Department Environmental Chemistry

Open master thesis topics 2023

Active transport pathways of (cationic) psychoactive drugs in aquatic invertebrates

Start:
Ideally, we aim for a start in October 2023. However, the start of the project is flexible.

Background:

Aquatic organisms are exposed to a large variety of organic contaminants, including psychoactive drugs such as anti-depressants. Potential adverse effects caused by such compounds are driven by the internal concentration at the target site (i.e., specific receptors) in the organism. Toxicokinetic (TK) processes such as uptake, internal distribution, biotransformation, and elimination determine these internal concentrations. Our recent observations indicate that for (cationic) psychoactive drugs such as citalopram, transporter facilitated active uptake may be an important toxicokinetic process which results in higher bioaccumulation potential under field conditions (i.e. lower exposure concentrations, higher temperatures) than under laboratory conditions.  

Study goal:

The goal of this project is to investigate the influence of active transport pathways of psychoactive drugs (i.e. citalopram, amphetamine, and propranolol) on toxicokinetics in the aquatic invertebrate key species Gammarus pulex and Hyalella azteca. We are working with aquatic invertebrates as they play an important role in aquatic food webs by linking detritus with higher trophic levels such as fish. Furthermore, this research supports the establishment of new test guidelines using invertebrates as alternative to regulatory required bioaccumulation studies with fish and thus improve animal welfare.

Tasks:

This project will start by performing uptake and elimination experiments accompanied with studies on transporters including saturation and inhibition assays. Samples will be analysed by an automated solid phase extraction system coupled with liquid-chromatography and high-resolution tandem mass spectrometry (online-SPE LC-HRMS/MS). Furthermore, biotransformation products will be identified by suspect screening. The obtained results will be evaluated by using toxicokinetic modelling.

Prerequisites:

We are looking for a biology, chemistry or environmental science student, or any other natural science student with some laboratory experience and who is motivated to learn more about environmental chemistry and ecotoxicology.

If you are interested please contact Juliane Hollender or Johannes Raths.
 

 

Identification of Human Synthetic Antioxidant Metabolites in Wastewater

Possible starting date: February 2023 or later

Description:

Synthetic antioxidants (SAOs) are chemicals of emerging concern, since they are ubiquitously present in everyday life products, such as plastics. With the outbreak of the Covid-19 pandemic, they are of even more interest, as they are contained in facemasks. Consequently, it is expected that human take them up. Upon entrance into the human body, metabolization is expected, in order to increase their polarity and to enhance their excretion. After excretion, they end up in wastewater treatment plants, whose wastewater can be analyzed after sample preparation with high-performance liquid chromatography coupled to high resolution tandem mass spectrometry (HPLC-HRMS/MS).

As their name says, SAOs possess antioxidant characteristics, as they can undergo reactions with radicals, to prevent oxidation of the product they protect. The resulting oxidized products may be identical to the human metabolites, as many biotransformation reactions are of oxidative nature. The aim of this project is to identify human metabolites of SAOs in wastewater water and thereby indirectly human exposure. In a second step, the goal is to develop an experiment to identify oxidation products of these compounds in order to ensure that the identified metabolites exclusively originate from human metabolism.

This project will start with a data analysis part of previously acquired HPLC-HRMS/MS data on wastewater samples. Several software tools will be used for screening SAO. The results will be used in the second part to design and execute an experiment for the identification of oxidized products followed by hands on HPLC-HRMS/MS measurements.

We are looking for a chemistry or environmental science student with some background in biogeochemistry or any other natural science student with some laboratory experience and who is motivated to learn more about environmental chemistry. The start of the project is flexible. If you are interested, please contact

Corina Meyer or

Prof. Dr. Juliane Hollender

 

Environmental behavior and analytical chemistry of natural toxins

Starting date to be discussed

Natural toxins present a threat to water quality. Those from cyanobacteria are directly released into the surface waters when the cells die. Cyanobacterial blooms are increasing in frequency and intensity also related to climate change. The World Health Organization recognises few liver toxins and neurotoxins produced by cyanobacteria. But more than 2000 bioactive metabolites from cyanobacteria are known to date. Why have we not studied them yet? Only 1% of these compounds are commercially available, which makes it very challenging to study them. We work with laboratory cultures and field samples of cyanobacteria to develop analytical tools, assess photochemical and biotransformation and conduct monitoring in Swiss lakes. We are interested in prioritizing abundant and persistent metabolites to then study their abatement during drinking water treatment and their toxicological and ecological roles.

Within this topic we have several opportunities for a Master thesis for example on:

  1. Environmental fate processes of cyanotoxins
  2. Analytical tools to identify cyanopeptides by mass spectrometry
  3. Cyanotoxins and bioactive metabolites in Swiss Lakes
  4. Interaction of herbivores with cyanobacterial toxins in the Swiss Alps

The common aims of these projects are to become familiar with the world of cyanopeptides and to gain experience identifying metabolites by mass spectrometry.

Depending on the specific focus of each project, you will also learn how to set up and run photochemical or biotransformation experiments to assess half-lives of cyanopeptide under simulated environmental conditions. The more analytical oriented projects will dive deeper into the identification of cyanopeptides by analyzing measured and predicted mass spectra by various software tools, which are the analytical fingerprint of a molecule. The projects on herbivores interaction will work with food choice experiments to explore avoidance and tolerance behavior and study bioaccumulation with toxicokinetic experiments.

For a successful thesis, you should 

  • have strong interest in environmental and analytical chemistry
  • have first experience (practical courses, internships) regarding laboratory work
  • be proficient in speaking and writing in English
  • be enthusiastic and motivated

Keywords: cyanobacteria, toxins, mass spectrometry

Advisors: Dr. Elisabeth (Lilli) Janssen

Please contact:
elisabeth.janssen@eawag.ch

Evaluation of organic micropollutant abatement in advanced wastewater treatment

Starting date: to be discussed

Short description:

The presence of micropollutants in treated wastewater is of increasing concern, due to their release and potential impacts to organisms in receiving waters and drinking water resources downstream of wastewater treatment plants (WWTPs). The new Swiss water protection act implemented as of January 2016 aims at reducing the concentrations of these compounds through advanced wastewater treatment. Ozonation and treatment with powdered activated carbon (PAC) were originally the methods of choice to reach a sufficient abatement of micropollutants. The application of granular activated carbon (GAC) filtration and the combination of ozonation with activated carbon treatment were only recently evaluated and can also fulfill the requirements of the new water protection act. Installation of advanced wastewater treatment is successfully ongoing, however, there are open questions regarding the abatement of micropollutants during GAC filtration, the use of sustainable PAC materials, and also on the formation of ozonation transformation products (OTPs) and their abatement during post-treatment with GAC or sand filtration.

In the master thesis, LC-MS/MS (TripleQuad or high-resolution mass spectrometry) measurements either on target micropollutants or on suspect OTPs will be done to answer specific open questions. This is an interdisciplinary project in the two departments environmental chemistry & process engineering. Contact us if you are interested in this project and have a background on environmental chemical analysis.

Keywords: LC-MS/MS, advanced wastewater treatment

Supervisors: Christa McArdell, Marc Böhler

Assessing ecosystem health through isotopic fingerprints of the phosphorus metabolism

Understanding the impact of human activities on the metabolic state of soil and aquatic environments is of paramount importance to implement measures for maintaining ecosystem services and sustainable access to food, water, and energy. In this project, we explore variations of natural abundance oxygen isotope ratios in phosphate as a new proxy for the holistic assessment of metabolic activity. Given the crucial importance of phosphoryl transfer reactions in fundamental biological processes, we hypothesize that changes in natural abundance 18O/16O ratios in phosphate also reflect shifts in the metabolic state of the environmental microbiome as a response to anthropogenic impact.

Master students will have the opportunity to work in two complementary areas during their master thesis. First, students will implement new sample preparation procedures for measurements of 18O/16O ratios in phosphate by high-resolution mass spectrometry. Subsequently, these methods will be applied to quantify the oxygen isotope fractionation resulting from activity of the most important enzymes involved in the phosphorus metabolism of selected microorganisms.

Supervision: Thomas Hofstetter (thomas.hofstetter@eawag.ch), Nora Bernet (nora.bernet@eawag.ch)