Detecting microplastics in marine sediments - a methods comparison of isolation and extraction procedures
Citation:
Cashman, M., K. Ho, S. Robinson, S. Russo, T. Boving, AND R. Burgess. Detecting microplastics in marine sediments - a methods comparison of isolation and extraction procedures. NAC SETAC 25th Annual Meeting, Boston, MA, April 08 - 09, 2019.
Impact/Purpose:
Mircoplastics, or small (<5 millimeter) pieces of plastic are polluting marine environments. Many researchers have shown that there is substantial microplastic pollution in marine sediments, but scientists do not know their ultimate abundance or expanse. There are many existing methods for quantifying microplastics in marine sediments, but procedural differences make it difficult to compare results from one method to another. This research compares five current microplastic extraction methods for their ability to recover a variety of different microplastics from marine sediments. The results are of interest to managers and scientists in Regions, States, Tribes and Programmatic Offices as they make decisions on the best methods to extract, isolate and identify microplastics.
Description:
Despite frequent field observations of microplastics (i.e., plastic particles <5mm in size) there is a critical knowledge gap of their fate and effects in marine and estuarine environments. Many microplastics ultimately accumulate in marine sediments because of physicochemical and biological processes but precise amounts are currently uncertain. Numerous methods exist for the extraction and isolation of microplastics from marine sediments, but major procedural differences prevent meaningful comparison among methods. These differences may result in altered recoveries of varying polymer types, sizes, and shapes from environmental samples. To address the impacts of these differences, we conducted a systematic assessment and comparison of five commonly used methods for microplastic isolation and identification in two representative marine sediments. Methods were selected to reflect the range of procedures in the scientific literature. Known quantities of five different microplastic types were amended to silty and sandy sediments. These microplastics reflect a range of polymers, sizes, and shapes that are commonly identified in published field surveys. Methods were assessed on their ability to isolate amended microplastics from each sediment sample. Mean recoveries of microplastics ranged from 0 to 87%, depending on polymer type. Statistical analysis indicated significant interactions between method and microplastic type for both sediments. This research allows for the quantitative comparison of the performance of the five methods, as well as provides initial recommendations for routine microplastic monitoring procedures in marine sediments.