Solid Waste and Urban Rivers in the Amazon
The production of solid waste has exceeded the limits of the world’s population, causing numerous environmental problems, with an estimated two-fold increase by 2030. In this context, urban rivers are concentration points for this waste, especially plastics, with the ability to retain the debris or transport it elsewhere with the direct impact of rainfall, tides, and vegetation in this process.
Figure 1. Confluence of the Tucunduba River with the Guamá River. Source: LAPMAR
Home to 14 river basins, Belém is a capital city in the Amazon region impacted by urban pollution. Urban growth, coupled with inadequate waste disposal and poor basic sanitation, has a direct influence on the city’s coastal pollution, which is intensified during rainy periods when waste is transported from the streets to the river channels.
The chain of impacts caused by waste disposal is wide-ranging, such as the obstruction of waterways and contamination of organisms and the population. Researchers from the Federal University of Pará (UFPA) assessed Belém’s urban rivers to quantitatively evaluate the transportation of solid waste by water bodies and the impact of rainfall and tides on the process.
Figure 2. Tucunduba River with solid waste on the margin. Source: LAPMAR.
Records of macroplastics ranged from plastic bottles and packaging to tires and furniture. The quantity of items transported is greater during the rainy season in the region due to its direct relationship with the flooding of river courses.
The research showed that increased rainfall combined with periods of ebbing tide (runoff phase) promotes waste transportation, establishing a network for transporting waste discarded in the city to the ocean.
Figure 3. Evaluated rivers, Tamandaré River (yellow) and Tucunduba River (blue). Source: Rosa et al., 2022. Available in: https://www.sciencedirect.com/science/article/abs/pii/S0269749124019961?via%3Dihub.
The research monitored two urban rivers in Belém with different levels of vegetation. The river with the lowest vegetation index recorded a debris transport rate around 189 times higher during rainy periods compared to the region’s less rainy season. For the river with the highest vegetation index, this value was around 6 times higher in the rainy seasons.
The researchers point to vegetation and urban sanitation as the main factors in the transportation of pollutants in the river course, as well as drawing attention to the need for more studies to measure the impacts on the local ecosystem. Monitoring urban rivers, improving basic sanitation, and ensuring proper waste disposal – such as recycling and energy generation – are crucial to preventing the issue from escalating and causing further environmental damage.
Figure 4. Plastic waste found in the Tucunduba River. Source: LAPMAR.
References
AL-ZAWAIDAH, Hadeel; RAVAZZOLO, Diego; FRIEDRIC, Heide. Macroplastics in rivers: present knowledge, issues and challenges. Environmental Science: Nano, Londres, v. 8, n. 12, p. 4501-4513, dez. 2020.
CHEN, Chi-Yun; LU, Tien-Hsuan; YANG, Ying-Fei; LIAO, Chung-Min. Toxicokinetic/toxicodynamic-based risk assessment of freshwater fish health posed by microplastics at environmentally relevant concentrations. Environmental Science: Nano, Londres, v. 8, n. 12, p. 4501-4513, dez. 2020.
ROSA, Gabriel Pompeu; COSTA, Mauricio da Silva da; MONTEIRO, Sury de Moura. Export of macro plastics over a tidal cycle by through small urban rivers in the Amazon. Environmental Science: Nano, Londres, v. 8, n. 12, p. 4501-4513, dez. 2020.
VAN EMMERIK, Tim; MELLINK, Yvette; HAUK, Rahel; WALDSCHLÄGER, Kryss; SCHREYERS, Louise. Rivers as plastic reservoirs. Environmental Science: Nano, Londres, v. 8, n. 12, p. 4501-4513, dez. 2020.
