UNDERSTANDING THE DEGRADATION, TOXICITY, AND ENVIRONMENTAL IMPACT OF MACROPLASTICS IN STREAMS

Riverine systems have shown to be major contributors of macroplastics (>4mm in diameter) to the global ocean. Yet, few studies have evaluated the degradation and potential ecosystem impacts of macroplastics within these freshwater environments. Recent studies have suggested that biofilms which grow on the surface of macroplastics bioaccumulate metals over time. In the mid-Atlantic region of the United States, the cumulative application of road salt has led to increased concentrations of metals in stream water via reverse cation exchange in soils. Therefore, biofilms could theoretically bioaccumulate higher concentrations of metals in streams with higher salinity, if controlling for geology and land cover. In this study, we deployed replicates of 5 common debris types (DASANI® polyethylene terephthalate (PET) plastic water bottles and their polypropylene (PP) caps, Coca Cola™ aluminum cans; and Hefty® polyethylene plastic bags), both suspended and buried, in three southeastern Pennsylvania streams for a total of 45 days; all three streams had the same underlying geology, yet varying salinity. Upon collection, biofilm metabolism was determined through the light/dark method; assessing gross primary production and community respiration to calculate the net primary production. Total metal concentrations on the surface of the debris were determined using x-ray fluorescence spectrometry. Select metal concentrations (Al, Ba, Cd, Cr, Cu, Pb, Sb, and Zn) were compared to the respective non-deployed material to determine the relative state of weathering. In addition, the bioavailability of metals was determined using an acetic acid extraction and inductively coupled plasma mass spectrometry. The study results provide valuable insights into the degradation and potential ecosystem impacts of macroplastics in riverine systems.