Assistant Professor California State University, Bakersfield, United States
Abstract: Plastic pollution is ubiquitous across terrestrial and aquatic ecosystems due to the widespread use of plastic and its resistance to degradation. Microplastics (particles < 5 mm) are the subject of growing concern due to their potential harmful effects on animal and human health. Thus, it is important to understand the pathways that facilitate microplastic transport from anthropogenic sources such as industrial or residential areas, to terrestrial, coastal, and freshwater ecosystems. Wet deposition events and stormwater runoff have been identified as important contributors to waterway pollution. Wet deposition carries atmospheric pollutants to the ground via rainwater; stormwater runoff collects pollutants as rainwater travels across the surfaces of landscape features that include buildings, streets, trees, and lawns, mixing with wet deposition and entering storm drainage systems. To investigate the seasonal links to microplastic and nutrient transport by landscape features, wet deposition and stormwater runoff was collected opportunistically during rain events during the wet seasons of winter and spring in the arid climate of Bakersfield, CA U.S.A. Sampling locations were selected by land-use type (e.g., buildings, pond) and water samples were fractionated to separate particles by size class, digested with 30% hydrogen peroxide, and vacuum filtered onto 1.2 µm filters. Filters were counted for anthropogenic microparticles (plastic and natural-based [e.g., cotton microfibers]) and particles were classified by morphology, size, and color. In addition, nutrient (nitrogen and phosphate) concentrations were measured for each sample using colorimetric methods. Preliminary results tied both microplastic and nutrient patterns to landscape features. Findings showed that microplastic deposition (472 particles/m2) and concentration (9.52 particles/L-1) was higher in wet deposition collected in areas with tree cover compared to microplastic deposition (346 particles/m2) and concentration (4.78 particles/L-1) in open areas. Nitrogen and phosphate compounds were also found in higher levels in areas with tree coverage compared to nutrients in open areas (NO3–N = 12.2 mg/L; NO2–N = 0.0672 mg/L; NH3–N =4.56 mg/L PO4-3). These findings suggest that intercepting landscape features increase the abundance and concentration of microplastics and nutrients in wet deposition and potentially in stormwater runoff. Results from this research will be able to contribute novel information on how much microplastics and nutrients are present in stormwater runoff relative to their presence in wet deposition, and how these patterns link to landscape features, ultimately informing our understanding of how pollutants are transported across the landscape.
