Robert A Root

Interests

Research

geochemistry, metal speciation, EXAFS, XANES, X-ray spectroscopy, weathering, contaminant transport, medical mineralogy

Courses

Scholarly Contributions

Chapters

• Kong, S., Root, R. A., & Chorover, J. D. (2018). Organic acid effect on arsenate bioaccessibility in gastric and alveolar simulated biofluid systems. In Environmental Arsenic in a Changing World. CRC Press.

Journals/Publications

• Kadoya, W. M., Madeira, C. L., Hoppe-Jones, C., Solsten, T., Snyder, S. A., Root, R. A., Sierra-Alvarez, R., Chorover, J., & Field, J. A. (2021). The Role of Manganese Dioxide in the Natural Formation of Organochlorines. ACS ES&T Water, 1(12), 2523-2530.
• Menezes, O., Yu, Y., Root, R. A., Gavazza, S., Chorover, J., Sierra-Alvarez, R., & Field, J. A. (2021). Iron(II) monosulfide (FeS) minerals reductively transform the insensitive munitions compounds 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO). Chemosphere, 285, 131409.
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  As military applications of the insensitive munitions compounds (IMCs) 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO) increase, there is a growing need to understand their environmental fate and to develop remediation strategies to mitigate their impacts. Iron (II) monosulfide (FeS) minerals are abundant in freshwater and marine sediments, marshes, and hydrothermal environments. This study shows that FeS solids can reduce DNAN and NTO to their corresponding amines under anoxic ambient conditions. The reactions between IMCs and the FeS minerals were surface-mediated since they did not occur when only dissolved Fe and S were present. Mackinawite, a tetragonal FeS with a layered structure, reduced DNAN mainly to 2-methoxy-5-nitroaniline (MENA), which in turn was partially reduced to 2-4-diaminoanisole (DAAN). The layered structure of mackinawite provided intercalation sites likely responsible for partial adsorption of MENA and DAAN. Mackinawite entirely reduced NTO to 3-amino-1,2,4-triazol-5-one (ATO). The reduction of IMCs showed concurrent oxidation of mackinawite to goethite and elemental sulfur. A commercial FeS product, composed mainly of pyrrhotite and troilite, reduced DNAN to DAAN and NTO to ATO. At pH 6.5, DNAN and NTO transformation rates were 667 and 912 μmol h m, respectively, on the mackinawite surface and 417 and 1344 μmol h m, respectively, on the commercial FeS surface. This is the first report of the reduction of a nitro-heterocyclic compound (NTO) by FeS minerals. The evidence indicates that DNAN and NTO can be rapidly transformed to their succeeding amines in anoxic subsurface environments and aquatic sediments rich in FeS minerals.
• Moravec, B., Keifer, V., Root, R. A., White, A. M., Wang, Y., Olshansky, Y., Mcintosh, J. C., & Chorover, J. D. (2021). Experimental weathering of a volcaniclastic critical zone profile: Key role of colloidal constituents in aqueous geochemical response. Chemical Geology, 559(5), 119886. doi:10.1016/j.chemgeo.2020.119886
• Nakaoa, A., Unoa, S., Yanaia, J., Kuboterab, H., Tanakac, R., Root, R. A., & Kosaki, T. (2021). Distance-dependence from volcano for Asian dust inclusions in Andosols: A key to control soil ability to retain radiocesium. Geoderma, 385, 1-9. doi:doi.org/10.1016/j.geoderma.2020.114889
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  The fine-sized mica in Allophanic Andosols is not originated from volcanic ashes.The δ18O values of fine-quartz in the Andosols is similar to those of Asian dust.The quartz content associatively increased with mica as further away from a volcano.Asian-dust-derived mica is crucial to increase RCs retention ability in Andosols.
• Vázquez-Ortega, A., Perdrial, N., Reinoso-Maset, E., Root, R. A., O'Day, P. A., & Chorover, J. (2021). Phosphate controls uranium release from acidic waste-weathered Hanford sediments. Journal of hazardous materials, 416, 126240.
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  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 PO-free conditions, attributable to the dissolution of becquerelite and boltwoodite formed during weathering. Contrastingly, negligible U was released from PO-reacted sediments, where meta-ankoleite was identified as the main U-mineral phase. Linear combination fits of U L-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 PO in U release at contaminated sites.
• Wang, D., Root, R. A., & Chorover, J. (2021). Biochar-templated surface precipitation and inner-sphere complexation effectively removes arsenic from acid mine drainage. Environmental science and pollution research international, 28(33), 45519-45533.
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  Treatment of aqueous leachate from acid mine tailings with pristine biochar (BC) resulted in the removal of more than 90% of the dissolved arsenic with an attendant rapid and sustained pH buffering from 3 to 4. Pine forest waste BC was transformed to a highly effective adsorbent for arsenic remediation of acid mine drainage (AMD) because the dissolved iron induced "activation" of BC through accumulation of highly reactive ferric hydroxide surface sites. Physicochemical properties of the BC surface, and molecular mechanisms of Fe, S, and As phase transfer, were investigated using a multi-method, micro-scale approach (SEM, XRD, FTIR, XANES, EXAFS, and STXM). Co-located carbon and iron analysis with STXM indicated preferential iron neo-precipitates at carboxylic BC surface sites. Iron and arsenic X-ray spectroscopy showed an initial precipitation of ferrihydrite on BC, with concurrent adsorption/coprecipitation of arsenate. The molecular mechanism of arsenic removal involved bidentate, binuclear inner-sphere complexation of arsenate at the surfaces of pioneering ferric precipitates. Nucleation and crystal growth of ferrihydrite and goethite were observed after 1 h of reaction. The high sulfate activity in AMD promoted schwertmannite precipitation beginning at 6 h of reaction. At reaction times beyond 6 h, goethite and schwertmannite accumulated at the expense of ferrihydrite. Results indicate that the highly functionalized surface of BC acts as a scaffolding for the precipitation and activation of positively charged ferric hydroxy(sulf)oxide surface sites from iron-rich AMD, which then complex oxyanion arsenate, effectively removing it from porewaters. Graphical abstract.
• Hammond, C. M., Root, R. A., Maier, R. M., & Chorover, J. (2020). Arsenic and iron speciation and mobilization during phytostabilization of pyritic mine tailings. Geochimica et cosmochimica acta, 286, 306-323.
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  Particulate and dissolved metal(loid) release from mine tailings is of concern in (semi-) arid environments where tailings can remain barren of vegetation for decades and, therefore, become highly susceptible to dispersion by wind and water. Erosive weathering of metalliferous tailings can lead to arsenic contamination of adjacent ecosystems and increased risk to public health. Management via phytostabilization with the establishment of a vegetative cap using organic amendments to enhance plant growth has been employed to reduce both physical erosion and leaching. However, prior research suggests that addition of organic matter into the oxic weathering zone of sulfide tailings has the potential to promote the mobilization of arsenate. Therefore, the objective of the current work was to assess the impacts of phytostabilization on the molecular-scale mechanisms controlling arsenic speciation and lability. These impacts, which remain poorly understood, limit our ability to mitigate environmental and human health risks. Here we report on subsurface biogeochemical transformations of arsenic and iron from a three-year phytostabilization field study conducted at a Superfund site in Arizona, USA. Legacy pyritic tailings at this site contain up to 3 g kg arsenic originating from arsenopyrite that has undergone oxidation to form arsenate-ferrihydrite complexes in the top 1 m. Tailings were amended in the top 20 cm with 100, 150, or 200 g kg (300-600 T ha) of composted organic matter and seeded with native halotolerant plant species. Treatments and an unamended control received irrigation of 360 ± 30 mm y in addition to 250 ± 160 mm y of precipitation. Cores to 1 m depth were collected annually for three years and sectioned into 20 cm increments for analysis by synchrotron iron and arsenic X-ray absorption spectroscopy (XAS) coupled with quantitative wet chemical and mass balance methods. Results revealed that > 80% of arsenic exists in ammonium oxalate-extractable and non-extractable phases, including dominantly ferrihydrite and jarosite. Arsenic release during arsenopyrite oxidation resulted in both downward translocation and As attenuation by stable Fe(oxyhydr)oxide and Fe (hydroxy)sulfate minerals over time, highlighting the need for sampling at multiple depths and time points for accurate interpretation of arsenic speciation, lability, and translocation in weathering profiles. Less than 1% of total arsenic was highly-labile, i.e. water-extractable, from all treatments, depths, and years, and more than 99% of arsenate released by arsenopyrite weathering was attenuated by association with secondary minerals. Although downward translocation of both arsenic and iron was detected during phytostabilization by temporal enrichment analysis, a similar trend was measured for the uncomposted control, indicating that organic amendment associated with phytostabilization practices did not significantly increase arsenic mobilization over non-amended controls.
• Manjón, I., Ramírez-Andreotta, M. D., Sáez, A. E., Root, R. A., Hild, J., Janes, M. K., & Alexander-Ozinskas, A. (2020). Environmental monitoring and exposure science dataset to calculate ingestion and inhalation of metal(loid)s through preschool gardening. Data in brief, 29, 105050.
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  Metal(loid) contamination may pose an increased risk of exposure to children residing near legacy and active resource extraction sites. Children may be exposed to arsenic, cadmium, and/or lead by ingestion and/or inhalation while engaging in school or home outdoor activities via environmental media including water, soil, dust, and locally grown produce. It is thus critical to collect site-specific data to best assess these risks. This data article provides gastric and lung bioaccessibility assay (IVBA) data, as well as environmental monitoring data for water, soil, dust, and garden produce collected from preschools (N = 4) in mining communities throughout Nevada County, California in 2018. Arsenic, cadmium, and lead concentrations in the aforementioned media and synthetic gastric and lung fluids were measured by inductively coupled plasma-mass spectrometry (ICP-MS). This dataset provides useful metal(loid) concentrations for future risk assessments for similar settings.
• Ramirez, M. D., Abrell, L. M., Kilungo, A. P., Mclain, J. E., & Root, R. A. (2019). Partnering for action: community monitoring of harvested rainwater in underserved, rural, and urban Arizona communities. Water Resources IMPACT.
• Root, R. A. (2020). Arsenic and iron speciation and mobilization during phytostabilization of pyritic mine tailings. Geochimica et Cosmochimica Acta.
• Root, R. A. (2020). Environmental monitoring and exposure science dataset to calculate ingestion and inhalation of metal(loid)s through preschool gardening. Data in Brief.
• Root, R. A. (2020). Resolving Deep Critical Zone Architecture in Complex Volcanic Terrain. JGR Earth Surface, 125(1), 1-24. doi:https://doi.org/10.1029/2019JF005189
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  Critical zone (CZ) structure, including the spatial distribution of minerals, elements, and fluid‐filled pores, evolves on geologic time scales resulting from both top‐down climatic forcing and bottom‐up geologic controls. Climate and lithology may be imprinted in subsurface structure as depth‐dependent trends in geophysical, geochemical, mineralogical, and biological data sets. As the weathering profile is as much (or more) a product of past environmental conditions, development of predictive models requires understanding the relative roles of climatic forcing and the geologic template on which CZ processes evolve. Doing so in complex volcanic terrains with high initial bedrock porosity and distinct depositional and hydrothermal alteration histories is particularly challenging. To resolve CZ structure in a rhyolitic catchment in the Valles Caldera National Preserve (NM, USA), this study combined geophysics, drilling, and laboratory analyses to produce depth‐resolved porosity,geochemistry, and mineralogy data sets to >40 m in depth. Quantitative X‐ray diffraction analysis showed that local mineral transformations control complex chemical enrichment/depletion (τ) patterns.Using linear discriminant analysis, key variables enabled separation of complex‐layered geology into discrete zones. Contemporary, matrix‐dominated weathering processes and modern hydrologic fluxes occur dominantly within the top 15 m of the weathering profile. This zone is convoluted by incomplete primary mineral weathering and overprinted by post‐eruption weathering and metasomatism. Matrix weathering transitions to fracture surface weathering driven by deep percolation of slower moving, longer residence time meteoric waters at depth. By altering initial conditions and weathering trajectory, geologic legacy is a critical factor in how this subsurface landscape evolved and functions.
• Root, R. A. (2020). Resolving Deep Critical Zone Architecture in Complex Volcanic Terrain. Journal of Geophysical Research: Earth Surface.
• Dinali, G. S., Root, R. A., Amistadi, M. K., Chorover, J., Lopes, G., & Guimaraes, G. (2019). Rare earth elements (REY) sorption on soils of contrasting mineralogy and texture. Environment International, 128, 279-291.
• Hottenstein, J. D., Neilson, J. W., Gil-Loaiza, J., Root, R. A., White, S. A., Chorover, J., & Maier, R. M. (2019). Soil Microbiome Dynamics During Pyritic Mine Tailing Phytostabilization: Understanding Microbial Bioindicators of Soil Acidification. Frontiers in microbiology, 10, 1211.
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  Challenges to the reclamation of pyritic mine tailings arise from acid generation that severely constrains the growth of natural revegetation. While acid mine drainage (AMD) microbial communities are well-studied under highly acidic conditions, fewer studies document the dynamics of microbial communities that generate acid from pyritic material under less acidic conditions that can allow establishment and support of plant growth. This research characterizes the taxonomic composition dynamics of microbial communities present during a 6-year compost-assisted phytostabilization field study in extremely acidic pyritic mine tailings. A complementary microcosm experiment was performed to identify successional community populations that enable the acidification process across a pH gradient. Taxonomic profiles of the microbial populations in both the field study and microcosms reveal shifts in microbial communities that play pivotal roles in facilitating acidification during the transition between moderately and highly acidic conditions. The potential co-occurrence of organoheterotrophic and lithoautotrophic energy metabolisms during acid generation suggests the importance of both groups in facilitating acidification. Taken together, this research suggests that key microbial populations associated with pH transitions could be used as bioindicators for either sustained future plant growth or for acid generation conditions that inhibit further plant growth.
• Manjón, I., Ramírez-Andreotta, M. D., Sáez, A. E., Root, R. A., Hild, J., Janes, M. K., & Alexander-Ozinskas, A. (2020). Ingestion and inhalation of metal(loid)s through preschool gardening: An exposure and risk assessment in legacy mining communities. The Science of the total environment, 134639.
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  Children residing in mining towns are potentially disproportionately exposed to metal(loid)s via ingestion and dust inhalation, thus, increasing their exposure when engaging in school or home gardening or playing outside. This citizen science study assessed preschool children's potential arsenic (As), cadmium (Cd), and lead (Pb) exposure via locally grown produce, water, incidental soil ingestion, and dust inhalation at four sites. Participants were trained to properly collect water, soil, and vegetable samples from their preschools in Nevada County, California. As, Cd, and Pb concentrations in irrigation sources did not exceed the U.S. EPA's maximum contaminant and action levels. In general, garden and playground As and Pb soil concentrations exceeded the U.S. EPA Regional Screening Level, CalEPA Human Health Screening Level, and California Department of Toxic Substances Control Screening Level. In contrast, all Cd concentrations were below these recommended screening levels. Dust samples (
• Root, R. A. (2019). Ingestion and Inhalation of Metal(loid)s Through Preschool Gardening: An Exposure and Risk Assessment in Legacy Mining Communities. Science of The Total Environment.
• Root, R. A. (2019). Rare earth elements (REY) sorption on soils of contrasting mineralogy and texture.
• Root, R. A. (2019). Soil Microbiome Dynamics During Pyritic Mine Tailing Phytostabilization: Understanding Microbial Bioindicators of Soil Acidification. Frontiers in Microbiology.
• Root, R. A., Mclain, J. E., Kilungo, A. P., Abrell, L. M., & Ramirez, M. D. (2019). Partnering for action: community monitoring of harvested rainwater in underserved, rural, and urban Arizona communities. Water Resources IMPACT.
• Abrell, L., Chorover, J., Field, J. A., Khatiwada, R., Sierra-alvarez, R., & Root, R. A. (2018). Abiotic reduction of insensitive munition compounds by sulfate green rust. Environmental Chemistry, 15(5), 259-266. doi:10.1071/en17221
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  Environmental context There is a growing need to understand how insensitive munitions compounds behave in natural environments, particularly in soils, where non-combusted residues accumulate. Here, we tested the ability of sulfate green rust, a naturally occurring mineral, to transform munitions compounds by reacting with the mineral surface. Our results show that both the munitions compounds and the mineral structures are transformed in an oxidation–reduction reaction that alters the compounds’ environmental fates. Abstract Abiotic transformation of contaminants by redox-active mineral surfaces plays an important role in the fate and behaviour of pollutants in soils and sediments. However, there is very little information on such transformations for the insensitive munitions compounds (IMCs), 3-nitro-1,2,4-triazol-5-one (NTO) and 2,4-dinitroanisole (DNAN), developed in recent years to replace the traditional munition compounds in explosive mixtures. We tested the ability of sulfate green rust to transform NTO and DNAN (0.5 mM) under anoxic conditions at pH 8.4 in laboratory experiments, by using green rust supplied at 10 g kg−1 (w/w) solid concentration. Results indicate that NTO and DNAN underwent rapid abiotic reduction to their organic amine daughter products. NTO was completely transformed to 5-amino-1,2 4-triazol-3-one (ATO) within 20 min of reaction. This is the first report of NTO reduction by a naturally occurring mineral. Similarly, DNAN was rapidly transformed to 2-methoxy-5-nitroaniline (MENA) and 4-methoxy-5-nitroaniline (iMENA). The reduction occurred with an intriguing staggered regioselectivity. Over the first 10 min, the para-nitro group of DNAN was selectively reduced to generate iMENA. Thereafter, the ortho-nitro group was preferentially reduced, generating MENA. Both iMENA and MENA were subsequently transformed to the final reduction product 2,4-diaminoanisol (DAAN) within 1 day. Iron Kα X-ray absorption near-edge spectroscopy (XANES) studies of reacted solids indicated oxidative transformation of the green rust to lepidocrocite-like mineral forms. These results indicate that the IMCs can be rapidly transformed in soil, sediment or aquatic environments containing green rust.
• Hammond, C. M., Root, R. A., Maier, R. M., & Chorover, J. (2018). Mechanisms of Arsenic Sequestration by Prosopis juliflora during the Phytostabilization of Metalliferous Mine Tailings. ENVIRONMENTAL SCIENCE & TECHNOLOGY, 52(3), 1156-1164.
• Huskey, D. A., Curlango-Rivera, G., Root, R. A., Wen, F., Amistadi, M. K., Chorover, J., & Hawes, M. C. (2018). Trapping of lead (Pb) by corn and pea root border cells. PLANT AND SOIL, 430(1-2), 205-217.
• Khatiwada, R., Abrell, L., Li, G., Root, R. A., Sierra-Alvarez, R., Field, J. A., & Chorover, J. (2018). Adsorption and oxidation of 3-nitro-1,2,4-triazole-5-one (NTO) and its transformation product (3-amino-1,2,4-triazole-5-one, ATO) at ferrihydrite and birnessite surfaces. ENVIRONMENTAL POLLUTION, 240, 200-208.
• Khatiwada, R., Olivares, C., Abrell, L., Root, R. A., Sierra-Alvarez, R., Field, J. A., & Chorover, J. (2018). Oxidation of reduced daughter products from 2,4-dinitroanisole (DNAN) by Mn(IV) and Fe(III) oxides. CHEMOSPHERE, 201, 790-798.
• Khatiwada, R., Root, R. A., Abrell, L., Sierra-Alvarez, R., Field, J. A., & Chorover, J. (2018). Abiotic reduction of insensitive munition compounds by sulfate green rust. ENVIRONMENTAL CHEMISTRY, 15(5), 259-266.
• Olshansky, Y., Masaphy, S., Root, R. A., & Rytwo, G. (2018). Immobilization of Rhus vernicifera laccase on sepiolite; effect of chitosan and copper modification on laccase adsorption and activity. APPLIED CLAY SCIENCE, 152, 143-147.
• Olshansky, Y., Root, R. A., & Chorover, J. (2018). Wet-dry cycles impact DOM retention in subsurface soils. BIOGEOSCIENCES, 15(3), 821-832.
• Root, R. A. (2018). Abiotic reduction of insensitive munition compounds by sulfate green rust. Environmental Chemistry.
• Root, R. A. (2018). Adsorption and oxidation of 3-nitro-1,2,4-triazole-5-one (NTO) and its transformation product (3-amino-1,2,4-triazole-5-one, ATO) at ferrihydrite and birnessite surfaces. Environmental Pollution.
• Root, R. A. (2018). Immobilization of Rhus vernicifera laccase on sepiolite; effect of chitosan and copper modification on laccase adsorption and activity. Applied Clay Science.
• Root, R. A. (2018). Mechanisms of Arsenic Sequestration by Prosopis juliflora during the Phytostabilization of Metalliferous Mine Tailings. Environmental Science and Technology.
• Root, R. A. (2018). Oxidation of reduced daughter products from 2,4-dinitroanisole (DNAN) by Mn(IV) and Fe(III) oxides. Chemosphere.
• Root, R. A. (2018). Trapping of lead (Pb) by corn and pea root border cells.
• Root, R. A. (2018). Wet–dry cycles impact DOM retention in subsurface soils. Biogeosciences.
• Root, R. A., Chorover, J., Thomas, A., Sáez, E., & Lantz, R. C. (2018). Oxidative Weathering Decreases Bioaccessibility of Toxic Metal(loid)s in PM10 Emissions From Sulfide Mine Tailings. GeoHealth.
• Valentin-Vargas, A., Neilson, J. W., Root, R. A., Chorover, J., & Maier, R. M. (2018). Treatment impacts on temporal microbial community dynamics during phytostabilization of acid-generating mine tailings in semiarid regions. SCIENCE OF THE TOTAL ENVIRONMENT, 618, 357-368.
• Honeker, L. K., Neilson, J. W., Root, R. A., Gil-Loaiza, J., Chorover, J., & Maier, R. M. (2017). Bacterial Rhizoplane Colonization Patterns of Buchloe dactyloides Growing in Metalliferous Mine Tailings Reflect Plant Status and Biogeochemical Conditions. MICROBIAL ECOLOGY, 74(4), 853-867.
• Root, R. A. (2017). Bacterial Rhizoplane Colonization Patterns of Buchloe dactyloides Growing in Metalliferous Mine Tailings Reflect Plant Status and Biogeochemical Conditions. Microbial Ecology.
• Root, R. A. (2017). Mechanisms of Arsenic Sequestration by Prosopis juliflora during the Phytostabilization of Metalliferous Mine Tailings. Environ. Sci. Technol..
• Root, R. A., & Root, R. A. (2017). A XANES and Raman investigation of sulfur speciation and structural order in Murchison and Allende meteorites. Meteoritics and Planetary Science.
• Gil-Loaiza, J., White, S. A., Root, R. A., Solis-Dominguez, F. A., Hammond, C. M., Chorover, J., & Maier, R. M. (2016). Phytostabilization of mine tailings using compost-assisted direct planting: Translating greenhouse results to the field. SCIENCE OF THE TOTAL ENVIRONMENT, 565, 451-461.
• Honeker, L. K., Root, R. A., Chorover, J., & Maier, R. M. (2016). Resolving colocalization of bacteria and metal(loid)s on plant root surfaces by combining fluorescence in situ hybridization (FISH) with multiple-energy micro-focused X-ray fluorescence (ME mu XRF). JOURNAL OF MICROBIOLOGICAL METHODS, 131, 23-33.
• Pohlmann, M., Dontsova, K., Root, R., Ruiz, J., Troch, P., & Chorover, J. (2016). Pore water chemistry reveals gradients in mineral transformation across a model basaltic hillslope. GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 17(6), 2054-2069.
• Ramirez-Andreotta, M. D., Lothrop, N., Wilkinson, S. T., Root, R. A., Artiola, J. F., Klimecki, W., & Loh, M. (2016). Analyzing Patterns of Community Interest at a Legacy Mining Waste Site to Assess and Inform Environmental Health Literacy Efforts. Journal of environmental studies and sciences, 6(3), 543-555.
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  Understanding a community's concerns and informational needs is crucial to conducting and improving environmental health research and literacy initiatives. We hypothesized that analysis of community inquiries over time at a legacy mining site would be an effective method for assessing environmental health literacy efforts and determining whether community concerns were thoroughly addressed. Through a qualitative analysis, we determined community concerns at the time of being listed as a Superfund site. We analyzed how community concerns changed from this starting point over the subsequent years, and whether: 1) communication materials produced by the USEPA and other media were aligned with community concerns; and 2) these changes demonstrated a progression of the community's understanding resulting from community involvement and engaged research efforts. We observed that when the Superfund site was first listed, community members were most concerned with USEPA management, remediation, site-specific issues, health effects, and environmental monitoring efforts related to air/dust and water. Over the next five years, community inquiries shifted significantly to include exposure assessment and reduction methods and issues unrelated to the site, particularly the local public water supply and home water treatment systems. Such documentation of community inquiries over time at contaminated sites is a novel method to assess environmental health literacy efforts and determine whether community concerns were thoroughly addressed.
• Rodriguez-Freire, L., Moore, S. E., Sierra-Alvarez, R., Root, R. A., Chorover, J., & Field, J. A. (2016). Arsenic remediation by formation of arsenic sulfide minerals in a continuous anaerobic bioreactor. BIOTECHNOLOGY AND BIOENGINEERING, 113(3), 522-530.
• Root, R. A. (2016). Analyzing patterns of community interest at a legacy mining waste site to assess and inform environmental health literacy efforts. Journal of Environmental Studies and Sciences.
• Root, R. A. (2016). Arsenic remediation by formation of arsenic sulfide minerals in a continuous anaerobic bioreactor. Biotechnology and Bioengineering.
• Root, R. A. (2016). Phytostabilization of mine tailings using compost-assisted direct planting: Translating greenhouse results to the field. Science of the Total Environment.
• Root, R. A. (2016). Pore water chemistry reveals gradients in mineral transformation across a model basaltic hillslope. Geochemistry, Geophysics, Geosystems.
• Root, R. A. (2016). Resolving colocalization of bacteria and metal(loid)s on plant root surfaces by combining fluorescence in situ hybridization (FISH) with multiple-energy micro-focused X-ray fluorescence (ME μXRF). Journal of Microbiological Methods.
• Root, R. A. (2016). Soil lysimeter excavation for coupled hydrological, geochemical, and microbiological investigations. Journal of Visualized Experiments.
• Nelson, K. N., Neilson, J. W., Root, R. A., Chorover, J., & Maier, R. M. (2015). Abundance and Activity of 16S rRNA, AmoA and NifH Bacterial Genes During Assisted Phytostabilization of Mine Tailings. INTERNATIONAL JOURNAL OF PHYTOREMEDIATION, 17(5), 493-502.
• Root, R. A. (2015). Abundance and Activity of 16S rRNA, AmoA and NifH Bacterial Genes During Assisted Phytostabilization of Mine Tailings. International Journal of Phytoremediation.
• Root, R. A. (2015). Toxic metal(loid) speciation during weathering of iron sulfide mine tailings under semi-arid climate. Applied Geochemistry.
• Root, R. A., Hayes, S. M., Hammond, C. M., Maier, R. M., & Chorover, J. (2015). Toxic metal(loid) speciation during weathering of iron sulfide mine tailings under semi-arid climate. APPLIED GEOCHEMISTRY, 62, 131-149.
• Hayes, S. M., Root, R. A., Perdrial, N., Maier, R. M., & Chorover, J. (2014). Surficial weathering of iron sulfide mine tailings under semi-arid climate. GEOCHIMICA ET COSMOCHIMICA ACTA, 141, 240-257.
• Rodriguez-Freire, L., Sierra-Alvarez, R., Root, R., Chorover, J., & Field, J. A. (2014). Biomineralization of arsenate to arsenic sulfides is greatly enhanced at mildly acidic conditions. WATER RESEARCH, 66, 242-253.
• Root, R. A. (2014). Bioaccessibility, release kinetics, and molecular speciation of arsenic and lead in geo-dusts from the Iron King Mine Federal Superfund site in Humboldt, Arizona. Reviews on Environmental Health.
• Root, R. A. (2014). Biomineralization of arsenate to arsenic sulfides is greatly enhanced at mildly acidic conditions. Water Research.
• Root, R. A. (2014). Surficial weathering of iron sulfide mine tailings under semi-arid climate. Geochimica et Cosmochimica Acta.
• Root, R. A., & Root, R. A. (2014). Environmental factors influencing the structural dynamics of soil microbial communities during assisted phytostabilization of acid-generating mine tailings: A mesocosm experiment. Science of the Total Environment.
• Valentin-Vargas, A., Root, R. A., Neilson, J. W., Chorover, J., & Maier, R. M. (2014). Environmental factors influencing the structural dynamics of soil microbial communities during assisted phytostabilization of acid-generating mine tailings: A mesocosm experiment. SCIENCE OF THE TOTAL ENVIRONMENT, 500, 314-324.
• Gao, X., Root, R. A., Farrell, J., Ela, W., & Chorover, J. (2013). Effect of silicic acid on arsenate and arsenite retention mechanisms on 6-L ferrihydrite: A spectroscopic and batch adsorption approach. APPLIED GEOCHEMISTRY, 38, 110-120.
• Root, R. A. (2013). Effect of silicic acid on arsenate and arsenite retention mechanisms on 6-L ferrihydrite: A spectroscopic and batch adsorption approach.
• Root, R. A. (2013). Microscale Speciation of Arsenic and Iron in Ferric-Based Sorbents Subjected to Simulated Landfill Conditions.
• Root, R. A., Fathordoobadi, S., Alday, F., Ela, W., & Chorover, J. (2013). Microscale Speciation of Arsenic and Iron in Ferric-Based Sorbents Subjected to Simulated Landfill Conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY, 47(22), 12992-13000.
• Root, R. A. (2012). Response of Key Soil Parameters during Compost-Assisted Phytostabilization in Extremely Acidic Tailings: Effect of Plant Species.
• Solis-Dominguez, F. A., White, S. A., Hutter, T. B., Amistadi, M. K., Root, R. A., Chorover, J., & Maier, R. M. (2012). Response of Key Soil Parameters during Compost-Assisted Phytostabilization in Extremely Acidic Tailings: Effect of Plant Species. ENVIRONMENTAL SCIENCE & TECHNOLOGY, 46(2), 1019-1027.
• Root, R. A. (2009). Speciation and natural attenuation of arsenic and iron in a tidally influenced shallow aquifer.
• Root, R. A., Vlassopoulos, D., Rivera, N. A., Rafferty, M. T., Andrews, C., & O'Day, P. A. (2009). Speciation and natural attenuation of arsenic and iron in a tidally influenced shallow aquifer. GEOCHIMICA ET COSMOCHIMICA ACTA, 73(19), 5528-5553.
• Campbell, K. M., Root, R., O'Day, P. A., & Hering, J. G. (2008). A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: I. Laboratory development. ENVIRONMENTAL SCIENCE & TECHNOLOGY, 42(2), 497-503.
• Campbell, K. M., Root, R., O'Day, P. A., & Hering, J. G. (2008). A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: II. Field application to Haiwee Reservoir sediment. ENVIRONMENTAL SCIENCE & TECHNOLOGY, 42(2), 504-510.
• Root, R. A., & Root, R. A. (2008). A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: II. Field application to Haiwee reservoir sediment. Environmental Science and Technology.
• Root, R. A. (2007). Arsenic sequestration by sorption processes in high-iron sediments. Geochimica et Cosmochimica Acta.
• Root, R. A., Dixit, S., Campbell, K. M., Jew, A. D., Hering, J. G., & O'Day, P. A. (2007). Arsenic sequestration by sorption processes in high-iron sediments. GEOCHIMICA ET COSMOCHIMICA ACTA, 71(23), 5782-5803.
• Root, R. A. (2004). The influence of sulfur and iron on dissolved arsenic concentrations in the shallow subsurface under changing redox conditions. Proceedings of the National Academy of Sciences of the United States of America.
• Root, R. A. (2004). X-ray absorption spectroscopic study of Fe reference compounds for the analysis of natural sediments. American Mineralogist.

Proceedings Publications

• Root, R. A. (2018). Organic acid effect on arsenate bioaccessibility in gastric and alveolar simulated biofluid systems. In Environmental Arsenic in a ChangingWorld - 7th International Congress and Exhibition Arsenic in the Environment, 2018.

Presentations

• Ramirez, M. D., Ramirez, M. D., Sandhaus, S., Sandhaus, S., Sandoval, F., Sandoval, F., Kilungo, A. P., Kilungo, A. P., Mclain, J. E., Mclain, J. E., Root, R. A., Root, R. A., Abrell, L. M., Abrell, L. M., Buxner, S. R., Buxner, S. R., Kaufmann, D. B., Kaufmann, D. B., Cortez, I., , Cortez, I., et al. (2021). Building a transdisciplinary, bilingual community science program to advance environmental health in underserved communities. Citizen Science AssociationCitizen Science Association.
• Thomas, R., Root, R. A., Curlango-Rivera, G., & Mclain, J. E. (2020, December). Heavy metal(loid) contamination of medicinal plants: implications for public health of indigenous people. AGU Fall Meeting. Virtual: American Geophysical Union.
• Chorover, J. D., Moravec, B. G., White, A. M., Root, R. A., Olshansky, Y., & Mcintosh, J. C. (2019, Dec). Connections between shallow and deep structure of an extrusive critical zone influence hydrochemical response. AGU Fall Meeting. San Francisco, CA: AGU.
• Hottenstein, J. D., Neilson, J. W., Gil-Loaiza, J., Root, R. A., Chorover, J. D., & Maier, R. M. (2019, Jan). Soil Microbiome Dynamics during Revegetation of Pyritic Mine Tailings: Understanding Microbial Bioindicators of Soil Acidification. SSSA International Soils Meeting. San Diego, CA: SSSA.
• Kaufmann, D., Villagomez, N., Davis, L., Moses, A., Solis-Leon, J., Sandoval, F., Root, R. A., Kilungo, A. P., Mclain, J. E., Abrell, L. M., & Ramirez, M. D. (2019, March). Project Harvest Be Informed. Grow Smarter. Brown Bag Seminar,. Tucson, AZ: Water Research Resource Center, Villagomez-Marquez N. Davis L, and Kaufmann D,.
• Mollaneda, J., Wang, Y., Amistadi, M. K., Root, R. A., Troch, P. A., & Chorover, J. D. (2019, Dec). Transport Induced Mineral Dissolution Through Intensive Hydrological Cycles in Incipient Basalt Hillslopes. AGU Fall Meeting. San Francisco, CA: AGU.
• Moravec, B. G., Root, R. A., Carr, B., White, A. M., Mcintosh, J. C., & Chorover, J. D. (2019, Dec). Linking near surface geophysics to critical zone architecture and biogeochemical processes. AGU Fall Meeting. San Francisco, CA: AGU.
• Moravec, B. G., White, A., Root, R. A., Carr, B. J., Mcintosh, J. C., & Chorover, J. D. (2019, September). Resolving Critical Zone structures and weatherinf profiles across a geologically complex sub-alpine watershed. GSA Annual Meeting. Phoenix, AZ: GSA.
• Ramirez, M. D., Abrell, L. M., Mclain, J. E., Kilungo, A. P., & Root, R. A. (2019, April). Project Harvest: A Co-Created Citizen Science Rainwater Harvesting Program in Rural and Urban Arizona Communities. 2nd Cobre Valley Forum on Water. Globe, Gila County, Arizona..
• Ramirez, M. D., Davis, L., Buxner, S. R., Kilungo, A. P., Root, R. A., Mclain, J. E., Abrell, L. M., & Sandoval, F. (2019, March). Effect of environmental monitoring method on participant self-efficacy for science in underrepresented communities. Citizen Science Conference. Raleigh, North Carolina: Citizen Science Association.
• Ramirez, M. D., Root, R. A., & Solis-Leon, J. (2019, Dec). Metal(loid)s in Rooftop Harvested Rainwater near Hazardous Waste and Toxic Release Sites. AGU Fall Meeting. San Francisco, CA: AGU.
• Chorover, J., Root, R., Hammond, C., & Maier, R. (2017, APR 2). Biogeochemical transformation of metal(loid)s in a disturbed critical zone. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY.
• Root, R. A. (2017, April). Mineral resource recovery has driven the Anthropocene; now what?. University of Vermont, Department of Geology, Seminar Series. University of Vermont, Burlington VT.
• Root, R., Maier, R., & Chorover, J. (2017, APR 2). Stabilization of metalliferous mine tailings during mesocosm-scale phytostabilization. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY.
• Root, R. A. (2015, October). Coupling biogeochemical cycles and metal(loid) lability in sediments. LCLS/SSRL Users meeting. SLAC/Stanford University: LCLS/SSRL Users Meeting.
• Chorover, J., Root, R., Hammond, C., Valentin, A., & Maier, R. (2013, SEP 8). Toxic metal(loid) speciation is controlled by iron mineral (bio)weathering inphyto-stabilized mine tailings. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY.
• Root, R. A., Hammond, C. M., Adel, A., Amistadi, M. K., Maier, R. M., & Chorover, J. (2013, SEP 8). (Bio)geochemical mechanisms of metalloid phytostabilization in arid mine tailings. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY.
• Vargas, A. V., Nelson, K. N., Root, R. A., Chorover, J., & Maier, R. M. (2013, SEP 8). Analysis of the metabolic potential and phylogenetic composition of rhizosphere microbial communities during the phytostabilization of metalliferous mine tailings. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY.
• Root, R. A., O'day, P., Hering, J., Campbell, K., & Vlassopoulos, D. (2008, JUL). Predicting arsenic behavior in high-iron subsurface environments. GEOCHIMICA ET COSMOCHIMICA ACTA.

Poster Presentations

• Ramirez, M. D., Ramirez, M. D., Abrell, L. M., Abrell, L. M., Buxner, S. R., Buxner, S. R., Cortez, I., Cortez, I., Davis, L., Davis, L., Dewey, M., Dewey, M., Foley, T., Foley, T., Henriquez, P., Henriquez, P., Jones, M., Jones, M., Kaufmann, D., , Kaufmann, D., et al. (2021). Engaging Diverse Communities for Environmental Health Justice. National Science Foundation’s AISL PI meetingNational Science Foundation.
• Moses, A. J., Abrell, L. M., Buxner, S. R., Kilungo, A. P., Mclain, J. E., Obergh, V., Root, R. A., Sandoval, F., & Ramirez, M. D. (2020, November). Indicator organism presence in urban and rural Arizona community garden soils watered with harvested rainwater. ASA-CSSA-SSSA International Annual Meetings. Virtual: Agronomy Societies.
• Sonia, M., Abrell, L. M., Villagomez-Marquez, N., Palawat, K., Ramirez, M. D., Mclain, J. E., Root, R. A., Buxner, S. R., Kilungo, A. P., & Flor, S. (2020, August). What's in your rainwater? Inorganic and organic contaminants measured in roof-harvested rainwater. KEYS Research Internship Showcase. Tucson, Arizona (Virtual): Keep Engaging Youth in Science Internship Program.
• Villagomez-Marquez, N., Abrell, L. M., Buxner, S. R., Kilungo, A. P., Mclain, J. E., Root, R. A., Flor, S., Ramirez, M. D., & Chorover, J. D. (2020, October). Pesticides detected in roof-harvested rainwater in rural and urban Arizona communities. Emerging Contaminants Summit. Westminster, Colorado (Virtual).
• Carter, A., Thomas, R., Huskey, D., Curlango-Rivera, G., Root, R. A., Ottman, M. J., Hawes, M. C., & Mclain, J. E. (2019, July). Plant root border cell interactions with uranium and cadmium: a potential phytoremediation tool. Botany 2019: Sky Islands and Desert Seas Conference. Tucson, Arizona: Botanical Society of America, others.
• Minke, A., Cuello, J. L., Root, R. A., & Mclain, J. E. (2018, February). Using freshwater algae to remove Pb from water. University of Arizona Water Resources Research Center 2018 Annual Conference. Tucson, Arizona: University of Arizona Water Resources Research Center.
• Ramirez, M. D., Root, R. A., & Alfaifi, T. (2018, April). Translocation assessment of Al, Zn, As,Pb,Ni and Cd in three culturally relevant crops: sesame (Sesamum indicum), corchorus (Corchorus olitorius), and arugula (Eruca vesicaria). SWESx. The University of Arizona.
• Ramirez, M. D., Sandoval, F., Root, R. A., Mclain, J. E., Kilungo, A. P., Buxner, S. R., Abrell, L. M., Montijo, F., & Villagomez-Marquez, N. (2018, March). Investigating emerging organic contaminants in harvested rainwater via co-created citizen science: what is in your rainwater?. Science of the Environment Earth Day Poster Presentation. Tucson, Arizona: University of Arizona Department of Soil, Water and Environmental Science.
• Ramirez, M. D., Sandoval, F., Root, R. A., Mclain, J. E., Kilungo, A. P., Buxner, S. R., Abrell, L. M., Moses, A., & Solis-Leon, J. (2018, March). Socio-demographics in citizen science: does governance model matter?. Science of the Environment Earth Day Poster Presentation. Tucson, Arizona: University of Arizona Department of Soil, Water and Environmental Science.
• Sandoval, F., Root, R. A., Ramirez, M. D., Mclain, J. E., Kilungo, A. P., Buxner, S. R., Abrell, L. M., Davis, L., Kaufmann, D., & Sandhaus, S. (2018, May). Advancing Informal Environmental Health STEM Learning through Co-Created Citizen Science. Teaching and Learning in the Food-Energy-Water Nexus: Toward a National and Collaborative for Food, Energy and Water Systems (NC-FEW).. Washington, DC.
• Hayes, S. M., Root, R., Perdrial, N., & Chorover, J. (2012, MAR 25). Oxidative mineral weathering of mine tailings: Coupled mineral and toxic metal transformations at the Iron King Superfund Site. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY.
• Root, R. A., Hayes, S. M., Schowalter, C., & Chorover, J. (2010, JUN). Coupled arsenic and sulfur speciation in semi-arid mine tailings. GEOCHIMICA ET COSMOCHIMICA ACTA.
• Illera, V., O'Day, P. A., Choi, S., Rivera, N. A., Root, R., Rafferty, M., & Vlassopoulos, D. (2006, SEP 10). Immobilization of arsenic in a contaminated soil using ferrous sulfate and type V Portland cement. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY.

Others

• Root, R. A. (2019). Data_Sheet_1_Soil Microbiome Dynamics During Pyritic Mine Tailing Phytostabilization: Understanding Microbial Bioindicators of Soil Acidification.docx. https://doi.org/10.3389/fmicb.2019.01211.s001
  More info

  Challenges to the reclamation of pyritic mine tailings arise from in situ acid generation that severely constrains the growth of natural revegetation. While acid mine drainage (AMD) microbial communities are well-studied under highly acidic conditions, fewer studies document the dynamics of microbial communities that generate acid from pyritic material under less acidic conditions that can allow establishment and support of plant growth. This research characterizes the taxonomic composition dynamics of microbial communities present during a 6-year compost-assisted phytostabilization field study in extremely acidic pyritic mine tailings. A complementary microcosm experiment was performed to identify successional community populations that enable the acidification process across a pH gradient. Taxonomic profiles of the microbial populations in both the field study and microcosms reveal shifts in microbial communities that play pivotal roles in facilitating acidification during the transition between moderately and highly acidic conditions. The potential co-occurrence of organoheterotrophic and lithoautotrophic energy metabolisms during acid generation suggests the importance of both groups in facilitating acidification. Taken together, this research suggests that key microbial populations associated with pH transitions could be used as bioindicators for either sustained future plant growth or for acid generation conditions that inhibit further plant growth.
• Root, R. A., & Root, R. A. (2017, August). Wet-dry cycles impact DOM retention in subsurface soils. https://doi.org/10.5194/bg-2017-262
• Root, R. A. (2014). Abundance and Activity of 16S rRNA, AmoA and NifH Bacterial Genes During Assisted Phytostabilization of Mine Tailings. Figshare.