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Indiscriminate use of glyphosate impregnates river epilithic biofilms in southern Brazil ABSTRACT: Epilithic biofilms are communities of microorganisms composed mainly of microbial cells, extracellular polymeric substances from the metabolism of microorganisms, and inorganic materials. Biofilms are a useful tool to assess the impact of anthropic action on aquatic environments including the presence of pesticide residues such as glyphosate. The present work seeks to monitor the occurrence of glyphosate and AMPA residues in epilithic biofilms occurring in a watershed. For this, epilithic biofilm samples were collected in the Guaporé River watershed in the fall and spring seasons of 2016 at eight points. Physicochemical properties of the water and biofilms were determined. The determination of glyphosate and AMPA was performed using an ultra-high performance liquid chromatograph coupled to a tandem mass spectrometer. The concentrations of glyphosate and AMPA detected in epilithic biofilms vary with the season (from 90 to 305 μg kg-1 for glyphosate and from 50 to 240 μg kg-1 for AMPA, in fall and spring, respectively) and are strongly influenced by the amount of herbicide applications. Protected locations and those with poor access not demonstrate the presence of these contaminants. In the other seven points of the Guaporé River watershed, glyphosate was detected in concentrations ranging from 10 to 305 μg kg-1 , and concentrations of AMPA ranged from 50 to 670 μg kg-1. An overview of the contamination in the Guaporé watershed shows that the most affected areas are located in the Marau sub-watershed, which are strongly influenced by the presence of the city of Marau. This confirms the indiscriminate use of glyphosate in the urban area (weed control, domestic gardens and horticulture) and constitutes a problem for human and animal health. The results showed that biofilms can accumulate glyphosate resulting from the contamination of water courses and are sensitive to the sources of pollution and pesticides present in rivers.

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Southern Brazil is an agricultural region that is experiencing strong growth in both cereal and animal production. The intensification of agricultural practices, as well as the growing urbanization in this region, also generates strong anthropogenic pressures on the aquatic environment. In Brazil, the lack of sewage treatment and the wide use of waste (liquid or solid) for the fertilization of soils are likely to favor the spread of pharmaceuticals in the surrounding environment. Considering the benefits of the determination of anthropogenic markers in the environment, the study aimed to monitor the presence of carbamazepine (CBZ) and sucralose (SCR) in the Guaporé River, representative of a southern Brazilian rural watershed. Both carbamazepine and sucralose are measured in water by polar organic chemical integrative samplers (POCIS) (CBZ: lower than limit of detection (< LOD) to 746 μg g−1 and SCR: 

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