title: 20 years of long-term atrazine monitoring in a shallow aquifer in western Germany.
abstract: Atrazine was banned in Germany in 1991 due to findings of atrazine concentrations in ground- and drinking waters exceeding threshold values. Monitoring of atrazine concentrations in the groundwater since then provides information about the resilience of the groundwater quality to changing agricultural practices. In this study, we present results of a monitoring campaign of atrazine concentrations in the Zwischenscholle aquifer. This phreatic aquifer is exposed to intensive agricultural land use and susceptible to contaminants due to a shallow water table. In total 60 observation wells (OWs) have been monitored since 1991, of which 15 are sampled monthly today. Descriptive statistics of monitoring data were derived using the "regression on order statistics" (ROS) data censoring approach, estimating values for nondetects. The monitoring data shows that even 20 years after the ban of atrazine, the groundwater concentrations of sampled OWs remain on a level close to the threshold value of 0.1 μg l(-1) without any considerable decrease. The spatial distribution of atrazine concentrations is highly heterogeneous with OWs exhibiting permanently concentrations above the regulatory threshold on the one hand and OWs were concentrations are mostly below the limit of quantification (LOQ) on the other hand. A deethylatrazine-to-atrazine ratio (DAR) was used to distinguish between diffuse - and point-source contamination, with a global mean value of 0.84 indicating mainly diffuse contamination. Principle Component Analysis (PCA) of the monitoring dataset demonstrated relationships between the metabolite desisopropylatrazine, which was found to be exclusively associated with the parent compound simazine but not with atrazine, and between deethylatrazine, atrazine, nitrate, and the specific electrical conductivity. These parameters indicate agricultural impacts on groundwater quality. The findings presented in this study point at the difficulty to estimate mean concentrations of contamination for entire aquifers and to evaluate groundwater quality based on average parameters. However, analytical data of monthly sampled single observation wells provide adequate information to characterize local contamination and evolutionary trends of pollutant concentration.
authors.affiliation: Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Electronic address: david.vonberg@t-online.de.
authors.forename: David
authors.initials: D
authors.lastname: Vonberg
authors.affiliation: Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Electronic address: j.vanderborght@fz-juelich.de.
authors.forename: Jan
authors.initials: J
authors.lastname: Vanderborght
authors.affiliation: Erftverband, Am Erftverband 6, 50126 Bergheim, Germany. Electronic address: nils.cremer@erftverband.de.
authors.forename: Nils
authors.initials: N
authors.lastname: Cremer
authors.affiliation: Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Electronic address: t.puetz@fz-juelich.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pütz
authors.affiliation: Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Electronic address: m.herbst@fz-juelich.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Herbst
authors.affiliation: Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Electronic address: h.vereecken@fz-juelich.de.
authors.forename: Harry
authors.initials: H
authors.lastname: Vereecken
mesh_terms: D001280:Atrazine / Q000031:analogs & derivatives / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods*; D005843:Geography; D005858:Germany; D060587:Groundwater / Q000737:chemistry*; D009566:Nitrates / Q000032:analysis; D025341:Principal Component Analysis; D012044:Regression Analysis; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D009566:Nitrates; D014874:Water Pollutants, Chemical; C446541:deethylatrazine; D001280:Atrazine
keywords: Atrazine; DAR; DEA; DIA; DOC; Data censoring; Groundwater monitoring; HPLC; K(d); K(f); K(oc); LOQ; Nondetects; OW; PC; PCA; Principle component analysis; ROS; SPE; WFD; Water Framework Directive; deethylatrazine; deethylatrazine to atrazine ratio; deisopropylatrazine; dissolved organic carbon; high-performance liquid chromatography; hydraulic conductivity [L T(−1)]; limits of quantification; observation well; organic carbon normalized distribution coefficient [L(3) M(−1)]; principal component; principal component analysis; regression on order statistics; solid phase extraction; sorption distribution coefficient [L(3) M(−1)]