Occurrence of arsenite in surface and groundwater associated with a perennial stream located in Western Nebraska, USA

Dissolved arsenic typically results from chemical weathering of arsenic rich sediments and is most often found in oxidized forms in surface water. The mobility of arsenic is controlled by its valence state and also by its association with iron oxides minerals, the forms of which are both influenced by abiotic and biotic processes in aqueous environment. In this study, speciation methods were used to measure and confirm the presence of reduced arsenic species in the surface water of Frenchman creek, a gaining stream that crosses the Colorado- Nebraska border. Selective extraction analysis of aquifer and stream bed sediments shows that the bulk of the arsenic occurs with labile iron-rich oxy(hydroxide) minerals. Total dissolved arsenic in surface and groundwater ranged from ~3–18 μg L–1, and reduced arsenic species comprise about 41% of the total dissolved arsenic (16.0 μg L–1) in Frenchman creek. Leachable arsenic in the aquifer sediment samples ranged up to 1553 μg kg–1, while samples from Frenchman creek bed sediments contained 4218 μg kg–1. Dynamic surface and groundwater interaction sustains arsenite in iron-rich surface headwaters, and the implied toxicity of reduced arsenic in this hydrogeological setting, which can be important in surface water environments around the globe

Nitrate-Stimulated Release of Naturally Occurring Sedimentary Uranium

Groundwater uranium (U) concentrations have been measured above the U.S. EPA maximum contaminant level (30 μg/L) in many U.S. aquifers, including in areas not associated with anthropogenic contamination by milling or mining. In addition to carbonate, nitrate has been correlated to uranium groundwater concentrations in two major U.S. aquifers. However, to date, direct evidence that nitrate mobilizes naturally occurring U from aquifer sediments has not been presented. Here, we demonstrate that the influx of high-nitrate porewater through High Plains alluvial aquifer silt sediments bearing naturally occurring U(IV) can stimulate a nitrate-reducing microbial community capable of catalyzing the oxidation and mobilization of U into the porewater. Microbial reduction of nitrate yielded nitrite, a reactive intermediate, which was further demonstrated to abiotically mobilize U from the reduced alluvial aquifer sediments. These results indicate that microbial activity, specifically nitrate reduction to nitrite, is one mechanism driving U mobilization from aquife

Transient Nature of Long-Term Nonprogression and Broad Virus-Specific Proliferative T-Cell Responses with Sustained Thymic Output in HIV-1 Controllers

HIV-1(+) individuals who, without therapy, conserve cellular anti-HIV-1 responses, present with high, stable CD4(+) T-cell numbers, and control viral replication, facilitate analysis of atypical viro-immunopathology. In the absence of universal definition, immune function in such HIV controllers remains an indication of non-progression.CD4 T-cell responses to a number of HIV-1 proteins and peptide pools were assessed by IFN-gamma ELISpot and lymphoproliferative assays in HIV controllers and chronic progressors. Thymic output was assessed by sjTRECs levels. Follow-up of 41 HIV-1(+) individuals originally identified as "Long-term non-progressors" in 1996 according to clinical criteria, and longitudinal analysis of two HIV controllers over 22 years, was also performed. HIV controllers exhibited substantial IFN-gamma producing and proliferative HIV-1-specific CD4 T-cell responses to both recombinant proteins and peptide pools of Tat, Rev, Nef, Gag and Env, demonstrating functional processing and presentation. Conversely, HIV-specific T-cell responses were limited to IFN-gamma production in chronic progressors. Additionally, thymic output was approximately 19 fold higher in HIV controllers than in age-matched chronic progressors. Follow-up of 41 HIV-1(+) patients identified as LTNP in 1996 revealed the transitory characteristics of this status. IFN-gamma production and proliferative T-cell function also declines in 2 HIV controllers over 22 years.Although increased thymic output and anti-HIV-1 T-cell responses are observed in HIV controllers compared to chronic progressors, the nature of nonprogressor/controller status appears to be transitory

Influence of Nitrate on Biogeochemical Uranium Redox Cycling and Mobility in Fluvial Sediments

Uranium (U) is a common contaminant in alluvial aquifer systems all over the world. U in the environment exists in two redox states: reduced U(IV) and oxidized U(VI). Oxidized U(VI) species tend to be more soluble and therefore more groundwater mobile than reduced U(IV) species. Thus, redox reactions have a strong control over U mobility into groundwater. A 2015 metadata analysis revealed a statistically significant correlation between groundwater uranium and nitrate, a strong oxidizing agent, in two major US aquifers. Subsequent column experiments using reduced U(IV)-bearing natural sediments confirmed that additions of nitrate to alluvial aquifer sediments will stimulate U(VI) mobilization. However, nitrate dependent Fe(II) oxidation also occurred concurrently and a series of batch U(VI) adsorption experiments demonstrated that more U(VI) was adsorbed onto sediments after oxidation than before oxidation with an increase in the amount of oxidized Fe in the sediments. Thus, an increase in the amount of bicarbonate is required for the net mobilization of U(VI) into groundwater in addition to the input of nitrate. The net input of oxidants, like nitrate, is assumed to always result in net oxidation of reduced chemical species, like Fe(II), sulfide, and U(IV). This paradigm was challenged by results from a field experiment conducted at DOE field challenge site at Rifle Mountain, CO where of a low mass of oxygenated water resulted in a decrease in groundwater U and an increase in dissolved organic carbon. This was tested using batch bioreactors containing a bicarbonate buffered medium and reduced oxbow lake sediments (Riverton, WY). Following the addition of a low level of nitrate, U(VI) decreased concurrently with increases in Fe(II) and sulfide, indicating the establishment of reducing conditions. Nitrate was reduced to nitrite and DOC and cell abundance increased through the duration of the experiment. These results demonstrate that net reducing conditions may persist even with the input of an oxidant

Nebraska Statewide Groundwater-Level Monitoring Report 2023

This report is a synthesis of groundwater-level monitoring programs in Nebraska. It is a continuation of the series of annual reports and maps produced by the Conservation and Survey Division (CSD) of the University of Nebraska in cooperation with the U.S. Geological Survey (USGS) since the 1950s. Groundwater-level monitoring began in Nebraska in 1930 to survey the state’s groundwater resources and observe changes in its availability on a regular basis. The CSD and USGS cooperatively developed, maintained, and operated an observation-well network throughout the state. These two agencies were responsible for collecting and archiving this information, and for making it available to the citizens

Nitrate stimulated microbial and viral activity and the subsequent influence on uranium mobility in sedimentary systems

Mobilization of naturally-occurring uranium(U) has been recognized to give rise to geogenic U groundwater contamination in aquifers. In addition to carbonate ligand complexation, nitrate has been demonstrated to play a role in controlling U mobility by altering uranium solubility through redox reactions. Nitrate is a common anthropogenic contaminant often prevalent at high concentrations in alluvial aquifers overlaying managed land. Alluvial deposition processes that form these aquifers create a lithologically heterogeneous subsurface with defined contacts between sands, silts, and clays. This leads to deposition of organic carbon and accumulation of reduced metals/radionuclides, including U(IV), in the finer grained silts and clays. The addition of high nitrate porewater into uranium-bearing alluvial aquifer silt sediments stimulated a nitrate reducing microbial community capable of catalyzing U(IV) oxidation and mobilization of U into porewaters. However, metadata from an aquifer wide study and a subsequent experiment revealed that this result is concentration dependent. Low concentrations of nitrate bearing pore-water added into organic-rich, uranium bearing sediments and resulted in a decrease in dissolved U(VI), consistent with reduction. XANES analysis of sediments supported U(VI) reduction with the precipitation of U(IV). U(VI) reduction activity occurred concurrent with an increase in dissolved organic carbon (DOC) and cell and virus abundance and activity. Metagenome assembled genomes from the microbial community revealed the metabolic potential indicating complex carbon degradation, fermentation, mineralization as well as the potential for anaerobic respiration of nitrate, metal/radionuclides, and sulfate. The virome recovered from the samples indicated a change in viral community in response to nitrate amendments and viral-encoded carbohydrate active enzymes were upregulated indicating a coupled response of both viral and microbial community regulating nitrate stimulated carbon biogeochemical cycling. These data together suggest that the addition of an electron acceptor in to organic carbon reduced sediments stimulates not only microbial but also viral activity leading to upregulation of genes associated with carbon biogeochemical cycling in sedimentary systems. While genes associated with metal oxidation are observed, net reduction of uranium prevails leading to uranium immobilization at low nitrate concentrations. Thus together these data indicate a tipping point whereby the influx of nitrate into the reduced environment can influence uranium mobility in DOC and carbon cycling supporting microbial activity and reducing conditions subsurface systems

Significantly higher lymphoproliferative responses to HIV-1 recombinant antigens mounted by HIV controllers (HIC) compared to HIV-1⁺ viraemic chronic progressors (vCP) and aviraemic chronic progressors (aCP) despite comparable IFN-γ release to HIV-1 peptide pools.

<p>Broad IFN-γ and proliferative responses to HIV-1 Gag p24 in HICs. Box plots show the median with IQR indicated. Whiskers represent the 10^th–90^th percentiles. The Mann-Whitney test was used to compare responses between patient groups, and the Wilcoxon signed rank test to compare paired responses from the same patient. *p<0.05, **p<0.01, ***p<0.001. (a) Lymphoproliferative response to rTat, rRev, rNef, rp24 (Gag) and rgp120 (Env), from HICs (n = 6), vCPs (n = 6) and aCPs (n = 8). The threshold for positivity (SI ≥3) is marked. (b) IFN-γ release (spot forming cells per million PBMC), from HICs (n = 6), vCPs (n = 6) and aCPs (n = 8), in response to stimulation with Tat, Rev, Nef and Gag p24 overlapping peptides. Data represent mean values of triplicate wells with <10% variation among triplicates. The threshold of 20 SFC/10⁶ PBMC is marked. (c) Summation of IFN-γ release in response to stimulation with individual overlapping Gag p24 peptides (1–22) compared to the response to the peptide pool and rp24 protein. Data from two representative HICs is shown. (d) Summation of lymphoproliferative responses, of two representative HICs, to stimulation with individual overlapping Gag p24 peptides (1–22) compared to the response to rp24 protein.</p

Higher levels of thymic output in HIV controllers (HIC) compared to age-matched chronic progressors (CP).

<p>(a) Electrophoresis gel showing an example of TREC levels in PBMC of HIC4 compared to the positive control, cord blood. (b) TREC levels in PBMC of 6 HICs compared to previously published data of PBMC from chronic progressors <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0005474#pone.0005474-Imami3" target="_blank">[26]</a>. The two cohorts are age-matched (p = 0.3823; median age HIC 41.2 years, range 26.9–60.2; median age CP 36.5 years, range 20.2–57.7). The CD4 count was significantly higher in HICs than HAART naïve CPs (p<0.0001; HIC median 913.5 cells/µl blood, range 588–1331; CP median 254.5 cells/µl blood, range 13–551).</p