Pollutants

The European Decision EU 2015/495 included three steroidal estrogens, estrone, 17β-estradiol and 17α-ethinyl estradiol, in the "watch-list" of the Water Framework Directive (WFD). As consequence, these substances have to be chemically monitored at the level of their environmental quality standards, which can be challenging. This project aimed to identify reliable effect-based methods (EBMs) for screening of endocrine disrupting compounds, to harmonise monitoring and data interpretation methods, and to contribute to the current WFD review process. Water and wastewater samples were collected across Europe and analysed using chemical analyses and EBMs. The results showed that 17β-estradiol equivalents were comparable among methods, while results can vary between methods based on the relative potencies for individual substances. Further, derived 17β-estradiol equivalents were highly correlated with LC-MS/MS analyses. This study shows that the inclusion of effect-based screening methods into monitoring programmes for estrogens in surface waterbodies would be a valuable complement to chemical analysis.

The presence of antibiotics in treated wastewater and consequently in surface and groundwater resources raises concerns about the formation and spread of antibiotic resistance. Improving the removal of antibiotics during wastewater treatment therefore is a prime objective of environmental engineering. Here we obtained a detailed picture of the fate of sulfonamide antibiotics during activated sludge treatment using a combination of analytical methods. We show that pterin-sulfonamide conjugates, which are formed when sulfonamides interact with their target enzyme to inhibit folic acid synthesis, represent a major biotransformation route for sulfonamides in laboratory batch experiments with activated sludge. The same major conjugates were also present in the effluents of nine Swiss wastewater treatment plants. The demonstration of this biotransformation route, which is related to bacterial growth, helps explain seemingly contradictory views on optimal conditions for sulfonamide removal. More importantly, since pterinsulfonamide conjugates show retained antibiotic activity, our findings suggest that risk from exposure to sulfonamide antibiotics may be less reduced during wastewater treatment than previously assumed. Our results thus further emphasize the inadequacy of focusing on parent compound removal and the importance of investigating biotransformation pathways and removal of bioactivity to properly assess contaminant removal in both engineered and natural systems.

Extracellular enzymes are major drivers of biogeochemical nutrient and carbon cycling in surface water. While photoinactivation is regarded as a major inactivation process of these enzymes, the underlying molecular changes have received little attention. This study demonstrate how light exposure leads to a rapid loss of phosphatase, aminopeptidase and glucosidase activities of biofilm samples and model enzymes. Here, an optimized proteomics approach allowed simultaneous observation of inactivation and molecular changes. Site-specific fingerprints of degradation kinetics have been generated and visualized in the three-dimensional proteins. Oxidation of tryptophan, the chromophoric target, initiated secondary reactions. Evidence was obtained that tyrosine residues act as intramolecular antioxidants, reflected in decelerated decay of tryptophan- and enhanced decay of tyrosine-containing peptides. In addition, subsequent methionine oxidation and disulfide reduction contribute to heterogeneous photodamage. The proximity to tryptophan residues explains >95% of the photodamage across the protein structures. The presence of redox-active organic matter or a model antioxidant in solution quenched not only photoinactivation and tryptophan oxidation but also all subsequent damage. The developed analytical approach can be applied to other research questions in environmental sciences where site-specific damage in a protein is essential.

Silver nanoparticles (AgNPs) are widely used as antimicrobial agents. During their life cycle, some of theAgNPs are released into natural environments, where chronic exposure to them can continue to causeharmful effects on microorganisms. However, very little is known about long-term impacts on importantecosystem compartments such as periphyton, a microbial community of algae and bacteria that coverssubmerged surfaces and contributes importantly to primary production and other ecosystem processes.Thus, the present study focused on assessing the accumulation of citrate-coated AgNPs and dissolved Ag⁺in periphyton and on testing chronic effects on periphyton community structure and a range of functionalendpoints. Stream periphyton grown in microcosms was exposed to 0.1, 1 and 10 μM AgNPs and 0.1 μMAgNO₃ (a source of Ag⁺ ions) for up to 21 days. By that time, 84 to 98% of the total available silver in themicrocosms was strongly associated with the periphyton. The strongest and broadest impacts on functionalendpoints were observed at the highest AgNP concentration (10 μM), which caused a decline in algalprimary production and microbial respiration but a simultaneous increase in bacterial secondary productionand total biomass accrual. The community structure of both phototrophs and heterotrophs was alsochanged. Overall, our results reveal that periphyton strongly accumulates AgNPs, leading to a shift of communitymetabolism towards heterotrophy, with possible consequences for trophic transfer in aquatic foodwebs exposed to Ag contamination.