The presence of xenobiotics in the aquatic environment has drawn scientific concern due to possible detrimental effects on the ecosystems. With EU Decision 2015/495, a first Watch list of compounds that could potentially represent a threat for the environment was created, with the objective of gathering high quality monitoring data and support their prioritization. Literature data are still very scarce and the presence of many of the compounds has not been investigated thoroughly. In this study, all the 17 compounds of the EU Watch list 2015/495 were monitored in 14 sampling locations, comprised of freshwater and, for the first time, wastewater. The study was carried out in the Ebro delta, in the north east of Spain, a representative and crucial area not only for its environmental and naturalistic significance, but also for Spain’s productivity, especially as regards rice agriculture. Results show that contamination originates both from wastewater treatment plants (WWTPs) and agricultural activities. High levels of pharmaceuticals were detected in wastewater, with azithromycin and diclofenac present at mean concentrations of 1.65 μg/L and 636 ng/L respectively. In freshwater samples, besides antibiotics and diclofenac, substantial contamination by pesticides was reported, with oxadiazon reaching up to 591 ng/L and imidacloprid being present in 93% of samples. Moreover, the study provided insight into the origin of the selected contaminants. The removal of the studied micropollutants in WWTPs was low to moderate. The assessment of risk quotients, calculated based on the available PNECs, demonstrated that the concentrations recorded for these compounds may pose a significant risk in most sampling sites.

An analytical methodology using automatic thermal desorption (ATD) and GC/MS was developed for the determination of 28 pesticides of different chemical classes (dichlobenil, carbofuran, trifluralin, clopyralid, carbaryl, flazasulfuron, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, cyprodinil, bromoxynil, fluroxypyr, oxadiazon, myclobutanil, buprofezin, picloram, trinexapac-p-ethyl, ioxynil, diflufenican, tebuconazole, bifenthrin, isoxaben, alphacypermethrin, fenoxaprop and tau-fluvalinate) commonly used in nonagricultural areas in atmospheric samples. This methodology was developed to evaluate the indoor and outdoor atmospheric contamination by nonagricultural pesticides. Pesticides were sampled passive sampling tubes containing Tenax® adsorbent. Since most of these pesticides are polar (clopyralid, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, bromoxynil, fluroxypyr, picloram, trinexapac-p-ethyl and ioxynil), a derivatisation step is required. For this purpose, a silylation step using N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MtBSTFA) was added before thermal desorption. This agent was chosen since it delivers very specific ions on electronic impact (m/z = M-57). This method was established with special consideration for optimal thermal desorption conditions (desorption temperature, desorb flow and duration; trap heating duration and flow; outlet split), linear ranges, limits of quantification and detection which varied from 0.005 to 10 ng and from 0.001 to 2.5 ng, respectively, for an uncertainty varied from 8 to 30 %. The method was applied in situ to the analysis of passive tubes exposed during herbicide application to an industrial site in east of France.