Quantification of microplastic presence in Texas waterways and inflows to the Gulf of Mexico

Plastics, first invented in the early 20th century, are long chain polymerized hydrocarbons. Plastics are a staple of everyday life; from packaging, to toys, to clothing, plastic has become a constant in day-to-day life. It is easy to see why, due to its structural stability, ability to withstand breakdown, and wide range of applications. Plastic’s prolific use has allowed for its entry to the environment at every level. Microplastics are plastic particles and fibers that are less than 5 millimeters in size. Microplastics originate as macroplastics which degrade to smaller sizes, or from products that are manufactured at this size. Research has been conducted to quantify microplastics in the Gulf of Mexico, in source waters of the Mississippi River, and in some coastal areas. There is a paucity of data on microplastics in Texas coastal rivers and bays. The purpose of this project is to provide baseline data on the presence of microplastics in Texas waterways that feed into the Gulf of Mexico in 2019 to 2020. Water samples were collected at 19 locations from Galveston to the U.S., Mexico border. They were collected at the water surface and 60% of the depth at the time of collection. All samples were filtered through a 0.45 μm, cellulose, membrane filter followed by visual sorting of suspected microplastics. A Fourier-transform infrared microscope (μFTIR) was used for materials confirmation. Microplastic concentrations across all sampled locations averaged 4.0 ± 2.9 microplastics per liter. Polyethylene Terephthalate was the most common microplastic found, accounting for 39% of microplastics. Polystyrene was 33%, while other material types were all less than 10% individually. Total loading to the Texas coastal zone was estimated at ~27 trillion microplastics annually, equaling ~220 kg. The results of this study are expected to help regulators understand the scale and scope of microplastics pollution in coastal Texas and to help inform future waterway management decisions.