Advancing plastic pollution hotspotting at the subnational level: Brazil as a case study in the Global South.

Identifying sources is crucial for proposing effective actions to combat marine litter pollution. Here, we used an innovative approach to identify hotspots of mismanaged plastic waste (MPW) within Brazil and subsequent leakage to the ocean, based on population density, socio-economic conditions, municipal solid waste management and environmental parameters. We estimated plastic waste generation and MPW for each of the 5570 Brazilian municipalities, which totaled 3.44 million metric tons per year. Then, we estimated the probability of litter mobilization and transport (P) and the relative risk of leakage to the ocean (MPW × P). The Guanabara Bay and La Plata River comprised the main oceanic entry hotspots of litter produced in Brazil. The use of national databases allowed us to increase spatial and temporal granularity, offering a detailed baseline for the application of prevention and mitigation actions. However, overcoming data limitations is still a challenge in Brazil as in other Global South countries.

How far are we from robust estimates of plastic litter leakage to the environment?

Litter pollution is a global concern, and identifying sources and pathways is crucial for proposing preventative actions. Existing models of plastic litter leakage to the environment have provided worldwide estimates at a country-based level, but only a few initiatives address subnational scales. Adding relevant parameters and improving models is needed to reduce the limitations of global estimates. However, availability of information, which varies among countries and is critical in the Global South, may preclude such improvements. To understand the potentialities and limitations of subnational estimates of plastic litter leakage to the environment, we reviewed the parameters used in the literature and addressed data usability, considering Brazil as a case study. We gathered data on parameters identified for all 5570 Brazilian municipalities and evaluated their usability considering reliability and temporal and geographic granularity. We identified 51 parameters that are either currently used in models or could improve estimates, including parameters regarding territory, population density, socioeconomic condition, and solid waste generation, composition, collection, and final destination, selective waste collection, recycling, and hydrology. Only 29.4% of parameters were linked to data sources with good or very good usability, while most of them presented average usability (45.1%) and 7.8% were not linked to any data source. This panorama of low data usability reveals uncertainties and explicit difficulties of estimating plastic litter leakage to the environment, including mobilization from the terrestrial environment to the ocean. The Brazilian scenario reflects current data availability conditions and the difficulties of countries in the Global South to robustly understand plastic litter leakage and face land-based sources of marine litter.

Considerations on the effects of tidal regimes in the movement of floating litter in an estuarine environment: Case study of the estuarine system of Santos-São Vicente, Brazil.

Floating litter in the estuarine system of Santos-São Vicente is common and is part of day-to-day activities of various users of the area. The objective of the present study was to carry out a quali-quantitative evaluation of the occurrence of floating litter, to infer their sources, and to identify environmental factors that are likely to control occurrence and distribution, with particular emphasis on the effects of tidal regimes. Six sampling stations were selected along the aforementioned estuary and visited monthly between July 2010 and January 2012. Floating litter was counted from a fixed sampling station. Plastics prevailed (89.64%) and their main source was domestic activities (55.41%). More litter was found during ebb spring tides, with higher concentrations obeying confluence patterns of the estuary's channels. Results indicated that occurrence can be attributed to the deficiency in basic sewage system in the area and the deliberate disposal into the estuary by the local population.