Towards improving the accuracy of plastic cycle in urban regions

Plastic contamination has been receiving considerable attention during the last few decades (Siegfried et al., 2017). In the present study, the authors extended process-based eco-hydrology models, NICE (National Integrated Catchment-based Eco-hydrology) and NICE-BGC (BioGeochemical Cycle) (Nakayama, 2017), to link them with plastic debris model (Nakayama and Osako, 2023a, 2023b), and applied to all of the 109 first-class (class A) river basins throughout Japan. The model included advection, dispersion, diffusion, settling, dissolution and deterioration due to light and temperature, interaction with suspended matter (heteroaggregation), resuspension, and biofouling. These processes could help to evaluate effect of mismanaged plastic waste (MPW) and point sources (tyres, personal care products, dust, and laundry) on spatio-temporal dynamics of macro- and micro-plastics there. The result clarified the finer resolution slightly decreased the flux of macro-plastics, particularly in the urban regions. The model also revealed that the amount of micro-plastic flux calculated by accumulating point information at sewage treatment plants could be replaced by analysis using grid data categorized for treatment methods (sewage, septic tank, untreated) in each grid instead of global data of per capita emission and treatment rates (Jones et al., 2021). The result also clarified that the plastic cycle, particularly micro-plastic, in rivers flowing through urban areas has been significantly altered (Wagner et al., 2019). Finaly, the author evaluated the method to improve plastic cycle in urban regions towards understanding of urban plastic cycle with fewer inventory data (Strokal et al., 2021). These results help to quantify impacts of plastic waste on biosphere in urban systems, and may aid development of solutions and measures to reduce plastic input to the ocean.

 

References

Jones, E.R., et al. 2021. Earth System Science Data, 13, 237-254, doi:10.5194/essd-13-237-2021.

Nakayama, T. 2017. Journal of Geophysical Research: Biogeosciences, 122, 966-988, doi:10.1002/2016JG003743.

Nakayama, T., Osako, M. 2023a. Ecological Modelling, 476, 110243, doi:10.1016/j.ecolmodel.2022.110243.

Nakayama, T., Osako, M. 2023b. Global and Planetary Change, 221, 104037, doi:10.1016/j.gloplacha.2023.104037.

Siegfried, M., et al. 2017. Water Research, 127, 249-257, doi:10.1016/j.watres.2017.10.011.

Strokal, M., et al. 2021. Urban Sustainability, 1, 24, doi:10.1038/s42949-021-00026-w.

Wagner, S., et al. 2019. Environmental Science & Technology, 53, 10082-10091, doi:10.1021/acs.est.9b03048.