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2009-08-12 Förslag till examensarbeten (20p) vid Institutionen för vatten och miljö (SLU, Uppsala)
Rumsliga mönster hos vegetation För att studera vegetation i större områden använder man oftast provytor. Sedan använder man olika miljövariabler för att försöka förklara likheter och skillnader i artsammansättning. Om provytorna ligger nära varandra är det dock stor chans att de har liknande artsammansättning bara av den anledning att de ligger nära varandra och endast till en mindre del till följd av skillnader i några miljövariabler. Man säger att ytorna är rumsligt autokorrelerade. Detta examensarbete går ut på att studera rumslig autokorrelation för några arter. Dels i data från eget fältarbete i ett försöksområde straxt söder om Ultuna, och dels i den stickprovsdesign som används i Ståndortskarteringen eller IM-programmet (Integrerad miljöövervakning). Arbetet kommer att omfatta en hel del statistiska analyser och hanterande av stora datamängder. Om eget fältarbete ingår utförs det under sommaren, företrädesvis juli-september. Kontaktperson:
Does feeding selectivity of oligochaetes affect toxicity test results, and ultimately the validity/credibility of standardized tests? Recently, Åkerblom and Goedkoop showed that larvae of the midge Chironomus riparius almost exclusively feed on food additions that are added during standardized toxicity tests. Stable isotope analyses of larvae and food resources revealed that larvae obtained 97% of their carbon from added food (Tetraphyll®). The finding that test organisms almost exclusively feed on uncontaminated added food may result in erroneous LC50-values and NOECs, and ultimately provide an underestimation of the toxicity of test compounds. Chironomus larvae feed on surface sediment, but oligochaetes are known as subsurface deposit-feeders and are believed to be less selective feeders. Therefore, we propose to perform toxicity tests with oligochaetes to study how their feeding behavior affects test compound exposure pathways and ultimately the outcome of toxicity tests. Our working hypothesis is that oligochaetes to a larger extent than Chironomus feeds on contaminated sediment and therefore assimilate less carbon/energy from added food particles. This could likely be tested in a design that follows the proposed oligochaete whole-sediment toxicity test. Also studies of the differences in the uptake of test compounds by oligochaetes and Chironomus can be included. Key words: Oligochaetes, toxicity tests, bioavailability, uptake pathways, pesticides. Contact Willem Goedkoop (willem.goedkoop@ma.slu.se, tel. 018-673112) for more info.
Hydrology's role in landscape-scale patterns of water chemistry Water quality and its influence on aquatic ecology is often studied at specific points in a landscape. But ecology and water resources are not based on a single point, but rather the network of watercourses in a landscape. Recent efforts to define the patterns of water chemistry have identified the need for spatially distributed hydrology (i.e. specific discharge) to understand how landscape scale patterns of water chemistry are created. Several inventories of water chemistry from over 70 stream junctions in a 80 km2 basin in Västerbotten have been taken. Similar resolution in discharge, however, is lacking. An ex-jobbare is sought to work on filling this gap and making an analysis of the water chemistry data supported by better data on flows. The project will include several weeks of field measurements, followed by modeling of specific discharge supported by GIS data. The goal will be to turn the existing landscape scale maps of water chemistry into maps of fluxes where sources and sinks of critical components such as mercury, can be identified. For further information, please contact:
The hydrology of mercury losses from forested catchments Mercury contamination in fish is a major problem for Swedish lakes. Forestry (i.e. logging) has recently been identified as a potential contributor to the problem. The hypothesized connection between logging and mercury are changes in hydrology. A paired catchment study has been initiated to study the effect of logging on mercury outputs from soils to surface waters. The study is located on two 50 ha catchments near Bjurholm in Västerbotten. While there is a general understanding that clear-cutting increases runoff, this project provides an opportunity for achieving one of the first, spatially distributed analyses of the effects of logging on catchment hydrology. During the spring and summer of 2005, an intensive study of soil moisture and groundwater in relation to topography, soils and flow will be conducted. The goal is to model the flow paths, soil moisture and hydrological connectivity before the forest is harvested in the winter of 2005-2006. The project will involve fieldwork, modeling and GIS. We seek an ex-jobbare to conduct this task in cooperation with a project team of several senior scientists and one doctoral student. For further information, please contact:
Forest Clear-cutting and Water: What Isotope Hydrology can tell us? "Water is a mirror of the landscape" and in Sweden that mirror shows mostly forests. But what happens when we harvest the forest? Plans to dramatically increase forest growth and harvest for biofuels have renewed research on the aquatic effects of forest harverst and how to mitigate them. Changes in the amount and pathways of water flow are believed to underlie many of the environmental affects created by forest harvest, including.erosion, pulses of nitrate in runoff, and long-term increases in mercury loading to aquatic ecosystems. Isotope hydrology provides a way to try to define these effects. In the proposed Ex-jobb, isotope hydrograph separation will be applied to several new studies of cleracut and/or stump harvested catchments. The goal is to see if these techniques can identify changes in the amount of "new water" entering the stream during spring flood and spring flood and rain events. These changes can then be related to key parameters in runoff chemistry (methylmercury, nitrogen, organic carbon) that are being studied in the harvested catchments. For further information contact:
Can High-Resolution GIS predict the landscape scale variability of stream chemistry? Riparian soils are a major control on the chemistry headwater streams. But what controls the chemistry and structure of riparian soils? Our hypothesis is that differences in riparian soils result from the influence of drainage from the local upslope "mini-catchment" over the course of thousands of years. LIDAR, a breakthrough in GIS, with cm-resolution in digital elevation models makes it possible to identify and characterize these "mini-catchments". This Ex-jobb will test the hypothesis that the topography upslope from a riparian zone is a major control on the soils of that riparian zone. The data will be a newly created LIDAR DEM, and a detailed soil survey of transects through several hundred riparian soils on the Krycklan Catchment. (www.ccrew.sek.slu.se) Field work will make more detailed chemical analyses on a stratified sample of these mapped riparian soils. For further information contact:
Does Forestry contribute to mercury in Swedish fish: "Water is a mirror of the landscape." In Sweden that mirror reflects mostly forests, and the fish in many lakes of that forest landscape have levels of mercury that are above that which is safe for human consumption. Does forest harvest contribute to this problem? Plans to dramatically increase forest growth and harvest for biofuels have renewed research on the aquatic effects of forest harvest and how to mitigate them. The role of forestry in the mercury contamination of Swedish fish remains a sensitive issue, with much speculation but far too little data. This project will, in cooperation with major forest companies, help to address that problem with a synoptic survey of recently harvested sites. The goal is to locate ca 50 headwater streams where a significant part of the catchment was harvested in the last five years. A similar number of control sites will be located. These sites will be identified from the GIS databases maintained by forest companies. Once located, the sites will be sampled in the autumn. The data will then be analyzed to see what site characteristics and water chemistry data are correlated to the concentration of mercury (both total Hg and the more bioavailable methylmercury form.) The working hypothesis is that recent forest harvest operations will be associated with higher levels of mercury and methylmercury. For further information contact:
Forest Harvest Impact on Mercury in Surface Waters: Testing the "groundwater level" hypothesis. "Water is a mirror of the landscape" and in Sweden that mirror shows mostly forests. But what happens when we harvest the forest? Plans to dramatically increase forest growth and harvest for biofuels have renewed research on the aquatic effects of forest harvest and how to mitigate them. Changes in the amount and pathways of water flow are believed to underlie many of the environmental affects created by forest harvest, including erosion, pulses of nitrate in runoff, and long-term increases in mercury loading to aquatic ecosystems. In a paired catchment study near Bjurholm, in Västerbotten, two entire catchments have been harvested in 2006. The concentrations of mercury in runoff, a serious pollutant, have increased. Is this due simply to rises in the ground and the groundwater level after harvest? An ex-jobbare is sought to test this hypothesis, with a focus on modelling groundwater levels before and after harvest. As data for the project, a month of field work will complement previous measurements. Additional project employment during the summer is possible. For further information contact:
Do Riparian soils define the chemistry of runoff water in the forest landscape? Our research group has hypothesized that flow paths through riparian soils are the major determinant of water chemistry (including mercury, trace metal and carbon concentrations) in the forest landscape. If this is true, then it will help us predict how forest management and climate will influence water chemistry. To test this hypothesis, a riparian "observatory" was established in the Krycklan Catchment during the summer. (www.ccrew.sek.slu.se). The soil water chemistry and hydrology of the 15 riparian study sites in the observatory will be observed and analyzed to see whether they confirm the "riparian hypothesis". An ex-jobbare is sought to spend a month in the field (Vindeln, Västerbotten) collecting data, and then analyse the results. Additional project employment during the summer is possible. For further information contact:
Continuous water chemistry in headwater streams: How much more can it tell us about carbon balances in the forest landscape? Researchers are trying to determine whether boreal forests are a source or sink of carbon in the global carbon cycle. "The aquatic conduit" for carbon has been receiving increasing attention in this work - that is the amount of carbon leaving the landscape in runoff water. One challenge in defining this component of the carbon balance is the possibility for rapid changes in carbon flux and concentrations in conjunction with episodes of high flow. Recent advances in instrumentation may make it possible to continuously register both the organic and inorganic carbon content in runoff. An ex-jobbare is sought to run a field study using new sensors for continuous registration of organic and inorganic carbon in runoff during the summer. The work would be located in the Krycklan Catchment (www.ccrew.sek.slu.se) near Vindeln. For further information contact:
Aqua Incognita: Defining the output of dissolved carbon from headwaters 90% of stream length is in headwaters streams, but there is no systematic estimate of the chemistry of these streams. Several years of work have gone into seeking relationships between downstream chemistry and headwaters, supported by GIS. Now an Ex-jobb could bring this work to fruition by making an estimate of dissolved carbon outputs from all forested headwaters in Sweden. This will be the first test of whether “Aqua Incognita” can be defined. It will also provide useful information on Sweden’s carbon balance, since export of organic carbon from soils is not included in regional carbon balances. This aquatic term of the C balance has been missing due to lack of data, which this project could provide. For further information contact:
Identifying credible parameter sets for modeling temporal variation in soil solution DOC using INCA-C at a boreal catchment Background: All relevant data including climate variables, soil and stream solution DOC, soil carbon content and some degradation rates are available for a 10 year period between 1996-2005. The candidate will be provided with a training in the INCA-C model. Tasks: Analysis of parameter sensitivity and model uncertainty with respect to soil solution DOC driven by climate variables (soil temperature, soil moisture and water flux), model parameters (sorption and desorption rates, Q10 temperature control, mineralization rates) and litter inputs. Contact: Literature Froberg, M., Berggren, D., Bergkvist, B., Bryant, C. and Mulder, J., 2006. Concentration and fluxes of dissolved organic carbon (DOC) in three norway spruce stands along a climatic gradient in sweden. Biogeochemistry, 77(1): 1-23. Futter, M.N. et al., 2007. Modeling the mechanisms that control in-stream dissolved organic carbon dynamics in upland and forested catchments. Water Resources Research, 43(2): W02424, doi:10.1029/2006WR004960. Kalbitz, K., Solinger, S., Park, J.H., Michalzik, B. and Matzner, E., 2000. Controls on the dynamics of dissolved organic matter in soils: a review. Soil Science, 165: 277-304. Köhler, S.J., Buffam, I., Laudon, H. and Bishop, K., 2008. Climate's control of intra-annual and interannual variability of total organic carbon concentration and flux in two contrasting boreal landscape elements. J. Geophys. Res., 113: G03012. Monteith, D.T. et al., 2007. Dissolved organic carbon trends resulting from changes in atmospheric deposition chemistry. Nature, 450: 537-U9. Mulholland, P., 2003. Large-scale patterns in Dissolved Organic Carbon Concentration, Flux, and Sources., Aquatic Ecosystems: Interactivity of Dissolved Organic Matter. Elsevier, New York, pp. 139-159.
Intensivundersökning av relevansen i depositionsmätningar Deposition i form av nederbörd på öppet fält och krondropp i skog görs ofta på månadsbas. Detta input är helt avgörande för kemiska budgetar i avrinningsområden. Vissa ämnen, som t.ex. NO3, är utsatt för snabb transformering och därmed kan erhållna värden avvika från de verkliga. Det behövs intensiv provtagning av enskilda nederbördstillfällen med omgående kemisk analys för att klargöra hur lång tid provinsamlingen kan pågå. Detta innebär fältstudier med vistelse på plats och transport av prover till laboratorium. IM programmet erbjuder goda förutsättningar för sådana studier vid försöksstationerna. Sedan ingår givetvis litteraturstudier, sammanställning av data, redovisning och rapportskrivning. Ansvarig Lars Lundin och IM Hälsningar Lars L (med stöd av IM Sällskapet)
Naturlig och artificiell påverkan på vattenkemi Vattenkemin undersöks i många avseenden. Prover insamlas och analyseras men ibland lagras prover för senare analys. Proverna fryses då ofta. Detta kan påverka olika ämnens halter och osäkerheter uppstår avseende sanna värden. En längre tidserie från en station har lagrats frysta i ca 20 år men nu analyserats. Det finns från stationen ämneshalter både för en period innan "frysuppehållet" och därefter. Det är utomordentligt lämpligt att söka utvärdera frysningens effekter just på denna tidserie. Därvid jämförs tidsperioderna före och efter "frysperioden" både för den aktuella stationen och som jämförelse värden från närliggande station där kontinuerlig analys utförts på icke frysta prover. Resultaten är viktiga i mycket av den långsiktiga monitoring som genomförs vid SLU och ofta på uppdrag av Naturvårdsverket. Arbetet genomförs genom att sammanställa dataserier, analysera dessa och påvisa vad frysning medför. Dessutom genomförs litteraturstudier och övrig samverkan med laboratorium. Ansvarig Lars Lundin och Stefan Löfgren Hälsningar Lars L
Askåterföring till skogsmark - effekter på skogstillväxt, mark och vatten Askan från skogsbiobränsle återförs idag i betydande utsträckning till skogsmarken. Ett av syftena med återföringen är att motverka markförsurning och på sikt även försurningen av ytvatten. Studier har visat att pH, basmättnadsgrad etc. ökar särskilt i markens humusskikt, men vilka effekter detta leder till i ytvattnen är ej tillräckligt väl utrett. Resultaten från skogsmarkskalkning med doser liknande de som används vid askåterföring indikerar att effekterna är små eller obefintliga på ytvattnen, men är dessa slutsatser giltiga även för mer lättlösliga ämnen som aska? Askåterföring förväntas även leda till ökad skogstillväxt på vissa typer av marker. Arbetet innebär litteraturstudier med syfte att sammanställa befintlig kunskap och att utgående från den tolka och dra slutsatser om troliga effekter av askåterföring på skogstillväxt samt mark- och vattenkemin i behandlade områden. Slutsatserna ska användas för att skapa scenarier som underlag för en samhällsekonomiska konsekvensanalys inom ramen för FoMa-projektet "Askåterföring till skogsmark - samhällsekonomisk konsekvensanalys". Studenten förväntas ha goda kunskaper i mark- och vattenkemi och måste ha förmåga att kunna läsa rapporter på svenska. Ett arvode om 15 000 kr utgår för arbetet. Inom ramen för FoMa-projektet utförs ett ekonomiskt inriktat examensarbete vid Inst. f. skogsekonomi vid SLU i Umeå. Ett begränsat samarbete förutsätts mellan de naturvetenskapligt respektive ekonomiskt inriktade studenterna. Kontaktperson: Doc. Stefan Löfgren, Inst. f. vatten och miljö, SLU, 070-69 55 177, Stefan.Lofgren@vatten.slu.se
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