Suspect screening of natural toxins in surface water reservoirs
[eng] Natural toxins include a multitude of toxic secondary metabolites produced by animals, bacteria, fungi algae, and plants that are generally not intended as environmental contaminants of concern for water quality. However, the presence of anthropogenic waste in the aquatic environment, both wit...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/173967 |
| Acceso en línea: | https://hdl.handle.net/2445/173967 http://hdl.handle.net/10803/670813 |
| Access Level: | acceso abierto |
| Palabra clave: | Espectrometria de masses Cromatografia de líquids Quimiometria Polifenols Toxines Contaminació de l'aigua Mass spectrometry Liquid chromatography Chemometrics Polyphenols Toxins Water pollution |
| Sumario: | [eng] Natural toxins include a multitude of toxic secondary metabolites produced by animals, bacteria, fungi algae, and plants that are generally not intended as environmental contaminants of concern for water quality. However, the presence of anthropogenic waste in the aquatic environment, both with the climate changes and the increase of temperatures, is creating favorable conditions for the development of undesired organisms able to produce natural toxins that sum with other well known anthropogenic pollutants such as pesticides. Among them, natural toxins produced by algae (cyanotoxins), fungi (mycotoxins), and plants (phytotoxins) are the most encountered in surface water environments. Some of them have various toxic effects on the human body. Carcinogenic, dermotoxic, and neurotoxic effects are generally associated with these compounds. Concern about the effects of cyanobacteria on human health has recently grown in many countries. Several human and livestock poisoning events, due to the contamination of water sources (especially lakes) attributed to toxic cyanobacterial bloom, resulted in a dramatic rise of interest in these toxins. Despite that, their presence in surface water was not evenly regulated, and only the highly toxic microcystin-LR was limited at 1 µg/L by the Drinking Water Directive (Consolidated text: Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption) of the World Health Organization. Additionally, studies on their occurrence, chemical persistence, buoyancy, and the algal blooms onset prediction in the environment are still scarce. The environmental risk assessment is difficult and the degree of toxicity into surface water ecosystems is still poorly studied. Their fate in the environment can be described by distribution coefficients such as the octanol-water partitioning (Kow). Other data able to define other distribution and partition parameters are generally obtained using in-silico prediction tools. The identification and quantification are still difficult due to the availability of certified standards. Moreover, these compounds are found mixed with other groups of chemicals at low concentrations. Most of the published methods for their determination are specifically designed to identify a single compound or a group of toxins with similar characteristics, making stressful and time-consuming the process to identify other known-unknown compounds using non-targeted approaches. Since the dangerousness of natural toxins in surface water was recently reported by different authors, valuable data were produced and published to assess their presence and concentration in surface water environments. Several analytical techniques have been reported for their qualitative and quantitative analysis, among them MALDI- TOF/MS, LC-ESI/HRMS, LC-ESI-QqQ are the most used. However, due to the thousands of compounds and their extreme heterogeneity, suspect screening has taken a central role as screening purposes. Over the years, the suspect screening involved the use of in-silico approaches for the tentative identification of natural toxins, becoming one of the preferred methods for the suspect analysis of known-unknown compounds in surface water. It is of primary importance to develop and optimize new methods able to identify natural toxins in a various range of polarities, ranging from the most hydrophobic to the highest water affine. The screening approaches are generally focused on cyanotoxins with no implementations regarding plant toxins and mycotoxins which are very poorly studied in surface water. In this framework, this thesis has aimed to increase the knowledge about natural toxins in surface water. The first part of the study was focused on the recent advances in the detection of natural toxins retrieving a multitude of analytical approaches for their determination in surface and drinking water. Finally, two suspect screening approaches using suspect and target analysis with data- dependent (DDA) and data-independent acquisition (DIA) methods exploring the performances for the determination of multitargeted compounds have been proposed. The tentative compounds have been firstly filtered using a suspect list of 2784 compounds retrieved by different databases available in the literature. The validated methods were then applied to analyse surface water samples coming from different sites in Europe. The presence of natural toxins produced by both plants, fungi, and cyanobacteria is a reality in different water environments showing their presence at low levels also in unexpected zones with not favorable conditions for their production. Almost 80% of the natural toxins encountered were phytotoxins, while a small number of cyanotoxins and mycotoxins have been tentatively identified. The chemical diversity is generally driven by the botanical diversity and the anthropization of the area. Besides, the seasonality and the precipitations are crucial parameters to understand the presence of phytotoxins respect to the cyanotoxins which have been encountered also in unexpected seasons. However, the quantification was not possible for all natural toxins, since only 32 standards were available in our study. In conclusion, the work presented in this thesis, allowed to fill some of the gaps in the analysis of natural toxins presenting two approaches to increase the knowledge about the identification of natural toxins in surface waters. In the future, should be crucial to update the latest determination approaches with the newest quantification strategies to finally implement the suspect screening approaches and reach both determination and quantification of suspect compounds when standards are not available. |
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