Microplastics (MPs), defined as particles with diameters <5 mm and including nanoplastics (NPs), with diameters <1 μm, are characterized by large specific surface areas and hydrophobicity. In aquatic ...and terrestrial environments, MPs interact with co-occurring organic pollutants through sorption and desorption, which alters the environmental behavior of the pollutants, such as their toxicity, bioaccumulation, degradation, and transport. In this review, we summarize the results of current studies of the interactions between MPs and organic contaminants, and focus on the different mechanisms and subsequent ecological risks of contaminant transfer among environmental media, MPs and organisms. The sorption/desorption of organic pollutants on/from MPs is discussed with respect to solution conditions and the properties of both the MPs and the pollutants. More importantly, the ability of MPs to alter the toxicity, bioaccumulation, degradation, and transport of organic pollutants through these interactions is considered as well. We then examine the interrelationships of the different environmental behaviors of MPs and organic pollutants and the roles played by environmental processes. Finally, we identify the remaining knowledge gaps that must be filled in further studies in order to accurately evaluate the environmental risks of MPs and their associated organic pollutants.
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•Sorption/desorption of OPs on MPs controls their bioavailability and environmental behavior.•Plastic/pollutant properties and environmental conditions determine the sorption/desorption.•Through altered bioaccumulation and biotransformation, MPs affect the toxicity of OPs.•Through vector effects and altered bioavailability, MPs affect degradation and transportation of OPs.•Research gaps: standard method, techniques for NPs, impact on humans, and environmental processes.
In this study, we explored the aging processes of a commercial polyethylene (PE) mulch film under UV irradiation and compared the laboratory aged films with films aged in nature. Overall, the aged ...films obtained from laboratory conditions were similar with that from natural conditions. Among the investigated factors, UV irradiation was crucial in the aging of the films, producing cracks and oxygen-containing functional groups on the films surface, constantly with natural aging. The formation of cracks induced a decrease of mechanical strength as well as the formation of MPs on the surface. The chemical oxidations detected by Fourier-transform infrared spectroscopy (FTIR) usually happened after the observed physical changes during aging. Moreover, a protocol was developed for laboratory preparation of MPs with characteristics similar with that from environmental aging and PE MPs with sizes of 2–400 μm could be produced in large amounts at relatively short period of time.
Contamination of fine plastic particles (FPs), including micrometer to millimeter plastics (MPs) and nanometer plastics (NPs), in the environment has caught great concerns. FPs are strong adsorbents ...for hydrophobic toxic pollutants and may affect their fate and toxicity in the environment; however, such information is still rare. We studied joint toxicity of FPs with phenanthrene to Daphnia magna and effects of FPs on the environmental fate and bioaccumulation of 14C-phenanthrene in fresh water. Within the five sizes particles we tested (from 50 nm to 10 μm), 50-nm NPs showed significant toxicity and physical damage to D. magna. The joint toxicity of 50-nm NPs and phenanthrene to D. magna showed an additive effect. During a 14-days incubation, the presence of NPs significantly enhanced bioaccumulation of phenanthrene-derived residues in daphnid body and inhibited the dissipation and transformation of phenanthrene in the medium, while 10-μm MPs did not show significant effects on the bioaccumulation, dissipation, and transformation of phenanthrene. The differences may be attributed to higher adsorption of phenanthrene on 50-nm NPs than 10-μm MPs. Our findings underlined the high potential ecological risks of FPs, and suggested that NPs should be given more concerns, in terms of their interaction with hydrophobic pollutants in the environment.
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•Nano-plastics (NPs) and phenanthrene had additive joint toxicity to D. magna.•NPs enhanced bioaccumulation of phenanthrene-derived residues in daphnid body.•NPs inhibited dissipation and transformation of phenanthrene in the medium.•Microplastics (MPs) did not show significant effects.
Compared to microplastics, nanoplastics had additive toxic effects with phenanthrene, increased bioaccumulation in D. magna, and inhibited its dissipation in the environment.
Plastic debris, in particular, microplastics and nanoplastics, is becoming an emerging class of pollutants of global concern. Aging can significantly affect the physicochemical properties of ...plastics, and therefore, may influence the fate, transport, and effects of these materials. Here, we show that aging by UV or O3 exposure drastically enhanced the mobility and contaminant-mobilizing ability of spherical polystyrene nanoplastics (PSNPs, 487.3 ± 18.3 nm in diameter) in saturated loamy sand. Extended Derjaguin–Landau–Verwey–Overbeek calculations and pH-dependent transport experiments demonstrated that the greater mobility of the aged PSNPs was mainly the result of surface oxidation of the nanoplastics, which increased not only the surface charge negativity, but more importantly, hydrophilicity of the materials. The increased mobility of the aged PSNPs significantly contributed to their elevated contaminant-mobilizing abilities. Moreover, aging of PSNPs enhanced the binding of both nonpolar and polar contaminants, further increasing the contaminant-mobilizing ability of PSNPs. Interestingly, aging enhanced binding of nonpolar versus polar compounds via distinctly different mechanisms: increased binding of nonpolar contaminants (tested using pyrene) was mainly the result of the modification of the polymeric structure of PSNPs that exacerbated slow desorption kinetics; for polar compounds (4-nonylphenol), aging induced changes in surface properties also resulted in irreversible adsorption of contaminants through polar interactions, such as hydrogen bonding. The findings further underline the significant effects of aging on environmental fate and implications of nanoplastics.
The impact of nanometer-scale plastics (<1000 nm nanoplastics, NPs) on the bioaccumulation of hydrophobic organic pollutants, and especially polycyclic aromatic hydrocarbons (PAHs), in marine ...organisms has become of urgent concern. However, simultaneous determinations of the bioaccumulation of NPs and PAHs have been hindered by the lack of an efficient digestion method that removes background interference from the tissue without altering the surface properties of the plastic and destroying the PAHs. To solve this problem, an enzymatic digestion-based protocol using proteinase K and subsequent quantification methods were developed on a typical marine benthic invertebrate – the clamworm Perinereis aibuhitensis. Enzymatic digestion removed 91% of the biological tissues, comparable to the amount removed using 65% HNO3 (93% removed) and better than that removed using 30% H2O2 or 10% KOH digestion (76% and 66%, respectively). After enzymatic digestion, roughly 92% of the NPs and 88% of the amount of pyrene were recovered, without significant modification of the NPs or pyrene degradation. By contrast, the NP and pyrene recovery achieved with HNO3 digestion was only 1.4% and 0.1%, respectively. The newly developed protocol was successfully applied to a 96-h bioaccumulation study. The use of radioactively labeled 14C-pyrene and fluorescently labeled NPs allowed the simultaneous quantification of NPs and PAHs in the clamworm and revealed a bioconcentration factor (BCF) of 1.96 ± 0.93 and 402.7 ± 47.0, respectively. The quantification of NPs and pyrene indicated that NP-adsorbed pyrene accounted for <1% of the total pyrene accumulation in the clamworm body when the concentration of NPs in seawater was as low as 0.4 mg/L. Our enzymatic digestion and dual-labeling technique thus provides the first reported BCF value of NPs in a marine benthic organism and new insights into the vector effects of these particles on the bioaccumulation of organic contaminants in a marine ecosystem.
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•An enzymatic hydrolysis-based digestion method was developed on clamworm.•The method recovered 92% NPs and 88% pyrene with digest efficiency of 91%.•The method did not cause NPs surface modification and pyrene degradation.•Fluorescent NPs and 14C-pyrene were used to study bioaccumulation in clamworms.•After 96 h, NPs and pyrene had BCFs of 1.96 ± 0.93 and 402.7 ± 47.0 in clamworms.
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•Bioaccumulation and transformation of TBBPA was studied in earthworm Metaphire guillelmi.•TBBPA was transformed into metabolites shortly after taken up for detoxification.•Large ...amount of 14C-bound-residue formed in the digestive tract.•High concentrations of bioavailable metabolites were detected in organs.•Hydrophobic diMeO-TBBPA formed in organ region and depurated through feces.
The mechanisms underlying the bioaccumulation and detoxification of tetrabromobisphenol A (TBBPA) by terrestrial invertebrates are poorly understood. We used uniformly ring-14C-labelled TBBPA to investigate the bioaccumulation kinetics, metabolites distribution, and subsequent detoxification strategy of TBBPA in the geophagous earthworm Metaphire guillelmi in soil. The modeling of bioaccumulation kinetics showed a higher biota-soil-accumulation-factor of total 14C than that of the parent compound TBBPA, indicating that most of the ingested TBBPA was transformed into metabolites or sequestered as bound residues in the earthworms. Bound-residue formation in the digestive tract may hinder the accumulation of TBBPA in other parts of the body. Nonetheless, via the circulatory system, TBBPA was transferred to other tissues, especially the clitellum region, where sensitive organs are located. In the clitellum region, TBBPA was quickly transformed to less toxic dimethyl TBBPA ether and rapidly depurated through feces. We conclude that the detoxification of TBBPA in M. guillelmi occurred via bound-residue formation in the digestive tract as well as the generation and depuration of O-methylation metabolites. Our results provided direct evidence of TBBPA detoxification in earthworms. Further researches are needed to confirm whether O-methylation coupled with depuration is a common detoxification strategy for phenolic xenobiotics in other soil organisms needs to be determined.
Salvia miltiorrhiza is one of the most important traditional Chinese medicinal plants because of its excellent performance in treating coronary heart disease. Phenolic acids mainly including caffeic ...acid, rosmarinic acid and salvianolic acid B are a group of active ingredients in S. miltiorrhiza. Abscisic acid (ABA), gibberellin (GA) and ethylene are three important phytohormones. In this study, effects of the three phytohormones and their interactions on phenolic production in S. miltiorrhiza hairy roots were investigated. The results showed that ABA, GA and ethylene were all effective to induce production of phenolic acids and increase activities of PAL and TAT in S. miltiorrhiza hairy roots. Effects of phytohormones were reversed by their biosynthetic inhibitors. Antagonistic actions between the three phytohormones played important roles in the biosynthesis of phenolic acids. GA signaling is necessary for ABA and ethylene-induced phenolic production. Yet, ABA and ethylene signaling is probably not necessary for GA3-induced phenolic production. The complex interactions of phytohormones help us reveal regulation mechanism of secondary metabolism and scale-up production of active ingredients in plants.
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•BPS dissipated quickly in an oxic soil, with a half-life of 2.8 days.•Major fate of BPS in soil was mineralization and NER-formation.•More than half of NERs were attributed to ...physico-chemically entrapped BPS.•Microorganisms could decrease release kinetic constant of the entrapped BPS.•BPS-derived NERs were unstable and are potentially bioavailable.
The environmental fate and persistence of bisphenol S (BPS), a substitute for bisphenol A (BPA), are unclear. This study used 14C-labeled BPS to examine the fate, biodegradation, and residue properties of BPS incubated in an oxic soil for 28 days. BPS dissipated quickly, with a half-life of 2.8 days. Most of the BPS was mineralized (53.6 ± 0.2% of initial amount by day 28) or transformed into non-extractable residues (NERs) (45.1 ± 0.3%), with generation of minor extractable residues (3.7 ± 0.2%) containing two metabolites. NERs were formed mainly via physico-chemical entrapment (51.1 ± 2.4% of the total NERs, consisting almost exclusively of BPS) and ester-linkages (31.5 ± 3.0% of the total NERs, consisting of both BPS and polar metabolites). When mixed with fresh soil, BPS-derived NERs became unstable and bioavailable. Subsequent mineralization was determined for 19.5 ± 1.1% of the total NERs and 35.5 ± 2.6% of the physico-chemically entrapped BPS. A fate model was used to describe the kinetics of NER formation, which indicated that microbial activity in soil could have strongly reduced the kinetic rate of the release of physico-chemically entrapped NERs into free form and therefore increased the stability of this type of NERs in soil. Our results provide unique insights into the fate of BPS in soil and suggest that while BPS is biodegradable, it includes the formation of large amounts of reversibly physico-chemically entrapped and covalently bound ester-linked NERs. The instability of these NERs should be considered in assessments on environmental persistence and risks of BPS. Our study also points out the environmental importance of NERs of agrochemicals.
The fate of organic pollutants in the environment, especially the formation and stability of non-extractable (i.e., bound) residues (NERs) determines their environmental risk. Using 14C-tracers, we ...studied the fate of the carcinogen phenanthrene in active or sterilized oxic loamy soil in the absence and presence of the geophagous earthworm Metaphire guillelmi and characterized the NERs derived from phenanthrene. After incubation of 14C-phenanthrene in active soil for 28 days, 40 ± 3.1% of the initial amount was mineralized and 70.1 ± 1.9% was converted to NERs. Most of the NERs (>92%) were bound to soil humin. Silylation of the humin-bound residues released 45.3 ± 5.3% of these residues, which indicated that they were physically entrapped, whereas the remainder of the residues were chemically bound or biogenic. By contrast, in sterilized soil, only 43.4 ± 12.6% of the phenanthrene was converted to NERs and all of these residues were completely released upon silylation, which underlines the essential role of microbial activity in NER formation. The presence of M. guillelmi in active soil significantly inhibited phenanthrene mineralization (24.4 ± 2.6% mineralized), but NER formation was not significantly affected. Only a small amount of phenanthrene-derived residues (1.9–5.3% of the initial amount) accumulated in the earthworm body. When humin-bound residues were mixed with fresh soil, 33.9% (humin recovered from active soils) and 12.4% (humin recovered from sterilized soils) of the residues were mineralized after 75 days of incubation, respectively, which indicated a high bioavailability of NERs, albeit lower than the initial addition of phenanthrene. Our results indicated that many phenanthrene-derived NERs, especially those physically entrapped, are still bioavailable and may pose a toxic threat to soil organisms.
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•The major fate of phenanthrene in the oxic soil was formation of CO2 and humin-bound residues.•Microbial activity played an essential role in bound-residue formation.•Humin-bound residues were >40% via physical entrapment.•M. guillelmi inhibited mineralization but did not alter bound-residue formation.•Humin-bound residues were bioavailable and mineralizable in fresh soil.
Phenanthrene in oxic rice paddy soil was mostly mineralized to CO2 or converted to humin-bound residues. Mineralization of phenanthrene was inhibited by the earthworm Metaphire guillelmi. Humin-bound residues could be mineralized again when mixing with fresh soil.
We put forward and numerically analyze a D-shaped surface plasmon resonance fiber sensor with high figure of merit (FOM), within the detection range of 1.33–1.41. The sensing area is coated with ...platinum (Pt) grating, aluminum oxide (Al
2
O
3
) nanofilm, and graphene film. Plasmonic resonance of Pt grating can be excited by the core mode of the D-shaped fiber, so as to detect the change of refractive index (RI). The addition of graphene and Al
2
O
3
layers is to enhance the nearfield electric intensity of the Pt grating, thus improving the sensing performance. Especially, the FOM of the designed sensor can be consumedly improved by the Al
2
O
3
/graphene/Pt grating hybrid nanostructure, up to 432 RIU
−1
, with a high RI sensitivity of 11,252 nm/RIU in near-infrared region. The influence of the three nanolayers on the sensing performance is carefully calculated and analyzed. The designed sensor would be a candidate for biological applications, environmental monitoring, and medical diagnostics.
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