Uptake of Per- and Polyfluoroalkyl Substances (PFAS) by Plants

Bc. Saša Žůrková

Master's thesis

Abstract:

Currently, more and more attention is paid to a group of chemicals called per- and polyfluorinated substances (PFAS). These substances include a wide variety of synthetic compounds that are widely used in industry due to their exceptional properties. However, their extensive use and resistance to degradation have led to their widespread presence in the environment. PFAS have been found in soil, water, or air. Through contaminated water and soil, PFAS have penetrated plant roots to the fruits or seeds of cultivated crops, where they become part of the food chain. This contamination poses a potential health risk to the human population and ecosystems. Concerns about the toxicity and persistence of PFAS have recently led to efforts to prevent PFAS from contaminating the food chain. Therefore, some representatives of the PFAS group are gradually being restricted. It is an effort to prevent PFAS, which have already entered the environment, from escaping into water and subsequently into plants. The use of biochar, which can sorb contaminants on its surface and also improve soil properties, may potentially be suitable for PFAS sorption in soil. At the same time, it is also possible to use waste materials (wood, sewage sludge, agricultural residues, food waste) to produce biochar, which represents a sustainable cycle of dealing with these materials. In this work, the effect of biochar on the uptake of PFAS by Cucurbita pepo L., a variety of zucchini, was investigated in the pot experiment. The presence or absence of biochar made from sewage sludge or wood was chosen as a factor. The plants were irrigated with 5 representatives of PFAS, namely HFPO-DA, HFPO-TA, HFPO-TeA, PFOA, and PFOS, at a concentration of 10 µg/L for 41 days. The chosen concentration of PFAS in the irrigation water was consulted with the scientific literature. A total of 78.15 µg of each contaminant was added to each plant. Subsequently, the amount of contaminants that got into the fruits was evaluated, and their potential risk when consumed by an adult and a child was estimated. No statistically significant difference was observed between the amount of contaminants in fruits grown on variants with and without biochar. Contaminants were found in the fruits of plants grown on all variants treated with the PFAS solution. HFPO-DA was the most detected in fruits across the variants, followed by PFOA and PFOS. Contaminants HFPO-TeA and HFPO-TA were the least detected in fruits. The reason for the different uptake of contaminants by plants could be the different molecular weights and structure of the contaminants. The risk for an adult would be the consumption of 352 ng of PFAS per week, for a child the risk would be the consumption of 88 ng of PFAS per week. This risk dose would be reached by consuming 143 to 306 g of zucchini, depending on the variant. This represents a real consumable dose during the week, as 300 grams is the average weight of a zucchini fruit. For a child, the risk dose would be reached by consuming 36 to 77 g of zucchini, depending on the variant, which again represents a realistic dose that a child could consume in a week.

Keywords

PFOA, PFOS, accumulation, zucchini, biochar

Language used: English

Date on which the thesis was submitted / produced: 22. 4. 2024

Thesis defence

• Date of defence: 21. 5. 2024
• Supervisor: Ing. Filip Mercl, Ph.D.
• Reader: Catarina Cruzeiro, externi

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Master programme:
Waste Technology