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Causes of coastal waters pollution with nutrients, chemicals and plastics worldwide
Summary
Researchers developed a global model to quantify how rivers transport nutrients, chemicals, microplastics, and macroplastics from land sources to coastal waters across more than 10,000 sub-basins. They found that sewage is responsible for 40-95% of phosphorus and microplastics reaching the oceans, while agricultural runoff and mismanaged waste dominate nitrogen and macroplastic pollution. The study reveals that nearly 45% of global land area qualifies as a multi-pollutant hotspot, home to 89% of the world's population.
Worldwide, coastal waters contain pollutants such as nutrients, plastics, and chemicals. Rivers export those pollutants, but their sources are not well studied. Our study aims to quantify river exports of nutrients, chemicals, and plastics to coastal waters by source and sub-basin worldwide. We developed a new MARINA-Multi model for 10,226 sub-basins. The global modelled river export to seas is approximately 40,000 kton of nitrogen, 1,800 kton of phosphorous, 45 kton of microplastics, 490 kton of macroplastics, 400 ton of triclosan and 220 ton of diclofenac. Around three-quarters of these pollutants are transported to the Atlantic and Pacific oceans. Diffuse sources contribute by 95-100 % to nitrogen (agriculture) and macroplastics (mismanaged waste) in seas. Point sources (sewage) contribute by 40-95 % to phosphorus and microplastics in seas. Almost 45 % of global sub-basin areas are multi-pollutant hotspots hosting 89 % of the global population. Our findings could support strategies for reducing multiple pollutants in seas.