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- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- Lundin, Lars-Christer, et al.
(författare)
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Continuous long-term measurements of soil-plant-atmosphere variables at a forest site
- 1999
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Ingår i: Agricultural and Forest Meteorology. - 0168-1923 .- 1873-2240. ; 98-99, s. 53-73
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Tidskriftsartikel (refereegranskat)abstract
- It is a major challenge in modem science to decrease the uncertainty in predictions of global climate change. One of the largest uncertainties in present-day global climate models resides with the understanding of processes in the soil-vegetation-atmosphere-transfer (SVAT) system. Continuous, long-term data are needed in order to correctly quantify balances of water, energy and CO2 in this system and to correctly model it. It is the objective of this paper to demonstrate how a combined system of existing sensor, computer, and network technologies could be set up to provide continuous and reliable long-term SVAT-process data from a forested site under almost all environmental conditions. The Central Tower Site (CTS) system was set up in 1993-1994 in a 25 m high boreal forest growing on a highly heterogeneous till soil with a high content of stones and blocks. It has successfully monitored relevant states and fluxes in the system, such as atmospheric fluxes of momentum, heat, water vapour and CO2, atmospheric profiles of temperature, water vapour, CO2, short-and long-wave radiation, heat storage in soil and trees, sap-dow and a variety of ecophysiological properties, soil-water contents and tensions, and groundwater levels, rainfall and throughfall. System uptime has been more than 90% for most of its components during the first 5 years of operation. Results from the first 5 years of operation include e.g., budgets for energy, water and CO2, information on important but rarely occurring events such as evaporation from snow-covered canopies, and reactions of the forest to extreme drought. The carbon budget shows that the forest may be a sink of carbon although it is still growing. The completeness of the data has made it possible to test the internal consistency of SVAT models. The pioneering set-up at the CTS has been adopted by a large number of SVAT-monitoring sites around the world. Questions concerning tower maintenance, long-term calibration plans, maintenance of sensors and data-collection system, and continuous development of the computer network to keep it up to date are, however, only partly of interest as a research project in itself. It is thus difficult to get it funded from usual research-funding agencies. The full value of data generated by the CTS system can best be appreciated after a decade or more of continuous operation. Main uses of the data would be to evaluate how SVAT models handle the natural variability of climate conditions, quantification of water. carbon and energy budgets during various weather conditions, rind development of new parameterisation schemes in global and regional climate models.
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| 8. |
- Skiöld, Torbjörn, et al.
(författare)
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Chronology of Proterozoic orogenic processes at the Archaean continental margin in northern Sweden
- 1993
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Ingår i: Precambrian Research. - 0301-9268 .- 1872-7433. ; 64:1-4, s. 225-238
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Tidskriftsartikel (refereegranskat)abstract
- The Proterozoic Svecofennian orogeny was characterized by the rapid formation of great amounts of juvenile continental crust and extensive remobilization of older crust. This paper considers U---Pb zircon ages and some geochemical and lithostratigraphic features of the Svecofennian in the continental-margin area between the Skellefte ore district and the boundary of the Archaean craton farther north in Sweden. New U---Pb zircon ages constrain the igneous activity of Svecofennian crust formation in northern Sweden to between 1930 and 1870 Ma ago. The same time constraints apply also to crust formation farther east in Finland. Orogeny along the entire Archaean-Proterozoic boundary zone was thus simultaneous and does not represent an east-to-west event succession. It is argued that rocks with similar major element compositions but distinctly different trace element characteristics were formed simultaneously but in different plate-tectonic environments. By ≈ 1875 Ma ago, the Svecofennian volcanic arc had matured and a variety of syn- to late-orogenic igneous rocks appeared in both tensional and compressional settings. Shortly thereafter, the Svecofennian magmatic activity ceased altogether, probably as a result of collision between the arc and the Archaean continent in the north. It is also suggested that pre-Svecofennian rifting of the Archaean craton had created a passive continental margin and that the transition to an active margin with subsequent island-arc magmatism and subduction beneath the Archaean craton commenced prior to 1930 Ma ago. It may well have been initiated by a relative drift of the Archaean craton towards the present southwest as a consequence of the formation of the collisional Proterozoic Lapland Granulite Belt in the northernmost Baltic Shield.
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| 9. |
- 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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| 10. |
- 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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