Persistent organic pollutants sorbed in plastic resin pellet — “Nurdles” from coastal areas of Central Chile
Graphical abstract
Introduction
Plastic pollution has been a major concern worldwide. Two main scenarios have been globally described, the macro scenario characterized by the presence of macroplastics with dimensions >25 mm (Romeo et al., 2015) and the micro scenario characterized by the presence of microplastics with dimension <5 mm (Derraik, 2002). Macroplastic pollution has been well described due to the damage it has produced in the aquatic environment, causing the death of the marine fauna and the pollution of the environment (Kühn et al., 2015). Microplastic pollution is characterized by the small dimensions of the fragments. The primary sources of microplastics are identified as i) derived from hand and facial cleansers, cosmetic preparations, air blast cleaning media, microfibers coming from urban liquid waste (domiciliary waste and from plastic processing plants) and ii) secondary sources coming from unintentional plastic resin pellets spills and the fragmentation of macroplastic as a result of its photodegradation and abrasion due to wave action (Gouin et al., 2011).
Plastic resin pellets, commonly referred to as nurdles, are a type of marine debris originated from plastic particles used to manufacture large scale plastic products (i.e., industrial feedstock of plastic products) and can be spilled into the environment during production, packaging, and transportation. Typically, such pellets are in the shape of a cylinder or disk with diameters of <5 mm. They are generally constituted of polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), polyoxymethylene (POM) and polycarbonate. Because their melting temperature range up to 352 °F (177.8 °C), plastic pellets are used for their resistance to corrosion, their wide range of chemicals, creep, impact and flame resistance. Nurdles can be released to the environment as a loss of industrial process production or as a result of spills during terrestrial and marine transport (Ryan et al., 2018). Due to their characteristic buoyancy and lightness, polyethylene (PE) and polypropylene (PP) pellets can play a role as vectors of chemicals, which are transported by surface runoff, streams, rivers and eventually end up in the ocean (Yeo et al., 2015). In addition, because of their chemical nature, plastic resins sorb and concentrate pollutants (Mato et al., 2001; Wardrop et al., 2016), in particular hydrophobic chemical products, including polycyclic aromatic hydrocarbons (PAH) and Persistent Organic Pollutants (POPs) such as polychlorinated biphenyls (PCB), polybrominated diethyl ethers (PBDEs), and other organic chemicals (Koelmans, 2015).
POPs are substances of international concern because they are resistant to environmental degradation through chemical, biological, and photolytic processes. Due to their persistence, POPs bioaccumulate with potential adverse impacts on human health and the environment. For these reasons, the Stockholm Convention (SC) on POPs, which is a global treaty, has a pursuit to protect human health and the environment (UNEP, 2014). From 152 signatory countries, Chile has ratified the SC in 2005.
Despite of the last decade, questions about their role as vectors enhancing the bioaccumulation of POPs in aquatic environments are still pending (Gouin et al., 2011; Teuten et al., 2007, Teuten et al., 2009; Hammer et al., 2012; Browne et al., 2013; Rochman, 2015; Lusher, 2015). In nature, complex mixtures of toxicants are present and can be transferred by ad- and absorption on microplastics, causing synergic interactions between them to enhance toxicity in the organism (Jung et al., 2018). For instance, PBDEs are assimilated in the amphipod Allorchestes compressa by microplastic ingestion (Chua et al., 2014); the algae Tetraselmis chuii growth was affected when exposed to microplastics plus pharmaceuticals (Prata et al., 2018) and finally, Pomatoschistus microps's activity of isocitrate dehydrogenase was decreased by combined exposure to pyrene and polyethylene microbeads (Oliveira et al., 2013).
The coastal areas of central Chile are characterized by the presence of a high number of different industrial activities (Ahumada and Vargas, 2005; Parra and Faranda, 1993; Gonzalez et al., 1999; Pozo et al., 2012 and Pozo et al., 2014). Three main embayments are located in this part of the country: Concepción, Coronel and San Vicente bay. These three embayments are highly influenced by industrial activities such as harbor, artisanal fishing, and tourism, which have considerably contributed to the deposition of chemicals and loads of others solid wastes in this coastal ecosystem (Ahumada and Vargas, 2005; Parra and Faranda, 1993; Gonzalez et al., 1999; Pozo et al., 2012 and 2014). Since these coastal areas, in particular, the beach sites, are also commonly used for touristic purposes during the summer period, the potential risk of human exposure to those chemicals should be taken into account. Evidence of plastic resin pellets associated with POPs adsorption have been reported under the pellet watch network (Takada, 2013), reporting levels of PCBs in the range of 5 to 605 ng/g-pellet (Ogata et al., 2009); however, since then, no information has been available for POP levels in other coastal areas of central Chile with microplastics as sorbent materials. Gouin et al. (2011), has evaluated the physicochemical capacities of accumulation of persistent bioaccumulative toxic substances (PBT) in microplastics, revealing its role as a vector of chemicals. Therefore, the aim of this study was to determine and characterize (physically and chemically) plastic resin pellets found in coastal areas of central Chile and their chemical burden, in particular POPs, such as PCBs, PBDEs and organochlorine pesticides (OCPs: DDTs, HCHs, HCB, PeCB). This investigation will provide new information for spatial distribution and likely a time trend for previously measured POPs.
Section snippets
Material and Methods
Plastic resin pellets (>1 g for each site) were sampled in the central coast of Chile at Coliumo Bay (36° 31.77′S, 72° 57.37′W) (Coliumo and Dichato), Concepción Bay (36°32′2.44″S, 72°56′46.86″W) (Penco, Bellavista and El Morro beach), San Vicente Bay (36°43′14.99″S, 73°7′14.99″W) (Lenga Beach) and Peninsula de Hualpén (36° 41′22″S, 73° 06′ 09″W) (Desembocadura beach) (Table SM1), during winter 2018 (July 20 and August 20, 2018). Pellet samples were only found at Lenga Beach (Fig. 1). At each
Results and Discussion
Results show the occurrence of POPs in plastic resin pellets obtained from San Vicente Bay in Central Chile (Table 1). From all the studied areas (n = 7 beaches), pellets were only found at Lenga Beach in San Vicente bay.
The physical and chemical characterization of the pellets showed an average size diameter of 4.0 ± 0.6 mm and color abundance of white (32%) (W) and yellowing (68%) (Y) pellet. Yellowing occurs as the results of oxidation of phenolic antioxidation agents to byproducts with
Conclusions
Plastic resin pellets (nurdles) were only found at Lenga Beach located in San Vicente Bay of Central Chile. The prevalent polymer plastic-type detected was high-density polyethylene, which showed a selective capacity to trap chemicals depending on their physicochemical properties (Kow > 5). From all POPs analysis ƩPCBs showed the highest concentrations, followed by PBDEs (with exception of one outlier value at Site 1), with BDE209 as the main congener, and finally by organochlorine pesticides.
Authors contribution
Karla Pozo: Coordinator of the Project and sampling design. Analysis of data and discussion. Revision of entire manuscript.
Williams Urbina: Sampling at the study area, Analysis of pellets using FT-IR, and organization of data.
Victoria Gómez: Analysis of data and comparison, with other studies and discussion of results, analysis of physic-chemicals data and correlations between pellet type and chemicals.
Mariett Torres: Elaboration of analytical protocols, and material for sampling campaigns
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors thank Fondecyt grant no 1161673 (PI: Karla Pozo) and CIPA, CONICYT Regional, GORE BIO BIO, R17A10003, in Chile. This research was supported by the RECETOX Research Infrastructure (LM2015051 and CZ.02.1.01/0.0/0.0/16_013/0001761).
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