Laboratory calibration of POCIS: kinetic accumulation of 59 polar organic contaminants and evaluation of candidate performance reference compounds
Résumé
organic micropollutants in water (Alvarez et al., 2004). It is still in development concerning its domain of validity (e.g. molecules sampled, type of water studied, optimal exposure duration) and its performances, including the definition of molecules sampling rates, repeatability, accuracy of the evaluation of time-weighted average (TWA) concentrations. Performance reference compounds (PRCs) enable to decrease the effect of variable environmental conditions, so they can be used to obtain more reliable TWA concentrations in situ. To our knowledge, for POCIS, only one PRC has been identified to date: deisopropylatrazine-d5, that has been used and proved efficient for polar herbicides monitoring in freshwater (Mazzella et al., 2007, 2010). In order to obtain in situ TWA contaminant concentrations, POCIS needs to be calibrated in laboratory for each molecule of interest. Our work was based on laboratory calibration of POCIS for 5 alkylphenols, 9 hormones, 12 pesticides, 29 pharmaceuticals, 3 phenols and 1 UV filter in a flow-through system. This system was composed of 2 aquaria (50 L) containing i) spiked tap water (circa 3 μg/L) and non-spiked POCIS for the determination of accumulation kinetics or ii) non-spiked tap water and spiked POCIS for the determination of desorption kinetics. In both experiments, water temperature, pH, conductivity and dissolved organic carbon were controlled. Agitation in the aquaria was ensured via a submerged pump. The resulting flow velocity was 10±5 cm/s and was directed perpendicularly towards POCIS surface. Triplicate POCIS were analyzed at 0, 1, 3, 6 and 12 hours and at 1, 3, 7, 11, 14, 21 and 28 days. We will present various results depending of molecules such as the duration of linear accumulation phase and sampling rates, sampling repeatability and possible PRCs. As for example, linear accumulation phase for estrogenic hormones seems to be 21 days, since at 28 days the equilibrium regime begins to be reached. For betablockers, linear accumulation phase is shorter: less than 14 days. Sampling rates for this 2 families of compound vary from 0.058 L/d for sotalol to 0.537 L/d for 17-a-estradiol. Concerning the desorption experiments, atenolol-d7 and sotalol-d6 for example show a good potential as PRCs. Indeed, a desorption of 70% for atenolol-d7 and 50% for sotalol-d6 was observed in 24 days.