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Poster De Conférence Année : 2015

Assessment of silicone rods for passive sampling of pesticides in freshwaters

Résumé

Passive sampling has recently been developed as an alternative to grab or average automated sampling, in order to obtain, at lower cost, more realistic estimates of the average concentrations of contaminants in aquatic environments. This technique allows the accumulation of chemicals from large amounts of water, resulting in ultratrace level detection and smoothed integrative sampling over periods ranging from days to months. In small agricultural watersheds, pesticide concentrations quickly fluctuate due to episodic events such as heavy rain. Monitoring of such compounds by a reactive passive sampler appears as an alternative to grab sampling. Silicone rod, investigated in this work, is a reactive, single-use and low cost passive sampler. This new passive sampler was inspired by research works on the analytical technique SBSE (Stir Bar Sorptive Extraction) and first trials of in situ exposition as "Passive SBSE" (Assoumani et al., 2013) and MESCO (Vrana et al., 2001). The nature and mass of pesticides sorbed on in situ exposed silicone rods can be used as qualitative and semi-quantitative measures, to assess trends and gradients of contamination in aquatic environments. For quantitative purposes, the estimation of the average concentration of contaminants in water requires the determination of kinetic parameters (Rs, equilibration time). Even if sampling rates (Rs) are obtained in laboratory thanks to the calibration of the passive sampler for each compound, performance reference compounds (PRCs) (Huckins et al., 2002) have to be loaded on samplers prior to their deployment in order to correct the measured concentration in relation to exposure conditions by using their dissipation data. The first aim of this study was to calibrate silicone rods as a passive sampling technique for the water monitoring of 27 pesticides (herbicides, fungicides and insecticides) and metabolites with a large range of polarity (1.5 < log Kow < 5.51). A laboratory calibration system was designed to control temperature and flow velocity conditions in order to determine Rs for the targeted compounds. During the calibration step, the concentration of pesticides was maintained constant using spiked silicone sheets (Rusina et al., 2010) as diffusive source of contaminants in water. Silicone rods showed a great affinity for pesticides with log Kow > 3, whereas polar pesticides have been less sorbed. Sampling rates of the pesticides were in most cases positively related to their hydrophobicity. In a second part of this study, desorption kinetics of deuterium labelled pesticides were monitored and the corresponding elimination rate constants were calculated. These results allowed us to define a new set of deuterium labelled compounds as potential PRCs for correction of environmental influences (temperature and flow velocity) on time-weighted average pesticide concentrations determined by silicone rods. Calibration constants and PRC correction were applied to field data and allowed to highlight a clear gradient of contamination in a river located in a vineyard watershed.
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Dates et versions

hal-02602018 , version 1 (16-05-2020)

Identifiants

Citer

A. Martin, Antoine Jolivet, A. Assoumani, B. El Moujahid, Marina Coquery, et al.. Assessment of silicone rods for passive sampling of pesticides in freshwaters. XV Symposium on pesticide chemistry "environmental risk assessment and management", Sep 2015, Piacenza, Italy. pp.1, 2015. ⟨hal-02602018⟩
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