Development and application of a screening method for insecticides and fungicides in surface waters by liquid chromatography high resolution mass spectrometry (LC-HRMS)
Modern pesticides, such as many insecticides and fungicides, are widely used among agricultural practices in Switzerland. A total of 39 synthetic insecticides and 74 synthetic fungicides, for a total of 655 tons, are sold in Switzerland annually and applied on agricultural fields between March and October. The interest in insecticides and fungicides has increased in the last years because of the larg applied amount and the potential ecotoxicological environmental impact. However, only few studies have been carried out on catchment scale, only focusing on restricted insecticide and fungicide families, and a broad-compound screening on agricultural applied insecticides and fungicides was never performed in Switzerland. To overcome this lack of knowledge, such a screening was developed and applied in this thesis. Based on a previous study, a substance selection was established among all (in Switzerland) registered insecticides and fungicides, according to applied amount, distribution coefficient between water phase and soil (Koc) and in-soil half-life (DT50soil). For the selected 45 organic, polar to semi-polar substances (19 insecticides, 18 fungicides, 8 metabolites), a screening method using solid phase extraction followed by LC-HRMS was optimized and validated for the targeted compounds. Particularly, the normalized collision energies were optimized, and characteristic MS2 fragments and retention times were determined in order to unequivocally identify the targeted compounds. In addition to this, absolute and relative recoveries and limits of detections in environmental samples were determined. 95% of the analytes showed less than 20% losses during solid phase extraction and evaporation; and the relative recoveries showed to be in the good range (80-120%) for most of the analyzed compounds. Furthermore, the determined limits of quantification (LOQs) were in the low ng/L range; 75% of the compounds showed LOQs below 2.5 ng/L. Moreover, in order to cover the whole insecticides and fungicides palette, an exact mass screening for all registered insecticides and fungicides was performed for the environmental samples using high resolution mass spectrometry. The screening was performed in five selected catchments distributed over the whole Swiss plateau. The five catchments (Surb, Limpach, Salmsacher Aach, Mentue, Furtbach) should be representative for the Swiss agricultural land use, representing the major field crops as well as insecticide and fungicide intensive special crops.
The broad screening verified that most insecticides were detected in generally low concentrations (below 15 ng/L in time-proportional composite samples), however two compounds (diazinon and pirimicarb) exceeded chronic environmental quality standards (EQS). The insecticide group of neonicotinoides was the insecticide family with the most findings, highlighting the environmental importance of this compound class. Fungicides were generally detected with concentrations ranging between 0.3 and 50 ng/L, but several compounds showed higher concentrations (e.g. cyprodinil up to 660 ng/L). In the case of cyprodinil, fenpropidin and spiroxamin, the detected concentrations exceeded the defined EQS values. The Furtbach (characterized by a high vegetable density as well as high urban areas in its catchment) showed the highest insecticide concentrations and the most findings, whereas the Mentue (high density of field crops such as cereals and oilseed rape) was the “cleanest” river with generally the lowest insecticide concentrations. On the other hand, the Surb (highest vineyard density) and the Limpach (highest potato density) showed the highest fungicide concentrations, whereas the Salsacher Aach was the river with the lowest concentrations. Overall, the Furtbach was the catchment showing the highest contamination regarding insecticides and fungicides with the most findings and the highest median values. Intensive crops, such as vegetables, orchards, vineyards and potatoes, showed to be relevant for the insecticide and fungicide load into surface waters. In the suspect screening, 18 additional substances were detected and confirmed in at least one sample.
The combined quantitative and qualitative (targeted and suspect screening) approach successfully covered and evaluated the insecticide and fungicide contamination in Swiss surface waters.