Study of sediment cores to establish the history of organic and inorganic contaminants through the Anthropocene

Sediments are excellent archives for studying the long-term variations of pollutants in the environment. For this reason, records derived from the chemical analysis of sediment cores are useful to trace the history of pollutant emissions.

This study aimed to study the vertical variation of organic contaminants (OCs) and metals sediment cores collected in two sites (northern and southern part) of the L´Albufera Natural Park (Valencia, Spain) to obtain information regarding historical variation in the composition of sediments. Other sediment characteristics, such as organic matter, organic carbon content, humidity, were also studied.

A sediment core sampler (57 mm inner diameter, 1.00 m length; Beeker, Eijelkamp) was used to extract the cores from the lake of L’Albufera. The cores were sampled from boat. The sediment cores were 80–87 cm in length and 5 cm in diameter. The tubes were kept upright in a bucket with ice until they arrived at the laboratory where they were frozen. Once frozen, the tubes were cut into 8 segments of the same thickness (8 slices of 10 cm) using a stainless steel cutter. Pharmaceuticals, pesticides, poly and perfluoroalkyl substances (PFASs) and phosphorous flame retardants (PFRs) were analysed using Orbitrap Exploris 120 mass spectrometer. The compounds were extracted by different extraction methods and determined both, using wide target screening against a positive list of compounds and non-target screening applying ddMS2 of the 4 more intense ions in each cycle as well as all ions fragmentation. Both positive and negative ionization were used.

 Several pollutants, especially pesticides such as Azoxystrobin, Imazalil, Molinate, Tebuconazole, Thiabendazole and Tricyclazol were detected in the sediment in contact with water. Some infiltration of the compounds in the inner layers of sediments were also detected. Superficial sediments provide information on the actual deposited material and the actual status of pollution but the study of sediment profiles provides information on the historical variation in the composition of sediments settled. These sediments can also be used to examine pollution mechanisms, which are significant for predicting future pollution tendencies and assessing potential environmental risks.

Acknowledgments: This work has been supported by Grant RTI2018-097158-B-C31 funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe” and the grant of the Generalitat Valenciana Prometeo Programme CIPROM/2021/032. Y. Soriano also thanks MCIN/AEI/ 10.13039/501100011033 and ERDF for their Predoc contract (PRE2019-089042).