INVESTIGATING THE FATE OF MICROPLASTIC PARTICLES IN THE MOHAWK AND HUDSON WATERSHEDS, NEW YORK STATE

We are investigating whether microplastic particles (<1.0 mm in diameter) from personal-care products are reaching major waterways of eastern New York state. In 2013, samples of planktonic material were collected at 17 sites in the near-shore channels of the lower Mohawk River between Utica and Waterford, NY, and the upper Hudson River between Selkirk and Troy, NY. Samples were obtained by pouring ~150 to 250 gallons of river water through a stack of sieves (2.0, 1.0, 0.5, 0.25, 0.125, and 0.063 mm screens; material >1.0 mm was discarded). Samples are undergoing wet peroxide oxidation and transmitted-light and scanning electron microscope examination. Results to date indicate that microplastic particles are present in the planktonic sediment load, but in relatively low quantities. Notably, we have yet to find the spherical microplastic particles (“microbeads”) that are commonly associated with personal-care products. Instead, much of the plastic material we have recovered is in the form of fragments and fibers. Given these results, we reexamined the source of the microplastic particles under consideration: personal-care products containing plastic abrasives. We separated the microplastic particles from nine personal-care products (seven scrubs and two toothpastes) by rinsing each product through sieves with 0.5 mm and 0.063 mm mesh. All nine of the products contain irregularly-shaped translucent plastic particles that mimic the appearance of angular quartz grains, while three of the products also contain spherical microbeads. In six of the products, all of the particles pass through the 0.5 mm sieve; in the other three, the population of particles trapped by the >0.5 mm screen is dominated by microbeads. Most particles float at the surface, but some remain suspended within the water column. Our investigation suggests that the distribution of microplastic particles in the fluvial environment, and by extension, in the marine environment, is more complex than might be expected. Castañeda et al. (2014) found spherical microbeads >0.5 mm in diameter deposited within sediment in the St. Lawrence River channel. In light of our investigation, their results suggest that while at least some of the load of larger, spherical microbeads sinks, the fate of the smaller irregular microplastic particles remains unresolved.