Microplastics in ballast water and limiting movement in the global aquatic environment: A case study

Approximately 98 % of microplastics (MP) entering the marine environment originate from human activities on land, such as untreated wastewater discharges. Polluted water is used by ships as ballast. This article describes research in which MP was detected in purified ballast water (BW) samples before discharging overboard. It demonstrates that MP can be unknowingly and inadvertently transported and disposed of in other waters worldwide, increasing pollution risks and threatening ecosystems and human health. The MP identified by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR FT-IR) originates from plastic products that undergo slight degradation in the marine environment but break down into smaller fragments. SEM/EDS analysis revealed signs of degradation of these particles and the presence of heavy chemical elements on their surfaces. Ballast water samples collected from five ships involved in the study were isolated with an average of n = 26 particles per litre. Considering that the average ballast water volume per ship is approximately 36,000 m, the total MP released can be estimated at n = 936 million particles, which is a significant amount. The results prompted the authors to develop technical improvements to the ships' ballast water treatment systems to limit the spread of pollution. The model developed is also discussed in this article. The current work indicates the characterisation of ballast water and highlights an area where extensive further research is necessary.