Science.gov

Sample records for dissolved metal concentration

  1. [Concentrations and Speciation of Dissolved Heavy Metal in Rainwater in Guiyang, China].

    PubMed

    Zhu, Zhao-zhou; Li, Jun; Wang, Zhi-ru

    2015-06-01

    In order to understand the pollution situation, as well as seasonal changes in characteristics and speciation of dissolved heavy metals in acid rain control zone, the concentrations of dissolved heavy metals in rainwater collected at Guiyang were measured using inductively coupled plasma mass spectrometry (ICP-MS). And the speciation of dissolved heavy metals was further simulated by PHREEQC model. The results showed that the dissolved Co, Ni, Cu, Zn and Cd concentrations were low and not higher than the national standards for drinking water quality in China. The dissolved Pd concentrations were high in fall and winter and higher than the national standards for drinking water quality in China. The Co and Ni in rainwater mainly came from the crust and there was almost no human impact. The Cu, Zn, Cd and Pd pollutions in rainwater were affected by human activity with different levels. The degrees of contamination in autumn and winter were more serious than those in spring and summer. The free metal ion species was the dominant form of dissolved heavy metal, accounting for 47.27%-95.28% of the dissolved metal in rainwater from Guiyang city. The free metal ion species was followed in abundance by Metal-Oxalate and Metal-sulfate complexes that accounted for 0.72% -51.87% and 0.50%-7.66%, respectively. The acidity of rainwater, acid type as well as content of ligand more likely controlled the distribution of dissolved heavy metal in precipitation.

  2. Seasonality of diel cycles of dissolved trace-metal concentrations in a Rocky Mountain stream

    USGS Publications Warehouse

    Nimick, D.A.; Cleasby, T.E.; McCleskey, R.B.

    2005-01-01

    Substantial diel (24-h) cycles in dissolved (0.1-??m filtration) metal concentrations were observed during summer low flow, winter low flow, and snowmelt runoff in Prickly Pear Creek, Montana. During seven diel sampling episodes lasting 34-61.5 h, dissolved Mn and Zn concentrations increased from afternoon minimum values to maximum values shortly after sunrise. Dissolved As concentrations exhibited the inverse timing. The magnitude of diel concentration increases varied in the range 17-152% for Mn and 70-500% for Zn. Diel increases of As concentrations (17-55%) were less variable. The timing of minimum and maximum values of diel streamflow cycles was inconsistent among sampling episodes and had little relation to the timing of metal concentration cycles, suggesting that geochemical rather than hydrological processes are the primary control of diel metal cycles. Diel cycles of dissolved metal concentrations should be assumed to occur at any time of year in any stream with dissolved metals and neutral to alkaline pH. ?? Springer-Verlag 2005.

  3. Seasonality of Diel Cycles of Dissolved Trace-Metal Concentrations in a Rocky Mountain Stream

    NASA Astrophysics Data System (ADS)

    Nimick, D. A.; Cleasby, T. E.; McCleskey, R. B.

    2004-12-01

    Substantial diel (24-hour) cycles in dissolved (0.1-μ m filtration) metal concentrations were observed during summer low flow, winter low flow, and snowmelt runoff in Prickly Pear Creek in southwestern Montana. The stream was alkaline (pH of 7.65-9.06), and dissolved metal concentrations were relatively low (1.8-7.1 μ g/L for As, 18-57 μ g/L for Mn, and 12-123 μ g/L for Zn). The metals are derived from abandoned mine lands in the stream's headwaters; As also is derived from geothermal sources. During seven diel sampling episodes, each lasting 34-61.5 hours, concentrations of dissolved Mn and Zn increased from minimum values in the afternoon to maximum values shortly after sunrise. The timing of diel cycles of dissolved As concentrations exhibited the inverse pattern. The magnitude of concentration increases during individual 24-hour periods ranged from 17-152% for Mn and 70-500% for Zn, and correlated positively with the magnitude of diel increases of pH and temperature, indicating that geochemical processes involving reactive inorganic and organic surfaces on and in the streambed probably control these diel metal cycles. Diel increases of As concentrations (17-55%) were proportionally smaller and less variable among the seasonal sampling episodes than for Mn and Zn, and they correlated poorly with diel increases of pH and temperature. Streamflow among the seven sampling episodes ranged from 0.35-3.3 m3/s. The timing of minimum and maximum values of diel streamflow cycles was inconsistent among sampling episodes and had little relation to the timing of metal concentration cycles, indicating that hydrological processes are not a primary control of diel metal cycles. Diel cycles of dissolved metal concentrations may occur at any time of year and during various hydrologic conditions in all streams with dissolved metals and neutral to alkaline pH.

  4. Diel cycles in dissolved metal concentrations in streams: Occurrence and possible causes

    USGS Publications Warehouse

    Nimick, D.A.; Gammons, C.H.; Cleasby, T.E.; Madison, J.P.; Skaar, D.; Brick, C.M.

    2003-01-01

    Substantial diel (24-hour) cycles in dissolved (0.1-??m filtration) metal concentrations were observed during low flow for 18 sampling episodes at 14 sites on 12 neutral and alkaline streams draining historical mining areas in Montana and Idaho. At some sites, concentrations of Cd, Mn, Ni, and Zn increased as much as 119, 306, 167, and 500%, respectively, from afternoon minimum values to maximum values shortly after sunrise. Arsenic concentrations exhibited the inverse temporal pattern with increases of up to 54%. Variations in Cu concentrations were small and inconsistent. Diel metal cycles are widespread and persistent, occur over a wide range of metal concentrations, and likely are caused primarily by instream geochemical processes. Adsorption is the only process that can explain the inverse temporal patterns of As and the divalent metals. Diel metal cycles have important implications for many types of water-quality studies and for understanding trace-metal mobility.

  5. Assessing time-integrated dissolved concentrations and predicting toxicity of metals during diel cycling in streams

    USGS Publications Warehouse

    Balistrieri, Laurie S.; Nimick, David A.; Mebane, Christopher A.

    2012-01-01

    Evaluating water quality and the health of aquatic organisms is challenging in systems with systematic diel (24 hour) or less predictable runoff-induced changes in water composition. To advance our understanding of how to evaluate environmental health in these dynamic systems, field studies of diel cycling were conducted in two streams (Silver Bow Creek and High Ore Creek) affected by historical mining activities in southwestern Montana. A combination of sampling and modeling tools were used to assess the toxicity of metals in these systems. Diffusive Gradients in Thin Films (DGT) samplers were deployed at multiple time intervals during diel sampling to confirm that DGT integrates time-varying concentrations of dissolved metals. Thermodynamic speciation calculations using site specific water compositions, including time-integrated dissolved metal concentrations determined from DGT, and a competitive, multiple-metal biotic ligand model incorporated into the Windemere Humic Aqueous Model Version 6.0 (WHAM VI) were used to determine the chemical speciation of dissolved metals and biotic ligands. The model results were combined with previously collected toxicity data on cutthroat trout to derive a relationship that predicts the relative survivability of these fish at a given site. This integrative approach may prove useful for assessing water quality and toxicity of metals to aquatic organisms in dynamic systems and evaluating whether potential changes in environmental health of aquatic systems are due to anthropogenic activities or natural variability.

  6. Influence of low dissolved oxygen concentration in body fluid on corrosion fatigue behaviors of implant metals.

    PubMed

    Morita, M; Sasada, T; Nomura, I; Wei, Y Q; Tsukamoto, Y

    1992-01-01

    In their previous study, the authors carried out a fatigue test for AISI 316, 316L stainless steels and COP1 alloy in a living animal body and observed a remarkable deterioration in the fatigue durability of these metals. In that study, it was concluded that the reason the corrosion resistance of the metals was reduced in the living body was that the low concentration of dissolved oxygen gas in the body fluid (the partial pressure pO2; 28-78 mmHg) was insufficient to form the chromium oxide passivation film on the metal surface, and the base metal (iron) was released into the environmental fluid in ionic form. In this paper, with the concentration of dissolved oxygen gas in a physiological normal saline solution being set equivalent to that of living body fluid, fatigue tests on AISI 316 were made to simulate the stress corrosion behavior of the metal in the living body. As a result, remarkable deterioration of fatigue strength was observed in the low O2 concentrated normal saline solution, which was the same as that in the living animal body.

  7. Trace metal concentrations in post-hatching cuttlefish Sepia officinalis and consequences of dissolved zinc exposure.

    PubMed

    Le Pabic, Charles; Caplat, Christelle; Lehodey, Jean-Paul; Milinkovitch, Thomas; Koueta, Noussithé; Cosson, Richard Philippe; Bustamante, Paco

    2015-02-01

    In this study, we investigated the changes of 13 trace metal and metalloid concentrations (i.e. Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, V, Zn) and their subcellular fractionation in juvenile cuttlefish Sepia officinalis reared in controlled conditions between hatching and 2 months post-hatching. In parallel, metallothionein concentrations were determined. Our results highlighted contrasting changes of studied metals. Indeed, As and Fe concentrations measured in hatchlings suggested a maternal transfer of these elements in cuttlefish. The non-essential elements Ag and Cd presented the highest accumulation during our study, correlated with the digestive gland maturation. During the 6 first weeks of study, soluble fractions of most of essential trace metals (i.e. Co, Cr, Cu, Fe, Se, Zn) slowly increased consistently with the progressive needs of cuttlefish metabolism during this period. In order to determine for the first time in a cephalopod how metal concentrations and their subcellular distributions are impacted when the animals are trace metal-exposed, we studied previously described parameters in juveniles exposed to dissolved Zn at environmental (i.e. 50 μg l(-1)) and sublethal (i.e. 200 μg l(-1)) levels. Moreover, oxidative stress (i.e. glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase activities, and lipid peroxidation (LPO)) was assessed in digestive gland and gills after 1 and 2 months exposures. Our results highlighted no or low ability of this stage of life to regulate dissolved Zn accumulation during the studied period, consistently with high sensitivity of this organism. Notably, Zn exposures caused a concentration-dependent Mn depletion in juvenile cuttlefish, and an increase of soluble fraction of Ag, Cd, Cu without accumulation modifications, suggesting substitution of these elements (i.e. Mn, Ag, Cd, Cu) by Zn. In parallel, metallothionein concentrations decreased in individuals most exposed to Zn. Finally, no

  8. Concentrations and distributions of metals associated with dissolved organic matter from the Suwannee River (GA, USA)

    USGS Publications Warehouse

    Kuhn, M. Keshia; Neubauer, Elisabeth; Hofmann, Thilo; von der Kammer, Frank; Aiken, George R.; Maurice, Patricia A.

    2015-01-01

    Concentrations and distributions of metals in Suwannee River (SR) raw filtered surface water (RFSW) and dissolved organic matter (DOM) processed by reverse osmosis (RO), XAD-8 resin (for humic and fulvic acids [FA]), and XAD-4 resin (for “transphilic” acids) were analyzed by asymmetrical flow field-flow fractionation (AsFlFFF). SR samples were compared with DOM samples from Nelson's Creek (NLC), a wetland-draining stream in northern Michigan; previous International Humic Substances Society (IHSS) FA and RO samples from the SR; and an XAD-8 sample from Lake Fryxell (LF), Antarctica. Despite application of cation exchange during sample processing, all XAD and RO samples contained substantial metal concentrations. AsFlFFF fractograms allowed metal distributions to be characterized as a function of DOM component molecular weight (MW). In SR RFSW, Fe, Al, and Cu were primarily associated with intermediate to higher than average MW DOM components. SR RO, XAD-8, and XAD-4 samples from May 2012 showed similar MW trends for Fe and Al but Cu tended to associate more with lower MW DOM. LF DOM had abundant Cu and Zn, perhaps due to amine groups that should be present due to its primarily algal origins. None of the fractograms showed obvious evidence for mineral nanoparticles, although some very small mineral nanoparticles might have been present at trace concentrations. This research suggests that AsFlFFF is important for understanding how metals are distributed in different DOM samples (including IHSS samples), which may be key to metal reactivity and bioavailability.

  9. METHOD OF DISSOLVING URANIUM METAL

    DOEpatents

    Slotin, L.A.

    1958-02-18

    This patent relates to an economicai means of dissolving metallic uranium. It has been found that the addition of a small amount of perchloric acid to the concentrated nitric acid in which the uranium is being dissolved greatly shortens the time necessary for dissolution of the metal. Thus the use of about 1 or 2 percent of perchioric acid based on the weight of the nitric acid used, reduces the time of dissolution of uranium by a factor of about 100.

  10. Dissolved, particulate and acid-leachable trace metal concentrations in North Atlantic precipitation collected on the Global Change Expedition

    SciTech Connect

    Lim, B.; Jickells, T.D. )

    1990-12-01

    Atmospheric inputs of trace metals into surface waters are an important pathway for the oceanic biogeochemical cycling of many trace constituents. Rainwater samples from six precipitation events were collected on board ship during legs 3 and 4 of the Global Change Expedition over the North Atlantic Ocean and analyzed for dissolved, particulate (Al and Pb), and acid-leachable trace metals (Al, Fe, Mn, Cd, Cu, Pb, Zn). Acid-leachable concentrations of the elements were similar to reported values from the North Atlantic and Pacific Oceans which were measured using comparable acidification procedures. Concentrations of dissolved and particulate Al and Pb were determined in rain events acid-leachable and total trace metal concentrations suggest that the acid-leachable fraction of metals can significantly underestimate total concentrations of crustal elements in rain. The solubilities of Al and Pb in precipitation were variable and mean solubilities of the elements were 13% and 45%, respectively. Recycled sea salt components were less than 14% for Al, Fe, Mn, Pb, Cd, Cu, and Zn, indicating that the net trace metal flux is from the atmosphere to the oceans. Deep sea particle fluxes for these metals through the western tropical North Atlantic exceed atmospheric deposition fluxes by a factor of 18 to 41. 57 refs., 2 figs., 12 tabs.

  11. [Effect of the change in sulphate and dissolved oxygen mass concentration on metal release in old cast iron distribution pipes].

    PubMed

    Wu, Yong-li; Shi, Bao-you; Sun, Hui-fang; Zhang, Zhi-huan; Gu, Jun-nong; Wang, Dong-sheng

    2013-09-01

    To understand the processes of corrosion by-product release and the consequent "red water" problems caused by the variation of water chemical composition in drinking water distribution system, the effect of sulphate and dissolved oxygen (DO) concentration on total iron release in corroded old iron pipe sections historically transporting groundwater was investigated in laboratory using small-scale pipe section reactors. The release behaviors of some low-level metals, such as Mn, As, Cr, Cu, Zn and Ni, in the process of iron release were also monitored. The results showed that the total iron and Mn release increased significantly with the increase of sulphate concentration, and apparent red water occurred when sulphate concentration was above 400 mg x L(-1). With the increase of sulfate concentration, the effluent concentrations of As, Cr, Cu, Zn and Ni also increased obviously, however, the effluent concentrations of these metals were lower than the influent concentrations under most circumstances, which indicated that adsorption of these metals by pipe corrosion scales occurred. Increasing DO within a certain range could significantly inhibit the iron release.

  12. A Record of Dissolved Metal Concentrations in the Lena River During the Period of Ice Breakup

    NASA Astrophysics Data System (ADS)

    Monson, O. D.; Guay, C. K.; Holmes, R. M.; Zhulidov, A. V.

    2004-12-01

    The PARTNERS project is a 5-year research program (2002-2007) funded by the Arctic System Science Program of the U.S. National Science Foundation. The objective of the PARTNERS project is to measure several biogeochemical parameters in the six largest rivers that drain the watershed of the Arctic Ocean (Yenisey, Lena, Ob, Mackenzie, Yukon, and Kolyma) as a means to study the origins and fates of continental runoff. As part of the PARTNERS field program for 2004, samples were collected on the Lena River in the spring (May-June) during the period of peak discharge and ice breakup. Samples were collected from the bank at the town of Zhigansk (66.75 N, 23.38 E) once daily from May 28th through June 7th, 2004. The river was completely ice covered at the beginning of this period. The river level rose dramatically each day until ice breakup, which occurred on May 30th. Following breakup, the river level began to drop steadily. Visual observation of daily water samples indicated a darkening of the tannic brown color of the river water as discharge levels increased up until breakup, suggesting an increase in DOC concentrations associated with the peak discharge and ice breakup period. Water samples for metals analyses were syringe filtered in the field through 0.45 um polypropylene and 0.02 um Anotop filter discs and acidified under clean conditions upon return to the laboratory. The samples were analyzed by high-resolution ICPMS for a suite of metals including Ba, Cd, Ce, Co, Cr, Cs, Cu, Fe, Li, Mn, Mo, Ni, Pb, Rb, Re, Sr, Tl, U, V, and Zn. Here we report the results from these analyses as a daily time series of metal concentrations bracketing the ice breakup and peak discharge events. During this relatively short amount of time, significant fluctuations in metal concentrations were observed, which are likely related to concurrent fluctuations in DOC concentrations and other changes in river chemistry occurring during this dynamic period of the annual hydrologic cycle in

  13. Dissolved concentrations, sources, and risk evaluation of selected metals in surface water from Mangla Lake, Pakistan.

    PubMed

    Saleem, Muhammad; Iqbal, Javed; Shah, Munir H

    2014-01-01

    The present study is carried out for the assessment of water quality parameters and selected metals levels in surface water from Mangla Lake, Pakistan. The metal levels (Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr, and Zn) were determined by flame atomic absorption spectrophotometry. Average levels of Cd, Co, Cr, Ni, and Pb were higher than the allowable concentrations set by national and international agencies. Principal component analysis indicated significant anthropogenic contributions of Cd, Co, Cr, Ni, and Pb in the water reservoir. Noncarcinogenic risk assessment was then evaluated using Hazard Quotient (HQ(ing/derm)) and Hazard Index (HI(ing/derm)) following USEPA methodology. For adults and children, Cd, Co, Cr, and Pb (HQ(ing) > 1) emerged as the most important pollutants leading to noncarcinogenic concerns via ingestion route, whereas there was no risk via dermal contact of surface water. This study helps in establishing pollutant loading reduction goal and the total maximum daily loads, and consequently contributes to preserve public health and develop water conservation strategy.

  14. Dissolved Concentrations, Sources, and Risk Evaluation of Selected Metals in Surface Water from Mangla Lake, Pakistan

    PubMed Central

    Saleem, Muhammad; Iqbal, Javed; Shah, Munir H.

    2014-01-01

    The present study is carried out for the assessment of water quality parameters and selected metals levels in surface water from Mangla Lake, Pakistan. The metal levels (Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr, and Zn) were determined by flame atomic absorption spectrophotometry. Average levels of Cd, Co, Cr, Ni, and Pb were higher than the allowable concentrations set by national and international agencies. Principal component analysis indicated significant anthropogenic contributions of Cd, Co, Cr, Ni, and Pb in the water reservoir. Noncarcinogenic risk assessment was then evaluated using Hazard Quotient (HQing/derm) and Hazard Index (HIing/derm) following USEPA methodology. For adults and children, Cd, Co, Cr, and Pb (HQing > 1) emerged as the most important pollutants leading to noncarcinogenic concerns via ingestion route, whereas there was no risk via dermal contact of surface water. This study helps in establishing pollutant loading reduction goal and the total maximum daily loads, and consequently contributes to preserve public health and develop water conservation strategy. PMID:24744690

  15. Dissolved Trace Metals in the Tay Estuary

    NASA Astrophysics Data System (ADS)

    Owens, R. E.; Balls, P. W.

    1997-04-01

    Dissolved trace metals have been studied over an annual cycle in the relatively pristine Tay estuary (Scotland). The absence of a major anthropogenic signal has enabled some of the more subtle natural processes controlling trace metal distributions to be identified. Concentration ranges of dissolved metals in the Tay are similar to, or lower than, those observed in more industrialized estuaries. All metals behave non-conservatively in the Tay. Interactions with biogenic and detrital particulate phases are important in controlling dissolved trace metal concentrations. The degradation of organic matter appears to be particularly important for Cu. Removal of dissolved metals was observed in the turbidity maximum zone; a simple model was used to demonstrate that this could be accounted for by adsorption onto suspended particulate matter. At high salinity, coincident peaks of all six metals with ammonia and phosphate are attributed to sewage inputs from Dundee at the mouth of the estuary.

  16. Dissolved Trace Metal Concentrations over the Peru Shelf and in the Subsurface Oxygen Minimum Zone Off Peru

    NASA Astrophysics Data System (ADS)

    Parker, C.; Bruland, K. W.

    2014-12-01

    The Peru coast is the site of one of the largest fisheries in the world, and home to some of the highest f-ratios ever recorded. As a result of this highly productive surface water, an intense subsurface oxygen minimum zone (OMZ) persists. Despite the import of the effect of OMZs due to their predicted increase with global warming, there is very little trace metal data from this region. Here we present dissolved trace metal data from the U.S. GEOTRACES Eastern Pacific Zonal Transect over the Peru shelf and through the OMZ. Results suggest a sink of Pb, Cd, Sc, Cu and Ga in the suboxic region of the shelf, and a shelf source of Co and Fe. Trace metal concentrations within the OMZ will also be discussed. As many of these metals have not been analyzed in this region previously, this work can serve as a baseline for future comparison and adds to the understanding of global trace metal distributions.

  17. Dissolved heavy metal concentrations of the Kralkızı, Dicle and Batman dam reservoirs in the Tigris River basin, Turkey.

    PubMed

    Varol, Memet

    2013-10-01

    Water samples were collected at monthly intervals during 1 year of monitoring from Kralkızı, Dicle and Batman dam reservoirs in the Tigris River basin to assess the concentrations of dissolved heavy metals and to determine their spatial and seasonal variations. The results indicated that dissolved heavy metal concentrations in the reservoirs were very low, reflecting the natural background levels. The lowest total metal concentrations in the three dam reservoirs were detected at sampling sites close to the dam wall. However, the highest total concentrations were observed at sites, which are located at the entrance of the streams to the reservoirs. Fe, Cr and Ni were the most abundant elements in the reservoirs, whereas Cd and As were the less abundant. The mean concentrations of dissolved metals in the dam reservoirs never exceeded the maximum permitted concentrations established by EC (European Community), WHO and USEPA drinking water quality guidelines. All heavy metals showed significant seasonal variations. As, Cd, Cr, Cu, Fe, Ni and Pb displayed higher values in the dry season, while higher values for Zn in the wet season. Cluster analysis grouped all ten sampling sites into three clusters. Clusters 1 and 2, and cluster 3 corresponded to relatively low polluted and moderate polluted regions, respectively. PCA/FA demonstrated the dissolved metals in the dam reservoirs controlled by natural sources.

  18. Impacts of dust deposition on dissolved trace metal concentrations (Mn, Al and Fe) during a mesocosm experiment

    NASA Astrophysics Data System (ADS)

    Wuttig, K.; Wagener, T.; Bressac, M.; Dammshäuser, A.; Streu, P.; Guieu, C.; Croot, P. L.

    2013-04-01

    The deposition of atmospheric dust is the primary process supplying trace elements abundant in crustal rocks (e.g. Al, Mn and Fe) to the surface ocean. Upon deposition, the residence time in surface waters for each of these elements differs according to their chemical speciation and biological utilization. Presently, however, the chemical and physical processes occurring after atmospheric deposition are poorly constrained, principally because of the difficulty in following natural dust events in situ. In the present work we examined the temporal changes in the biogeochemistry of crustal metals (in particular Al, Mn and Fe) after an artificial dust deposition event. The experiment was contained inside trace metal clean mesocosms (0-12.5 m depths) deployed in the surface waters of the northwestern Mediterranean, close to the coast of Corsica within the frame of the DUNE project (a DUst experiment in a low Nutrient, low chlorophyll Ecosystem). Two consecutive artificial dust deposition events, each mimicking a wet deposition of 10 g m-2 of dust, were performed during the course of this DUNE-2 experiment. The changes in dissolved manganese (Mn), iron (Fe) and aluminum (Al) concentrations were followed immediately after the seeding with dust and over the following week. The Mn, Fe and Al inventories and loss or dissolution rates were determined. The evolution of the inventories after the two consecutive additions of dust showed distinct behaviors for dissolved Mn, Al and Fe. Even though the mixing conditions differed from one seeding to the other, Mn and Al showed clear increases directly after both seedings due to dissolution processes. Three days after the dust additions, Al concentrations decreased as a consequence of scavenging on sinking particles. Al appeared to be highly affected by the concentrations of biogenic particles, with an order of magnitude difference in its loss rates related to the increase of biomass after the addition of dust. In the case of

  19. Assessing the concentration, speciation, and toxicity of dissolved metals during mixing of acid-mine drainage and ambient river water downstream of the Elizabeth Copper Mine, Vermont, USA

    USGS Publications Warehouse

    Balistrieri, L.S.; Seal, R.R.; Piatak, N.M.; Paul, B.

    2007-01-01

    The authors determine the composition of a river that is impacted by acid-mine drainage, evaluate dominant physical and geochemical processes controlling the composition, and assess dissolved metal speciation and toxicity using a combination of laboratory, field and modeling studies. Values of pH increase from 3.3 to 7.6 and the sum of dissolved base metal (Cd + Co + Cu + Ni + Pb + Zn) concentrations decreases from 6270 to 100 ??g/L in the dynamic mixing and reaction zone that is downstream of the river's confluence with acid-mine drainage. Mixing diagrams and PHREEQC calculations indicate that mixing and dilution affect the concentrations of all dissolved elements in the reach, and are the dominant processes controlling dissolved Ca, K, Li, Mn and SO4 concentrations. Additionally, dissolved Al and Fe concentrations decrease due to mineral precipitation (gibbsite, schwertmannite and ferrihydrite), whereas dissolved concentrations of Cd, Co, Cu, Ni, Pb and Zn decrease due to adsorption onto newly formed Fe precipitates. The uptake of dissolved metals by aquatic organisms is dependent on the aqueous speciation of the metals and kinetics of complexation reactions between metals, ligands and solid surfaces. Dissolved speciation of Cd, Cu, Ni and Zn in the mixing and reaction zone is assessed using the diffusive gradients in thin films (DGT) technique and results of speciation calculations using the Biotic Ligand Model (BLM). Data from open and restricted pore DGT units indicate that almost all dissolved metal species are inorganic and that aqueous labile or DGT available metal concentrations are generally equal to total dissolved concentrations in the mixing zone. Exceptions occur when labile metal concentrations are underestimated due to competition between H+ and metal ions for Chelex-100 binding sites in the DGT units at low pH values. Calculations using the BLM indicate that dissolved Cd and Zn species in the mixing and reaction zone are predominantly inorganic

  20. Dissolved metal concentrations in surface waters from west-central Indiana contaminated with acidic mine drainage

    SciTech Connect

    Allen, S.K.; Allen, J.M.; Lucas, S.

    1996-02-01

    A significant amount of coal mining activity in the west-central region of Indiana, has resulted in a large number of sites where surface waters are contaminated with acidic mine drainage (AMD). Contamination of drinking and irrigation water supplies is of concern mainly due to elevated levels of toxic metals. Abandoned mine sites are frequently located near occupied houses and farms in rural areas. Consequently, constituents of surface waters contaminated by AMD have the potential to be transported into sub-surface drinking water wells and irrigation water supplies. The extent of surface water contamination in west-central Indiana by AMID is not well characterized. For this reason, samples of surface waters that are contaminated with AMD were collected from a wide variety of locations in west-central Indiana and subjected to metals analysis.

  1. Impacts of dust deposition on dissolved trace metal concentrations (Mn, Al and Fe) during a mesocosm experiment

    NASA Astrophysics Data System (ADS)

    Wuttig, K.; Wagener, T.; Bressac, M.; Dammshäuser, A.; Streu, P.; Guieu, C.; Croot, P. L.

    2012-10-01

    The deposition of atmospheric dust is the primary process supplying trace elements abundant in crustal rocks (e.g. Al, Mn and Fe) to the surface ocean. Upon deposition, the residence time in surface waters for each of these elements differs according to their chemical speciation and biological utilization. Presently however their behavior after atmospheric deposition is poorly constrained, principally because of the difficulty in following natural dust events in-situ. In the present work we examined the temporal changes in the biogeochemistry of crustal metals (in particular Al, Mn and Fe) after an artificial dust deposition event. The experiment was contained inside trace metal clean mesocosms (0-12.5 m depths) deployed in the surface waters of the Northwestern Mediterranean, close to the coast of Corsica in the frame of the DUNE project (a DUst experiment in a low Nutrient low chlorophyll Ecosystem). Two consecutive artificial dust deposition events, each mimicking a wet deposition of 10 g m-2 of dust, were performed during the course of this DUNE-2 experiment. The changes in dissolved manganese (dMn), iron (dFe) and aluminium (dAl) concentrations were followed immediately and over the following week and their inventories and loss or dissolution rates were determined. The evolution of the inventories after the two consecutive additions of dust showed distinct behaviors for dMn, dAl and dFe. Even though the mixing conditions differed from one seeding to the other, dMn and dAl showed clear increases directly after both seedings due to dissolution processes. Three days after the dust additions, dAl concentrations decreased as a consequence of scavenging on sinking particles. dAl appeared to be highly affected by the concentrations of biogenic particles, with an order of magnitude difference in its loss rates related to the increase of biomass after the addition of dust. For dFe concentrations, the first dust addition decreased the concentrations through scavenging

  2. Contribution of groundwater discharge to the coastal dissolved nutrients and trace metal concentrations in Majorca Island: karstic vs detrital systems.

    PubMed

    Tovar-Sánchez, Antonio; Basterretxea, Gotzon; Rodellas, Valentí; Sánchez-Quiles, David; García-Orellana, Jordi; Masqué, Pere; Jordi, Antoni; López, José M; Garcia-Solsona, Ester

    2014-10-21

    Submarine groundwater discharge (SGD) and derived nutrient (NO2(-), NO3(-), NH4(+), PO4(3-), and SiO2) and trace element (Cd, Co, Cu, Fe, Mo, Ni, Pb, V and Zn) loadings to the coastal sea were systematically assessed along the coast of Majorca Island, Spain, in a general survey around the island and in three representative coves during 2010. We estimated that brackish water discharges through the shoreline are important contributors to the DIN, SiO2, Fe, and Zn budgets of the nearshore waters. Furthermore, our results showed that SGD-derived elements are conditioned by the hydrogeological formations of the aquifer and discharge type. Thus, while rapid discharges through karstic conduits are enriched in SiO2 and Zn, the large detrital aquifers of the island typically present enhanced concentrations of Fe. The estimated total annual inputs of chemicals constituents discharged by SGD to the coastal waters were as follows: DIN: 610 × 10(3) kg yr(-1), SiO2: 1400 × 10(3) kg yr(-1), Fe: 3.2 × 10(3) kg yr(-1), and Zn: 2.0 × 10(3) kg yr(-1). Our results provide evidence that SGD is a major contributor to the dissolved pool of inorganic nutrients and trace metals in the nearshore waters of Majorca.

  3. Diurnal variations in, and influences on, concentrations of particulate and dissolved arsenic and metals in the mildly alkaline Wallkill River, New Jersey, USA

    USGS Publications Warehouse

    Barringer, J.L.; Wilson, T.P.; Szabo, Z.; Bonin, J.L.; Fischer, J.M.; Smith, N.P.

    2008-01-01

    Diurnal variations in particulate and dissolved As and metal concentrations were observed in mildly alkaline water from a wetlands site on the Wallkill River in northwestern New Jersey. The site, underlain by glacial sediments over dolomite bedrock, is 10 km downstream from a mined area of the Franklin Marble, host to Zn ores, also As and Mn minerals. In mid-September 2005, maxima and minima in dissolved-oxygen-concentration and pH, typically caused by photosynthesis and respiration, occurred at 2000 and 0800 hours. Concentrations of dissolved As (1.52-1.95 ??g/L) peaked at dusk (2000 hours), whereas dissolved Mn and Zn concentrations (76.5-96.9 and 8.55-12.8 ??g/L, respectively) were lowest at dusk and peaked at 1000 hours. These opposing cycles probably reflect sorption and desorption of As (an anion), and Mn and Zn (cations) as pH varied throughout the 24-h period. Doubly-peaked cycles of B, Cl, SO4, and nutrients also were observed; these may result from upstream discharges of septic-system effluent. Both recoverable amd particulate Al, Fe, Mn, and Zn concentrations peaked between 0200 and 0600 hours. The particulate metals cycle, with perturbations at 0400 hours, may be influenced by biological activity. ?? 2007 Springer-Verlag.

  4. Dissolved metals and associated constituents in abandoned coal-mine discharges, Pennsylvania, USA. Part 2: Geochemical controls on constituent concentrations

    USGS Publications Warehouse

    Cravotta, C.A.

    2008-01-01

    Water-quality data for discharges from 140 abandoned mines in the Anthracite and Bituminous Coalfields of Pennsylvania reveal complex relations among the pH and dissolved solute concentrations that can be explained with geochemical equilibrium models. Observed values of pH ranged from 2.7 to 7.3 in the coal-mine discharges (CMD). Generally, flow rates were smaller and solute concentrations were greater for low-pH CMD samples; pH typically increased with flow rate. Although the frequency distribution of pH was similar for the anthracite and bituminous discharges, the bituminous discharges had smaller median flow rates; greater concentrations of SO4, Fe, Al, As, Cd, Cu, Ni and Sr; comparable concentrations of Mn, Cd, Zn and Se; and smaller concentrations of Ba and Pb than anthracite discharges with the same pH values. The observed relations between the pH and constituent concentrations can be attributed to (1) dilution of acidic water by near-neutral or alkaline ground water; (2) solubility control of Al, Fe, Mn, Ba and Sr by hydroxide, sulfate, and/or carbonate minerals; and (3) aqueous SO4-complexation and surface-complexation (adsorption) reactions. The formation of AlSO4+ and AlHSO42 + complexes adds to the total dissolved Al concentration at equilibrium with Al(OH)3 and/or Al hydroxysulfate phases and can account for 10-20 times greater concentrations of dissolved Al in SO4-laden bituminous discharges compared to anthracite discharges at pH of 5. Sulfate complexation can also account for 10-30 times greater concentrations of dissolved FeIII concentrations at equilibrium with Fe(OH)3 and/or schwertmannite (Fe8O8(OH)4.5(SO4)1.75) at pH of 3-5. In contrast, lower Ba concentrations in bituminous discharges indicate that elevated SO4 concentrations in these CMD sources could limit Ba concentrations by the precipitation of barite (BaSO4). Coprecipitation of Sr with barite could limit concentrations of this element. However, concentrations of dissolved Pb, Cu, Cd, Zn

  5. Influence of in-stream diel concentration cycles of dissolved trace metals on acute toxicity to one-year-old cutthroat trout (Oncorhynchus clarki lewisi)

    USGS Publications Warehouse

    Nimick, D.A.; Harper, D.D.; Farag, A.M.; Cleasby, T.E.; MacConnell, Elizabeth; Skaar, D.

    2007-01-01

    Extrapolating results of laboratory bioassays to streams is difficult, because conditions such as temperature and dissolved metal concentrations can change substantially on diel time scales. Field bioassays conducted for 96 h in two mining-affected streams compared the survival of hatchery-raised, metal-nai??ve westslope cutthroat trout (Oncorhynchus clarki lewisi) exposed to dissolved (0.1-??m filtration) metal concentrations that either exhibited the diel variation observed in streams or were controlled at a constant value. Cadmium and Zn concentrations in these streams increased each night by as much as 61 and 125%, respectively, and decreased a corresponding amount the next day, whereas Cu did not display a diel concentration cycle. In High Ore Creek (40 km south of Helena, MT, USA), survival (33%) after exposure to natural diel-fluctuating Zn concentrations (range, 214-634 ??g/L; mean, 428 ??g/L) was significantly (p = 0.008) higher than survival (14%) after exposure to a controlled, constant Zn concentration (422 ??g/L). Similarly, in Dry Fork Belt Creek (70 km southeast of Great Falls, MT, USA), survival (75%) after exposure to diel-fluctuating Zn concentrations (range, 266-522 ??g/L; mean, 399 ??g/L) was significantly (p = 0.022) higher than survival (50%) in the constant-concentration treatment (392 ??g/L). Survival likely was greater in these diel treatments, both because the periods of lower metal concentrations provided some relief for the fish and because toxicity during periods of higher metal concentrations was lessened by the simultaneous occurrence each night of lower water temperatures, which reduce the rate of metal uptake. Based on the present study, current water-quality criteria appear to be protective for streams with diel concentration cycles of Zn (and, perhaps, Cd) for the hydrologie conditions tested. ?? 2007 SETAC.

  6. Influence of in-stream diel concentration cycles of dissolved trace metals on acute toxicity to one-year-old cutthroat trout (Oncorhynchus clarki lewisi).

    PubMed

    Nimick, David A; Harper, David D; Farag, Aïda M; Cleasby, Thomas E; MacConnell, Elizabeth; Skaar, Don

    2007-12-01

    Extrapolating results of laboratory bioassays to streams is difficult, because conditions such as temperature and dissolved metal concentrations can change substantially on diel time scales. Field bioassays conducted for 96 h in two mining-affected streams compared the survival of hatchery-raised, metal-naïve westslope cutthroat trout (Oncorhynchus clarki lewisi) exposed to dissolved (0.1-microm filtration) metal concentrations that either exhibited the diel variation observed in streams or were controlled at a constant value. Cadmium and Zn concentrations in these streams increased each night by as much as 61 and 125%, respectively, and decreased a corresponding amount the next day, whereas Cu did not display a diel concentration cycle. In High Ore Creek (40 km south of Helena, MT, USA), survival (33%) after exposure to natural diel-fluctuating Zn concentrations (range, 214-634 microg/L; mean, 428 microg/L) was significantly (p = 0.008) higher than survival (14%) after exposure to a controlled, constant Zn concentration (422 microg/L). Similarly, in Dry Fork Belt Creek (70 km southeast of Great Falls, MT, USA), survival (75%) after exposure to diel-fluctuating Zn concentrations (range, 266-522 microg/L; mean, 399 microg/L) was significantly (p = 0.022) higher than survival (50%) in the constant-concentration treatment (392 microg/L). Survival likely was greater in these diel treatments, both because the periods of lower metal concentrations provided some relief for the fish and because toxicity during periods of higher metal concentrations was lessened by the simultaneous occurrence each night of lower water temperatures, which reduce the rate of metal uptake. Based on the present study, current water-quality criteria appear to be protective for streams with diel concentration cycles of Zn (and, perhaps, Cd) for the hydrologic conditions tested.

  7. Chemical characteristics of dissolved organic matter (DOM) in relation to heavy metal concentrations in soil water from boreal peatlands after clear-cut harvesting

    NASA Astrophysics Data System (ADS)

    Kiikkilä, O.; Nieminen, T.; Starr, M.; Ukonmaanaho, L.

    2012-04-01

    Boreal peatlands form an important terrestrial carbon reserve and are a major source of dissolved organic matter (DOM) to surface waters, particularly when disturbed through forestry practices such as draining or timber harvesting. Heavy metals show a strong affinity to organic matter and so, along with DOM, heavy metals can be mobilized and transported from the soil to surface waters and sediments where they may become toxic to aquatic organisms and pass up the food chain. The complexation of heavy metals with DOM can be expected to be related and determined by the chemical characteristics of DOM and oxidation/reducing conditions in the peat. We extracted interstitial water from peat samples and determined the concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and Al, Cu, Zn and Fe in various fractions of DOM isolated by adsorption properties (XAD-8 fractionation) and molecular-weight (ultrafiltration). The peat samples were taken from 0-30 and 30-50 cm depth in drained peatland catchments two years after whole-tree or stem-only clear-cut harvesting (Scots pine or Norway spruce) had been carried out. The samples from the upper layer had been subject to alternating saturation/aeration conditions while the deeper layer had been continuously under the water table. The fractionation of DOC and DON according to both adsorption properties and molecular-weight fractions clearly differed between the upper and lower peat layers. While the hydrophobic acid fraction contained proportionally more DOC and DON than the hydrophilic acid fraction in the upper peat layer the results were vice versa in the lower peat layer. High-molecular-weight compounds (> 100 kDa) were proportionally more abundant in the upper and low-molecular-weight compounds (< 1 kDa) in the lower peat layer. These differences are assumed to reflect differences in the aerobic/ anaerobic conditions and degree of decomposition between the two layers. The concentrations of Zn, Al

  8. Cellular partitioning of nanoparticulate versus dissolved metals in marine phytoplankton.

    PubMed

    Bielmyer-Fraser, Gretchen K; Jarvis, Tayler A; Lenihan, Hunter S; Miller, Robert J

    2014-11-18

    Discharges of metal oxide nanoparticles into aquatic environments are increasing with their use in society, thereby increasing exposure risk for aquatic organisms. Separating the impacts of nanoparticle from dissolved metal pollution is critical for assessing the environmental risks of the rapidly growing nanomaterial industry, especially in terms of ecosystem effects. Metal oxides negatively affect several species of marine phytoplankton, which are responsible for most marine primary production. Whether such toxicity is generally due to nanoparticles or exposure to dissolved metals liberated from particles is uncertain. The type and severity of toxicity depends in part on whether phytoplankton cells take up and accumulate primarily nanoparticles or dissolved metal ions. We compared the responses of the marine diatom, Thalassiosira weissflogii, exposed to ZnO, AgO, and CuO nanoparticles with the responses of T. weissflogii cells exposed to the dissolved metals ZnCl2, AgNO3, and CuCl2 for 7 d. Cellular metal accumulation, metal distribution, and algal population growth were measured to elucidate differences in exposure to the different forms of metal. Concentration-dependent metal accumulation and reduced population growth were observed in T. weissflogii exposed to nanometal oxides, as well as dissolved metals. Significant effects on population growth were observed at the lowest concentrations tested for all metals, with similar toxicity for both dissolved and nanoparticulate metals. Cellular metal distribution, however, markedly differed between T. weissflogii exposed to nanometal oxides versus those exposed to dissolved metals. Metal concentrations were highest in the algal cell wall when cells were exposed to metal oxide nanoparticles, whereas algae exposed to dissolved metals had higher proportions of metal in the organelle and endoplasmic reticulum fractions. These results have implications for marine plankton communities as well as higher trophic levels, since

  9. Time series models for prediction the total and dissolved heavy metals concentration in road runoff and soil solution of roadside embankments

    NASA Astrophysics Data System (ADS)

    Aljoumani, Basem; Kluge, Björn; sanchez, Josep; Wessolek, Gerd

    2017-04-01

    Highways and main roads are potential sources of contamination for the surrounding environment. High traffic rates result in elevated heavy metal concentrations in road runoff, soil and water seepage, which has attracted much attention in the recent past. Prediction of heavy metals transfer near the roadside into deeper soil layers are very important to prevent the groundwater pollution. This study was carried out on data of a number of lysimeters which were installed along the A115 highway (Germany) with a mean daily traffic of 90.000 vehicles per day. Three polyethylene (PE) lysimeters were installed at the A115 highway. They have the following dimensions: length 150 cm, width 100 cm, height 60 cm. The lysimeters were filled with different soil materials, which were recently used for embankment construction in Germany. With the obtained data, we will develop a time series analysis model to predict total and dissolved metal concentration in road runoff and in soil solution of the roadside embankments. The time series consisted of monthly measurements of heavy metals and was transformed to a stationary situation. Subsequently, the transformed data will be used to conduct analyses in the time domain in order to obtain the parameters of a seasonal autoregressive integrated moving average (ARIMA) model. Four phase approaches for identifying and fitting ARIMA models will be used: identification, parameter estimation, diagnostic checking, and forecasting. An automatic selection criterion, such as the Akaike information criterion, will use to enhance this flexible approach to model building

  10. TOTAL DISSOLVED AND BIOAVAILABLE METALS AT LAKE TEXOMA MARINAS

    EPA Science Inventory

    Dissolved metals in water and total metals in sediments have been measured at marina areas in Lake Texoma during June 1999 to October 2001, and October 2001, respectively. The metals most often found in the highest concentrations in marina water were Na and Ca, followed by Mg an...

  11. TOTAL DISSOLVED AND BIOAVAILABLE METALS AT LAKE TEXOMA MARINAS

    EPA Science Inventory

    Dissolved metals in water and total metals in sediments have been measured at marina areas in Lake Texoma during June 1999 to October 2001, and October 2001, respectively. The metals most often found in the highest concentrations in marina water were Na and Ca, followed by Mg an...

  12. Summary of Dissolved Concentration Limits

    SciTech Connect

    Yueting Chen

    2001-06-11

    According to the Technical Work Plan titled Technical Work Plan for Waste Form Degradation Process Model Report for SR (CRWMS M&O 2000a), the purpose of this study is to perform abstractions on solubility limits of radioactive elements based on the process-level information and thermodynamic databases provided by Natural Environment Program Operations (NEPO) and Waste Package Operations (WPO). The scope of this analysis is to produce solubility limits as functions, distributions, or constants for all transported radioactive elements identified by the Performance Assessment Operations (PAO) radioisotope screening. Results from an expert elicitation for solubility limits of most radioactive elements were used in the previous Total System Performance Assessments (TSPAs). However, the elicitation conducted in 1993 does not meet the criteria set forth by the U.S. Nuclear Regulatory Commission (NRC) due to lack of documentation and traceability (Kotra et al. 1996, Section 3). Therefore, at the Waste Form Abstraction Workshop held on February 2-4, 1999, at Albuquerque, New Mexico, the Yucca Mountain Site Characterization Project (YMP) decided to develop geochemical models to study solubility for the proposed Monitored Geologic Repository. WPO/NEPO is to develop process-level solubility models, including review and compilation of relevant thermodynamic data. PAO's responsibility is to perform abstractions based on the process models and chemical conditions and to produce solubility distributions or response surfaces applicable to the proposed repository. The results of this analysis and conceptual model will feed the performance assessment for Total System Performance Assessment--Site Recommendation (TSPA-SR) and Total System Performance Assessment--License Application (TSPA-LA), and to the Waste Form Degradation Process Model Report section on concentration limits.

  13. Mercury, monomethyl mercury, and dissolved organic carbon concentrations in surface water entering and exiting constructed wetlands treated with metal-based coagulants, Twitchell Island, California

    USGS Publications Warehouse

    Stumpner, Elizabeth B.; Kraus, Tamara E.C.; Fleck, Jacob A.; Hansen, Angela M.; Bachand, Sandra M.; Horwath, William R.; DeWild, John F.; Krabbenhoft, David P.; Bachand, Philip A.M.

    2015-09-02

    Following coagulation, but prior to passage through the wetland cells, coagulation treatments transferred dissolved mercury and carbon to the particulate fraction relative to untreated source water: at the wetland cell inlets, the coagulation treatments decreased concentrations of filtered total mercury by 59–76 percent, filtered monomethyl mercury by 40–70 percent, and dissolved organic carbon by 65–86 percent. Passage through the wetland cells decreased the particulate fraction of mercury in wetland cells that received coagulant-treated water. Changes in total mercury, monomethyl mercury, and dissolved organic carbon concentrations resulting from wetland passage varied both by treatment and season. Despite increased monomethyl mercury in the filtered fraction during wetland passage between March and August, the coagulation-wetland systems generally decreased total mercury (filtered plus particulate) and monomethyl mercury (filtered plus particulate) concentrations relative to source water. Coagulation—either alone or in association with constructed wetlands—could be an effective way to decrease concentrations of mercury and dissolved organic carbon in surface water as well as the bioavailability of mercury in the Sacramento–San Joaquin Delta.

  14. Fluctuation of dissolved heavy metal concentrations in the leachate from anaerobic digestion of municipal solid waste in commercial scale landfill bioreactors: The effect of pH and associated mechanisms.

    PubMed

    Xie, S; Ma, Y; Strong, P J; Clarke, W P

    2015-12-15

    Heavy metals present in landfill leachate have infrequently been related to complete anaerobic degradation municipal solid waste (MSW) due to discrete ages of deposited MSW layers and leachate channelling in landfills. In this study, anaerobic digestion of MSW was performed in two enclosed 1000 tonne bioreactors using a unique flood and drain process. Leachates were characterised in terms of pH, soluble chemical oxygen demand, volatile fatty acids (VFAs), ammonium nitrogen and heavy metals over the entire course of digestion. All parameters, including pH, fluctuated during acidogenesis, acetogenesis and methanogenesis, which strongly impacted on the dynamics of dissolved heavy metal concentrations. The simulation of dissolution and precipitation processes indicated that metal sulphide precipitation was not a factor as metal concentrations exceeded solubility limits. The correlation of pH and dissolved heavy metal concentrations indicated that other, mechanisms were involved in the homogenised conditions within the bioreactors. Beside dissolution and precipitation, the main processes most likely involved in metal distributions were adsorption (Zn, Cu, Ni, Pb and Cd), complexation (Cr) or combinations of both process (As and Co).

  15. DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS

    SciTech Connect

    NA

    2004-11-22

    The purpose of this study is to evaluate dissolved concentration limits (also referred to as solubility limits) of elements with radioactive isotopes under probable repository conditions, based on geochemical modeling calculations using geochemical modeling tools, thermodynamic databases, field measurements, and laboratory experiments. The scope of this modeling activity is to predict dissolved concentrations or solubility limits for 14 elements with radioactive isotopes (actinium, americium, carbon, cesium, iodine, lead, neptunium, plutonium, protactinium, radium, strontium, technetium, thorium, and uranium) important to calculated dose. Model outputs for uranium, plutonium, neptunium, thorium, americium, and protactinium are in the form of tabulated functions with pH and log (line integral) CO{sub 2} as independent variables, plus one or more uncertainty terms. The solubility limits for the remaining elements are either in the form of distributions or single values. The output data from this report are fundamental inputs for Total System Performance Assessment for the License Application (TSPA-LA) to determine the estimated release of these elements from waste packages and the engineered barrier system. Consistent modeling approaches and environmental conditions were used to develop solubility models for all of the actinides. These models cover broad ranges of environmental conditions so that they are applicable to both waste packages and the invert. Uncertainties from thermodynamic data, water chemistry, temperature variation, and activity coefficients have been quantified or otherwise addressed.

  16. DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS

    SciTech Connect

    P. Bernot

    2005-07-13

    The purpose of this study is to evaluate dissolved concentration limits (also referred to as solubility limits) of elements with radioactive isotopes under probable repository conditions, based on geochemical modeling calculations using geochemical modeling tools, thermodynamic databases, field measurements, and laboratory experiments. The scope of this activity is to predict dissolved concentrations or solubility limits for elements with radioactive isotopes (actinium, americium, carbon, cesium, iodine, lead, neptunium, plutonium, protactinium, radium, strontium, technetium, thorium, and uranium) relevant to calculated dose. Model outputs for uranium, plutonium, neptunium, thorium, americium, and protactinium are provided in the form of tabulated functions with pH and log fCO{sub 2} as independent variables, plus one or more uncertainty terms. The solubility limits for the remaining elements are either in the form of distributions or single values. Even though selection of an appropriate set of radionuclides documented in Radionuclide Screening (BSC 2002 [DIRS 160059]) includes actinium, transport of Ac is not modeled in the total system performance assessment for the license application (TSPA-LA) model because of its extremely short half-life. Actinium dose is calculated in the TSPA-LA by assuming secular equilibrium with {sup 231}Pa (Section 6.10); therefore, Ac is not analyzed in this report. The output data from this report are fundamental inputs for TSPA-LA used to determine the estimated release of these elements from waste packages and the engineered barrier system. Consistent modeling approaches and environmental conditions were used to develop solubility models for the actinides discussed in this report. These models cover broad ranges of environmental conditions so they are applicable to both waste packages and the invert. Uncertainties from thermodynamic data, water chemistry, temperature variation, and activity coefficients have been quantified or

  17. Dissolved Concentration Limits of Radioactive Elements

    SciTech Connect

    Y. Chen; E.R. Thomas; F.J. Pearson; P.L. Cloke; T.L. Steinborn; P.V. Brady

    2003-06-20

    The purpose of this study is to evaluate dissolved concentration limits (also referred to as solubility limits) of radioactive elements under possible repository conditions, based on geochemical modeling calculations using geochemical modeling tools, thermodynamic databases, and measurements made in laboratory experiments and field work. The scope of this modeling activity is to predict dissolved concentrations or solubility limits for 14 radioactive elements (actinium, americium, carbon, cesium, iodine, lead, neptunium, plutonium, protactinium, radium, strontium, technetium, thorium, and uranium), which are important to calculated dose. Model outputs are mainly in the form of look-up tables plus one or more uncertainty terms. The rest are either in the form of distributions or single values. The results of this analysis are fundamental inputs for total system performance assessment to constrain the release of these elements from waste packages and the engineered barrier system. Solubilities of plutonium, neptunium, uranium, americium, actinium, thorium, protactinium, lead, and radium have been re-evaluated using the newly updated thermodynamic database (Data0.ymp.R2). For all of the actinides, identical modeling approaches and consistent environmental conditions were used to develop solubility models in this revision. These models cover broad ranges of environmental conditions so that they are applicable to both waste packages and the invert. Uncertainties from thermodynamic data, water chemistry, temperature variation, activity coefficients, and selection of solubility controlling phase have been quantified or otherwise addressed. Moreover, a new blended plutonium solubility model has been developed in this revision, which gives a mean solubility that is three orders of magnitude lower than the plutonium solubility model used for the Total System Performance Assessment for the Site Recommendation. Two alternative neptunium solubility models have also been

  18. An advanced passive diffusion sampler for the determination of dissolved gas concentrations

    NASA Astrophysics Data System (ADS)

    Gardner, P.; Solomon, D. K.

    2009-06-01

    We have designed and tested a passive headspace sampler for the collection of noble gases that allows for the precise calculation of dissolved gas concentrations from measured gas mixing ratios. Gas permeable silicon tubing allows for gas exchange between the headspace in the sampler volume and the dissolved gases in the adjacent water. After reaching equilibrium, the aqueous-phase concentration is related to the headspace concentration by Henry's law. Gas exchange between the water and headspace can be shut off in situ, preserving the total dissolved gas pressure upon retrieval. Gas samples are then sealed in an all metal container, retaining even highly mobile helium. Dissolved noble gas concentrations measured in these diffusion samplers are in good agreement with traditional copper tube aqueous-phase samples. These significantly reduce the laboratory labor in extracting the gases from a water sample and provide a simple and robust method for collecting dissolved gas concentrations in a variety of aqueous environments.

  19. The seasonal influence on the spatial distribution of dissolved selected metals in Lake Naivasha, Kenya

    NASA Astrophysics Data System (ADS)

    Kamau, Joseph Nyingi; Gachanja, Anthony; Ngila, Catherine; Kazungu, Johnson Michael; Zhai, Mingzhe

    Lake Naivasha is the only freshwater Lake in Rift Valley, in Kenya. It lies in a fertile semi-arid basin. The Lake has no surface water outlet and is presumed to be under stress. Dissolved metals are directly taken up by bacteria, algae, plants, and planktonic and benthic organisms. Dissolved metals can also adsorb to particulate matter in water column and enter aquatic organisms through various routes. Cadmium, copper, lead and zinc may bioaccumulate within lower organisms, yet they do not biomagnify up the food chain as do mercury and selenium. This study reports on the levels and distribution of dissolved heavy metals and investigates the influence of physicochemical parameters on metal mobilization. The bioavailability of selected metals was investigated by relating the levels of dissolved metals to that in fish. Water abstraction for irrigation and domestic use, compounded with organic matter inflow will affect physicochemical parameters and hence influences the mobilization of heavy metals. Dissolved Zn correlated highly with sediment pH (r = 0.67) indicating that dissolution increases with increase in pH. In addition, the fact that the pH also correlated positively with organic matter r = 0.50, Eh r = 0.63, temperature r = 0.56 and dissolved oxygen r = 56, would suggest that organic bound Zn contributed significantly to the concentration of dissolved Zn. In situ flux experiments indicated that the fringing papyrus reeds located along the shores of Lake Naivasha provided sites for metal immobilization due to their coprecipitation on redox sensitive.

  20. The effect of membrane filtration on dissolved trace element concentrations

    USGS Publications Warehouse

    Horowitz, A.J.; Lum, K.R.; Garbarino, J.R.; Hall, G.E.M.; Lemieux, C.; Demas, C.R.

    1996-01-01

    The almost universally accepted operational definition for dissolved constituents is based on processing whole-water samples through a 0.45-??m membrane filter. Results from field and laboratory experiments indicate that a number of factors associated with filtration, other than just pore size (e.g., diameter, manufacturer, volume of sample processed, amount of suspended sediment in the sample), can produce substantial variations in the 'dissolved' concentrations of such elements as Fe, Al, Cu, Zn, Pb, Co, and Ni. These variations result from the inclusion/exclusion of colloidally- associated trace elements. Thus, 'dissolved' concentrations quantitated by analyzing filtrates generated by processing whole-water through similar pore- sized membrane filters may not be equal/comparable. As such, simple filtration through a 0.45-??m membrane filter may no longer represent an acceptable operational definition for dissolved chemical constituents. This conclusion may have important implications for environmental studies and regulatory agencies.

  1. Effect of membrane filtration artifacts on dissolved trace element concentrations

    USGS Publications Warehouse

    Horowitz, Arthur J.; Elrick, Kent A.; Colberg, Mark R.

    1992-01-01

    Among environment scientists, the current and almost universally accepted definition of dissolved constituents is an operational one; only those materials which pass through a 0.45-??m membrane filter are considered to be dissolved. Detailed laboratory and field studies on Fe and Al indicate that a number of factors associated with filtration, other than just pore size, can substantially alter 'dissolved' trace element concentrations; these include: filter type, filter diameter, filtration method, volume of sample processed, suspended sediment concentration, suspended sediment grain-size distribution, concentration of colloids and colloidally associated trace elements and concentration of organic matter. As such, reported filtered-water concentrations employing the same pore size filter may not be equal. Filtration artifacts may lead to the production of chemical data that indicate seasonal or annual 'dissolved' chemical trends which do not reflect actual environmental conditions. Further, the development of worldwide averages for various dissolved chemical constituents, the quantification of geochemical cycles, and the determination of short- or long-term environmental chemical trends may be subject to substantial errors, due to filtration artifacts, when data from the same or multiple sources are combined. Finally, filtration effects could have a substantial impact on various regulatory requirements.

  2. Dissolved oxygen concentration affects hybrid striped bass growth

    USDA-ARS?s Scientific Manuscript database

    Management of dissolved oxygen (DO) concentration in ponds at night during the growing season is important because fish growth and yield are greater in ponds with higher nightly DO concentrations. Three studies were conducted to quantify performance traits and metabolic responses of hybrid striped b...

  3. Impact of Stream Channel Urbanization on Dissolved Oxygen Concentrations

    NASA Astrophysics Data System (ADS)

    Van Orden, E. T.

    2011-12-01

    Dissolved oxygen concentration in freshwater streams is an important regulator of ecosystem processes and indicator of stream health. This study attempts to investigate the impacts of urbanization and temperature on dissolved oxygen fluctuations in streams. Field measurements, laboratory experiments, and analysis of diurnal cycles of dissolved oxygen are evaluated in eight streams of the Baltimore and Anacostia watersheds along an urban to rural gradient. Temperature and dissolved oxygen measurements were taken from 8 long-term monitoring sites (5 Baltimore Long Term Ecological Research sites and 3 Anacostia branch sites monitored by the U.S. Geological Survey) in order to characterize fluctuations in dissolved oxygen influenced by changes in land use and temperature. Laboratory experiments investigating changes in 5-day biochemical oxygen demand across 3 different temperatures (4, 15, and 20 degrees Celsius) across land use were conducted using a temperature controlled incubator. Biochemical oxygen demand typically increased with increasing temperature and varied with land use. There were strong relationships between routine dissolved oxygen and temperature seasonally in streams of the Baltimore Long-Term Ecological Research site and Anacostia watershed. Land use and temperature may influence biochemical oxygen demand in streams and impact seasonal dynamics of dissolved oxygen.

  4. Iron oxides, dissolved silica, and regulation of marine phosphate concentration

    NASA Astrophysics Data System (ADS)

    Planavsky, N.; Reinhard, C.; Lyons, T.

    2008-12-01

    Phosphorous concentrations in iron oxide-rich sediments reflect orthophosphate levels in the water column from which iron oxides precipitated. Sediment P/Fe ratios are also strongly influenced by the concentrations of dissolved species that inhibit orthophosphate-to-ferrihydrite sorption, most notably silica. It may, therefore, be possible to use P/Fe ratios in iron oxide-rich sediments to estimate past dissolved P concentrations, if one considers the evolution of the silica cycle. A compilation of Fe and P data in iron oxide-rich sediments through time reveals an increase in P/Fe ratios after the Jurassic. We propose that this trend indicates evolution of the iron-oxide phosphate removal mechanism caused by decreasing levels of sorption inhibition by dissolved silica. The large difference in P/Fe ratios in Cenozoic versus older iron-oxide rich sediments can be linked with Si drawdown caused by the proliferation of siliceous plankton in the Cretaceous. There is also a late Mesozoic or Cenozoic increase in V/Fe ratios, which provides additional evidence for lower ferrihydrite anion sorption efficiency prior to diatom radiation. P/Fe ratios in iron oxide-rich sediments from the early and middle Phanerozoic are comparable to the ratios in iron formations previously presented as evidence for an early Precambrian phosphate crisis (Bjerrum and Canfield, 2002, Nature, 417:159-162). Given the compelling evidence for higher Si concentrations in the Precambrian compared to the Phanerozoic and dissolved P concentrations comparable to modern levels throughout the Phanerozoic, the presented trend of P/Fe ratios suggests dissolved P concentrations were higher in Precambrian than Phanerozoic oceans. High dissolved P levels in the Precambrian may have been linked to inhibited carbonate fluorapatite (CFA) formation as a result of persistently high levels of carbonate supersaturation. Carbonate ion substitution into CFA scales with the ambient carbonate ion activity and increases

  5. Octanol-solubility of dissolved and particulate trace metals in contaminated rivers: implications for metal reactivity and availability.

    PubMed

    Turner, Andrew; Mawji, Edward

    2005-05-01

    The lipid-like, amphiphilic solvent, n-octanol, has been used to determine a hydrophobic fraction of dissolved and particulate trace metals (Al, Cd, Co, Cu, Mn, Ni, Pb, Zn) in contaminated rivers. In a sample from the River Clyde, southwest Scotland, octanol-solubility was detected for all dissolved metals except Co, with conditional octanol-water partition coefficients, D(ow), ranging from about 0.2 (Al and Cu) to 1.25 (Pb). In a sample taken from the River Mersey, northwest England, octanol-solubility was detected for dissolved Al and Pb, but only after sample aliquots had been spiked with individual ionic metal standards and equilibrated. Spiking of the River Clyde sample revealed competition among different metals for hydrophobic ligands. Metal displacement from hydrophobic complexes was generally most significant following the addition of ionic Al or Pb, although the addition of either of these metals had little effect on the octanol-solubility of the other. In both river water samples hydrophobic metals were detected on the suspended particles retained by filtration following their extraction in n-octanol. In general, particulate Cu and Zn (up to 40%) were most available, and Al, Co and Pb most resistant (<1%) to octanol extraction. Distribution coefficients defining the concentration ratio of octanol-soluble particle-bound metal to octanol-soluble dissolved metal were in the range 10(3.3)-10(5.3)mlg(-1). The presence of hydrophobic dissolved and particulate metal species has implications for our understanding of the biogeochemical behaviour of metals in aquatic environments. Specifically, such species are predicted to exhibit characteristics of non-polar organic contaminants, including the potential to penetrate the lipid bilayer. Current strategies for assessing the bioavailability and toxicity of dissolved and particulate trace metals in natural waters may, therefore, require revision.

  6. Investigating Factors that Affect Dissolved Oxygen Concentration in Water

    ERIC Educational Resources Information Center

    Jantzen, Paul G.

    1978-01-01

    Describes activities that demonstrate the effects of factors such as wind velocity, water temperature, convection currents, intensity of light, rate of photosynthesis, atmospheric pressure, humidity, numbers of decomposers, presence of oxidizable ions, and respiration by plants and animals on the dissolved oxygen concentration in water. (MA)

  7. Investigating Factors that Affect Dissolved Oxygen Concentration in Water

    ERIC Educational Resources Information Center

    Jantzen, Paul G.

    1978-01-01

    Describes activities that demonstrate the effects of factors such as wind velocity, water temperature, convection currents, intensity of light, rate of photosynthesis, atmospheric pressure, humidity, numbers of decomposers, presence of oxidizable ions, and respiration by plants and animals on the dissolved oxygen concentration in water. (MA)

  8. CONTINUOUS DISSOLVER EXTRACTOR FOR PROCESSING METAL

    DOEpatents

    Lemon, R.B.; Buckham, J.A.

    1959-02-01

    An apparatus is presented for the continuous dissolution of metal slugs in an aqueous acid and sequential continuous extraction of selected metal values from the acid solution by counter-current contact with an organic solvent. The apparatus comprises a cylindrical tank divided into upper and lower sections. Dissolution of the metal slug takes place in the lower section and the solution so produced is continuously fed to the topmost plate of the upper extraction section. An immiscible organic extractant is continuously passed by a pulsing pump into the lowermost unit of the extraction section. Suitable piping and valving permits of removing the aqueous raffinate solution from the lowermost portion of the extraction section, and simultaneous removal of organic solvent extractant containing the desired product from the uppermost portion of the extraction section.

  9. Are nanosized or dissolved metals more toxic in the environment? A meta-analysis.

    PubMed

    Notter, Dominic A; Mitrano, Denise M; Nowack, Bernd

    2014-12-01

    Recently, much has been written about the extreme urgency of elaborating the regulations for engineered nanomaterials. Such regulations are needed both from lawmakers, to protect people from potentially adverse effects, and from industry representatives, to prove that nanoproducts are produced carefully and with caution to avoid possible lawsuits. However, developing regulations has proven to be a difficult task, and an ambiguous topic where errors can easily occur. In the present study, the authors present a meta-analysis of 3 different nanomaterials (nano-Ag, nano-ZnO, and nano-CuO) in which data from ecotoxicity studies and published half-maximal effective concentration (EC50) values are compared for both the nano form and the corresponding dissolved metal. A ratio equal to 1 means that the particle is as toxic as the dissolved metal ion, whereas a lower ratio signifies that the nano form is less toxic than the dissolved metal based on total metal concentrations. The results show that for 93.8% (Ag), 100% (Cu), and 81% (Zn) of the ratios considered, the nano form is less toxic than the dissolved metal in terms of total metal concentration. Very few of the studies surveyed found a ratio of EC50 values for (dissolved/nano) that was larger than 2 (Ag: 1.1%; Cu: 0%; Zn: 2.8%). Hence, a reduction in existing metal concentration thresholds by a factor of 2 in current freshwater and soil regulations for ecotoxicity may be sufficient to protect organisms and compartments from the nano form of these metals as well. © 2014 SETAC.

  10. Riverine dissolved carbon concentration and yield in subtropical catchments, Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, Pei-Hao; Shih, Yu-ting; Huang, -Chuan, Jr.

    2017-04-01

    Dissolved carbon is not highly correlated to carbon cycle, but also a critical water quality indicator and affected by interaction of terrestrial and aquatic environment at catchment scale. However, the rates and extent of the dissolved carbon export are still poorly understood and scarcely quantified especially for typhoon events. In this study, regular and events' data of riverine dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) were monitored to estimate the export. Meanwhile, the hydrological model and mixing model were used for determination of DOC and DIC flow pathways at 3 sites of Tsengwen reservoir in southern Taiwan in 2014-2015. Results showed that the mean DOC concentration was 1.5 - 2.2 mg l-1 (flow weighted) without seasonal variation. The average DOC yield was 3.1 ton-C km-2 yr-1. On the other hand, DIC concentration ranged from 15 to 25.8 mg l-1, but DIC concentration in dry season was higher than wet season. Mean annual DIC yield was 51 ton-C km-2 yr-1. The export-ratio of DOC:DIC was 1:16.5, which was extremely lower than that of worldwide large rivers (DOC:DIC=1:4.5 in average) and other mountainous rivers (DOC:DIC=1:4.6 in average). Both DOC and DIC concentration showed the dramatically discrepant change in typhoon events. The DOC concentration increased to 4-8 folds rapidly before the flood peak. However, DIC concentration was diluted to one third with discharge simultaneously and returned slowly to base concentration in more than a week. According to the hydrological model, events contributed 14.6% of the annual discharge and 21.9% and 11.1% of DOC and DIC annual flux, respectively. Furthermore, 68.9% of events' discharge derived from surface runoff which carried out 91.3% of DOC flux and 51.1% of DIC flux. It implied that increases of surface runoff transported DOC form near soil surface, but diluted DIC concentration likely implied the contribution of groundwater. Our study characterized the specialty of dissolved carbon

  11. Removal of dissolved heavy metals and radionuclides by microbial spores

    SciTech Connect

    Revis, N.W.; Hadden, C.T.; Edenborn, H.

    1997-11-01

    Microbial systems have been shown to remove specific heavy metals from contaminated aqueous waste to levels acceptable to EPA for environmental release. However, systems capable of removing a variety of heavy metals from aqueous waste to environmentally acceptable levels remain to be reported. The present studies were performed to determine the specificity of spores of the bacterium Bacillus megaterium for the adsorption of dissolved metals and radionuclides from aqueous waste. The spores effectively adsorbed eight heavy metals from a prepared metal mix and from a plating rinse waste to EPA acceptable levels for waste water. These results suggest that spores have multiple binding sites for the adsorption of heavy metals. Spores were also effective in adsorbing the radionuclides {sup 85}strontium and {sup 197}cesium. The presence of multiple sites in spores for the adsorption of heavy metals and radionuclides makes this biosorbent a good candidate for the treatment of aqueous wastes associated with the plating and nuclear industries. 17 refs., 4 tabs.

  12. Measurement of Relative Dissolved Gas Concentrations Using Underwater Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Bell, R. J.; Toler, S.; van Amerom, F. H.; Wenner, P.; Hall, M.; Edkins, J.; Gassig, S.; Short, R.; Byrne, R.

    2004-12-01

    The deployment of underwater mass spectrometer (UMS) systems in marine and lacustrine environments has provided chemical data of exceptional temporal and spatial resolution. UMS instruments operate moored, tethered, remotely, or autonomously, allowing users to customize deployments to suit a wide variety of situations. The ability to collect and analyze real-time data enables prompt, intelligent sampling decisions based on observed analyte distributions. UMS systems can simultaneously detect a wide variety of analytes generated by biological, chemical, physical, geothermal and anthropogenic activities. A polydimethylsiloxane (PDMS) membrane separates the sample-stream from the spectrometer's vacuum chamber. This membrane is selective against water and charged species, yet highly permeable to volatile organic compounds (VOC) and simple gases. Current detection limits for dissolved gases and VOCs are on the order of ppm and ppb respectively. Semi-quantitative proof-of-concept applications have included horizontal mapping of gas gradients, characterization of geothermal vent water, and observation of dissolved gas profiles. Horizontal gradients in dissolved gas concentrations were determined in Lake Maggiore, St Petersburg, Florida. The UMS was positioned on a remotely-guided surface vehicle, and real-time gas concentration data were transmitted to shore via wireless ethernet. Real-time observations allowed intensive sampling of areas with strong gas gradients. Oxygen and CO2 exhibited patchy distributions and their concentrations varied inversely, presumably in response to biological activity. The UMS signal for methane depended on the instrument's proximity to organic rich sediments. Geothermal vent water was characterized while the UMS was deployed in Yellowstone Lake, Wyoming, on a tethered Eastern Oceanics remotely operated vehicle (ROV). Observations of dissolved vent-gas compositions were obtained to depths of 30m. Distinct differences in dissolved vent

  13. Dissolved and particulate metals dynamics in a human impacted estuary from the SW Atlantic

    NASA Astrophysics Data System (ADS)

    La Colla, Noelia S.; Negrin, Vanesa L.; Marcovecchio, Jorge E.; Botté, Sandra E.

    2015-12-01

    In order to evaluate metal behavior in urban stressed estuaries, the distribution of major elements (Fe and Mn) and trace elements (Cd and Cu) between suspended particulate matter (SPM) and subsuperficial seawater in the Bahía Blanca Estuary, Argentina, was studied. Four different impacted areas were selected to study the spatial and temporal distribution of these metals in an estuary in continuous industrial development and where an environmental law was implemented to supervise industrial discharges in waters. Sampling was performed within intertidal areas. Physicochemical conditions usually influence the partitioning of metals between the dissolved and particulate fraction thus, salinity, pH, turbidity, temperature and dissolved oxygen were also measured. Dissolved metals were analyzed with atomic absorption spectrophotometry (AAS) and the particulate fraction with inductively coupled plasma optical emission spectrometry (ICP OES). Metals concentration ranges, within the dissolved fraction (μg/L), were from below the method detection limit for all the elements to 4.7 in the case of Cd, 6.0 for Cu and 62 for Fe. Minimum and maximum values in the particulate fraction (μg/g, d.w.) were from below the method detection limit to 11 for Cd; from 24 to 220 for Cu and from 630 to 1500 for Mn. For Fe, concentrations ranged from 2.2 to 9.6 (%). The general order of the dissolved/particulate partition coefficients (Log10Kds) for the studied metals, considering mean values, were: Fe (7.0) > Cu (4.2) > Cd (3.3). The metals values as well as the physicochemical parameters showed temporal variations and many correlations were found among them. Log10Kd Fe values were the highest, highlighting its strong affinity for particles. Metals concentrations were sometimes higher than those from other polluted areas as well as from previous studies from the same estuary, which highlights the potential impact of these elements in the study area. The concentrations of particulate metals

  14. Complexation with dissolved organic matter and solubility control of heavy metals in a sandy soil.

    PubMed

    Weng, Liping; Temminghoff, Erwin J M; Lofts, Stephen; Tipping, Edward; Van Riemsdijk, Willem H

    2002-11-15

    The complexation of heavy metals with dissolved organic matter (DOM) in the environment influences the solubility and mobility of these metals. In this paper, we measured the complexation of Cu, Cd, Zn, Ni, and Pb with DOM in the soil solution at pH 3.7-6.1 using a Donnan membrane technique. The results show that the DOM-complexed species is generally more significant for Cu and Pb than for Cd, Zn, and Ni. The ability of two advanced models for ion binding to humic substances, e.g., model VI and NICA-Donnan, in the simulation of metal binding to natural DOM was assessed by comparing the model predictions with the measurements. Using the default parameters of fulvic and humic acid, the predicted concentrations of free metal ions from the solution speciation calculation using the two models are mostly within 1 order of magnitude difference from the measured concentrations, except for Ni and Pb in a few samples. Furthermore, the solid-solution partitioning of the metals was simulated using a multisurface model, in which metal binding to soil organic matter, dissolved organic matter, clay, and iron hydroxides was accounted for using adsorption and cation exchange models (NICA-Donnan, Donnan, DDL, CD-MUSIC). The model estimation of the dissolved concentration of the metals is mostly within 1 order of magnitude difference from those measured except for Ni in some samples and Pb. The solubility of the metals depends mainly on the metal loading over soil sorbents, pH, and the concentration of inorganic ligands and DOM in the soil solution.

  15. Bead and Process for Removing Dissolved Metal Contaminants

    SciTech Connect

    Summers, Bobby L., Jr.; Bennett, Karen L.; Foster, Scott A.

    2005-01-18

    A bead is provided which comprises or consists essentially of activated carbon immobilized by crosslinked poly (carboxylic acid) binder, sodium silicate binder, or polyamine binder. The bead is effective to remove metal and other ionic contaminants from dilute aqueous solutions. A method of making metal-ion sorbing beads is provided, comprising combining activated carbon, and binder solution (preferably in a pin mixer where it is whipped), forming wet beads, and heating and drying the beads. The binder solution is preferably poly(acrylic acid) and glycerol dissolved in water and the wet beads formed from such binder solution are preferably heated and crosslinked in a convection oven.

  16. Dissolved air flotation treatment of concentrated fish farming wastewaters.

    PubMed

    Jokela, P; Ihalainen, E; Helnänen, J; Viitasaari, M

    2001-01-01

    Fish farming wastewaters contain nutrients, phosphorus and nitrogen, which promote eutrophication in the typically shallow farming sites in Finland. Fish farming wastewater treatment is problematic because of large quantities of very dilute wastewater (200-600 m3/kg fish produced). In practice wastewater treatment is concentrated on suspended solids removal. Treatment can be done in two steps: concentration of the very dilute wastewater and subsequent treatment of the concentrated wastewater. Dissolved air flotation pilot trials were conducted using two types of concentrated wastewaters: settled solids from a sludge hopper of a cultivation basin and swirl separator concentrate. Two different pilot plants were used and performances compared. Both mechanical treatment and precipitation by ferric salts were applied. Depending on the influent quality, 70 to 90% phosphorus reductions were achieved without chemicals. Chemical precipitation and flotation produced 90% phosphorus reductions and effluent concentrations at the level of 0.05 mgP/l when 13 m3/(m2h) hydraulic loading was used.

  17. Dissolved Neodymium Isotopes and Concentrations in the South Pacific

    NASA Astrophysics Data System (ADS)

    Basak, C.; Pahnke, K.

    2013-12-01

    The isotopic composition of dissolved Neodymium (expressed as ɛNd) in seawater is becoming increasingly established as a tracer for present and past water mass structure and flow paths. The South Pacific represents the largest sector of the Southern Ocean and harbors major areas of bottom and intermediate water mass formation and is therefore a key area for understanding present and past deep ocean circulation. While more dissolved Nd data are becoming available from different ocean basins, the South Pacific is still understudied with respect to the distribution of Nd isotopes and concentrations. In this study we have analyzed dissolved Nd isotopes and concentrations from 11 water column profiles across the South Pacific between 46°S and 69°S that sample all water masses. Our data show that the bottom water in the vicinity of the Ross Sea (Ross Sea Bottom water, RSBW) is represented by an ɛNd value of ~ -7, while the overlying Circumpolar Deep Water (CDW) carries a signature of ɛNd = -8 to -9. The characteristic Nd isotopic signal of RSBW can be tracked along its flow path into the southeast Pacific where it progressively looses its signal through interaction with ambient CDW. The easternmost stations, closer to South America, exhibit an excursion towards radiogenic ɛNd at ≤2000 m water depth. This change towards more positive ɛNd coincides with low oxygen and high phosphate concentrations representing Pacific Deep Water (PDW) and possibly indicates water mass mixing of CDW with more radiogenic PDW. While the Nd isotopic composition shows apparent variations between stations and different water masses, the concentration profiles show a rather uniform and gradual increase with depth, a pattern typical for open ocean settings. Spatial and vertical contrasts in Nd isotopic values throughout the South Pacific indicate that Nd isotopes can be used as a water mass tracer in this region. It is reasonable to infer that local lithology in the Ross Sea influenced

  18. Micro-Winkler titration method for dissolved oxygen concentration measurement.

    PubMed

    Helm, Irja; Jalukse, Lauri; Vilbaste, Martin; Leito, Ivo

    2009-08-26

    In this report a gravimetric micro-Winkler titration method for determination of dissolved oxygen concentration in water is presented. Mathematical model of the method taking into account all influence factors is derived and an uncertainty analysis is carried out to determine the uncertainty contributions of all influence factors. The method is highly accurate: the relative expanded uncertainties (k=2) are around 1% in the case of small (9-10 g) water samples. The uncertainty analysis carried out in characterizing the uncertainty of the method is the most comprehensive published for a micro-Winkler method, resulting in experimentally obtained estimates for all uncertainty sources of practical significance (around 20 uncertainty sources altogether).

  19. Corals concentrate dissolved inorganic carbon to facilitate calcification.

    PubMed

    Allison, Nicola; Cohen, Itay; Finch, Adrian A; Erez, Jonathan; Tudhope, Alexander W

    2014-12-22

    The sources of dissolved inorganic carbon (DIC) used to produce scleractinian coral skeletons are not understood. Yet this knowledge is essential for understanding coral biomineralization and assessing the potential impacts of ocean acidification on coral reefs. Here we use skeletal boron geochemistry to reconstruct the DIC chemistry of the fluid used for coral calcification. We show that corals concentrate DIC at the calcification site substantially above seawater values and that bicarbonate contributes a significant amount of the DIC pool used to build the skeleton. Corals actively increase the pH of the calcification fluid, decreasing the proportion of DIC present as CO2 and creating a diffusion gradient favouring the transport of molecular CO2 from the overlying coral tissue into the calcification site. Coupling the increases in calcification fluid pH and [DIC] yields high calcification fluid [CO3(2-)] and induces high aragonite saturation states, favourable to the precipitation of the skeleton.

  20. Understanding Dissolved and Colloidal Metal Transport and Transformation - Pathways for Aquatic Toxicity

    NASA Astrophysics Data System (ADS)

    Kimball, B. A.; Besser, J. M.

    2004-05-01

    Hundreds of miles of streams in the western United States are affected by the release of metals from weathering of mineralized bedrock and mine wastes. In many cases, historical mining has accelerated these weathering processes and increased concentrations of metals in affected streams. Copper and zinc are two metals that affect aquatic health in such streams. Aquatic toxicity from copper and zinc is thought to be related principally to their dissolved concentrations. But there are alternative pathways that may lead to toxicity. Movement of many metals associated with mine drainage is affected by iron colloidal solids. The initial precipitation of iron hydroxides results in nanometer-sized colloids that subsequently aggregate to form a continuum of particle sizes from about one nanometer to greater than one micrometer. This behavior makes the popular or legal definition of dissolved metals at 0.45 micrometers meaningless in streams affected by mine drainage. Ultrafiltration, using tangential-flow across 10,000-Dalton membranes, provides a means to understand dissolved and colloidal metal concentrations. When ultrafiltration is combined with methods to determine mass loading, it is possible to quantify sources and chemical reactions affecting metals. For example, results from a mass-loading study in Mineral Creek, Colorado, indicate that copper and zinc are contributed to the stream from both mined and unmined sources. As the pH of Mineral Creek changes in response to both neutral and acidic inflows, copper was repeatedly transferred between dissolved and colloidal phases through sorption reactions. When the colloidal phase was dominant, the total load of copper consistently decreased because the colloids are entrained by algae on cobbles and strained by the streambed during hyporheic exchange. Zinc load also decreased during transport, but this was a result of the physical process of water exchange with the hyporheic zone, and not a result of colloidal

  1. Measuring Hydrogen Concentrations in Metals

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1985-01-01

    Commercial corrosion-measurement system adapted to electrochemical determination of hydrogen concentrations in metals. New technique based on diffusion of hydrogen through foil specimen of metal. In sample holder, hydrogen produced on one side of foil, either by corrosion reaction or by cathodic current. Hydrogen diffused through foil removed on other side by constant anode potential, which leads to oxidation of hydrogen to water. Anode current is measure of concentration of hydrogen diffusing through foil. System used to study hydrogen uptake, hydrogen elimination by baking, effect of heat treatment, and effect of electroplating on high-strength steels.

  2. Measuring Hydrogen Concentrations in Metals

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1985-01-01

    Commercial corrosion-measurement system adapted to electrochemical determination of hydrogen concentrations in metals. New technique based on diffusion of hydrogen through foil specimen of metal. In sample holder, hydrogen produced on one side of foil, either by corrosion reaction or by cathodic current. Hydrogen diffused through foil removed on other side by constant anode potential, which leads to oxidation of hydrogen to water. Anode current is measure of concentration of hydrogen diffusing through foil. System used to study hydrogen uptake, hydrogen elimination by baking, effect of heat treatment, and effect of electroplating on high-strength steels.

  3. Diverse stoichiometry of dissolved trace metals in the Indian Ocean

    PubMed Central

    Thi Dieu Vu, Huong; Sohrin, Yoshiki

    2013-01-01

    Trace metals in seawater are essential to organisms and important as tracers of various processes in the ocean. However, we do not have a good understanding of the global distribution and cycling of trace metals, especially in the Indian Ocean. Here we report the first simultaneous, full-depth, and basin-scale section-distribution of dissolved (D) Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in the Indian Ocean. Our data reveal widespread co-limitation for phytoplankton production by DFe and occurrence of redox-related processes. The stoichiometry of the DM/phosphorus ratio agrees within a factor of 5 between deep waters in the Indian and Pacific, whereas it shows variability up to a factor of 300 among water masses within the Indian Ocean. This indicates that a consistent mechanism controls the stoichiometry in the deep waters, which are significantly depleted in Mn, Fe, and Co compared to requirements for phytoplankton.

  4. METAL-COLLOID PARTITIONING IN ARTIFICIAL INTERSTITIAL WATERS OF MARINE SEDIMENTS: INFLUENCES OF SALINITY, PH AND COLLOIDAL ORGANIC CARBON CONCENTRATION

    EPA Science Inventory

    For decades, heavy metals have been deposited into marine sediments as a result of anthropogenic activities. Depending on their bioavailability, these metals may represent a risk to benthic organisms. Dissolved interstitial water metal concentrations have been shown to be better ...

  5. Organic complexation and its control of the dissolved concentrations of copper and zinc in the Scheldt estuary

    NASA Astrophysics Data System (ADS)

    van den Berg, Constant M. G.; Merks, Adri G. A.; Duursma, Egbert K.

    1987-06-01

    Cathodic stripping voltammetry (CSV) is used to determine total (after UV-irradiation) and labile dissolved metal concentrations as well as complexing ligand concentrations in samples from the river Scheldt estuary. It was found that even at high added concentrations of catechol (1 m M for copper and 0·4 m M for iron) and of APDC (1 m M for zinc) only part of the dissolved metal was labile (5-58% for copper, 34-69% for zinc, 10-38% for iron); this discrepancy could be explained by the low solubility of iron which is largely present as colloidal material, and by competition for dissolved copper and zinc by organic complexing ligands. Ligand concentrations varied between 28 and 206 n M for copper and between 22 and 220 n M for zinc; part of the copper complexing ligands could be sub-divided into strong complexing sites with concentrations between 23 and 121 n M and weaker sites with concentrations between 44 and 131 n M. Values for conditional stability constants varied between (log K' values) 13·0 and 14·8 for strong and between 11·5 and 12·1 for weaker copper complexing ligands, whereas for zinc the values were between 8·6 and 10·6. The average products of ligand concentrations and conditional stability constants ( a-coefficients) were 6 × 10 2 for zinc and 6 × 10 6 for copper. The dissolved zinc concentration was found to co-vary with the zinc complexing ligand concentration throughout the estuary. It is argued that the zinc concentration is regulated, in this estuary at least, by interactions with dissolved organic complexing ligands. A similar relationship was apparent between the dissolved copper and the strong copper complexing ligand concentration. The total copper complexing ligand concentrations were much greater than the dissolved copper concentrations, suggesting that only strongly complexed copper is kept in solution. These results provide evidence for the first time that interactions of copper and zinc with dissolved organic complexing ligands

  6. Antarctic snow: metals bound to high molecular weight dissolved organic matter.

    PubMed

    Calace, Nicoletta; Nardi, Elisa; Pietroletti, Marco; Bartolucci, Eugenia; Pietrantonio, Massimiliana; Cremisini, Carlo

    2017-05-01

    In this paper we studied some heavy metals (Cu, Zn, Cd, Pb, As, U) probably associated to high molecular weight organic compounds present in the Antarctic snow. Snow-pit samples were collected and analysed for high molecular weight fraction and heavy metals bound to them by means of ultrafiltration treatment. High molecular weight dissolved organic matter (HMW-DOM) recovered by ultrafiltration showed a dissolved organic carbon concentration (HMW-DOC) of about 18-83% of the total dissolved organic carbon measured in Antarctic snow. The characterisation of HMW-DOM fraction evidenced an ageing of organic compounds going from surface layers to the deepest ones with a shift from aliphatic compounds and proteins/amino sugars to more high unsaturated character and less nitrogen content. The heavy metals associated to HMW-DOM fraction follows the order: Zn > Cu > Pb > Cd ∼ As ∼ U. The percentage fraction of metals bound to HMW-DOM respect to total metal content follows the order: Cu > Pb > Zn, Cd in agreement with humic substance binding ability (Irwing-William series). Going down to depth of trench, all metals except arsenic, showed a high concentration peak corresponding to 2.0-2.5 m layer. This result was attributed to particular structural characteristic of organic matter able to form different type of complexes (1:1, 1:2, 1:n) with metals. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Temporal distribution of dissolved trace metal in the coastal waters of Southwestern Bay of Bengal, India.

    PubMed

    Padhi, R K; Biswas, S; Mohanty, A K; Prabhu, R K; Satpathy, K K; Nayak, L

    2013-08-01

    The objective of the present study was to characterize the concentrations of selected dissolved trace metals in the coastal waters (500 m from shore) of Kalpakkam, Tamil Nadu, India. The order of dissolved concentration of these metals was found to be as follows: Co (cobalt) < Cd (cadmium) < Cr (chromium) < Mn (manganese) < Cu (copper) < Ni (nickel) < Pb (lead) < Zn (zinc). The levels of these trace metals were found to be relatively low as compared to the reported values for other Indian coastal waters, which indicates negligible pollution at this location. Cadmium was the only metal found to increase its concentration during the monsoon period, suggesting its allochthonous input. Factor analysis indicated that chromium, nickel, zinc, cobalt, copper, manganese, and lead were of common origin, and external inputs through land runoff had nominal or little impact, typifying in-situ regeneration and remineralization linkage with their temporal variation. However, levels of zinc, cobalt, and copper remained relatively high during the summer period, and abrupt increases in their concentration during December (monsoon season) may be due to their dual (autochthonous as well as allochthonous) input.

  8. Measurement of Solubility of Metallic Lithium Dissolved in Molten LiCl-Li2O

    NASA Astrophysics Data System (ADS)

    Burak, Adam J.; Simpson, Michael F.

    2016-10-01

    The solubility of lithium metal in molten LiCl-Li2O mixtures has been measured at various concentrations of Li2O ranging from 0 wt.% to 2.7 wt.% at a temperature of approximately 670-680°C. After contacting molten lithium with molten LiCl-Li2O for several hours to achieve equilibrium saturation, samples were taken by freezing the salt onto a room-temperature steel rod and dissolving in water for analysis. Both volume of hydrogen gas generated and volume of titrated HCl were measured to investigate two different approaches to calculating the lithium concentration. There appeared to be no effect of Li2O concentration on the Li solubility in the salt. But the results vary between different methods of deducing the amount of dissolved Li. The H2 collection method is recommended, but care must be taken to ensure all of the H2 has been included.

  9. Historical backcasting of metal concentrations in the Chattahoochee River, Georgia: Population growth and environmental policy

    USGS Publications Warehouse

    Neumann, Klaus; Lyons, W.B.; Graham, E.Y.; Callender, E.

    2005-01-01

    The impact of increasing urbanization on the quality of a river system has been investigated by examining the current concentration of trace metals in the Chattahoochee River south of Atlanta, GA, and comparing these to previously published historical sediment data from reservoirs along the river. The lack of historical data for dissolved metal concentrations prior to ???1980 requires an approach using these historic metal data from sediment cores. Core data are combined with current suspended load and dissolved metal data to "backcast" dissolved metal concentrations in the metro-Atlanta portion of the Chattahoochee River. The data suggest that the per capita input of dissolved trace metals have actually decreased since the 1920s, but anthropogenic inputs of metal are still a substantial water quality issue. ?? 2005 Elsevier Ltd. All rights reserved.

  10. Temporal Dynamics of Dissolved Oxygen Concentrations in the Hyporheic Zone.

    NASA Astrophysics Data System (ADS)

    Reeder, W. J.; Quick, A. M.; Farrell, T. B.; Benner, S. G.; Feris, K. P.; Tonina, D.

    2016-12-01

    Dissolved oxygen (DO) concentration profiles and DO consumption rates are primary indicators of the redox state of porewaters in the hyporheic zone (HZ). Previous studies (mostly numeric) of reactive solute transport, in the HZ, are steady state and give a fixed, in time, view of the biogeochemical activity and redox state of the HZ. Through the use of a novel, multichannel fiber optic DO measurement system and a robotic surface probe system in a large flume experiment, we have been able to track DO concentration, in the HZ, over time and at high spatial and temporal resolutions never achieved before. Our research shows that in carbon-limited systems (i.e., ones in which organic carbon replenishment is largely episodic), DO concentration profiles and consumption rates will vary as a function of time. As the most readily available organic carbon is consumed, (first near the bed surface/water interface) respiration rates, in that area, will drop and DO will be transported deeper into the HZ. Over time, and lacking either an external source of bioavailable carbon or an alternate electron donor substrate, microbial metabolic activity will slow substantially and the majority of the HZ will be rendered oxic. Hyporheic fluxes affect the time scale of biological reactions resulting in faster growth of the aerobic zone in high-flux systems. While this temporal variability can result in a multitude of DO consumption curves (DO vs. residence time), the careful application of dimensional analysis can collapse the consumption curves to a single characteristic curve that accounts for a wide range of morphology and reactivity.

  11. Metal Ion Speciation and Dissolved Organic Matter Composition in Soil Solutions

    NASA Astrophysics Data System (ADS)

    Benedetti, M. F.; Ren, Z. L.; Bravin, M.; Tella, M.; Dai, J.

    2014-12-01

    Knowledge of the speciation of heavy metals and the role of dissolved organic matter (DOM) in soil solution is a key to understand metal mobility and ecotoxicity. In this study, soil column-Donnan membrane technique (SC-DMT) was used to measure metal speciation of Cd, Cu, Ni, Pb, and Zn in eighteen soil solutions, covering a wide range of metal sources and concentrations. DOM composition in these soil solutions was also determined. Our results show that in soil solution Pb and Cu are dominant in complex form, whereas Cd, Ni and Zn mainly exist as free ions; for the whole range of soil solutions, only 26.2% of DOM is reactive and consists mainly of fulvic acid (FA). The metal speciation measured by SC-DMT was compared to the predicted ones obtained via the NICA-Donnan model using the measured FA concentrations. The free ion concentrations predicted by speciation modelling were in good agreement with the measurements. Diffusive gradients in thin-films gels (DGT) were also performed to quantify the labile metal species in the fluxes from solid phase to solution in fourteen soils. The concentrations of metal species detected by DGT were compared with the free ion concentrations measured by DMT and the maximum concentrations calculated based on the predicted metal speciation in SC-DMT soil solutions. It is concluded that both inorganic species and a fraction of FA bound species account for the amount of labile metals measured by DGT, consistent with the dynamic features of this technique. The comparisons between measurements using analytical techniques and mechanistic model predictions provided mutual validation in their performance. Moreover, we show that to make accurate modelling of metal speciation in soil solutions, the knowledge of DOM composition is the crucial information, especially for Cu; like in previous studies the modelling of Pb speciation is not optimal and an updated of Pb generic binding parameters is required to reduce model prediction uncertainties.

  12. The release of dissolved nutrients and metals from coastal sediments due to resuspension

    USGS Publications Warehouse

    Kalnejais, Linda H.; Martin, William R.; Bothner, Michael H.

    2010-01-01

    Coastal sediments in many regions are impacted by high levels of contaminants. Due to a combination of shallow water depths, waves, and currents, these sediments are subject to regular episodes of sediment resuspension. However, the influence of such disturbances on sediment chemistry and the release of solutes is poorly understood. The aim of this study is to quantify the release of dissolved metals (iron, manganese, silver, copper, and lead) and nutrients due to resuspension in Boston Harbor, Massachusetts, USA. Using a laboratory-based erosion chamber, a range of typical shear stresses was applied to fine-grained Harbor sediments and the solute concentration at each shear stress was measured. At low shear stress, below the erosion threshold, limited solutes were released. Beyond the erosion threshold, a release of all solutes, except lead, was observed and the concentrations increased with shear stress. The release was greater than could be accounted for by conservative mixing of porewaters into the overlying water, suggesting that sediment resuspension enhances the release of nutrients and metals to the dissolved phase. To address the long-term fate of resuspended particles, samples from the erosion chamber were maintained in suspension for 90. h. Over this time, 5-7% of the particulate copper and silver was released to the dissolved phase, while manganese was removed from solution. Thus resuspension releases solutes both during erosion events and over a longer timescale due to reactions of suspended particles in the water column. The magnitude of the annual solute release during erosion events was estimated by coupling the erosion chamber results with a record of bottom shear stresses simulated by a hydrodynamic model. The release of dissolved copper, lead, and phosphate due to resuspension is between 2% and 10% of the total (dissolved plus particulate phase) known inputs to Boston Harbor. Sediment resuspension is responsible for transferring a significant

  13. Aerobic sludge digestion under low dissolved oxygen concentrations.

    PubMed

    Arunachalam, RaviSankar; Shah, Hemant K; Ju, Lu-Kwang

    2004-01-01

    Low dissolved oxygen (DO) concentrations occur commonly in aerobic digesters treating thickened sludge, with benefits of smaller digester size, much reduced aeration cost, and higher digestion temperature (especially important for plants in colder areas). The effects of low DO concentrations on digestion kinetics were studied using the sludge from municipal wastewater treatment plants in Akron, Ohio, and Los Lunas, New Mexico. The experiments were conducted in both batch digestion and a mixed mode of continuous, fed-batch, and batch operations. The low DO condition was clearly advantageous in eliminating the need for pH control because of the simultaneous occurrence of nitrification and denitrification. However, when compared with fully aerobic (high DO) systems under constant pH control (rare in full-scale plants), low DO concentrations and a higher solids loading had a negative effect on the specific volatile solids (VS) digestion kinetics. Nonetheless, the overall (volumetric) digestion performance depends not only on the specific digestion kinetics, but also the solids concentration, pH, and digester temperature. All of the latter factors favor the low DO digestion of thickened sludge. The significant effect of temperature on low DO digestion was confirmed in the mixed-mode study with the Akron sludge. When compared with the well-known empirical correlation between VS reduction and the product (temperature x solids retention time), the experimental data followed the same trend, but were lower than the correlation predictions. The latter was attributed to the lower digestible VS in the Akron sludge, the slower digestion at low DO concentrations, or both. Through model simulation, the first-order decay constant (kd) was estimated as 0.004 h(-1) in the mixed-mode operations, much lower than those (0.011 to 0.029 h(-1)) obtained in batch digestion. The findings suggested that the interactions among sludges with different treatment ages may have a substantially

  14. Nanomaterials in Biosolids Inhibit Nodulation, Shift Microbial Community Composition, and Result in Increased Metal Uptake Relative to Bulk/Dissolved Metals.

    PubMed

    Judy, Jonathan D; McNear, David H; Chen, Chun; Lewis, Ricky W; Tsyusko, Olga V; Bertsch, Paul M; Rao, William; Stegemeier, John; Lowry, Gregory V; McGrath, Steve P; Durenkamp, Mark; Unrine, Jason M

    2015-07-21

    We examined the effects of amending soil with biosolids produced from a pilot-scale wastewater treatment plant containing a mixture of metal-based engineered nanomaterials (ENMs) on the growth of Medicago truncatula, its symbiosis with Sinorhizobium meliloti, and on soil microbial community structure. Treatments consisted of soils amended with biosolids generated with (1) Ag, ZnO, and TiO2 ENMs introduced into the influent wastewater (ENM biosolids), (2) AgNO3, Zn(SO4)2, and micron-sized TiO2 (dissolved/bulk metal biosolids) introduced into the influent wastewater stream, or (3) no metal added to influent wastewater (control). Soils were amended with biosolids to simulate 20 years of metal loading, which resulted in nominal metal concentrations of 1450, 100, and 2400 mg kg(-1) of Zn, Ag, and Ti, respectively, in the dissolved/bulk and ENM treatments. Tissue Zn concentrations were significantly higher in the plants grown in the ENM treatment (182 mg kg(-1)) compared to those from the bulk treatment (103 mg kg(-1)). Large reductions in nodulation frequency, plant growth, and significant shifts in soil microbial community composition were found for the ENM treatment compared to the bulk/dissolved metal treatment. These results suggest differences in metal bioavailability and toxicity between ENMs and bulk/dissolved metals at concentrations relevant to regulatory limits.

  15. Effects of dissolved organic matter from a eutrophic lake on the freely dissolved concentrations of emerging organic contaminants.

    PubMed

    Xiao, Yi-Hua; Huang, Qing-Hui; Vähätalo, Anssi V; Li, Fei-Peng; Chen, Ling

    2014-08-01

    The authors studied the effects of dissolved organic matter (DOM) on the bioavailability of bisphenol A (BPA) and chloramphenicol by measuring the freely dissolved concentrations of the contaminants in solutions containing DOM that had been isolated from a mesocosm in a eutrophic lake. The abundance and aromaticity of the chromophoric DOM increased over the 25-d mesocosm experiment. The BPA freely dissolved concentration was 72.3% lower and the chloramphenicol freely dissolved concentration was 56.2% lower using DOM collected on day 25 than using DOM collected on day 1 of the mesocosm experiment. The freely dissolved concentrations negatively correlated with the ultraviolent absorption coefficient at 254 nm and positively correlated with the spectral slope of chromophoric DOM, suggesting that the bioavailability of these emerging organic contaminants depends on the characteristics of the DOM present. The DOM-water partition coefficients (log KOC ) for the emerging organic contaminants positively correlated with the aromaticity of the DOM, measured as humic acid-like fluorescent components C1 (excitation/emission=250[313]/412 nm) and C2 (excitation/emission=268[379]/456 nm). The authors conclude that the bioavailability of emerging organic contaminants in eutrophic lakes can be affected by changes in the DOM.

  16. Dissolved sulfide in groundwater with elevated arsenic concentrations at Winthrop, Maine

    NASA Astrophysics Data System (ADS)

    He, Y.; Zheng, Y.; Zheng, Y.; Locke, D. C.; Simpson, J. H.; Stute, M.

    2001-12-01

    Although sulfur is a biogeochemically significant element because of its strong influence on and response to redox conditions, there are relatively few reliable data sets of trace levels of dissolved sulfide \\(less than1 uM \\) in groundwaters This circumstance results from the relatively high detection limit \\(˜ 1uM \\) of methylene blue colorimetry and the general lack of sensitive methods for field analysis. We were motivated to investigate trace levels of dissolved sulfide because highly insoluble sulfide precipitates of many elements such as As and Fe represent important removal pathways for these metals in reducing groundwaters. Using differential pulse cathodic stripping voltammetry \\(DPCSV\\) capable of detecting 4 nM of dissolved sulfide, we observed that at a site in Winthrop, Maine, groundwater sulfide concentrations ranged from less than 4 nM to ˜ 2000 nM for about a dozen multi-level observation wells under a landfill cap and less than 4 nM to ˜ 7300 nM from several nearby monitoring wells outside the landfill. Sulfide concentrations generally increased when oxygen reduction potential \\(ORP\\) values became more negative. Determination of sulfide should be carried out within 1 hr of sample collection. Samples taken by two methods, \\(1\\) PTFE syringes with luer-lock valves and \\(2\\) BOD bottles show a rapid decline of sulfide following sampling, with up to 90% and 60% losses, respectively, after 24 hrs of storage at 4 ° C. Despite the three orders of magnitude range of dissolved sulfide, arsenic and iron concentrations were all elevated in observational wells installed in a roughly 25 m by 20 m rectangle under the landfill cap, suggesting that As remains mobile under mildly sulfate-reducing conditions. In one well outside of the landfill area, with extremely negative ORP \\(-321 mV\\) and ˜ 7300 nM of dissolved sulfide, groundwater was very low in dissolved As, Fe, and sulfate, suggesting that precipitation of arsenopyrite could be a

  17. Geochemistry of dissolved trace metals (cadmium, copper, zinc) in the Scheldt estuary, southwestern Netherlands: Impact of seasonal variability

    NASA Astrophysics Data System (ADS)

    Zwolsman, John J. G.; Van Eck, Bert T. M.; Van Der Weijden, Cornelis H.

    1997-04-01

    The distribution of dissolved Cd, Cu, and Zn in the Scheldt estuary has been studied during eight axial surveys, carried out between February 1987 and February 1988. The observed metal-salinity profiles depend on the season. During spring and summer, when the river water is anoxic (containing traces of dissolved sulfide), the dissolved metal concentrations in the riverine endmember are extremely low. This observation is ascribed to formation of sparingly soluble metal sulfides in the water column. During winter, when the river water is not totally devoid of oxygen (10-40% saturation), the dissolved Cu and Zn concentrations in the riverine endmember are an order of magnitude higher, but rapid removal is apparent in the very low salinity zone. Flocculation (of organometal complexes) or coagulation (of colloid-associated metals), sediment resuspension and formation of particulate Fe and Mn oxyhydroxides are likely to be involved in the removal process. At higher salinities, maxima of dissolved Zn (at 6-9 × 10 -3), Cu (at 9-18 × 10 -3), and Cd (at 12-21 × 10 -3) are consistently found over the year. These maxima are ascribed to dissolution and desorption of particulate metal forms with increasing salinity. Reoxidation of trace metal sulfides during transport from the anoxic (or suboxic) upper estuary to the fully oxygenated lower estuary is suggested as the first step in the mobilization process. During phytoplankton blooms, desorption of Cd and Zn (but not Cu) is suppressed, which is attributed to the pH increase related to primary production, and to biological uptake. The impact of mobilization processes in the Scheldt estuary is reflected by effective dissolved Cd and Cu concentrations which are much higher than the observed metal concentrations in the river water. Based on these findings, it is expected that restoration of the dissolved oxygen concentration, which is a major goal of the present-day management of the Scheldt estuary, will lead to an increase in

  18. Seasonal variation and sources of dissolved trace metals in Maó Harbour, Minorca Island.

    PubMed

    Martínez-Soto, Marly C; Tovar-Sánchez, Antonio; Sánchez-Quiles, David; Rodellas, Valentí; Garcia-Orellana, Jordi; Basterretxea, Gotzon

    2016-09-15

    The environmental conditions of semi-enclosed coastal water-bodies are directly related to the catchment, human activities, and oceanographic setting in which they are located. As a result of low tidal forcing, and generally weak currents, waters in Mediterranean harbours are poorly renewed, leading to quality deterioration. Here, we characterise the seasonal variation of trace metals (i.e. Co, Cd, Cu, Fe, Mo, Ni, Pb, and Zn) in surface waters, and trace metal content in sediments from Maó Harbour, a semi-enclosed coastal ecosystem in the NW Mediterranean Sea. Our results show that most of the dissolved trace metals in the waters of Maó Harbour exhibit a marked inner-outer concentration gradient, suggesting a permanent input into the inner part of the harbour. In general, metal concentrations in the waters of Maó Harbour are higher than those in offshore waters. Concentration of Cu (21±8nM), Fe (9.2±3.2nM) and Pb (1.3±0.4nM) are particularly high when compared with other coastal areas of the Mediterranean Sea. The concentration of some metals such as Cu and Zn increases during summertime, when the human population and boat traffic increase during the tourism season, and when resuspension from the metal enriched sediments is higher. The evaluation of the metal sources in the harbour reveals that, compared with other putative sources such as runoff, aerosol deposition and fresh groundwater discharges, contaminated sediments are the main source of the metals found in the water column, most likely through vessel-driven resuspension events. This study contributes to the understanding of the processes that control the occurrence and distribution of trace metals in Maó Harbour, thus aiding in the effective management of the harbour, and enhancing the overall quality of the seawater ecosystem. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Linking dissolved organic matter composition to metal bioavailability in agricultural soils: effect of anionic surfactants

    NASA Astrophysics Data System (ADS)

    Hernandez-Soriano, M. C.; Jimenez-Lopez, J. C.

    2015-04-01

    The bioavailability of metals in soil is only partially explained by their partition among the solid and aqueous phase and is more related to the characterization of their speciation in the soil solution. The organic ligands in solution that largely determine metal speciation involve complex mixtures and the characterization of fluorescence components of dissolved organic matter (DOM) can identify pools of molecules that participate in metal speciation, this being essential for risk assessment. The bioavailability of Cd, Cu, Pb and Zn in three agricultural soils was examined in the laboratory to recreate irrigation with greywater enriched in anionic surfactants (Aerosol 22 and Biopower). Field capacity and saturation regimes were considered for this study. Irrigation with aqueous solutions of the anionic surfactants increased total DOM concentrations and metals in the soil solution (Pb > Cu > Zn > Cd). Significant correlation (p < 0.05) between the readily available pool of metals with the concentration of DOM was determined for Cu (r = 0.67), Pb (r = 0.82) and Zn (r = 0.68). However, speciation analysis performed with the software WHAM indicated that mobilisation of DOM and metals into the soluble phase resulted in a low concentration of free ion activities and promoted the formation of metal-organo complexes. The characterization of fluorescence components revealed that DOM in soil solution from soils irrigated with Aerosol 22 was enriched in a reduced quinone-like and a humic-like component. Besides, fluorescence quenching provided further evidence of metal complexation with organic ligands in solution. Hence, metal mobilization in soil irrigated with surfactant enriched greywater occurs with solubilisation of high affinity organic ligands, which substantially decreases the potential risk of metal toxicity.

  20. Dissolved metal contamination in the East River-Long Island sound system: potential biological effects.

    PubMed

    Sweeney, Alison; Sañudo-Wilhelmy, Sergio A

    2004-04-01

    A suite of dissolved trace metals (Ag, Cd, Cu and Pb), inorganic nutrients (NO(3), PO(4)), and chlorophyll a was measured along a 55 mile transect from the East River into western and central Long Island Sound. The main objectives of this study were to determine the relative levels of contamination from sewage, and to assess its possible biological impact on local waters. The East River-Long Island Sound system receives large volumes of treated sewage and industrial effluent as a result of the heavy urbanization of the area. Despite these strong environmental pressures, this study is among the first to report dissolved metal levels from that region. Consistent with the locations of anthropogenic sources, a strong east-west concentration gradient was observed for Ag, Pb, NO(3) and PO(4) with the highest levels found in the East River. In contrast, dissolved Cd and Cu were relatively constant throughout the area of study, suggesting that sewage sources have a more limited influence on the levels of those metals. Remobilization from contaminated sediments may represent the primary source of Cd and Cu to the Long Island Sound under low-runoff conditions in summer. Chlorophyll a concentrations, used as an indicator of total biomass, were also low in the East River. These low chlorophyll concentrations could not be explained by nutrient or light limitation, water column stratification, or to advection of phytoplankton out of the river during tidal flushing. These preliminary results suggest a potential toxic effect of sewage on the biological communities of the East River.

  1. Measuring freely dissolved water concentrations of PCBs using LDPE passive samplers and performance reference compounds (PRCs)

    EPA Science Inventory

    Low-Density polyethylene (LDPE) sheets are often used as passive samplers for aquatic environmental monitoring to measure the dissolved concentrations of hydrophobic organic contaminants (HOCs). These concentrations are then used to evaluate the potential for ecological and human...

  2. Measuring freely dissolved water concentrations of PCBs using LDPE passive samplers and performance reference compounds (PRCs)

    EPA Science Inventory

    Low-Density polyethylene (LDPE) sheets are often used as passive samplers for aquatic environmental monitoring to measure the dissolved concentrations of hydrophobic organic contaminants (HOCs). These concentrations are then used to evaluate the potential for ecological and human...

  3. Stabilization of dissolved trace metals at hydrothermal vent sites: Impact on their marine biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Sander, Sylvia G.; Powell, Zach D.; Koschinsky, Andrea; Kuzmanovski, Stefan; Kleint, Charlotte

    2014-05-01

    Hydrothermal vents have long been neglected as a significant source of several bioactive trace metals as it was assumed that elements such as Fe, Mn, and Cu etc., precipitate in extensor forming poly-metallic sulfide and oxy-hydroxy sediments in the relative vicinity of the emanation site. However, recently this paradigm has been reviewed since the stabilization of dissolved Fe and Cu from hydrothermal vents was observed [1, 2] and increased concentrations of trace metals can be traced from their hydrothermal source thousands of kilometres through the ocean basins [3]. Furthermore several independent modelling attempts have shown that not only a stabilization of dissolved hydrothermal Fe and Cu is possible [4] but also that hydrothermalism must be a significant source of Fe to be able to balance the Fe-biogeochemical cycle [5]. Here we present new data that gives further evidence of the presence of copper stabilising organic and inorganic compounds in samples characterized by hydrothermal input. We can show that there are systematic differences in copper-complexing ligands at different vent sites such as 5°S on the Mid Atlantic Ridge, Brother Volcano on the Kermadec Arc, and some shallow hydrothermal CO2 seeps in the Bay of Plenty, New Zealand and the Mediterranean Sea. Quantitative and qualitative voltammetric data convincingly indicates that inorganic sulphur and organic thiols form the majority of the strong copper-complexing ligand pool in many of these hydrothermal samples. On average, the high temperature vents had a significantly higher copper binding capacity than the diffuse vents due to higher inorganic sulphur species concentrations. References: [1] Sander, S. G., et al. 2007. Organic complexation of copper in deep-sea hydrothermal vent systems. Environmental Chemistry 4: 81-89 [2] Bennett, S. A., et al. 2008. The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes. Earth and Planetary Science Letters 270: 157-167. [3] Wu J

  4. Leaching and retention of dissolved metals in particulate loaded pervious concrete columns.

    PubMed

    Vadas, Timothy M; Smith, Malcolm; Luan, Hongwei

    2017-04-01

    This study examined metal leaching and retention in pervious concrete with or without embedded particulate matter. Particulate matter was collected from an adjacent parking lot and from a nearby parking garage as examples of weathered and un-weathered particulate matter. Particle size distributions were similar, but metal content was 3-35-fold higher and organic matter content was 3-fold higher in the parking garage particulate matter compared to the parking lot particulate matter. Replicate columns were established with either no particulate added as the control, or 20 g of parking lot or parking garage particulate matter. Synthetic rainwater was passed through the columns at variable rainfall intensity or fixed intensity to assess leaching. Metals were leached at higher concentrations from the parking garage particulate amended column, but from all columns less than 1% of the metal mass leached. Rainfall intensity did not have a large effect on leached metal concentrations, only varying effluent by about 2-fold. Synthetic stormwater with elevated dissolved Cu, Zn, Cd and Pb concentrations was passed through the same columns and metal removal efficiencies were on the order of 85-95%, 30-95%, 60-90%, and 95+% for each metal, respectively. After loading the column with a year's worth of stormwater metal exposure, removal efficiencies in the no particulate and parking lot particulate amended columns decreased, while parking garage particulate amended columns performed similarly with a small drop in Cu and Pb removal efficiencies. Generally, columns with no particulate and parking lot particulate amendments performed similarly, suggesting the pervious concrete is responsible for the majority of the initial metal retention. The parking garage particulate amended columns retained more metals from stormwater, perhaps due to an increase in pH that promoted surface precipitation as hydroxides or carbonate species on the pervious concrete, or due to complexation in the

  5. Toxic effects of dissolved heavy metals on Desulfovibrio vulgaris and Desulfovibrio sp. strains.

    PubMed

    Cabrera, G; Pérez, R; Gómez, J M; Abalos, A; Cantero, D

    2006-07-31

    Biological treatment of metal-containing wastewaters with sulphate-reducing bacteria (SRB) is an attractive technique for the bioremediation of this kind of medium. In order to design a suitable engineering process to address this environmental problem, it is crucial to understand the inhibitory effect of dissolved heavy metals on these bacteria. Batch studies were carried out to evaluate the toxic effects of several heavy metal ions [Cr(III), Cu(II), Mn(II), Ni(II) and Zn(II)] on two cultures of SRB (Desulfovibrio vulgaris and Desulfovibrio sp.). The experimental data indicate that SRB show different responses to each metal. At the highest metal concentration tolerated for each metal, the precipitation levels for D. vulgaris were as follows: 24.7%-15 ppm Cr(III), 45%-4 ppm Cu(II), 60%-10 ppm Mn(II), 96%-8.5 ppm Ni(II) and 9%-20 ppm Zn(II). The corresponding values for Desulfovibrio sp. were: 25.5%-15 ppm Cr(III), 71%-4 ppm Cu(II), 66.2%-10 ppm Mn(II), 96.1%-8.5 ppm Ni(II) and 93%-20 ppm Zn(II). Results obtained in batch studies will be taken into account for the subsequent design of a sulphate-reducing bioreactor to reduce levels of heavy metals present in different types of contaminated media.

  6. Effect of overlying water pH, dissolved oxygen, salinity and sediment disturbances on metal release and sequestration from metal contaminated marine sediments.

    PubMed

    Atkinson, Clare A; Jolley, Dianne F; Simpson, Stuart L

    2007-11-01

    Experiments were undertaken to examine the key variables affecting metal release and sequestration processes in marine sediments with metal concentrations in sediments reaching up to 86, 240, 700, and 3000 mg kg(-1) (dry weight) for Cd, Cu, Pb and Zn, respectively. The metal release and sequestration rates were affected to a much greater extent by changes in overlying water pH (5.5-8.0) and sediment disturbance (by physical mixing) than by changes in dissolved oxygen concentration (3-8 mg l(-1)) or salinity (15-45 practical salinity units). The physical disturbance of sediments was also found to release metals more rapidly than biological disturbance (bioturbation). The rate of oxidative precipitation of released iron and manganese increased as pH decreased and appeared to greatly influence the sequestration rate of released lead and zinc. Released metals were sequestered less rapidly in waters with lower dissolved oxygen concentrations. Sediments bioturbated by the benthic bivalve Tellina deltoidalis caused metal release from the pore waters and higher concentrations of iron and manganese in overlying waters than non-bioturbated sediments. During 21-day sediment exposures, T. deltoidalis accumulated significantly higher tissue concentrations of cadmium, lead and zinc from the metal contaminated sediments compared to controls. This study suggests that despite the fact that lead and zinc were most likely bound as sulfide phases in deeper sediments, the metals maintain their bioavailability because of the continued cycling between pore waters and surface sediments due to physical mixing and bioturbation.

  7. SITE demonstration of the Dynaphore/Forager Sponge technology to remove dissolved metals from contaminated groundwater

    SciTech Connect

    Esposito, C.R.; Vaccaro, G.

    1995-10-01

    A Superfund Innovative Technology Evaluation (SITE) demonstration was conducted of the Dynaphore/Forager Sponge technology during the week of April 3, 1994 at the N.L. Industries Superfund Site in Pedricktown, New Jersey. The Forager Sponge is an open-celled cellulose sponge incorporating an amine-containing chelating polymer that selectively absorbs dissolved heavy metals in both cationic and anionic states. This technology is a volume reduction technology in which heavy metal contaminants from an aqueous medium are concentrated into a smaller volume for facilitated disposal. The developer states that the technology can be used to remove heavy metals from a wide variety of aqueous media, such as groundwater, surface waters and process waters. The sponge matrix can be directly disposed, or regenerated with chemical solutions. For this demonstration the sponge was set up as a mobile pump-and-treat system which treated groundwater contaminated with heavy metals. The demonstration focused on the system`s ability to remove lead, cadmium, chromium and copper from the contaminated groundwater over a continuous 72-hour test. The removal of heavy metals proceeded in the presence of significantly higher concentrations of innocuous cations such as calcium, magnesium, sodium, potassium and aluminum.

  8. Dissolved Divalent Metal and pH Effects on Amino Acid Polymerization: A Thermodynamic Evaluation.

    PubMed

    Kitadai, Norio

    2017-03-01

    Polymerization of amino acids is a fundamentally important step for the chemical evolution of life. Nevertheless, its response to changing environmental conditions has not yet been well understood because of the lack of reliable quantitative information. For thermodynamics, detailed prediction over diverse combinations of temperature and pH has been made only for a few amino acid-peptide systems. This study used recently reported thermodynamic dataset for the polymerization of the simplest amino acid "glycine (Gly)" to its short peptides (di-glycine and tri-glycine) to examine chemical and structural characteristics of amino acids and peptides that control the temperature and pH dependence of polymerization. Results showed that the dependency is strongly controlled by the intramolecular distance between the amino and carboxyl groups in an amino acid structure, although the side-chain group role is minor. The polymerization behavior of Gly reported earlier in the literature is therefore expected to be a typical feature for those of α-amino acids. Equilibrium calculations were conducted to examine effects of dissolved metals as a function of pH on the monomer-polymer equilibria of Gly. Results showed that metals shift the equilibria toward the monomer side, particularly at neutral and alkaline pH. Metals that form weak interaction with Gly (e.g., Mg(2+)) have no noticeable influence on the polymerization, although strong interaction engenders significant decrease of the equilibrium concentrations of Gly peptides. Considering chemical and structural characteristics of Gly and Gly peptides that control their interactions with metals, it can be expected that similar responses to the addition of metals are applicable in the polymerization of neutral α-amino acids. Neutral and alkaline aqueous environments with dissolved metals having high affinity with neutral α-amino acids (e.g., Cu(2+)) are therefore not beneficial places for peptide bond formation on the primitive

  9. Dissolved Divalent Metal and pH Effects on Amino Acid Polymerization: A Thermodynamic Evaluation

    NASA Astrophysics Data System (ADS)

    Kitadai, Norio

    2017-03-01

    Polymerization of amino acids is a fundamentally important step for the chemical evolution of life. Nevertheless, its response to changing environmental conditions has not yet been well understood because of the lack of reliable quantitative information. For thermodynamics, detailed prediction over diverse combinations of temperature and pH has been made only for a few amino acid-peptide systems. This study used recently reported thermodynamic dataset for the polymerization of the simplest amino acid "glycine (Gly)" to its short peptides (di-glycine and tri-glycine) to examine chemical and structural characteristics of amino acids and peptides that control the temperature and pH dependence of polymerization. Results showed that the dependency is strongly controlled by the intramolecular distance between the amino and carboxyl groups in an amino acid structure, although the side-chain group role is minor. The polymerization behavior of Gly reported earlier in the literature is therefore expected to be a typical feature for those of α-amino acids. Equilibrium calculations were conducted to examine effects of dissolved metals as a function of pH on the monomer-polymer equilibria of Gly. Results showed that metals shift the equilibria toward the monomer side, particularly at neutral and alkaline pH. Metals that form weak interaction with Gly (e.g., Mg2+) have no noticeable influence on the polymerization, although strong interaction engenders significant decrease of the equilibrium concentrations of Gly peptides. Considering chemical and structural characteristics of Gly and Gly peptides that control their interactions with metals, it can be expected that similar responses to the addition of metals are applicable in the polymerization of neutral α-amino acids. Neutral and alkaline aqueous environments with dissolved metals having high affinity with neutral α-amino acids (e.g., Cu2+) are therefore not beneficial places for peptide bond formation on the primitive

  10. DISSOLVED ORGANIC CARBON (DOC) CONCENTRATIONS IN SMALL STREAMS OF THE GEORGIA PIEDMONT

    EPA Science Inventory

    Dissolved organic matter (DOM) supports microbial activity and contributes to transport of N and P in streams. We have studied the impact of land uses on dissolved organic carbon (DOC) concentrations in 17 Georgia Piedmont headwater streams since January 2001. We classified the w...

  11. DISSOLVED ORGANIC CARBON (DOC) CONCENTRATIONS IN SMALL STREAMS OF THE GEORGIA PIEDMONT

    EPA Science Inventory

    Dissolved organic matter (DOM) supports microbial activity and contributes to transport of N and P in streams. We have studied the impact of land uses on dissolved organic carbon (DOC) concentrations in 17 Georgia Piedmont headwater streams since January 2001. We classified the w...

  12. Investigating extent of dissolved organic carbon stabilization by metal based coagulant in a wetland environment

    NASA Astrophysics Data System (ADS)

    Henneberry, Y.; Mourad, D.; Kraus, T.; Bachand, P.; Fujii, R.; Horwath, W.

    2008-12-01

    This study is part of a larger project designed to investigate the feasibility of using metal-based coagulants to remove dissolved organic carbon (DOC) from island drainage water in the San Joaquin Delta and subsequently retaining the metal-DOC precipitate (floc) in wetlands constructed at the foot of levees to promote levee stability. Dissolved organic carbon is a constituent of concern as some forms of DOC can be converted to carcinogenic compounds during drinking water treatment. The focus of this work is to assess floc stability over time and to determine whether floc can be permanently sequestered as part of wetland sediment. Drainage water collected seasonally from Twitchell Island was coagulated with ferric sulfate and polyaluminum chloride at optimal and 50%-optimal dosage levels. Floc was incubated in the laboratory under anaerobic conditions for six weeks under various conditions including different DOC concentrations, microbial inoculants, and addition of nutrients. Preliminary results indicate the floc is a stable system; little to no DOC was released from the floc into the water column under incubations with native microbial inoculate. In addition, floc incubated with previously coagulated water appeared to remove additional DOC from the water column. Future work will involve field and laboratory studies using 13C labeled plant material to examine the effects of fresh plant matter and the effects of peat soil DOC on floc stability, in order to elucidate mechanisms behind carbon stabilization by metal-based floc.

  13. Comparative examination of effects of binding of different metals on chromophores of dissolved organic matter.

    PubMed

    Yan, Mingquan; Korshin, Gregory V

    2014-03-18

    This study quantified the binding of dissolved organic matter (DOM) from Suwannee River with nine metals, Ca(II), Mg(II), Fe(III), Al(III), Cu(II), Cd(II), Cr(III), Eu(III), and Th(IV), using a differential absorbance approach. The differential spectra of DOM were closely fitted with six Gaussian bands that were present for all of the metals at varying pH values. Their maxima were located at ca. 200, 240, 276, 316, 385, and 547 nm (denoted as A0, A1, A2, A3, A4, and A5, respectively). The relative contributions and signs of the Gaussian bands were metal-specific and correlated to some degree with the covalent-bonding index of the ions and applicable complexation constants of the NICA-Donnan model. The intensity of band A4 was linearly proportional to the concentration of DOM-complexed metal, although these correlations formed two groups with different slopes, reflecting the nature of DOM-metal interactions. The results demonstrate that differential spectra yield results indicative of the nature and extent of metal and DOM interactions.

  14. Use of lichen biomass to monitor dissolved metals in natural waters

    SciTech Connect

    Beck, J.N.; Ramelow, G.J. )

    1990-02-01

    The use of lichens for monitoring airborne metals is based on their immobility and a tendency to accumulate metals to a high degree by the trapping of atmospheric particles and by adsorptive ion exchange processes in which dissolved metals in rainwater are picked up by cellular membranes. The powerful metal-accumulating ability of lichens has been demonstrated in the laboratory. This strong metal accumulating ability of lichen biomass from aqueous solutions would seem to make lichen material an ideal biomonitor of dissolved metals in natural waters. To test this the present study was initiated to monitor dissolved zinc, copper, lead, nickel, cadmium, iron, manganese, chromium, and mercury in an industrially-impacted bayou in southwestern Louisiana. The results obtained with lichen biomonitors will be compared with other studies of the same metals in periphyton and sediments from this waterway.

  15. Metal and phytochelatin content in phytoplankton from freshwater lakes with different metal concentrations

    SciTech Connect

    Knauer, K.; Xue, H.B.; Sigg, L.; Ahner, B.

    1998-12-01

    The trace metal (Cu, Zn, Cd, Mn) and phytochelatin (an intracellular chelator for metal ions) cellular content were determined in phytoplankton samples originating from four lakes. The lakes differ in their metal concentrations and in other conditions (pH, trophic state, organic matter). Total and intracellular contents of Cu and Cd were related to the experimentally determined free metal ion concentration and the total and intracellular content of Mn to the dissolved Mn. The intracellular Zn content was tightly regulated over a broad range of [Zn{sup 2+}]. Phytochelatin concentrations were measurable in phytoplankton communities from three of the lakes, in spite of low levels of free Cu, Zn, and Cd ion concentrations. Culture experiments showed that the concentration of intracellular phytochelatin in Scendesmus subspicatus and in a natural algal community increased upon addition of copper in a similar concentration range as in the lakes. Phytochelatin concentrations were below detection in the phytoplankton collected from the highly contaminated Lake Orta, perhaps suggesting that this algal community has adapted in some other way to high metal concentrations. Although the authors only sampled a few lakes, the lack of any clear relationship between phytochelatin and metal concentrations calls into question the feasibility of using phytochelatins as a bioindicator of metal exposure in lakes.

  16. Dissolved and particulate metals in water from Sonora Coast: a pristine zone of Gulf of California: metals in water from Sonora Coast.

    PubMed

    García-Rico, Leticia; Tejeda-Valenzuela, Lourdes; Jara-Marini, Martín E; Gómez-Álvarez, Agustín

    2011-05-01

    The purpose of this study was to investigate the distribution of metals (Cd, Pb, Hg, Cu, Fe, Mn, and Zn) in dissolved and particulate fractions in seawater from Bacochibampo Bay, Northern part of Mexico. Water samples were collected from November 2004 to October 2005. Metal analysis was done by graphite furnace atomic absorption spectroscopy. Results indicated highest concentrations of dissolved Cd and Zn in the sites localized at the mouth and center of the bay. During summer and spring, the highest levels of Cd, Mn, and Fe were detected, Zn in fall, and Pb and Cu in winter and spring. Mercury was the only metal that was not found in this fraction. In particulate fraction, Fe, Hg, and Mn were the most abundant elements in all the sampling sites, followed by Zn, Cu, Pb, and Cd. The highest levels of the majority of the metals were observed in the coastline, suggesting a continental and/or urban source for these chemicals. The highest level of Cd was detected during the summer and the rest of the metals in the fall. Statistically significant correlations were observed between dissolved and particulate forms of Pb:Mn, Cu:Fe, and Cu:Mn. The mean partition coefficient values were as follows: Fe>Mn>Cu>Pb>Cd>Zn. All dissolved metal concentrations found, except Pb, were lower than EPA-recommended water quality values. The levels of dissolved metals in this study reveal low bioavailability and toxic potential. However, further toxicological and sediment chemistry studies in this area are needed for a full risk assessment.

  17. Assessment of metals bound to marine plankton proteins and to dissolved proteins in seawater.

    PubMed

    García-Otero, Natalia; Barciela-Alonso, María Carmen; Bermejo-Barrera, Pilar; Moreda-Piñeiro, Antonio; Jiménez, María S; Gómez, María T; Castillo, Juan R

    2013-12-04

    Studies based on laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) have been performed to assess metal bound to dissolved proteins and proteins from marine plankton after two-dimensional polyacrylamide gel electrophoresis (2D PAGE). Dissolved proteins were pre-concentrated from surface seawater (60 L) by tangential ultrafiltration with 10 kDa molecular weight cut-off (MWCO) membranes and further centrifugal ultrafiltration (10 kDa) before proteins isolation by methanol/chloroform/water precipitation. Proteins isolation from plankton was assessed after different trichloroacetic acid (TCA)/acetone and methanol washing stages, and further proteins extraction with a phenol solution. LA-ICP-MS analysis of the electrophoretic profiles obtained for dissolved proteins shows the presence of Cd, Cr, Cu, and Zn in five spots analyzed. These proteins exhibit quite similar molecular weights (within the 10-14 kDa range) and pIs (from 5.8 to 7.3). Cd, Cr, Cu, and Zn have also been found to be associated to proteins isolated from plankton samples. In this case, Cd has been found to be bound to proteins of quite different molecular weight (9, 13 and 22 kDa) and pIs (4.5, 5.2, 5.5, and 10). However, trace elements such as Cr, Cu and Zn appear to be mainly bound to plankton proteins of low molecular weight and variable pI.

  18. Dissolved Trace Metal and Organic Matter Relationships over Various Fluvial Scales

    NASA Astrophysics Data System (ADS)

    Shiller, A. M.; Bianchi, T. S.; Aiken, G. R.

    2006-05-01

    The fluvial mobilization of many dissolved trace elements is affected by dissolved organic matter, primarily through complexation. We have examined the metal-DOC relationship through various means including: a) metal-DOC comparisons over large scales, b) metal-DOC comparisons between watersheds of differing landscapes, and c) an incubation experiment designed to see how changing DOC composition affects metal speciation. Our compilation of data includes time series samples from the lower Mississippi River, the Loch Vale Watershed, the Pearl River (MS), and the Yukon River as well as short time series and grab samples from a wide variety of streams and rivers in the Yukon Basin. When pooled together, overall relationships between DOC and the concentrations of certain trace elements (e.g., Fe, Cu, Zn) are observed. In many cases this probably reflects competition between adsorption and organic complexation and suggests the possibility that complexation and adsorption constants in these systems vary less than the amounts of organic matter and adsorbing surfaces. In other words, it may be possible to develop a simple one-site, one- ligand model to approximately (or, at least, conceptually) describe fluvial trace element behavior. We also observe, when comparing watersheds of the Yukon River Basin, differences in both DOC and associated dissolved metal concentrations. If DOC is truly a master variable for these trace elements, then prediction of how climate change will affect DOC mobilization from various environments will lead to predictions of dissolved trace elements will also be affected. However, some caution is required for these generalizations. Because DOC tends to vary inversely with pH and conductivity on global fluvial scales, the importance of other controlling factors cannot be ignored. To further investigate DOC metal relationships we have also used column partitioning methods the examine metal speciation during a photo-incubation experiment. The

  19. The measurement of dissolved and gaseous carbon dioxide concentration

    NASA Astrophysics Data System (ADS)

    Zosel, J.; Oelßner, W.; Decker, M.; Gerlach, G.; Guth, U.

    2011-07-01

    In this review the basic principles of carbon dioxide sensors and their manifold applications in environmental control, biotechnology, biology, medicine and food industry are reported. Electrochemical CO2 sensors based on the Severinghaus principle and solid electrolyte sensors operating at high temperatures have been manufactured and widely applied already for a long time. Besides these, nowadays infrared, non-dispersive infrared and acoustic CO2 sensors, which use physical measuring methods, are being increasingly used in some fields of application. The advantages and drawbacks of the different sensor technologies are outlined. Electrochemical sensors for the CO2 measurement in aqueous media are pointed out in more detail because of their simple setup and the resulting low costs. A detailed knowledge of the basic detection principles and the windows for their applications is necessary to find an appropriate decision on the technology to be applied for measuring dissolved CO2. In particular the pH value and the composition of the analyte matrix exert important influence on the results of the measurements.

  20. Water quality and processes affecting dissolved oxygen concentrations in the Blackwater River, Canaan Valley, West Virginia

    USGS Publications Warehouse

    Waldron, M.C.; Wiley, J.B.

    1996-01-01

    The water quality and environmental processes affecting dissolved oxygen were determined for the Blackwater River in Canaan Valley, West Virginia. Canaan Valley is oval-shaped (14 miles by 5 miles) and is located in the Allegheny Mountains at an average elevation of 3,200 feet above sea level. Tourism, population, and real estate development have increased in the past two decades. Most streams in Canaan Valley are a dilute calcium magnesium bicarbonate-type water. Streamwater typicaly was soft and low in alkalinity and dissolved solids. Maximum values for specific conductance, hardness, alkalinity, and dissolved solids occurred during low-flow periods when streamflow was at or near baseflow. Dissolved oxygen concentrations are most sensitive to processes affecting the rate of reaeration. The reaeration is affected by solubility (atmospheric pressure, water temperature, humidity, and cloud cover) and processes that determine stream turbulence (stream depth, width, velocity, and roughness). In the headwaters, photosynthetic dissolved oxygen production by benthic algae can result in supersaturated dissolved oxygen concentrations. In beaver pools, dissolved oxygen consumption from sediment oxygen demand and carbonaceous biochemical oxygen demand can result in dissolved oxygen deficits.

  1. Effects of dissolved oxygen concentration on biodegradation of 2,4-dichlorophenoxyacetic acid.

    PubMed Central

    Shaler, T A; Klecka, G M

    1986-01-01

    Batch experiments were conducted to examine the effects of dissolved oxygen concentration on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by an enrichment culture of 2,4-D-utilizing bacteria. A modified Monod equation was found to describe the relationship between the specific growth rate and the concentrations of both the organic substrate and dissolved oxygen. Values for the maximum specific growth rate, yield, and Monod coefficient for growth on 2,4-D were 0.09 h-1, 0.14 g/g, and 0.6 mg/liter, respectively. The half-saturation constant for dissolved oxygen was estimated to be 1.2 mg/liter. These results suggest that dissolved oxygen concentrations below 1 mg/liter may be rate limiting for the biodegradation of chlorinated aromatic compounds such as 2,4-D, which have a requirement for molecular oxygen as a cosubstrate for metabolism. PMID:3729394

  2. Distribution of dissolved and particulate trace metals in Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Taylor, M.; Hendy, I. L.; Aciego, S.; Meyer, K.

    2014-12-01

    Iron (Fe) is an essential biolimiting micronutrient, however, the bioavailablility of Fe is dependent on source and speciation. In a high nutrient/low chlorophyll region of the ocean such as the Arctic, sea ice is an important aggregator of dissolved and particulate Fe from aerosol, lithogenic, and biogenic sources. While particulate Fe is less bioavailable than dissolved Fe, it is far more abundant in sea ice. As a result, sea ice directly enhances productivity by ice entrapment of mineral dust particulates containing Fe, which can be released into the surface ocean waters during melting. In seawater underlying sea ice, Fe can be concentrated up to two orders of magnitude higher than in the ice-free open ocean (Lannuzel et al., 2011). A transect of sea ice cores were collected in the spring of 2014 offshore of Barrow, AK, and the Canadian Arctic Archipelago to capture a gradient of sediment contributions from shelf sediments to aeolian sediments. At Barrow, AK, land fast first year ice was sampled. In the Canadian Arctic, both multi-year (pack ice) and first year (land fast) ice cores were retrieved. First year ice cores were between 100-150 cm thick and the multi year core was 195 cm thick. Cores were subsampled by depth and filtered. The resulting ice core sediments were analyzed for elemental composition, and multistep Fe-leaching experiments were conducted to determine the fraction of soluble Fe. Thus we have ascertained the solubility of particulate Fe prior to onset of melt season. Dissolved trace metals were also analyzed to ascertain changes in concentration with ice core depth of lithogenic elements (Mn, Al) and biologically important elements (Si, Mo, Cu, Zn). Preliminary results show some enrichment of lithogenic inputs near surface, indicating dust deposition, and lower portions of the cores, suggesting resuspended sediments from the continental shelf. Concentrations of some biologically important elements decrease with depth, suggesting possible

  3. Effects of cyanide and dissolved oxygen concentration on biological Au recovery.

    PubMed

    Kita, Yoshito; Nishikawa, Hiroshi; Takemoto, Tadashi

    2006-07-25

    The number of discarded electric devices containing traces of Au is currently increasing. It is desirable to recover this Au because of its valuable physicochemical properties. Au is usually dissolved with relatively high concentrations of cyanide, which is associated with environmental risk. Chromobacterium violaceum is able to produce and detoxify small amounts of cyanide, and may thus be able to recover Au from discarded electric devices. This study investigated the effects of cyanide and dissolved oxygen concentration on biological Au recovery. Cyanide production by C. violaceum was sufficient to dissolve Au, while maintaining a high cyanide concentration did not enhance Au dissolution. Increased oxygen concentration enhanced Au dissolution from 0.04 to 0.16 mmol/l within the test period of 70 h. Electrochemical measurement clarified this phenomenon; the rest potential of Au in the cyanide solution produced by C. violaceum increased from -400 to -200 mV, while in the sterile cyanide solution, it was constant in cyanide concentrations ranging from 0 to 1.5 mmol/l and increased in dissolved oxygen concentrations ranging from 0 to 0.25 mmol/l. Therefore, it was clarified that dissolved oxygen concentration is the main factor affecting the efficiency of cyanide leaching of gold by using bacteria.

  4. Metal concentrations of tadpoles in experimental ponds

    USGS Publications Warehouse

    Sparling, D.W.; Lowe, T.P.

    1996-01-01

    Anuran tadpoles are found in a variety of habitats, many of which are acidified or have high ambient concentrations of metals from anthropogenic sources. A few studies that have been conducted on metals in tadpoles demonstrate that they can contain high concentrations of some metals but have not demonstrated clear relationships between ambient conditions and metal concentrations. This study examines the influence of soil, water treatment, amphibian species, and body portion analyzed on metal concentration in tadpoles. In northern cricket frogs, gray treefrogs, and green frogs, concentrations of Al and Fe exceeded I0000 g.g-1 and Mg and Mn exceeded 1000 g g-1. Body concentrations of Ba, Be, Fe, Mg, Mn, Ni, Pb, and Sr increased with soil concentrations. Acidification reduced body concentrations of Be and Sr, and pH correlated with Be, Mg, and Sr. Gray treefrogs had significantly lower concentrations of most metals compared to northern cricket frogs, possibly because of differences in microhabitats and soil ingestion. More than half of most metals was sequestered in the gut coil of green frog tadpoles, probably mixed with soil. Depending on bio-availability, many of the metals in gut coils and whole bodies of these tadpoles could be potentially toxic to predators.

  5. Silver nanoparticle toxicity to Daphnia magna is a function of dissolved silver concentration.

    PubMed

    Newton, Kim M; Puppala, Hema L; Kitchens, Christopher L; Colvin, Vicki L; Klaine, Stephen J

    2013-10-01

    The most persistent question regarding the toxicity of silver nanoparticles (AgNPs) is whether this toxicity is due to the nanoparticles themselves or the silver ions (Ag(+)) they release. The present study investigates the role of surface coating and the presence of dissolved organic carbon on the toxicity of AgNPs to Daphnia magna and tests the hypothesis that the acute toxicity of AgNPs is a function of dissolved Ag produced by nanoparticle dissolution. Toxicity of silver nitrate (AgNO3) and AgNPs with surface coatings-gum arabic (AgGA), polyethylene glycol (AgPEG), and polyvinylpyrrolidone (AgPVP)-at 48 h was assessed in US Environmental Protection Agency moderately hard reconstituted water alone and augmented with Suwannee River dissolved organic carbon (DOC). As expected, AgNO3 was the most toxic to D. magna and AgPVPs were the least toxic. In general, Suwannee River DOC presence reduced the toxicity of AgNO3, AgGAs, and AgPEG, while the toxicity of AgPVPs was unaffected. The measured dissolved Ag concentrations for all AgNPs and AgNO3 at the 48-h median lethal concentration in moderately hard reconstituted water were similar. The presence of Suwannee River DOC decreased the ratio of measured dissolved Ag to measured total Ag concentration. These results support the hypothesis that toxicity of AgNPs to D. magna is a function of dissolved Ag concentration from these particles.

  6. Methods of deoxygenating metals having oxygen dissolved therein in a solid solution

    DOEpatents

    Zhang, Ying; Fang, Zhigang Zak; Sun, Pei; Xia, Yang; Zhou, Chengshang

    2017-06-06

    A method of deoxygenating metal can include forming a mixture of: a metal having oxygen dissolved therein in a solid solution, at least one of metallic magnesium and magnesium hydride, and a magnesium-containing salt. The mixture can be heated at a deoxygenation temperature for a period of time under a hydrogen-containing atmosphere to form a deoxygenated metal. The deoxygenated metal can then be cooled. The deoxygenated metal can optionally be subjected to leaching to remove by-products, followed by washing and drying to produce a final deoxygenated metal.

  7. Effect of dissolved oxygen concentration on iron efficiency: Removal of three chloroacetic acids.

    PubMed

    Tang, Shun; Wang, Xiao-mao; Mao, Yu-qin; Zhao, Yu; Yang, Hong-wei; Xie, Yuefeng F

    2015-04-15

    The monochloroacetic, dichloroacetic and trichloroacetic acid (MCAA, DCAA and TCAA) removed by metallic iron under controlled dissolved oxygen conditions (0, 0.75, 1.52, 2.59, 3.47 or 7.09 mg/L DO) was investigated in well-mixed batch systems. The removal of CAAs increased first and then decreased with increasing DO concentration. Compared with anoxic condition, the reduction of MCAA and DCAA was substantially enhanced in the presence of O2, while TCAA reduction was significantly inhibited above 2.59 mg/L. The 1.52 mg/L DO was optimum for the formation of final product, acetic acid. Chlorine mass balances were 69-102%, and carbon mass balances were 92-105%. With sufficient mass transfer from bulk to the particle surface, the degradation of CAAs was limited by their reduction or migration rate within iron particles, which were dependent on the change of reducing agents and corrosion coatings. Under anoxic conditions, the reduction of CAAs was mainly inhibited by the available reducing agents in the conductive layer. Under low oxic conditions, the increasing reducing agents and thin lepidocrocite layer were favorable for CAA dechlorination. Under high oxic conditions, the redundant oxygen competing for reducing agents and significant lepidocrocite growth became the major restricting factors. Various CAA removal mechanisms could be potentially applied to explaining the effect of DO concentration on iron efficiency for contaminant reduction in water and wastewater treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

  9. DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

  10. Dissolved volatile concentrations in an ore-forming magma

    USGS Publications Warehouse

    Lowenstern, J. B.

    1994-01-01

    Infrared spectroscopic measurements of glass inclusions within quartz phenocrysts from the Plinian fallout of the 22 Ma tuff of Pine Grove show that the trapped silicate melt contained high concentrations of H2O and CO2. Intrusive porphyries from the Pine Grove system are nearly identical in age, composition, and mineralogy to the tephra, and some contain high-grade Mo mineralization. Assuming that the porphyry magmas originally contained similar abundances of volatile components as the erupted rocks, they would have been saturated with fluid at pressures far greater than those at which the porphyries were emplaced and mineralized. The data are consistent with formation of Climax-type Mo porphyry deposits by prolonged fluid flux from a large volume of relatively Mo-poor (1-5 ppm) magma. -from Author

  11. The effect of solids retention time on dissolved methane concentration in anaerobic membrane bioreactors.

    PubMed

    Yeo, Hyeongu; Lee, Hyung-Sool

    2013-01-01

    We assessed the effect of solids retention times (SRT) on dissolved methane concentration in a lab-scale anaerobic membrane bioreactor (AnMBR) operated at SRT 20d and 40d at ambient temperature (23 +/- 1 degrees C). Daily methane production was 196 +/- 17 mL/d and 285 +/- 18 mL/d for SRT 20d and 40d, respectively. In comparison, the average concentration of dissolved methane in AnMBR permeates was 9.9 +/- 2.3 mg/L for SRT 20d (close to thermodynamic equilibrium), which was decreased to 4.3 +/- 0.3 mg/L for SRT 40d. We often found oversaturation of dissolved methane at SRT 20d, which means that mass transfer of dissolved methane from liquid to gas phase is dynamic at this short SRT. However, we never detected oversaturation of dissolved methane at SRT 40d, due to slow endogenous decay kinetics. Higher daily methane production at SRT 40d than that at SRT 20d indicates that methane was supplementarily produced from biomass electrons by endogenous decay. This study shows that operation of AnMBRs under long SRT can keep low dissolved methane concentration in AnMBR permeate, along with high methane yield.

  12. Hypolimnetic concentrations of dissolved oxygen, nutrients, and trace elements in Coeur d'Alene Lake, Idaho

    USGS Publications Warehouse

    Woods, P.F.

    1989-01-01

    A reconnaissance study of Coeur d'Alene Lake, Idaho done from May through November 1987 assessed water quality throughout the lake. Particular emphasis was on hypolimnetic concentrations of dissolved oxygen, nutrients, and trace elements. Study results enabled refinement of the sampling protocol in a U.S. Geological Survey research proposal for a large-scale investigation of nutrient enrichment and trace element contamination problems affecting the 129.5 sq kilometer lake in northern Idaho. Hypolimnetic dissolved-oxygen concentrations as low as 4.1 mg/L in November and the frequent occurrence of supersaturated dissolved-oxygen concentrations during June through August indicated nutrient enrichment. Secchi-disc depths in the lake 's central and southern areas were typical of mesotrophic conditions, whereas oligotrophic conditions prevailed in the northern area. Throughout the study, hypolimnetic concentrations of total recoverable zinc exceeded chronic and acute toxicity criteria for freshwater aquatic life. (USGS)

  13. The effect of membrane filtration artifacts on dissolved trace element concentrations

    USGS Publications Warehouse

    Horowitz, A.J.; Elrick, K.A.; Colberg, M.R.

    1992-01-01

    Among environment scientists, the current and almost universally accepted definition of dissolved constituents is an operational one only those materials which pass through a 0.45-??m membrane filter are considered to be dissolved. Detailed laboratory and field studies on Fe and Al indicate that a number of factors associated with filtration, other than just pore size, can substantially alter 'dissolved' trace element concentrations; these include: filter type, filter diameter, filtration method, volume of sample processed, suspended sediment concentration, suspended sediment grain-size distribution, concentration of colloids and colloidally-associated trace elements and concentration of organic matter. As such, reported filtered-water concentrations employing the same pore size filter may not be equal. Filtration artifacts may lead to the production of chemical data that indicate seasonal or annual 'dissolved' chemical trends which do not reflect actual environmental conditions. Further, the development of worldwide averages for various dissolved chemical constituents, the quantification of geochemical cycles, and the determination of short- or long-term environmental chemical trends may be subject to substantial errors, due to filtration artifacts, when data from the same or multiple sources are combined. Finally, filtration effects could have a substantial impact on various regulatory requirements.

  14. Effect of Dissolved Oxygen Concentration on Development and Hatching of Channel Catfish Ictalurus punctatus Eggs

    USDA-ARS?s Scientific Manuscript database

    Recommendations on required dissolved oxygen (DO) concentrations in channel catfish hatcheries vary widely. This study was conducted to determine effects of DO concentration on development and hatching success of channel catfish eggs. Five channel catfish spawns were collected from a pond at the T...

  15. Production Responses of Channel Catfish to Minimum Daily Dissolved Oxygen Concentrations in Earthen Ponds

    USDA-ARS?s Scientific Manuscript database

    The purpose of this study was to determine the effects of the minimum daily dissolved oxygen (DO) concentration on production parameters of channel catfish Ictalurus punctatus in earthen ponds. Fifteen one-acre ponds (5 ponds per treatment) were managed as High Oxygen (minimum DO concentrations aver...

  16. Effect of dissolved oxygen concentration on growth of fingerling hybrid striped bass

    USDA-ARS?s Scientific Manuscript database

    Management of dissolved oxygen (DO) concentration in production ponds is important because fish growth and yield are greater in ponds with higher DO concentrations. The purpose of this study was to evaluate growth and metabolic responses of hybrid striped bass (Morone chrysops x M. saxatilis; HSB) f...

  17. Effect of daily minimum pond dissolved oxygen concentration on hybrid striped bass fingerling yield

    USDA-ARS?s Scientific Manuscript database

    Management of dissolved oxygen (DO) concentration in ponds at night during the growing season is important because fish growth and yield are greater in ponds with higher nightly DO concentrations. The purpose of this study was to quantify the production and water quality responses of hybrid striped ...

  18. Method of dissolving metal oxides with di- or polyphosphonic acid and a redundant

    DOEpatents

    Horwitz, Earl P.; Chiarizia, Renato

    1996-01-01

    A method of dissolving metal oxides using a mixture of a di- or polyphosphonic acid and a reductant wherein each is present in a sufficient amount to provide a synergistic effect with respect to the dissolution of metal oxides and optionally containing corrosion inhibitors and pH adjusting agents.

  19. Trace metal concentrations in oxidation ponds

    SciTech Connect

    Suffern, J.S.; Fitzgerald, C.M.; Szluha, A.T.

    1981-11-01

    Heavy metal concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the wastewater, sludge, and biotic components of the Oak Ridge National Laboratory oxidation ponds were examined to determine whether metals accumulated in tilapia. Results indicated that metal levels in the wastewater and biotic components are generally low and that the major metal reservoir is the sludge. Metals did not accumulate beyond established standards in the muscle or liver of tilapia grown in the oxidation ponds. This result may be partially due to the rapid growth rates of these fish (1-2 g fish/sup -1//day/sup -1/), with new tissue developing more rapidly than metals can accumulate. Another factor may be that the high concentrations of organic complexes in the ponds lower the availability of metals to the biota.

  20. Monitoring dissolved copper concentrations in Chesapeake Bay, U.S.A.

    PubMed

    Hall, W S; Bushong, S J; Hall, L W; Lenkevich, M J; Pinkney, A E

    1988-07-01

    Dissolved copper and selected water chemistry parameters were monitored for 11 months in Chesapeake Bay, U.S.A. Dissolved copper concentrations in four recreational marinas, a large harbor, two major river systems, and a heavily used shipping canal ranged from below detectable levels to 80 μg L(-1) (\\-X=11.7 μg L(-1)). Dissolved copper was detected >91% of the time at five locations. Lowest copper concentrations were found in Potomac River, Baltimore Harbor, Pier One Marina, and C & D Canal (\\-X=6-10 μg L(-1); slightly higher levels of dissolved copper were found in Choptank River (\\-X=12 μg L(-1)). Highest levels of copper were detected in Port Annapolis, Hartge, and Piney Narrows Marinas (\\-X=13-18 μg L(-1)), with the highest values observed in the study (70 and 80 μg L(-1)) found in two of these marinas. Copper in the three marinas with highest dissolved copper levels could have been toxic to some of the more sensitive aquatic species. Intensive study of one marina indicated that a likely source of dissolved copper was the recreational boats housed in the marina.

  1. Dissolved and labile concentrations of Cd, Cu, Pb, and Zn in the South Fork Coeur d'Alene River, Idaho: Comparisons among chemical equilibrium models and implications for biotic ligand models

    USGS Publications Warehouse

    Balistrieri, L.S.; Blank, R.G.

    2008-01-01

    In order to evaluate thermodynamic speciation calculations inherent in biotic ligand models, the speciation of dissolved Cd, Cu, Pb, and Zn in aquatic systems influenced by historical mining activities is examined using equilibrium computer models and the diffusive gradients in thin films (DGT) technique. Several metal/organic-matter complexation models, including WHAM VI, NICA-Donnan, and Stockholm Humic model (SHM), are used in combination with inorganic speciation models to calculate the thermodynamic speciation of dissolved metals and concentrations of metal associated with biotic ligands (e.g., fish gills). Maximum dynamic metal concentrations, determined from total dissolved metal concentrations and thermodynamic speciation calculations, are compared with labile metal concentrations measured by DGT to assess which metal/organic-matter complexation model best describes metal speciation and, thereby, biotic ligand speciation, in the studied systems. Results indicate that the choice of model that defines metal/organic-matter interactions does not affect calculated concentrations of Cd and Zn associated with biotic ligands for geochemical conditions in the study area, whereas concentrations of Cu and Pb associated with biotic ligands depend on whether the speciation calculations use WHAM VI, NICA-Donnan, or SHM. Agreement between labile metal concentrations and dynamic metal concentrations occurs when WHAM VI is used to calculate Cu speciation and SHM is used to calculate Pb speciation. Additional work in systems that contain wide ranges in concentrations of multiple metals should incorporate analytical speciation methods, such as DGT, to constrain the speciation component of biotic ligand models. ?? 2008 Elsevier Ltd.

  2. Metal leaching from MSWI bottom ash as affected by salt or dissolved organic matter.

    PubMed

    Olsson, S; Gustafsson, J P; Kleja, D Berggren; Bendz, D; Persson, I

    2009-02-01

    In order to manage municipal solid waste incineration (MSWI) bottom ash safely, risk assessments, including the prediction of leaching under different field conditions, are necessary. In this study, the influence of salt or dissolved organic matter (DOM) in the influent on metal leaching from MSWI bottom ash was investigated in a column experiment. The presence of salt (0.1M NaCl) resulted in a small increase of As leaching, whereas no impact on leachate concentration was found when lakewater DOM (35.1mg/l dissolved organic carbon) was added. Most of the added DOM was retained within the material. Further, X-ray spectroscopy revealed that Cu(II) was the dominating form of Cu and that it probably occurred as a CuO-type mineral. The Cu(2+) activity in the MSWI bottom ash leachate was most likely determined by the dissolution of CuO together with the formation of Cu-DOM complexes and possibly also by adsorption to (hydr)oxide minerals. The addition of lake DOM in the influent resulted in lower saturation indices for CuO in the leachates, which may be due to slow CuO dissolution kinetics in combination with strong Cu-DOM complexation.

  3. Trace metal concentrations in shallow ground water

    USGS Publications Warehouse

    Zelewski, L.M.; Krabbenhoft, D.P.; Armstrong, D.E.

    2001-01-01

    Trace metal clean sampling and analysis techniques were used to examine the temporal patterns or Hg, Cu, and Zn concentrations in shallow ground water, and the relationships between metal concentrations in ground water and in a hydrologically connected river. Hg, Cu, and Zn concentrations in ground water ranged from 0.07 to 4.6 ng L-1, 0.07 to 3.10 ??g L-1, and 0.17 to 2.18 ??g L-1, respectively. There was no apparent seasonal pattern in any of the metal concentrations. Filtrable Hg, Cu, and Zn concentrations in the North Branch of the Milwaukee River ranged from below the detection limit to 2.65 ng Hg L-1, 0.51 to 4.30 ??g Cu L-1, and 0.34 to 2.33 ??g Zn L-1. Thus, metal concentrations in ground water were sufficiently high to account for a substantial fraction of the filtrable trace metal concentration in the river. Metal concentrations in the soil ranged from 8 to 86 ng Hg g-1, 10 to 39 ??g Cu g-1, and 15 to 84 ??g Zn g-1. Distribution coefficients, KD, in the aquifer were 7900, 22,000, and 23,000 L kg-1 for Hg, Cu, and Zn, respectively. These values were three to 40 times smaller than KD values observed in the Milwaukee River for suspended particulate matter.

  4. Rare earth element concentrations in dissolved and acid available particulate forms for eastern UK rivers

    NASA Astrophysics Data System (ADS)

    Neal, C.

    2007-01-01

    Variations in concentration of yttrium (Y), lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm) and gadolinium (Gd) among rivers of eastern England and the border with Scotland are described in relation to the dissolved (<0.45 µM) fraction and acid-available particulate (AAP) fractions. The rivers cover a range of rural, agricultural and urban/industrial environments. Yttrium and the lanthanides show significant levels of both dissolved and acid-available particulate forms (typically about 40% in the dissolved form). For the dissolved phase, Y and the lanthanides are linearly correlated with each other and with iron: most of this dissolved component may be in a micro-particulate/colloidal form. The Y and lanthanide relationships show marked scatter and there are anomalously high La concentrations at times for the rivers Great Ouse, Thames and Wear that are probably linked to pollutant sources. For the Ouse, and especially for one of its tributaries, the Swale, relatively high Sm concentrations are probably associated with mineralisation within the catchment and contamination of the associated flood plain. For the AAP components, there are strong linear relationships with Y and the lanthanides across all the rivers. There is also a strong link between these AAP associated REE and AAP iron, although the scatter is greater and the industrial rivers have a lower lanthanide to iron ratio, probably due to iron-rich contaminants.

  5. Significance of groundwater discharge along the coast of Poland as a source of dissolved metals to the southern Baltic Sea

    USGS Publications Warehouse

    Szymczycha, Beata; Kroeger, Kevin D.; Pempkowiak, Janusz

    2016-01-01

    Fluxes of dissolved trace metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) via groundwater discharge along the southern Baltic Sea have been assessed for the first time. Dissolved metal concentrations in groundwater samples were less variable than in seawater and were generally one or two orders of magnitude higher: Cd (2.1–2.8 nmol L− 1), Co (8.70–8.76 nmol L− 1), Cr (18.1–18.5 nmol L− 1), Mn (2.4–2.8 μmol L− 1), Pb (1.2–1.5 nmol L− 1), Zn (33.1–34.0 nmol L− 1). Concentrations of Cu (0.5–0.8 nmol L− 1) and Ni (4.9–5.8 nmol L− 1) were, respectively, 32 and 4 times lower, than in seawater. Groundwater-derived trace metal fluxes constitute 93% for Cd, 80% for Co, 91% for Cr, 6% for Cu, 66% for Mn, 4% for Ni, 70% for Pb and 93% for Zn of the total freshwater trace metal flux to the Bay of Puck. Groundwater-seawater mixing, redox conditions and Mn-cycling are the main processes responsible for trace metal distribution in groundwater discharge sites.

  6. Influence of dissolved oxygen concentration on the pharmacokinetics of alcohol in humans.

    PubMed

    Baek, In-hwan; Lee, Byung-yo; Kwon, Kwang-il

    2010-05-01

    Ethanol oxidation by the microsomal ethanol oxidizing system requires oxygen for alcohol metabolism, and a higher oxygen uptake increases the rate of ethanol oxidation. We investigated the effect of dissolved oxygen on the pharmacokinetics of alcohol in healthy humans (n = 49). The concentrations of dissolved oxygen were 8, 20, and 25 ppm in alcoholic drinks of 240 and 360 ml (19.5% v/v). Blood alcohol concentrations (BACs) were determined by converting breath alcohol concentrations. Breath samples were collected every 30 min when the BAC was higher than 0.015%, 20 min at BAC < or =0.015%, 10 min at BAC < or =0.010%, and 5 min at BAC < or =0.006%. The high dissolved oxygen groups (20, 25 ppm) descended to 0.000% and 0.050% BAC faster than the normal dissolved oxygen groups (8 ppm; p < 0.05). In analyzing pharmacokinetic parameters, AUC(inf) and K(el) of the high oxygen groups were lower than in the normal oxygen group, while C(max) and T(max) were not significantly affected. In a Monte Carlo simulation, the lognormal distribution of mean values of AUC(inf) and t(1/2) was expected to be reduced in the high oxygen group compared to the normal oxygen group. In conclusion, elevated dissolved oxygen concentrations in alcoholic drinks accelerate the metabolism and elimination of alcohol. Thus, enhanced dissolved oxygen concentrations in alcohol may have a role to play in reducing alcohol-related side effects and accidents.

  7. Nonaqueous method for dissolving lanthanide and actinide metals

    DOEpatents

    Crisler, L.R.

    1975-11-11

    Lanthanide and actinide beta-diketonate complex molecular compounds are produced by reacting a beta-diketone compound with a lanthanide or actinide element in the elemental metallic state in a mixture of carbon tetrachloride and methanol.

  8. Problems associated with using filtration to define dissolved trace element concentrations in natural water samples

    USGS Publications Warehouse

    Horowitz, A.J.; Lum, K.R.; Garbarino, J.R.; Hall, G.E.M.; Lemieux, C.; Demas, C.R.

    1996-01-01

    Field and laboratory experiments indicate that a number of factors associated with filtration other than just pore size (e.g., diameter, manufacturer, volume of sample processed, amount of suspended sediment in the sample) can produce significant variations in the 'dissolved' concentrations of such elements as Fe, Al, Cu, Zn, Pb, Co, and Ni. The bulk of these variations result from the inclusion/exclusion of colloidally associated trace elements in the filtrate, although dilution and sorption/desorption from filters also may be factors. Thus, dissolved trace element concentrations quantitated by analyzing filtrates generated by processing whole water through similar pore-sized filters may not be equal or comparable. As such, simple filtration of unspecified volumes of natural water through unspecified 0.45-??m membrane filters may no longer represent an acceptable operational definition for a number of dissolved chemical constituents.

  9. Concentration of viruses and dissolved DNA from aquatic environments by vortex flow filtration.

    PubMed Central

    Paul, J H; Jiang, S C; Rose, J B

    1991-01-01

    Vortex flow filtration (VFF) was used to concentrate viruses and dissolved DNA from freshwater and seawater samples taken in Florida, the Gulf of Mexico, and the Bahamas Bank. Recoveries of T2 phage and calf thymus DNA added to artificial seawater and concentrated by VFF were 72.8 and 80%, respectively. Virus concentrations determined by transmission electron microscopy of VFF-concentrated samples ranged from 3.4 x 10(7)/ml for a eutrophic Tampa Bay sample to 2.4 x 10(5) for an oligotrophic oceanic surface sample from the southeastern Gulf of Mexico. Viruslike particles were also observed in a sample taken from a depth of 1,500 m in the subtropical North Atlantic Ocean. Filtration of samples through Nuclepore or Durapore filters (pore size, 0.2 micron) prior to VFF reduced phage counts by an average of two-thirds. Measurement of dissolved-DNA content by Hoechst 33258 fluorescence in environmental samples concentrated by VFF yielded values only ca. 35% of those obtained for samples concentrated by ethanol precipitation (the standard dissolved-DNA method). However, ethanol precipitation of VFF-concentrated extracts resulted in an increase in measurable DNA, reaching 80% of the value obtained by the standard method. These results indicate that a portion of the naturally occurring dissolved DNA is in a form inaccessible to nucleases and Hoechst stain, perhaps bound to protein or other polymeric material, and is released upon ethanol precipitation. Viral DNA contents estimated from viral counts averaged only 3.7% (range, 0.9 to 12.3%) of the total dissolved DNA for samples from freshwater, estuarine, and offshore oligotrophic environments.(ABSTRACT TRUNCATED AT 250 WORDS) Images PMID:1768090

  10. Combining modelling and monitoring to determine fluxes of water, dissolved and particulate metals through the Dover Strait

    NASA Astrophysics Data System (ADS)

    Prandle, D.; Ballard, G.; Flatt, D.; Harrison, A. J.; Jones, S. E.; Knight, P. J.; Loch, S.; McManus, J.; Player, R.; Tappin, A.

    1996-02-01

    Contaminant fluxes in a shelf sea system are determined from a series of interrelated studies involving monitoring, modelling and theoretical development. Year-long measurements of currents through the Dover Strait were made in 1990-1991 using both shore-based high frequency (HF) radar and a bottom-mounted acoustic Doppler current profiler (ADCP). These measurements were combined to determine both the residual component of tidal flow and the wind-forced residual flow resulting in an estimate of the net long term flow into the North Sea of 94,000 m 3 s -1—a value in close agreement with the most recent high resolution modelling of Salomon et al. (1993). The temporal variability in these radar and ADCP observations are compared with synoptic wind, tide gauge and numerical model data. The fluxes of the dissolved metals Cd, Cu, Ni, Pb and Zn through the Straits are then calculated using concentrations in the Strait derived from a study by McManus and Prandle (1994). The latter involved multiple regression of model simulations of dispersion (with the model flow through the Dover Strait corresponding to the above monitored value) against data from four surveys in the southern North Sea carried out in 1988-1989 as part of the North Sea Project. The mean concentrations determined from this inverse modelling technique depend directly on the net water flux through the Strait. Thus, since it is shown here that the results for the more conservative metals Cd, Cu, Ni and Zn agree closely with direct measurements by Statham et al. (1993), this lends further confidence to this new estimate of net flow derived from monitoring. The flux of suspended sediments is calculated using time and cross-sectionally averaged suspended sediment concentrations obtained during a cruise in June 1990 (Jones et al., 1993). The particulate metal fluxes are calculated by combining these suspended sediment concentrations with the dissolved metal concentrations and publised Kd (partitioning

  11. User's manual for estimation of dissolved-solids concentrations and loads in surface water

    USGS Publications Warehouse

    Liebermann, T.D.; Middelburg, R.F.; Irvine, S.A.

    1987-01-01

    Dissolved solids in surface water are an important indicator of overall water quality. Ordinarily, dissolved-solids concentrations and loads are estimated by indirect methods that are based on periodic chemical analyses. Three computer programs , FLAGIT, DVCOND, and SLOAD, were developed to provide a consistent and accurate method of estimating dissolved-solids concentrations and loads. FLAGIT retrieves daily values of specific conductance and discharge and periodic water quality analyses from the U.S. Geologic Survey 's National Water Data Storage and Retrieval System data base, deletes incomplete data, and flags possible data errors. DVCOND fills in missing daily values of specific conductance, when appropriate, by linear interpolation. Using water quality data, SLOAD computes 3 yr moving regressions of dissolved-solids loads as a function of specific conductance and discharge. SLOAD then applies the regression coefficients to the daily values data to estimate daily dissolved-solids loads that are summed by month and by year. Separate regressions are used to estimate the mass fractions of six major ions. The theoretical basis and underlying assumptions of the procedures are presented, with documentation of the programs and their use. (USGS)

  12. Novel Apparatus for the Real-Time Quantification of Dissolved Gas Concentrations and Isotope Ratios

    NASA Astrophysics Data System (ADS)

    Gupta, M.; Leen, J.; Baer, D. S.; Owano, T. G.; Liem, J.

    2013-12-01

    Measurements of dissolved gases and their isotopic composition are critical in studying a variety of phenomena, including underwater greenhouse gas generation, air-surface exchange, and pollution migration. These studies typically involve obtaining water samples from streams, lakes, or ocean water and transporting them to a laboratory, where they are degased. The gases obtained are then generally measured using gas chromatography and isotope ratio mass spectrometry for concentrations and isotope ratios, respectively. This conventional, off-line methodology is time consuming, significantly limits the number of the samples that can be measured and thus severely inhibits detailed spatial and temporal mapping of gas concentrations and isotope ratios. In this work, we describe the development of a new membrane-based degassing device that interfaces directly to Los Gatos Research (cavity enhanced laser absorption or Off-Axis ICOS) gas analyzers (cavity enhanced laser absorption or Off-Axis ICOS analyzers) to create an autonomous system that can continuously and quickly measure concentrations and isotope ratios of dissolved gases in real time in the field. By accurately controlling the water flow rate through the membrane degasser, gas pressure on the outside of the membrane, and water pressure on the inside of the membrane, the system is able to generate precise and highly reproducible results. Moreover, by accurately measuring the gas flow rates in and out of the degasser, the gas-phase concentrations (ppm) could be converted into dissolved gas concentrations (nM). We will present detailed laboratory test data that quantifies the linearity, precision, and dynamic range of the system for the concentrations and isotope ratios of dissolved methane, carbon dioxide, and nitrous oxide. By interfacing the degassing device to a novel cavity-enhanced spectrometer (developed by LGR), preliminary data will also be presented for dissolved volatile organics (VOC) and other

  13. Declines in Dissolved Silica Concentrations in Western Virginia Streams (1988- 2003)

    NASA Astrophysics Data System (ADS)

    Grady, A. E.; Scanlon, T. M.; Galloway, J. N.

    2006-12-01

    Dissolved silica concentrations in western Virginia streams showed a significant bias toward declines (p<0.0001) over the time period from 1988-2003. Streams with the greatest declines were those that had the highest mean dissolved silica concentrations, specific to watersheds underlain by basaltic and granitic bedrock. We examined potential geochemical, hydrological, and biological factors that could account for the observed widespread declines, focusing on six core watersheds where weekly stream chemistry data were available. No relationships were evident between stream water dissolved silica concentrations and pH, a finding supported by the results from a geochemical model applied to the dominant bedrock mineralogy. Along with changes in watershed acidity, changes in precipitation and discharge were also discounted since no significant trends were observed over the study period. Analyses of two longer-term datasets that extend back to 1979 revealed that the initiation of the dissolved silica declines coincided with the timing of a gypsy moth (Lymantria dispar) defoliation event. We develop a conceptual model centered on benthic diatoms, which are found within each of the six core watersheds but in greater abundance in the more silica-rich streams. Gypsy moth defoliation lead to greater sunlight penetration and enhanced nitrate concentrations in the streams, which could have spurred population growth and silica uptake. The model can explain why the observed declines are primarily driven by decreased concentrations during low-flow conditions. This study illustrates lasting effects of disturbance on watershed biogeochemistry, in this case causing decadal-scale variability in stream water dissolved silica concentrations.

  14. Tracking Dissolved Methane Concentrations near Active Seeps and Gas Hydrates: Sea of Japan.

    NASA Astrophysics Data System (ADS)

    Snyder, G. T.; Aoki, S.; Matsumoto, R.; Tomaru, H.; Owari, S.; Nakajima, R.; Doolittle, D. F.; Brant, B.

    2015-12-01

    A number of regions in the Sea of Japan are known for active gas venting and for gas hydrate exposures on the sea floor. In this investigation we employed several gas sensors mounted on a ROV in order to determine the concentrations of dissolved methane in the water near these sites. Methane concentrations were determined during two-second intervals throughout each ROV deployment during the cruise. The methane sensor deployments were coupled with seawater sampling using Niskin bottles. Dissolved gas concentrations were later measured using gas chromatography in order to compare with the sensor results taken at the same time. The observed maximum dissolved methane concentrations were much lower than saturation values, even when the ROV manipulators were in contact with gas hydrate. Nonetheless, dissolved concentrations did reach several thousands of nmol/L near gas hydrate exposures and gas bubbles, more than two orders of magnitude over the instrumental detection limits. Most of the sensors tested were able to detect dissolved methane concentrations as low as 10 nmol/L which permitted detection when the ROV approached methane plume sites, even from several tens of meters above the sea floor. Despite the low detection limits, the methane sensors showed variable response times when returning to low-background seawater (~5nM). For some of the sensors, the response time necessary to return to background values occurred in a matter of minutes, while for others it took several hours. Response time, as well as detection limit, should be an important consideration when selecting methane sensors for ROV or AUV investigations. This research was made possible, in part, through funding provided by the Japanese Ministry of Economy, Trade and Industry (METI).

  15. ACUTE SENSITIVITY OF JUVENILE SHORTNOSE STURGEON TO LOW DISSOLVED OXYGEN CONCENTRATIONS

    EPA Science Inventory

    Campbell, Jed G. and Larry R. Goodman. 2004. Acute Sensitivity of Juvenile Shortnose Sturgeon to Low Dissolved Oxygen Concentrations. EPA/600/J-04/175. Trans. Am. Fish. Soc. 133(3):772-776. (ERL,GB 1155).

    There is considerable concern that factors such as eutrophication, ...

  16. ACUTE SENSITIVITY OF JUVENILE SHORTNOSE STURGEON TO LOW DISSOLVED OXYGEN CONCENTRATIONS

    EPA Science Inventory

    Campbell, Jed G. and Larry R. Goodman. 2004. Acute Sensitivity of Juvenile Shortnose Sturgeon to Low Dissolved Oxygen Concentrations. EPA/600/J-04/175. Trans. Am. Fish. Soc. 133(3):772-776. (ERL,GB 1155).

    There is considerable concern that factors such as eutrophication, ...

  17. Watershed land use as a determinant of metal concentrations in freshwater systems.

    PubMed

    Das, Biplob; Nordin, Rick; Mazumder, Asit

    2009-12-01

    Concentrations of Fe, Mn, Cu, dissolved organic matter (DOM), and pH were synthesized from 30 publications to determine the factors regulating concentrations and behavior of metals in freshwater systems. Results from the review suggest that contrasting watershed land use can directly (erosion and runoff) and indirectly (in-lake processes including metal-DOM-pH interactions) affect the metal concentrations in freshwater systems. Among the watershed land uses considered here, concentrations of Fe, Mn, and Cu were observed in the following order: arctic lakes < forested < agricultural < urbanized < mined. A drastic difference in mean metal concentrations has been observed when undisturbed or low impact watersheds (arctic and forested) were changed by agricultural, urban, and mining developments. Relationships between metal concentrations and pH revealed that metals precipitate at high pH (pH > 5). Additionally, at pH < 5, metal concentrations were significantly correlated with DOM due to metal-DOM complexation. High ratios of metal: DOM occur only at low DOM concentrations. Collectively, two general conclusions can be drawn from this review. First, lakes, rivers, and streams with urbanized watersheds are the most susceptible to increased concentrations of metals. Secondly, these results also suggest that regardless of high or low DOM in the water column, pH would affect metal concentrations in freshwater systems. Nonetheless, free metal ions would be higher in freshwater systems with acidic water and low DOM.

  18. Use of bioadsorbents for removing dissolved metals from dilute solutions

    SciTech Connect

    Watson, J.S.; Scott, C.D. )

    1988-01-01

    Certain microorganisms and other biological materials are able to absorb different metal ions, and this capability can be used to recovery metals from dilute sources or to remove trace impurities from wastewaters. Incorporation of the biosorbent into cross-linked gelatin beads permits them to be used in packed beds where high removal efficiencies can be obtained. Removal of strontium, an important contaminant in radioactive wastewaters, is a significant problem, and selected biosorbents immobilized in gel beds have been shown to have a significant affinity for strontium. Adsorption column performance and the roles of both the gel material and incorporated microorganisms are described.

  19. Effect of dissolved oxygen concentration on nitrite accumulation in nitrifying sequencing batch reactor.

    PubMed

    Sánchez, Omar; Bernet, Nicolas; Delgenès, Jean-Philippe

    2007-08-01

    A mathematical model based on Activated Sludge Model No. 3 (International Water Association, London) and laboratory-scale experiments were used to investigate ammonia conversion by nitrification in a sequencing batch reactor (SBR). The purpose of the study was to assess the effect of dissolved oxygen concentration on nitrite accumulation in the SBR. As the dissolved oxygen concentration in the SBR depends on the balance between oxygen consumption and oxygen transfer rates, ammonium conversion was measured for different air flowrate values to obtain different dissolved oxygen concentration profiles during the cycle. The ammonia concentration in the feeding medium was 500 mg ammonium as nitrogen (N-NH4(+))/L, and the maximum nitrite concentration achieved during a cycle was approximately 50 mg nitrite as nitrogen (N-NO2)/L. The air flow supplied to the reactor was identified as a suitable parameter to control nitrite accumulation in the SBR. This identification was carried out based on experimental results and simulation with a calibrated model. At a low value of the volumetric mass-transfer coefficient (kLa), the maximum nitrite concentration achieved during a cycle depends strongly on k(L)a, whereas, at a high value of k(L)a, the maximum nitrite concentration was practically independent of kL(a).

  20. Dissolved trace element concentrations in the East River-Long Island Sound system: relative importance of autochthonous versus allochthonous sources.

    PubMed

    Buck, Nathaniel J; Gobler, Christopher J; Sañudo-Wilhelmy, Sergio A

    2005-05-15

    Dissolved trace metal (Ag, Cd, Cu, Fe, Ni, Pb, and Zn), inorganic nutrient (NO3, NH4, PO4, H4SiO4), and DOC concentrations were measured at 43 stations during low (July 2000) and high (April 2001) river discharge conditions in surface waters of Long Island Sound (LIS). To evaluate the impact of fluvial sources to the total metal budget of the sound, samples were collected from major tributaries discharging into LIS (Thames, Quinnipiac, Housatonic, Connecticut, and East Rivers). To compare LIS with other coastal embayments, samples were also collected from five LIS coastal embayments (Manhassett Bay, Huntington Harbor, Oyster Bay, Hempstead Harbor, and Port Jefferson Harbor), which are monitored by the U.S. National Status and Trends Program. Metal and nutrient distributions identified two biogeochemical regimes within LIS: an area of relatively high nutrient and metal concentrations in the East River/Narrows region in western LIS and an area in the eastern region of the sound that had comparatively lower concentrations. Mass balance estimates indicated that, during low flow conditions, the East River was the dominant allochthonous source of most trace metals (Ag, Cd, Cu, Ni, Zn) and inorganic nutrients (NO3 and PO4); during high flow conditions, the most influential source of these constituents was the Connecticut River. Mass balance estimates also evidenced a large autochthonous source of Cu, Ni, and Zn, as their spatial distributions displayed elevated concentrations away from point sources such as the East River. Principal component analysis suggested that metal and nutrient distributions in the LIS system were influenced by different seasonal processes: remobilization from contaminated sediments, anthropogenic inputs from sewage discharges and phytoplankton scavenging during the spring freshet, and benthic remobilization during summer conditions.

  1. New Concentric Electrode Metal-Semiconductor-Metal Photodetectors

    NASA Technical Reports Server (NTRS)

    Towe, Elias

    1996-01-01

    A new metal-semiconductor-metal (MSM) photodetector geometry is proposed. The new device has concentric metal electrodes which exhibit a high degree of symmetry and a design flexibility absent in the conventional MSM device. The concentric electrodes are biased to alternating potentials as in the conventional interdigitated device. Because of the high symmetry configuration, however, the new device also has a lower effective capacitance. This device and the conventional MSM structure are analyzed within a common theoretical framework which allows for the comparison of the important performance characteristics.

  2. Role of microgel formation in scavenging of chromophoric dissolved organic matter and heavy metals in a river-sea system.

    PubMed

    Shiu, Ruei-Feng; Lee, Chon-Lin

    2017-04-15

    We use riverine and marine dissolved organic carbon (DOC) polymers to examine their aggregation behavior, and to evaluate the roles of microgel formation in scavenging of chromophoric dissolved organic matter (CDOM) and heavy metals in a river-sea system. Our results indicate that riverine and marine microgels did not exhibit very much difference in size and self-assembly curve; however, the assembly effectiveness ([microgel]/DOC) of marine samples was much higher than riverine. Instead of concentration of DOC, other factors such as types and sources of DOC polymers may control the microgel abundance in aquatic environments. After filtering water samples (microgels removed), the CDOM and selected metals (Cu, Ni, Mn) in the filtrate were quantified. CDOM and metals were concurrently removed to an extent via DOC polymer re-aggregation, which also suggested that the microgels had sequestering capability in CDOM and metals. This finding provides an alternative route for CDOM and heavy metals removal from the water column. As such the process of re-aggregation into microgels should then be considered besides traditional phase partitioning in the assessment of the ecological risk and fate of hazardous materials.

  3. [Influence of the Concentration of Dissolved Oxygen on Embryonic Development of the Common Toad (Bufo bufo)].

    PubMed

    Dmitrieva, E V

    2015-01-01

    Several series of experiments investigating the influence of dissolved oxygen concentrations on the growth rates and mortality in the embryogenesis of the common toad Bufo bufo were carried out. The experiments showed that, when the eggs develop singly, the lack of oxygen does not lead to an increase in mortality by the time of hatching and results only in a change in the dynamics of mortality: mortality occurs at an earlier stage of development than in the conditions of normal access to oxygen. Taking into account the combined effect of the density of eggs and the dissolved oxygen concentration, we increase the accuracy of analysis of the experimental results and improve the interpretation of the results. In the conditions of different initial density of eggs, the impact of the concentration of dissolved oxygen on mortality and rates of development of the common toad embryos is manifested in different ways. At high density, only a small percentage of embryos survives by the time of hatching, and the embryos are significantly behind in their development compared with the individuals that developed in normal oxygen conditions. The lack of oxygen dissolved in the water slows down the development of embryos of the common toad.

  4. Composition, removal, redox, and metal complexation properties of dissolved organic nitrogen in composting leachates.

    PubMed

    He, Xiao-Song; Xi, Bei-Dou; Zhang, Zong-Yong; Gao, Ru-Tai; Tan, Wen-Bing; Cui, Dong-Yu; Yuan, Ying

    2015-01-01

    This study investigated the composition, removal, redox, and metal complexation characteristics of dissolved organic nitrogen (DON) in composting leachates. Results showed that the leachate-derived DON comprised proteinaceous compounds and amines, and most of them were integrated into the fulvic- and humic-like substances. Neutral, basic, acidic, hydroxylic, aromatic, and sulfuric amino acids all were detected in the influent leachates. However, most of them were removed by the biological and physical processes, and only neutral amino acids were detected in the effluent. The DON was not the main contributor to the redox capability of the leachate dissolved organic matter (DOM). However, it exhibited a strong capability for metal complexation. The amines formed strong complexes with the metals Mo, Co, Cr, and Ni, while the proteinaceous matter interacted with the metals Cr and Ni. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. The Role of Dissolved Gas in Ionic Liquid Electrolytes for Secondary Lithium Metal Batteries

    DTIC Science & Technology

    2013-01-07

    devices use lithium - ion batteries comprised of a graphite anode and metal oxide cathode. Lithium , being the third-lightest element, is already synonymous...support shuttling lithium ions ( battery cycling) such as the separator, electrolyte, and cathode and anode superstructures contribute most of the...The Role of Dissolved Gas in Ionic Liquid Electrolytes for Secondary Lithium Metal Batteries Johanna K. Stark1, Yi Ding2, and Paul A. Kohl1

  6. Fluoride, Nitrate, and Dissolved-Solids Concentrations in Ground Waters of Washington

    USGS Publications Warehouse

    Lum, W. E.; Turney, Gary L.

    1984-01-01

    This study provides basic data on ground-water quality throughout the State. It is intended for uses in planning and management by agencies and individuals who have responsibility for or interest in, public health and welfare. It also provides a basis for directing future studies of ground-water quality toward areas where ground-water quality problems may already exist. The information presented is a compilation of existing data from numerous sources including: the Washington Departments of Ecology and Social and Health Services, the Environmental Protection Agency, as well as many other local, county, state and federal agencies and private corporations. Only data on fluoride, nitrate, and dissolved-solids concentrations in ground water are presented, as these constituents are among those commonly used to determine the suitability of water for drinking or other purposes. They also reflect both natural and man-imposed effects on water quality and are the most readily available water-quality data for the State of Washington. The percentage of wells with fluoride, nitrate, or dissolved-solids concentrations exceeding U.S. Environmental Protection Agency Primary and Secondary Drinking Water Regulations were about 1, about 3, and about 3, respectively. Most high concentrations occurred in widely separated wells. Two exceptions were: high concentrations of nitrate and dissolved solids in wells on the Hanford Department of Energy Facility and high concentrations of nitrate in the lower Yakima River basin. (USGS)

  7. Urban Impact of Dissolved Metals in the Paso del Norte Segment of the Rio Grande

    ERIC Educational Resources Information Center

    Freiwan, Sumayeh Ahmad

    2013-01-01

    The Paso del Norte segment of the Rio Grande experiences two seasons per year; the (wet) irrigation season and the (dry) non-irrigation season. The goal of this study was to improve the understanding of occurrence and contribution of dissolved metals in this region during the non-irrigation season. The objectives of this study were to (1) evaluate…

  8. Urban Impact of Dissolved Metals in the Paso del Norte Segment of the Rio Grande

    ERIC Educational Resources Information Center

    Freiwan, Sumayeh Ahmad

    2013-01-01

    The Paso del Norte segment of the Rio Grande experiences two seasons per year; the (wet) irrigation season and the (dry) non-irrigation season. The goal of this study was to improve the understanding of occurrence and contribution of dissolved metals in this region during the non-irrigation season. The objectives of this study were to (1) evaluate…

  9. High dissolved methane concentrations in the deep-water Ulleung Basin, East Sea of Korea

    NASA Astrophysics Data System (ADS)

    Ryu, Byong-Jae; Chun, Jong-Hwa

    2014-05-01

    As a part of the Korean National Gas Hydrate Program, a production test in the Ulleung Basin is planned to be performed in 2015. The targets are the gas hydrate-bearing sand reservoirs, which were found during the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) in 2010. To ensure a safe production test, an environmental program has been conducted by the Korea Institute of Geoscience and Mineral Resources (KIGAM) since 2012. This program includes a baseline survey using a KIGAM Seafloor Observation System (KISOS) and R/V TAMHAE II of KIGAM, development of a KIGAM Seafloor Monitoring System (KIMOS), and seafloor monitoring on various potential hazards associated with the dissociated gas from gas hydrates using the KIMOS during the production test. A survey for measuring the dissolved methane concentrations in the area at and nearby the gas hydrate production testing site was performed using R/V TAMHAE II and the KISOS. The water samples were also collected and analyzed to measure the dissolved methane concentrations by the SBE carousel water sampler installed in the KISOS and gas chromatography (GC) at KIGAM. The dissolved methane concentrations were also measured using a Frantech METS methane sensor installed in the KISOS. No dissolved methane anomaly was detected at the site where any evidence of gas hydrate presence has not been observed. On the other hand, the water analysis showed high dissolved methane concentrations at the water depth above and within the gas hydrate stability zone (GHSZ) at the site where gas hydrates were identified by drilling. However, these dissolved methane anomalies within the GHSZ were not detected by methane sensor. To examine these uncertain dissolved methane anomalies within the GHSZ, the water samples will be collected and analyzed once again, and the analytical result will be also carefully compared with the data collected using the methane sensor and deep ocean mass spectrometer (DOMS) developed by the University of

  10. Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) for dissolved metal ion removal.

    PubMed

    Su, Yiming; Adeleye, Adeyemi S; Keller, Arturo A; Huang, Yuxiong; Dai, Chaomeng; Zhou, Xuefei; Zhang, Yalei

    2015-05-01

    Sulfide-modified nanoscale zerovalent iron (S-nZVI) is attracting a lot of attention due to its ease of production and high reactivity with organic pollutants. However, its structure is still poorly understood and its potential application in heavy metal remediation has not been explored. Herein, the structure of S-nZVI and its cadmium (Cd) removal performance under different aqueous conditions were carefully investigated. Transmission electron microscopy (TEM) with an energy-dispersive X-ray spectroscopy (EDS) analysis suggested that sulfur was incorporated into the zerovalent iron core. Scanning electron microscopy (SEM) with EDS analysis demonstrated that sulfur was also homogeneously distributed within the nanoparticles. When the concentration of Na2S2O4 was increased during synthesis, a flake-like structure (FeSx) increased significantly. S-nZVI had an optimal Cd removal capacity of 85 mg/g, which was >100% higher than for pristine nZVI. Even at pH 5, over 95% removal efficiency was observed, indicating sulfide compounds played a crucial role in metal ion removal and particle chemical stability. Oxygen impaired the structure of S-nZVI but enhanced Cd removal capacity to about 120 mg/g. Particle aging had no negative effect on removal capacity of S-nZVI, and Cd-containing mixtures remained stable in a two months experiment. S-nZVI can efficiently sequester dissolved metal ions from different contaminated water matrices. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Concentrations of dissolved and particulate Polychlorinated Biphenyls in water from the Saginaw River, Michigan

    USGS Publications Warehouse

    Verbrugge, David A.; Giesy, John P.; Mora, Miguel A.; Williams, Lisa L.; Rossmann, Ronald; Moll, Russell A.; Tuchman, Marc

    1995-01-01

    The Saginaw River receives water from a major drainage basin in the east-central portion of the lower peninsula of Michigan. Historically the river has been contaminated with polychlorinated biphenyls (PCBs) from several sources. The present study was conducted to determine the concentrations of PCBs in both the dissolved and particulate phases of water in the lower Saginaw River, as well as the relative contribution of PCBs from the lower portion of the river relative to more upstream locations. Water samples were collected in 1990–1991, during a range of discharge conditions. Suspended particulates were collected from water onto glass-fiber filters by use of a “Penta-plate” filtration apparatus. Filtered water was subsequently passed through XAD-2 macroreticular resin to collect the “dissolved” PCBs. Concentrations of PCBs in both phases were determined by congener specific gas chromatography with electron capture detection. Total concentrations of PCBs ranged from 11 to 31 ng/L. The concentrations of PCBs in the dissolved phase ranged from 1.9 to 16 ng/L. The ratio of total PCBs bound to suspended particulates, relative to dissolved PCBs, was 2:1 and remained fairly constant for discharges less than approximately 400 M3/sec. The loading of total PCBs to Saginaw Bay was estimated to be 225 kg/yr, of which approximately 60% was found to be contributed by the lower 8 km of the Saginaw River.

  12. Geochemistry of Dissolved Trace Metals in the Waters of Bahia Magdalena, Baja California Sur, Pacific Coast, Mexico

    NASA Astrophysics Data System (ADS)

    Suresh Babu, S.

    2016-12-01

    Forty two samples were acquired from the surface and bottom water profiles along 5 transects spread over Bahia Magdalena lagoon, Baja California Sur to assess the behavior of trace metals in a high influenced upwelling region on the Pacific coast. To elaborate the fate of metals, also the physico-chemical parameters (pH, temperature, salinity, conductivity, dissolved oxygen). Determination of the concentrations of trace metals (Fe, Mn, Cr, Cu, Co, Pb, Ni, Zn, Cd As, Hg) were measured using Atomic absorption spectrometry. The results demonstrated high values of As, Ni and Co which is attributed to the local geology and phosphate deposits. Low values of Fe and Mn are attested to the oxic conditions of the lagoon which are responsible for the oxidation of Fe and Mn. The region witnesses raised temperatures (28.92ºC) and salinities of 35.2 PSU for its arid climatic conditions and high rates of evaporation. In general, the region presented minor quantities of dissolved trace metals due to dispersion and high intense interaction with the open sea. The results were also compared with other studies to understand the enrichment pattern in this side of the pacific coast which experiences various geothermal activities and upwelling phenomenon.

  13. The Distribution between the Dissolved and the Particulate Forms of 49 Metals across the Tigris River, Baghdad, Iraq

    PubMed Central

    Hamad, Samera Hussein; Schauer, James Jay; Shafer, Martin Merrill; Abed Al-Raheem, Esam; Satar, Hyder

    2012-01-01

    The distribution of dissolved and particulate forms of 49 elements was investigated along transect of the Tigris River (one of the major rivers of the world) within Baghdad city and in its major tributary (Diyala River) from 11 to 28 July 2011. SF-ICP-MS was used to measure total and filterable elements at 17 locations along the Tigris River transect, two samples from the Diyala River, and in one sample from the confluence of the two rivers. The calculated particulate forms were used to determine the particle-partition coefficients of the metals. No major changes in the elements concentrations down the river transect. Dissolved phases dominated the physical speciation of many metals (e.g., As, Mo, and Pt) in the Tigris River, while Al, Fe, Pb, Th, and Ti were exhibiting high particulate fractions, with a trend of particle partition coefficients of [Ti(40) > Th(35) > Fe(15) > Al(13) > Pb(4.5)] ∗ 106 L/kg. Particulate forms of all metals exhibited high concentrations in the Diyala River, though the partition coefficients were low due to high TSS (~270 mg/L). A comparison of Tigris with the major rivers of the world showed that Tigris quality in Baghdad is comparable to Seine River quality in Paris. PMID:23304083

  14. Concentrations of particulate and dissolved cylindrospermopsin in 21 Aphanizomenon-dominated temperate lakes.

    PubMed

    Rücker, Jacqueline; Stüken, Anke; Nixdorf, Brigitte; Fastner, Jutta; Chorus, Ingrid; Wiedner, Claudia

    2007-11-01

    The cyanobacterial toxin cylindrospermopsin (CYN) is widely distributed in German lakes, but volumetric data for risk assessment are lacking and it is unclear which cyanobacterial species produce CYN in Europe. We therefore analyzed CYN concentration and cyanobacterial composition of 21 German lakes in 2005. CYN was detected in 19 lakes (102 of 115 samples). In total, 45 samples contained particulate CYN only, and 57 contained both dissolved and particulate CYN. The concentrations were 0.002-0.484 microg L(-1) for particulate CYN and 0.08-11.75 microg L(-1) for dissolved CYN with a maximum of 12.1 microg L(-1) total CYN. A drinking water guideline value of 1 microg L(-1) proposed by Humpage and Falconer [2003. Oral toxicity of the cyanobacterial toxin CYN in male Swiss albino mice: determination of no observed adverse effect level for deriving a drinking water guideline value. Environ. Toxicol. 18, 94-103] was exceeded in 18 samples from eight lakes due to high concentrations of dissolved CYN. CYN occurrence in the German lakes could not be ascribed to the three known CYN-producing species Cylindrospermopsis raciborskii, Anabaena bergii and Aphanizomenon flos-aquae, which were detected in some lakes in low abundances. The highest correlation coefficients were observed between particulate CYN and the native Aphanizomenon gracile. It occurred in 98 CYN-positive samples, was the most abundant Nostocales and was the only Nostocales in five samples. This indicates that A. gracile is a potential CYN producer in German lakes.

  15. Land use affects total dissolved nitrogen and nitrate concentrations in tropical montane streams in Kenya.

    PubMed

    Jacobs, Suzanne R; Breuer, Lutz; Butterbach-Bahl, Klaus; Pelster, David E; Rufino, Mariana C

    2017-12-15

    African tropical montane forests are facing fast and dynamic changes in land use. However, the impacts of these changes on stream water quality are understudied. This paper aims at assessing the effect of land use and physical catchment characteristics on stream water concentrations of dissolved organic carbon (DOC), total dissolved nitrogen (TDN), nitrate (NO3-N) and dissolved organic nitrogen (DON) in the Mau Forest, the largest tropical montane forest in Kenya. We conducted five synoptic stream water sampling campaigns at the outlets of 13-16 catchments dominated by either natural forest, smallholder agriculture or commercial tea and tree plantations. Our data show a strong effect of land use on TDN and NO3-N, with highest concentrations in stream water of catchments dominated by tea plantations (1.80±0.50 and 1.62±0.60mgNl(-1), respectively), and lowest values in forested catchments (0.55±0.15 and 0.30±0.08mgNl(-1), respectively). NO3-N concentration increased with stream temperature and specific discharge, but decreased with increasing catchment area. DOC concentrations increased with catchment area and precipitation and decreased with specific discharge, drainage density and topographic wetness index. Precipitation and specific discharge were also strong predictors for DON concentrations, with an additional small positive effect of tree cover. In summary, land use affects TDN and NO3-N concentrations in stream water in the Mau Forest region in Kenya, while DOC and DON were more related to hydrologic regimes and catchment properties. The importance of land use for NO3-N and TDN concentrations emphasizes the risk of increased nitrogen export along hydrological pathways caused by intensified land use and conversion of land to agricultural uses, which might result in deterioration of drinking water quality and eutrophication in surface water in tropical Africa. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  16. Dissolved and particulate trace metal micronutrients under the McMurdo Sound seasonal sea ice: basal sea ice communities as a capacitor for iron

    NASA Astrophysics Data System (ADS)

    Noble, Abigail; Saito, Mak; Moran, Dawn; Allen, Andrew

    2013-10-01

    Dissolved and particulate metal concentrations are reported from three sites beneath and at the base of the McMurdo Sound seasonal sea ice in the Ross Sea of Antarctica. This dataset provided insight into Co and Mn biogeochemistry, supporting a previous hypothesis for water column mixing occurring faster than scavenging. Three observations support this: first, Mn-containing particles with Mn/Al ratios in excess of the sediment were present in the water column, implying the presence of bacterial Mn-oxidation processes. Second, dissolved and labile Co were uniform with depth beneath the sea ice after the winter season. Third, dissolved Co:PO43- ratios were consistent with previously observed Ross Sea stoichiometry, implying that over-winter scavenging was slow relative to mixing. Abundant dissolved Fe and Mn were consistent with a winter reserve concept, and particulate Al, Fe, Mn, and Co covaried, implying that these metals behaved similarly. Elevated particulate metals were observed in proximity to the nearby Islands, with particulate Fe/Al ratios similar to that of nearby sediment, consistent with a sediment resuspension source. Dissolved and particulate metals were elevated at the shallowest depths (particularly Fe) with elevated particulate P/Al and Fe/Al ratios in excess of sediments, demonstrating a sea ice biomass source. The sea ice biomass was extremely dense (chl a >9500 μg/L) and contained high abundances of particulate metals with elevated metal/Al ratios. A hypothesis for seasonal accumulation of bioactive metals at the base of the McMurdo Sound sea ice by the basal algal community is presented, analogous to a capacitor that accumulates iron during the spring and early summer. The release and transport of particulate metals accumulated at the base of the sea ice by sloughing is discussed as a potentially important mechanism in providing iron nutrition during polynya phytoplankton bloom formation and could be examined in future oceanographic expeditions.

  17. Dissolved and particulate trace metal micronutrients under the McMurdo Sound seasonal sea ice: basal sea ice communities as a capacitor for iron.

    PubMed

    Noble, Abigail E; Moran, Dawn M; Allen, Andrew E; Saito, Mak A

    2013-01-01

    Dissolved and particulate metal concentrations are reported from three sites beneath and at the base of the McMurdo Sound seasonal sea ice in the Ross Sea of Antarctica. This dataset provided insight into Co and Mn biogeochemistry, supporting a previous hypothesis for water column mixing occurring faster than scavenging. Three observations support this: first, Mn-containing particles with Mn/Al ratios in excess of the sediment were present in the water column, implying the presence of bacterial Mn-oxidation processes. Second, dissolved and labile Co were uniform with depth beneath the sea ice after the winter season. Third, dissolved Co:PO(3-) 4 ratios were consistent with previously observed Ross Sea stoichiometry, implying that over-winter scavenging was slow relative to mixing. Abundant dissolved Fe and Mn were consistent with a winter reserve concept, and particulate Al, Fe, Mn, and Co covaried, implying that these metals behaved similarly. Elevated particulate metals were observed in proximity to the nearby Islands, with particulate Fe/Al ratios similar to that of nearby sediment, consistent with a sediment resuspension source. Dissolved and particulate metals were elevated at the shallowest depths (particularly Fe) with elevated particulate P/Al and Fe/Al ratios in excess of sediments, demonstrating a sea ice biomass source. The sea ice biomass was extremely dense (chl a >9500 μg/L) and contained high abundances of particulate metals with elevated metal/Al ratios. A hypothesis for seasonal accumulation of bioactive metals at the base of the McMurdo Sound sea ice by the basal algal community is presented, analogous to a capacitor that accumulates iron during the spring and early summer. The release and transport of particulate metals accumulated at the base of the sea ice by sloughing is discussed as a potentially important mechanism in providing iron nutrition during polynya phytoplankton bloom formation and could be examined in future oceanographic

  18. Dissolved and particulate trace metal micronutrients under the McMurdo Sound seasonal sea ice: basal sea ice communities as a capacitor for iron

    PubMed Central

    Noble, Abigail E.; Moran, Dawn M.; Allen, Andrew E.; Saito, Mak A.

    2013-01-01

    Dissolved and particulate metal concentrations are reported from three sites beneath and at the base of the McMurdo Sound seasonal sea ice in the Ross Sea of Antarctica. This dataset provided insight into Co and Mn biogeochemistry, supporting a previous hypothesis for water column mixing occurring faster than scavenging. Three observations support this: first, Mn-containing particles with Mn/Al ratios in excess of the sediment were present in the water column, implying the presence of bacterial Mn-oxidation processes. Second, dissolved and labile Co were uniform with depth beneath the sea ice after the winter season. Third, dissolved Co:PO3−4 ratios were consistent with previously observed Ross Sea stoichiometry, implying that over-winter scavenging was slow relative to mixing. Abundant dissolved Fe and Mn were consistent with a winter reserve concept, and particulate Al, Fe, Mn, and Co covaried, implying that these metals behaved similarly. Elevated particulate metals were observed in proximity to the nearby Islands, with particulate Fe/Al ratios similar to that of nearby sediment, consistent with a sediment resuspension source. Dissolved and particulate metals were elevated at the shallowest depths (particularly Fe) with elevated particulate P/Al and Fe/Al ratios in excess of sediments, demonstrating a sea ice biomass source. The sea ice biomass was extremely dense (chl a >9500 μg/L) and contained high abundances of particulate metals with elevated metal/Al ratios. A hypothesis for seasonal accumulation of bioactive metals at the base of the McMurdo Sound sea ice by the basal algal community is presented, analogous to a capacitor that accumulates iron during the spring and early summer. The release and transport of particulate metals accumulated at the base of the sea ice by sloughing is discussed as a potentially important mechanism in providing iron nutrition during polynya phytoplankton bloom formation and could be examined in future oceanographic

  19. Molecular weight and chemical reactivity of dissolved trace metals (Cd, Cu, Ni) in surface waters from the Mississippi River to Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Wen, Liang-Saw; Santschi, Peter H.; Warnken, Kent W.; Davison, William; Zhang, Hao; Li, Hsiu-Ping; Jiann, Kuo-Tung

    2011-05-01

    It is generally assumed that estuarine mixing is continuous for metals from terrestrial sources, gradually decreasing towards the open ocean endmember. Here we show that, chemical reactivity, determined by ion exchange method, and molecular weight distributions, obtained using cross-flow ultrafiltration, of dissolved Cd, Cu, and Ni in the surface waters of the Gulf of Mexico varied systematically across the estuarine mixing zone of the Mississippi River. Most size or chemical affinity fractions of dissolved metals (<0.4 μm) were linearly related to salinity (10.8-36.6), suggesting that the distribution of these elements was mainly controlled by continuous mixing processes. Dissolved concentrations across the salinity gradient ranged for Cd: 87-187 pM; Cu: 1.4-18.3 nM; and Ni: 2.6-18.8 nM, with highest values near the Mississippi river mouth, and lowest concentrations in a warm core ring in the Gulf of Mexico. Dissolved Cd was mostly present as a truly dissolved (<10 kDa, 97 ± 1%) and cationic fraction (Chelex-100 extractable, 94 ± 4%). A novel observation across the estuarine mixing zone was that colloidal metal concentrations were identical to either inert (for Cu, Ni) or AMPG-labile anionic (Cu, Cd) fractions. The difference in behavior between Cu and the other two metals might indicate differences in the biopolymeric nature of the metal-organic chelates. In particular, the anionic-organic Cd fractions accounted for just 3 ± 1%, on average. However, for Cu, it was 24 ± 4%, and for Ni, it was 9 ± 6%. The fractions of the total dissolved metal fractions that were "inert" averaged 31 ± 10% for Cu and 29 ± 12% for Ni. Small but noticeable amounts (6 ± 3%) of dissolved inert Cd fractions were also present. Apparent non-local transport processes, likely associated with cross-shelf sediment resuspension processes, could have been responsible for the relatively high concentrations of 'inert' and 'anionic' metal fractions in high salinity coastal waters, and

  20. Impact of solute concentration on the electrocatalytic conversion of dissolved gases in buffered solutions

    NASA Astrophysics Data System (ADS)

    Shinagawa, Tatsuya; Takanabe, Kazuhiro

    2015-08-01

    To maintain local pH levels near the electrode during electrochemical reactions, the use of buffer solutions is effective. Nevertheless, the critical effects of the buffer concentration on electrocatalytic performances have not been discussed in detail. In this study, two fundamental electrochemical reactions, oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR), on a platinum rotating disk electrode are chosen as model gas-related aqueous electrochemical reactions at various phosphate concentrations. Our detailed investigations revealed that the kinetic and limiting diffusion current densities for both the ORR and HOR logarithmically decrease with increasing solute concentration (log |jORR | = - 0.39 c + 0.92 , log |jHOR | = - 0.35 c + 0.73) . To clarify the physical aspects of this phenomenon, the electrolyte characteristics are addressed: with increasing phosphate concentration, the gas solubility decrease, the kinematic viscosity of the solution increase and the diffusion coefficient of the dissolved gases decrease. The simulated limiting diffusion currents using the aforementioned parameters match the measured ones very well (log |jORR | = - 0.43 c + 0.99 , log |jHOR | = - 0.40 c + 0.54) , accurately describing the consequences of the electrolyte concentration. These alterations of the electrolyte properties associated with the solute concentration are universally applicable to other aqueous gas-related electrochemical reactions because the currents are purely determined by mass transfer of the dissolved gases.

  1. Statistical evaluation of biogeochemical variables affecting spatiotemporal distributions of multiple free metal ion concentrations in an urban estuary.

    PubMed

    Dong, Zhao; Lewis, Christopher G; Burgess, Robert M; Coull, Brent; Shine, James P

    2016-05-01

    Free metal ion concentrations have been recognized as a better indicator of metal bioavailability in aquatic environments than total dissolved metal concentrations. However, our understanding of the determinants of free ion concentrations, especially in a metal mixture, is limited, due to underexplored techniques for measuring multiple free metal ions simultaneously. In this work, we performed statistical analyses on a large dataset containing repeated measurements of free ion concentrations of Cu, Zn, Pb, Ni, and Cd, the most commonly measured metals in seawater, at five inshore locations in Boston Harbor, previously collected using an in-situ equilibrium-based multi-metal free ion sampler, the 'Gellyfish'. We examined correlations among these five metals by season, and evaluated effects of 10 biogeochemical variables on free ion concentrations over time and location through multivariate regressions. We also explored potential clustering among the five metals through a principal component analysis. We found significant correlations among metals, with varying patterns over season. Our regression results suggest that instead of dissolved metals, pH, salinity, temperature and rainfall were the most significant determinants of free metal ion concentrations. For example, a one-unit decrease in pH was associated with a 2.2 (Cd) to 99 (Cu) times increase in free ion concentrations. This work is among the first to reveal key contributors to spatiotemporal variations in free ion concentrations, and demonstrated the usefulness of the Gellyfish sampler in routine sampling of free ions within metal mixtures and in generating data for statistical analyses.

  2. An improved biofilter to control the dissolved organic nitrogen concentration during drinking water treatment.

    PubMed

    Zhang, Huining; Gu, Li; Liu, Bing; Gan, Huihui; Zhang, Kefeng; Jin, Huixia; Yu, Xin

    2016-09-01

    Dissolved organic nitrogen (DON) is a key precursor of numerous disinfection by-products (DBPs), especially nitrogenous DBPs (N-DBPs) formed during disinfection in drinking water treatment. To effectively control DBPs, reduction of the DON concentration before the disinfection process is critical. Traditional biofilters can increase the DON concentration in the effluent, so an improved biofilter is needed. In this study, an improved biofilter was set up with two-layer columns using activated carbon and quartz sand under different influent patterns. Compared with the single-layer filter, the two-layer biofilter controlled the DON concentration more efficiently. The two-point influent biofilter controlled the DON concentration more effectively than the single-point influent biofilter. The improved biofilter resulted in an environment (including matrix, DO, and pH) suitable for microbial growth. Along the depth of the biofilter column, the environment affected the microbial biomass and microbial activity and thus affected the DON concentration.

  3. Long-term simulations of dissolved oxygen concentrations in Lake Trout lakes

    NASA Astrophysics Data System (ADS)

    Jabbari, A.; Boegman, L.; MacKay, M.; Hadley, K.; Paterson, A.; Jeziorski, A.; Nelligan, C.; Smol, J. P.

    2016-02-01

    Lake Trout are a rare and valuable natural resource that are threatened by multiple environmental stressors. With the added threat of climate warming, there is growing concern among resource managers that increased thermal stratification will reduce the habitat quality of deep-water Lake Trout lakes through enhanced oxygen depletion. To address this issue, a three-part study is underway, which aims to: analyze sediment cores to understand the past, develop empirical formulae to model the present and apply computational models to forecast the future. This presentation reports on the computational modeling efforts. To this end, a simple dissolved oxygen sub-model has been embedded in the one-dimensional bulk mixed-layer thermodynamic Canadian Small Lake Model (CSLM). This model is currently being incorporated into the Canadian Land Surface Scheme (CLASS), the primary land surface component of Environment Canada's global and regional climate modelling systems. The oxygen model was calibrated and validated by hind-casting temperature and dissolved oxygen profiles from two Lake Trout lakes on the Canadian Shield. These data sets include 5 years of high-frequency (10 s to 10 min) data from Eagle Lake and 30 years of bi-weekly data from Harp Lake. Initial results show temperature and dissolved oxygen was predicted with root mean square error <1.5 °C and <3 mgL-1, respectively. Ongoing work is validating the model, over climate-change relevant timescales, against dissolved oxygen reconstructions from the sediment cores and predicting future deep-water temperature and dissolved oxygen concentrations in Canadian Lake Trout lakes under future climate change scenarios. This model will provide a useful tool for managers to ensure sustainable fishery resources for future generations.

  4. Epstein-Plesset theory based measurements of concentration of nitrogen gases dissolved in aerated water

    NASA Astrophysics Data System (ADS)

    Sasaki, Masashi; Yamashita, Tatsuya; Ando, Keita

    2016-11-01

    Microbubble aeration is used to dissolved gases into water and is an important technique in agriculture and industry. We can measure concentration of dissolved oxygen (DO) in aerated water by commercial DO meters. However, there do not exist commercially available techniques to measure concentration to dissolved nitrogen (DN). In the present study, we propose the method to measure DN in aerated water with the aid of Epstein-Plesset-type analysis. Gas-supersaturated tap water is produced by applying aeration with micro-sized air bubbles and is then stored in a glass container open to the atmosphere. Diffusion-driven growth of bubbles nucleated at the container surface is recorded with a video camera. The bubble growth rate is compare to the extended Epstein-Plesset theory that models mass transfer of both DO and DN into the surface-attached bubbles base on the diffusion equation. Given the DO measurements, we can obtain the DN level by fitting in the comparison.

  5. Map showing concentration of dissolved solids in water from the principal aquifer, Sugar House quadrangle, Salt Lake County, Utah

    USGS Publications Warehouse

    Mower, R.W.

    1973-01-01

    The concentration of dissolved solids in water from the principal aquifer ranges from about 100 mg/l (milligrams per liter) to as much as 800 mg/l. Water containing the least dissolved solids occurs in an arcuate, mile-wide band along the southern border of the Sugar House quadrangle. Water containing the most dissolved solids occurs in a 3½-mile–wide band in the northern part of the valley, as shown by the map.

  6. Naturally dissolved arsenic concentrations in the Alpine/Mediterranean Var River watershed (France).

    PubMed

    Barats, Aurélie; Féraud, Gilbert; Potot, Cécile; Philippini, Violaine; Travi, Yves; Durrieu, Gaël; Dubar, Michel; Simler, Roland

    2014-03-01

    A detailed study on arsenic (As) in rocks and water from the Var River watershed was undertaken aiming at identifying (i) the origin and the distribution of As in this typical Alpine/Mediterranean basin, and (ii) As input into the Mediterranean Sea. Dissolved As concentrations in the Var River range from 0.1 to 4.5 μg⋅L(-1), due to high hydrological variability and the draining through different geological formations. In the upper part of the Var drainage basin, in the Tinée and the Vésubie valleys, high levels of dissolved As concentrations occur (up to 263 μg⋅L(-1)). The two main sources of As in rocks are the Hercynian metamorphic rocks and the Permian argilites. Highly heterogeneous distribution of As in waters draining through metamorphic rocks is probably related to ore deposits containing arsenopyrite. As, U, W and Mo concentrations in water and rocks correspond to the formation of As-rich ore deposits around Argentera granite by hydrothermal fluids deposited at the end of the Hercynian chain formation, which occurred about 300 My ago. In 2009, weekly monitoring was performed on the Var River (15 km upstream of the mouth), highlighting an average dissolved As concentration (<0.45 μm) of 2.7 ± 0.9 μg⋅L(-1), which is significantly higher than the world-average baseline for river water (0.83 μg⋅L(-1)). Taking the average annual discharge (49.4 m(3)⋅s(-1)) into account and the As levels in the dissolved phase and in deposits of the Var River, dissolved As input into the Mediterranean Sea would be 4. 2± 1.4 tons⋅year(-1) which represents 59% of the total As flux. This study also reveals a probable non-conservative As behaviour, i.e., possible transfer between aqueous and solid phases, during the mixing of the Var River with a tributary.

  7. Removal of inorganic mercury and methylmercury from surface waters following coagulation of dissolved organic matter with metal-based salts

    USGS Publications Warehouse

    Henneberry, Y.K.; Kraus, T.E.C.; Fleck, J.A.; Krabbenhoft, D.P.; Bachand, P.M.; Horwath, W.R.

    2011-01-01

    The presence of inorganic mercury (IHg) and methylmercury (MeHg) in surface waters is a health concern worldwide. This study assessed the removal potential use of metal-based coagulants as a means to remove both dissolved IHg and MeHg from natural waters and provides information regarding the importance of Hg associations with the dissolved organic matter (DOM) fraction and metal hydroxides. Previous research indicated coagulants were not effective at removing Hg from solution; however these studies used high concentrations of Hg and did not reflect naturally occurring concentrations of Hg. In this study, water collected from an agricultural drain in the Sacramento-San Joaquin Delta was filtered to isolate the dissolved organic matter (DOM) fraction. The DOM was then treated with a range of coagulant doses to determine the efficacy of removing all forms of Hg from solution. Three industrial-grade coagulants were tested: ferric chloride, ferric sulfate, and polyaluminum chloride. Coagulation removed up to 85% of DOM from solution. In the absence of DOM, all three coagulants released IHg into solution, however in the presence of DOM the coagulants removed up to 97% of IHg and 80% of MeHg. Results suggest that the removal of Hg is mediated by DOM-coagulant interactions. There was a preferential association of IHg with the more aromatic, higher molecular weight fraction of DOM but no such relationship was found for MeHg. This study offers new fundamental insights regarding large-scale removal of Hg at environmentally relevant regarding large-scale removal of Hg at environmentally relevant concentrations.

  8. Spatial variability of dissolved phosphorous concentrations and alkaline phosphatase activity in the East China Sea

    NASA Astrophysics Data System (ADS)

    Liu, H.; Chang, J.; Ho, T.; Gong, G.

    2010-12-01

    The concentrations of dissolved inorganic phosphorus (DIP) and alkaline phosphatase activity (APA) have been determined at about 25 sampling stations in the East China Sea since 2003. The stations are mainly distributed from the Changjiang river mouth to northern Taiwan and east to the shelf break. In addition to the Changjiang discharge, we have found a specific nutrient source around a coastal site (122° 2’30’’ E, 28° 40’ N). Elevated DIP and nitrate concentrations have been constantly observed around the sampling station for 8 years, where the surface DIP concentrations are generally around 0.3 µM. The nutrient source may either originate from ground water discharge or coastal upwelling, where lower temperature has been observed in the water column around the station. In general, APA has been negatively correlated with DIP concentrations in the studies sites, with lowest APA around the high DIP station and the Changjiang river mouth.

  9. Evaluation of Chemical Clarification Polymers and Methods for Removal of Dissolved Metals from CDF Effluent

    DTIC Science & Technology

    2006-07-01

    chemical flocculation . Clarification is intended for removal of solids from CDF effluent, and in doing so, much of the metals contamination is also...removed with the solids. Likewise, the ability of the chemical flocculation to remove dissolved phase contaminants should also be considered...since this may be an important, simultaneous benefit. As effluent discharge standards become more stringent, the benefits of new chemical flocculation

  10. Passive sampling methods for contaminated sediments: scientific rationale supporting use of freely dissolved concentrations.

    PubMed

    Mayer, Philipp; Parkerton, Thomas F; Adams, Rachel G; Cargill, John G; Gan, Jay; Gouin, Todd; Gschwend, Philip M; Hawthorne, Steven B; Helm, Paul; Witt, Gesine; You, Jing; Escher, Beate I

    2014-04-01

    Passive sampling methods (PSMs) allow the quantification of the freely dissolved concentration (Cfree ) of an organic contaminant even in complex matrices such as sediments. Cfree is directly related to a contaminant's chemical activity, which drives spontaneous processes including diffusive uptake into benthic organisms and exchange with the overlying water column. Consequently, Cfree provides a more relevant dose metric than total sediment concentration. Recent developments in PSMs have significantly improved our ability to reliably measure even very low levels of Cfree . Application of PSMs in sediments is preferably conducted in the equilibrium regime, where freely dissolved concentrations in the sediment are well-linked to the measured concentration in the sampler via analyte-specific partition ratios. The equilibrium condition can then be assured by measuring a time series or a single time point using passive samplers with different surface to volume ratios. Sampling in the kinetic regime is also possible and generally involves the application of performance reference compounds for the calibration. Based on previous research on hydrophobic organic contaminants, it is concluded that Cfree allows a direct assessment of 1) contaminant exchange and equilibrium status between sediment and overlying water, 2) benthic bioaccumulation, and 3) potential toxicity to benthic organisms. Thus, the use of PSMs to measure Cfree provides an improved basis for the mechanistic understanding of fate and transport processes in sediments and has the potential to significantly improve risk assessment and management of contaminated sediments.

  11. Distribution of dissolved and particulate radiocesium concentrations along rivers and the relations between radiocesium concentration and deposition after the nuclear power plant accident in Fukushima.

    PubMed

    Tsuji, Hideki; Yasutaka, Tetsuo; Kawabe, Yoshishige; Onishi, Takeo; Komai, Takeshi

    2014-09-01

    This study involved measurement of concentrations of dissolved and particulate radiocesium ((134)Cs and (137)Cs) in river water, and determination of the quantitative relations between the amount of deposited (137)Cs and (137)Cs concentrations in river waters after the Fukushima Daiichi nuclear power plant accident. First, the current concentrations of dissolved and particulate (134)Cs·(137)Cs were determined in a river watershed from 20 sampling locations in four contaminated rivers (Abukuma, Kuchibuto, Shakado, and Ota). Distribution characteristics of different (137)Cs forms varied with rivers. Moreover, a higher dissolved (137)Cs concentration was observed at the sampling location where the (137)Cs deposition occurred much more heavily. In contrast, particulate (137)Cs concentration along the river was quite irregular, because fluctuations in suspended solids concentrations occur easily from disturbance and heavy precipitation. A similar tendency with dissolved (137)Cs distribution was observed for the (137)Cs concentration per unit weight of suspended solids. Regression analysis between deposited (137)Cs and dissolved/particulate (137)Cs concentrations was performed for the four rivers. The results showed a strong correlation between deposited (137)Cs and dissolved (137)Cs, and a relatively weak correlation between deposited (137)Cs and particulate (137)Cs concentration for each river. However, if the particulate (137)Cs concentration was converted to (137)Cs concentration per unit weight of suspended solid, the values showed a strong correlation with deposited (137)Cs.

  12. [Concentration of heavy metals in pregnant women].

    PubMed

    Jacyszyn, K; Walas, J; Malinowski, A; Latkowski, T; Cwynar, L

    1982-01-01

    Copper, zinc, and lead concentrations were measured in two groups 72 pregnant women. Twenty-one of them, making up the control group, lived and worked in Wrocław. The other 51 women, the second group, had lived more than five years in Lubin-Polkowice and worked in the local non-ferrous metal plants. They were particularly endangered by their exposure to copper, zinc, and lead concentrations. Pregnancy was normal in all cases. Maternal blood, umbilical cord blood, placenta homogenate, and amniotic fluid were examined by techniques of atom-absorption spectrometry. The metals tested were conspicuously absorbed by placental tissue, but no danger to the pregnant women could be established.

  13. Characteristics of Metals Concentrations in in the Animas and ...

    EPA Pesticide Factsheets

    The accidental release of 11.3 million liters (~ 3,000,000 gallons) of acidic mine water from the Gold King Mine (GKM) in southwestern Colorado on August 5, 2015, created high concentrations of dissolved and particulate metals into the Animas River over about a 12-hour period. The release traveled as a coherent plume through 550 km (342 miles) of the Animas and San Juan Rivers over an 8-day period before ultimately reaching Lake Powell, Utah. Extensive monitoring of water and sediments by EPA, States, Tribes and others was augmented by water quality modeling to characterize the release. Presented at the New Mexico Water Institute Symposium, 2nd Annual Conference on Environmental Conditions of the Animas and San Juan Watersheds with Emphasis on Gold King Mine and Other Mine Waste Issues.

  14. Trends in nitrate and dissolved-solids concentrations in ground water, Carson Valley, Douglas County, Nevada, 1985-2001

    USGS Publications Warehouse

    Rosen, Michael R.

    2003-01-01

    Analysis of trends in nitrate and total dissolved-solids concentrations over time in Carson Valley, Nevada, indicates that 56 percent of 27 monitoring wells that have long-term records of nitrate concentrations show increasing trends, 11 percent show decreasing trends, and 33 percent have not changed. Total dissolved-solids concentrations have increased in 52 percent of these wells and are stable in 48 percent. None of these wells show decreasing trends in total dissolved-solids concentrations. The wells showing increasing trends in nitrate and total dissolved-solids concentrations were always in areas that use septic waste-disposal systems. Therefore, the primary cause of these increases is likely the increase in septic-tank usage over the past 40 years.

  15. New method for the direct determination of dissolved Fe(III) concentration in acid mine waters

    USGS Publications Warehouse

    To, T.B.; Nordstrom, D.K.; Cunningham, K.M.; Ball, J.W.; McCleskey, R.B.

    1999-01-01

    A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II) >> Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), AI(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand (14 mg/L). Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2 ??g/L (40 nM) using GFAAS and 20 ??g/L (0.4 ??M) by colorimetry.A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II)???Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes

  16. The impact of seasonality and elevation on dissolved greenhouse gas concentrations in a northeastern Wyoming watershed

    NASA Astrophysics Data System (ADS)

    Kuhn, C.; Bettigole, C.; Raymond, P. A.; Glick, H.; Seegmiller, L.; Oliver, C.; Khadka, A.; Routh, D.

    2014-12-01

    Quantification of river and stream contributions to global carbon emission budgets using field-based measurements is key to understanding how freshwater streams act as conduits between terrestrial and atmospheric carbon pools. In order to better characterize drivers of this process, this study quantifies: a) emissions of carbon dioxide and methane from a semi-arid, high plains riverine system with montaine headwaters in order to establish baseline data for the watershed; b) the impact of stream order, seasonality and elevation on dissolved gas concentrations to better understand the spatial and temporal heterogeneity of dissolved carbon gases. To achieve the latter objective, we conducted field surveys in first and second order streams in the Clear Creek drainage of the Powder River Basin watershed. We took direct measurements of stream gases using headspace sampling at thirty sites along an elevation gradient ranging from 1,203-3,346 meters. We also intensely monitored five transects throughout the descending limb of spring runoff (June 8th-August 12th) to investigate how temperature and discharge volume impact greenhouse gas concentrations. Clear Creek, located in northeastern Wyoming, is approximately 118.4 km long with a drainage area of 2,968 km2. The creek flows east out of Bighorn National Forest where it turns northeast to converge with the Powder River about ten miles before the Montana border. The stream straddles the Middle Rockies and Northwestern Great Plains ecoregions and experiences an abrupt shift in soil type, riparian vegetation, underlying geology and stream geometry as the stream exits the mountains and enters the agricultural alluvial floodplain. These site specific biological and physical changes along the elevation gradient affect dissolved greenhouse gas concentrations.

  17. Removal of Chromophoric Dissolved Organic Matter and Heavy Metals in a River-Sea System: Role of Aquatic Microgel Formation

    NASA Astrophysics Data System (ADS)

    Shiu, R. F.; Lee, C. L.

    2016-12-01

    Dissolved organic carbon (DOC) polymers are complex and poorly understood mixture of organic macromolecules in environment system. Portions of these polymers spontaneously form microgels that play key roles in many biogeochemical reactions, including mediating aggregation processes, element cycling, and pollutant mobility. However, the detailed interaction of microgels-heterogeneous materials in aquatic systems is still lacking. Insight into the interaction between surrounding materials and microgels from different types of aquatic DOC polymers are extremely important, as it is crucial in determining the fate and transport of these materials. Here, we use riverine and marine DOC polymers to examine their aggregation behavior, and to evaluate the roles of microgel formation in scavenging of chromophoric dissolved organic matter (CDOM) and heavy metals in a river-sea system. Our results indicate that riverine and marine microgels did not exhibit too much difference in size ( 3-5 μm) and self-assembly curve; however, the assembly effectiveness ([microgel]/DOC) of marine samples was much higher than riverine. Instead of concentration of DOC, other factors such as types and sources of DOC polymers may control the microgel abundance in aquatic environments. After filtering water samples (microgels removed), the CDOM and selected metals (Cu, Ni, Mn) in the filtrate were quantified. CDOM and metals were concurrently removed to an extent via DOC polymer re-aggregation, which also suggested that the microgels had the sequestering capability in CDOM and metals. This finding provides an alternative route for CDOM and heavy metals removal from the water column. As such the process of re-aggregation into microgels should then be considered besides traditional phase partitioning in the assessment of the ecological risk and fate of pollutant.

  18. Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

    SciTech Connect

    Prasetyaningrum, A. Ratnawati,; Jos, B.

    2015-12-29

    Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O{sub 3}) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flow rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.

  19. Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

    NASA Astrophysics Data System (ADS)

    Prasetyaningrum, A.; Ratnawati, Jos, B.

    2015-12-01

    Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O3) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flow rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.

  20. Frequency-duration analysis of dissolved-oxygen concentrations in two southwestern Wisconsin streams

    USGS Publications Warehouse

    Greb, Steven R.; Graczyk, David J.

    2007-01-01

    Historically, dissolved-oxygen (DO) data have been collected in the same manner as other water-quality constituents, typically at infrequent intervals as a grab sample or an instantaneous meter reading. Recent years have seen an increase in continuous water-quality monitoring with electronic dataloggers. This new technique requires new approaches in the statistical analysis of the continuous record. This paper presents an application of frequency-duration analysis to the continuous DO records of a cold and a warm water stream in rural southwestern Wisconsin. This method offers a quick, concise way to summarize large time-series data bases in an easily interpretable manner. Even though the two streams had similar mean DO concentrations, frequency-duration analyses showed distinct differences in their DO-concentration regime. This type of analysis also may be useful in relating DO concentrations to biological effects and in predicting low DO occurrences.

  1. Modelling the concentrations of dissolved contaminants (Cd, Cu, Ni, Pb, Zn) in floodplain soils.

    PubMed

    Rennert, Thilo; Rabus, Widar; Rinklebe, Jörg

    2017-04-01

    Central European floodplain soils are often contaminated with potentially toxic metals. The prediction of their aqueous concentrations is a prerequisite for an assessment of environmental concerns. We tested the aqueous concentrations of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) derived from multi-surface adsorption modelling (on hydrous iron, aluminum and manganese oxides, clay and soil organic matter) against those analyzed in situ in the soil solution of four horizons of floodplain soils at the Elbe River, Germany. The input data for the reactive metals were derived from a seven-step sequential extraction scheme or from extraction with 0.43 M nitric acid (HNO3) and evaluated in four modelling scenarios. In all scenarios, measured and modelled concentrations were positively related, except partially for Pb. Close reproduction of the measured data was obtained using measured data of accompanying cations and anions together with amounts of reactive metals from both the sequential extraction or from 0.43 M HNO3 extraction, except for Cu, which was often strongly overestimated, and partially Cd. We recommend extraction with 0.43 M HNO3 to quantify reactive metals in soil because the modelling results were metal-specific with better or equal results using the single extractant, the application of which is also less laborious. Approximations of ion concentrations and water contents yielded similar results. Modelled solid-phase speciation of metals varied with pH and differed from that from sequential extraction. Multi-surface modelling may be an effective tool to predict both aqueous concentrations and solid-phase speciation of metals in soil.

  2. Size characterization of dissolved metals and organic matter in source waters to streams in developed landscapes.

    PubMed

    Luan, Hongwei; Vadas, Timothy M

    2015-02-01

    Individual and mixed water samples from wastewater treatment plant effluents, stormwater runoff, streams from developed areas were characterized with respect to organic matter concentration and spectral properties and metal concentration and size distribution. In addition, asymmetric flow-field flow fractionation coupled to inductively coupled plasma mass spectrometry was used to measure concentration, size distribution and association of metals in the colloidal size range. Results reveal that Fe, Cu, Zn and Pb in the colloidal size range were mainly associated with the less than 5 nm, or less than 10 kDa size range. Cu was most strongly associated with organic matter, while Zn and Pb were mixed between Fe and organic matter. Effluent showed higher binding capacity for metals, while stormwater, even with higher organic matter concentrations showed more exchangeable metals. Upon mixing of source waters, colloidal metal concentrations and size distributions were conserved.

  3. Concentrations of dissolved oxygen in the lower Puyallup and White rivers, Washington, August and September 2000 and 2001

    USGS Publications Warehouse

    Ebbert, J.C.

    2002-01-01

    The U.S. Geological Survey, Washington State Department of Ecology, and Puyallup Tribe of Indians conducted a study in August and September 2001 to assess factors affecting concentrations of dissolved oxygen in the lower Puyallup and White Rivers, Washington. The study was initiated because observed concentrations of dissolved oxygen in the lower Puyallup River fell to levels ranging from less than 1 milligram per liter (mg/L) to about 6 mg/L on several occasions in September 2000. The water quality standard for the concentration of dissolved oxygen in the Puyallup River is 8 mg/L.This study concluded that inundation of the sensors with sediment was the most likely cause of the low concentrations of dissolved oxygen observed in September 2000. The conclusion was based on (1) knowledge gained when a dissolved-oxygen sensor became covered with sediment in August 2001, (2) the fact that, with few exceptions, concentrations of dissolved oxygen in the lower Puyallup and White Rivers did not fall below 8 mg/L in August and September 2001, and (3) an analysis of other mechanisms affecting concentrations of dissolved oxygen.The analysis of other mechanisms indicated that they are unlikely to cause steep declines in concentrations of dissolved oxygen like those observed in September 2000. Five-day biochemical oxygen demand ranged from 0.22 to 1.78 mg/L (mean of 0.55 mg/L), and river water takes only about 24 hours to flow through the study reach. Photosynthesis and respiration cause concentrations of dissolved oxygen in the lower Puyallup River to fluctuate as much as about 1 mg/L over a 24-hour period in August and September. Release of water from Lake Tapps for the purpose of hydropower generation often lowered concentrations of dissolved oxygen downstream in the White River by about 1 mg/L. The effect was smaller farther downstream in the Puyallup River at river mile 5.8, but was still observable as a slight decrease in concentrations of dissolved oxygen caused by

  4. Impact of dissolved oxygen concentration on some key parameters and production of rhG-CSF in batch fermentation.

    PubMed

    Krishna Rao, Dasari V; Ramu, Chatadi T; Rao, Joginapally V; Narasu, Mangamoori L; Bhujanga Rao, Adibhatla Kali S

    2008-09-01

    The impact of different levels of agitation speed, carbondioxide and dissolved oxygen concentration on the key parameters and production of rhG-CSF in Escherichia coli BL21(DE3)PLysS were studied. Lower carbondioxide concentrations as well as higher agitation speeds and dissolved oxygen concentrations led to reduction in the acetate concentrations, and enhanced the cell growth, but inhibited plasmid stability and rhG-CSF expression. Similarly, higher carbondioxide concentrations and lower agitation speeds as well as dissolved oxygen concentrations led to enhanced acetate concentrations, but inhibited the cell growth and protein expression. To address the bottlenecks, a two-stage agitation control strategy (strategy-1) and two-stage dissolved oxygen control strategy (strategy-2) were employed to establish the physiological and metabolic conditions, so as to improve the expression of rhG-CSF. By adopting strategy-1 the yields were improved 1.4-fold over constant speed of 550 rpm, 1.1-fold over constant dissolved oxygen of 45%, respectively. Similarly, using strategy-2 the yields were improved 1.6-fold over constant speed of 550 rpm, 1.3-fold over constant dissolved oxygen of 45%, respectively.

  5. Application of passive sampling for measuring dissolved concentrations of organic contaminants in the water column at three marine superfund sites

    EPA Science Inventory

    At contaminated sediment sites, including U.S. EPA Superfund sites, it is critical to measure water column concentrations of freely dissolved contaminants to understand the complete exposure of aquatic organisms to hydrophobic organic contaminants (HOCs). However, historically a...

  6. Application of passive sampling for measuring dissolved concentrations of organic contaminants in the water column at three marine superfund sites

    EPA Science Inventory

    At contaminated sediment sites, including U.S. EPA Superfund sites, it is critical to measure water column concentrations of freely dissolved contaminants to understand the complete exposure of aquatic organisms to hydrophobic organic contaminants (HOCs). However, historically a...

  7. Long-term changes in dissolved oxygen concentrations in the ocean caused by protracted global warming

    NASA Astrophysics Data System (ADS)

    Matear, R. J.; Hirst, A. C.

    2003-12-01

    In the Earth's geological record massive marine ecological change has been attributed to the occurrence of widespread anoxia in the ocean [, 2002; , 2002; , 1996]. Climate change projection till the end of this century predict a 4 to 7% decline in the dissolve oxygen in the ocean [, 2002; , 2000; , 2001; , 1998] suggesting the potential for global warming to eventually drive the deep ocean anoxic. To examine the multicentury impact of protracted global warming on oceanic concentrations of dissolved oxygen, we use a climate system model and a low-order oceanic biogeochemical model. The models are integrated for an atmospheric equivalent CO2 concentration, which is specified to triple according to a standard scenario from the late nineteenth to the late twenty-first century, and then is subsequently held constant at that elevated level for an additional 6 centuries. For the present day, the model successfully reproduced the large-scale features of the dissolved oxygen field in the ocean. In the global warming simulation, the physical model displays marked changes in high-latitude oceanic stratification and overturning, including near-cessation of deep water renewal for depths greater than about 1.5 km during the period of elevated stable CO2 concentration. Our model predicts a decline in oxygen concentration through most of the subsurface ocean. Concentration changes in the thermocline waters result mainly from solubility changes in the upstream source waters, while changes in the deep waters result mainly from lack of ventilation and ongoing consumption of oxygen by remineralization of sinking particulate organic matter. Changes in the upper 2 km of the ocean generally show signs of equilibration by the end of the integration, but at greater depths, there occurs a slow but steady decline through to the end of the integration. By the end of the integration, we simulate a doubling of the volume of hypoxic water (less than 10 μmol/kg) in the thermocline of the eastern

  8. Effect of dissolved oxygen concentration on lettuce growth in floating hydroponics.

    PubMed

    Goto, E; Both, A J; Albright, L D; Langhans, R W; Leed, A R

    1996-12-01

    Lettuce (Lactuca sativa L., cv. Ostinata) growth experiments were carried out to study the effect of dissolved oxygen (DO) concentration on plant growth in a floating hydroponic system. Pure O2 and N2 gas were supplied to the hydroponic system for precise DO control. This system made it easy to increase the DO concentration beyond the maximum (or saturation) concentration possible when bubbling air into water. Eleven day old lettuce seedlings were grown for 24 days under various DO concentrations: sub-saturated, saturated, and super-saturated. There was no significant difference in fresh weight, shoot and root dry weights among the DO concentrations: 2.1 (25% of saturated at 24 degrees C), 4.2 (50%), 8.4 (saturated), and 16.8 (200%) mg/L. The critical DO concentration for vigorous lettuce growth was considered to be lower than 2.1 mg/L. Neither root damage nor delay of shoot growth was observed at any of the studied DO concentrations.

  9. Influence of dissolved organic matter on the environmental fate of metals, nanoparticles, and colloids

    USGS Publications Warehouse

    Aiken, George R.; Hsu-Kim, Heileen; Ryan, Joseph N.

    2011-01-01

    We have known for decades that dissolved organic matter (DOM) plays a critical role in the biogeochemical cycling of trace metals and the mobility of colloidal particles in aquatic environments. In recent years, concerns about the ecological and human health effects of metal-based engineered nanoparticles released into natural waters have increased efforts to better define the nature of DOM interactions with metals and surfaces. Nanomaterials exhibit unique properties and enhanced reactivities that are not apparent in larger materials of the same composition1,2 or dissolved ions of metals that comprise the nanoparticles. These nanoparticle-specific properties generally result from the relatively large proportion of the atoms located at the surface, which leads to very high specific surface areas and a high proportion of crystal lattice imperfections relative to exposed surface area. Nanoscale colloids are ubiquitous in nature,2 and many engineered nanomaterials have analogs in the natural world. The properties of these materials, whether natural or manmade, are poorly understood, and new challenges have been presented in assessing their environmental fate. These challenges are particularly relevant in aquatic environments where interactions with DOM are key, albeit often overlooked, moderators of reactivity at the molecular and nanocolloidal scales.

  10. Water extraction kinetics of metals, arsenic and dissolved organic carbon from industrial contaminated poplar leaves.

    PubMed

    Shahid, Muhammad; Xiong, Tiantian; Castrec-Rouelle, Maryse; Leveque, Tibo; Dumat, Camille

    2013-12-01

    In industrial areas, tree leaves contaminated by metals and metalloids could constitute a secondary source of pollutants. In the present study, water extraction kinetics of inorganic elements (IE: Pb, Zn, Cd, As, Fe and Mn), dissolved organic carbon, pH and biological activity were studied for industrial contaminated poplar leaves. Moreover, the distribution of the IE through the size fractions of the associated top soil was measured. High quantities of Mn, Zn and As and polysaccharides were released in the solution from the strongly contaminated leaves. The kinetic of release varied with time and metal type. The solution pH decreased while dissolved organic contents increased with time after 30 days. Therefore, these contaminated leaves could constitute a source of more available organic metals and metalloids than the initial inorganic process particles. However, the distribution of the IE through the size fractions of the top soil suggested that a great part of the released IE was adsorbed, reducing in consequence their transfers and bioavailability. It's concluded that mobility/bioavailability and speciation of metals and metalloids released from the decomposition of polluted tree leaves depends on soil characteristics, pollutant type and litter composition, with consequences for environmental risk assessment.

  11. Concentrations of dissolved herbicides and pharmaceuticals in a small river in Luxembourg.

    PubMed

    Meyer, Berenike; Pailler, Jean-Yannick; Guignard, Cédric; Hoffmann, Lucien; Krein, Andreas

    2011-09-01

    Urban and agricultural areas affect the hydraulic patterns as well as the water quality of receiving drainage systems, especially of catchments smaller than 50 km(2). Urban runoff is prone to contamination due to pollutants like pesticides or pharmaceuticals. Agricultural areas are possible sources of nutrient and herbicide contamination for receiving water bodies. The pollution is derived from leaching by subsurface flow, as well as wash-off and erosion caused by surface runoff. In the Luxembourgish Mess River catchment, the pharmaceutical and pesticide concentrations are comparable with those detected by other authors in different river systems worldwide. Some investigated pesticide concentrations infringe current regulations. The maximum allowable concentration for diuron of 1.8 μg l( - 1) is exceeded fourfold by measured 7.41 μg l( - 1) in a flood event. The load of dissolved pesticides reaching the stream gauge is primarily determined by the amount applied to the surfaces within the catchment area. Storm water runoff from urban areas causes short-lived but high-pollutant concentrations and moderate loads, whereas moderate concentrations and high loads are representative for agricultural inputs to the drainage system. Dissolved herbicides, sulfonamides, tetracyclines, analgesics and hormones can be used as indicators to investigate runoff generation processes, including inputs from anthropogenic sources. The measurements prove that the influence of kinematic wave effects on the relationship between hydrograph and chemographs should not be neglected in smaller basins. The time lag shows that it is not possible to connect analysed substances of defined samples to the corresponding section of the hydrograph.

  12. Estimating dissolved organic carbon concentration in turbid coastal waters using optical remote sensing observations

    NASA Astrophysics Data System (ADS)

    Cherukuru, Nagur; Ford, Phillip W.; Matear, Richard J.; Oubelkheir, Kadija; Clementson, Lesley A.; Suber, Ken; Steven, Andrew D. L.

    2016-10-01

    Dissolved Organic Carbon (DOC) is an important component in the global carbon cycle. It also plays an important role in influencing the coastal ocean biogeochemical (BGC) cycles and light environment. Studies focussing on DOC dynamics in coastal waters are data constrained due to the high costs associated with in situ water sampling campaigns. Satellite optical remote sensing has the potential to provide continuous, cost-effective DOC estimates. In this study we used a bio-optics dataset collected in turbid coastal waters of Moreton Bay (MB), Australia, during 2011 to develop a remote sensing algorithm to estimate DOC. This dataset includes data from flood and non-flood conditions. In MB, DOC concentration varied over a wide range (20-520 μM C) and had a good correlation (R2 = 0.78) with absorption due to coloured dissolved organic matter (CDOM) and remote sensing reflectance. Using this data set we developed an empirical algorithm to derive DOC concentrations from the ratio of Rrs(412)/Rrs(488) and tested it with independent datasets. In this study, we demonstrate the ability to estimate DOC using remotely sensed optical observations in turbid coastal waters.

  13. Adsorption of Pb and Zn from binary metal solutions and in the presence of dissolved organic carbon by DTPA-functionalised, silica-coated magnetic nanoparticles.

    PubMed

    Hughes, D L; Afsar, A; Harwood, L M; Jiang, T; Laventine, D M; Shaw, L J; Hodson, M E

    2017-09-01

    The ability of diethylenetriaminepentaacetic acid (DTPA)-functionalised, silica-coated magnetic nanoparticles to adsorb Pb and Zn from single and bi-metallic metal solutions and from solutions containing dissolved organic carbon was assessed. In all experiments 10 mL solutions containing 10 mg of nanoparticles were used. For single metal solutions (10 mg L(-1) Pb or Zn) at pH 2 to 8, extraction efficiencies were typically >70%. In bi-metallic experiments, examining the effect of a background of either Zn or Pb (0.025 mmol L(-1)) on the adsorption of variable concentrations (0-0.045 mmol L(-1)) of the other metal (Pb or Zn, respectively) adsorption was well modelled by linear isotherms (R(2) > 0.60; p ≤ 0.001) and Pb was preferentially adsorbed relative to Zn. In dissolved organic carbon experiments, the presence of fulvic acid (0, 2.1 and 21 mg DOC L(-1)) reduced Pb and Zn adsorption from 0.01, 0.1 and 1.0 mmol L(-1) solutions. However, even at 21 mg DOC L(-1) fulvic acid, extraction efficiencies from 0.01 to 0.1 mmol L(-1) solutions remained >80% (Pb) and >50% (Zn). Decreases in extraction efficiency were significant between initial metal concentrations of 0.1 and 1.0 mmol L(-1) indicating that at metal loadings between c. 100 mg kg(-1) and 300 mg kg(-1) occupancy of adsorption sites began to limit further adsorption. The nanoparticles have the potential to perform effectively as metal adsorbents in systems containing more than one metal and dissolved organic carbon at a range of pH values. Copyright © 2017. Published by Elsevier Ltd.

  14. Variations in dissolved organic nitrogen concentration in biofilters with different media during drinking water treatment.

    PubMed

    Zhang, Huining; Zhang, Kefeng; Jin, Huixia; Gu, Li; Yu, Xin

    2015-11-01

    Dissolved organic nitrogen (DON) is potential precursor of disinfection byproducts (DBPs), especially nitrogenous DBPs. In this study, we investigated the impact of biofilters on DON concentration changes in a drinking water plant. A small pilot plant was constructed next to a sedimentation tank in a drinking water plant and included activated carbon, quartz sand, anthracite, and ceramsite biofilters. As the biofilter layer depth increased, the DON concentration first decreased and then increased, and the variation in DON concentration differed among the biofilters. In the activated carbon biofilter, the DON concentration was reduced by the largest amount in the first part of the column and increased by the largest amount in the second part of the column. The biomass in the activated carbon filter was less than that in the quartz sand filter in the upper column. The heterotrophic bacterial proportion among bacterial flora in the activated carbon biofilter was the largest, which might be due to the significant reduction in DON in the first part of the column. Overall, the results indicate that the DON concentration in biofiltered water can be controlled via the selection of appropriate biofilter media. We propose that a two-layer biofilter with activated carbon in the upper layer and another media type in the lower layer could best reduce the DON concentration.

  15. Seasonal variations in concentration and lability of dissolved organic carbon in Tokyo Bay

    NASA Astrophysics Data System (ADS)

    Kubo, A.; Yamamoto-Kawai, M.; Kanda, J.

    2015-01-01

    Concentrations of recalcitrant and bioavailable dissolved organic carbon (DOC) and their seasonal variations were investigated at three stations in Tokyo Bay, Japan, and in two freshwater sources flowing into the bay. On average, recalcitrant DOC (RDOC), as a remnant of DOC after 150 days of bottle incubation, accounted for 78% of the total DOC in Shibaura sewage treatment plant (STP) effluent, 67% in the upper Arakawa River water, 66% in the lower Arakawa River water, and 78% in surface bay water. Bioavailable DOC (BDOC) concentrations, defined as DOC minus RDOC, were lower than RDOC at all stations. In freshwater environments, RDOC concentrations were almost constant throughout the year. In the bay, RDOC was higher during spring and summer than in autumn and winter because of freshwater input and biological production. The relative concentration of RDOC in the bay derived from phytoplankton, terrestrial, and open-oceanic waters was estimated to be 8-10, 21-32, and 59-69%, respectively, based on multiple regression analysis of RDOC, salinity, and chl a. In addition, comparison with previous data from 1972 revealed that concentrations of RDOC and BDOC have decreased by 33 and 74% at freshwater sites and 39 and 76% in Tokyo Bay, while the ratio of RDOC to DOC has increased. The change in DOC concentration and composition was probably due to increased amounts of STP effluent entering the system. Tokyo Bay exported mostly RDOC to the open ocean because of the remineralization of BDOC.

  16. Fast-freezing with liquid nitrogen preserves bulk dissolved organic matter concentrations, but not its composition

    NASA Astrophysics Data System (ADS)

    Thieme, Lisa; Graeber, Daniel; Kaupenjohann, Martin; Siemens, Jan

    2016-08-01

    Freezing can affect concentrations and spectroscopic properties of dissolved organic matter (DOM) in water samples. Nevertheless, water samples are regularly frozen for sample preservation. In this study we tested the effect of different freezing methods (standard freezing at -18 °C and fast-freezing with liquid nitrogen) on DOM concentrations measured as organic carbon (DOC) concentrations and on spectroscopic properties of DOM from different terrestrial ecosystems (forest and grassland). Fresh and differently frozen throughfall, stemflow, litter leachate and soil solution samples were analyzed for DOC concentrations, UV-vis absorption and fluorescence excitation-emission matrices combined with parallel factor analysis (PARAFAC). Fast-freezing with liquid nitrogen prevented a significant decrease of DOC concentrations observed after freezing at -18 °C. Nonetheless, the share of PARAFAC components 1 (EXmax < 250 nm (340 nm), EXmax: 480 nm) and 2 (EXmax: 335 nm, EXmax: 408 nm) to total fluorescence and the humification index (HIX) decreased after both freezing treatments, while the shares of component 3 (EXmax: < 250 nm (305 nm), EXmax: 438 nm) as well as SUVA254 increased. The contribution of PARAFAC component 4 (EXmax: 280 nm, EXmax: 328 nm) to total fluorescence was not affected by freezing. We recommend fast-freezing with liquid nitrogen for preservation of bulk DOC concentrations of samples from terrestrial sources, whereas immediate measuring is preferable to preserve spectroscopic properties of DOM.

  17. Numerical simulation of dissolved oxygen concentration in water flow over stepped spillways.

    PubMed

    Cheng, Xiangju; Chen, Xuewei

    2013-05-01

    This study developed an improved Eulerian model for the simulation of an air-water flow field over stepped spillways. The improved drag model applied different drag coefficients for bubbles and for free surface flows or gas cavities. Void fraction and turbulence correction were used in determining the bubble drag coefficient. The calculated air entrainment and air-water velocity could be adapted using these parameters. With the improved drag model, the Eulerian simulations predicted the location of the inception point, the distributions of air void fraction, velocity distributions, and pressure distributions. The change in the dissolved oxygen (DO) concentration from upstream of the stepped spillways, to downstream, was simulated based on the improved computational fluid dynamics model and the transport equation for DO transferring. The numerical DO concentration coincided with the experimental results. Therefore, the improved CFD model and the numerical methods presented here can provide possible optimization tools for strong air entrainment flows.

  18. Effects of reduced dissolved oxygen concentrations on physiology and fluorescence of hermatypic corals and benthic algae

    PubMed Central

    Smith, Jennifer E.; Thompson, Melissa

    2014-01-01

    While shifts from coral to seaweed dominance have become increasingly common on coral reefs and factors triggering these shifts successively identified, the primary mechanisms involved in coral-algae interactions remain unclear. Amongst various potential mechanisms, algal exudates can mediate increases in microbial activity, leading to localized hypoxic conditions which may cause coral mortality in the direct vicinity. Most of the processes likely causing such algal exudate induced coral mortality have been quantified (e.g., labile organic matter release, increased microbial metabolism, decreased dissolved oxygen availability), yet little is known about how reduced dissolved oxygen concentrations affect competitive dynamics between seaweeds and corals. The goals of this study were to investigate the effects of different levels of oxygen including hypoxic conditions on a common hermatypic coral Acropora yongei and the common green alga Bryopsis pennata. Specifically, we examined how photosynthetic oxygen production, dark and daylight adapted quantum yield, intensity and anatomical distribution of the coral innate fluorescence, and visual estimates of health varied with differing background oxygen conditions. Our results showed that the algae were significantly more tolerant to extremely low oxygen concentrations (2–4 mg L−1) than corals. Furthermore corals could tolerate reduced oxygen concentrations, but only until a given threshold determined by a combination of exposure time and concentration. Exceeding this threshold led to rapid loss of coral tissue and mortality. This study concludes that hypoxia may indeed play a significant role, or in some cases may even be the main cause, for coral tissue loss during coral-algae interaction processes. PMID:24482757

  19. Temporal Variability of Stemflow Dissolved Organic Carbon (DOC) Concentrations and Quality from Morphologically Contrasting Deciduous Canopies

    NASA Astrophysics Data System (ADS)

    van Stan, J. T.; Levia, D. F.; Inamdar, S. P.; Mitchell, M. J.; Mage, S. M.

    2010-12-01

    Dissolved organic carbon (DOC) inputs from canopy-derived hydrologic fluxes play a significant role in the terrestrial carbon budgets of forested ecosystems. However, no studies known to the authors have examined the variability of both DOC concentrations and quality for stemflow across time scales, nor has any study to date evaluated the effects of canopy structure on stemflow DOC characteristics. This investigation seeks to rectify this knowledge gap by examining the variability of stemflow DOC concentrations and quality across contrasting canopy morphologies and time scales (seasonal, storm and intrastorm). Bulk and intrastorm stemflow samples from a less dense, rough-barked, more plagiophile (Liriodendron tulipifera L. (tulip poplar)) and a denser, thin-barked, more erectophile (Fagus grandifolia Ehrh. (American beech)) canopy were collected and analyzed for DOC quality using metrics derived from UV-vis spectroscopy (E2:E3 ratio, SUVA254, select spectral slope (S), and spectral slope ratios (SR)). Our results suggest that stemflow DOC concentrations and quality change as crown architectural traits enhance or diminish hydrologic retention time within the canopy. The architecture of L. tulipifera canopies likely retards the flow of intercepted water, increasing chemical exchange with bark and foliar surfaces. UV-vis metrics indicated that this increased chemical exchange, particularly with bark surfaces, generally enhanced aromatic hydrocarbon content and increased molecular weight. Because leaf presence influenced DOC quality, stemflow DOC characteristics also varied seasonally in response to canopy condition. At the inter- and intrastorm scale, stemflow DOC concentration and quality varied with meteorological and antecedent canopy conditions. Since recent studies have linked stemflow production to preferential subsurface transport of dissolved chemistries, trends in DOC speciation and fluxes described in this study may impact soil environments within wooded

  20. Effects of reduced dissolved oxygen concentrations on physiology and fluorescence of hermatypic corals and benthic algae.

    PubMed

    Haas, Andreas F; Smith, Jennifer E; Thompson, Melissa; Deheyn, Dimitri D

    2014-01-01

    While shifts from coral to seaweed dominance have become increasingly common on coral reefs and factors triggering these shifts successively identified, the primary mechanisms involved in coral-algae interactions remain unclear. Amongst various potential mechanisms, algal exudates can mediate increases in microbial activity, leading to localized hypoxic conditions which may cause coral mortality in the direct vicinity. Most of the processes likely causing such algal exudate induced coral mortality have been quantified (e.g., labile organic matter release, increased microbial metabolism, decreased dissolved oxygen availability), yet little is known about how reduced dissolved oxygen concentrations affect competitive dynamics between seaweeds and corals. The goals of this study were to investigate the effects of different levels of oxygen including hypoxic conditions on a common hermatypic coral Acropora yongei and the common green alga Bryopsis pennata. Specifically, we examined how photosynthetic oxygen production, dark and daylight adapted quantum yield, intensity and anatomical distribution of the coral innate fluorescence, and visual estimates of health varied with differing background oxygen conditions. Our results showed that the algae were significantly more tolerant to extremely low oxygen concentrations (2-4 mg L(-1)) than corals. Furthermore corals could tolerate reduced oxygen concentrations, but only until a given threshold determined by a combination of exposure time and concentration. Exceeding this threshold led to rapid loss of coral tissue and mortality. This study concludes that hypoxia may indeed play a significant role, or in some cases may even be the main cause, for coral tissue loss during coral-algae interaction processes.

  1. Passive sampling methods for contaminated sediments: Scientific rationale supporting use of freely dissolved concentrations

    PubMed Central

    Mayer, Philipp; Parkerton, Thomas F; Adams, Rachel G; Cargill, John G; Gan, Jay; Gouin, Todd; Gschwend, Philip M; Hawthorne, Steven B; Helm, Paul; Witt, Gesine; You, Jing; Escher, Beate I

    2014-01-01

    Passive sampling methods (PSMs) allow the quantification of the freely dissolved concentration (Cfree) of an organic contaminant even in complex matrices such as sediments. Cfree is directly related to a contaminant's chemical activity, which drives spontaneous processes including diffusive uptake into benthic organisms and exchange with the overlying water column. Consequently, Cfree provides a more relevant dose metric than total sediment concentration. Recent developments in PSMs have significantly improved our ability to reliably measure even very low levels of Cfree. Application of PSMs in sediments is preferably conducted in the equilibrium regime, where freely dissolved concentrations in the sediment are well-linked to the measured concentration in the sampler via analyte-specific partition ratios. The equilibrium condition can then be assured by measuring a time series or a single time point using passive samplers with different surface to volume ratios. Sampling in the kinetic regime is also possible and generally involves the application of performance reference compounds for the calibration. Based on previous research on hydrophobic organic contaminants, it is concluded that Cfree allows a direct assessment of 1) contaminant exchange and equilibrium status between sediment and overlying water, 2) benthic bioaccumulation, and 3) potential toxicity to benthic organisms. Thus, the use of PSMs to measure Cfree provides an improved basis for the mechanistic understanding of fate and transport processes in sediments and has the potential to significantly improve risk assessment and management of contaminated sediments. Integr Environ Assess Manag 2014;10:197–209. © 2014 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of SETAC. PMID:24288295

  2. A comparison of four porewater sampling methods for metal mixtures and dissolved organic carbon and the implications for sediment toxicity evaluations.

    PubMed

    Cleveland, Danielle; Brumbaugh, William G; MacDonald, Donald D

    2017-06-09

    Evaluations of sediment quality conditions are commonly conducted using whole-sediment chemistry analyses but can be enhanced by evaluating multiple lines of evidence, including measures of the bioavailable forms of contaminants. In particular, porewater chemistry data provide information that is directly relevant for interpreting sediment toxicity data. Various methods for sampling porewater for trace metals and dissolved organic carbon (DOC), which is an important moderator of metal bioavailability, have been employed. The present study compares the peeper, push point, centrifugation, and diffusive gradients in thin films (DGT) methods for the quantification of 6 metals and DOC. The methods were evaluated at low and high concentrations of metals in 3 sediments having different concentrations of total organic carbon and acid volatile sulfide and different particle-size distributions. At low metal concentrations, centrifugation and push point sampling resulted in up to 100 times higher concentrations of metals and DOC in porewater compared with peepers and DGTs. At elevated metal levels, the measured concentrations were in better agreement among the 4 sampling techniques. The results indicate that there can be marked differences among operationally different porewater sampling methods, and it is unclear if there is a definitive best method for sampling metals and DOC in porewater. Environ Toxicol Chem 2017;9999:1-10. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America. Published 2017 Wiley Periodicals Inc., on behalf of SETAC.

  3. [Interpretation of spatial distribution pattern for dissolved inorganic nitrogen concentration in coastal estuary using hyperspectral data].

    PubMed

    Zhang, Dong; Xu, Yong; Zhang, Ying; Li, Huan

    2010-06-01

    Choosing dissolved inorganic nitrogen (DIN) as one of the representative nutritional salt monitoring indexes, a hyperspectral remotely sensed inversion model was built and applied to quantitatively retrieve water quality parameters with its spatial distribution patterns in coastal estuary with high suspended sediment concentration (SSC). It was found that when SSC was larger than 0.1 kg/m3, DIN concentration had a notable inverse correlation with SSC and the correlation coefficient R2 reached 0.617. Based on this conclusion, firstly the in-situ observed water surface remote sensing reflectance was resampled according to the spectral response characters of Hyperion sensor. And then, statistical correlation analysis between reflectance and DIN concentration was carried out. The results showed that band reflectance of R804 and R630 representing the second and first reflectance peak of water spectrum curve were sensitive to the variation of DIN concentration. And then, a pseudo remotely sensed sand parameter index R804 x R630/(R804 - R630) was calculated for the construction of the nonlinear DIN quantitative reversion model. Correlation coefficient R2 between observed and simulated DIN concentrations for 29 calibrating samples and 10 validating samples were 0.746 and 0.67, while their mean absolute errors reached 109.07 and 147.58 microg/L, respectively. The model was then applied on Hyperion hyperspectral image to get the spatial distribution character of DIN concentration in Sheyanghe river estuary and the DIN concentration was between 52 to 513 microg/L. Results indicated that in coastal estuary which was dominated by suspended sediments, the diffusive trends of DIN concentration reversed by remote sensing techniques had an intimate relationship with motions of tidal current and transportation attributes of SSC. As the hydrodynamic conditions were unclear, hyperspectral remote sensing technique was an effective technical way for dynamic survey of DIN concentration.

  4. Factors Controlling Dissolved Oxygen Concentration in the Hyporheic Zone Induced by Fish Egg Nests

    NASA Astrophysics Data System (ADS)

    Ford, A.; Cardenas, M. B.; Kaufman, M.; Zheng, L.; Kessler, A. J.

    2014-12-01

    There is currently limited research on the effects of bed depressions, such as those associated with fish nests, on hyporheic flow and biogeochemistry. A series of flume experiments are in progress, with the aim of understanding the effects of bed depressions on the hyporheic flow of oxygenated water. This study focuses on fish nests, also called redds, which represent a typical depression or scour feature. Previous research has shown that redd topography induces hyporheic circulation, but experiments regarding the oxygen concentration in and around the redds have not been conducted. We are determining the ways in which redds affect dissolved oxygen distribution and how this is controlled by hyporheic flow. The oxygen concentration across the cross-sectional plane of a fish nest is measured using a planar optode and microsensors. Hydraulic measurements include pressure measurements along the sediment-water interface and dye visualization. The redd design is based on a salmonid redd, which consists of a scour feature and a tailspin. The salmonid eggs are found in the tailspin. We hypothesize that the oxygen concentration will be greatest in close proximity to the gravel base of the redd and concentration will decrease with increasing depth and distance from the redd. Higher oxygen concentrations in the tailspin supports the placement of fish eggs within that area as opposed to a less oxygenated area of the streambed. Thus, fish nests are likely bio-engineered to optimize hyporheic flow and biogeochemistry to improve egg viability.

  5. Dissolved and particulate organic carbon in the North Inlet estuary, South Carolina: what controls their concentrations

    SciTech Connect

    Wolaver, T.G.; Hutchinson, S.; Marozas, M.

    1986-03-01

    Water samples have been taken daily at 1030 EST from three locations within North Inlet (South Carolina) since June of 1980 in order to evaluate the tidal, seasonal, and eventually annual variability in carbon concentrations within this system and generate hypotheses explaining the observed trends. Dissolved organic carbon (DOC) concentrations within North Inlet (South Carolina) vary inversely with salinity (r/sup 2/ = 0.65), suggesting the main source of DOC in North Inlet is freshwater entering from the adjacent forested watershed. This assertion is supported by an observed decrease of tidal water salinity with the onset of streamflow. DOC variability is also associated with (1) groundwater advection and/or runoff and seepage from the marsh surface; (2) removal from tidal water via either physical sorption or biological uptake; (3) sampling location; and (4) origin of water mass. Particulate organic carbon (POC) concentrations vary seasonally, higher values found during the summer. POC variability is controlled by a series of physical and biological factors. Evidence suggests that in the smaller tidal creeks, POC concentrations are associated with (1) rain events scouring the marsh surface, (2) phytoplankton concentrations varying as a function of tidal stage, and (3) removal of particulate material from the marsh surface on the ebb tide. In the larger tidal creeks tidal water velocity appears to be the main factor influencing POC values. 20 references, 5 figures, 2 table.

  6. Seasonal variations in concentration and composition of dissolved organic carbon in Tokyo Bay

    NASA Astrophysics Data System (ADS)

    Kubo, A.; Yamamoto-Kawai, M.; Kanda, J.

    2014-07-01

    Concentrations of recalcitrant and bioavailable dissolved organic carbon (DOC) and their seasonal variations were investigated at three stations in Tokyo Bay, Japan, and in two freshwater sources flowing into the bay to evaluate the significance of DOC degradation for the carbon budget in coastal waters and carbon export to the open ocean. Recalcitrant DOC (RDOC) was differentiated from bioavailable DOC (BDOC) as a remnant of DOC after 150 days of bottle incubation. On average, RDOC accounted for 78% of the total DOC in Shibaura sewage treatment plant (STP) effluent, 67% in the upper Arakawa River water, 66% in the lower Arakawa River water, and 78% in surface bay water. RDOC concentrations were higher than BDOC at all stations. In freshwater environments, RDOC concentrations were almost constant throughout the year. In the bay, RDOC was higher during spring and summer than during autumn and winter. The relative abundance of RDOC in the bay derived from phytoplankton, terrestrial, and open oceanic waters was estimated to be 9%, 33%, and 58%, respectively, by multiple regression analysis of RDOC, salinity, and chl a. In addition, comparison with previous data from 1972 revealed that concentrations of RDOC and BDOC have decreased by 33% and 74% at freshwater sites and 39% and 76% at Tokyo Bay, while the ratio of RDOC to DOC has increased. The change in DOC concentration and composition was probably due to increased amounts of sewage treatment plant effluent entering the system. Tokyo Bay exported DOC, mostly RDOC, to the open ocean because of remineralization of BDOC.

  7. Hydrologic control of dissolved organic matter concentration and quality in a semiarid artificially drained agricultural catchment

    NASA Astrophysics Data System (ADS)

    Bellmore, Rebecca A.; Harrison, John A.; Needoba, Joseph A.; Brooks, Erin S.; Kent Keller, C.

    2015-10-01

    Agricultural practices have altered watershed-scale dissolved organic matter (DOM) dynamics, including in-stream concentration, biodegradability, and total catchment export. However, mechanisms responsible for these changes are not clear, and field-scale processes are rarely directly linked to the magnitude and quality of DOM that is transported to surface water. In a small (12 ha) agricultural catchment in eastern Washington State, we tested the hypothesis that hydrologic connectivity in a catchment is the dominant control over the concentration and quality of DOM exported to surface water via artificial subsurface drainage. Concentrations of dissolved organic carbon (DOC) and humic-like components of DOM decreased while the Fluorescence Index and Freshness Index increased with depth through the soil profile. In drain discharge, these characteristics were significantly correlated with drain flow across seasons and years, with drain DOM resembling deep sources during low-flow and shallow sources during high flow, suggesting that DOM from shallow sources bypasses removal processes when hydrologic connectivity in the catchment is greatest. Assuming changes in streamflow projected for the Palouse River (which contains the study catchment) under the A1B climate scenario (rapid growth, dependence on fossil fuel, and renewable energy sources) apply to the study catchment, we project greater interannual variability in annual DOC export in the future, with significant increases in the driest years. This study highlights the variability in DOM inputs from agricultural soil to surface water on daily to interannual time scales, pointing to the need for a more nuanced understanding of agricultural impacts on DOM dynamics in surface water.

  8. Impact of environmental factors on dissolved organic carbon concentrations in German bogs under grassland

    NASA Astrophysics Data System (ADS)

    Frank, Stefan; Tiemeyer, Bärbel; Freibauer, Annette

    2013-04-01

    Peatlands cover about 5% of Germany's land area. Agricultural use combined with drainage increases the greenhouse gas emissions and alters the dissolved organic carbon (DOC) concentrations in the soil- and groundwater of these ecosystems. Cycling of DOC is influenced by a complex interaction of environmental factors such as peat characteristics, groundwater level, meteorological conditions, pH-value and ionic strength. Reasons for elevated DOC concentrations are debated in literature, but only a few studies on the dynamic of DOC in raised bogs in Germany have been conducted so far. In Germany, raised bogs are mainly used as grassland. Therefore, five grassland study sites and one natural reference have been selected. The bog "Ahlenmoor" has a deep, medium to weakly decomposed peat layer. There, three study sites represent different land use intensities with a corresponding groundwater table (intensive grassland, extensive grassland, natural reference). The bog relict "Großes Moor" is characterised by a shallow amorphous peat layer, which is partly mixed with sand. There, three sites in an extensive grassland were chosen to study the effects of soil carbon concentrations (9 to 48 %) and groundwater levels. At each site, nine suction plates (three replicates in each depth) and three tensiometers were installed in 15, 30 and 60 cm. Soil water was sampled fortnightly from June 2011 to December 2012 and analysed for electrical conductivity, pH-value and DOC concentration. Compared to most literature values, DOC concentrations at our study sites were very high (on average, 197 to 55 mg/L). At the "Ahlenmoor", an increase in agricultural intensity and a lower groundwater table increases both the DOC concentrations and their variability in the soil water in order intensive grassland > extensive grassland > natural site. Surprisingly, soil carbon concentration and groundwater table gradients as investigated in the "Großes Moor" did only lead to minor differences in the

  9. On chip steady liquid-gas phase separation for flexible generation of dissolved gas concentration gradient.

    PubMed

    Xu, Bi-Yi; Hu, Shan-Wen; Yan, Xiao-Na; Xia, Xing-Hua; Xu, Jing-Juan; Chen, Hong-Yuan

    2012-04-07

    In this study, steady liquid-gas phase separation is realized by applying a hydrophobic small microchannel array (SMA) to bridge two large microchannels, one for liquid phase and one for gas phase. In this structure, a capillary pressure difference between that in the SMA and the larger channel results in a steady liquid-gas interface. The generated liquid-gas interface allows for fast gas dissolving speed. By coupling the liquid-gas interface with a one directional fluidic field, a steady dissolved gas concentration gradient (DgCG) is generated. The DgCG distribution is easily designable for linear or exponential modes, providing improved flexibility for gas participated processes on chip. To demonstrate its applicability, a CO(2) DgCG chip is fabricated and applied for screening CaCO(3) crystal growth conditions in the DgCG chip. Crystals with transitional structures are successfully fabricated, which is consistent with the CO(2) DgCG distribution. This journal is © The Royal Society of Chemistry 2012

  10. Long term in situ monitoring of total dissolved iron concentrations on the MoMAR observatory

    NASA Astrophysics Data System (ADS)

    Laes-Huon, Agathe; Legrand, Julien; Tanguy, Virginie; Cathalot, Cecile; Blandin, Jérôme; Rolin, Jean-Francois; Sarradin, Pierre-Marie

    2015-04-01

    Nowadays the scientific community wants relevant monitoring with an increase in spatial and temporal distribution of key chemicals. The hydrothermal ecosystems characterized by strong physico-chemical gradients are also of particular interest as they present an unique fauna, sustained by microbial chemosynthesis. The characterization of the chemical environment in the hydrothermal vent ecosystems implies the use of in situ instrumentation which is a serious challenge in the marine environment (Prien et al. 2007). The CHEMINI (CHEmical MINIaturised analyser), presented here, is a chemical in situ analyser specialized for deep sea uses (Vuillemin et al. 2007). It was first deployed on the autonomous deep sea observatory MoMAR (Monitoring of the Mid-Atlantic Ridge, FIXO3, Fixed point Open Ocean Observatories) in 2010. The first part of the presentation will focus on the description of the CHEMINI, then on the results obtained on the MoMAR observatory during the last 4 years. CHEMINI, implemented on the TEMPO ecological module determined total dissolved iron concentrations associated with an optode and a temperature probe. Several months of total iron concentrations, of T°C and videos were recorded permitting the study of the temporal dynamics of faunal assemblages and their habitat on the Lucky strike vent (-1700m, Cuvelier et al. 2011). Long term in situ analysis of total dissolved iron (31st of August 2013 - 23rd of February 2014, [DFe] = 7.12 +- 2.11 µmol L-1, n = 519) at the Eiffel Tower edifice is presented in details. The daily analyzed in situ standard (25µmol.L-1) showed an excellent reproducibility (1.07%, n=522). CHEMINI was reliable, robust over time for in situ analysis. The averaged total dissolved iron concentrations for the 6 months period remain low but they correlated significantly with temperature showing a spectra frequency with a maximal contribution around 4-5 days for both variables. The analytical results will be commented and the future

  11. Powder-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2016-05-03

    A powder-based adsorbent and a related method of manufacture are provided. The powder-based adsorbent includes polymer powder with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the powder-based adsorbent includes irradiating polymer powder, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Powder-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  12. Foam-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2015-06-02

    Foam-based adsorbents and a related method of manufacture are provided. The foam-based adsorbents include polymer foam with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the foam-based adsorbents includes irradiating polymer foam, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Foam-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  13. Selective sequential precipitation of dissolved metals in mine drainage from coal mine

    NASA Astrophysics Data System (ADS)

    Yim, Giljae; Bok, Songmin; Ji, Sangwoo; Oh, Chamteut; Cheong, Youngwook; Han, Youngsoo; Ahn, Joosung

    2017-04-01

    In abandoned mines in Korea, a large amount of mine drainage continues to flow out and spread pollution. In purification of the mine drainage a massive amount of sludge is generated as waste. Since this metal sludge contains high Fe, Al and Mn oxides, developing the treatment method to recover homogeneous individual metal with high purity may beneficial to recycle waste metals as useful resources and reduce the amount of sludge production. In this regard, we established a dissolved metals selective precipitation process to treat Waryong Industry's mine drainage. The process that selectively precipitates metals dissolved in mine drainage is a continuous Fe-buffer-Al process, and each process consists of the neutralization tank, the coagulation tank, and the settling tank. Based on this process, this study verified the operational applicability of the Fe and Al selective precipitation. Our previous study revealed that high-purity Fe and Al precipitates could be recovered at a flow rate of 1.5 ton/day, while the lower purity was achieved when the rate was increased to about 3 ton/day due to the difficulty in reagent dosage control. In the current study was conducted to increase the capacity of the system to recover Fe and Al as high-purity precipitates at a flow rate of 10 ton/day with the ensured continuous operations by introducing an automatic reagent injection system. The previous study had a difficulty in controlling the pH and operating system continuously due to the manually controlled reagent injection system. To upgrade this and ensure the optimal pH in a stable way, a continuous reagent injection system was installed. The result of operation of the 10 ton/day system confirmed that the scaled-up process could maintain the stable recovery rates and purities of precipitates on site.

  14. Metal concentrations in water and sediments from tourist beaches of Acapulco, Mexico.

    PubMed

    Jonathan, M P; Roy, P D; Thangadurai, N; Srinivasalu, S; Rodríguez-Espinosa, P F; Sarkar, S K; Lakshumanan, C; Navarrete-López, M; Muñoz-Sevilla, N P

    2011-04-01

    A survey on the metal concentrations (As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V, Zn) in beach water and sediments is reported from the tourist destination of Acapulco city on the Pacific coast of Mexico. The concentration of dissolved trace metals (DTMs) in beach water and acid leachable trace metals (ALTMs) in sediments indicated that they are anthropogenic in nature due to the increased tourist activities in the crowded beach locations. The statistical analysis indicates Fe and Mn play a major role as metal scavengers in both the medium (water and sediment) and the higher value of other metals is site specific in the study area, indicating that they are transported from the local area. Comparison results suggest that the beach water quality has deteriorated more than the sediments and special care needs to be taken to restore the beach quality. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. Quantifying dissolved organic carbon concentrations in upland catchments using phenolic proxy measurements

    NASA Astrophysics Data System (ADS)

    Peacock, Mike; Burden, Annette; Cooper, Mark; Dunn, Christian; Evans, Chris D.; Fenner, Nathalie; Freeman, Chris; Gough, Rachel; Hughes, David; Hughes, Steve; Jones, Tim; Lebron, Inma; West, Mike; Zieliński, Piotr

    2013-01-01

    SummaryConcentrations of dissolved organic carbon (DOC) in soil and stream waters in upland catchments are widely monitored, in part due to the potential of DOC to form harmful by-products when chlorinated during treatment of water for public supply. DOC can be measured directly, though this is expensive and time-consuming. Light absorbance in the UV-vis spectrum is often used as a surrogate measurement from which a colour-carbon relationship between absorbance and DOC can be derived, but this relationship can be confounded by numerous variables. Through the analysis of data from eight sites in England and Wales we investigate the possibility of using the concentration of phenolic compounds in water samples as a proxy for DOC concentration. A general model using data from all the sites allowed DOC to be calculated from phenolics at an accuracy of 81-86%. A detailed analysis at one site revealed that a site-specific calibration was more accurate than the general model, and that this compared favourably with a colour-carbon calibration. We therefore recommend this method for use where estimates of DOC concentration are needed, but where time and money are limiting factors, or as an additional method to calculate DOC alongside colour-carbon calibrations. Tests demonstrated only small amounts of phenolic degradation over time; a loss of 0.92 mg L-1 after 8 months in storage, and so this method can be used on older samples with limited loss of accuracy.

  16. The Appearance, Taste, and Concentrations of Zolpidem Dissolved in Still Water and Carbonated Beverages.

    PubMed

    Heide, Gunhild; Hjelmeland, Knut; Brochmann, Gerd-Wenche; Karinen, Ritva; Høiseth, Gudrun

    2017-08-15

    Zolpidem is a sedative that could be used to drug victims, but its suitability to dissolve in drinks is unknown. In this small study, we added either crushed or whole tablets of zolpidem hemitartrate to carbonated beverages or still water to observe how this affected the taste and appearance. Also, concentrations were measured by ultra-high performance liquid chromatography tandem mass spectrometry at different time intervals. Two crushed tablets (20 mg) in cider (250 mL) lead to a maximum concentration of 84 mg/L zolpidem base after 30 min, while the corresponding concentration after adding fifteen tablets (150 mg) was 467 mg/L. There was little change in taste, but froth and turbidity were observed when adding high doses to carbonated beverages. Carbonated beverages spiked with 20 mg of crushed zolpidem hemitartrate tablets reached concentrations that could cause impairment. Spiking with 150 mg could possibly be lethal if several mouthfuls were ingested. © 2017 American Academy of Forensic Sciences.

  17. An anion-exchange method to concentrate dissolved DNA from aquifer water.

    PubMed

    Li, Zhen; Briggs, Brandon R; Sheridan, Peter P; Shields, Malcolm S

    2013-04-01

    A rapid DNA isolation method was developed to concentrate dissolved DNA (dDNA) in aquifer water for molecular analysis. The aquifer dDNA from the Eastern Snake River Plain Aquifer (ESRPA) was extracted and concentrated using a new method with an anion-exchange Mustang® Q membrane. The concentration of aquifer dDNA in this study ranged from 60 to 264.5 ng l−1 in ESRPA aquifer wells. DNA stability in ESRPA aquifer water was also tested in this study. The dDNA extracted from aquifer water samples was used for PCR amplification of bacterial 16S rRNA genes for terminal restriction fragment length polymorphism (T-RFLP) analysis and construction of 16S rRNA gene clone libraries. The ureC gene, IncP, IncQ and IncW plasmid genes were also PCR amplified from dDNA samples. Based on the results, dDNA is relatively stable in aquifer water and can be concentrated by Q membrane method for molecular analysis. The quality of isolated dDNA was suitable as a PCR template.

  18. Raising and controlling study of dissolved oxygen concentration in closed-type aeration tank.

    PubMed

    Chen, C K; Lo, S L

    2005-07-01

    This study investigated the promotion and control of dissolved oxygen (DO) concentration of the closed-type aeration tank via practical experiments in the wastewater treatment system of a 5-star hotel in Taipei. As with limited and treasured space in Taiwan, before the completion of the sewer system construction in cities, to utilize the mat foundation under large buildings as the space of sewage treatment plant still has been one of the alternatives of those sewage treatments. However, aeration tanks constructed in the mat foundation of buildings have smaller effective water depth, which will cause a lower total transfer amount of DO. Controlling the total exhaust gas flow rate can increase the pressure on such closed-type aeration tanks. The DO concentration thus may increase according to Henry's Law. Furthermore, it may enable operators to adjust the DO concentration of the aeration tank more precisely and thus sustain optimal operating conditions in these treatment facilities. Practical experiments indicated that the DO concentration of aeration tank maintains an average of 3.8 mg l(-1), obtaining the optimum operating conditions. The efficiency of the biological treatment facilities in the mat foundation could be markedly improved.

  19. Millimolar concentrations of zinc and other metal cations cause sedimentation of DNA.

    PubMed Central

    Kejnovsky, E; Kypr, J

    1998-01-01

    We demonstrate that DNA sediments in the presence of millimolar concentrations of zinc or related metal cations and that EDTA entirely dissolves the sediment. The sedimentation is promoted by alkaline pH but the pH dependence is abolished by submillimolar concentrations of phosphate anions. We suspect that the metal cations generate sedimenting particles of insoluble hydroxides or phosphates for which DNA has a strong affinity. The events involved in DNA-metal phosphate co-sedimentation are similar to the processes that enable calcium phosphate-assisted transfection. Hence, work with even submillimolar concentrations of zinc and most other metal cations, which many DNA-binding proteins need for their activities, requires care to avoid the sedimentation of DNA. Literature reporting about zinc effects on DNA is discussed from the point of view of the present results. PMID:9826751

  20. Validity of using semipermeable membrane devices for determining aqueous concentrations of freely dissolved PAHs

    USGS Publications Warehouse

    Prest, Harry; Petty, J.D.; Huckins, J.N.

    1998-01-01

    An in-depth review of the recent contribution to this journal by Gustafson and Dickhut [1] prompts us to share our concerns regarding some of their conclusions. The paper presents data comparing three techniques for determining aqueous concentrations of freely dissolved polycyclic aromatic hydrocarbons (PAHs) gas sparging, lipid-containing semipermeable membrane devices (SPMDs) of the U.S. Geological Survey (USGS) design, and filtration followed by sorption using XAD-2 resin. Space limitations force us to limit our comments to problems resulting from an apparent lack of understanding of how SPMDs function. Several recent publications [2–13] have described the theoretical and practical considerations of SPMD usage. Gustafson and Dickhut fail to cite any papers describing SPMDs published after 1992, even though some 18 papers have been published in American and European journals since then and several SPMD studies have been presented at many major meetings.

  1. Evaluation of Electrodialysis as Part of an Improved Method to Concentrate Dissolved Organic Matter from Seawater

    NASA Astrophysics Data System (ADS)

    Chang, V.; Koprivnjak, J.; Ingall, E.; Pfromm, P.; Perdue, E. M.

    2004-12-01

    A major obstacle in the study of marine dissolved organic matter (DOM) has been isolating from seawater sufficient quantities for analysis of this highly dilute and chemically complex material. This research explores the application of electrodialysis (ED) in combination with reverse osmosis (RO) as a method to concentrate DOM from seawater. RO methods recover a significant fraction (90%) of DOM from fresh waters with little physical or chemical alteration, and similar high recoveries of DOM have been observed in preliminary tests using estuarine waters of varying salinity. Unfortunately, the extent to which DOM in saline waters can be concentrated by RO is very limited, because RO membranes co-concentrate inorganic salts with DOM. At an early stage of processing, osmotic pressures become too high and/or inorganic salts precipitate from solution and foul the RO membrane. To realize the potentially high recoveries of DOM from saline waters, RO must be coupled with an independent method for removal of inorganic salts. Electrodialysis, which is a well-established process for removal of inorganic salts from aqueous solutions, is such a method. In ED, a feed stream of the sample to be de-ionized and a receiving stream of a solution that will accept the removed ions are pumped through adjacent layers of a membrane stack, which consists of several layers of alternating anion and cation exchange membranes. The membranes are made from highly crosslinked polymers and are non-porous. The direction and velocity of diffusion of the cations and anions are further mediated by a DC electrical current that flows through the membrane stack. In the first stage of testing of the ED process, samples of near-seawater salinity (28 ppt) containing 4 ppm of dissolved organic carbon were collected at the Skidaway Institute of Oceanography in Savannah Georgia. Using ED, salinity was reduced by 87% in these samples with retention of more than 95% of the DOM. These experiments indicate that ED

  2. A review of the effects of dissolved ozone on the corrosion behavior of metals and alloys

    SciTech Connect

    Brown, B.E.; Duquette, D.J.

    1994-12-31

    Ozone is currently being considered as a possible replacement for chlorine based compounds as a biocide. Yet, a review of current literature related to the corrosion behavior of metals and alloys exposed to ozonated solutions indicates that there is considerable confusion concerning the effects of this strong oxidant. Some studies indicate that dissolved ozone will increase the corrosion rates of alloys such as carbon steel or brasses when compared to aerated solutions. Others indicate a beneficial effect of ozone, while still others indicate a neutral effect. Virtually all of these reports are for fresh waters, few relate to localized corrosion behavior, and most are anecdotal in that they report observations from service conditions with poorly defined variables. This review attempts to summarize the various corrosion rates reported in the literature, as well as present data obtained in laboratory studies of metals exposed to ozone in chloride containing environments, including artificial sea water. 28 refs.

  3. Metal concentrations in the tissues of the hydrothermal vent mussel Bathymodiolus: reflection of different metal sources.

    PubMed

    Koschinsky, Andrea; Kausch, Matteo; Borowski, Christian

    2014-04-01

    Hydrothermal vent mussels of the genus Bathymodiolus are ideally positioned for the use of recording hydrothermal fluxes at the hydrothermal vent sites they inhabit. Barium, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Pb, Sr, and U concentrations in tissue sections of Bathymodiolus mussels from several hydrothermal fields between 15°N and 9°S at the Mid-Atlantic Ridge were determined and compared to the surrounding fluids and solid substrates in the habitats. Elements generally enriched in hydrothermal fluids, such as Fe, Cu, Zn, Pb and Cd, were significantly enriched in the gills and digestive glands of the hydrothermal mussels. The rather small variability of Zn (and Mn) and positive correlation with K and earth alkaline metals may indicate a biological regulation of accumulation. Enrichments of Mo and U in many tissue samples indicate that particulate matter such as hydrothermal mineral particles from the plumes can play a more important role as a metal source than dissolved metals. Highest enrichments of Cu in mussels from the Golden Valley site indicate a relation to the ≥400 °C hot heavy-metal rich fluids emanating in the vicinity. In contrast, mussels from the low-temperature Lilliput field are affected by the Fe oxyhydroxide sediment of their habitat. In a comparison of two different sites within the Logatchev field metal distributions in the tissues reflected small-scale local variations in the metal content of the fluids and the particulate material. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Influence of Dissolved Metals on N-Nitrosamine Formation under Amine-based CO2 Capture Conditions.

    PubMed

    Wang, Zimeng; Mitch, William A

    2015-10-06

    As the prime contender for postcombustion CO2 capture technology, amine-based scrubbing has to address the concerns over the formation of potentially carcinogenic N-nitrosamine byproducts from reactions between flue gas NOx and amine solvents. This bench-scale study evaluated the influence of dissolved metals on the potential to form total N-nitrosamines in the solvent within the absorber unit and upon a pressure-cooker treatment that mimics desorber conditions. Among six transition metals tested for the benchmark solvent monoethanolamine (MEA), dissolved Cu promoted total N-nitrosamine formation in the absorber unit at concentrations permitted in drinking water, but not the desorber unit. The Cu effect increased with oxygen concentration. Variation of the amine structural characteristics (amine order, steric hindrance, -OH group substitution and alkyl chain length) indicated that Cu promotes N-nitrosamine formation from primary amines with hydroxyl or carboxyl groups (amino acids), but not from secondary amines, tertiary amines, sterically hindered primary amines, or amines without oxygenated groups. Ethylenediaminetetraacetate (EDTA) suppressed the Cu effect. The results suggested that the catalytic effect of Cu may be associated with the oxidative degradation of primary amines in the absorber unit, a process known to produce a wide spectrum of secondary amine products that are more readily nitrosatable than the pristine primary amines, and that can form stable N-nitrosamines. This study highlighted an intriguing linkage between amine degradation (operational cost) and N-nitrosamine formation (health hazards), all of which are challenges for commercial-scale CO2 capture technology.

  5. Effect of dissolved oxygen concentration on nitrate removal from groundwater using a denitrifying submerged filter.

    PubMed

    Gómez, M A; Hontoria, E; González-López, J

    2002-03-29

    A unidirectional submerged filter system was employed to purify groundwater contaminated with nitrate by biological denitrification. The influence of the concentration of dissolved oxygen (DO) in the process was tested using ethanol, methanol and sucrose as carbon sources. Inorganic-nitrogen removal, growth of the biofilm, platable denitrifying bacteria and nitrate reducing bacteria in biofilm were studied. With regard to the type of electron donor used, the presence of oxygen decreased the removal efficiency of inorganic nitrogen and caused an increase of nitrite concentration in the treated water. These negative effects depended on utilised carbon source. Biological denitrification with alcohols such as ethanol and methanol was less affected by DO than with sucrose. The development of the biofilm was also influenced by the DO concentration as excess O(2) caused reduced biofilm growth. These biofilms developed in oxygen presence had a smaller bacterial density and a lower denitrifying bacteria versus nitrate reducing bacteria ratio, which led to an unfavorable inorganic nitrogen removal and presence of nitrite in the treated water. All these effects are more pronounced when sucrose is used as carbon source.

  6. Toxicity of a dissolved pyrethroid mixture to Hyalella azteca at environmentally relevant concentrations.

    PubMed

    Brander, Susanne M; Werner, Inge; White, J Wilson; Deanovic, Linda A

    2009-07-01

    Use of pyrethroid pesticides, which are highly toxic to aquatic organisms, has increased substantially over the past decade. In 2006, the pyrethroid pesticides cyfluthrin and permethrin were measured in Sacramento-San Joaquin (SSJ) Delta (CA, USA) water at 5 and 24 ng/L (pptr), respectively. To elucidate any interactions between the two pyrethroids, a 10-d laboratory exposure was performed with 7- to 14-d-old amphipods (Hyalella azteca). Cyfluthrin and permethrin were tested singly and in combination at detected levels and also at half and twice the detected levels, both with and without the addition of 25 ppb of piperonyl butoxide (PBO). Mortality in all treatments was significantly higher than in controls, with the median lethal concentration (LC50) for permethrin with PBO (13.9 ng/L) and the LC50s with and without PBO for cyfluthrin (5.7 and 2.9 ng/L, respectively) at or below levels measured in SSJ Delta water samples. The LC50 for permethrin alone was estimated to be 48.9 ng/L. To evaluate combined toxicity, logistic regression models containing terms for concentrations of cyfluthrin, permethrin, and PBO, as well as models containing all possible combinations of these terms and interactions, were run and compared using Akaike's information criterion. The most parsimonious set of models indicated slight antagonism between cyfluthrin and permethrin. Results indicate that a dissolved mixture of cyfluthrin and permethrin is toxic at environmentally relevant concentrations in the water column.

  7. Diminished Stream Nitrate Concentrations Linked to Dissolved Organic Carbon Dynamics After Leaf Fall

    NASA Astrophysics Data System (ADS)

    Sebestyen, S. D.; Shanley, J. B.; Boyer, E. W.; Doctor, D. H.; Kendall, C.

    2004-05-01

    Thermodynamic coupling of the nitrogen and carbon cycles has broad implications for controls on catchment nutrient fluxes. In the northeast US, leaf fall occurs in early October and the availability of organic carbon increases as the leaves decompose. At the Sleepers River Research Watershed in northeastern Vermont (USA), we sampled stream chemistry from seven nested catchments to determine how stream dissolved organic carbon (DOC) and nitrate vary as a function of flow conditions, land-use, and basin size in response to leaf fall. Following leaf fall, nitrate concentration patterns were quantitatively different from other times of the year. Under baseflow conditions, stream and soil water DOC concentrations were higher than normal, whereas nitrate concentrations declined sharply at the five smallest catchments and more modestly at the two largest catchments. Under high flow conditions, flushing of nitrate was observed, as is typical for stormflow response at Sleepers River. Our field data suggest that in-stream processing of nitrate is likely thermodynamically and kinetically favorable under baseflow but not at higher flow conditions when expanding variable source areas make hydrological connections between nitrate source areas and streams. We are working to evaluate this hypothesis with isotopic and other monitoring data, and to model the coupled interactions of water, DOC, and nitrate fluxes in these nested catchments.

  8. Effect of dissolved oxygen concentration on the bioflocculation process in high loaded MBRs.

    PubMed

    Faust, L; Temmink, H; Zwijnenburg, A; Kemperman, A J B; Rijnaarts, H H M

    2014-12-01

    High-loaded membrane bioreactors (HL-MBRs), i.e. MBRs which are operated at extremely short sludge and hydraulic retention times, can be applied to flocculate and concentrate sewage organic matter. The concentrated organics can be used for energy recovery, or for the production of more valuable organic chemicals. Little is known about the effect of the dissolved oxygen concentration (DO) on this bioflocculation process. To examine this effect, two HL-MBRs were operated, respectively at a low (1 mg L(-1)) and a higher (4 mg L(-1)) DO. The higher DO resulted in a better flocculation efficiency, i.e. 92% of the colloidal COD in the sewage flocculated compared to 69% at the lower DO. The difference was attributed to a higher microbial production of extracellular polymeric substances at a DO of 4 mg L(-1) and to more multivalent cations (calcium, iron and aluminium) being distributed to the floc matrix. In addition, the HL-MBR that was operated at a DO of 4 mg L(-1) gave a bigger mean floc size, a lower supernatant turbidity, better settleability and better membrane filterability than the HL-MBR that was operated at a DO of 1 mg L(-1). Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Dissolved organic carbon modulates mercury concentrations in insect subsidies from streams to terrestrial consumers

    PubMed Central

    Chaves-Ulloa, Ramsa; Taylor, Brad W.; Broadley, Hannah J.; Cottingham, Kathryn L.; Baer, Nicholas A.; Weathers, Kathleen C.; Ewing, Holly A.; Chen, Celia Y.

    2016-01-01

    Mercury (Hg) concentrations in aquatic environments have increased globally, exposing consumers of aquatic organisms to high Hg levels. For both aquatic and terrestrial consumers, exposure to Hg depends on their food sources as well as environmental factors influencing Hg bioavailability. The majority of the research on the transfer of methylmercury (MeHg), a toxic and bioaccumulating form of Hg, between aquatic and terrestrial food webs has focused on terrestrial piscivores. However, a gap exists in our understanding of the factors regulating MeHg bioaccumulation by non-piscivorous terrestrial predators, specifically consumers of adult aquatic insects. Because dissolved organic carbon (DOC) binds tightly to MeHg, affecting its transport and availability in aquatic food webs, we hypothesized that DOC affects MeHg transfer from stream food webs to terrestrial predators feeding on emerging adult insects. We tested this hypothesis by collecting data over two years from 10 low-order streams spanning a broad DOC gradient in the Lake Sunapee watershed in New Hampshire. We found that streamwater MeHg concentration increased linearly with DOC concentration. However, streams with the highest DOC concentrations had emerging stream prey and spiders with lower MeHg concentrations than streams with intermediate DOC concentrations; a pattern that is similar to fish and larval aquatic insects. Furthermore, high MeHg concentrations found in spiders show that MeHg transfer in adult aquatic insects is an overlooked but potentially significant pathway of MeHg bioaccumulation in terrestrial food webs. Our results suggest that although MeHg in water increases with DOC, MeHg concentrations in stream and terrestrial consumers did not consistently increase with increases in streamwater MeHg concentrations. In fact, there was a change from a positive to a negative relationship between aqueous exposure and bioaccumulation at streamwater MeHg concentrations associated with DOC above around 5

  10. Risk assessment of dissolved trace metals in drinking water of Karachi, Pakistan.

    PubMed

    Karim, Zahida

    2011-06-01

    Health risk caused by the exposure to trace metals in water through different exposure pathways was investigated. Graphite furnace atomic absorption spectrometry was used for the determination of trace metals (nickel, copper, chromium, lead, cobalt, manganese and iron) in drinking water samples. The concentration of metals was compared with the world health organization (WHO) drinking water quality guideline values. Risk of metals on human health was evaluated using Hazard Quotient (HQ). Hazard quotients of all metals through oral ingestion and dermal absorption are found in the range of 1.11 × 10⁻² to 1.35 × 10⁻¹ and 8.52 × 10⁻⁵ to 9.75 × 10⁻², respectively. The results of the present study reflect the unlikely potential for adverse health effects to the inhabitants of Karachi due to the oral ingestion and dermal absorption of water containing these metals.

  11. The Influence of Subsurface Processes on the Concentration and Composition of Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Aiken, G.

    2004-12-01

    Microbial and geochemical interactions in the subsurface can result in chemical alteration and fractionation of organic matter thereby altering the nature and composition of dissolved organic matter (DOM) in groundwater and in surface waters dominated by ground water inflow. In this paper, the results of a study designed to determine the effectiveness of subsurface processes for removing DOM from two surface waters in Southern California will be presented. The recharge zones immediately underneath two infiltration basins, Anaheim Lake and Kraemer Basin, were found to be very active with respect to changes in the amounts and reactivities of the DOM. In all cases, dissolved organic carbon (DOC) concentrations decrease as water moves from the basins into the regional aquifer system. Data obtained from relatively shallow wells located near the infiltration basins (travel times less than 30 days) indicate that a large amount of DOM is removed during the first stages of transport in the subsurface. Parcels of water from both basins were followed for up to 360 days as the water moved away from the infiltration basins. DOC concentrations and specific ultraviolet absorbance (SUVA), an excellent indicator of aromatic carbon content of DOM, continued to decrease substantially with a general decrease in DOC concentration of about 70%. Regardless of initial DOC concentrations present in the infiltration basins, values decreased to approximately 1.3 mg C/L at the furthest points sampled. Analyses of organic matter isolates obtained by chromatographic methods indicated greater removal of aromatic molecules and preservation of branched chain aliphatic and alicyclic structures more resistant to biodegradation. Compared to samples from a wide range of environments, the DOM in the down gradient wells most closely resembled similar materials obtained from other groundwater systems and those of microbial origin. These results suggest that subsurface processes are significant in the

  12. Effects of Dissolved Oxygen Concentration on Oxygen Consumption and Development of Channel Catfish Eggs and Fry: Implications for Hatchery Management

    USDA-ARS?s Scientific Manuscript database

    Channel catfish spawns were incubated under controlled conditions to determine the effect of dissolved oxygen (DO) concentration on development and survival. Routine metabolic rate and limiting oxygen concentration were determined on eggs, sac fry and swim-up fry. Eight channel catfish spawns were s...

  13. Dissolved low-molecular weight thiol concentrations from the U.S. GEOTRACES North Atlantic Ocean zonal transect

    NASA Astrophysics Data System (ADS)

    Swarr, Gretchen J.; Kading, Tristan; Lamborg, Carl H.; Hammerschmidt, Chad R.; Bowman, Katlin L.

    2016-10-01

    Low-molecular weight thiols, including cysteine and glutathione, are biomolecules involved in a variety of metabolic pathways and act as important antioxidant and metal buffering agents. In this last capacity, they represent a potential mechanism for modulating the bioavailability and biogeochemistry of many trace elements in the ocean, particularly for chalcophilic elements (e.g., Cu, Zn, Cd, Ag and Hg). For this reason, and in the context of the international GEOTRACES program that seeks to understand the biogeochemistry of trace elements in the ocean, we measured the concentration of individual dissolved low-molecular weight thiols during the U.S. GEOTRACES North Atlantic Zonal Transect (USGNAZT). Only two thiols were identified, cysteine and glutathione, in contrast to results from the northeast subarctic Pacific Ocean, where the dipeptides glycine-cysteine and arginine-cysteine were also present and γ-glutamylcysteine was dominant. Concentrations of cysteine and glutathione in the North Atlantic Ocean were lower than in the Pacific and ranged from below detection ( 0.01 nM) to 0.61 nM of cysteine and up to 1.0 nM of glutathione, with cysteine generally more abundant than glutathione. Vertical profiles of cysteine and glutathione were broadly consistent with their biological production, being more abundant in surface water and usually below detection at depths greater than about 200 m. Subsurface concentration maxima, often co-incident with the deep chlorophyll maximum, were frequently observed but not universal. We conclude that cysteine and glutathione do not make up significant portions of complexation capacity for Cu and Zn in the upper open ocean but could be important for Cd, Hg, and potentially other chalcophiles. Extremely low concentrations of cysteine and glutathione in deep water suggest that higher molecular-weight thiols are a more important ligand class for chalcophiles in that portion of the ocean.

  14. Dissolved Low-Molecular Weight Thiol Concentrations from the U.S. GEOTRACES North Atlantic Ocean Zonal Transect

    NASA Astrophysics Data System (ADS)

    Lamborg, C. H.

    2016-02-01

    Low-molecular weight thiols, including cysteine and glutathione, are biomolecules involved in a variety of metabolic pathways and act as important antioxidant and metal buffering agents. In this last capacity, they represent a potential mechanism for modulating the bioavailability and biogeochemistry of many trace elements in the ocean, particularly for chalcophilic elements (e.g., Cu, Zn, Cd, Ag and Hg). For this reason, and in the context of the international GEOTRACES program that seeks to understand the biogeochemistry of trace elements in the ocean, we measured the concentration of individual dissolved low-molecular weight thiols during the U.S. GEOTRACES North Atlantic Zonal Transect (USGNAZT). Only two thiols were identified, cysteine and glutathione, in contrast to results from the northeast subarctic Pacific Ocean, where the dipeptides glycine-cysteine and arginine-cysteine were also present and ?-glutamylcysteine was dominant. Concentrations of cysteine and glutathione in the North Atlantic Ocean were lower than in the Pacific and ranged from below detection ( 0.01 nM) to 0.61 nM of cysteine and up to 1.0 nM of glutathione, with cysteine generally more abundant than glutathione. Vertical profiles of cysteine and glutathione were broadly consistent with their biological production, being more abundant in surface water and usually below detection at depths greater than about 200 m. Subsurface concentration maxima, often co-incident with the deep chlorophyll maximum, were frequently observed but not universal. We conclude that cysteine and glutathione do not make up significant portions of complexation capacity for Cu and Zn in the upper open ocean but could be important for Cd, Hg, and potentially other chalcophiles. Extremely low concentrations of cysteine and glutathione in deep water suggest that higher molecular-weight thiols are a more important ligand class for chalcophiles in that portion of the ocean.

  15. Heavy metal behavior and dissolved organic matter (DOM) characterization of vermicomposted pig manure amended with rice straw.

    PubMed

    Zhu, Weiqin; Yao, Wu; Zhang, Zhi; Wu, Yang

    2014-11-01

    Vermicomposting is an eco-friendly method for disposing of livestock and poultry manure. In addition, dissolved organic matter (DOM) can serve as a carrier that enhances the migration and transformation of heavy metals. Here, pig manure amended with rice straw was vermicomposted with Eisenia fetida. The DOM content, molecular weight distribution, and spectroscopic properties of the amended pig manure were measured before and after vermicomposting. The Cu and Zn concentrations in the earthworms increased from 8.24 and 17.63 to 40.75 and 362.78 mg/kg separately after vermicomposting, and the earthworms also increased the heavy metal availability in the vermicompost. Relative to the DOM properties of conventional compost, the DOM molecular weight decreased and varied widely following vermicomposting, and the C/N ratio of the DOM in the vermicompost treatments decreased from 10.37 to 8.60. The Fourier transform far-infrared (FTIR) and fluorescence spectra of the DOM indicated that the amounts of oxygen-containing structures increased while the ratio of humic acid to fulvic acid decreased following vermicomposting. Accordingly, the earthworms augmented the heavy metal mitigation risk in the pig manure. This augment potentially resulted from the decreased humic acid-to-fulvic acid (HA/FA) ratio from DOM structural changes.

  16. Selective Extraction of Metals from Pacific Sea Nodules with Dissolved Sulfur Dioxide

    NASA Astrophysics Data System (ADS)

    Khalafalla, Sanaa E.; Pahlman, John E.

    1981-08-01

    How to tritrate a rock? … The following article illustrates the possibility of titrating a metallic constituent in a mineral with a selective reagent to an endpoint of near complete metal extraction. A very rapid and efficient—almost instantaneous and quantitative—method has been devised to differentially leach manganese, nickel, and cobalt to the exclusion of copper and iron from deep-sea nodules.1 In this method, a given weight of raw sea nodules ground to -200 mesh in an aqueous slurry is contacted for 10 min at room temperature and ambient pressure with a specified quantity of SO2. An independent leaching parameter R has been defined as the ratio of the number of moles of SO2 in the leaching solution to the weight of sea nodules. Variation of metal extraction with R generates sigmoidal curves characteristic of the metals extracted. A threshold value of R is required to initiate the leaching of a given metal from the mixed oxides. Once this threshold is reached, the metal recovery can rise above 95% in less than 10 minutes. For increasing value of R the extractability of various metals from Pacific sea nodules by SO2 follows the order: Mn > Ni > Co ≫ Fe, Al, Cu. Disparity in the R values permits a variety of selective leaching systems and metal separations simply by changing the quantity of SO2 in the contacting solution. Success in this leaching system depends on comminuting the nodules to less than 100 mesh. Above this critical size, leaching is slowed due to the inaccessibility of the inner particle reacting groups to the SO2 leaching agent, resulting in lower and nonselective extractions of preferred metal values. Leaching with HCl solutions of the same pH level as dissolved SO2 yielded mixed, slow, and incomplete metal extractions. This finding rules out any interpretation based on hydrogen ion from the ionization of sulfurous acid as the leaching agent. The leaching curves observed in the new system resemble the complexometric titration curves of

  17. Salicylhydroxamic acid (SHAM) inhibition of the dissolved inorganic carbon concentrating process in unicellular green algae

    SciTech Connect

    Goyal, A.; Tolbert, N.E. )

    1990-03-01

    Rates of photosynthetic O{sub 2} evolution, for measuring K{sub 0.5}(CO{sub 2} + HCO{sub 3}{sup {minus}}) at pH 7, upon addition of 50 micromolar HCO{sub 3}{sup {minus}} to air-adapted Chlamydomonas, Dunaliella, or Scenedesmus cells, were inhibited up to 90% by the addition of 1.5 to 4.0 millimolar salicylhydroxamic acid (SHAM) to the aqueous medium. The apparent K{sub i}(SHAM) for Chlamydomonas cells was about 2.5 millimolar, but due to low solubility in water effective concentrations would be lower. Salicylhydroxamic acid did not inhibit oxygen evolution or accumulation of bicarbonate by Scenedesmus cells between pH 8 to 11 or by isolated intact chloroplasts from Dunaliella. Thus, salicylhydroxamic acid appears to inhibit CO{sub 2} uptake, whereas previous results indicate that vanadate inhibits bicarbonate uptake. These conclusions were confirmed by three test procedures with three air-adapted algae at pH 7. Salicylhydroxamic acid inhibited the cellular accumulation of dissolved inorganic carbon, the rate of photosynthetic O{sub 2} evolution dependent on low levels of dissolved inorganic carbon (50 micromolar NaHCO{sub 3}), and the rate of {sup 14}CO{sub 2} fixation with 100 micromolar ({sup 14}C)HCO{sub 3}{sup {minus}}. Salicylhydroxamic acid inhibition of O{sub 2} evolution and {sup 14}CO{sub 2}-fixation was reversed by higher levels of NaHCO{sub 3}. Thus, salicylhydroxamic acid inhibition was apparently not affecting steps of photosynthesis other than CO{sub 2} accumulation. Although salicylhydroxamic acid is an inhibitor of alternative respiration in algae, it is not known whether the two processes are related.

  18. Risk ranking of bioaccessible metals from fly ash dissolved in simulated lung and gut fluids.

    PubMed

    Twining, John; McGlinn, Peter; Loi, Elaine; Smith, Kath; Gieré, Reto

    2005-10-01

    Power plant fly ash from two fuels, coal and a mixture of coal and shredded tires, were evaluated for trace metal solubility in simulated human lung and gut fluids (SLF and SGF, respectively) to estimate bioaccessibility. The proportion of bioaccessible to total metal ranged from zero (V) to 80% (Zn) for coal-derived ash in SLF and from 2 (Th) to 100% (Cu) for tire-derived fly ash in SGF. The tire-derived ash contained much more Zn. However, Zn ranked only 5th of the various toxic metals in SGF compared with international regulations for ingestion. On the basis of total concentrations, the metals closestto exceeding limits based on international regulations for inhalation were Cr, Pb, and Al. On dissolution in SLF, the most limiting metals were Pb, Cu, and Zn. For metals exposed to SGF there was no relative change in the top metal, Al, before and after dissolution but the second-ranked metal shifted from Pb to Ni. In most cases only a proportion of the total metal concentrations in either fly ash was soluble, and hence bioaccessible, in either biofluid. When considering the regulatory limits for inhalation of particulates, none of the metal concentrations measured were as hazardous as the fly ash particulates themselves. However, on the basis of the international ingestion regulations for Al, the maximum mass of fly ash that could be ingested is only 1 mg per day (10 mg based on bioaccessibility). It is possible that such a small mass could be consumed by exposed individuals or groups.

  19. Geochemistry of dissolved trace elements and heavy metals in the Dan River Drainage (China): distribution, sources, and water quality assessment.

    PubMed

    Meng, Qingpeng; Zhang, Jing; Zhang, Zhaoyu; Wu, Tairan

    2016-04-01

    Dissolved trace elements and heavy metals in the Dan River drainage basin, which is the drinking water source area of South-to-North Water Transfer Project (China), affect large numbers of people and should therefore be carefully monitored. To investigate the distribution, sources, and quality of river water, this study integrating catchment geology and multivariate statistical techniques was carried out in the Dan River drainage from 99 river water samples collected in 2013. The distribution of trace metal concentrations in the Dan River drainage was similar to that in the Danjiangkou Reservoir, indicating that the reservoir was significantly affected by the Dan River drainage. Moreover, our results suggested that As, Sb, Cd, Mn, and Ni were the major pollutants. We revealed extremely high concentrations of As and Sb in the Laoguan River, Cd in the Qingyou River, Mn, Ni, and Cd in the Yinhua River, As and Sb in the Laojun River, and Sb in the Dan River. According to the water quality index, water in the Dan River drainage was suitable for drinking; however, an exposure risk assessment model suggests that As and Sb in the Laojun and Laoguan rivers could pose a high risk to humans in terms of adverse health and potential non-carcinogenic effects.

  20. Effects of fluoride and dissolved oxygen concentrations on the corrosion behavior of pure titanium and titanium alloys.

    PubMed

    Nakagawa, Masaharu; Matsuya, Shigeki; Udoh, Koichi

    2002-06-01

    The effects of dissolved-oxygen concentration and fluoride concentration on the corrosion behaviors of commercial pure titanium, Ti-6Al-4V and Ti-6Al-7Nb alloys and experimentally produced Ti-0.2Pd and Ti-0.5Pt alloys were examined using the corrosion potential measurements. The amount of dissolved Ti was analyzed by inductively coupled plasma mass spectroscopy. A decrease in the dissolved-oxygen concentration tended to reduce the corrosion resistance of Ti and Ti alloys. If there was no fluoride, however, corrosion did not occur. Under low dissolved-oxygen conditions, the corrosion of pure Ti and Ti-6Al-4V and Ti-6Al-7Nb alloys might easily take place in the presence of small amounts of fluoride. They were corroded by half or less of the fluoride concentrations in commercial dentifrices. The Ti-0.2Pd and Ti-0.5Pt alloys did not corrode more, even under the low dissolved-oxygen conditions and a fluoride-containing environment, than pure Ti and Ti-6Al-4V and Ti-6Al-7Nb alloys. These alloys are expected to be useful as new Ti alloys with high corrosion resistance in dental use.

  1. Dissolved methane concentration profiles and air-sea fluxes from 41°S to 27°N

    NASA Astrophysics Data System (ADS)

    Kelley, Cheryl A.; Jeffrey, Wade H.

    2002-07-01

    Water column samples from a transect cruise from southern Chile through the Panama Canal to the Gulf of Mexico were used to determine dissolved methane depth profiles and air-sea methane fluxes. In the Gulf of Mexico, surface concentrations were approximately 40% supersaturated with respect to the atmosphere, whereas near the equator and in the Peru upwelling region, 10-20% supersaturation generally occurred. These saturation ratios translate into an average flux of methane from the sea surface to the atmosphere of 0.38 μmol m-2 d-1. In addition, water column profiles of dissolved methane indicate that subsurface maxima in dissolved methane concentrations are a consistent feature of the open ocean, except near the equator. At the equator, the subsurface peak at the base of the mixed layer may be bowed down by the Equatorial Undercurrent. The highest methane concentration (12 nM) was observed in the Peru upwelling region.

  2. Response of dissolved carbon and nitrogen concentrations to moderate nutrient additions in a tropical montane forest of south Ecuador

    NASA Astrophysics Data System (ADS)

    Velescu, Andre; Valarezo, Carlos; Wilcke, Wolfgang

    2016-05-01

    In the past two decades, the tropical montane rain forests in south Ecuador experienced increasing deposition of reactive nitrogen mainly originating from Amazonian forest fires, while Saharan dust inputs episodically increased deposition of base metals. Increasing air temperature and unevenly distributed rainfall have allowed for longer dry spells in a perhumid ecosystem. This might have favored mineralization of dissolved organic matter (DOM) by microorganisms and increased nutrient release from the organic layer. Environmental change is expected to impact the functioning of this ecosystem belonging to the biodiversity hotspots of the Earth. In 2007, we established a nutrient manipulation experiment (NUMEX) to understand the response of the ecosystem to moderately increased nutrient inputs. Since 2008, we have continuously applied 50 kg ha-1 a-1 of nitrogen (N), 10 kg ha-1 a-1 of phosphorus (P), 50 kg + 10 kg ha-1 a-1 of N and P and 10 kg ha-1 a-1 of calcium (Ca) in a randomized block design at 2000 m a.s.l. in a natural forest on the Amazonia-exposed slopes of the south Ecuadorian Andes. Nitrogen concentrations in throughfall increased following N+P additions, while separate N amendments only increased nitrate concentrations. Total organic carbon (TOC) and dissolved organic nitrogen (DON) concentrations showed high seasonal variations in litter leachate and decreased significantly in the P and N+P treatments, but not in the N treatment. Thus, P availability plays a key role in the mineralization of DOM. TOC/DON ratios were narrower in throughfall than in litter leachate but their temporal course did not respond to nutrient amendments. Our results revealed an initially fast, positive response of the C and N cycling to nutrient additions which declined with time. TOC and DON cycling only change if N and P supply are improved concurrently, while NO3-N leaching increases only if N is separately added. This indicates co-limitation of the microorganisms by N and P

  3. Impact of wetland decline on decreasing dissolved organic carbon concentrations along the Mississippi River continuum

    DOE PAGES

    Duan, Shuiwang; He, Yuxiang; Kaushal, Sujay S.; ...

    2017-01-09

    Prior to discharging to the ocean, large rivers constantly receive inputs of dissolved organic carbon (DOC) from tributaries or fringing floodplains and lose DOC via continuous in situ processing along distances that span thousands of kilometers. Current concepts predicting longitudinal changes in DOC mainly focus on in situ processing or exchange with fringing floodplain wetlands, while effects of heterogeneous watershed characteristics are generally ignored. We analyzed results from a 17-year time-series of DOC measurements made at seven sites and three expeditions along the entire Mississippi River main channel with DOC measurements made every 17 km. The results show a clearmore » downstream decrease in DOC concentrations that was consistent throughout the entire study period. Downstream DOC decreases were primarily (~63–71%) a result of constant dilutions by low-DOC tributary water controlled by watershed wetland distribution, while in situ processing played a secondary role. We estimate that from 1780 to 1980 wetland loss due to land-use alterations caused a ca. 58% decrease in in DOC concentrations in the tributaries of the Mississippi River. DOC reductions caused by watershed wetland loss likely impacted the capacity for the river to effectively remove nitrogen via denitrification, which can further exacerbate coastal hypoxia. Lastly, these findings highlight the importance of watershed wetlands in regulating DOC longitudinally along the headland to ocean continuum of major rivers.« less

  4. Novel method for online monitoring of dissolved N2O concentrations through a gas stripping device.

    PubMed

    Mampaey, Kris E; van Dongen, Udo G J M; van Loosdrecht, Mark C M; Volcke, Eveline I P

    2015-01-01

    Nitrous oxide emissions from wastewater treatment plants are currently measured by online gas phase analysis or grab sampling from the liquid phase. In this study, a novel method is presented to monitor the liquid phase N2O concentration for aerated as well as non-aerated conditions/reactors, following variations both in time and in space. The monitoring method consists of a gas stripping device, of which the measurement principle is based on a continuous flow of reactor liquid through a stripping flask and subsequent analysis of the N2O concentration in the stripped gas phase. The method was theoretically and experimentally evaluated for its fit for use in the wastewater treatment context. Besides, the influence of design and operating variables on the performance of the gas stripping device was addressed. This method can easily be integrated with online off-gas measurements and allows to better investigate the origin of the gas emissions from the treatment plant. Liquid phase measurements of N2O are of use in mitigation of these emissions. The method can also be applied to measure other dissolved gasses, such as methane, being another important greenhouse gas.

  5. Concentration dynamics and biodegradability of dissolved organic matter in wetland soils subjected to experimental warming.

    PubMed

    Wang, Hang; Holden, Joseph; Zhang, Zhijian; Li, Meng; Li, Xia

    2014-02-01

    Dissolved organic matter (DOM) is the most bioavailable soil organic pool. Understanding how DOM responds to elevated temperature is important for forecasting soil carbon (C) dynamics under climate warming. Here a 4.5-year field microcosm experiment was carried out to examine temporal DOM concentration dynamics in soil pore-water from six different subtropical wetlands. Results are compared between control (ambient temperature) and warmed (+5°C) treatments. UV-visible and fluorescence spectroscopy was performed to reveal DOM structural complexity at the end of the warming incubation. Elevated temperature resulted in initially (1 to 2.5 years) high pore-water DOM concentrations in warmed samples. These effects gradually diminished over longer time periods. Of the spectral indices, specific UV absorbance at 280 nm and humification index were significantly higher, while the signal intensity ratio of the fulvic-like to humic-like fluorescence peak was lower in warmed samples, compared to the control. Fluorescence regional integration analysis further suggested that warming enhanced the contribution of humic-like substances to DOM composition for all tested wetlands. These spectral fingerprints implied a declined fraction of readily available substrates in DOM allocated to microbial utilization in response to 4.5 years of warming. As a negative feedback, decreased DOM biodegradability may have the potential to counteract initial DOM increases and alleviate C loss in water-saturated wetland soils.

  6. Dissolved oxygen concentration in the medium during cell culture: Defects and improvements.

    PubMed

    Zhang, Kuan; Zhao, Tong; Huang, Xin; He, Yunlin; Zhou, Yanzhao; Wu, Liying; Wu, Kuiwu; Fan, Ming; Zhu, Lingling

    2016-03-01

    In vitro cell culture has provided a useful model to study the effects of oxygen on cellular behavior. However, it remains unknown whether the in vitro operations themselves affect the medium oxygen levels and the living states of cells. In addition, a prevailing controversy is whether reactive oxygen species (ROS) production is induced by continuous hypoxia or reoxygenation. In this study, we have measured the effects of different types of cell culture containers and the oxygen environment where medium replacement takes place on the actual oxygen tension in the medium. We found that the deviations of oxygen concentrations in the medium are much greater in 25-cm(2) flasks than in 24-well plates and 35-mm dishes. The dissolved oxygen concentrations in the medium were increased after medium replacement in normoxia, but remained unchanged in glove boxes in which the oxygen tension remained at a low level (11.4, 5.7, and 0.5% O2 ). We also found that medium replacement in normoxia increased the number of ROS-positive cells and reduced the cell viability; meanwhile, medium replacement in a glove box did not produce the above effects. Therefore, we conclude that the use of 25-cm(2) flasks should be avoided and demonstrate that continuous hypoxia does not produce ROS, whereas the reoxygenation that occurs during the harvesting of cells leads to ROS and induces cell death. © 2015 International Federation for Cell Biology.

  7. In vivo noninvasive monitoring of dissolved oxygen concentration within an implanted tissue-engineered pancreatic construct.

    PubMed

    Goh, Fernie; Sambanis, Athanassios

    2011-09-01

    The function of an implanted tissue-engineered pancreatic construct is influenced by many in vivo factors; however, assessing its function is based primarily on end physiologic effects. As oxygen significantly affects cell function, we established a dual perfluorocarbon method that utilizes (19)F nuclear magnetic resonance spectroscopy, with perfluorocarbons as oxygen concentration markers, to noninvasively monitor dissolved oxygen concentration (DO) in βTC-tet cell-containing alginate beads and at the implantation milieu. Beads were implanted in the peritoneal cavity of normal and streptozotocin-induced diabetic mice. Using this method, the feasibility of acquiring real-time in vivo DO measurements was demonstrated. Results showed that the mouse peritoneal environment is hypoxic and the DO is further reduced when βTC-tet cell constructs were implanted. The DO within cell-containing beads decreased considerably over time and could be correlated with the relative changes in the number of viable encapsulated cells. The reduction of construct DO due to the metabolic activity of the βTC-tet cells was also compatible with the implant therapeutic function, as observed in the reversal of hyperglycemia in diabetic mice. The importance of these findings in assessing implant functionality and host animal physiology is discussed. © Mary Ann Liebert, Inc.

  8. Small-scale heterogeneity of dissolved gas concentrations in marine continental shelf waters

    NASA Astrophysics Data System (ADS)

    Tortell, Philippe D.

    2005-11-01

    Marine continental shelf waters are known to contribute significantly to the global air-sea fluxes of many gases. Biogeochemical cycles in these regions are highly dynamic, and it is thus often difficult to fully resolve the spatial and temporal distribution of gases in the upper water column. High-frequency, real-time gas measurements with a membrane inlet mass spectrometer (MIMS) reveal significant small-scale heterogeneity in the distribution of CO2, O2/Ar ratios, and dimethylsulfide (DMS) in continental shelf waters of the Eastern Subarctic Pacific Ocean and Bering Sea. Decorrelation length scales for the gas distributions ranged from 15 to 25 km, with significant variability observed on subkilometer spatial scales. In the case of DMS, a number of rapid excursions were observed over distances that would be difficult to resolve with conventional methods. Across most of the sampling transects, CO2 and O2/Ar ratios were correlated, suggesting that biological processes dominated the cycling of these gases. In contrast, DMS concentrations were generally uncoupled from CO2 and O2/Ar, although concentrations often did change sharply across hydrographic and productivity fronts. The results presented here suggest that previous field studies may have underestimated the true spatial variability of dissolved gases (DMS in particular) in surface waters of highly dynamic marine systems. High-frequency gas measurements have significant promise for unraveling complex biogeochemical cycles in these regions.

  9. Influence of groundwater recharge and well characteristics on dissolved arsenic concentrations in southeastern Michigan groundwater

    USGS Publications Warehouse

    Meliker, J.R.; Slotnick, M.J.; Avruskin, G.A.; Haack, S.K.; Nriagu, J.O.

    2009-01-01

    Arsenic concentrations exceeding 10 ??g/l, the United States maximum contaminant level and the World Health Organization guideline value, are frequently reported in groundwater from bedrock and unconsolidated aquifers of southeastern Michigan. Although arsenic-bearing minerals (including arsenian pyrite and oxide/hydroxide phases) have been identified in Marshall Sandstone bedrock of the Mississippian aquifer system and in tills of the unconsolidated aquifer system, mechanisms responsible for arsenic mobilization and subsequent transport in groundwater are equivocal. Recent evidence has begun to suggest that groundwater recharge and characteristics of well construction may affect arsenic mobilization and transport. Therefore, we investigated the relationship between dissolved arsenic concentrations, reported groundwater recharge rates, well construction characteristics, and geology in unconsolidated and bedrock aquifers. Results of multiple linear regression analyses indicate that arsenic contamination is more prevalent in bedrock wells that are cased in proximity to the bedrock-unconsolidated interface; no other factors were associated with arsenic contamination in water drawn from bedrock or unconsolidated aquifers. Conditions appropriate for arsenic mobilization may be found along the bedrock-unconsolidated interface, including changes in reduction/oxidation potential and enhanced biogeochemical activity because of differences between geologic strata. These results are valuable for understanding arsenic mobilization and guiding well construction practices in southeastern Michigan, and may also provide insights for other regions faced with groundwater arsenic contamination. ?? Springer-Verlag 2008.

  10. Light climate and dissolved organic carbon concentration influence species-specific changes in fish zooplanktivory

    USGS Publications Warehouse

    Weidel, Brian C.; Baglini, Katherine; Jones, Stuart E.; Kelly, Patrick T.; Solomon, Christopher T.; Zwart, Jacob A.

    2017-01-01

    Dissolved organic carbon (DOC) in lakes reduces light penetration and limits fish production in low nutrient lakes, reportedly via reduced primary and secondary production. Alternatively, DOC and light reductions could influence fish by altering their visual feeding. Previous studies report mixed effects of DOC on feeding rates of zooplanktivorous fish, but most investigators tested effects of a single concentration of DOC against clear-water, turbid, or algal treatments. We used a controlled laboratory study to quantify the effects of a DOC gradient (3–19 mg L−1) on average light climate and the zooplankton feeding rate of 3 common, north temperate fishes. Light availability, which was inversely related to DOC concentration, had a positive and linear effect on zooplankton consumption by juvenile largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus), explaining 22% and 28% of the variation in consumption, respectively. By contrast, zooplankton feeding rates by fathead minnow (Pimephales promelas) were best predicted by a nonlinear, negative influence of light (R2 = 0.13). In bluegill feeding trials we found a general trend for positive selection of larger zooplankton (Cladocera and Chaoboridae); however, the light climate did not influence the selection of prey type. Largemouth bass selected for larger-bodied zooplankton, with weak evidence that selectivity for large Cladocera changed from negative to neutral selection based on electivity values across the light gradient. Our results suggest that the effect of DOC on the light climate of lakes may directly influence fish zooplanktivory and that this influence may vary among fish species.

  11. Influence of groundwater recharge and well characteristics on dissolved arsenic concentrations in southeastern Michigan groundwater.

    PubMed

    Meliker, Jaymie R; Slotnick, Melissa J; Avruskin, Gillian A; Haack, Sheridan K; Nriagu, Jerome O

    2009-02-01

    Arsenic concentrations exceeding 10 microg/l, the United States maximum contaminant level and the World Health Organization guideline value, are frequently reported in groundwater from bedrock and unconsolidated aquifers of southeastern Michigan. Although arsenic-bearing minerals (including arsenian pyrite and oxide/hydroxide phases) have been identified in Marshall Sandstone bedrock of the Mississippian aquifer system and in tills of the unconsolidated aquifer system, mechanisms responsible for arsenic mobilization and subsequent transport in groundwater are equivocal. Recent evidence has begun to suggest that groundwater recharge and characteristics of well construction may affect arsenic mobilization and transport. Therefore, we investigated the relationship between dissolved arsenic concentrations, reported groundwater recharge rates, well construction characteristics, and geology in unconsolidated and bedrock aquifers. Results of multiple linear regression analyses indicate that arsenic contamination is more prevalent in bedrock wells that are cased in proximity to the bedrock-unconsolidated interface; no other factors were associated with arsenic contamination in water drawn from bedrock or unconsolidated aquifers. Conditions appropriate for arsenic mobilization may be found along the bedrock-unconsolidated interface, including changes in reduction/oxidation potential and enhanced biogeochemical activity because of differences between geologic strata. These results are valuable for understanding arsenic mobilization and guiding well construction practices in southeastern Michigan, and may also provide insights for other regions faced with groundwater arsenic contamination.

  12. Correlating total dissolved solid concentration changes with GRACE-based changes in water table depth

    NASA Astrophysics Data System (ADS)

    Gibbons, A.; Famiglietti, J. S.; Reager, J. T.

    2012-12-01

    NASA's Gravity Recovery and Climate Experiment (GRACE) mission has been used to monitor monthly groundwater storage variations in some of the world's largest basins. However, only large-scale changes in groundwater storage (> 150,000 km2) can be inferred because of the coarse resolution of the monthly GRACE solution. Such studies have also failed to address groundwater quality, which is nearly matched by the importance of its quantity. This study correlated in-situ total dissolved solid (TDS) concentrations to GRACE-derived changes in groundwater table depth for the High Plains groundwater basin of the central United States. The change in groundwater storage was calculated from the change in total water storage by subtracting the other hydrologic components (surface water, snow water equivalent, and soil moisture) using observed and modeled records. The GRACE-derived change in monthly groundwater storage was converted to water table depth changes using specific yield data for the High Plains aquifer. The GRACE groundwater storage variation was down-scaled by spatially interpolating in situ water-level data using kriging. Observed TDS concentrations were also spatially interpolated with kriging. A correlation coefficient was calculated to evaluate the validity of the relationship between changes in quantity and changes in quality. This work has implications for improving groundwater management practices by estimating groundwater quality on a global scale using remote sensing.

  13. Concentration, sources and flux of dissolved organic carbon of precipitation at Lhasa city, the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Li, C.

    2015-12-01

    Dissolved organic carbon (DOC) plays important role in climate system, but few data are available on the Tibetan Plateau (TP). In this study 89 precipitation samples were collected at Lhasa, the largest city of southern Tibet, from March to December 2013. The average concentration and wet deposition fluxes of DOC was 1.10 mg C/L and 0.62 g C m-2.yr-1, respectively. Seasonally, low DOC concentration and high flux appeared during monsoon period, which were in line with heavy precipitation amount, reflecting dilution effect of precipitation for the DOC. Compared to other regions, the values of Lhasa were lower than those of large cites (e.g. Beijing and Seoul) mainly because of less air pollution of Lhasa. The relationship between DOC and ion analysis showed that DOC of Lhasa was derived mainly from the natural sources, followed by burning activities. Furthermore, △14C value of DOC indicated that fossil combustion contributed around 20% of the precipitation DOC of Lhasa, indicating that the atmosphere of Lhasa has been influenced by vehicle emissions. Therefore, although atmosphere of Lhasa is relatively clean, pollutants emitted from local sources cannot be ignored.

  14. Structurally colored biopolymer thin films for detection of dissolved metal ions in aqueous solution

    NASA Astrophysics Data System (ADS)

    Cathell, Matthew David

    Natural polymers, such as the polysaccharides alginate and chitosan, are noted sorbents of heavy metals. Their polymer backbone structures are rich in ligands that can interact with metal ions through chelation, electrostatics, ion exchange and nonspecific mechanisms. These water-soluble biopolymer materials can be processed into hydrogel thin films, creating high surface area interfaces ideal for binding and sequestering metal ions from solution. By virtue of their uniform nanoscale dimensions (with thicknesses smaller than wavelengths of visible light) polymer thin films exhibit structure-based coloration. This phenomenon, frequently observed in nature, causes the transparent and essentially colorless films to reflect light in a wide array of colors. The lamellar film structures act as one-dimensional photonic crystals, allowing selective reflection of certain wavelengths of light while minimizing other wavelengths by out-of-phase interference. The combination of metal-binding and reflective properties make alginate and chitosan thin films attractive candidates for analyte sensing. Interactions with metal ions can induce changes in film thicknesses and refractive indices, thus altering the path of light reflected through the film. Small changes in dimensional or optical properties can lead to shifts in film color that are perceivable by the unaided eye. These thin films offer the potential for optical sensing of toxic dissolved materials without the need for instrumentation, external power or scientific expertise. With the use of a spectroscopic ellipsometer and a fiber optic reflectance spectrometer, the physical and optical characteristics of biopolymer thin films have been characterized in response to 50 ppm metal ion solutions. It has been determined that metal interactions can lead to measurable changes in both film thicknesses and effective refractive indices. The intrinsic response behaviors of alginate and chitosan, as well as the responses of modified

  15. The evaluation of water quality and metal concentrations of Titiwangsa Lake, Selangor, Peninsular Malaysia.

    PubMed

    Said, Khaled S A; Shuhaimi-Othman, M; Ahmad, A K

    2012-05-15

    A study of water quality parameters (temperature, conductivity, total dissolved solid, dissolved oxygen, pH and water hardness) in Titiwangsa Lake was conducted in January, April, July and October 2010. The water quality parameters were tested and recorded at different sampling stations chosen randomly using hydrolab data sonde 4 and surveyor 4 a water quality multi probe (USA). Six metals i.e., cadmium, chromium, lead, nickel, zinc and copper were determined in five different compartments of the lake namely water, total suspended solids, plankton, sediment and fish. The metals concentration were determined by Inductively Coupled Plasma Mass Spectrometer (ICP-MS), perkin elmer elan, model 9000. The water quality parameters were compared with National Water Quality Standard (NWQS Malaysia) while metal concentrations were compared with Malaysian and international standards. The study shows that water quality parameters are of class 2. This condition is suitable for recreational activities where body contact is allowed and suitable for sensitive fishing activities. Furthermore, metal concentrations were found to be lower than the international standards, therefore toxic effects for these metals would be rarely observed and the adverse effects to aquatic organisms would not frequently occur.

  16. The determination of water quality and metal concentrations of Ampang Hilir Lake, Selangor, Peninsular Malaysia.

    PubMed

    Said, Khaled S A; Shuhaimi-Othman, M; Ahmad, A K

    2012-05-01

    A study of water quality parameters (temperature, conductivity, total dissolved solid, dissolved oxygen, pH and water hardness) in Ampang Hilir Lake was conducted in January, April, July and October 2010. The water quality parameters were tested and recorded at different sampling stations chosen randomly using Hydrolab Data Sonde 4 and Surveyor 4 a water quality multi probe (USA). Six metals which were cadmium, chromium, lead, nickel, zinc and copper were determined in five different compartments of the lake namely water, total suspended solids, plankton, sediment and fish. The metals concentration were determined by Inductively Coupled Plasma Mass Spectrometer (ICP-MS), Perkin Elmer Elan, model 9000.The water quality parameters were compared with National Water Quality Standard (NWQS Malaysia) while metal concentrations were compared with Malaysian and international standards. The study shows that water quality parameters are of class 2. This condition is suitable for recreational activities where body contact is allowed and suitable for sensitive fishing activities. Furthermore, metal concentrations were found to be lower than the international standards, therefore toxic effects for these metals would be rarely observed and the adverse effects to aquatic organisms would not frequently occur.

  17. The wide spectrum high biocidal potency of Bioxy formulation when dissolved in water at different concentrations

    PubMed Central

    Dagher, Fadi

    2017-01-01

    Traditional surface disinfectants that have long been applied in medicine, animal husbandry, manufacturing and institutions are inconvenient at best and dangerous at worst. Moreover, some of these substances have adverse environmental impacts: for example, quaternary ammonium compounds (“quats”) are reproductive toxicants in both fish and mammals. Halogens are corrosive both to metals and living tissues, are highly reactive, can be readily neutralized by metals, and react with organic matter to form toxic, persistent by-products such as dioxins and furans. Aldehydes may be carcinogenic to both human and animals upon repeated exposures, are corrosive, cross-link living tissues and many synthetic materials, and may lose efficacy when pathogens enzymatically adapt to them. Alcohols are flammable and volatile and can be enzymatically degraded by certain bacterial pathogens. Quats are highly irritating to mucous membranes and over time can induce pathogen resistance, especially if they are not alternated with functionally different disinfectants. In contrast, peracetic acid (PAA), a potent oxidizer, liberates hydrogen peroxide (itself a disinfectant), biodegrades to carbon dioxide, water and oxygen, and is at least as efficacious as contact biocides e.g., halogens and aldehydes. Nevertheless, the standard form of liquid PAA is highly corrosive, is neutralized by metals and organic matter, gives off noxious odours and must be stored in vented containers. For the reasons stated above, Bioxy formulations were developed, a series of powder forms of PAA, which are odourless, stable in storage and safe to transport and handle. They generate up to 10% PAA in situ when dissolved in water. A 0.2% aqueous solution of Bioxy (equivalent to 200 ppm PAA) effected a 6.76 log reduction in Methicillin-resistant Staphylococcus aureus (MRSA) within 2 minutes after application. A 5% aqueous solution of Bioxy achieved a 3.93 log reduction in the bovine tuberculosis bacillus

  18. Adsorption of Dissolved Metals in the Berkeley Pit using Thiol-Functionalized Self-Assembled Monolayers on Mesoporous Supports (Thiol-SAMMS)

    SciTech Connect

    Betancourt, Amaury P.; Mattigod, Shas V.; Wellman, Dawn M.

    2010-03-07

    The Berkeley Pit in Butte, Montana, is heavily contaminated with dissolved metals. Adsorption and extraction of these metals can be accomplished through the use of a selective adsorbent. For this research, the adsorbent used was thiol-functionalized Self-Assembled Monolayers on Mesoporous Supports (thiol-SAMMS), which was developed at Pacific Northwest National Laboratory (PNNL). Thiol-SAMMS selectively binds to numerous types of dissolved metals. The objective of this research was to evaluate the loading and kinetics of aluminum, beryllium, copper, and zinc on thiol-SAMMS. For the loading tests, a series of Berkeley Pit water to thiol-SAMMS ratios (mL:g) were tested. These ratios were 1000:1, 500:1, 100:1, and 50:1. Berkeley Pit water is acidic (pH {approx} 2.5). This can affect the performance of SAMMS materials. Therefore, the effect of pH was evaluated by conducting parallel series of loading tests wherein the Berkeley Pit water was neutralized before or after addition of thiol-SAMMS, and a series of kinetics tests wherein the Berkeley Pit water was neutralized before addition of thiol-SAMMS for the first test and was not neutralized for the second test. For the kinetics tests, one Berkeley Pit water to thiol-SAMMS ratio was tested, which was 2000:1. The results of the loading and kinetics tests suggest that a significant decrease in dissolved metal concentration at Berkeley Pit could be realized through neutralization of Berkeley Pit water. Thiol-SAMMS technology has a limited application under the highly acidic conditions posed by the Berkeley Pit. However, thiol-SAMMS could provide a secondary remedial technique which would complete the remedial system and remove dissolved metals from the Berkeley Pit to below drinking water standards.

  19. Dissolved heavy metal determination and ecotoxicological assessment: a case study of the corumbataí river (são paulo, Brazil).

    PubMed

    Aparecida Maranho, Lucineide; Teresinha Maranho, Leila; Grossi Botelho, Rafael; Luiz Tornisielo, Valdemar

    2014-09-29

    The aim of this one-year study (August 2009 to July 2010) was to evaluate the Corumbataí River water polluted by anthropogenic sources and see how it affects the reproduction of the microcrustacean Ceriodaphnia dubia (Richard, 1984) in laboratory conditions over seven days of exposure to water samples collected monthly at six different locations. We determined the concentrations of zinc (Zn), copper (Cu), nickel (Ni), lead (Pb), and cadmium (Cd), as well as physicochemical parameters such as dissolved oxygen, conductivity, water temperature, and pH. Dissolved oxygen and conductivity demonstrated anthropogenic influence, as dissolved oxygen concentration decreased and conductivity increased from the upstream to the downstream stretch of the river. The effects on C. dubia were observed in the months with high precipitation, but the toxicity cannot be associated with any particular contaminant. Heavy metal levels kept well below the limit values. Zn and Pb had the highest concentrations in the water during the sampling period, probably due to the industrial and agricultural influence. However, these levels do not seem to be associated with precipitation, which suggests that their primary source was industry. Physicochemical parameters, the ecotoxicological assay, and determination of heavy metals proved to be efficient tools to evaluate aquatic environments.

  20. The dissolved uranium concentration and (234)U/(238)U activity ratio in groundwaters from spas of southeastern Brazil.

    PubMed

    Bonotto, Daniel Marcos

    2017-01-01

    This paper describes the natural radioactivity due to (238)U and (234)U in 75 water sources from spas located in 14 municipalities in São Paulo and Minas Gerais states, Brazil. These waters are extensively utilized for drinking in public places, bottling and bathing purposes, among other uses. The water samples were taken from springs and pumped tubular wells drilled into different aquifer systems in the Paraná and Southeastern Shield hydrogeological provinces. The measurements of alpha-emitting radionuclides were also accompanied by the monitoring of temperature, pH, Eh, electrical conductivity, dissolved gases (O2, CO2, H2S, radon, thoron) and major constituents. The dissolved U concentration data were lognormally distributed. The median and mean values corresponded to 0.02 and 0.09 μg/L, respectively. Significant relationships were found among the (234)U/(238)U activity ratio (AR) of dissolved uranium, the total dissolved solids (TDS) and dissolved bicarbonate contents, and also between the AR and dissolution rate in the monitored sites. The logU versus AR diagram used for the hydrogeochemical prospecting of concealed U deposits indicated that the water sources were mainly from reduced environments. The possibility of using the reciprocal of the dissolved U concentration and AR data to determine mixing volumes of different groundwater masses was demonstrated. The highest dissolved U concentration (4.82 μg/L) was well below the maximum allowed by WHO. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Spatial distribution and sources of dissolved trace metals in surface water of the Wei River, China.

    PubMed

    Jing, Li; Fadong, Li; Qiang, Liu; Shuai, Song; Guangshuai, Zhao

    2013-01-01

    For this study, 34 water samples were collected along the Wei River and its tributaries. Multivariate statistical analyses were employed to interpret the environmental data and to identify the natural and anthropogenic trace metal inputs to the surface waters of the river. Our results revealed that Zn, Se, B, Ba, Fe, Mn, Mo, Ni and V were all detected in the Wei River. Compared to drinking water guidelines, the primary trace metal pollution components (B, Ni, Zn and Mn) exceeded drinking water standard levels by 47.1, 50.0, 44.1 and 26.5%, respectively. Inter-element relationships and landscape features of trace metals conducted by hierarchical cluster analysis (HCA) identified a uniform source of trace metals for all sampling sites, excluding one site that exhibited anomalous concentrations. Based on the patterns of relative loadings of individual metals calculated by principal component analysis (PCA), the primary trace metal sources were associated with natural/geogenic contributions, agro-chemical processes and discharge from local industrial sources. These results demonstrated the impact of human activities on metal concentrations in the Wei River.

  2. Changes in glucose fermentation pathways by an enriched bacterial culture in response to regulated dissolved H2 concentrations.

    PubMed

    Zheng, Hang; Zeng, Raymond J; Duke, Mikel C; O'Sullivan, Cathryn A; Clarke, William P

    2015-06-01

    It is well established that metabolic pathways in the fermentation of organic waste are primarily controlled by dissolved H2 concentrations, but there is no reported study that compares observed and predicted shifts in fermentation pathways induced by manipulating the dissolved H2 concentration. A perfusion system is presented that was developed to control dissolved H2 concentrations in the continuous fermentation of glucose by a culture highly enriched towards Thermoanaerobacterium thermosaccharolyticum (86 ± 9% relative abundance) from an originally diverse consortia in the leachate of a laboratory digester fed with municipal solid waste. Media from a 2.5 L CSTR was drawn through sintered steel membrane filters to retain biomass, allowing vigorous sparging in a separate chamber without cellular disruption. Through a combination of sparging and variations in glucose feeding rate from 0.8 to 0.2 g/L/d, a range of steady state fermentations were performed with dissolved H2 concentrations as low as an equivalent equilibrated H2 partial pressure of 3 kPa. Trends in product formation rates were simulated using a H2 regulation partitioning model. The model correctly predicted the direction of products redistribution in response to H2 concentration changes and the acetate and butyrate formation rates when H2 concentrations were less than 6 kPa. However, the model over-estimated acetate, ethanol and butanol productions at the expense of butyrate production at higher H2 concentrations. The H2 yield at the lowest dissolved H2 concentration was 2.67 ± 0.08 mol H2 /mol glucose, over 300% higher than the yield achieved in a CSTR operated without sparging. © 2014 Wiley Periodicals, Inc.

  3. Assessment of metal concentrations found within a North Sea drill cuttings pile.

    PubMed

    Breuer, Eric; Shimmield, Graham; Peppe, Oliver

    2008-07-01

    North Sea drill cuttings piles are a distinct anthropogenic legacy resulting from the exploration and production of North Sea oil reserves. The need to understand metal cycling within the piles becomes increasingly important with the imminent decommissioning of many North Sea platforms and the subsequent fate of associated cuttings piles. This paper presents results of the simultaneous analysis of geochemical carrier substances (Mn and Fe oxyhydroxides), along with dissolved (<0.2 microm) and total (>0.2 microm) metal (Ba, Co, Cr, Cu, Mo, Pb, V) concentrations from a North Sea cuttings pile and surrounding sediment. These data are examined in conjunction with in situ measured porewater oxygen and sulfide. Results show a rapid removal of oxygen within the top few millimeters of the cuttings pile along with elevated concentrations of total hydrocarbons and solid phase metal concentrations compared to the surrounding environment.

  4. Rates of zinc and trace metal release from dissolving sphalerite at pH 2.0-4.0

    USGS Publications Warehouse

    Stanton, M.R.; Gemery-Hill, P. A.; Shanks, Wayne C.; Taylor, C.D.

    2008-01-01

    High-Fe and low-Fe sphalerite samples were reacted under controlled pH conditions to determine nonoxidative rates of release of Zn and trace metals from the solid-phase. The release (solubilization) of trace metals from dissolving sphalerite to the aqueous phase can be characterized by a kinetic distribution coefficient, (Dtr), which is defined as [(Rtr/X(tr)Sph)/(RZn/X(Zn) Sph)], where R is the trace metal or Zn release rate, and X is the mole fraction of the trace metal or Zn in sphalerite. This coefficient describes the relationship of the sphalerite dissolution rate to the trace metal mole fraction in the solid and its aqueous concentration. The distribution was used to determine some controls on metal release during the dissolution of sphalerite. Departures from the ideal Dtr of 1.0 suggest that some trace metals may be released via different pathways or that other processes (e.g., adsorption, solubility of trace minerals such as galena) affect the observed concentration of metals. Nonoxidative sphalerite dissolution (mediated by H+) is characterized by a "fast" stage in the first 24-30 h, followed by a "slow" stage for the remainder of the reaction. Over the pH range 2.0-4.0, and for similar extent of reaction (reaction time), sphalerite composition, and surface area, the rates of release of Zn, Fe, Cd, Cu, Mn and Pb from sphalerite generally increase with lower pH. Zinc and Fe exhibit the fastest rates of release, Mn and Pb have intermediate rates of release, and Cd and Cu show the slowest rates of release. The largest variations in metal release rates occur at pH 2.0. At pH 3.0 and 4.0, release rates show less variation and appear less dependent on the metal abundance in the solid. For the same extent of reaction (100 h), rates of Zn release range from 1.53 ?? 10-11 to 5.72 ?? 10-10 mol/m2/s; for Fe, the range is from 4.59 ?? 10-13 to 1.99 ?? 10-10 mol/m2/s. Trace metal release rates are generally 1-5 orders of magnitude slower than the Zn or Fe rates

  5. The relationship of metals, bifenthrin, physical habitat metrics, grain size, total organic carbon, dissolved oxygen and conductivity to Hyalella sp. abundance in urban California streams.

    PubMed

    Hall, Lenwood W; Anderson, Ronald D

    2013-01-01

    The objectives of this study were to determine the relationship between Hyalella sp. abundance in four urban California streams and the following parameters: (1) 8 bulk metals (As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn) and their associated sediment Threshold Effect Levels (TELs); (2) bifenthrin sediment concentrations; (3) 10 habitat metrics and total score; (4) grain size (% sand, silt and clay); (5) Total Organic Carbon (TOC); (6) dissolved oxygen; and (7) conductivity. California stream data used for this study were collected from Kirker Creek (2006 and 2007), Pleasant Grove Creek (2006, 2007 and 2008), Salinas streams (2009 and 2010) and Arcade Creek (2009 and 2010). Hyalella abundance in the four California streams generally declined when metals concentrations were elevated beyond the TELs. There was also a statistically significant negative relationship between Hyalella abundance and % silt for these 4 California streams as Hyalella were generally not present in silt areas. No statistically significant relationships were reported between Hyalella abundance and metals concentrations, bifenthrin concentrations, habitat metrics, % sand, % clay, TOC, dissolved oxygen and conductivity. The results from this study highlight the complexity of assessing which factors are responsible for determining the abundance of amphipods, such as Hyalella sp., in the natural environment.

  6. Dissolving, trapping and detrapping mechanisms of hydrogen in bcc and fcc transition metals

    NASA Astrophysics Data System (ADS)

    You, Yu-Wei; Kong, Xiang-Shan; Wu, Xue-Bang; Xu, Yi-Chun; Fang, Q. F.; Chen, J. L.; Luo, G.-N.; Liu, C. S.; Pan, B. C.; Wang, Zhiguang

    2013-01-01

    First-principles calculations are performed to investigate the dissolving, trapping and detrapping of H in six bcc (V, Nb, Ta, Cr, Mo, W) and six fcc (Ni, Pd, Pt, Cu, Ag, Au) metals. We find that the zero-point vibrations do not change the site-preference order of H at interstitial sites in these metals except Pt. One vacancy could trap a maximum of 4 H atoms in Au and Pt, 6 H atoms in V, Nb, Ta, Cr, Ni, Pd, Cu and Ag, and 12 H atoms in Mo and W. The zero-point vibrations never change the maximum number of H atoms trapped in a single vacancy in these metals. By calculating the formation energy of vacancy-H (Vac-Hn) complex, the superabundant vacancy in V, Nb, Ta, Pd and Ni is demonstrated to be much more easily formed than in the other metals, which has been found in many metals including Pd, Ni and Nb experimentally. Besides, we find that it is most energetically favorable to form Vac-H1 complex in Pt, Cu, Ag and Au, Vac-H4 in Cr, Mo and W, and Vac-H6 in V, Nb, Ta, Pd and Ni. At last, we examine the detrapping behaviors of H atoms in a single vacancy and find that with the heating rate of 10 K/min a vacancy could accommodate 4, 5 and 6 H atoms in Cr, Mo and W at room temperature, respectively. The detrapping temperatures of all H atoms in a single vacancy in V, Nb, Ta, Ni, Pd, Cu and Ag are below room temperature.

  7. Particulate phases are key in controlling dissolved iron concentrations in the (sub)tropical North Atlantic

    NASA Astrophysics Data System (ADS)

    Milne, Angela; Schlosser, Christian; Wake, Bronwyn D.; Achterberg, Eric P.; Chance, Rosie; Baker, Alex R.; Forryan, Alex; Lohan, Maeve C.

    2017-03-01

    The supply and bioavailability of iron (Fe) controls primary productivity and N2 fixation in large parts of the global ocean. An important, yet poorly quantified, source to the ocean is particulate Fe (pFe). Here we present the first combined dataset of particulate, labile-particulate (L-pFe), and dissolved Fe (dFe) from the (sub)tropical North Atlantic. We show a strong relationship between L-pFe and dFe, indicating a dynamic equilibrium between these two phases whereby particles "buffer" dFe and maintain the elevated concentrations observed. Moreover, L-pFe can increase the overall "available" (L-pFe + dFe) Fe pool by up to 55%. The lateral shelf flux of this available Fe was similar in magnitude to observed soluble aerosol-Fe deposition, a comparison that has not been previously considered. These findings demonstrate that L-pFe is integral to Fe cycling and hence plays a role in regulating carbon cycling, warranting its inclusion in Fe budgets and biogeochemical models.

  8. Direct measurement of local dissolved oxygen concentration spatial profiles in a cell culture environment.

    PubMed

    Kagawa, Yuki; Matsuura, Katsuhisa; Shimizu, Tatsuya; Tsuneda, Satoshi

    2015-06-01

    Controlling local dissolved oxygen concentration (DO) in media is critical for cell or tissue cultures. Various biomaterials and culture methods have been developed to modulate DO. Direct measurement of local DO in cultures has not been validated as a method to test DO modulation. In the present study we developed a DO measurement system equipped with a Clark-type oxygen microelectrode manipulated with 1 μm precision in three-dimensional space to explore potential applications for tissue engineering. By determining the microelectrode tip position precisely against the bottom plane of culture dishes with rat or human cardiac cells in static monolayer culture, we successfully obtained spatial distributions of DO in the medium. Theoretical quantitative predictions fit the obtained data well. Based on analyses of the variance between samples, we found the data reflected "local" oxygen consumption in the vicinity of the microelectrode and the detection of temporal changes in oxygen consumption rates of cultured cells was limited by the diffusion rate of oxygen in the medium. This oxygen measuring system monitors local oxygen consumption and production with high spatial resolution, and can potentially be used with recently developed oxygen modulating biomaterials to design microenvironments and non-invasively monitor local DO dynamics during culture. © 2015 Wiley Periodicals, Inc.

  9. Dissolved black carbon in the global cryosphere: Concentrations and chemical signatures

    NASA Astrophysics Data System (ADS)

    Khan, Alia L.; Wagner, Sasha; Jaffe, Rudolf; Xian, Peng; Williams, Mark; Armstrong, Richard; McKnight, Diane

    2017-06-01

    Black carbon (BC) is derived from the incomplete combustion of biomass and fossil fuels and can enhance glacial recession when deposited on snow and ice surfaces. Here we explore the influence of environmental conditions and the proximity to anthropogenic sources on the concentration and composition of dissolved black carbon (DBC), as measured by benzenepolycaroxylic acid (BPCA) markers, across snow, lakes, and streams from the global cryosphere. Data are presented from Antarctica, the Arctic, and high alpine regions of the Himalayas, Rockies, Andes, and Alps. DBC concentrations spanned from 0.62 μg/L to 170 μg/L. The median and (2.5, 97.5) quantiles in the pristine samples were 1.8 μg/L (0.62, 12), and nonpristine samples were 21 μg/L (1.6, 170). DBC is susceptible to photodegradation when exposed to solar radiation. This process leads to a less condensed BPCA signature. In general, DBC across the data set was composed of less polycondensed DBC. However, DBC from the Greenland Ice Sheet (GRIS) had a highly condensed BPCA molecular signature. This could be due to recent deposition of BC from Canadian wildfires. Variation in DBC appears to be driven by a combination of photochemical processing and the source combustion conditions under which the DBC was formed. Overall, DBC was found to persist across the global cryosphere in both pristine and nonpristine snow and surface waters. The high concentration of DBC measured in supraglacial melt on the GRIS suggests that DBC can be mobilized across ice surfaces. This is significant because these processes may jointly exacerbate surface albedo reduction in the cryosphere.Plain Language SummaryHere we present <span class="hlt">dissolved</span> black carbon (DBC) results for snow and glacial melt systems in Antarctica, the Arctic, and high alpine regions of the Himalayas, Rockies, Andes, and Alps. Across the global cryosphere, DBC composition appears to be a result of photochemical processes occurring</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1816385F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1816385F"><span>The soil organic carbon content of anthropogenically altered organic soils effects the <span class="hlt">dissolved</span> organic matter quality, but not the <span class="hlt">dissolved</span> organic carbon <span class="hlt">concentrations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frank, Stefan; Tiemeyer, Bärbel; Bechtold, Michel; Lücke, Andreas; Bol, Roland</p> <p>2016-04-01</p> <p><span class="hlt">Dissolved</span> organic carbon (DOC) is an important link between terrestrial and aquatic ecosystems. This is especially true for peatlands which usually show high <span class="hlt">concentrations</span> of DOC due to the high stocks of soil organic carbon (SOC). Most previous studies found that DOC <span class="hlt">concentrations</span> in the soil solution depend on the SOC content. Thus, one would expect low DOC <span class="hlt">concentrations</span> in peatlands which have anthropogenically been altered by mixing with sand. Here, we want to show the effect of SOC and groundwater level on the quantity and quality of the <span class="hlt">dissolved</span> organic matter (DOM). Three sampling sites were installed in a strongly disturbed bog. Two sites differ in SOC (Site A: 48%, Site B: 9%) but show the same mean annual groundwater level of 15 and 18 cm below ground, respectively. The SOC content of site C (11%) is similar to Site B, but the groundwater level is much lower (-31 cm) than at the other two sites. All sites have a similar depth of the organic horizon (30 cm) and the same land-use (low-intensity sheep grazing). Over two years, the soil solution was sampled bi-weekly in three depths (15, 30 and 60 cm) and three replicates. All samples were analyzed for DOC and selected samples for <span class="hlt">dissolved</span> organic nitrogen (DON) and delta-13C and delta-15N. Despite differences in SOC and groundwater level, DOC <span class="hlt">concentrations</span> did not differ significantly (A: 192 ± 62 mg/L, B: 163 ± 55 mg/L and C: 191 ± 97 mg/L). At all sites, DOC <span class="hlt">concentrations</span> exceed typical values for peatlands by far and emphasize the relevance even of strongly disturbed organic soils for DOC losses. Individual DOC <span class="hlt">concentrations</span> were controlled by the temperature and the groundwater level over the preceding weeks. Differences in DOM quality were clearer. At site B with a low SOC content, the DOC:DON ratio of the soil solution equals the soil's C:N ratio, but the DOC:DON ratio is much higher than the C:N ratio at site A. In all cases, the DOC:DON ratio strongly correlates with delta-13C. There is no</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012OcSci...8....1C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012OcSci...8....1C"><span>Using <span class="hlt">dissolved</span> oxygen <span class="hlt">concentrations</span> to determine mixed layer depths in the Bellingshausen Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Castro-Morales, K.; Kaiser, J.</p> <p>2012-01-01</p> <p><span class="hlt">Concentrations</span> of oxygen (O2) and other <span class="hlt">dissolved</span> gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes. The mixed layer depth (zmix) may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of air-sea exchange differ for gases and heat, so that zmix defined using oxygen may be different than zmix defined using temperature or density. Here, we propose to define an O2-based mixed layer depth, zmix(O2), as the depth where the relative difference between the O2 <span class="hlt">concentration</span> and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by analysis of O2 profiles from the Bellingshausen Sea (west of the Antarctic Peninsula) and corroborated by visual inspection. Comparisons of zmix(O2) with zmix based on potential temperature differences, i.e., zmix(0.2 °C) and zmix(0.5 °C), and potential density differences, i.e., zmix(0.03 kg m-3) and zmix(0.125 kg m-3), showed that zmix(O2) closely follows zmix(0.03 kg m-3). Further comparisons with published zmix climatologies and zmix derived from World Ocean Atlas 2005 data were also performed. To establish zmix for use with biological production estimates in the absence of O2 profiles, we suggest using zmix(0.03 kg m-3), which is also the basis for the climatology by de Boyer Montégut et al. (2004).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.B42A..03K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.B42A..03K"><span>Hydrologically Driven Dynamics of <span class="hlt">Dissolved</span> Organic Carbon <span class="hlt">Concentration</span> and Composition in a Headwater Stream Ecosystem</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kaplan, L. A.; McLaughlin, C.; Hogan, K. R.; Newbold, J. D.</p> <p>2011-12-01</p> <p>A 34-year record of <span class="hlt">dissolved</span> organic carbon (DOC) <span class="hlt">concentrations</span> and compositions was used to assess the role of hydrologic variability in the carbon cycle of a headwater stream. The DOC <span class="hlt">concentration</span> record is characterized by sharply increasing values during storms and annual minima associated with soil freezing in winter (Fig. 1). Baseflow discharge accounts for approximately 67% of the total runoff in this 3rd-order stream in the Pennsylvania Piedmont but storm flows transport approximately 75% of the DOC flux. The annual DOC flux varies as much as 3-fold and this variability is driven by unusual events such as major storms and prolonged droughts. During storms DOC quality changes as water moves to the stream through organic matter-rich upper soil horizons, by passing terrestrial controls on DOC content. The pool of biodegradable DOC (BDOC) as a percentage of total DOC increases from 33% to 73% with the most labile BDOC class increasing 4-fold while the semi-labile BDOC pool increases 2-fold. Storms also alter the structure and productivity of benthic bacterial communities that metabolize DOC in streams, though the impacts are tempered by stability of streambed substrata. For example, a February storm reduced the biomass and productivity of bacteria attached to sediments by 48% and 90%, respectively, while reducing the biomass of bacteria attached to rocks by 21% but increasing bacterial productivity by 22%. Molecular fingerprints of community compositions revealed a stable "climax community" whose alteration is influenced by the magnitude of the storm flows and eventually returns to its original composition. Actual measurements of carbon cycling based on whole-stream releases and sampling the stream bed microbial community are not feasible during storms, but we argue that for headwater streams it is the post-disturbance condition rather than any processing which occurs during storm flows that shapes the magnitude and dynamics of carbon cycling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JGRG..112.1009G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JGRG..112.1009G"><span>Declines in <span class="hlt">dissolved</span> silica <span class="hlt">concentrations</span> in western Virginia streams (1988-2003): Gypsy moth defoliation stimulates diatoms?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grady, Amy E.; Scanlon, Todd M.; Galloway, James N.</p> <p>2007-03-01</p> <p><span class="hlt">Dissolved</span> silica <span class="hlt">concentrations</span> in western Virginia streams showed a significant bias toward declines (p < 0.0001) over the time period from 1988 to 2003. Streams with the greatest declines were those that had the highest mean <span class="hlt">dissolved</span> silica <span class="hlt">concentrations</span>, specific to watersheds underlain by basaltic and granitic bedrock. We examined potential geochemical, hydrological, and biological factors that could account for the observed widespread declines, focusing on six core watersheds where weekly stream chemistry data were available. No relationships were evident between stream water <span class="hlt">dissolved</span> silica <span class="hlt">concentrations</span> and pH, a finding supported by the results from a geochemical model applied to the dominant bedrock mineralogy. Along with changes in watershed acidity, changes in precipitation and discharge were also discounted since no significant trends were observed over the study period. Analyses of two longer-term data sets that extend back to 1979 revealed that the initiation of the <span class="hlt">dissolved</span> silica declines coincided with the timing of a gypsy moth (Lymantria dispar) defoliation event. We develop a conceptual model centered on benthic diatoms, which are found within each of the six core watersheds but in greater abundance in the more silica-rich streams. Gypsy moth defoliation led to greater sunlight penetration and enhanced nitrate <span class="hlt">concentrations</span> in the streams, which could have spurred population growth and silica uptake. The model can explain why the observed declines are primarily driven by decreased <span class="hlt">concentrations</span> during low-flow conditions. This study illustrates lasting effects of disturbance on watershed biogeochemistry, in this case causing decadal-scale variability in stream water <span class="hlt">dissolved</span> silica <span class="hlt">concentrations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ECSS...99..121B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ECSS...99..121B"><span>Short-term (24 h) effects of mild and severe hypoxia (20% and 5% <span class="hlt">dissolved</span> oxygen) on <span class="hlt">metal</span> partitioning in highly contaminated estuarine sediments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Banks, Joanne; Ross, D. Jeff; Keough, Michael J.</p> <p>2012-03-01</p> <p>The effects of a short-term (24 h) reduction in bottom-water <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> (DO) on <span class="hlt">metal</span> (Cd, Cu, Fe, Mn, Pb and Zn) partitioning within <span class="hlt">metal</span>-contaminated sediments in replicated, undisturbed sediment/water chambers show that even very brief periods of hypoxia may significantly increase the <span class="hlt">dissolved</span> fraction of these heavy <span class="hlt">metals</span> within contaminated sediments, increasing their potential for ecological harm. This study used treatments consisting of three DO levels (75%, 20% and 5% saturation) representing ambient conditions, mild hypoxia and severe hypoxia. Although contaminant loads were very high in these sediments, pore-water <span class="hlt">concentrations</span> were relatively low. Total sediment and dilute acid (1 M HCl) extracted <span class="hlt">metals</span> were unaffected by low DO treatments but a diffusive gradient in thin-films samplers (DGTs), detected a two-fold increase in pore-water Cd and a five-fold increase in pore-water Cu in surface sediments (0-3 cm depth) under low oxygen conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/19547','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/19547"><span>Sources, transformations, and hydrological processes that control stream nitrate and <span class="hlt">dissolved</span> organic matter <span class="hlt">concentrations</span> during snowmelt in an upland forest</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Stephen D. Sebestyen; Elizabeth W. Boyer; James B. Shanley; Carol Kendall; Daniel H. Doctor; George R. Aiken; Nobuhito Ohte</p> <p>2008-01-01</p> <p>We explored catchment processes that control stream nutrient <span class="hlt">concentrations</span> at an upland forest in northeastern Vermont, USA, where inputs of nitrogen via atmospheric deposition are among the highest in the nation and affect ecosystem functioning. We traced sources of water, nitrate, and <span class="hlt">dissolved</span> organic matter (DOM) using stream water samples collected at high...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=260070','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=260070"><span>Comparative production of channel catfish and channel x blue hybrid catfish subjected to two minimum <span class="hlt">dissolved</span> oxygen <span class="hlt">concentrations</span></span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>The effect of daily minimum <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> on growth and yield (kg/ha) of the channel catfish (Ictalurus punctatus) and the channel x blue hybrid catfish (I. punctatus female x I. furcatus male), which shared the Jubilee strain of channel catfish as the maternal parent, was evaluated...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016BGeo...13.5567C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016BGeo...13.5567C"><span>Trends in soil solution <span class="hlt">dissolved</span> organic carbon (DOC) <span class="hlt">concentrations</span> across European forests</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Camino-Serrano, Marta; Graf Pannatier, Elisabeth; Vicca, Sara; Luyssaert, Sebastiaan; Jonard, Mathieu; Ciais, Philippe; Guenet, Bertrand; Gielen, Bert; Peñuelas, Josep; Sardans, Jordi; Waldner, Peter; Etzold, Sophia; Cecchini, Guia; Clarke, Nicholas; Galić, Zoran; Gandois, Laure; Hansen, Karin; Johnson, Jim; Klinck, Uwe; Lachmanová, Zora; Lindroos, Antti-Jussi; Meesenburg, Henning; Nieminen, Tiina M.; Sanders, Tanja G. M.; Sawicka, Kasia; Seidling, Walter; Thimonier, Anne; Vanguelova, Elena; Verstraeten, Arne; Vesterdal, Lars; Janssens, Ivan A.</p> <p>2016-10-01</p> <p><span class="hlt">Dissolved</span> organic carbon (DOC) in surface waters is connected to DOC in soil solution through hydrological pathways. Therefore, it is expected that long-term dynamics of DOC in surface waters reflect DOC trends in soil solution. However, a multitude of site studies have failed so far to establish consistent trends in soil solution DOC, whereas increasing <span class="hlt">concentrations</span> in European surface waters over the past decades appear to be the norm, possibly as a result of recovery from acidification. The objectives of this study were therefore to understand the long-term trends of soil solution DOC from a large number of European forests (ICP Forests Level II plots) and determine their main physico-chemical and biological controls. We applied trend analysis at two levels: (1) to the entire European dataset and (2) to the individual time series and related trends with plot characteristics, i.e., soil and vegetation properties, soil solution chemistry and atmospheric deposition loads. Analyses of the entire dataset showed an overall increasing trend in DOC <span class="hlt">concentrations</span> in the organic layers, but, at individual plots and depths, there was no clear overall trend in soil solution DOC. The rate change in soil solution DOC ranged between -16.8 and +23 % yr-1 (median = +0.4 % yr-1) across Europe. The non-significant trends (40 %) outnumbered the increasing (35 %) and decreasing trends (25 %) across the 97 ICP Forests Level II sites. By means of multivariate statistics, we found increasing trends in DOC <span class="hlt">concentrations</span> with increasing mean nitrate (NO3-) deposition and increasing trends in DOC <span class="hlt">concentrations</span> with decreasing mean sulfate (SO42-) deposition, with the magnitude of these relationships depending on plot deposition history. While the attribution of increasing trends in DOC to the reduction of SO42- deposition could be confirmed in low to medium N deposition areas, in agreement with observations in surface waters, this was not the case in high N deposition areas. In</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22652964','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22652964"><span>Nucleoside-5'-phosphorothioate analogues are biocompatible antioxidants <span class="hlt">dissolving</span> efficiently amyloid beta-<span class="hlt">metal</span> ion aggregates.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Amir, Aviran; Shmuel, Eran; Zagalsky, Rostislav; Sayer, Alon H; Nadel, Yael; Fischer, Bilha</p> <p>2012-07-28</p> <p>Amyloid beta (Aβ) peptide is known to precipitate and form aggregates with zinc and copper ions in vitro and, in vivo in Alzheimer's disease (AD) patients. <span class="hlt">Metal</span>-ion-chelation was suggested as therapy for the <span class="hlt">metal</span>-ion-induced Aβ aggregation, <span class="hlt">metal</span>-ion overload, and oxidative stress. In a quest for biocompatible <span class="hlt">metal</span>-ion chelators potentially useful for AD therapy, we tested a series of nucleoside 5'-phosphorothioate derivatives as re-solubilization agents of Cu(+)/Cu(2+)/Zn(2+)-induced Aβ-aggregates, and inhibitors of Fenton reaction in Cu(+) or Fe(2+)/H(2)O(2) system. The most promising chelator in this series was found to be APCPP-γ-S. This nucleotide was found to be more efficient than EDTA in re-solubilization of Aβ(40)-Cu(2+) aggregates as observed by the lower diameter, d(H), (86 vs. 64 nm, respectively) obtained in dynamic light scattering measurements. Likewise, APCPP-γ-S <span class="hlt">dissolved</span> Aβ(40)-Cu(+) and Aβ(42)-Cu(2+)/Zn(2+) aggregates, as monitored by (1)H-NMR and turbidity assays, respectively. Furthermore, addition of APCPP-γ-S to nine-day old Aβ(40)-Cu(2+)/Zn(2+) aggregates, resulted in size reduction as observed by transition electron microscopy (diameter reduction from 2.5 to 0.1 μm for Aβ(40)-Cu(2+) aggregates). APCPP-γ-S proved to be more efficient than ascorbic acid and GSH in reducing OH radical production in Fe(2+)/H(2)O(2) system (IC(50) values 85, 216 and, 92 μM, respectively). Therefore, we propose APCPP-γ-S as a potential AD therapy capable of both reducing OH radical production and re-solubilization of Aβ(40/42)-M(n+) aggregates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2626252','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2626252"><span>Generation of Hydroxyl Radicals from <span class="hlt">Dissolved</span> Transition <span class="hlt">Metals</span> in Surrogate Lung Fluid Solutions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vidrio, Edgar; Jung, Heejung; Anastasio, Cort</p> <p>2008-01-01</p> <p>Epidemiological research has linked exposure to atmospheric particulate matter (PM) to several adverse health effects, including cardiovascular and pulmonary morbidity and mortality. Despite these links, the mechanisms by which PM causes adverse health effects are poorly understood. The generation of hydroxyl radical (·OH) and other reactive oxygen species (ROS) through transition <span class="hlt">metal</span>-mediated pathways is one of the main hypotheses for PM toxicity. In order to better understand the ability of particulate transition <span class="hlt">metals</span> to produce ROS, we have quantified the amounts of ·OH produced from <span class="hlt">dissolved</span> iron and copper in a cell-free, surrogate lung fluid (SLF). We also examined how two important biological molecules, citrate and ascorbate, affect the generation of ·OH by these <span class="hlt">metals</span>. We have found that Fe(II) and Fe(III) produce little ·OH in the absence of ascorbate and citrate, but that they efficiently make ·OH in the presence of ascorbate and this is further enhanced when citrate is also added. In the presence of ascorbate, with or without citrate, the oxidation state of iron makes little difference on the amount of ·OH formed after 24 hours. In the case of Cu(II), the production of ·OH is greatly enhanced in the presence of ascorbate, but is inhibited by the addition of citrate. The mechanism for this effect is unclear, but appears to involve formation of a citrate-copper complex that is apparently less reactive than free, aquated copper in either the generation of HOOH or in the Fenton-like reaction of copper with HOOH to make ·OH. By quantifying the amount of ·OH that Fe and Cu can produce in surrogate lung fluid, we have provided a first step into being able to predict the amounts of ·OH that can be produced in the human lung from exposure to PM containing known amounts of transition <span class="hlt">metals</span>. PMID:19148304</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19148304','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19148304"><span>Generation of Hydroxyl Radicals from <span class="hlt">Dissolved</span> Transition <span class="hlt">Metals</span> in Surrogate Lung Fluid Solutions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vidrio, Edgar; Jung, Heejung; Anastasio, Cort</p> <p>2008-01-01</p> <p>Epidemiological research has linked exposure to atmospheric particulate matter (PM) to several adverse health effects, including cardiovascular and pulmonary morbidity and mortality. Despite these links, the mechanisms by which PM causes adverse health effects are poorly understood. The generation of hydroxyl radical (.OH) and other reactive oxygen species (ROS) through transition <span class="hlt">metal</span>-mediated pathways is one of the main hypotheses for PM toxicity. In order to better understand the ability of particulate transition <span class="hlt">metals</span> to produce ROS, we have quantified the amounts of .OH produced from <span class="hlt">dissolved</span> iron and copper in a cell-free, surrogate lung fluid (SLF). We also examined how two important biological molecules, citrate and ascorbate, affect the generation of .OH by these <span class="hlt">metals</span>. We have found that Fe(II) and Fe(III) produce little .OH in the absence of ascorbate and citrate, but that they efficiently make .OH in the presence of ascorbate and this is further enhanced when citrate is also added. In the presence of ascorbate, with or without citrate, the oxidation state of iron makes little difference on the amount of .OH formed after 24 hours. In the case of Cu(II), the production of .OH is greatly enhanced in the presence of ascorbate, but is inhibited by the addition of citrate. The mechanism for this effect is unclear, but appears to involve formation of a citrate-copper complex that is apparently less reactive than free, aquated copper in either the generation of HOOH or in the Fenton-like reaction of copper with HOOH to make .OH. By quantifying the amount of .OH that Fe and Cu can produce in surrogate lung fluid, we have provided a first step into being able to predict the amounts of .OH that can be produced in the human lung from exposure to PM containing known amounts of transition <span class="hlt">metals</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012BGeo....9.3231B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012BGeo....9.3231B"><span>Distributions of <span class="hlt">dissolved</span> trace <span class="hlt">metals</span> (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boye, M.; Wake, B. D.; Lopez Garcia, P.; Bown, J.; Baker, A. R.; Achterberg, E. P.</p> <p>2012-08-01</p> <p>Comprehensive synoptic datasets (surface water down to 4000 m) of <span class="hlt">dissolved</span> cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb) and silver (Ag) are presented along a section between 34° S and 57° S in the southeastern Atlantic Ocean and the Southern Ocean to the south off South Africa. The vertical distributions of Cu and Ag display nutrient-like profiles similar to silicic acid, and of Cd similar to phosphate. The distribution of Mn shows a subsurface maximum in the oxygen minimum zone, whereas Pb <span class="hlt">concentrations</span> are rather invariable with depth. Dry deposition of aerosols is thought to be an important source of Pb to surface waters close to South Africa, and dry deposition and snowfall may have been significant sources of Cu and Mn at the higher latitudes. Furthermore, the advection of water masses enriched in trace <span class="hlt">metals</span> following contact with continental margins appeared to be an important source of trace elements to the surface, intermediate and deep waters in the southeastern Atlantic Ocean and the Antarctic Circumpolar Current. Hydrothermal inputs may have formed a source of trace <span class="hlt">metals</span> to the deep waters over the Bouvet Triple Junction ridge crest, as suggested by relatively enhanced <span class="hlt">dissolved</span> Mn <span class="hlt">concentrations</span>. The biological utilization of Cu and Ag was proportional to that of silicic acid across the section, suggesting that diatoms formed an important control over the removal of Cu and Ag from surface waters. However, uptake by dino- and nano-flagellates may have influenced the distribution of Cu and Ag in the surface waters of the subtropical Atlantic domain. Cadmium correlated strongly with phosphate (P), yielding lower Cd / P ratios in the subtropical surface waters where phosphate <span class="hlt">concentrations</span> were below 0.95 μM. The greater depletion of Cd relative to P observed in the Weddell Gyre compared to the Antarctic Circumpolar Current could be due to increase Cd uptake induced by iron-limiting conditions in these high-nutrient-low-chlorophyll waters</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012BGD.....9.3579B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012BGD.....9.3579B"><span>Distributions of <span class="hlt">dissolved</span> trace <span class="hlt">metals</span> (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boye, M.; Wake, B. D.; Lopez Garcia, P.; Bown, J.; Baker, A. R.; Achterberg, E. P.</p> <p>2012-03-01</p> <p>Comprehensive synoptic datasets (surface water down to 4000 m) of <span class="hlt">dissolved</span> cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb) and silver (Ag) are presented along a section between 34° S and 57° S in the southeastern Atlantic Ocean and the Southern Ocean to the south off South Africa. The vertical distributions of Cu, Ag, and of Cd display nutrient-like profiles similar to silicic acid, and phosphate, respectively. The distribution of Mn shows a subsurface maximum in the oxygen minimum zone, whereas Pb <span class="hlt">concentrations</span> are rather invariable with depth. Dry deposition of aerosols is thought to be an important source of Pb to surface waters close to South Africa, and dry deposition and snowfall may have been significant sources of Cu and Mn at the higher latitudes. Furthermore, the advection of water-masses enriched in trace <span class="hlt">metals</span> following contact with continental margins appeared to be an important source of trace elements to the surface, intermediate and deep waters in the southeastern Atlantic Ocean and the Antarctic Circumpolar Current. Hydrothermal inputs appeared to have formed a source of trace <span class="hlt">metals</span> to the deep waters over the Bouvet Triple Junction ridge crest, as suggested by relatively enhanced <span class="hlt">dissolved</span> Mn <span class="hlt">concentrations</span>. The biological utilization of Cu and Ag was proportional to that of silicic acid across the section, suggesting that diatoms formed an important control over the removal of Cu and Ag from surface waters. However uptake by dino- and nano-flagelattes may have influenced the distribution of Cu and Ag in the surface waters of the subtropical Atlantic domain. Cadmium correlated strongly with phosphate (P), yielding lower Cd/P ratios in the subtropical surface waters where phosphate <span class="hlt">concentrations</span> were below 0.95 μM. The greater depletion of Cd relative to P observed in the Weddell Gyre compared to the Antarctic Circumpolar Current could be due to increase Cd-uptake induced by iron-limiting conditions in these High-Nutrient Low</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AcSpe..61.1180Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AcSpe..61.1180Z"><span>Analysis of total and <span class="hlt">dissolved</span> heavy <span class="hlt">metals</span> in surface water of a Mexican polluted river by total reflection X-ray fluorescence spectrometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zarazua, G.; Ávila-Pérez, P.; Tejeda, S.; Barcelo-Quintal, I.; Martínez, T.</p> <p>2006-11-01</p> <p>The present area of study is located in the Upper Course of the Lerma River (UCLR). The Lerma is one of the most important rivers of Mexico, where it drains highly populated and industrialized regions. The aim of the present study is to determine the heavy <span class="hlt">metal</span> <span class="hlt">concentration</span> of Cr, Mn, Fe, Cu and Pb in <span class="hlt">dissolved</span> and total phases of the UCLR by means of Total Reflection X-ray Fluorescence Spectrometry (TXRF). The surface water samples were collected at 8 sites distributed following the stream flow direction of the river. Four sampling campaigns were carried out in each site in a 1-year period. A sample preparation method was applied in order to obtain the total and <span class="hlt">dissolved</span> fraction and to destroy the organic matter. The total heavy <span class="hlt">metal</span> average <span class="hlt">concentration</span> decrease in the following order: Fe (2566 μg/L) > Mn (300 μg/L) > Cu (66 μg/L) > Cr (21 μg/L) > Pb (15 μg/L). In general, the heavy <span class="hlt">metal</span> <span class="hlt">concentrations</span> in water of the UCLR are below the maximum permissible limits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017408','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017408"><span>Use of <span class="hlt">dissolved</span> H2 <span class="hlt">concentrations</span> to determine distribution of microbially catalyzed redox reactions in anoxic groundwater</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Lovley, D.R.; Chapelle, F.H.; Woodward, J.C.</p> <p>1994-01-01</p> <p>The potential for using <span class="hlt">concentrations</span> of <span class="hlt">dissolved</span> H2 to determine the distribution of redox processes in anoxic groundwaters was evaluated. In pristine aquifers in which standard geochemical measurements indicated that Fe-(III) reduction, sulfate reduction, or methanogenesis was the terminal electron accepting process (TEAP), the H2 <span class="hlt">concentrations</span> were similar to the H2 <span class="hlt">concentrations</span> that have previously been reported for aquatic sediments with the same TEAPs. In two aquifers contaminated with petroleum products, it was impossible with standard geochemical analyses to determine which TEAPs predominated in specific locations. However, the TEAPs predicted from measurements of <span class="hlt">dissolved</span> H2 were the same as those determined directly through measurements of microbial processes in incubated aquifer material. These results suggest that H2 <span class="hlt">concentrations</span> may be a useful tool for analyzing the redox chemistry of nonequilibrium groundwaters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/26435','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/26435"><span><span class="hlt">Dissolved</span>-solids <span class="hlt">concentrations</span> and hydrochemical facies in water of the Edwards-Trinity aquifer system, west-central Texas</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bush, P.W.; Ulery, R.L.; Rittmaster, R.L.</p> <p>1994-01-01</p> <p>Much of the Edwards-Trinity aquifer system contains freshwater, but sizable parts contain marginally fresh or slightly saline water. The predominant water type in the aquifer system is calcium bicarbonate; however, one of seven other hydrochemical facies characterizes the water in places. The median <span class="hlt">dissolved</span>-solids <span class="hlt">concentration</span> of water samples from the Edwards aquifer in the Balcones fault zone is 297 mg/L (milligrams per liter); the interquartile range is 93 mg/L. In the freshwater zone of the Edwards aquifer updip of a freshwater/saline-water transition zone, the water is almost exclusively calcium bicarbonate. The median <span class="hlt">dissolved</span>-solids <span class="hlt">concentration</span> of water samples from the Trinity aquifer in the Hill Country is 537 mg/L and the interquartile range is 573 mg/L. Four bicarbonate and sulfate facies, spread vertically throughout the saturated section, characterize most of the Hill Country analyses; calcium bicarbonate predominates. The median <span class="hlt">concentration</span> of <span class="hlt">dissolved</span> solids in water samples from the Edwards-Trinity aquifer in the Edwards Plateau is 379 mg/L and the interquartile range is 547 mg/L. Freshwater is nearly everywhere in the southern and northeastern parts of the aquifer, and mostly slightly saline water is in the northwestern part. The distribution of hydrochemical facies shows a similar pattern to <span class="hlt">dissolved</span>-solids <span class="hlt">concentration</span>, with bicarbonate water nearly everywhere in the southern and northeastern parts of the aquifer. Sulfate and chloride facies characterize the northwestern part of the Edwards Plateau. The median <span class="hlt">concentration</span> of <span class="hlt">dissolved</span> solids among water samples from the Edwards-Trinity aquifer in the Trans-Pecos is 929 mg/L and the interquartile range is 1,626 mg/L. Fresh, calcium bicarbonate water predominates in the southern part, and more saline mixed and sulfate waters are the most common in the northwestern part.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70137397','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70137397"><span>A data reconnaissance on the effect of suspended-sediment <span class="hlt">concentrations</span> on <span class="hlt">dissolved</span>-solids <span class="hlt">concentrations</span> in rivers and tributaries in the Upper Colorado River Basin</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Tillman, Fred D; Anning, David W.</p> <p>2014-01-01</p> <p>The Colorado River is one of the most important sources of water in the western United States, supplying water to over 35 million people in the U.S. and 3 million people in Mexico. High <span class="hlt">dissolved</span>-solids loading to the River and tributaries are derived primarily from geologic material deposited in inland seas in the mid-to-late Cretaceous Period, but this loading may be increased by human activities. High <span class="hlt">dissolved</span> solids in the River causes substantial damages to users, primarily in reduced agricultural crop yields and corrosion. The Colorado River Basin Salinity Control Program was created to manage <span class="hlt">dissolved</span>-solids loading to the River and has focused primarily on reducing irrigation-related loading from agricultural areas. This work presents a reconnaissance of existing data from sites in the Upper Colorado River Basin (UCRB) in order to highlight areas where suspended-sediment control measures may be useful in reducing <span class="hlt">dissolved</span>-solids <span class="hlt">concentrations</span>. Multiple linear regression was used on data from 164 sites in the UCRB to develop <span class="hlt">dissolved</span>-solids models that include combinations of explanatory variables of suspended sediment, flow, and time. Results from the partial t-test, overall likelihood ratio, and partial likelihood ratio on the models were used to group the sites into categories of strong, moderate, weak, and no-evidence of a relation between suspended-sediment and <span class="hlt">dissolved</span>-solids <span class="hlt">concentrations</span>. Results show 68 sites have strong or moderate evidence of a relation, with drainage areas for many of these sites composed of a large percentage of clastic sedimentary rocks. These results could assist water managers in the region in directing field-scale evaluation of suspended-sediment control measures to reduce UCRB <span class="hlt">dissolved</span>-solids loading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70028311','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70028311"><span>Response of oxidative enzyme activities to nitrogen deposition affects soil <span class="hlt">concentrations</span> of <span class="hlt">dissolved</span> organic carbon</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Waldrop, M.P.; Zak, D.R.</p> <p>2006-01-01</p> <p>Recent evidence suggests that atmospheric nitrate (NO3- ) deposition can alter soil carbon (C) storage by directly affecting the activity of lignin-degrading soil fungi. In a laboratory experiment, we studied the direct influence of increasing soil NO 3- <span class="hlt">concentration</span> on microbial C cycling in three different ecosystems: black oak-white oak (BOWO), sugar maple-red oak (SMRO), and sugar maple-basswood (SMBW). These ecosystems span a broad range of litter biochemistry and recalcitrance; the BOWO ecosystem contains the highest litter lignin content, SMRO had intermediate lignin content, and SMBW leaf litter has the lowest lignin content. We hypothesized that increasing soil solution NO 3- would reduce lignolytic activity in the BOWO ecosystem, due to a high abundance of white-rot fungi and lignin-rich leaf litter. Due to the low lignin content of litter in the SMBW, we further reasoned that the NO3- repression of lignolytic activity would be less dramatic due to a lower relative abundance of white-rot basidiomycetes; the response in the SMRO ecosystem should be intermediate. We increased soil solution NO3- <span class="hlt">concentrations</span> in a 73-day laboratory incubation and measured microbial respiration and soil solution <span class="hlt">dissolved</span> organic carbon (DOC) and phenolics <span class="hlt">concentrations</span>. At the end of the incubation, we measured the activity of ??-glucosidase, N-acetyl-glucosaminidase, phenol oxidase, and peroxidase, which are extracellular enzymes involved with cellulose and lignin degradation. We quantified the fungal biomass, and we also used fungal ribosomal intergenic spacer analysis (RISA) to gain insight into fungal community composition. In the BOWO ecosystem, increasing NO 3- significantly decreased oxidative enzyme activities (-30% to -54%) and increased DOC (+32% upper limit) and phenolic (+77% upper limit) <span class="hlt">concentrations</span>. In the SMRO ecosystem, we observed a significant decrease in phenol oxidase activity (-73% lower limit) and an increase in soluble phenolic <span class="hlt">concentrations</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11561954','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11561954"><span><span class="hlt">Dissolved</span> gaseous mercury <span class="hlt">concentration</span> and mercury evasional flux from seawater in front of a chlor-alkali plant.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ferrara, R; Lanzillotta, E; Ceccarini, C</p> <p>2001-08-01</p> <p>The <span class="hlt">dissolved</span> gaseous mercury <span class="hlt">concentration</span> and mercury degassing rate have been measured in a marine area polluted by a chlor-alkali plant (Rosignano Solvay, Italy), which uses mercury in chlorine production. During the summer the DGM <span class="hlt">concentration</span> (130 pg l(-1)) and the evasional flux (14 ng m(-2) h(-1)) were 3-4 times higher than those measured at the control stations. A seasonal behaviour has been highlighted at all the sampling sites, with minimum levels in the winter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23374419','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23374419"><span>Effect of exchangeable cation <span class="hlt">concentration</span> on sorption and desorption of <span class="hlt">dissolved</span> organic carbon in saline soils.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Setia, Raj; Rengasamy, Pichu; Marschner, Petra</p> <p>2013-11-01</p> <p>Sorption is a very important factor in stabilization of <span class="hlt">dissolved</span> organic carbon (DOC) in soils and thus C sequestration. Saline soils have significant potential for C sequestration but little is known about the effect of type and <span class="hlt">concentration</span> of cations on sorption and release of DOC in salt-affected soils. To close this knowledge gap, three batch sorption and desorption experiments were conducted using soils treated with solutions either low or high in salinity. In Experiment 1, salinity was developed with either NaCl or CaCl2 to obtain an electrical conductivity (EC) in a 1:5 soil: water extract (EC1:5) of 2 and 4 dS m(-1). In Experiments 2 and 3, NaCl and CaCl2 were added in various proportions (between 25 and 100%) to obtain an EC1:5 of 0.5 and 4 dS m(-1), respectively. At EC1:5 of 4 dS m(-1), the sorption of DOC (derived from wheat straw) was high even at a low proportion of added Ca(2+) and did not change with proportion of Ca added, but at EC1:5 of 0.5 dS m(-1) increasing proportion of Ca(2+) added increased DOC sorption. This can be explained by the differences in exchangeable Ca(2+) at the two salinity levels. At EC1:5 of 4 dS m(-1), the exchangeable Ca(2+) <span class="hlt">concentration</span> did not increase beyond a proportion of 25% Ca(2+), whereas it increased with increasing Ca(2+) proportion in the treatments at EC1:5 of 0.5 dS m(-1). The DOC sorption was lowest with a proportion of 100% as Na(+). When Ca(2+) was added, DOC sorption was highest, but least was desorbed (with deionised water), thus sorption and desorption of added DOC were inversely related. The results of this study suggest that DOC sorption in salt-affected soils is mainly controlled by the levels of exchangeable Ca(2+) irrespective of the Ca(2+) <span class="hlt">concentration</span> in the soil solution which has implications on carbon stabilization in salt-affected soils.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/circ/1980/0715k/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/circ/1980/0715k/report.pdf"><span>Evaluation of planning alternatives for maintaining desirable <span class="hlt">dissolved</span>-oxygen <span class="hlt">concentrations</span> in the Willamette River, Oregon</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Rickert, David A.; Rinella, F.A.; Hines, W.G.; McKenzie, S.W.</p> <p>1980-01-01</p> <p>For nearly half a century the Willamette River in Oregon experienced severe <span class="hlt">dissolved</span>-oxygen problems related to large loads of organically rich waste waters from industries and municipalities. Since the mid-1950 's <span class="hlt">dissolved</span> oxygen quality has gradually improved owing to low-flow augmentation, the achievement of basinwide secondary treatment, and the use of other waste-management practices. As a result, summer <span class="hlt">dissolved</span>-oxygen levels have increased, salmon runs have returned, and the overall effort is widely regarded as a singular water-quality success. To document the improved <span class="hlt">dissolved</span>-oxygen regimen, the U.S. Geological Survey conducted intensive studies of the Willamette during the summer low-flow seasons of 1973 and 1974. During each summer the mean daily <span class="hlt">dissolved</span>-oxygen levels were found to be higher than 5 milligrams per liter throughout the river. Because of the basinwide secondary treatment, carbonaceous deoxygenation rates were low. In addition, almost half of the biochemical oxygen demand entering the Willamette was from diffuse (nonpoint) sources rather than outfalls. These results indicated that point-source biochemical oxygen demand was no longer the primary cause of <span class="hlt">dissolved</span>-oxygen depletion. Instead, the major causes of deoxygenation were nitrification in a shallow ' surface active ' reach below Salem and an anomalous oxygen demand (believed to be primarily of benthal origin) in Portland Harbor. (Woodard-USGS)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28525787','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28525787"><span><span class="hlt">Metals</span> in the Scheldt estuary: From environmental <span class="hlt">concentrations</span> to bioaccumulation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Van Ael, Evy; Blust, Ronny; Bervoets, Lieven</p> <p>2017-09-01</p> <p>To investigate the relationship between <span class="hlt">metal</span> <span class="hlt">concentrations</span> in abiotic compartments and in aquatic species, sediment, suspended matter and several aquatic species (Polychaeta, Oligochaeta, four crustacean species, three mollusc species and eight fish species) were collected during three seasons at six locations along the Scheldt estuary (the Netherlands-Belgium) and analysed on their <span class="hlt">metal</span> content (Ag, Cd, Co, Cr, Cu, Ni, Pb, Zn and the metalloid As). Sediment and biota tissue <span class="hlt">concentrations</span> were significantly influenced by sampling location, but not by season. Measurements of Acid Volatile Sulphides (AVS) <span class="hlt">concentrations</span> in relation to Simultaneously Extracted <span class="hlt">Metals</span> (SEM) in the sediment suggested that not all <span class="hlt">metals</span> in the sediment will be bound to sulphides and some <span class="hlt">metals</span> might be bioavailable. For all <span class="hlt">metals</span> but zinc, highest <span class="hlt">concentrations</span> were measured in invertebrate species; Ag and Ni in periwinkle, Cr, Co and Pb in Oligochaete worms and As, Cd and Cu in crabs and shrimp. Highest <span class="hlt">concentrations</span> of Zn were measured in the kidney of European smelt. In fish, for most of the <span class="hlt">metals</span>, the <span class="hlt">concentrations</span> were highest in liver or kidney and lowest in muscle. For Zn however, highest <span class="hlt">concentrations</span> were measured in the kidney of European smelt. For less than half of the <span class="hlt">metals</span> significant correlations between sediment <span class="hlt">metal</span> <span class="hlt">concentrations</span> and bioaccumulated <span class="hlt">concentrations</span> were found (liver/hepatopancreas or whole organism). To calculate the possible human health risk by consumption, average and maximum <span class="hlt">metal</span> <span class="hlt">concentrations</span> in the muscle tissues were compared to the minimum risk levels (MRLs). <span class="hlt">Concentrations</span> of As led to the highest risk potential for all consumable species. Cadmium and Cu posed only a risk when consuming the highest contaminated shrimp and shore crabs. Consuming blue mussel could result in a risk for the <span class="hlt">metals</span> As, Cd and Cr. Copyright © 2017 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25947245','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25947245"><span>Glucose <span class="hlt">concentration</span> alters <span class="hlt">dissolved</span> oxygen levels in liquid cultures of Beauveria bassiana and affects formation and bioefficacy of blastospores.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mascarin, Gabriel Moura; Jackson, Mark A; Kobori, Nilce Naomi; Behle, Robert W; Dunlap, Christopher A; Delalibera Júnior, Ítalo</p> <p>2015-08-01</p> <p>The filamentous fungus Beauveria bassiana is an economically important pathogen of numerous arthropod pests and is able to grow in submerged culture as filaments (mycelia) or as budding yeast-like blastospores. In this study, we evaluated the effect of <span class="hlt">dissolved</span> oxygen and high glucose <span class="hlt">concentrations</span> on blastospore production by submerged cultures of two isolates of B. bassiana, ESALQ1432 and GHA. Results showed that maintaining adequate <span class="hlt">dissolved</span> oxygen levels coupled with high glucose <span class="hlt">concentrations</span> enhanced blastospore yields by both isolates. High glucose <span class="hlt">concentrations</span> increased the osmotic pressure of the media and coincided with higher <span class="hlt">dissolved</span> oxygen levels and increased production of significantly smaller blastospores compared with blastospores produced in media with lower <span class="hlt">concentrations</span> of glucose. The desiccation tolerance of blastospores dried to less than 2.6 % moisture was not affected by the glucose <span class="hlt">concentration</span> of the medium but was isolate dependent. Blastospores of isolate ESALQ1432 produced in media containing 140 g glucose L(-1) showed greater virulence toward whitefly nymphs (Bemisia tabaci) as compared with blastospores produced in media containing 40 g glucose L(-1). These results suggest a synergistic effect between glucose <span class="hlt">concentration</span> and oxygen availability on changing morphology and enhancing the yield and efficacy of blastospores of B. bassiana, thereby facilitating the development of a cost-effective production method for this blastospore-based bioinsecticide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24184125','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24184125"><span>Risk assessment, statistical source identification and seasonal fluctuation of <span class="hlt">dissolved</span> <span class="hlt">metals</span> in the Subarnarekha River, India.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Giri, Soma; Singh, Abhay Kumar</p> <p>2014-01-30</p> <p>Surface water samples were collected from 21 sampling sites throughout the Subarnarekha River during pre monsoon, monsoon and post monsoon seasons. The <span class="hlt">concentrations</span> of <span class="hlt">metals</span> were determined using inductively coupled plasma-mass spectrometry (ICP-MS) for the seasonal fluctuation, source apportionment and risk assessment. The results demonstrated that <span class="hlt">concentrations</span> of the <span class="hlt">metals</span> showed significant seasonality and most variables exhibited higher levels in the pre monsoon season. Principal component analysis (PCA) outcome of four factors together explained 76.9% of the variance with >1 initial eigenvalue indicated both innate and anthropogenic activities are contributing factors as source of <span class="hlt">metal</span> profusion in Subarnarekha River. Risk of <span class="hlt">metals</span> on human health was then evaluated using hazard quotients (HQ) by ingestion and dermal pathways for adult and child and it was indicated that As with HQingestion>1, was the most important pollutant leading to non-carcinogenic concerns. The largest contributors to chronic risks were As, V and Co, in all the seasons. The HQdermal of all the elements for adult and child were below unity, suggesting that the <span class="hlt">metals</span> posed little hazards via dermal absorption indicating that the oral intake was the primary exposure pathway.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25702935','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25702935"><span>Review of polyoxymethylene passive sampling methods for quantifying freely <span class="hlt">dissolved</span> porewater <span class="hlt">concentrations</span> of hydrophobic organic contaminants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Arp, Hans Peter H; Hale, Sarah E; Elmquist Kruså, Marie; Cornelissen, Gerard; Grabanski, Carol B; Miller, David J; Hawthorne, Steven B</p> <p>2015-04-01</p> <p>Meth ods involving polyoxymethylene (POM) as a passive sampler are increasing in popularity to assess contaminant freely <span class="hlt">dissolved</span> porewater <span class="hlt">concentrations</span> in soils and sediments. These methods require contaminant-specific POM-water partition coefficients, KPOM . Certain methods for determining KPOM perform reproducibly (within 0.2 log units). However, other methods can give highly varying KPOM values (up to 2 log units), especially for polycyclic aromatic hydrocarbons (PAHs). To account for this variation, the authors tested the influence of key methodological components in KPOM determinations, including POM thickness, extraction procedures, and environmental temperature and salinity, as well as uptake kinetics in mixed and static systems. All inconsistencies in the peer-reviewed literature can be accounted for by the likelihood that thick POM materials (500 μm or thicker) do not achieve equilibrium (causing negative biases up to 1 log unit), or that certain POM extraction procedures do not ensure quantitative extraction (causing negative biases up to 2 log units). Temperature can also influence KPOM , although all previous literature studies were carried out at room temperature. The present study found that KPOM values at room temperature are independent (within 0.2 log units) of POM manufacture method, of thickness between 17 μm and 80 μm, and of salinity between 0% and 10%. Regarding kinetics, monochloro- to hexachloro-polychlorinated biphenyls (PCBs) were within 0.2 log units of equilibrium after 28 d in the mixed system, but only dichloro-PCBs achieved near equilibrium after 126 d in the static system. Based on these insights, recommended methods and KPOM values to facilitate interlaboratory reproducibility are presented. © 2015 SETAC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28453974','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28453974"><span>Influences of <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> on biocathodic microbial communities in microbial fuel cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rago, Laura; Cristiani, Pierangela; Villa, Federica; Zecchin, Sarah; Colombo, Alessandra; Cavalca, Lucia; Schievano, Andrea</p> <p>2017-08-01</p> <p><span class="hlt">Dissolved</span> oxygen (DO) at cathodic interface is a critical factor influencing microbial fuel cells (MFC) performance. In this work, three MFCs were operated with cathode under different DO conditions: i) air-breathing (A-MFC); ii) water-submerged (W-MFC) and iii) assisted by photosynthetic microorganisms (P-MFC). A plateau of maximum current was reached at 1.06±0.03mA, 1.48±0.06mA and 1.66±0.04mA, increasing respectively for W-MFC, P-MFC and A-MFC. Electrochemical and microbiological tools (Illumina sequencing, confocal microscopy and biofilm cryosectioning) were used to explore anodic and cathodic biofilm in each MFC type. In all cases, biocathodes improved oxygen reduction reaction (ORR) as compared to abiotic condition and A-MFC was the best performing system. Photosynthetic cultures in the cathodic chamber supplied high DO level, up to 16mgO2L(-1), which sustained aerobic microbial community in P-MFC biocathode. Halomonas, Pseudomonas and other microaerophilic genera reached >50% of the total OTUs. The presence of sulfur reducing bacteria (Desulfuromonas) and purple non-sulfur bacteria in A-MFC biocathode suggested that the recirculation of sulfur compounds could shuttle electrons to sustain the reduction of oxygen as final electron acceptor. The low DO <span class="hlt">concentration</span> limited the cathode in W-MFC. A model of two different possible microbial mechanisms is proposed which can drive predominantly cathodic ORR. Copyright © 2017 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11385849','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11385849"><span>Closed-loop identification and control application for <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> in a full-scale coke wastewater treatment plant.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yoo, C K; Cho, J H; Kwak, H J; Choi, S K; Chun, H D; Lee, I</p> <p>2001-01-01</p> <p>The objective of this paper is to apply a closed-loop identification to actual <span class="hlt">dissolved</span> oxygen control system in the coke wastewater treatment plant. It approximates the <span class="hlt">dissolved</span> oxygen dynamics to a high order model using the integral transform method and reduces it to the first-order plus time delay (FOPTD) or second-order plus time delay (SOPTD) for the PID controller tuning. To experiment the process identification on the real plant, a simple set-point change of the speed of surface aerator under the closed-loop control without any mode change was used as an activation signal of the identification. The full-scale experimental results show a good identification performance and a good tracking ability for set-point change. As a result of improved control performance, the fluctuation of <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> variation has been decreased and the electric power saving has been accomplished.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19908907','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19908907"><span>Measuring low picogram per liter <span class="hlt">concentrations</span> of freely <span class="hlt">dissolved</span> polychlorinated biphenyls in sediment pore water using passive sampling with polyoxymethylene.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hawthorne, Steven B; Miller, David J; Grabanski, Carol B</p> <p>2009-11-15</p> <p>Studies into bioaccumulation of polychlorinated biphenyls (PCBs) have increasingly focused on congeners that are freely <span class="hlt">dissolved</span> in sediment interstitial pore water. Because of their low water solubilities and their tendency to persist and <span class="hlt">concentrate</span> as they progress in the food chain, interest has grown in methods capable of measuring individual PCB congeners at low part-per-quadrillion (picogram per liter) <span class="hlt">concentrations</span>. Obtaining large volumes of pore water is difficult (or impossible), which makes conventional analytical approaches incapable of attaining suitable detection limits. In the present study, nondepletive sampling is used to achieve very low detection limits of freely <span class="hlt">dissolved</span> PCBs, while requiring no separation of the sediment and water slurry. Commercially available 76 microm thick polyoxymethylene (POM) coupons were placed directly into wet sediments and left to reach equilibrium with the pore water and sediment PCBs for up to 84 days, with 28 days found to be sufficient. Freely <span class="hlt">dissolved</span> <span class="hlt">concentrations</span> were then calculated by dividing the PCB <span class="hlt">concentration</span> found in the POM by its POM/water partitioning coefficient (K(POM)). The K(POM) values required for determining water <span class="hlt">concentrations</span> were measured using two spiked sediments and two historically contaminated sediments for all 62 PCB congeners that are present at greater than trace <span class="hlt">concentrations</span> in commercial Aroclors. Log K(POM) values ranged from ca. 4.6 for dichloro-congeners to ca. 7.0 for octachloro-congeners and correlate well with octanol/water coefficients (K(OW)) (r(2) = 0.947) so that a simple linear equation can be used to calculate <span class="hlt">dissolved</span> <span class="hlt">concentrations</span> within a factor of 2 or better for congeners having no measured K(POM) value. Detection limits for freely <span class="hlt">dissolved</span> PCBs ranged from ca. 20 pg/L (part-per-quadrillion) for dichloro-congeners down to ca. 0.2 pg/L for higher-molecular-weight congeners. Sorption isotherms were found to be linear (r(2) > 0.995) over at least 3</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.water.usgs.gov/ofr2004-1214/','USGSPUBS'); return false;" href="http://pubs.water.usgs.gov/ofr2004-1214/"><span><span class="hlt">Dissolved</span> Pesticide and Organic Carbon <span class="hlt">Concentrations</span> Detected in Surface Waters, Northern Central Valley, California, 2001-2002</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Orlando, James L.; Jacobson, Lisa A.; Kuivila, Kathryn</p> <p>2004-01-01</p> <p>Field and laboratory studies were conducted to determine the effects of pesticide mixtures on Chinook salmon under various environmental conditions in surface waters of the northern Central Valley of California. This project was a collaborative effort between the U.S. Geological Survey (USGS) and the University of California. The project focused on understanding the environmental factors that influence the toxicity of pesticides to juvenile salmon and their prey. During the periods January through March 2001 and January through May 2002, water samples were collected at eight surface water sites in the northern Central Valley of California and analyzed by the USGS for <span class="hlt">dissolved</span> pesticide and <span class="hlt">dissolved</span> organic carbon <span class="hlt">concentrations</span>. Water samples were also collected by the USGS at the same sites for aquatic toxicity testing by the Aquatic Toxicity Laboratory at the University of California Davis; however, presentation of the results of these toxicity tests is beyond the scope of this report. Samples were collected to characterize <span class="hlt">dissolved</span> pesticide and <span class="hlt">dissolved</span> organic carbon <span class="hlt">concentrations</span>, and aquatic toxicity, associated with winter storm runoff concurrent with winter run Chinook salmon out-migration. Sites were selected that represented the primary habitat of juvenile Chinook salmon and included major tributaries within the Sacramento and San Joaquin River Basins and the Sacramento?San Joaquin Delta. Water samples were collected daily for a period of seven days during two winter storm events in each year. Additional samples were collected weekly during January through April or May in both years. <span class="hlt">Concentrations</span> of 31 currently used pesticides were measured in filtered water samples using solid-phase extraction and gas chromatography-mass spectrometry at the U.S. Geological Survey's organic chemistry laboratory in Sacramento, California. <span class="hlt">Dissolved</span> organic carbon <span class="hlt">concentrations</span> were analyzed in filtered water samples using a Shimadzu TOC-5000A total organic carbon</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2011-title46-vol5/pdf/CFR-2011-title46-vol5-sec148-285.pdf','CFR2011'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2011-title46-vol5/pdf/CFR-2011-title46-vol5-sec148-285.pdf"><span>46 CFR 148.285 - <span class="hlt">Metal</span> sulfide <span class="hlt">concentrates</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2011&page.go=Go">Code of Federal Regulations, 2011 CFR</a></p> <p></p> <p>2011-10-01</p> <p>... 46 Shipping 5 2011-10-01 2011-10-01 false <span class="hlt">Metal</span> sulfide <span class="hlt">concentrates</span>. 148.285 Section 148.285... MATERIALS THAT REQUIRE SPECIAL HANDLING Special Requirements for Certain Materials § 148.285 <span class="hlt">Metal</span> sulfide <span class="hlt">concentrates</span>. (a) When information given by the shipper under § 148.60 of this part indicates that the...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2013-title46-vol5/pdf/CFR-2013-title46-vol5-sec148-285.pdf','CFR2013'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2013-title46-vol5/pdf/CFR-2013-title46-vol5-sec148-285.pdf"><span>46 CFR 148.285 - <span class="hlt">Metal</span> sulfide <span class="hlt">concentrates</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2013&page.go=Go">Code of Federal Regulations, 2013 CFR</a></p> <p></p> <p>2013-10-01</p> <p>... 46 Shipping 5 2013-10-01 2013-10-01 false <span class="hlt">Metal</span> sulfide <span class="hlt">concentrates</span>. 148.285 Section 148.285... MATERIALS THAT REQUIRE SPECIAL HANDLING Special Requirements for Certain Materials § 148.285 <span class="hlt">Metal</span> sulfide <span class="hlt">concentrates</span>. (a) When information given by the shipper under § 148.60 of this part indicates that the...</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2014-title46-vol5/pdf/CFR-2014-title46-vol5-sec148-285.pdf','CFR2014'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2014-title46-vol5/pdf/CFR-2014-title46-vol5-sec148-285.pdf"><span>46 CFR 148.285 - <span class="hlt">Metal</span> sulfide <span class="hlt">concentrates</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2014&page.go=Go">Code of Federal Regulations, 2014 CFR</a></p> <p></p> <p>2014-10-01</p> <p>... 46 Shipping 5 2014-10-01 2014-10-01 false <span class="hlt">Metal</span> sulfide <span class="hlt">concentrates</span>. 148.285 Section 148.285... MATERIALS THAT REQUIRE SPECIAL HANDLING Special Requirements for Certain Materials § 148.285 <span class="hlt">Metal</span> sulfide <span class="hlt">concentrates</span>. (a) When information given by the shipper under § 148.60 of this part indicates that the...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24694698','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24694698"><span>Modeling <span class="hlt">metal</span> binding by <span class="hlt">dissolved</span> humic substance: a revisit to the fluorometric titration approach.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Hao; Meng, Wei; Lei, Kun</p> <p>2014-01-01</p> <p>It is desirable to directly investigate <span class="hlt">metal</span> cation binding by <span class="hlt">dissolved</span> humic substance (HS) in environmental samples without isolation and purification of the HS. This is commonly achieved by the fluorometric titration approach, in which the variations of the HS components' fluorescence when titrated with <span class="hlt">metal</span> cations, such as cupric ions (Cu(2+)), were commonly resolved by a well-established chemometric tool called parallel factor analysis and fit to a classical nonlin ear equation to obtain cation binding parameters. The nonlinear expression was derived based on the two assumptions that a given HS component (e.g., L) binds Cu(2+) with a 1:1 stoichiometry, forming only the complex LCu, and that other ligands competing with L for Cu(2+) are not explicitly considered. Given the deviations (e.g., the presence of multiple HS components competing for Cu(2+) and a likely 2:1 binding stoichiometry in addition to the 1:1 binding) from the assumptions, the fitting-derived binding parameters reported in past studies are questionable; those studies commonly reported high goodness-of-fit (R(2)) as a support of the validity of the assumptions. This study deconstructed the current equation and examined it with two organic ligand components in a simulated study to see what conditions could also yield a good fit. It turned out that high a R(2) value ranging between 0.9971 and 1.0 was observed despite the deviations from the above-mentioned assumptions. In addition, this study re-evaluated some published experimental data from these past studies and found that the fitting-derived parameters could not be accounted for based on the above-mentioned assumptions. The findings in this study therefore indicate that the current fluorometric titration approach is problematic when investigating HS component interactions with <span class="hlt">metal</span> ions in situ. The combination of ion-selective electrode and fluorometric titration may be an alternative to the current fluorometric titration approach alone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011OcScD...8.1505C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011OcScD...8.1505C"><span>Using <span class="hlt">dissolved</span> oxygen <span class="hlt">concentrations</span> to determine mixed layer depths in the Bellingshausen Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Castro-Morales, K.; Kaiser, J.</p> <p>2011-06-01</p> <p><span class="hlt">Concentrations</span> of oxygen (O2) and other <span class="hlt">dissolved</span> gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes; for example, in the context of net and gross biological production estimates. The mixed layer depth (zmix) may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of air-sea exchange differ for gases and heat, so that zmix defined using O2 may be different to zmix defined using temperature or density. Here, we propose to define an O2-based mixed layer depth, zmix(O2), as the depth where the relative difference between the O2 <span class="hlt">concentration</span> and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by numerical analysis of O2 profiles in coastal areas of the Southern Ocean and corroborated by visual inspection. Comparisons of zmix(O2) with zmix based on potential temperature differences, i.e. zmix(Δθ = 0.2 °C) and zmix(Δθ = 0.5 °C), and potential density differences, i.e. zmix(Δσθ = 0.03 kg m-3) and zmix(Δσθ = 0.125 kg m-3), showed that zmix(O2) closely follows zmix(Δσθ = 0.03 kg m-3). Further comparisons with published zmix climatologies and zmix derived from World Ocean Atlas 2005 data were also performed. To establish zmix for use with biological production estimates in the absence of O2 profiles, we suggest using zmix(Δσθ = 0.03 kg m-3), which is also the basis for the climatology by de Boyer Montégut et al. (2004).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JMS....73..284O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JMS....73..284O"><span>Diatom stratigraphy and long-term <span class="hlt">dissolved</span> silica <span class="hlt">concentrations</span> in the Baltic Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olli, Kalle; Clarke, Annemarie; Danielsson, Åsa; Aigars, Juris; Conley, Daniel J.; Tamminen, Timo</p> <p>2008-10-01</p> <p>In many parts of the world coastal waters with anthropogenic eutrophication have experienced a gradual depletion of <span class="hlt">dissolved</span> silica (DSi) stocks. This could put pressure on spring bloom diatom populations, e.g. by limiting the intensity of blooms or by causing shifts in species composition. In addition, eutrophication driven enhanced diatom growth is responsible for the redistribution of DSi from the water phase to the sediments, and changes in the growth conditions may be reflected in the sediment diatom stratigraphy. To test for changes in diatom communities we have analyzed four sediment cores from the Baltic Sea covering approximately the last 100 years. The sediment cores originate from the western Gulf of Finland, the Kattegat, the Baltic Proper and the Gulf of Riga. Three out of the four cores reveal only minor changes in composition of diatom assemblages, while the Gulf of Riga core contains major changes, occurring after the second World War. This area is set apart from the other Baltic Sea basins by a high frequency of low after spring bloom DSi <span class="hlt">concentrations</span> (< 2 µmol L - 1 ) during a relatively well defined time period from 1991-1998. In 1991 to 1993 a rapid decline of DSi spring <span class="hlt">concentrations</span> and winter stocks (down to 5 µmol L - 1 ) in the Gulf was preceded by exceptionally intense diatom spring blooms dominated by the heavily silicified species Thalassiosira baltica (1991-1992; up to 5.5 mg ww L - 1 ). T. baltica has been the principal spring bloom diatom in the Gulf of Riga since records began in 1975. DSi consumption and biomass yield experiments with cultured T. baltica suggest that intense blooms can potentially exhaust the DSi stock of the water column and exceed the annual Si dissolution in the Gulf of Riga. The phytoplankton time series reveals another exceptional T. baltica bloom period in 1981-1983 (up to 8 mg L - 1 ), which, however, took place before the regular DSi measurements. These periods may be reflected in the conspicuous</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26233328','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26233328"><span>Maximizing biomass <span class="hlt">concentration</span> in baker's yeast process by using a decoupled geometric controller for substrate and <span class="hlt">dissolved</span> oxygen.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chopda, Viki R; Rathore, Anurag S; Gomes, James</p> <p>2015-11-01</p> <p>Biomass production by baker's yeast in a fed-batch reactor depends on the metabolic regime determined by the <span class="hlt">concentration</span> of glucose and <span class="hlt">dissolved</span> oxygen in the reactor. Achieving high biomass <span class="hlt">concentration</span> in turn is dependent on the dynamic interaction between the glucose and <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span>. Taking this into account, we present in this paper the implementation of a decoupled input-output linearizing controller (DIOLC) for maximizing biomass in a fed-batch yeast process. The decoupling is based on the inversion of 2×2 input-output matrix resulting from global linearization. The DIOLC was implemented online using a platform created in LabVIEW employing a TCP/IP protocol via the reactor's built-in electronic system. An improvement in biomass yield by 23% was obtained compared to that using a PID controller. The results demonstrate superior capability of the DIOLC and that the cumulative effect of smoother control action contributes to biomass maximization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27338563','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27338563"><span>Role of <span class="hlt">Dissolved</span> Organic Matter in Sorption of Perfluorooctanoic Acid to <span class="hlt">Metal</span> Oxides.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yang, Kai-Hsing; Ruan, Ci-Jie; Lin, Yen-Ching; Fang, Meng-Der; Wu, Chung-Hsin; Hong, Pui-Kwan Andy; Lin, Cheng-Fang</p> <p>2016-08-01</p> <p>Perfluorooctanoic acid (PFOA) is an important perfluorinated chemical of significant environmental concern. It has been widely found at high <span class="hlt">concentrations</span> in the environment. We have exposed sediment constituent minerals SiO2, Fe2O3, and Al2O3 to PFOA and humic acid (HA) and studied the adsorption of PFOA by introducing the adsorbates in different orders. The results suggest concurrent sorption of PFOA and HA to the mineral surface or enhanced PFOA sorption when both are introduced to the aqueous phase. However, when PFOA is introduced to the mineral surface that has already been exposed to and extensively coated with HA, little PFOA adsorption occurs, which implies that PFOA released to rivers rich in <span class="hlt">dissolved</span> organic matter (DOM, i.e. HA) may be immune to sorptive retention by the sediment and be transported downstream unabated. DOM thus can play a significant role in the transport and fate of PFOA in the natural water system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1510725C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1510725C"><span>Understanding and modelling the variability in <span class="hlt">Dissolved</span> Organic Carbon <span class="hlt">concentrations</span> in catchment drainage</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coleman, Martin; Waldron, Susan; Scott, Marian; Drew, Simon</p> <p>2013-04-01</p> <p>Our knowledge of dynamic natural habitats could be improved through the deployment of automated sensor technology. <span class="hlt">Dissolved</span> organic carbon <span class="hlt">concentrations</span>, [DOC], are of interest to water companies as purification removes this pool and currently in environmental science, due in part to rising DOC levels and also as respiration of this C pool can lead to an increased CO2 efflux. Manual sampling of catchment drainage systems has revealed seasonal patterns in DOC (Williams, P.J.L., 1995) and that hydrological events export most DOC(Raymond, P.A. and J.E. Saiers, 2010). However, manual sampling precludes detailed characterisation of the dynamic fluctuation of DOC over shorter but important time periods e.g. immediately prior to an event; the transition from base flow to a surface run-off dominated system as surface flow pathways defrost. Such insight is only gained through deployment of continuous-monitoring equipment. Since autumn 2010 we have deployed an S::CAN Spectrolyser (which from absorbance gives a measurement of [DOC]) in a 7.5 kilometre squared peaty catchment draining Europe's largest windfarm, Whitelee. Since autumn 2011, we have an almost complete time series of [DOC] every 30. Here [DOC] has ranged from 12.2 to 58.4 mg/l C and during event flow DOC had a maximum variation of 23.5 mg/l within a single day. Simultaneously with the Spectrolyser, we have logged stage height, pH and conductivity using an In-Situ Inc MD Troll 9000. Generally there is an inverse relationship between [DOC] and both pH and conductivity, but a positive relationship (albeit with seasonal differences) with [DOC] and stage height, from which we can infer hydrological changes in the source of the DOC. Here, in addition to presenting the time series of the data, and a more accurate export budget estimate, I will explore statistical methods for the handling of large datasets. Trends in the data of such large and dynamic data sets are challenging to model. Simple relationships with stage</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/49618','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/49618"><span>Trace <span class="hlt">metal</span> <span class="hlt">concentrations</span> in estuaries and coastal regions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hunt, C.D.</p> <p>1994-12-31</p> <p>Estuaries and coastal regions are highly variable in the physical and hydrographic conditions. As a result of heavy urbanization and industrialization of the head waters of most estuaries, there are substantial localized inputs of contaminants to the estuary. These factors combined with the flushing characteristics of individual estuaries to create relatively unique features that result in variation in the typical levels of trace <span class="hlt">metals</span> for these systems. This makes intercomparison of the estuaries difficult. Comparability among estuaries becomes even more difficult when <span class="hlt">metals</span> analyses are conducted without proper control of field and laboratory contamination, now firmly established in the trace <span class="hlt">metal</span> analytical literature as a prerequisite for reliable marine trace <span class="hlt">metals</span> analysis. This paper compares the <span class="hlt">concentrations</span> of selected trace <span class="hlt">metal</span> (Ag, Cd, Cu, Ni, Pb, and Zn) <span class="hlt">concentrations</span> in the waters of several major estuaries of the United States. The basis of comparison is that all samples war collected under rigid trace <span class="hlt">metal</span> clean collection and analysis procedures. Generally, <span class="hlt">metal</span> <span class="hlt">concentrations</span> within the estuaries are similar. <span class="hlt">Metal</span> <span class="hlt">concentrations</span> in the higher salinity coastal regions are more similar in <span class="hlt">concentration</span>. The comparison provides a baseline of typical <span class="hlt">concentrations</span> of these trace <span class="hlt">metals</span> in the coastal waters against which future analytical results can be compared.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24047546','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24047546"><span>Passive sampling: an effective method for monitoring seasonal and spatial variability of <span class="hlt">dissolved</span> hydrophobic organic contaminants and <span class="hlt">metals</span> in the Danube river.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vrana, Branislav; Klučárová, Veronika; Benická, Eva; Abou-Mrad, Ninette; Amdany, Robert; Horáková, Soňa; Draxler, Astrid; Humer, Franko; Gans, Oliver</p> <p>2014-01-01</p> <p>Application of passive samplers is demonstrated for assessment of temporal and spatial trends of <span class="hlt">dissolved</span> polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and priority <span class="hlt">metals</span> in the middle stretch of the Danube river. Free <span class="hlt">dissolved</span> <span class="hlt">concentrations</span> of PAHs, measured using SPMD samplers, ranged from 5 to 72 ng L(-1). <span class="hlt">Dissolved</span> PCBs in water were very low and they ranged from 5 to 16 pg L(-1). <span class="hlt">Concentration</span> of mercury, cadmium, lead and nickel, measured using DGT samplers, were relatively constant along the monitored Danube stretch and in the range <0.1, <1-20, 18-74, and 173-544 ng L(-1), respectively. <span class="hlt">Concentrations</span> of PAHs decreased with increasing temperature, which reflects the seasonality in emissions to water. This has an implication for the design of future monitoring programs aimed at assessment of long term trends. For such analysis time series should be constructed of data from samples collected always in the same season of the year.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5358677','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5358677"><span>Analysis of environmental issues related to small-scale hydroelectric development. VI. <span class="hlt">Dissolved</span> oxygen <span class="hlt">concentrations</span> below operating dams</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cada, G.F.; Kumar, K.D.; Solomon, J.A.; Hildebrand, S.G.</p> <p>1982-01-01</p> <p>Results are presented of an effort aimed at determining whether or not water quality degradation, as exemplified by <span class="hlt">dissolved</span> oxygen <span class="hlt">concentrations</span>, is a potentially significant issue affecting small-scale hydropower development in the US. The approach was to pair operating hydroelectric sites of all sizes with <span class="hlt">dissolved</span> oxygen measurements from nearby downstream US Geological Survey water quality stations (acquired from the WATSTORE data base). The USGS data were used to calculate probabilities of non-compliance (PNCs), i.e., the probabilities that <span class="hlt">dissolved</span> oxygen <span class="hlt">concentrations</span> in the discharge waters of operating hydroelectric dams will drop below 5 mg/l. PNCs were estimated for each site, season (summer vs remaining months), and capacity category (less than or equal to 30 MW vs >30 MW). Because of the low numbers of usable sites in many states, much of the subsequent analysis was conducted on a regional basis. During the winter months (November through June) all regions had low mean PNCs regardless of capacity. Most regions had higher mean PNCs in summer than in winter, and summer PNCs were greater for large-scale than for small-scale sites. Among regions, the highest mean summer PNCs were found in the Great Basin, the Southeast, and the Ohio Valley. To obtain a more comprehensive picture of the effects of season and capacity on potential <span class="hlt">dissolved</span> oxygen problems, cumulative probability distributions of PNC were developed for selected regions. This analysis indicates that low <span class="hlt">dissolved</span> oxygen <span class="hlt">concentrations</span> in the tailwaters below operating hydroelectric projects are a problem largely confined to large-scale facilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23973544','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23973544"><span><span class="hlt">Concentration</span> and characteristics of <span class="hlt">dissolved</span> carbon in the Sanjiang Plain influenced by long-term land reclamation from marsh.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Guo, Y D; Lu, Y Z; Song, Y Y; Wan, Z M; Hou, A X</p> <p>2014-01-01</p> <p>Since the 1960s, the marshes in the Sanjiang Plain, Northeast China, which are an important reservoir for <span class="hlt">dissolved</span> carbon, have undergone long-term reclamation to farmland, resulting in elevated marsh loss and degradation on a large scale. This study compared the <span class="hlt">concentrations</span> of <span class="hlt">dissolved</span> carbon, as well as the chemical characteristics of <span class="hlt">dissolved</span> organic carbon (DOC), in natural marshes, a degraded marsh, and drainage ditches sampled during the growing seasons between 2008 and 2010 to clarify the temporal-spatial variability of the <span class="hlt">dissolved</span> carbon in the fluvial system influenced by the long-term reclamation. The results show that the average <span class="hlt">concentrations</span> of total <span class="hlt">dissolved</span> carbon (TDC) and DOC are considerably greater in the natural marshes than in the degraded marsh and drainage ditches. The average DOC <span class="hlt">concentration</span> for the natural marshes, approximately 35.53 ± 5.15 mg L(-1), is approximately 2.39 times that in the degraded marsh (14.84 ± 4.21 mg L(-1)) and 2.77 times the average value in the ditches (12.84 ± 4.49 mg L(-1)). The <span class="hlt">dissolved</span> inorganic carbon (DIC) exhibits increased trends in the drainage ditches compared with the natural marshes, whereas the hydrophobic fraction of DOC is present at lower <span class="hlt">concentrations</span> in the degraded marsh and ditches. Fluorescence indices also indicate that the DOC in the degraded marsh and ditches has a simpler humification structure. In total, the long-term reclamation has led to great variability in the DOC <span class="hlt">concentration</span> and chemical characteristics in the fluvial system. Changes in the DOC production potential and hydrological regimes due to sustained reclamation are deemed the predominant causes of this effect. The continuously decreased DOC <span class="hlt">concentration</span> and high variability of DOC in the surface fluvial systems are inevitable if reclamation continues in the Sanjiang Plain. More importantly, the presence of tyrosine and tryptophan-like substances in the ditches indicates that there has been extensive</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/sir/2014/5012/pdf/sir2014-5012.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/sir/2014/5012/pdf/sir2014-5012.pdf"><span><span class="hlt">Dissolved</span>-solids sources, loads, yields, and <span class="hlt">concentrations</span> in streams of the conterminous United States</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Anning, David W.; Flynn, Marilyn E.</p> <p>2014-01-01</p> <p>Results from the trend analysis and from the SPARROW model indicate that, compared to monitoring stations with no trends or decreasing trends, stations with increasing trends are associated with a smaller percentage of the predicted <span class="hlt">dissolved</span>-solids load originating from geologic sources, and a larger percentage originating from urban lands and road deicers. Conversely, compared to stations with increasing trends or no trends, stations with decreasing trends have a larger percentage of the predicted <span class="hlt">dissolved</span>-solids load originating from geologic sources and a smaller percentage originating from urban lands and road deicers. Stations with decreasing trends also have larger percentages of predicted <span class="hlt">dissolved</span>-solids load originating from cultivated lands and pasture lands, compared to stations with increasing trends or no trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=111608&keyword=Exchange+AND+rate+AND+effects&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78280996&CFTOKEN=76953179','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=111608&keyword=Exchange+AND+rate+AND+effects&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78280996&CFTOKEN=76953179"><span>ION EXCHANGE SOFTENING: EFFECTS ON <span class="hlt">METAL</span> <span class="hlt">CONCENTRATIONS</span></span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>A corrosion control pipe loop study to evaluate the effect of ion exchange water softening on <span class="hlt">metal</span> leaching from household plumbing materials was conducted on two different water qualities having different pH's and hardness levels. The results showed that removing hardness ions ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=111608&keyword=TIC&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=111608&keyword=TIC&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>ION EXCHANGE SOFTENING: EFFECTS ON <span class="hlt">METAL</span> <span class="hlt">CONCENTRATIONS</span></span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>A corrosion control pipe loop study to evaluate the effect of ion exchange water softening on <span class="hlt">metal</span> leaching from household plumbing materials was conducted on two different water qualities having different pH's and hardness levels. The results showed that removing hardness ions ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19738957','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19738957"><span>Modeling chlorophyll-a and <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> in tropical floodplain lakes (Paraná River, Brazil).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rocha, R R A; Thomaz, S M; Carvalho, P; Gomes, L C</p> <p>2009-06-01</p> <p>The need for prediction is widely recognized in limnology. In this study, data from 25 lakes of the Upper Paraná River floodplain were used to build models to predict chlorophyll-a and <span class="hlt">dissolved</span> oxygen <span class="hlt">concentrations</span>. Akaike's information criterion (AIC) was used as a criterion for model selection. Models were validated with independent data obtained in the same lakes in 2001. Predictor variables that significantly explained chlorophyll-a <span class="hlt">concentration</span> were pH, electrical conductivity, total seston (positive correlation) and nitrate (negative correlation). This model explained 52% of chlorophyll variability. Variables that significantly explained <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> were pH, lake area and nitrate (all positive correlations); water temperature and electrical conductivity were negatively correlated with oxygen. This model explained 54% of oxygen variability. Validation with independent data showed that both models had the potential to predict algal biomass and <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> in these lakes. These findings suggest that multiple regression models are valuable and practical tools for understanding the dynamics of ecosystems and that predictive limnology may still be considered a powerful approach in aquatic ecology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27834048','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27834048"><span>Distribution and health risk assessment of <span class="hlt">dissolved</span> heavy <span class="hlt">metals</span> in the Three Gorges Reservoir, China (section in the main urban area of Chongqing).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhao, Xin; Li, Ting-Yong; Zhang, Tao-Tao; Luo, Wei-Jun; Li, Jun-Yun</p> <p>2017-01-01</p> <p>The Three Gorges Project (TGP) is the largest hydropower station ever built in the world. A better understanding of the <span class="hlt">concentrations</span> of heavy <span class="hlt">metals</span> in the aquatic environment of the Three Gorges Reservoir (TGR) is crucial for national drinking water security and sustainable ecosystem development. To thoroughly investigate the impact of heavy <span class="hlt">metals</span> on water quality after the impoundment to the maximum level of 175 m in the TGR, the <span class="hlt">concentrations</span> of the <span class="hlt">dissolved</span> heavy <span class="hlt">metals</span> (Cr, Cu, Zn, Cd, Pb, As) were measured in April and August 2015, by inductively coupled plasma mass spectrometry (ICP-MS). (1) Except Zn and Pb, most of the heavy <span class="hlt">metal</span> <span class="hlt">concentrations</span> in the water of the TGR reached the level of the National Surface Water Environmental Quality Standards (GB3838-2002) I of China, revealing that the water quality of the TGR was good overall. (2) There were significant positive correlations among the <span class="hlt">concentrations</span> of Cu, As, and Cd, revealing that they may exhibit similar geochemical behaviors. (3) The spatial distribution of the heavy <span class="hlt">metal</span> <span class="hlt">concentrations</span> was diverse and complex. The Zn <span class="hlt">concentration</span> obviously increased in the rainy season from upstream to downstream in the Yangtze River, while the other heavy <span class="hlt">metals</span> exhibited no significant changes in their <span class="hlt">concentrations</span>. The distribution characteristics of the heavy <span class="hlt">metal</span> <span class="hlt">concentrations</span> on both sides and the middle of the river were different at different sites. (4) The health risk of the six elements was assessed through a human health risk assessment (HHRA), and the assessment results were lower than the maximum acceptable risk level designed by the US EPA and International Commission on Radiological Protection (ICRP). The HHRA model in the aquatic environment revealed that the risk of non-carcinogenic heavy <span class="hlt">metals</span> (Cu, Zn, and Pb) was at a negligible risk level of 10(-11)∼10(-9) a(-1). At all the study sites, the risk of carcinogenic heavy <span class="hlt">metals</span> (Cr, Cd, and As) was higher than the risk of non</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23219386','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23219386"><span>Diurnal variations of <span class="hlt">dissolved</span> and colloidal organic carbon and trace <span class="hlt">metals</span> in a boreal lake during summer bloom.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pokrovsky, O S; Shirokova, L S</p> <p>2013-02-01</p> <p>This work describes variation of element <span class="hlt">concentration</span> in surface water of a subarctic organic-rich lake during the diurnal cycle of photosynthesis. An unusually hot summer 2010 in European part of subarctic Russia produced elevated surface water temperature (28-30 °C) and caused massive cyanobacterial bloom. Diurnal variation of ~40 <span class="hlt">dissolved</span> macro and trace elements and organic carbon were recorded in the humic Lake Svyatoe in the White Sea drainage basin. Two days continuous measurements with 3 h sampling steps at the surface (0.5 m) allowed tracing cyanobacterial activity via pH and O₂ measurement and revealed constant <span class="hlt">concentrations</span> (within ±20-30%) of all major elements (Na, Mg, Cl, SO₄, K, Ca), organic and inorganic carbon and most trace elements (Li, B, Sc, Ti, Ni, Cu, Ga, As, Rb, Sr, Y, Zr, Mo, Sb, medium and heavy REEs, Hf, Pb, Th, U). The <span class="hlt">concentration</span> of Mn demonstrated a factor of 3 decrease during the day following Mn adsorption onto cyanobacterial cells due to ~1 pH unit raise during the photosynthesis and Mn release during the night due to desorption from the cell surface. The role of Mn(II) photo-oxidation by reactive oxygen species could be also pronounced, although its contribution to Mn diurnal variation was much smaller than the adsorption at the cell surfaces. Similar pattern, but with much lesser variations (c.a., 10-20%), was recorded for Ba and Fe. On-site ultrafiltration technique allowed to distinguish between low molecular weight (LMW) complexes (<1 kDa) and high molecular weight (HMW) colloids (1 kDa-0.22 μm) and to assess their diurnal pattern. Colloidal Al and Fe were the highest during the night, when the contribution of HMW allochthonous colloids was maximal. Typical insoluble trivalent and tetravalent elements exhibited constant complexation (>80-90%) with HMW allochthonous organics, independent on the diel photosynthetic cycle. Finally, biologically-relevant <span class="hlt">metals</span> (Cu, Co, Cr, V, and Ni) demonstrated significant variations</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=257180','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=257180"><span>Effect of daily minimum <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> on production of channel x blue hybrid catfish</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>As the channel x blue hybrid catfish is stocked by an increasing number of catfish farmers, it is important to quantify the production response of this fish to pond <span class="hlt">dissolved</span> oxygen management strategies. The purpose of this study was to quantify the production and water quality responses of the cha...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27479633','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27479633"><span>Measuring <span class="hlt">Concentrations</span> of <span class="hlt">Dissolved</span> Methane and Ethane and the (13) C of Methane in Shale and Till.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hendry, M Jim; Barbour, S Lee; Schmeling, Erin E; Mundle, Scott O C</p> <p>2017-01-01</p> <p>Baseline characterization of <span class="hlt">concentrations</span> and isotopic values of <span class="hlt">dissolved</span> natural gases is needed to identify contamination caused by the leakage of fugitive gases from oil and gas activities. Methods to collect and analyze baseline <span class="hlt">concentration</span>-depth profiles of <span class="hlt">dissolved</span> CH4 and C2 H6 and δ(13) C-CH4 in shales and Quaternary clayey tills were assessed at two sites in the Williston Basin, Canada. Core and cuttings samples were stored in Isojars(®) in a low O2 headspace prior to analysis. Measurements and multiphase diffusion modeling show that the gas <span class="hlt">concentrations</span> in core samples yield well-defined and reproducible depth profiles after 31-d equilibration. No measurable oxidative loss or production during core sample storage was observed. <span class="hlt">Concentrations</span> from cuttings and mud gas logging (including IsoTubes(®) ) were much lower than from cores, but correlated well. Simulations suggest the lower <span class="hlt">concentrations</span> from cuttings can be attributed to drilling time, and therefore their use to define gas <span class="hlt">concentration</span> profiles may have inherent limitations. Calculations based on mud gas logging show the method can provide estimates of core <span class="hlt">concentrations</span> if operational parameters for the mud gas capture cylinder are quantified. The δ(13) C-CH4 measured from mud gas, IsoTubes(®) , cuttings, and core samples are consistent, exhibiting slight variations that should not alter the implications of the results in identifying the sources of the gases. This study shows core and mud gas techniques and, to a lesser extent, cuttings, can generate high-resolution depth profiles of <span class="hlt">dissolved</span> hydrocarbon gas <span class="hlt">concentrations</span> and their isotopes. © 2016, National Ground Water Association.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23896418','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23896418"><span>Maternal exposure to <span class="hlt">metals--concentrations</span> and predictors of exposure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Callan, A C; Hinwood, A L; Ramalingam, M; Boyce, M; Heyworth, J; McCafferty, P; Odland, J Ø</p> <p>2013-10-01</p> <p>A variety of <span class="hlt">metals</span> are important for biological function but have also been shown to impact health at elevated <span class="hlt">concentrations</span>, whereas others have no known biological function. Pregnant women are a vulnerable population and measures to reduce exposure in this group are important. We undertook a study of maternal exposure to the <span class="hlt">metals</span>, aluminium, arsenic, copper, cobalt, chromium, lithium, manganese, nickel, selenium, tin, uranium and zinc in 173 participants across Western Australia. Each participant provided a whole blood and urine sample, as well as drinking water, residential soil and dust samples and completed a questionnaire. In general the <span class="hlt">concentrations</span> of <span class="hlt">metals</span> in all samples were low with the notable exception of uranium (blood U mean 0.07 µg/L, range <0.01-0.25 µg/L; urinary U mean 0.018 µg/g creatinine, range <0.01-0.199 µg/g creatinine). Factors that influenced biological <span class="hlt">concentrations</span> were consumption of fish which increased urinary arsenic <span class="hlt">concentrations</span>, hobbies (including mechanics and welding) which increased blood manganese <span class="hlt">concentrations</span> and iron/folic acid supplement use which was associated with decreased <span class="hlt">concentrations</span> of aluminium and nickel in urine and manganese in blood. Environmental <span class="hlt">concentrations</span> of aluminium, copper and lithium were found to influence biological <span class="hlt">concentrations</span>, but this was not the case for other environmental <span class="hlt">metals</span> <span class="hlt">concentrations</span>. Further work is underway to explore the influence of diet on biological <span class="hlt">metals</span> <span class="hlt">concentrations</span> in more detail. The high <span class="hlt">concentrations</span> of uranium require further investigation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70111598','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70111598"><span>Effect of water hardness and <span class="hlt">dissolved</span>-solid <span class="hlt">concentration</span> on hatching success and egg size in bighead carp</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Chapman, Duane C.; Deters, Joseph E.</p> <p>2009-01-01</p> <p>Bighead carp Hypophthalmichthys nobilis is an Asian species that has been introduced to the United States and is regarded as a highly undesirable invader. Soft water has been said to cause the bursting of Asian carp eggs and thus has been suggested as a factor that would limit the spread of this species. To evaluate this, we subjected fertilized eggs of bighead carp to waters with a wide range of hardness and <span class="hlt">dissolved</span>-solid <span class="hlt">concentrations</span>. Hatching rate and egg size were not significantly affected by the different water qualities. These results, combined with the low hardness (28–84 mg/L) of the Yangtze River (the primary natal habitat of Hypophthalmichthys spp.), suggest that managers and those performing risk assessments for the establishment of Hypophthalmichthys spp. should be cautious about treating low hardness and <span class="hlt">dissolved</span>-solid <span class="hlt">concentrations</span> as limiting factors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1322105','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1322105"><span>Fiber-based adsorbents having high adsorption capacities for recovering <span class="hlt">dissolved</span> <span class="hlt">metals</span> and methods thereof</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra</p> <p>2016-09-06</p> <p>A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of <span class="hlt">dissolved</span> <span class="hlt">metals</span>, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1131019','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1131019"><span>Fiber-based adsorbents having high adsorption capacities for recovering <span class="hlt">dissolved</span> <span class="hlt">metals</span> and methods thereof</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Janke, Christopher J; Dai, Sheng; Oyola, Yatsandra</p> <p>2014-05-13</p> <p>A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of <span class="hlt">dissolved</span> <span class="hlt">metals</span>, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20508984','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20508984"><span><span class="hlt">Concentrations</span> of some heavy <span class="hlt">metals</span> in water, suspended solids, and biota species from Maluan Bay, China and their environmental significance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Zaosheng; Yan, Changzhou; Pan, Qikun; Yan, Yijun</p> <p>2011-04-01</p> <p><span class="hlt">Concentrations</span> of heavy <span class="hlt">metals</span> (Cu, Zn, Cd, and Pb) in surface water (including total recoverable, <span class="hlt">dissolved</span>, suspended solids) and in aufwuchs encrusted on Moerella iridescens Benson from seven selected sites and two reference sites in Maluan Bay were investigated in order to understand current <span class="hlt">metal</span> contamination due to industrialization and urbanization in Xiamen, China. The muscle tissues of the study species (Penceus penicillatus, Scylla serrata Forskal, Harengula zunasi Bleeker, Tillapia nilotica) from a trawling area within Maluan Bay were also analyzed in order to evaluate its safety as seafood. Based on the obtained data, <span class="hlt">metal</span> <span class="hlt">concentrations</span> in surface water were compared with Marine Seawater Quality Standards of China and the US EPA acute and chronic criteria, which showed that Maluan Bay may be subjected to different levels of contamination by the <span class="hlt">metals</span>. <span class="hlt">Metal</span> <span class="hlt">concentrations</span> under study in the edible parts (muscle) of the investigated biota species were within the safety permissible levels for human consumption. Through Pearson's correlation analysis, the relationships between <span class="hlt">metal</span> <span class="hlt">concentrations</span> in surface water and in M. iridescens were evaluated. Copper <span class="hlt">concentrations</span> in M. iridescens were more strongly positively correlated with particulate copper in suspended solids and total recoverable copper in water rather than with <span class="hlt">dissolved</span> copper at the sampling sites. The data suggested that copper-rich suspended solids contributed substantially to copper accumulation by M. iridescens and played a critical role in the pathway of copper into the food chain. The conclusions of this investigation are likely to be applicable to other relevant scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25728204','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25728204"><span>The spatial distribution of <span class="hlt">dissolved</span> and particulate heavy <span class="hlt">metals</span> and their response to land-based inputs and tides in a semi-enclosed industrial embayment: Jiaozhou Bay, China.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Changyou; Liang, Shengkang; Li, Yanbin; Li, Keqiang; Wang, Xiulin</p> <p>2015-07-01</p> <p>In order to evaluate heavy <span class="hlt">metal</span> contamination in surface waters in the Jiaozhou Bay (JZB), a typical semi-enclosed bay in the north of China, and to identify the response of heavy <span class="hlt">metal</span> distribution to terrigenous sources and tides, the land-based discharge flux of <span class="hlt">dissolved</span> Cu, Pb, Zn and Cd and their particulates, as well as their <span class="hlt">concentrations</span>, were synchronously surveyed in JZB in flood season and normal season respectively. The survey results showed that the amount of <span class="hlt">dissolved</span> Cu clearly increased from the estuaries to the offshore waters during the flood season, especially from the Dagu estuary to the mouth of JZB. The same trend was observed for Pb. The isopleths of <span class="hlt">dissolved</span> Zn during the flood season presented a different pattern in which a clear decrease was observed from the Lianwan, Moshui and Dagu estuaries to the offshore waters. However, the particulate Cu isopleths during the flood season, which had the same pattern as those of particulate Pb, Zn and Cd, showed a clear decrease from the Dagu estuary to the mouth of JZB. The isopleths for <span class="hlt">dissolved</span> and particulate Cu during the normal season showed a clear decrease from the northeast to the entrance of JZB, and the same trend was observed for Pb, Zn and Cd. Observations based on synchronous investigations of the fluvial fluxes of the selected <span class="hlt">metals</span> and their average <span class="hlt">concentrations</span> in JZB showed that these patterns were controlled by the strong external fluvial inputs, especially from the Dagu River. The diurnal change in the Cu, Pb, Zn and Cd <span class="hlt">concentrations</span> showed a periodicity with a cycle length of approximately 12 h in JZB, which indicates the noticeable impact of the semi-diurnal tide. The weighed average <span class="hlt">concentration</span> from freshwater inputs calculated for <span class="hlt">dissolved</span> Cu, Pb, Zn and Cd were higher than their average <span class="hlt">concentrations</span> in JZB. This indicated that JZB had been contaminated with these <span class="hlt">metals</span>, whose <span class="hlt">concentrations</span> were also higher than those found in uncontaminated waters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.9651O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.9651O"><span>Long term patterns in <span class="hlt">dissolved</span> organic carbon, major elements and trace <span class="hlt">metals</span> in boreal headwater catchments: Trends, mechanisms and heterogeneity.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oni, Stephen; Futter, Martyn; Bishop, Kevin; Kohler, Stephan; Ottosson-Lofvenius, Mikael; Laudon, Hjalmar</p> <p>2013-04-01</p> <p>The effects of climate change are currently apparent in the boreal landscape of northern Sweden. Warmer temperature and declining acid deposition are affecting runoff chemistry. These effects are mediated by landscape type. Markedly different responses are observed in streams draining forest and mire landscape elements. Here, we assess long-term water quality time-series from three nested headwater streams draining upland forest (C2), peat/mire (C4) and mixed (C7) (forest and mire) catchments. Temporal trends in weather and runoff (1981-2008); <span class="hlt">dissolved</span> organic carbon <span class="hlt">concentration</span> [DOC] (1993-2010) and other water quality parameters (1987-2011) were assessed. Historically, sulfate deposition is low in the region and is further declining. There was no significant annual trend in precipitation or runoff but a significant monotonic increasing trend existed in air temperature and length of growing season. Stream [DOC] was positively correlated with some trace <span class="hlt">metals</span> (copper, iron and zinc) and negatively with several other chemical parameters (e.g. sulfate, conductivity, calcium). Both sulfate and conductivity showed declining trends, while a significant increase was observed in pH during winter and spring. Calcium and magnesium showed monotonic decreasing trends. The declining trajectories of stream base cation and sulfate <span class="hlt">concentrations</span> during other times of the year were not accompanied by changes in pH and alkalinity. Water temperature increased significantly both annually and in most months while iron and DOC <span class="hlt">concentrations</span> showed significant increases in autumn months. Though all streams showed significant positive trends in [DOC] in autumn, only C2 had a significant annual increasing trend. There was also a shift in the magnitude of variability in spring [DOC] and increasing trend of summer baseflow [DOC] in C2 and C7.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012BGD.....919121O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012BGD.....919121O"><span>Long term patterns in <span class="hlt">dissolved</span> organic carbon, major elements and trace <span class="hlt">metals</span> in boreal headwater catchments: trends, mechanisms and heterogeneity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oni, S. K.; Futter, M. N.; Bishop, K.; Köhler, S. J.; Ottosson-Löfvenius, M.; Laudon, H.</p> <p>2012-12-01</p> <p>The boreal landscape is a complex, spatio-temporally varying mosaic of forest and mire landscape elements that control surface water hydrology and chemistry. Here, we assess long-term water quality time-series from three nested headwater streams draining upland forest (C2), peat/mire (C4) and mixed (C7) (forest and mire) catchments. Temporal trends in weather and runoff (1981-2008); <span class="hlt">dissolved</span> organic carbon <span class="hlt">concentration</span> [DOC] (1993-2010) and other water quality parameters (1987-2011) were assessed. There was no significant annual trend in precipitation or runoff but a significant monotonic increasing trend existed in air temperature and length of growing season. Stream [DOC] was positively correlated with some trace <span class="hlt">metals</span> (copper, iron and zinc) and negatively with several other chemical parameters (e.g. sulfate, conductivity, calcium). Both sulfate and conductivity showed declining trends, while a significant increase was observed in pH during winter and spring. Calcium and magnesium showed monotonic decreasing trends. The declining trajectories of stream base cation and sulfate <span class="hlt">concentrations</span> during other times of the year were not accompanied by changes in pH and alkalinity. Water temperature increased significantly both annually and in most months while iron and DOC <span class="hlt">concentrations</span> showed significant increases in autumn months. Though all streams showed significant positive trends in [DOC] in autumn, only C2 had a significant annual increasing trend. There was also a shift in the magnitude of variability in spring [DOC] and increasing trend of summer baseflow [DOC] in C2 and C7.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811974M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811974M"><span>Long-term trends in <span class="hlt">dissolved</span> iron and DOC <span class="hlt">concentration</span> linked to nitrate depletion in riparian soils</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Musolff, Andreas; Selle, Benny; Fleckenstein, Jan H.; Oosterwoud, Marieke R.; Tittel, Jörg</p> <p>2016-04-01</p> <p>The instream <span class="hlt">concentrations</span> of <span class="hlt">dissolved</span> organic carbon (DOC) are rising in many catchments of the northern hemisphere. Elevated <span class="hlt">concentrations</span> of DOC, mainly in the form of colored humic components, increase efforts and costs of drinking water purification. In this study, we evaluated a long-term dataset of 110 catchments draining into German drinking water reservoirs in order to assess sources of DOC and drivers of a potential long-term change. The average DOC <span class="hlt">concentrations</span> across the wide range of different catchments were found to be well explained by the catchment's topographic wetness index. Higher wetness indices were connected to higher average DOC <span class="hlt">concentrations</span>, which implies that catchments with shallow topography and pronounced riparian wetlands mobilize more DOC. Overall, 37% of the investigated catchments showed a significant long-term increase in DOC <span class="hlt">concentrations</span>, while 22% exhibited significant negative trends. Moreover, we found that increasing trends in DOC were positively correlated to trends in <span class="hlt">dissolved</span> iron <span class="hlt">concentrations</span> at pH≤6 due to remobilization of DOC previously sorbed to iron minerals. Both, increasing trends in DOC and <span class="hlt">dissolve</span> iron were found to be connected to decreasing trends and low <span class="hlt">concentrations</span> of nitrate (below ~6 mg/L). This was especially observed in forested catchments where atmospheric N-depositions were the major source for nitrate availability. In these catchments, we also found long-term increases of phosphate <span class="hlt">concentrations</span>. Therefore, we argue that <span class="hlt">dissolved</span> iron, DOC and phosphate were jointly released under iron-reducing conditions when nitrate as a competing electron acceptor was too low in <span class="hlt">concentrations</span> to prevent the microbial iron reduction. In contrast, we could not explain the observed increasing trends in DOC, iron and phosphate <span class="hlt">concentrations</span> by the long-term trends of pH, sulfate or precipitation. Altogether this study gives strong evidence that both, source and long-term increases in DOC are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26712661','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26712661"><span><span class="hlt">Concentration</span> of precious <span class="hlt">metals</span> during their recovery from electronic waste.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cayumil, R; Khanna, R; Rajarao, R; Mukherjee, P S; Sahajwalla, V</p> <p>2016-11-01</p> <p>The rapid growth of electronic devices, their subsequent obsolescence and disposal has resulted in electronic waste (e-waste) being one of the fastest increasing waste streams worldwide. The main component of e-waste is printed circuit boards (PCBs), which contain substantial quantities of precious <span class="hlt">metals</span> in <span class="hlt">concentrations</span> significantly higher than those typically found in corresponding ores. The high value and limited reserves of minerals containing these <span class="hlt">metals</span> makes urban mining of precious <span class="hlt">metals</span> very attractive. This article is focused on the <span class="hlt">concentration</span> and recovery of precious <span class="hlt">metals</span> during pyro-metallurgical recycling of waste PCBs. High temperature pyrolysis was carried out for ten minutes in a horizontal tube furnace in the temperature range 800-1350°C under Argon gas flowing at 1L/min. These temperatures were chosen to lie below and above the melting point (1084.87°C) of copper, the main <span class="hlt">metal</span> in PCBs, to study the influence of its physical state on the recovery of precious <span class="hlt">metals</span>. The heat treatment of waste PCBs resulted in two different types of solid products, namely a carbonaceous non-<span class="hlt">metallic</span> fraction (NMFs) and <span class="hlt">metallic</span> products, composed of copper rich foils and/or droplets and tin-lead rich droplets and some wires. Significant proportions of Ag, Au, Pd and Pt were found <span class="hlt">concentrated</span> within two types of <span class="hlt">metallic</span> phases, with very limited quantities retained by the NMFs. This process was successful in <span class="hlt">concentrating</span> several precious <span class="hlt">metals</span> such as Ag, Au, Pd and Pt in a small volume fraction, and reduced volumes for further processing/refinement by up to 75%. The amounts of secondary wastes produced were also minimised to a great extent. The generation of precious <span class="hlt">metals</span> rich <span class="hlt">metallic</span> phases demonstrates high temperature pyrolysis as a viable approach towards the recovery of precious <span class="hlt">metals</span> from e-waste.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28276732','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28276732"><span>Stable isotope mass balances versus <span class="hlt">concentration</span> differences of <span class="hlt">dissolved</span> inorganic carbon - implications for tracing carbon turnover in reservoirs.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Barth, Johannes A C; Mader, Michael; Nenning, Franziska; van Geldern, Robert; Friese, Kurt</p> <p>2017-08-01</p> <p>The aim of this study was to identify sources of carbon turnover using stable isotope mass balances. For this purpose, two pre-reservoirs in the Harz Mountains (Germany) were investigated for their <span class="hlt">dissolved</span> and particulate carbon contents (<span class="hlt">dissolved</span> inorganic carbon (DIC), <span class="hlt">dissolved</span> organic carbon, particulate organic carbon) together with their stable carbon isotope ratios. DIC <span class="hlt">concentration</span> depth profiles from March 2012 had an average of 0.33 mmol L(-1). Increases in DIC <span class="hlt">concentrations</span> later on in the year often corresponded with decreases in its carbon isotope composition (δ(13)CDIC) with the most negative value of -18.4 ‰ in September. This led to a carbon isotope mass balance with carbon isotope inputs of -28.5 ‰ from DOC and -23.4, -31.8 and -30.7 ‰ from algae, terrestrial and sedimentary matter, respectively. Best matches between calculated and measured DIC gains were achieved when using the isotope composition of algae. This shows that this type of organic material is most likely responsible for carbon additions to the DIC pool when its <span class="hlt">concentrations</span> and δ(13)CDIC values correlate negatively. The presented isotope mass balance is transferable to other surface water and groundwater systems for quantification of organic matter turnover.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/fs/2010/3073/pdf/fs20103073.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/fs/2010/3073/pdf/fs20103073.pdf"><span>Decadal-scale changes in <span class="hlt">dissolved</span>-solids <span class="hlt">concentrations</span> in groundwater used for public supply, Salt Lake Valley, Utah</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Thiros, Susan A.; Spangler, Larry</p> <p>2010-01-01</p> <p>Basin-fill aquifers are a major source of good-quality water for public supply in many areas of the southwestern United States and have undergone increasing development as populations have grown over time. During 2005, the basin-fill aquifer in Salt Lake Valley, Utah, provided approximately 75,000 acre-feet, or about 29 percent of the total amount of water used by a population of 967,000. Groundwater in the unconsolidated basin-fill deposits that make up the aquifer occurs under unconfined and confined conditions. Water in the shallow unconfined part of the groundwater system is susceptible to near-surface contamination and generally is not used as a source of drinking water. Groundwater for public supply is withdrawn from the deeper unconfined and confined parts of the system, termed the principal aquifer, because yields generally are greater and water quality is better (including lower <span class="hlt">dissolved</span>-solids <span class="hlt">concentrations</span>) than in the shallower parts of the system. Much of the water in the principal aquifer is derived from recharge in the adjacent Wasatch Range (mountain-block recharge). In many areas, the principal aquifer is separated from the overlying shallow aquifer by confining layers of less permeable, fine-grained sediment that inhibit the downward movement of water and any potential contaminants from the surface. Nonetheless, under certain hydrologic conditions, human-related activities can increase <span class="hlt">dissolved</span>-solids <span class="hlt">concentrations</span> in the principal aquifer and result in groundwater becoming unsuitable for consumption without treatment or mixing with water having lower <span class="hlt">dissolved</span>-solids <span class="hlt">concentrations</span>. <span class="hlt">Dissolved</span>-solids <span class="hlt">concentrations</span> in areas of the principal aquifer used for public supply typically are less than 500 milligrams per liter (mg/L), the U.S. Environmental Protection Agency (EPA) secondary (nonenforceable) drinking-water standard. However, substantial increases in <span class="hlt">dissolved</span>-solids <span class="hlt">concentrations</span> in the principal aquifer have been documented in some</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18983088','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18983088"><span>Evaluation of holistic approaches to predicting the <span class="hlt">concentrations</span> of <span class="hlt">metals</span> in field-cultivated rice.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tian, Yuan; Wang, Xiaorong; Luo, Jun; Yu, Hongxia; Zhang, Hao</p> <p>2008-10-15</p> <p>Measurements of <span class="hlt">metals</span> in soils by diffusive gradients in thin films (DGT) have previously been shown to be linearly related to <span class="hlt">metals</span> measured in shoots of plants grown in pots. We examine the relationships between <span class="hlt">metals</span> measured by DGT and other techniques with <span class="hlt">metals</span> in the roots and unpolished grains of rice cultivated under field conditions at 18 sites in Jiangsu province, China. Rhizosphere soils of rice were collected and the <span class="hlt">concentrations</span> of Cd, Cu, Pb, and Zn were determined on soil solution, acetic acid, and calcium chloride (CaCl2) extractions and by DGT. Simple linear regression analyses between <span class="hlt">concentrations</span> of <span class="hlt">metals</span> in plants and those measured using DGT and chemical extractions showed a very good fit for DGT measurements of the <span class="hlt">concentrations</span> of all four <span class="hlt">metals</span> in both rice roots and unpolished grains. Good fits were also found using soil solution and acetic acid extractions, but the correlation coefficients were lower than those obtained by DGT. CaCl2 extractions provided the poorest fits for all four <span class="hlt">metals</span>. Multivariate analyses were used to assess the impact of pH, <span class="hlt">dissolved</span> organic carbon (DOC), soil organic carbon (SOC), cation exchange capacity (CEC), and texture. Two principal components were extracted. The first was well correlated with SOC, DOC, and clay proportion and is therefore representative of "organic matter". The second primarily correlated positively with pH and negatively with CEC and is representative of "inorganic ions". When these principle components were included in multiple linear regression, correlation coefficients for plots involving <span class="hlt">metals</span> in soil solution and in extractions using acetic acid and CaCl2 were improved, but there was little change in the correlation coefficients for comparable plots using <span class="hlt">metals</span> measured by DGT. These results show for the first time that the DGT measurement quantitatively incorporates the main factors affecting bioavailability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/22071','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/22071"><span>A procedure for predicting <span class="hlt">concentrations</span> of <span class="hlt">dissolved</span> solids and sulfate ion in streams draining areas strip mined for coal</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bevans, H.E.</p> <p>1980-01-01</p> <p>Current trends in increased coal production necessitate the development of techniques to appraise the environmental degradation resulting from strip mining. A procedure is introduced for the prediction of <span class="hlt">dissolved</span>-solids and sulfate-ion <span class="hlt">concentrations</span> in streams draining strip-mined areas. <span class="hlt">Concentrations</span> are a function of the percentage of the drainage area that has been strip mined. These relationships are expressed by regression equations computed from data collected in streams draining strip-mined areas of Cherokee and Crawford Counties in southeast Kansas. High correlation coefficients indicate that the relationships may be useful in the evaluation of present or future strip-mining operations. (USGS)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/4607742','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/4607742"><span>Effect of <span class="hlt">dissolved</span> oxygen, temperature, initial cell count, and sugar <span class="hlt">concentration</span> on the viability of Saccharomyces cerevisiae in rapid fermentations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nagodawithana, T W; Castellano, C; Steinkraus, K H</p> <p>1974-09-01</p> <p>By using 7 x 10(8) cells of Saccharomyces cerevisiae per ml with which 25 degrees Brix honey solutions were fermented to 9.5% (wt/vol; 12% vol/vol) ethanol in 2.5 to 3 h at 30 C, i.e., rapid fermentation, the death rate was found to be high, with only 2.1% of the yeast cells surviving at the end of 3 h under anaerobic conditions. As the <span class="hlt">dissolved</span> oxygen in the medium was increased from 0 to 13 to 20 to 100% in rapid fermentations at 30 C, there was a progressive increase in the percentage of cells surviving. The ethanol production rate and total were not seriously affected by a <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> of 13%, but fermentation was retarded by 20% <span class="hlt">dissolved</span> oxygen and still further decreased as the <span class="hlt">dissolved</span> oxygen content reached 100%. When the fermentation temperature was decreased to 15 C (at 13% <span class="hlt">dissolved</span> oxygen), the rate of fermentation decreased, and the fermentation time to 9.5% ethanol (wt/vol) increased to 6 h. It was found that the higher the temperature between 15 and 30 C, the greater the rate of death as initial cell counts were increased from 1.1 x 10(7) to 7.8 x 10(8) cells per ml. At the lowest level of inoculum, 1.1 x 10(7) cells per ml, there was actual multiplication, even at 30 C; however, the fermentation was no longer rapid. The addition of 15% sugar, initially followed after an hour by the remaining 10%, or addition of the sugar in increments of 2.5 or 5% yielded a better survival rate of yeast cells than when the fermentation was initiated with 25% sugar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8710D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8710D"><span>Ancient <span class="hlt">dissolved</span> methane in inland waters at low <span class="hlt">concentrations</span> revealed by a new collection method for radiocarbon (^{14}C) analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dean, Joshua F.; Billett, Michael F.; Murray, Callum; Garnett, Mark H.</p> <p>2017-04-01</p> <p>Methane (CH4) is a powerful greenhouse gas and is released to the atmosphere from freshwater systems in numerous biomes globally. Radiocarbon (14C) analysis of methane can provide unique information about its age, source and rate of cycling in natural environments. Methane is often released from aquatic sediments in bubbles (ebullition), but <span class="hlt">dissolved</span> methane is also present in lakes and streams at lower <span class="hlt">concentrations</span>, and may not be of the same age or source. Obtaining sufficient non-ebullitive aquatic methane for 14C analysis remains a major technical challenge. Previous studies have shown that freshwater methane, in both <span class="hlt">dissolved</span> and ebullitive form, can be significantly older than other forms of aquatic carbon (C), and it is therefore important to characterise this part of the terrestrial C balance. We present a novel method to capture sufficient amounts of <span class="hlt">dissolved</span> methane from freshwater environments for 14C analysis by circulating water across a hydrophobic, gas-permeable membrane and collecting the methane in a large collapsible vessel. The results of laboratory and field tests show that reliable <span class="hlt">dissolved</span> δ13CH4 and 14CH4 samples can be readily collected over short time periods (˜4 to 24 hours), at relatively low cost and from a variety of surface water types. The initial results further support previous findings that <span class="hlt">dissolved</span> methane can be significantly older than other forms of aquatic C, especially in organic-rich catchments, and is currently unaccounted for in many terrestrial C balances and models. This method is suitable for use in remote locations, and could potentially be used to detect the leakage of unique 14CH4 signatures from point sources into waterways, e.g. coal seam gas and landfill gas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22484328','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22484328"><span><span class="hlt">Metal</span> <span class="hlt">concentrations</span> in the groundwater in Birjand flood plain, Iran.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mansouri, Borhan; Salehi, Javad; Etebari, Behrooz; Moghaddam, Hamid Kardan</p> <p>2012-07-01</p> <p>The objective of the present study was to investigate the <span class="hlt">concentration</span> of <span class="hlt">metals</span> (cadmium, lead, chromium, zinc, copper, and iron) were measured in groundwater at 30 sites from the Birjand flood plain of eastern Iran during the November 2010; identify any relationships between <span class="hlt">metals</span> and pH, total hardness. <span class="hlt">Metal</span> <span class="hlt">concentrations</span> in the groundwater samples were decreased in sequence of Zn > Fe > Cu > Cr > Pb > Cd, respectively. The results showed that the overall mean <span class="hlt">concentrations</span> of Cd, Pb, and Cr were at 0.000, 0.023, and 0.049 mg l(-1), respectively. The mean <span class="hlt">concentration</span> of Cu, Zn, and Fe were 0.109, 0.192, and 0.174 mg l(-1), respectively. Results also indicated that there were correlations among Cd, Cu, and Zn <span class="hlt">metals</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28116606','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28116606"><span><span class="hlt">Concentrations</span> of select <span class="hlt">dissolved</span> trace elements and anthropogenic organic compounds in the Mississippi River and major tributaries during the summer of 2012 and 2013.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bussan, Derek D; Ochs, Clifford A; Jackson, Colin R; Anumol, Tarun; Snyder, Shane A; Cizdziel, James V</p> <p>2017-02-01</p> <p>The Mississippi River drainage basin includes the Illinois, Missouri, Ohio, Tennessee, and Arkansas rivers. These rivers drain areas with different physiography, population centers, and land use, with each contributing a different suites of <span class="hlt">metals</span> and wastewater contaminants that can affect water quality. In July 2012, we determined 18 elements (Be, Rb, Sr, Cd, Cs, Ba, Tl, Pb, Mg, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) and chlorophyll-a (Chl-a) in the five major tributaries and in the Upper Mississippi River. The following summer, we determined both trace elements and 25 trace organic compounds at 10 sites in a longitudinal study of the main stem of the Mississippi River from Grafton, Illinois to Natchez, Mississippi. We detected wastewater contaminants, including pharmaceuticals and endocrine disrupting compounds, throughout the river system, with the highest <span class="hlt">concentrations</span> occurring near urban centers (St. Louis and Memphis). <span class="hlt">Concentrations</span> were highest for atrazine (673 ng L(-1)), DEET (540 ng L(-1)), TCPP (231 ng L(-1)), and caffeine (202 ng L(-1)). The Illinois, Missouri, and Yazoo rivers, which drain areas with intense agriculture, had relatively high <span class="hlt">concentrations</span> of Chl-a and atrazine. However, the Ohio River delivered higher loads of contaminants to the Mississippi River, including an estimated 177 kg day(-1) of atrazine, due to higher flow volumes. <span class="hlt">Concentrations</span> of heavy <span class="hlt">metals</span> (Ni, V, Co, Cu, Cd, and Zn) were relatively high in the Illinois River and low in the Ohio River, although <span class="hlt">dissolved</span> <span class="hlt">metal</span> <span class="hlt">concentrations</span> were below US EPA maximum contaminant levels for surface water. Multivariate analysis demonstrated that the rivers can be distinguished based on elemental and contaminant profiles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21103508','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21103508"><span>Increased <span class="hlt">metal</span> <span class="hlt">concentrations</span> in exhaled breath condensate of industrial welders.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hoffmeyer, Frank; Weiss, Tobias; Lehnert, Martin; Pesch, Beate; Berresheim, Hans; Henry, Jana; Raulf-Heimsoth, Monika; Broding, Horst Christoph; Bünger, Jürgen; Harth, Volker; Brüning, Thomas</p> <p>2011-01-01</p> <p>It was the aim of this study to evaluate the effect of different devices on the <span class="hlt">metal</span> <span class="hlt">concentration</span> in exhaled breath condensate (EBC) and to prove whether working conditions in different welding companies result in diverse composition of <span class="hlt">metallic</span> elements. The influence of two collection devices (ECoScreen, ECoScreen2) on detection of <span class="hlt">metallic</span> elements in EBC was evaluated in 24 control subjects. Properties of ECoScreen and a frequent use can alter EBC <span class="hlt">metal</span> content due to contamination from <span class="hlt">metallic</span> components. ECoScreen2 turned out to be favourable for <span class="hlt">metal</span> assessment. <span class="hlt">Concentrations</span> of iron, nickel and chromium in EBC sampled with ECoScreen2 were compared between non-exposed controls and industrial welders. <span class="hlt">Metal</span> <span class="hlt">concentrations</span> in EBC were higher in 36 welders recruited from three companies. Exposure to welding fumes could be demonstrated predominantly for increased iron <span class="hlt">concentrations</span>. <span class="hlt">Concentrations</span> of iron and nickel differed by working conditions, but chromium could not be detected in EBC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20821449','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20821449"><span>A comparison of the copper sensitivity of six invertebrate species in ambient salt water of varying <span class="hlt">dissolved</span> organic matter <span class="hlt">concentrations</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Arnold, W Ray; Cotsifas, Jeffrey S; Ogle, R Scott; Depalma, Sarah G S; Smith, D Scott</p> <p>2010-02-01</p> <p>The copper sensitivity of four saltwater invertebrates (the mussel Mytilus galloprovincialis, the oyster Crassostrea virginica, the sand dollar Dendraster excentricus, and the sea urchin Strongylocentrotus purpuratus) was determined experimentally using chronic-estimator embryo-larval test procedures. The effect of sample <span class="hlt">dissolved</span> organic matter (DOM) content on Cu bioavailability was determined for these species using commonly prescribed test procedures. Comparisons were made among these test results and test results reported previously for two other invertebrate species: the mussel Mytilus edulis and the copepod Eurytemora affinis. All six species exhibited a direct and significant relationship between the sample <span class="hlt">dissolved</span> organic carbon (DOC; a surrogate measure of DOM) and either the <span class="hlt">dissolved</span> Cu median lethal <span class="hlt">concentration</span> (LC50) values or median effect <span class="hlt">concentration</span> (EC50) values. This relationship is significant even when the DOM has different quality as evidenced by molecular fluorescence spectroscopy. Once normalized for the effects of DOM, the Cu sensitivity of these species from least to most sensitive were E. affinis < D. excitricus < C. virginica approximately S. purpuratus approximately M. edulis approximately M. galloprovincialis. This ranking of species sensitivity differs from the saltwater species sensitivity distribution proposed in 2003 by the U.S. Environmental Protection Agency. These results support the need to account for factors that modify Cu bioavailability in future saltwater Cu criteria development efforts. More specifically, Cu saltwater species sensitivity distribution data will need to be normalized by factors affecting Cu bioavailability to assure that accurate and protective criteria are subsequently developed for saltwater species and their uses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=518762','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=518762"><span>The influence of sulfur and iron on <span class="hlt">dissolved</span> arsenic <span class="hlt">concentrations</span> in the shallow subsurface under changing redox conditions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>O'Day, Peggy A.; Vlassopoulos, Dimitri; Root, Robert; Rivera, Nelson</p> <p>2004-01-01</p> <p>The chemical speciation of arsenic in sediments and porewaters of aquifers is the critical factor that determines whether <span class="hlt">dissolved</span> arsenic accumulates to potentially toxic levels. Sequestration of arsenic in solid phases, which may occur by adsorption or precipitation processes, controls <span class="hlt">dissolved</span> <span class="hlt">concentrations</span>. We present synchrotron x-ray absorption spectra of arsenic in shallow aquifer sediments that indicate the local structure of realgar (AsS) as the primary arsenic-bearing phase in sulfate-reducing conditions at <span class="hlt">concentrations</span> of 1–3 mmol·kg–1, which has not previously been verified in sediments at low temperature. Spectroscopic evidence shows that arsenic does not substitute for iron or sulfur in iron sulfide minerals at the molecular scale. A general geochemical model derived from our field and spectroscopic observations show that the ratio of reactive iron to sulfur in the system controls the distribution of solid phases capable of removing arsenic from solution when conditions change from oxidized to reduced, the rate of which is influenced by microbial processes. Because of the difference in solubility of iron versus arsenic sulfides, precipitation of iron sulfide may remove sulfide from solution but not arsenic if precipitation rates are fast. The lack of incorporation of arsenic into iron sulfides may result in the accumulation of <span class="hlt">dissolved</span> As(III) if adsorption is weak or inhibited. Aquifers particularly at risk for such geochemical conditions are those in which oxidized and reduced waters mix, and where the amount of sulfate available for microbial reduction is limited. PMID:15356340</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18273742','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18273742"><span>Polycyclic aromatic hydrocarbon (PAH) <span class="hlt">concentrations</span> in the <span class="hlt">dissolved</span>, particulate, and sediment phases in the Luan River watershed, China.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bai, Ya J; Li, Xi Q; Liu, Wen X; Tao, Shu; Wang, Lu G; Wang, Jing F</p> <p>2008-03-01</p> <p>Water and sediment samples were collected from the Luan River and its 5 tributaries to determine polycyclic aromatic hydrocarbons (PAHs) <span class="hlt">concentrations</span> in <span class="hlt">dissolved</span>, particulate, and sediment phases. The Luan River watershed, located in northeastern Hebei province, provides water to population centers such as Tianjian and Tangshan. Sampling locations were chosen at areas not under direct influence of industrial activities to examine the "background" PAH contamination across the watershed. PAH <span class="hlt">concentrations</span> in the <span class="hlt">dissolved</span>, particulate, and sediment phases ranged from 11.5 ng/L to 171.5 ng/L, 152.8 ng/g. d.w. to 1372.3 ng/g d.w., and 6.7 to 1585.7 ng/g d.w., respectively. Low molecular weight PAHs (with 2 to 3 rings) dominated the <span class="hlt">dissolved</span> and particulate phases, whereas medium and high molecular weight PAHs (with 4 to 6 rings) dominated the sediment phase. The isomer ratios of PAHs in sediments indicated that PAHs in Luan River originated from combustion processes and those PAHs underwent long-distance transport.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70185519','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70185519"><span>The chemistry of iron, aluminum, and <span class="hlt">dissolved</span> organic material in three acidic, <span class="hlt">metal</span>-enriched, mountain streams, as controlled by watershed and in-stream processes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McKnight, Diane M.; Bencala, Kenneth E.</p> <p>1990-01-01</p> <p>Several studies were conducted in three acidic, <span class="hlt">metal</span>-enriched, mountain streams, and the results are discussed together in this paper to provide a synthesis of watershed and in-stream processes controlling Fe, Al, and DOC (<span class="hlt">dissolved</span> organic carbon) <span class="hlt">concentrations</span>. One of the streams, the Snake River, is naturally acidic; the other two, Peru Creek and St. Kevin Gulch, receive acid mine drainage. Analysis of stream water chemistry data for the acidic headwaters of the Snake River shows that some trace <span class="hlt">metal</span> solutes (Al, Mn, Zn) are correlated with major ions, indicating that watershed processes control their <span class="hlt">concentrations</span>. Once in the stream, biogeochemical processes can control transport if they occur over time scales comparable to those for hydrologic transport. Examples of the following in-stream reactions are presented: (1) photoreduction and dissolution of hydrous iron oxides in response to an experimental decrease in stream pH, (2) precipitation of Al at three stream confluences, and (3) sorption of <span class="hlt">dissolved</span> organic material by hydrous iron and aluminum oxides in a stream confluence. The extent of these reactions is evaluated using conservative tracers and a transport model that includes storage in the substream zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70033658','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70033658"><span><span class="hlt">Dissolved</span> <span class="hlt">metals</span> and associated constituents in abandoned coal-mine discharges, Pennsylvania, USA. Part 1: Constituent quantities and correlations</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Cravotta, C.A.</p> <p>2008-01-01</p> <p>Complete hydrochemical data are rarely reported for coal-mine discharges (CMD). This report summarizes major and trace-element <span class="hlt">concentrations</span> and loadings for CMD at 140 abandoned mines in the Anthracite and Bituminous Coalfields of Pennsylvania. Clean-sampling and low-level analytical methods were used in 1999 to collect data that could be useful to determine potential environmental effects, remediation strategies, and quantities of valuable constituents. A subset of 10 sites was resampled in 2003 to analyze both the CMD and associated ochreous precipitates; the hydrochemical data were similar in 2003 and 1999. In 1999, the flow at the 140 CMD sites ranged from 0.028 to 2210 L s-1, with a median of 18.4 L s-1. The pH ranged from 2.7 to 7.3; <span class="hlt">concentrations</span> (range in mg/L) of <span class="hlt">dissolved</span> (0.45-??m pore-size filter) SO4 (34-2000), Fe (0.046-512), Mn (0.019-74), and Al (0.007-108) varied widely. Predominant metalloid elements were Si (2.7-31.3 mg L-1), B ( C > P = N = Se) were not elevated in the CMD samples compared to average river water or seawater. Compared to seawater, the CMD samples also were poor in halogens (Cl > Br > I > F), alkalies (Na > K > Li > Rb > Cs), most alkaline earths (Ca > Mg > Sr), and most metalloids but were enriched by two to four orders of magnitude with Fe, Al, Mn, Co, Be, Sc, Y and the lanthanide rare-earth elements, and one order of magnitude with Ni and Zn. The ochre samples collected at a subset of 10 sites in 2003 were dominantly goethite with minor ferrihydrite or lepidocrocite. None of the samples for this subset contained schwertmannite or was Al rich, but most contained minor aluminosilicate detritus. Compared to <span class="hlt">concentrations</span> in global average shale, the ochres were rich in Fe, Ag, As and Au, but were poor in most other <span class="hlt">metals</span> and rare earths. The ochres were not enriched compared to commercial ore deposits mined for Au or other valuable <span class="hlt">metals</span>. Although similar to commercial Fe ores in composition, the ochres are dispersed and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GBioC..29.1763P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GBioC..29.1763P"><span>Surface distribution of <span class="hlt">dissolved</span> trace <span class="hlt">metals</span> in the oligotrophic ocean and their influence on phytoplankton biomass and productivity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pinedo-González, Paulina; West, A. Joshua; Tovar-Sánchez, Antonio; Duarte, Carlos M.; Marañón, Emilio; Cermeño, Pedro; González, Natalia; Sobrino, Cristina; Huete-Ortega, María.; Fernández, Ana; López-Sandoval, Daffne C.; Vidal, Montserrat; Blasco, Dolors; Estrada, Marta; Sañudo-Wilhelmy, Sergio A.</p> <p>2015-10-01</p> <p>The distribution of bioactive trace <span class="hlt">metals</span> has the potential to enhance or limit primary productivity and carbon export in some regions of the world ocean. To study these connections, the <span class="hlt">concentrations</span> of Cd, Co, Cu, Fe, Mo, Ni, and V were determined for 110 surface water samples collected during the Malaspina 2010 Circumnavigation Expedition (MCE). Total <span class="hlt">dissolved</span> Cd, Co, Cu, Fe, Mo, Ni, and V <span class="hlt">concentrations</span> averaged 19.0 ± 5.4 pM, 21.4 ± 12 pM, 0.91 ± 0.4 nM, 0.66 ± 0.3 nM, 88.8 ± 12 nM, 1.72 ± 0.4 nM, and 23.4 ± 4.4 nM, respectively, with the lowest values detected in the Central Pacific and increased values at the extremes of all transects near coastal zones. Trace <span class="hlt">metal</span> <span class="hlt">concentrations</span> measured in surface waters of the Atlantic Ocean during the MCE were compared to previously published data for the same region. The comparison revealed little temporal changes in the distribution of Cd, Co, Cu, Fe, and Ni over the last 30 years. We utilized a multivariable linear regression model to describe potential relationships between primary productivity and the hydrological, biological, trace nutrient and macronutrient data collected during the MCE. Our statistical analysis shows that primary productivity in the Indian Ocean is best described by chlorophyll a, NO3, Ni, temperature, SiO4, and Cd. In the Atlantic Ocean, primary productivity is correlated with chlorophyll a, NO3, PO4, mixed layer depth, Co, Fe, Cd, Cu, V, and Mo. The variables salinity, temperature, SiO4, NO3, PO4, Fe, Cd, and V were found to best predict primary productivity in the Pacific Ocean. These results suggest that some of the lesser studied trace elements (e.g., Ni, V, Mo, and Cd) may play a more important role in regulating oceanic primary productivity than previously thought and point to the need for future experiments to verify their potential biological functions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B13G0281C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B13G0281C"><span>Development of a pre-<span class="hlt">concentration</span> system and auto-analyzer for <span class="hlt">dissolved</span> methane, ethane, propane, and butane <span class="hlt">concentration</span> measurements with a GC-FID</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chepigin, A.; Leonte, M.; Colombo, F.; Kessler, J. D.</p> <p>2014-12-01</p> <p><span class="hlt">Dissolved</span> methane, ethane, propane, and butane <span class="hlt">concentrations</span> in natural waters are traditionally measured using a headspace equilibration technique and gas chromatograph with flame ionization detector (GC-FID). While a relatively simple technique, headspace equilibration suffers from slow equilibration times and loss of sensitivity due to <span class="hlt">concentration</span> dilution with the pure gas headspace. Here we present a newly developed pre-<span class="hlt">concentration</span> system and auto-analyzer for use with a GC-FID. This system decreases the time required for each analysis by eliminating the headspace equilibration time, increases the sensitivity and precision with a rapid pre-<span class="hlt">concentration</span> step, and minimized operator time with an autoanalyzer. In this method, samples are collected from Niskin bottles in newly developed 1 L plastic sample bags rather than glass vials. Immediately following sample collection, the sample bags are placed in an incubator and individually connected to a multiport sampling valve. Water is pumped automatically from the desired sample bag through a small (6.5 mL) Liqui-Cel® membrane contactor where the <span class="hlt">dissolved</span> gas is vacuum extracted and directly flushed into the GC sample loop. The gases of interest are preferentially extracted with the Liqui-Cel and thus a natural pre-<span class="hlt">concentration</span> effect is obtained. Daily method calibration is achieved in the field with a five-point calibration curve that is created by analyzing gas standard-spiked water stored in 5 L gas-impermeable bags. Our system has been shown to substantially pre-<span class="hlt">concentrate</span> the <span class="hlt">dissolved</span> gases of interest and produce a highly linear response of peak areas to <span class="hlt">dissolved</span> gas <span class="hlt">concentration</span>. The system retains the high accuracy, precision, and wide range of measurable <span class="hlt">concentrations</span> of the headspace equilibration method while simultaneously increasing the sensitivity due to the pre-<span class="hlt">concentration</span> step. The time and labor involved in the headspace equilibration method is eliminated and replaced with the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23832677','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23832677"><span>Diurnal variations of total mercury, reactive mercury, and <span class="hlt">dissolved</span> gaseous mercury <span class="hlt">concentrations</span> and water/air mercury flux in warm and cold seasons from freshwaters of southwestern China.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fu, Xuewu; Feng, Xinbin; Yin, Runsheng; Zhang, Hui</p> <p>2013-10-01</p> <p>Diurnal variations of water total Hg, reactive Hg, and <span class="hlt">dissolved</span> gaseous Hg <span class="hlt">concentrations</span> and mercury flux were monitored at 2 sites in warm and cold seasons in an alkaline reservoir in southwestern China. <span class="hlt">Concentrations</span> of total Hg and reactive Hg, as well as Hg fluxes, usually exhibited a consistent diurnal trend, with elevated values observed during the day. The increasing reactive Hg <span class="hlt">concentrations</span> and Hg fluxes were highly related to the incident intensity of solar radiation, suggesting that sunlight-induced processes played an important role in the transformation of Hg in the study area. <span class="hlt">Dissolved</span> gaseous Hg <span class="hlt">concentrations</span> experienced different diurnal variations among the sampling sites, with peak <span class="hlt">dissolved</span> gaseous Hg at midday under sunny weather conditions and in the early morning under cloudy and/or partially cloudy weather conditions. The peak values of <span class="hlt">dissolved</span> gaseous Hg observed at midday agree well with previous results and highlight the sunlight-induced production of <span class="hlt">dissolved</span> gaseous Hg in freshwaters, whereas <span class="hlt">dissolved</span> gaseous Hg peaks at night suggest that microbial activity might be an additional mechanism for <span class="hlt">dissolved</span> gaseous Hg production in surface waters. Total Hg, reactive Hg, and <span class="hlt">dissolved</span> gaseous Hg <span class="hlt">concentrations</span> and Hg fluxes in the warm season were consistently higher than those in the cold season; this is probably attributable to the combined effect of seasonal variations of environmental parameters, transformation of Hg species, and microbial activities. © 2013 SETAC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=227530&keyword=lipid+AND+analysis+AND+methods&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=227530&keyword=lipid+AND+analysis+AND+methods&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span><span class="hlt">Dissolved</span> <span class="hlt">Concentrations</span> of PAHs and PCBs Are Often Over-predicted Using Sediment <span class="hlt">Concentrations</span> and Literature Koc Values</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>There is an increasing amount of chemical and biological evidence that using sediment <span class="hlt">concentrations</span> and commonly applied Koc values frequently overpredicts interstitial water <span class="hlt">concentrations</span> of HOCs, and thereby overestimates uptake and/or effects of those chemicals on exposed or...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=227530&keyword=burkhard&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=90759676&CFTOKEN=99673896','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=227530&keyword=burkhard&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=90759676&CFTOKEN=99673896"><span><span class="hlt">Dissolved</span> <span class="hlt">Concentrations</span> of PAHs and PCBs Are Often Over-predicted Using Sediment <span class="hlt">Concentrations</span> and Literature Koc Values</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>There is an increasing amount of chemical and biological evidence that using sediment <span class="hlt">concentrations</span> and commonly applied Koc values frequently overpredicts interstitial water <span class="hlt">concentrations</span> of HOCs, and thereby overestimates uptake and/or effects of those chemicals on exposed or...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JAP...111l6102K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JAP...111l6102K"><span>Catalytic behavior of <span class="hlt">metallic</span> particles in anisotropic etching of Ge(100) surfaces in water mediated by <span class="hlt">dissolved</span> oxygen</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kawase, Tatsuya; Mura, Atsushi; Nishitani, Keisuke; Kawai, Yoshie; Kawai, Kentaro; Uchikoshi, Junichi; Morita, Mizuho; Arima, Kenta</p> <p>2012-06-01</p> <p>The authors demonstrate that Ge(100) surfaces containing <span class="hlt">metallic</span> particles are etched anisotropically in water. This originates from the catalytic reduction of <span class="hlt">dissolved</span> oxygen (O2) in water to water molecules (H2O) on the <span class="hlt">metallic</span> particles, which is followed by the enhanced oxidation of Ge around the particles. The soluble nature of Ge oxide (GeO2) in water promotes the formation of inverted pyramidal etch pits composed of (111) microfacets. On the basis of the results, the authors propose strategies for avoiding unwanted surface roughening during the wet cleaning of Ge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23131623','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23131623"><span>A combined process of activated carbon adsorption, ion exchange resin treatment and membrane <span class="hlt">concentration</span> for recovery of <span class="hlt">dissolved</span> organics in pre-hydrolysis liquor of the kraft-based <span class="hlt">dissolving</span> pulp production process.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shen, Jing; Kaur, Ishneet; Baktash, Mir Mojtaba; He, Zhibin; Ni, Yonghao</p> <p>2013-01-01</p> <p>To recover <span class="hlt">dissolved</span> organics in pre-hydrolysis liquor (PHL) of the kraft-based <span class="hlt">dissolving</span> pulp production process, a new combined process concept of sequential steps of activated carbon adsorption, ion exchange resin treatment, and membrane <span class="hlt">concentration</span>, was proposed. The removal of lignin in the PHL was achieved in the activated carbon adsorption step, which also facilitates the subsequent operations, such as the membrane filtration and ion exchange resin treatment. The ion exchange resin treatment resulted in the removal/<span class="hlt">concentration</span> of acetic acid, which opens the door for acetic acid recovery. The membrane filtration is to recover/<span class="hlt">concentrate</span> the <span class="hlt">dissolved</span> sugars. The combined process resulted in the production of PHL-based <span class="hlt">concentrate</span> with relatively high <span class="hlt">concentration</span> of hemicellulosic sugars, i.e., 22.13%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/212003','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/212003"><span>Assessing <span class="hlt">metal</span> bioavailability from cytosolic <span class="hlt">metal</span> <span class="hlt">concentrations</span> in natural populations of aquatic insects</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cain, D.J.; Luoma, S.N.; Hornberger, M.I.</p> <p>1995-12-31</p> <p><span class="hlt">Metals</span> occur in a variety of forms in aquatic insects. Some of these forms may be irrelevant to effects of <span class="hlt">metals</span> on the animal, and might actually obscure links between tissue residues, <span class="hlt">metal</span> bioavailability and toxicity (e.g. <span class="hlt">metals</span> sorbed to external body parts, or associated with unpurged gut contents). Cytosolic <span class="hlt">metal</span> may be a sensitive indicator of <span class="hlt">metal</span> bioavailability and toxicity. The authors determined cytosolic <span class="hlt">metal</span> <span class="hlt">concentrations</span> in natural populations of the caddisfly (Trichoptera) Hydropsyche occidentalis. Cytosolic <span class="hlt">metal</span> <span class="hlt">concentrations</span> were compared to whole-body and sediment <span class="hlt">metal</span> <span class="hlt">concentrations</span>. Samples were collected along a contamination gradient over a 380 km reach of the Clark Fork River, Montana, in August of 1992 and 1993. <span class="hlt">Concentrations</span> of cytosolic Cd, Cu, and Pb correlated with <span class="hlt">concentrations</span> of these <span class="hlt">metals</span> in the whole body within years. Cytosolic <span class="hlt">metals</span> also correlated with levels of sediment contamination except at the most contaminated sites where <span class="hlt">metal</span> <span class="hlt">concentrations</span> in the cytosol were lower relative to sediments. The availability of Pb appeared to be low since the cytosolic Pb fraction represented less than 6% of the total Pb body burden. The cytosol contained appreciably higher proportions of the total Cd and Cu body burden than Pb. The cytosolic fraction of Cd and Cu also increased significantly between 1992 and 1993. This change reflected an increase in Cd and Cu exposure in 1993, apparently due to the mobilization of <span class="hlt">metals</span> during higher river flows that year. The shift in cytosolic <span class="hlt">metal</span> fractions demonstrates the dynamic nature of <span class="hlt">metal</span> partitioning in animals in nature. These shifts can be influenced by hydrologic and geochemical conditions, as well as biological processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15364512','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15364512"><span><span class="hlt">Metal</span> <span class="hlt">concentrations</span> in sediments and clams in four Moroccan estuaries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cheggour, M; Chafik, A; Fisher, N S; Benbrahim, S</p> <p>2005-03-01</p> <p><span class="hlt">Metals</span> (Cd, Cu, Ni, Zn, Mn and Fe) were analyzed seasonally over three years in sediments and in tissues of the clam Scrobicularia plana in four Moroccan Atlantic estuaries: Loukkos, Sebou, Bou Regreg and Oum er Rbia. Of these <span class="hlt">metals</span>, Cd was at the lowest <span class="hlt">concentrations</span> in sediment. <span class="hlt">Concentrations</span> of Cu, Zn, and to a lesser extent Ni, in sediments suggest greater contamination in Sebou and Bou Regreg than in the other estuaries. The fluctuations of Mn and Fe <span class="hlt">concentrations</span> in the fine surface sediments reflect their continental origin and show seasonal variations that indicate soil run-off following rain events. <span class="hlt">Concentrations</span> of Cu, Zn, and especially Ni in clam tissues in these estuaries were generally higher than in some other common bioindicator bivalve species. The seasonal variations in S. plana's tissue <span class="hlt">metal</span> <span class="hlt">concentrations</span> are linked to patterns of reproductive activity for all <span class="hlt">metals</span> except Cd and possibly Zn, whose tissue <span class="hlt">concentrations</span> may be regulated. Mn and Fe <span class="hlt">concentrations</span> in S. plana were positively correlated to sediment levels of these <span class="hlt">metals</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4882013','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4882013"><span>The Inflammatory Phenotype in Failed <span class="hlt">Metal-On-Metal</span> Hip Arthroplasty Correlates with Blood <span class="hlt">Metal</span> <span class="hlt">Concentrations</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Paukkeri, Erja-Leena; Korhonen, Riku; Hämäläinen, Mari; Pesu, Marko; Eskelinen, Antti; Moilanen, Teemu; Moilanen, Eeva</p> <p>2016-01-01</p> <p>Introduction Hip arthroplasty is the standard treatment of a painful hip destruction. The use of modern <span class="hlt">metal-on-metal</span> (MOM) bearing surfaces gained popularity in total hip arthroplasties during the last decade. Recently, worrisome failures due to adverse reaction to <span class="hlt">metal</span> debris (ARMD), including pseudotumor response, have been widely reported. However, the pathogenesis of this reaction remains poorly understood. The aim of the present study was to investigate the ARMD response by flow cytometry approach. Methods Sixteen patients with a failed Articular Surface Replacement (ASR) hip prosthesis were included in the study. Samples of pseudotumor tissues collected during revision surgery were degraded by enzyme digestion and cells were typed by flow cytometry. Whole blood chromium and cobalt <span class="hlt">concentrations</span> were analyzed with mass spectrometry before revision surgery. Results Flow cytometry analysis showed that the peri-implant pseudotumor tissue expressed two principal phenotypes, namely macrophage-dominated and T-lymphocyte-dominated response; the average portions being 54% (macrophages) and 25% (T-lymphocytes) in macrophage-dominated inflammation and 20% (macrophages) and 54% (T-lymphocytes) in T-lymphocyte-dominated response. The percentages of B-lymphocytes and granulocytes were lower in both phenotypes. Interestingly, the levels of blood chromium and cobalt were significantly higher in patients with macrophage-dominated response. Conclusions The results suggest that the adverse tissue reactions induced by MOM wear particles contain heterogeneous pathogeneses and that the <span class="hlt">metal</span> levels are an important factor in the determination of the inflammatory phenotype. The present results support the hypothesis that higher <span class="hlt">metal</span> levels cause cytotoxicity and tissue injury and macrophages are recruited to clear the necrotic debris. On the other hand, the adverse response developed in association with lower <span class="hlt">metal</span> levels is T-lymphocyte-dominated and is likely to reflect</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996EnGeo..27...54M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996EnGeo..27...54M"><span>Statistical comparisons of heavy-<span class="hlt">metal</span> <span class="hlt">concentrations</span> in river sediments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murray, K. S.</p> <p>1996-02-01</p> <p>Statistical t tests were used to determine lead, copper, and chromium enrichment in sediments from the Lower Branch of the Rouge River in southeast Michigan, USA. Both absolute <span class="hlt">metal</span> <span class="hlt">concentrations</span> and ratios of trace <span class="hlt">metal</span> to conservative <span class="hlt">metal</span> <span class="hlt">concentrations</span> were used to compare sampled sites along the Lower Branch of the Rouge River to background sites in the headwaters region. <span class="hlt">Concentration</span> ratios were used to reduce the effects of certain chemical and physical characteristics on the level of <span class="hlt">metal</span> contained in a given sediment. Results from the comparison of sample sites to the background reveal <span class="hlt">metal</span> enrichment at several sites, particularly along the highly urbanized, downstream section of the river. This section of the Lower Branch of the Rouge River exhibits significant lead and copper contamination, as well as measurable chromium enrichment when using either <span class="hlt">concentrations</span> alone or ratios as methods of comparison. The areas of <span class="hlt">metal</span> enrichment appear to coincide closely with areas of known anthropogenic activities. Of particular interest, however, is the enrichment of lead and copper at two upstream sites where the statistical tests suggest an anthropogenic source for the enrichment, but where no previously known cultural activities existed. These data prompted a historical search of records, which discovered several abandoned landfills immediately upstream of the <span class="hlt">metal</span> enrichment sites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22989643','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22989643"><span><span class="hlt">Concentration</span> and speciation of heavy <span class="hlt">metals</span> during water hyacinth composting.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Singh, Jiwan; Kalamdhad, Ajay S</p> <p>2012-11-01</p> <p>The Tessier sequential extraction method was employed to investigate the changes in heavy <span class="hlt">metals</span> speciation (Zn, Cu, Mn, Fe, Pb, Ni, Cd and Cr) during water hyacinth (Eichhornia crassipes) composting. Results showed that, the contents of total <span class="hlt">metals</span> <span class="hlt">concentration</span> were increased during the composting process. The largest proportion of <span class="hlt">metals</span> was found in the residual fraction which was in more stable form and is consequently considered unavailable for plant uptake. Reducible and oxidizable fractions of Ni, Pb and Cd were not found in all trials during water hyacinth composting. The <span class="hlt">concentrations</span> of Cu and Cd were very low comparative to the other <span class="hlt">metals</span>, but the percentage of exchangeable and carbonate fractions were similar as other <span class="hlt">metals</span>. From this study it can be concluded that the appropriate proportion of cattle manure addition (Trial 4) significantly reduced the mobile and easily available fractions (exchangeable and carbonate fractions) during the composting process. Copyright © 2012 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70032686','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70032686"><span>Sources, transformations, and hydrological processes that control stream nitrate and <span class="hlt">dissolved</span> organic matter <span class="hlt">concentrations</span> during snowmelt in an upland forest</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Sebestyen, S.D.; Boyer, E.W.; Shanley, J.B.; Kendall, C.; Doctor, D.H.; Aiken, G.R.; Ohte, N.</p> <p>2008-01-01</p> <p>We explored catchment processes that control stream nutrient <span class="hlt">concentrations</span> at an upland forest in northeastern Vermont, USA, where inputs of nitrogen via atmospheric deposition are among the highest in the nation and affect ecosystem functioning. We traced sources of water, nitrate, and <span class="hlt">dissolved</span> organic matter (DOM) using stream water samples collected at high frequency during spring snowmelt. Hydrochemistry, isotopic tracers, and end-member mixing analyses suggested the timing, sources, and source areas from which water and nutrients entered the stream. Although stream-<span class="hlt">dissolved</span> organic carbon (DOC) and <span class="hlt">dissolved</span> organic nitrogen (DON) both originated from leaching of soluble organic matter, flushing responses between these two DOM components varied because of dynamic shifts of hydrological flow paths and sources that supply the highest <span class="hlt">concentrations</span> of DOC and DON. High <span class="hlt">concentrations</span> of stream water nitrate originated from atmospheric sources as well as nitrified sources from catchment soils. We detected nitrification in surficial soils during late snowmelt which affected the nitrate supply that was available to be transported to streams. However, isotopic tracers showed that the majority of nitrate in upslope surficial soil waters after the onset of snowmelt originated from atmospheric sources. A fraction of the atmospheric nitrogen was directly delivered to the stream, and this finding highlights the importance of quick flow pathways during snowmelt events. These findings indicate that interactions among sources, transformations, and hydrologic transport processes must be deciphered to understand why <span class="hlt">concentrations</span> vary over time and over space as well as to elucidate the direct effects of human activities on nutrient dynamics in upland forest streams. Copyright 2008 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013CSR....52...97C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013CSR....52...97C"><span><span class="hlt">Concentration</span> and characterization of <span class="hlt">dissolved</span> organic matter in the surface microlayer and subsurface water of the Bohai Sea, China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Yan; Yang, Gui-Peng; Wu, Guan-Wei; Gao, Xian-Chi; Xia, Qing-Yan</p> <p>2013-01-01</p> <p>A total of 19 sea-surface microlayer and corresponding subsurface samples collected from the Bohai Sea, China in April 2010 were analyzed for chlorophyll a, <span class="hlt">dissolved</span> organic carbon (DOC) and its major compound classes including total <span class="hlt">dissolved</span> carbohydrates (TDCHO, including monosaccharides, MCHO, and polysaccharides, PCHO) and total hydrolysable amino acids (THAA, including <span class="hlt">dissolved</span> free, DFAA, and combined fraction, DCAA). The <span class="hlt">concentrations</span> of DOC in the subsurface water ranged from 130.2 to 407.7 μM C, with an average of 225.9±75.4 μM C, while those in the surface microlayer varied between 140.1 and 330.9 μM C, with an average of 217.8±56.8 μM C. The <span class="hlt">concentrations</span> of chlorophyll a, DOC, TDCHO and THAA in the microlayer were, respectively correlated with their subsurface water <span class="hlt">concentrations</span>, implying that there was a strong exchange effect between the microlayer and subsurface water. The <span class="hlt">concentrations</span> of DOC and TDCHO were negatively correlated with salinity, respectively, indicating that water mixing might play an important role in controlling the distribution of DOC and TDCHO in the water column. Major constituents of DCAA and DFAA present in the study area were glycine, alanine, glutamic acid, serine and histidine. Principal component analysis (PCA) was applied to examine the complex compositional differences that existed among the sampling sites. Our results showed that DFAA had higher mole percentages of glycine, valine and serine in the microlayer than in the subsurface water, while DCAA tended to have higher mole percentages of glutamic acid, aspartic acid, threonine, arginine, alanine, tyrosine, phenylalanine and leucine in the microlayer. The yields of TDCHO and THAA exhibited similar trends between the microlayer and subsurface water. Carbohydrate species displayed significant enrichment in the microlayer, whereas the DFAA and DCAA exhibited non-uniform enrichment in the microlayer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/464854','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/464854"><span>Distribution of polycyclic aromatic hydrocarbons in southern Chesapeake Bay surface water: Evaluation of three methods for determining freely <span class="hlt">dissolved</span> water <span class="hlt">concentrations</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gustafson, K.E.; Dickhut, R.M.</p> <p>1997-03-01</p> <p>Gas sparging, semipermeable-membrane devices (SPMDs), and filtration with sorption of <span class="hlt">dissolved</span> polycyclic aromatic hydrocarbons (PAHs) to XAD-2 resin were evaluated for determining the <span class="hlt">concentrations</span> of freely <span class="hlt">dissolved</span> PAHs in estuarine waters of southern Chesapeake Bay at sites ranging from rural to urban and highly industrialized. Gas sparging had significant sampling artifacts due to particle scavenging by rising bubbles, and SPMDs were kinetically limited for four-ring and larger PAHs relative to short-term temporal changes in water <span class="hlt">concentrations</span>. Filtration with sorption of the <span class="hlt">dissolved</span> contaminant fraction to XAD-2 resin was found to be the most accurate and feasible method for determining <span class="hlt">concentrations</span> of freely <span class="hlt">dissolved</span> PAHs in estuarine water. <span class="hlt">Concentrations</span> and distribution coefficients of <span class="hlt">dissolved</span> and particulate PAHs were measured using the filtration/XAD-2 method. <span class="hlt">Concentrations</span> of PAHs in surface waters of southern Chesapeake Bay were higher than those reported for the northern bay; <span class="hlt">concentrations</span> in the Elizabeth River were elevated relative to all other sites. A gradient for particulate PAHs was observed from urban to remote sites. No seasonal trends were observed in <span class="hlt">dissolved</span> or particle-bound PAH fractions at any site. Distributions of <span class="hlt">dissolved</span> and particulate PAHs in surface waters of the Chesapeake Bay are near equilibrium at all locations and during all seasons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007ECSS...75..151M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007ECSS...75..151M"><span>Modelling the migration opportunities of diadromous fish species along a gradient of <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> in a European tidal watershed</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maes, J.; Stevens, M.; Breine, J.</p> <p>2007-10-01</p> <p>The relationship between poor water quality and migration opportunities for fish remains poorly documented, although it is an essential research step in implementing EU water legislation. In this paper, we model the environmental constraints that control the movements of anadromous and catadromous fish populations that migrate through the tidal watershed of River Scheldt, a heavily impacted river basin in Western Europe. Local populations of sturgeon, sea lamprey, sea trout, Atlantic salmon, houting and allis shad were essentially extirpated around 1900. For remaining populations (flounder, three-spined stickleback, twaite shad, thinlip mullet, European eel and European smelt), a data driven logistic model was parameterized. The presence or absence of fish species in samples taken between 1995 and 2004 was modelled as a function of temperature, <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span>, river flow and season. Probabilities to catch individuals from all diadromous species but three-spined stickleback increased as a function of the interaction between temperature and <span class="hlt">dissolved</span> oxygen. The hypoxic zone situated in the freshwater tidal part of the estuary was an effective barrier for upstream migrating anadromous spawners since it blocked the entrance to historical spawning sites upstream. Similarly, habitat availability for catadromous fish was greatly reduced and restricted to lower brackish water parts of the estuary. The model was applied to infer preliminary <span class="hlt">dissolved</span> oxygen criteria for diadromous fish, to make qualitative predictions about future changes in fish distribution given anticipated changes in water quality and to suggest necessary measures with respect to watershed management.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25277967','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25277967"><span>Characterization and biotoxicity assessment of <span class="hlt">dissolved</span> organic matter in RO <span class="hlt">concentrate</span> from a municipal wastewater reclamation reverse osmosis system.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Ying-Xue; Gao, Yue; Hu, Hong-Ying; Tang, Fang; Yang, Zhe</p> <p>2014-12-01</p> <p>Reverse osmosis (RO) <span class="hlt">concentrate</span> from municipal wastewater reclamation reverse osmosis (mWRRO) system containing organic compounds may associate with toxic risk, and its discharge might pose an environmental risk. To identify a basis for the selection of feasible technology in treating RO <span class="hlt">concentrates</span>, the characteristics and biotoxicity of different fractions of <span class="hlt">dissolved</span> organic matter (DOM) in RO <span class="hlt">concentrates</span> from an mWRRO system were investigated. The results indicated that the hydrophilic neutrals (HIN), hydrophobic acids (HOA) and hydrophobic bases (HOB) accounted for 96% of the <span class="hlt">dissolved</span> organic carbon (DOC) of the total DOM in the RO <span class="hlt">concentrate</span>. According to the SEC chromatograph detected at 254 nm wavelength of UV, the DOM with molecular weight (MW) 1-3 kDa accounted for the majority of the basic and neutral fractions. The fluorescence spectra of the excitation emission matrix (EEM) indicated that most aromatic proteins, humic/fulvic acid-like and soluble microbial by-product-like substances existed in the fractions HOA and hydrophobic neutrals (HON). The genotoxicity and anti-estrogenic activity of the RO <span class="hlt">concentrate</span> were 1795.6 ± 57.2 μg 4-NQOL(-1) and 2.19 ± 0.05 mg TAM L(-1), respectively. The HIN, HOA, and HOB contributed to the genotoxicity of the RO <span class="hlt">concentrate</span>, and the HIN was with the highest genotoxic level of 1007.9 ± 94.8 μg 4-NQOL(-1). The HOA, HON, and HIN lead to the total anti-estrogenic activity of the RO <span class="hlt">concentrate</span>, and HOA occupied approximately 60% of the total, which was 1.3 ± 0.17 mg TAM L(-1). Copyright © 2014 Elsevier Ltd. All rights reserved.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013BGD....10.7257P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013BGD....10.7257P"><span>Effects of anomalous high temperatures on carbon dioxide, methane, <span class="hlt">dissolved</span> organic carbon and trace element <span class="hlt">concentrations</span> in thaw lakes in Western Siberia in 2012</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pokrovsky, O. S.; Shirokova, L. S.; Kirpotin, S. N.; Kulizhsky, S. P.; Vorobiev, S. N.</p> <p>2013-04-01</p> <p>During the anomalous hot summer in 2012, surface air temperatures in Western Siberia were 5 to 10 °C higher than those observed during the previous period of > 30 yr. This unusual climate phenomenon provided an opportunity to examine the effects of short-term natural heating of water in thermokarst ponds and lakes in discontinuous permafrost zones and compare these observations to previous field results obtained when the temperature was normal during the summer of 2010 in the same region. Thermokarst bodies of water shrank significantly, water levels dropped approximately 50 cm in large lakes and small (< 10-100 m2) ponds, and shallow soil depressions disappeared. Based on samples from ~ 40 bodies of water collected previously and in 2012, first-order features of changes in chemical composition in response to increased water temperatures (from 14.1 ± 2.2 to 23.8 ± 2.3 °C in 2010 and 2012, respectively) were established. In these thermokarst bodies of water that covered a full range of surface areas, the average conductivity and pH were almost unchanged, whereas <span class="hlt">dissolved</span> organic carbon (DOC), Cl- and SO42- <span class="hlt">concentrations</span> were higher by a factor of ~ 2 during summer 2012 compared to periods with normal temperatures. Similarly, most divalent <span class="hlt">metals</span> and insoluble trivalent and tetravalent elements were more <span class="hlt">concentrated</span> by a factor of 1.7-2.4 in the summer of 2012 than normal periods. The average <span class="hlt">concentrations</span> of <span class="hlt">dissolved</span> CO2 and CH4 during the hot summer of 2012 increased by factors of 1.4 and 4.9, respectively. For most of the trace elements bound to colloids, the degree of colloidal binding decreased by a factor of 1.44 ± 0.33 (for an average of 40 elements) during the hot summer of 2012 compared to normal periods. Increases in CO2 and CH4 <span class="hlt">concentrations</span> with the decreasing size of the body of water were well-pronounced during the hot summer of 2012. The <span class="hlt">concentrations</span> of CO2 and CH4 significantly increased by factors of 5 and 150, respectively, in small (</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSME34C0815K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSME34C0815K"><span><span class="hlt">Dissolved</span> Fe and Fe binding ligand <span class="hlt">concentrations</span> at the hydrothermal vent fields in the Coriolis Troughs, New Hebrides Island Arc</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kleint, C.; Hawkes, J. A.; Sander, S. G.; Koschinsky, A.</p> <p>2016-02-01</p> <p>It is globally accepted that hydrothermal vent fluids are highly enriched in Fe compared to the surrounding seawater and for long it was believed that the majority of the <span class="hlt">dissolved</span> Fe is precipitated either directly out of the fluid with seawater contact or from the plume within a short distance. Recent research at other deep-sea hydrothermal vents has shown, however, that organic ligands are able to keep Fe soluble and therefore facilitating its transport into the open ocean. This is important since Fe is also considered a limiting factor for primary production in large parts of the world`s surface ocean. The New Hebrides Island Arc is not studied well with respect to the fluid chemistry of its numerous vents. Up until now, no data is published for the crucial micronutrient Fe in these fluids. Several hydrothermal vent fluids, divided into mixing zone, outlet and pure fluid as well as one hydrothermal plume from the Coriolis Troughs have been analyzed with respect to total <span class="hlt">dissolved</span> Fe (dFe) and Fe binding ligands (FeL), using competitive ligand exchange - adsorptive cathodic stripping voltammetry (CLE - AdCSV) with Salicylaldoxime as the artificial ligand. Our dFe data for the hydrothermal plume show <span class="hlt">concentrations</span> ranging from 9.6 nM to 30.1 nM, being highly enriched compared to the surrounding seawater. Good correlation is observed between dFe and turbidity, which can be used as a proxy for hydrothermal plumes. Hydrothermal fluid samples collected near and directly from the vent outlet show total <span class="hlt">dissolved</span> Fe <span class="hlt">concentrations</span> varying from 0.46 µM up to 380 µM, respectively. We find enriched organic ligand <span class="hlt">concentrations</span> in the plume samples as well as in the samples taken near the hydrothermal vent outlets. Pure hydrothermal fluid samples with an in-situ temperature of up to 370 °C show different ligand properties than low to mid temperature samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711824P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711824P"><span><span class="hlt">Dissolved</span> greenhouse gas <span class="hlt">concentrations</span> as proxies for emissions: First results from a survey of 43 Alpine lakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pighini, Sylvie; Wohlfahrt, Georg; Miglietta, Franco</p> <p>2015-04-01</p> <p>Up to very recently, freshwater ecosystems were neglected in assessments of the global carbon cycle and considered merely as passive 'pipes' which transport carbon from the land to the oceans. This view has been challenged by an increasing number of studies showing that freshwater ecosystems may negate a substantial fraction of the carbon sink through carbon dioxide (CO2) and in particular methane (CH4) emissions and thus rather should be viewed as 'reactors' which process a large fraction of the terrigenous carbon. Most of our knowledge on freshwater CO2 and CH4 emissions to date derives from studies in tropical and boreal regions, while temperate freshwater ecosystems are understudied. This study is focused on lakes from the Alpine area and their content in <span class="hlt">dissolved</span> greenhouse gases, CH4 and CO2. We mostly aim to assess the content of <span class="hlt">dissolved</span> methane and carbon dioxide from the Alpine lakes in order to understand whether Alpine lakes could be potential CH4 and CO2 emitters. We also would like to relate <span class="hlt">concentrations</span> to lake characteristics and potential biotic and abiotic driving forces. A diverse set of 43 lakes, from Trentino, South Tirol (Italy) and North Tirol (Austria), was selected resulting in a gradient with respect to elevation (from 240 to 1700 m a.s.l.) and latitude (from 45.52° to 47.38°). Complementary to <span class="hlt">dissolved</span> CH4 and CO2 surface water samples, <span class="hlt">dissolved</span> oxygen and temperature were measured. Only water surface samples were considered. Analyses were done with a gas chromatographer equipped with a flame ionization detector (FID) for CH4 and a thermal conductivity detector (TCD) for CO2 determination. The first results show that all the sampled lakes were super-saturated in <span class="hlt">dissolved</span> methane and carbon dioxide <span class="hlt">concentrations</span>, at least partly to a degree that in the literature has been shown to result in substantial emissions to the atmosphere. To estimate emissions, CO2 and CH4 fluxes will be quantified using the eddy covariance and floating</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17899414','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17899414"><span>Multivariate analysis of heavy <span class="hlt">metals</span> <span class="hlt">concentrations</span> in river estuary.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alkarkhi, Abbas F M; Ahmad, Anees; Ismail, Norli; Easa, Azhar Mat</p> <p>2008-08-01</p> <p>Multivariate statistical techniques such as multivariate analysis of variance (MANOVA) and discriminant analysis (DA) were applied for analyzing the data obtained from two rivers in the Penang State of Malaysia for the <span class="hlt">concentration</span> of heavy <span class="hlt">metal</span> ions (As, Cr, Cd, Zn, Cu, Pb, and Hg) using a flame atomic absorption spectrometry (F-AAS) for Cr, Cd, Zn, Cu, Pb, As and cold vapor atomic absorption spectrometry (CV-AAS) for Hg. The two locations of interest with 20 sampling points of each location were Kuala Juru (Juru River) and Bukit Tambun (Jejawi River). MANOVA showed a strong significant difference between the two rivers in terms of heavy <span class="hlt">metal</span> <span class="hlt">concentrations</span> in water samples. DA gave the best result to identify the relative contribution for all parameters in discriminating (distinguishing) the two rivers. It provided an important data reduction as it used four parameters (Zn, Pb, Cd and Cr) affording 100% correct assignations. Results indicated that the two rivers were different in terms of heavy <span class="hlt">metals</span> <span class="hlt">concentrations</span> in water, and the major difference was due to the contribution of Zn. A negative correlation was found between discriminate functions (DF) and Cr and As, whereas positive correlation was exhibited with other heavy <span class="hlt">metals</span>. Therefore, DA allowed a reduction in the dimensionality of the data set, delineating a few indicator parameters responsible for large variations in heavy <span class="hlt">metal</span> <span class="hlt">concentrations</span>. Correlation matrix between the parameters exhibited a strong evidence of mutual dependence of these <span class="hlt">metals</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2480802','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2480802"><span>Tolerance of Oncomelania hupensis quadrasi to varying <span class="hlt">concentrations</span> of <span class="hlt">dissolved</span> oxygen and organic pollution*</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Garcia, Rolando G.</p> <p>1972-01-01</p> <p>Ecological investigations were made of habitats containing natural populations of the snail Oncomelania hupensis quadrasi and of habitats free from the snail in the island of Leyte, Philippines. This species of snail is a vector of Schistosoma japonicum in the Philippines. Snail-infested habitats had <span class="hlt">dissolved</span> oxygen levels of 3.8-9.85 ppm but snail-free habitats had levels of only 0.08-3.6 ppm. Snail-infested habitats were less polluted by organic matter than habitats that were snail-free. Larger numbers of chlorophyll-bearing algae were present in both the water and the soil of snail-infested habitats. Other factors, including temperature, pH, hydrogen carbonate alkalinity, and relative humidity, were also investigated. PMID:4538906</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28062458','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28062458"><span>Hyperosmotic Agents and Antibiotics Affect <span class="hlt">Dissolved</span> Oxygen and pH <span class="hlt">Concentration</span> Gradients in Staphylococcus aureus Biofilms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kiamco, Mia Mae; Atci, Erhan; Mohamed, Abdelrhman; Call, Douglas R; Beyenal, Haluk</p> <p>2017-03-15</p> <p>Biofilms on wound surfaces are treated topically with hyperosmotic agents, such as medical-grade honey and cadexomer iodine; in some cases, these treatments are combined with antibiotics. Tissue repair requires oxygen, and a low pH is conducive to oxygen release from red blood cells and epithelialization. We investigated the variation of <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> and pH with biofilm depth and the variation in oxygen consumption rates when biofilms are challenged with medical-grade honey or cadexomer iodine combined with vancomycin or ciprofloxacin. <span class="hlt">Dissolved</span> oxygen and pH depth profiles in Staphylococcus aureus biofilms were measured using microelectrodes. The presence of cadexomer iodine with vancomycin or ciprofloxacin on the surface of the biofilm permitted a measurable <span class="hlt">concentration</span> of oxygen at greater biofilm depths (101.6 ± 27.3 μm, P = 0.02; and 155.5 ± 27.9 μm, P = 0.016, respectively) than in untreated controls (30.1 μm). Decreases in pH of ∼0.6 and ∼0.4 units were observed in biofilms challenged with medical-grade honey alone and combined with ciprofloxacin, respectively (P < 0.001 and 0.01, respectively); the number of bacteria recovered from biofilms was significantly reduced (1.26 log) by treatment with cadexomer iodine and ciprofloxacin (P = 0.002) compared to the untreated control. Combining cadexomer iodine and ciprofloxacin improved <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> and penetration depth into the biofilm, while medical-grade honey was associated with a lower pH; not all treatments established a bactericidal effect in the time frame used in the experiments.IMPORTANCE Reports about using hyperosmotic agents and antibiotics against wound biofilms focus mostly on killing bacteria, but the results of these treatments should additionally be considered in the context of how they affect physiologically important parameters, such as oxygen <span class="hlt">concentration</span> and pH. We confirmed that the combination of a hyperosmotic agent and an antibiotic results</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25454126','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25454126"><span>Ion exchange membranes as novel passive sampling material for organic ions: application for the determination of freely <span class="hlt">dissolved</span> <span class="hlt">concentrations</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Oemisch, Luise; Goss, Kai-Uwe; Endo, Satoshi</p> <p>2014-11-28</p> <p>Many studies in pharmacology, toxicology and environmental science require a method for determining the freely <span class="hlt">dissolved</span> <span class="hlt">concentration</span> of a target substance. A recently developed tool for this purpose is equilibrium passive sampling with polymeric materials. However, this method has rarely been applied to ionic organic substances, primarily due to limited availability of convenient sorption materials. This study introduces ion exchange membranes (IEMs) as a novel passive sampling material for organic ions. The partitioning of 4-ethylbenzene-1-sulfonate, 2,4-dichlorophenoxyacetic acid and pentachlorophenol to one anion exchange membrane (FAS) and of difenzoquat, nicotine and verapamil to one cation exchange membrane (FKS) was investigated. All test substances exhibited a sufficiently high affinity for the respective IEM with logarithmic IEM-water partition coefficients >2.3. Sorption equilibrium was established quickly, within several hours for the FAS membrane and within 1-3 days for the FKS membrane. For permanently charged substances the partitioning to the IEMs was independent of pH, but was influenced by the salt composition of the test solution. For all test substances sorption to IEM was dependent on the substance <span class="hlt">concentration</span>. Bovine serum albumin-water partition coefficients determined by passive sampling with IEMs agree well with those determined by the conventional dialysis method. The results of this study indicate that IEMs exhibit the potential to measure freely <span class="hlt">dissolved</span> <span class="hlt">concentrations</span> of organic ions in a simple and time-saving manner. Copyright © 2014 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26812082','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26812082"><span>A DFT-based toxicity QSAR study of aromatic hydrocarbons to Vibrio fischeri: Consideration of aqueous freely <span class="hlt">dissolved</span> <span class="hlt">concentration</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Ying; Yang, Xianhai; Wang, Juying; Cong, Yi; Mu, Jingli; Jin, Fei</p> <p>2016-05-05</p> <p>In the present study, quantitative structure-activity relationship (QSAR) techniques based on toxicity mechanism and density functional theory (DFT) descriptors were adopted to develop predictive models for the toxicity of alkylated and parent aromatic hydrocarbons to Vibrio fischeri. The acute toxicity data of 17 aromatic hydrocarbons from both literature and our experimental results were used to construct QSAR models by partial least squares (PLS) analysis. With consideration of the toxicity process, the partition of aromatic hydrocarbons between water phase and lipid phase and their interaction with the target biomolecule, the optimal QSAR model was obtained by introducing aqueous freely <span class="hlt">dissolved</span> <span class="hlt">concentration</span>. The high statistical values of R(2) (0.956) and Q(CUM)(2) (0.942) indicated that the model has good goodness-of-fit, robustness and internal predictive power. The average molecular polarizability (α) and several selected thermodynamic parameters reflecting the intermolecular interactions played important roles in the partition of aromatic hydrocarbons between the water phase and biomembrane. Energy of the highest occupied molecular orbital (E(HOMO)) was the most influential descriptor which dominated the toxicity of aromatic hydrocarbons through the electron-transfer reaction with biomolecules. The results demonstrated that the adoption of freely <span class="hlt">dissolved</span> <span class="hlt">concentration</span> instead of nominal <span class="hlt">concentration</span> was a beneficial attempt for toxicity QSAR modeling of hydrophobic organic chemicals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B51D0052S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B51D0052S"><span>How do changes in <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> influence microbially-controlled phosphorus cycling in stream biofilms?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saia, S. M.; Locke, N. A.; Regan, J. M.; Carrick, H. J.; Buda, A. R.; Walter, M. T.</p> <p>2014-12-01</p> <p>Advances in molecular microbiology techniques (e.g. epi-fluorescent microscopy and PCR) are making it easier to study the influence of specific microorganisms on nutrient transport. Polyphosphate accumulating organisms (PAOs) are commonly used in wastewater treatment plants to remove excess phosphorus (P) from effluent water. PAOs have also been identified in natural settings but their ecological function is not well known. In this study, we tested the hypothesis that PAOs in natural environments would release and accumulate P during anaerobic and aerobic conditions, respectively. We placed stream biofilms in sealed, covered tubs and subjected them to alternating air (aerobic conditions) and N2 gas (anaerobic condition) bubbling for 12 hours each. Four treatments investigated the influence of changing <span class="hlt">dissolved</span> oxygen on micribially-controlled P cycling: (1) biofilms bubbled continuously with air, (2) biofilms bubbled alternatively with air and N2, (3) biocide treated biofilms bubbled continuously with air, and (4) biocide treated biofilms bubbled alternatively with air and N2. Treatments 3 and 4 serve as abiotic controls to treatments 1 and 2. We analyzed samples every 12 hours for soluble reactive P (SRP), temperature, <span class="hlt">dissolved</span> oxygen, and pH. We also used fluorescent microscopy (i.e. DAPI staining) and PCR to verify the presence of PAOs in the stream biofilms. SRP results over the course of the experiment support our hypothesis that anaerobic and aerobic stream conditions may impact PAO mediated P release and uptake, respectively in natural environments. The results of these experiments draw attention to the importance of microbiological controls on P mobility in freshwater ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311285&keyword=salinity&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311285&keyword=salinity&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>Statistical evaluation of biogeochemical variables affecting spatiotemporal distributions of multiple free <span class="hlt">metal</span> ion concentrationsin an urban estuary</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Free <span class="hlt">metal</span> ion <span class="hlt">concentrations</span> have been recognized as a better indicator of <span class="hlt">metal</span> bioavailability in aquatic environments than total <span class="hlt">dissolved</span> <span class="hlt">metal</span> <span class="hlt">concentrations</span>. However, our understanding of the determinants of free ion <span class="hlt">concentrations</span>, especially in a <span class="hlt">metal</span> mixture, is limite...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311285&keyword=chemosphere&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=91079535&CFTOKEN=63900006','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311285&keyword=chemosphere&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=91079535&CFTOKEN=63900006"><span>Statistical evaluation of biogeochemical variables affecting spatiotemporal distributions of multiple free <span class="hlt">metal</span> ion concentrationsin an urban estuary</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Free <span class="hlt">metal</span> ion <span class="hlt">concentrations</span> have been recognized as a better indicator of <span class="hlt">metal</span> bioavailability in aquatic environments than total <span class="hlt">dissolved</span> <span class="hlt">metal</span> <span class="hlt">concentrations</span>. However, our understanding of the determinants of free ion <span class="hlt">concentrations</span>, especially in a <span class="hlt">metal</span> mixture, is limite...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17955366','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17955366"><span>Heavy-<span class="hlt">metal</span> <span class="hlt">concentrations</span> in three owl species from Korea.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Jungsoo; Lee, Hang; Koo, Tae-Hoe</p> <p>2008-01-01</p> <p>This study presents <span class="hlt">concentrations</span> of heavy <span class="hlt">metals</span> (iron, zinc, manganese, copper, lead, and cadmium) in livers of three owl species from Korea. Essential trace elements (iron, zinc, manganese, and copper) did not differ among the owl species. We suggest that the essential elements are within the normal range and are maintained by normal homeostatic mechanisms. Lead and cadmium <span class="hlt">concentrations</span> in Eurasian Eagle Owls (Bubo bubo) were significantly lower than in Brown Hawk Owls (Nixos scutulata) and Collared Scops Owls (Otus lempiji). Lead and cadmium <span class="hlt">concentrations</span> in Korean owl species were at background levels; lead <span class="hlt">concentrations</span> in two Collared Scops Owls were above background <span class="hlt">concentrations</span>. Lead and cadmium <span class="hlt">concentrations</span> were similar to <span class="hlt">concentrations</span> previously reported in owls from other parts of the world. We suggest that lead and cadmium <span class="hlt">concentrations</span> in Korean owls are below toxic <span class="hlt">concentrations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22424449','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22424449"><span>Alkaline earth <span class="hlt">metal</span> cation exchange: effect of mobile counterion and <span class="hlt">dissolved</span> organic matter.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Indarawis, Katrina; Boyer, Treavor H</p> <p>2012-04-17</p> <p>The goal of this research was to provide an improved understanding of the interactions between alkaline earth <span class="hlt">metals</span> and DOM under conditions that are encountered during drinking water treatment with particular focus on cation exchange. Both magnetically enhanced and nonmagnetic cation exchange resins were converted to Na, Mg, Ca, Sr, and Ba mobile counterion forms as a novel approach to investigate the exchange behavior between the cations and the interactions between the cations and DOM. The results show that cation exchange is a robust process for removal of Ca(2+) and Mg(2+) considering competition with cations on the resin surface and presence of DOM. DOM was actively involved during the cation exchange process through complexation, adsorption, and coprecipitation reactions. In addition to advancing the understanding of ion exchange processes for water treatment, the results of this work are applicable to membrane pretreatment to minimize fouling, treatment of membrane <span class="hlt">concentrate</span>, and precipitative softening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=308345&keyword=superfund+AND+sites&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=308345&keyword=superfund+AND+sites&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>Application of Passive Sampling for Measuring <span class="hlt">Dissolved</span> <span class="hlt">Concentrations</span> of Organic Contaminants in the Water Column at Three U.S. EPA Marine Superfund Sites.</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>At contaminated sediment sites, including U.S. EPA Superfund sites, it is critical to measure water column <span class="hlt">concentrations</span> of freely <span class="hlt">dissolved</span> contaminants to understand the complete exposure of aquatic organisms to hydrophobic organic contaminants (HOCs). Historically, acquiring...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=308077&keyword=aquatic+AND+ecology+AND+Spain&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=308077&keyword=aquatic+AND+ecology+AND+Spain&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>Application of Passive Sampling for Measuring <span class="hlt">Dissolved</span> <span class="hlt">Concentrations</span> of Organic Contaminants in the Water Column at Three U.S. EPA Marine Superfund Sites</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>At contaminated sediment sites, including U.S. EPA Superfund sites, it is critical to measure water column <span class="hlt">concentrations</span> of freely <span class="hlt">dissolved</span> contaminants to understand the complete exposure of aquatic organisms to hydrophobic organic contaminants (HOCs). Historically acquiring ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=308345&keyword=chicago&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=91051568&CFTOKEN=57088457','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=308345&keyword=chicago&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=91051568&CFTOKEN=57088457"><span>Application of Passive Sampling for Measuring <span class="hlt">Dissolved</span> <span class="hlt">Concentrations</span> of Organic Contaminants in the Water Column at Three U.S. EPA Marine Superfund Sites.</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>At contaminated sediment sites, including U.S. EPA Superfund sites, it is critical to measure water column <span class="hlt">concentrations</span> of freely <span class="hlt">dissolved</span> contaminants to understand the complete exposure of aquatic organisms to hydrophobic organic contaminants (HOCs). Historically, acquiring...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=308077&keyword=Polyethylene&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78708047&CFTOKEN=35414825','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=308077&keyword=Polyethylene&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78708047&CFTOKEN=35414825"><span>Application of Passive Sampling for Measuring <span class="hlt">Dissolved</span> <span class="hlt">Concentrations</span> of Organic Contaminants in the Water Column at Three U.S. EPA Marine Superfund Sites</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>At contaminated sediment sites, including U.S. EPA Superfund sites, it is critical to measure water column <span class="hlt">concentrations</span> of freely <span class="hlt">dissolved</span> contaminants to understand the complete exposure of aquatic organisms to hydrophobic organic contaminants (HOCs). Historically acquiring ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JNuM..473..157J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JNuM..473..157J"><span>Corrosion investigations on zircaloy-4 and titanium <span class="hlt">dissolver</span> materials for MOX fuel dissolution in <span class="hlt">concentrated</span> nitric acid containing fluoride ions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jayaraj, J.; Krishnaveni, P.; Krishna, D. Nanda Gopala; Mallika, C.; Mudali, U. Kamachi</p> <p>2016-05-01</p> <p>Aqueous reprocessing of plutonium-rich mixed oxide fuels require fluoride as a dissolution catalyst in boiling nitric acid for an effective dissolution of the spent fuel. High corrosion rates were obtained for the candidate <span class="hlt">dissolver</span> materials zircaloy-4 (Zr-4) and commercial pure titanium (CP-Ti grade 2) in boiling 11.5 M HNO3 + 0.05 M NaF. Complexing the fluoride ions either with Al(NO3)3 or ZrO(NO3)2 aided in decreasing the corrosion rates of Zr-4 and CP-Ti. From the obtained corrosion rates it is concluded that CP-Ti is a better <span class="hlt">dissolver</span> material than Zr-4 for extended service life in boiling 11.5 M HNO3 + 0.05 M NaF, when complexed with 0.15 M ZrO(NO3)2. XPS analysis confirmed the presence of TiO2 and absence of fluoride on the surface of CP-Ti samples, indicating that effective complexation had occurred in solution leading to passivation of the <span class="hlt">metal</span> and imparting high corrosion resistance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12480349','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12480349"><span>Biomineralization of <span class="hlt">metal</span>-containing ores and <span class="hlt">concentrates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rawlings, Douglas E; Dew, David; du Plessis, Chris</p> <p>2003-01-01</p> <p>Biomining is the use of microorganisms to extract <span class="hlt">metals</span> from sulfide and/or iron-containing ores and mineral <span class="hlt">concentrates</span>. The iron and sulfide is microbially oxidized to produce ferric iron and sulfuric acid, and these chemicals convert the insoluble sulfides of <span class="hlt">metals</span> such as copper, nickel and zinc to soluble <span class="hlt">metal</span> sulfates that can be readily recovered from solution. Although gold is inert to microbial action, microbes can be used to recover gold from certain types of minerals because as they oxidize the ore, they open its structure, thereby allowing gold-solubilizing chemicals such as cyanide to penetrate the mineral. Here, we review a strongly growing microbially-based <span class="hlt">metal</span> extraction industry, which uses either rapid stirred-tank or slower irrigation technology to recover <span class="hlt">metals</span> from an increasing range of minerals using a diversity of microbes that grow at a variety of temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70175341','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70175341"><span>Experimental whole-lake increase of <span class="hlt">dissolved</span> organic carbon <span class="hlt">concentration</span> produces unexpected increase in crustacean zooplankton density</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Kelly, Patrick T.; Craig, Nicola; Solomon, Christopher T.; Weidel, Brian C.; Zwart, Jacob A.; Jones, Stuart E.</p> <p>2016-01-01</p> <p>The observed pattern of lake browning, or increased terrestrial <span class="hlt">dissolved</span> organic carbon (DOC) <span class="hlt">concentration</span>, across the northern hemisphere has amplified the importance of understanding how consumer productivity varies with DOC <span class="hlt">concentration</span>. Results from comparative studies suggest these increased DOC <span class="hlt">concentrations</span> may reduce crustacean zooplankton productivity due to reductions in resource quality and volume of suitable habitat. Although these spatial comparisons provide an expectation for the response of zooplankton productivity as DOC <span class="hlt">concentration</span> increases, we still have an incomplete understanding of how zooplankton respond to temporal increases in DOC <span class="hlt">concentration</span> within a single system. As such, we used a whole-lake manipulation, in which DOC <span class="hlt">concentration</span> was increased from 8 to 11 mg L−1 in one basin of a manipulated lake, to test the hypothesis that crustacean zooplankton production should subsequently decrease. In contrast to the spatially derived expectation of sharp DOC-mediated decline, we observed a small increase in zooplankton densities in response to our experimental increase in DOC <span class="hlt">concentration</span> of the treatment basin. This was due to significant increases in gross primary production and resource quality (lower seston carbon-to-phosphorus ratio; C:P). These results demonstrate that temporal changes in lake characteristics due to increased DOC may impact zooplankton in ways that differ from those observed in spatial surveys. We also identified significant interannual variability across our study region, which highlights potential difficulty in detecting temporal responses of organism abundances to gradual environmental change (e.g., browning).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26919470','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26919470"><span>Experimental whole-lake increase of <span class="hlt">dissolved</span> organic carbon <span class="hlt">concentration</span> produces unexpected increase in crustacean zooplankton density.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kelly, Patrick T; Craig, Nicola; Solomon, Christopher T; Weidel, Brian C; Zwart, Jacob A; Jones, Stuart E</p> <p>2016-08-01</p> <p>The observed pattern of lake browning, or increased terrestrial <span class="hlt">dissolved</span> organic carbon (DOC) <span class="hlt">concentration</span>, across the northern hemisphere has amplified the importance of understanding how consumer productivity varies with DOC <span class="hlt">concentration</span>. Results from comparative studies suggest these increased DOC <span class="hlt">concentrations</span> may reduce crustacean zooplankton productivity due to reductions in resource quality and volume of suitable habitat. Although these spatial comparisons provide an expectation for the response of zooplankton productivity as DOC <span class="hlt">concentration</span> increases, we still have an incomplete understanding of how zooplankton respond to temporal increases in DOC <span class="hlt">concentration</span> within a single system. As such, we used a whole-lake manipulation, in which DOC <span class="hlt">concentration</span> was increased from 8 to 11 mg L(-1) in one basin of a manipulated lake, to test the hypothesis that crustacean zooplankton production should subsequently decrease. In contrast to the spatially derived expectation of sharp DOC-mediated decline, we observed a small increase in zooplankton densities in response to our experimental increase in DOC <span class="hlt">concentration</span> of the treatment basin. This was due to significant increases in gross primary production and resource quality (lower seston carbon-to-phosphorus ratio; C:P). These results demonstrate that temporal changes in lake characteristics due to increased DOC may impact zooplankton in ways that differ from those observed in spatial surveys. We also identified significant interannual variability across our study region, which highlights potential difficulty in detecting temporal responses of organism abundances to gradual environmental change (e.g., browning). © 2016 John Wiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18436686','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18436686"><span>Liver <span class="hlt">metal</span> <span class="hlt">concentrations</span> in Greater Sage-grouse (Centrocercus urophasianus).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dailey, Rebecca N; Raisbeck, Merl F; Siemion, Roger S; Cornish, Todd E</p> <p>2008-04-01</p> <p>Greater Sage-grouse (Centrocercus urophasianus) are a species of concern due to shrinking populations associated with habitat fragmentation and loss. Baseline health parameters for this species are limited or lacking, especially with regard to tissue <span class="hlt">metal</span> <span class="hlt">concentrations</span>. To obtain a range of tissue <span class="hlt">metal</span> <span class="hlt">concentrations</span>, livers were collected from 71 Greater Sage-grouse from Wyoming and Montana. Mean +/- SE <span class="hlt">metal</span> <span class="hlt">concentrations</span> (mg/kg wet weight) in liver were determined for vanadium (V) (0.12 +/- 0.01), chromium (Cr) (0.50 +/- 0.02), manganese (Mn) (2.68 +/- 0.11), iron (Fe) (1,019 +/- 103), nickel (Ni) (0.40 +/- 0.04), cobalt (Co) (0.08 +/- 0.02), copper (Cu) (6.43 +/- 0.40), mercury (Hg) (0.30 +/- 0.09), selenium (Se) (1.45 +/- 0.64), zinc (Zn) (59.2 +/- 4.70), molybdenum (Mo) (0.93 +/- 0.07), cadmium (Cd) (1.44 +/- 0.14), barium (Ba) (0.20 +/- 0.03), and lead (Pb) (0.17 +/- 0.03). In addition to providing baseline data, <span class="hlt">metal</span> <span class="hlt">concentrations</span> were compared between sex, age (juvenile/adult), and West Nile virus (WNv) groups (positive/negative). Adult birds had higher <span class="hlt">concentrations</span> of Ni and Cd compared to juveniles. In addition, Zn and Cu <span class="hlt">concentrations</span> were significantly elevated in WNv-positive birds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23380032','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23380032"><span>Heavy <span class="hlt">metal</span> <span class="hlt">concentrations</span> in edible barnacles exposed to natural contamination.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dionísio, M; Costa, A; Rodrigues, A</p> <p>2013-04-01</p> <p>The giant barnacle Megabalanus azoricus is a popular seafood in the Azores. It is mainly caught in coastal environments and sold for domestic human consumption. This species is a filter feeder and can be used as a biomonitor of trace <span class="hlt">metal</span> bioavailabilities. To investigate consumption safety, the <span class="hlt">concentrations</span> of 10 trace <span class="hlt">metals</span> - As, Cd, Cr, Cu, Mn, Pb, Rb, Se, Sr and Zn - were evaluated in 3 body tissues of M. azoricus from 3 sites on 2 islands. There were no significant differences between the <span class="hlt">metal</span> loads of the barnacles from the different sites. However, the <span class="hlt">concentrations</span> of the total trace <span class="hlt">metal</span> loads revealed significant differences among the tissues (cirrus, muscles and ovaries). The <span class="hlt">concentrations</span> of some <span class="hlt">metals</span> in the body were not within the safety levels for consumers, based on the allowable standard levels for crustaceans issued by the European Union and of legislations in several countries. Alarming levels of As and Cd were found. Considering the absence of heavy industry in the region, a non-anthropogenic volcanic source was assumed to be the reason for the observed <span class="hlt">metal</span> levels. Barnacles, in particular M. azoricus, seem to be useful as bioindicators in this peculiar environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28764125','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28764125"><span>Vertical distribution and temporal dynamics of <span class="hlt">dissolved</span> (137)Cs <span class="hlt">concentrations</span> in soil water after the Fukushima Dai-ichi Nuclear Power Plant accident.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Iwagami, Sho; Onda, Yuichi; Tsujimura, Maki; Hada, Manami; Pun, Ishwar</p> <p>2017-11-01</p> <p>Radiocesium ((137)Cs) migration from headwater forested areas to downstream rivers has been investigated in many studies since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, which was triggered by a catastrophic earthquake and tsunami on 11 March 2011. The accident resulted in the release of a huge amount of radioactivity and its subsequent deposition in the environment. A large part of the radiocesium released has been shown to remain in the forest. The <span class="hlt">dissolved</span> (137)Cs <span class="hlt">concentration</span> and its temporal dynamics in river water, stream water, and groundwater have been reported, but reports of <span class="hlt">dissolved</span> (137)Cs <span class="hlt">concentration</span> in soil water remain sparse. In this study, soil water was sampled, and the <span class="hlt">dissolved</span> (137)Cs <span class="hlt">concentrations</span> were measured at five locations with different land-use types (mature/young cedar forest, broadleaf forest, meadow land, and pasture land) in Yamakiya District, located 35 km northwest of FDNPP from July 2011 to October 2012. Soil water samples were collected by suction lysimeters installed at three different depths at each site. <span class="hlt">Dissolved</span> (137)Cs <span class="hlt">concentrations</span> were analyzed using a germanium gamma ray detector. The <span class="hlt">dissolved</span> (137)Cs <span class="hlt">concentrations</span> in soil water were high, with a maximum value of 2.5 Bq/L in July 2011, and declined to less than 0.32 Bq/L by 2012. The declining trend of <span class="hlt">dissolved</span> (137)Cs <span class="hlt">concentrations</span> in soil water was fitted to a two-component exponential model. The rate of decline in <span class="hlt">dissolved</span> (137)Cs <span class="hlt">concentrations</span> in soil water (k1) showed a good correlation with the radiocesium interception potential (RIP) of topsoil (0-5 cm) at the same site. Accounting for the difference of (137)Cs deposition density, we found that normalized <span class="hlt">dissolved</span> (137)Cs <span class="hlt">concentrations</span> of soil water in forest (mature/young cedar forest and broadleaf forest) were higher than those in grassland (meadow land and pasture land). Copyright © 2017 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16782136','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16782136"><span>Baseline <span class="hlt">metal</span> <span class="hlt">concentrations</span> in Paramoera walkeri from East Antarctica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Palmer, Anne S; Snape, Ian; Stark, Jonathan S; Johnstone, Glenn J; Townsend, Ashley T</p> <p>2006-11-01</p> <p>Remediation of the Thala Valley waste disposal site near Casey Station, East Antarctica was conducted in the austral summer of 2003/2004. Biomonitoring of the adjacent marine environment was undertaken using the gammaridean amphipod Paramoera walkeri as a sentinel species [Stark, J.S., Johnstone, G.J., Palmer, A.S., Snape, I., Larner, B.L., Riddle, M.J., in press, . Monitoring the remediation of a near shore waste disposal site in Antarctica using the amphipod Paramoera walkeri and diffusive gradients in thin films (DGTs). Marine Pollution Bulletin and references therein]. Determination of uptake of <span class="hlt">metals</span> and hypothesis testing for differences that could be attributed to contamination required the establishment of baseline <span class="hlt">metal</span> <span class="hlt">concentrations</span> in P. walkeri. Baseline <span class="hlt">metal</span> <span class="hlt">concentrations</span> from two reference locations in the Windmill Islands are presented here. P. walkeri was a found to be a sensitive bioaccumulating organism that recorded spatial and temporal variability at the reference sites. Measurement of <span class="hlt">metals</span> in P. walkeri required the development of a simple digestion procedure that used <span class="hlt">concentrated</span> nitric acid. For the first time, rare earth <span class="hlt">metals</span> were determined with additional clean procedures required to measure ultra low <span class="hlt">concentrations</span> using magnetic sector ICP-MS. Certified and in-house reference materials were employed to ensure method reliability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70133414','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70133414"><span><span class="hlt">Dissolved</span> organic carbon <span class="hlt">concentration</span> controls benthic primary production: results from in situ chambers in north-temperate lakes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Godwin, Sean C.; Jones, Stuart E.; Weidel, Brian C.; Solomon, Christopher T.</p> <p>2014-01-01</p> <p>We evaluated several potential drivers of primary production by benthic algae (periphyton) in north-temperate lakes. We used continuous <span class="hlt">dissolved</span> oxygen measurements from in situ benthic chambers to quantify primary production by periphyton at multiple depths across 11 lakes encompassing a broad range of <span class="hlt">dissolved</span> organic carbon (DOC) and total phosphorous (TP) <span class="hlt">concentrations</span>. Light-use efficiency (primary production per unit incident light) was inversely related to average light availability (% of surface light) in 7 of the 11 study lakes, indicating that benthic algal assemblages exhibit photoadaptation, likely through physiological or compositional changes. DOC alone explained 86% of the variability in log-transformed whole-lake benthic production rates. TP was not an important driver of benthic production via its effects on nutrient and light availability. This result is contrary to studies in other systems, but may be common in relatively pristine north-temperate lakes. Our simple empirical model may allow for the prediction of whole-lake benthic primary production from easily obtained measurements of DOC <span class="hlt">concentration</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70161733','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70161733"><span>Lake transparency: a window into decadal variations in <span class="hlt">dissolved</span> organic carbon <span class="hlt">concentrations</span> in Lakes of Acadia National Park, Maine</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Roesler, Collin S.; Culbertson, Charles W.</p> <p>2016-01-01</p> <p>A forty year time series of Secchi depth observations from approximately 25 lakes in Acadia National Park, Maine, USA, evidences large variations in transparency between lakes but relatively little seasonal cycle within lakes. However, there are coherent patterns over the time series, suggesting large scale processes are responsible. It has been suggested that variations in colored <span class="hlt">dissolved</span> organic matter (CDOM) are primarily responsible for the variations in transparency, both between lakes and over time and further that CDOM is a robust optical proxy for <span class="hlt">dissolved</span> organic carbon (DOC). Here we present a forward model of Secchi depth as a function of DOC based upon first principles and bio-optical relationships. Inverting the model to estimate DOC <span class="hlt">concentration</span> from Secchi depth observations compared well with the measured DOC <span class="hlt">concentrations</span> collected since 1995 (RMS error < 1.3 mg C l-1). This inverse model allows the time series of DOC to be extended back to the mid 1970s when only Secchi depth observations were collected, and thus provides a means for investigating lake response to climate forcing, changing atmospheric chemistry and watershed characteristics, including land cover and land use.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/7003263','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/7003263"><span>Effect of <span class="hlt">dissolved</span> oxygen <span class="hlt">concentrations</span> on fish and invertebrates in large experimental channels</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Heuer, J.H.; Seawell, W.M.</p> <p>1987-07-01</p> <p>The responses of fish (smallmouth bass, channel catfish, golden shiners, and bluegill), zooplankton, and benthic macroinvertebrates to various levels of <span class="hlt">dissolved</span> oxygen (DO) were monitored in six large outdoor channels at TVA's Aquatic Research Laboratory at Browns Ferry Nuclear Plant. Nitrogen stripping was used to remove oxygen from the water, and aquatic organisms were exposed to target levels of 5, 4, 3, and 2 mg/L (2 channels) and to an untreated control from July 24, 1984 until September 24, 1984. Responses of adult golden shiners, bluegill, and channel catfish to DO were not consistent, probably because of predation by smallmouth bass on golden shiners and competition between bluegill and channel catfish. Bluegill spawned successfully only in the control. Cleaned nests were found in the 5 mg/L treatment and partially cleaned nests in the 3 and 4 mg/L treatments, but no evidence of nesting was found in the 2 mg/L treatment. 14 refs., 8 figs., 7 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24338099','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24338099"><span>Predicting <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> using kernel regression modeling approaches with nonlinear hydro-chemical data.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Singh, Kunwar P; Gupta, Shikha; Rai, Premanjali</p> <p>2014-05-01</p> <p>Kernel function-based regression models were constructed and applied to a nonlinear hydro-chemical dataset pertaining to surface water for predicting the <span class="hlt">dissolved</span> oxygen levels. Initial features were selected using nonlinear approach. Nonlinearity in the data was tested using BDS statistics, which revealed the data with nonlinear structure. Kernel ridge regression, kernel principal component regression, kernel partial least squares regression, and support vector regression models were developed using the Gaussian kernel function and their generalization and predictive abilities were compared in terms of several statistical parameters. Model parameters were optimized using the cross-validation procedure. The proposed kernel regression methods successfully captured the nonlinear features of the original data by transforming it to a high dimensional feature space using the kernel function. Performance of all the kernel-based modeling methods used here were comparable both in terms of predictive and generalization abilities. Values of the performance criteria parameters suggested for the adequacy of the constructed models to fit the nonlinear data and their good predictive capabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20390848','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20390848"><span>Scenarios of <span class="hlt">metal</span> <span class="hlt">concentrations</span> in the Arcediano Dam (State of Jalisco, Mexico).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hansen, Anne M; Gonzalez-Marquez, Luis C</p> <p>2010-01-01</p> <p>The city of Guadalajara, Jalisco, Mexico has 4.1 million inhabitants and a serious deficit in water supply. Once constructed, the Arcediano Dam will catch waters from the Verde and Santiago rivers, and after treatment will provide water to the city. The present study was undertaken to formulate scenarios and estimate risks of polluting the water that will be collected in the dam from the release of contaminants accumulated in sediments. Desorption of <span class="hlt">metals</span> from sediments was estimated through sampling of water and sediments, chemical analyses of the environmental samples, and numerical modeling of the water-sediment interactions. Water quality generally increased as the river flowed downstream from the El Salto sampling station to the site where the Arcediano Dam will be constructed. Aluminum exceeded the Mexican Criterion for Drinking Water Supply (MCDWS), at all sampling stations, whereas iron and manganese surpassed the criteria at some stations. Trace <span class="hlt">metals</span> were below their respective criteria. For sediment samples in the river, chrome, copper and zinc exceeded the Canadian Interim Sediment Quality Guidelines (ISQG), whereas manganese and nickel exceeded the probable effect level (PEL). Other <span class="hlt">metals</span> were below these limits. With exception of the El Salto sampling station, <span class="hlt">metals</span> were mostly enriched in iron-containing sediments, followed by aluminum-containing clays and, to a lesser extent, by manganese oxides. Therefore, the interaction of <span class="hlt">metals</span> with iron oxides was considered as the controlling adsorption mechanism. Simulations to estimate risks of water contamination by desorption of <span class="hlt">metals</span> from sediments indicate that manganese and nickel may reach <span class="hlt">concentrations</span> higher than the CDWS. In some cases, <span class="hlt">dissolved</span> <span class="hlt">concentrations</span> of lead and chrome may be higher than the respective CDWS, especially under conditions of high accumulation of sediments in the dam. Arsenic, copper and mercury <span class="hlt">concentrations</span> did not exceed the CDWS under the simulated conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1567395','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1567395"><span>Monitoring <span class="hlt">metal</span> <span class="hlt">concentrations</span> in tissues and single cells using ultramicrosensors.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Malinski, T; Grunfeld, S; Taha, Z; Tomboulian, P</p> <p>1994-01-01</p> <p>Intercellular and extracellular <span class="hlt">metal</span> <span class="hlt">concentrations</span> were measured using carbon fiber ultramicrosensors plated with mercury or with polymeric porphyrinic p-type semiconductors. <span class="hlt">Concentrations</span> of unbound nickel and lead ions were studied within individual BC3H-1 myocytes, and H4-11-C3 rat hepatoma cells. Unbound ions are predominantly solvated inorganic ions not coordinated to biological cellular components. Fabrication of ultramicrosensors appropriate for the cells under investigation is described, including procedures for sharpening and waxing the microsensors in order to control the shape, area, and dimensions of the electroactive surface. <span class="hlt">Metal</span> ion movement through cell membranes and intracellular ion diffusion in aorta tissue were studied. Images Figure 2. PMID:7843090</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26156374','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26156374"><span>Basin-scale transport of hydrothermal <span class="hlt">dissolved</span> <span class="hlt">metals</span> across the South Pacific Ocean.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Resing, Joseph A; Sedwick, Peter N; German, Christopher R; Jenkins, William J; Moffett, James W; Sohst, Bettina M; Tagliabue, Alessandro</p> <p>2015-07-09</p> <p>Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean. Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle. It has been thought that most of the <span class="hlt">dissolved</span> iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources and is thus of limited importance for ocean biogeochemistry. This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal <span class="hlt">dissolved</span> iron may facilitate its long-range oceanic transport. Such transport has been subsequently inferred from spatially limited oceanographic observations. Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal <span class="hlt">dissolved</span> iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. <span class="hlt">Dissolved</span> iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed. Based on our observations, we estimate a global hydrothermal <span class="hlt">dissolved</span> iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates. Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal <span class="hlt">dissolved</span> iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export production.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22542300','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22542300"><span><span class="hlt">Dissolved</span> organic carbon (DOC) <span class="hlt">concentrations</span> in UK soils and the influence of soil, vegetation type and seasonality.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>van den Berg, Leon J L; Shotbolt, Laura; Ashmore, Mike R</p> <p>2012-06-15</p> <p>Given the lack of studies which measured <span class="hlt">dissolved</span> organic carbon (DOC) over long periods, especially in non-forest habitat, the aim of this study was to expand the existing datasets with data of mainly non-forest sites that were representative of the major soil and habitat types in the UK. A further aim was to predict DOC <span class="hlt">concentrations</span> from a number of biotic and abiotic explanatory variables such as rainfall, temperature, vegetation type and soil type in a multivariate way. Pore water was sampled using Rhizon or Prenart samplers at two to three week intervals for 1 year. DOC, pH, organic carbon, carbon/nitrogen (C:N) ratios of soils and slope were measured and data on vegetation, soil type, temperature and precipitation were obtained. The majority of the variation in DOC <span class="hlt">concentrations</span> between the UK sites could be explained by simple empirical models that included annual precipitation, and soil C:N ratio with precipitation being negatively related to DOC <span class="hlt">concentrations</span> and C:N ratio being positively related to DOC <span class="hlt">concentrations</span>. Our study adds significantly to the data reporting DOC <span class="hlt">concentrations</span> in soils, especially in grasslands, heathlands and moorlands. Broad climatic and site factors have been identified as key factors influencing DOC <span class="hlt">concentrations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15052568','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15052568"><span>Dynamic headspace: a single-step extraction for isotopic analysis of microg/L <span class="hlt">concentrations</span> of <span class="hlt">dissolved</span> chlorinated ethenes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Morrill, Penny L; Lacrampe-Couloume, Georges; Lollar, Barbara Sherwood</p> <p>2004-01-01</p> <p>In this study a dynamic headspace method was developed to measure the carbon isotope values of <span class="hlt">dissolved</span> chlorinated ethenes at microg/L <span class="hlt">concentrations</span>. A gas chromatograph/combustion/isotope ratio mass spectrometer (GC/C/IRMS) was modified to include a headspace extraction system followed by a cryogenic trap. Extracting headspace from a 160 mL vial with 80 mL of aqueous solution and 40 g of NaCl for 8-12 min resulted in accurate and reproducible delta13C values for trichloroethene (TCE) and cis-1,2-dichloroethene (cDCE) at <span class="hlt">concentrations</span> of 50-75 microg/L. Based on these results a conservative lower limit of quantitation of 38 microg/L can be calculated for these compounds. For more volatile compounds such as tetrachloroethene (PCE) and vinyl chloride (VC), field data analyzed using this method indicate a lower limit of quantitation in the tens of microg /L range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.water.usgs.gov/wri984147','USGSPUBS'); return false;" href="http://pubs.water.usgs.gov/wri984147"><span><span class="hlt">Dissolved</span> organic carbon <span class="hlt">concentrations</span> and compositions, and trihalomethane formation potentials in waters from agricultural peat soils, Sacramento-San Joaquin Delta, California; implications for drinking-water quality</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Fujii, Roger; Ranalli, Anthony J.; Aiken, George R.; Bergamaschi, Brian A.</p> <p>1998-01-01</p> <p>Water exported from the Sacramento-San Joaquin River delta (Delta) is an important drinking-water source for more than 20 million people in California. At times, this water contains elevated <span class="hlt">concentrations</span> of <span class="hlt">dissolved</span> organic carbon and bromide, and exceeds the U.S. Environmental Protection Agency's maximum contaminant level for trihalomethanes of 0.100 milligrams per liter if chlorinated for drinking water. About 20 to 50 percent of the trihalomethane precursors to Delta waters originates from drainage water from peat soils on Delta islands. This report elucidates some of the factors and processes controlling and affecting the <span class="hlt">concentration</span> and quality of <span class="hlt">dissolved</span> organic carbon released from peat soils and relates the propensity of <span class="hlt">dissolved</span> organic carbon to form trihalomethanes to its chemical composition.Soil water was sampled from near-surface, oxidized, well-decomposed peat soil (upper soil zone) and deeper, reduced, fibrous peat soil (lower soil zone) from one agricultural field in the west central Delta over 1 year. <span class="hlt">Concentrations</span> of <span class="hlt">dissolved</span> organic carbon in the upper soil zone were highly variable, with median <span class="hlt">concentrations</span> ranging from 46.4 to 83.2 milligrams per liter. <span class="hlt">Concentrations</span> of <span class="hlt">dissolved</span> organic carbon in samples from the lower soil zone were much less variable and generally slightly higher than samples from the upper soil zone, with median <span class="hlt">concentrations</span> ranging from 49.3 to 82.3 milligrams per liter. The <span class="hlt">dissolved</span> organic carbon from the lower soil zone had significantly higher aromaticity (as measured by specific ultraviolet absorbance) and contained significantly greater amounts of aromatic humic substances (as measured by XAD resin fractionation and carbon-13 nuclear magnetic resonance analysis of XAD isolates) than the <span class="hlt">dissolved</span> organic carbon from the upper soil zone. These results support the conclusion that more aromatic forms of <span class="hlt">dissolved</span> organic carbon are produced under anaerobic conditions compared to aerobic conditions</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EnMan..53..959L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EnMan..53..959L"><span>Spatial and Seasonal Variation of <span class="hlt">Dissolved</span> Organic Carbon (DOC) <span class="hlt">Concentrations</span> in Irish Streams: Importance of Soil and Topography Characteristics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Wen; Xu, Xianli; McGoff, Nicola M.; Eaton, James M.; Leahy, Paul; Foley, Nelius; Kiely, Gerard</p> <p>2014-05-01</p> <p><span class="hlt">Dissolved</span> organic carbon (DOC) <span class="hlt">concentrations</span> have increased in many sites in Europe and North America in recent decades. High DOC <span class="hlt">concentrations</span> can damage the structure and functions of aquatic ecosystems by influencing water chemistry. This study investigated the spatial and seasonal variation of DOC <span class="hlt">concentrations</span> in Irish streams across 55 sites at seven time occasions over 1 year (2006/2007). The DOC <span class="hlt">concentrations</span> ranged from 0.9 to 25.9 mg/L with a mean value of 6.8 and a median value of 5.7 mg/L and varied significantly over the course of the year. The DOC <span class="hlt">concentrations</span> from late winter (February: 5.2 ± 3.0 mg/L across 55 sites) and early spring (April: 4.5 ± 3.5 mg/L) had significantly lower DOC <span class="hlt">concentrations</span> than autumn (October: mean 8.3 ± 5.6 mg/L) and early winter (December: 8.3 ± 5.1 mg/L). The DOC production sources (e.g., litterfall) or the accumulation of DOC over dry periods might be the driving factor of seasonal change in Irish stream DOC <span class="hlt">concentrations</span>. Analysis of data using stepwise multiple linear regression techniques identified the topographic index (TI, an indication of saturation-excess runoff potential) and soil conditions (organic carbon content and soil drainage characteristics) as key factors in controlling DOC spatial variation in different seasons. The TI and soil carbon content (e.g., soil organic carbon; peat occurrence) are positively related to DOC <span class="hlt">concentrations</span>, while well-drained soils are negatively related to DOC <span class="hlt">concentrations</span>. The knowledge of spatial and seasonal variation of DOC <span class="hlt">concentrations</span> in streams and their drivers are essential for optimum riverine water resources management.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16646441','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16646441"><span>Change of <span class="hlt">dissolved</span> gaseous mercury <span class="hlt">concentrations</span> in a southern reservoir lake (Tennessee) following seasonal variation of solar radiation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Hong; Dill, Christopher; Kuiken, Todd; Ensor, Melissa; Crocker, William Chad</p> <p>2006-04-01</p> <p>A 12-month field study was conducted consecutively from June 2003 to May 2004 to quantify temporal variations of <span class="hlt">dissolved</span> gaseous mercury (DGM) <span class="hlt">concentrations</span> in Cane Creek Lake, a southern reservoir lake (Cookeville, TN). Diurnal changes of DGM <span class="hlt">concentrations</span> in two periods (morning increase vs afternoon decrease with an around-noon peak) were observed, and the changes closely followed daily solar radiation variation trends. The diurnal patterns prevailed in the late spring and summer, but became vague in the late fall and winter. The monthly mean DGM <span class="hlt">concentrations</span> peaked at 40.8 pg L(-1) in July and reached the lowest at 14.2 pg L(-1) in December and 21.9 pg L(-1) in January; this DGM <span class="hlt">concentration</span> change closely followed the monthly mean solar radiation variation trend. The increase of the lake DGM <span class="hlt">concentration</span> from January to July and its decrease from July to December mirror the typical daily rhythm of DGM <span class="hlt">concentration</span> variations in the two periods. This finding supports the following hypothesis: The natural phenomenon of daily oscillation of freshwater DGM <span class="hlt">concentrations</span> that follows diurnal solar radiation variation would manifest on a seasonal scale. High DGM <span class="hlt">concentrations</span> were found in the spring and summer and low in the fall and winter (seasonal mean: 34.2, 37.5, 20.0, 24.4 pg L(-1), respectively). This seems to suggest an annual occurrence of two periods of the seasonal DGM level fluctuation (spring and summer high vs fall and winter low DGM levels). Linear relationships of the monthly mean DGM <span class="hlt">concentrations</span> were found with the monthly mean global solar radiation (R2 = 0.82, P < 0.05) and UVA radiation (R2 = 0.84, P < 0.05). Linear relationships of the seasonal mean DGM <span class="hlt">concentrations</span> were also found with the seasonal mean global solar radiation (R2 = 0.85, P = 0.08) and UVA radiation (R2 = 0.93, P < 0.05).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5467154','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5467154"><span>Heavy <span class="hlt">metal</span> <span class="hlt">concentrations</span> in tissues of Virginia river otters</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Anderson-Bledsoe, K.L.; Scanlon, P.F.</p> <p>1983-04-01</p> <p><span class="hlt">Concentrations</span> of lead, cadmium, zinc and copper in liver, kidney and bone samples of otter harvested during the 1979-1980 and 1980-1981 trapping seasons were determined by atomic absorption spectrophotometry. Correlations between <span class="hlt">metal</span> <span class="hlt">concentrations</span> and age for all three tissues were nonsignificant. Correlations among the <span class="hlt">concentrations</span> of the four elements in liver and kidney samples were also nonsignificant for otter samples in both years. The highest correlation coefficient (0.47) was found between zinc and copper <span class="hlt">concentrations</span> in liver samples from otters trapped during the 1979-1980 trapping season. (JMT)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28226277','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28226277"><span>Distribution of trace <span class="hlt">metals</span> (Cu, Pb, Ni, Zn) between particulate, colloidal and truly <span class="hlt">dissolved</span> fractions in wastewater treatment.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hargreaves, Andrew J; Vale, Peter; Whelan, Jonathan; Constantino, Carlos; Dotro, Gabriela; Campo, Pablo; Cartmell, Elise</p> <p>2017-05-01</p> <p>The distribution of Cu, Pb, Ni and Zn between particulate, colloidal and truly <span class="hlt">dissolved</span> size fractions in wastewater from a trickling filter treatment plant was investigated. Samples of influent, primary effluent, humus effluent, final effluent and sludge holding tank returns were collected and separated into particulate (i.e. > 0.45 μm), colloidal (i.e. 1 kDa to 0.45 μm), and truly <span class="hlt">dissolved</span> (i.e. < 1 kDa) fractions using membrane filters. In the influent, substantial proportions of Cu (60%), Pb (67%), and Zn (32%) were present in the particulate fraction which was removed in conjunction with suspended particles at the works in subsequent treatment stages. In final effluent, sizeable proportions of Cu (52%), Pb (32%), Ni (44%) and Zn (68%) were found within the colloidal size fraction. Calculated ratios of soluble <span class="hlt">metal</span> to organic carbon suggest the <span class="hlt">metal</span> to be adsorbed to or complexed with non-humic macromolecules typically found within the colloidal size range. These findings suggest that technologies capable of removing particles within the colloidal fraction have good potential to enhance <span class="hlt">metals</span> removal from wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23751809','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23751809"><span>Simultaneous nitrogen and organic carbon removal in aerobic granular sludge reactors operated with high <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Di Bella, Gaetano; Torregrossa, Michele</p> <p>2013-08-01</p> <p>Simultaneous nitrification and denitrification (SND) together with organic removal in granules is usually carried out without <span class="hlt">Dissolved</span> Oxygen (DO) <span class="hlt">concentration</span> control, at "low DO" (with a DO<30-50% of the saturation value, about 3-4 mg/L) to promote anoxic conditions within the aggregates. These conditions can sometimes be in detrimental of the stability of the granules itself due to a lack of shear force. In this work, the authors achieved SND without oxygen control with big sized granules. More specifically, the paper presents a experimentation focused on the analysis of two Sequencing Batch Reactors (SBRs), in bench scale, working with different aerobic sludge granules, in terms of granule size, and high DO <span class="hlt">concentration</span>, (with <span class="hlt">concentration</span> varying from anoxic conditions, about DO ∼0 mg/L, to values close to those of saturation, >7-8 mg/L, during feast and famine conditions respectively). In particular, different strategies of cultivation and several organic and nitrogen loading rate have been applied, in order to evaluate the efficiencies in SND process without <span class="hlt">dissolved</span> oxygen control. The results show that, even under conditions of high DO <span class="hlt">concentration</span>, nitrogen and organic matter can be simultaneously removed, with efficiency >90%. Nevertheless, the biological conditions in the inner layer of the granule may change significantly between small and big granules, during the feast and famine periods. From point of view of granule stability, it is also interesting that with a particle size greater than 1.5mm, after the cultivation start-up, the granules are presented stable for a long period (about 100 days) and, despite the variations of operational conditions, the granules breaking was always negligible. Copyright © 2013 Elsevier Ltd. All rights reserved.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19408313','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19408313"><span>Rapid depletion of <span class="hlt">dissolved</span> oxygen in 96-well microtiter plate Staphylococcus epidermidis biofilm assays promotes biofilm development and is influenced by inoculum cell <span class="hlt">concentration</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cotter, John J; O'Gara, James P; Casey, Eoin</p> <p>2009-08-01</p> <p>Biofilm-related research using 96-well microtiter plates involves static incubation of plates indiscriminate of environmental conditions, making oxygen availability an important variable which has not been considered to date. By directly measuring <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> over time we report here that <span class="hlt">dissolved</span> oxygen is rapidly consumed in Staphylococcus epidermidis biofilm cultures grown in 96-well plates irrespective of the oxygen <span class="hlt">concentration</span> in the gaseous environment in which the plates are incubated. These data indicate that depletion of <span class="hlt">dissolved</span> oxygen during growth of bacterial biofilm cultures in 96-well plates may significantly influence biofilm production. Furthermore higher inoculum cell <span class="hlt">concentrations</span> are associated with more rapid consumption of <span class="hlt">dissolved</span> oxygen and higher levels of S. epidermidis biofilm production. Our data reveal that oxygen depletion during bacterial growth in 96-well plates may significantly influence biofilm production and should be considered in the interpretation of experimental data using this biofilm model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15792307','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15792307"><span><span class="hlt">Concentration</span> of selected <span class="hlt">metals</span> in muscle of various fish species.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Andreji, Jaroslav; Stránai, Ivan; Massányi, Peter; Valent, Miroslav</p> <p>2005-01-01</p> <p>The purpose of this study was to assess <span class="hlt">concentration</span> of selected <span class="hlt">metals</span> (Fe, Mn, Zn, Cu, Ni, Co, Cr, Pb, Cd, and Hg) in the muscle of four common Slovak fish species (chub--Leuciscus cephalus, barbel--Barbus barbus, roach--Rutilus rutilus, and perch--Perca fluviatilis). Furthermore, correlations among the selected <span class="hlt">metals</span> and order of <span class="hlt">metal</span> accumulation in the fish muscle were determined. An electrofishing technique was used for collecting the fish from the Nitra River (Slovakia) in September 2003. <span class="hlt">Concentrations</span> of selected <span class="hlt">metals</span> were measured using an atomic absorption spectrophotometer Pye Unicam SP9. The <span class="hlt">concentrations</span> of <span class="hlt">metals</span> (mg/kg wet weight basis) ranged as follows: Fe 3.41-15.14; Mn 0.20-0.81; Zn 3.51-15.64; Cu 0.25-0.78; Ni 0.07-0.25; Co 0.05-0.19; Cr 0.11-0.42; Pb 0.20-5.81; Cd 0.06-0.56, and Hg 1.35-6.52. Significant correlations (P < 0.05) between Fe-Cu, Fe-Ni, Fe-Cr, Mn-Ni, Mn-Cr, Mn-Cr, Cu-Ni, and Ni-Cr were observed. The level of lead exceeded the maximum allowable <span class="hlt">concentration</span> in Slovakia by Codex Alimentarius for safe human consumption (0.2 mg/kg) in the majority of samples (97.2%). Content of Cd (0.23 +/- 0.13 mg/kg wet weight) and Hg (2.85 +/- 1.22 mg/kg wet weight) in the fish muscle exceeded maximum allowed levels in all samples. On average, the order of <span class="hlt">metal</span> <span class="hlt">concentrations</span> in the fish muscle was: Fe > Zn > Hg > Pb > Cu > Mn > Cd > Cr > Ni > Co.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27149152','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27149152"><span>The <span class="hlt">concentration</span> and changes in freely <span class="hlt">dissolved</span> polycyclic aromatic hydrocarbons in biochar-amended soil.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Oleszczuk, Patryk; Kuśmierz, Marcin; Godlewska, Paulina; Kraska, Piotr; Pałys, Edward</p> <p>2016-07-01</p> <p>The presence of polycyclic aromatic hydrocarbons (PAHs) in biochars hinders their environmental use. The aim of this study was to determine the freely <span class="hlt">dissolved</span> (Cfree) PAH content in soil amended with biochar in a long-term (851 days) field experiment. Biochar was added to the soil at a rate of 30 and 45 t/ha. The addition of biochar to the soil resulted in a decrease in Σ13 Cfree PAHs by 25 and 22%, in the soil with the addition of biochar at the rate of 30 and 45 t/ha, respectively. As far as individual PAHs are concerned, in most cases a reduction in Cfree was also observed (from 3.6 to 66%, depending on the biochar rate). During the first 105 days of the experiment, the content of Σ13 Cfree in the biochar-amended soil significantly decreased by 26% (30 t/ha) and 36% (45 t/ha). After this period of time until the end of the experiment, no significant changes in Cfree were observed, regardless of the biochar rate. However, the behavior of individual PAH groups differed depending on the number of rings and experimental treatment. Ultimately, after 851 days of the experiment the content of Σ13 Cfree PAHs was lower by 29% (30 t/ha) and 35% (45 t/ha) compared to the beginning of the study as well as lower by 40% (30 t/ha) and 42% (45 t/ha) than in the control soil. The log KTOC coefficients calculated for the biochar-amended soils were higher immediately after adding biochar and subsequently they gradually decreased, indicating the reduced strength of the interaction between biochar and the studied PAHs. The obtained results show that the addition of biochar to soil does not create a risk in terms of the content of Cfree PAHs. Copyright © 2016 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22350041','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22350041"><span>Normal <span class="hlt">concentrations</span> of heavy <span class="hlt">metals</span> in autistic spectrum disorders.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Albizzati, A; Morè, L; Di Candia, D; Saccani, M; Lenti, C</p> <p>2012-02-01</p> <p>Autism is a neurological-psychiatric disease. In the last 20 years we witnessed a strong increase of autism diagnoses. To explain this increase, some scientists put forward the hypothesis that heavy <span class="hlt">metal</span> intoxication may be one of the causes of autism. The origin of such an intoxication was hypothesised to be vaccines containing thimerosal as antimicrobic preservative. This preservative is mainly made up of mercury. The aim of our research was to investigate the correlation between autism and high biological <span class="hlt">concentrations</span> of heavy <span class="hlt">metals</span>. Seventeen autistic patients, between 6 and 16 years old (average: 11.52 DS: 3.20) (15 males and 2 females), were investigated, as well as 20 non autistic subjects from neuropsychiatric service between 6 and 16 years (average: 10.41 DS: 3.20) (15 males and 2 females). In both groups blood, urine and hair samples were analysed trough means of a semiquantitative analysis of heavy <span class="hlt">metal</span> dosing. The <span class="hlt">metals</span> analysed were Lead, mercury, cadmium and aluminium, since their build-up may give both neurological and psychiatric symptoms. The comparison of the mean values of the <span class="hlt">concentrations</span> between the groups, performed with ANOVA test, has shown no statistically relevant differences. There wasn't correlation between autism and heavy <span class="hlt">metal</span> <span class="hlt">concentration</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21670987','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21670987"><span>Assessment of potable water quality including organic, inorganic, and trace <span class="hlt">metal</span> <span class="hlt">concentrations</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nahar, Mst Shamsun; Zhang, Jing</p> <p>2012-02-01</p> <p>The quality of drinking water (tap, ground, and spring) in Toyama Prefecture, Japan was assessed by studying quality indicators including major ions, total carbon, and trace <span class="hlt">metal</span> levels. The physicochemical properties of the water tested were different depending on the water source. Major ion <span class="hlt">concentrations</span> (Ca(2+), K(+), Si(4+), Mg(2+), Na(+), SO(4)(2-), HCO(3)(-), NO(3)(-), and Cl(-)) were determined by ion chromatography, and the results were used to generate Stiff diagrams in order to visually identify different water masses. Major ion <span class="hlt">concentrations</span> were higher in ground water than in spring and tap water. The relationship between alkaline <span class="hlt">metals</span> (Na(+) and K(+)), alkaline-earth <span class="hlt">metals</span> (Ca(2+) and Mg(2+)), and HCO(3)(-) showed little difference between deep and shallow ground water. Toyama ground, spring, and tap water were all the same type of water mass, called Ca-HCO(3). The calculated total <span class="hlt">dissolved</span> solid values were below 300 mg/L for all water sources and met World Health Organization (WHO) water quality guidelines. Trace levels of As, Cd, Cr, Co, Cu, Fe, Pb, Mn, Mo, Ni, V, Zn, Sr, and Hg were detected in ground, spring, and tap water sources using inductively coupled plasma atomic emission spectrometry, and their levels were below WHO and Japanese water quality standard limits. Volatile organic carbon compounds were quantified by headspace gas chromatography-mass spectrometry, and the measured <span class="hlt">concentrations</span> met WHO and Japanese water quality guidelines. Total trihalomethanes (THMs) were the major contaminant detected in all natural drinking water sources, but the <span class="hlt">concentration</span> was highest in tap water (37.27 ± 0.05 μg/L). Notably, THMs <span class="hlt">concentrations</span> reached up to 1.1 ± 0.05 μg/L in deep ground water. The proposed model gives an accurate description of the organic, inorganic, and trace heavy <span class="hlt">metal</span> indicators studied here and may be used in natural clean water quality management.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22818738','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22818738"><span>Analyzing freely <span class="hlt">dissolved</span> <span class="hlt">concentrations</span> of cationic surfactant utilizing ion-exchange capability of polyacrylate coated solid-phase microextraction fibers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Yi; Droge, Steven T J; Hermens, Joop L M</p> <p>2012-08-24</p> <p>A 7-μm polyacrylate (PA) coated fiber was successfully employed to determine freely <span class="hlt">dissolved</span> <span class="hlt">concentrations</span> of cationic surfactants by solid-phase microextraction (SPME) and utilizing the capability of the PA-coating to sorb organic cations via ion-exchange at carboxylic groups. Measured fiber-water partitioning coefficients (K(fw)) were constant below a fiber loading of 2mmol per liter polyacrylate, allowing for simple and accurate analysis in a <span class="hlt">concentration</span> range that is relevant from a risk assessment point of view. Ion-exchange was confirmed to be the main sorption mechanism because of a decreasing K(fw) with either higher CaCl(2) <span class="hlt">concentrations</span> or lower pH, and maximum fiber uptake at the polyacrylate cation-exchange capacity (CEC, at 30mmol/L PA). Fiber-water sorption isotherms were established in various aqueous media in toxicological relevant <span class="hlt">concentrations</span>. The developed SPME method has a high potential for application in ecotoxicological studies, as demonstrated in sorption studies with humic acid in different electrolyte solutions at aqueous <span class="hlt">concentrations</span> down to the sub nM range. Cationic surfactant sorption affinities for humic acid also depend on medium composition but are orders of magnitude higher than to the PA fiber on a sorbent weight basis. Copyright © 2012 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18969037','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18969037"><span>Chromotropic acid-formaldehyde reaction in strongly acidic media. The role of <span class="hlt">dissolved</span> oxygen and replacement of <span class="hlt">concentrated</span> sulphuric acid.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fagnani, E; Melios, C B; Pezza, L; Pezza, H R</p> <p>2003-05-28</p> <p>The procedure for formaldehyde analysis recommended by the National Institute for Occupational Safety and Health (NIOSH) is the Chromotropic acid spectrophotometric method, which is the one that uses <span class="hlt">concentrated</span> sulphuric acid. In the present study the oxidation step associated with the aforementioned method for formaldehyde determination was investigated. Experimental evidence has been obtained indicating that when <span class="hlt">concentrated</span> H(2)SO(4) (18 mol l(-1)) is used (as in the NIOSH procedure) that acid is the oxidizing agent. On the other hand, oxidation through <span class="hlt">dissolved</span> oxygen takes place when <span class="hlt">concentrated</span> H(2)SO(4) is replaced by <span class="hlt">concentrated</span> hydrochloric (12 mol l(-1)) and phosphoric (14.7 mol l(-1)) acids as well as by diluted H(2)SO(4) (9.4 mol l(-1)). Based on investigations concerning the oxidation step, a modified procedure was devised, in which the use of the potentially hazardous and corrosive <span class="hlt">concentrated</span> H(2)SO(4) was eliminated and advantageously replaced by a less harmful mixture of HCl and H(2)O(2).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20488698','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20488698"><span>Effects of constant and shifting <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> on the growth and antibiotic activity of Xenorhabdus nematophila.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Yong-Hong; Fang, Xiang-Ling; Li, Yu-Ping; Zhang, Xing</p> <p>2010-10-01</p> <p>To evaluate the effects of <span class="hlt">dissolved</span> oxygen (DO) control strategy on cell growth and the production of antibiotic (cyclo(2-Me-BABA-Gly)) by Xenorhabdus nematophila. The effects of different agitation speeds and DO <span class="hlt">concentrations</span> on cell growth and antibiotic activity of X. nematophila YL001 were examined. Experiments showed that higher agitation speeds and DO <span class="hlt">concentrations</span> at earlier fermentation stage were favorable for cell growth and antibiotic production. At mid- and later-stage, properly decreasing DO <span class="hlt">concentration</span> can strengthen cell growth and antibiotic production. Based on the kinetic information about the effects of agitation speeds and DO <span class="hlt">concentrations</span> on the fermentation, the two-stage DO control strategy in which DO <span class="hlt">concentration</span> was controlled to 70% in the first 18 h, and then switched to 50% after 18 h, was established to improve the biomass and antibiotic activity. By applying this DO-shift strategy in X. nematophila YL001 fermentation, maximal antibiotic activity and biomass reached 252.0+/-6.10 U/mL and 30.04+/-2.50 g/L, respectively, thus was 18.99% and 15.36% more than in the cultures at constantly 50% DO. Copyright 2010 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24862001','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24862001"><span>Effects of inoculum type and bulk <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> on achieving partial nitrification by entrapped-cell-based reactors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rongsayamanont, Chaiwat; Limpiyakorn, Tawan; Khan, Eakalak</p> <p>2014-07-01</p> <p>An entrapment of nitrifiers into gel matrix is employed as a tool to fulfill partial nitrification under non-limiting <span class="hlt">dissolved</span> oxygen (DO) <span class="hlt">concentrations</span> in bulk solutions. This study aims to clarify which of these two attributes, inoculum type and DO <span class="hlt">concentration</span> in bulk solutions, is the decisive factor for partial nitrification in an entrapped-cell based system. Four polyvinyl alcohol entrapped inocula were prepared to have different proportions of nitrite-oxidizing bacteria (NOB) and nitrite-oxidizing activity. At a DO <span class="hlt">concentration</span> of 3 mg l(-1), the number of active NOB cells in an inoculum was the decisive factor for partial nitrification enhancement. However, when the DO <span class="hlt">concentration</span> was reduced to 2 mg l(-1), all entrapped cell inocula showed similar degrees of partial nitrification. The results suggested that with the lower bulk DO <span class="hlt">concentration</span>, the preparation of entrapped cell inocula is not useful as the DO level becomes the decisive factor for achieving partial nitrification. Copyright © 2014 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012OptLE..50...74S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012OptLE..50...74S"><span><span class="hlt">Dissolved</span> oxygen <span class="hlt">concentration</span> field measurement in micro-scale water flows using PtOEP/PS film sensor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Song, Dae Hun; Kim, Hyun Dong; Kim, Kyung Chun</p> <p>2012-01-01</p> <p>A planar optode system based on an oxygen quenchable luminophore platinum (II) octaethyporphrin (PtOEP) bound with thin polystyrene (PS) film and UV light-emitting diodes (UV-LEDs) was developed to measure the <span class="hlt">dissolved</span> oxygen (DO) <span class="hlt">concentration</span> field in micro-scale water flows. An intensity-based method adopting a pixel-to-pixel in situ calibration technique was used to visualize DO <span class="hlt">concentration</span> fields around an impinging micro-nozzle. The achievable spatial resolution of the acquired <span class="hlt">concentration</span> map could be as high as 2.94 μm. A micro-round water jet having 100% of DO was obliquely impinged on to a PtOEP/PS film coated plate placed in a 0% of DO water container. Velocity fields were obtained by computational fluid dynamics (CFD) analysis and it is demonstrated that the high DO <span class="hlt">concentration</span> region was coincided with the impingement area. The DO <span class="hlt">concentration</span> gradient due to DO diffusion was affected by the Reynolds number.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12475065','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12475065"><span>Storage mediums affect <span class="hlt">metal</span> <span class="hlt">concentration</span> in woodlice (Isopoda).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hendrickx, Frederik; Maelfait, Jean-Pierre; De Mayera, Ann; Tack, Filip M G; Verloo, Marc G</p> <p>2003-01-01</p> <p>Terrestrial invertebrates are becoming widely established as tools to assess heavy <span class="hlt">metal</span> pollution at contaminated sites. A practical and time saving method to sample terrestrial invertebrates consist of pitfall traps, often filled with a 4% formaldehyde solution and some detergent. The reliability of <span class="hlt">metal</span> <span class="hlt">concentrations</span> based on organisms captured and stored in this solution might however be questioned and we therefore tested the effect of formaldehyde on Zn, Cu, Cd and Pb <span class="hlt">concentration</span> experimentally in three isopod species. Our results showed that in many cases, significant decreases in Cu <span class="hlt">concentrations</span> compared to animals stored in a freezer were observed that could be as high as 40%, while Zn, Cd and Pb <span class="hlt">concentrations</span> increased. A regression analysis of individual dry weight on individual size revealed that formaldehyde decreases the dry weight substantially and in that way causes increased measurements of Zn, Cd and Pb <span class="hlt">concentrations</span>. We conclude that pitfall traps with formaldehyde should better not be used to collect animals in which <span class="hlt">concentrations</span> of heavy <span class="hlt">metals</span> or other toxic substances will be determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApWS....1..125G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApWS....1..125G"><span>Prediction of toxic <span class="hlt">metals</span> <span class="hlt">concentration</span> using artificial intelligence techniques</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gholami, R.; Kamkar-Rouhani, A.; Doulati Ardejani, F.; Maleki, Sh.</p> <p>2011-12-01</p> <p>Groundwater and soil pollution are noted to be the worst environmental problem related to the mining industry because of the pyrite oxidation, and hence acid mine drainage generation, release and transport of the toxic <span class="hlt">metals</span>. The aim of this paper is to predict the <span class="hlt">concentration</span> of Ni and Fe using a robust algorithm named support vector machine (SVM). Comparison of the obtained results of SVM with those of the back-propagation neural network (BPNN) indicates that the SVM can be regarded as a proper algorithm for the prediction of toxic <span class="hlt">metals</span> <span class="hlt">concentration</span> due to its relative high correlation coefficient and the associated running time. As a matter of fact, the SVM method has provided a better prediction of the toxic <span class="hlt">metals</span> Fe and Ni and resulted the running time faster compared with that of the BPNN.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70012081','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70012081"><span><span class="hlt">Concentration</span> of some platinum-group <span class="hlt">metals</span> in coal</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Finkelman, R.B.; Aruscavage, P. J.</p> <p>1981-01-01</p> <p>New data on some platinum group <span class="hlt">metals</span> in coal indicate that the <span class="hlt">concentration</span> of Pt is generally less than about 5 ppb, that of Pd is generally less than 1 ppb, and that of Rh is generally less than 0.5 ppb. No conclusive evidence was obtained concerning the mode of occurrence of these elements in coal. ?? 1981.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/40667','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/40667"><span><span class="hlt">Metal</span> <span class="hlt">concentrations</span> in urban riparian sediments along an urbanization gradient</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Daniel J. Bain; Ian D. Yesilonis; Richard V. Pouyat</p> <p>2012-01-01</p> <p>Urbanization impacts fluvial systems via a combination of changes in sediment chemistry and basin hydrology. While chemical changes in urban soils have been well characterized, similar surveys of riparian sediments in urbanized areas are rare. <span class="hlt">Metal</span> <span class="hlt">concentrations</span> were measured in sediments collected from riparian areas across the urbanization gradient in Baltimore, MD...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59961&keyword=UV+AND+photo&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78821947&CFTOKEN=43024025','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59961&keyword=UV+AND+photo&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78821947&CFTOKEN=43024025"><span>PHOTOCHEMICAL ALTERATION OF <span class="hlt">DISSOLVED</span> ORGANIC MATTER: EFFECTS ON THE <span class="hlt">CONCENTRATION</span> AND ACIDITIES OF IONIZABLE SITES IN <span class="hlt">DISSOLVED</span> ORGANIC MATTER IN THE SATILLA RIVER OF GEORGIA, USA</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The acid-base properties of humic substances, the major component of <span class="hlt">dissolved</span> organic matter (DOM), area major control on the alkalinity, or acid neutralizing capacity of freshwater systems. Alkalinity is one of the fundamental parameters measured in aquatic sciences, and is an ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59961&keyword=ecosystem+AND+destruction&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59961&keyword=ecosystem+AND+destruction&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>PHOTOCHEMICAL ALTERATION OF <span class="hlt">DISSOLVED</span> ORGANIC MATTER: EFFECTS ON THE <span class="hlt">CONCENTRATION</span> AND ACIDITIES OF IONIZABLE SITES IN <span class="hlt">DISSOLVED</span> ORGANIC MATTER IN THE SATILLA RIVER OF GEORGIA, USA</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The acid-base properties of humic substances, the major component of <span class="hlt">dissolved</span> organic matter (DOM), area major control on the alkalinity, or acid neutralizing capacity of freshwater systems. Alkalinity is one of the fundamental parameters measured in aquatic sciences, and is an ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMED21A0693D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMED21A0693D"><span>Variations in <span class="hlt">concentrations</span> and fluxes of <span class="hlt">dissolved</span> inorganic nutrients related to catchment scale human interventions in Pamba River, Kerala, India</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>David, S. E.; Jennerjahn, T. C.; Chattopadhyay, S.</p> <p>2012-12-01</p> <p>River basins are geo-hydrological units. Water flowing out of the basin bears the imprint of natural factors such as geology, soil, vegetation and rainfall along with anthropogenic factors including the type and degree of human intervention within the basin. Pamba, a small mountainous river in the SW coast of India with a population density of ~1,400 persons km-2 was studied for its varying land use and human interventions as the global database are biased towards temperate regions while little is know about the smaller catchments from tropical regions. Land use comprised of dense forest in the highland region together with forest plantation and the human impacted Sabarimala temple- the second largest pilgrim, settlement with mixed tree crop (smt) in the midland and lowland paddy cultivated region. 50-60 million devotees visiting Sabarimala during November to January every year associated with the ritual bathing, discharge of human wastes emanating from the influx of millions of pilgrims due to inadequate number of sanitary latrines and the lack of facilities for sewage collection and treatment caused several ecological variations during pilgrim season. In order to asses the effect of land use and pilgrims in combination with seasonal variations in hydrology we investigated the seasonal and spatial variations in physicochemical and nutrient <span class="hlt">concentrations</span>. Samples were collected from March 2010 to February 2012 during premonsoon (January-May), SW(June to September) and NE monsoon(October to December), from sites varying in land use. Nutrient budgets (load and yield) were calculated to quantify the inputs from various land use segments. Spatio-temporal variations in the physicochemical and <span class="hlt">dissolved</span> nutrient <span class="hlt">concentrations</span> were observed along the course of the river. Upstream forest region had highest <span class="hlt">dissolved</span> oxygen(DO) and pH together with lowest <span class="hlt">dissolved</span> inorganic nitrogen(DIN) values indicating almost pristine conditions. DIN in the temple region had the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25288526','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25288526"><span>Factors affecting total <span class="hlt">dissolved</span> solids <span class="hlt">concentration</span> of γ-ray-irradiated aqueous hexamethylenetetramine solution: a dosimetric study.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sife-Eldeen, Kh A</p> <p>2014-12-01</p> <p>A new γ-ray-radiation dosimetric system (TDS-HMTA), comprising a 'total <span class="hlt">dissolved</span> solids (TDS)' meter and 0.02 M aqueous hexamethylenetetramine (HMTA) solution, is introduced for medical and biological applications. Gamma-ray radiolysis of aqueous HTMA solutions increases the <span class="hlt">concentrations</span> (ppm) of TDS, which is measured by the TDS meter. The effects of HMTA <span class="hlt">concentration</span>, absorbed radiation dose, absorbed dose rate, and storage time on the TDS <span class="hlt">concentration</span> of irradiated HMTA solutions were studied. It was found that 0.02 M aqueous HMTA solution yields the highest sensitivity to γ-ray-radiation according to TDS <span class="hlt">concentration</span> measurements. The effect of absorbed radiation dose was studied in the range 1.64-435.5 kGy. The TDS <span class="hlt">concentration</span> increases linearly up to the maximum of the studied absorbed radiation dose range (R(2) = 0.9965). The overall coefficient of variation (CV %) associated with TDS <span class="hlt">concentration</span> measurements of 0.02 M HMTA solution as a function of absorbed dose was found to be 0.732%. The effect of dose rate on the TDS <span class="hlt">concentration</span> was studied in the range 0.33-3.31 kGy/h. It was found, also, that the TDS <span class="hlt">concentration</span> is relatively stable over a storage period of 144 h after irradiation with different doses. The tissue equivalency of 0.02 M aqueous HMTA solutions allow it to be used for radiation dose measurement during sterilization in human tissue banks. Therefore, this system (TDS-HMTA) could be considered as a promising candidate for γ-ray radiation dosimetry in technical, medical and research fields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016WRR....52.7711T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016WRR....52.7711T"><span>The direct and indirect effects of watershed land use and soil type on stream water <span class="hlt">metal</span> <span class="hlt">concentrations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Taka, M.; Aalto, J.; Virkanen, J.; Luoto, M.</p> <p>2016-10-01</p> <p>Identifying the factors controlling stream water pollutants is challenged by the diversity of potential sources, pathways, and processes. This study tests the effects of watershed characteristics on stream water <span class="hlt">metal</span> <span class="hlt">concentrations</span> across environmental gradients. By using an extensive data set of 83 watersheds in southern Finland and structural equation modeling (SEM), the direct and indirect effects of land use and soil type on <span class="hlt">metal</span> <span class="hlt">concentrations</span> were explored. Both land use and soil type resulted in statistically significant direct effects on <span class="hlt">metals</span>; for example, land use was found to control <span class="hlt">dissolved</span> <span class="hlt">metal</span> <span class="hlt">concentrations</span>, whereas soil type had the strongest links for total <span class="hlt">metal</span> <span class="hlt">concentrations</span>. The consideration of indirect correlation further strengthened the effects of soil type up to 50%, thus suggesting the dominant role of soil across land use intensities. Moreover, the results indicate that modified landscapes mediate the effect of natural soil processes in controlling stream <span class="hlt">metal</span> <span class="hlt">concentrations</span>. This work highlights the benefits of structural equation model framework, as the underlying paths for water quality are more likely to be identified, compared to traditional regression methods. Thus, the implementation of SEM on water quality studies is highly encouraged.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011GeoRL..38.8605Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011GeoRL..38.8605Z"><span>In situ Raman-based measurements of high <span class="hlt">dissolved</span> methane <span class="hlt">concentrations</span> in hydrate-rich ocean sediments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Xin; Hester, Keith C.; Ussler, William; Walz, Peter M.; Peltzer, Edward T.; Brewer, Peter G.</p> <p>2011-04-01</p> <p>Ocean sediment <span class="hlt">dissolved</span> CH4 <span class="hlt">concentrations</span> are of interest for possible climate-driven venting from sea floor hydrate decomposition, for supporting the large-scale microbial anaerobic oxidation of CH4 that holds the oceanic CH4 budget in balance, and for environmental issues of the oil and gas industry. Analyses of CH4 from recovered cores near vent locations typically show a maximum of ˜1 mM, close to the 1 atmosphere equilibrium value. We show from novel in situ measurement with a Raman-based probe that geochemically coherent profiles of <span class="hlt">dissolved</span> CH4 occur rising to 30 mM (pCH4 = 3 MPa) or an excess pressure ˜3× greater than CO2 in a bottle of champagne. Normalization of the CH4 Raman ν1 peak to the ubiquitous water ν2 bending peak provides a fundamental internal calibration. Very large losses of CH4 and fractions of other gases (CO2, H2S) must typically occur from recovered cores at gas rich sites. The new data are consistent with observations of microbial biomass and observed CH4 oxidation rates at hydrate rich sites and support estimates of a greatly expanded near surface oceanic pore water CH4 reservoir.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24794749','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24794749"><span>Regulation of responsiveness of phosphorescence toward <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> by modulating polymer contents in organic-inorganic hybrid materials.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Okada, Hiroshi; Tanaka, Kazuo; Chujo, Yoshiki</p> <p>2014-06-15</p> <p>Platinum(II) octaethylporphyrin (PtOEP)-loaded organic-inorganic hybrids were obtained via the microwave-assisted sol-gel condensation with methyltrimethoxysilane and poly(vinylpyrrolidone). From transparent and homogeneous hybrid films, the strong phosphorescence from PtOEP was observed. Next, the resulting hybrids were immersed in the aqueous buffer, and the emission intensity was monitored by changing the <span class="hlt">dissolved</span> oxygen level in the buffer. When the hybrid with relatively-higher amount of the silica element, the strong phosphorescence was observed even under the aerobic conditions. In contrast, the emission from the hybrids with lower amounts of the silica element was quenched under the hypoxic conditions. This is, to the best of our knowledge, the first example to demonstrate that the responsiveness of the phosphorescence intensity of PtOEP in hybrid films to the <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> in water can be modulated by changing the percentage of the contents in the material. Copyright © 2014 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=336790&keyword=Stephen+AND+king&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=336790&keyword=Stephen+AND+king&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>Characteristics of <span class="hlt">Metals</span> <span class="hlt">Concentrations</span> in in the Animas and San Juan Rivers during Passage of the Gold King Mine Release Plume</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The accidental release of 11.3 million liters (~ 3,000,000 gallons) of acidic mine water from the Gold King Mine (GKM) in southwestern Colorado on August 5, 2015, created high <span class="hlt">concentrations</span> of <span class="hlt">dissolved</span> and particulate <span class="hlt">metals</span> into the Animas River over about a 12-hour period. Th...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19110291','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19110291"><span>Effect of pH, ionic strength, <span class="hlt">dissolved</span> organic carbon, time, and particle size on <span class="hlt">metals</span> release from mine drainage impacted streambed sediments.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Butler, Barbara A</p> <p>2009-03-01</p> <p>Acid-mine drainage (AMD) input to a stream typically results in the stream having a reduced pH, increased <span class="hlt">concentrations</span> of <span class="hlt">metals</span> and salts, and decreased biological productivity. Removal and/or treatment of these AMD sources is desired to return the impacted stream(s) to initial conditions, or at least to conditions suitable for restoration of the aquatic ecosystem. Some expected changes in the water chemistry of the stream following removal of AMD input include an increase in pH, a decrease in ionic strength, and an increase in <span class="hlt">dissolved</span> organic carbon (DOC) <span class="hlt">concentrations</span> from increased biological activity in the absence of toxic <span class="hlt">metals</span> <span class="hlt">concentrations</span>. These changes in water chemistry may cause the existing contaminated bed sediments to become a source of <span class="hlt">metals</span> to the stream water. Streambed sediments, collected from North Fork Clear Creek (NFCC), Colorado, currently impacted by AMD, were assessed for the effects of pH, ionic strength, DOC <span class="hlt">concentration</span>, time, and particle size on <span class="hlt">metals</span> release using a factorial design. The design included two levels for each chemical parameter (ionic strength = 40 and 80% lower than ambient; pH = 6 and 8; and DOC = 1 and 3 mg/l higher than ambient), ten sampling times (from zero to 48 h), and two size fractions of sediments (63 microm < or = x < 2 mm and < 63 microm). Greater <span class="hlt">concentrations</span> of <span class="hlt">metals</span> were released from the smaller sized sediments compared with the larger, with the exception of Cu. A mild acid digestion (0.6M HCl) evaluated the amount of each <span class="hlt">metal</span> that could be removed easily from each of the sediment size fractions. Release of all <span class="hlt">metals</span> over all time points, treatments, and from both sediment sizes was less than 1% of the extractable <span class="hlt">concentrations</span>, with the exception of Mn, which ranged from 4 to 7% from the smaller sized sediment. Greater percentages of the 0.6M HCl-extractable <span class="hlt">concentrations</span> of Cu, Fe, and Zn were released from the larger sized sediment, while this was true for release of Cd and Mn from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26253185','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26253185"><span>Transfer of <span class="hlt">metal</span>(loid)s in a small vineyard catchment: contribution of <span class="hlt">dissolved</span> and particulate fractions in river for contrasted hydrological conditions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rabiet, M; Coquery, M; Carluer, N; Gahou, J; Gouy, V</p> <p>2015-12-01</p> <p>The use of inorganic pesticides in viticulture leads to the accumulation of <span class="hlt">metal</span>(loid)s in soils which can be transferred to the hydro-systems (groundwater and surface water) via several processes. This study reports on the occurrence and behavior of <span class="hlt">metal</span>(loid)s (Li, Al, Cr, Ni, Cu, Zn, As, Sr, and Ba), with a particular focus on Cu, Zn, and As, in a small stream draining a vineyard catchment. Base flow and flood events were monitored in order to assess the spatiotemporal variability of <span class="hlt">metal</span>(loid) <span class="hlt">concentrations</span> and to evaluate the contribution of the particulate fraction to the transfer of <span class="hlt">metal</span>(loid)s according to the hydrological conditions. Results show that very different patterns of <span class="hlt">metal</span>(loid)s were observed in the Morcille River according to the hydrological conditions. In base flow conditions, Cu and As were mainly transported in <span class="hlt">dissolved</span> phase, which contributed to more than 70 and 80%, respectively, of the total load during this period. On the contrary, during base flow, Zn was mainly transported as associated to particles (90%). During the two storm events monitored, the particulate fraction was dominant, as its represented around 74-80%, 97%, and 50-70% of the total Cu, Zn, and As load in the river, respectively. Thus, despite a weaker affinity for particles during floods (decrease of particulate content during floods), <span class="hlt">metal</span>(loid)s were mainly brought as particles, given that high amounts of suspended particulate matter (up to 2031 mg/L) were mobilized. Finally, comprehensive fluxes estimations confirmed that floods were responsible for more than 90% of the total Cu, Zn and 75% for As load transiting in the Morcille River in August within a very short period of time (less than 17%).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016WRR....52.7931T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016WRR....52.7931T"><span>Colloids and organic matter complexation control trace <span class="hlt">metal</span> <span class="hlt">concentration</span>-discharge relationships in Marshall Gulch stream waters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trostle, Kyle D.; Ray Runyon, J.; Pohlmann, Michael A.; Redfield, Shelby E.; Pelletier, Jon; McIntosh, Jennifer; Chorover, Jon</p> <p>2016-10-01</p> <p>This study combined <span class="hlt">concentration</span>-discharge analyses (filtration at 0.45 μm), cascade filtrations (at 1.2, 0.4, and 0.025 μm) and asymmetrical flow field flow fractionation (AF4) to probe the influence of colloidal carriers (<span class="hlt">dissolved</span> organic matter and inorganic nanoparticles) on observed <span class="hlt">concentration</span>-discharge relationships for trace <span class="hlt">metals</span> in a 155 ha forested catchment of the Santa Catalina Mountains Critical Zone Observatory (SCM CZO), Arizona. Many major elements (Na, Mg, Si, K, Ca) show no colloidal influence, and <span class="hlt">concentration</span>-discharge relationships for these species are explained by previous work. However, the majority of trace <span class="hlt">metals</span> (Al, Ti, V, Mn, Fe, Cu, Y, REE, U) show at least some influence of colloids on chemistry when filtered at the standard 0.45 μm cutoff. <span class="hlt">Concentration</span>-discharge slopes of trace <span class="hlt">metals</span> with modest colloidal influence are shallow (˜0.3) similar to that measured for <span class="hlt">dissolved</span> organic carbon (DOC, 0.24), whereas elements with greater colloidal influence have steeper <span class="hlt">concentration</span>-discharge slopes approaching that of Al (0.76), the element with the largest colloidal influence in this study (on average 68%). These findings are further supported by AF4 measurements that show distinct and resolvable pools of low hydrodynamic diameter DOC-sized material coexistent with larger diameter inorganic colloids, and the ratio of these carriers changes systematically with discharge because the DOC pool has a <span class="hlt">concentration</span>-discharge relationship with shallower slope than the inorganic colloidal pool. Together these data sets illustrate that positive <span class="hlt">concentration</span>-discharge slopes of trace <span class="hlt">metals</span> in stream waters may be explained as the relative partitioning of trace <span class="hlt">metals</span> between DOC and inorganic colloids, with contributions of the latter likely increasing as a result of increased prevalence of macropore flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70022363','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70022363"><span>Influence of acid volatile sulfides and <span class="hlt">metal</span> <span class="hlt">concentrations</span> on <span class="hlt">metal</span> partitioning in contaminated sediments</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Lee, J.-S.; Lee, B.-G.; Luoma, S.N.; Choi, H.J.; Koh, C.-H.; Brown, C.L.</p> <p>2000-01-01</p> <p>The influence of acid volatile sulfide (AVS) on the partitioning of Cd, Ni, and Zn in porewater (PW) and sediment as reactive <span class="hlt">metals</span> (SEM, simultaneously extracted <span class="hlt">metals</span>) was investigated in laboratory microcosms. Two spiking procedures were compared, and the effects of vertical geochemical gradients and infaunal activity were evaluated. Sediments were spiked with a Cd-Ni-Zn mixture (0.06, 3, 7.5 ??mol/g, respectively) containing four levels of AVS (0.5, 7.5, 15, 35 ??mol/g). The results were compared to sediments spiked with four levels of Cd-Ni-Zn mixtures at one AVS <span class="hlt">concentration</span> (7.5 ??mol/g). A vertical redox gradient was generated in each treatment by an 18-d incubation with an oxidized water column. [AVS] in the surface sediments decreased by 65-95% due to oxidation during incubation; initial [AVS] was maintained at 0.5-7.5 cm depth. PW <span class="hlt">metal</span> <span class="hlt">concentrations</span> were correlated with [SEM - AVS] among all data. But PW <span class="hlt">metal</span> <span class="hlt">concentrations</span> were variable, causing the distribution coefficient, Kd(pw) (the ratio of [SEM] to PW <span class="hlt">metal</span> <span class="hlt">concentrations</span>) to vary by 2-3 orders of magnitude at a given [SEM - AVS]. One reason for the variability was that vertical profiles in PW <span class="hlt">metal</span> <span class="hlt">concentrations</span> appeared to be influenced by diffusion as well as [SEM - AVS]. The presence of animals appeared to enhance the diffusion of at least Zn. The generalization that PW <span class="hlt">metal</span> <span class="hlt">concentrations</span> are controlled by [SEM - AVS] is subject to some important qualifications if vertical gradients are complicated, <span class="hlt">metal</span> <span class="hlt">concentrations</span> vary, or equilibration times differ.The influence of acid volatile sulfide (AVS) on the partitioning of Cd, Ni, and Zn in porewater (PW) and sediment as reactive <span class="hlt">metals</span> (SEM, simultaneously extracted <span class="hlt">metals</span>) was investigated in laboratory microcosms. Two spiking procedures were compared, and the effects of vertical geochemical gradients and infaunal activity were evaluated. Sediments were spiked with a Cd-Ni-Zn mixture (0.06, 3, 7.5 ??mol/g, respectively) containing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19058018','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19058018"><span>Effect of fertilizer application on soil heavy <span class="hlt">metal</span> <span class="hlt">concentration</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Atafar, Zahra; Mesdaghinia, Alireza; Nouri, Jafar; Homaee, Mehdi; Yunesian, Masoud; Ahmadimoghaddam, Mehdi; Mahvi, Amir Hossein</p> <p>2010-01-01</p> <p>A large amount of chemicals is annually applied at the agricultural soils as fertilizers and pesticides. Such applications may result in the increase of heavy <span class="hlt">metals</span> particularly Cd, Pb, and As. The objective of this study was to investigate the variability of chemical applications on Cd, Pb, and As <span class="hlt">concentrations</span> of wheat-cultivated soils. Consequently, a study area was designed and was divided into four subareas (A, B, C, and D). The soil sampling was carried out in 40 points of cultivated durum wheat during the 2006-2007 periods. The samples were taken to the laboratory to measure their heavy <span class="hlt">metal</span> <span class="hlt">concentration</span>, soil texture, pH, electrical conductivity, cationic exchange capacity, organic matter, and carbonate contents. The result indicated that Cd, Pb, and As <span class="hlt">concentrations</span> were increased in the cultivated soils due to fertilizer application. Although the statistical analysis indicates that these heavy <span class="hlt">metals</span> increased significantly (P value<0.05), the lead and arsenic <span class="hlt">concentrations</span> were increased dramatically compared to Cd <span class="hlt">concentration</span>. This can be related to overapplication of fertilizers as well as the pesticides that are used to replant plant pests, herbs, and rats.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26814136','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26814136"><span>Determination of size-dependent <span class="hlt">metal</span> distribution in <span class="hlt">dissolved</span> organic matter by SEC-UV/VIS-ICP-MS with special focus on changes in seawater.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rathgeb, Anna; Causon, Tim; Krachler, Regina; Hann, Stephan</p> <p>2016-04-01</p> <p>Iron is an essential micronutrient for all marine organisms, but it is also a growth limiting factor as the iron <span class="hlt">concentrations</span> in the open ocean are below 1 nmol/L in sea water iron is almost entirely bound to organic ligands of the <span class="hlt">dissolved</span> organic matter fraction, which are mostly of unknown structure. The input from rivers was traditionally considered as less important due to estuarine sedimentation processes of the mainly colloidal iron particles. However, recent studies have shown that this removal is not complete and riverine input may represent an important iron source in the open ocean. In this context, iron transport by land-derived natural organic matter (NOM), and <span class="hlt">dissolved</span> organic matter (DOM) have been identified as carrier mechanisms for riverine iron. The aim of this work is to characterize complexes containing iron and other <span class="hlt">metals</span> in waters simulating estuarine conditions in order to help understand which role iron-DOM compounds play in the open ocean. A method based on size-exclusion chromatography (SEC) with sequential UV/VIS and ICP-MS detection was developed for investigation of DOM size distribution and for assessment of the size-dependent <span class="hlt">metal</span> distribution in NOM-rich surface water. Furthermore, sample matrix experiments were also performed revealing a dependence of DOM size distribution upon seawater <span class="hlt">concentration</span> and different compounds present in seawater. Finally, efforts toward determination of DOM size with standardization with typical SEC standards indicate that only relative comparisons are possible with this approach, and that the sample matrix composition strongly influences obtained results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4825403','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4825403"><span>Determination of size‐dependent <span class="hlt">metal</span> distribution in <span class="hlt">dissolved</span> organic matter by SEC‐UV/VIS‐ICP‐MS with special focus on changes in seawater</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rathgeb, Anna; Causon, Tim; Krachler, Regina</p> <p>2016-01-01</p> <p>Iron is an essential micronutrient for all marine organisms, but it is also a growth limiting factor as the iron <span class="hlt">concentrations</span> in the open ocean are below 1 nmol/L in sea water iron is almost entirely bound to organic ligands of the <span class="hlt">dissolved</span> organic matter fraction, which are mostly of unknown structure. The input from rivers was traditionally considered as less important due to estuarine sedimentation processes of the mainly colloidal iron particles. However, recent studies have shown that this removal is not complete and riverine input may represent an important iron source in the open ocean. In this context, iron transport by land‐derived natural organic matter (NOM), and <span class="hlt">dissolved</span> organic matter (DOM) have been identified as carrier mechanisms for riverine iron. The aim of this work is to characterize complexes containing iron and other <span class="hlt">metals</span> in waters simulating estuarine conditions in order to help understand which role iron‐DOM compounds play in the open ocean. A method based on size‐exclusion chromatography (SEC) with sequential UV/VIS and ICP‐MS detection was developed for investigation of DOM size distribution and for assessment of the size‐dependent <span class="hlt">metal</span> distribution in NOM‐rich surface water. Furthermore, sample matrix experiments were also performed revealing a dependence of DOM size distribution upon seawater <span class="hlt">concentration</span> and different compounds present in seawater. Finally, efforts toward determination of DOM size with standardization with typical SEC standards indicate that only relative comparisons are possible with this approach, and that the sample matrix composition strongly influences obtained results. PMID:26814136</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B51E0334S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B51E0334S"><span>Influence of environmental parameters on the <span class="hlt">concentration</span> of subsurface <span class="hlt">dissolved</span> methane in two hydroelectric power plants in Brazil</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Silva, M. G.; Marani, L.; Alvala, P. C.</p> <p>2013-12-01</p> <p>Methane (CH4) is a trace gas in the atmosphere of great importance for atmospheric chemistry as one of the main greenhouse gases. There are different sources with the largest individual production associated with the degradation of organic matter submerged in flooded areas. The amount of <span class="hlt">dissolved</span> methane that reaches the surface depends on the production in the sediments and consumption in the water column. Both processes are associated with microbial activity and consequently dependent on the physico-chemical environmental conditions. The construction of hydroelectric dams cause flooding of areas near the river that can change the characteristics of the environment and cause changes in subsurface methane <span class="hlt">concentration</span>. In this work, we studied two hydroelectric plants located in Brazil: Batalha (17°20'39.52"S, 47°29'34.29"W), under construction when the samples were take, and Itaipu (25°24'45.00"S, 54°35'39.00"W) which has been floated over 30 years ago. The water samples to determine <span class="hlt">dissolved</span> methane were collected approximately 5 cm near the surface. In each collection point was measured depth, water temperature, pH and redox potential. The range of <span class="hlt">dissolved</span> methane between the two dams was similar: 0.07-10.33 μg/l (Batalha) and 0.15-10.93 μg/l (Itaipu). However, the Batalha's average (4.04 × 3.43 μg/l; median = 3.66 μg/l) was higher than that observed in Itaipu (2.15 × 1.59 μg/l; median = 2.53 μg/l). The influence of environmental parameters on the <span class="hlt">concentration</span> of <span class="hlt">dissolved</span> methane was evaluated by multivariate statistical techniques (Principal Component Analysis - PCA). All of the parameters had some correlation with <span class="hlt">dissolved</span> methane, however, the greatest contribution in Batalha was associated with pH while in Itaipu was the depth. The pH variation of the various points studied in Batalha may be associated with periods of drought and flooding of the river and hence the incorporation of organic matter in the environment. The organisms</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JPhy4.107..983O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JPhy4.107..983O"><span><span class="hlt">Concentrations</span> of heavy <span class="hlt">metals</span> in soil, Zimapan, México</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ongley, L. K.; Armienta, A.; Mango, H.</p> <p>2003-05-01</p> <p>Pb-Zn-Ag mining and ore pocessing have occurred continuously in Zimapán, México since at least 1632 and possibly since 1576 [1, 2]. This has resulted in the development of significant slag and tailings piles. Dissolution of ore and tailings has resulted in arsenic contamination of much of the water in the valley raising the possibility of arsenicosis of the residents [3, 4, 5]. INAA and ICP analysis of more than 175 sediment, soil and tailings samples demonstrate significant <span class="hlt">metal</span> and arsenic contamination of these unconsolidated materials. As, Cu, Pb, and Zn were among the measured elements. <span class="hlt">Metal</span> <span class="hlt">concentrations</span> in soils and sediments were highest within 1000 m of tailings or slag piles. Some of the highest soil <span class="hlt">metal</span> <span class="hlt">concentrations</span> were measured in a developing soil on top of a slag pile: As-14 700 mg/kg, Cu 8 638 mg/kg, Pb 41444 mg/kg, and Zn 16 976 mg/kg. Soils more than 4 000 m from the tailings and slag generally had less than 40 mg As/kg with Cu < 30 mg/kg, Pb < 64 mg/kg, and Zn < 200 mg/kg. Some rocks ftum the area also show elevated <span class="hlt">metal</span> <span class="hlt">concentrations</span>. For example, the As <span class="hlt">concentrations</span> in dikes and ores from Zimapàn averaged 1 242 and 30 800 mg/kg respectively. Average shale As <span class="hlt">concentrations</span> (74 mg/kg) match published data for shales that indicate “normal” As <span class="hlt">concentrations</span> range from 3-490 mg/kg are found world-wide [6]. Some of the soil contamination is natural, the result of the geologic processes responsible for the Pb-Zn ores. However, particularly near the tailings and slag piles, the soils are also contaminated by anthropogenic means: by dry particulate deposition from smelters, by windblown tailings, and possibly by ore and rock dust from the ore transport trucks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24956755','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24956755"><span>Generalized regression neural network-based approach for modelling hourly <span class="hlt">dissolved</span> oxygen <span class="hlt">concentration</span> in the Upper Klamath River, Oregon, USA.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Heddam, Salim</p> <p>2014-08-01</p> <p>In this study, a comparison between generalized regression neural network (GRNN) and multiple linear regression (MLR) models is given on the effectiveness of modelling <span class="hlt">dissolved</span> oxygen (DO) <span class="hlt">concentration</span> in a river. The two models are developed using hourly experimental data collected from the United States Geological Survey (USGS Station No: 421209121463000 [top]) station at the Klamath River at Railroad Bridge at Lake Ewauna. The input variables used for the two models are water, pH, temperature, electrical conductivity, and sensor depth. The performances of the models are evaluated using root mean square errors (RMSE), the mean absolute error (MAE), Willmott's index of agreement (d), and correlation coefficient (CC) statistics. Of the two approaches employed, the best fit was obtained using the GRNN model with the four input variables used.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15865194','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15865194"><span>Evaluation of capillary electrophoresis for determining the <span class="hlt">concentration</span> of <span class="hlt">dissolved</span> silica in geothermal brines.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Santoyo, E; García, R; Aparicio, A; Verma, Surendra P; Verma, M P</p> <p>2005-04-15</p> <p>The determination of silica <span class="hlt">concentrations</span> in geothermal brines is widely recognized as a difficult analytical task due to its complex chemical polymerization kinetics that occurs during sample collection and chemical analysis. Capillary electrophoresis (CE) has been evaluated as a new reliable analytical method to measure silica (as silicates) in geothermal brines. Synthetic and geothermal brine samples were used to evaluate CE methodology. A capillary electrophoresis instrument, Quanta 4000 (Waters-Millipore) coupled with a Waters 820 workstation was used to carry out the experimental work. The separation of silicates was completed in approximately 5.5 min using a conventional fused-silica capillary (75 microm i.d. x 375 microm o.d. x 60 cm total length). A hydrostatic injection (10 cm for 20 s at 25 degrees C) was employed for introducing the samples. The carrier electrolyte consisted of 10 mM sodium chromate, 3 mM tetradecyltrimethyl-ammonium hydroxide (TTAOH), 2 mM sodium carbonate, and 1 mM sodium hydroxide, adjusted to a pH 11.0 +/- 0.1. Silicates were determined using an indirect UV detection at a wavelength of 254 nm with a mercury lamp and with a negative power supply (-15 kV). A good reproducibility in the migration times (%R.S.D. approximately 1.6%) based on six non-consecutive injections of synthetic brine solutions was obtained. A linear response between silica <span class="hlt">concentration</span> and corrected peak area was observed. Ordinary (OLR) and weighted (WLR) linear regression models were used for calculating silica <span class="hlt">concentrations</span> in all samples using the corresponding fitted calibration curves. The analytical results of CE were finally compared with the most probable values of synthetic reference standards of silica using the Student's t-test. No significant differences were found between them at P = 0.01. Similarly, the atomic absorption spectrometry (AAS) results were also compared with the most probable <span class="hlt">concentrations</span> of the same reference standards, finding</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22266031','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22266031"><span>A simple <span class="hlt">dissolved</span> <span class="hlt">metals</span> mixing method to produce high-purity MgTiO{sub 3} nanocrystals</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pratapa, Suminar E-mail: suminar-pratapa@physics.its.ac.id; Baqiya, Malik A. E-mail: suminar-pratapa@physics.its.ac.id; Istianah, E-mail: suminar-pratapa@physics.its.ac.id; Lestari, Rina E-mail: suminar-pratapa@physics.its.ac.id; Angela, Riyan E-mail: suminar-pratapa@physics.its.ac.id</p> <p>2014-02-24</p> <p>A simple <span class="hlt">dissolved</span> <span class="hlt">metals</span> mixing method has been effectively used to produce high-purity MgTiO{sub 3} (MT) nanocrystals. The method involves the mixing of independently <span class="hlt">dissolved</span> magnesium and titanium <span class="hlt">metal</span> powders in hydrochloric acid followed by calcination. The phase purity and nanocrystallinity were determined by making use of laboratory x-ray diffraction data, to which Rietveld-based analyses were performed. Results showed that the method yielded only one type magnesium titanate powders, i.e. MgTiO{sub 3}, with no Mg{sub 2}TiO{sub 4} or MgTi{sub 2}O{sub 5} phases. The presence of residual rutile or periclase was controlled by adding excessive Mg up to 5% (mol) in the stoichiometric mixing. The method also resulted in MT nanocrystals with estimated average crystallite size of 76±2 nm after calcination at 600°C and 150±4 nm (at 800°C). A transmission electron micrograph confirmed the formation of the nanocrystallites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSCT44A0224W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSCT44A0224W"><span>Factors controlling <span class="hlt">concentration</span> and decomposition of <span class="hlt">dissolved</span> organic matter in pore water on the shelf of the East China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Y.; Wang, X.; Ye, Q.; Liu, M. S.; Zhang, J.</p> <p>2016-02-01</p> <p>Understanding of microbial communities and carbon cycling in marine sediment fills in the gap of biogeochemical cycle of carbon and nutrients in the largest carbon reservoir. Nevertheless, information on what factors controlling <span class="hlt">concentration</span> and decomposition of <span class="hlt">dissolved</span> organic matter (DOM)