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  • 1.
    Abong'o, Deborah
    et al.
    University of Nairobi, Kenya.
    Wandiga, Shem
    University of Nairobi. Kenya.
    Jumba, Isac
    University of Nairobi, Kenya.
    van den Brink, Paul
    Wageningen University, the Netherlands.
    Nazariwo, Betty
    Makerere University, Uganda.
    Madadi, Vincent
    University of Nairobi, Kenya.
    Wafula, Godfrey
    University of Nairobi, Kenya.
    Kylin, Henrik
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Nkedi-Kizza, Peter
    University of Florida, USA.
    Organochlorine pesticide residue levels in soil from the Nyando River catchment, Kenya2015Inngår i: Africa Journal of Physical Sciences, ISSN 2313-3317, Vol. 2, nr 1, s. 18-32Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Soil samples were collected from six locations representative of the Nyando River catchment area of the Lake Victoria over a period of two years. Sampling was done four times in the year in February, May, September and December 2005 and 2006 in farms where maize, tea, sugar cane, coffee, rice and vegetables have been grown over the years. This coincided with the effects of different seasons and farming activities on residue levels of the pesticides in use. The objective was to investigate levels and distribution of organochlorine pesticides that have either been banned or are restricted for use in Kenya. Organochlorine pesticides investigated were DDT, lindane, aldrin, dieldrin, heptachlor, endrin, endosulfan (both α- and β- isomers and endosulfan sulphate), the sum is called “total” or Σendosulfan and methoxychlor. Prior to the ban or restriction in use, these pesticides had found wide applications in public health for control of disease vectors and in agriculture for control of crop pests. The analysis revealed presence of all the targeted pesticides with the highest mean concentrations for methoxychlor 140 ± 1.5 μg/kg, Σendosulfan (30 ± 2.1 μg/kg), aldrin (18 ± 0.28 μg/kg), respectively. The results show the presence of these pesticides in soils in the basin and this could be impacting negatively on the ecosystem health of the area.

  • 2.
    Acosta Navarro, Juan Camilo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Anthropogenic influence on climate through changes in aerosol emissions from air pollution and land use change2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Particulate matter suspended in air (i.e. aerosol particles) exerts a substantial influence on the climate of our planet and is responsible for causing severe public health problems in many regions across the globe. Human activities have altered the natural and anthropogenic emissions of aerosol particles through direct emissions or indirectly by modifying natural sources. The climate effects of the latter have been largely overlooked. Humans have dramatically altered the land surface of the planet causing changes in natural aerosol emissions from vegetated areas. Regulation on anthropogenic and natural aerosol emissions have the potential to affect the climate on regional to global scales. Furthermore, the regional climate effects of aerosol particles could potentially be very different than the ones caused by other climate forcers (e.g. well mixed greenhouse gases). The main objective of this work was to investigate the climatic effects of land use and air pollution via aerosol changes.

    Using numerical model simulations it was found that land use changes in the past millennium have likely caused a positive radiative forcing via aerosol climate interactions. The forcing is an order of magnitude smaller and has an opposite sign than the radiative forcing caused by direct aerosol emissions changes from other human activities. The results also indicate that future reductions of fossil fuel aerosols via air quality regulations may lead to an additional warming of the planet by mid-21st century and could also cause an important Arctic amplification of the warming. In addition, the mean position of the intertropical convergence zone and the Asian monsoon appear to be sensitive to aerosol emission reductions from air quality regulations. For these reasons, climate mitigation policies should take into consideration aerosol air pollution, which has not received sufficient attention in the past.

  • 3.
    Addassi, Mouadh
    et al.
    Technical University of Denmark, Denmark.
    Schreyer, Lynn
    Washington State University, USA.
    Johannesson, Björn
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Lin, Hai
    University of Colorado Denver, USA.
    Pore-scale modeling of vapor transport in partially saturated capillary tube with variable area using chemical potential2016Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, nr 9, s. 7023-7035Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here we illustrate the usefulness of using the chemical potential as the primary unknown by modeling isothermal vapor transport through a partially saturated cylindrically symmetric capillary tube of variable cross-sectional area using a single equation. There are no fitting parameters and the numerical solutions to the equation are compared with experimental results with excellent agreement. We demonstrate that isothermal vapor transport can be accurately modeled without modeling the details of the contact angle, microscale temperature fluctuations, or pressure fluctuations using a modification of the Fick-Jacobs equation. We thus conclude that for a single, axisymmetric pore, the enhancement factor depends upon relative humidity boundary conditions at the liquid bridge interfaces, distance between liquid bridges, and bridge lengths.

  • 4. Addor, Nans
    et al.
    Rössler, Ole
    Köplin, Nina
    Huss, Matthias
    Weingartner, Rolf
    Seibert, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Robust changes and sources of uncertainty in the projected hydrological regimes of Swiss catchments2014Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 50, nr 10, s. 7541-7562Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Projections of discharge are key for future water resources management. These projections are subject to uncertainties, which are difficult to handle in the decision process on adaptation strategies. Uncertainties arise from different sources such as the emission scenarios, the climate models and their postprocessing, the hydrological models, and the natural variability. Here we present a detailed and quantitative uncertainty assessment, based on recent climate scenarios for Switzerland (CH2011 data set) and covering catchments representative for midlatitude alpine areas. This study relies on a particularly wide range of discharge projections resulting from the factorial combination of 3 emission scenarios, 10–20 regional climate models, 2 postprocessing methods, and 3 hydrological models of different complexity. This enabled us to decompose the uncertainty in the ensemble of projections using analyses of variance (ANOVA). We applied the same modeling setup to six catchments to assess the influence of catchment characteristics on the projected streamflow, and focused on changes in the annual discharge cycle. The uncertainties captured by our setup originate mainly from the climate models and natural climate variability, but the choice of emission scenario plays a large role by the end of the 21st century. The contribution of the hydrological models to the projection uncertainty varied strongly with catchment elevation. The discharge changes were compared to the estimated natural decadal variability, which revealed that a climate change signal emerges even under the lowest emission scenario (RCP2.6) by the end of the century. Limiting emissions to RCP2.6 levels would nevertheless reduce the largest regime changes by the end of the century by approximately a factor of two, in comparison to impacts projected for the high emission scenario SRES A2. We finally show that robust regime changes emerge despite the projection uncertainty. These changes are significant and are consistent across a wide range of scenarios and catchments. We propose their identification as a way to aid decision making under uncertainty.

  • 5. Aggarwal, Pradeep K.
    et al.
    Romatschke, Ulrike
    Araguas-Araguas, Luis
    Belachew, Dagnachew
    Longstaffe, Frederick J.
    Berg, Peter
    SMHI, Forskningsavdelningen, Hydrologi.
    Schumacher, Courtney
    Funk, Aaron
    Proportions of convective and stratiform precipitation revealed in water isotope ratios2016Inngår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 9, nr 8, s. 624-+Artikkel i tidsskrift (Fagfellevurdert)
  • 6.
    Ahlberg, Jesper
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Distributed snow modelling integrating ground penetrating radar data for improved runoff predictions in a Swedish mountain basin2009Inngår i: EGU General Assembly 2009, 2009Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Operational forecasts of snow melt runoff in Sweden are currently running with precipitation and temperature as the main input variables and calibrated with runoff data, and there is an interest to make better use of new measurement systems for distributed snow data. At the same time, various data assimilation techniques are becoming more frequently used in hydrological modeling, in order to reduce uncertainties related to both model structure errors and errors in input and calibration data. Thus, it is important to address not only what type of snow data that can be used to improve the model predictions, but also what type of input data and model structures that are optimal in relation to the available snow data. The objective of this study is to investigate to what extent the runoff predictions can be improved by assimilation of temporal and spatially distributed snow data, and if the improvements depend on the choice of model structures, for instance the use of energy balance or day-degree snow models. In order to achieve these objectives a new distributed snow model has been implemented into the hydrological modeling framework HYSS/HYPE. This model can easily be setup with either an energy balance model or a day-degree model for the snow pack calculations, and it is easy to run the model with different spatial resolutions. In the fully distributed case, snow drift processes are implicitly included in the model through a precipitation distribution model, based on topographical information and wind direction. The model was applied to a mountain basin in northern Sweden used for hydropower production, where extensive snow measurements were taken during the last two winters 2007-2009. A climate station is located at the outlet of the regulation lake, including automated point measurements of snow depth, snow mass (snow pillow), snow wetness and snow temperature. Distributed snow cover data was sampled using ground-penetrating radar from snow mobiles. Measurements were taken at the time of the maximum snow cover, providing a data set with snow depth, snow density, snow water equivalent along 20 km long transects in representative areas of the basin. The precipitation distribution model was calibrated using the distributed SWE data from the GPR measurements. Application of the calibrated model to previous years without available snow data show that the runoff predictions was improved compared to calibrations without the distributed snow data, however the improvements were larger for the energy balance compared to the day-degree model. Further developments will include assimilation of the temporal and spatial snow data to adjust the distribution of various input variables, for instance air temperature and wind speed.

  • 7.
    Ahlberg, Jesper
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Snow melt runoff simulations using ensemble Kalman filter assimilation of distributed snow data2010Konferansepaper (Annet vitenskapelig)
  • 8.
    Ahlgren, Joakim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). The Swedish Institute for the Marine Environment, PO Box 260, SE-40530 Göteborg, Sweden.
    Grimvall, Anders
    Omstedt, Anders
    Rolff, Carl
    Wikner, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). The Swedish Institute for the Marine Environment, PO Box 260, SE-40530 Göteborg, Sweden.
    Temperature, DOC level and basin interactions explain the declining oxygen concentrations in the Bothnian Sea2017Inngår i: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 170, s. 22-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hypoxia and oxygen deficient zones are expanding worldwide. To properly manage this deterioration of the marine environment, it is important to identify the causes of oxygen declines and the influence of anthropogenic activities. Here, we provide a study aiming to explain the declining oxygen levels in the deep waters of the Bothnian Sea over the past 20 years by investigating data from environmental monitoring programmes. The observed decline in oxygen concentrations in deep waters was found to be primarily a consequence of water temperature increase and partly caused by an increase in dissolved organic carbon (DOC) in the seawater (R-Adj(2). = 0.83) as well as inflow from the adjacent sea basin. As none of the tested eutrophication-related predictors were significant according to a stepwise multiple regression, a regional increase in nutrient inputs to the area is unlikely to explain a significant portion of the oxygen decline. Based on the findings of this study, preventing the development of anoxia in the deep water of the Bothnian Sea is dependent on the large-scale measures taken to reduce climate change. In addition, the reduction of the nutrient load to the Baltic Proper is required to counteract the development of hypoxic and phosphate-rich water in the Baltic Proper, which can form deep water in the Bothnian Sea. The relative importance of these sources to oxygen consumption is difficult to determine from the available data, but the results clearly demonstrate the importance of climate related factors such as temperature, DOC and inflow from adjacent basins for the oxygen status of the sea.

  • 9.
    Ahlkrona, Malva
    SMHI.
    Phospherous in a Biogeochemical Lake Model2002Rapport (Annet vitenskapelig)
    Abstract [en]

    BIOLA isa biogeochemical lake model within the V ASTRA research programme. The model's

    main purpose is to predict the ecological responses to changed nutrient loads. The phosphorus simulations were not satisfactory and the sediment was thought to be the critical part. The aim of this work was to improve the phosphorus simulations. Therefore a new sediment approach has been developed. Three main changes of the sediment processes were carried through:

    • Resuspension of sediments from erosion and transportation bottoms was added

    • The sediments were divided into an upper, aerobic, and a lower, anaerobic, layer

    • The relation between sorbed and dissolved phosphorus in the sediments was described by

    Langmuir isotherms, with a sorption 2.5 times higher at aerobic compared to anaerobic

    conditions

    The modelling of total phosphorus and blue-green algae was improved. Especially the timing of high concentration peaks was much better. One problem still lingering is the modelled oxygen levels, which were much higher than the observed levels. Therefore the model has not been tested for anaerobic conditions. A verage release rates from the sediments were 2.5 mg Pa-1 <luring the summer, which is reasonable. A 20-year simulation of step-response was run with increased and decreased nutrient loads. Roughly four years after the change, the model had reached a new equilibrium.

  • 10.
    Ahmed, Rafiq
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle.
    Seasonal Variation of Inorganic Nutrients (DSi, DIN and DIP) Concentration in Swedish River2007Independent thesis Advanced level (degree of Magister), 20 poäng / 30 hpOppgave
    Abstract [en]

    Rivers have been playing most important role as fresh water source and medium of nutrient transportation from terrestrial to aquatic ecosystem. Inorganic form of nutrients (DSi, DIN and DIP) are plant available mostly control the productivity of aquatic ecosystem. Transfer of these nutrients in higher concentrations cause harmful eutrophication in receiving water body.

    Study of dissolved inorganic nutrients concentrations in 12 Swedish rivers of different basin characteristics demonstrated both similar and varying behaviour from river to river and from season to season depending on catchment hydrology; land use and geology. Highest concentration did not coincide with the highest runoff. High DSi concentration observed in the unperturbed rivers however, high DIN and DIP concentration observed in agriculture dominated river followed by river basin dominated by industrial and urban activities. DSi and DIN concentration observed high in winter and decreased through spring to reach lowest in summer. DIP concentration although found low in summer but high concentration observed in early spring and early autumn. Rivers with low average runoff positively correlated with DSi and DIN concentration however, DIP demonstrated weak correlation.

  • 11. Aich, Valentin
    et al.
    Liersch, Stefan
    Vetter, Tobias
    Andersson, Jafet
    SMHI, Forskningsavdelningen, Hydrologi.
    Mueller, Eva N.
    Hattermann, Fred F.
    Climate or Land Use?-Attribution of Changes in River Flooding in the Sahel Zone2015Inngår i: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 7, nr 6, s. 2796-2820Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study intends to contribute to the ongoing discussion on whether land use and land cover changes (LULC) or climate trends have the major influence on the observed increase of flood magnitudes in the Sahel. A simulation-based approach is used for attributing the observed trends to the postulated drivers. For this purpose, the ecohydrological model SWIM (Soil and Water Integrated Model) with a new, dynamic LULC module was set up for the Sahelian part of the Niger River until Niamey, including the main tributaries Sirba and Goroul. The model was driven with observed, reanalyzed climate and LULC data for the years 1950-2009. In order to quantify the shares of influence, one simulation was carried out with constant land cover as of 1950, and one including LULC. As quantitative measure, the gradients of the simulated trends were compared to the observed trend. The modeling studies showed that for the Sirba River only the simulation which included LULC was able to reproduce the observed trend. The simulation without LULC showed a positive trend for flood magnitudes, but underestimated the trend significantly. For the Goroul River and the local flood of the Niger River at Niamey, the simulations were only partly able to reproduce the observed trend. In conclusion, the new LULC module enabled some first quantitative insights into the relative influence of LULC and climatic changes. For the Sirba catchment, the results imply that LULC and climatic changes contribute in roughly equal shares to the observed increase in flooding. For the other parts of the subcatchment, the results are less clear but show, that climatic changes and LULC are drivers for the flood increase; however their shares cannot be quantified. Based on these modeling results, we argue for a two-pillar adaptation strategy to reduce current and future flood risk: Flood mitigation for reducing LULC-induced flood increase, and flood adaptation for a general reduction of flood vulnerability.

  • 12. Aich, Valentin
    et al.
    Liersch, Stefan
    Vetter, Tobias
    Fournet, Samuel
    Andersson, Jafet
    SMHI, Forskningsavdelningen, Hydrologi.
    Calmanti, Sandro
    van Weert, Frank H. A.
    Hattermann, Fred F.
    Paton, Eva N.
    Flood projections within the Niger River Basin under future land use and climate change2016Inngår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 562, s. 666-677Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study assesses future flood risk in the Niger River Basin (NRB), for the first time considering the simultaneous effects of both projected climate change and land use changes. For this purpose, an ecohydrological process-based model (SWIM) was set up and validated for past climate and land use dynamics of the entire NRB. Model runs for future flood risks were conducted with an ensemble of 18 climate models, 13 of them dynamically downscaled from the CORDEX Africa project and five statistically downscaled Earth System Models. Two climate and two land use change scenarios were used to cover a broad range of potential developments in the region. Two flood indicators (annual 90th percentile and the 20-year return flood) were used to assess the future flood risk for the Upper, Middle and Lower Niger as well as the Benue. The modeling results generally show increases of flood magnitudes when comparing a scenario period in the near future (2021-2050) with a base period (1976-2005). Land use effects are more uncertain, but trends and relative changes for the different catchments of the NRB seem robust. The dry areas of the Sahelian and Sudanian regions of the basin show a particularly high sensitivity to climatic and land use changes, with an alarming increase of flood magnitudes in parts. A scenario with continuing transformation of natural vegetation into agricultural land and urbanization intensifies the flood risk in all parts of the NRB, while a "regreening" scenario can reduce flood magnitudes to some extent. Yet, land use change effects were smaller when compared to the effects of climate change. In the face of an already existing adaptation deficit to catastrophic flooding in the region, the authors argue for a mix of adaptation and mitigation efforts in order to reduce the flood risk in the NRB. (C) 2016 Elsevier B.V. All rights reserved.

  • 13. Akselsson, Cecilia
    et al.
    Olsson, Jonas
    SMHI, Forskningsavdelningen, Hydrologi.
    Belyazid, Salim
    Capell, Réne
    SMHI, Forskningsavdelningen, Hydrologi.
    Can increased weathering rates due to future warming compensate for base cation losses following whole-tree harvesting in spruce forests?2016Inngår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 128, nr 1-2, s. 89-105Artikkel i tidsskrift (Fagfellevurdert)
  • 14. Ala-aho, P.
    et al.
    Soulsby, C.
    Pokrovsky, O. S.
    Kirpotin, S. N.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Serikova, Svetlana
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Manasypov, R.
    Lim, A.
    Krickov, I.
    Kolesnichenko, L. G.
    Laudon, H.
    Tetzlaff, D.