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Review

Organic Contaminants and Interactions with Micro- and Nano-Plastics in the Aqueous Environment: Review of Analytical Methods

by
Julia Reichel
1,
Johanna Graßmann
1,
Oliver Knoop
1,
Jörg E. Drewes
1 and
Thomas Letzel
1,2,*
1
Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall 3, 85748 Garching, Germany
2
Analytisches Forschungsinstitut für Non-Target Screening GmbH (AFIN-TS GmbH), Am Mittleren Moos 48, 86167 Augsburg, Germany
*
Author to whom correspondence should be addressed.
Molecules 2021, 26(4), 1164; https://doi.org/10.3390/molecules26041164
Submission received: 10 January 2021 / Revised: 7 February 2021 / Accepted: 18 February 2021 / Published: 22 February 2021
(This article belongs to the Special Issue Feature Review Articles in Analytical Chemistry-Part I)
Browse Figure
Versions Notes

Abstract

:
Micro- and nanoplastic particles are increasingly seen not only as contaminants themselves, but also as potential vectors for trace organic chemicals (TOrCs) that might sorb onto these particles. An analysis of the sorbed TOrCs can either be performed directly from the particle or TOrCs can be extracted from the particle with a solvent. Another possibility is to analyze the remaining concentration in the aqueous phase by a differential approach. In this review, the focus is on analytical methods that are suitable for identifying and quantifying sorbed TOrCs on micro- and nano-plastics. Specific gas chromatography (GC), liquid chromatography (LC) and ultraviolet-visible spectroscopy (UV-VIS) methods are considered. The respective advantages of each method are explained in detail. In addition, influencing factors for sorption in the first place are being discussed including particle size and shape (especially micro and nanoparticles) and the type of polymer, as well as methods for determining sorption kinetics. Since the particles are not present in the environment in a virgin state, the influence of aging on sorption is also considered.

1. Introduction

Micro- and nanoplastic particles can serve both as sources and sinks for pollutants in the environment. Therefore, on the one hand, sorption of pollutants on microplastics might pose a problem; on the other hand, microplastic itself must be considered as a contaminant. Monomers, additives, plasticizers, and others can desorb and may cause additional potential risks [1,2,3,4,5,6,7].
In recently published reviews, sorption of trace organic chemicals (TOrCs) on micro- and nanoplastics has already been examined in detail [8,9,10,11]. In these studies, the focus is on the influence of the physical properties of particles (such as size, surface, crystallinity) and the resulting interaction properties of TOrCs and polymers. The sorption mechanisms and ecotoxicological factors are also considered. In contrast to the previously published articles, the purpose of this article is to provide an overview of suitable analytical approaches for determining the sorption of TOrCs on particles. The focus is on GC, HPLC, and UV-VIS methods. Furthermore, typical sorption strategies will be discussed.
Concerns about the possible harmful effects of microplastics relates not only to the particles themselves but also to their ability to transport pollutants. Those pollutants can be divided into two groups: (i) hydrophobic chemicals adsorbed from the aquatic environment due to their affinity for the hydrophobic surface of plastics and (ii) additives, monomers, and oligomers present as constituents of polymers [12]. Adsorbed hydrophobic pollutants with low water solubility become more mobile indirectly by binding to plastic particles. Thus, their transport on particles can increase their distribution in environmental matrices and organisms as well as their bioavailability.
The sorption processes depend mainly on the nature of the polymer and can be divided into adsorption to the surface or absorption into the polymer [5,13,14]. The principle of both sorption types is to achieve an equilibrium of TOrCs concentrations between the solid and liquid phases. The sorption equilibrium can be reached either quickly by adsorption (onto particles) or slower by absorption (into the particle structure) [15]. In recent years, the analysis of pure micro- and nanoplastics has gained great interest but also the analysis of sorbed TOrCs on these particles [8,16]. With optical analysis methods like Raman spectroscopy or Fourier-transform infrared spectroscopy (FTIR) analysis, quantitative analyses of particles and analyses of particle size as well as shape can be conducted [17,18]. Thermal analysis methods such as pyrolysis gas chromatography-mass spectrometry (Pyr-GC/MS) can be used to analyze TOrCs or the additives in the polymers [19,20]. This review summarizes the current state-of-the-art in analyzing the degree of TOrCs sorption on micro- and nanoparticles.

2. Analysis of TOrCs on Micro- and Nanoplastic Particles: Typical Methods and Techniques

Analysis of sorbed TOrCs on particles in a liquid phase can be performed in either the aqueous or gas phase, or on the particles, respectively [5,13,20,21]. Different techniques like GC/MS, HPLC-DAD, UHPLC-MS/MS, UV spectrometer, or liquid scintillation counting are commonly used for this purpose [21,22,23,24].

2.1. General Experimental Design of Sorption Experiments

Principally, the experimental design studying sorption kinetics or processes in aqueous suspensions is identical in all experimental approaches. Selected particles and TOrCs are added to a liquid phase such as ultrapure water, freshwater, sea water, or synthetic water containing humic acids to mimic natural organic matter [13,20,25]. Variations in pH, salinity, or humic substances are made to simulate different environmental conditions [26,27,28]. Some studies use microparticles, additive-free particles, or extracted particles from cosmetics covering a certain size range [29,30]. Commonly targeted TOrCs used as sorbates in these investigations represent antibiotics, additives, pesticides, biocides, endocrine disrupting chemicals, hormones, or disinfection byproducts [24,31,32,33,34,35,36]. A schematic of the sample preparation is shown in Figure 1. In the aqueous solution, particles and TOrCs are incubated for a certain period of time and the suspension is subsequently shaken for various time periods (Table 1 and Table 2). Subsequently, the particles must be separated from the aqueous phase for analysis. This is achieved for instance by filtration or centrifugation [20,37,38]. The analysis of the sorbed substances happens either directly on the particles or indirectly by solvent extraction (e.g., n-hexane, dichloromethane) decoupled from the particles [13,20,39,40]. An indirect analysis of the aqueous phase via liquid/liquid extraction or by a passive sampler is also possible [4,21,41,42]. Due to the remaining concentration in the aqueous phase, an assessment can be made on the amount of sorbed substances on the particles [43]. Furthermore, the gas phase can also be investigated [5,44].
The final analysis can be performed by various analytical techniques, such as GC/MS, GC/ECD, HPLC/MS, HPLC/UV, liquid scintillation counter, or spectrophotometer [4,6,24,30,45,46,47,48,49]. An overview of the workflow from a sample preparation for the analytical technique is illustrated in Figure 1. A detailed consideration of the different analytical techniques is presented in the following sections.

2.2. GC/MS

With GC/MS, volatile substances can be determined. This method is often used for the investigation of sorbed substances on polymer particles [13,26,45,46]. In a GC/MS analysis, either the aqueous phase, the particles, or the gas phase can be examined for TOrCs [5,13,39]. An overview of different sorption studies of microplastic particles performed with GC/MS is shown in Table 1. The advantages of GC analysis are that it allows direct analysis of TOrCs from the particle, requires little sample preparation, and is, thus, quick to perform (2–3 h per sample) [20,50,51]. By coupling with, e.g., a pyrolysis unit, polymers can be identified in addition to sorbed TOrCs [50]. In combination with an MS, detailed results for target and non-target analysis can be provided.

2.2.1. Direct Analysis by Pyrolysis and TED-GC/MS

Currently, GC/MS analysis is mainly used for microplastic analysis and polymer identification. For this purpose, the GC/MS is coupled with a pyrolysis unit (Pyr) or a thermal-extraction-desorption (TED)/thermogravimetric (TGA) unit [19,50,51,52,53,54]. A recently published review provides a good summary of these methods [55]. In general, only the polymer can be identified and quantified with the thermoanalytical systems. A determination of size is not possible. An established method for the identification of plastics in various environmental matrices is Pyrolysis-GC/MS. [52,56,57,58,59,60]. One advantage of this method is that both micro- and nanoplastics can be analyzed [61]. Recently, pyrolysis methods have been developed further by coupling with for instance a sequential pyrolysis, a double shot pyrolysis, or a thermal desorption (TD) unit with pyrolysis [19,20,50,53]. The aim of these methods is to identify not only the polymer itself but also additives or sorbed substances.
Double shot pyrolysis can be run in two different modes [53]: (1) in desorption mode, the volatile substances such as additives are desorbed; (2) in pyrolysis mode, the polymers are degraded. In sequential pyrolysis, several runs with different temperature maxima are performed in series [50].
TD-Pyr-GC/MS (thermodesorption-pyrolysis-GC/MS) combines these two systems into one analytical setup to investigate sorbed TOrCs before analyzing the polymer [20]. After method development, the TOrCs can be identified in the first step and the polymer type in the second step.
Another method for the determination of polymers and additives is via Thermal-Extraction-Desorption-GC/MS (TED-GC/MS) coupled with thermogravimetric analysis (TGA) [54]. In TGA, the polymers are heated and their volatile decomposition products are trapped on a solid-phase adsorber such as a Gerstel Twister or a Sorb-Star® [62,63]. The trapped substances are heated and then analyzed by GC/MS. An advantage of this method is that the number of particles can also be quantified.
The benefit of these thermoanalytical systems is that the samples can be analyzed in a short amount of time (2–3 h) [20]. There is no need for complex extraction procedures, but the samples can usually be analyzed directly. Often, however, there is a carry-over of the samples during the Pyr-GC/MS [64]. Therefore, it is recommended to run many blanks to identify and eliminate them. Analytical reproducibility can also be problematic [64].

2.2.2. GC/MS Analysis after Extraction of Sorbents

For indirect analysis of sorbed substances or additives, these can be extracted from the microplastic particles with solvents, see Table 1. Table 1 shows the phase that is analyzed to obtain the concentrations of TOrCs. For this purpose, the trace organic chemical can be extracted from the particle, for instance by means of soxhlet extraction [65]. The TOrCs are washed off the particle with a solvent (e.g., dichloromethane), concentrated, purified, and finally analyzed. Another possibility is the indirect determination of the concentration via the aqueous phase [21,41]. Therefore, a liquid/liquid extraction is performed. A portion of the aqueous solution is mixed with a solvent (e.g., hexane), placed in an ultrasonic bath and then stirred. The upper solution layer is then used for the GC/MS analysis [41].

2.3. HPLC

In addition to GC, high performance liquid chromatography (HPLC) is also an established chromatographic method for determining the sorption of TOrCs on micro- and nanoparticles [67,68,69]. Samples are usually filtered prior to analysis and the concentration on the particles is then determined indirectly via the supernatant.
Another method is solvent extraction of the particles or solid phase extraction. The HPLC is typically coupled to a UV-detector (UV), a diode array detector (DAD), a fluorescence detector (FD), or a mass spectrometer [38,47,67,70]. A summary of selected studies performed by HPLC is shown in Table 2. In most studies, chromatography was performed with a C-18 column, which captures nonpolar to intermediate polar TOrCs [22,28,34,38,48,67,70,71,72,73,74,75,76]. Advantages of an HPLC analysis are that an individual separation of the individual molecules takes place and detailed results can be (re)produced [47,70,71].

2.4. Further Analytical Techniques for the Determination of Sorbed TOrCs

Besides the GC and LC methods for the identification of sorbed substances, other methods such as ultraviolet/visible spectroscopy (UV/VIS) or spectrophotometers can also be used [30,80,81], see Table 3. Here, a direct analysis of the sorbed substances is not possible; therefore, the supernatant is analyzed. During UV/VIS analysis, the concentrations of the pollutants were calculated from their absorbance. The advantages of UV-VIS analysis are the robustness of the system, the easy handling, the short measuring times, and that it is available in most laboratories.
Measurement by liquid scintillation counting is another method for analyzing sorbed TOrCs in laboratory experiments [6,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84]. For this purpose, a 14C labeled standard of the trace substance is used. The concentration of the trace compound is then determined by counting the decay of the 14C trace compound using liquid scintillation counting.

3. Analysis of TOrCs on Micro- and Nanoplastic Particles: Typical Sorption Strategies

In the initial microplastic studies, the focus was mainly on detection in environmental systems to get an overview of the distribution of the plastic [84,85]. A detailed review by Li et al. (2019) summarizes the occurrence of microplastics in freshwater systems in terms of microplastic sources, distribution, sampling, and processing methods, as well as polymer characterization [86]. The difficulties of qualitative and quantitative analyses are also addressed. In order to investigate the distribution of micro- and nanoplastics in general, numerous studies have been conducted in fresh water and salt water [87,88,89,90,91]. In these studies, the analysis of the particles was performed using Raman and µFTIR.
Recently, many reviews have been published dealing with interactions between plastic particles (micro and nano) and TOrCs [8,9,11,92,93,94,95]. Firstly, the plastic itself is examined more closely, including polymer type, the specific surface of the particles with their functional groups and physicochemical properties, crystallinity, polarity, and additives [8,16,55,92,96]. The factors of the surrounding matrix, such as salinity, pH, dissolved organic matter (DOM), coexisting organic contaminants, and ionic strength [9,93] are also considered. The main retention mechanisms from TOrCs to micro- and nanoplastics are pore filling, hydrophobic hydrogen bonding, π-π-, electrostatic interactions, and van der Waals forces [9]. A further important issue is the ageing of polymers and the resulting influence on the sorption of TOrCs [97]. Finally, the influences of the plastic and TOrCs are examined regarding their toxicological relevance for the aquatic environment and the possible impact on human health [11,94,95].

3.1. Strategies Characterizing the Polymer Type

Several methods are available to identify the polymer type of the plastic particle, such as physical characterization (e.g., microscopy) and chemical characterization (e.g., Fourier transform infrared (FTIR) and Raman spectroscopy) and were summarized in a recent review by Shim et al., 2017 [16]. Spectroscopic analysis of polymers requires purification and isolation of environmental samples [97]. FTIR and Raman spectroscopy are non-destructive and the polymer type can be determined with the help of a database [16]. Thermoanalytical methods such as Pyr-GC/MS, TED-GC/MS can be used to identify and quantify polymers by their characteristic products, presented by La Nasa et al. (2020) and Yakovenko et al. (2020) [55,96]. Thermoanalytical methods have no size limitations and several polymer types can be identified in parallel. However, a minimum amount of polymer is required. For example, a minimum of 10 mg is required for a TED-GC/MS analysis or 60 µg for a Pyr-GC/MS analysis [52,54].
Main characteristics affecting sorption on a plastic particle are crystallinity, density, structure, hydrophobicity, and the glass transition temperature TG. These factors were discussed comprehensively in detail in a recently published short review [8]. In a study comparing the sorption of different polycyclic aromatic hydrocarbons (PAHs) with low-density polyethylene (LDPE) and high-density polyethylene (HDPE), the density of the polymers was observed to have a negative effect on the sorption rate. The sorption capacity decreased with increasing density of the polymers used [14]. However, the density of polymers with crystalline and amorphous components, such as HDPE, was determined by the ratio of crystallinity. In amorphous materials, the hydrophobic bonds are less stable than in crystalline materials [98]. Since only the amorphous fraction can dissolve substances, polymers with a high crystallinity content should have a limited absorption capacity [99,100]. The amorphous region within polymers can be classified as either glassy or rubbery, which is also an indication of sorption capability [12]. The surface appearance is also important for sorption processes. Napper et al. (2015) showed that rough polyethylene (PE) microplastic particles adsorbed more DDT and phenanthrene than smooth ones [29]. The crystallinity of polymers can be measured by X-ray diffraction [101].
Notably, desorption hysteresis was only observed for nonpolar/weakly polar contaminants, likely because nonpolar compounds tended to adsorb in the inner matrices of glassy polymeric structure of polystyrene (resulting in physical entrapment of adsorbates), whereas polar compounds favored surface adsorption [32]. The glass transition temperature (Tg) defines whether a polymeric rubber-like or glass-like material is present. The Tg can be determined by using a thermogravimetric differential scanning calorimetry analyzer (TG-DSC) [73]. Rubber-like polymers are normally above their Tg values if they are not plasticized. At room temperature, this results in greater flexibility, which facilitates sorption of impurities. Glassy polymers are usually below their Tg and are also referred to as condensed (glasslike) [2]. In general, rubbery polymers (such as HDPE, LDPE, or PP) are expected to allow greater diffusion of impurities into the polymer than glassy polymers (such as polyethylene terephthalate (PET) or polyvinyl chloride (PVC)) [2,3]. However, there are exceptions, such as polystyrene (PS). The average sorption capacity is higher than the Tg predicts [1,2,4,5]. A possible explanation for this is the presence of benzene. The phenyl group increases the distance between the polymer chains and can facilitate adhesion and integration of impurities into the polymer [2,5]. However, when comparing polyethylene (PE) and PS in the adsorption and desorption of triclosan, a higher sorption rate was found on PE particles. Triclosan also desorbed faster from the PE particles [34].
A summary of studies in which the sorption capacity of TOrCs and their mechanisms were tested on different particle types is shown in Table 4. Here, reference particles were used in all experiments and were, therefore, not further analyzed in any of the studies.

3.2. Strategies Characterizing Particle Size and Shape (Micro vs. Nano)

Micro- and nanoplastic particles may be derived from fragmentation of larger plastic items by means of photolytic, mechanical, and biological degradation without significant chemical degradation [85,102,103]. Thereby, microplastic particles can further disintegrate into nanoplastics [104,105,106]. As the surface area increases with decreasing particle size, it is assumed that smaller particles are of greater ecotoxicological relevance since the capacity for adsorption of TOrCs increases.
Typical methods for particle sizing can be performed by microscope, FTIR, and Raman spectroscopy [16]. However, there are also limitations. A determination with an optical microscope is often only possible up to 100 µm because smaller particles can also consist of sediment particles [107]. No distinction is then possible using an optical microscope. A FTIR analysis is possible up to 10 µm, a Raman analysis is limited to 100 nm [108,109]. The relationship between particle, surface size, and sorption capacity is considered in more detail in the recently published review by Wang et al., 2020 [9].
In a study by Li et al. using different PS microparticles, it was shown that the sorption capacity of triclosan increases with decreasing particle size of PS [72]. During sorption experiments with micro- and nanoplastic particles, aggregation must also be taken into account. This can happen between two similar (homoaggregation) or two different (heteroaggregation) particles [1]. Aggregation is generally controlled by the ionic strength and valence of the electrolytes in the surrounding media; however, the polymer coating of the particles may also play a role [1,110]. Wang et al. (2019) also showed that the sorption of phenanthrene on the particles was reduced by aggregation of the particles [37]. It has also been shown that nanoparticles agglomerate more and, thus, the specific surface area is reduced again, which can lead to low sorption [37]. A new study by Sun et al. (2020) shows that the agglomeration is strongly dependent on the surrounding matrix [111]. Nanoplastic particles are stable in fresh water due to the Brownian motion and structural layer force, but aggregate in brackish or seawater. In a study with nano-PS, however, it was also shown that the aggregation of the nanoparticles does not change the sorption capacity [70]. The sorption isotherms were the same for aggregated and non-aggregated particles. This indicates that the TOrCs were reaching the sorption sites on the original nanoparticles regardless of the aggregation state. In order to enable comparison of data, the methods for detection, analysis and toxicological assessment of nanoplastics, which are currently still in their initial stages, must first be improved [112].

3.3. Strategies Characterizing Weathered/Aged Particles

Factors that can influence the aging of plastics are, e.g., UV-radiation, temperature, salt content in the environment, and biofilm formation [113]. These causes the plastic to break into smaller and smaller pieces and additives can be released. Induced aging of particles can be carried out for instance by Photo-Fenton oxidation, UV-irradiation, or microbial degradation [79,97].
Investigating aged and unaged microplastic particles, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and FTIR can be used to determine the physical dimensions, morphologies, and chemical compositions [73,78,101,114]. The specific surface area and micropore volume can be studied with an accelerated surface and porosimetry system (ASAP) [83].
Differences in the sorption of aged particles compared to untreated particles are evident in the sorption mechanisms. It was shown that the adsorption of TOrCs in untreated PS particles is based on π-π interaction, whereas in aged PS particles, electrostatic interaction and hydrogen bonding prevail [78]. The results of this study indicated that aging of PS significantly changed the adsorption behavior via the changes of oxygen-containing functional groups and specific surface area. Considering aged and non-aged PP particles in combination with the trace substance triclosan, the aged ones have a higher adsorption capacity than pure microplastics [73]. The sorption affinity was increased with the increase of ionic strength. Study results suggest that particles exposed to weathering processes and the simultaneous presence of several organic trace compounds may affect the biological ecosystem in the natural environment [79]. This is in contrast to a study by Koelmans et al. (2016) on microplastics and hydrophobic organic chemicals (HOCs). The authors conclude that more HOCs accumulate in natural prey and, thus, the risks from microplastics are not increased [10]. Aged PS particles are shown to generally exhibit higher levels of oxygenated functionality with lower surface hydrophobicity than unaged particles, which also influences the sorption capacity [79]. Due to the UV aging of the particles, the surface becomes rougher. In a study by Fan et al. (2021), it was shown that the surface area of PVC particles increased by 1.85 times and that of PLA by 2.66 times [31]. At the same time, the zeta potential decreased and the adsorption capacity of the particles increased due to the aging process. Charge neutralization is one of the important mechanisms of adsorption. Studies show that the surface charge of the adsorbent is closely related to its ability to absorb pollutants [31,115,116].

3.4. TOrC–Microplastics Sorption and Desorption Kinetics

For the determination of the ad- and absorption kinetics, the above-mentioned analytical approaches can be applied in general [33,67,77]. However, there can be some limitations for smaller particles concerning the sampling frequency, since filtration for the separation of particles from the liquid phase requires longer periods of time with decreasing size of the investigated particles. Hence, if the analytical method requires a separation by filtration, such a limitation needs to be considered in the experimental design, especially for particles in the sub-micrometer range. Studies either did not report such limitations since the particles were either too big (>1 µm) to encounter the problem [9,30,39,48,76,77], or a filtration step was avoided, i.e., by negligible depletion solid phase extraction, the aqueous boundary layer permeation method, head space extraction techniques, or else [4,5,32,82].
For the investigation of the desorption kinetics, another issue needs to be overcome. Since the equilibrium of the sorption mechanism is mostly on the side for the polymer phase, especially for hydrophobic compounds, low aqueous concentration TOrCs must be expected and slow desorption kinetics must also be assumed [117,118]. For hydrophobic compounds, a third phase can be included since TOrCs-sink within the experimental design, such as either virgin polymer particles or another sorptive phase, such as solid-phase microextraction. Here, the sorbent acting as sink should be available in excess to ensure the desorption from the loaded polymer particles as the limiting step [32,117,119].
A desorption hysteresis is reported to be higher for hydrophobic compounds than for polar compounds, but also depends strongly on the polymer. For PE [118], and glassy polymeric domains of PS [32], a significant hysteresis for hydrophobic compounds has been reported. Therefore, desorption of hydrophobic compounds even within more complex matrices such as gut fluids is more unlikely than for polar compounds [120]. The desorption hysteresis is also a critical parameter of TOrC–polymer interaction concerning bioaccessibility and, therefore, the environmental impact [10].

4. Conclusions and Outlook

Established analytical methods for the determination of micro- and nanoplastic particles are FTIR, Raman spectroscopy, and thermal methods such as TED-GC/MS and Pyr-GC/MS. FTIR and Raman spectroscopy can be used to identify polymers, but these methods are limited in size [52,54,108,109].
Considering sample preparations for the generation of sorption kinetics, properties, or processes, the experimental set-up is in most cases the same: the selected particles are incubated with the defined TOrCs over a defined period of time. Afterwards, the aqueous phase is separated from the particle phase. The following analysis of the sorbed TOrCs can be performed either via the filtrate or the particles.
For a simple and fast target analysis of TOrCs in the supernatant, a UV-VIS method is recommended, since this is easy to use and is available in most laboratories. Specific absorbance of individual trace compounds can be determined. However, this method is not as sensitive as separation coupled detections, such as with HPLC and GC. Using HPLC coupled with a UV, MS, FD, or DAD, this technique provides more detailed results because the molecules can be separated individually. Direct trace analysis of the particle is not possible with either UV-VIS or HPLC methods. The most established method for polymer analysis is a GC based one. By coupling specific systems such as TED-GC/MS, TD-Pyr-GC/MS, double shot pyrolysis, or sequential pyrolysis the possibility is even offered to perform a direct TOrCs analysis of the particles followed by polymer analysis.
Considering future research, the focus should be mainly on the following points:
(1)
Up to now, either the sorbed TOrCs on the particles or the supernatant have only been analyzed. For the preparation of a mass balance, a complete analysis of particles and aqueous phase would be interesting.
(2)
In most conducted studies, the TOrCs are individually adsorbed onto the polymer. However, it is not to be expected that TOrCs will occur individually in the environment, but are present in mixtures. Napper et al. (2015) and Velzeboer et al. (2014) investigated the competitive sorption of phenanthrene and DDT on PE and PVC, respectively, and both found that DDT sorbed slightly more than phenanthrene [29,45]. Future studies should focus more on how TOrCs affect each other regarding sorption strength and capacity.
(3)
The largest challenge in the analysis of TOrCs on micro- and nanoplastic particles will certainly be the removal of inorganics and larger organics such as biofilms without adversely affecting the sorbed TOrCs.

Author Contributions

Conceptualization, J.R., J.G. and T.L.; methodology, J.R., J.G. and T.L.; validation J.R., J.G. and T.L.; formal analysis, J.R., J.G. and T.L.; investigation, J.R., J.G., O.K. and T.L.; resources, J.E.D.; writing—original draft preparation, J.R., J.G., O.K. and T.L.; writing—review and editing, J.R., J.G., O.K., T.L. and J.E.D.; visualization, J.R.; supervision, J.G., T.L., J.E.D.; project administration, O.K. and J.E.D. All authors have read and agreed to the published version of the manuscript.

Funding

This research was partially funded by the German Federal Ministry of Education and Research (BMBF) in the project SubµTrack, grant number 02WPL1443A.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data is contained within the article.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Alimi, O.S.; Budarz, J.F.; Hernandez, L.M.; Tufenkji, N. Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport. Environ. Sci. Technol. 2018, 52, 1704–1724. [Google Scholar] [CrossRef] [PubMed]
  2. Pascall, M.A.; Zabik, M.E.; Zabik, M.J.; Hernandez, R.J. Uptake of Polychlorinated Biphenyls (Pcbs) from an Aqueous Medium by Polyethylene, Polyvinyl Chloride, and Polystyrene Films. J. Agric. Food Chem. 2005, 53, 164–169. [Google Scholar] [CrossRef] [PubMed]
  3. Rochman, C.M.; Hoh, E.; Hentschel, B.T.; Kaye, S. Long-Term Field Measurement of Sorption of Organic Contaminants to Five Types of Plastic Pellets: Implications for Plastic Marine Debris. Environ. Sci. Technol. 2013, 47, 1646–1654. [Google Scholar] [CrossRef]
  4. Lee, H.; Shim, W.J.; Kwon, J.-H. Sorption capacity of plastic debris for hydrophobic organic chemicals. Sci. Total Environ. 2014, 1545–1552. [Google Scholar] [CrossRef]
  5. Hüffer, T.; Hofmann, T. Sorption of non-polar organic compounds by micro-sized plastic particles in aqueous solution. Environ. Pollut. 2016, 214, 194–201. [Google Scholar] [CrossRef] [PubMed]
  6. Teuten, E.L.; Rowland, S.J.; Galloway, T.S.; Thompson, R.C. Potential for Plastics to Transport Hydrophobic Contaminants. Environ. Sci. Technol. 2007, 4, 7759–7764. [Google Scholar] [CrossRef]
  7. Karapanagioti, H.K.; Klontza, I. Testing phenanthrene distribution properties of virgin plastic pellets and plastic eroded pellets found on Lesvos island beaches (Greece). Mar. Environ. Res. 2008, 65, 283–290. [Google Scholar] [CrossRef] [Green Version]
  8. Mei, W.; Chen, G.; Bao, J.; Song, M.; Li, Y.; Luo, C. Interactions between microplastics and organic compounds in aquatic environments: A mini review. Sci. Total Environ. 2020, 736, 139472. [Google Scholar] [CrossRef] [PubMed]
  9. Wang, F.; Zhang, M.; Sha, W.; Wang, Y.; Hao, H.; Dou, Y.; Li, Y. Sorption Behavior and Mechanisms of Organic Contaminants to Nano and Microplastics. Molecules 2020, 25, 1827. [Google Scholar] [CrossRef] [PubMed]
  10. Koelmans, A.A.; Bakir, A.; Burton, G.A.; Janssen, C.R. Microplastic as a Vector for Chemicals in the Aquatic Environment: Critical Review and Model-Supported Reinterpretation of Empirical Studies. Environ. Sci. Technol. 2016, 50, 3315–3326. [Google Scholar] [CrossRef] [PubMed]
  11. Menéndez-Pedriza, A.; Jaumot, J. Interaction of Environmental Pollutants with Microplastics: A Critical Review of Sorption Factors, Bioaccumulation and Ecotoxicological Effects. Toxics 2020, 8, 40. [Google Scholar] [CrossRef]
  12. Teuten, E.L.; Saquing, J.M.; Knappe, D.R.U.; Barlaz, M.A.; Jonsson, S.; Björn, A.; Rowland, S.J.; Thompson, R.C.; Galloway, T.S.; Yamashita, R.; et al. Transport and release of chemicals from plastics to the environment and to wildlife. Philos. Trans. R. Soc. B Biol. Sci. 2009, 364, 2027–2045. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  13. Seidensticker, S.; Zarfl, C.; Cirpka, O.A.; Fellenberg, G.; Grathwohl, P. Shift in Mass Transfer of Wastewater Contaminants from Microplastics in the Presence of Dissolved Substances. Environ. Sci. Technol. 2017, 51, 12254–12263. [Google Scholar] [CrossRef]
  14. Fries, E.; Zarfl, C. Sorption of polycyclic aromatic hydrocarbons (PAHs) to low and high density polyethylene (PE). Environ. Sci. Pollut. Res. 2012, 19, 1296–1304. [Google Scholar] [CrossRef]
  15. Karapanagioti, H.K.; Werner, D. Sorption of Hydrophobic Organic Compounds to Plastics in the Marine Environment: Sorption and Desorption Kinetics. In The Handbook of Environmental Chemistry; Springer International Publishing: Basel, Switzerland, 2018; pp. 205–219. [Google Scholar]
  16. Shim, W.J.; Hong, S.H.; Eo, S.E. Identification methods in microplastic analysis: A review. Anal. Methods 2017, 9, 1384–1391. [Google Scholar] [CrossRef]
  17. Araujo, C.F.; Nolasco, M.M.; Ribeiro, A.M.; Ribeiro-Claro, P.J. Identification of microplastics using Raman spectroscopy: Latest developments and future prospects. Water Res. 2018, 142, 426–440. [Google Scholar] [CrossRef] [PubMed]
  18. Käppler, A.; Fischer, D.; Oberbeckmann, S.; Schernewski, G.; Labrenz, M.; Eichhorn, K.-J.; Voit, B. Analysis of environmental microplastics by vibrational microspectroscopy: FTIR, Raman or both? Anal. Bioanal. Chem. 2016, 408, 8377–8391. [Google Scholar] [CrossRef] [PubMed]
  19. La Nasa, J.; Biale, G.; Mattonai, M.; Modugno, F. Microwave-assisted solvent extraction and double-shot analytical pyrolysis for the quali-quantitation of plasticizers and microplastics in beach sand samples. J. Hazard. Mater. 2020, 401, 123287. [Google Scholar] [CrossRef]
  20. Reichel, J.; Graßmann, J.; Letzel, T.; Drewes, J.E. Systematic Development of a Simultaneous Determination of Plastic Particle Identity and Adsorbed Organic Compounds by Thermodesorption–Pyrolysis GC/MS (TD-Pyr-GC/MS). Molecules 2020, 25, 4985. [Google Scholar] [CrossRef]
  21. Zhang, J.; Chen, H.; He, H.; Cheng, X.; Ma, T.; Hu, J.; Yang, S.; Li, S.; Zhang, L. Adsorption behavior and mechanism of 9-Nitroanthracene on typical microplastics in aqueous solutions. Chemosphere 2020, 245, 125628. [Google Scholar] [CrossRef] [PubMed]
  22. Xu, B.; Liu, F.; Brookes, P.C.; Xu, J. Microplastics play a minor role in tetracycline sorption in the presence of dissolved organic matter. Environ. Pollut. 2018, 240, 87–94. [Google Scholar] [CrossRef] [PubMed]
  23. Wang, F.; Shih, K.M.; Li, X.Y. The partition behavior of perfluorooctanesulfonate (PFOS) and perfluorooctanesulfonamide (FOSA) on microplastics. Chemosphere 2015, 119, 841–847. [Google Scholar] [CrossRef] [PubMed]
  24. Bakir, A.; Rowland, S.J.; Thompson, R.C. Transport of persistent organic pollutants by microplastics in estuarine conditions. Estuar. Coast. Shelf Sci. 2014, 140, 14–21. [Google Scholar] [CrossRef] [Green Version]
  25. Guo, X.; Wang, J. Sorption of antibiotics onto aged microplastics in freshwater and seawater. Mar. Pollut. Bull. 2019, 149, 110511. [Google Scholar] [CrossRef] [PubMed]
  26. Seidensticker, S.; Grathwohl, P.; Lamprecht, J.; Zarfl, C. A Combined Experimental and Modeling Study to Evaluate Ph-Dependent Sorption of Polar and Non-Polar Compounds to Polyethylene and Polystyrene Microplastics. Environ. Sci. Eur. 2018, 30, 30. [Google Scholar] [CrossRef]
  27. Llorca, M.; Schirinzi, G.; Martínez, M.; Barceló, D.; Farré, M. Adsorption of perfluoroalkyl substances on microplastics under environmental conditions. Environ. Pollut. 2018, 235, 680–691. [Google Scholar] [CrossRef] [PubMed]
  28. Wu, C.; Zhang, K.; Huang, X.; Liu, J. Sorption of pharmaceuticals and personal care products to polyethylene debris. Environ. Sci. Pollut. Res. 2016, 23, 8819–8826. [Google Scholar] [CrossRef] [PubMed]
  29. Napper, I.E.; Bakir, A.; Rowland, S.J.; Thompson, R.C. Characterisation, quantity and sorptive properties of microplastics extracted from cosmetics. Mar. Pollut. Bull. 2015, 99, 178–185. [Google Scholar] [CrossRef] [Green Version]
  30. Ma, J.; Zhao, J.; Zhu, Z.; Li, L.; Yu, F. Effect of microplastic size on the adsorption behavior and mechanism of triclosan on polyvinyl chloride. Environ. Pollut. 2019, 254, 113104. [Google Scholar] [CrossRef]
  31. Fan, X.; Zou, Y.; Geng, N.; Liu, J.; Hou, J.; Li, D.; Yang, C.; Li, Y. Investigation on the adsorption and desorption behaviors of antibiotics by degradable MPs with or without UV ageing process. J. Hazard. Mater. 2021, 401, 123363. [Google Scholar] [CrossRef]
  32. Liu, J.; Ma, Y.; Zhu, D.; Xia, T.; Qi, Y.; Yao, Y.; Guo, X.; Ji, R.; Chen, W. Polystyrene Nanoplastics-Enhanced Contaminant Transport: Role of Irreversible Adsorption in Glassy Polymeric Domain. Environ. Sci. Technol. 2018, 52, 2677–2685. [Google Scholar] [CrossRef]
  33. Gong, W.; Jiang, M.; Han, P.; Liang, G.; Zhang, T.; Liu, G. Comparative analysis on the sorption kinetics and isotherms of fipronil on nondegradable and biodegradable microplastics. Environ. Pollut. 2019, 254, 112927. [Google Scholar] [CrossRef] [PubMed]
  34. Chen, X.; Gu, X.; Bao, L.; Ma, S.; Mu, Y. Comparison of adsorption and desorption of triclosan between microplastics and soil particles. Chemosphere 2020, 263, 127947. [Google Scholar] [CrossRef]
  35. Wu, P.; Cai, Z.; Jin, H.; Tang, Y. Adsorption mechanisms of five bisphenol analogues on PVC microplastics. Sci. Total Environ. 2019, 650, 671–678. [Google Scholar] [CrossRef]
  36. Liu, X.; Xu, J.; Zhao, Y.; Shi, H.; Huang, C.H. Hydrophobic Sorption Behaviors of 17beta-Estradiol on Environmental Microplastics. Chemosphere 2019, 226, 726–735. [Google Scholar] [CrossRef]
  37. Wang, J.; Liu, X.; Liu, G.; Zhang, Z.; Wu, H.; Cui, B.; Bai, J.; Zhang, W. Size effect of polystyrene microplastics on sorption of phenanthrene and nitrobenzene. Ecotoxicol. Environ. Saf. 2019, 173, 331–338. [Google Scholar] [CrossRef]
  38. Zuo, L.-Z.; Li, H.-X.; Lin, L.; Sun, Y.-X.; Diao, Z.-H.; Liu, S.; Zhang, Z.-Y.; Xu, X.-R. Sorption and desorption of phenanthrene on biodegradable poly(butylene adipate co-terephtalate) microplastics. Chemosphere 2019, 215, 25–32. [Google Scholar] [CrossRef]
  39. Qiu, Y.; Zheng, M.; Wang, L.; Zhao, Q.; Lou, Y.; Shi, L.; Qu, L. Sorption of polyhalogenated carbazoles (PHCs) to microplastics. Mar. Pollut. Bull. 2019, 146, 718–728. [Google Scholar] [CrossRef]
  40. Zhang, X.; Zheng, M.; Yin, X.; Wang, L.; Lou, Y.; Qu, L.; Liu, X.; Zhu, H.; Qiu, Y. Sorption of 3,6-dibromocarbazole and 1,3,6,8-tetrabromocarbazole by microplastics. Mar. Pollut. Bull. 2019, 138, 458–463. [Google Scholar] [CrossRef]
  41. Lin, W.; Jiang, R.; Wu, J.; Wei, S.; Yin, L.; Xiao, X.; Hu, S.; Shen, Y.; Ouyang, G. Sorption properties of hydrophobic organic chemicals to micro-sized polystyrene particles. Sci. Total Environ. 2019, 690, 565–572. [Google Scholar] [CrossRef]
  42. Wang, W.; Wang, J. Different partition of polycyclic aromatic hydrocarbon on environmental particulates in freshwater: Microplastics in comparison to natural sediment. Ecotoxicol. Environ. Saf. 2018, 147, 648–655. [Google Scholar] [CrossRef] [PubMed]
  43. Bartonitz, A.; Anyanwu, I.N.; Geist, J.; Imhof, H.K.; Reichel, J.; Graßmann, J.; Drewes, J.E.; Beggel, S. Modulation of PAH toxicity on the freshwater organism G. roeseli by microparticles. Environ. Pollut. 2020, 260, 113999. [Google Scholar] [CrossRef] [PubMed]
  44. Hüffer, T.; Weniger, A.-K.; Hofmann, T. Sorption of organic compounds by aged polystyrene microplastic particles. Environ. Pollut. 2018, 236, 218–225. [Google Scholar] [CrossRef]
  45. Velzeboer, I.; Kwadijk, C.J.A.F.; Koelmans, A.A. Strong Sorption of PCBs to Nanoplastics, Microplastics, Carbon Nanotubes, and Fullerenes. Environ. Sci. Technol. 2014, 48, 4869–4876. [Google Scholar] [CrossRef] [PubMed]
  46. Zhang, X.; Zheng, M.; Wang, L.; Lou, Y.; Shi, L.; Jiang, S. Sorption of three synthetic musks by microplastics. Mar. Pollut. Bull. 2018, 126, 606–609. [Google Scholar] [CrossRef]
  47. Liu, X.; Shi, H.; Xie, B.; Dionysiou, D.D.; Zhao, Y. Microplastics as Both a Sink and a Source of Bisphenol A in the Marine Environment. Environ. Sci. Technol. 2019, 53, 10188–10196. [Google Scholar] [CrossRef]
  48. Liu, Z.; Qin, Q.; Hu, Z.; Yan, L.; Ieong, U.-I.; Xu, Y. Adsorption of chlorophenols on polyethylene terephthalate microplastics from aqueous environments: Kinetics, mechanisms and influencing factors. Environ. Pollut. 2020, 265, 114926. [Google Scholar] [CrossRef]
  49. Yu, H.; Yang, B.; Waigi, M.G.; Peng, F.; Li, Z.; Hu, X. The effects of functional groups on the sorption of naphthalene on microplastics. Chemosphere 2020, 261, 127592. [Google Scholar] [CrossRef]
  50. Fries, E.; Dekiff, J.H.; Willmeyer, J.; Nuelle, M.T.; Ebert, M.; Remy, D. Identification of polymer types and additives in marine microplastic particles using pyrolysis-GC/MS and scanning electron microscopy. Environ. Sci. Process. Impacts 2013, 15, 1949–1956. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  51. Dümichen, E.; Barthel, A.-K.; Braun, U.; Bannick, C.G.; Brand, K.; Jekel, M.; Senz, R. Analysis of polyethylene microplastics in environmental samples, using a thermal decomposition method. Water Res. 2015, 85, 451–457. [Google Scholar] [CrossRef]
  52. Fischer, M.; Scholz-Böttcher, B.M. Simultaneous Trace Identification and Quantification of Common Types of Microplastics in Environmental Samples by Pyrolysis-Gas Chromatography–Mass Spectrometry. Environ. Sci. Technol. 2017, 51, 5052–5060. [Google Scholar] [CrossRef]
  53. Herrera, M.; Matuschek, G.; Kettrup, A. Fast identification of polymer additives by pyrolysis-gas chromatography/mass spectrometry. J. Anal. Appl. Pyrolysis 2003, 70, 35–42. [Google Scholar] [CrossRef]
  54. Duemichen, E.; Braun, U.; Senz, R.; Fabian, G.; Sturm, H. Assessment of a new method for the analysis of decomposition gases of polymers by a combining thermogravimetric solid-phase extraction and thermal desorption gas chromatography mass spectrometry. J. Chromatogr. A 2014, 1354, 117–128. [Google Scholar] [CrossRef] [PubMed]
  55. La Nasa, J.; Biale, G.; Fabbri, D.; Modugno, F. A Review on Challenges and Developments of Analytical Pyrolysis and Other Thermoanalytical Techniques for the Quali-Quantitative Determination of Microplastics. J. Anal. Appl. Pyrolysis 2020, 149, 104841. [Google Scholar] [CrossRef]
  56. Fischer, M.; Goßmann, I.; Scholz-Böttcher, B.M. Fleur de Sel—An interregional monitor for microplastics mass load and composition in European coastal waters? J. Anal. Appl. Pyrolysis 2019, 144, 104711. [Google Scholar] [CrossRef]
  57. Nuelle, M.-T.; Dekiff, J.H.; Remy, D.; Fries, E. A new analytical approach for monitoring microplastics in marine sediments. Environ. Pollut. 2014, 184, 161–169. [Google Scholar] [CrossRef]
  58. Kebelmann, K.; Hornung, A.; Karsten, U.; Griffiths, G. Intermediate pyrolysis and product identification by TGA and Py-GC/MS of green microalgae and their extracted protein and lipid components. Biomass Bioenergy 2013, 49, 38–48. [Google Scholar] [CrossRef]
  59. Funck, M.; Yildirim, A.; Nickel, C.; Schram, J.; Schmidt, T.C.; Tuerk, J. Identification of microplastics in wastewater after cascade filtration using Pyrolysis-GC–MS. MethodsX 2020, 7, 100778. [Google Scholar] [CrossRef] [PubMed]
  60. Peters, C.A.; Hendrickson, E.; Minor, E.C.; Schreiner, K.; Halbur, J.; Bratton, S.P. Pyr-GC/MS analysis of microplastics extracted from the stomach content of benthivore fish from the Texas Gulf Coast. Mar. Pollut. Bull. 2018, 137, 91–95. [Google Scholar] [CrossRef] [PubMed]
  61. Ter Halle, A.; Jeanneau, L.; Martignac, M.; Jardé, E.; Pedrono, B.; Brach, L.; Gigault, J. Nanoplastic in the North Atlantic Subtropical Gyre. Environ. Sci. Technol. 2017, 51, 13689–13697. [Google Scholar] [CrossRef]
  62. Duemichen, E.; Eisentraut, P.; Celina, M.; Braun, U. Automated thermal extraction-desorption gas chromatography mass spectrometry: A multifunctional tool for comprehensive characterization of polymers and their degradation products. J. Chromatogr. A 2019, 1592, 133–142. [Google Scholar] [CrossRef] [PubMed]
  63. Dümichen, E.; Eisentraut, P.; Gerhard, C.; Barthel, A.; Senz, R.; Braun, U. Fast identification of microplastics in complex environmental samples by a thermal degradation method. Chemosphere 2017, 174, 572–584. [Google Scholar] [CrossRef] [PubMed]
  64. Rial-Otero, R.; Galesio, M.; Capelo, J.L.; Simal-Gándara, J. A Review of Synthetic Polymer Characterization by Pyrolysis–Gc–Ms. Chromatographia 2009, 70, 339–348. [Google Scholar] [CrossRef]
  65. Llorca, M.; Ábalos, M.; Vega-Herrera, A.; Adrados, M.A.; Abad, E.; Farré, M. Adsorption and Desorption Behaviour of Polychlorinated Biphenyls onto Microplastics’ Surfaces in Water/Sediment Systems. Toxics 2020, 8, 59. [Google Scholar] [CrossRef]
  66. Endo, S.; Takizawa, R.; Okuda, K.; Takada, H.; Chiba, K.; Kanehiro, H.; Ogi, H.; Yamashita, R.; Date, T. Concentration of polychlorinated biphenyls (PCBs) in beached resin pellets: Variability among individual particles and regional differences. Mar. Pollut. Bull. 2005, 50, 1103–1114. [Google Scholar] [CrossRef]
  67. Guo, X.; Pang, J.; Chen, S.; Jia, H. Sorption properties of tylosin on four different microplastics. Chemosphere 2018, 209, 240–245. [Google Scholar] [CrossRef]
  68. Li, S.; Liu, H.; Gao, R.; Abdurahman, A.; Dai, J.; Zeng, F. Aggregation kinetics of microplastics in aquatic environment: Complex roles of electrolytes, pH, and natural organic matter. Environ. Pollut. 2018, 237, 126–132. [Google Scholar] [CrossRef]
  69. Zhao, L.; Rong, L.; Xu, J.; Lian, J.; Wang, L.; Sun, H. Sorption of five organic compounds by polar and nonpolar microplastics. Chemosphere 2020, 257, 127206. [Google Scholar] [CrossRef] [PubMed]
  70. Liu, L.; Fokkink, R.; Koelmans, A.A. Sorption of polycyclic aromatic hydrocarbons to polystyrene nanoplastic. Environ. Toxicol. Chem. 2016, 35, 1650–1655. [Google Scholar] [CrossRef]
  71. Li, J.; Zhang, K.; Zhang, H. Adsorption of antibiotics on microplastics. Environ. Pollut. 2018, 237, 460–467. [Google Scholar] [CrossRef] [PubMed]
  72. Li, Y.; Li, M.; Li, Z.; Yang, L.; Liu, X. Effects of particle size and solution chemistry on Triclosan sorption on polystyrene microplastic. Chemosphere 2019, 231, 308–314. [Google Scholar] [CrossRef] [PubMed]
  73. Wu, X.; Liu, P.; Huang, H.; Gao, S. Adsorption of triclosan onto different aged polypropylene microplastics: Critical effect of cations. Sci. Total Environ. 2020, 717, 137033. [Google Scholar] [CrossRef]
  74. Puckowski, A.; Cwięk, W.; Mioduszewska, K.; Stepnowski, P.; Białk-Bielińska, A. Sorption of pharmaceuticals on the surface of microplastics. Chemosphere 2020, 263, 127976. [Google Scholar] [CrossRef] [PubMed]
  75. Zhang, H.; Liu, F.-F.; Wang, S.-C.; Huang, T.-Y.; Li, M.-R.; Zhu, Z.-L.; Liu, G.-Z. Sorption of fluoroquinolones to nanoplastics as affected by surface functionalization and solution chemistry. Environ. Pollut. 2020, 262, 114347. [Google Scholar] [CrossRef] [PubMed]
  76. Xu, B.; Liu, F.; Brookes, P.C.; Xu, J. The sorption kinetics and isotherms of sulfamethoxazole with polyethylene microplastics. Mar. Pollut. Bull. 2018, 131, 191–196. [Google Scholar] [CrossRef]
  77. Guo, X.; Chen, C.; Wang, J. Sorption of sulfamethoxazole onto six types of microplastics. Chemosphere 2019, 228, 300–308. [Google Scholar] [CrossRef] [PubMed]
  78. Liu, P.; Lu, K.; Li, J.; Wu, X.; Qian, L.; Wang, M.; Gao, S. Effect of aging on adsorption behavior of polystyrene microplastics for pharmaceuticals: Adsorption mechanism and role of aging intermediates. J. Hazard. Mater. 2020, 384, 121193. [Google Scholar] [CrossRef]
  79. Ho, W.-K.; Law, J.C.-F.; Zhang, T.; Leung, K.S.-Y. Effects of Weathering on the Sorption Behavior and Toxicity of Polystyrene Microplastics in Multi-solute Systems. Water Res. 2020, 187, 116419. [Google Scholar] [CrossRef]
  80. Xia, Y.; Zhou, J.-J.; Gong, Y.-Y.; Li, Z.-J.; Zeng, E.Y. Strong influence of surfactants on virgin hydrophobic microplastics adsorbing ionic organic pollutants. Environ. Pollut. 2020, 265, 115061. [Google Scholar] [CrossRef] [PubMed]
  81. Li, H.; Wang, F.; Li, J.; Deng, S.; Zhang, S. Adsorption of three pesticides on polyethylene microplastics in aqueous solutions: Kinetics, isotherms, thermodynamics, and molecular dynamics simulation. Chemosphere 2020, 264, 128556. [Google Scholar] [CrossRef]
  82. Bakir, A.; Rowland, S.J.; Thompson, R.C. Enhanced desorption of persistent organic pollutants from microplastics under simulated physiological conditions. Environ. Pollut. 2014, 185, 16–23. [Google Scholar] [CrossRef] [PubMed]
  83. Liu, J.; Zhang, T.; Tian, L.; Liu, X.; Qi, Z.; Ma, Y.; Ji, R.; Chen, W. Aging Significantly Affects Mobility and Contaminant-Mobilizing Ability of Nanoplastics in Saturated Loamy Sand. Environ. Sci. Technol. 2019, 53, 5805–5815. [Google Scholar] [CrossRef]
  84. Thompson, R.C.; Olsen, Y.; Mitchell, R.P.; Davis, A.; Rowland, S.J.; John, A.W.; McGonigle, D.; Russell, A.E. Lost at Sea: Where Is All the Plastic? Science 2004, 304, 838. [Google Scholar] [CrossRef]
  85. Barnes, D.K.A.; Galgani, F.; Thompson, R.C.; Barlaz, M. Accumulation and fragmentation of plastic debris in global environments. Philos. Trans. R. Soc. B Biol. Sci. 2009, 364, 1985–1998. [Google Scholar] [CrossRef] [Green Version]
  86. Li, C.; Busquets, R.; Campos, L.C. Assessment of microplastics in freshwater systems: A review. Sci. Total Environ. 2020, 707, 135578. [Google Scholar] [CrossRef]
  87. Imhof, H.K.; Wiesheu, A.C.; Anger, P.M.; Niessner, R.; Ivleva, N.P.; Laforsch, C. Variation in plastic abundance at different lake beach zones—A case study. Sci. Total Environ. 2018, 613–614, 530–537. [Google Scholar] [CrossRef]
  88. Cincinelli, A.; Martellini, T.; Guerranti, C.; Scopetani, C.; Chelazzi, D.; Giarrizzo, T. A potpourri of microplastics in the sea surface and water column of the Mediterranean Sea. TrAC Trends Anal. Chem. 2019, 110, 321–326. [Google Scholar] [CrossRef]
  89. Kazour, M.; Jemaa, S.; Issa, C.; Khalaf, G.; Amara, R. Microplastics pollution along the Lebanese coast (Eastern Mediterranean Basin): Occurrence in surface water, sediments and biota samples. Sci. Total Environ. 2019, 696, 133933. [Google Scholar] [CrossRef] [PubMed]
  90. Llorca, M.; Vega-Herrera, A.; Schirinzi, G.; Savva, K.; Abad, E.; Farré, M. Screening of suspected micro(nano)plastics in the Ebro Delta (Mediterranean Sea). J. Hazard. Mater. 2021, 404, 124022. [Google Scholar] [CrossRef]
  91. Simon-Sánchez, L.; Grelaud, M.; Garcia-Orellana, J.; Ziveri, P. River Deltas as hotspots of microplastic accumulation: The case study of the Ebro River (NW Mediterranean). Sci. Total Environ. 2019, 687, 1186–1196. [Google Scholar] [CrossRef] [PubMed]
  92. Tourinho, P.S.; Kočí, V.; Loureiro, S.; van Gestel, C.A. Partitioning of chemical contaminants to microplastics: Sorption mechanisms, environmental distribution and effects on toxicity and bioaccumulation. Environ. Pollut. 2019, 252, 1246–1256. [Google Scholar] [CrossRef] [PubMed]
  93. Yu, F.; Yang, C.; Zhu, Z.; Bai, X.; Ma, J. Adsorption behavior of organic pollutants and metals on micro/nanoplastics in the aquatic environment. Sci. Total Environ. 2019, 694, 133643. [Google Scholar] [CrossRef]
  94. Huang, W.; Song, B.; Liang, J.; Niu, Q.; Zeng, G.; Shen, M.; Deng, J.; Luo, Y.; Wen, X.; Zhang, Y. Microplastics and associated contaminants in the aquatic environment: A review on their ecotoxicological effects, trophic transfer, and potential impacts to human health. J. Hazard. Mater. 2020, 405, 124187. [Google Scholar] [CrossRef]
  95. Shen, M.; Zhang, Y.; Zhu, Y.; Song, B.; Zeng, G.; Hu, D.; Wen, X.; Ren, X. Recent advances in toxicological research of nanoplastics in the environment: A review. Environ. Pollut. 2019, 252, 511–521. [Google Scholar] [CrossRef]
  96. Yakovenko, N.; Carvalho, A.; Ter Halle, A. Emerging use thermo-analytical method coupled with mass spectrometry for the quantification of micro(nano)plastics in environmental samples. TrAC Trends Anal. Chem. 2020, 131, 115979. [Google Scholar] [CrossRef]
  97. Liu, P.; Zhan, X.; Wu, X.; Li, J.; Wang, H.; Gao, S. Effect of weathering on environmental behavior of microplastics: Properties, sorption and potential risks. Chemosphere 2020, 242, 125193. [Google Scholar] [CrossRef] [PubMed]
  98. Parida, S.K.; Dash, S.; Patel, S.; Mishra, B. Adsorption of organic molecules on silica surface. Adv. Colloid Interface Sci. 2006, 121, 77–110. [Google Scholar] [CrossRef] [PubMed]
  99. Andrady, A.L. The plastic in microplastics: A review. Mar. Pollut. Bull. 2017, 119, 12–22. [Google Scholar] [CrossRef] [PubMed]
  100. Endo, S.; Koelmans, A.A. Sorption of Hydrophobic Organic Compounds to Plastics in the Marine Environment: Equilibrium. In The Handbook of Environmental Chemistry; Springer International Publishing: Basel, Switzerland, 2016; pp. 185–204. [Google Scholar]
  101. Ding, L.; Mao, R.; Ma, S.; Guo, X.; Zhu, L. High temperature depended on the ageing mechanism of microplastics under different environmental conditions and its effect on the distribution of organic pollutants. Water Res. 2020, 174, 115634. [Google Scholar] [CrossRef] [PubMed]
  102. Roy, P.K.; Hakkarainen, M.; Varma, I.K.; Albertsson, A.-C. Degradable Polyethylene: Fantasy or Reality. Environ. Sci. Technol. 2011, 45, 4217–4227. [Google Scholar] [CrossRef]
  103. Browne, M.A.; Galloway, T.; Thompson, R. Microplastic-an emerging contaminant of potential concern? Integr. Environ. Assess. Manag. 2007, 3, 559–561. [Google Scholar] [CrossRef]
  104. Lambert, S.; Wagner, M. Characterisation of nanoplastics during the degradation of polystyrene. Chemosphere 2016, 145, 265–268. [Google Scholar] [CrossRef] [Green Version]
  105. Mattsson, K.; Hansson, L.-A.; Cedervall, T. Nano-plastics in the aquatic environment. Environ. Sci. Process. Impacts 2015, 17, 1712–1721. [Google Scholar] [CrossRef] [PubMed]
  106. da Costa, J.P.; Santos, P.S.; Duarte, A.C.; Rocha-Santos, T. (Nano)plastics in the environment—Sources, fates and effects. Sci. Total Environ. 2016, 566–567, 15–26. [Google Scholar] [CrossRef] [PubMed]
  107. Song, Y.K.; Hong, S.H.; Jang, M.; Han, G.M.; Rani, M.; Lee, J.; Shim, W.J. A comparison of microscopic and spectroscopic identification methods for analysis of microplastics in environmental samples. Mar. Pollut. Bull. 2015, 93, 202–209. [Google Scholar] [CrossRef] [PubMed]
  108. Löder, M.G.J.; Kuczera, M.; Mintenig, S.; Lorenz, C.; Gerdts, G. Focal plane array detector-based micro-Fourier-transform infrared imaging for the analysis of microplastics in environmental samples. Environ. Chem. 2015, 12, 563–581. [Google Scholar] [CrossRef]
  109. Sobhani, Z.; Zhang, X.; Gibson, C.; Naidu, R.; Megharaj, M.; Fang, C. Identification and visualisation of microplastics/nanoplastics by Raman imaging (i): Down to 100 nm. Water Res. 2020, 174, 115658. [Google Scholar] [CrossRef] [PubMed]
  110. Lowry, G.V.; Gregory, K.B.; Apte, S.C.; Lead, J.R. Transformations of Nanomaterials in the Environment. Environ. Sci. Technol. 2012, 46, 6893–6899. [Google Scholar] [CrossRef]
  111. Sun, H.; Jiao, R.; Wang, D. The difference of aggregation mechanism between microplastics and nanoplastics: Role of Brownian motion and structural layer force. Environ. Pollut. 2020, 268, 115942. [Google Scholar] [CrossRef]
  112. Koelmans, A.A.; Besseling, E.; Shim, W.J. Nanoplastics in the Aquatic Environment. Critical Review. In Marine Anthropogenic Litter; Springer Science and Business Media LLC: Berlin/Heidelberg, Germany, 2015; pp. 325–340. [Google Scholar]
  113. Jahnke, A.; Arp, H.P.H.; Escher, B.I.; Gewert, B.; Gorokhova, E.; Kühnel, D.; Ogonowski, M.; Potthoff, A.; Rummel, C.; Schmitt-Jansen, M.; et al. Reducing Uncertainty and Confronting Ignorance about the Possible Impacts of Weathering Plastic in the Marine Environment. Environ. Sci. Technol. Lett. 2017, 4, 85–90. [Google Scholar] [CrossRef]
  114. Liu, G.; Zhu, Z.; Yang, Y.; Sun, Y.; Yu, F.; Ma, J. Sorption behavior and mechanism of hydrophilic organic chemicals to virgin and aged microplastics in freshwater and seawater. Environ. Pollut. 2019, 246, 26–33. [Google Scholar] [CrossRef] [PubMed]
  115. Sun, W.; Jiang, B.; Wang, F.; Xu, N. Effect of carbon nanotubes on Cd(II) adsorption by sediments. Chem. Eng. J. 2015, 264, 645–653. [Google Scholar] [CrossRef]
  116. Anirudhan, T.; Bringle, C.; Radhakrishnan, P. Heavy metal interactions with phosphatic clay: Kinetic and equilibrium studies. Chem. Eng. J. 2012, 200–202, 149–157. [Google Scholar] [CrossRef]
  117. Endo, S.; Yuyama, M.; Takada, H. Desorption kinetics of hydrophobic organic contaminants from marine plastic pellets. Mar. Pollut. Bull. 2013, 74, 125–131. [Google Scholar] [CrossRef]
  118. Razanajatovo, R.M.; Ding, J.; Zhang, S.; Jiang, H.; Zou, H. Sorption and desorption of selected pharmaceuticals by polyethylene microplastics. Mar. Pollut. Bull. 2018, 136, 516–523. [Google Scholar] [CrossRef]
  119. Cornelissen, G.; van Noort, P.C.; Govers, H.A. Desorption Kinetics of Chlorobenzenes, Polycyclic Aromatic Hydrocarbons, and Polychlorinated Biphenyls: Sediment Extraction with Tenax and Effects of Contact Time and Solute Hydrophobicity. Environ. Toxicol. Chem. 1997, 16, 1351–1357. [Google Scholar] [CrossRef]
  120. Liu, X.; Gharasoo, M.; Shi, Y.; Sigmund, G.; Hüffer, T.; Duan, L.; Wang, Y.; Ji, R.; Hofmann, T.; Chen, W. Key Physicochemical Properties Dictating Gastrointestinal Bioaccessibility of Microplastics-Associated Organic Xenobiotics: Insights from a Deep Learning Approach. Environ. Sci. Technol. 2020, 54, 12051–12062. [Google Scholar] [CrossRef] [PubMed]
Molecules 26 01164 g001 550
Figure 1. Workflow from a sample preparation of sorption experiments for analytical detection techniques. First, the particles and the TOrCs are incubated in aqueous solution for a certain period of time. This is followed by the separation of the particles and the aqueous phase. Depending on the choice of analytical technique, either the aqueous or the particle phase is processed. The analysis is either based on a gas chromatography method followed by high resolution/mass spectrometry (HR/MS), mass spectrometry (MS) or electron capture detection (ECD) analysis or based on a high performance liquid chromatography (HPLC) method followed by MS/MS, MS, ultraviolet (UV), diode-array detector (DAD) or fluorescence detector (FLD). Further analytical methods are liquid scintillation counter and spectrophotometer.
Figure 1. Workflow from a sample preparation of sorption experiments for analytical detection techniques. First, the particles and the TOrCs are incubated in aqueous solution for a certain period of time. This is followed by the separation of the particles and the aqueous phase. Depending on the choice of analytical technique, either the aqueous or the particle phase is processed. The analysis is either based on a gas chromatography method followed by high resolution/mass spectrometry (HR/MS), mass spectrometry (MS) or electron capture detection (ECD) analysis or based on a high performance liquid chromatography (HPLC) method followed by MS/MS, MS, ultraviolet (UV), diode-array detector (DAD) or fluorescence detector (FLD). Further analytical methods are liquid scintillation counter and spectrophotometer.
Molecules 26 01164 g001
Table
Table 1. Summary of GC/MS methods to analyze sorbed substances on various microplastic particles like polyethylene (PE), polystyrene (PS), polyamide (PA), polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA).
Table 1. Summary of GC/MS methods to analyze sorbed substances on various microplastic particles like polyethylene (PE), polystyrene (PS), polyamide (PA), polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA).
Particle TypeParticle Size (µm)SorbateAnalytical MethodAnalyzed PhaseReference
PE260Phenanthrene, Tonalide, Benzophenone GC/MS after extraction with cyclohexaneParticle (Extraction)[13]
PE, PSPE: 260, PS: 250 Atrazine, Benzotriazole, Caffeine, Carbamazepine, Carbendazim, DEET, Diazinon, Diclofenac, Ibuprofen, MCPA, Mecoprop, 4-Nonylphenol, Phenanthrene, Propiconazole, Tris(2-chloroisopropyl)-phosphate (TCPP), Tebuconazole, Terbutryn, Torasemide, TriclosanGC/MS, LC-MS/MS after extraction with cyclohexaneParticle (Extraction)[26]
PA, PE, PVC, PS<250n-Hexane, Cyclohexane, Benzene, Toluene, Chlorobenzene, Ethylbenzoate, NaphtaleneHeadspace GC/MS or in-tube-microextractionGaseous phase[5]
PS (aged)125–250 Various aliphatics and aromaticsGC/MS headspace from three-phase systemGaseous phase[44]
PE, PS, Fullerene, SedimentPE: 10–180 PS: 0.07 17 Polychlorinated biphenyls (PCBs)GC/MS after extraction with pentane-dichloromethaneAqueous phase via passive sampler[45]
PE, PP, PS320–440 8 Polycyclic aromatic hydrocarbons (PAHs), 4 Hexachlorocyclohexanes (HCHs), 2 Chlorinated benzenes (CBs)GC-ECD after extraction with n-hexaneAqueous phase and PDMS phase[4]
PP450–850Tonalide, Musk xylene, Musk ketoneGC/MS after extraction with n-hexane and dichloromethaneParticle (extraction)[46]
PS, PE, PETPE: 3–16
PS:10
PET: <300 		38 PCB congenersGC-HRMS after soxhlet extraction with dichloromethaneParticle (extraction)[65]
PE, PP (environmental samples)<500PCBs (IUPAC nos. 28, 52, 101, 118, 138, 153, 180)GC-ECD after soxhlet extraction with dichloromethaneParticle (extraction)[66]
PS2; 1; 0.1Eighteen unsubstituted hydrophobic organic chemicals (HOCs)GC/MS after liquid / liquid extractionAqueous phase via passive sampler[41]
PE, PS, PVC<150Five polyhalogenated carbazoles (PHCs)GC/MS after washing with n-hexane and dichloromethaneParticle (extraction)[39]
PE, PP, PS100–1509-NitroanthraceneGC/MS after liquid/liquid extractionAqueous phase[21]
PP450–8503,6-Dibromocarbazole and 1,3,6,8- Tetrabromocarbazole GC/MS after extraction with n-hexane and dichloromethaneParticle (extraction)[40]
PS, PE, PMMAPS: 40, 41, 0.078 PMMA: 48 PE: 48 Phenanthrene, Triclosan, α-CypermethrinTD-Pyr-GC/MSParticle (directly)[20]
Table
Table 2. Summary of HPLC methods to analyze sorbed substances on micro- and nanoplastic particles like polybutylenadipat-terephthalat (PBAT), low-density polyethylene (LD-PE) or high-density polyethylene (HD-PE).
Table 2. Summary of HPLC methods to analyze sorbed substances on micro- and nanoplastic particles like polybutylenadipat-terephthalat (PBAT), low-density polyethylene (LD-PE) or high-density polyethylene (HD-PE).
Particle TypeParticle Size (µm)SorbateAnalytical MethodAnalysisReference
PS0.5, 0.235, 0.80, 30, 50, 102, 170Phenanthrene, NitrobenzeneHPLCSupernatant[37]
PE, PP, PS, PVC<200TylosinHPLC + DADSupernatant[67]
PA, PE, PET, PS, PVC, PP100, 150SulfamethoxazoleHPLCSupernatant[77]
PBAT, PE, PSPBAT: 2338 ± 486,
PE: 2628 ±623/Reference Particles: PE: 400PS: 250 		PhenanthreneHPLC + -UVSupernatant[38]
PE, PS, soil PE: 225 ± 41
PS: 313 ± 48		TriclosanHPLC + UVMethanol extraction of the particles [34]
PE, PS, PP, PA, PVC75–180Sulfadiazine, Amoxicillin, Tetracycline, Ciprofloxacin, TrimethoprimHPLC + UVSupernatant[71]
PS75.4, 106.9, 150.5, 214.6 TriclosanHPLC + UVSupernatant[72]
PS0.07Phenanthrene, Anthracene, Fluoranthene, Pyrene, Benzo[a]anthracene, Chrysene, Benzo[b]fluoranthene, Benzo[k]fluoranthene, Benzo[a]pyrene, Benzo [g,h,i] peryleneHPLC + FDExtraction via Polyoxymethylene sheets[70]
PS (aged)50.4 ± 11.9 Atorvastatin, AmlodipineHPLC + UVSupernatant[78]
PET<1504-Chlorophenol, 2,4,6-Trichlorophenol, Fulvic acidHPLC + UVSupernatant[48]
PP (aged)<180 TriclosanHPLC + UVSupernatant[73]
PP, LD-PE, HD-PE, PVC63–125Enrofloxacin, Ciprofloxacin, Norfloxacin, 5-Fluorouracil, Methotrexate, Flubendazole, Fenbendazole, Propranolol, NadololHPLC + DADSupernatant[74]
PS (weathered)139–2074-Hydroxybenzophenone, Benzophenone-1, ethylhexyl methoxycinnamate, OctocryleneUHPLC + S/MSSupernatant[79]
PVC, PLA PLA: 250–550
PVC: 75–150		Tetracycline, CiprofloxacinHPLCSupernatant[31]
nano-PS, carboxyl-functionalized
polystyrene nano-PS-COOH		Nano-PS: 0.05
Nano-PS-COOH: 0.055 		Norfloxacin, LevofloxacinHPLC + FDSupernatant[75]
PE, PS, PP<280 TetracyclineHPLC + FDSupernatant[22]
PE250–280Carbamazepine, 4-
methylbenzylidene camphor, Triclosan, 17α-ethinyl estradiol		HPLC + PAD (Solid phase extraction)Supernatant[28]
PE150SulfamethoxazoleHPLC + UVSupernatant[76]
Table
Table 3. Summary of UV/VIS spectroscopic methods to analyze sorbed substances on micro- and nanoplastic particles.
Table 3. Summary of UV/VIS spectroscopic methods to analyze sorbed substances on micro- and nanoplastic particles.
Polymer TypeParticle Size (µm)SorbateAnalytical MethodAnalysisReference
PVC<1.74TriclosanUV/VIS (282 nm)Supernatant[30]
PVC, PP, PS, PE<1000Co-existing surfactantsUV/VIS (665, 618, 627, 546, 224 nm)Supernatant[80]
PE710–850Imidacloprid, Buprofezin, DifenoconazoleUV SpectrophotometerSupernatant[81]
Table
Table 4. Sorption capacity of different polymers. The following criteria were considered for study selection: particles should be approximately the same size and sorption mechanisms and capacities should be addressed.
Table 4. Sorption capacity of different polymers. The following criteria were considered for study selection: particles should be approximately the same size and sorption mechanisms and capacities should be addressed.
Polymer TypeSorbateSorbate AnalyticsSorption Capacity MechanismsReference
PE, PP, PS, PVCTylosinHPLC + DADPE < PP < PS < PVCelectrostatic interactions, surface complexation and hydrophobic interactions[67]
PE, PS, soilTriclosanHPLC + UVPE > PS = soilPS: π-π interactions,
PE: liquid-film and intra-particle diffusion		[34]
PE, PS, PP, PA, PVCSulfadiazine, Amoxicillin, Tetracycline, Ciprofloxacin, TrimethoprimHPLC + UVPA > PS, PP, PVC, PEPolar–polar interactions[71]
PS, PP, PETetracyclineHPLC-FDPS > PP > PEPolar interactions, π-π interactions[22]
PE, PP, PVC3,6-dibromocarbazole, 3,6-dichlorocarbazole, 3,6-diiodocarbazole, 2,7-dibromocarbazole, 3-bromocarbazoleGC/MS after washing with n-hexane and dichloromethanePVC >> PP, PEIntraparticle, film diffusion[39]
PE, PS, soilTriclosanHPLC + UVPE > PS = soilPE: hydrophobic interactions PS: π-π interactions[34]
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Reichel, J.; Graßmann, J.; Knoop, O.; Drewes, J.E.; Letzel, T. Organic Contaminants and Interactions with Micro- and Nano-Plastics in the Aqueous Environment: Review of Analytical Methods. Molecules 2021, 26, 1164. https://doi.org/10.3390/molecules26041164

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Reichel J, Graßmann J, Knoop O, Drewes JE, Letzel T. Organic Contaminants and Interactions with Micro- and Nano-Plastics in the Aqueous Environment: Review of Analytical Methods. Molecules. 2021; 26(4):1164. https://doi.org/10.3390/molecules26041164

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Reichel, Julia, Johanna Graßmann, Oliver Knoop, Jörg E. Drewes, and Thomas Letzel. 2021. "Organic Contaminants and Interactions with Micro- and Nano-Plastics in the Aqueous Environment: Review of Analytical Methods" Molecules 26, no. 4: 1164. https://doi.org/10.3390/molecules26041164

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