Plastics have long been an environmental contaminant of concern as both large-scale plastic debris and as micro- and nano-plastics with demonstrated wide-scale ubiquity. Research in the past decade has focused on the potential toxicological risks posed by microplastics, as well as their unique fate and transport brought on by their colloidal nature. These efforts have been slowed by the lack of analytical techniques with sufficient sensitivity and selectivity to adequately detect and characterize these contaminants in environmental and biological matrices. To improve analytical analyses, microplastic tracers are developed with recognizable isotopic, metallic, or fluorescent signatures capable of being identified amidst a complex background. Here we describe the synthesis, characterization, and application of a novel synthetic copolymer nanoplastic based on polystyrene (PS) and poly(2-vinylpyridine) (P2VP) intercalated with gold, platinum or palladium nanoparticles that can be capped with different polymeric shells meant to mimic the intended microplastic. In this work, particles with PS and polymethylmethacrylate (PMMA) shells are used to examine the behavior of microplastic particles in estuarine sediment and coastal waters. The micro- and nanoplastic tracers, with sizes between 300 and 500 nm in diameter, were characterized using multiple physical, chemical, and colloidal analysis techniques. The metallic signatures of the tracers allow for quantification by both bulk and single-particle inductively-coupled plasma mass spectrometry (ICP-MS and spICP-MS, respectively). As a demonstration of environmental applicability, the tracers were equilibrated with sediment collected from Bellingham Bay, WA, United States to determine the degree to which microplastics bind and sink in an estuary based of grain size and organic carbon parameters. In these experiments, between 80 and 95% of particles were found to associate with the sediment, demonstrative of estuaries being a major anticipated sink for these contaminants. These materials show considerable promise in their versatility, potential for multiplexing, and utility in studying micro- and nano-plastic transport in real-world environments.
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Critical Gaps in Nanoplastics Research and Their Connection to Risk Assessment
Reports of plastics, at higher levels than previously thought, in the water that we
drink and the air that we breathe, are generating considerable interest and
concern. Plastics have been recorded in almost every environment in the
world with estimates on the order of trillions of microplastic pieces. Yet, this
may very well be an underestimate of plastic pollution as a whole. Once
microplastics (<5 mm) break down in the environment, they nominally enter
the nanoscale (<1,000 nm), where they cannot be seen by the naked eye or
even with the use of a typical laboratory microscope. Thus far, research has
focused on plastics in the macro- (>25 mm) and micro-size ranges, which are
easier to detect and identify, leaving large knowledge gaps in our understanding of
nanoplastic debris. Our ability to ask and answer questions relating to the
transport, fate, and potential toxicity of these particles is disadvantaged by the
detection and identification limits of current technology. Furthermore, laboratory
exposures have been substantially constrained to the study of commercially
available nanoplastics; i.e., polystyrene spheres, which do not adequately
reflect the composition of environmental plastic debris. While a great deal of
plastic-focused research has been published in recent years, the pattern of the
work does not answer a number of key factors vital to calculating risk that takes
into account the smallest plastic particles; namely, sources, fate and transport,
exposure measures, toxicity and effects. These data are critical to inform
regulatory decision making and to implement adaptive management strategies
that mitigate risk to human health and the environment. This paper reviews the
current state-of-the-science on nanoplastic research, highlighting areas where
data are needed to establish robust risk assessments that take into account plastics
pollution. Where nanoplastic-specific data are not available, suggested
substitutions are indicated.
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- Award ID(s):
- 1935028
- NSF-PAR ID:
- 10441772
- Date Published:
- Journal Name:
- Frontiers in toxicology
- Volume:
- 5
- ISSN:
- 2673-3080
- Page Range / eLocation ID:
- 1154538-54
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Plastic pollution is a defining environmental contaminant and is considered to be one of the greatest environmental threats of the Anthropocene, with its presence documented across aquatic and terrestrial ecosystems. The majority of this plastic debris falls into the micro (1 lm–5 mm) or nano (1–1000 nm) size range and comes from primary and secondary sources. Its small size makes it cumbersome to isolate and analyze reproducibly, and its ubiquitous distribution creates numerous challenges when controlling for background contamination across matrices (e.g., sediment, tissue, water, air). Although research on microplastics represents a relatively nascent subfield, burgeoning interest in questions surrounding the fate and effects of these debris items creates a pressing need for harmonized sampling protocols and quality control approaches. For results across laboratories to be reproducible and omparable, it is imperative that guidelines based on vetted protocols be readily available to research groups, many of which are either new to plastics research or, as with any new subfield, have arrived at current approaches through a process of trial-and-error rather than in consultation with the greater scientific community. The goals of this manuscript are to (i) outline the steps necessary to conduct general as well as matrix-specific quality assurance and quality control based on sample type and associated constraints, (ii) briefly review current findings across matrices, and (iii) provide guidance for the design of sampling regimes. Specific attention is paid to the source of microplastic pollution as well as the pathway by which contamination occurs, with details provided regarding each step in the process from generating appropriate questions to sampling design and collection.more » « less
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Abstract In aquatic ecosystems, plastic litter is a substrate for biofilms. Biofilms on plastic and natural surfaces share similar composition and activity, with some differences due to factors such as porosity. In freshwaters, most studies have examined biofilms on benthic substrates, while little research has compared the activity and composition of biofilms on buoyant plastic and natural surfaces. Additionally, the influence of substrate size and successional stage on biofilm composition has not been commonly assessed. We incubated three plastics of distinct textures that are buoyant in rivers, low‐density polyethylene (rigid; 1.7 mm thick), low‐density polyethylene film (flexible; 0.0254 mm thick), and foamed polystyrene (brittle; 6.5 mm thick), as well as wood substrates (untreated oak veneer; 0.6 mm thick) in the Chicago River. Each material was incubated at three sizes (1, 7.5, and 15 cm2). Substrates were incubated at 2–10 cm depths and removed weekly for 6 weeks. On each substrate we measured chlorophyll concentration, biofilm biomass, respiration, and flux of nitrogen gas. We sequenced 16S and 23S rRNA genes at Weeks 1, 3, and 6 to capture biofilm community composition across successional stages. Chlorophyll, biomass, and N2flux were similar across substrates, but respiration was greater on wood than plastics. Bacterial and algal richness and diversity were highest on foam and wood compared to polyethylene substrates. Bacterial biofilm community composition was distinct between wood and plastic substrates, while the algal community was distinct on wood and foam, which were different from each other and polyethylene substrates. These results indicate that polymer properties influence biofilm alpha and beta diversity, which may affect transport and distribution of plastic pollution and associated microbes, as well as biogeochemical processes in urban rivers. This study provides valuable insights into the effects of substrate on biofilm characteristics, and the ecological impacts of plastic pollution on urban rivers.
Practitioner Points Plastic physical and chemical properties act as forces of selection for biofilm.
Biofilm activity was similar among three different types of plastic.
Community composition between plastic and wood was different.
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