Contaminants of emerging concern in the Duero river basin: Presence and comparison between a nature reserve and an agricultural area

Water quality in natural reserves is paramount for preserving biodiversity, maintaining ecological balance, and safeguarding ecosystem health. The Villafáfila Nature Reserve, a protected lagoon complex that is recognized as a pivotal wetland in the northern part of the Iberian Peninsula is facing increasing threats from contaminants of emerging concern (CEC), which can compromise water quality and pose significant risks to aquatic life and environmental integrity. In this study, we aim to elucidate the occurrence and concentration of CEC in The Villafáfila Nature Reserve, and evaluate its good quality state compared with an intensively exploited agriculture area in a nearby locality of Tordesillas. The study offers insights into the presence and concentration of emerging contaminants in the Spanish Duero River basin, aiding the development of standardized monitoring protocols and regulatory frameworks applicable globally. To assess the pollution status of its waters by CEC, samples were collected from wells, lagoons, and springs impacted by agrochemicals, farms and tourism. Out of the 55 CEC measured, 47 were detected in groundwater samples, with 16 of them exhibiting a median concentration within the range of 2.184 - 43.38 ngL-1. Notably, the UV filter BP3 along with its metabolite 4DHB, AVO, 4MBC, and the stimulant CFF were present in all samples. Additionally, BP, BP1, 4HB, CPAA, MeBZT, UVP, AZIT, CBZ, SPY, SMD, and TMP were found with a detection frequency more than 50%. The highest concentrations were observed for BP (412.51 ngL-1), CFF (328.18 ngL-1), and BP3 (106.01 ngL-1), with CBZ, acSDZ, and ATM concentrations surpassing 100 ngL-1. This pioneering study in the Duero River basin aims to enhance knowledge of these two particular areas and guide adaptive measures in wastewater treatment systems, ultimately minimizing risks to aquifers and protected areas.