Leaving a plastic legacy: Current and future scenarios for mismanaged plastic waste in rivers

• Published in: The Science of the total environment 2023-04, Vol.869, p.161821, Article 161821
• Main Authors: Nyberg, Björn, Harris, Peter T., Kane, Ian, Maes, Thomas
• Format: Article
• Language: English
• Subjects: Environmental mitigation; Future scenarios; Plastic pollution; Rivers
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.161821

Mismanaged plastic waste (MPW) entering the riverine environment is concerning, given that most plastic pollution never reaches the oceans, and it has a severe negative impact on terrestrial ecosystems. However, significant knowledge gaps on the storage and remobilization of MPW within different rivers over varying timescales remain. Here we analyze the exposure of river systems to MPW to better understand the sedimentary processes that control the legacy of plastic waste. Using a conservative approach, we estimate 0.8 million tonnes of MPW enter rivers annually in 2015, affecting an estimated 84 % of rivers by surface area, globally. By 2060, the amount of MPW input to rivers is expected to increase nearly 3-fold, however improved plastic waste strategies through better governance can decrease plastic pollution by up to 72 %. Currently, most plastic input occurs along anthropogenically modified rivers (49 %) yet these represent only 23 % of rivers by surface area. Another 17 % of MPW occur in free-flowing actively migrating meandering rivers that likely retain most plastic waste within sedimentary deposits, increasing retention times and likelihood of biochemical weathering. Active braided rivers receive less MPW (14 %), but higher water discharge will also increase fragmentation to form microplastics. Only 20 % of plastic pollution is found in non-migrating and free-flowing rivers; these have the highest probability of plastics remaining within the water column and being transferred downstream. This study demonstrates the spatial variability in MPW affecting different global river systems with different retention, fragmentation, and biochemical weathering rates of plastics. Targeted mitigation strategies and environmental risk assessments are needed at both international and national levels that consider river system dynamics. [Display omitted] •Plastic waste in different river systems and future scenarios are analyzed.•Rivers received ∼0.8MT of plastic waste in 2015 increasing 3-fold by 2060.•23 % of rivers are human impacted yet receive 49 % of total plastic waste input.•Actively migrating meandering and braided rivers are large sinks of MPW (31 %).•Targeted mitigation strategies are required for different river systems.