Efeitos da morfodinâmica costeira na distribuição espacial de micropartículas antropogênicas
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Data
2023-08-14
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Universidade Estadual Paulista (Unesp)
Resumo
As micropartículas antrópicas (MPA, <5mm) tornaram-se uma das principais ameaças aos ambientes marinhos, devido a sua natureza onipresente e os efeitos prejudiciais sobre a biota e os ecossistemas. A distribuição espacial de MPA, incluindo celulose modificada e microplástico (MP), em sedimentos de diferentes feições deposicionais (planície de maré, praia e duna frontal) e em água estuarina e marinha foi estuda em área de proteção ambiental do litoral sul do estado de São Paulo, Brasil. Amostras sedimentares e de água foram submetidas a análise de MPA em relação a quantidade, forma, cor, tamanho e composição química. Adicionalmente as amostras sedimentares foram submetidas à análise granulométrica. Os sedimentos lamosos da planície de maré retêm a maior concentração de MPA, com 20.500 particles/kg na porção supramareal e 18.500 particles/kg na porção inframareal. Isto pode refletir à condição de baixa ação hidrodinâmica do rio que favorece o transporte e deposição das MPA junto aos sedimentos, caracterizando a planície de maré como o principal sumidouro de MPA. Enquanto os sedimentos arenosos da praia se caracterizam por menores concentrações de MPA, 5.900 partículas/kg na face praial e 4.700 partículas/kg no pós-praia. A diferença na abundância de MPA entre os dois setores praiais reflete a hidrodinâmica das feições, uma vez que a face praial está sob ação direta de ondas e correntes o que gera sucessivos ciclos de erosão e deposição das MPA. Enquanto no pós-praia, as MPA são controladas pelo fluxo e refluxo das ondas. A menor concentração de MPA nos sedimentos foi observada em amostras de dunas eólicas frontais (4.350 partículas/kg) que se caracterizam pelos sedimentos arenosos mais finos, o que reflete o transporte eólico das partículas. Entre as amostras de água analisadas, a concentração de MPA foi maior nas amostras de água marinha (85 partículas/l) do que na água estuarina (35 partículas/l). As fibras foram a forma predominante de MPA nos sedimentos (99-100%) e nas águas (80-95%). A composição química das fibras foi de 73% celulose modificada, 16% exibiam apenas a assinatura de corante e 11% micropartículas plásticas. Os resultados demonstram que para compreender a distribuição espacial de MPA em sedimentos e águas costeiras é importante analisar as partículas antrópicas a partir de uma perspectiva integrada, onde dados de abundância, características e composição das MPA, são interpretados juntamente com resultados de granulometria dos sedimentos, condições hidrodinâmicas e morfologia de diferentes feições deposicionais costeiras.
The spatial distribution of anthropogenic microparticles (AMP, <5mm), including modified cellulose and microplastic (MP), in sediments of different depositional features (tidal flat, beach and foredune), and in estuarine and marine water was studied in an environmental protection area of the southern coast of the state of São Paulo, Brazil. Sedimentary and water samples were subjected to AMP analysis for abundance, shape, color, size and chemical composition. In addition, the sedimentary samples were submitted to grain size analysis. Mud tidal flat sediments exhibited the highest concentration of AMP, with 20,500 particles/kg in the supratidal 18,500 particles/kg in the infratidal portion. This can be attributed to the low hydrodynamic action of the river that promotes the transport and deposition of AMP along with the sediments, thus distinguish the tidal flat sediments as the primary sink for these particles. While sandy sediments are characterized by a decrease in AMP concentration, 5,900 particles/kg in the beachface and 4,700 particles/kg in the backshore. The difference in AMP abundance between the two beach sectors reflects the hydrodynamics of the features. Since the beachface is under the direct action of waves and currents, which generates successive cycles of AMP erosion and deposition. While in the backshore, the AMP are controlled by the swash and backwash of the waves. The lowest concentration of AMP in the sediments was observed in samples of foredune sediments (4,350 particles/kg) which are characterized by finer sandy sediments, reflecting the eolian transport of the particles. Among the analyzed waters, the AMP concentration was higher in marine water samples (85 particles/l) followed by estuarine water (35 particles/l). Fibers were the predominant shape of AMP in sediments (99-100%) and waters (80-95 The chemical composition of the fibers was 73% modified cellulose, 16% exhibited dye signature only and 11% were MP. The results demonstrate that, in order to comprehend the spatial distribution of AMP in coastal sediments and waters, it is important to analyse anthropogenic particles from an integrated perspective, where data on abundance, characteristics and composition of AMP are interpreted toheher with results of sediment granulometry, hydrodynamic conditions, and morphology of different coastal depositional features.
The spatial distribution of anthropogenic microparticles (AMP, <5mm), including modified cellulose and microplastic (MP), in sediments of different depositional features (tidal flat, beach and foredune), and in estuarine and marine water was studied in an environmental protection area of the southern coast of the state of São Paulo, Brazil. Sedimentary and water samples were subjected to AMP analysis for abundance, shape, color, size and chemical composition. In addition, the sedimentary samples were submitted to grain size analysis. Mud tidal flat sediments exhibited the highest concentration of AMP, with 20,500 particles/kg in the supratidal 18,500 particles/kg in the infratidal portion. This can be attributed to the low hydrodynamic action of the river that promotes the transport and deposition of AMP along with the sediments, thus distinguish the tidal flat sediments as the primary sink for these particles. While sandy sediments are characterized by a decrease in AMP concentration, 5,900 particles/kg in the beachface and 4,700 particles/kg in the backshore. The difference in AMP abundance between the two beach sectors reflects the hydrodynamics of the features. Since the beachface is under the direct action of waves and currents, which generates successive cycles of AMP erosion and deposition. While in the backshore, the AMP are controlled by the swash and backwash of the waves. The lowest concentration of AMP in the sediments was observed in samples of foredune sediments (4,350 particles/kg) which are characterized by finer sandy sediments, reflecting the eolian transport of the particles. Among the analyzed waters, the AMP concentration was higher in marine water samples (85 particles/l) followed by estuarine water (35 particles/l). Fibers were the predominant shape of AMP in sediments (99-100%) and waters (80-95 The chemical composition of the fibers was 73% modified cellulose, 16% exhibited dye signature only and 11% were MP. The results demonstrate that, in order to comprehend the spatial distribution of AMP in coastal sediments and waters, it is important to analyse anthropogenic particles from an integrated perspective, where data on abundance, characteristics and composition of AMP are interpreted toheher with results of sediment granulometry, hydrodynamic conditions, and morphology of different coastal depositional features.
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Palavras-chave
Poluição, Poluição marinha, Sedimentos marinhos, Sedimentos estuarinos, Fibras, Celulose modificada, Microplástico, Granulometria