Per- and polyfluoroalkyl substances in tropical environments: degradation, dispersion and biomagnification

Todos os Santos Bay, PFAS, Biomagnification, Biomonitoring.

Per- and polyfluoroalkyl substances (PFAS) are widely used in several applications such as surfactants, pesticides, aqueous firefighting foam, etc. These compounds are known worldwide not only for their versatility but also due to their persistent, toxic, and bioaccumulative characteristics. PFAS have been detected in several environmental matrices. Once in the environment, a variety of natural processes (e.g., degradation, dispersion, and biomagnification) drives the pathways, toxicity, and transport of these compounds, however, these natural processes are still poorly understood in tropical environments. The main objective of this thesis was to establish links between the presence of PFAS in biotic and abiotic compartments in tropical environments and the processes that control their distribution. The study was carried out in mangrove soils (Jaguaripe-BA), in ocean waters (Western Tropical Atlantic Ocean), and in the food web of an estuary (Subaé-BA river). Initially, a manipulative degradation experiment of a PFAS-based formicide (i.e., Sulfluramid) was carried out in mangrove soils. The anoxic environment of the mangrove soils acted as a reservoir of contaminants, delaying the export of more toxic degradation products to adjacent areas. In the following study, the occurrence of PFAS along a transect in the western Tropical Atlantic Ocean (TAO) (15oN-23oS) was studied to assess the influence of physical oceanographic processes on the dispersion of these compounds. Different spatial and vertical PFAS profiles were observed along the water column between the TAO zones (i.e., North Atlantic, Ecuador, South Atlantic, and Brazilian coastal waters). Surface currents, coastal upwelling, and the origin of water masses were important factors in explaining the concentrations of PFAS and the vertical distributions of the compounds along the TAO transect. Finally, in the biomagnification study, PFAS were found in all 21 species studied, distributed over 3 trophic levels in the Subaé estuary. The biomagnification of sulfonic perfluorooctane (PFOS), N-Ethyl perfluoro-octane sulfonamide (EtFOSA), and perfluoronanoic acid (PFNA) was also observed. PFAS profiles found in the Subaé estuary indicated the presence of diffuse sources of these compounds. The results showed that the presence and behavior of PFAS in tropical environments are related to several factors including the use of these compounds, their properties and sources the environment, in addition to the chemical and biological natural processes that control the interaction of PFAS with the environment.