Depth-dependent responses of soil organic carbon under nitrogen deposition.

Emerging evidence points out that the responses of soil organic carbon (SOC) to nitrogen (N) addition differ along the soil profile, highlighting the importance of synthesizing results from different soil layers. Here, using a global meta-analysis, we found that N addition significantly enhanced topsoil (0-30 cm) SOC by 3.7% (±1.4%) in forests and grasslands. In contrast, SOC in the subsoil (30-100 cm) initially increased with N addition but decreased over time. The model selection analysis revealed that experimental duration and vegetation type are among the most important predictors across a wide range of climatic, environmental, and edaphic variables. The contrasting responses of SOC to N addition indicate the importance of considering deep soil layers, particularly for long-term continuous N deposition. Finally, the lack of depth-dependent SOC responses to N addition in experimental and modeling frameworks has likely resulted in the overestimation of changes in SOC storage under enhanced N deposition.

Enhancing soil health and nutrient availability for Carrizo citrange (X Citroncirus sp.) through bokashi and biochar amendments: An exploration into indoor sustainable soil ecosystem management.

This study investigated the efficacy of organic soil amendments: bokashi (Bok), biochar (BC), and their combination (Bok_BC) in promoting soil health, nutrient availability, and growth of Carrizo citrange (X Citroncirus sp. Rutaceae, Parentage Citrus sinensis × Poncirus trifoliata) under indoor greenhouse settings. Results indicate significant alterations in soil parameters like total carbon (C), total nitrogen (N), and C:N ratio due to Bok, BC, and Bok_BC treatments. BC treatments boosted total C, while Bok increased total N, compared to controls. A note-worthy 25 % average decrease in C:N ratio was observed with Bok and Bok_BC, nearing the optimal 24:1 C:N for microbial growth. This highlights the potential of waste by-products in balancing nutrient release to benefit soil health and plant development. Analysis of nitrite (NO2-), nitrate (NO3-), and ammonium (NH4-N) levels revealed a dynamic relationship between soil treatments and time. Bok and Bok_BC amendments combined with both fertilizer doses [700 and 1400 Electrical Conductivity, EC] showed an initial NH4-N spike (averaging 1513 and 1288 µg N/g dry, respectively), outperforming control soils (average 503 µg N/g dry). Other key elements like phosphorus, potassium, calcium, and chlorine also experienced initial surges in Bok and Bok_BC soils before declining, suggesting a gradual nutrient release. The concentration of potentially toxic elements remained mostly stable or inconclusive, warranting further exploration. Bok, BC, and Bok_BC treatments considerably influenced germination rate and plant growth. The germination rate averaged 24.2 %, 23 %, and 22.5 % for Bok, BC, and Bok_BC, compared to the 15.9 % control. Plant height increased with Bok, BC, and Bok_BC to 18.4 cm, 18.7 cm, and 16.4 cm, respectively, from the 14.8 cm control. The results remained consistent across fertilizer doses, emphasizing the soil amendments' role in bolstering soil and plant health. In summary, the research underscores the potential of carbon-based amendments like bokashi and biochar in enhancing soil health, reducing reliance on synthetic fertilizers, and fostering sustainable soil ecosystems. The insights are pivotal for advancing sustainable agriculture in indoor greenhouse settings for nursery plant production.

Disparities in Drinking Water Manganese Concentrations in Domestic Wells and Community Water Systems in the Central Valley, CA, USA.

Over 1.3 million Californians rely on unmonitored domestic wells. Existing probability estimates of groundwater Mn concentrations, population estimates, and sociodemographic data were integrated with spatial data delineating domestic well communities (DWCs) to predict the probability of high Mn concentrations in extracted groundwater within DWCs in California's Central Valley. Additional Mn concentration data of water delivered by community water systems (CWSs) were used to estimate Mn in public water supply. We estimate that 0.4% of the DWC population (2342 users) rely on groundwater with predicted Mn > 300 µg L-1. In CWSs, 2.4% of the population (904 users) served by small CWSs and 0.4% of the population (3072 users) served by medium CWS relied on drinking water with mean point-of-entry Mn concentration >300 µg L-1. Small CWSs were less likely to report Mn concentrations relative to large CWSs, yet a higher percentage of small CWSs exceed regulatory standards relative to larger systems. Modeled calculations do not reveal differences in estimated Mn concentration between groundwater from current regional domestic well depth and 33 m deeper. These analyses demonstrate the need for additional well-monitoring programs that evaluate Mn and increased access to point-of-use treatment for domestic well users disproportionately burdened by associated costs of water treatment.

Firing Increases Arsenic Leaching from Ceramic Water Filters via Arsenic and Iron Phase Transformations.

Ceramic water filters (CWFs) are produced globally using local clay sources and can effectively remove bacterial pathogens during point-of-use water treatment. The ceramic production process involves firing clay mixed with burnout material at temperatures of 800-1100 °C, which induces mineralogical changes leading to increased arsenic (As) leaching from CWF material compared to source clay. Unfired clay and fired CWFs from Cambodia, Canada, and Mexico, CWF from Laos, and test-fired clay from the United States were analyzed to determine the extent of As leaching from CWFs that range in As (<1 to 16 mg kg-1) and iron (Fe) (0.6 to 5%) content. Deionized water, NaOH, HCl, and oxalate extractions showed that firing increased As solubility and decreased Fe solubility compared to unfired clay, with up to 8 mg kg-1 of water-soluble As in Cambodian CWFs. X-ray absorption spectra of the Cambodian clay and CWF showed a decrease in the Fe-O distance from 2.01 to 1.91 Å and decreased Fe coordination number from 6.3 to 4.6 after firing, indicating a decrease in Fe-O coordination. Arsenic(V) was the dominant species in Cambodia clay and CWF, existing primarily as a surface complex with average As-Fe distance of 3.28 Å in clay while in CWF As was either an outer-sphere As(V) phase or a discrete arsenate phase with no significant As-Fe scattering contribution within the resolution of the data. Improved understanding of molecular-scale processes that cause increased As leaching from CWFs provides a basis for assessing As leaching potential prior to CWF factory capital investment as well as engineered solutions (e.g., modified firing temperature, material amendments, and leaching prior to distribution) to mitigate As exposure from CWFs.

Oxidation of V(IV) by Birnessite: Kinetics and Surface Complexation.

Vanadium is a redox-active metal that has been added to the EPA's Contaminant Candidate List with a notification level of 50 µg L-1 due to mounting evidence that VV exposure can lead to adverse health outcomes. Groundwater V concentration exceeds the notification level in many locations, yet geochemical controls on its mobility are poorly understood. Here, we examined the redox interaction between VIV and birnessite (MnO2), a well-characterized oxidant and a scavenger of many trace metals. In our findings, birnessite quickly oxidized sparingly soluble VIV species such as häggite [V2O3(OH)2] into highly mobile and toxic vanadate (HnVO4(3-n)-) in continuously stirred batch reactors under neutral pH conditions. Synchrotron X-ray absorption spectroscopic (XAS) analysis of in situ and ex situ experiments showed that oxidation of VIV occurs in two stages, which are both rapid relative to the measured dissolution rate of the VIV solid. Concomitantly, the reduction of birnessite during VIV oxidation generated soluble MnII, which led to the formation of the MnIII oxyhydroxide feitknechtite (ß-MnOOH) upon back-reaction with birnessite. XAS analysis confirmed a bidentate-mononuclear edge-sharing complex formed between VV and birnessite, although retention of VV was minimal relative to the aqueous quantities generated. In summary, we demonstrate that Mn oxides are effective oxidants of VIV in the environment with the potential to increase dissolved V concentrations in aquifers subject to redox oscillations.

Mobilization of Arsenic and Other Naturally Occurring Contaminants during Managed Aquifer Recharge: A Critical Review.

Population growth and climate variability highlight the need to enhance freshwater security and diversify water supplies. Subsurface storage of water in depleted aquifers is increasingly used globally to alleviate disparities in water supply and demand often caused by climate extremes including floods and droughts. Managed aquifer recharge (MAR) stores excess water supplies during wet periods via infiltration into shallow underlying aquifers or direct injection into deep aquifers for recovery during dry seasons. Additionally, MAR can be designed to improve recharge water quality, particularly in the case of soil aquifer treatment and riverbank filtration. While there are many potential benefits to MAR, introduction of recharge water can alter the native geochemical and hydrological conditions in the receiving aquifer, potentially mobilizing toxic, naturally occurring (geogenic) contaminants from sediments into groundwater where they pose a much larger threat to human and ecosystem health. On the basis of the present literature, arsenic poses the most widespread challenge at MAR sites due to its ubiquity in subsurface sediments and toxicity at trace concentrations. Other geogenic contaminants of concern include fluoride, molybdenum, manganese, and iron. Water quality degradation threatens the viability of some MAR projects with several sites abandoning operations due to arsenic or other contaminant mobilization. Here, we provide a critical review of studies that have uncovered the geochemical and hydrological mechanisms controlling mobilization of arsenic and other geogenic contaminants at MAR sites worldwide, including both infiltration and injection sites. These mechanisms were evaluated based on site-specific characteristics, including hydrological setting, native aquifer geochemistry, and operational site parameters (e.g., source of recharge water and recharge/recovery cycling). Observed mechanisms of geogenic contaminant mobilization during MAR via injection include shifting redox conditions and, to a lesser extent, pH-promoted desorption, mineral solubility, and competitive ligand exchange. The relative importance of these mechanisms depends on various site-specific, operational parameters, including pretreatment of injection water and duration of injection, storage, and recovery phases. This critical review synthesizes findings across case studies in various geochemical, hydrological, and operational settings to better understand controls on arsenic and other geogenic contaminant mobilization and inform the planning and design of future MAR projects to protect groundwater quality. This critical review concludes with an evaluation of proposed management strategies for geogenic contaminants and identification of knowledge gaps regarding fate and transport of geogenic contaminants during MAR.

Long-term nitrogen loading alleviates phosphorus limitation in terrestrial ecosystems.

Increased human-derived nitrogen (N) deposition to terrestrial ecosystems has resulted in widespread phosphorus (P) limitation of net primary productivity. However, it remains unclear if and how N-induced P limitation varies over time. Soil extracellular phosphatases catalyze the hydrolysis of P from soil organic matter, an important adaptive mechanism for ecosystems to cope with N-induced P limitation. Here we show, using a meta-analysis of 140 studies and 668 observations worldwide, that N stimulation of soil phosphatase activity diminishes over time. Whereas short-term N loading (≤5 years) significantly increased soil phosphatase activity by 28%, long-term N loading had no significant effect. Nitrogen loading did not affect soil available P and total P content in either short- or long-term studies. Together, these results suggest that N-induced P limitation in ecosystems is alleviated in the long-term through the initial stimulation of soil phosphatase activity, thereby securing P supply to support plant growth. Our results suggest that increases in terrestrial carbon uptake due to ongoing anthropogenic N loading may be greater than previously thought.

Enzymes, Manganese, or Iron? Drivers of Oxidative Organic Matter Decomposition in Soils.

Oxidative decomposition of soil organic matter determines the proportion of carbon that is either stored or emitted to the atmosphere as CO2. Full conversion of organic matter to CO2 requires oxidative mechanisms that depolymerize complex molecules into smaller, soluble monomers that can be respired by microbes. Current models attribute oxidative depolymerization largely to the activity of extracellular enzymes. Here we show that reactive manganese (Mn) and iron (Fe) intermediates, rather than other measured soil characteristics, best predict oxidative activity in temperate forest soils. Combining bioassays, spectroscopy, and wet-chemical analysis, we found that oxidative activity in surface litters was most significantly correlated to the abundance of reactive Mn(III) species. In contrast, oxidative activity in underlying mineral soils was most significantly correlated to the abundance of reactive Fe(II/III) species. Positive controls showed that both Mn(III) and Fe(II/III) species are equally potent in generating oxidative activity, but imply conventional bioassays have a systematic bias toward Fe. Combined, our results highlight the coupled biotic-abiotic nature of oxidative mechanisms, with Mn-mediated oxidation dominating within Mn-rich organic soils and Fe-mediated oxidation dominating Fe-rich mineral soils. These findings suggest microbes rely on different oxidative strategies depending on the relative availability of Fe and Mn in a given soil environment.

Manganese, Arsenic, and Carbonate Interactions in Model Oxic Groundwater Systems.

Manganese and arsenic both threaten groundwater quality globally, but their chemical behavior leads to both co-contamination and separation of these contaminants from individual well to regional scales. Here we tested manganese and arsenic retention under conditions commonly found within aquifer redox fluctuating and transition zones where both arsenic and iron phases are present in oxidized forms, but manganese persists as reduced and soluble Mn(II). Analysis of column aqueous breakthrough data and characterization of solid-phase products using X-ray photoelectron (XPS) and absorption spectroscopies (XAS) show that the addition of bicarbonate increased manganese retention but decreased arsenic retention, while the presence of manganese and arsenic together increased both arsenic and manganese retention. In the presence of O2 arsenic remained oxidized as arsenate under all conditions measured; however, reduced Mn(II) was oxidized to an average Mn oxidation state of ∼3 in the absence of arsenate. The presence of arsenate partially inhibited Mn(II) oxidation likely by blocking ferrihydrite surfaces needed to catalyze Mn(II) oxidation by O2 and by stabilizing Mn(II) via ternary complex formation. These results highlight the interactions between reduced and oxidized contaminants that can contribute to the co-occurrence or physical separation of manganese and arsenic in groundwater systems under changing or stratified redox conditions.

Dust Sources in the Salton Sea Basin: A Clear Case of an Anthropogenically Impacted Dust Budget.

The Salton Sea Basin in California suffers from poor air quality, and an expanding dry lakebed (playa) presents a new potential dust source. In 2017-18, depositing dust was collected approximately monthly at five sites in the Salton Sea Basin and analyzed for total elemental and soluble anion content. These data were analyzed with Positive Matrix Factorization (PMF). The PMF method resolved seven dust sources with distinct compositional markers: Playa (Mg, SO42-, Na, Ca, Sr), Colorado Alluvium (U, Ca), Local Alluvium (Al, Fe, Ti), Agricultural Burning (K, PO43-), Sea Spray (Na, Cl-, Se), Anthropogenic Trace Metals (Sb, As, Zn, Cd, Pb, Na), and Anthropogenic Copper (Cu). All sources except Local Alluvium are influenced or caused by current or historic anthropogenic activities. PMF attributed 55 to 80% of the measured dust flux to these six sources. The dust fluxes at the site where the playa source was dominant (89 g m-2 yr-1) were less than, but approaching the scale of, those observed at Owens Lake playas in the late 20th century. Playa emissions in the Salton Sea region were most intense during the late spring to early summer and contain high concentrations of evaporite mineral tracers, particularly Mg, Ca, and SO42-.

Manganese-Driven Carbon Oxidation at Oxic-Anoxic Interfaces.

The formation of reactive manganese (Mn) species is emerging as a key regulator of carbon oxidation rates, and thus CO2 emissions, in soils and sediments. Many subsurface environments are characterized by steep oxygen gradients, forming oxic-anoxic interfaces that enable rapid redox cycling of Mn. Here, we examined the impact of Mn(II)aq oxidation along oxic-anoxic interfaces on carbon oxidation in soils using laboratory-based diffusion reactors. A combination of cyclic voltammetry, X-ray absorption spectroscopy, and X-ray microprobe imaging revealed a tight coupling between Mn(II)aq oxidation and carbon oxidation at the oxic-anoxic interface. Specifically, zones of Mn(II)aq oxidation across the oxic-anoxic transition also exhibited the greatest lignin oxidation potential, carbon solubilization, and oxidation. Microprobe imaging further revealed that the generation of Mn(III)-dominated precipitates coincided with carbon oxidation. Combined, our findings demonstrate that biotic Mn(II)aq oxidation, specifically the formation of Mn(III) species, contributes to carbon oxidation along oxic-anoxic interfaces in soils and sediments. Our results suggest that we should regard carbon oxidation not merely as a function of molecular composition, which insufficiently predicts rates, but in relation to microenvironments favoring the formation of critically important oxidants such as Mn(III).

The Effect of a Receding Saline Lake (The Salton Sea) on Airborne Particulate Matter Composition.

The composition of ambient particulate matter (PM) and its sources were investigated at the Salton Sea, a shrinking saline lake in California. To investigate the influence of playa exposure on PM composition, PM samples were collected during two seasons and at two sites around the Salton Sea. To characterize source composition, soil samples were collected from local playa and desert surfaces. PM and soil samples were analyzed for 15 elements using mass spectrometry and X-ray diffraction. The contribution of sources to PM mass and composition was investigated using Al-referenced enrichment factors (EFs) and source factors resolved from positive matrix factorization (PMF). Playa soils were found to be significantly enriched in Ca, Na, and Se relative to desert soils. PMF analysis resolved the PM10 data with four source factors, identified as Playa-like, Desert-like, Ca-rich, and Se. Playa-like and desert-like sources were estimated to contribute to a daily average of 8.9% and 45% of PM10 mass, respectively. Additionally, playa sources were estimated to contribute to 38-68% of PM10 Na. PM10 Se concentrations showed strong seasonal variations, suggesting a seasonal cycle of Se volatilization and recondensation. These results support the importance of playas as a source of PM mass and a controlling factor of PM composition.

Depth Stratification Leads to Distinct Zones of Manganese and Arsenic Contaminated Groundwater.

Providing access to safe drinking water is a global challenge, for which groundwater is increasingly being used throughout the world. However, geogenic contaminants limit the suitability of groundwater for domestic purposes over large geographic areas across most continents. Geogenic contaminants in groundwater are often evaluated individually, but here we demonstrate the need to evaluate multiple contaminants to ensure that groundwater is safe for human consumption and agricultural usage. We compiled groundwater chemical data from three aquifer regions across the world that have been reported to have widespread As and Mn contamination including the Glacial Aquifer in the U.S., the Ganges-Brahmaputra-Mehta Basin within Bangladesh, and the Mekong Delta in Cambodia, along with newly sampled wells in the Yangtze River Basin of China. The proportion of contaminated wells increase by up to 40% in some cases when both As and Mn contaminants are considered. Wilcoxon rank-sum analysis indicates that Mn contamination consistently occurs at significantly shallower depths than As contaminated wells in all regions. Arsenic concentrations in groundwater are well predicted by redox indicators (Eh and dissolved oxygen) whereas Mn shows no significant relationship with either parameter. These findings illustrate that the number of safe wells may be drastically overestimated in some regions when Mn contamination is not taken into account and that depth may be used as a distinguishing variable in efforts to predict the presence of groundwater contaminants regionally.

Aquifer Arsenic Cycling Induced by Seasonal Hydrologic Changes within the Yangtze River Basin.

Consumption of groundwater containing >10 µg L(-1) arsenic (As) adversely impacts more than 100 million people worldwide. Multiyear trends in aquifer As concentrations have been documented, but strong seasonal variations are not commonly observed. Here we report dramatic seasonal changes in As concentrations and aquifer chemistry within the Jianghan Plain of the Yangtze River, China. At some wells, concentrations fluctuate by more than an order of magnitude within a single year (100-1200 µg L(-1)). Groundwater extraction and sustained water levels of surface channels during the dry season induces a strong downward hydraulic gradient, seasonally supplying oxidizing (oxygen, nitrate) water to the otherwise anoxic aquifer. Oxygen and/or nitrate addition promotes a transient drop in As concentrations for 1-3 months. When recharge ceases, reducing, low-arsenic conditions are reestablished by reactive, endogenous organic carbon. Temporal variability in As concentrations is especially problematic because it increases the probability of false-negative well testing during low-arsenic seasons. However, periods of low As may also provide a source of less toxic water for irrigation or other uses. Our results highlight the vulnerability and variability of groundwater resources in the Jianghan Plain and other inland basins within Asia to changing geochemical conditions, both natural and anthropogenic, and reinforce that continued monitoring of wells in high-risk regions is essential.

Draft genome sequence of a black yeast fungus Exophiala xenobiotica isolated from La Brea Tar Pits.

A 30.28 Mb draft genome sequence was assembled and annotated for the melanized ascomycetous fungus Exophiala xenobiotica NRRL_64630 (Pezizomycotina; Chaetothyriales) isolated from La Brea Tar Pits, Los Angeles, California. Species identification was made by phylogenetic assessment of the Internal Transcribed Spacer. This is the first isolated fungal species from this historic space.

New insights into thallium(I) behaviors at birnessite surfaces: Effects of an organic buffer and goethite.

Understanding the environmental behavior of thallium (Tl) is crucial due to its high toxicity and increasing anthropogenic presence. This study investigated the adsorption and redox behaviors of Tl(I) with acid birnessite (AcBi) in the presence of 1,4-piperazine-diethanesulfonic acid (PIPES) and goethite under diffusion-limited conditions using Donnan reactors in aerobic and anaerobic environments. Our findings indicate that Tl(I) preferentially adsorbs onto AcBi, with capacities 20 to 100 times higher than onto goethite, even when AcBi is partial reduced by PIPES. No net Tl(I) oxidation occurred in the Donnan reactors, likely due to complex electron transfer processes between Tl(I), birnessite, and PIPES. Any Tl(III) generated from Tl(I) oxidation by birnessite was rapidly reduced back to Tl(I) by PIPES. This was confirmed in batch experiments where reduced Tl(III) on birnessite surfaces and in Tl(III) salts. These findings highlight the need to assess the impact of Good's buffers on redox reactions involving manganese oxides and Tl, while also providing insights into the competitive retention of Tl on manganese and iron (hydr)oxides, with implications for Tl mobility and bioavailability in natural environments.

Dependence of arsenic fate and transport on biogeochemical heterogeneity arising from the physical structure of soils and sediments.

Reduction of As(V) and Fe(III) is commonly the dominant process controlling the fate and transport of As in soils and sediments. However, the physical structure of such environments produces complex heterogeneity in biogeochemical processes controlling the fate and transport of As. To resolve the role of soil and sediment physical structure on the distribution of biogeochemical processes controlling the fate and transport of As, we examined the biogeochemical transformations of As and Fe within constructed aggregates-a fundamental unit of soil structure. Spherical aggregates were made with As(V)- or As(III)-bearing, ferrihydrite-coated quartz that was fused with agarose and placed in a cylindrical reactor; advective flow of anoxic solutes was then initiated around the aggregates to examine As release from a dual-pore domain system. To examine the impact of biotic As(V) and Fe(III) reduction, constructed aggregates having As(V)-bearing, ferrihydrite-coated quartz inoculated with sp. ANA-3 were placed in flow-through reactors under anoxic and aerated advective flow. Consistent with desorption from advective columns, As(III) is released to advecting water more prevalently than As(V) within abiotic aggregate systems, indicating a greater lability and concomitant enhanced propensity for transport of As(III) relative to As(V). During reaction with , As release to advecting water was similar between anoxic and aerated systems for the first 20 d; thereafter, the anoxic advecting solutes increased As release relative to the aerated counterpart. With aerated advecting solutes, Fe remained oxidized (or was oxidized) in the aggregate exterior, forming a protective barrier that limited As release to the advective channel. However, anaerobiosis within the aggregate interior, even with aerated advective flow, promotes internal repartitioning of As to the exterior region.

Small Community Water Systems Have the Highest Prevalence of Mn in Drinking Water in California, USA.

Manganese (Mn) is currently regulated as a secondary contaminant in California, USA; however, recent revisions of the World Health Organization drinking water guidelines have increased regulatory attention of Mn in drinking water due to increasing reports of neurotoxic effects in infants and children. In this study, Mn concentrations reported to California's Safe Drinking Water Information System were used to estimate the potentially exposed population within California based on system size. We estimate that between 2011 and 2021, over 525,000 users in areas with reported Mn data are potentially exposed to Mn concentrations exceeding the WHO health-based guideline (80 µg L-1), and over 34,000 users are potentially exposed to Mn concentrations exceeding the U.S. Environmental Protection Agency health-advisory limit (300 µg L-1). Water treatment significantly decreased Mn concentrations compared to intake concentrations for all system sizes. However, smaller water systems have a wider range and a higher skew of Mn concentrations in finished water than larger systems. Additionally, higher Mn concentrations were found in systems above the maximum contaminant levels for chromium and arsenic. The treatment of these primary contaminants appears to also remove Mn. Lastly, data missingness remains a barrier to accurately assess public exposure to Mn in very small, small, and medium community water system-delivered water.

Vanadate Retention by Iron and Manganese Oxides.

Anthropogenic emissions of vanadium (V) into terrestrial and aquatic surface systems now match those of geogenic processes, and yet, the geochemistry of vanadium is poorly described in comparison to other comparable contaminants like arsenic. In oxic systems, V is present as an oxyanion with a +5 formal charge on the V center, typically described as H x VO4 (3-x)-, but also here as V(V). Iron (Fe) and manganese (Mn) (oxy)hydroxides represent key mineral phases in the cycling of V(V) at the solid-solution interface, and yet, fundamental descriptions of these surface-processes are not available. Here, we utilize extended X-ray absorption fine structure (EXAFS) and thermodynamic calculations to compare the surface complexation of V(V) by the common Fe and Mn mineral phases ferrihydrite, hematite, goethite, birnessite, and pyrolusite at pH 7. Inner-sphere V(V) complexes were detected on all phases, with mononuclear V(V) species dominating the adsorbed species distribution. Our results demonstrate that V(V) adsorption is exergonic for a variety of surfaces with differing amounts of terminal -OH groups and metal-O bond saturations, implicating the conjunctive role of varied mineral surfaces in controlling the mobility and fate of V(V) in terrestrial and aquatic systems.