| 1. |
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| 2. |
- Isaksson, E, et al.
(författare)
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Ice cores from Svalbard :useful archives of past climate and pollution history.
- 2003
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Ingår i: Physics and chemistry of the earth. Part A. - : Elsevier BV. - 1464-1895 .- 1873-4642 .- 1474-7065. ; 28:28-32, s. 1217-1228
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Tidskriftsartikel (refereegranskat)abstract
- Ice cores from the relatively low-lying ice caps in Svalbard have not been widely exploited in climatic and environmental studies due to uncertainties about the effect of melt water percolation. However, results from two recent Svalbard ice cores, at Lomonosovfonna (1250 m asl) and Austfonna (750 m asl), have shown that with careful site selection, high-resolution sampling and multiple chemical analyses, it is possible to recover ice cores with partly preserved annual signals. These cores are estimated to cover at least the past 600 years and have been dated using a combination of known reference horizons and glacial modeling. The δ18O data from both Lomonosovfonna and Austfonna ice cores suggest that the 20th century was the warmest during the past 600 years. A comparison of the ice core and sea ice records from this period suggests that sea ice extent and Austfonna δ18O are linked over the past 400 years. This may reflect the position of the storm tracks and their direct influence on the relatively low altitude Austfonna. Lomonosovfonna may be less sensitive to such changes and primarily record atmospheric changes due to its higher elevation. The anthropogenic influence on Svalbard environment is illustrated by increased levels of non-sea-salt sulphate, nitrate, acidity, fly-ash and organic contaminants particularly during the second half of 1900s. Decreased concentrations of some components in recent decades most likely reflect emission and use restrictions. However, some current-use organic pesticide compounds show growing concentrations in near surface layers.
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| 3. |
- Moakhar, Mohsen Oveisy, et al.
(författare)
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A palaeomagnetic analysis of rapakivi intrusions and related dykes in the Fennoscandian Shield
- 2000
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Ingår i: Physics and chemistry of the earth. Part A. - 1464-1895 .- 1873-4642. ; 25:5, s. 489-494
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Tidskriftsartikel (refereegranskat)abstract
- In the Fennoscandian Shield (Baltica) there are seven major rapakivi plutons and fifteen minor ones ranging in age from ca 1.66 to 1.50 Ga. These plutons are distributed in a broad WNW zone and if the most eastern pluton is excluded there is a westward trend of decreasing age of the intrusions. A palaeomagnetic study has been performed on 4 minor plutons (Rödö, Mårdsjö, Norsjö and Mullnäset) and associated dykes in central Sweden. The results were combined with palaeomagnetic data from other rapakivi complexes in Fennoscandia in order to test if a stationary hot spot may be the origin of these anorogenic intrusions. Plotting the pole positions of this study together with poles of other complexes, poles calculated from rapakivi rocks and related dykes in Finland are located at somewhat lower latitudes and more eastern longitudes than poles of corresponding rocks in Sweden, probably reflecting an APW related to the general age differences between the plutons. The palaeolatitudes for the Fennoscandian Shield at the time of the rapakivi intrusions are restricted to a latitudinal range between ca 16° south and 27° north and there is a weak trend of increasing palaeolatitude with decreasing age of the rocks. A trend of gradually changing palaeolatitudinal positions has also been observed for the intrusion of Proterozoic anorthosite-rapakivi plutons in the Ukranian Shield. Such differences in palaeolatitudes is not expected in case of a single stationary hot spot being the source of the rapakivi intrusions, as the rock then should carry a magnetization reflecting the same latitudinal position.
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| 4. |
- Larsen, F, et al.
(författare)
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A preliminary analysis of the groundwater recharge to the Karoo formations, mid-Zambezi basin, Zimbabwe
- 2002
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Ingår i: Physics and Chemistry of the Earth. - 1474-7065. ; 27:11-22, s. 765-772
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Tidskriftsartikel (refereegranskat)abstract
- A multi-disciplinary study is being carried out on recharge to the Karoo sandstone aquifer in the western part of Zimbabwe, where recharge is controlled by the presence of a thick, confining basalt layer. The aquifer is geographically extensive, and has been identified throughout the southern part of the mid-Zambezi basin (Fig. 1). The potential for groundwater abstraction seems to be huge. The key issues in this part of the study are the extent of the recharge area and the recharge rates. The direct recharge area has previously been considered to be the area of outcrop of Karoo Forest sandstone, before it dips below an impervious basalt cover. However,, resistivity profiling shows that the basalt at the basin margin is weathered and fractured, and probably permeable, while the basalt deeper into the basin is fresh, solid and impermeable. Field and laboratory analysis of 22 groundwater samples support this extension of the recharge area to include a large area below the fractured basalt. CO2 gas pressures, calculated with the code PHREEQC using field measurements of pH and alkalinity, show that below the fractured basalt the groundwater is an open system in contact with atmospheric CO2. The C-14 and nitrate concentrations in this groundwater also indicate that recent infiltration takes place. The chloride contents of the rainfall and the groundwater in the recharge area have been measured to calculate direct recharge from rainfall. These data indicate that the direct recharge is in the range of 10-130 mm/yr, with an average value of 25 mm/yr. Preliminary results of recharge estimate using Cl-36 data suggests lower direct infiltration rates, but further studies are needed. The combination of hydro-chemical, isotopic and geophysical investigations show that the recharge area extends well beyond the sandstone outcrop area, northwards beneath the basalt some 20 km beyond the basalt margin.
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| 5. |
- Forsman, Åsa, 1972-, et al.
(författare)
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Generic structures of decision support systems for evaluation of policy measures to reduce catchment-scale nitrogen fluxes
- 2003
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Ingår i: Physics and Chemistry of the Earth. - 1474-7065 .- 1873-5193. ; 28:14-15, s. 589-598
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Tidskriftsartikel (refereegranskat)abstract
- Decision support systems (DSSs) for evaluation of different policy measures have two important functions: To assess how considered policy measures may influence the behavior of actors, and to predict the effects of a given set of actions generated from the anticipated behavior. So far, almost all attempts to construct DSSs for environmental management have focused on assessing the impact of a set of actions on the environment. Here, we describe the generic structure of a DSS that enables more complete evaluation of regional or national policies to reduce nitrogen inputs to water. In particular, we expound the principles for linking models of farm economic behavior to catchment-scale models of the transport and transformation of nitrogen in soil and water. First, we define system boundaries for nitrogen fluxes through the agricultural sector and the ambient environment to create a basis for model integration. Thereafter, we show how different modules operating on different temporal and spatial scales can be interlinked. Finally, we demonstrate how statistical emulators or meta-models can be derived to reduce the computational burden and increase the transparency of the DSS. In particular, we show when and how the temporal or spatial resolution of model inputs can be reduced without significantly influencing the estimates of annual nitrogen fluxes on a catchment scale.
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| 6. |
- Achite, Mohammed, et al.
(författare)
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An improved adaptive neuro-fuzzy inference system for hydrological drought prediction in Algeria
- 2023
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Ingår i: Physics and Chemistry of the Earth. - 1474-7065. ; 131
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Tidskriftsartikel (refereegranskat)abstract
- Drought has negative impacts on water resources, food security, soil degradation, desertification and agricultural productivity. The meteorological and hydrological droughts prediction using standardized precipitation/runoff indices (SPI/SRI) is crucial for effective water resource management. In this study, we suggest ANFISWCA, an adaptive neuro-fuzzy inference system (ANFIS) optimized by the water cycle algorithm (WCA), for hydrological drought forecasting in semi-arid regions of Algeria. The new model was used to predict SRI at 3-, 6-, 9-, and 12-month accumulation periods in the Wadi Mina basin, Algeria. The results of the model were assessed using four criteria; determination coefficient, mean absolute error, variance accounted for, and root mean square error, and compared with those of the standalone ANFIS model. The findings suggested that throughout the testing phase at all the sub-basins, the proposed hybrid model outperformed the conventional model for estimating drought. This study indicated that the WCA algorithm enhanced the ANFIS model's drought forecasting accuracy. The proposed model could be employed for forecasting drought at multi-timescales, deciding on remedial strategies for dealing with drought at study stations, and aiding in sustainable water resources management.
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| 7. |
- Acocella, V, et al.
(författare)
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Surface deformation induced by pluton emplacement: The case of Amiata (Italy)
- 2001
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Ingår i: PHYSICS AND CHEMISTRY OF THE EARTH PART A-SOLID EARTH AND GEODESY. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1464-1895. ; 26:4-5, s. 355-362
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Tidskriftsartikel (refereegranskat)abstract
- The Amiata area was uplifted during the Pliocene as a consequence of pluton emplacement in an extensional setting. In the Middle Pleistocene, a fissural eruption filled a depression within the uplifted area. Field analysis and analogue models are integrat
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| 8. |
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| 9. |
- Arvidsson, Kristina, et al.
(författare)
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A hydrogeological study of the Nhandugue River, Mozambique – A major groundwater recharge zone
- 2011
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Ingår i: Physics and Chemistry of the Earth. - : Elsevier BV. - 1474-7065. ; 36:14-15, s. 789-797
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Tidskriftsartikel (refereegranskat)abstract
- The Nhandugue River flows over the western margin of the Urema Rift, the southernmost extension of the East African Rift System, and marks the north-western border of Gorongosa National Park, Mozambique. It constitutes one of the major indispensable water resources for the ecosystem that the park protects. Our study focused on the hydrogeological conditions at the western rift margin by resistivity measurements, soil sampling and discharge measurements. The resistivity results suggest that the area is heavily faulted and constitutes a major groundwater recharge zone. East of the rift margin the resistivity indicate that solid gneiss is fractured and weathered, and is overlain by sandstone and alluvial sediments. The top 10-15 m of the alluvial sequence is interpreted as sand. The sand layer extends back to the rift margin thus also covering the gneiss. The sandstone outcrops a few kilometers from the rift margin and dips towards east/south-east. Further into the rift valley, the sand is underlain by lenses of silt and clay on top of sand mixed with finer matter. In the lower end of the investigated area the lenses of silt and clay appears as a more or less continuous layer between the two sand units. The topmost alluvial sand constitutes an unconfined aquifer under which the solid gneiss forms a hydraulic boundary and the fractured gneiss an unconfined aquifer. The sandstone is an unconfined aquifer in the west, becoming semi-confined down dip. The lenses of silt and clay forms an aquitard and the underlying sand mixed with finer matter a semi-confined aquifer. The surface runoff decreases downstream and it is therefore concluded that surface water infiltrates as recharge to the aquifers and moves as groundwater in an east/south-eastward direction.
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| 10. |
- Baresel, Christian, et al.
(författare)
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Estimating subsurface nitrogen accumulation–depletion in catchments by input–output flow analysis
- 2006
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Ingår i: Physics and Chemistry of the Earth. - : Elsevier BV. - 1474-7065 .- 1873-5193. ; 31:17, s. 1030-1037
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Tidskriftsartikel (refereegranskat)abstract
- We use input-output analysis of nitrogen flows between various sources-sectors and natural waters in the Swedish Norrstrom drainage basin for investigating and bounding the implication range of some uncertainty sources for results of subsurface nitrogen accumulation-depletion in this basin. We quantify different possible base and extreme assumptions of nitrogen discharges and transport pathways from agriculture to surface and groundwater in the basin. The results are robust in showing considerable nitrogen accumulation-depletion flow interactions taking place between the basin's mobile water and accumulated nitrogen pools in soils, sediments and/or relatively immobile subsurface water zones for all different scenario assumptions. Similar scenario robustness is also found in resulting relative contributions of different active nitrogen source-sectors to nitrogen flows in natural water systems. In the Norrstrom basin, and possibly more generally, nitrogen accumulation-depletion flows to and from accumulated legacies for the future or from the past appear therefore to be more important for water quality than current nitrogen discharges from active source-sectors.
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