Microplastics in Galway Bay: A comparison of sampling and separation methods

• Published in: Marine pollution bulletin Vol. 135; pp. 932 - 940
• Main Authors: Pagter, Elena, Frias, João, Nash, Róisín
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2018; Elsevier BV
• Subjects: Bays; Benthic grabs; Comparative analysis; Comparative studies; Confidence; Corers; Current distribution; Density; Elutriation; Environmental Monitoring - instrumentation; Environmental Monitoring - methods; Geologic Sediments - analysis; Gravity; Gravity corers; Litter; Marine; Marine pollution; Marine sediments; Microplastics; MSFD; Plastics; Plastics - analysis; Pollutants; Pollution; Sampling; Sampling methods; Sediment; Sediments; Separation; Separation processes; Separation techniques; Sodium; Sodium chloride; Sodium tungstate; Statistical analysis; Subtidal sediment; Surveys; Tungsten Compounds - chemistry; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - isolation & purification; MSFD; Subtidal sediment; Pollution; Marine; Benthic grabs
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2018.08.013

Microplastics, an emerging pollutant, are recognised as having a ubiquitous distribution in the environment. Currently several benthic sampling tools are being employed to collect subtidal marine sediment, however, there are no comparative studies on the efficiency of these tools to sample for microplastics or the subsequent extraction methods of microplastics from these marine sediments. This study addresses these knowledge gaps by comparing commonly applied benthic sampling tools (Van Veen grab, box corer, gravity corer) and a variety of density separation methods (elutriation column, sodium chloride solution, sodium tungstate dihydrate solution) for microplastic collection and processing. Each sampling tool was tested at the same station and the collected sediment was used to assess the extraction performance for the different density separation techniques. No statistically significant differences were found between the concentrations of microplastics extracted for any of the sampling tools. However, there were significant differences between the density separation methods using sodium tungstate dihydrate and sodium chloride solution and the elutriation method. This preliminary study provides evidence that the sampling tools tested are both suitable and proficient at determining the abundance of microplastics in sediments. Sodium tungstate dihydrate proved to be a novel and feasible option for dense liquid separation of microplastics in subtidal marine sediments. These results will allow for more confidence in data quality when comparing future surveys applying different benthic sampling tools. •A new and efficient option for heavy liquid separation of MPs from marine sediments is Sodium tungstate dihydrate•Sodium chloride is the most feasible option for large scale monitoring purposes•All commonly used benthic grabs may be used for sampling microplastics in subtidal sediments•Elutriation design can hinder the efficiency and introduce contamination of sediment samples•Preliminary results show the sediment station sampled in Galway Bay had an average 104 microplastics per kg of dry sediment.