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Article

Emerging Contaminants from Bioplastic Pollution in Marine Waters

by
Amedeo Boldrini
1,2,
Nicola Gaggelli
1,
Francesco Falcai
1,
Alessio Polvani
1,2,
Luigi Talarico
1,
Luisa Galgani
1,
Riccardo Cirrone
1,3,
Xinyu Liu
1,3 and
Steven Loiselle
1,4,*
1
Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
2
Center for Colloids and Surface Science (CSGI)-Siena Research Group, University of Florence, Via della Lastruccia 3, 50019 Firenze, Italy
3
NBFC-National Biodiversity Future Centre, 90121 Palermo, Italy
4
National Interuniversity Consortium of Materials Science and Technology (INSTM)—Siena Research Unit, Via G. Giusti 9, 50121 Firenze, Italy
*
Author to whom correspondence should be addressed.
Water 2024, 16(24), 3676; https://doi.org/10.3390/w16243676
Submission received: 13 November 2024 / Revised: 12 December 2024 / Accepted: 18 December 2024 / Published: 20 December 2024
(This article belongs to the Section Water Quality and Contamination)
Browse Figures
Graphical abstract
"> Figure 1
<p>FTIR spectra of BB4, BB8, and BB9 plastic samples over the range 4000–400 cm<sup>−1</sup>.</p> "> Figure 2
<p><sup>1</sup>H-NMR spectra of BB4 (red), BB8 (green), and BB9 (blue) plastic samples in deuterated acetone, showing characteristic signals of aromatic protons of phthalate esters.</p> "> Figure 3
<p>Chromatograms of each biobag compared to a 3 mg/L standard solution of phthalate ester mix, with relative peak assignment.</p> "> Figure 4
<p>The aromatic region of <sup>1</sup>H-NMR spectra of seawater samples after exposure to biobags for 120 days; asterisk (*) indicates the peaks assigned to H3/H4 and H2/H5 of phthalate.</p> ">
Versions Notes

Abstract

:
The increasing presence of compostable bioplastics as substitutes for conventional fossil-based plastics necessitates a deeper understanding of their environmental impacts, particularly in marine ecosystems, where they often accumulate. This study examines the leaching potential of different phthalic acid esters (PAEs) from commercial biodegradable plastic bags into natural seawater over a three-month period. Degradation experiments were conducted to investigate the release of PAEs under direct solar radiation exposure and in shielded conditions. 1H-NMR analysis of the seawater confirmed the release of phthalates, with higher concentrations observed in the samples exposed to sunlight. The leaching rate ranged from 264–342 microgram/g plastic under light exposure to 20–167 microgram/g in dark conditions. These results indicate that the accumulation of compostable plastic waste in coastal marine environments leads to the release of phthalic acid esters, with potential implications for marine ecosystem health and human exposure to these emerging contaminants.

Graphical Abstract">
Graphical Abstract

1. Introduction

Plastics constitute a wide class of synthetic, semi-synthetic, and natural polymers, characterized by an elevated molecular weight and long hydrocarbon chains. Fossil-based plastics are commonly referred to as “conventional” or “traditional” and are ubiquitous in industrial and household uses [1]. One of the key features of plastic-based products is their resistance to degradation. However, this aspect has generated a number of challenges for waste management [2], resulting in an estimated 5 to 13 million tons of plastic waste released yearly into the aquatic environment [3].
Inland-generated plastic litter can be transported through rivers to the marine environment, where it can accumulate, alongside local plastic pollution related to fishing activities and aquaculture [4]. The physical degradation of macroplastics to the nanoscale has a number of impacts. Fragments are ingested by aquatic fauna and can act as carriers of multiple pollutants. Their hydrophobic properties and high surface area-to-volume ratio favor the adsorption of heavy metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) [5] that can bioaccumulate.
Even without their capacity to accumulate pollutants from their surroundings, additives present in nearly all plastic products can be released during degradation [6]. Additives are used as antioxidants, stabilizers, plasticizers, and flame retardants, with common examples including bisphenol A, nonylphenol, and polybrominated diphenyl ethers [7]. These compounds are incorporated into the surface or physically dispersed into the polymer structure; the absence of a chemical bond allows their leaching in both controlled recycling processes [8] as well as during uncontrolled degradation in the environment [9]. The degree and rate of leaching will depend on a wide range of factors, including temperature, local chemical conditions [10], and irradiance [11]. Upon release, additives or their byproducts can accumulate, representing a potentially important ecotoxicological risk.
Biodegradable plastics represent a promising replacement for traditional synthetic polymers, providing new waste disposal opportunities such as composting. According to the IUPAC, biodegradable plastics are polymeric compounds capable of being decomposed by enzymatic processes into carbon dioxide, water, methane, inorganic compounds, and biomass. Bioplastics refer to materials fully or partially made of renewable biomass sources and include poly(lactic acid), polyhydroxyalkanoates, and bio-based poly(butylene succinate), as well as plastics based on starch, cellulose, proteins, and lignin [12,13]. Not all bioplastics are necessarily biodegradable, depending on their polymer structure [14].
The degradation of biodegradable materials is not solely influenced by the intrinsic properties of the polymer (length of the chain, degree of crystallinity, and molecular complexity) or the additives incorporated during their production, but it is also determined by the local conditions [15]. Compostable plastics must degrade within a defined timeframe and under specific conditions [16].
Polylactic acid (PLA) is a compostable bioplastic, the main degradation product of which, lactic acid, is an approved food additive. Its release or that of its derivatives poses no harm to the environment [17]. Polybutylene adipate-co-terephthalate (PBAT) also shows good compostability due to its aliphatic chains. An increase in PBAT crystallinity during biodegradation suggests that the amorphous domain tends to decompose faster than the rigid aromatic segment [18]. PBAT is certified as compostable according to the ASTM D6400 [19] criteria of biodegradation, disintegration, and compost quality [20]. PLA/PBAT mixtures have found a growing use as sheets and films in packaging applications.
To evaluate the real opportunities of a widespread use of bioplastics, a more complete understanding of the additives used during production stages, their presence in the final products, and their potential release into the environment is required. The most common additives used in bioplastics are plasticizers, such as phthalate acid esters (PAEs), applied to improve softness and flexibility as well as to facilitate handling during production stages.
Despite their usefulness, the release of PAEs into the environment can have significant consequences. PAEs released from the polymer may occur during any phase of the product life cycle (e.g., production, practical use, weathering, recycling). Being primarily lipophilic and highly persistent, they can be easily absorbed and bioaccumulate [21].
Phthalic acid esters, or phthalates, are a family of dialkyl and alkyl aryl esters of phthalic acid. They are colorless, odorless, and liquid at room temperature, characterized by low volatility and solubility in water [22]. The most common phthalates used in consumer products are dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), benzyl butyl phthalate (BzBP), dicyclohexyl phthalate (DCHP), di-2-ethylhexyl phthalate (DEHP), diisobutyl phthalate (DiBP), diisononyl phthalate (DiNP), diisodecyl phthalate (DiDP), di-n-hexyl phthalate (DnHP), and di-n-octyl phthalate (DnOP). When leached into the environment, phthalates undergo different reaction pathways depending on local conditions. In aquatic ecosystems, photolysis, hydrolysis, and microbial degradation are the main causes of their transformation. In general, phthalic acid diesters are first degraded to the corresponding monoesters and then to phthalic acid [23,24].
Phthalates are known to impact the environment as well as human health, as exposure has been associated with impaired reproductive capacity and carcinogenesis [25,26,27]. Leaching from conventional plastics related to food, pharmaceuticals, and construction materials has led to their presence in the environment [28]. Recent regulations (REACH) by the European Chemicals Agency contain 14 phthalates categorized as toxic for reproduction and endocrine disruptors, due to their capacity to mimic estrogens and impact hormonal functions and pathways [27,29]. DMP, DEP, DBP, BzBP, DEHP, and DnOP have been listed as priority pollutants by the United States Environmental Protection Agency (US EPA) [30].
Biodegradability represents a possibility to limit the presence and impact of plastic pollution. However, this requires specific conditions to be met, most importantly that the biodegradable plastic reaches appropriate waste-treatment plants [31]. If these conditions are not met, the increased use of bioplastic bags, combined with non-optimal waste management, will lead to their further accumulation in both aquatic and terrestrial environments.
There have been numerous studies on the impacts of conventional plastic pollution on the aquatic environment. However, there is limited information on the potential impacts regarding the growing use of biodegradable plastics. The present study focused on the release of phthalic acid esters from widely used commercial biodegradable plastic bags to determine the leaching potential of these materials in seawater under conditions of sunlight and in darkness.

2. Materials and Methods

2.1. Experimental Design

Marine water (20 L) was sampled from the coastal waters near Livorno, Italy (oligotrophic waters of the Tyrrhenian Sea) (pH = 8.18 ± 0.01, salinity 38 PSU). Vacuum filtration was performed using a 0.45 μm Millipore filter (47 mm) to reduce the concentrations of phytoplankton and particulate matter.
Nine different shopping bags, declared compostable and biodegradable (biobags, BB), were purchased from local stores, and three of them (BB4, BB8, and BB9) were randomly selected. Three strips from each bag were cut (approximately 2 cm × 4 cm) from different parts of the bag to have more homogeneity and representativeness of the composite sample. All strips had similar total surface areas and a similar total weight for each bag (Table 1).
Eight 500 mL microcosms were prepared to simulate two different environmental conditions. Four quartz microcosms, nearly transparent to solar radiation in the UV and visible wavelengths, were used to simulate conditions of full exposure to solar radiation. Acid-cleaned dark glass microcosms of the same volume, with an attenuation of 99% of the solar UV wavelengths and 90% of visible light, were used to simulate dark conditions. Biobag strips from BB4 were placed in one quartz microcosm (BB4-LIGHT) with a similar set of strips placed into one dark glass microcosm (BB4-DARK). The same procedure was applied to the other two biobag samples, resulting in three LIGHT conditions, one for each selected biobag strip, and the corresponding three DARK conditions containing individual biobag strips. The two remaining microcosms (one quartz and one dark glass) were filled with seawater and used as the control (BLANK). All microcosms were sealed with glass stoppers to prevent evaporation.
The eight microcosms were set on a rooftop in a fixed position, with the stoppered side below to avoid shadow or additional reflectance. All microcosms were placed vertically in the same position to ensure a similar solar irradiance (LIGHT, CONTROL) and temperature (LIGHT, DARK, CONTROL). They were exposed to local environmental conditions for 120 days. The temperature was continuously monitored by a digital thermometer data logger placed between the microcosms. An average temperature of 30.2 ± 0.1 °C was recorded during the entire period. It should be noted that differences in daily temperature dynamics between the digital thermometer, dark glass, and quartz microcosms were likely to have occurred (lower daytime temperature, higher nighttime temperature), with the average temperature being slightly higher in the DARK conditions. UV-Visible solar irradiance was measured continuously near the surface of the quartz and dark-glass microcosms with a four-channel radiometer (10-nm waveband and center wavelengths of 380, 440, 590, and 670, Skye Instruments, Llandrindod Wells, UK). The total exposure of the plastic samples in the quartz flasks over the treatment period was 7413 and 371 kJ/m2 of plastic for UVA (380 nm) and UVB (315 nm) radiation, accounting for the spectral attenuation of the seawater and the plastic at half the depth of the microcosm. The average values of the daily recorded UVA and UVB exposure were 1464 and 74.4 kJ/m2 per day, respectively.
After 120 days, biobag strips were removed from seawater, washed with ultrapure water, dried, weighed, and stored at room temperature. Seawater samples were transferred to polyethylene containers and stored in the dark at 4 °C.

2.2. Chemicals and Selected Phthalates

A standard mixture of six phthalate esters (DMP, DEP, DBP, BzBP, DEHP, and DnOP), TraceCERT®, certified reference material, was purchased from Merck KGaA (Milan, Italy).
For dilution and mobile phase preparation, ultrapure (UP) water (18.2 MΩ cm, Direct-Pure, RephiLe Bioscience, Boston, MA, USA, filtered with a 0.2 µm PES filter), acetonitrile (ACN) (gradient grade, ≥99.9%), and methanol (ACS reagent, ≥99.8%) were purchased from Merck KGaA (Milan, Italy). Chloroform (ACS, 99.8% purity) was purchased from Carlo Erba.
NMR solvents were purchased from Merck KGaA (Milan, Italy): acetone-d6 (99.9 atom % D), chloroform-d (CDCl3) (99.8 atom % D), and deuterium oxide (D2O) (99.9% atom D, contains 0.05 wt. % TSP-d4, 3-(trimethylsilyl) propionic-2,2,3,3-d4 sodium salt).
Solid-phase extraction (SPE) columns were purchased from Phenomenex (Torrance, CA, USA): Strata-X-AW 33 µm Polymeric Weak Anion, 100 mg/3 mL; Strata-X 33 µm Polymeric Reversed Phase, 200 mg/3 mL.

2.3. FTIR and 1H-NMR Spectroscopy

Fourier-transform infrared spectroscopy (FTIR) and 1H-NMR were used to investigate the chemical composition, patent protected, of the selected biobags before the experiment, using a Bruker Alpha II FTIR spectrometer in attenuated total reflectance (ATR) mode [32]. Three scans were performed at three different points on the surface, over a range of 4000–400 cm−1, with 24 scans per measurement and a resolution of 4 cm−1.
1H-NMR measurements were carried out on both the biobags and on the seawater before and after biobag leaching using a Bruker 600 MHz spectrometer. One-dimensional (1D) spectra were acquired at T = 298 ± 0.1 K by a common pulse sequence without solvent suppression, with an FID of 32,768 points, 512 scans, a spectral width of 6000 Hz, a 90° pulse of 8.0 μs, and a relaxation delay of 1.0 s. Two-dimensional (2D) COSY sequences, with 1024 points in the F2 dimension, 256 increments with 16 transients each, and a relaxation delay of 3.0 s, were employed to support the identification of spin systems over a spectral width of 6000 Hz.
For NMR structural characterization, 0.1 g of each biobag was solubilized in 5 mL of chloroform following a solubility test with different solvents [33], evaporated under a nitrogen stream, and re-dissolved in CDCl3. To assess the presence of phthalates within the biobags, ≃0.075 g of each sample was solubilized in deuterated acetone. 1D and 2D COSY spectra were acquired [34]. A 1D spectrum of a 10 mg/L solution of the standard phthalate esters mix in methanol was acquired in D2O, using the same sequence with water suppression.
The NMR analysis of seawater samples was performed on 540 µL of the solution from each flask, including the blank, and by adding 60 µL of D2O containing 0.05% m/m of TSP-d4 as a chemical shift reference and concentration standard. For each seawater sample, 1H-NMR experiments were performed using the noesypr1d pulse sequence [35], with a free induction decay (FID) of 32,768 points, over a spectral width of 6000 Hz, 256 scans, and a relaxation delay of 2.0 sec. To estimate the phthalate concentration in seawater samples, we used peak integrals at 7.94 and 8.10 ppm, calibrating our results to the integral of the TSP-d4, which was arbitrarily assigned a unit value. Equation (1) was then applied to convert integrals into concentrations expressed in mg/L.
m x = A x / A ref × m ref / MW ref / no . H ref × MW x / no . H x
where mref is the concentration (mg/L) of the internal standard; Ax and Aref are the peak areas of the analyzed species and internal standard, respectively; MWx and MWref are the molecular weights; no.Hx and no.Href are the number of hydrogen atoms corresponding to the peaks of compound x and the internal standard, respectively.

2.4. HPLC-DAD Analysis

A Dionex Ultimate-3000 high-performance liquid chromatography (HPLC) system, equipped with a diode array detector (DAD), was used to perform quantification of phthalate esters in biobags and in seawater samples. Analyses were carried out following [36] with a Kinetex C18 EVO 100 Å column (150 × 2.1 mm, 2.6 μm, Phenomenex Torrance California) under isothermal conditions at T = 298 K. The mobile phase was ultrapure water (line A) and acetonitrile (line B) with a constant flow rate of 0.400 mL/min and a sample injection volume of 5 μL. The detector was set to 220 nm. The total run time was 40 min (Supplementary Materials).
For HPLC analysis, a sample of each biobag was weighed and then solubilized in 3.5 mL of chloroform [33], evaporated under a nitrogen stream, re-dissolved in 2 mL of methanol, and filtered with a 0.22 μm PTFE filter, previously tested to ensure no contamination and sample loss.
For the eight seawater samples, a preliminary solid-phase extraction (SPE) was performed before HPLC and 1H-NMR analysis.

2.5. Statistical Analysis

Datasets showed near-normal distributions (skewness < 1.5), allowing for the use of a mean-based approach (t-test) for direct comparison between conditions, with α set to 0.05. Bonferroni correction for multiple comparisons.

3. Results and Discussion

3.1. Biobag Composition Characterization

The FTIR spectra of the biobags (Figure 1) were compared to spectra from previous studies on biodegradable plastic materials [37,38]. The results showed the presence of poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) blends. BB4 and BB9 spectra shared a high degree of similarity, suggesting a similar blending ratio of the two polymers. A likely low interfacial interaction of the two biodegradable polymers allowed the identification of the respective functional groups, the peak positions of which did not result in variations with respect to the spectra of pure compounds. The infrared spectrum of BB9 was similar to BB4, except for a slight shift of 1–2 cm−1, suggesting an analogous chemical composition.
BB8 exhibited additional bands that were associated with a higher percentage of PLA. The absorption at 1759 cm−1 can be attributed to the C-O stretching vibration of carbonyl, which is found at higher frequencies compared to PBAT, where the ester group is conjugated with the aromatic ring. The peaks at 1453 and 1365 cm−1 represent, respectively, the C-H asymmetric and symmetric bending vibrations of the CH3 group; the asymmetric vibration is likely overlapped with the -CH2-bending of PBAT, which is expected at slightly higher frequencies (≃1465 cm−1). The band at 1390 cm−1 can be associated with the C-H deformation of the α-carbon. The peak at 1080 cm−1 represents an exception, assigned to the O-C-C stretching of PBAT-saturated ester linkage, which was absent in the spectra of BB4 and BB9.
1The H-NMR spectroscopy of all three biobags showed similar spectra (Supplementary Materials); peak assignment confirmed the presence of a mixture of PLA and PBAT in varying concentrations.

3.2. Detection and Quantification of Phthalate Esters in Biobag Samples

The investigation of phthalate presence on all biobags was initially conducted by 1H-NMR. Sample spectrums (Figure 2) exhibit two distinct signals within the region 7.80–7.60 ppm that can be attributed to phthalate compounds, according to comparison with the spectrum of the standard phthalates mix (Supplementary Materials). Phthalate esters have two pairs of chemically equivalent aromatic protons coupling differently to each other and producing two symmetric complex multiplets. A slight variation of chemical shift, approximately 0.07 ppm, was observed due to the different solvents used.
Quantification using HPLC was performed using a nine-point calibration curve for each phthalate under study. Concentration ranged from 0.05 to 10 mg/L, with each compound showing good linearity (R2 >0.99) (Supplementary Materials). Phthalate concentrations in the biobags showed relative differences between biobags (Table 2). DMP, DBP, and DEHP were present in all three samples (Figure 3), with concentrations ranging between 17.2–95.5, 332.0–436.1, and 95.3–770.5 μg/g, respectively. DEP was not present in the BB9 sample, while BB4 and BB8 exhibited a similar concentration (25.5 and 24.9 μg/g); in contrast, DnOP was only found in BB9, with a concentration of 56.2 μg/g. Our findings were similar to the results found by Xu et al. [39] in plastic express packaging bags.

3.3. Detection of Phthalates in Seawater Samples After Degradation Experiments

Microcosm seawater samples from light and dark conditions were analyzed to assess the leaching potential of phthalic compounds after exposure to natural environmental conditions for 120 days, comparing the degradation processes that included photodegradation (LIGHT) and excluded photodegradation (DARK).
Phthalate leaching into seawater was determined by 1H-NMR spectra. In all seawater samples containing biobags, resonances associated with the aromatic moiety of phthalate esters were observed, corresponding to the presence of two multiplets at 8.10 and 7.94 ppm, assigned to H3/H4 and H2/H5 of the aromatic ring, respectively. The control microcosm seawater (BLANK) did not show the presence of phthalate in either LIGHT or DARK conditions after 120 days of treatment (Figure 4).
The effect of different environmental conditions was evidenced by the intensity of the 1H-NMR signals for seawater samples (Figure 4). All seawater samples under LIGHT conditions showed higher intensity peaks compared to their DARK condition counterparts. Furthermore, the peaks of the BB4 samples were more intense than the others. All NMR spectra were acquired using the same conditions and parameters. A comparison with a spectrum of monomethyl phthalate [40] confirmed that these peaks were attributable to phthalate derivatives, as the signal was comparable in terms of chemical shift and multiplicity.
It should be noted that polymeric chains could have been cleaved during the biobag degradation processes in seawater, whether thermal, photo, or microbial. For quantification, we considered a generic hydrolyzed phthalate without side chains (C8H4O4) as a reference to estimate phthalate leaching using two dominant chemical shifts (ppm). Concentrations in seawater of phthalate amount (mg/L), estimated using Equation (1), at both ppm, provided similar values (Table 3).
Seawater hydrolyzed phthalate estimates were then compared to the weight of biobag samples present in each microcosm to determinate its leaching potential (μg/g of biobag, Table 4). The leaching results were consistent with the study of Xu et al. [39] despite the different matrix and conditions.
Considering the total concentration of the six phthalates determined in the original biobag samples, it was possible to estimate a percentage of phthalates leached, as hydrolyzed phthalate, from the original biobag, considering the different biobag samples and different environmental conditions. Phthalate leaching was greater (p = 0.03) in the LIGHT samples exposed to solar radiation compared to the samples that underwent thermal and microbial degradation (DARK). Samples exposed to a light environment resulted in a leaching percentage that was double that in the BB4 and BB9 biobags, with similar fractions of PLA and PBAT. For the samples with a higher percentage of PLA (BB8), there was a more than 10× increase in leaching percentage.
According to the last report of Plastics Europe [41], in 2022, 400 million tons of plastic materials were produced globally, of which 0.5% consisted of bioplastic. This translates to an annual production of 2 million tons of bioplastic. Only a fraction of plastic produced ends up in the environment; this percentage depends on a range of factors. This fraction has been estimated to be approximately 0.5% for marine plastic pollution. Once present, this plastic waste undergoes different degradation pathways based on local conditions, such as temperature, solar irradiance, and water depth, leading to the release of additives and their derivatives. According to our results, with an average leaching rate of 200 μg/g, there is a potential release of several tons of phthalate esters per year, with consequent impacts on the environment and human health. This estimate agrees with a recent study of leaching from conventional plastics to the aquatic environment. Despite the different polymer types, the estimated amount of released additives into the environment is within the same range [42].
It should be noted that leaching potential was also the focus of an HPLC analysis of the seawater samples. With respect to the total phthalate concentration estimated by 1H-NMR analysis, both the limit of detection (LOD) and the limit of quantification (LOQ) of the HPLC method (Table 5) should have been sufficient to provide a second estimate of leached phthalate. However, no peaks attributable to the six phthalate esters were detected, further supporting the hypothesis that degradation of the polymeric chains had occurred in the seawater. As degradation could have followed multiple pathways, including hydrolysis, photolysis, thermal degradation, and biodegradation, phthalic acid derivatives were likely present in the hydrolyzed form. This is supported by the corresponding multiplet in 1H-NMR analysis and the loss of the singlet in the biobag samples, where the aromatic moiety was symmetric. The lack of detection of phthalate esters by HPLC showed that the method developed for the present study was not appropriate for the identification of the degradation products of PAEs. This is likely due to different retention times and interactions between the stationary phase of the SPE cartridge and C18 columns employed, which occurs mainly with the side chains.

4. Conclusions

Although compostable bioplastics provide several waste management benefits, this study demonstrated that there is a clear potential for the release of additives and monomers into the environment during degradation, whether controlled in a composting facility or in the natural environment. Additives, including plasticizers and stabilizers, are not covalently bound to the polymer matrix and therefore can be progressively released during use and aging. Phthalic acid esters are among the most common plasticizers used in conventional plastics, yet very little is known about their leaching potential in biodegradable materials. These additives are particularly important in biodegradable polymers, which often exhibit poorer mechanical properties.
In the present study, biodegradable plastic bags (biobags) were found to contain four different phthalic acid esters. The release of these into seawater was confirmed by NMR analysis during a controlled degradation experiment. Furthermore, the leaching potential was shown to increase significantly in conditions where photodegradation occurred compared to conditions where only thermal and biological degradation processes occurred.
As endocrine disruptors, the release of phthalates during the accumulation of biodegradable plastic bags in the marine environment poses direct risks to fish and invertebrates. Larger side-chain diesters of phthalic acid, such as DEHP and DnOP, have lower solubility and are likely to pose a greater risk in the form of microplastics. Given the increased use of bioplastics, the impacts of high molecular weight phthalates on the marine environment warrant further study. Furthermore, more attention on the correct use and recycling of biodegradable plastic is fundamental to reduce exposure and related health and environmental risks.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/w16243676/s1, Figure S1: FTIR spectra of BB4 (A), BB8 (B), BB9 (C) plastic samples over the range 4000–400 cm−1. Each spectrum was obtained by averaging three acquisitions of three different points on the sample surface. Figure S2: 1H-NMR spectrum of BB4 plastic sample in CDCl3. Figure S3: COSY spectrum of BB4 plastic sample in CDCl3. Figure S4: PLA protons producing NMR shift (CH and CH3) (left). All possible arrangements of PBAT monomeric units (T = terephthalic acid, A = adipic acid, B = 1,4-butanediol), leading to different shifting for the central tetramethylene moiety of the 1,4-butanediol (right). Figure S5: 1H-NMR spectrum of a 10 mg/L solution of PAEs MIX in D2O, showing characteristic signals of aromatic protons of phthalate esters. Figure S6: HPLC-DAD chromatogram of a 10 mg/L standard solution of phthalate ester mix. Figure S7: HPLC-DAD chromatograms of BB4 (A), BB8 (B) and BB9 (C) plastic sample compared to the chromatogram of a 3 mg/L standard solution of PAEs mix. Table S1: HPLC elution method. Table S2: Report of calibration curves of six phthalate esters included in the PAEs mix, built by plotting the corresponding peak areas to the concentration of nine standard solutions.

Author Contributions

Conceptualization, S.L., N.G. and A.B.; data curation, A.B., S.L., N.G., F.F.; formal analysis, A.B., N.G. and F.F.; investigation, A.B., N.G., F.F. and S.L.; methodology, A.B., A.P., L.T. and F.F.; project administration, S.L. and N.G.; supervision, S.L., L.G. and N.G.; visualization, A.B., N.G., X.L. and R.C.; writing—original draft, A.B., N.G. and L.T.; writing—review and editing: S.L., A.P. and N.G. All authors have read and agreed to the published version of the manuscript.

Funding

The authors acknowledge the support of the Italian Ministry of University and Research, PNRR, Missione 4 Componente 2, “Dalla ricerca all’impresa”, Investimento 1.4, Project CN00000033 and of the Programma Operativo Nazionale (PON) “Ricerca e Innovazione” 2014–2020.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Conflicts of Interest

The authors declare no conflicts of interest.

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Water 16 03676 g001
Figure 1. FTIR spectra of BB4, BB8, and BB9 plastic samples over the range 4000–400 cm−1.
Figure 1. FTIR spectra of BB4, BB8, and BB9 plastic samples over the range 4000–400 cm−1.
Water 16 03676 g001
Water 16 03676 g002
Figure 2. 1H-NMR spectra of BB4 (red), BB8 (green), and BB9 (blue) plastic samples in deuterated acetone, showing characteristic signals of aromatic protons of phthalate esters.
Figure 2. 1H-NMR spectra of BB4 (red), BB8 (green), and BB9 (blue) plastic samples in deuterated acetone, showing characteristic signals of aromatic protons of phthalate esters.
Water 16 03676 g002
Water 16 03676 g003
Figure 3. Chromatograms of each biobag compared to a 3 mg/L standard solution of phthalate ester mix, with relative peak assignment.
Figure 3. Chromatograms of each biobag compared to a 3 mg/L standard solution of phthalate ester mix, with relative peak assignment.
Water 16 03676 g003
Water 16 03676 g004
Figure 4. The aromatic region of 1H-NMR spectra of seawater samples after exposure to biobags for 120 days; asterisk (*) indicates the peaks assigned to H3/H4 and H2/H5 of phthalate.
Figure 4. The aromatic region of 1H-NMR spectra of seawater samples after exposure to biobags for 120 days; asterisk (*) indicates the peaks assigned to H3/H4 and H2/H5 of phthalate.
Water 16 03676 g004
Table 1. Total weight of biobag strips at the beginning of the experiment and microcosm types (500 mL).
Table 1. Total weight of biobag strips at the beginning of the experiment and microcosm types (500 mL).
Light ExposureBiobagTotal Sample Weight (g)Container
LightBB42.150Quartz flasks
BB81.296
BB91.921
BLANK-
DarkBB42.256Dark glass bottles
BB81.015
BB91.988
BLANK-
Table 2. Phthalate esters identified in biobag samples (BB4, BB8, BB9) from HPLC-DAD analysis and their corresponding concentrations expressed as mg/L and μg per gram of biobag.
Table 2. Phthalate esters identified in biobag samples (BB4, BB8, BB9) from HPLC-DAD analysis and their corresponding concentrations expressed as mg/L and μg per gram of biobag.
Sample Weight (mg)Phthalate EsterRT (min)Conc. (mg/L)Conc. (μg/g)
BB48.6DMP2.280.4195.58
DEP4.630.1125.58
DBP11.771.67389.07
DEHP24.253.31770.47
BB87.1DMP2.260.1335.49
DEP4.690.08824.79
DBP11.771.55436.06
DEHP24.250.51143.94
BB96.0DMP2.180.05217.33
DBP11.760.99332.00
DEHP24.250.2795.33
DnOP25.390.16856.00
Table 3. Amount of phthalate (mg/L) released from different biobag samples and microcosms measured in seawater.
Table 3. Amount of phthalate (mg/L) released from different biobag samples and microcosms measured in seawater.
BB4 LIGHTBB4 DARKBB8 LIGHTBB8 DARKBB9 LIGHTBB9 DARK
7.94 ppm1.4250.8930.6960.0651.1430.470
8.10 ppm1.5230.6170.7090.0200.8930.624
Table 4. Quantification of hydrolyzed phthalates present in microcosm expressed as mg/L and µg per gram of BB.
Table 4. Quantification of hydrolyzed phthalates present in microcosm expressed as mg/L and µg per gram of BB.
Average Phthalate Concentration in Microcosm (mg/L)Leachate Concentration per Biobag (μg/g)Leachate %
BB4 LIGHT1.47342.7926.77
BB4 DARK0.756167.3313.07
BB8 LIGHT0.70271.0342.33
BB8 DARK0.04320.943.27
BB9 LIGHT1.018264.9752.92
BB9 DARK0.55137.5827.48
Table 5. Limit of detection and quantification for the five phthalates detected in the original biobag.
Table 5. Limit of detection and quantification for the five phthalates detected in the original biobag.
CompoundLOD
(µg/L)		LOQ
(µg/L)
DMP3.39 ± 0.6411.23 ± 2.13
DEP5.21 ± 1.1517.36 ± 3.83
DBP4.71 ± 0.315.71 ± 1.01
DEHP4.60 ± 0.7115.32 ± 2.36
DnOP8.62 ± 1.8228.74 ± 6.06
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MDPI and ACS Style

Boldrini, A.; Gaggelli, N.; Falcai, F.; Polvani, A.; Talarico, L.; Galgani, L.; Cirrone, R.; Liu, X.; Loiselle, S. Emerging Contaminants from Bioplastic Pollution in Marine Waters. Water 2024, 16, 3676. https://doi.org/10.3390/w16243676

AMA Style

Boldrini A, Gaggelli N, Falcai F, Polvani A, Talarico L, Galgani L, Cirrone R, Liu X, Loiselle S. Emerging Contaminants from Bioplastic Pollution in Marine Waters. Water. 2024; 16(24):3676. https://doi.org/10.3390/w16243676

Chicago/Turabian Style

Boldrini, Amedeo, Nicola Gaggelli, Francesco Falcai, Alessio Polvani, Luigi Talarico, Luisa Galgani, Riccardo Cirrone, Xinyu Liu, and Steven Loiselle. 2024. "Emerging Contaminants from Bioplastic Pollution in Marine Waters" Water 16, no. 24: 3676. https://doi.org/10.3390/w16243676

APA Style

Boldrini, A., Gaggelli, N., Falcai, F., Polvani, A., Talarico, L., Galgani, L., Cirrone, R., Liu, X., & Loiselle, S. (2024). Emerging Contaminants from Bioplastic Pollution in Marine Waters. Water, 16(24), 3676. https://doi.org/10.3390/w16243676

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