title: Two decades of chemical imaging of solutes in sediments and soils--a review.
abstract: The increasing appreciation of the small-scale (sub-mm) heterogeneity of biogeochemical processes in sediments, wetlands and soils has led to the development of several methods for high-resolution two-dimensional imaging of solute distribution in porewaters. Over the past decades, localised sampling of solutes (diffusive equilibration in thin films, diffusive gradients in thin films) followed by planar luminescent sensors (planar optodes) have been used as analytical tools for studies on solute distribution and dynamics. These approaches have provided new conceptual and quantitative understanding of biogeochemical processes regulating the distribution of key elements and solutes including O2, CO2, pH, redox conditions as well as nutrient and contaminant ion species in structurally complex soils and sediments. Recently these methods have been applied in parallel or integrated as so-called sandwich sensors for multianalyte measurements. Here we review the capabilities and limitations of the chemical imaging methods that are currently at hand, using a number of case studies, and provide an outlook on potential future developments for two-dimensional solute imaging in soils and sediments.
authors.affiliation: Rhizosphere Ecology and Biogeochemistry Group, Department of Forest and Soil Sciences, Institute of Soil Research, University of Natural Resources and Life Sciences Vienna, Konrad Lorenz-Strasse 24, 3430 Tulln, Austria. Electronic address: jakob.santner@boku.ac.at.
authors.forename: Jakob
authors.initials: J
authors.lastname: Santner
authors.affiliation: Nordic Center for Earth Evolution (NordCEE), University of Southern Denmark, Campusvej 55, 5230 Odense, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Larsen
authors.affiliation: Rhizosphere Ecology and Biogeochemistry Group, Department of Forest and Soil Sciences, Institute of Soil Research, University of Natural Resources and Life Sciences Vienna, Konrad Lorenz-Strasse 24, 3430 Tulln, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kreuzeder
authors.affiliation: Nordic Center for Earth Evolution (NordCEE), University of Southern Denmark, Campusvej 55, 5230 Odense, Denmark; Scottish Marine Institute, Scottish Association for Marine Science, Oban, Scotland, PA37 1QA, UK; Greenland Climate Research Centre (CO Greenland Institute of Natural Resources), Kivioq 2, Box 570, 3900 Nuuk, Greenland; Arctic Research Centre, Aarhus University, 8000 Aarhus, Denmark.
authors.forename: Ronnie N
authors.initials: RN
authors.lastname: Glud
keywords: Chemical imaging; Diffusive equilibration in thin films (DET); Diffusive gradients in thin films (DGT); Luminescent sensors; Planar optodes; Solute