Suggestion of a performance reference compound for the pocis and application for quantitative determination of polar herbicides in freshwaters
Proposition d'un composé de référence et de performance pour les POCIS et son application pour la quantification d'herbicides polaires dans les eaux de surface
Résumé
In this work, we performed an in situ calibration of the Polar Organic Chemicals Integrative Sampler (POCIS) [1] and suggested the use of a performance reference compound (PRC). The PRC approach was initially developed for the Semipermeable Membrane Devices (SPMDs) [2]. PRCs are (analytically) non-interfering compounds with moderate to relatively high fugacity from SPMDs, which are added to the receiving phase prior to the field deployment. The determination of the dissipation rates of these compounds is essential for correcting the effects of several environmental parameters (e.g. biofouling, flow velocity, temperature, etc.) on the sampling rates. Multiple PRCs are generally needed to cover the wide range of environmental exposure conditions and for this purpose we determined the desorptions of several herbicides from the POCIS sorbent. The atrazine-desisopropyl (DIA) was characterized by a really high elimination kinetic constant in comparison with the other compounds. Thus, we suggested the use of the DIA as unique PRC and we investigated its in situ dissipation kinetic rate. A field validation of the PRC approach was performed with the comparison between the time-weighted average (TWA) concentrations estimated with either the POCIS or with an automated sampler. The POCIS estimates were dramatically lower than the concentrations obtained with the automated sampler whereas the corrected values (with the PRC use) were really closer. Such a result showed that the use of the DIA as unique PRC might give an acceptable correction of the sampling rates and a good estimate of the TWA concentrations of several polar herbicides such as triazines, phenylureas and chloroacetanilides.