Intensive application of pesticides for agricultural purposes led to the detection of these compounds in groundwater. Therefore, it is necessary to consider measures to improve agricultural production in order to protect groundwater, as the basic drinking water resource. On the other hand, the main processes that control the fate and transport of pollutants in the environment are the processes of sorption and biodegradation. Therefore, the objective of this doctoral dissertation was to investigated the impact of the application of carbon based materials, as well as their microbiologically inoculated forms, on the sorption and biodegradation potential of compounds of interest, such as organophosphorus pesticides, alachlor and pentachlorobenzene during transport through the alluvial sediment of the Danube in order to protect groundwater. The results of the characterization of the Danube geosorbent showed that it is sandy aquifer material with a low content of organic carbon. Carbon based adsorbents were produced by the process of slow pyrolysis at 400°C in the case of biochar, and by the process of hydrothermal carbonization at 180, 200 and 220°C in the case of hydrochars from two different starting biomasses (biomass originating from miscanthus and sugar beet shreds). On the other hand, the results of biochar characterization show that biochars originating from the biomass of miscanthus and sugar beet shreds have larger specific surfaces compared to hydrochars originating from the same biomass. On the basis of the physical characterization of the investigated carbon based materials, it can be concluded that the obtained carbon based adsorbents are mesoporous with a dominant content of mesopores with a small specific surface compared to e.g. specific surface area of activated carbon. Elemental analysis of biochars showed that biochars originating from the miscanthus plant have a higher proportion of aromatic structures, as indicated by a lower H/C ratio compared to biochars originating from sugar beet shreds. In order to determine the adsorption affinity, static adsorption tests were set up for selected compounds of interest. Very high adsorption affinities were obtained for both types of biochar, which is well correlated with pore diameter and specific surface area. In order to further evaluate the impact of the addition of carbon material on the transport of selected compounds through the alluvial sediment, column (dynamic) experiments were used. In these experiments, it was observed that the addition of carbon materials to the column filled with alluvial sediment of the Danube increases the retardation of all tested organophosphorus pesticides, pentachlorobenzene, while in the case of alachlor, no increased retardation was observed except in the case of the addition of sugar beet shred biochar, sugar beet shred hydrochar obtained at 180°C and hydrochar miscanthus obtained at 220°C where a different trend was shown. The longer retention time of these pesticides on the sediment column is a consequence of hydrophobic interactions between the tested compounds and the organic matter of the sediment. The retardation coefficients (Rd) for the alluvial sediment of the Danube in the case of transport of pentachlorobenzene and alachlor were 45 and 20 which is consistent with the hydrophobicity of the investigated compounds. Retardation coefficients for experiments with the addition of inoculated carbon based materials were in the range Rd =4–300 for all tested compounds. The degree of biodegradation ranged from λ=0.01–10. The highest biodegradation coefficient was observed for pentachlorobenzene during transport through the Danube geosorbent, which may be a consequence of simultaneous adsorption on carbon adsorbents, organic matter of the geosorbent, and biosorption. Additionally, the presence of microorganisms in the geosorbent that have the potential to biodegrade this compound can lead to its degradation.