We report measurements of seasonal variability in the C‐N stable isotope ratios of plants collected across the habitat mosaic of San Francisco Bay, its marshes, and its tributary river system. Analyses of 868 plant samples were binned into 10 groups (e.g., terrestrial riparian, freshwater phytoplankton, salt marsh) to determine whether C‐N isotopes can be used as biomarkers for tracing the origins of organic matter in this river‐marsh‐estuary complex. Variability of δ13C and δ15N was high (~5–10‰) within each plant group, and we identified three modes of variability: (1) between species and their microhabitats, (2) over annual cycles of plant growth and senescence, and (3) between living and decomposing biomass. These modes of within‐group variability obscure any source specific isotopic signatures, confounding the application of C‐N isotopes for identifying the origins of organic matter. A second confounding factor was large dissimilarity between the δ13C‐δ15N of primary producers and the organic matter pools in the seston and sediments. Both confounding factors impede the application of C‐N isotopes to reveal the food supply to primary consumers in ecosystems supporting diverse autotrophs and where the isotopic composition of organic matter has been transformed and become distinct from that of its parent plant sources. Our results support the advice of others: variability of C‐N stable isotopes within all organic‐matter pools is high and must be considered in applications of these isotopes to trace trophic linkages from primary producers to primary consumers. Isotope‐based approaches are perhaps most powerful when used to complement other tools, such as molecular biomarkers, bioassays, direct measures of production, and compilations of organic‐matter budgets.
The speciation of U(VI) sorbed to synthetic hydroxyapatite was investigated using a combination of U LIII-edge XAS, synchrotron XRD, batch uptake measurements, and SEM-EDS. The mechanisms of U(VI) removal by apatite were determined in order to evaluate the feasibility of apatite-based in-situ permeable reactive barriers (PRBs). In batch U(VI) uptake experiments with synthetic hydroxyapatite (HA), near complete removal of dissolved uranium (>99.5%) to <0.05 μM was observed over a range of total U(VI) concentrations up to equimolar of the total P in the suspension. XRD and XAS analyses of U(VI)-reacted HA at sorbed concentrations ≤4700 ppm U(VI) suggested that uranium(VI) phosphate, hydroxide, and carbonate solids were not present at these concentrations. Fits to EXAFS spectra indicate the presence of Ca neighbors at 3.81 Å. U-Ca separation, suggesting that U(VI) adsorbs to the HA surfaces as an inner-sphere complex. Uranium(VI) phosphate solid phases were not detected in HA with 4700 ppm sorbed U(VI) by backscatter SEM or EDS, in agreement with the surface complexation process. In contrast, U(VI) speciation in samples that exceeded 7000 ppm sorbed U(VI) included a crystalline uranium(VI) phosphate solid phase, identified as chernikovite by XRD. At these higher concentrations, a secondary, uranium(VI) phosphate solid was detected by SEM-EDS, consistent with chernikovite precipitation. Autunite formation occurred at total U:P molar ratios ≥0.2. Our findings provide a basis for evaluating U(VI) sorption mechanisms by commercially available natural apatites for use in development of PRBs for groundwater U(VI) remediation.
","language":"English","publisher":"ACS","doi":"10.1021/es0108483","issn":"0013936X","usgsCitation":"Fuller, C.C., Bargar, J., Davis, J., and Piana, M., 2002, Mechanisms of uranium interactions with hydroxyapatite: Implications for groundwater remediation: Environmental Science & Technology, v. 36, no. 2, p. 158-165, https://doi.org/10.1021/es0108483.","productDescription":"8 p.","startPage":"158","endPage":"165","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":207771,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1021/es0108483"},{"id":232973,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"36","issue":"2","noUsgsAuthors":false,"publicationDate":"2001-12-05","publicationStatus":"PW","scienceBaseUri":"505a5372e4b0c8380cd6cabe","contributors":{"authors":[{"text":"Fuller, C. C.","contributorId":29858,"corporation":false,"usgs":true,"family":"Fuller","given":"C.","email":"","middleInitial":"C.","affiliations":[],"preferred":false,"id":403394,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Bargar, J.R.","contributorId":82466,"corporation":false,"usgs":true,"family":"Bargar","given":"J.R.","email":"","affiliations":[],"preferred":false,"id":403396,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Davis, J.A.","contributorId":71694,"corporation":false,"usgs":true,"family":"Davis","given":"J.A.","email":"","affiliations":[],"preferred":false,"id":403395,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Piana, M.J.","contributorId":22940,"corporation":false,"usgs":true,"family":"Piana","given":"M.J.","email":"","affiliations":[],"preferred":false,"id":403393,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70024998,"text":"70024998 - 2002 - A hydrogen-based subsurface microbial community dominated by methanogens","interactions":[],"lastModifiedDate":"2018-11-26T08:50:19","indexId":"70024998","displayToPublicDate":"2002-01-01T00:00:00","publicationYear":"2002","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2840,"text":"Nature","active":true,"publicationSubtype":{"id":10}},"title":"A hydrogen-based subsurface microbial community dominated by methanogens","docAbstract":"The search for extraterrestrial life may be facilitated if ecosystems can be found on Earth that exist under conditions analogous to those present on other planets or moons. It has been proposed, on the basis of geochemical and thermodynamic considerations, that geologically derived hydrogen might support subsurface microbial communities on Mars and Europa in which methanogens form the base of the ecosystem1-5. Here we describe a unique subsurface microbial community in which hydrogen-consuming, methane-producing Archaea far outnumber the Bacteria. More than 90% of the 16s ribosomal DNA sequences recovered from hydrothermal waters circulating through deeply buried igneous rocks in Idaho are related to hydrogen-using methanogenic microorganisms. Geochemical characterization indicates that geothermal hydrogen, not organic carbon, is the primary energy source for this methanogen-dominated microbial community. These results demonstrate that hydrogen-based methanogenic communities do occur in Earth's subsurface, providing an analogue for possible subsurface microbial ecosystems on other planets.","language":"English","publisher":"Springer","doi":"10.1038/415312a","issn":"00280836","usgsCitation":"Chapelle, F.H., O'Neil, K., Bradley, P., Methe, B., Ciufo, S., Knobel, L., and Lovley, D.R., 2002, A hydrogen-based subsurface microbial community dominated by methanogens: Nature, v. 415, no. 6869, p. 312-315, https://doi.org/10.1038/415312a.","productDescription":"4 p.","startPage":"312","endPage":"315","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":232972,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":207770,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1038/415312a"}],"volume":"415","issue":"6869","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059e427e4b0c8380cd4644f","contributors":{"authors":[{"text":"Chapelle, F. H.","contributorId":101697,"corporation":false,"usgs":true,"family":"Chapelle","given":"F.","email":"","middleInitial":"H.","affiliations":[],"preferred":false,"id":403391,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"O'Neil, Kyle","contributorId":82491,"corporation":false,"usgs":true,"family":"O'Neil","given":"Kyle","affiliations":[],"preferred":false,"id":403388,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Bradley, P. M. 0000-0001-7522-8606","orcid":"https://orcid.org/0000-0001-7522-8606","contributorId":29465,"corporation":false,"usgs":true,"family":"Bradley","given":"P. M.","affiliations":[],"preferred":false,"id":403386,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Methe, B.A.","contributorId":96052,"corporation":false,"usgs":true,"family":"Methe","given":"B.A.","email":"","affiliations":[],"preferred":false,"id":403390,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Ciufo, S.A.","contributorId":40380,"corporation":false,"usgs":true,"family":"Ciufo","given":"S.A.","email":"","affiliations":[],"preferred":false,"id":403387,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Knobel, L.L.","contributorId":83115,"corporation":false,"usgs":true,"family":"Knobel","given":"L.L.","affiliations":[],"preferred":false,"id":403389,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Lovley, Derek R.","contributorId":107852,"corporation":false,"usgs":true,"family":"Lovley","given":"Derek","middleInitial":"R.","affiliations":[],"preferred":false,"id":403392,"contributorType":{"id":1,"text":"Authors"},"rank":7}]}} ,{"id":70024991,"text":"70024991 - 2002 - Choosing appropriate techniques for quantifying groundwater recharge","interactions":[],"lastModifiedDate":"2018-11-26T07:40:17","indexId":"70024991","displayToPublicDate":"2002-01-01T00:00:00","publicationYear":"2002","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1923,"text":"Hydrogeology Journal","active":true,"publicationSubtype":{"id":10}},"title":"Choosing appropriate techniques for quantifying groundwater recharge","docAbstract":"Various techniques are available to quantify recharge; however, choosing appropriate techniques is often difficult. Important considerations in choosing a technique include space/time scales, range, and reliability of recharge estimates based on different techniques; other factors may limit the application of particular techniques. The goal of the recharge study is important because it may dictate the required space/time scales of the recharge estimates. Typical study goals include water-resource evaluation, which requires information on recharge over large spatial scales and on decadal time scales; and evaluation of aquifer vulnerability to contamination, which requires detailed information on spatial variability and preferential flow. The range of recharge rates that can be estimated using different approaches should be matched to expected recharge rates at a site. The reliability of recharge estimates using different techniques is variable. Techniques based on surface-water and unsaturated-zone data provide estimates of potential recharge, whereas those based on groundwater data generally provide estimates of actual recharge. Uncertainties in each approach to estimating recharge underscore the need for application of multiple techniques to increase reliability of recharge estimates.
","language":"English","publisher":"Springer","doi":"10.1007/s10040-001-0176-2","usgsCitation":"Scanlon, B., Healy, R.W., and Cook, P.G., 2002, Choosing appropriate techniques for quantifying groundwater recharge: Hydrogeology Journal, v. 10, no. 1, p. 18-39, https://doi.org/10.1007/s10040-001-0176-2.","productDescription":"22 p.","startPage":"18","endPage":"39","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":232867,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"10","issue":"1","noUsgsAuthors":false,"publicationDate":"2002-01-17","publicationStatus":"PW","scienceBaseUri":"5059f5d7e4b0c8380cd4c45b","contributors":{"authors":[{"text":"Scanlon, Bridget R.","contributorId":74093,"corporation":false,"usgs":true,"family":"Scanlon","given":"Bridget R.","affiliations":[],"preferred":false,"id":403368,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Healy, Richard W. 0000-0002-0224-1858 rwhealy@usgs.gov","orcid":"https://orcid.org/0000-0002-0224-1858","contributorId":658,"corporation":false,"usgs":true,"family":"Healy","given":"Richard","email":"rwhealy@usgs.gov","middleInitial":"W.","affiliations":[{"id":5044,"text":"National Research Program - Central Branch","active":true,"usgs":true}],"preferred":true,"id":403369,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Cook, Peter G.","contributorId":192638,"corporation":false,"usgs":false,"family":"Cook","given":"Peter","email":"","middleInitial":"G.","affiliations":[],"preferred":false,"id":403370,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70024946,"text":"70024946 - 2002 - Simulation of the mobility of metal-EDTA complexes in groundwater: The influence of contaminant metals","interactions":[],"lastModifiedDate":"2018-11-26T09:27:30","indexId":"70024946","displayToPublicDate":"2002-01-01T00:00:00","publicationYear":"2002","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1565,"text":"Environmental Science & Technology","onlineIssn":"1520-5851","printIssn":"0013-936X","active":true,"publicationSubtype":{"id":10}},"title":"Simulation of the mobility of metal-EDTA complexes in groundwater: The influence of contaminant metals","docAbstract":"Reactive transport simulations were conducted to model chemical reactions between metal−EDTA (ethylenediaminetetraacetic acid) complexes during transport in a mildly acidic quartz−sand aquifer. Simulations were compared with the results of small-scale tracer tests wherein nickel−, zinc−, and calcium−EDTA complexes and free EDTA were injected into three distinct chemical zones of a plume of sewage-contaminated groundwater. One zone had a large mass of adsorbed, sewage-derived zinc; one zone had a large mass of adsorbed manganese resulting from mildly reducing conditions created by the sewage plume; and one zone had significantly less adsorbed manganese and negligible zinc background. The chemical model assumed that the dissolution of iron(III) from metal−hydroxypolymer coatings on the aquifer sediments by the metal−EDTA complexes was kinetically restricted. All other reactions, including metal−EDTA complexation, zinc and manganese adsorption, and aluminum hydroxide dissolution were assumed to reach equilibrium on the time scale of transport; equilibrium constants were either taken from the literature or determined independently in the laboratory. A single iron(III) dissolution rate constant was used to fit the breakthrough curves observed in the zone with negligible zinc background. Simulation results agreed well with the experimental data in all three zones, which included temporal moments derived from breakthrough curves at different distances downgradient from the injections and spatial moments calculated from synoptic samplings conducted at different times. Results show that the tracer cloud was near equilibrium with respect to Fe in the sediment after 11 m of transport in the Zn-contaminated region but remained far from equilibrium in the other two zones. Sensitivity studies showed that the relative rate of iron(III) dissolution by the different metal−EDTA complexes was less important than the fact that these reactions are rate controlled. Results suggest that the published solubility for ferrihydrite reasonably approximates the Fe solubility of the hydroxypolymer coatings on the sediments. Aluminum may be somewhat more soluble than represented by the equilibrium constant for gibbsite, and its dissolution may be rate controlled when reacting with Ca−EDTA complexes.
A marine methylotroph, designated strain MB2T, was isolated for its ability to grow on methyl bromide as a sole carbon and energy source. Methyl chloride and methyl iodide also supported growth, as did methionine and glycine betaine. A limited amount of growth was observed with dimethyl sulfide. Growth was also noted with unidentified components of the complex media marine broth 2216, yeast extract and Casamino acids. No growth was observed on methylated amines, methanol, formate, acetate, glucose or a variety of other substrates. Growth on methyl bromide and methyl iodide resulted in their oxidation to CO2 with stoichiometric release of bromide and iodide, respectively. Strain MB2T exhibited growth optima at NaCl and Mg2+ concentrations similar to that of seawater. Phylogenetic analysis of the 16S rDNA sequence placed this strain in the alpha-Proteobacteria in proximity to the genera Ruegeria and Roseobacter. It is proposed that strain MB2T (= ATCC BAA-92T = DSM 14336T) be designated Leisingera methylohalidivorans gen. nov., sp. nov..
","language":"English","publisher":"ICSP and the BAM Division of the IUMS","doi":"10.1099/00207713-52-3-851","issn":"14665026","usgsCitation":"Schaefer, J., Goodwin, K., McDonald, I., Murrell, J., and Oremland, R.S., 2002, Leisingera methylohalidivorans gen. nov., sp. nov., a marine methylotroph that grows on methyl bromide: International Journal of Systematic and Evolutionary Microbiology, v. 52, no. 3, p. 851-859, https://doi.org/10.1099/00207713-52-3-851.","productDescription":"9 p.","startPage":"851","endPage":"859","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":478710,"rank":10000,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.1099/00207713-52-3-851","text":"Publisher Index Page"},{"id":207862,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1099/ijs.0.01960-0"},{"id":233113,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"52","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a463fe4b0c8380cd675e2","contributors":{"authors":[{"text":"Schaefer, J.K.","contributorId":17256,"corporation":false,"usgs":true,"family":"Schaefer","given":"J.K.","email":"","affiliations":[],"preferred":false,"id":403157,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Goodwin, K.D.","contributorId":45472,"corporation":false,"usgs":true,"family":"Goodwin","given":"K.D.","email":"","affiliations":[],"preferred":false,"id":403160,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"McDonald, I.R.","contributorId":23313,"corporation":false,"usgs":true,"family":"McDonald","given":"I.R.","email":"","affiliations":[],"preferred":false,"id":403158,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Murrell, J.C.","contributorId":25731,"corporation":false,"usgs":true,"family":"Murrell","given":"J.C.","email":"","affiliations":[],"preferred":false,"id":403159,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Oremland, Ronald S. 0000-0001-7382-0147 roremlan@usgs.gov","orcid":"https://orcid.org/0000-0001-7382-0147","contributorId":931,"corporation":false,"usgs":true,"family":"Oremland","given":"Ronald","email":"roremlan@usgs.gov","middleInitial":"S.","affiliations":[{"id":37277,"text":"WMA - Earth System Processes Division","active":true,"usgs":true},{"id":438,"text":"National Research Program - Western Branch","active":true,"usgs":true}],"preferred":true,"id":403161,"contributorType":{"id":1,"text":"Authors"},"rank":5}]}} ,{"id":70024920,"text":"70024920 - 2002 - Energy budget above a high-elevation subalpine forest in complex topography","interactions":[],"lastModifiedDate":"2018-11-19T10:55:39","indexId":"70024920","displayToPublicDate":"2002-01-01T00:00:00","publicationYear":"2002","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":681,"text":"Agricultural and Forest Meteorology","active":true,"publicationSubtype":{"id":10}},"title":"Energy budget above a high-elevation subalpine forest in complex topography","docAbstract":"Components of the energy budget were measured above a subalpine coniferous forest over two complete annual cycles. Sensible and latent heat fluxes were measured by eddy covariance. Bowen ratios ranged from 0.7 to 2.5 in the summer (June–September) depending upon the availability of soil water, but were considerably higher (∼3–6) during winter (December–March). Energy budget closure averaged better than 84% on a half-hourly basis in both seasons with slightly greater closure during the winter months. The energy budget showed a dependence on friction velocity (u∗), approaching complete closure at u∗ values greater than 1 m s−1. The dependence of budget closure on u∗explained why energy balance was slightly better in the winter as opposed to summer, since numerous periods of high turbulence occur in winter. It also explained the lower degree of energy closure (∼10% less) during easterly upslope flow since these periods were characterized by low wind speeds (U<4 m s−1) and friction velocities (
This research compared raw filtered waters (RFWs), XAD resin isolates (XAD-8 and XAD-4), and reverse osmosis (RO) isolates of several surface water samples from McDonalds Branch, a small freshwater fen in the New Jersey Pine Barrens (USA). RO and XAD-8 are two of the most common techniques used to isolate natural organic matter (NOM) for studies of composition and reactivity; therefore, it is important to understand how the isolates differ from bulk (unisolated) samples and from one another. Although, any comparison between the isolation methods needs to consider that XAD-8 is specifically designed to isolate the humic fraction, whereas RO concentrates a broad range of organic matter and is not specific to humics. The comparison included for all samples: weight average molecular weight (Mw), number average molecular weight (Mn), polydispersity (ρ), absorbance at 280 nm normalized to moles C (ε280) (RFW and isolates); and for isolates only: elemental analysis, % carbon distribution by 13C NMR, and aqueous FTIR spectra. As expected, RO isolation gave higher yield of NOM than XAD-8, but also higher ash content, especially Si and S. Mwdecreased in the order: RO>XAD-8>RFW>XAD-4. The Mw differences of isolates compared with RFW may be due to selective isolation (fractionation), or possibly in the case of RO to condensation or coagulation during isolation. 13C NMR results were roughly similar for the two methods, but the XAD-8 isolate was slightly higher in ‘aromatic’ C and the RO isolate was slightly higher in heteroaliphatic and carbonyl C. Infrared spectra indicated a higher carboxyl content for the XAD-8 isolates and a higher ester:carboxyl ratio for the RO isolates. The spectroscopic data thus are consistent with selective isolation of more hydrophobic compounds by XAD-8, and also with potential ester hydrolysis during that process, although further study is needed to determine whether ester hydrolysis does indeed occur. Researchers choosing between XAD and RO isolation methods for NOM need to consider first the purpose of the isolation; i.e., whether humic fractionation is desirable. Beyond that, they should consider the C yield and ash content, as well as the potential for alteration of NOM by ester hydrolysis (XAD) or condensation/coagulation (RO). Furthermore, the RO and XAD methods produce different fractions or isolates so that researchers should be careful when comparing the compositions and reactivities of NOM samples isolated by these two different techniques.
Dimethenamid [2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)acetamide] and flufenacet [N-(4-fluorophenyl)-N-(1-methylethyl)-2-(5-(trifluoromethyl)-1,3,4- thiadiazol-2-yl)oxy] were isolated by C-18 solid-phase extraction and separated from their ethanesulfonic acid (ESA) and oxanilic acid (OXA) degradates during their elution using ethyl acetate for the parent compound, followed by methanol for the polar degradates. The parent compounds were detected using gas chromatography-mass spectrometry in selected-ion mode. The ESA and OXA degradates were detected using high-performance liquid chromatography-electrospray mass spectrometry (HPLC-ESPMS) in negative-ion mode. The method detection limits for a 123-mL sample ranged from 0.01 to 0.07 μg/L. These methods are compatible with existing methods and thus allow for analysis of 17 commonly used herbicides and 18 of their degradation compounds with one extraction. In a study of herbicide transport near the mouth of the Mississippi River during 1999 and 2000, dimethenamid and its ESA and OXA degradates were detected in surface water samples during the annual spring flushes. For flufenacet, the only detections at the study site were for the ESA degradates in samples collected at the peak of the herbicide spring flush in 2000. The low frequency of detections in surface water likely is due to dimethenamid and flufenacet being relatively new herbicides. In addition, detectable amounts of the stable degradates have not been detected in ground water.
","language":"English","publisher":"ACS","doi":"10.1021/jf010779b","issn":"00218561","usgsCitation":"Zimmerman, L., Schneider, R., and Thurman, E., 2002, Analysis and detection of the herbicides dimethenamid and flufenacet and their sulfonic and oxanilic acid degradates in natural water: Journal of Agricultural and Food Chemistry, v. 50, no. 5, p. 1045-1052, https://doi.org/10.1021/jf010779b.","productDescription":"8 p.","startPage":"1045","endPage":"1052","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":232858,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":207699,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1021/jf010779b"}],"volume":"50","issue":"5","noUsgsAuthors":false,"publicationDate":"2002-02-02","publicationStatus":"PW","scienceBaseUri":"5059eaf4e4b0c8380cd48b13","contributors":{"authors":[{"text":"Zimmerman, L.R.","contributorId":28624,"corporation":false,"usgs":true,"family":"Zimmerman","given":"L.R.","email":"","affiliations":[],"preferred":false,"id":402820,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Schneider, R.J.","contributorId":97283,"corporation":false,"usgs":true,"family":"Schneider","given":"R.J.","email":"","affiliations":[],"preferred":false,"id":402821,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Thurman, E.M.","contributorId":102864,"corporation":false,"usgs":true,"family":"Thurman","given":"E.M.","affiliations":[],"preferred":false,"id":402822,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70024837,"text":"70024837 - 2002 - Surface complexation and precipitate geometry for aqueous Zn(II) sorption on ferrihydrite I: X-ray absorption extended fine structure spectroscopy analysis","interactions":[],"lastModifiedDate":"2018-11-26T08:59:33","indexId":"70024837","displayToPublicDate":"2002-01-01T00:00:00","publicationYear":"2002","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1759,"text":"Geochimica et Cosmochimica Acta","active":true,"publicationSubtype":{"id":10}},"title":"Surface complexation and precipitate geometry for aqueous Zn(II) sorption on ferrihydrite I: X-ray absorption extended fine structure spectroscopy analysis","docAbstract":"“Two-line” ferrihydrite samples precipitated and then exposed to a range of aqueous Zn solutions (10−5 to 10−3 M), and also coprecipitated in similar Zn solutions (pH 6.5), have been examined by Zn and Fe K-edge X-ray absorption spectroscopy. Typical Zn complexes on the surface have Zn-O distances of 1.97(.02) Å and coordination numbers of about 4.0(0.5), consistent with tetrahedral oxygen coordination. This contrasts with Zn-O distances of 2.11(.02) Å and coordination numbers of 6 to 7 in the aqueous Zn solutions used in sample preparation. X-ray absorption extended fine structure spectroscopy (EXAFS) fits to the second shell of cation neighbors indicate as many as 4 Zn-Fe neighbors at 3.44(.04) Å in coprecipitated samples, and about two Zn-Fe neighbors at the same distance in adsorptionsamples. In both sets of samples, the fitted coordination number of second shell cations decreases as sorption density increases, indicating changes in the number and type of available complexing sites or the onset of competitive precipitation processes. Comparison of our results with the possible geometries for surface complexes and precipitates suggests that the Zn sorption complexes are inner sphere and at lowest adsorption densities are bidentate, sharing apical oxygens with adjacent edge-sharing Fe(O,OH)6 octahedra. Coprecipitation samples have complexes with similar geometry, but these are polydentate, sharing apices with more than two adjacent edge-sharing Fe(O,OH)6 polyhedra. The results are inconsistent with Zn entering the ferrihydrite structure (i.e., solid solution formation) or formation of other Zn-Fe precipitates. The fitted Zn-Fe coordination numbers drop with increasing Zn density with a minimum of about 0.8(.2) at Zn/(Zn + Fe) of 0.08 or more. This change appears to be attributable to the onset of precipitation of zinc hydroxide polymers with mainly tetrahedral Zn coordination. At the highest loadings studied, the nature of the complexes changes further, and a second type of precipitate forms. This has a structure based on a brucite layer topology, with mainly octahedral Zn coordination. Amorphous zinc hydroxide samples prepared for comparison had a closely similar local structure. Analysis of the Fe K-edge EXAFS is consistent with surface complexation reactions and surface precipitation at high Zn loadings with little or no Fe-Zn solid solution formation. The formation of Zn-containing precipitates at solution conditions two or more orders of magnitude below their solubility limit is compared with other sorption and spectroscopic studies that describe similar behavior.
Previous investigations demonstrated that respiratoly reductive dechlorination of vinyl chloride (VC) can be efficient even at H2 concentrations (≤2 nM) that are characteristic of SO4-reducing conditions. In the study reported here, microorganisms indigenous to a lake-bed sediment completely mineralized [1,2-14C] ethene to 1414CO2 when incubated under SO4-reducing conditions. Together, these observations argue for a novel mechanism for the net anaerobic oxidation of VC to CO2: reductive dechlorination of VC to ethene followed by anaerobic oxidation of ethene to CO2. Moreover, the results of this study suggest that reliance on ethene and/or ethane accumulation as a quantitative indicator of complete reductive dechlorination of chioroethene contaminants may not be warranted.
A reactive transport model based on one-dimensional transport and equilibrium chemistry is applied to synoptic data from an acid mine drainage stream. Model inputs include streamflow estimates based on tracer dilution, inflow chemistry based on synoptic sampling, and equilibrium constants describing acid/base, complexation, precipitation/dissolution, and sorption reactions. The dominant features of observed spatial profiles in pH and metal concentration are reproduced along the 3.5-km study reach by simulating the precipitation of Fe(III) and Al solid phases and the sorption of Cu, As, and Pb onto freshly precipitated iron(III) oxides. Given this quantitative description of existing conditions, additional simulations are conducted to estimate the streamwater quality that could result from two hypothetical remediation plans. Both remediation plans involve the addition of CaCO3 to raise the pH of a small, acidic inflow from ∼2.4 to ∼7.0. This pH increase results in a reduced metal load that is routed downstream by the reactive transport model, thereby providing an estimate of post-remediation water quality. The first remediation plan assumes a closed system wherein inflow Fe(II) is not oxidized by the treatment system; under the second remediation plan, an open system is assumed, and Fe(II) is oxidized within the treatment system. Both plans increase instream pH and substantially reduce total and dissolved concentrations of Al, As, Cu, and Fe(II+III) at the terminus of the study reach. Dissolved Pb concentrations are reduced by ∼18% under the first remediation plan due to sorption onto iron(III) oxides within the treatment system and stream channel. In contrast, iron(III) oxides are limiting under the second remediation plan, and removal of dissolved Pb occurs primarily within the treatment system. This limitation results in an increase in dissolved Pb concentrations over existing conditions as additional downstream sources of Pb are not attenuated by sorption.
Following the aggressive invasion of the bivalve, Potamocorbula amurensis, in the San Francisco Bay-Delta in 1986, selenium contamination in the benthic food web increased. Concentrations in this dominant (exotic) bivalve in North Bay were three times higher in 1995–1997 than in earlier studies, and 1990 concentrations in benthic predators (sturgeon and diving ducks) were also higher than in 1986. The contamination was widespread, varied seasonally and was greater in P. amurensis than in co-occurring and transplanted species. Selenium concentrations in the water column of the Bay were enriched relative to the Sacramento River but were not as high as observed in many contaminated aquatic environments. Total Se concentrations in the dissolved phase never exceeded 0.3 μg Se per l in 1995 and 1996; Se concentrations on particulate material ranged from 0.5 to 2.0 μg Se per g dry weight (dw) in the Bay. Nevertheless, concentrations in P. amurensis reached as high as 20 μg Se per g dw in October 1996. The enriched concentrations in bivalves (6–20 μg Se per g dw) were widespread throughout North San Francisco Bay in October 1995 and October 1996. Concentrations varied seasonally from 5 to 20 μg Se per g dw, and were highest during the periods of lowest river inflows and lowest after extended high river inflows. Transplanted bivalves (oysters, mussels or clams) were not effective indicators of either the degree of Se contamination in P. amurensis or the seasonal increases in contamination in the resident benthos. Se is a potent environmental toxin that threatens higher trophic level species because of its reproductive toxicity and efficient food web transfer. Bivalves concentrate selenium effectively because they bioaccumulate the element strongly and lose it slowly; and they are a direct link in the exposure of predaceous benthivore species. Biological invasions of estuaries are increasing worldwide. Changes in ecological structure and function are well known in response to invasions. This study shows that changes in processes such as cycling and effects of contaminants can accompany such invasions.
The transport and attachment behaviors of Spumella guttula (Kent), a nanoflagellate (protist) found in contaminated and uncontaminated aquifer sediments in Cape Cod, Mass., were assessed in flowthrough and static columns and in a field injection-and-recovery transport experiment involving an array of multilevel samplers. Transport of S. guttula harvested from low-nutrient (10 mg of dissolved organic carbon per liter), slightly acidic, granular (porous) growth media was compared to earlier observations involving nanoflagellates grown in a traditional high-nutrient liquid broth. In contrast to the highly retarded (retardation factor of ∼3) subsurface transport previously reported for S. guttula, the peak concentration of porous-medium-grown S. guttulatraveled concomitantly with that of a conservative (bromide) tracer. About one-third of the porous-medium-grown nanoflagellates added to the aquifer were transported at least 2.8 m downgradient, compared to only ∼2% of the broth-grown nanoflagellates. Flowthrough column studies revealed that a vital (hydroethidine [HE]) staining procedure resulted in considerably less attachment (more transport) of S. guttula in aquifer sediments than did a staining-and-fixation procedure involving 4′,6′-diamidino-2-phenylindole (DAPI) and glutaraldehyde. The calculated collision efficiency (∼10−2 for porous-medium-grown, DAPI-stained nanoflagellates) was comparable to that observed earlier for the indigenous community of unattached groundwater bacteria that serve as prey. The attachment of HE-labeled S. guttula onto aquifer sediment grains was independent of pH (over the range from pH 3 to 9) suggesting a primary attachment mechanism that may be fundamentally different from that of their prey bacteria, which exhibit sharp decreases in fractional attachment with increasing pH. The high degree of mobility of S. guttula in the aquifer sediments has important ecological implications for the protistan community within the temporally changing plume of organic contaminants in the Cape Cod aquifer.