Compound-Specific Stable Isotope Fractionation of Pesticides and Pharmaceuticals in a Mesoscale Aquifer Model.
Compound-specific isotope analysis (CSIA) receives increasing interest for its ability to detect natural degradation of pesticides and pharmaceuticals. Despite recent laboratory studies, CSIA investigations of such micropollutants in the environment are still rare. To explore the certainty of information obtainable by CSIA in a near-environmental setting, a pulse of the pesticide bentazone, the pesticide metabolite 2,6-dichlorobenzamide (BAM), and the pharmaceuticals diclofenac and ibuprofen was released into a mesoscale aquifer with quasi-two-dimensional flow. Concentration breakthrough curves (BTC) of BAM and ibuprofen demonstrated neither degradation nor sorption. Bentazone was transformed but did not sorb significantly, whereas diclofenac showed both degradation and sorption. Carbon and nitrogen CSIA could be accomplished in similar concentrations as for "traditional" priority pollutants (low μg/L range), however, at the cost of uncertainties (0.4-0.5‰ (carbon), 1‰ (nitrogen)). Nonetheless, invariant carbon and nitrogen isotope values confirmed that BAM was neither degraded nor sorbed, while significant enrichment of (13)C and in particular (15)N corroborated transformation of diclofenac and bentazone. Retardation of diclofenac was reflected in additional (15)N sorption isotope effects, whereas isotope fractionation of transverse dispersion could not be identified. These results provide a benchmark on the performance of CSIA to monitor the reactivity of micropollutants in aquifers and may guide future efforts to accomplish CSIA at even lower concentrations (ng/L range).
Institute of Groundwater Ecology, Helmholtz Zentrum München , Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
Heide K V
HK
Schürner
Institute of Groundwater Ecology, Helmholtz Zentrum München , Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
Michael P
MP
Maier
Center for Applied Geosciences, University of Tübingen , Hölderlinstraße 12, 72074 Tübingen, Germany.
Dominik
D
Eckert
Institute of Groundwater Ecology, Helmholtz Zentrum München , Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
Ramona
R
Brejcha
Institute of Groundwater Ecology, Helmholtz Zentrum München , Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
Claudia-Constanze
CC
Neumann
Institute of Groundwater Ecology, Helmholtz Zentrum München , Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
Christine
C
Stumpp
Center for Applied Geosciences, University of Tübingen , Hölderlinstraße 12, 72074 Tübingen, Germany.
Olaf A
OA
Cirpka
Institute of Groundwater Ecology, Helmholtz Zentrum München , Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
Martin
M
Elsner
D001673:Biodegradation, Environmental; D002247:Carbon Isotopes; D005591:Chemical Fractionation; D060587:Groundwater; D010575:Pesticides; D004364:Pharmaceutical Preparations
D002247:Carbon Isotopes; D010575:Pesticides; D004364:Pharmaceutical Preparations