Assessment and Comparison of Microplastic Contamination in Atlantic Navigation Routes with Known Uncertainty

Microplastics (MP) have been found
in various environments worldwide.
However, not many studies focus on the open ocean due to logistical
restraints. Between January and May 2020, the NRP Sagres sampled 123
linear paths of subsurface water of the Atlantic Ocean, passing by
Cape Verde, the east coast of South America, and the west coast of
Africa. The water was sampled through the ship’s water system.
The membranes were analyzed by the Hydrographic Institute of Portugal
and the Norwegian Institute for Water Research by micro-FTIR. The
contamination levels were reported with uncertainty, for 99% confidence
level (CL), normalized for filtered water volume and the distance
traveled during sampling. Uncertainties were calculated through a
detailed ″bottom-up″ evaluation. MP were found in about
a third of the stations (48 out of 123), and most of those stations
(43 out of 48) presented concentrations below 1 m–3 km–1. The sites
where higher concentrations were registered were the port of the island
of Santiago (Cape Verde) ((5.9 ± 5.2) m–3 km–1), the Guanabara Bay in Rio
de Janeiro (Brazil) ((41 ± 27) m–3 km–1), and close to South Africa ((4.9 ± 2.4) m–3 km–1). Most MP
found were polyamide, polyester, polyethylene, ethylene vinyl acetate,
and poly(methyl methacrylate). The estimated contamination levels
cannot be directly compared with information obtained in other studies
due to differences in how MP were determined and the unknown uncertainty
of their measured values. This article presents a relevant and reliable
contribution to understanding the MP distribution in the Atlantic
Ocean.