid erosion of the central Transantarctic Mountains at the Eocene-Oligocene transition: Evidence from skewed (U-Th)/He date distributions near Beardmore Glacier

      He, John; Thomson, Stuart N.; Reiners, Peter W.; Hemming, Sidney R.; Licht, Kathy J.; Department of Geosciences, University of Arizona (Elsevier BV, 2021-08)
      Apatite (U-Th)/He thermochronology has the potential to reconstruct records of erosional exhumation that are critical to understanding interactions between climate, tectonics, and the cryosphere at high latitudes on million-year timescales. However this approach is often hindered by the problem of intrasample single-grain date dispersion. Here we present an extensive new apatite (U-Th)/He dataset (n = 361) from the central Transantarctic Mountains of East Antarctica between 160°E to 170°W and 84 to 86°S, and show that apparently uninterpretable data in most samples are a reflection of inadequate sampling of skewed date distributions. We outline a workflow for interpreting such dispersed data and demonstrate that geologically meaningful age interpretations are possible in the case of rapidly cooled samples, despite the wide array of potential causes for date dispersion. We show that for samples and compilations with a large number of single-grain analyses (n > ∼25), the youngest probability distribution peak represents the most likely time of fast cooling through the apatite (U-Th)/He closure temperature. When fewer grains are analyzed, the youngest peak is represented best by the minimum date or first quartile date, depending on sample size. Using this workflow, we show that since the latest Eocene, up to 8.8 km of exhumation occurred to incise the deepest point of the Beardmore Glacier trough. Rapid incision began at c. 37-34 Ma (at the latest by 34±3 Ma), coinciding with or slightly preceding the initiation of Antarctic glaciation at the Eocene-Oligocene transition, and contributed to at least 2.6 km of exhumation within the first 3-6 million years, at an apparent exhumation rate of no less than 0.4 mm/a. © 2021 Elsevier B.V.
    • Okun loops and anelastic relaxation in the G7

      Hawkins, Raymond J.; Li, Yichu; Wyant College of Optical Sciences, University of Arizona (Elsevier BV, 2021-08)
      We show that Okun loops – loop deviations from Okun's law – are an expected outcome of extending Okun's law to allow for observed time dependence in the response of unemployment to a change in output, and are an example of anelastic relaxation in economics. We extend prior work on these loops by documenting their regular appearance in the United States economy since WWII and their appearance in all G7 countries. We also find that the anelastic form of Okun's law provides a statistically significant and operationally parsimonious representation of output–unemployment dynamics in all G7 countries.
    • Oxidative phosphorylation K0.5ADP in vitro depends on substrate oxidative capacity: Insights from a luciferase-based assay to evaluate ADP kinetic parameters

      Willis, Wayne; Willis, Elizabeth; Kuzmiak-Glancy, Sarah; Kras, Katon; Hudgens, Jamie; Barakati, Neusha; Stern, Jennifer; Mandarino, Lawrence; Department of Medicine, Division of Endocrinology, University of Arizona (Elsevier BV, 2021-08)
      The K0.5ADP of oxidative phosphorylation (OxPhos) identifies the cytosolic ADP concentration which elicits one-half the maximum OxPhos rate. This kinetic parameter is commonly measured to assess mitochondrial metabolic control sensitivity. Here we describe a luciferase-based assay to evaluate the ADP kinetic parameters of mitochondrial ATP production from OxPhos, adenylate kinase (AK), and creatine kinase (CK). The high sensitivity, reproducibility, and throughput of the microplate-based assay enabled a comprehensive kinetic assessment of all three pathways in mitochondria isolated from mouse liver, kidney, heart, and skeletal muscle. Carboxyatractyloside titrations were also performed with the assay to estimate the flux control strength of the adenine nucleotide translocase (ANT) over OxPhos in human skeletal muscle mitochondria. ANT flux control coefficients were 0.91 ± 0.07, 0.83 ± 0.06, and 0.51 ± 0.07 at ADP concentrations of 6.25, 12.5, and 25 μM, respectively, an [ADP] range which spanned the K0.5ADP. The oxidative capacity of substrate combinations added to drive OxPhos was found to dramatically influence ADP kinetics in mitochondria from several tissues. In mouse skeletal muscle ten different substrate combinations elicited a 7-fold range of OxPhos Vmax, which correlated positively (R2 = 0.963) with K0.5ADP values ranging from 2.3 ± 0.2 μM to 11.9 ± 0.6 μM. We propose that substrate-enhanced capacity to generate the protonmotive force increases the OxPhos K0.5ADP because flux control at ANT increases, thus K0.5ADP rises toward the dissociation constant, KdADP, of ADP-ANT binding. The findings are discussed in the context of top-down metabolic control analysis. © 2021 Elsevier B.V.
    • Nonlinear ultrasonics-based technique for monitoring damage progression in reinforced concrete structures

      Basu, Sukanya; Thirumalaiselvi, A.; Sasmal, Saptarshi; Kundu, Tribikram; Civil and Architectural Engineering and Mechanics, University of Arizona (Elsevier BV, 2021-08)
      In reinforced concrete (RC), material nonlinearity is evident even in its undamaged state due to the inherent microstructure. In the present work, damage progression in RC structure at different levels of damage is investigated using linear and nonlinear ultrasonic techniques. The primary focus of this study is to monitor the structure from its initiation stage(s) of damage to advanced stages. Ultrasonic velocity tomography is first implemented to identify the weaker regions and map any damage occurring at various levels of loading. Two critical regions are identified from ultrasonic tomography and further damage characterization is carried out using various ultrasonic techniques to quantitatively assess the progression of damage in these two regions. The linear ultrasonic techniques such as time-of-flight (TOF) and attenuation, and the nonlinear ultrasonic techniques such as sub- and super- harmonic, energy distribution, etc. are employed to detect the damage progression. It is found that the changes in linear parameters due to damage progression in RC structure are often insignificant and inconsistent. However, some of the nonlinear ultrasonics-based techniques are found to be very efficient to monitor the damage progression. A relatively new and promising nonlinear ultrasonic technique, namely the sideband peak count-index (or SPC-I) provides a very clear and consistent indication of damage at the early stage. The present study shows that during the initial stages of damage, SPC-I based nonlinear technique performs significantly better (at both regions as identified through ultrasonic tomography) than other linear and nonlinear techniques, whereas at higher damage stage the superiority of this nonlinear ultrasonic technique slowly diminishes. The present study also shows that out of all nonlinear ultrasonics-based techniques considered here, SPC-I technique provides the highest sensitivity to the damage progression and can be effectively used as a very robust nonlinear ultrasonic tool for identifying the onset and progression of damage in RC structures. © 2021 Elsevier B.V.
    • Evaluating surrogate correlation models and iodinated haloacetic acid formation of iodinated contrast media after LPUV/Cl2, LPUV/NH2Cl, and LPUV/H2O2

      Lopez-Prieto, Israel J.; Daniels, Kevin D.; Wu, Shimin; Snyder, Shane A.; University of Arizona, Department of Chemical and Environmental Engineering (Elsevier BV, 2021-08)
      Iodinated X-ray contrast media (ICM) are a class of pharmaceuticals that are ubiquitously found at trace levels (μg/L) in wastewater, surface water, groundwater, and drinking water. Due to their polar features, they are not effectively removed during conventional water treatment and provide an iodine source for the formation of iodinated-disinfection by-products (I-DBPs) during disinfection. This work examined the suitability of organic parameters (i.e. total organic carbon (TOC), ultraviolet absorbance (UVA254), total fluorescence (TF) and specific ultraviolet absorbance (SUVA)), as surrogate correlation models to estimate the removal of seven target ICMs. Three advanced oxidation processes (AOPs), LPUV/H2O2, LPUV/Cl2 and LPUV/NH2Cl, were applied to develop the surrogate correlation models. Pearson correlation coefficients were compared with linear correlation models to determine the ideal surrogate parameter for each model type. The formation of iodinated-haloacetic acids (I-HAAs) were also monitored for each AOP treatment. Results did not show any significant differences for ICM attenuation across the AOP treatments, illustrating UV photolysis is the main driving force to attenuate ICMs. Surrogate correlation models demonstrated a good correlation (R2 = 0.8211 and 0.7887) and strong Pearson correlation (R = 0.9602 and 0.8881) for UVA254 during LPUV/Cl2 and LPUV/H2O2 treatment. Additionally, two I-HAA, monoidoacetic acid (MIAA) and bromoiodoacetic acid (BIAA), were detected (up to 2.4 μg/L) after LPUV/Cl2 and LPUV/NH2Cl AOP treatment. © 2021 Elsevier Ltd.
    • Phosphate controls uranium release from acidic waste-weathered Hanford sediments

      Vázquez-Ortega, Angélica; Perdrial, Nicolas; Reinoso-Maset, Estela; Root, Robert A.; O’Day, Peggy A.; Chorover, Jon; Department of Environmental Science, University of Arizona (Elsevier BV, 2021-08)
      Mineral dissolution and secondary phase precipitation may control the fate of inorganic contaminants introduced to soils and sediments during liquid waste discharges. When the solutions are aggressive enough to induce transformation of native minerals, incorporated contaminants may be released during dissolution due to percolation of meteoric waters. This study evaluated the release of uranium (U) from Hanford sediments that had been previously reacted for 180 or 365 days with liquid waste solutions containing U with and without 3 mM dissolved phosphate at pH 2 and 3. Flow-through column experiments were conducted under continuous saturated flow with a simulated background porewater (BPW; pH ~7) for 22 d. Up to 5% of the total U was released from the sediments reacted under PO4-free conditions, attributable to the dissolution of becquerelite and boltwoodite formed during weathering. Contrastingly, negligible U was released from PO4-reacted sediments, where meta-ankoleite was identified as the main U-mineral phase. Linear combination fits of U LIII-edge EXAFS spectra of sediments before and after BPW leaching and thermodynamic calculations suggest that the formed becquerelite and meta-ankoleite transformed into schoepite and a phosphuranylite-type phase, respectively. These results demonstrate the stabilization of U as recalcitrant uranyl minerals formed in sediments and highlight the key role of PO4 in U release at contaminated sites.
    • Impact of multiple uncertainties on gravimetric variations across randomly heterogeneous aquifers during pumping

      Maina, Fadji Zaouna; Guadagnini, Alberto; Riva, Monica; Department of Hydrology and Atmospheric Sciences, University of Arizona (Elsevier BV, 2021-08)
      We evaluate the relative importance of the uncertainty related to parameters characterizing partially saturated groundwater flow on head and gravity changes associated with pumping tests taking place in homogeneous and heterogeneous porous media. We frame our study in a Global Sensitivity Analysis setting and assess the way imperfect knowledge of such parameters influences the probability distribution (pdf) of head and gravimetric variations recorded during well operation. We rely on a set of detailed computational analyses and conceptualize uncertain model parameters as random quantities. Randomly heterogeneous domains are treated by considering main geostatistical descriptors (i.e., variance and correlation scale) of three-dimensional spatial distributions of system properties as affected by uncertainty. We quantify the effects of the latter on the resulting pdf of (ensemble) mean and variance of head and gravity changes through a numerical Monte Carlo approach. While all uncertain parameters are influential to gravity changes in both homogeneous and randomly heterogeneous scenarios, consistent with the integral nature of gravity observations, our study enables us to quantify their relative importance. Values of Ensemble mean and variance of head and gravity changes associated with randomly heterogeneous fields are generally more influenced by the variance rather than by the correlation scale of the spatially heterogeneous parameters considered. Uncertainty in the correlation scale is more influential to the shape, and hence on extreme values, of the probability distribution of these moments.
    • Brine-driven destruction of clay minerals in Gale crater, Mars

      Bristow, T. F.; Grotzinger, J. P.; Rampe, E. B.; Cuadros, J.; Chipera, S. J.; Downs, G. W.; Fedo, C. M.; Frydenvang, J.; McAdam, A. C.; Morris, R. V.; et al. (American Association for the Advancement of Science (AAAS), 2021-07-08)
      Mars’ sedimentary rock record preserves information on geological (and potential astrobiological) processes that occurred on the planet billions of years ago. The Curiosity rover is exploring the lower reaches of Mount Sharp, in Gale crater on Mars. A traverse from Vera Rubin ridge to Glen Torridon has allowed Curiosity to examine a lateral transect of rock strata laid down in a martian lake ~3.5 billion years ago. We report spatial differences in the mineralogy of time-equivalent sedimentary rocks <400 meters apart. These differences indicate localized infiltration of silica-poor brines, generated during deposition of overlying magnesium sulfate–bearing strata. We propose that destabilization of silicate minerals driven by silica-poor brines (rarely observed on Earth) was widespread on ancient Mars, because sulfate deposits are globally distributed. Copyright © 2021 The Authors, some rights reserved.
    • How do non-human primates represent others' awareness of where objects are hidden?

      Horschler, Daniel J.; Santos, Laurie R.; MacLean, Evan L.; School of Anthropology, University of Arizona; Cognitive Science Program, University of Arizona; Department of Psychology, University of Arizona; College of Veterinary Medicine, University of Arizona (Elsevier BV, 2021-07)
      Although non-human primates (NHPs) generally appear to predict how knowledgeable agents use knowledge to guide their behavior, the cognitive mechanisms that enable this remain poorly understood. We assessed the conditions under which NHPs' representations of an agent's awareness break down. Free-ranging rhesus macaques (Macaca mulatta) watched as an agent observed a target object being hidden in one of two boxes. While the agent could no longer see the boxes, the box containing the object flipped open and the object either changed in size/shape (Experiment 1) or color (Experiment 2). Monkeys looked longer when the agent searched for the object incorrectly rather than correctly following the color change (a non-geometric manipulation), but not the size/shape change (a geometric manipulation). Even though the agent maintained knowledge of the object's location in both cases, monkeys no longer expected the agent to search correctly after it had been geometrically (but not non-geometrically) manipulated. Experiment 3 confirmed that monkeys were sensitive to the color manipulation used in Experiment 2, making it unlikely that a failure to perceive the color manipulation accounted for our findings. Our results show that NHPs do not always expect that knowledgeable agents will act on their knowledge to obtain their goals, consistent with heuristic-based accounts of how NHPs represent others' mental states. These findings also suggest that geometric changes that occur outside the agent's perceptual access may disrupt attribution of awareness more so than non-geometric changes. © 2021 Elsevier B.V.