Antifouling paint particles (APP) are generated during the maintenance of boats and are shed from abandoned structures and grounded ships. Although they afford a highly visible, colourful reflection ...of contamination in the vicinity of the source, little systematic study has been undertaken regarding the distribution, composition and effects of APP in the wider marine environment. This paper reviews the state of knowledge in respect of APP, with particular emphasis on those generated by recreational boatyards. The likely biogeochemical pathways of the biocidal and non-biocidal metals in current use (mainly Cu and Zn) are addressed in light of recent research and an understanding of the more general behaviour of contaminants in marine systems.
Analyses of paint fragment composites from recreational facilities in the UK reveal chemical compositions that are similar to those representing the net signal of the original formulations; significantly, dry weight concentrations of Cu and Zn of up to about 35% and 15%, respectively, are observed and, relative to ambient dusts and sediment, elevated concentrations of other trace metals, like Ba, Cd, Cr, Ni, Pb and Sn, occur. These metals leach more rapidly from APP than a painted surface due to the greater surface area of pigments and additives exposed to the aqueous medium. In suspension, APP are subject to greater and more rapid environmental variation (e.g. salinity, pH, dissolved oxygen) than painted hulls, while settled APP represent an important source of persistent and degradable biocides to poorly circulating environments. Through diffusion and abrasion, high concentrations of contaminants are predicted in interstitial waters that may be accumulated directly by benthic invertebrates. Animals that feed non-selectively and that are exposed to or ingest paint-contaminated sediment are able to accelerate the leaching, deposition and burial of biocides and other substances, and represent an alternative vehicle for contaminant entry into the marine foodchain. Clearly, an extensive understanding of biocide behaviour on painted surfaces is not sufficient for predictive or management purposes regarding APP. Greater caution is required by boaters and boatyards during the removal and disposal of solid wastes, and more awareness or stricter enforcement of relevant codes of practice or legislation is recommended.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
About 200 second-hand plastic toys sourced in the UK have been analyzed by X-ray fluorescence spectrometry for hazardous elements (As, Ba, Cd, Cr, Hg, Pb, Sb, Se) and Br as a proxy for brominated ...flame retardants. Each element was detected in >20 toys or components thereof with the exception of As, Hg, and Se, with the frequent occurrence of Br, Cd, and Pb and at maximum concentrations of about 16000, 20000, and 5000 μg g–1, respectively, of greatest concern from a potential exposure perspective. Migration was evaluated on components of 26 toys under simulated stomach conditions (0.07 M HCl) with subsequent analysis by inductively coupled plasma spectrometry. In eight cases, Cd or Pb exceeded their migration limits as stipulated by the current EU Toy Safety Directive (17 and 23 μg g–1, respectively), with Cd released from yellow and red Lego bricks exceeding its limit by 1 order of magnitude. Two further cases were potentially noncompliant based on migratable Cr, with one item also containing >250 μg g–1 migratable Br. While there is no retroactive regulation on second-hand toys, consumers should be aware that old, mouthable, plastic items may present a source of hazardous element exposure to infants.
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•Paint particles are often overlooked in the micro-debris and microplastic pools.•The sources, behaviour and impacts of paint in the marine environment are reviewed.•Paint particle emissions may be ...as high as 35% of the synthetic micro-debris input.•Paint is regularly detected in sea surface trawls, sediments and animal digestive tracts.•Hazardous additives in micro-paint particles render them more harmful than microplastics.
Because paint particles consist of a resin (polymer) combined with one or more additives, they bear compositional similarities with microplastics. Despite these shared characteristics, however, paint particles are often undetected, deliberately overlooked or evade classification in the pool of micro-debris (all synthetic debris of < 5 mm in size), and in particular in the marine setting where an extensive body of microplastic literature exists. Accordingly, the present paper provides a critical insight into the physico-chemical properties, sources, distributions, behaviour and toxicity of paint particles in the marine environment.
Paint particles contain a greater proportion of additives than plastics and, consequently, are more brittle, angular, opaque, dense, heterogeneous and layered than microplastics of equivalent dimensions. Land-based sources of paint particles, including deteriorating or disturbed coatings on roads and building, are transported to the ocean with other microplastics via urban runoff, water treatment facilities and the atmosphere. However, inputs of paint particles are enhanced significantly and more directly by the disturbance, erosion and weathering of coatings on coastal structures, boats and ships. Estimates of paint particle emissions to the marine environment vary widely, with calculated contributions to the total synthetic micro-debris input as high as 35%. Upper estimates are consistent with available (albeit limited) quantitative information on the relative abundance of paint particles amongst synthetic material captured by sea surface trawls and ingested by marine animals. Of greatest environmental concern is the high chemical toxicity of paint particles compared with similarly-sized microplastics and other synthetic debris. This results from the contemporary and historical use of high concentrations of hazardous inorganic additives in marine antifouling and land-based paints, and the relatively ready mobilisation of harmful ions, like Cu+/Cu2+, TBT+, Pb2+ and CrO42−, from the matrix. Recommendations arising from this review include greater use of particulate capturing devices, waste collection systems and recycling facilities during paint disturbance, raising awareness of the potential impacts of discarded paint amongst users, and alerting the microplastic community to the significance of paint particles and developing means by which they are isolated from environmental samples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
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•We review the addition, recycling and regulation of hazardous metals in plastics.•Hazardous metals occur widely in plastics in societal circulation and lost in nature.•Metal ...diffusion from the matrix is the main health and environmental concern.•Historical metal additives pose a greater risk than metals acquired from the environment.
Historically, many additives and catalysts used in plastics were based on compounds of toxic metals (and metalloids), like arsenic, cadmium, chromium(VI), and lead. Despite subsequent restrictions, hazardous additives remain in plastics in societal circulation because of the pervasiveness of many products and the more general contamination of recycled goods. However, little is understood about their presence and impacts in the environment, with most studies focusing on the role of plastics in acquiring metals from their surroundings through, for example, adsorption. Accordingly, this paper provides a review of the uses of hazardous, metal-based additives in plastics, the relevant European regulations that have been introduced to restrict or prohibit usage in various sectors, and the likely environmental impacts of hazardous additives once plastics are lost in nature. Examination of the literature reveals widespread occurrence of hazardous metals in environmental plastics, with impacts ranging from contamination of the waste stream to increasing the density and settling rates of material in aquatic systems. A potential concern from an ecotoxicological perspective is the diffusion of metals from the matrix of micro- and nanoplastics under certain physico-chemical conditions, and especially favorable here are the acidic environments encountered in the digestive tract of many animals (birds, fish, mammals) that inadvertently consume plastics. For instance, in vitro studies have shown that the mobilization of Cd and Pb from historical microplastics can greatly exceed concentrations deemed to be safe according to migration limits specified by the current European Toy Safety Directive (17 mg kg−1 and 23 mg kg−1, respectively). When compared with concentrations of metals typically adsorbed to plastics from the environment, the risks from pervasive, historical additives are far more significant.
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Samples of microplastic (n = 924) from two beaches in south west England have been analysed by field-portable-x-ray fluorescence (FP-XRF) spectrometry, configured in a low-density mode and with a ...small-spot facility, for the heavy metals, Cd and Pb, and the halogen, Br. Primary plastics in the form of pre-production pellets were the principal type of microplastic (>70%) on both beaches, with secondary, irregularly-shaped fragments representing the remainder of samples. Cadmium and Pb were detected in 6.9% and 7.5% of all microplastics, respectively, with concentrations of either metal that exceeded 103 μg g−1 usually encountered in red and yellow pellets or fragments. Respective correlations of Cd and Pb with Se and Cr were attributed to the presence of the coloured, inorganic pigments, cadmium sulphoselenide and lead chromate. Bromine, detected in 10.4% of microplastics and up to concentrations of about 13,000 μg g−1, was mainly encountered in neutrally-coloured pellets. Its strong correlation with Sb, whose oxides are effective fire suppressant synergists, suggests the presence of a variety of brominated flame retardants arising from the recycling of plastics originally used in casings for heat-generating electrical equipment. The maximum bioaccessible concentrations of Cd and Pb, evaluated using a physiological extraction based on the chemical characteristics of the proventriculus-gizzard of the northern fulmar, were about 50 μg g−1 and 8 μg g−1, respectively. These concentrations exceed those estimated for the diet of local seabirds by factors of about 50 and 4, respectively.
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•Microplastics (pellets and fragments) were collected from two beaches in SW England .•Cd was detected by XRF in 7% of samples with a maximum concentration of 3390 μg g−1 .•Pb was detected in 7.5% of plastics with a maximum concentration of 5330 μg g−1.•Br was detected in 10% of plastics with a maximum concentration of 13,300 μg g−1.•Elemental bioaccessibilities are low but accessible concentrations could be significant.
XRF analysis of beached microplastics reveals the common occurrence of the hazardous elements, Cd, Pb and Br.
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A
bstract
In six-dimensional supergravity, there is a natural sense in which matter lying in certain representations of the gauge group is “generic,” in that other “exotic” matter representations ...require more fine tuning. From considerations of the dimensionality of the moduli space and anomaly cancellation conditions, we find that the generic sets of matter representations are well-defined for 6D supergravity theories with gauge groups containing arbitrary numbers of nonabelian factors and U(1) factors. These generic matter representations also match with those that arise in the most generic F-theory constructions, both in 6D and in 4D, with non-generic matter representations requiring more exotic singularity types. The analysis of generic versus exotic matter illuminates long-standing puzzles regarding F-theory models with multiple U(1) factors and provides a useful framework for analyzing the 6D “swampland” of apparently consistent low-energy theories that cannot be realized through known string constructions. We note also that the matter content of the standard model is generic by the criteria used here only if the global structure is SU(3)
c
× SU(2)
L
× U(1)
Y
/
ℤ
6
.
A
bstract
We analyze the anomaly constraints on 6D supergravity theories with a single abelian U(1) gauge factor. For theories with charges restricted to
q
= ±1
,
±2 and no tensor multiplets, ...anomaly-free models match those models that can be realized from F-theory compactifications almost perfectly. For theories with tensor multiplets or with larger charges, the F-theory constraints are less well understood. We show, however, that there is an infinite class of distinct massless charge spectra in the “swampland” of theories that satisfy all known quantum consistency conditions but do not admit a realization through F-theory or any other known approach to string compactification. We also compare the spectra of charged matter in abelian theories with those that can be realized from breaking nonabelian SU(2) and higher rank gauge symmetries.
Commercially-important species of fish and a crustacean from four sites in the Musa estuary and a site in the Persian Gulf have been analysed for the presence and location of microplastics (MPs). A ...total of 828 MPs were detected in the guts (gastrointestinal tracts), skin, muscle, gills and liver of demersal and pelagic fish (Platycephalus indicus, Saurida tumbil, Sillago sihama, Cynoglossus abbreviatus) from all five sites and in the exoskeleton and muscle of the tiger prawn, Penaeus semisulcatus, from three sites. On an individual basis, MPs were most abundant in P. indicus (mean = 21.8) and least frequently encountered in P. semisulcatus (mean = 7.8), but when normalized on a mass basis, MPs ranged from 0.16 g-1 for C. abbreviatus to 1.5 g-1 for P. semisulcatus. Microscopic analyses (polarized light, fluorescence, SEM/EDS) revealed that MPs were mainly fibrous fragments (with a few angular fragments) of various colour and size (<100 μm to > 1000 μm) and with strong C and O signatures. Additional particles detected that were distinctly different in colour, morphology, brittleness and elemental composition (part-metallic, and containing Cu) were suspected of being fragments of antifouling paint. The means of entry of MPs into tissues not involved in digestion are unclear but could be related to translocation or adherence. Regardless of the mode of accumulation, the presence of MPs in heavily fished species of fish and crustacean raises concerns about the potential transfer of synthetic materials into humans.
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•Microplastics (MPs) have been determined in tissues of fish and crustaceans from the Musa estuary and Persian Gulf.•828 MPs of mainly a fibrous nature were detected in all tissues and species examined.•Mean abundance ranged from 7.8 in tiger prawn to 21.8 in bartail flathead.•The means by which MPs enter non-digestive tissues is unclear.•The occurrence of MPs in seafood for human consumption is cause for concern.
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The loading of chemical pollutants into stream systems can result in isolation of aquatic communities upstream of the discharge. Ecological theory suggests that isolation will result in species ...richness losses, but this potential indirect effect of stream pollution is not widely studied. Here, I present a study of fish assemblage structure in watersheds that have been longitudinally fragmented by abandoned mine drainage. A number of headwater streams in the Clarion River watershed of the upper Ohio River Basin, Pennsylvania, USA, have escaped any direct effects of abandoned mine drainage but have been isolated by severe pollution lower in the watershed. I evaluated the effects of watershed fragmentation on fish species richness, composition, and abundance by comparing the fish assemblages of 22 headwater streams embedded in watersheds receiving mine effluent with the assemblages of 34 reference streams with no apparent blockages to dispersal. I used a general linear model to evaluate the effect of isolation on species richness while accounting for stream size and water quality. I also used non-metric multidimensional scaling and permutational analysis of variance to evaluate differences in fish species composition between isolated and reference streams. Controlling for the effect of stream size, reference streams had a mean richness of 3.63 species (±0.27 SE), but isolated streams had a mean species richness of just 1.02 (±0.33), a 3.5× difference. Species occupying isolated stream systems were a nested subset of fish species in reference streams. Species composition also differed between isolated and reference streams, with higher relative abundance of Creek Chubs (Semotilus atromaculatus Mitchill, 1818) and lower relative abundances of Mottled Sculpin (Cottus bairdii Girard, 1850) and Brook Trout (Salvelinus fontinalis Mitchill, 1814) in isolated streams. These results illustrate an important indirect effect of water pollution in dendritic watersheds and provide evidence for the importance of connectivity in maintaining aquatic biodiversity.
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