Suspected and non-targeted analysis of environmental contaminants in water and sediments of L’Albufera Natural Park by liquid chromatography-high resolution mass spectrometry

The increasing worldwide release of anthropogenic chemicals compounds into the aquatic ecosystems has led serious contamination of freshwater resources.  This study investigated the chemical composition of the water and sediments of L'Albufera Natural Park, Valencia, Spain, an area heavily impacted by intensive agriculture, surrounded by an industrial belt, highly urbanized and historically polluted. The goal was to assess the different water sources and anthropogenic influence in this managed area using nontarget analysis (NTA) combined with high-resolution mass spectrometry (HRMS). Surface water and sediment samples were collected from 51 sites during two sampling events in the May/June 2019 and September/October 2019. These two periods were selected because the most relevant crop in the area are rice fields and these two periods coincides with the starting of the cultivation and the harvest. The HRMS data was processed using Compound Discoverer™ version 3.3, and the results were analyzed using Principal Component Analysis (PCA). Agricultural practices are one of the most important sources of contaminants (mostly pesticides) including at concentrations >100 ng L^-1 acetamiprid, azoxystrobin, chlorfenvinfos, chlorpyrifos, difenoconazole, dimethoate, fluvalinate, imazalil, imidacloprid, omethoate, propazine, tebuconazole, terbumeton deethyl, terbuthylazine, thiabendazole and tricyclazole. Increased presence and intensity of organic contaminants along the waterway was observed, indicating significant anthropogenic influence in the area. The NTA and post-processing were evaluated for reproducibility, demonstrating robustness with a 71.2% average reproducibility for compounds detected the 2 sampling trips. A detection frequency of 80% was the set criterion for detected compounds suggested as tracers. To prioritize samples, hierarchical cluster analysis was employed, and potential tracers for each water source were determined. Additionally, urban-influenced contaminants such as insect repellents, pharmaceuticals, and non-agricultural herbicides were identified along the channels that transports treated wastewater to the Natural Park. This study highlights the impact of human activities on L’Albufera Natural Park and demonstrates the effectiveness of NTA in differentiating and tracking water sources. The results emphasize the importance of reproducibility in NTA and provide guidance on implementing monitoring strategies by prioritizing samples based on chemical compositions.