An innovative receiving phase for passive sampling of polar and apolar pesticides in surface waters
Développement d'une phase réceptrice innovante pour l'échantillonnage passif de pesticides dans les eaux de surface
Résumé
Silicone rubber (SR) has been successfully implemented as a receiving phase in various passive samplers (MESCO, Passive SBSE and silicone rod/sheet). Indeed, SR is mechanically resistant, insoluble in common solvents used for compound desorption, and enable a thermal desorption at high temperature. Nevertheless, SR is an hydrophobic material which permit mainly enrichment of apolar organic compounds (log Kow > 3) from water (organochlorine pesticides, PAHs, PCBs, etc.). To remedy this lack of measurement representativity, the use of an other passive sampler in co-deployement for polar organics, as Polar Organic Chemical Integrative Sampler (POCIS), is the stategy preferred. This work aimed at testing the affinity of an innovative material for more polar organic compounds using passive samplers with a single receiving phase. In this way, a Polar/Apolar Composite Silicone Rubber (PACSiR) was developed for sorption of a wide range of organics compounds. First, this innovative composite material was assessed in laboratory for pesticides sorption whith a large range of physico-chemical properties. Then, PACSiR was shaped and calibrated as a passive sampler in laboratory, to be finally applied for the monitoring of several pesticides in surface waters. Extraction recoveries determined experimentally for 22 pesticides were similar or higher for all pesticides than for SR. The enhancement of extraction performances is the highest for polar pesticides, with log Kow below 3, which are poorly sorbed on SR. Kinetics of uptake of pesticides in calibration system were mainly described by a pseudo-linear equation model for 14 days exposure. Sampling rate and partition coeficient were determined for calculation of time weighted average concentration (TWAC). Sampling rates for PACSiR passive sampler were 1.3 to 12.5 higher than for SR depending on the pesticide. Consequently, PACSiR enable to reach lower LOQ than SR for polar pesticides. Finally, results of field exposition of passive samplers in rivers were compared with grab sampling to access the occurrence of pesticides and to estimate the TWACs during field exposition. This study demonstrated that the PACSiR is a sensitive receiving phase for pesticides which can greatly improved sorption properties comparared to SR and permitted to reach lower LOQ for polar pesticides. Further experimental investigations on accumulation of other organic compounds will be carried out (hormones, pharmaceuticals, PAHs and PCBs).