Arsenic immobilization and transformation by biofilms developed over riverbed sediments

Biofilms are complex communities of autotrophic and heterotrophic organisms immersed in a matrix mainly composed by polysaccharides. They are ubiquitous over wet surfaces and provide protection for microorganisms. In river environments there is evidence that biofilms play an important role in the biogeochemical cycles of nutrients and contaminants. The objective of this work is to evaluate the effect of the fluvial epipsammic biofilm on the retention and transformation of As and to understand its interaction with this metalloid in the Anllóns River (Galicia, NW Spain), where As pollution has been observed. The results revealed that biofilms play a key role in As biogeochemistry in freshwater environments, favouring As immobilization, especially in environments where As and P occur simultaneously, and promoting As detoxification by inhibiting the reduction of AsV to AsIII and methylating inorganic As