In recent decades, mining-related activities in the Lusatian lignite mining area have led to an extensive pyrite weathering, contributing thereby to the elevation of sulfate and iron concentrations in the groundwater and surface water.

Due to the complicated pathways of pyrite oxidation and the complex spatial distribution of the pyrite-bearing layers, it is difficult to develop a comprehensive restoration plan. Therefore, developing a quick and non-intrusive geophysical measuring technique for estimating pyrite oxidation in various depths and areas is highly desirable. Previous laboratory studies have shown the effect of iron bearing minerals on the nuclear magnetic resonance (NMR) response signal. However, further research is required to link these findings to the subsurface pyrite oxidation state or the accompanied sulfate concentrations in the groundwater.

To this end, column experiments containing different pyrite mass-percentages are performed under various redox conditions. The pyrite oxidation in the columns is measured via the mass balance between the inlet, the initial content, and the outlet. In addition, laboratory NMR is used to constantly monitor the column for the entire experiment duration. For modeling purposes, we developed a PHREEQC-based reactive transport model to simulate pyrite oxidation inside the columns. A comparison between the model results, laboratory NMR data, and the experimental measurements provides a basis for the future surface-based NMR applications in the field.

The outcome ultimately enables us to estimate the groundwater contamination due to pyrite oxidation with a NMR-based technique that is less time-consuming, more reliable, and less labor-intensive.

In Germany, all nuclear power plants have been shut down and some are already in various stages of decommissioning. All waste volumes that are not deposited in a repository must pass through officially approved clearance procedures, which are regulated in the German Radiation Protection Ordinance (StrlSchV 2021). After clearance, the materials can be fed into further material cycles or disposed of in accordance with the type of release. The release values of the Radiation Protection Ordinance are based on the 10 µSv criterion. This criterion is intended to ensure the protection of the population from ionizing radiation.

Numerical groundwater models can be used to simulate the distribution of radionuclides and provide information on concentrations in space and time, which can be used as input parameters for calculating possible ingestion doses for different exposure paths.

The basic transport processes of advection, diffusion, dispersion, and sorption are implemented in the simulation codes "Simulation of Processes in Groundwater (SPRING)" (König et al. 2023), “DuMux – Dune for Multiphase flow and transport” (Koch et al. 2021) and "distributed density-driven flow (d3f++)" (Fein & Schneider 1999, Fein 2004). Decay chains can also be modeled in the codes.

The model area represents a simple 2D model and a generic landfill body with its various layer compartments and an associated aquifer. In a further model, the infiltration of precipitation water into contaminated soil with mass transport into the saturated zone is considered. This work presents the first results of the generic numerical groundwater models.

The main objectives of this research are to access ground water,a primary source of drinking water in the urban areas of Hawler Erbil and Bnaslawa in northern Iraq, and the non -carcinogenic human health risks of nitrate contamination associated with drinking water quality. For this purpose, twenty seven ground water samples were collected from wells to asses the hydrogeochemical characteristics and ground water quality for both natural and anthropogenic purposes during the wet (May 2020) and dry (September 2020) seasons.During the wet and dry seasons, NO3 in ground water ranged from 14to 61 mg/L and 12 to 60 mg/L with an average value of 35.7 and 29 mg /L, respectively. Approximately 25.92% of the samples exceeded the permissible limit of the WHO (2011) drinking water standard.the ratio of NO3 /Na vs.Cl/Na and SO4/Na vs. NO3 /Na indicate the effect of agricultural activities and waste water leakage from cesspools or septic tanks on the quality of ground water during the wet and dry seasons. The entropy weighted water quality index method ranked 62.5% and 75% of the urban ground water as not recommended for drinking, the remaing samples are moderately suitable in both wet and dry seasons.Due to high nitrate in drinking water, non-carcinogenic human health risk levels vary as infants >child> adults.The main findings obtained from this study can assist policymakers in better understanding the hydrogeochemical properties of ground water in terms of drinking water safety, thereby facilitating the management of water resources to take the necessary measures.

Understanding the biogeochemical processes that lead to the enrichment of dissolved phosphorus in groundwater is crucial, especially as concentrations exceeding 1 mg L^-1 occur in many floodplain and delta aquifers. These elevated concentrations of primarily inorganic orthophosphate can cause eutrophication in surface waters and mobilize toxic elements like arsenic.

Here, we provide a comprehensive overview of the biogeochemistry of phosphorus within groundwater systems, aiming to elucidate how phosphorus interactions with other elements influence its behaviour. Our methods include chemical analyses of groundwater and aquifer materials, laboratory and field experiments, isotope analysis, and geochemical modeling.

Our findings indicate three primary processes responsible for the release of phosphorus into groundwater: apatite weathering; microbial mineralization of organic matter, which generates dissolved phosphorus as a by-product; and the reductive dissolution of iron-(hydr)oxides that serve as hosts for phosphorus. Additionally, phosphorus undergoes microbial processing during its transport, as evidenced by phosphate-bound stable oxygen isotope analysis. Phosphorus may also be immobilized by (co-)precipitation of secondary minerals (e.g., calcium-phosphates or iron minerals) or through surface adsorption. Notably, phosphorus immobilization often takes precedence over arsenic immobilization, enhancing the mobility of the latter.

The occurrence of these mobilization and/or immobilization processes largely depends on local groundwater characteristics and the aquifer's mineralogical composition. Our results highlight the intricate links between the fate of phosphorus and the biogeochemical cycles of calcium, carbon, iron, arsenic, and possibly sulphur, suggesting potential strategies for in-situ groundwater remediation approaches.