Quantifying and source tracking microplastics in an estuarine environment

The prevalence of microplastics in marine environments is well documented, but little is known of the accumulation patterns in estuarine environments and its land-based sources (i.e., wastewater effluents, and stormwater runoff). To investigate the behaviors of microplastics in estuarine environments, the samples were collected in the mouth of the Raritan River, NJ, along the river plume and the Hudson Raritan Bay targeting frontal zones, and into the ocean. Samples were collected during summer low flow and spring low and high flow conditions. To investigate the potential sources, samples were collected from various hydraulically connected stormwater outfalls and the influent and effluent of wastewater treatment plants (WWTPs). The focus of this study was on microplastics in the 500-2000 μm size range. The highest concentration of surface water was in the mouth of the Raritan during summer low flow. The concentrations of microplastics ranged from 0-2.75 MP/m3 in the Raritan, 400-600 MP/m3 in stormwater, and was frequently 0 MP/m3 in wastewater effluent, suggesting stormwater may serve as an understudied source. Polymers were characterized by attenuated total reflectance FTIR and polyethylene was the most prevalent type. Polymer types and concentrations were compared between the different waters and similarities between surface water, wastewater influent, and stormwater were found. Additionally, a linear correlation was found between the total concentration of particles in a sample following oxidation and density separation and its microplastic concentration for wastewater influent, surface water, and stormwater. If this correlation is also observed in other locations, it may serve as a method for rapid estimation of total microplastic by techniques that count total particles. These results have implications for understanding the behavior of microplastic in varying flow conditions and in frontal zones as well as reveal potentially important sources of microplastics in the estuarine environment.M.S.Includes bibliographical reference