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Up till now, the diclofenac (DCF) transformation into its nitrogen-derivatives, N -nitroso-DCF (NO-DCF) and 5-nitro-DCF (NO 2 -DCF), has been mainly investigated in wastewater treatment plant under nitrification or denitrification processes. This work reports, for the first time, an additional DCF microbial mediated nitrosation pathway of DCF in soil under strictly anoxic conditions probably involving codenitrification processes and fungal activities. This transformation pathway was investigated by using field observations data at a soil aquifer system (Katari watershed, Bolivia) and by carrying out soil slurry batch experiments. It was also observed for diphenylamine (DPA). Field measurements revealed the occurrence of NO-DCF, NO 2 -DCF and NO-DPA in groundwater samples at concentration levels in the 6–68 s/L range. These concentration levels are more significant than those previously reported in wastewater treatment plant effluents taking into account dilution processes in soil. Interestingly, the p -benzoquinone imine of 5-OH-DCF was also found to be rather stable in surface water. In laboratory batch experiments under strictly anoxic conditions, the transformation of DCF and DPA into their corresponding N -nitroso derivatives was well correlated to denitrification processes. It was also observed that NO-DCF evolved into NO 2 -DCF while NO-DPA was stable. In vitro experiments showed that the Fisher-Hepp rearrangement could not account for NO 2 -DCF formation. One possible mechanism might be that NO-DCF underwent spontaneous NO loss to give the resulting intermediates diphenylaminyl radical or nitrenium cation which might evolve into NO 2 -DCF in presence of NO 2 radical or nitrite ion, respectively. [ABSTRACT FROM AUTHOR]

The increasing demand for water and irrigation in the semi-arid Bolivian Altiplano requires a better knowledge of the available resources, particularly groundwater. The aim of this study is to provide a first insight into the hydrogeological structure (0–200 m deep) and groundwater dynamics of the Katari-Lago Menor Basin aquifer located between the Eastern Cordillera and Lake Titicaca, Bolivia. This aquifer is studied using geophysical data (a total of 187 Time Domain Electromagnetic (TDEM) soundings), piezometric data (97 groundwater level measurements) and geochemical data (52 groundwater samples), combined with geological, lithological and topographical information. The results allowed identifying stratigraphic models consistent with the Quaternary sediments being hydraulically connected and behaving as a single regional basin-aquifer. This basin-aquifer is delimited by the most ancient lake invasions towards the southern, western and northern sides and by the lower limit of rock glaciers towards the eastern side. A large portion of the aquifer presents an unconfined behaviour varying from 50 to 150 m while the confined portion varies from 100 to 150 m. Groundwater flow within the Katari and Lago Menor Basin aquifer is composed of several interconnected groundwater flow systems. The main groundwater flow system starts in the high mountain ranges of the Eastern Cordillera, follows the topographic Piedmont gradient (NE to SW) and discharges in a series of wetlands. This multidisciplinary approach proved to be an appropriate method to derive a consistent picture of the hydrogeological functioning of the Katari-Lago Menor Basin aquifer. • Performance of a groundwater basin-scale multidisciplinary study. • TDEM surveys were efficient to investigate the structure of a basin-scale aquifer. • Continuity of Quaternary layers behaving hydraulically as a single aquifer. • 3D schematic structure and dynamics of a major aquifer in the Bolivian Altiplano. • Basis for the development of a 3D numerical groundwater model. [ABSTRACT FROM AUTHOR]