Thallium isotope composition of the upper continental crust and rivers—An investigation of the continental sources of dissolved marine thallium     

Sune G. Nielsen  Mark Rehkämper  Per Andersson  Peter W. Swarzenski  Detlef Günther 《Geochimica et cosmochimica acta》2005,69(8):2007-2019

The thallium (Tl) concentrations and isotope compositions of various river and estuarine waters, suspended riverine particulates and loess have been determined. These data are used to evaluate whether weathering reactions are associated with significant Tl isotope fractionation and to estimate the average Tl isotope composition of the upper continental crust as well as the mean Tl concentration and isotope composition of river water. Such parameters provide key constraints on the dissolved Tl fluxes to the oceans from rivers and mineral aerosols.The Tl isotope data for loess and suspended riverine detritus are relatively uniform with a mean of ε²⁰⁵Tl = −2.0 ± 0.3 (ε²⁰⁵Tl represents the deviation of the ²⁰⁵Tl/²⁰³Tl isotope ratio of a sample from NIST SRM 997 Tl in parts per 10⁴). For waters from four major and eight smaller rivers, the majority were found to have Tl concentrations between 1 and 7 ng/kg. Most have Tl isotope compositions very similar (within ±1.5 ε²⁰⁵Tl) to that deduced for the upper continental crust, which indicates that no significant Tl isotope fractionation occurs during weathering. Based on these results, it is estimated that rivers have a mean natural Tl concentration and isotope composition of 6 ± 4 ng/kg and ε²⁰⁵Tl = −2.5 ± 1.0, respectively.In the Amazon estuary, both additions and losses of Tl were observed, and these correlate with variations in Fe and Mn contents. The changes in Tl concentrations have much lower amplitudes, however, and are not associated with significant Tl isotope effects. In the Kalix estuary, the Tl concentrations and isotope compositions can be explained by two-component mixing between river water and a high-salinity end member that is enriched in Tl relative to seawater. These results indicate that Tl can display variable behavior in estuarine systems but large additions and losses of Tl were not observed in the present study.  相似文献   

Fourier-transform Infrared Spectroscopy (FTIRS), a New Method to Infer Past Changes in Tree-line Position and TOC using Lake Sediment     

Peter Rosén  Per Persson 《Journal of Paleolimnology》2006,35(4):913-923

This study tests the hypothesis that Fourier-transform infrared spectroscopy (FTIRS) of lake sediments can be used to infer past changes in tree-line position and total organic carbon (TOC) content of lake water. A training set of 100 lakes from northern Sweden spanning a broad altitudinal and TOC gradient from 0.7 to 14.9 mg/l was used to assess whether vegetation zones and TOC can be modelled from FTIR spectra of surface sediments (0–1 cm) using principal component analysis (PCA) and partial least squares (PLS) regression. Preliminary results show that FTIRS of lake sediments can be used to reconstruct past changes in tree line and the TOC content of lake water, which is hardly surprising since FTIRS registers the properties of organic and minerogenic material derived from the water mass and the drainage area. The FTIRS model for TOC gives a root mean squared error (RMSECV) of calibration of 1.4 mg/l (10% of the gradient) assessed by internal cross-validation (CV) yielding an R_cv² of 0.64. This should be compared with a near-infrared spectroscopy (NIRS) and diatom transfer function for TOC from the same set of lakes, which have a R_cv² of 0.61 and 0.31, and RMSECV of 1.6 and 2.3 mg/l, respectively. The FTIRS-TOC model was applied to a Holocene sediment core from a tree-line lake and the results show similar trends as inferences from NIRS and pollen from the same core. Overall, the results indicate that changes in FTIR spectra from lake sediments reflect differences in catchment vegetation and TOC, and that FTIRS-models based on surface-sediment samples can be applied to sediment cores for retrospective analysis.  相似文献   

Performance of the In Situ Microcosm Technique for Measuring the Degradation of Organic Chemicals in Aquifers     

Per H. Nielsen  Thomas H. Christensen  Hans-Jørgen Albrechtsen  Robert W. Gillham 《Ground Water Monitoring & Remediation》1996,16(1):130-140

An in situ microcosm (ISM) consists of a stainless steel cylinder isolating about 2 L of the aquifer and is equipped with valves allowing for loading and sampling from the ground surface. During the last five years, this technique has been used frequently to study the degradation of organic chemicals in polluted and pristine aquifers representing different redox environments. The ISM technique has great potential for providing field-relevant degradation potentials and rate constants, but care must be taken in using the equipment and interpreting the results. This paper provides details concerning the installation and operation of an ISM and presents experiences concerning data interpretation and monitoring of redox conditions.  相似文献   

Modelling of uranium and neptunium chemistry in a deep rock environment     

Iréne Lundén  Karin Andersson  Gunnar Skarnemark 《Aquatic Geochemistry》1996,2(4):345-358

According to the present concept for final storage of spent nuclear fuel in Sweden, the spent fuel, encapsulated in copper or copper/steel canisters, will be placed in tunnels in a deep rock formation. The canisters will be surrounded by compacted bentonite clay acting as a buffer material. In connection with a safety analysis of such a storage facility, the total solubility of certain elements (e.g., uranium) as well as the transport properties (e.g., retardation due to sorption on mineral surfaces) of the long-lived radionuclides released from the canister have to be predicted or measured. The chemical conditions, governing the solubility and speciation of trace elements encountered in and around the repository depend on interactions between the ground water and the engineering materials in the repository and a production of oxidants due to radiolysis in the spent fuel. In the present study the speciation and solubility of uranium and neptunium in a bentonite-ground water system and in ground waters with compositions measured at a site at äspö, SE Sweden, have been calculated. The calculations have been carried out using a recent version of the geochemical computer code PHREEQE and the database HATCHES 5.0. Predictions of the uranium and neptunium concentrations in the ground water in the vicinity of a damaged high level waste repository have also been performed. The uranium concentration in the water in the bentonite barrier is predicted to be of the same order of magnitude or lower than that found in some granitic ground waters. For neptunium the calculations are uncertain due to the small amount of experimentally determined thermodynamic data and few verifications under the conditions (pH - Eh - carbonate concentration) considered. The predicted concentrations (ca 10^–12 m, corresponds to ca 0.006 Bq/l) may be regarded as high, considering the high toxicity of neptunium and its long half-life.  相似文献   

Time dependence of organic matter decay and mixing processes in Framvaren, a permanently anoxic fjord in South Norway     

David W. Dyrssen  Per O. J. Hall  Conny Haraldsson  Melissa Chierici  Jens M. Skei  H. Göte östlund 《Aquatic Geochemistry》1996,2(2):111-129

Three different layers have been identified in Framvaren, which has a maximum water depth of 184 m. One oxic layer above the redoxcline at 18–20 m. One anoxic layer from 20 to 100 m which is occasionally ventilated by a flow over the sill (which has a depth of 2.5 m), and finally a stagnant layer below 100 m. Using the release rate of silica from the bottom and measurements of the concentration of HTO it is possible to make some calculations on the annual volume of interleaving in the layers 25–50 m, 50–75 m, and 75–100 m together with the advective flows. Reliable values of the sulfide concentration were obtained by precipitating and weighing HgS together with careful protection of all anoxic water samples with argon. The light yellow color of the precipitate in the depth range 25 to 80 m indicates that the occasional ventilation will cause such reactions as 0.50₂ + H₂S S(colloidal) + H₂O. The elemental sulfur, being stabilized with HS^–, is set free upon the precipitation of HgS. The new data for the concentration of sulfide give an acceptable stoichiometry for the decay reaction of organic matter. This is not the case with the data of Yao and Millero. The mean values for the concentrations of ammonium and phosphate agree with the new data of Yao and Millero. The mol/mol C/N ratio of 10.1 found in trapped material by Naess and coworkers (1988) agrees with the stoichiometry of the dissolved constituents, i.e. C/N = 9.92 ± 0.45. A denitrification reaction is suggested to explain the high values of C/N. The vertical diffusion coefficient at 100 m calculated from the depth profile of silica was 0.92 × 10^–6 m² s^–1 which lies in the range of values given by Fröyland. Finally, the ¹⁴C age of the total dissolved inorganic carbon (Ct) in the water below 90 m was about 1600 years indicating a bioproduction in the period 8000 years B.P. to A.D. 1853 when a channel was opened between the fjord outside (Helvikfjord) and Framvaren.  相似文献   

Levels and patterns of polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls in surface sediments from the western Baltic Sea (Arkona Basin) and the Oder River estuarine system     

D. Dannenberger  R. Andersson  C. Rappe 《Marine pollution bulletin》1997,34(12):1016-1024

Surface sediment samples were collected from the western Baltic Sea (Arkona Basin) and the Oder River estuarine system in May and August 1995 and analysed for polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls. Contents of PCDF (sum) and PCDD (sum) varied from 2.5 to 820.0 pg g⁻¹ dw and from 12.7 to 2991.0 pg g⁻¹ dw, respectively. PCB contents (sum of 23 congeners) ranged between < 130.0 and 16267.0 pg g⁻¹ dw. Only slight variations in PCDF/D and PCB contents on dry weight basis were found between the Oder River estuarine system and the open Baltic Sea. TOC-normalization of the data showed an approximately homogen PCDF/D distribution in the study area. The distribution pattern for PCDF/D and PCB may be attributed to high sediment dynamics combined with transport processes from the temporary sedimentation basin (Oderhaff) to the deeper parts of the Baltic Sea.  相似文献   

Gold in the volcanogenic mercury-rich sulfide deposit Långsele,Skellefte ore district,northern Sweden     

Per Nysten 《Mineralium Deposita》1986,21(2):116-120

The mineralogy of gold from a volcanogenic sulfide deposit in northern Sweden (Långsele) was studied. The enrichment of gold and silver in massive ore occurs associated with an intrusive metadolerite vein which can be traced across the ore. The emplacement of this vein mobilized the precious metals together with galena and Pb-Sb sulfosalts into fractures and low pressure zones. A high mercury content at L»ngsele (average 250 ppm) has influenced the gold mineralogy. Thus, gold occurs as Au-Ag amalgam, native gold and rarely as aurostibite (AuSb₂). The results of microprobe analyses of amalgam cluster around Au_0.45Ag_0.45Hg_0.10. The composition of ternary amalgam is discussed in connection with the synthetic Au-Ag-Hg system. Furthermore, native gold was found myrmekitically integrown with stibnite which has been interpreted as a breakdown product of aurostibite at low temperature.  相似文献   

Intrinsic biodegradation of toluene coupled to the microbial reduction of ferric iron: laboratory column experiments     

Zuoping Zheng  Per Aagaard  Gijs D. Breedveld 《Environmental Geology》2002,42(6):649-656

Intrinsic biodegradation of toluene coupled with the microbial reduction of ferric iron (Fe(III)) as the terminal electron acceptor was studied by using laboratory column experiments under continuous flow conditions. Columns were packed with contaminated aquifer sediment and N₂-purged groundwater taken from the western part of the Gardermoen aquifer. The columns were operated anaerobically at 8 °C (in-situ temperature). Chloride was initially used to characterize flow properties of the columns. Intrinsic biodegradation of toluene, including abiotic loss and biological loss, was estimated by comparing breakthrough curves of toluene for live columns and sterilized control columns based on mass balance in steady-state conditions. The column experiments were run at two different flow velocities. The estimated average intrinsic rate was -0.73 and -0.53 mM day^-1 for pore-water velocities of 1.75 and 2.68 cm h^-1, respectively, corresponding to -0.27 and -0.22 mM day^-1 in biological loss rate. The results indicate that intrinsic biodegradation of toluene could be used as an efficient remediation approach for contaminated groundwater at the Gardermoen fire-fighting training site.  相似文献   

Sorption and anaerobic biodegradation of soluble aromatic compounds during groundwater transport. 2. Computer modeling     

Zuoping Zheng  Per Aagaard  Gijs D. Breedveld 《Environmental Geology》2002,41(8):933-941

. The natural attenuation of a binary mixture of toluene and 1,2,4-trimethylbenzene, which was previously experimentally demonstrated in anaerobic column experiments, was simulated with the newly-developed PHREEQC model to reveal the biogeochemical processes involved. The processes considered in this model include advection, diffusion, sorption, redox reactions (e.g., oxidation of toluene and 1,2,4-trimethylbenzene coupled to the reduction of microbial ferric iron), precipitation of secondary minerals such as siderite and magnetite, and dissolution of hydrous ferric oxides, as well as other thermodynamic equilibrium reactions. The functions of advection and diffusion built into the PHREEQC were conventionally simulated. The sorption was kinetically simulated based on a bicontinuum model, whereas biodegradation was described using a multiple-term Monod model. The processes mentioned above were coupled with a geochemical equilibrium model. The consistency between the experimental and modeling results indicates that the processes defined and the controlling parameters chosen could describe the coupled interactions between transport and biogeochemical reactions for the studied system. The discrepancy between modeling and experimental observations, however, also revealed the limitation of the modeling approach. In general, the model approach, which incorporates simplified mathematical representations of the true physico-chemical dynamics of the sorption and biodegradation processes of toluene and 1,2,4-trimethylbenzene under anaerobic conditions is a very efficient and good predictive tool in management and remediation of contaminant groundwater aquifers.  相似文献   

Inorganic nutrient acquisition in a shallow clearwater lake – dominance of benthic microbiota     

Eva Andersson  Anna-Kristina Brunberg 《Aquatic Sciences - Research Across Boundaries》2006,68(2):172-180

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