Environmental Pollution 186 (2014) 248e256
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Occurrence and spatial distribution of microplastics in sediments from Norderney Jens H. Dekiff a, b, Dominique Remy b, Jörg Klasmeier a, Elke Fries a, *,1 a b
Institute of Environmental Systems Research, University of Osnabrueck, Barbarastraße 12, D-49076 Osnabrueck, Germany Department of Biology/Chemistry, Division of Ecology, University of Osnabrueck, Barbarastraße 13, D-49076 Osnabrueck, Germany
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 August 2013 Received in revised form 18 November 2013 Accepted 27 November 2013
The spatial distribution of small potential microplastics (SPM) (1 mm) was also examined. Small microparticles were extracted from 36 one kg sediment samples and analysed by visual microscopic inspection and partly by thermal desorption pyrolysis gas chromatography/mass spectrometry. The smallest particle size that could be analysed with this method was estimated to be 100 mm. The mean number of SPM at the three sampling sites (n ¼ 12) was 1.7, 1.3 and 2.3 particles per kg dry sediment, respectively. SPM were identified as polypropylene, polyethylene, polyethylene terephthalate, polyvinylchloride, polystyrene and polyamide. The organic plastic additives found were benzophenone, 1,2-benzenedicarboxylic acid, dimethyl phthalate, diethylhexyl phthalate, dibutyl phthalate, diethyl phthalate, phenol and 2,4-di-tert-butylphenol. Particles were distributed rather homogenously and the occurrence of SPM did not correlate with that of VPD. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Marine plastic debris Organic polymer additives Microplastics North sea Pyrolysis Gas chromatography Mass spectrometry Density separation
1. Introduction Marine plastic debris occurs in seas and oceans from the poles to the equator and from remote shorelines to highly populated coastlines (e.g. Derraik, 2002; Barnes et al., 2009). Microplastics that are invisible to the naked eye constitute a large share of the global problem (Andrady, 2011; Cole et al., 2011). Microplastics can be ingested by a number of marine species (Boerger et al., 2010; Graham and Thompson, 2009; Jacobsen et al., 2010; Lazar and Gra can, 2011; Murray and Cowie, 2011). In addition, the chemical effects of organic plastic additives (OPAs) must be considered. OPAs can leach out of the matrix over time, having a toxic and endocrine disruptive effect on marine organisms when plastics are ingested (Andrady, 2011; Oehlmann et al., 2009; Teuten et al., 2007, 2009; Fries et al., 2013). Descriptor 10 (European Parliament and the Council, 2010), an amendment to the European Marine Strategy Framework Directive (MSFD) (Directive 2008/56/EC, European Parliament and the
* Corresponding author. E-mail address: [email protected] (E. Fries). 1 Present address: Water, Environment and Eco-technologies Division, Bureau de Recherches Géologiques et Minières (BRGM), 3 Avenue Claude Guillemin, B.P. 36009, 45060 Orléans cedex 02, France. 0269-7491/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.envpol.2013.11.019
Council, 2008), claims that “properties and quantities of marine litter do not cause harm to the coastal and marine environment”. Due to the potential of sediments to accumulate marine debris (Browne et al., 2010; Claessens et al., 2011; Corcoran et al., 2009; Imhof et al., 2012; Reddy et al., 2006; Thompson et al., 2004; Fries et al., 2013; Nuelle et al., 2013), beaches and estuaries are suitable for monitoring plastic pollution. Taking samples from beaches is easier and cheaper than sea water sampling or ocean sediment sampling using bottom trawls because it does not require expensive, time-consuming sea cruises. However, monitoring data on the spatial distribution of microplastics in sediments remain a rarity. The North Sea, and particularly the tidal mudflats of the Wadden Sea, is a diverse, complex ecosystem that acts as a very valuable habitat for marine life with a high degree of biodiversity. At the same time, the North Sea is surrounded by the densely populated, industrialised nations of northern Europe. Approximately 185 million people live in riparian states, and millions of tourists visit the North Sea area every year for recreation (OSPAR, 2010). Various industries and major ports are located on bays or the estuaries of large rivers leading to the sea such as the Rhine, Elbe and Thames. With regard to human offshore activities, the North Sea is affected by intensive fishing and marine traffic, merchant and passenger ships, as well as pleasure craft and military vessels. A number of regional programmes such as the Convention for the Protection of
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Fig. 1. (A) Map of the island of Norderney showing the location of the urbanised area on western Norderney and its distance to the study area; (B) Satellite picture of sample area showing the extinction of the beach and the locations of the sampling site to the north of the island; symbols show the three sample sites: N1 square; N2 circle; N3 triangle (source: (A) LGLN, modified; (B) Google Earth, GeoBasis-DE/BKG, modified).
the Marine Environment of the north-east Atlantic, OSPAR for short, set quality objectives, promote the monitoring of the current environmental status, and manage potential actions and measures. In this article, the occurrence of plastic debris and related OPAs in beach sediments was investigated on the North Sea island of Norderney. The aim of the study was to determine whether spatial variability of microplastics must be taken into account within monitoring programmes. Emphasis was placed on studying the heterogeneity of microplastic concentrations at small spatial and temporal scales. This approach included an assessment of the quantity and material types of microplastics, including the identification of OPAs in recently formed drift line sediments, as well as an analysis of their small-scale spatial distribution patterns. Tests were also performed to determine whether a correlation exists between the occurrence of visible plastic debris (VPD) (>1 mm) on the surface of the sediments and the occurrence of invisible microplastics (1 mm) into large microplastics (1 mm e 5 mm), mesoplastics (5 mm e 25 mm) and macroplastics (>25 mm), while the invisible fraction (5 mm or one piece >25 cm in size within an area of 0.25 m2. Six of the 20 accumulations were randomly chosen by lot, and sediment samples were taken from a 0.25 m2 square defined as described below. In addition, six spots in the same area without any visible occurrence of plastics were randomly sampled. All sampling spots were marked by a wooden square frame with a side length of 0.5 m. Only the upper 3 cm layer was sampled. Approximately 3 kg sediments were
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Table 1 Detailed information and sampling scheme for sampling sites. Sampling site
Geographical coordinates of site onset
Study aim
Location
Elongation of site
Number of samples
Drift line sample name
Distance of sampling sites from site onset [m]
N1
53.721983 7.242500
Heterogeneity at small spatial and temporal scale
Northern coastline
100 m
12
N2
53.722333 7.245483
Heterogeneity at small spatial and temporal scale
Northern coastline
100 m
12
1.I 1.II 1.III 1.IV 1.V 1.VI 2.I 2.II 2.III 2.IV 2.V 2.VI
18 20 22 48 71 95 17 28 51 57 66 84
N3
53.718950 7.286317
Correlation between small potential microplastics and visible plastic debris
Dune valley, about 800 m in length perpendicular to the northern coastline
Approx. 200 m
12
Fig. 2. Sample design for drift line sampling sites IeVI at sampling locations N1 and N2. Twelve samples (numbered squares) were taken from each sampling site, six from an upper 100 m stretch of the drift line and six from a younger drift line that was closer to the water line. The distance between both drift lines was approx. 16 m (the exact distance of the sample locations from the site onset is given in Table 1). collected from each 0.25 m2 square using a stainless steel spoon and stored in brown glass bottles. The spoon was cleaned between samples using sea water and lint-free paper. The bottles were sealed and stored in the laboratory at room temperature until required for analysis. In the laboratory, 2 kg wet sediments from each bulk sample were transferred to two ultrapure water-rinsed ceramic bowls that were then covered with aluminium foil. The bowls were placed in a drying cabinet at 60 C until the sediments had
dried. One kg dry sediments (approximately 600 ml) was weighed out and sieved through a 1 mm mesh. The residue (>1 mm) was visually inspected by the naked eye for particles resembling plastics. The remainder (91%) for common polymer types (Nuelle et al., 2013).
2.2. Identification of SPM and OPAs Optical analysis of extracted SPM was performed using a Wild M3Z stereomicroscope by Leica Microsystems (Wetzlar, Germany) at 6.5e40-fold magnification with light from a cold-light source KL 1500 electronic produced by Schott (Mainz,
Fig. 3. (A) Overview of sampling site N3; (B) example of a 0.25 m2 sampling spot containing visible plastic accumulation; (C) schematic sampling design for site N3 showing the dune course (black line), the 20 locations with visible plastic accumulations (grey squares: sediment samples were taken; white squares: no sediment samples were taken) and locations without any visible plastic where sediment samples were taken (black squares).
J.H. Dekiff et al. / Environmental Pollution 186 (2014) 248e256 Germany). The microscope was equipped with a digital single-lens reflex camera (Nikon D40x, Tokyo, Japan). In order to evaluate the presence of an observer bias during visual sorting of SPMs, an exemplary sample extract was examined by three members of the research group. SPM were weighed using a micro-balance (Sartorius, Göttingen, Germany). SPM were then analysed by thermal desorption pyrolysis gas chromatography/ mass spectrometry (TD-Pyr-GC/MS) to verify that they are microplastics and to determine the polymer types. Additionally, this method allows for determining OPAs (for details about the method see Fries et al., 2013). Two coloured fibres extracted from sediment samples and a cotton denim fibre were also analysed by TD-Pyr-GC/MS. In order to assess the background contamination of OPAs, an empty thermal desorption tube and a sample of activated carbon, exposed to laboratory air for one week, were also analysed. Polymers were identified by fingerprints and characteristic peaks by comparing the pyrograms obtained to those from the analysis of polymer standard materials (Tsuge et al., 2011; Fries et al., 2013). OPAs were identified by the NIST library and by mass spectra for those obtained from the analysis of authentic standards. Statistical data analysis was performed using Microsoft Office Excel 2003 (version 11.0, Microsoft Corporation) and SPSS software (version 16.0, SPSS Inc.). Data was initially tested for homogeneity of variance (Levene test) and normal distribution (ShapiroeWilk test). For pairwise comparisons, either a t-test or, in the case of non-normally distributed data, a nonparametric ManneWhitney test was applied. A one-way analysis of variance (ANOVA) was conducted for multiple group comparisons. All tests were performed at a significance level (p) of 0.05.
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fragment and a number of pellets (see Fig. 4AeD) were additionally identified after sieving in the >1 mm fraction collected at N3. 3.3. Occurrence of SPM
3. Results
The three samples representing procedural blanks showed no background contamination with non-fibrous particles. A total of 59 SPM (1 mm found at sample site N3. (AeD): particles found in the sediment fraction >1 mm after sieving; (E) visible plastics collected directly from the beach.
Fries et al. (2013). The results are shown in Table 2. In total, 15 out of 32 analysed SPM were successfully assigned to a particular polymer type: 6 particles were polypropylene (PP), 4 particles were polyethylene (PE), 2 particles were polyethylene terephthalate (PET), and there was 1 particle each of polyvinylchloride (PVC), polystyrene (PS) and polyamide (PA). Concerning the identification of PA, several typical pyrolysis products such as 1-butanamine and 1,4-butanediamine reported by Tsuge et al. (2011) were missing in the pyrogram obtained from particle #49. PA seems reasonable with regard to the fibrous and artificial nature of the object, due to its common use in such synthetic fibres. The pyrograms of the other 17 SPM analysed could not be attributed to a pyrogram published in the cited literature. The pyrograms of these particles mainly exhibited low-intensity signals, with major peaks originating from different isomers of decene and cyclosiloxanes and could therefore not be attributed to a certain material. The pyrograms of the two analysed fibres found in sediment samples collected from Norderney were relatively similar, with 13 major peaks derived mainly from alkenes and cyclosiloxanes. With regard to pyrolysis products and relative signal intensities, no matches published in the cited literature were obtained for these pyrograms. The pyrogram obtained from analysing the cotton denim fibre did not show any similar fingerprints to those obtained from the analysis of the two fibres.
3.7. Identification of OPAs Thermal desorption chromatograms of seven microplastics for which polymer types were successfully determined by Pyr-GC/MS were analysed for organic compounds potentially derived from incorporated OPAs. The results are shown in Table 3. 1,2benzenedicarboxylic acid, benzophenone, phenol, 2,4-di-tertbutylphenol, diethyl phthalate (DEP) dimethyl phthalate (DMP), diethylhexyl phthalate (DEHP), and dibutyl phthalate (DBP) were identified in at least one particle. Identification of DEP, DBP, DEHP and 2,4-di-tert-butylphenol was additionally verified by comparing their mass spectra with those obtained from GC/MS analysis of pure standard solutions. Concerning the occurrence of background contamination, TD-Pyr-GC/MS of an empty sample tube exhibited very small peaks from which only phenanthrene and decanoic acid could be identified. The activated carbon laboratory blank showed additional peaks of various alkenes (e.g. 1-decene, cyclohexadecene, tetradecene), decanal-based aldehydes (e.g. decanal, tetradecanal, hexadecanal), as well as 2-furanmethanol, dianhydro-alpha glucopyranose and phthalatic acid which may have resulted from laboratory air or could be due to the production and transportation of activated charcoal tubes.
4. Discussion 4.1. Analytical recommendations The assessment of the quantities and properties of small microplastics carried out in this study was based on the preliminary visual sorting and pre-selection of SPM. A wide range of natural substances (e.g. plant or animal parts, calcareous structures and especially coloured and colourless minerals) and other non-plastic anthropogenic materials (e.g. tar, glass) were also present in the sediment samples. It was often very difficult to distinguish visually these from microplastics. A test conducted by three independent observers resulted in different quantitative statements for the same sample extract, ranging from one to four SPM determined. Since plastics may be discoloured by H2O2 treatment, impairing visual sorting, this step is only recommended if a large quantity of biogenic organic material is present in sediments (Nuelle et al., 2013). The AIO method including efficiency, reproducibility and utility is discussed in detail and compared to other more common techniques in Nuelle et al. (2013). In terms of handling, the minimum particle size required for Pyr-GC/MS analysis is estimated to be around 100 mm, which therefore constitutes the method’s lower size boundary for detection. The use of an auto-sampler is recommended in order to increase time efficiency within the analysis. The Pyr-GC/MS method for identifying polymers showed that 47% of a subsample of 32 particles optically identified as SPM could be assigned to a common polymer type. The optical analysis of microparticles should followed by a chemical analysis of SPM, in particular for small particles since their optical identification turned out to be difficult. In terms of application Pyr-GC/MS, the existing database should be extended by less common polymers. Since most of the identified polymers contained OPAs, we suggest using them as indicators for distinguishing between natural materials and polymers during beach monitoring programmes to support the assessment of microplastic pollution in the environment. In addition, we recommend monitoring of OPAs in microplastics found in the environment and assessment of their potential toxicity during implementation of the MSFD (European Parliament and the Council, 2008). The main advantage of using sequential PyrGC/MS over commonly applied FT-IR spectroscopy (Reddy et al., 2006; Hidalgo-Ruz et al., 2012; Claessens et al., 2011) is that polymer types and OPAs can be analysed in one run. In terms of the determination of OPAs, Pyr-GC/MS is preferred over methods based on solvent extraction (e.g. Hirai et al., 2011) involving blank issues and high solvent use. For quantification issues, however, extraction efficiencies have to be evaluated for various OPAs from different polymers.
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distinguishing between natural and artificial fibres during visual inspection, the assessment of microplastic fibres was also impeded by a procedural contamination. Observations within the laboratory revealed that laboratory surfaces exhibited significant quantities of mainly blue and red, but also green and black fibres visually resembling those in the analysed sediment samples (Fries et al., 2013). In a medical study that assessed the occurrence of synthetic fibres in human lung tissue, the authors reported considerable fibre contamination from the ambient air (Pauly et al., 1998). The sources of these fibres remain unknown. Some were optically similar to denim fibres. However, due to the negative resemblance with the database of standard polymers they could not be attributed to common polymers. The similar quantities of coloured fibres in blanks and sediment samples indicate that most if not all of these fibres were introduced during the analytical procedure. However, it can not be completely ruled out that the commercial aquarium sand used for blank sediments had been contaminated with fibres during production and storage. 4.3. Spatial distribution of SPM Due to the occurrence of fibres in procedural blank samples, their spatial distribution was not studied. Only particles were considered for the quantitative assessment. SPM were distributed rather homogenously on both drift lines. Sediments from these drift lines were formed by two different high tides; hence the plastics found in the first 3 cm layer of sediments may have been deposited within the semidiurnal tide pattern. The similar contamination levels generated are an indication that the quantities of SPM deposited were similar within the small time scale during which the two drift lines were formed. Quantities of washed
Fig. 5. Optical images of SPM in sediment samples collected from sampling sites N1 and N2. (A) SPM extracted from the upper drift line at N1; (B) SPM extracted from the lower drift line at N1; (C) SPM extracted from the upper drift line at N2, (D) SPM extracted from the lower drift line at N2 (numbers correspond to the individual sample spots according to Fig. 2 green numbers: polymer type was identified by TD-Pyr-GC/ MS, red numbers: polymer type could not be determined TD-Pyr-GC/MS; the scale bar at the bottom shows increments of 100 mm). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
4.2. Fibre contamination Large quantities of coloured and colourless fibres were found in investigated sediments. In addition to difficulties encountered in
Fig. 6. Optical images of SPM in sediment samples collected from sampling site N3. (A) sampling spots with visible plastics; (B) sampling spots without visible plastics (numbers correspond to the individual sample spots according to Fig. 3: green numbers: polymer type was identified by TD-Pyr-GC/MS, red numbers: polymer type could not be determined by TD-Pyr-GC/MS; the scale bar at the bottom shows increments of 100 mm). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Fig. 7. Number of small potential microplastics/kg (equivalent to 600 ml) dry sediment for each sampling spot from sampling sites N1 and N2 (the numbers of the spots correspond to those given in Fig. 2).
Fig. 8. Mean number of small potential microplastics/kg dry sediment collected from sampling sites N1, N2 and N3 (error bars reflect standard error of the mean).
up plastic debris may vary on a larger time scale as a result of seasonal changes in wind and water current conditions, heavy weather events such as storms and corresponding high tides, as well as the shifting extent of entries from fishing and recreational activities (Velander and Mocogni, 1998; Storrier et al., 2007; Ribic et al., 2012). A homogenous distribution of SPM was also observed along each 100 m stretch and along a longitude of 500 m. This indicates that the prevailing factors that affect the spatial distribution of plastic debris in sediments, such as wind and water currents, are similar on the studied scale of about 500 m. According to our knowledge, this is the first report published on the spatial variation of microplastics in sediments on a small scale. The results of our study identify Norderney beach as suitable site for plastics monitoring. However, since the results presented reflect the particular situation of the selected study area, further data is required on the spatial distribution of microplastics on other beaches. The aim of this study was to provide initial insight into the spatial distribution and temporal deposition of microplastics. A
wider beach monitoring campaign is recommended in order to obtain information on a larger scale. In addition, the sampling design applied provides information about recently generated drift line sediments within a relatively small area. Broad-scale spatial distribution patterns along the beach and vertically across the width of the beach remain unknown. In fact, it is thought that the latter is particularly difficult to obtain for Norderney and other beaches of North Sea barrier islands. This is because the tidal dynamics continually move and relocate the upper sediment layer and associated microplastic burden. Such full-scale sampling efforts require a larger number of samples in combination with an advanced sampling design, and could benefit from consultation with sedimentologists. 4.4. Correlation of SPM with VPD The sampling site chosen for studying the correlation between the occurrence SPM and VPD was selected because it had not been
J.H. Dekiff et al. / Environmental Pollution 186 (2014) 248e256 Table 2 Polymer types, numbers of particles (see Figs. 5 and 6) and characteristic peaks occurring in the pyrograms of microplastics (PP: polypropylene; PE: polyethylene; PET: polyethylene terephthalate; PVC: polyvinylchloride; polyamide: PA; polystyrene: PS). Polymer type No of particle PE PP
PET
PVC
PA PS
Characteristic compounds
#31, #36, #54, #58 Octane, homologous series of alkenes (C9.) #25, #34, #37, #40, 2,4-Dimethyl-1-heptene, #50, and #59 2-undecene, 3-hexene, 4-Isopropyl-1,3-cyclohexanedione, 2 cyclohexyl-octane, 2,4-dimethyl-3-cyclohexene, nonenyl succinic anhydride, 1,1,3,5-tetramethyl cyclohexane, and 2-(2-methylprop-2-enyl) cyclohexane. 2,4 dimethyl-1-heptene #8, #35 1,2-Propanedione-1-phenyl, benzenecarboxylic acid, divinyl terephthalate, terephthalatic acid, 2-(benzyloxy)ethyl vinyl terephthalate, and ethan-1,2-diyl divinyl diterephthalate #29 o-Xylene, p-xylene, naphthalene, 1-methylnapthalene, 2-methylnapthalene, acenaphthene, fluroene, and anthracene #49 1-Methylpyrrolidine and cyclopentanone #23 2,4 Dimethyl-1-heptene, 2-undecene, 3-hexene, 4-isopropyl-1, 3-cyclohexanedione, 2-cyclohexyl-octane, 2,4-dimethyl-3-cyclohexene, nonenyl succinic anhydride, 1,1,3,5-tetramethyl cyclohexane, and 2-(2-methylprop-2-enyl) cyclohexan
subjected to heavy tidal dynamics and there had been no beach cleaning programmes. The types and diversity of macroplastics and the occurrence of industrial virgin plastic pellets suggest that these plastics were probably washed from the sea to the gentle slope of the dune basis during a high water event that was intense enough to reach the outer edges of the beach berm. The presence of VPD showed no significant correlation with the occurrence of SPM. In addition, the two types of spots did not differ in terms of types of polymers. Our results demonstrate that SPM were distributed homogenously whereas VPD primarily accumulated in the zone at the basis of the dune belt. An increased quantity of macroplastics at downwind sites and a homogenous distribution of microplastics
Table 3 Polymer types, numbers of particles (see Figs. 5 and 6) and organic plastic additives (OPAs) of small microplastics found in sediments at Norderney (PP: polypropylene; PE: polyethylene; PET: polyethylene terephthalate; PVC: polyvinylchloride; DEP: diethyl phthalate; DMP: dimethyl phthalate, DEHP: diethylhexyl phthalate DBP: dibutyl phthalate). Polymer type
No of particle
OPA
PP
#25, #34, #50
PP PP PE
#25, #34 #50 #58
PET
#8, #35
PET PVC
#35 #29
1,2-Benzenedicarboxylic acid, DEP Benzophenone Phenol, DMP 1,2-Benzenedicarboxylic acid, benzophenone, phenol, DEP, 1,2-Benzenedicarboxylic acid, DEP Benzophenone 1,2-Benzenedicarboxylic acid, benzophenone, phenol, 2, 4-di-tert-butylphenol, DEP, DEHP, phthalatic anhydride, DBP
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were also observed by Browne et al. (2010). Microplastics, mesoplastics and macroplastics may be subjected to different distribution patterns that cannot yet be explained. The homogeneous distribution of SPM across sample site N3 also complies with the low spatial variability found with drift line samples from sites N1 and N2. This indicates that the statement in descriptor 10 of the MSFD (European Commission, 2010) on the high variability of microplastics in sediments could not be applied to for small spatial scales. 4.5. Quantitative comparison A comparably small quantity of microplastics similar to those of the SPM found in this study was only found in a study of beaches in Singapore (Ng and Obbard, 2006). Other studies (Reddy et al., 2006; Browne et al., 2010; Costa et al., 2010; Claessens et al., 2011; Browne et al., 2011; Liebezeit and Dubaish, 2012) reported quantities more than ten times higher. Data for the Kachelotplate and beaches of Spiekeroog, another East Frisian barrier island located east of Norderney (Liebezeit and Dubaish, 2012) are of particular interest to compare to those obtained in this study although microparticles were counted only under a microscope whereas a chemical verification was not performed. The similarity in local wind and current conditions as well as coastline geography, especially between Norderney and Spiekeroog, suggests a roughly similar contamination level of microplastics. On the Kachelotplate and on Spiekeroog the highest number of granules was 496/10 g sediment and 38/10 g sediment, respectively. Fragments were completely missing Liebezeit and Dubaish (2012). The numbers of SPM in sediments from Norderney presented in this article were considerably lower. Furthermore, nearly all of the SPM were fragments, while the large abundance of granular microplastics reported in the latter study was not observed. Differences in terms of quantity and the predominant types of microplastics exhibited in different studies could be also explained by significant methodological differences. To enable comparison of microplastic quantities between different studies, a chemical identification of SPM is insdispensable. This study demonstrated the good applicability of a Pyr-GC/MS that therefore is especially recommended for application in beach monitoring campaigns also targeting at plastic additives. 5. Conclusions This study provides the first report about the spatial distribution of SPM in beach sediments of the North Sea island of Norderney. Almost 50% of the SPM could be unequivocally identified to be of plastic material. The distribution of SPM was homogenous within a length of 500 m. This suggests that, at the small scale, the spatial distribution and temporal deposition of particles does not need to be taken into account when monitoring microplastics at the selected beach, which makes the northern coastline ideal for use as a monitoring site. The absence of a correlation between SPM and VPD indicate that microplastics should be monitored separately. This needs to be taken into consideration when developing future standardised monitoring protocols; microplastics monitoring should not be restricted to sites featuring large quantities of visible plastics. The results of this work also demonstrate the need to consider the procedural contamination of sediments by fibres, and highlight the considerable difficulties encountered in the visual sorting and verification of microplastics. These methodological aspects require further improvement. The occurrence of toxic OPAs and compounds with endocrine effects in the small microplastics extracted demonstrate that it is essential to fill knowledge gaps regarding actual effects on marine biota and subsequent impacts on the ecosystem by assessing risks to suitable model organisms
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during ingestion. A holistic understanding of microplastics pollution, including OPAs, is required in order to be able to lay down rules for the Good Environmental Status of the North Sea ecosystem as requested by the MSFD and to establish effective countermeasures. Acknowledgements We would like to thank Martin Schulze Dieckhoff of the Niedersächsischer Landesbetrieb für Wasserwirtschaft, Küsten- und Naturschutz for collaborating with us and accommodating us. We are also grateful to Simon Hummel and Alexander Pietsch for the support they gave us during sampling. Our special thanks go to Sara König and Jana Willmeyer who supported the sampling campaign at Norderney and the Pyr-GC/MS analysis, respectively. References Andrady, A.L., 2011. Microplastics in the marine environment. Mar. Pollut. Bull. 62, 1596e1605. Barnes, D.K.A., Galgani, F., Thompson, R.C., Barlaz, M., 2009. Accumulation and fragmentation of plastic debris in global environments. Philos. Trans. R. Soc. B Biol. Sci. 364, 1985e1998. Boerger, C.M., Lattin, G.L., Moore, S.L., Moore, C.J., 2010. Plastic ingestion by planktivorous fishes in the North Pacific Central Gyre. Mar. Pollut. Bull. 60, 2275e2278. Browne, M.A., Galloway, T.S., Thompson, R.C., 2010. Spatial patterns of plastic debris along estuarine shorelines. Environ. Sci. Technol. 44, 3404e3409. Browne, M.A., Crump, P., Niven, S.J., Teuten, E., Tonkin, A., Galloway, T., Thompson, R.C., 2011. Accumulation of microplastic on shorelines worldwide: sources and sinks. Environ. Sci. Technol. 45, 9175e9179. Claessens, M., Meester, S.D., Landuyt, L.V., Clerck, K.D., Janssen, C.R., 2011. Occurrence and distribution of microplastics in marine sediments along the Belgian coast. Mar. Pollut. Bull. 62, 2199e2204. Cole, M., Lindeque, P., Halsband, C., Galloway, T.S., 2011. Microplastics as contaminants in the marine environment: a review. Mar. Pollut. Bullet. 62, 2588e2597. Corcoran, P.L., Biesinger, M.C., Grifi, M., 2009. Plastics and beaches: a degrading relationship. Mar. Pollut. Bullet. 58, 80e84. Costa, M.F., Ivar do Sul, J.A., Silva-Cavalcanti, J.S., Araújo, M.C.B., Spengler, A., Tourinho, P.S., 2010. On the importance of size of plastic fragments and pellets on the strandline: a snapshot of a Brazilian beach. Environ. Monit. Assess. 168, 299e304. Derraik, J.G.B., 2002. The pollution of the marine environment by plastic debris: a review. Mar. Pollut. Bull. 44, 842e852. European Parliament and the Council, 2008. Directive 2008/56/EC of the European Parliament and of the Council of 17 June 2008 establishing a framework for community action in the field of marine environmental policy (Marine Strategy Framework Directive). Official J. Eur. Union 51 (164), 19e40. European Parliament and the Council, 2010. Commission Decision 2010/477/EU of 1 September 2010 on criteria and methodological standards on good environmental status of marine waters (notified under document C(2010) 5956). Official J. Eur. Union 53 (232), 14e24. Fries, E., Dekiff, J.H., Willmeyer, J., Nülle, M.-T., Ebert, M., Remy, D., 2013. Identification of polymer types and additives in marine microplastic particles using pyrolysis-GC/MS and scanning electron microscopy. Submitt. Environ. Sci. Process. Impacts 15, 1949e1956. Galgani, F., Hanke, G., Werner, S., Oosterbaan, L., Nilsson, P., Fleet, D., Kinsey, Thompson, R.C., van Franeker, J., Vlachogianni, T., Scoullos, M., Veiga, J.M., Palatinus, Matiddi, M., Maes, T., Korpinen, S., Budziak, A., Leslie, H., Gago, J.,
Liebezeit, G., European Marine Strategy Framework Directive Working Group on Good Environmental Status (WG-GES), July, 2013. Monitoring Guidance for Marine Litter in European Seas. Draft Report. Graham, E.R., Thompson, J.T., 2009. Deposit- and suspension-feeding sea cucumbers (Echinodermata) ingest plastic fragments. J. Exp. Mar. Biol. Ecol. 368, 22e29. Hidalgo-Ruz, V., Gutow, L., Thompson, R.C., Thiel, M., 2012. Microplastics in the marine environment: a review of the methods used for identification and quantification. Environ. Sci. Technol. 46, 3060e3075. Hirai, H., Takada, H., Ogata, Y., Yamashita, R., Mizukawa, K., Saha, M., Kwan, C., Moore, C., Gray, H., Laursen, D., Zettler, E.R., Farrington, J.W., Reddy, C.M., Peacock, E.E., Ward, M.W., 2011. Organic micropollutants in marine plastics debris from the open ocean and remote and urban beaches. Mar. Pollut. Bull. 62, 1683e1692. Imhof, H.K., Schmid, J., Niessner, R., Ivleva, N.P., Laforsch, C., 2012. A novel, highly efficient method for the separation and quantification of plastic particles in sediments of aquatic environments. Limnol. Oceanogr. Methods 10, 524e537. Jacobsen, J.K., Massey, L., Gulland, F., 2010. Fatal ingestion of floating net debris by two sperm whales (Physeter macrocephalus). Mar. Pollut. Bull. 60, 765e767. JRC (Joint Research Centre) MSFD GES Technical Subgroup on Marine Litter, 2011. Marine Litter e Technical Recommendations for the Implementation of MSFD Requirements (Luxembourg). Lazar, B., Gra can, R., 2011. Ingestion of marine debris by loggerhead sea turtles, Caretta caretta, in the Adriatic Sea. Mar. Pollut. Bull. 62, 43e47. Liebezeit, G., Dubaish, F., 2012. Microplastics in beaches of the East Frisian islands Spiekeroog and Kachelotplate. Bull. Environ. Contam. Toxicol. 89, 213e217. Murray, F., Cowie, P.R., 2011. Plastic contamination in the decapod crustacean Nephrops norvegicus (Linnaeus, 1758). Mar. Pollut. Bull. 62, 1207e1217. Ng, K.L., Obbard, J.P., 2006. Prevalence of microplastics in Singapore’s coastal marine environment. Mar. Pollut. Bull. 52, 761e767. Nuelle, M.-T., Dekiff, J.H., Willmeyer, J., Remy, D., Fries, E., 2013. A new analytical approach to monitor microplastics in marine sediments (submitted for publication). Environ. Pollut. 184, 161e169. Oehlmann, J., Schulte-Oehlmann, U., Kloas, W., Jagnytsch, O., Lutz, I., Kusk, K.O., Wollenberger, L., Santos, E.M., Paull, G.C., Van Look, K.J.W., Tyler, C.R., 2009. A critical analysis of the biological impacts of plasticizers on wildlife. Philos. Trans. R. Soc. B Biol. Sci. 364, 2047e2062. OSPAR, 2010. Quality Status Report 2010 (London, United Kingdom). Pauly, J.L., Stegmeier, S.J., Allaart, H.A., Cheney, R.T., Zhang, P.J., Mayer, A.G., Streck, R.J., 1998. Inhaled cellulosic and plastic fibers found in human lung tissue. Cancer Epidemiol. Biomark. Prev. 7, 419e428. Reddy, M.S., Basha, S., Adimurthy, S., Ramachandraiah, G., 2006. Description of the small plastics fragments in marine sediments along the AlangeSosiya shipbreaking yard, India. Estuar. Coast. Shelf Sci. 68, 656e660. Ribic, C.A., Sheavly, S.B., Rugg, D.J., Erdmann, E.S., 2012. Trends in marine debris along the U.S. Pacific Coast and Hawai’i 1998e2007. Mar. Pollut. Bull. 64, 994e 1004. Storrier, K.L., McGlashan, D.J., Bonellie, S., Velander, K., 2007. Beach litter deposition at a selection of beaches in the firth of forth, Scotland. J. Coast. Res. 23, 813e 822. Teuten, E.L., Rowland, S.J., Galloway, T.S., Thompson, R.C., 2007. Potential for plastics to transport hydrophobic contaminants. Environ. Sci. Technol. 41, 7759e7764. Teuten, E.L., Saquing, J.M., Knappe, D.R.U., Barlaz, M.A., Jonsson, S., Bjorn, A., Rowland, S.J., et al., 2009. Transport and release of chemicals from plastics to the environment and to wildlife. Philos. Trans. R. Soc. B Biol. Sci. 364, 2027e 2045. Thompson, R.C., Olsen, Y., Mitchell, R.P., Davis, A., Rowland, S.J., John, A.W.G., McGonigle, D., Russel, A.E., 2004. Lost at sea: where is all the plastic? Science 304, 838. Tsuge, S., Ohtani, H., Watanabe, C., 2011. Pyrolyis-GC/MS Data Book of Synthetic Polymers. Pyrograms, Thermograms and MS of Pyrolyzates. Elsevier, Amsterdam. Velander, K.A., Mocogni, M., 1998. Maritime litter and sewage contamination at Cramond Beach Edinburgh e a comparative study. Mar. Pollut. Bull. 36, 385e 389.
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Environmental Pollution journal homepage: www.elsevier.com/locate/envpol
Occurrence and spatial distribution of microplastics in sediments from Norderney Jens H. Dekiff a, b, Dominique Remy b, Jörg Klasmeier a, Elke Fries a, *,1 a b
Institute of Environmental Systems Research, University of Osnabrueck, Barbarastraße 12, D-49076 Osnabrueck, Germany Department of Biology/Chemistry, Division of Ecology, University of Osnabrueck, Barbarastraße 13, D-49076 Osnabrueck, Germany
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 August 2013 Received in revised form 18 November 2013 Accepted 27 November 2013
The spatial distribution of small potential microplastics (SPM) (1 mm) was also examined. Small microparticles were extracted from 36 one kg sediment samples and analysed by visual microscopic inspection and partly by thermal desorption pyrolysis gas chromatography/mass spectrometry. The smallest particle size that could be analysed with this method was estimated to be 100 mm. The mean number of SPM at the three sampling sites (n ¼ 12) was 1.7, 1.3 and 2.3 particles per kg dry sediment, respectively. SPM were identified as polypropylene, polyethylene, polyethylene terephthalate, polyvinylchloride, polystyrene and polyamide. The organic plastic additives found were benzophenone, 1,2-benzenedicarboxylic acid, dimethyl phthalate, diethylhexyl phthalate, dibutyl phthalate, diethyl phthalate, phenol and 2,4-di-tert-butylphenol. Particles were distributed rather homogenously and the occurrence of SPM did not correlate with that of VPD. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Marine plastic debris Organic polymer additives Microplastics North sea Pyrolysis Gas chromatography Mass spectrometry Density separation
1. Introduction Marine plastic debris occurs in seas and oceans from the poles to the equator and from remote shorelines to highly populated coastlines (e.g. Derraik, 2002; Barnes et al., 2009). Microplastics that are invisible to the naked eye constitute a large share of the global problem (Andrady, 2011; Cole et al., 2011). Microplastics can be ingested by a number of marine species (Boerger et al., 2010; Graham and Thompson, 2009; Jacobsen et al., 2010; Lazar and Gra can, 2011; Murray and Cowie, 2011). In addition, the chemical effects of organic plastic additives (OPAs) must be considered. OPAs can leach out of the matrix over time, having a toxic and endocrine disruptive effect on marine organisms when plastics are ingested (Andrady, 2011; Oehlmann et al., 2009; Teuten et al., 2007, 2009; Fries et al., 2013). Descriptor 10 (European Parliament and the Council, 2010), an amendment to the European Marine Strategy Framework Directive (MSFD) (Directive 2008/56/EC, European Parliament and the
* Corresponding author. E-mail address: [email protected] (E. Fries). 1 Present address: Water, Environment and Eco-technologies Division, Bureau de Recherches Géologiques et Minières (BRGM), 3 Avenue Claude Guillemin, B.P. 36009, 45060 Orléans cedex 02, France. 0269-7491/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.envpol.2013.11.019
Council, 2008), claims that “properties and quantities of marine litter do not cause harm to the coastal and marine environment”. Due to the potential of sediments to accumulate marine debris (Browne et al., 2010; Claessens et al., 2011; Corcoran et al., 2009; Imhof et al., 2012; Reddy et al., 2006; Thompson et al., 2004; Fries et al., 2013; Nuelle et al., 2013), beaches and estuaries are suitable for monitoring plastic pollution. Taking samples from beaches is easier and cheaper than sea water sampling or ocean sediment sampling using bottom trawls because it does not require expensive, time-consuming sea cruises. However, monitoring data on the spatial distribution of microplastics in sediments remain a rarity. The North Sea, and particularly the tidal mudflats of the Wadden Sea, is a diverse, complex ecosystem that acts as a very valuable habitat for marine life with a high degree of biodiversity. At the same time, the North Sea is surrounded by the densely populated, industrialised nations of northern Europe. Approximately 185 million people live in riparian states, and millions of tourists visit the North Sea area every year for recreation (OSPAR, 2010). Various industries and major ports are located on bays or the estuaries of large rivers leading to the sea such as the Rhine, Elbe and Thames. With regard to human offshore activities, the North Sea is affected by intensive fishing and marine traffic, merchant and passenger ships, as well as pleasure craft and military vessels. A number of regional programmes such as the Convention for the Protection of
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Fig. 1. (A) Map of the island of Norderney showing the location of the urbanised area on western Norderney and its distance to the study area; (B) Satellite picture of sample area showing the extinction of the beach and the locations of the sampling site to the north of the island; symbols show the three sample sites: N1 square; N2 circle; N3 triangle (source: (A) LGLN, modified; (B) Google Earth, GeoBasis-DE/BKG, modified).
the Marine Environment of the north-east Atlantic, OSPAR for short, set quality objectives, promote the monitoring of the current environmental status, and manage potential actions and measures. In this article, the occurrence of plastic debris and related OPAs in beach sediments was investigated on the North Sea island of Norderney. The aim of the study was to determine whether spatial variability of microplastics must be taken into account within monitoring programmes. Emphasis was placed on studying the heterogeneity of microplastic concentrations at small spatial and temporal scales. This approach included an assessment of the quantity and material types of microplastics, including the identification of OPAs in recently formed drift line sediments, as well as an analysis of their small-scale spatial distribution patterns. Tests were also performed to determine whether a correlation exists between the occurrence of visible plastic debris (VPD) (>1 mm) on the surface of the sediments and the occurrence of invisible microplastics (1 mm) into large microplastics (1 mm e 5 mm), mesoplastics (5 mm e 25 mm) and macroplastics (>25 mm), while the invisible fraction (5 mm or one piece >25 cm in size within an area of 0.25 m2. Six of the 20 accumulations were randomly chosen by lot, and sediment samples were taken from a 0.25 m2 square defined as described below. In addition, six spots in the same area without any visible occurrence of plastics were randomly sampled. All sampling spots were marked by a wooden square frame with a side length of 0.5 m. Only the upper 3 cm layer was sampled. Approximately 3 kg sediments were
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Table 1 Detailed information and sampling scheme for sampling sites. Sampling site
Geographical coordinates of site onset
Study aim
Location
Elongation of site
Number of samples
Drift line sample name
Distance of sampling sites from site onset [m]
N1
53.721983 7.242500
Heterogeneity at small spatial and temporal scale
Northern coastline
100 m
12
N2
53.722333 7.245483
Heterogeneity at small spatial and temporal scale
Northern coastline
100 m
12
1.I 1.II 1.III 1.IV 1.V 1.VI 2.I 2.II 2.III 2.IV 2.V 2.VI
18 20 22 48 71 95 17 28 51 57 66 84
N3
53.718950 7.286317
Correlation between small potential microplastics and visible plastic debris
Dune valley, about 800 m in length perpendicular to the northern coastline
Approx. 200 m
12
Fig. 2. Sample design for drift line sampling sites IeVI at sampling locations N1 and N2. Twelve samples (numbered squares) were taken from each sampling site, six from an upper 100 m stretch of the drift line and six from a younger drift line that was closer to the water line. The distance between both drift lines was approx. 16 m (the exact distance of the sample locations from the site onset is given in Table 1). collected from each 0.25 m2 square using a stainless steel spoon and stored in brown glass bottles. The spoon was cleaned between samples using sea water and lint-free paper. The bottles were sealed and stored in the laboratory at room temperature until required for analysis. In the laboratory, 2 kg wet sediments from each bulk sample were transferred to two ultrapure water-rinsed ceramic bowls that were then covered with aluminium foil. The bowls were placed in a drying cabinet at 60 C until the sediments had
dried. One kg dry sediments (approximately 600 ml) was weighed out and sieved through a 1 mm mesh. The residue (>1 mm) was visually inspected by the naked eye for particles resembling plastics. The remainder (91%) for common polymer types (Nuelle et al., 2013).
2.2. Identification of SPM and OPAs Optical analysis of extracted SPM was performed using a Wild M3Z stereomicroscope by Leica Microsystems (Wetzlar, Germany) at 6.5e40-fold magnification with light from a cold-light source KL 1500 electronic produced by Schott (Mainz,
Fig. 3. (A) Overview of sampling site N3; (B) example of a 0.25 m2 sampling spot containing visible plastic accumulation; (C) schematic sampling design for site N3 showing the dune course (black line), the 20 locations with visible plastic accumulations (grey squares: sediment samples were taken; white squares: no sediment samples were taken) and locations without any visible plastic where sediment samples were taken (black squares).
J.H. Dekiff et al. / Environmental Pollution 186 (2014) 248e256 Germany). The microscope was equipped with a digital single-lens reflex camera (Nikon D40x, Tokyo, Japan). In order to evaluate the presence of an observer bias during visual sorting of SPMs, an exemplary sample extract was examined by three members of the research group. SPM were weighed using a micro-balance (Sartorius, Göttingen, Germany). SPM were then analysed by thermal desorption pyrolysis gas chromatography/ mass spectrometry (TD-Pyr-GC/MS) to verify that they are microplastics and to determine the polymer types. Additionally, this method allows for determining OPAs (for details about the method see Fries et al., 2013). Two coloured fibres extracted from sediment samples and a cotton denim fibre were also analysed by TD-Pyr-GC/MS. In order to assess the background contamination of OPAs, an empty thermal desorption tube and a sample of activated carbon, exposed to laboratory air for one week, were also analysed. Polymers were identified by fingerprints and characteristic peaks by comparing the pyrograms obtained to those from the analysis of polymer standard materials (Tsuge et al., 2011; Fries et al., 2013). OPAs were identified by the NIST library and by mass spectra for those obtained from the analysis of authentic standards. Statistical data analysis was performed using Microsoft Office Excel 2003 (version 11.0, Microsoft Corporation) and SPSS software (version 16.0, SPSS Inc.). Data was initially tested for homogeneity of variance (Levene test) and normal distribution (ShapiroeWilk test). For pairwise comparisons, either a t-test or, in the case of non-normally distributed data, a nonparametric ManneWhitney test was applied. A one-way analysis of variance (ANOVA) was conducted for multiple group comparisons. All tests were performed at a significance level (p) of 0.05.
251
fragment and a number of pellets (see Fig. 4AeD) were additionally identified after sieving in the >1 mm fraction collected at N3. 3.3. Occurrence of SPM
3. Results
The three samples representing procedural blanks showed no background contamination with non-fibrous particles. A total of 59 SPM (1 mm found at sample site N3. (AeD): particles found in the sediment fraction >1 mm after sieving; (E) visible plastics collected directly from the beach.
Fries et al. (2013). The results are shown in Table 2. In total, 15 out of 32 analysed SPM were successfully assigned to a particular polymer type: 6 particles were polypropylene (PP), 4 particles were polyethylene (PE), 2 particles were polyethylene terephthalate (PET), and there was 1 particle each of polyvinylchloride (PVC), polystyrene (PS) and polyamide (PA). Concerning the identification of PA, several typical pyrolysis products such as 1-butanamine and 1,4-butanediamine reported by Tsuge et al. (2011) were missing in the pyrogram obtained from particle #49. PA seems reasonable with regard to the fibrous and artificial nature of the object, due to its common use in such synthetic fibres. The pyrograms of the other 17 SPM analysed could not be attributed to a pyrogram published in the cited literature. The pyrograms of these particles mainly exhibited low-intensity signals, with major peaks originating from different isomers of decene and cyclosiloxanes and could therefore not be attributed to a certain material. The pyrograms of the two analysed fibres found in sediment samples collected from Norderney were relatively similar, with 13 major peaks derived mainly from alkenes and cyclosiloxanes. With regard to pyrolysis products and relative signal intensities, no matches published in the cited literature were obtained for these pyrograms. The pyrogram obtained from analysing the cotton denim fibre did not show any similar fingerprints to those obtained from the analysis of the two fibres.
3.7. Identification of OPAs Thermal desorption chromatograms of seven microplastics for which polymer types were successfully determined by Pyr-GC/MS were analysed for organic compounds potentially derived from incorporated OPAs. The results are shown in Table 3. 1,2benzenedicarboxylic acid, benzophenone, phenol, 2,4-di-tertbutylphenol, diethyl phthalate (DEP) dimethyl phthalate (DMP), diethylhexyl phthalate (DEHP), and dibutyl phthalate (DBP) were identified in at least one particle. Identification of DEP, DBP, DEHP and 2,4-di-tert-butylphenol was additionally verified by comparing their mass spectra with those obtained from GC/MS analysis of pure standard solutions. Concerning the occurrence of background contamination, TD-Pyr-GC/MS of an empty sample tube exhibited very small peaks from which only phenanthrene and decanoic acid could be identified. The activated carbon laboratory blank showed additional peaks of various alkenes (e.g. 1-decene, cyclohexadecene, tetradecene), decanal-based aldehydes (e.g. decanal, tetradecanal, hexadecanal), as well as 2-furanmethanol, dianhydro-alpha glucopyranose and phthalatic acid which may have resulted from laboratory air or could be due to the production and transportation of activated charcoal tubes.
4. Discussion 4.1. Analytical recommendations The assessment of the quantities and properties of small microplastics carried out in this study was based on the preliminary visual sorting and pre-selection of SPM. A wide range of natural substances (e.g. plant or animal parts, calcareous structures and especially coloured and colourless minerals) and other non-plastic anthropogenic materials (e.g. tar, glass) were also present in the sediment samples. It was often very difficult to distinguish visually these from microplastics. A test conducted by three independent observers resulted in different quantitative statements for the same sample extract, ranging from one to four SPM determined. Since plastics may be discoloured by H2O2 treatment, impairing visual sorting, this step is only recommended if a large quantity of biogenic organic material is present in sediments (Nuelle et al., 2013). The AIO method including efficiency, reproducibility and utility is discussed in detail and compared to other more common techniques in Nuelle et al. (2013). In terms of handling, the minimum particle size required for Pyr-GC/MS analysis is estimated to be around 100 mm, which therefore constitutes the method’s lower size boundary for detection. The use of an auto-sampler is recommended in order to increase time efficiency within the analysis. The Pyr-GC/MS method for identifying polymers showed that 47% of a subsample of 32 particles optically identified as SPM could be assigned to a common polymer type. The optical analysis of microparticles should followed by a chemical analysis of SPM, in particular for small particles since their optical identification turned out to be difficult. In terms of application Pyr-GC/MS, the existing database should be extended by less common polymers. Since most of the identified polymers contained OPAs, we suggest using them as indicators for distinguishing between natural materials and polymers during beach monitoring programmes to support the assessment of microplastic pollution in the environment. In addition, we recommend monitoring of OPAs in microplastics found in the environment and assessment of their potential toxicity during implementation of the MSFD (European Parliament and the Council, 2008). The main advantage of using sequential PyrGC/MS over commonly applied FT-IR spectroscopy (Reddy et al., 2006; Hidalgo-Ruz et al., 2012; Claessens et al., 2011) is that polymer types and OPAs can be analysed in one run. In terms of the determination of OPAs, Pyr-GC/MS is preferred over methods based on solvent extraction (e.g. Hirai et al., 2011) involving blank issues and high solvent use. For quantification issues, however, extraction efficiencies have to be evaluated for various OPAs from different polymers.
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distinguishing between natural and artificial fibres during visual inspection, the assessment of microplastic fibres was also impeded by a procedural contamination. Observations within the laboratory revealed that laboratory surfaces exhibited significant quantities of mainly blue and red, but also green and black fibres visually resembling those in the analysed sediment samples (Fries et al., 2013). In a medical study that assessed the occurrence of synthetic fibres in human lung tissue, the authors reported considerable fibre contamination from the ambient air (Pauly et al., 1998). The sources of these fibres remain unknown. Some were optically similar to denim fibres. However, due to the negative resemblance with the database of standard polymers they could not be attributed to common polymers. The similar quantities of coloured fibres in blanks and sediment samples indicate that most if not all of these fibres were introduced during the analytical procedure. However, it can not be completely ruled out that the commercial aquarium sand used for blank sediments had been contaminated with fibres during production and storage. 4.3. Spatial distribution of SPM Due to the occurrence of fibres in procedural blank samples, their spatial distribution was not studied. Only particles were considered for the quantitative assessment. SPM were distributed rather homogenously on both drift lines. Sediments from these drift lines were formed by two different high tides; hence the plastics found in the first 3 cm layer of sediments may have been deposited within the semidiurnal tide pattern. The similar contamination levels generated are an indication that the quantities of SPM deposited were similar within the small time scale during which the two drift lines were formed. Quantities of washed
Fig. 5. Optical images of SPM in sediment samples collected from sampling sites N1 and N2. (A) SPM extracted from the upper drift line at N1; (B) SPM extracted from the lower drift line at N1; (C) SPM extracted from the upper drift line at N2, (D) SPM extracted from the lower drift line at N2 (numbers correspond to the individual sample spots according to Fig. 2 green numbers: polymer type was identified by TD-Pyr-GC/ MS, red numbers: polymer type could not be determined TD-Pyr-GC/MS; the scale bar at the bottom shows increments of 100 mm). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
4.2. Fibre contamination Large quantities of coloured and colourless fibres were found in investigated sediments. In addition to difficulties encountered in
Fig. 6. Optical images of SPM in sediment samples collected from sampling site N3. (A) sampling spots with visible plastics; (B) sampling spots without visible plastics (numbers correspond to the individual sample spots according to Fig. 3: green numbers: polymer type was identified by TD-Pyr-GC/MS, red numbers: polymer type could not be determined by TD-Pyr-GC/MS; the scale bar at the bottom shows increments of 100 mm). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Fig. 7. Number of small potential microplastics/kg (equivalent to 600 ml) dry sediment for each sampling spot from sampling sites N1 and N2 (the numbers of the spots correspond to those given in Fig. 2).
Fig. 8. Mean number of small potential microplastics/kg dry sediment collected from sampling sites N1, N2 and N3 (error bars reflect standard error of the mean).
up plastic debris may vary on a larger time scale as a result of seasonal changes in wind and water current conditions, heavy weather events such as storms and corresponding high tides, as well as the shifting extent of entries from fishing and recreational activities (Velander and Mocogni, 1998; Storrier et al., 2007; Ribic et al., 2012). A homogenous distribution of SPM was also observed along each 100 m stretch and along a longitude of 500 m. This indicates that the prevailing factors that affect the spatial distribution of plastic debris in sediments, such as wind and water currents, are similar on the studied scale of about 500 m. According to our knowledge, this is the first report published on the spatial variation of microplastics in sediments on a small scale. The results of our study identify Norderney beach as suitable site for plastics monitoring. However, since the results presented reflect the particular situation of the selected study area, further data is required on the spatial distribution of microplastics on other beaches. The aim of this study was to provide initial insight into the spatial distribution and temporal deposition of microplastics. A
wider beach monitoring campaign is recommended in order to obtain information on a larger scale. In addition, the sampling design applied provides information about recently generated drift line sediments within a relatively small area. Broad-scale spatial distribution patterns along the beach and vertically across the width of the beach remain unknown. In fact, it is thought that the latter is particularly difficult to obtain for Norderney and other beaches of North Sea barrier islands. This is because the tidal dynamics continually move and relocate the upper sediment layer and associated microplastic burden. Such full-scale sampling efforts require a larger number of samples in combination with an advanced sampling design, and could benefit from consultation with sedimentologists. 4.4. Correlation of SPM with VPD The sampling site chosen for studying the correlation between the occurrence SPM and VPD was selected because it had not been
J.H. Dekiff et al. / Environmental Pollution 186 (2014) 248e256 Table 2 Polymer types, numbers of particles (see Figs. 5 and 6) and characteristic peaks occurring in the pyrograms of microplastics (PP: polypropylene; PE: polyethylene; PET: polyethylene terephthalate; PVC: polyvinylchloride; polyamide: PA; polystyrene: PS). Polymer type No of particle PE PP
PET
PVC
PA PS
Characteristic compounds
#31, #36, #54, #58 Octane, homologous series of alkenes (C9.) #25, #34, #37, #40, 2,4-Dimethyl-1-heptene, #50, and #59 2-undecene, 3-hexene, 4-Isopropyl-1,3-cyclohexanedione, 2 cyclohexyl-octane, 2,4-dimethyl-3-cyclohexene, nonenyl succinic anhydride, 1,1,3,5-tetramethyl cyclohexane, and 2-(2-methylprop-2-enyl) cyclohexane. 2,4 dimethyl-1-heptene #8, #35 1,2-Propanedione-1-phenyl, benzenecarboxylic acid, divinyl terephthalate, terephthalatic acid, 2-(benzyloxy)ethyl vinyl terephthalate, and ethan-1,2-diyl divinyl diterephthalate #29 o-Xylene, p-xylene, naphthalene, 1-methylnapthalene, 2-methylnapthalene, acenaphthene, fluroene, and anthracene #49 1-Methylpyrrolidine and cyclopentanone #23 2,4 Dimethyl-1-heptene, 2-undecene, 3-hexene, 4-isopropyl-1, 3-cyclohexanedione, 2-cyclohexyl-octane, 2,4-dimethyl-3-cyclohexene, nonenyl succinic anhydride, 1,1,3,5-tetramethyl cyclohexane, and 2-(2-methylprop-2-enyl) cyclohexan
subjected to heavy tidal dynamics and there had been no beach cleaning programmes. The types and diversity of macroplastics and the occurrence of industrial virgin plastic pellets suggest that these plastics were probably washed from the sea to the gentle slope of the dune basis during a high water event that was intense enough to reach the outer edges of the beach berm. The presence of VPD showed no significant correlation with the occurrence of SPM. In addition, the two types of spots did not differ in terms of types of polymers. Our results demonstrate that SPM were distributed homogenously whereas VPD primarily accumulated in the zone at the basis of the dune belt. An increased quantity of macroplastics at downwind sites and a homogenous distribution of microplastics
Table 3 Polymer types, numbers of particles (see Figs. 5 and 6) and organic plastic additives (OPAs) of small microplastics found in sediments at Norderney (PP: polypropylene; PE: polyethylene; PET: polyethylene terephthalate; PVC: polyvinylchloride; DEP: diethyl phthalate; DMP: dimethyl phthalate, DEHP: diethylhexyl phthalate DBP: dibutyl phthalate). Polymer type
No of particle
OPA
PP
#25, #34, #50
PP PP PE
#25, #34 #50 #58
PET
#8, #35
PET PVC
#35 #29
1,2-Benzenedicarboxylic acid, DEP Benzophenone Phenol, DMP 1,2-Benzenedicarboxylic acid, benzophenone, phenol, DEP, 1,2-Benzenedicarboxylic acid, DEP Benzophenone 1,2-Benzenedicarboxylic acid, benzophenone, phenol, 2, 4-di-tert-butylphenol, DEP, DEHP, phthalatic anhydride, DBP
255
were also observed by Browne et al. (2010). Microplastics, mesoplastics and macroplastics may be subjected to different distribution patterns that cannot yet be explained. The homogeneous distribution of SPM across sample site N3 also complies with the low spatial variability found with drift line samples from sites N1 and N2. This indicates that the statement in descriptor 10 of the MSFD (European Commission, 2010) on the high variability of microplastics in sediments could not be applied to for small spatial scales. 4.5. Quantitative comparison A comparably small quantity of microplastics similar to those of the SPM found in this study was only found in a study of beaches in Singapore (Ng and Obbard, 2006). Other studies (Reddy et al., 2006; Browne et al., 2010; Costa et al., 2010; Claessens et al., 2011; Browne et al., 2011; Liebezeit and Dubaish, 2012) reported quantities more than ten times higher. Data for the Kachelotplate and beaches of Spiekeroog, another East Frisian barrier island located east of Norderney (Liebezeit and Dubaish, 2012) are of particular interest to compare to those obtained in this study although microparticles were counted only under a microscope whereas a chemical verification was not performed. The similarity in local wind and current conditions as well as coastline geography, especially between Norderney and Spiekeroog, suggests a roughly similar contamination level of microplastics. On the Kachelotplate and on Spiekeroog the highest number of granules was 496/10 g sediment and 38/10 g sediment, respectively. Fragments were completely missing Liebezeit and Dubaish (2012). The numbers of SPM in sediments from Norderney presented in this article were considerably lower. Furthermore, nearly all of the SPM were fragments, while the large abundance of granular microplastics reported in the latter study was not observed. Differences in terms of quantity and the predominant types of microplastics exhibited in different studies could be also explained by significant methodological differences. To enable comparison of microplastic quantities between different studies, a chemical identification of SPM is insdispensable. This study demonstrated the good applicability of a Pyr-GC/MS that therefore is especially recommended for application in beach monitoring campaigns also targeting at plastic additives. 5. Conclusions This study provides the first report about the spatial distribution of SPM in beach sediments of the North Sea island of Norderney. Almost 50% of the SPM could be unequivocally identified to be of plastic material. The distribution of SPM was homogenous within a length of 500 m. This suggests that, at the small scale, the spatial distribution and temporal deposition of particles does not need to be taken into account when monitoring microplastics at the selected beach, which makes the northern coastline ideal for use as a monitoring site. The absence of a correlation between SPM and VPD indicate that microplastics should be monitored separately. This needs to be taken into consideration when developing future standardised monitoring protocols; microplastics monitoring should not be restricted to sites featuring large quantities of visible plastics. The results of this work also demonstrate the need to consider the procedural contamination of sediments by fibres, and highlight the considerable difficulties encountered in the visual sorting and verification of microplastics. These methodological aspects require further improvement. The occurrence of toxic OPAs and compounds with endocrine effects in the small microplastics extracted demonstrate that it is essential to fill knowledge gaps regarding actual effects on marine biota and subsequent impacts on the ecosystem by assessing risks to suitable model organisms
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