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For managing the freshwater in the worldwide coastal aquifers, it is imperative to understand the hydrogeochemical processes and flow patterns in the mixing freshwater/saltwater zone. The Egyptian Nile Delta aquifer is a typical example. The management of seawater intrusion (SWI) requires detailed investigations of the intrusion wedge and the dynamic processes in the mixing zone. Thus, a multidisciplinary approach was applied based on holistic hydrogeochemical, statistical analysis, and DC resistivity measurements to investigate the lateral and vertical changes in groundwater characteristics undergoing salinization stressor. The results of cross plots and ionic deviations of major ions, hydrochemical facies evolution diagram (HFE-D), and seawater mixing index (SMI) were integrated with the resistivity results to show the status of the SWI where the intrusion phase predominates in ~2/3 of the study are (~70 km radius) and the compositional thresholds of Na, Mg, Cl, and SO4 are 600, 145, 1200, and 600 mg/L, respectively, indicating that the wells with higher concentrations than these thresholds are affected by SWI. Moreover, the results demonstrate the efficiency of combining hydrogeochemical facies from heatmap and resistivity investigations to provide a large-scale characterization of natural and anthropogenic activities controlling aquifer salinization to support decision-makers for the long-term management of coastal groundwater.

Sediment, often considered a by-product of various activities within river basin management to be disposed of, or a pollutant to be controlled, is increasingly being acknowledged as a resource in need of management. The paper deals with the possibility of reusing sediment from two Slovak reservoirs (Klusov and Ruzin) as an alternative raw material in concrete production. Concrete specimens were prepared by a combination of original reservoir sediment, reservoir sediment mechanically activated by dry milling, reservoir sediment mechanically activated by dry milling together with biomass incinerator fly-ash as a binder. To improve the strength properties of specimens, sodium hydroxide (NaOH) was used as a sediment activator. Mixtures containing 40% of binder replacement by the above-mentioned combinations of original and treated sediments were tested for flexural and compressive strengths after 28, 90 and 365 days of curing. The results showed that the mixtures prepared from sediments milled without and with addition of fly ash as cement replacement satisfied the strength requirements for the compressive strength class C16/20 according to the European standard except the composites prepared with NaOH as the sediment activator. Addition of NaOH into composites in the concentration of 5 M as an activator of sediment indicated the negative impact on compressive and flexural strengths and thus NaOH was not an effective pozzolanic activator for sediments. This study reveals that the sediment may be considered as 40% cement substitution in building materials.

Particle size is a fundamental property of any sediment, which can provide important information about its nature and provenance. The particle size distribution requires precise determination using a rapid and reliable method with a high resolution. Grain size is the essential factor influencing the heavy metal contents in sediment and is the most fundamental property of sediment particles, affecting their entrainment, transport and deposition. The aim of this paper is to present the results of the effect of particle size on heavy metal (Cu, Zn, Fe, Pb and As) distributions in sediments. Dependence between the distribution of metals in the examined profile of the sediments from Ruzin water reservoir on the different size of particles and depth is unambiguous for Cu, Zn and Fe with exception of Pb and As.