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Laboratory experiments were performed on chalk samples from Denmark and Israel to determine diffusion and distribution coefficients. Batch tests were used to define sorption isotherms for naphthalene and o-xylene. Linear sorption isotherms were observed and described with Henry-isotherms. Because of the high purity and low contents of clay minerals and organic carbon, Danish and white Israeli chalk generally have low retardation capacities. Contrarily, gray Israeli chalk, with organic carbon fractions as high as 1.092%, remarkably retards organic contaminants. The K(OC) concept is not applicable to predicting distribution coefficients based on the organic carbon content in the chalk samples. Effective diffusivities of o-xylene, naphthalene, and several artificial tracers were determined using through-diffusion experiments. Based on measured diffusion coefficients and available literature values, a chalk specific exponent of 2.36 for Archie's law was derived, allowing a satisfactory estimate of relative diffusivities in chalk. A field-scale tracer test with uranine and lithium was performed in the Negev desert (Israel) to examine the transferability of diffusivities determined on small rock samples in the laboratory. Due to low recovery rates of the tracer, a modified single fissure dispersion model was used for inverse modeling of the breakthrough curves. Resulting diffusivities deviate insignificantly from the laboratory values, which are considered to be representative for the investigated part of the aquifer and applicable in transport models.

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Wastewater from defect sewers can affect groundwater quality. An assessment of this environmental impact for a city of 50 000 inhabitants (Rastatt, SW Germany) was done using marker species distributions, condition monitoring of the sewer network, lab‐scale analogy experiments, and specifically instrumented in‐situ test sites near defect sewers. The studies revealed elevated concentrations of iodated X‐ray contrast media (up to 360 ng/L amidotrizoic acid) and boron concentrations in the urban groundwater which are directly related to leaky sewers. Other common pharmaceuticals could not be detected in the groundwater. Observation wells were installed based on the information from a sewer defect database. These wells focusing on specific sewer leakages show significant changes in groundwater quality parameters.

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