| 1. |
- Amakawa, Hiroshi, et al.
(författare)
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Isotopic compositions of Ce, Nd and Sr in ferromanganese nodules from the Pacific and Atlantic Oceans, the Baltic and Barents Seas, and the Gulf of Bothnia
- 1991
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Ingår i: Earth and Planetary Science Letters. - 0012-821X .- 1385-013X. ; 105:4, s. 554-565
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Tidskriftsartikel (refereegranskat)abstract
- Ferromanganese nodules from the Pacific and Atlantic Oceans, the Barents and Baltic Seas, and the Gulf of Bothnia were analyzed for the isotopic compositions of Ce, Nd and Sr and the abundances of REE, Ba and Sr. REE patterns of Barents, Baltic and Bothnian samples show no Ce anomaly, or even a negative one, in contrast to the positive anomaly observed for the Pacific and Atlantic samples. Moreover, the Baltic and Bothnian samples have distinctly low εNd values; average εNd values of the four regions are as follows: Pacific -5, Barents -10, Atlantic -11 and Baltic inclusive of Gulf of Bothnia -19. The characteristic low εNd values of the Baltic samples are indicative of the influence of Precambrian rocks from the Baltic shield. Of particular interest is the feature of the Ce isotopic composition that εCe values of the samples from the Pacific are negative and those from the other three regions positive. This novel finding might suggest a difference in sources of Ce between the Pacific and other regions. These results demonstrate that Ce isotopic ratios can be a useful tracer in marine geochemistry, in combination with isotopic compositions of Nd and Sr.
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| 2. |
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| 3. |
- Andersson, Per, et al.
(författare)
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A rapid preconcentration method for multielement analysis of natural freshwaters
- 1991
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Ingår i: Water Research. - 0043-1354 .- 1879-2448. ; 25:5, s. 617-620
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Tidskriftsartikel (refereegranskat)abstract
- This study describes an inexpensive and rapid preconcentration method which can be applied directly in the field. It is based on coprecipitation with magnesium hydroxide and has been applied for Al, Fe, Mn, Zn, Cu, Ni, V, Cr, Co, Cd, Be, Y, Sc and Yb in freshwaters. The method has been tested using inductively coupled plasma-atomic emission spectrometry (ICP-AES) by adding known amounts of metals to distilled water and natural freshwater. The detection limit for ICP-AES can be enhanced more than two orders of magnitude for Al, Y, Sc, Yb and approximately one order of magnitude for the other tested elements.
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| 4. |
- Andersson, Per S., et al.
(författare)
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238U-234U and 232Th-230Th in the Baltic Sea and in river water
- 1995
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Ingår i: Earth and Planetary Science Letters. - 0012-821X .- 1385-013X. ; 130:1-4, s. 217-234
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Tidskriftsartikel (refereegranskat)abstract
- The concentration (C) of dissolved238U,234U,232Th and230Th in fresh and brackish waters from the Baltic Sea were determined using TIMS. The brackish waters range in salinity from that of sea water (SW) to 2.5‰. C238U in oxygen-saturated, surface waters is well correlated with salinity and shows quasi-conservative behavior, as does Sr. Samples from the redox water interface show depletion in C238U, demonstrating that dissolved U is being removed by FeMn oxyhydroxides. From a simple mixing relationship for the brackish water,δ234U* = 1000‰ was calculated for the fresh water source in the northern Baltic. A study of the Kalixälven River over an annual cycle yields highδ234U during spring and summer discharge and lower values during fall and winter, showing that different sources contribute to the U load in the river during different seasons. C232Th and C230Th in river water are governed by the discharge, reflecting the importance of the increased abundance of small particles ( < 0.45 μm) for the232Th230Th load at high discharge.232Th/238U in river water is about 40 times less than in detrital material. In the brackish water, C232Th drops 2 orders of magnitude in the low salinity region ( < 5‰), reaching a value close to that of sea water at a salinity of 7.5‰. Almost all of the riverine232Th must be deposited in the low-salinity regions of the estuary.The230Th/232Th in river waters is about twice the equilibrium value for232Th/238U (3.8). In the brackish waters,230Th/232Th is greater by a factor of 10-100 than both river water and SW. The big increase in230Th/232Th in the Baltic Sea waters over the riverine input indicates that the Th isotopes enter the estuary as a mixture of two carrier phases. We infer that about 96% of232Th in river water is carried by detrital particles, whereas the other phase (solution, colloidal) has a much higher232Th/232Th. Entering the estuary, the detrital particles sediment out rapidly, whereas the non-detrital phase is removed more slowly, causing a marked increase in230Th/232Th in the brackish water. In SW,230Th/232Th is closer to river input and detrital material than in brackish water. We conclude that in the deep sea,232Th is almost exclusively dominated by windblown dust and can be used to monitor dust flux. The230Th excess in Baltic rivers is produced in U-rich,232Th-poor peatlands and trapped in authigenic particles and transported with the particles. Time scales for producing the230Th excess are ≈ 2000-8000 yr. This is younger than, but comparable to, the time of the latest deglaciation, which ended some 9000 yr ago when the mires were forming. These results have implications for the possible mobility of actinides stored in repositories.
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| 7. |
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| 8. |
- Andersson, P. S., et al.
(författare)
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Particle transport of 234U-238U in the Kalix River and in the Baltic Sea
- 1998
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Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 62:3, s. 385-392
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Tidskriftsartikel (refereegranskat)abstract
- The role of particles for U isotope transport was investigated in the Kalix River watershed, a particle-poor, Fe/Mn-rich river in northern Sweden, and in the Baltic Sea estuary. Particles >0.45 μm are strongly enriched in U and contain 20-50% of the total riverine uranium budget and <1% of the total U in brackish waters (3-7 PSU). The particles have high δ234U which is close to that of dissolved U in the associated water, indicating that U on particles is dominantly nondetrital and isotopically exchanges rapidly with the ambient dissolved U. Particles at the river mouth are dominated by nondetrital Fe-Mn oxyhydroxides. Uranium and Fe are strongly correlated, clearly demonstrating that secondary Fe-oxyhydroxide is the major carrier of U in river water. There is no evidence for significant association of U with Mn-oxyhydroxide. Apparent U distribution coefficients ... were calculated for U between the authigenic Fe on particles and the solution. These values appear to be relatively constant throughout the year. This suggests an equilibrium between Fe in solution and authigenic Fe-oxyhydroxides on detrital particles. High values of .... calculated for one summer as well as high U concentrations in brackish waters can be explained by U scavenging by biogenic phases with low authigenic Fe content.
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| 9. |
- Andersson, Per S., et al.
(författare)
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Strontium, dissolved and particulate loads in fresh and brackish waters : the Baltic Sea and Mississippi delta
- 1994
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Ingår i: Earth and Planetary Science Letters. - 0012-821X .- 1385-013X. ; 124:1-4, s. 195-210
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Tidskriftsartikel (refereegranskat)abstract
- A study was conducted of the isotopic composition and concentration of Sr and of major elements in dissolved and suspended loads of fresh and brackish waters. The purpose was to establish the contributions of different parent rocks and minerals to Sr during weathering and transport and to identify the role of Fe_Mn oxyhydroxides in the redistribution of Sr in the water column during the sedimentary cycle. Studies were conducted on a profile across an oxic-anoxic boundary in the Baltic and on rivers covering behavior over an annual cycle. In general, the 87Sr/86Sr ratios differ between particulate and dissolved loads, with more radiogenic Sr in the particulate loads. These differences are attributed to differential weathering of minerals, where high Rb/Sr minerals dominate the particulate load and low Rb/Sr the dissolved load. There is broad correlation of 87Sr/86Sr with K/Al in the suspended load. The differences in 87Sr/86Sr between suspended and dissolved load are highly variable and are related to the Fe or Mn concentration on the particulates. In samples with high Fe/Al, the difference becomes small. A good correlation was found between Sr/Al and Fe/Al or Mn/Al in the particulates both in brackish and fresh waters. Sr is removed from solution both in rivers and in the Baltic Sea whenever there is formation of Fe_Mn oxyhydroxide particulates. This precipitation greatly diminishes the difference in isotopic composition of the dissolved and suspended loads. As the particles containing Fe_Mn oxyhydroxides settle, they dissolve in anoxic zones and release Sr. This provides a mechanism for Sr redistribution in the water column. Sr is thus only quasi-conservative in environments where Fe_Mn oxyhydroxides form or dissolve. From consideration of the isotopic differences in Sr between dissolved and suspended loads, it follows that the net Sr input depends upon weathering characteristics of the contributing mineral phases. Changes in weathering mechanisms due to climate change may cause Sr isotopic shifts in the marine environment.
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| 10. |
- Andersson, Per S., et al.
(författare)
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The sources and transport of Sr and Nd isotopes in the Baltic Sea
- 1992
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Ingår i: Earth and Planetary Science Letters. - 0012-821X .- 1385-013X. ; 113:4, s. 459-472
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Tidskriftsartikel (refereegranskat)abstract
- We have determined the concentration and isotopic composition of Sr and Nd in waters from the Baltic Sea. The Baltic Sea is an intracontinental, stratified, brackish water, estuarine-like system, and the rivers emptying into it drain a suite of terranes ranging from Proterozoic-Archean in the north to Phanerozoic in the south. The sampled brackish waters range in salinity from seawater (SW) at 35.289‰ to a minimum of 2.460‰ at the surface in the innermost part of the Gulf of Bothnia. The Sr concentrations show generally conservative behavior, indicating a simple two-component mixing. However, small deviations (3-70 ‰) from a perfect mixing line reveal that the imprints from rivers with different Sr concentrations are preserved in the blending. Strontium concentrations from a depth profile across the redoxcline in the Baltic proper indicate that vertical particle transport alters the Sr concentration in the water. Our estimated concentration of Sr in the average freshwater input to the Baltic is 0.03 ppm, which is only about 0.4% of the SW concentration. The Sr isotopic data range from εSr(SW) = 0 in seawater to εSrBW(SW) = 7.8 in the least saline Baltic water (BW) sample in the Gulf of Bothnia. The isotopic composition of Sr versus 1/Sr in the Baltic Sea follows an almost perfect mixing line, which shows that seawater Sr is mixed with much more radiogenic components. Calculated end-member values of εSr*(SW) for each sample show that the riverine input into the Gulf of Bothnia has εSr*(SW) = 120-200and10-50 ε units in the Baltic proper. These values are in general agreement with direct measurements of river waters in each region. However, the calculated values in the Gulf of Bothnia are lower than the measured river water input in this region, which indicates the presence of less radiogenic Sr, presumably originating from the river waters draining the southern part of the basin which are partially transported northward and mixed with Sr from the Gulf of Bothnia rivers. The Nd concentration in the Baltic Sea is not conservative, varying between 5 and 45 ppt, with the highest concentrations in the bottom waters due to vertical particulate transport. A plot of εNd(O) in Baltic water yields a good correlation with the calculated freshwater end member εSr*(SW). The data show that it is possible to unravel the different freshwater sources into the Baltic and to identify the zones of particulate removal of both non-conservative species such as the REE and of quasi-conservative species such as Sr. The use of isotopic tracers in this estuarine environment may provide a much better insight into mixing and element transport. It should also be possible to trace lateral movements of freshwater inputs
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