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The main aim of this study was to determine the sorption and biodegradation parameters of trichloroethene (TCE) and tetrachloroethene (PCE) as input data required for their fate and transport modelling in a Quaternary sandy aquifer. Sorption was determined based on batch and column experiments, while biodegradation was investigated using the compound-specific isotope analysis (CSIA). The aquifer materials medium (soil 1) to fine (soil 2) sands and groundwater samples came from the representative profile of the contaminated site (south-east Poland). The sorption isotherms were approximately linear (TCE, soil 1, Kd = 0.0016; PCE, soil 1, Kd = 0.0051; PCE, soil 2, Kd = 0.0069) except for one case in which the best fitting was for the Langmuir isotherm (TCE, soil 2, Kf = 0.6493 and Smax = 0.0145). The results indicate low retardation coefficients (R) of TCE and PCE; however, somewhat lower values were obtained in batch compared to column experiments. In the column experiments with the presence of both contaminants, TCE influenced sorption of PCE, so that the R values for both compounds were almost two times higher. Non-significant differences in isotope compositions of TCE and PCE measured in the observation points (δ13C values within the range of −23.6 ÷ −24.3 ‰ and −26.3 ÷−27.7 ‰, respectively) indicate that biodegradation apparently is not an important process contributing to the natural attenuation of these contaminants in the studied sandy aquifer.

The presence of pharmaceuticals in the environment, and in groundwater, has been recognized as a great environmental concern. Biodegradation and sorption are the main processes leading to the removal of contamination from the water phase. The aim of this study was to determine the transport processes of selected pharmaceuticals (antipyrine, atenolol, carbamazepine, caffeine, diclofenac, ketoprofen, sulfamethoxazole) in selected sediments (coarse sand, medium sand, sandy loam) in laboratory experiments. Moreover, the impact of flow velocities on the sorption and degradation rates of the selected compounds was studied. Column experiments were performed at three flow velocities, under abiotic and biotic conditions, applying conservative (bromide) and reactive tracers (pharmaceuticals). From the breakthrough curves, retardation factors and degradation rates were determined and the influence of variable flow conditions on transport parameters was evaluated. Low observed concentrations and recoveries of atenolol indicated a strong influence of sorption on its transport. Diclofenac, caffeine, and carbamazepine were also affected by sorption but to a lesser extent. Sulfamethoxazole, ketoprofen, and antipyrine were recovered nearly completely, indicating an almost conservative transport behavior. Biodegradation was small for all the compounds, as the results from biotic and abiotic column experiments were similar. Transport of the tested pharmaceuticals was not influenced by different flow velocities, as similar modelled degradation rates and retardation factors were found for all tested flow velocities.often overlooked, which corresponds to ignoring the effect of different flow velocities on the fate of contaminants. Reducing the complexity at field sites, laboratory experiments in column studies can help to identify the specific sorption and biodegradation rates of pharmaceuticals.Column experiments are frequently used to study the transport of contaminants like micropollutants, such as pharmaceuticals [7]. Numerous studies have proven the usefulness of column experiments, as they are relatively fast, uncomplicated to manage, and their boundary conditions can be easily controlled. Moreover, different scenarios may be simulated, for example, managed aquifer recharge [8], seepage through the vadose zone [9], transport through an aquifer [10,11], and bank filtration [12][13][14].Column studies have been utilized to study the influence of physico-chemical conditions within an aquifer on pharmaceutical transport, with an emphasis on changes in pH [11], redox conditions [13,15], or temperature [16]. Also, the influence of the sediment type on transport behavior was studied and the following properties were found particularly crucial: Sediment grain size [17], available mineral surfaces [18], or total organic carbon content [19]. However, little is known on the impact of flow velocity on pharmaceutical transport in groundwater [20].The effect of pore-water velocity on contaminant transport has been presented in the literatur...

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