Preliminary Investigation into Atmospheric Microplastic Deposition and Transportation in Auckland, New Zealand

Abstract

Microplastics (MPs) have emerged as a new environmental pollutant stemming from the ever-increasing volume of plastic and plastic waste being produced globally. Previous studies have suggested that atmospheric transportation processes may be the main pathway by which MPs are dispersed ubiquitously throughout our environment. However, little is known about the concentration of MP in the atmosphere or the underlying transportation processes. High concentrations of MPs in the air may pose a health risk to both people and wildlife. This thesis explores the temporal and spatial characteristics of MP air pollution in the city of Auckland, New Zealand, with the aim of improving our understanding of the processes which determine the concentration, characteristics and sources of atmospheric MPs. Two sampling sites were chosen in central Auckland, Sampling took place over 9 weeks commencing on 11/09/2020. Total atmosphere fallout was collected using a glass funnel into a bottle. MPs were found in all the samples, with a mean deposition rate of 4171 ± 4377 fragments/m2/day and 23 ± 51 fibers/m2/day. This indicates that there are high concentrations of MP in Auckland’s atmosphere compared to other studies. The mean diameter of MP fragments was comparatively small (10-25μm) and consistent with the size and shape of atmospheric MP observed in locations which are remote from human activity, suggesting the dominance of long-range transportation processes. A significant correlation was not found between meteorological factors and MP deposition rate in this study. Results from bivariate polar plots showed winds from the northeast with a speed around 15 m/s were associated with the highest MP deposition rates. Back trajectory analysis using the HYSPLIT model of rain events observed during the study period showed the airmasses coming from the ocean to the northeast were associated with the highest MP deposition rates. These results suggest the possibility that some of the MPs detected in Auckland may come from marine environments. Further research is needed to investigate longer term trends in MP pollution, and the underlying processes driving them, in the Auckland region.