Abstract:
This chapter presents the outcomes of a case study which focused on understanding the environmental risks and transport processes of microplastics (MPs) in urban river sediments. Sediment samples obtained from twenty-two sampling points along the Brisbane River, Australia, over four different climatic seasons revealed relatively high concentrations of MPs in the sediments, with abundance ranging from 0.18 to 129.20 mg kg−1. The environmental risk posed by MPs was assessed by analysing their impacts on other pollutants present in the sediments, namely, nutrients (TC, TN, TP) and fourteen metals (Al, As, Cr, Co, Cu, Fe, Mg, Mn, Ni, Cd, Se, Sr, Zn, Pb) commonly present in urban aquatic environments. All three nutrient parameters were found to have a strong positive relationship with MPs concentration, while negatively correlated to MPs hazard index. The tested metals in Brisbane River sediments were observed to be correlated more with MPs hazard index rather than MPs concentration. Additionally, a three dimensional hydrodynamic and particle transport modelling framework developed showed that sedimental MPs with lower density and slow settling velocity (such as PE and PP) have higher mobility, while dense MP particles (such as PA and PET) are more likely to accumulate in the river sediments close to source points.