This review of 68 studies compares the methodologies used for the identification and quantification of microplastics from the marine environment. Three main sampling strategies were identified: selective, volume-reduced, and bulk sampling. Most sediment samples came from sandy beaches at the high tide line, and most seawater samples were taken at the sea surface using neuston nets. Four steps were distinguished during sample processing: density separation, filtration, sieving, and visual sorting of microplastics. Visual sorting was one of the most commonly used methods for the identification of microplastics (using type, shape, degradation stage, and color as criteria). Chemical and physical characteristics (e.g., specific density) were also used. The most reliable method to identify the chemical composition of microplastics is by infrared spectroscopy. Most studies reported that plastic fragments were polyethylene and polypropylene polymers. Units commonly used for abundance estimates are “items per m2” ...

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Microplastics in the Marine Environment: A Review of the Methods Used for Identification and Quantification

Plastic debris has significant environmental and economic impacts in marine systems. Monitoring is crucial to assess the efficacy of measures implemented to reduce the abundance of plastic debris, but it is complicated by large spatial and temporal heterogeneity in the amounts of plastic debris and by our limited understanding of the pathways followed by plastic debris and its long-term fate. To date, most monitoring has focused on beach surveys of stranded plastics and other litter. Infrequent surveys of the standing stock of litter on beaches provide crude estimates of debris types and abundance, but are biased by differential removal of litter items by beachcombing, cleanups and beach dynamics. Monitoring the accumulation of stranded debris provides an index of debris trends in adjacent waters, but is costly to undertake. At-sea sampling requires large sample sizes for statistical power to detect changes in abundance, given the high spatial and temporal heterogeneity. Another approach is to monitor the impacts of plastics. Seabirds and other marine organisms that accumulate plastics in their stomachs offer a cost-effective way to monitor the abundance and composition of small plastic litter. Changes in entanglement rates are harder to interpret, as they are sensitive to changes in population sizes of affected species. Monitoring waste disposal on ships and plastic debris levels in rivers and storm-water runoff is useful because it identifies the main sources of plastic debris entering the sea and can direct mitigation efforts. Different monitoring approaches are required to answer different questions, but attempts should be made to standardize approaches internationally.

/pdf/monitoring-the-abundance-of-plastic-debris-in-the-marine-cfovsmwupg.pdf

Monitoring the abundance of plastic debris in the marine environment

Plastic waste in the marine environment: A review of sources, occurrence and effects.

Although plastic debris is constantly accumulating in aquatic environments, the impact on aquatic ecosystems is not yet fully understood. A first important step to assess the consequences of plastic debris in aquatic ecosystems is the establishment of a reliable, verified, and standardized method to quantify the amount of plastic particles in the environment. We improved the density separation approach by the construction of the so called Munich Plastic Sediment Separator (MPSS). It enables a reliable separation of different ecologically relevant size classes of plastic particles from sediment samples. A ZnCl2-solution (1.6–1.7 kg/L) as separation fluid allows for an extraction of plastic particles ranging from large fragments to small microplastic particles (S-MPP, <1 mm). Subsequent identification and quantification of the particles with spatial resolution down to 1 µm can be performed using Raman microspectroscopy. Our study is the first providing validated recovery rates of 100% for large microplastic particles (L-MPP, 1–5 mm) and 95.5% for S-MPP. The recovery rate for S-MPP, using the MPSS, was significantly higher than the value obtained by application of classical density separation setup (39.8%). Moreover, our recovery rates were significantly higher than those based on froth flotation (55.0% for L-MPP) commonly used in recycling industries. Hence, our improved method can be used for a reliable and time-efficient separation, identification and quantification of plastic fragments down to S-MPP. This will help foster studies quantifying the increasing contamination of aquatic environments with microplastic particles, which is a crucial prerequisite for future risk assessment and management strategies.

https://aslopubs.onlinelibrary.wiley.com/doi/epdf/10.4319/lom.2012.10.524

A novel, highly efficient method for the separation and quantification of plastic particles in sediments of aquatic environments

Occurrence and spatial distribution of microplastics in sediments from Norderney.

Beach Litter Sampling Strategies: is there a ‘Best’ Method?

Maritime litter and sewage contamination at Cramond Beach Edinburgh — A comparative study

Preliminary studies of man-made litter in the Firth of Forth, Scotland

Nutrient levels were monitored over a twelve month period in Bemersyde Moss, a shallow wetland in southern Scotland. The Moss is used by a variety of waterfowl, both as a winter roost by approximately 100-250 greylag geese (Anser anser) and in summer as a breeding colony for over 14,000 pairs of black-headed gulls (Laws ridibundus). It is surrounded by agricultural land, which along with the birds has an effect on nutrient levels. Phosphate phosphorus (PO4-P) and combined inorganic nitrogen (NH4-N, NO3-N and NO2-N) concentrations were analysed at fortnightly intervals, both in the drains flowing into the wetland and in the wetland itself. Abiotic parameters including pH, conductivity, temperature, depth, dissolved oxygen were also recorded. P and MH4-N showed high concentration in summer due to the influx of birds and use by livestock. Although some of the NO3-N could be attributed to the oxidation of NH4-N, increased levels in the spring and late autumn/early winter were measured in the field drains, suggesting an input from the surrounding arable fields. It was concluded that birds and livestock were making a major contribution to P and N levels within the wetland.

Marina Mocogni

Papers

Beach Litter Sampling Strategies: is there a ‘Best’ Method?

Maritime litter and sewage contamination at Cramond Beach Edinburgh — A comparative study

Preliminary studies of man-made litter in the Firth of Forth, Scotland

Seasonal variations in nutrient levels in Bemersyde Moss, Borders Region, Scotland.