Seas and oceans are nowadays recognized to be affected by microplastic (MP) pollution, with MPs commonly defined as plastic fragments particles having, in general, less than 5.0 mm length. Threat to marine ecosystems and human health are the main issues regarding MP pollution, with recently observed relation between the use of fishing nets and the presence of microfibers. These fibers could aggregate to originate clusters, which can precipitate contaminating marine sediments, or even be ingested by a wide range of marine organisms, including bivalves cultured for human consumption, such as oysters. Hence, the monitoring of the presence of MPs by proper protocols is still necessary. The National Oceanic and Atmospheric Administration (NOAA) proposes two distinct MP extraction protocols for sandy and bed sediments, which, however, have been shown to suffer from many limitations. Conversely, to what concerns oysters, published protocols are usually time consuming, requiring a KOH 24–48 hour oxidation step. In this context, the aim of this study is to show how an iterative adaptation of the NOAA protocol allows the extraction of MPs from marine sediments, regardless of their characteristics. The method tested on PE-LD/PET/PA/PE-HD of different shapes (fragments, fibers and spheres) is based on density separation and oxidation treatments which were both carefully tuned. Final recoveries were higher than 85% for all the micropolymers (100% for PE and PA), avoiding any alteration of MPs polymer structure, necessary to proceed for a spectroscopic identification. Furthermore, a new protocol for the extraction of MPs from oysters was derived, highlighting its efficacy (recoveries higher than 84% for all polymer types tested) and time-saving peculiarity (complete degradation of the organic matrix within 1 h). Finally, both protocols were successfully applied in sediments collected from a fishing ground and close by a highly anthropic area (Porto, Portugal) and in oysters collected in an estuarine area, revealing the not negligible presence of many microfibers.
Iterative protocols for the extraction and quantitation of microplastics from marine sediments and oysters
Luca Rivoira;Michele Castiglioni;Irene Ingrando;Maria Concetta Bruzzoniti;
2021-01-01
Abstract
Seas and oceans are nowadays recognized to be affected by microplastic (MP) pollution, with MPs commonly defined as plastic fragments particles having, in general, less than 5.0 mm length. Threat to marine ecosystems and human health are the main issues regarding MP pollution, with recently observed relation between the use of fishing nets and the presence of microfibers. These fibers could aggregate to originate clusters, which can precipitate contaminating marine sediments, or even be ingested by a wide range of marine organisms, including bivalves cultured for human consumption, such as oysters. Hence, the monitoring of the presence of MPs by proper protocols is still necessary. The National Oceanic and Atmospheric Administration (NOAA) proposes two distinct MP extraction protocols for sandy and bed sediments, which, however, have been shown to suffer from many limitations. Conversely, to what concerns oysters, published protocols are usually time consuming, requiring a KOH 24–48 hour oxidation step. In this context, the aim of this study is to show how an iterative adaptation of the NOAA protocol allows the extraction of MPs from marine sediments, regardless of their characteristics. The method tested on PE-LD/PET/PA/PE-HD of different shapes (fragments, fibers and spheres) is based on density separation and oxidation treatments which were both carefully tuned. Final recoveries were higher than 85% for all the micropolymers (100% for PE and PA), avoiding any alteration of MPs polymer structure, necessary to proceed for a spectroscopic identification. Furthermore, a new protocol for the extraction of MPs from oysters was derived, highlighting its efficacy (recoveries higher than 84% for all polymer types tested) and time-saving peculiarity (complete degradation of the organic matrix within 1 h). Finally, both protocols were successfully applied in sediments collected from a fishing ground and close by a highly anthropic area (Porto, Portugal) and in oysters collected in an estuarine area, revealing the not negligible presence of many microfibers.
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