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TY  - THES
AU  - Vonberg, David
TI  - Atrazine in the environment 20 years after its ban : long-term monitoring of a shallow aquifer (in western Germany) and soil residue analysis
VL  - 293
PB  - RWTH Aachen
VL  - Dissertation
CY  - Jülich
M1  - RWTH-2015-04985
SN  - 978-3-95806-099-9
T2  - Schriften des Forschungszentrums Jülich. Reihe Energie & Umwelt = Energy & environment
SP  - 1 Online-Ressource (149 Seiten) : Illustrationen, Diagramme, Karten
PY  - 2015
N1  - Druckausgabe: 2015. - Onlineausgabe: 2015. - Auch veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2016
N1  - Dissertation, RWTH Aachen, 2015
AB  - Atrazine, one of the worldwide most widespread herbicides, was banned in Germany in 1991 and in the European Union in 2004, due to findings of atrazine concentrations in ground- and drinking waters exceeding the threshold value of 0.1 µg L-1. Nevertheless atrazine and the metabolite deethylatrazine were still detected in German aquifers more than 10 years after its prohibition, often without any considerable decreasing trend in groundwater concentration. Because atrazine was already found to be persistent in soils for more than two decades after the last application, the hypothesis was raised that a continued release of atrazine residues from the soil into groundwaters might sustain atrazine groundwater concentrations on elevated levels. The overall objective of this study was to investigate the occurrence and concentration trends of atrazine and its main metabolites in the groundwater-soil environment after the prohibition of its use. Accordingly, in this study results of i) 20 years of atrazine groundwater monitoring of a a shallow aquifer in western Germany since its ban and ii) atrazine soil residue analyses in the vadose zone of the same study area 21 years after its ban are presented. The phreatic Zwischenscholle aquifer located in the Lower Rhine Embayment is exposed to intensive agricultural land use and is highly susceptible to contaminants due to a shallow water table. In total 60 observation wells (OWs) have been monitored since 1991, of which 11 are sampled monthly today. Descriptive statistics of monitoring data were derived using the “regression on order statistics” (ROS) data censoring approach, estimating values for nonquantifiable values rather than substitute them by e.g. half of the limit of quantification and taking the risk of biasing statistical parameters. 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 other OWs with concentrations mostly below the limit of quantification (LOQ) on the other hand. Here atrazine concentrations show upward, downward or approximately constant trends. The deethylatrazine-to-atrazine ratio (DAR) was used to distinguish between diffuse – and point-source contaminations. A DAR around unity (slightly smaller for thin vadose zones like for the investigated aquifer) suggests a contamination of an aquifer by diffuse pathways, resulting in significant metabolization of atrazine to deethylatrazine due to a longer contact time to soil microorganisms. Conversely, point-source contaminations where the contaminant enters the aquifer directly by e.g. macropore flow results in negligible deethylation and hence a DAR close to zero. A global mean DAR value of 0.84 for the monitoring data of the Zwischenscholle aquifer indicates mainly diffuse contamination. Also most of the DARs for single observation wells suggest mainly diffuse pollution, except for one OW with a mean DAR of 0.02, clearly indicating point-source contamination. Principle Component Analysis (PCA) of the monitoring dataset demonstrated relationships between the metabolite deisopropylatrazine and its parent compound simazine but not with atrazine, and deethylatrazine, atrazine, nitrate, and the specific electrical conductivity. These parameters indicate diffuse agricultural impacts on groundwater quality.   The groundwater monitoring findings 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. For atrazine soil residue analysis three soil cores reaching down to the groundwater table (approximately 3 m below soil surface) were taken in an agricultural field where atrazine was applied prior to its ban. It is uncertain if atrazine was applied in total two or three times with a recommended dose of 0.96 kg ha-1. Eight layers were separated (0-10 cm, 10-30 cm, 30-60 cm, 60-100 cm, 100-150 cm, 150-200 cm, 200-250 cm, 250-300 cm) for atrazine residue analysis and soil parameters (grain size distribution, pH, cation exchange capacity (CECeff) and organic carbon content). Soil samples of each layer were extracted using accelerated solvent extraction (ASE) and analyzed by LC-MS/MS analysis. Prior to this analysis, a method validation was conducted to find optimum extraction parameter combinations. For all extractions a methanol/water (4:1, v/v) solvent was used. The highest quantifiable atrazine extraction yield amongst all extraction parameter combinations between 100°C and 135°C and 100 bar, 150 bar and 207 bar was obtained for 100°C and 207 bar. Atrazine yields were generally higher for higher pressures. Possibly the higher pressure facilitates soil matrix penetration by the solvent. Extractions using 135°C and the highest pressure of 207 bar resulted in quantified concentration of atrazine 31 
LB  - PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
UR  - https://publications.rwth-aachen.de/record/484062
ER  -