Microplastic Concentrations in the Normans Kill Watershed Across Four Seasons
Abstract. Question: Do microplastic counts in local stream water vary by season? Method: We sampled six sites quarterly and filtered 2 L per sample. Findings: Concentrations peaked after spring runoff, 3.1 times the autumn baseline. Conclusion: Stormwater inputs, not wastewater, best explain the seasonal pattern.
Introduction
Microplastics are plastic fragments under 5 mm that enter streams through runoff, laundry effluent, and tire wear. Few studies report seasonal data for small upstate tributaries.
Methods
Water was drawn 10 cm below the surface and vacuum-filtered through 0.45 µm membranes. Particles were counted under 40× magnification. Concentration was computed as:
C = N⁄V (particles L−1)
Results
Mean concentration was highest in spring (Figure 1) and lowest in autumn.
Discussion
The spring peak coincides with snowmelt and heavy rain, which points to surface runoff as the main pathway. Sites downstream of the treatment plant showed no higher counts.
References
Browne, M. A., et al. (2011). Accumulation of microplastic on shorelines worldwide. Environmental Science & Technology, 45(21), 9175–9179.