قالب وردپرس درنا توس
Home / Science / Multidecadal increase of plastic particles in coastal ocean sediments

Multidecadal increase of plastic particles in coastal ocean sediments



Abstract

We analyzed coastal sediments of the Santa Barbara Basin, California, for historical changes in microplastic deposition with a box core that extended over the years 1834-2009. The sediment was visually sorted by plastic and a subset confirmed as plastic polymers by FTIR spectroscopy (Fourier transform infrared spectroscopy). After correcting contaminants introduced during sample processing, we noted an exponential increase in plastic deposition from 1945 to 2009 with a doubling time of 15 years. This increase closely correlated with global plastic production and the increase in the Southern California coastal population over the same period. Increased plastic loading in sediments has unknown consequences for deposit-eating benthic organisms. This increase in plastic deposition in the years after the Second World War can be used as a geological replacement for the great acceleration of the Anthropocene in the sediment record.

INTRODUCTION

An estimated 4.8 million to 12.7 million tonnes of plastic waste arrive each year in the ocean ( 1 ). Larger population groups produce more waste, and it is predicted that the world population in coastal regions will increase disproportionately ( 2 ). As the coastal population grows and the production of synthetic clothing and plastics increases, fibers from wastewater in coastal areas become more important ( 2 ). Previous studies with a focus on buoyant plastics collected at the ocean surface have shown that the frequency of microplastic surface waste in the Northeast Pacific from 1972-1987 to 1999-2010 ( 3 increases by one to two powers of ten. 4 ), but no significant increase of surface plastics in subtropical latitudes of the Northeast Atlantic from 1986 to 2008 ( 5 ). It is clearly necessary to assess longer-term accumulation rates in coastal ecosystems other than surface waters. Here, we analyze the deposition of microplastic particles in coastal ocean sediments off southern California and show a significant and unabated increase in plastic deposition after World War II. The sediments (Figure S1) had a well-defined annual varve structure (Figure 1), which allowed one to set a clear chronological order. The Santa Barbara Basin was chosen for its unique sedimentary structure. The high surface productivity in the Santa Barbara Channel combined with limited water movement due to the Santa Barbara Coast in the north, the Channel Islands in the south, and the high easterly (230 m) and west (475 m) sills create an anaerobic area Groundwater that minimizes bioturbation and allows conservation of seasonal laminae couplets in the millimeter range, with each couplet representing one year (Figure 1) ( 6 ). Full methods can be found at the end of this work.

Fig. 1 X-ray of the sediment box core.

The chronology was assigned by listing individual Varven couplets. A 1 to 2 cm thick bacterial mat at the top of the core indicates that near-surface sediments were intact.

"data-icon-position =" "data-hide-link-title =" 0 ">

Fig. 1 X-ray of the sediment core.

The chronology was assigned by listing individual pairs of varves. A 1 to 2 cm thick bacterial mat on the top of the core indicates that superficial sediments were intact.

Plastics in the Sediment Core

Plastics were present in each 0.5 cm cross-section of the core and visually identified (average 2.2 years per shift), even in the pre-1945 shifts, before plastic polymers were produced in large quantities or widely distributed ( 1 7 8 ) The year 1945 was also the end of the World War II and led to many social shifts in production and industry and is the year marks the beginning of the great acceleration of the Anthropocene ( 9 10 ) c particles were found in fibers, fragments, films and quasi-spherical particles (Fig. 2). The physical properties of each particle were recorded, including length, width, color, particle type, and amount of biofouling (Figure S2). The majority of the core plastics were fibers, which formed 77% of the particles (Figure S3). The contamination samples from 1836 to 1945 were dominated by fibers with 89.1% of the total particles (Fig. S3). In layers after 1945, 67.5% of the particles were fibers (Fig. S3). Although predominantly bright fibers have been described in the previous literature and many neutral fibers have been overlooked ( 2 ), the most common fiber color was white (64.5%). The second most common particle category was fragments containing 14% of the total particles, although there was much more in the post-1945 samples than in the pre-1945 samples (20.8% versus 5.8%) (Figure S3). In total, 9.7% of the samples after 1945 were films, compared with 4.9% of the samples before 1945. At the core, almost no globular plastic particles were found (Fig. S3).

Fig. 2 Plastic particles from box core.

Examples of [ A ) fibers, [ B ) fragments, C foil, and [ D ) spherical Particle.

"data-icon-position =" "data-hide-link-title =" 0 ">

Fig. 2 Plastic particles from box core.

Examples for ( A ) Fibers, ( B ) Fragments, C ) Film and ( D ) spherical particles.

Identification of plastics by FTIR spectroscopy

19659025] Fourier Transform Infrared (FTIR) identifications of plastic particles (Figure 3) were sometimes difficult because the particle size, especially the narrow width of the fibers, was low, but 87.5% of the visually identified plastic particles were definite or likely Plastic polymers based on agreement with standard plastic reference spectra (Table S1) were identified in the core, included polystyrene (PS), polyethylene (PE). These include low density polyethylene (LDPE), polyvinyl chloride (PVC), nylon (polyamide), polyester, PE terephthalate (PET), polypropylene (PP) and the box core liner (with distinctive FTIR signature).

fig. 3 FTIR spectra of plastic standards and sediment samples.

PET, polyethylene terephthalate; LDPE, low density PE; PS, polystyrene; PVC, polyvinyl chloride; HDPE, high density PE; Unclear sediment sample, not identified.

"data-icon-position =" "data-hide-link-title =" 0 ">

Fig. 3 FTIR spectra of plastic standards and sediment samples. [19659028] PET, polyethylene terephthalate, LDPE, Low density PE; PS, polystyrene; PVC, polyvinyl chloride; HDPE, high density PE; unclear sediment sample, unidentified.

Plastic deposition rate

The plastic deposition rate (particles) * 100 cm -2 year -1 ) were calculated separately for the four individual particle types from 1836 to 2009 (Fig. S4): Fibers dominated the rivers (Fig. S4B) .The majority of the plastic parts before 1945 were fibers The average contamination value of 7.8 particles was 100 cm -2 year -1 for all pre-1945 samples of all samples deducted after 1945, resulting in the net change in p deposits rates over the period since 1945 (Fig. 4A). Accordingly, plastic deposition rates in the Santa Barbara Basin increased exponentially from 1945 to 2009 with an average doubling time of 15 years (Figure 4A).

4 The exponential increase in microplastic deposition in sediment correlates significantly with the exponential increase in global plastic production over the same period (1945-2010).

( A ) Overall plastic deposition rate corrected for contamination over time. All four types of plastic together, 1945-2009, with the average of 1836-1945 subtracted. ( B ) Plastic deposition rate in sediment compared to worldwide plastic production, 1950-2010. Worldwide plastic production numbers of PlasticsEurope ( 8 ).

"data-icon-position =" "data-hide-link-title =" 0 ">

Fig. 4 The exponential increase in microplastic deposition in sediment correlates significantly with the exponential increase in global plastic production in the sediment same period (1945-2010).

( A ) Total plastic deposition rate over time, corrected for contamination: All four plastic types together, 1945-2009, with the average value subtracted from 1836-1945 ( B ) Plastic deposition rate in sediments compared to worldwide plastic production, 1950-2010 PlasticsEurope ( 8 ).

Plastic deposition rates and environmental factors

Remains of corrected plastic deposition rate of total plastics from the adjusted Exponential of 4A show that 1984, 1994 and 2002-2005 had unusually high plastic deposits. In the years 1978, 1985, 1998 and 2007 were the Ablageru abnormally low (Fig. S5A). Attempts to relate these anomalies to years of anomalous rainfall and hence coastal effluent showed that plastic sediment residue was not related to precipitation residues in Santa Barbara or Los Angeles County ( P > 0.05). Fig. S5C) ( 11 12 ) or the Oceanic Niño Index (ONI), a measure of El Niño ( P > 0.05, Fig. S5B) ( 13 ). Much of the sediment in the Santa Barbara basin is supplied by the river, which is most likely a source of microplastic ashore in the basin. Transformations of food webs in the highly productive surface waters over the Santa Barbara Basin are also likely to facilitate the transport of plastics to the sediment through ingestion, fecal pellet formation, biofouling, and sinking.

Plastic Fibers and Contamination

Because Fibers Dominate Numbers The particle deposition rate of only fibers, as opposed to fragments, films, and spherical particles, is treated separately in FIG. S6 (A and B). The deposition rate of both categories of particles treated separately also increased exponentially. The rate of increase of combined fragments, films and spherical particles after 1945 did not differ significantly from the accumulation rate of fibers alone [AnalysisofCovariance(ANCOVA) P > 0.05]. Since these rates are indistinguishable and the entire core has been removed and processed at once, we have no reason to believe that the processing contamination of plastic fibers in the last decades of the core would be different than in the pre-1945 core period.

Plastic Deposition Rates and Social Trends

Multidecad changes in plastic deposition rates in the Santa Barbara Basin are directly related to the increase in global plastic production (Pearson Correlation, r = 0.91, P <0.01, Fig. 4B). Plastic deposition rates are also associated with population growth in the districts of Santa Barbara, Ventura, Los Angeles, Kern and San Luis Obispo (Pearson Correlation, r = 0.81, P <0 , 05).

DISCUSSION

The close correlation between plastic deposition and global plastic production suggests a direct correlation between the exponential increase in plastic production and plastic consumption and its impact on the watershed of the Santa Barbara basin, ocean ecosystems. Our results show that such a rise is now detectable not only in surface ocean water but also in a benthic ecosystem, as noted in the sediment record. This result requires limiting the waste plastic stream entering the ocean as plastic sedimentation directly reflects ever-increasing production trends.

The close relationship between the increase in the coastal population of the Santa Barbara River Basin and the plastic deposit coincides with Browne et al. . ( 2 ) and Eriksen et al. . ( 14 ), both of which found more marine debris in areas of higher population density. However, these studies used current population spatial patterns to derive the impact of population increase on microplastic frequency. However, our study appears to be the first to analyze continuous temporal trends. This close link suggests that this growing rate of plastic deposition will continue to increase in future unless there are changes in policy or waste management.

The core was sieved through a 104 μm sieve, thereby determining the minimum size of detectable particles. The vast majority of the particles were between 500 and 1000 microns in length, and this tendency was consistent throughout the core. This could be related to a visual sorting of the nucleus and the absence of some smaller particles (Figure S2). It is noteworthy, however, that these predominant particles of 104 to 1000 microns are among the smallest registered particles in a sediment study ( 15 ) and show that small microplastics find their way to the marine benthos where they are likely to be taken from feeders for benthic deposits.

This deposited microplastic can enter the benthic food web. Benthic animals have been shown to trap and trap plastic ( 16 18 ), and microplastics are found in sediments, especially in urban, populated areas ( 2 ). The plastics that enter the benthic food web are not only hydrocarbon chains, but may also contain harmful additives and dyes ( 19 ) and adsorb persistent organic pollutants such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and dichlorodiphenyltrichloroethane from the environment ( 20 21 ). These microplastics are picked up by small animals near the base of the food web and can accumulate along with their harmful additives in the food web. This affects much larger animals ( 22 23 ). Swallowed plastics have been shown to cause, among other things, liver toxicity ( 21 ) and brain damage ( 23 ). For these ecological and toxicological reasons, it is essential to understand how much plastic is in coastal sediments, how long has it accumulated, and how far are the storage pathways into the food web? However, we hypothesize that the box core is representative of the variability of deposition rate across the basin, due to the close alignment of the stratigraphic events between the cal echoes sedimentary cores and SPR0901-06KC, the youngest and most accurately dated Santa Barbara basin, is occupied sediment core ( 6 24 ). The box core was first sampled and examined for fishotoliths. Future nuclei should be studied at all stages of sampling and sub-sampling, with particular attention to the limitation of contamination, in particular by microfibers. The use of a micro FTIR would be helpful in future studies to identify the smallest particles.

The Anthropocene

To initiate a new geological epoch, the Anthropocene, Zalasiewicz et al. . ( 9 ) identified the need for more geological proxies in the sediment dataset to characterize the change from before 1945 to after 1945, the beginning of the "great acceleration" of modern civilization. Although they considered the release of plutonium in New Mexico in 1945 probably the easiest to identify, they suggested that plastic, especially in non-biologically treated sediment, would probably be a very useful stratigraphic marker ( 9 10 ). Although plastics were found in near-surface sediment samples ( 25 26 ) and even in some selected layers of nuclei that showed a temporal increase ( 27 ), this is the case first known study on a continuous investigation in non-biological sediment. Considering contamination in the air and in the processing of plastics, our results show that this high acceleration has a close correlation between global plastic production, regional population growth and plastic deposited in sediment records, the consequences of which are feeding benthic organisms and oceans are affected by deposits food webs are barely known.

MATERIALS AND METHODS

Collection of sediment core

In October 2010, the Scripps Institution of Oceanography Cal used a box core to collect sediments from the Santa Barbara Basin off the coast of California – Echos Research Cruise (Fig. S1 ) at 34 ° 17.228 ° N, 120 ° 02.135 & # 39; W and a water depth of approx. 580 m. Site 1, the site of the box core MV1012-ST46.9-BC1 (BC1), was selected as a reoccupation of the 893 location of the Ocean Drilling Program.

Depiction and dating of the sediment core

Color photographs of the nucleus were taken on the deck of the ship taken before the subcoring. The box core was removed from the ginning equipment on deck by undercutting with rectangular plastic core liners 76 cm long and 15 cm wide. The box core was drilled with only one plastic core liner. The split core section was placed in the core liner and placed in Hybar trilaminate membrane bags with oxygen absorbers, purged with nitrogen, vacuum sealed and stored at 4 ° C.

A thin vertical plate (2 cm thick) was cut off the side of each sub-core with a saw. Vertical core plates were X-rayed at the Scripps Institution of Oceanography Geological Collections using a Geotek MSCL-XR core scanner that combined single two-dimensional images to produce composite X-ray images. The core plates were scanned at 1 mm intervals in a linear, non-rotating scan.

X-rays and color photographs were used to develop a high-resolution chronology for the nucleus. Several age models have been developed to assign data to the stratigraphy of the Santa Barbara basin. The traditional age model was based on the seasonal varve pair count and was used to create a chronology for the top 35 cm of the box core (Fig. 1) ( 28 ).

Sieving and Drying of the Sediment Core

The 76 cm sub-core was cross cut every 0.5 cm with very fine wire and the location of each cut was recorded. Then the sediment samples were stored frozen before further processing. Transverse samples were oven dried overnight at 50 ° C, washed, and then sieved in metal sieves using a 104μm tube. m-mesh over a 65 μm wet-sieved m-mesh. The> 104μm M fraction was first sorted on fish shoots under a dissecting microscope by W.J. before being sorted for microplastics. The nuclear chronology was resolved to the top and bottom of the 0.5 cm transverse samples; The data assigned to the top and bottom edges were averaged and used to assign data to samples in cross-section.

Sampling of the Sediment Core for Plastics

The samples used in the present analysis were the fraction> 104 μm from the box core. The samples were visually sorted under a Wild M5 dissecting microscope at 12x magnification for probable microplastic pieces photographed with either a Canon Powershot S5 IS or a Canon E0S Rebel T5i camera. The measurements were carried out with a calibrated eyepiece micrometer with a resolution of 66 μm.

The sediment was sorted in small aliquots on a black sediment sorting dish with screened squares. Sorted plastic parts were taken from the sediments, counted, measured to length with an eyepiece micrometer (Fig. S2) and photographed for length and shape. In some cases, plastic fibers were so curved or twisted that a maximum length of the vacation was measured instead of an actual length. A description of the physical appearance, color, amount and location of particulate contamination and whether it had agglomerated with other particles was recorded. They were categorized into categories: fiber, film, fragment and spherical (Figure 2 and Figure S3). Sorted plastic parts were stored in four-cavity palaeontological slides and glass covers until later analyzed by FTIR. Whenever not sorted actively, the sump was covered to limit the contamination of microplastic from the laboratory space in the air.

Plastic particles initially differed visually from biological or sedimentary particles by their color and shape; The sediment consisted predominantly of foraminifera tests, shells, and striped biological film that looked like it was once alive. Some shapes seemed to dominate the natural material in the sample. In contrast, plastic consisted mainly of elongated fibers or sharp-edged fragments, which did not all look alike. It has been shown that brightly colored plastics are often overrated compared to more boring, biologically colored plastic parts ( 2 ), which is why the sediments were sorted against a black background to reduce this deviation. Potential microspheres were examined under 50X magnification to determine if the pore matrix common to the foraminifests tests could be detected; often the matrix was visible at higher magnification, and the sphere was then considered biological. If films had stripes that made them look as though they had once lived (eg, part of a molt), they were not counted either. When the origin of a particle was questioned, it was generally considered to be part of the sediment and not removed for further FTIR analysis or counted as part of the plastic frequency counts. To reduce the bias of sampling between multiple sorters, all images of plastic parts were personally examined by the older author to determine if they are probably plastic or probably biological. Questionable images were removed from the lists of plastics.

Identification of Plastics Using FTIR Spectroscopy

To determine whether visually identified plastics are plastic polymers, we analyzed a subset of particles using an FTIR spectrometer with a total attenuated total reflection diamond crystal attachment (Nicolet 6700 with Smart-iTR). , All spectra were recorded at a resolution of 4 cm -1 . The FTIR spectra for particles collected from the ocean were compared to published standards ( 2 15 29 30 ) to try to identify whether the particles were around Plastic, biological material or sedimentary material is. The spectra were analyzed by eFTIR software (www.essentialFTIR.com). The plastic was also identified, if possible, as a type of plastic. At least 10% of the particles from every fifth 0.5 cm cross-sediment layer from the box core were identified by FTIR. The trilaminate bag and the core liner in which the core was stored were also tested by FTIR to identify sources of contamination.

Plastic Deposit Rates

The box core had a surface area of ​​approximately 174 cm 2 . To calculate the plastic deposition rates, the number of pieces of plastic particles in a 0.5 cm transverse layer was divided by the time interval represented by the transverse layer and normalized to 100 cm during one year 2 Seabed (No. Particle * 100 cm -2 year -1 ). The plastic deposition rate (particle * 100 cm -2 year -1 ) was calculated for the four individual particle types from 1836 to 2009 (Fig. S4). Pieces of core lining identified by FTIR were treated separately from other fragments. Fibers dominated the rivers (Fig. S4B).

The deposition rate of particles in layers from 1836-1945 was averaged to indicate the base contamination of plastic particles. Contamination levels before 1945 were relatively constant throughout the region from 1836 to 1945 (left of the gray line in Fig. S4), which is why averaging is appropriate here. Any pre-1945 plastic was considered to be contaminated due to the small volume of plastic that was in production at the time ( 7 ) and the fact that some plastics (PET, polyester, polypropylene, etc.) were not yet contaminated Contamination treated invented. The soil sample of the core, which corresponded to 1834, was removed from the analysis as it was known that it had a high level of contamination by contact with the bottom of the box core liner during processing. The average from 1836 to 1945 was then subtracted from the deposition rate of all other samples to correct the base contamination.

Baseline corrected deposition rates from 1945 to 2009 were plotted against time and an exponential function was adjusted. Residuals of plastic deposition rates were calculated from the exponential function (Figure 4A). Deposition rates were calculated for fragments, films, and spherical particles (Figure S6A) that were separated from fibers (Figure S6B), and both had an exponential increase, with no significant difference between them (ANCOVA, P > 0.05).

Plastic deposition rates and environmental factors

The remnants of the exponential plastic expansion were compared with the precipitation residues of the urban watershed, which flows into the Santa Barbara basin (Figure S5). Rainfall records from downtown Los Angeles and downtown Santa Barbara were collected annually for Los Angeles from 1 July to 30 June 1877-2017 ( 11 ) and from September to August 1899-2017 for Santa Barbara ( 12 ). The residues of the 50-year-old precipitants were compared with the residues of the plastic deposit. The remnants of the plastic deposition were also compared with the ONI ( 13 ) for correlation with the El Niño-Southern Oscillation.

Plastic deposition rates and social trends

The Southern California Coastal Population (Santa Barbara), Ventura, Core, Los Angeles and San Luis Obispo Counties) from 1950 to 2010 ( 31 32 and worldwide plastics production from 1950 to 2010 ( 8 ]) were also compared to plastic deposition rates (Figure 4B).

Statistical analysis

The relationship between plastic deposition and global plastic production in Figure 4B was used Pearson's Product Moment Correlation was calculated and found to be significant ( P <0.01).) The relationships between precipitation and 50-year precipitation and the ONI (Figure S5) were determined using the Pearson Correlation was calculated and found to be insignificant ( P > 0.05) .The exponential growth curves in Figures 4A and 6 were attached to a simple expon adapted with two parameters and showed a significant adaptation ( P <0.001). The rate of increase of combined fragments, films and spherical particles after 1945 (Figure S6A) was compared to the accumulation rate of fibers alone (Figure S6B) using an ANCOVA test and no significant difference was found ( P > 0.05).

ZUSATZMATERIALIEN

Ergänzungsmaterial zu diesem Artikel finden Sie unter http://advances.sciencemag.org/cgi/content/full/5/9/eaax0587/ DC1

Ergänzungstext

Abb. S1. Bathymetrie und Probenahmestellen im Santa-Barbara-Becken.

Abb. S2. Größenverteilung der Partikelproben.

Abb. S3. Verteilung der Partikelproben.

Abb. S4. Ablagerungsraten einzelner Kunststofftypen im Zeitverlauf, 1836–2009.

Abb. S5. Plastische Ablagerungen und Wetterrückstände.

Abb. S6. Ablagerungsraten von Kunststofftypen nach Beseitigung des Kontaminationswertes.

Tabelle S1. FTIR-Spektroskopie-Untersuchung des Boxkerns.

Referenzen ( 33 40 )

Dies ist ein Open-Access-Artikel, der unter den Bedingungen der Creative Commons Attribution-Lizenz vertrieben wird gestattet die uneingeschränkte Verwendung, Verbreitung und Vervielfältigung auf jedem Medium, sofern das Originalwerk ordnungsgemäß zitiert wird.

VERWEISE UND ANMERKUNGEN
  • 19
  • S. Freinkel, Plastik: Eine giftige Liebesgeschichte (Houghton Mifflin Harcourt Publishing Company, 2011), S. 324.

  • ] ↵
  • NICODOM, Analytische Mittel und kommerzielle Materialien: Inorganic Library of FTIR Spectra (Nicolet, Version 2.0, 1998), vol . 4.

  • M. Forrest, Y. Davies, J. Davies, Die Rapra-Sammlung von Infrarotspektren von Kautschuken, Kunststoffen und thermoplastischen Elastomeren (Smithers Rapra Publishing, 2007).

  • Danksagung: Wir danken dem Kapitän, der Besatzung und den wissenschaftlichen Parteien der Cal-Echoes-Kreuzfahrt an Bord der R / V Melville unterstützt von UC Ship Funds-Programm, das den Sedimentkern für diese Forschung lieferte. Wir danken B. Fissel, R. Norris, A. Hangsterfer und D. Hartsook für die Hilfe bei der Verarbeitung und Abbildung des Sedimentkerns. I. Dove, E. Baron Lopez und S. Higgs für ihre Hilfe bei der Analyse von Mikroplastiken im Kern; K. Blincow, A. Madigan und L. Sala für die weitere Unterstützung; und M. Sailor für die Ermöglichung der FTIR-Arbeit. Finanzierung: Diese Studie wurde von dem California Sea Grant (NOAA NA14OAR4170075 an D. Checkley), einem NSF Graduate Research Fellowship an WJ, NSF California, unterstützt NSF / OCE-10-26607) und private Spender. Autorenbeiträge: J.A.B. konzipierte das Projekt, analysierte den Kern auf Mikroplastik, führte die FTIR-Analyse und Datenanalyse durch und verfasste den ursprünglichen Entwurf des Manuskripts. W.J. sammelte den Kern auf See und führte alle vorläufigen Analysen und Datierungen des Kerns durch sowie das Schreiben des ursprünglichen Methodenteils und das Editieren des Manuskripts. M.D.O. leitete und überwachte das Projekt, half bei der Datenanalyse und überprüfte und editierte das Manuskript. Interessenkonflikte: Die Autoren erklären, dass sie keine Interessenkonflikte haben. Daten- und Materialverfügbarkeit: Alle Daten sind im CCE-LTER-Primärdatenkatalog von NSF, Datazoo, verfügbar (doi: 10.6073 / pasta / bc67741feef7204467674e8f2b3a9ed4 und doi: 10.6073 / pasta3a9ed4 und doi: 10.6073 / pasta4 Autoren, einige Rechte vorbehalten; exklusiver Lizenznehmer der American Association for the Advancement of Science. Kein Anspruch auf Originalarbeiten der US-Regierung. Verteilt unter einer Creative Commons Attribution License 4.0 (CC BY).


    Source link