Biofilm-influenced weathering of polypropylene films submerged in field samples from freshwater and marine ecosystems

Abstract

Polymers in aquatic ecosystems are susceptible to degradation by natural weathering where abiotic factors and biotic factors induce changes to the physiochemical properties of the materials. The extent of plastic weathering depends on both on the material and the location, though few studies have considered the joint effects of abiotic and biotic factors present in different environments on a single plastic material. This study used microscopy, Fourier-Transform Infrared Spectroscopy (FTIR), and goniometry to evaluate biofilm growth through morphological and chemical changes of polypropylene (PP) films incubated in filtered water as a control, lake water, and ocean water. With results from the qualitative and quantitative characterizations, biofilm growth was indicated on all samples by 16 weeks. The most notable changes occurred to films immersed in ocean water as opposed to freshwater or the control. After removal of biofilm, PP degradation was also confirmed. Finally, amplicon sequencing of the 16srRNA gene on samples immersed in ocean water revealed that proteobacteria can survive on polypropylene surfaces without supplement for at least 8 weeks while PP degrades oxidatively. This work suggests that biofilm-influenced degradation can induce, and therefore accelerate polyolefin aging in the environment, especially in the presence of ocean microbial consortia.