Assistant Professor California State University, Bakersfield, United States
Abstract: There is currently an ever-growing crisis of plastic pollution in the environment worldwide. Plastics are durable, can persist for decades or longer in the environment, and often fragment into microplastics (plastics particles < 5 mm) that can be incorporated into food webs. Microplastics are now ubiquitous; due to the potential impacts they can pose to wildlife health and ecosystem processes, it is important to understand the sources, pathways, and fates of microplastics in the environment. In this study we explored the seasonal patterns of microplastics in connection with river and wastewater treatment plant (WWTP) effluent habitats, which could be sources of plastic pollution and contributing to the movement of plastics in the environment. River water and WWTP effluent samples were collected from sites during the wet and dry seasons (n = 3 sites/habitat/season), digested with 30% hydrogen peroxide, and vacuum filtered onto 1.2µm filters. Filters were stained with Rose Bengal to differentiate plastic-based anthropogenic particles from natural-based anthropogenic particles (e.g., cotton microfiber). Anthropogenic microparticles were enumerated and classified based on morphology and color. Preliminary results revealed anthropogenic particle concentration was an average 1.7 × more during the dry season (295 No. m-3) compared to the wet season (173 particles m-3); however, anthropogenic particle concentrations were not significantly impacted by season, habitat, nor their interaction (all P > 0.05). Microplastic particles comprised over 64% of the total anthropogenic particles across river and WWTP effluent habitats and seasons. Microfibers were the most abundant particle morphology, with up to 2.3 × more plastic microfibers during the dry season compared to the wet season with the abundance of natural-based anthropogenic particles similar across seasons. Season did significantly affect the ‘community’ composition (i.e., morphology-color combination) of anthropogenic particles (P = 0.0197), with wet and dry season each having a unique anthropogenic particle community regardless of habitat type. Indicator analyses also revealed that red and grey-colored microfibers were specifically indicative of the dry season (all P < 0.05). These findings indicate that there are unique seasonal microplastic patterns, suggesting connections to seasonal changes in precipitation and possible connections to changes linked with anthropogenic seasonal activities. Future studies should delve deeper into seasonal environmental conditions that could impact plastic pollution in the environment.
