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  • Microplastics  (2)
  • Dissolved organic carbon  (1)
  • American Chemical Society  (2)
  • Université de Tunis El Manar. Faculté des Sciences de Tunis  (1)
  • American Chemical Society (ACS)
  • 1
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Walsh, A. N., Reddy, C. M., Niles, S. F., McKenna, A. M., Hansel, C. M., & Ward, C. P. Plastic formulation is an emerging control of its photochemical fate in the ocean. Environmental Science & Technology, 55(18), (2021): 12383–12392, https://doi.org/10.1021/acs.est.1c02272.
    Description: Sunlight exposure is a control of long-term plastic fate in the environment that converts plastic into oxygenated products spanning the polymer, dissolved, and gas phases. However, our understanding of how plastic formulation influences the amount and composition of these photoproducts remains incomplete. Here, we characterized the initial formulations and resulting dissolved photoproducts of four single-use consumer polyethylene (PE) bags from major retailers and one pure PE film. Consumer PE bags contained 15–36% inorganic additives, primarily calcium carbonate (13–34%) and titanium dioxide (TiO2; 1–2%). Sunlight exposure consistently increased production of dissolved organic carbon (DOC) relative to leaching in the dark (3- to 80-fold). All consumer PE bags produced more DOC during sunlight exposure than the pure PE (1.2- to 2.0-fold). The DOC leached after sunlight exposure increasingly reflected the 13C and 14C isotopic composition of the plastic. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry revealed that sunlight exposure substantially increased the number of DOC formulas detected (1.1- to 50-fold). TiO2-containing bags photochemically degraded into the most compositionally similar DOC, with 68–94% of photoproduced formulas in common with at least one other TiO2-containing bag. Conversely, only 28% of photoproduced formulas from the pure PE were detected in photoproduced DOC from the consumer PE. Overall, these findings suggest that plastic formulation, especially TiO2, plays a determining role in the amount and composition of DOC generated by sunlight. Consequently, studies on pure, unweathered polymers may not accurately represent the fates and impacts of the plastics entering the ocean.
    Description: Funding was provided by the Seaver Institute, the Gerstner Family Foundation, Woods Hole Oceanographic Institution, and the National Science Foundation Graduate Research Fellowship Program (A.N.W.). The Ion Cyclotron Resonance user facility at the National High Magnetic Field Laboratory is supported by the National Science Foundation Division of Chemistry and Division of Materials Research through DMR-1644779 and the State of Florida.
    Keywords: Plastic pollution ; Marine debris ; Additives ; Dissolved organic carbon ; Photochemical oxidation ; FT-ICR-MS ; Titanium dioxide
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-10-21
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Colson, B. C., & Michel, A. P. M. Flow-through quantification of microplastics using impedance spectroscopy. ACS Sensors, 6(1), (2021): 238–244, doi:10.1021/acssensors.0c02223.
    Description: Understanding the sources, impacts, and fate of microplastics in the environment is critical for assessing the potential risks of these anthropogenic particles. However, our ability to quantify and identify microplastics in aquatic ecosystems is limited by the lack of rapid techniques that do not require visual sorting or preprocessing. Here, we demonstrate the use of impedance spectroscopy for high-throughput flow-through microplastic quantification, with the goal of rapid measurement of microplastic concentration and size. Impedance spectroscopy characterizes the electrical properties of individual particles directly in the flow of water, allowing for simultaneous sizing and material identification. To demonstrate the technique, spike and recovery experiments were conducted in tap water with 212–1000 μm polyethylene beads in six size ranges and a variety of similarly sized biological materials. Microplastics were reliably detected, sized, and differentiated from biological materials via their electrical properties at an average flow rate of 103 ± 8 mL/min. The recovery rate was ≥90% for microplastics in the 300–1000 μm size range, and the false positive rate for the misidentification of the biological material as plastic was 1%. Impedance spectroscopy allowed for the identification of microplastics directly in water without visual sorting or filtration, demonstrating its use for flow-through sensing.
    Description: The authors thank the Richard Saltonstall Charitable Foundation and the National Academies Keck Futures Initiative (NAKFI DBS13) for their funding support.
    Keywords: Microplastics ; Plastics ; Impedance spectroscopy ; Dielectric properties ; Instrumentation ; Particle detection ; Flow-through ; Environmental sensing
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2024-03-01
    Description: Ces dernières années, la contamination par les microplastiques (MP) est devenue une préoccupation mondiale. Les particules (〈 5 mm) représentent de plus en plus une menace globale et persistante pour l'ensemble des écosystèmes. Dans cette étude, l'abondance et les propriétés (taille, forme et type de polymère) des MPs dans les échantillons d'eau de surface de la mer et les sédiments du sable ont été étudiés dans quatre zones côtières de la mer Méditerranée (Golfe de Tunis, îles Pilau et Plane, plage de Ghar El Melh et Chatt Mami). Les îles ont montré l'abondance moyenne des MPs la plus élevée (0,007 à 1,967 éléments/m³), suivi de la plage de Ghar El Melh (0,019 à 0,068 éléments/g), du Chatt Mami (0,012 à 0,057 éléments/g) et du golfe de Tunis (0,009 à 0,053 éléments/m³). Les résultats ont montré que les MPs détectés dans tous les échantillons, indiquant une vaste répartition toute au long de la côte tunisienne. Les MPs représentatifs des quatre sites ont été préparés pour l'identification des polymères par Spectroscopie Infrarouge à Transformée de Fourier (FTIR ATR). Au total, neuf types de polymères ont été détectés (PVC, PET, PP, PE, PS, PA, PVDF et PEHD). Les formes identifiées dans cette étude sont (Fragments, Films, Filaments et Granulés) avec une prédominance des fragments détectés sur la surface de l'eau et les filaments détectés dans les sédiments ainsi qu’une contribution assez faible des granulés. Cette étude a permis donc de générer des données originales sur la présence de MPs dans les sédiments et les surfaces de l'eau côtiers de la côte nord tunisienne.
    Description: These last years, Microplastic contamination (MP) has become a global concern. Particles (〈 5 mm) increasingly represent a global and persistent threat to all ecosystems. In this study, the abundance and properties (size, shape and polymer type) of MPs in sea surface water samples and sand sediments were studied in four coastal areas of the Mediterranean Sea (Gulf from Tunis, Pilau and Plane islands, Ghar El Melh and Chatt Mami beach). The islands showed the highest average abundance of MPs (0.007 to 1.967 elements/m³), followed by Ghar El Melh beach (0.019 to 0.068 elements/g), Chatt Mami (0.012 to 0.057 elements/g) and the Gulf of Tunis (0.009 to 0.053 elements/m³). The results showed that MPs detected in all samples, indicating a wide distribution along the Tunisian coast. Representative MPs from the four sites were prepared for polymer identification by Fourier Transform Infrared Spectroscopy (FTIR-ATR). In total, nine types of polymers were detected (PVC, PET, PP, PE, PS, PA, PVDF and HDPE). The forms identified in this study are (Fragments, Films, Filaments and Granules) with a predominance of fragments detected on the water surface and filaments detected in sediments as well as a low contribution of granules. This study generated original data on the presence of MPs in sediments and coastal water surfaces of the Tunisian north coast.
    Description: Masters
    Keywords: Microplastiques ; Sédiments ; Eaux de surface ; FTIR-ATR ; Microplastics ; Surface water ; Sediment
    Repository Name: AquaDocs
    Type: Thesis/Dissertation
    Format: 110 pp
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