Details

Autor(en) / Beteiligte

• Hansen, Claus Toni
• Ritz, Christian
• Gerhard, Daniel
• Jensen, Jens Erik
• Streibig, Jens Carl

Titel

Re-evaluation of groundwater monitoring data for glyphosate and bentazone by taking detection limits into account

Ist Teil von

• The Science of the total environment, 2015-12, Vol.536, p.68-71

Ort / Verlag

Netherlands: Elsevier B.V

Erscheinungsjahr

2015

Quelle

MEDLINE

Beschreibungen/Notizen

• Current regulatory assessment of pesticide contamination of Danish groundwater is exclusively based on samples with pesticide concentrations above detection limit. Here we demonstrate that a realistic quantification of pesticide contamination requires the inclusion of “non-detect” samples i.e. samples with concentrations below the detection limit, as left-censored observations. The median calculated pesticide concentrations are shown to be reduced 104 to 105 fold for two representative herbicides (glyphosate and bentazone) relative to the median concentrations based upon observations above detection limits alone. The size of glyphosate contamination in Danish groundwater without including samples with glyphosate below detection level is 10,000 to 100,000 higher than doing a parametric event-time model, where non-detect samples are left censored. The trend lines are rather similar. The broken lines are the EU drinking water directive maximum value 0.1μgl−1 and the dotted line the detection limit of 0.01μgL−1. Numbers are number of samples above detection line and total number of samples. [Display omitted] •It is imperative to include all samples – including those falling below detection levels.•Samples with pesticide concentrations below detection limits result in left-censored observations.•Groundwater pesticide medians are 104–105 lower when including than when excluding “non-detect”•Excluding “non-detect” samples significantly overestimates pesticide load in groundwater.