Non-negligible vector effect of micro(nano)plastics on tris(1,3-dichloro-2-propyl) phosphate in zebrafish quantified by toxicokinetic model.

Micro(nano)plastics (MNPs) inevitably interact with coexisting contaminants and can act as vectors to affect their fate in organisms. However, the quantitative contribution of MNPs in the in vivo bioaccumulation and distribution of their coexisting contaminants remains unclear. Here, by selecting tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) as the typical coexisting contaminant, we quantified the contribution of MNPs to bioaccumulation and distribution of TDCIPP with toxicokinetic models. Results indicated that MNPs differentially facilitated TDCIPP bioaccumulation and distribution, and NPs slowed down TDCIPP depuration more significantly than MPs. Model analysis further revealed increasing contributions of MNPs to whole-fish TDCIPP bioaccumulation over time, with NPs (33-42%) contributing more than MPs (12-32%) at 48 h exposure. NPs contributed more than MPs to TDCIPP distribution in the liver (13-19% for MPs; 36-52% for NPs) and carcass (24-45% for MPs; 57-71% for NPs). The size-dependent vector effect might be attributed to the fact that MNPs promote contaminant transfer by damaging biofilm structure and increasing tissue membrane permeability, with NPs exerting stronger effects. This work demonstrated the effectiveness of using modeling tools to understand the relative importance of MNPs as contaminant vectors in the TK process and highlighted the higher contaminant transfer potential of NPs under combined exposure scenarios.

Microplastics could alter invasive plant community performance and the dominance of Amaranthus palmeri.

The increase in alien plant invasions poses a major threat to global biodiversity and ecosystem stability. However, the presence of microplastics (MPs) as an environmental stressor could impact the interactions between invasive and native species in an invasive plant community. Nevertheless, the community alterations and underlying mechanisms resulting from these interactions remain unclear. Herein, we systematically investigated the impacts of polyethylene (PE) and polypropylene (PP) on invasive plant communities invaded by Amaranthus palmeri through soil seed bank. The results illustrated that MPs markedly declined community height and biomass, and altered community structure, low-dose MPs could prominently increase community invasion resistance, but reduced community stability. The niche width and niche overlap of A. palmeri and S. viridis declined when exposed to high-dose MPs, but MPs elicited a significant rise in the niche width of S. salsa. PP had the potential to reduce the diversity of invasive plant community. Structural equation model revealed that PP addition could change soil total phosphorus content, thereby leading to a reduction of the community stability. Our study helps to fill the knowledge gap regarding the effects of MPs on invasive plant communities and provide new perspectives for invasive plant management.

Nanoplastics enhance the intestinal damage and genotoxicity of sulfamethoxazole to medaka juveniles (Oryzias melastigma) in coastal environment.

Antibiotics and nanoplastics are widely detected in the coastal ecosystem. However, the transcriptome mechanism elucidating the effect of antibiotics and nanoplastics co-exposure on the gene expression of aquatic organisms in coastal environment is still unclear. Here, single and joint effects of sulfamethoxazole (SMX) and polystyrene nanoplastics (PS-NPs) on the intestinal health and gene expression of medaka juveniles (Oryzias melastigma), which live in coastal environment, were investigated. The SMX and PS-NPs co-exposure decreased intestinal microbiota diversity compared to the PS-NPs, and caused more adverse effect on the intestinal microbiota composition and intestinal damage compared to the SMX, indicating that PS-NPs might enhance the toxicity of SMX on the medaka intestine. The increased abundance of Proteobacteria in the intestine was observed in the co-exposure group, which might induce the intestinal epithelium damage. In addition, the differentially expressed genes (DEGs) were mainly involved in the drug metabolism-other enzymes, drug metabolism-cytochrome P450, metabolism of xenobiotics by cytochrome P450 pathways in visceral tissue after the co-exposure. The expression of the host immune system genes (e.g., ifi30) could be associated with the increased pathogens in intestinal microbiota. This study is useful for understanding the toxicity effect of antibiotics and NPs on aquatic organisms in coastal ecosystem.

Effect of different additions of low-density polyethylene and microplastics polyadipate/butylene terephthalate on soil bacterial community structure.

The stress produced from biodegradable plastics on soil ecosystem is a rising global concern. However, effects of such microplastics (MPs) on soil ecology are still debatable. In this study, the biodegradable microplastic PBAT (polyadipate/butylene terephthalate) was used as the target object, compared with the traditional microplastic LDPE (low-density polyethylene). A pot experiment and was high-throughput sequencing analysis used to determine the effect of different additions of MPs on soil bacterial community structure and the correlation between soil bacterial community structure and chemical properties was investigated. Compared with LDPE, the results showed that EC, TN, TP, NH4+-N, and NO3--N changed obviously with the increasing of PBAT addition (p < 0.05), but pH changed little and the community richness was significantly higher in soils with low PBAT addition than that with higher PBAT addition. PBAT is beneficial to soil nitrogen fixation, but it will significantly reduce the soil P content and affect the nitrification and denitrification reaction. It suggested that addition of PBAT MPs and its addition amount result in changes in soil fertility, community abundance, and structure and composition of bacterial communities in soil samples, while the presence of PBAT MPs might affect soil carbon-nitrogen cycle.

Physicochemical and biological changes on naturally aged microplastic surfaces in real environments over 10 months.

Microplastics (MPs) undergo aging over time, which can influence their behavior in the environment. While laboratory-simulated studies have investigated MP aging, research on natural aging in various real environments remains limited. This study aims to investigate the physical, chemical and biological changes that occur in five types of MPs after more than 10 months of natural aging in three different real environments: seawater, air and soil. Results are compared with previous laboratory experiments. The surface roughness of all types of aged MPs was found to be higher in seawater than in air and soil, which differed from previous simulated studies that showed the highest roughness in air. All aged MPs exhibited the occurrence of hydroxyl and carbonyl groups due to the oxidation processes. Interestingly, the MPs aged in soil showed the lowest level of these functional groups, while in seawater or air, some MPs demonstrated the highest. This contrasts with previous studies indicating the highest level of oxygen-containing functional groups in aged MPs in air. Bacterial analysis identified fourteen bacterial phyla on the surface of aged MPs in all three real environments, with varying abundance in specific environments. Notably, the composition of bacterial communities in the microplastisphere was determined by the surrounding environments, independent of MP types. Natural aging is more complex than laboratory simulations, and the degree of MP aging increases with the complexity of environmental factors. These findings enhance our understanding of the natural aging of MPs in different real environments.

Microplastics decrease the toxicity of sulfamethoxazole to marine algae (Skeletonema costatum) at the cellular and molecular levels.

Microplastics (MPs) and sulfamethoxazole (SMX) are ubiquitous in various aquatic environments, but little is known about their joint toxicity mechanism on marine organisms. This study investigated the individual and joint toxicity of SMX and five MPs, including polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS) and bioplastic polylactic acid (PLA), on Skeletonema costatum. The inhibition rates (IR) of the single MPs systems (50 mg/L) followed the order of PP > PE > PLA > PS > PET, while the addition of 0.3 mg/L SMX significantly decreased the toxicity of PP, PE and PLA in the joint system due to the "shelter" effect from MPs adsorption. As for the PS and SMX joint system, the malondialdehyde (MDA), reactive oxygen species (ROS) levels and superoxide dismutase (SOD) activity were higher than those of the other joint systems. The metabolomic results showed that SMX downregulated glycerophospholipid and amino acid metabolism. PS caused the downregulation of glycerophospholipids, carbohydrates and amino acid via the hetero-aggregation with algae. The co-exposure of SMX and PS alleviated the perturbation of alanine, aspartate and glutamate metabolism of algae compared with SMX. These findings enhance our understanding of the potential mechanisms of the MPs and organic pollutants joint toxicity in the marine environment.

A descriptive and comparative analysis on the adsorption of PPCPs by molecularly imprinted polymers.

Molecularly imprinted polymers (MIPs) have aroused great attention as a new material for the removal or detection of pharmaceuticals and personal care products (PPCPs). However, it is not clear about the superiority and deficiency of MIPs in the process of removing or detecting PPCPs. Herein, we evaluated the performance of MIPs in the aspects of adsorption capacity, binding affinity, adsorption rate, and compatibility to other techniques, and proposed ways to improve its performance. Without regard to the selectivity of MIPs, for the PPCPs adsorption, MIPs surprisingly did not always perform better than the conventional adsorbents (non-imprinted polymers, biochar, activated carbon and resin), indicating that MIPs should be used where selectivity is crucial, for example recovery of specific PPCPs in an environmental sample extraction process. Compared to the traditional solid-phase extraction for PPCPs detection pretreatment, the usage of MIPs as substitute extraction agents could obtain high selectivity of specific substance, due to the uniformity and effectiveness of the specific sites. A promising development in the future would be to combine other simple and rapid quantitative technologies, such as electro/photochemical sensor and catalytic degradation, to realize rapid and sensitive detection of trace PPCPs.

Effect of LDPE and biodegradable PBAT primary microplastics on bacterial community after four months of soil incubation.

Biodegradable plastics would be gradually degraded by microbes after being used and discarded, forming biodegradable microplastics (BMPs). It is however not clear if it, like conventional microplastics, can affect the original soil ecological balance. In this study, the non-degradable LDPE (low density polyethylene) was used as the reference primary microplastic, and the BMP PBAT (polyadipate/butylene terephthalate) was used as the test object. The effects of the amount of PBAT on soil physical-chemical properties, bacterial community were investigated using high throughput sequencing. The results showed that when the highest amount of PBAT applied was up to 250 times higher than the normal application amount, resulted in a certain dose-effect, and a higher amount of PBAT would reduce the content of NO3--N and TP. The lower amount of PBAT relatively increased the diversity of soil bacterial communities, and the relative abundance of the unique Azotobacter increased with increasing PBAT amount. The abundance of bacterial community in soil with different PBAT amounts was significantly correlated with the soil's physical-chemical properties. In addition, Mesorhizobium, TM7a and Azotobacter were observed to be highly tolerant bacteria in PBAT containing soil which can be actively explored to study the biodegradation of BMPs PBAT.

A review of interactions of microplastics and typical pollutants from toxicokinetics and toxicodynamics perspective.

The widespread microplastics (MPs) pollution has become a concerning environmental issue. The interactions between MPs and typical pollutants may change the bioaccumulation, and toxicity of pollutants, leading to high uncertainty in risk assessment. Still, significant gaps remain in the knowledge available to integrate these interactions in the perspectives of toxicokinetics (TK) and toxicodynamics (TD), which is also an essential part of quantitative toxicological research. This review systematically summarizes the interaction between MPs and typical pollutants in TK and TD processes. MPs can be acted as the vector or sink of pollutants to increase or decrease their bioaccumulation, and also may not affect their bioaccumulation due to no interaction. The adverse outcome pathway (AOP) framework enables novel approaches for determining the interaction between MPs and pollutants in the TD process. MPs can directly or indirectly enhance, reduce and not affect the toxicity of pollutants. A series of factors influencing the interaction in TK and TD processes are summarized, including MPs characteristics and exposure scenarios. TK-TD approach can quantitatively understand the interaction between MPs and pollutants based on the mechanism. Given the current knowledge gap in TK and TD processes, future perspectives on combined exposure research are proposed.

Riverine flux of dissolved phosphorus to the coastal sea may be overestimated, especially in estuaries of gated rivers: Implications of phosphorus adsorption/desorption on suspended sediments.

The flux of terrestrial dissolved inorganic phosphorous (DIP, i.e. PO43-) via rivers into coastal seas is usually calculated by simply multiplying its concentration with the corresponding water flow at the river mouth. Subsequent adsorption/desorption of DIP onto suspended sediment and the influence of salinity in the estuary are often overlooked. A series of DIP adsorption/desorption experiments under different salinities (0, 5, 15, 30) and suspended sediment concentrations (1-40 g L-1) were conducted in order to assess the potential influence of these factors on the overall DIP loading to the coastal zone. The effect of different sea-salt ions on DIP adsorption/desorption was also assessed by comparing different experimental solutions (NaCl solution, artificial seawater and real seawater). In estuaries, the adsorption of DIP to suspended sediments was greater than desorption, and the net adsorption increased with increasing concentration of suspended sediments and salinity. This enhanced DIP adsorption onto suspended sediment reduces the riverine discharge of DIP to coastal ecosystems. Disregarding this process, especially for the gated estuaries with high sediment resuspension, potentially leads to an overestimation of the terrestrial DIP input to the coastal region.

Polyethylene terephthalate and di-(2-ethylhexyl) phthalate in surface and core sediments of Bohai Bay, China: Occurrence and ecological risk.

Bohai Bay, a typical semi-enclosed bay, is close to the Beijing-Tianjin-Hebei Region, the economic center of north China. The release of emerging contaminants was considerably increasing with the fast urbanization and industrialization along the coastline. However, such data, e.g. plastic polymers, are still limited. Here, polyethylene terephthalate (PET) and di-(2-ethylhexyl) phthalate (DEHP) in surface sediments and sediment cores from the coastal area of Bohai Bay were investigated. The ranges of PET and DEHP concentrations in surface sediments are 1.49-13.90 mg/kg and 0.23-19.26 mg/kg, respectively. The relatively high contents of PET and DEHP were found near the Haihe River estuary, indicating the importance of riverine input. The PET and DEHP profiles in the cores dated by the 210Pb method showed increasing trends with time. The PET in Bohai Bay was low risk evaluated by the potential ecological risk assessment. Low ecological risks of DEHP to the benthic organisms were found in the sediments, using the environmental risk limits, risk quotient, threshold effect level and probable effect level methods. The pollution levels of PET and DEHP in Bohai Bay obtained in this study may provide important data for making pollution control strategies.

Microplastisphere may induce the enrichment of antibiotic resistance genes on microplastics in aquatic environments: A review.

Microplastics have been proven to be hotspots of bacterial pathogens and antibiotic resistance genes (ARGs). The enrichment of ARGs in microplastisphere, the specific niche for diverse microbial communities attached to the surface of microplastic, has attracted worldwide attention. By collecting 477 pairs of ARG abundance data belonging to 26 ARG types, based on the standardized mean difference (SMD) under the random effect model, we have performed the first meta-analysis of the ARG enrichment on microplastics in aquatic environments in order to quantitatively elucidate the enrichment effect, with comparison of non-microplastic materials. It was found that ARGs enriched on the microplastics were more abundant than that on the inorganic substrates (SMD = 0.26) and natural water environments (SMD = 0.10), but lower abundant than that on the natural organic substrates (SMD = -0.52). Furthermore, microplastics in freshwater tended to have a higher degree of ARG enrichment than those in saline water and sewage. The biofilm formation stage, structure, and component of microplastisphere may play a significant role in the enrichment of ARGs.

Vertical migration of microplastics along soil profile under different crop root systems.

Microplastics are highly accumulated in soils and supposed to migrate vertically due to water infiltration, fauna activities, and root growth. In this study, the vertical migration of microplastics along soil profile under three crop roots (corn, soybean, and ryegrass) was analyzed by a laboratory-scale incubation experiment. When microplastics were initially distributed in the surface layer, crop roots showed little effects on the vertical migration of microplastics. But in terms of homogenous microplastic distribution along soil profile, corn roots could contribute to the upward movement of microplastics in the middle layers (7-12 cm). It could be related to more pores and fissures created by primary and secondary corn roots and buoyancy effects once the pores and fissures were filled with water. Additionally, a significant positive correlation between microplastic numbers and tertiary roots of ryegrass has been observed and indicated the microplastic retention ability of fine crop roots. According to the results, in contrast to the downward microplastic migration caused by water infiltration and soil fauna activities, crop roots tended to move microplastics upwards or maintain them in soil layers.

Estimation of soil microplastic input derived from plastic gauze using a simplified model.

Plastic gauzes have been widely used in the BTH region against haze events and for agricultural practices. The breakage of plastic gauzes would lead to the release of microplastics into soils, but it is difficult to estimate the inputs due to their wide implementation. In this study, we have conducted an estimation model based on the remote sensing technology for plastic gauze identification and the data from field experiments and literature. This model first managed to interpret the distribution of plastic gauzes from the Landsat8 images with the average overall accuracy at 0.92 and the average kappa at 0.77. By deeming the implementation duration of plastic gauzes from their distribution and using the breakage rates of plastic materials in soils reported in the literature, the model estimated that on average 1629.68 tons of microplastics have been released to soils from plastic gauze annually in the BTH region. Comparing with the microplastics released from other sources (e.g., personal care products, household dusts, laundry, and tire wear), plastic gauze could be a considerable contributor to soil microplastics.

Distributions, temporal trends and ecological risks of polyethylene terephthalate (PET) and di-(2-ethylhexyl) phthalate (DEHP) in sediments of Jiaozhou Bay, China.

Spatiotemporal distribution and ecological risk of the polyethylene terephthalate (PET) plastic polymer and plasticizer di-(2-ethylhexyl) phthalate (DEHP) were investigated using both surface and core sediments in Jiaozhou Bay, China. The concentrations of PET and DEHP ranged 210.6-1929.7 µg/kg and 0-591.2 µg/kg, respectively. The depth profiles of PET and DEHP in the sediment cores indicated that PET and DEHP pollution increased since the 1970s, which is in accord with the regional PET and DEHP consumption history. The levels of PET in Jiaozhou Bay was found to represent low ecological risk based on the assessment models for Potential Ecological Risk factor and Potential Ecological Risk. The amounts of DEHP also posed a low risk to the aquatic organisms in the sediment phase as indicated by the Risk Quotient method.

An optimized density-based approach for extracting microplastics from soil and sediment samples.

Microplastic pollution in the environment has received growing attention worldwide. A major impediment for accurate measurements of microplastics in environmental matrixes is to extract the particles. The most commonly-used method for separation from soil or sediment is flotation in dense liquid based on the relatively low density of plastic particles. This study provides an improved and optimized process for extraction of microplastic particles by modifying the floatation technique and floatation solution. Microplastics in soils and sediments are extracted by adding 200 g dry soil or sediment sample to 1.3 L mix of the saturated NaCl and NaI solutions in a volume ratio of 1:1 and aerating for 40 s then filtering the supernatant. The accuracy and precision of the new approach is validated by recovery experiments using soil and sediment samples spiked with six common microplastic compounds: polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and expanded polystyrene (EPS), and comparison with the previous method. The optimized approach is further compared with the previous approach using the real soil and sediment samples.