PERVASIVE MICROPLASTIC POLLUTION FOUND IN THE MOHAWK RIVER, NEW YORK STATE

The Mohawk River is the second largest channelized waterbody in New York State and the largest tributary to the Hudson River. Among the emerging contaminants threatening the Mohawk River are microplastics, typically defined as plastic smaller than 5 millimeters, whether intentionally manufactured to be that size or resulting from the fragmentation and breakdown of larger plastic products. Microplastic particles represent a threat to the health of organisms living within the river and those that feed on them, including humans. The majority of wastewater treatment plants (WWTPs) in New York State are not equipped to filter out small plastic particles, and combined sewer systems provide a direct means for plastic waste to enter waterways during heavy precipitation events. Microplastic particles can also be introduced directly to the river in runoff and from tributaries.

The main goal of this project was to quantify the microplastic load in the Mohawk River as a starting point for assessing the level of environmental risk represented by microplastic pollution. Planktonic samples were collected using a manta trawl with a 333-micron net towed on average 1.7 km upstream by a rigid inflatable boat. Sediment grab samples were collected from the channel bottom with a 6-inch Ekman grab sampler. Raman spectroscopy and SEM/EDX were used to identify and characterize particles. Microplastic particles were found in all of the 63 planktonic samples and 64 sediment grab samples collected in the Mohawk River and Erie Canal between Rome and Cohoes, New York, in 2016. Both abundance (number of particles) and proportions of particle types (fragment, foam, pellet/bead, film, fiber) varied in planktonic samples along the length of the channel, with the highest abundances found in samples taken downstream from Utica (512 and 521) and Schenectady (439). Microplastic abundance was generally lower in sediment grab samples, with fibers dominating the particle population. Variations in abundance in planktonic samples suggest that microplastics are being sequestered within the river, perhaps in wetland areas, while variations in proportions of plastic types likely reflect the influence of local inputs, such as surface runoff, combined sewer overflows, and WWTP effluent.