| 1. |
- Routh, Joyanto, 1968-, et al.
(författare)
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Trace-element geochemistry of Onion Creek near Van Stone lead-zinc mine (Washington, USA) — Chemical analysis and geochemical modeling
- 1996
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Ingår i: Chemical Geology. - : Elsevier. - 0009-2541 .- 1872-6836. ; 133:1, s. 211-224
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Tidskriftsartikel (refereegranskat)abstract
- Van Stone lead-zinc mine in Washington is a possible contamination source of Columbia River water. Breaching of an old tailings pond, seepage of contaminated water, and surficial transport of mine tailings have increased trace-element (TE) concentrations in the Onion Creek water and sediments. Chemical analyses of water and sediment samples indicate high TE levels near the breached tailings pond. TE contamination indices for sediments indicate high values of Pb, Zn, and other TE’s which decrease downstream. High Kd values (> 104) for several TE’s (e.g., Al, Cd, Fe, Mn, Pb, V, and Zn) suggest their enrichment in the solid phase. TE concentrations in Onion Creek water and sediment sharply attenuate downstream due to: (1) enhanced carbonate dissolution, thereby increasing pH and immobilizing TE’s; (2) sorption to oxides; and (3) change in lithology from carbonate to granite. Speciation model MINTEQA2 was used to study the effect on TE dispersion due to dissolution-precipitation reactions and adsorption to ferrihydrite. In addition to the field and chemical data, the model also supports the hypothesis that Onion Creek sediments are the major sink for TE’s at VSM. Model runs indicate precipitation of Al, Ba, Ca, Fe, Mg, and Mn minerals from oversaturation, whereas TE’s with low concentrations (Cr, Cu, Ni, Se) or geochemically more mobile (As, Mo, Sb) remain dissolved in water. Near the tailings ponds, high pH and abundance of sorption sites in sediments contribute to the complete adsorption of Pb and Zn species. Because ambient conditions result in the sorption of most Pb and Zn ions, Onion Creek water quality meets EPA regulatory standards. These species will persist in Onion Creek sediments as sorbed or insoluble complexes, and without drastic pH changes (< 4.0) they will remain immobilized. However, continued TE enrichment in sediments will prove hazardous to filter feeding and aquatic organisms.
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| 2. |
- Routh, Joyanto, 1968-, et al.
(författare)
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Sedimentary organic matter sources and depositional environment in the Yegua formation (Brazos County, Texas)
- 1999
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Ingår i: Organic Geochemistry. - : Elsevier. - 0146-6380 .- 1873-5290. ; 30:11, s. 1437-1453
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Tidskriftsartikel (refereegranskat)abstract
- The complex depositional environment of the Eocene Yegua formation (Brazos County, Texas) can be better understood by integrating organic matter (OM) geochemistry with stratigraphy. Yegua sediments represent parasequences separated by exposure surfaces. Organic petrography and geochemistry (biomarkers, C/N ratios, and carbon isotopes) indicate the presence of both terrestrial and marine OM in transgressive sediments. In contrast, regressive sediments contain only terrestrial OM. These differences relate to contrasting OM sources and depositional styles on the shelf. OM in the sediments is immature and the potential for generating hydrocarbons is poor. The study suggests that organic geochemical data can help in distinguishing transgressive and regressive environments in sedimentary formations.
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| 3. |
- Berglund, B. E., et al.
(författare)
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Holocene forest dynamics and climate changes in the Abisko area, northern Sweden : the Sonesson model of vegetation history reconsidered and confirmed
- 1996
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Ingår i: Ecological Bulletins. - 0346-6868. ; 1996:1, s. 15-30
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Tidskriftsartikel (refereegranskat)abstract
- A new palaeoecological and palaeoclimatic project in the subalpine Abisko area, N Scandes, founded upon the pollen zone system defined by Sonesson is described. This model of vegetation history has been confirmed, although the chronology is partly revised. Sonesson's pollen diagrams are combined with new results from a lake sediment sequence at the tree-limit, which include sedimentologic, mineral magnetic, oxygen isotope and plant macrofossil studies. Since the deglaciation at c9000-8500 14C yr BP the vegetation of the Abisko area has generally been dominated by a subalpine birch Betula woodland tundra. The cliamte has generally been subarctic-oceanic since the deglaciation except for the period c.5500-3500 BP when temperate-continental conditions prevailed. This climatic development differs from the situation in the central Scandes.
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| 4. |
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| 5. |
- Zdanowicz, Christian, et al.
(författare)
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Basal debris entrainment and transport in glaciers of southwestern Bylot Island, Canadian Arctic
- 1996
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Ingår i: Annals of Glaciology. - 0260-3055 .- 1727-5644. ; 22:1, s. 107-113
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT. Glaciers on southwestern Bylot Island in the Canadian Arctic flow from an alpine setting in high-grade crystalline Archean terrane, on to coastal lowlands underlain by clastic sedimentary strata of Cretaceous to Tertiary age. We have used the contrasting mineralogy of the substrate as a tool to study subglacialentrainment and transport of debris in two large piedmont glaciers on Bylot Island. High chlorite/ and mica-illite/smectite ratios indicate that most basal debris is derived from crystalline rocks underlying the upper reaches of the glaciers. The subglacial accretion of Cretaceous-Tertiary sediments appears restricted to the lowermost part ofthe basal zone and is most noticeable near the glaciers' termini. lce associated with discrete silty-sandy debris layers is characterized by an isotopic signature indicative of refreezing of meltwater at the glacier sole. The compositional, textural and isotopic characteristics of basal sediment and ice lead us to conclude that subglacial entrainment through basal ice accretion occurs in both the upper and marginal parts of the glaciers
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| 6. |
- Strandh, Heléne, 1968-
(författare)
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Mineral dissolution from molecular to field scale
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mineral reactivity contributes to the global biogeochemical cycling of elements. CO2is consumed during the chemical weathering of many silicates and during formation of carbonates in the oceans. The balance of nutrients in soils and waters is coupled to the release of elements during weathering and the retention of elements during mineral precipitation. Dissolution of many minerals involves acid neutralization and the rate of most mineral reactions is dependent on the pH of the solution. The acid input to the atmosphere has increased drastically during the last century affecting our environment severely, with problems such as deterioration of the bronze-age rock carvings in the world heritage area Tanum, SW Sweden.This thesis compiles studies of quantum chemical calculations of the siloxane bond strength, laboratory dissolution experiments of quartz and brucite as well as field studies of the water chemistry of a rock surface in Tanum, SW Sweden.Quartz consists of only SiO2and provides the possibility to investigate specifically the siloxane bond, which is present in most silicates. Quartz dissolution is performed using plug-flow reactors during long-term experiments. This produced among the slowest rates reported in the literature, which suggests that long runtime is needed to approach natural dissolution rates. A rate minimum was obtained at pH 3-4, which was observed also after a short reaction time. Alkali metal cations increased the rate at pH>3, and KCl decreased the rate at pH<3, similar to results obtained for feldspar dissolution. The alkali metal effects and the pH dependence of the quartz dissolution emphasize the importance of surface species for the dissolution kinetics of silicate minerals, which may indicate the rate determining mechanisms in natural weathering environments.Quantum chemical methods are used to investigate the effects of different surface species on the siloxane bond strength. Direct adsorption of alkali metal cations reduces the bond strength for alkaline surface models and increases the bond strength for acid surface models, indicating that the surface species contribute to the rate of the quartz dissolution. Interaction with water molecules proved to be very important for the ion specific effects. For effects from protonation and deprotonation of the quartz surface, the hydration was essential. Further quantum chemical calculations showed that the pH dependence of the dissolution rate at high surface charge coverage could be due to acid-base repulsion within the surface layer.Brucite is a fast dissolving mineral that gives the possibility to investigate the rate dependence on the transport of ions. Rotating disc experiments are used to separate between surface reaction controls and molecular diffusion controls. Numerical modeling of the fluid equations is used to model a reaction zone near the brucite surface. The experiments and the model revealed that the solution pH determines the reaction mechanism in terms of surface reaction or diffusion reaction control. This is important information for the conclusion of the rate controlling mechanism of fast dissolving minerals on a rock surface.The water chemistry on the rock surface in Tanum gives information of rate controlling factors that can be used to reduce the chemical weathering rate. Extensive sampling of deposition, influenced by sea salt and acid rain, and runoff is performed on a rock surface in Tanum, SW Sweden. Two rock surfaces are investigated and compared; a roof protected, washed surface and a reference surface. The chemical weathering rate calculated as anorthite dissolution was 10 times slower than in literature data, due to a difference between the specific surface area and the reactive surface area in field. The chemical weathering rate of both surfaces was correlated with temperature and large differences in dissolution rate between the two ponds are due to differences in temperature and pH. Control of these parameters should give a surface that is preserved longer than an unprotected rock surface.
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| 7. |
- Stegmann, Bo
(författare)
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Försurad skogsmark i Gävleborgs län 1949-1989 : En undersökning av markförsurningens omfattning under tiden 1949-1989
- 1990
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I slutet av 1940-talet anlades en kraftledning längs med södra Norrlandskusten. 1949 påbörjades ett avsnitt av kraftledningen genom Gävleborgs län. I början av 1960-talet anlades en parallell kraftledning och 1962 påbörjades avsnittet genom Gävleborgs län.Jordprover togs i samband med anläggandet av kraftledningarna. Resistivitet och PH uppmättes för att utröna korrosionsrisken på kraftledningsstolparna. 1989 upprepades provtagningar vid 25 stolpar längs med kraftledningen. Mark-PH uppmättes för att se förändringar i pH under perioderna 1949–1962, 1962–1989 och 1949–1989. Kalkhalten bestämdes för att se markens eventuella buffringsförmåga mot pH- sänkning.Provgropar grävdes i kraftledningsgatan 15–2 m in skogen. Provtagning gjordes från samma djup som 1949 och 1962. pH mättes på samma sätt som 1949 och 1962 dvs. I vattensuspension. Mätvärdena grupperades i 4 nivåer, 0,0m, 0,2–0,3m, 0,4–0,5m och 0,6–0,7m. Minskningen i pH- medelvärden är signifikant på alla nivåer utom två. Vid uträkningen av pH-medelvärden har pH behandlats som icke- logaritmiska värden. pH- medelvärden från andra markundersökningar som resultaten från Gävleborgsundersökningen jämförs med är framräknade på likartat sätt. I bilaga har pH- medelvärden framräknats som logaritmiska värden. Kalkhalten bestämdes för samtliga mineraljordprover och inget av dessa innehöll en kalkhalt >0,1%. Deposition av luftburna försurande ämnen har för tiden 1949–1989 varit den dominerande försurningskällan.
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| 8. |
- Stegmann, Bo
(författare)
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Näringsbalansen i skogsmark i Gävleborg : en pilotstudie
- 1994
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- En preliminär nettobalansberäkning gjordes för det utbytbara Ca-, K- och Mg- förrådet i morän i skogsmark. Beräkningen avser en tidsperiod på 80-100år, motsvarande en skogsgeneration. I redovisningen av beräkningarna uttryckes dessa värden per år.
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| 9. |
- Ulrich, G. A., et al.
(författare)
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Sulfur Cycling in the Terrestrial Subsurface : Commensal Interactions, Spatial Scales, and Microbial Heterogeneity
- 1998
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Ingår i: Microbial Ecology. - : Springer. - 0095-3628 .- 1432-184X. ; 36:2, s. 141-151
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Tidskriftsartikel (refereegranskat)abstract
- Microbiological, geochemical, and isotopic analyses of sediment and water samples from the unconsolidated Yegua formation in east-central Texas were used to assess microbial processes in the terrestrial subsurface. Previous geochemical studies suggested that sulfide oxidation at shallow depths may provide sulfate for sulfate-reducing bacteria (SRB) in deeper aquifer formations. The present study further examines this possibility, and provides a more detailed evaluation of the relationship between microbial activity, lithology, and the geochemical environment on meter-to-millimeter scales. Sediment of varied lithology (sands, silts, clays, lignite) was collected from two boreholes, to depths of 30 m. Our findings suggest that pyrite oxidation strongly influences the geochemical environment in shallow sediments ( 5 m), and produces acidic waters (pH 3.8) that are rich in sulfate (28 mM) and ferrous iron (0.3 mM). Sulfur and iron-oxidizing bacteria are readily detected in shallow sediments; they likely play an indirect role in pyrite oxidation. In consistent fashion, there is a relative paucity of pyrite in shallow sediments and a low 34S/32S-sulfate ratio (0.2ￜ) (reflecting contributions from 34S-depleted sulfides) in shallow regions. Pyrite oxidation likely provides a sulfate source for both oxic and anoxic aquifers in the region. A variety of assays and direct-imaging techniques of 35S-sulfide production in sediment cores indicates that sulfate reduction occurs in both the oxidizing and reducing portions of the sediment profile, with a high degree of spatial variability. Narrow zones of activity were detected in sands that were juxtaposed to clay or lignite-rich sediments. The fermentation of organic matter in the lignite-rich laminae provides small molecular weight organic acids to support sulfate reduction in neighboring sands. Consequently, sulfur cycling in shallow sediments, and sulfate transport represent important mechanisms for commensal interaction among subsurface microorganisms by providing electron donors for chemoautotrophic bacteria and electron acceptors for SRB. The activity of SRB is linked to the availability of suitable electron donors from spatially distinct zones.
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| 10. |
- Estmark Kalinowski, Birgitta
(författare)
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Dissolution Kinetics and Alteration Products of Micas and Epidote in Acidic Solutions at Room Temperature
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The reaction kinetics of the weathering of several phyllosilicates and one sorosilicate were stud ied experimentally. The alteration products were characterised by various methods in clud ing XRD, HRTEM, SEM, FTIR, NMR and Mössbauer spectroscopy. Weathering of silicates is of particular concern to our knowledge of several areas in low temperature geochemistry, such as el e ment cy cling, ground water chemistry and soil formation. The importance of these processes ex tends to the long-term nutrient supply to forest ecosystems and control of soil and water acidity, es pe cial ly in Scandinavia.Several soil models designed to predict the impact of acid rain on the soil chemistry rely on kinetic data of mineral weathering. The reaction kinetics for minerals are used in such models to predict chang es in soil chem is try. This enables calculation of the effect of acid rain (i. e. critical load) in a 100-year per spec tive. For some minerals relatively little knowledge is available for the reaction kinetics. There fore the dissolution kinetics of muscovite, biotite, phlogopite, vermiculite and epi dote were studied over the pH range 1 to 6.5 at room temperature using flow-through reactors.Silica release rates based on specific surface area are about the same for as divers silicates as epidote (sorosilicate), K-feldspar (tectosilicate) and phlogopite (phyllosilicate). At pH 3 log R = -15.41, -15.5 and -15.46 respectively for these min er als. However, the framework of Si and Al is likely to determine with what ease cations positioned in between the conformation of Si and Al tetrahedra are re leased. For example, K in micas have transportation channels due to the layer struc ture and ought there fore to be released easier than in K-feldspar. In most cases Si is the most slowly released element in silicates, but in epidote, Si and Ca are the fastest released elements from the structure, while Al and Fe are retained. Leaching of inter framework cations creates strain and charge im bal ance in the silicate structure, causing Si to be more readily released in base cation containing silicates than in quartz. Released Si may repolymerise directly at the surface of silicates or interlayers. Amor phous silica gel has been detected, as a weathering product between packages of 2:1 layers in bi otite, using AEM. Iron(hydr)oxides have been found as the end-product of biotite weathering. Re sid u al layer calculations based on the solution composition show that Al and Fe form an enriched layer with a thickness of 1-2 nm at the surface of epidote.Biotite and phlogopite probably alter to trioctahedral vermiculite from the edges and inwards. Mössbauer spectroscopy shows that weathering of biotite as well as ver micu lite is accompanied by oxidation. Al-hydroxy polymers are introduced in the in ter lay er during weathering of phlogopite and vermiculite, which is supported by both XRD and 27Al MAS-NMR analyses. Additions of KCl and AlCl3 to the reactant solutions show that release rates, exfoliation and oxidation processes decrease with increased concentrations for both biotite and phlogopite. Leaching of interlayer cat i ons seems thus to initiate oxidation of ferrous iron.
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