Discovery of microplastics in the Alabama River: Distributions, transport and loads, sources, and relative comparison with world rivers

The present study investigated microplastic (MP) contamination in the Alabama River. Concentration and size distributions, transport and loads, and potential sources of MPs were studied. Results showed that MP concentrations in the Alabama River and world polluted rivers are comparable. The concentration fluctuated by season and location with no clear and consistent distribution trends. The study revealed that MPs in the Alabama River likely did not travel long distances and sedimentation on the riverbed may be a major sink for MPs. Polyethylene terephthalate (PET, 21.7 %) was the most abundant polymer found in the samples. Other less abundant polymer types were polymethyl pentene (PMP, 16.1 %), polypropylene (PP, 13.8 %), polyvinyl chloride (PVC, 12.4 %), polybutylene terephthalate (PBT, 12 %), acrylonitrile butadiene styrene (ABS, 6.7 %), and polyethylene (PE, 5.3 %). Approximately 90 % MPs were less than 2.5 mm long with 50 % being less than 1 mm, which are in consumable size range for many sensitive aquatic organisms. It was estimated that hundreds of billions to trillions of MPs enter Mobile Bay per day. This poses potential exposures and risks to aquatic life in the Bay and the Gulf of Mexico (hereafter called Gulf of America). Microplastic concentrations were quantitatively correlated with the watershed drainage into the river and human pollution suggesting contributions of human activities to MP contamination. The present study provides a first look at MP contamination in the Alabama River. Continuous monitoring of MP and ecotoxicity studies are needed to investigate ecosystem consequences of MPs in the Alabama River.