Mobility and Mobilisation of heavy metals and PAHs in partially water repellent urban soils

Marisa Matranga, Friederike Lang, Technische Universität Berlin, Technische Universität Berlin
2012
Water repellency has been found to be a crucial parameter in controlling preferential transport of water and solutes in the soil. This thesis investigates the impact of water repellency on solute and water fluxes in a contaminated former sewage site. Moreover this thesis examines the impact of water repellency on the mobilisation potential of heavy metals and PAHs by dispersion experiments. We tested the hypothesis whether preferential flow decreases the risk of groundwater contamination, since
more » ... ontamination, since water repellent soil parts are bypassed, or if it increases, since hydraulic shear forces may cause a rapid downward transport of colloid-bound contaminants through the vadose zone (1). Moreover we assume that hydrophobic compounds are chemically inert and therefore act to a lesser extend as a source for contaminants than hydrophilic compounds (2). Furthermore we suppose that the moisture-related temporal and spatial extend and severity of water repellency influences the formation and stability of preferential flow paths (3) and hence the collection performance of plate lysimeters (4). To address the first hypothesis the long-term spatial and temporal course of solute fluxes sampled by zero-tension and tension lysimeters are analysed and physico-chemical factors which control the mobility of dissolved and colloid-bound contaminants in the soil are identified (1). The second hypothesis was tested by determining the impact of soil hydrophobicity on the mobilisation potential of contaminants using laboratory dispersion experiments (2). The influence of the initial soil moisture regime on the formation and stability of preferential flow paths was evaluated using dye tracer experiments (3). Finally the collection performance of zero-tension and tension lysimeters under rainfed conditions and under different initial soil moisture conditions was studied (4). The results of the lysimeter study show that the annual contaminant mass fluxes in soil solutions sampled by tension lysimeters were positive related to the mean lysimeter co [...]
doi:10.14279/depositonce-3251 fatcat:k3elgx35bbbell7lrh6fxt5k6m