Modulation of emerging pollutants toxicity by sodium dodecyl sulfate in a marine green microalga

Pollutants of emerging concern (PECs) are a major threat to the marine ecosystem. Their presence in the environment is exacerbated by the disposal of effluents. Moreover, chemical interactions can interfere in the bioavailability and toxicity of these substances. Therefore, this study was developed to better understand how chemical mixtures affect the toxicity of PECs diclofenac sodium (DCF) and zinc oxide nanomaterial (ZnO NM) when mixed with sodium dodecyl sulfate (SDS). The green microalga Tetraselmis sp. was used as a representative of the marine phytoplanktonic community. First, isolated toxicity assays were conducted with DCF, ZnO NM, and SDS. SDS interaction in binary mixture with the NM and the pharmaceutical was also analyzed due to the surfactant's ability to stabilize chemicals. For this purpose, assays were performed according to an Isobologram with fixed radius design. According to the EC50_48h values obtained in the isolated toxicity assays, the harmfulness of the pollutants to Tetraselmis sp. was SDS > DCF > ZnO NM. The modulation of toxicity due to the SDS binary mixture was notable with both PECs. Using Isobologram and Abbott models, it was observed the predominance of synergistic interactions in the ZnO NM + SDS mixture, where possibly the surfactant enhances nanoparticle dissolution. The DCF + SDS mixture was marked by antagonistic interactions, possibly through micellar encapsulation of the pharmaceutical. The predictions according to the Könemann model indicate additive interactions for both binary combinations. However, the predictive models employed present limitations, as they disregard the chemical nature of the substances.