RESUMO
Plastic production continues to increase every year, yet it is widely acknowledged that a significant portion of this material ends up in ecosystems as microplastics (MPs). Among all the environmental compartments affected by MPs, the atmosphere remains the least well-known. Here, we conducted a one-year simultaneous monitoring of atmospheric MPs deposition in ten urban areas, each with different population sizes, economic activities, and climates. The objective was to assess the role of the atmosphere in the fate of MPs by conducting a nationwide quantification of atmospheric MP deposition. To achieve this, we deployed collectors in ten different urban areas across continental Spain and the Canary Islands. We implemented a systematic sampling methodology with rigorous quality control/quality assurance, along with particle-oriented identification and quantification of anthropogenic particle deposition, which included MPs and industrially processed natural fibres. Among the sampled MPs, polyester fibres were the most abundant, followed by acrylic polymers, polypropylene, and alkyd resins. Their equivalent sizes ranged from 22 µm to 398 µm, with a median value of 71 µm. The particle size distribution of MPs showed fewer large particles than expected from a three-dimensional fractal fragmentation pattern, which was attributed to the higher mobility of small particles, especially fibres. The atmospheric deposition rate of MPs ranged from 5.6 to 78.6 MPs m-2 day-1, with the higher values observed in densely populated areas such as Barcelona and Madrid. Additionally, we detected natural polymers, mostly cellulosic fibres with evidence of industrial processing, with a deposition rate ranging from 6.4 to 58.6 particles m-2 day-1. There was a positive correlation was found between the population of the study area and the median of atmospheric MP deposition, supporting the hypothesis that urban areas act as sources of atmospheric MPs. Our study presents a systematic methodology for monitoring atmospheric MP deposition.
RESUMO
Plastics are widely used by society, and their degradation into millimetre fragments, called microplastics (MPs), has become a global environmental threat to ecosystems and human health. However, airborne MPs' presence and fallout fluxes from the atmosphere are poorly understood and can vary significantly by different conditions, especially in megacities of low- and middle-income countries, where high levels of vehicular air pollution, a high-density population, high plastic use, and inadequate disposal are environmental threats related to airborne MPs. In this study, we investigate the amount, chemical composition, and morphological characteristics of outdoor and indoor airborne MPs fallout in the megacity of São Paulo and assess the influence of weather and seasons on airborne MPs fallout. The results were as follows: MPs were found in all samples with an average fallout rate of 309.40 ± 214.71 MPs/m2/day in the indoor environment, and 123.20 ± 47.09 MPs/m2/day in the outdoor environment; MPs concentrations were higher in the indoor environment than the outdoor environment, with more fibres than particles; polyester fibres (100%), polyethylene (59%) and polypropylene (26%) particles were the dominant polymers indoors, while in outdoors, polyester fibres (76%) and polyethylene (67%) and polyethylene terephthalate (25%) particles were dominant. Fragment was the dominant morphology of particles found in indoor and outdoor samples (64% and 74%, respectively). Outdoor MPs fallout correlated positively with rainfall, wind velocity, and relative humidity. This evidence is the first on airborne MPs in a Latin America megacity and highlights the relevant role that this source plays in different environments.