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Factors controlling spatial patterns and time trends of multiple pesticides in groundwater (Hesbaye chalk aquifer, Belgium)
Hakoun, Vivien; Orban, Philippe; Dassargues, Alain et al.
20169th IAHS Conference on Groundwater Quality
 

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Keywords :
Groundwater; Herbicides compounds; Nitrate; Tritium; Time trend
Abstract :
[en] Groundwater contamination by pesticides compounds (parent and degradation by-products) is a well identified environmental issue, however factors influencing their spatial patterns and time trends remain unclear. In this context, 18 years long time series (1996-2013) of 3 banned (atrazine, diuron, simazine), 2 metabolites (deethyaltrazine –DEA, and 2,6-dichlorobenzamide –BAM) and one regulated (bentazone) pesticides compounds are explored, taking into account concentrations below detection limits. Using a bivariate and multivariate (PCA and hierarchical clustering) statistical framework, these time series are related to nitrate (NO3-) and the fraction of young water recharged since 50 years, land use, to aquifer settings (i.e. confining conditions, thickness of the unsaturated zone) and to groundwater table fluctuations. Results show that pesticides compounds are always below detection limits in the confined area where old groundwater lies. However these compounds are detected every year in the unconfined zone with maximal concentrations exceeding the current European water drinking standard of 100 ng.L-1 every year since 2007 for atrazine. We find the greatest significant (p-value < 0.05) positive correlations between the trio atrazine-DEA (tau=0.62), atrazine-NO3- (tau=0.48) and DEA-NO3- (tau=0.49). We identify positive correlations between most compounds, atrazine (tau=0.44), bentazone (tau=0.36), simazine (tau=0.71); DEA (tau=0.58) and BAM (tau=0.44), and water table fluctuations with periods spanning several years. We determine two groups (6 and 9 sites each) of site which relate to the discharge and recharge areas. Sites from the recharge area where higher diuron, simazine and BAM concentrations occurs correlate with a dense localized urban area. Atrazine and bentazone relates to sites with thin unsaturated zones and high mixing in the wells. Our analysis reveals critical factors affecting 7 pesticides compounds. It improves our understanding of the interplay between land use, aquifer settings and transient processes (water fluctuations) on controlling pesticides concentrations in groundwater.
Disciplines :
Geological, petroleum & mining engineering
Author, co-author :
Hakoun, Vivien ;  Université de Liège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement
Orban, Philippe  ;  Université de Liège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement
Dassargues, Alain  ;  Université de Liège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement
Brouyère, Serge  ;  Université de Liège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement
Language :
English
Title :
Factors controlling spatial patterns and time trends of multiple pesticides in groundwater (Hesbaye chalk aquifer, Belgium)
Publication date :
25 July 2016
Number of pages :
14
Event name :
9th IAHS Conference on Groundwater Quality
Event organizer :
Southern University of Science and Technology
Event place :
Shenzhen, China
Event date :
July 24-28, 2016
Audience :
International
European Projects :
FP7 - 265063 - ADVOCATE - Advancing Sustainable In Situ Remediation for Contaminated Land and Groundwater
Funders :
CE - Commission Européenne [BE]
Available on ORBi :
since 25 August 2016

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