| 1. |
- Andersson, Per S., et al.
(författare)
-
The isotopic composition of Nd in a boreal river : a reflection of selective weathering and colloidal transport
- 2001
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 65:4, s. 521-527
-
Tidskriftsartikel (refereegranskat)abstract
- In this study the Nd concentrations (CNd) from 18 months of weekly sampling of filtered water (<0.45 μm) in the Kalix River, northern Sweden, are reported with εNd(0) and 147Sm/144Nd ratios determined in samples representing major flow events as well as maxima and minima in CNd. The CNd varies by a factor of ten, between 200 pmol/L to 2100 pmol/L, and there is a strong relation between high discharge and high CNd. The Nd in the Kalix River is mainly transported on particles (>90%), dominated by a colloidal phase primarily composed of organic C and Fe. The εNd(0) and 147Sm/144Nd only vary within a narrow range, -27.1 to -24.8 and 0.103 to 0.110 respectively, with no obvious relationship to CNd and discharge. The εNd(0) and 147Sm/144Nd in the river water is significantly lower than in the unweathered till and average bedrock in the catchment and show a closer resemblance with the isotopic characteristics found in humic substances and plant material. These data show that the isotopic composition of Nd exported from a large boreal drainage basin does not directly reflect that of the bulk bedrock in the catchment. The isotopic composition is controlled by selective weathering and the Nd transport is dominated by organic colloidal particles.
|
|
| 2. |
|
|
| 3. |
- Dahlqvist, Anna, et al.
(författare)
-
The Rebound Effect in Energy-Intensive Industries : A Factor Demand Model with Asymmetric Price Response
- 2021
-
Ingår i: Energy Journal. - : International Association for Energy Economics. - 0195-6574 .- 1944-9089. ; 42:3, s. 177-204
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of this paper is to estimate industry-specific direct rebound effects and to relate these effects to industry energy efficiency programs. The rebound effect represents economic behavior that will offset energy savings from energy efficiency improvements. The paper focuses on four energy intense sectors in Sweden; pulp and paper, iron and steel, chemical, and mining, during 2001-2012. We apply a factor demand model that allows for asymmetric energy price responses, i.e. that firms respond differently to increasing and decreasing energy prices. The results show considerable rebound effects. For electricity and non-fossil fuels, efficiency improvements could even ‘backfire’. To mitigate this effect, policies, such as voluntary energy efficiency programs, should be combined with an increase in energy taxes if the ambition is to reduce overall energy use.
|
|
| 4. |
- Dahlqvist, Ralf, et al.
(författare)
-
The concentration and isotopic composition of diffusible Nd in fresh and marine waters
- 2005
-
Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X .- 1385-013X. ; 233:1-2, s. 9-16
-
Tidskriftsartikel (refereegranskat)abstract
- Variations in the Nd isotopic composition of ocean water through time, recorded in marine deposits, are suggested to document changes in erosional input and ocean circulation. Thus characterization of the dissolved Nd component in seawater is important. But few attempts have been made to directly measure truly dissolved Nd. Here we report Nd data, obtained using the technique of diffusive gradients in thin-films (DGT) designed to measure in situ, diffusible labile trace metals in aqueous solutions. The method samples free ions and possibly very small complexes. The concentration and isotopic composition of Nd in fresh, brackish and seawater have been determined with DGT, analyzed with thermal ionization mass-spectrometry, and compared with filtered and bulk water samples. Concentrations measured in water samples and with DGT show that the relative amount of diffusible Nd increases with salinity, from being about 10% in the fresh water to 42% in seawater. At each sampled site, the isotopic composition of Nd in the water shows a similar isotopic composition, within errors, with Nd sampled using the DGT method. These results indicate that there is a complete exchange between the particulate/colloidal fraction and the truly dissolved phase. Therefore our findings suggest that solute Nd reflects both the isotopic composition of the marine sediments and the bulk water.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Ingri, Johan, et al.
(författare)
-
Size distribution of colloidal trace metals and organic carbon during a coastal bloom in the Baltic Sea
- 2004
-
Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 91:1-4, s. 117-130
-
Tidskriftsartikel (refereegranskat)abstract
- The physico-chemical speciation of organic carbon and selected metals was measured during a coastal bloom in Ekhagen Bay, Baltic Sea, using ultrafiltration.One important objective with the study was to see if any depletion of trace metals could be measured in the directly bioavailable fraction (<1000 Da, the soluble low molecular weight fraction, LMW) during a plankton bloom. Filters with five different cut-offs were used (1 kD (1000 Da), 5 kD, 10 kD, 100 kD and 0.22 μm) in order to delineate the size distribution of colloidal organic carbon (COC) and trace metals. During the bloom in May, LMW Al, Co, Cu, Mn and Ni concentrations decreased although the colloidal and particulate concentrations were relatively high. Data show that desorption of colloidal and particulate bound trace metals to the LMW fraction was slower than the process depleting the LMW fraction. Estimates of the maximum active uptake of Cu, Ni and Mn by the phytoplankton, and the loss of non-bioactive Al from the LMW fraction, indicate that processes other than active uptake by phytoplankton must contribute to the observed depletion of trace metals in the LMW fraction. Hence, in order to estimate the bioavailable pool of trace metals for plankton during bloom conditions, these other processes must be understood and quantified. Transparent Exopolymeric Particles (TEP, reflecting sugar-rich phytoplankton exudates) increased around eight times during the plankton bloom. We hypothesize that the formation of TEP is a process that might be important for the transfer of trace metals from the LMW to the particulate fraction during the phytoplankton bloom, but the significance of TEP for this depletion in Baltic Sea surface water remains to be shown.
|
|
