Tritium/helium-3 (3H/3He) and chlorofluorocarbons (CFCs) were investigated as environmental tracers in ground water from Jeju Island (Republic of Korea), a basaltic volcanic island. Ground-water mixing was evaluated by comparing 3H and CFC-12 concentrations with lumped-parameter dispersion models, which distinguished old water recharged before the 1950s with negligible 3H and CFC-12 from younger water. Low 3H levels in a considerable number of samples cannot be explained by the mixing models, and were interpreted as binary mixing of old and younger water; a process also identified in alkalinity and pH of ground water. The ground-water CFC-12 age is much older in water from wells completed in confined zones of the hydro-volcanic Seogwipo Formation in coastal areas than in water from the basaltic aquifer. Major cation concentrations are much higher in young water with high nitrate than those in uncontaminated old water. Chemical evolution of ground water resulting from silicate weathering in basaltic rocks reaches the zeolite–smectite phase boundary. The calcite saturation state of ground water increases with the CFC-12 apparent (piston flow) age. In agricultural areas, the temporal trend of nitrate concentration in ground water is consistent with the known history of chemical fertilizer use on the island, but increase of nitrate concentration in ground water is more abrupt after the late 1970s compared with the exponential growth of nitrogen inputs.
We modeled yellow-billed loon (Gavia adamsii) habitat preferences in a 23,500 km2 area of northern Alaska using intensive aerial surveys and landscape-scale habitat descriptors. Of the 757 lakes censused, yellow-billed loons occupied 15% and Pacific loons (G. pacifica) 42%. Lake area, depth, proportion of shoreline in aquatic vegetation, shoreline complexity, hydrological connectivity (stream present within 100 m or absent), and an area–connectivity interaction were positive, significant predictors of yellow-billed loon presence in a multivariate logistic regression model, but distance to nearest river or Beaufort Sea coast were not. Predicted yellow-billed loon presence was 13 and 4.7 times more likely on deep and medium lakes, respectively, than on shallow lakes that freeze to the bottom. On small lakes (<60 ha), predicted yellow-billed loon presence was 4.8–1.7 times more likely on lakes with hydrological connectivity than without, but connectivity was not important at most lake sizes (65–750 ha). Yellow-billed loon broods depend on fish available in the brood-rearing lake, and we suggest that a dependable supply of fish is more likely in larger lakes, those deep enough to have open water under winter ice, and those near streams. Highly convoluted shorelines and those with aquatic vegetation provide loon nesting and brood-rearing sites, as well as fish habitat. Pacific loon absence was a significant, positive predictor when added to the habitat model, indicating that yellow-billed loons were four times more likely on lakes without Pacific loons.
","language":"English","publisher":"Springer","doi":"10.1007/s10750-006-0042-2","issn":"00188158","usgsCitation":"Earnst, S.L., Platte, R., and Bond, L., 2006, A landscape-scale model of yellow-billed loon (Gavia adamsii) habitat preferences in northern alaska: Hydrobiologia, v. 567, no. 1, p. 227-236, https://doi.org/10.1007/s10750-006-0042-2.","productDescription":"10 p.","startPage":"227","endPage":"236","numberOfPages":"10","costCenters":[{"id":290,"text":"Forest and Rangeland Ecosystem Science Center","active":false,"usgs":true}],"links":[{"id":236885,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":210075,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1007/s10750-006-0042-2"}],"volume":"567","issue":"1","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059e432e4b0c8380cd464b4","contributors":{"authors":[{"text":"Earnst, Susan L. susan_earnst@usgs.gov","contributorId":4446,"corporation":false,"usgs":true,"family":"Earnst","given":"Susan","email":"susan_earnst@usgs.gov","middleInitial":"L.","affiliations":[{"id":289,"text":"Forest and Rangeland Ecosys Science Center","active":true,"usgs":true}],"preferred":true,"id":417382,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Platte, Robert","contributorId":105680,"corporation":false,"usgs":true,"family":"Platte","given":"Robert","affiliations":[],"preferred":false,"id":417384,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Bond, Laura","contributorId":89103,"corporation":false,"usgs":true,"family":"Bond","given":"Laura","affiliations":[],"preferred":false,"id":417383,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70028629,"text":"70028629 - 2006 - Denitrification in nitrate-rich streams: Application of N2:Ar and 15N-tracer methods in intact cores","interactions":[],"lastModifiedDate":"2018-10-26T10:47:56","indexId":"70028629","displayToPublicDate":"2006-01-01T00:00:00","publicationYear":"2006","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1450,"text":"Ecological Applications","active":true,"publicationSubtype":{"id":10}},"displayTitle":"Denitrification in nitrate-rich streams: Application of N2:Ar and 15N-tracer methods in intact cores","title":"Denitrification in nitrate-rich streams: Application of N2:Ar and 15N-tracer methods in intact cores","docAbstract":"Rates of benthic denitrification were measured using two techniques, membrane inlet mass spectrometry (MIMS) and isotope ratio mass spectrometry (IRMS), applied to sediment cores from two NO3−‐rich streams draining agricultural land in the upper Mississippi River Basin. Denitrification was estimated simultaneously from measurements of N2:Ar (MIMS) and 15N[N2] (IRMS) after the addition of low‐level 15NO3− tracer (15N:N = 0.03–0.08) in stream water overlying intact sediment cores. Denitrification rates ranged from about 0 to 4400 μmol N·m−2·h−1 in Sugar Creek and from 0 to 1300 μmol N·m−2·h−1 in Iroquois River, the latter of which possesses greater streamflow discharge and a more homogeneous streambed and water column. Within the uncertainties of the two techniques, there is good agreement between the MIMS and IRMS results, which indicates that the production of N2 by the coupled process of nitrification/denitrification was relatively unimportant and surface‐water NO3− was the dominant source of NO3− for benthic denitrification in these streams. Variation in stream NO3− concentration (from about 20 μmol/L during low discharge to 1000 μmol/L during high discharge) was a significant control of benthic denitrification rates, judging from the more abundant MIMS data. The interpretation that NO3− concentration directly affects denitrification rate was corroborated by increased rates of denitrification in cores amended with NO3−. Denitrification in Sugar Creek removed ≤11% per day of the in‐stream NO3− in late spring and removed roughly 15–20% in late summer. The fraction of NO3− removed in Iroquois River was less than that of Sugar Creek. Although benthic denitrification rates were relatively high during periods of high stream flow, when NO3concentrations were also high, the increase in benthic denitrification could not compensate for the much larger increase in stream NO3− fluxes during high flow. Consequently, fractional NO3− losses were relatively low during high flow.
Climate change and climate variability, population growth, and land use change drive the need for new hydrologic knowledge and understanding. In the mountainous West and other similar areas worldwide, three pressing hydrologic needs stand out: first, to better understand the processes controlling the partitioning of energy and water fluxes within and out from these systems; second, to better understand feedbacks between hydrological fluxes and biogeochemical and ecological processes; and, third, to enhance our physical and empirical understanding with integrated measurement strategies and information systems. We envision an integrative approach to monitoring, modeling, and sensing the mountain environment that will improve understanding and prediction of hydrologic fluxes and processes. Here extensive monitoring of energy fluxes and hydrologic states are needed to supplement existing measurements, which are largely limited to streamflow and snow water equivalent. Ground‐based observing systems must be explicitly designed for integration with remotely sensed data and for scaling up to basins and whole ranges.
","language":"English","publisher":"American Geophysical Union","doi":"10.1029/2005WR004387","usgsCitation":"Bales, R.C., Molotch, N.P., Painter, T.H., Dettinger, M., Rice, R., and Dozier, J., 2006, Mountain hydrology of the western United States: Water Resources Research, v. 42, no. 8, Article W08432; 13 p., https://doi.org/10.1029/2005WR004387.","productDescription":"Article W08432; 13 p.","onlineOnly":"N","additionalOnlineFiles":"N","costCenters":[{"id":552,"text":"San Francisco Bay-Delta","active":false,"usgs":true},{"id":5079,"text":"Pacific Regional Director's Office","active":true,"usgs":true}],"links":[{"id":477359,"rank":1,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.1029/2005wr004387","text":"Publisher Index Page"},{"id":237264,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"42","issue":"8","noUsgsAuthors":false,"publicationDate":"2006-08-26","publicationStatus":"PW","scienceBaseUri":"505a5eb5e4b0c8380cd70c02","contributors":{"authors":[{"text":"Bales, Roger C.","contributorId":189659,"corporation":false,"usgs":false,"family":"Bales","given":"Roger","email":"","middleInitial":"C.","affiliations":[],"preferred":false,"id":416887,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Molotch, Noah P. 0000-0003-4733-8060","orcid":"https://orcid.org/0000-0003-4733-8060","contributorId":203466,"corporation":false,"usgs":false,"family":"Molotch","given":"Noah","email":"","middleInitial":"P.","affiliations":[{"id":36627,"text":"University of Colorado, Boulder","active":true,"usgs":false}],"preferred":false,"id":416888,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Painter, Thomas H.","contributorId":193067,"corporation":false,"usgs":false,"family":"Painter","given":"Thomas","email":"","middleInitial":"H.","affiliations":[],"preferred":false,"id":416892,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Dettinger, Michael D. 0000-0002-7509-7332 mddettin@usgs.gov","orcid":"https://orcid.org/0000-0002-7509-7332","contributorId":146383,"corporation":false,"usgs":true,"family":"Dettinger","given":"Michael D.","email":"mddettin@usgs.gov","affiliations":[],"preferred":false,"id":416891,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Rice, Robert","contributorId":149915,"corporation":false,"usgs":false,"family":"Rice","given":"Robert","affiliations":[],"preferred":false,"id":416890,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Dozier, Jeff","contributorId":190695,"corporation":false,"usgs":false,"family":"Dozier","given":"Jeff","email":"","affiliations":[],"preferred":false,"id":416889,"contributorType":{"id":1,"text":"Authors"},"rank":6}]}} ,{"id":70028249,"text":"70028249 - 2006 - Adequacy of selected evapotranspiration approximations for hydrologic simulation","interactions":[],"lastModifiedDate":"2012-03-12T17:20:44","indexId":"70028249","displayToPublicDate":"2006-01-01T00:00:00","publicationYear":"2006","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2529,"text":"Journal of the American Water Resources Association","active":true,"publicationSubtype":{"id":10}},"title":"Adequacy of selected evapotranspiration approximations for hydrologic simulation","docAbstract":"Evapotranspiration (ET) approximations, usually based on computed potential ET (PET) and diverse PET-to-ET conceptualizations, are routinely used in hydrologic analyses. This study presents an approach to incorporate measured (actual) ET data, increasingly available using micrometeorological methods, to define the adequacy of ET approximations for hydrologic simulation. The approach is demonstrated at a site where eddy correlation-measured ET values were available. A baseline hydrologic model incorporating measured ET values was used to evaluate the sensitivity of simulated water levels, subsurface recharge, and surface runoff to error in four ET approximations. An annually invariant pattern of mean monthly vegetation coefficients was shown to be most effective, despite the substantial year-to-year variation in measured vegetation coefficients. The temporal variability of available water (precipitation minus ET) at the humid, subtropical site was largely controlled by the relatively high temporal variability of precipitation, benefiting the effectiveness of coarse ET approximations, a result that is likely to prevail at other humid sites.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Journal of the American Water Resources Association","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1111/j.1752-1688.2006.tb04486.x","issn":"1093474X","usgsCitation":"Sumner, D.M., 2006, Adequacy of selected evapotranspiration approximations for hydrologic simulation: Journal of the American Water Resources Association, v. 42, no. 3, p. 699-711, https://doi.org/10.1111/j.1752-1688.2006.tb04486.x.","startPage":"699","endPage":"711","numberOfPages":"13","costCenters":[],"links":[{"id":210099,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1111/j.1752-1688.2006.tb04486.x"},{"id":236917,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"42","issue":"3","noUsgsAuthors":false,"publicationDate":"2007-06-08","publicationStatus":"PW","scienceBaseUri":"5059e6f3e4b0c8380cd47748","contributors":{"authors":[{"text":"Sumner, D. M.","contributorId":100827,"corporation":false,"usgs":true,"family":"Sumner","given":"D.","email":"","middleInitial":"M.","affiliations":[],"preferred":false,"id":417229,"contributorType":{"id":1,"text":"Authors"},"rank":1}]}} ,{"id":70028176,"text":"70028176 - 2006 - Potential effects of recurrent low oxygen conditions on the Illinois Cave amphipod","interactions":[],"lastModifiedDate":"2012-03-12T17:20:43","indexId":"70028176","displayToPublicDate":"2006-01-01T00:00:00","publicationYear":"2006","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2201,"text":"Journal of Cave and Karst Studies","active":true,"publicationSubtype":{"id":10}},"title":"Potential effects of recurrent low oxygen conditions on the Illinois Cave amphipod","docAbstract":"The caves of Illinois' sinkhole plain are the sole habitat of the Illinois Cave amphipod (Gammarus acherondytes), a federally endangered species. The sinkhole plain is a hydrologically-connected sequence of karstified limestone that constitutes an extensive karst aquifer which serves as an important source of potable water for area residents. During this investigation, we examined the ground-water quality in caves within two ground-water basins: 1) Illinois Caverns, where the amphipod is now present after previously reported to have been extirpated from the lower reaches, and 2) Stemler Cave, where the amphipod is reported to have been extirpated. The chemical composition of cave streams in Illinois Caverns and Stemler Cave were compared to determine which parameters, if any, could have contributed to the loss of G. acherondytes from Stemler Cave. Stream water in Stemler Cave contained higher concentrations of organic carbon, potassium, silica, chloride, fluoride, sulfate, iron and manganese than Illinois Caverns. Perhaps most importantly, dissolved oxygen (DO) concentrations in Stemler Cave were, during periods of low flow, substantially lower than in Illinois Caverns. Based on land use, there are probably at least eight times more private septic systems in the Stemler Cave ground-water basin than in the Illinois Caverns ground-water basin. Low DO concentrations were likely the result of microbial breakdown of soil organic matter and wastewater treatment system effluent, and the oxidation of pyrite in bedrock. The near-hypoxic DO in Stemler Cave that occurred during low-flow conditions, and, we speculate, a limited range of G. acherondytes within the Stemler Cave ground-water basin due to a metabolic advantage of the stygophilic aquatic invertebrates over the stygobitic G. acherodytes, resulted in the apparent loss of G. acherondytes from Stemler Cave.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Journal of Cave and Karst Studies","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","issn":"10906924","usgsCitation":"Panno, S., Hackley, K.C., Kelly, W., Hwang, H., Wilhelm, F., Taylor, S., and Stiff, B., 2006, Potential effects of recurrent low oxygen conditions on the Illinois Cave amphipod: Journal of Cave and Karst Studies, v. 68, no. 2, p. 55-63.","startPage":"55","endPage":"63","numberOfPages":"9","costCenters":[],"links":[{"id":236809,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"68","issue":"2","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a7edce4b0c8380cd7a7c3","contributors":{"authors":[{"text":"Panno, S.V.","contributorId":102990,"corporation":false,"usgs":true,"family":"Panno","given":"S.V.","email":"","affiliations":[],"preferred":false,"id":416922,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Hackley, Keith C.","contributorId":12166,"corporation":false,"usgs":true,"family":"Hackley","given":"Keith","email":"","middleInitial":"C.","affiliations":[],"preferred":false,"id":416917,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Kelly, W.R.","contributorId":74120,"corporation":false,"usgs":true,"family":"Kelly","given":"W.R.","email":"","affiliations":[],"preferred":false,"id":416920,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Hwang, H.-H.","contributorId":6981,"corporation":false,"usgs":true,"family":"Hwang","given":"H.-H.","email":"","affiliations":[],"preferred":false,"id":416916,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Wilhelm, F.M.","contributorId":94844,"corporation":false,"usgs":true,"family":"Wilhelm","given":"F.M.","email":"","affiliations":[],"preferred":false,"id":416921,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Taylor, S.J.","contributorId":26872,"corporation":false,"usgs":true,"family":"Taylor","given":"S.J.","email":"","affiliations":[],"preferred":false,"id":416918,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Stiff, B.J.","contributorId":42015,"corporation":false,"usgs":true,"family":"Stiff","given":"B.J.","email":"","affiliations":[],"preferred":false,"id":416919,"contributorType":{"id":1,"text":"Authors"},"rank":7}]}} ,{"id":70184332,"text":"70184332 - 2006 - Changes in organic matter biodegradatility influencing sulfate reduction in an aquifer contaminated by landfill leachate","interactions":[],"lastModifiedDate":"2017-03-07T14:33:10","indexId":"70184332","displayToPublicDate":"2006-01-01T00:00:00","publicationYear":"2006","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2729,"text":"Microbial Ecology","active":true,"publicationSubtype":{"id":10}},"title":"Changes in organic matter biodegradatility influencing sulfate reduction in an aquifer contaminated by landfill leachate","docAbstract":"In situ experiments were conducted to measure sulfate reduction rates and identify rate-limiting factors in a shallow, alluvial aquifer contaminated with municipal landfill leachate. Single-well, push–pull tests conducted in a well adjacent to the landfill with >8 mM dissolved organic carbon (DOC) exhibited a sulfate reduction rate of 3.2 μmol SO4−2 (L sediment)−1 day−1, a value in close agreement with laboratory-derived estimates. Identical tests conducted in wells located 90 m downgradient where DOC levels remained high (>3 mM) showed no detectable sulfate consumption, and laboratory assays confirmed this observation. However, the rates of sulfate reduction in sediment samples obtained from this site were three times larger when they were amended with filter-sterilized groundwater from the upgradient location. The effect of various amendments on sulfate reduction rates was further examined in laboratory incubations using sediment collected from the downgradient site amended with 35S sulfate. Unamended sediments showed only weak conversion of the tracer to 35S sulfide (5 to 7 cpm/cm2), whereas the addition of Desulfovibrio cells increased 35S sulfide production to 44 cpm/cm2. However, the application of heat-killed Desulfovibrio had a similar stimulatory effect, as did a lactate amendment. Collectively, these findings indicate that the lack of measurable sulfate reduction at the downgradient site was not due to the absence of the necessary metabolic potential, the presence of lower sulfate concentration, or the quantity of electron donor, but by its biodegradability. The findings also indicate that field bioaugmentation attempts should be interpreted with caution.
","language":"English","publisher":"Springer Science+Business Media, Inc.","doi":"10.1007/s00248-006-9043-y","usgsCitation":"Harris, S.H., Istok, J.D., and Suflita, J.M., 2006, Changes in organic matter biodegradatility influencing sulfate reduction in an aquifer contaminated by landfill leachate: Microbial Ecology, v. 51, no. 4, p. 535-542, https://doi.org/10.1007/s00248-006-9043-y.","productDescription":"8 p. ","startPage":"535","endPage":"542","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":336960,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"51","issue":"4","noUsgsAuthors":false,"publicationDate":"2006-05-06","publicationStatus":"PW","scienceBaseUri":"58bfd4ffe4b014cc3a3ba536","contributors":{"authors":[{"text":"Harris, Steve H. Jr.","contributorId":54889,"corporation":false,"usgs":true,"family":"Harris","given":"Steve","suffix":"Jr.","email":"","middleInitial":"H.","affiliations":[],"preferred":false,"id":681029,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Istok, Jonathan D.","contributorId":35468,"corporation":false,"usgs":true,"family":"Istok","given":"Jonathan","email":"","middleInitial":"D.","affiliations":[],"preferred":false,"id":681030,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Suflita, Joseph M.","contributorId":187604,"corporation":false,"usgs":false,"family":"Suflita","given":"Joseph","email":"","middleInitial":"M.","affiliations":[],"preferred":false,"id":681031,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70184334,"text":"70184334 - 2006 - Extracellular and intracellular uptake of zinc in a photosynthetic biofilm matrix: ","interactions":[],"lastModifiedDate":"2018-10-26T08:25:35","indexId":"70184334","displayToPublicDate":"2006-01-01T00:00:00","publicationYear":"2006","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1103,"text":"Bulletin of Environmental Contamination and Toxicology","active":true,"publicationSubtype":{"id":10}},"title":"Extracellular and intracellular uptake of zinc in a photosynthetic biofilm matrix: ","docAbstract":"No abstract available.
","language":"English","publisher":"Springer","doi":"10.1007/s00128-006-1028-5","usgsCitation":"Morris, J., and Meyer, J., 2006, Extracellular and intracellular uptake of zinc in a photosynthetic biofilm matrix: : Bulletin of Environmental Contamination and Toxicology, v. 77, no. 1, p. 30-35, https://doi.org/10.1007/s00128-006-1028-5.","productDescription":"6 p. ","startPage":"30","endPage":"35","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":336962,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"77","issue":"1","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"58bfd4ffe4b014cc3a3ba534","contributors":{"authors":[{"text":"Morris, J.M.","contributorId":91675,"corporation":false,"usgs":true,"family":"Morris","given":"J.M.","email":"","affiliations":[],"preferred":false,"id":681036,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Meyer, J.S.","contributorId":85741,"corporation":false,"usgs":true,"family":"Meyer","given":"J.S.","email":"","affiliations":[],"preferred":false,"id":681037,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70031081,"text":"70031081 - 2006 - Resolving structural influences on water-retention properties of alluvial deposits","interactions":[],"lastModifiedDate":"2018-10-26T08:45:29","indexId":"70031081","displayToPublicDate":"2006-01-01T00:00:00","publicationYear":"2006","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":3674,"text":"Vadose Zone Journal","active":true,"publicationSubtype":{"id":10}},"title":"Resolving structural influences on water-retention properties of alluvial deposits","docAbstract":"With the goal of improving property-transfer model (PTM) predictions of unsaturated hydraulic properties, we investigated the influence of sedimentary structure, defined as particle arrangement during deposition, on laboratory-measured water retention (water content vs. potential [θ(ψ)]) of 10 undisturbed core samples from alluvial deposits in the western Mojave Desert, California. The samples were classified as having fluvial or debris-flow structure based on observed stratification and measured spread of particle-size distribution. The θ(ψ) data were fit with the Rossi–Nimmo junction model, representing water retention with three parameters: the maximum water content (θmax), the ψ-scaling parameter (ψo), and the shape parameter (λ). We examined trends between these hydraulic parameters and bulk physical properties, both textural—geometric mean, M g, and geometric standard deviation, σg, of particle diameter—and structural—bulk density, ρb, the fraction of unfilled pore space at natural saturation, A e, and porosity-based randomness index, Φs, defined as the excess of total porosity over 0.3. Structural parameters Φs and A e were greater for fluvial samples, indicating greater structural pore space and a possibly broader pore-size distribution associated with a more systematic arrangement of particles. Multiple linear regression analysis and Mallow's C p statistic identified combinations of textural and structural parameters for the most useful predictive models: for θmax, including A e, Φs, and σg, and for both ψo and λ, including only textural parameters, although use of A e can somewhat improve ψo predictions. Textural properties can explain most of the sample-to-sample variation in θ(ψ) independent of deposit type, but inclusion of the simple structural indicators A e and Φs can improve PTM predictions, especially for the wettest part of the θ(ψ) curve.
","language":"English","publisher":"ACSESS","doi":"10.2136/vzj2005.0088","issn":"15391663","usgsCitation":"Winfield, K., Nimmo, J., Izbicki, J., and Martin, P.M., 2006, Resolving structural influences on water-retention properties of alluvial deposits: Vadose Zone Journal, v. 5, no. 2, p. 706-719, https://doi.org/10.2136/vzj2005.0088.","productDescription":"14 p.","startPage":"706","endPage":"719","costCenters":[{"id":154,"text":"California Water Science Center","active":true,"usgs":true},{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":211648,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.2136/vzj2005.0088"},{"id":238975,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"5","issue":"2","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505aa9dbe4b0c8380cd85ff1","contributors":{"authors":[{"text":"Winfield, K.A.","contributorId":85396,"corporation":false,"usgs":true,"family":"Winfield","given":"K.A.","email":"","affiliations":[],"preferred":false,"id":429947,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Nimmo, J. R. 0000-0001-8191-1727","orcid":"https://orcid.org/0000-0001-8191-1727","contributorId":58304,"corporation":false,"usgs":true,"family":"Nimmo","given":"J. R.","affiliations":[],"preferred":false,"id":429946,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Izbicki, J. A. 0000-0003-0816-4408","orcid":"https://orcid.org/0000-0003-0816-4408","contributorId":28244,"corporation":false,"usgs":true,"family":"Izbicki","given":"J. A.","affiliations":[],"preferred":false,"id":429944,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Martin, P. M.","contributorId":39003,"corporation":false,"usgs":true,"family":"Martin","given":"P.","email":"","middleInitial":"M.","affiliations":[],"preferred":false,"id":429945,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70031078,"text":"70031078 - 2006 - Effect of reduced winter precipitation and increased temperature on watershed solute flux, 1988-2002, Northern Michigan","interactions":[],"lastModifiedDate":"2012-03-12T17:21:01","indexId":"70031078","displayToPublicDate":"2006-01-01T00:00:00","publicationYear":"2006","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1007,"text":"Biogeochemistry","active":true,"publicationSubtype":{"id":10}},"title":"Effect of reduced winter precipitation and increased temperature on watershed solute flux, 1988-2002, Northern Michigan","docAbstract":"Since 1987 we have studied weekly change in winter (December-April) precipitation, snowpack, snowmelt, soil water, and stream water solute flux in a small (176-ha) Northern Michigan watershed vegetated by 65-85 year-old northern hardwoods. Our primary study objective was to quantify the effect of change in winter temperature and precipitation on watershed hydrology and solute flux. During the study winter runoff was correlated with precipitation, and forest soils beneath the snowpack remained unfrozen. Winter air temperature and soil temperature beneath the snowpack increased while precipitation and snowmelt declined. Atmospheric inputs declined for H+, NO 3- , NH 4+ , dissolved inorganic nitrogen (DIN), and SO 42- . Replicated plot-level results, which could not be directly extrapolated to the watershed scale, showed 90% of atmospheric DIN input was retained in surface shallow (<15 cm deep) soils while SO 42- flux increased 70% and dissolved organic carbon (DOC) 30-fold. Most stream water base cation (C B), HCO 3- , and Cl- concentrations declined with increased stream water discharge, K+, NO 3- , and SO 42- remained unchanged, and DOC and dissolved organic nitrogen (DON) increased. Winter stream water solute outputs declined or were unchanged with time except for NO 3- and DOC which increased. DOC and DIN outputs were correlated with the percentage of winter runoff and stream discharge that occurred when subsurface flow at the plot-level was shallow (<25 cm beneath Oi). Study results suggest that the percentage of annual runoff occurring as shallow lateral subsurface flow may be a major factor regulating solute outputs and concentrations in snowmelt-dominated ecosystems. ?? Springer 2006.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Biogeochemistry","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1007/s10533-005-1810-1","issn":"01682563","usgsCitation":"Stottlemyer, R., and Toczydlowski, D., 2006, Effect of reduced winter precipitation and increased temperature on watershed solute flux, 1988-2002, Northern Michigan: Biogeochemistry, v. 77, no. 3, p. 409-440, https://doi.org/10.1007/s10533-005-1810-1.","startPage":"409","endPage":"440","numberOfPages":"32","costCenters":[],"links":[{"id":211622,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1007/s10533-005-1810-1"},{"id":238942,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"77","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a05fee4b0c8380cd5107c","contributors":{"authors":[{"text":"Stottlemyer, R.","contributorId":44493,"corporation":false,"usgs":true,"family":"Stottlemyer","given":"R.","email":"","affiliations":[],"preferred":false,"id":429938,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Toczydlowski, D.","contributorId":9790,"corporation":false,"usgs":true,"family":"Toczydlowski","given":"D.","email":"","affiliations":[],"preferred":false,"id":429937,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70030410,"text":"70030410 - 2006 - Landslides triggered by the 2004 Niigata Ken Chuetsu, Japan, earthquake","interactions":[],"lastModifiedDate":"2012-03-12T17:21:03","indexId":"70030410","displayToPublicDate":"2006-01-01T00:00:00","publicationYear":"2006","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1436,"text":"Earthquake Spectra","active":true,"publicationSubtype":{"id":10}},"title":"Landslides triggered by the 2004 Niigata Ken Chuetsu, Japan, earthquake","docAbstract":"The Niigata Ken Chuetsu earthquake triggered a vast number of lanslides in the epicentral region. Landslide concentrations were among the highest ever measured after an earthquake, and most of the triggered landslides were relatively shallow failures parallel to the steep slope faces. The dense concentration of landslides can be attributed to steep local topography in relatively weak geologic units, adverse hydrologic conditions caused by significant antecedent rainfall, and very strong shaking. Many of the landslides could be discerned from high-resolution satellite imagery acquired immediately after the earthquake. ?? 2006, Earthquake Engineering Research Institute.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Earthquake Spectra","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1193/1.2173021","issn":"87552930","usgsCitation":"Kieffer, D., Jibson, R., Rathje, E., and Kelson, K., 2006, Landslides triggered by the 2004 Niigata Ken Chuetsu, Japan, earthquake: Earthquake Spectra, v. 22, no. SUPPL. 1, https://doi.org/10.1193/1.2173021.","costCenters":[],"links":[{"id":211780,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1193/1.2173021"},{"id":239134,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"22","issue":"SUPPL. 1","noUsgsAuthors":false,"publicationDate":"2006-03-01","publicationStatus":"PW","scienceBaseUri":"505a4468e4b0c8380cd66a9f","contributors":{"authors":[{"text":"Kieffer, D.S.","contributorId":103080,"corporation":false,"usgs":true,"family":"Kieffer","given":"D.S.","email":"","affiliations":[],"preferred":false,"id":427044,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Jibson, R.","contributorId":75331,"corporation":false,"usgs":true,"family":"Jibson","given":"R.","email":"","affiliations":[],"preferred":false,"id":427043,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Rathje, E.M.","contributorId":19777,"corporation":false,"usgs":true,"family":"Rathje","given":"E.M.","affiliations":[],"preferred":false,"id":427041,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Kelson, K.","contributorId":73816,"corporation":false,"usgs":true,"family":"Kelson","given":"K.","affiliations":[],"preferred":false,"id":427042,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70030357,"text":"70030357 - 2006 - Episodic fresh surface waters in the Eocene Arctic Ocean","interactions":[],"lastModifiedDate":"2012-03-12T17:21:02","indexId":"70030357","displayToPublicDate":"2006-01-01T00:00:00","publicationYear":"2006","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2840,"text":"Nature","active":true,"publicationSubtype":{"id":10}},"title":"Episodic fresh surface waters in the Eocene Arctic Ocean","docAbstract":"It has been suggested, on the basis of modern hydrology and fully coupled palaeoclimate simulations, that the warm greenhouse conditions that characterized the early Palaeogene period (55-45 Myr ago) probably induced an intensified hydrological cycle with precipitation exceeding evaporation at high latitudes. Little field evidence, however, has been available to constrain oceanic conditions in the Arctic during this period. Here we analyse Palaeogene sediments obtained during the Arctic Coring Expedition, showing that large quantities of the free-floating fern Azolla grew and reproduced in the Arctic Ocean by the onset of the middle Eocene epoch (???50 Myr ago). The Azolla and accompanying abundant freshwater organic and siliceous microfossils indicate an episodic freshening of Arctic surface waters during an ???800,000-year interval. The abundant remains of Azolla that characterize basal middle Eocene marine deposits of all Nordic seas probably represent transported assemblages resulting from freshwater spills from the Arctic Ocean that reached as far south as the North Sea. The termination of the Azolla phase in the Arctic coincides with a local sea surface temperature rise from ???10??C to 13??C, pointing to simultaneous increases in salt and heat supply owing to the influx of waters from adjacent oceans. We suggest that onset and termination of the Azolla phase depended on the degree of oceanic exchange between Arctic Ocean and adjacent seas. ?? 2006 Nature Publishing Group.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Nature","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1038/nature04692","issn":"00280836","usgsCitation":"Brinkhuis, H., Schouten, S., Collinson, M., Sluijs, A., Damste, J., Dickens, G., Huber, M., Cronin, T.M., Onodera, J., Takahashi, K., Bujak, J., Stein, R., Van Der Burgh, J., Eldrett, J., Harding, I., Lotter, A., Sangiorgi, F., Cittert, H., De Leeuw, J.W., Matthiessen, J., Backman, J., and Moran, K., 2006, Episodic fresh surface waters in the Eocene Arctic Ocean: Nature, v. 441, no. 7093, p. 606-609, https://doi.org/10.1038/nature04692.","startPage":"606","endPage":"609","numberOfPages":"4","costCenters":[],"links":[{"id":487649,"rank":10000,"type":{"id":41,"text":"Open Access External Repository Page"},"url":"https://digitalcommons.uri.edu/gsofacpubs/1721","text":"External Repository"},{"id":212005,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1038/nature04692"},{"id":239406,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"441","issue":"7093","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a0a10e4b0c8380cd521aa","contributors":{"authors":[{"text":"Brinkhuis, H.","contributorId":89719,"corporation":false,"usgs":true,"family":"Brinkhuis","given":"H.","affiliations":[],"preferred":false,"id":426842,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Schouten, S.","contributorId":7064,"corporation":false,"usgs":true,"family":"Schouten","given":"S.","email":"","affiliations":[],"preferred":false,"id":426822,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Collinson, M.E.","contributorId":49600,"corporation":false,"usgs":true,"family":"Collinson","given":"M.E.","email":"","affiliations":[],"preferred":false,"id":426836,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Sluijs, A.","contributorId":42035,"corporation":false,"usgs":true,"family":"Sluijs","given":"A.","affiliations":[],"preferred":false,"id":426832,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Damste, J.S.S.","contributorId":47117,"corporation":false,"usgs":true,"family":"Damste","given":"J.S.S.","affiliations":[],"preferred":false,"id":426834,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Dickens, G.R.","contributorId":88101,"corporation":false,"usgs":true,"family":"Dickens","given":"G.R.","email":"","affiliations":[],"preferred":false,"id":426841,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Huber, M.","contributorId":79703,"corporation":false,"usgs":true,"family":"Huber","given":"M.","email":"","affiliations":[],"preferred":false,"id":426840,"contributorType":{"id":1,"text":"Authors"},"rank":7},{"text":"Cronin, T. M. 0000-0002-2643-0979","orcid":"https://orcid.org/0000-0002-2643-0979","contributorId":42613,"corporation":false,"usgs":true,"family":"Cronin","given":"T.","email":"","middleInitial":"M.","affiliations":[{"id":40020,"text":"Florence Bascom Geoscience Center","active":true,"usgs":true}],"preferred":false,"id":426833,"contributorType":{"id":1,"text":"Authors"},"rank":8},{"text":"Onodera, J.","contributorId":31572,"corporation":false,"usgs":true,"family":"Onodera","given":"J.","email":"","affiliations":[],"preferred":false,"id":426829,"contributorType":{"id":1,"text":"Authors"},"rank":9},{"text":"Takahashi, K.","contributorId":10998,"corporation":false,"usgs":true,"family":"Takahashi","given":"K.","affiliations":[],"preferred":false,"id":426823,"contributorType":{"id":1,"text":"Authors"},"rank":10},{"text":"Bujak, J.P.","contributorId":49928,"corporation":false,"usgs":true,"family":"Bujak","given":"J.P.","email":"","affiliations":[],"preferred":false,"id":426837,"contributorType":{"id":1,"text":"Authors"},"rank":11},{"text":"Stein, R.","contributorId":18507,"corporation":false,"usgs":true,"family":"Stein","given":"R.","affiliations":[],"preferred":false,"id":426826,"contributorType":{"id":1,"text":"Authors"},"rank":12},{"text":"Van Der Burgh, J.","contributorId":59629,"corporation":false,"usgs":true,"family":"Van Der Burgh","given":"J.","email":"","affiliations":[],"preferred":false,"id":426838,"contributorType":{"id":1,"text":"Authors"},"rank":13},{"text":"Eldrett, J.S.","contributorId":30441,"corporation":false,"usgs":true,"family":"Eldrett","given":"J.S.","email":"","affiliations":[],"preferred":false,"id":426828,"contributorType":{"id":1,"text":"Authors"},"rank":14},{"text":"Harding, I.C.","contributorId":35946,"corporation":false,"usgs":true,"family":"Harding","given":"I.C.","email":"","affiliations":[],"preferred":false,"id":426830,"contributorType":{"id":1,"text":"Authors"},"rank":15},{"text":"Lotter, A.F.","contributorId":19366,"corporation":false,"usgs":true,"family":"Lotter","given":"A.F.","email":"","affiliations":[],"preferred":false,"id":426827,"contributorType":{"id":1,"text":"Authors"},"rank":16},{"text":"Sangiorgi, F.","contributorId":15828,"corporation":false,"usgs":true,"family":"Sangiorgi","given":"F.","affiliations":[],"preferred":false,"id":426825,"contributorType":{"id":1,"text":"Authors"},"rank":17},{"text":"Cittert, H.V.K.V.","contributorId":15409,"corporation":false,"usgs":true,"family":"Cittert","given":"H.V.K.V.","email":"","affiliations":[],"preferred":false,"id":426824,"contributorType":{"id":1,"text":"Authors"},"rank":18},{"text":"De Leeuw, J. W.","contributorId":64406,"corporation":false,"usgs":true,"family":"De Leeuw","given":"J.","email":"","middleInitial":"W.","affiliations":[],"preferred":false,"id":426839,"contributorType":{"id":1,"text":"Authors"},"rank":19},{"text":"Matthiessen, J.","contributorId":37531,"corporation":false,"usgs":true,"family":"Matthiessen","given":"J.","email":"","affiliations":[],"preferred":false,"id":426831,"contributorType":{"id":1,"text":"Authors"},"rank":20},{"text":"Backman, J.","contributorId":49596,"corporation":false,"usgs":true,"family":"Backman","given":"J.","email":"","affiliations":[],"preferred":false,"id":426835,"contributorType":{"id":1,"text":"Authors"},"rank":21},{"text":"Moran, K.","contributorId":96479,"corporation":false,"usgs":true,"family":"Moran","given":"K.","email":"","affiliations":[],"preferred":false,"id":426843,"contributorType":{"id":1,"text":"Authors"},"rank":22}]}} ,{"id":70028918,"text":"70028918 - 2006 - Intradaily variability of water quality in a shallow tidal lagoon: Mechanisms and implications","interactions":[],"lastModifiedDate":"2018-10-29T07:38:50","indexId":"70028918","displayToPublicDate":"2006-01-01T00:00:00","publicationYear":"2006","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1584,"text":"Estuaries and Coasts","active":true,"publicationSubtype":{"id":10}},"title":"Intradaily variability of water quality in a shallow tidal lagoon: Mechanisms and implications","docAbstract":"Although surface water quality and its underlying processes vary over time scales ranging from seconds to decades, they have historically been studied at the lower (weekly to interannual) frequencies. The aim of this study was to investigate intradaily variability of three water quality parameters in a small freshwater tidal lagoon (Mildred Island, California). High frequency time series of specific conductivity, water temperature, and chlorophylla at two locations within the habitat were analyzed in conjunction with supporting hydrodynamic, meteorological, biological, and spatial mapping data. All three constituents exhibited large amplitude intradaily (e.g., semidiurnal tidal and diurnal) oscillations, and periodicity varied across constituents, space, and time. Like other tidal embayments, this habitat is influenced by several processes with distinct periodicities including physical controls, such as tides, solar radiation, and wind, and biological controls, such as photosynthesis, growth, and grazing. A scaling approach was developed to estimate individual process contributions to the observed variability. Scaling results were generally consistent with observations and together with detailed examination of time series and time derivatives, revealed specific mechanisms underlying the observed periodicities, including interactions between the tidal variability, heating, wind, and biology. The implications for monitoring were illustrated through subsampling of the data set. This exercise demonstrated how quantities needed by scientists and managers (e.g., mean or extreme concentrations) may be misrepresented by low frequency data and how short-duration high frequency measurements can aid in the design and interpretation of temporally coarser sampling programs. The dispersive export of chlorophylla from the habitat exhibited a fortnightly variability corresponding to the modulation of semidiurnal tidal currents with the diurnal cycle of phytoplankton variability, demonstrating how high frequency interactions can govern long-term trends. Process identification, as through the scaling analysis here, can help us anticipate changes in system behavior and adapt our own interactions with the system.
A survey of diffuse CO2 efflux, soil temperature and soil-gas chemistry over areas of localized vegetation-kill on and around the resurgent dome of Long Valley caldera California was performed to evaluate the premise that gaseous and thermal anomalies are related to renewed intrusion of magma. Some kill sites are long-lived features and others have developed in the past few years. Total anomalous CO2 emissions from the thirteen areas average around 8.7 t per day; but the majority of the emissions come from four sites west of the Casa Diablo geothermal power plant. Geochemical analyses of the soil-gases from locations west and east of the plant revealed the presence of isobutane related to plant operations. The δ13C values of diffuse CO2 range from − 5.7‰ to − 3.4‰, similar to values previously reported for CO2 from hot springs and thermal wells around Long Valley.
At many of the vegetation-kill sites soil temperatures reach boiling at depths ≤ 20 cm. Soil temperature/depth profiles at two of the high-emissions areas indicate that the conductive thermal gradient in the center of the areas is around 320 °C m− 1. We estimate total heat loss from the two areas to be about 6.1 and 2.3 MW. Given current thinking on the rate of hydrothermal fluid flow across the caldera and using the CO2 concentration in the thermal fluids, the heat and CO2 loss from the kill areas is easily provided by the shallow hydrothermal system, which is sourced to the west of the resurgent dome. We find no evidence that the development of new areas of vegetation kill across the resurgent dome are related to new input of magma or magmatic fluids from beneath the resurgent dome. Our findings indicate that the areas have developed as a response to changes in the shallow hydrologic system. Some of the changes are likely related to fluid production at the power plant, but at distal sites the changes are more likely related to seismicity and uplift of the dome.
Our experiments conducted under controlled laboratory conditions demonstrate diel uptake and release of zinc (Zn) in lab-cultured biofilm exposed to Zn concentrations that are present in some mining-impacted streams (1–2 mg Zn/l). Specifically, at constant pH, temperature, and aqueous Zn concentrations in the exposure water, biofilm accumulated Zn during the light periods of the photocycle and released Zn during the dark periods of the photocycle. The range of Zn uptake measured in biofilm during one light period in these laboratory experiments (0.6–8.3 mg Zn/g dw biofilm) encompassed the estimated Zn uptake (1.5–3.7 mg Zn/g dw biofilm) necessary to attribute aqueous diel Zn cycling in a mining-impacted stream in Montana (High Ore Creek) to uptake in biofilm. This is relevant to in situ studies of diel Zn cycling because we controlled three important parameters that naturally fluctuate daily in the field, thus demonstrating the potential for biofilm to remove large percentages of Zn from some mining-impacted streams. Researchers, modelers, regulators, and reclamation teams working in metals-contaminated streams should be aware of diel metal cycling, because the highest Zn concentrations (and therefore, perhaps the most toxic conditions) in the water column might occur at night, and the greatest exposure of grazers of phototrophs to dietborne Zn might occur during daylight hours.
Natural attenuation of contaminants in groundwater depends on an adequate supply of electron acceptors to stimulate biodegradation. In an alluvial aquifer contaminated with leachate from an unlined municipal landfill, the mechanism of recharge infiltration was investigated as a source of electron acceptors. Water samples were collected monthly at closely spaced intervals in the top 2 m of the saturated zone from a leachate-contaminated well and an uncontaminated well, and analyzed for δ18O, δ2H, non-volatile dissolved organic carbon (NVDOC), SO42−, NO3− and Cl−. Monthly recharge amounts were quantified using the offset of the δ18O or δ2H from the local meteoric water line as a parameter to distinguish water types, as evaporation and methanogenesis caused isotopic enrichment in waters from different sources. Presence of dissolved SO42− in the top 1 to 2 m of the saturated zone was associated with recharge; SO42− averaged 2.2 mM, with maximum concentrations of 15 mM. Nitrate was observed near the water table at the contaminated site at concentrations up to 4.6 mM. Temporal monitoring of δ2H and SO42− showed that vertical transport of recharge carried SO42− to depths up to 1.75 m below the water table, supplying an additional electron acceptor to the predominantly methanogenic leachate plume. Measurements of δ34S in SO42−indicated both SO42− reduction and sulfide oxidation were occurring in the aquifer. Depth-integrated net SO42− reduction rates, calculated using the natural Cl−gradient as a conservative tracer, ranged from 7.5 × 10− 3 to 0.61 mM·d− 1 (over various depth intervals from 0.45 to 1.75 m). Sulfate reduction occurred at both the contaminated and uncontaminated sites; however, median SO42− reduction rates were higher at the contaminated site. Although estimated SO42− reduction rates are relatively high, significant decreases in NVDOC were not observed at the contaminated site. Organic compounds more labile than the leachate NVDOC may be present in the root zone, and SO42− reduction may be coupled to methane oxidation. The results show that sulfur (and possibly nitrogen) redox processes within the top 2 m of the aquifer are directly related to recharge timing and seasonal water level changes in the aquifer. The results suggest that SO42−reduction associated with the infiltration of recharge may be a significant factor affecting natural attenuation of contaminants in alluvial aquifers.
It has been long known that land surface topography governs both groundwater flow patterns at the regional‐to‐continental scale and on smaller scales such as in the hyporheic zone of streams. Here we show that the surface topography can be separated in a Fourier‐series spectrum that provides an exact solution of the underlying three‐dimensional groundwater flows. The new spectral solution offers a practical tool for fast calculation of subsurface flows in different hydrological applications and provides a theoretical platform for advancing conceptual understanding of the effect of landscape topography on subsurface flows. We also show how the spectrum of surface topography influences the residence time distribution for subsurface flows. The study indicates that the subsurface head variation decays exponentially with depth faster than it would with equivalent two‐dimensional features, resulting in a shallower flow interaction.
Leachate plume emanating from an old unlined municipal landfill site near the city of Norman, Oklahoma, is discharging into the underlying alluvial aquifer. Subsurface imaging techniques, electrical resistivity tomography and electrical conductivity (EC) logging, were used on the site to detect and map the position of the leachate plume. Anomalous EC zones, delineated with the two methods, correlated with the occurrence of the plume detected by water chemistry analyses from multilevel monitoring wells. Specific conductance, a potential indicator of leachate contamination, ranged from 1861 to 7710 μS/cm in contaminated zones and from 465 to 2180 μS/cm in uncontaminated ground water. Results are in agreement with those from earlier studies that the leachate plume emerges from the landfill along preferential pathways. Additionally, there are indications that the leading edge of the plume has migrated, at least, 200 m away from the landfill in the direction of ground water flow.