The Amazon River, a major source of organic contaminants in the tropical North Atlanticl

Article from the CNRS/INSU website published on July 15, 2019

Organic additives for plastics, such as organophosphate esters and bisphenols, as well as other emerging organic contaminants, such as perfluorinated compounds, are increasingly detected in the environment and are of concern because of their suspected toxicity. During the "Sargasso II" transatlantic expedition, a team of researchers from the Mediterranean Institute of Oceanography (MIO/PYTHÉAS, CNRS / University of Toulon / IRD / AMU) and the Laboratory for Space Geophysics and Oceanography Studies (LEGOS/OMP, UPS / CNRS / CNES / IRD) took and analysed seawater samples between Cape Verde and Martinique. The results indicate that the Amazon River is an important source of organic contaminants in the tropical North Atlantic.

Environmental pollution by plastics has received considerable scientific and media attention and has been identified as one of the major global challenges of this century. Additives, such as organophosphate esters (OPEs) and bisphenols (BPs), which are added to plastics during their manufacture to make them more flexible, flexible or heat-resistant, can be released from the polymer matrix and interact with the hormone system of organisms by acting, among other things, as an endocrine disrupter. Together with other organic contaminants, such as perfluorinated compounds (PFCs) used in technical clothing because of their water and oil repellent properties, they pose a threat, particularly to aquatic environments that receive significant inputs of contaminants, including effluents from wastewater treatment plants or directly from industries. Coastal environments are therefore suspected to be particularly affected, but data from the open ocean - which would allow comparisons to be made - are very scarce.

To investigate the presence of 9 OPEs, 6 BPs and 5 PFCs in tropical waters of the North Atlantic, samples were collected, processed by solid phase extraction (SPE) in clean rooms and analyzed by gas chromatography - mass spectrometry (GC-MS). The results are surprising and indicate that the highest concentrations (more than 1.3 µg L-1 total contaminants) were detected offshore, about 1200 km from the mouth of the Amazon River, and not near the African or Caribbean coasts as expected. The currentology of the study area, the spatial distribution of salinity and chlorophyll (measured from the attenuation coefficient at 490 nm wavelength) confirmed that the Amazon was most likely responsible for the contaminant concentrations observed offshore.
These results were confirmed with the Ichthyop transport model, by calculating backwards over time the last 180 days of trajectories of water bodies sampled by virtual particles at the times and geographical coordinates of the different sampling sites. The study indicates that most of the water bodies sampled originated from the Amazon plume and were then transported north/northeast by the North Brazil Current and its retroreflection.

This work therefore not only provides crucial data on the presence of OPEs, BPs and PFCs in the ocean environment of the tropical North Atlantic, but also reinforces previous research findings that these contaminants can be transported over long distances by water bodies, highlighting their potential to harm the environment.



The Amazon River: A Major Source of Organic Plastic Additives to the Tropical North Atlantic?, Natascha Schmidt, Vincent Fauvelle, Anouck Ody, Javier Castro-Jiménez, Julien Jouanno, Thomas Changeux, Thierry Thibaut and Richard Sempéré, Environmental Science and Technology 53, 7513–7521., DOI: 10.1021/acs.est.9b01585