Global multi-pollutant modelling: uncovering new perspectives for river exports of nutrients, plastics, and chemicals

This thesis assesses river exports of nutrients, plastics, and chemicals to coastal waters worldwide across sub-basins in the 21st century under socio-economic disparities and climate-driven hydrological changes. Using the new MARINA-Multi model, results show that in 2010, diffuse sources contributed by >95% to river exports of nitrogen and macroplastics, while point sources contributed by about 40% to river exports of phosphorus and microplastics globally. Future multi-pollutant scenarios indicate that 56%–78% of the global population is expected to live in more polluted river sub-basins by 2100, with the Indian Ocean receiving alarming pollutant levels. Income-based disparities further shape 2050 water quality: high-income sub-basins experience plastic pollution pressures from urbanisation, while low-income sub-basins in Africa and South Asia face the highest exposure to multiple river pollutants. Many African sub-basins show greater variation in river exports of multiple pollutants due to future climate-driven hydrological uncertainties. Therefore, new perspectives for advancing multi-pollutant modelling widen the scope of models, link sectors, and address uncertainties.