부산대학교 도서관

In the framework of the Life+ InSiTrate project, a pilot-plant was established to demonstrate the viability of inducing in-situ heterotrophic denitrification to remediate nitrate (NO 3 −)-polluted groundwater. Two injection wells supplied acetic acid by pulses to an alluvial aquifer for 22 months. The monitoring was performed by regular sampling at three piezometers and two wells located downstream. In the present work, the pilot-plant monitoring samples were used to test the usefulness of the isotopic tools to evaluate the efficiency of the treatment. The laboratory microcosm experiments determined an isotopic fractionation (ε) for N-NO 3 − of −12.6‰ and for O-NO 3 − of −13.3‰. These ε 15N NO3/N2 and ε 18O NO3/N2 values were modelled by using a Rayleigh distillation equation to estimate the percentage of the induced denitrification at the pilot-plant while avoiding a possible interference from dilution due to non-polluted water inputs. In some of the field samples, the induced NO 3 − reduction was higher than 50% with respect to the background concentration. The field samples showed a reduced slope between δ 18O-NO 3 − and δ 15N-NO 3 − (0.7) compared to the laboratory experiments (1.1). This finding was attributed to the reoxidation of NO 2 − to NO 3 − during the treatment. The NO 3 − isotopic characterization also permitted the recognition of a mixture between the denitrified and partially or non-denitrified groundwater in one of the sampling points. Therefore, the isotopic tools demonstrated usefulness in assessing the implementation of the field-scale induced denitrification strategy. Unlabelled Image • Laboratory calculated ε 15N and ε 18O allowed estimating field-scale denitrification. • The induced nitrate reduction at the pilot-plant was higher than 50%. • Lower δ 18O-NO 3 − values at field compared to laboratory suggested NO 2 − reoxidation. • Denitrified and non-denitrified water mixing at the EW was proven isotopically. [ABSTRACT FROM AUTHOR]