In order to obtain a more comprehensive picture of the contamination of Swiss groundwater with polar organic micropollutants...
[[ element.title ]]
[[ element.title ]]
Identification of LC-HRMS nontarget signals in groundwater after source related prioritization
Groundwater is a major drinking water resource but its quality with regard to organic micropollutants (MPs) is insufficiently assessed. Therefore, we aimed to investigate Swiss groundwater more comprehensively using liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS). First, samples from 60 sites were classified as having high or low urban or agricultural influence based on 498 target compounds associated with either urban or agricultural sources. Second, all LC-HRMS signals were related to their potential origin (urban, urban and agricultural, agricultural, or not classifiable) based on their occurrence and intensity in the classified samples. A considerable fraction of estimated concentrations associated with urban and/or agricultural sources could not be explained by the 139 detected targets. The most intense nontarget signals were automatically annotated with structure proposals using MetFrag and SIRIUS4/CSI:FingerID with a list of >988,000 compounds. Additionally, suspect screening was performed for 1162 compounds with predicted high groundwater mobility from primarily urban sources. Finally, 12 nontargets and 11 suspects were identified unequivocally (Level 1), while 17 further compounds were tentatively identified (Level 2a/3). amongst these were 13 pollutants thus far not reported in groundwater, such as: the industrial chemicals 2,5-dichlorobenzenesulfonic acid (19 detections, up to 100 ng L-1), phenylphosponic acid (10 detections, up to 50 ng L-1), triisopropanolamine borate (2 detections, up to 40 ng L-1), O-des[2-aminoethyl]-O-carboxymethyl dehydroamlodipine, a transformation product (TP) of the blood pressure regulator amlodipine (17 detections), and the TP SYN542490 of the herbicide metolachlor (Level 3, 33 detections, estimated concentrations up to 100–500 ng L-1). One monitoring site was far more contaminated than other sites based on estimated total concentrations of potential MPs, which was supported by the elucidation of site-specific nontarget signals such as the carcinogen chlorendic acid, and various naphthalenedisulfonic acids. Many compounds remained unknown, but overall, source related prioritisation proved an effective approach to support identification of compounds in groundwater.
Benchmarking of the quantification approaches for the non-targeted screening of micropollutants and their transformation products in groundwater
A wide range of micropollutants can be monitored with non-targeted screening; however, the quantification of the newly discovered compounds is challenging. Transformation products (TPs) are especially problematic because analytical standards are rarely available. Here, we compared three quantification approaches for non-target compounds that do not require the availability of analytical standards. The comparison is based on a unique set of concentration data for 341 compounds, mainly pesticides, pharmaceuticals, and their TPs in 31 groundwater samples from Switzerland. The best accuracy was observed with the predicted ionization efficiency-based quantification, the mean error of concentration prediction for the groundwater samples was a factor of 1.8, and all of the 74 micropollutants detected in the groundwater were quantified with an error less than a factor of 10. The quantification of TPs with the parent compounds had significantly lower accuracy (mean error of a factor of 3.8) and could only be applied to a fraction of the detected compounds, while the mean performance (mean error of a factor of 3.2) of the closest eluting standard approach was similar to the parent compound approach.
Kruve, A.; Kiefer, K.; Hollender, J. (2021) Benchmarking of the quantification approaches for the non-targeted screening of micropollutants and their transformation products in groundwater, Analytical and Bioanalytical Chemistry, 413, 1549-1559, doi:10.1007/s00216-020-03109-2, Institutional Repository
Chlorothalonil transformation products in drinking water resources: widespread and challenging to abate
Chlorothalonil, a fungicide applied for decades worldwide, has recently been banned in the European Union (EU) and Switzerland due to its carcinogenicity and the presence of potentially toxic transformation products (TPs) in groundwater. The spread and concentration range of chlorothalonil TPs in different drinking water resources was examined (73 groundwater and four surface water samples mainly from Switzerland). The chlorothalonil sulfonic acid TPs (R471811, R419492, R417888) occurred more frequently and at higher concentrations (detected in 65-100% of the samples, ≤2200 ngL-1) than the phenolic TPs (SYN507900, SYN548580, R611968; detected in 10-30% of the samples, ≤130 ngL-1). The TP R471811 was found in all samples and even in 52% of the samples above 100 ngL-1, the drinking water standard in Switzerland and other European countries. Therefore, the abatement of chlorothalonil TPs was investigated in laboratory and pilot-scale experiments and along the treatment train of various water works, comprising aquifer recharge, UV disinfection, ozonation, advanced oxidation processes (AOPs), activated carbon treatment, and reverse osmosis. The phenolic TPs can be abated during ozonation (second order rate constant kO3 ∼104 M-1s-1) and by reaction with hydroxyl radicals (OH) in AOPs (kOH ∼109 M-1s-1). In contrast, the sulfonic acid TPs, which occurred in higher concentrations in drinking water resources, react only very slowly with ozone (kO3 <0.04 M-1s-1) and OH (kOH <5.0 × 107 M-1s-1) and therefore persist in ozonation and OH-based AOPs. Activated carbon retained the very polar TP R471811 only up to a specific throughput of 25 m3kg-1 (20% breakthrough), similarly to the X-ray contrast agent diatrizoic acid. Reverse osmosis was capable of removing all chlorothalonil TPs by ≥98%.
Kiefer, K.; Bader, T.; Minas, N.; Salhi, E.; Janssen, E. M. -L.; von Gunten, U.; Hollender, J. (2020) Chlorothalonil transformation products in drinking water resources: widespread and challenging to abate, Water Research, 183, 116066 (11 pp.), doi:10.1016/j.watres.2020.116066, Institutional Repository
Pflanzenschutzmittel-Metaboliten im Grundwasser. Ergebnisse aus der NAQUA-Pilotstudie "Screening"
Mit Screening-Methoden wurden ausgewählte Grundwasser-Proben im Rahmen einer Pilotstudie der Nationalen Grundwasserbeobachtung NAQUA auf mehrere hundert Wirkstoffe und Metaboliten von Pflanzenschutzmitteln (PSM) sowie weitere Mikroverunreinigungen untersucht. Es galt zu prüfen, ob und welche «neuen» PSM-Wirkstoffe oder -Metaboliten die Grundwasserqualität beeinträchtigen und in das NAQUA-Langzeitmonitoring integriert werden sollten. Mehr als 20 PSM-Metaboliten wurden erstmals im Grundwasser nachgewiesen. Diejenigen des Fungizids Chlorthalonil waren aufgrund hoher Konzentrationen und weiter Verbreitung besonders auffällig.
Kiefer, K.; Müller, A.; Singer, H.; Hollender, J.; Reinhardt, M. (2019) Pflanzenschutzmittel-Metaboliten im Grundwasser. Ergebnisse aus der NAQUA-Pilotstudie "Screening", Aqua & Gas, 99(11), 14-23, Institutional Repository
New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMS
Groundwater is a major drinking water resource, but its quality is threatened by a broad variety of anthropogenic micropollutants (MPs), originating from agriculture, industry, or households, and undergoing various transformation processes during subsurface passage. To determine a worst-case impact of pesticide application in agriculture on groundwater quality, a target and suspect screening for more than 300 pesticides and more than 1100 pesticide transformation products (TPs) was performed in 31 Swiss groundwater samples which predominantly originated from areas with intensive agriculture. To assess additional urban contamination sources, more than 250 common urban MPs were quantified. Most of the screened pesticide TPs were experimentally observed by the pesticide producers within the European pesticide registration. To cover very polar pesticide TPs, vacuum-assisted evaporative concentration was used for enrichment, followed by liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS). Based on intensity, isotope pattern, retention time, and in silico fragmentation, the suspect hits were prioritised and verified. We identified 22 suspects unequivocally and five tentatively; 13 TPs are reported here for the first time to be detected in groundwater. In 13 out of 31 groundwater samples, the total concentration of the 20 identified and quantified suspects (1 pesticide and 19 pesticide TPs) exceeded the total concentration of the 519 targets (236 pesticides and TPs; 283 urban MPs) for which we screened. Pesticide TPs had higher concentrations than the parent pesticides, illustrating their importance for groundwater quality. The newly identified very polar chlorothalonil TP R471811 was the only compound detected in all samples with concentrations ranging from 3 to 2700 ng/L. Agricultural MP concentration and detection frequency correlated with agricultural land use in the catchment, except for aquifers, where protective top layers reduced MP transport from the surface. In contrast to agricultural MPs, urban MPs displayed almost no correlation with land use. The dominating entry pathway of urban MPs was river bank filtration.
Kiefer, K.; Müller, A.; Singer, H.; Hollender, J. (2019) New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMS, Water Research, 165, 114972 (11 pp.), doi:10.1016/j.watres.2019.114972, Institutional Repository