Drivers of Microplastics in an Irish River : An analysis of the catchment parameters, local sources and hydraulic factors influencing the diffusion of microplastics in the sediments of the River Barrow, Ireland.

Sammanfattning

Microplastic (MP) pollution in freshwater systems is a growing concern, yet its drivers in small river catchments remain poorly understood. This project aims to investigate the potential factors influencing the distribution of MP along the River Barrow in southern Ireland. Building on the work of Murphy et al. (2022), who sampled MP at 16 sites along the river in 2018 and 2019, this project expands the analysis by integrating catchment characteristics (catchment area, population, share of urban; industrial, agricultural and natural land uses), Point Source Pressures data (numbers of facilities and closet facility for landfills wastewater treatment plants, combined sewer outlet, industries and urban wastewater discharges), hydrological and hydraulic parameters (length of upstream drainage, drainage density, river slope, river section and velocity) to identify potential drivers of MP’s concentrations. Correlation analysis revealed that agricultural land use and wastewater discharges (urban wastewater treatment plants and combined sewer outfalls (C-SO)) were significantly associated with microplastic concentrations in the river (P < 0.05). In contrast, urban and industrial land use, as well as other types of Point Source Pressures, and hydraulic and hydrological parameters showed no significant correlation. The regression models identified that the number of wastewater discharges and C-SOs are the most significant; however, the models explained only a small proportion of the variance, indicating the influence of other drivers and more complex interactions. Limitations regarding the number of sampling sites and details about source points may also constrain the explanatory power. The findings highlight the need for standardised MP sampling protocols and targeted policy interventions to reduce MP pollution from agricultural and residential sources in the Barrow catchment.