Sökning: "Retention processes"

Visar resultat 1 - 5 av 172 avhandlingar innehållade orden Retention processes.

  1. 1. Studies of an elusive element : processes that influence the net retention of mercury in lake sediments and peatlands

    Författare :Johan Rydberg; Richard Bindler; Carl Lamborg; Umeå universitet; []
    Nyckelord :Mercury; retention; lake sediments; peatlands; environmental archives; sedimentation; diagenesis; vegetation; permafrost; Environmental Science; miljövetenskap;

    Sammanfattning : Because of its toxic nature mercury is a threat to both wildlife and human health, and thus, it is an element of concern in the environment. Currently much of the mercury emitted to the atmosphere is derived from anthropogenic sources – both direct emissions and re-emission of already deposited anthropogenic mercury. LÄS MER

  3. 2. Particulate phosphorus accumulation and net retention in constructed wetlands receiving agricultural runoff : Critical analysis of factors affecting retention estimates

    Författare :Karin Johannesson; Karin Tonderski; Stefan Weisner; Uno Wennergren; Ben Surridge; Linköpings universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Phosphorus retention; constructed wetlands; agriculture; sampling strategy;

    Sammanfattning : Övergödning är ett allvarligt miljöproblem, som bland annat orsakar omfattande blomningar av alger och blågrönbakterier. I söt- och brackvatten är fosfor ofta det mest begränsande näringsämnet för dessa organismer, varför en minskning av fosfortillförseln är nödvändig för att nå förbättringar. LÄS MER

  4. 3. Hydrodynamic control of retention in heterogeneous aquifers and fractured rock

    Författare :Hua Cheng; Vladimir Cvetkovic; Chin-Fu Tsang; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Aquifer; Fracture; groundwater; First-order solution; Monte-Carlo simulation; Nu-clear waste; Heterogeneity; Retention processes; Matrix diffusion; Prediction; Evaluation; Travel time; Flow rate; ; Water engineering; Vattenteknik;

    Sammanfattning : In this thesis, fluid flow and solute transport in heterogeneous aquifers and particularly in frac-tured rock have been investigated using Lagrangian Stochastic Advective-Reaction (LaSAR) framework. The heterogeneity of the aquifer structure or fracture configuration, as well as the various reaction/retention processes have been considered in the modelling approach. LÄS MER

  5. 4. Polybrominated dibenzo-p-dioxins : Natural formation mechanisms and biota retention, maternal transfer, and effects

    Författare :Kristina Arnoldsson; Peter Haglund; Patrik Andersson; Walter Vetter; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; polybrominated dibenzo-p-dioxins; PBDDs; Baltic Sea; uptake; retention; maternal transfer; metabolism; bioavailability; natural formation; precursor; bromoperoxidase; bromophenol; photochemical transformation; oxidative coupling; hydroxylated polybrominated diphenyl ethers; Chemistry; Kemi; analytisk kemi; Analytical Chemistry;

    Sammanfattning : Polybrominated dibenzo-p-dioxins (PBDD) and dibenzofurans (PBDF) are a group of compounds of emerging interest as potential environmental stressors. Their structures as well as toxic responses are similar to the highly characterized toxicants polychlorinated dibenzo-p-dioxins. LÄS MER

  7. 5. Material migration in tokamaks: Studies of deposition processes and characterisation of dust particles

    Författare :Armin Weckmann; Marek Rubel; Per Petersson; Daniel Primetzhofer; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; tokamak; fusion; plasma; material migration; particle transport; TEXTOR; PWI; plasma-wall interaction; plasma facing components; PFC; PFM; plasma facing materials; ALT limiter; MoF6; tracer experiment; molybdenum hexafluoride; future energy source; fuel retention; deuterium retention;

    Sammanfattning : Thermonuclear fusion may become an attractive future power source. The most promising of all fusion machine concepts is the tokamak. Despite decades of active research, still huge tasks remain before a fusion power plant can go online. One of these important tasks deals with the interaction between the fusion plasma and the reactor wall. LÄS MER