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The Guadiana Basin is a transnational basin, presenting historical contamination with potentially toxic metals (PTM), which origin can be both natural and anthropogenic. This study explores the use of a set of observational, chemical and ecotoxicological assays with Heterocypris incongruens, Vibrio fischeri, Pseudokirchneriella subcapitata, Thamnocephalus platyurus, identifying the most sensitive to be included in a toolbox to analyze the quality of freshwater sediments related to this type of contamination. The study included the analysis of a reservoir and streams sediments of Guadiana basin, in two consecutive years with different climate conditions 2017 (dry year) and 2018 (normal year). The results showed high chemical variability along the basin, with greater contamination with PTM in the reservoir sediments. The calculated Enrichment Factors (EF) indicated high anthropogenic contamination by Cd, followed by Pb (EF > 1.5). The geoaccumulation index (Igeo) revealed that the sediments were severely polluted with Cd, and slightly polluted with Pb and Cu, inducing a higher sublethal toxicity to Heterocypris incongruens. Among the parameters evaluated, and after the use of multivariate statistical techniques, the toolbox for assessing sediments quality, in similar climate and geological conditions, should include the analysis of: meteorology, land use/cover in the area, granulometry, organic matter content, PTM concentrations, contamination indices (e.g., Igeo and EF), and sublethal bioassays with H. incongruens (total sediment analysis) and Vibrio fisheri luminescence inhibition (pore water analysis)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Occurrence of pharmaceuticals in the aquatic environment is nowadays a well-established issue that has become a matter of both scientific and public concern. Tons of different classes of pharmaceuticals find their way to the environment at variable degrees, after their use and excretion through wastewater and sewage treatment systems. The main goal of this study was to correlate the dynamics and the environmental risk of pharmaceuticals with different temporal and hydrological patterns, at the Guadiana Basin (South of Portugal). Water samples were collected bimonthly during 2017 (classified as a drought year) and 2018 (post-drought year) in: Zebro, Álamos and Amieira (intermittent hydrological streams), and Lucefécit (perennial hydrological stream). The pharmaceuticals quantified in higher concentrations, out of 27 investigated, were diclofenac (up to 4806 ng L - 1 ), ibuprofen (3161 ng L - 1 ), hydrochlorothiazide (2726 ng L - 1 ) and carbamazepine (3223 ng L - 1 ). Zebro and Álamos presented the highest contamination by this group of environmental hazardous substances, which may be correlated with the presence of wastewater treatment plants upstream the sampling point of each stream. Furthermore, the highest concentrations occurred mainly during the dry period (2017), when the flow was nearly inexistent in Zebro, and in Álamos after the first heavy rainfalls. In specific periods, the high concentrations of pharmaceuticals detected may induce risk for the organisms of lowest trophic levels, damaging the balance of the ecosystems at these streams. The risk quotient optimised approach (RQf) integrating exposure, toxicity and persistence factors, ranks the pharmaceuticals investigated in terms of risk for the aquatic ecosystems as follows: diclofenac, ibuprofen and carbamazepine (high risk), clarithromycin (moderate risk), acetaminophen, ofloxacin and bezafibrate (endurable risk), and hydrochlorothiazide (negligible risk)., Competing Interests: Declaration of competing interest The authors declare that there are no conflicts of interest., (Copyright © 2019 Elsevier B.V. All rights reserved.)