Microplastics
(MPs, <5 mm) have been reported as emerging environmental
contaminants, but reliable data are still lacking. We compared the
two most promising techniques for MP analysis, namely, Raman and Fourier
transform infrared (FTIR) spectroscopy, by analyzing MPs extracted
from North Sea surface waters. Microplastics >500 μm were
visually
sorted and manually analyzed by μ-Raman and attenuated total
reflection (ATR)-FTIR spectroscopy. Microplastics ≤500 μm
were concentrated on gold-coated filters and analyzed by automated
single-particle exploration coupled to μ-Raman (ASPEx-μ-Raman)
and FTIR imaging (reflection mode). The number of identified MPs >500
μm was slightly higher for μ-Raman (+23%) than ATR-FTIR
analysis. Concerning MPs ≤500 μm, ASPEx-μ-Raman
quantified two-times higher MP numbers but required a four-times higher
analysis time compared to FTIR imaging. Because ASPEx-μ-Raman
revealed far higher MP concentrations (38–2621 particles m–3) compared to the results of previous water studies
(0–559 particles m–3), the environmental
concentration of MPs ≤500 μm may have been underestimated
until now. This may be attributed to the exceptional increase in concentration
with decreasing MP size found in this work. Our results demonstrate
the need for further research to enable time-efficient routine application
of ASPEx-μ-Raman for reliable MP counting down to 1 μm.
Microplastic pollution within the marine environment is of pressing concern globally. Accordingly, spatial monitoring of microplastic concentrations, composition and size distribution may help to identify sources and entry pathways, and hence allow initiating focused mitigation. Spatial distribution patterns of microplastics were investigated in two compartments of the southern North Sea by collecting sublittoral sediment and surface water samples from 24 stations. Large microplastics (500−5000 µm) were detected visually and identified using attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. The remaining sample was digested enzymatically, concentrated onto filters and analyzed for small microplastics (11−500 µm) using Focal Plane Array (FPA) FTIR imaging. Microplastics were detected in all samples with concentrations ranging between 2.8-1188.8 particles kg-1 for sediments and 0.1-245.4 particles m-3 for surface waters. On average 98% of microplastics were <100 µm in sediments and 86% in surface waters. The most prevalent polymer types in both compartments were polypropylene, acrylates/polyurethane/varnish, and polyamide. However, polymer composition differed significantly between sediment and surface water samples as well as between the Frisian Islands and the English Channel sites. These results show that microplastics are not evenly distributed, in neither location nor size, which is illuminating regarding the development of monitoring protocols.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.