The interactions of plastic with tar and other petroleum derivatives in the marine environment: A general perspective

Plastic and oil pollution are closely linked to our dependence on petroleum derivatives. Their excessive use and inefficiencies in their management, have led to negative impacts on marine ecosystems since their very introduction. Agglomerates of tar, plastic, paraffins, and other petrochemicals and oil derivatives with naturally occurring materials, are increasingly widespread in coastal environments, stalling as an iconic and readable sign of environmental degradation. Starting from a historical review of the available reports on the occurrence of similar aggregates dating back to 1971, we highlight how most of these observations are based on the morphological description of the petroleum residues with no chemical fingerprinting and are mainly related to materials stranded on the coastline, with few and unclear indications for the open sea. We discuss here a list of scientific questions and knowledge gaps, that need to be examined by future studies.

Microplastics in sea ice: A fingerprint of bubble flotation

Sea ice is heavily contaminated with microplastics (MPs), with the repeatedly confirmed increased number of larger-sized particles, deficit of fibers, and prevalence of materials denser than the surrounding water. To get insight into the drivers behind such a specific pattern, sets of laboratory experiments were performed on the formation of ice by cooling from the surface of fresh and salty (NaCl, 34 g/L) water, with particles of different sizes from heavy plastics (HPP) distributed initially over the bottom of the experimental volume. After freezing, about 50-60 % of HPP were trapped in ice in all the runs. Vertical distribution of HPP, plastic mass distribution, ice salinity (in saltwater experiments), and bubble concentration (in freshwater experiments) were recorded. Formation of bubbles on hydrophobic surfaces was the main cause of the entrapment of HPP into ice, with convection playing a secondary role. Supplementary bubble formation experiments with the same particles in water demonstrated that at larger fragments and fibers, several bubbles grow at the same time, so particle rising and residing at the surface is stable. Smaller HPP experience rising/sinking cycles with minimum time spent at the surface: one bubble is enough to cause a particle rising, but it is most often lost when colliding with the water surface. Application of the results to oceanic conditions is discussed. Oversaturation with gases due to various physical/biological/chemical processes and liberation of bubbles from methane seeps and melting permafrost are common in Arctic waters. Convective water motions are able to relocate HPP in vertical. Based on applied research, the bubble nucleation and growth, the hydrophobicity of weathered surfaces, the effectiveness of flotation methods for plastic particles are discussed. Interaction of plastic particles with bubbles is an important feature, still completely overlooked in the context of MPs behavior in marine environment.

Microplastics distribution in bottom sediments of the Baltic Sea Proper

An abundance of microplastics particles (0.2-5 mm, MPs) in bottom sediments is analyzed based on 53 samples (3 to 215 m deep) obtained in 8 cruises of research vessels across the Baltic Sea Proper in March-October 2015-2016. MPs content varied between stations from 103 up to 10,179 items kg^-1 d.w., with the bulk mean of 863 ± 1371 items kg^-1 d.w., showing a statistically significant increase with water depth. As many as 74.5% of MPs are of fibrous shape, followed by films (19.8%) and fragments (5.7%). The distributions of fibres, fragments, films, and different types of natural bottom sediments are significantly different, highlighting the specific behaviour of each of these kinds of bottom deposits. A statistically significant correlation between water depth and fibres content is found. Based on the analysis of oceanographic factors and sedimentological principles, an erosion/transition/accumulation pattern for fibres in the Baltic Sea Proper is outlined. Fibres can be considered as a specific type of "synthetic sediment", while principles of distribution of other MPs are not yet certain.

Dataset on geosynthetic material debris contamination of the South-East Baltic shore

The database gives information on the contamination of the shore of the South-Eastern Baltic with the debris of geosynthetic materials for the period 2018–2020. This new type of coastal pollution enters the natural environment due to the destruction of coastal protection structures and construction activities. The database contains sections: (1) a list of types of geosynthetic material residues, their photographic images and photographs illustrating examples of finds in natural conditions [1 List_geosynthetic_debris_SEB], (2) monitoring data on the contamination of the beach strip with the debris of geotextiles, braids from gabions, geocontainers (big bags), geocells and geogrids for the beaches of the South-Eastern Baltic for the period 2018–2020 [2 Monitoring_geosynthetic_debris_SEB]; (3) statistical distributions of the found geosynthetic debris by size [3 Scales_geosynthetic_debris_SEB] and (4) results of test surveys on the shores of Lithuania and Poland adjacent to Kaliningrad Oblast. All data refer to the beaches of the Kaliningrad Oblast (Russia), including the Russian parts of the Vistula and Curonian Spits, but also contains information on a one-time assessment of the pollution of the beaches of the adjacent territories: the Polish shore from the Poland-Russia border on the Vistula Spit to the mouth of the Vistula River, the Lithuanian shore from the border Lithuania-Russia on the Curonian Spit to the border of Latvia-Lithuania. Materials were collected during field surveys within the ERANET-RUS_Plus joint project EI-GEO, ID 212 (RFBR 18-55-76002 ERA_a, BMBF 01DJ18005).

Microplastic contamination of sandy beaches of national parks, protected and recreational areas in southern parts of the Baltic Sea

The distribution of small (0.5-2 mm, S-MPs) and large (2-5 mm, L-MPs) microplastics and mesoplastic particles in 51 samples of surface beach sands at 7 locations along the southern shore of the Baltic Sea was investigated. MPs particles (3267 in total) were found at all the sites and in all the beach zones. The bulk mean MPs (0.5-5 mm) contamination is 68 ± 117 (median 33) items/kg DW (n = 51). The results were confirmed by μ-Raman spectroscopy analysis. National park areas did not differ substantially from other beaches. Expanded polystyrene fragments accounted for about 38% of the total collected particles. Fibres were the predominant type of MPs (55%). The highest contamination was found within the current wrack line (60.1 ± 36.6 items/kg DW of S-MPs). A consistent picture for S-MPs was observed at the beach face, where the mean values in different locations varied between 21.0 and 58.1 items/kg DW, with a bulk mean of 30.4 ± 13.7 items/kg DW.

Investigations of plastic contamination of seawater, marine and coastal sediments in the Russian seas: a review

Twelve seas with an integral coastline length of about 38,000 km wash upon the Russian coasts. They belong to the basins of the Atlantic, the Arctic, and the Pacific Oceans and stretch over temperate, subpolar, and polar climate zones. This review of 32 studies published between 2015 and August 2020 analyses the available peer-reviewed scientific publications related to the topic of plastic contamination. At present, plastic contamination of the marine environments is confirmed by field investigations in 7 out of 12 Russian seas. Pollution levels vary widely: from 0.6 to 336,000 items/m3 for microplastics in water and from 1.3 to 10,179 items/kg (DW)-in sediments, while median macroplastics abundance is around 1.0 item/m2 at the coast. One monitoring survey of the Barents Sea reported mean macroplastics concentration in the upper 60 m as 0.011 mg/m3 and 2.9 kg/km2 at the sea floor. The identification of the polymer types with spectroscopy techniques is performed only in 9 studies (28%); most researchers use visual identification which makes the results difficult to compare. Most projects aimed at the plastic contamination research use their own collection and extraction methods that poorly agree with other studies. Since the pollution levels in most of the areas are relatively low, sampling is inhomogeneous in space and time. The most extensively studied areas are the beaches of the Baltic Sea, while the least examined is the Arctic region. Our study highlights the need for a discussion on harmonizing sampling methodology and identification techniques among different studies.

Environmental Impact of Geosynthetics in Coastal Protection

Geosynthetic materials are applied in measures for coastal protection. Weathering or any damage of constructions, as shown by a field study in Kaliningrad Oblast (Russia), could lead to the littering of the beach or the sea (marine littering) and the discharge of possibly harmful additives into the marine environment. The ageing behavior of a widely used geotextile made of polypropylene was studied by artificial accelerated ageing in water-filled autoclaves at temperatures of 30 to 80 °C and pressures of 10 to 50 bar. Tensile strength tests were used to evaluate the progress of ageing, concluding that temperature rather than pressure was the main factor influencing the ageing of geotextiles. Using a modified Arrhenius equation, it was possible to calculate the half-life for the loss of 50% of the strain, which corresponds to approximately 330 years. Dynamic surface leaching and ecotoxicological tests were performed to determine the possible release of contaminants. No harmful effects on the test organisms were observed.

From macro to micro, from patchy to uniform: Analyzing plastic contamination along and across a sandy tide-less coast

In search of an effective method to evaluate plastic contamination, macrolitter (>25 mm), mesolitter (5-25 mm), large microlitter (2-5 mm), large and small microplastics (2-5 mm and 0.5-2 mm) abundances in surface beach sands were simultaneously determined by two methods in four beach zones at six locations along the 100-km-long marine coast of the Curonian Spit National Park and the neighboring cities. Mean (median) content of plastic items per m² is 0.85 (0.33) for macro-, 1.48 (0.40) for meso-, 3.35 (0.68) for large microlitter, and 3235 (1800) for microplastics (0.5-5 mm). The distribution of litter and microplastics (0.5-5 mm) is highly variable along and across the beach. The abundance of small-microplastics (0.5-2 mm) at the beach face is similar for all the locations and replicates. Swash-zone mixing, water percolation, importance of sediment pore size (rather than grain size), natural sorting of plastic particles at the beach face are considered.

Microplastics in Baltic bottom sediments: Quantification procedures and first results

Microplastics in the marine environment are known as a global ecological problem but there are still no standardized analysis procedures for their quantification. The first breakthrough in this direction was the NOAA Laboratory Methods for quantifying synthetic particles in water and sediments, but fibers numbers have been found to be underestimated with this approach. We propose modifications for these methods that will allow us to analyze microplastics in bottom sediments, including small fibers. Addition of an internal standard to sediment samples and occasional empty runs are advised for analysis quality control. The microplastics extraction efficiency using the proposed modifications is 92±7%. Distribution of microplastics in bottom sediments of the Russian part of the Baltic Sea is presented. Microplastic particles were found in all of the samples with an average concentration of 34±10 items/kg DW and have the same order of magnitude as neighbor studies reported.

Plastic pollution on the Baltic beaches of Kaliningrad region, Russia

Contamination of sandy beaches of the Baltic Sea in Kaliningrad region is evaluated on the base of surveys carried out from June 2015 to January 2016. Quantity of macro/meso/microplastic objects in the upper 2cm of the sandy sediments of the wrack zone at 13 sampling sites all along the Russian coast is reported. Occurrence of paraffin and amber pieces at the same sites is pointed out. Special attention is paid to microplastics (range 0.5-5mm): its content ranges between 1.3 and 36.3 items per kg dry sediment. The prevailing found type is foamed plastic. No sound differences in contamination are discovered between beaches with high and low anthropogenic load. Mean level of contamination is of the same order of magnitude as has been reported by other authors for the Baltic Sea beaches.

On some physical and dynamical properties of microplastic particles in marine environment

Simplified physical models and geometrical considerations reveal general physical and dynamical properties of microplastic particles (0.5-5mm) of different density, shape and size in marine environment. Windage of extremely light foamed particles, surface area and fouling rate of slightly positively buoyant microplastic spheres, films and fibres and settling velocities of negatively buoyant particles are analysed. For the Baltic Sea dimensions and under the considered idealised external conditions, (i) only one day is required for a foamed polystyrene particle to cross the sea (ca. 250km); (ii) polyethylene fibres should spend about 6-8months in the euphotic zone before sinking due to bio-fouling, whilst spherical particles can be retained on the surface up to 10-15years; (iii) for heavy microplastic particles, the time of settling through the water column in the central Gotland basin (ca. 250m) is less than 18h. Proper physical setting of the problem of microplastics transport and developing of physically-based parameterisations are seen as applications.