Department Environmental Chemistry

Starting date: Late summer/autumn 2024

Description / Project:

Complex mixtures of trace organic contaminants (TrOCs) resulting from human activities and released into the environment pose a significant threat to ecosystems. Microbial biotransformation holds potential for removing these contaminants, but there is limited mechanistic understanding of the factors driving this process. Activated sludge treatment in wastewater treatment plants (WWTPs) serves as a partial barrier to prevent TrOCs from entering the environment, yet treatment efficiency varies among compounds and facilities.

In this project, we are first determining the biotransformation capacity of activated sludge for 200 TrOCs, including common pharmaceuticals and pesticides. To achieve this, we conduct a 72-hour lab batch assay using activated sludge from a typical wastewater treatment plant. We spike the sludge with our target TrOCs and measure the concentration over time using HPLC-MS to determine the rate constants.

Further, we aim to assess and characterize the transformation products (TPs) formed during the biotransformation experiment, using Compound Discoverer software on our MS data. We will then explore the agreement of the found TPs with predicted transformation pathways based on enviPath.org.

Methods:

Preparation and execution of a four day batch assay with activated sludge in the lab (3 weeks). Measuring with automated HPLC-MS, including method development (3-4 weeks). Analytic evaluation of the MS-data using Skyline and R (2 weeks). Assessment and characterization of TPs using Compound Discoverer.

What we expect from you:
Students with specific interest in (environmental) analytic chemistry. No prior knowledge of Skyline, Compound Discoverer, or R is required.

Supervisor / Contact:
Prof. Kathrin Fenner / Martina Kalt

Short description:

Historic investigations of underwater munitions disposal in Swiss lakes and shooting ranges in the Swiss Alps point to substantial chemical  contamination of soils, sediments, and water through military activities. However, munitions compounds including nitroaromatic, nitramine and nitrate ester explosives and their transformation products have been detected rather infrequently in field campaigns and led to the conclusion of a negligible environmental problem. 

In this project, which we carry out in collaboration with the Swiss Federal Office for Defence Procurement (armasuisse), we  will revisit this interpretation and test the hypothesis that limited sampling strategies and standardized but insensitive analytical methods could be the reason for overlooked munitions-related contamination.

Supervision: Thomas Hofstetter, Chloé Udressy

Starting date: Fall 2024

Short description:

Per- and polyfluoroalkyl substances (PFASs) are a wide-ranging group of persistent organic pollutants characterized by the presence of high strength carbon-fluorine bonds with widespread use in industry and consumer products. PFAS pollution is of global concern due to its ubiquitous occurrence in the environment, the potential for some compounds to bioaccumulate, and toxicological effects from chronic exposure at trace concentrations. Yet, much is still unknown about the thousands of different PFAS structures identified to date. Low PFAS threshold values have been set in the EU drinking water directive, and freshwater quality standards are under consideration. Wastewater treatment plants are an important point source for PFASs into aquatic systems, aggregating a variety of potential industrial and municipal sources.

The aim of the master thesis is to determine the occurrence PFASs in Swiss wastewater treatment plants using a combination of targeted analysis and non-targeted screening techniques. The student will gain hands-on experience working with state-of-the-art LC-HRMS (high-resolution mass spectrometry) analytical techniques using automated high-throughput online solid-phase extraction sample preparation. They will develop skills quantitate PFASs in complex environmental matrices (wastewater and sludge). Additionally, they will analyse data-intensive high-resolution MS data, working to elucidate and confirm suspected compounds of interest. These results help develop a quantitative understanding of the fate and transport of PFASs that enter and leave the wastewater treatment process. Ultimately, this project will help stakeholders identify important PFASs and potential sources in waste streams as well as provide crucial data to guide national use and discharge limits.

Keywords: PFAS, LC-HRMS, wastewater treatment

Supervisors: Steven Chow, Christa McArdell, Juliane Hollender, Heinz Singer

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.
 

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