Covering mine tailings with uncontaminated soil is a common strategy to mitigate environmental impacts and promote ecosystem recovery during post-mining land reclamation. Topsoil is often stockpiled for future use as a capping layer, but prolonged storage alters its physical, chemical, and microbial properties, often hindering revegetation. This study evaluated soil health parameters within the 28-meter depth profile of a 14-year-old copper mine topsoil stockpile to identify key indicators of revegetation success in semi-arid ecosystem. Using non-invasive root phenotyping in rhizoboxes, filled with soils collected from different depth layers, we monitored plant growth and assessed how biochemical variability in stockpile materials affects germination and early establishment. Machine learning models integrating soil properties, plant responses, and sequenced soil bacterial/archaeal and fungal DNA, identified key indicators influencing plant performance. Results revealed significant heterogeneity in soil quality across depths, with distinct biochemical and microbial profiles shaping vegetation establishment. The upper 10 m exhibited greater potential for supporting growth, with seedling survival reaching 95 %, whereas deeper layers showed drastically reduced survival, sometimes as low as 0 %, due to microbial shifts to anoxic conditions and elevated Fe and Mn toxicity. Fungal communities played a dominant role in germination, while archaea were more influential during later plant establishment. Soil parameter comparisons before and after the experiment indicated recovery processes initiated by plant-soil feedback, including fungal community renewal. These findings highlight the role of stockpile formation in preserving soil health attributes critical for ecological recovery and provide practical insights for optimizing land reclamation in semi-arid ecosystems.

Anthropogenic metal contamination in aqueous resources poses risks to human and environmental health. Such solutions can contain critical materials such as rare earth elements (REE) and uranium (U) that are vital for economic security and the green economy. One approach to remediate these solutions is "aqueous mining" to generate non-traditional metal resources. The practical implementation of such an approach requires the recovery of metals in an economical, green, and selective manner. Bioinspired glycolipid surfactants are promising materials for such an application because they are non-toxic, biodegradable, and selective for critical materials. Six glycolipid-functionalized media were examined for the recovery of REE and U as a function of pH. At pH 7, U adsorption exceeded REE in 5 of the 6 media with nearly 100 % of U absorbed by media containing either a single-chain galactolipid, two-chain rhamnolipid, or a two-chain xylolipid. REE sorption was the highest in the two-chain rhamnolipid medium reaching 96 %. The single-chain glucolipid medium sorbed little to no metal. Due to its good performance, the two-chain rhamnolipid medium was further evaluated at pH ranging from 7 to 2.75. Adsorption of both REE and U remained near 100 % from pH 7 to 3.25. At pH 3, REE adsorption dropped to ∼20 % but U remained near 90 %. At pH 2.75 neither REE (∼0 %) nor U (∼10 %) were strongly bound. To examine glycolipid-media stability, the media were washed three times followed by total carbon analysis to examine glycolipid loss. Glycolipid loss ranged from <4 % to 26 % in the first wash with decreasing losses in the subsequent washing steps. Despite exhibiting the most loss, sorption activity of both the single and double chain rhamnolipids remained high, achieving nearly 100 % of theoretical maximum sorption. Future work will focus on further characterizing high-performing glycolipid sorbents to assess industrial applicability compared to existing technologies.

Stockpiling and storage of topsoil for use in reclamation and revegetation are common practices for many mining operations. However, stockpiling can lead to significant changes in topsoil physical and biogeochemical properties that may be detrimental to reclamation. The objective of this research was to assess the effect of long-term stockpiling on soil biogeochemical properties in a semiarid region. We hypothesized that soil properties would change systematically with depth reflecting a shift to anaerobic conditions and resulting in a general decrease in soil health. To address this hypothesis, boreholes > 20-m deep were drilled into a 14-year-old topsoil stockpile at a copper mine in Arizona and samples collected every 75 cm. Samples were analyzed for soil DNA biomass, texture, general agronomic properties, mineral composition, oxalate and dithionite extraction of active mineral phases, and total elemental composition. Depth profiles revealed non-systematic changes in biogeochemical variables with depth, including variation in soil DNA biomass, organic matter (OM), extractable nitrate (NO3-N) and ammonium (NH4-N) nitrogen, plant-available manganese (Mn) and iron (Fe), and oxalate-extractable Mn and Fe. Differences in biogeochemical properties were associated with zones of variable redox state mediated by OM content and layer depth. Anaerobic zones were observed at depths greater than 4 m where OM > 1

Self-sustaining vegetation in metal-contaminated areas is essential for rebuilding ecological resilience and community stability in degraded lands. Metal-tolerant plants originating from contaminated post-mining areas may hold the key to successful plant establishment and growth. Yet, little is known about the impact of metal toxicity on reproductive strategies, metal accumulation, and allocation patterns at the seed stage. Our research focused on the metal tolerant Atriplex lentiformis. Specifically, we examined the effects of toxic metal(loid) concentration in soils on variability in its reproductive strategies, including germination patterns, elemental uptake, and allocation within the seeds. We employed advanced imaging techniques like synchrotron X-ray fluorescence microscopy (2D scans and 3D tomograms) combined with inductively coupled plasma mass spectrometry to reveal significant differences in metal(loid) concentration and distribution within the seed structures of A. lentiformis from contrasting habitats. Exclusive Zn hotspots of high concentrations were found in the seeds of the metallicolous accession, primarily in the sensitive tissues of shoot apical meristems and root zones of the seed embryos. Our findings offer novel insights into phenotypic variability and metal tolerance and accumulation in plants from extreme environments. This knowledge can be applied to enhance plant survival and performance in land restoration efforts.

Rhamnolipid biosurfactants have tremendous potential across a wide variety of applications, including metals recovery, food additives, enhanced oil recovery, cosmetics and personal care formulations, and antibiofilm applications. Naturally derived rhamnolipids from a variety of biological sources will play an important role in introducing these materials to market applications. However, nature only provides a few rhamnolipid molecular structures in high quantity for use in these applications. This is in stark contrast to synthetic rhamnolipids, which offer a wide variety of structures in high-purity with each structure having its own unique set of physical and chemical properties. Beyond rhamnolipids, synthetic approaches to making these materials can include incorporation of other sugars with the potential to create large libraries of novel glycolipids. This chapter compares the important differences between synthetic and biological rhamnolipids, followed by an overview of the synthesis process, and finally discusses and compares characteristic properties of rhamnolipids as well as other glycolipids.

The use of surfactants spans most industrial fields due to their useful tensio-active properties. These typically chemically synthesized molecules face increasing scrutiny and regulation due to some combination of low biodegradability, toxicity, and a manufacturing process that requires nonrenewable resources such as petroleum-derived hydrocarbons. The resulting need for highly efficient environmental-friendly substitutes that are synthetized from renewable sources has been an important driver for microbial surfactant (biosurfactant) research. Recent advances have led to the commercial scale-up and new applications for biosurfactants, particularly glycolipids such as rhamnolipids produced by Pseudomonas and sophorolipids produced by Starmerella bombicola and other yeasts. The emerging market availability of these biosurfactants is certainly a remarkable achievement, and we anticipate that this is only the beginning. There is a long way to go to reach the full potential of the entire diversity of biosurfactants and their applications that have been discovered. We predict there will be a continuing acceleration in new developments in this area as we begin to discover and bring to fruition the full potential of these amazing molecules. Biosurfactant research is wide ranging, including: the search for new molecules and for microorganisms that produce them; the physicochemical characterization of biosurfactants; the use of genetic engineering and of -omics strategies to develop microbes with enhanced productivity or new biosynthetic capabilities; the use of nonconventional substrates and fermentation processes for the large-scale production of biosurfactants; and the use of green chemistry and enzymatic catalysis and for the production of novel bioinspired surfactants. These advances in biosurfactant research are presented in this book and some will be highlighted in this final summary chapter.

The exceptionally long and protracted aridity in the Atacama Desert (AD), Chile, provides an extreme, terrestrial ecosystem that is ideal for studying microbial community dynamics under hyperarid conditions. Our aim was to characterize the temporal response of hyperarid soil AD microbial communities to ex situ simulated rainfall (5% g water/g dry soil for 4 weeks) without nutrient amendment. We conducted replicated microcosm experiments with surface soils from two previously well-characterized AD hyperarid locations near Yungay at 1242 and 1609 masl (YUN1242 and YUN1609) with distinct microbial community compositions and average soil relative humidity levels of 21 and 17%, respectively. The bacterial and archaeal response to soil wetting was evaluated by 16S rRNA gene qPCR, and amplicon sequencing. Initial YUN1242 bacterial and archaeal 16S rRNA gene copy numbers were significantly higher than for YUN1609. Over the next 4 weeks, qPCR results showed significant increases in viable bacterial abundance, whereas archaeal abundance decreased. Both communities were dominated by 10 prokaryotic phyla (Actinobacteriota, Proteobacteria, Chloroflexota, Gemmatimonadota, Firmicutes, Bacteroidota, Planctomycetota, Nitrospirota, Cyanobacteriota, and Crenarchaeota) but there were significant site differences in the relative abundances of Gemmatimonadota and Chloroflexota, and specific actinobacterial orders. The response to simulated rainfall was distinct for the two communities. The actinobacterial taxa in the YUN1242 community showed rapid changes while the same taxa in the YUN1609 community remained relatively stable until day 30. Analysis of inferred function of the YUN1242 microbiome response implied an increase in the relative abundance of known spore-forming taxa with the capacity for mixotrophy at the expense of more oligotrophic taxa, whereas the YUN1609 community retained a stable profile of oligotrophic, facultative chemolithoautotrophic and mixotrophic taxa. These results indicate that bacterial communities in extreme hyperarid soils have the capacity for growth in response to simulated rainfall; however, historic variations in long-term hyperaridity exposure produce communities with distinct putative metabolic capacities.

Critical to the environmental sustainability of hard rock mining is the reclamation of disturbed lands following mine closure through revegetation. Improved understanding of associations between above- and belowground processes that characterize successful plant establishment is critical to the implementation of more efficient revegetation strategies for nutrient-poor mine waste materials. The specific objective of this five-year temporal study was to identify progressive biotic and abiotic indicators of primary soil development on mine waste rock (WR) on a slope hydroseeded with native plant species and to quantify comparative effects of plant lifeform on soil development. Aboveground plant diversity and belowground substrate properties were measured annually at 67 m intervals along transects following the slope contour. Seeded WR was compared to unseeded WR and the adjacent native ecosystem. A temporal increase in WR microbial biomass was observed in seeded WR relative to unseeded areas. Microbial community analysis found the unseeded WR to be defined by oligotrophic microbes, whereas targeted grass and shrub root zones samples demonstrated significant increases in specific cellulose and lignin degrading and N-cycling phylotypes. More extensive chemical and biological fertility development was observed in shrub root zones relative to grass. Ten chemical and biological indicators increased significantly in shrub WR relative to unseeded WR, whereas grass WR was only enriched in bacterial 16S rRNA gene copy number/g substrate and bacterial/archaeal and fungal diversity. In addition, the shrub root zone had significantly higher nitrogen-cycling potential than grass root zones or unseeded WR. Thus, both grasses and shrubs improve belowground WR development; however, shrub establishment had greater fertility outcomes. Concurrent belowground fertility development is critical to sustainable plant establishment. Coupled evaluation of above- and belowground metrics provides an improved quantitative assessment of revegetation progress and a valuable tool to guide management decisions.

Identifying and exploiting cost-effective and green methods of metal recovery from natural and contaminated aqueous systems is widely recognized as necessary to supplement the supply of critical elements, decrease the environmental impacts associated with hardrock mining, and remediate metal-contaminated waters. This research examines a novel approach based on rhamnolipid-facilitated chemical precipitation of metals. Three techniques were assessed to remove the rhamnolipid:metal complex from solution: mixing only, and mixing following by filtration or centrifugation. Recent advances in the ability to synthetically produce rhamnolipid surfactants allowed investigation of a variety of rhamnolipid structures. Rhamnolipids differing in the length and number of hydrophobic tails were assessed to remove Pb, La, and Mg from single metal solutions. In general, removal increased with increased rhamnolipid hydrophobicity and with the addition of an active removal step (filtration or centrifugation). Filtration removed up to 96% of all metals while centrifugation removed up to 97% for Pb and La and 60% for Mg. Results suggest tailoring the rhamnolipid structure and removal methods may enable selective metal removal to achieve specific outcomes. Future studies in mixed-metal and real-world solutions will be needed to confirm the viability of these techniques in complex systems.

Background Plant-microbe associations play central roles in ecosystem functioning, with some critical microbes significantly influencing the growth and health of plants. Additionally, some microbes are highly associated with other microbes in either competitive or cooperative microbe-microbe associations. Here, we aimed to determine whether there is overlap between critical microbes in plant-microbe and microbe-microbe associations by using guayule (a rubber-producing crop) as a model plant. Methods Using marker gene amplicon sequencing, we characterized the bacterial/archaeal and fungal communities in soil samples collected from a guayule agroecosystem at six time points that represent changes in guayule productivity and growth stage. The critical microbes in guayule-microbe associations were phylotypes whose relative abundances were positively (positive taxa) or negatively (negative taxa) associated with guayule productivity. Network analysis was used to identify the critical microbes in microbe-microbe associations. Results Some positive taxa in guayule-microbe associations were ammonia-oxidizing archaea (AOA) and bacteria (AOB) and arbuscular mycorrhizal fungi (AMF), and negative taxa included some microbes resistant to aridity. Some of the critical microbes in microbe-microbe associations were fungal plant pathogens. There were 9 phylotypes representing the overlap between critical microbes in guayule-microbe and microbe-microbe associations. This overlap group included AOB, phototrophic bacteria, AMF, and saprotrophic fungi, along with unique taxa of unknown function. Conclusions Our study highlighted the association of the soil microbiome with the growth and health of guayule. Our systematic approach narrowed down the immense number of microbial taxa to a ‘most wanted’ list that we define as critical to the entire guayule agroecosystem.

Successful phytoremediation of acidic metal-contaminated mine tailings requires amendments to condition tailings properties prior to plant establishment. This conditioning process is complex and includes multiple changes in tailings bio-physico-chemical properties. The objective of this project is to identify relationships between tailings properties, the soil microbiome, and plant stress response genes during growth of Atriplex lentiformis in compost-amended (10 %, 15 %, 20 % w/w) mine tailings. Analyses include RNA-Seq for plant root gene expression, 16S rRNA amplicon sequencing for bacterial/archaeal communities, metal concentrations in both tailings and plant organs, and phenotypic measures of plant stress. Zn accumulation in A. lentiformis leaves varied with compost levels and was the highest in the intermediate treatment (15 %, TC15). Microbial analysis identified Alicyclobacillus, Hydrotalea, and Pseudolabrys taxa with the highest relative abundance in TC15, and these taxa were strongly associated with Zn accumulation. Furthermore, we identified 190 root genes with significant gene expression changes. These root genes were associated with different pathways including, abscisic acid and auxin signaling, defense responses, ion channels, metal ion binding, oxidative stress, transcription regulation, and transmembrane transport. However, root gene expression changes were not driven by the increasing levels of compost. For example, there were 15 genes that were up-regulated in TC15, whereas 106 genes were down-regulated in TC15. The variables analyzed explained 86 % of the variance in Zn accumulation in A. lentiformis leaves. Importantly, Zn accumulation was driven by Zn shoot concentrations, leaf stress symptoms, plant root genes, and microbial taxa. Therefore, our results suggest there are strong plant-microbiome associations that drive Zn accumulation in A. lentiformis and different plant gene pathways are involved in alleviating varying levels of metal stress. Future work is needed to gain a mechanistic understanding of these plant-microbiome interactions to optimize phytoremediation strategies as they will govern the success or failure of the revegetation process.

Arsenic is ubiquitous in soil and water environments and is consistently at the top of the Agency for Toxic Substances Disease Registry (ATSDR) substance priority list. It has been shown to induce toxicity even at low levels of exposure. One of the major routes of exposure to arsenic is through drinking water. This review presents current information related to the distribution of arsenic in the environment, the resultant impacts on human health, especially related to diabetes, which is one of the most prevalent chronic diseases, regulation of arsenic in drinking water, and approaches for treatment of arsenic in drinking water for both public utilities and private wells. Taken together, this information points out the existing challenges to understanding both the complex health impacts of arsenic and to implementing the treatment strategies needed to effectively reduce arsenic exposure at different scales.

ADVERTISEMENT RETURN TO ISSUEPREVViewpointNEXTDouble-Network Hydrogel: A Potential Practical Adsorbent for Critical Metals Extraction and Recovery from WaterJinming Luo*Jinming LuoState Environmental Protection Key Laboratory of Environmental Health Impact Assessment of Emerging Contaminants, School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China*(J.L.) Email: [email protected]More by Jinming LuoView Biographyhttps://orcid.org/0000-0001-8698-7624, Raina M. MaierRaina M. MaierDepartment of Environmental Science, University of Arizona, 1177 E Fourth Street, Tucson, Arizona 85721, United StatesMore by Raina M. Maierhttps://orcid.org/0000-0002-0421-4677, Deyou YuDeyou YuEngineering Research Center for Eco-Dyeing and Finishing of Textiles, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou, 310018, P.R. ChinaMore by Deyou Yuhttps://orcid.org/0000-0003-0410-4424, Baicang LiuBaicang LiuKey Laboratory of Deep Earth Science and Engineering (Ministry of Education), College of Architecture and Environment, Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610207, P. R. ChinaMore by Baicang Liuhttps://orcid.org/0000-0003-3219-1924, Nanwen ZhuNanwen ZhuState Environmental Protection Key Laboratory of Environmental Health Impact Assessment of Emerging Contaminants, School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. ChinaMore by Nanwen Zhu, Gary L. AmyGary L. AmyDepartment of Environmental Engineering and Earth Sciences, Clemson University, 342 Computer Court, Anderson, South Carolina 29625, United StatesMore by Gary L. Amy, and John C. CrittendenJohn C. CrittendenBrook Byers Institute for Sustainable Systems, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United StatesMore by John C. Crittendenhttps://orcid.org/0000-0002-9048-7208Cite this: Environ. Sci. Technol. 2022, 56, 8, 4715–4717Publication Date (Web):March 31, 2022Publication History Received21 February 2022Published online31 March 2022Published inissue 19 April 2022https://pubs.acs.org/doi/10.1021/acs.est.2c01298https://doi.org/10.1021/acs.est.2c01298article-commentaryACS PublicationsCopyright © 2022 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views3822Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (2 MB) Get e-Alertsclose Get e-Alerts

Understanding the temporal effects of organic matter input and water influx on metal lability and translocation is critical to evaluate the success of the phytostabilization of metalliferous mine tailings. Trends of metal lability, e.g., V, Cr, Mn, Co, Ni, Cu, Zn, and Pb, were investigated for three years following a direct-planting phytostabilization trial at a Superfund mine tailings site in semi-arid central Arizona, USA. Unamended tailings were characterized by high concentrations (mmol kg−1) of Fe (2100), S (3100), As (41), Zn (39), and Pb (11), where As and Pb greatly exceeded non-residential soil remediation levels established by Arizona. Phytostabilization treatments included a no-compost control, 100 g kg−1 compost with seed, and 200 g kg−1 compost with and without seed to the top 20 cm of the tailings profile. All plots received supplemental irrigation, effectively doubling the mean annual precipitation. Tailings cores up to 90 cm were collected at the time of planting and every summer for 3 years. The cores were sub-sectioned at 20 cm increments and analyzed via total digestion and an operationally defined sequential extraction for elemental analysis and the calculation of a mass transfer coefficient normalized to Ti as an assigned immobile element. The results indicate that Pb was recalcitrant and relatively immobile in the tailings environment for both the uncomposted control and composted treatments with a maximum variation in the total concentration of 9–14 mmol kg−1 among all samples. Metal lability and translocation above the redox boundary (ca. 30 cm depth) was governed by acid generation, where surficial pH was measured as low as 2.7 ± 0.1 in year three and strongly correlated with the increased lability of Mn, Co, Ni, Cu, and Zn. There was no significant pH effect on the lability of V, Cr, or Pb. Translocation to depths was greatest for Mn and Co; however, Zn, Ni, Cr, and Cu were also mobilized. The addition of organic matter enhanced the mobilization of Cr from the near surface to 40–60 cm depth (pH > 6) over the three-year phytostabilization study compared to the control. The increased enrichment of some metals at 60–90 cm indicates that the long-term monitoring of elemental translocation is necessary to assess the efficacy of phytostabilization to contain subsurface metal contaminants and thereby protect the surrounding community from exposure.

Soil contamination with trace metal(loid) elements (TME) is a global concern. This has focused interest on TME-tolerant plants, some of which can hyperaccumulate extraordinary amounts of TME into above-ground tissues, for potential treatment of these soils. However, intra-species variability in TME hyperaccumulation is not yet sufficiently understood to fully harness this potential. Particularly, little is known about the rhizosphere microbial communities associated with hyperaccumulating plants and whether or not they facilitate TME uptake. The aim of this study is to characterize the diversity and structure of Arabidopsis halleri rhizosphere-influenced and background (i.e., non-Arabidopsis) soil microbial communities in four plant populations with contrasting Zn and Cd hyperaccumulation traits, two each from contaminated and uncontaminated sites. Microbial community properties were assessed along with geographic location, climate, abiotic soil properties, and plant parameters to explain variation in Zn and Cd hyperaccumulation. Site type (TME-contaminated vs. uncontaminated) and location explained 44% of bacterial/archaeal and 28% of fungal community variability. A linear discriminant effect size (LEfSe) analysis identified a greater number of taxa defining rhizosphere microbial communities than associated background soils. Further, in TME-contaminated soils, the number of rhizosphere-defining taxa was 6-fold greater than in the background soils. In contrast, the corresponding ratio for uncontaminated sites, was 3 and 1.6 for bacteria/archaea and fungi, respectively. The variables analyzed explained 71% and 76% of the variance in Zn and Cd hyperaccumulation, respectively; however, each hyperaccumulation pattern was associated with different variables. A. halleri rhizosphere fungal richness and diversity associated most strongly with Zn hyperaccumulation, whereas soil Cd and Zn bioavailability had the strongest associations with Cd hyperaccumulation. Our results indicate strong associations between A. halleri TME hyperaccumulation and rhizosphere microbial community properties, a finding that needs to be further explored to optimize phytoremediation technology that is based on hyperaccumulation.

Microbial communities in incipient soil systems serve as the only biotic force shaping landscape evolution. However, the underlying ecological forces shaping microbial community structure and function are inadequately understood. We used amplicon sequencing to determine microbial taxonomic assembly and metagenome sequencing to evaluate microbial functional assembly in incipient basaltic soil subjected to precipitation. Community composition was stratified with soil depth in the pre-precipitation samples, with surficial communities maintaining their distinct structure and diversity after precipitation, while the deeper soil samples appeared to become more uniform. The structural community assembly remained deterministic in pre- and post-precipitation periods, with homogenous selection being dominant. Metagenome analysis revealed that carbon and nitrogen functional potential was assembled stochastically. Sub-populations putatively involved in the nitrogen cycle and carbon fixation experienced counteracting assembly pressures at the deepest depths, suggesting the communities may functionally assemble to respond to short-term environmental fluctuations and impact the landscape-scale response to perturbations. We propose that contrasting assembly forces impact microbial structure and potential function in an incipient landscape; in situ landscape characteristics (here homogenous parent material) drive community structure assembly, while short-term environmental fluctuations (here precipitation) shape environmental variations that are random in the soil depth profile and drive stochastic sub-population functional dynamics.

Mining of uranium for defense-related purposes has left a substantial legacy of pollution that threatens human and environmental health. Contaminated waters in the arid southwest are of particular concern, as water resource demand and water scarcity issues become more pronounced. The development of remediation strategies to treat uranium impacted waters will become increasingly vital to meet future water needs. Ion flotation is one technology with the potential to address legacy uranium contamination. The green biosurfactant rhamnolipid has been shown to bind uranium and act as an effective collector in ion flotation. In this study, uranium contaminated groundwater (similar to 440 mu g L-1 U) from the Monument Valley processing site in northeast Arizona was used as a model solution to test the uranium removal efficacy of ion flotation with biosynthetic (bio-mRL) and three synthetic monorhamnolipids with varying hydrophobic chain lengths: Rha-C10-C10, Rha-C12-C12, and Rha-C14-C14. At the groundwater's native pH 8, and at an adjusted pH 7, no uranium was removed from solution by any collector. However, at pH 6.5 bio-mRL and Rha-C10-C10 removed 239.2 mu g L-1 and 242.4 mu g L-1 of uranium, respectively. By further decreasing the pH to 5.5, bio-mRL was able to reduce the uranium concentration to near or below the Environmental Protection Agency maximum contaminant level of 30 mu g L-1. For the Rha-C12-C12 and Rha-C14-C14 collector ligands, decreasing the pH to 7 or below reduced the foam stability and quantity, such that these collectors were not suitable for treating this groundwater. To contextualize the results, a geochemical analysis of the groundwater was conducted, and a consideration of uranium speciation is described. Based on this study, the efficacy of monorhamnolipid-based ion flotation in real world groundwater has been demonstrated with suitable solution conditions and collectors identified.

ADVERTISEMENT RETURN TO ISSUEPREVCorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to "Recovery of Critical Metals from Aqueous Sources"Serife E. Can SenerSerife E. Can SenerMore by Serife E. Can Senerhttps://orcid.org/0000-0002-8085-7367, Valerie M. ThomasValerie M. ThomasMore by Valerie M. Thomashttps://orcid.org/0000-0002-0968-8863, David E. HoganDavid E. HoganMore by David E. Hogan, Raina M. MaierRaina M. MaierMore by Raina M. Maierhttps://orcid.org/0000-0002-0421-4677, Michael Carbajales-DaleMichael Carbajales-DaleMore by Michael Carbajales-Dale, Mark D. BartonMark D. BartonMore by Mark D. Barton, Tanju KaranfilTanju KaranfilMore by Tanju Karanfilhttps://orcid.org/0000-0003-0986-5628, John C. CrittendenJohn C. CrittendenMore by John C. Crittendenhttps://orcid.org/0000-0002-9048-7208, and Gary L. AmyGary L. AmyMore by Gary L. AmyCite this: ACS Sustainable Chem. Eng. 2021, 9, 44, 15072Publication Date (Web):October 26, 2021Publication History Received6 October 2021Published online26 October 2021Published inissue 8 November 2021https://pubs.acs.org/doi/10.1021/acssuschemeng.1c06821https://doi.org/10.1021/acssuschemeng.1c06821correctionACS PublicationsCopyright © 2021 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views849Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (489 KB) Get e-AlertscloseSUBJECTS:Coal,Manufacturing,Power,Seawater,Water Get e-Alerts

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 vegetated-canopy and gap soils. The specific aim of this study was to characterize canopy vs 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 (USA). 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 open-space expansion in deserts.