Distribution of suspected microplastics within surface waters of two New Brunswick rivers

Abstract

Microplastics (MPs) are pervasive contaminants in aquatic environments; however, little is known about their distribution and impacts in freshwaters. This study examines the distribution and abundance of suspected microplastics in surface water samples from two rivers in rural watersheds of New Brunswick, Canada. Both rivers are subject to point sources of microplastic input from wastewater treatment plants (WWTPs), as well as diffuse inputs from the atmosphere, surface-water runoff, and human activities. The Kennebecasis is more developed than the Nashwaak, with a greater number of WWTPs and increased human activities. Surface water samples from the rivers were collected at sites upstream and downstream of WWTP effluent discharge points and at intermediate sites spaced evenly along the river stretches sampled. Suspected MPs were present at all sites and 72% were blue-coloured fibres. Surface water samples from the Kennebecasis contained a greater abundance of suspected MPs compared to those from the Nashwaak (p = 0.03). Suspected MP abundance was significantly higher downstream of four WWTPs compared to upstream (p = 0.03) and intermediate sites (p = 0.02). Results help understand the input, transport, and fate of MPs in rivers from watersheds with low population density. These findings are an important first step in establishing the scope of MP contamination within freshwaters from Atlantic Canada.