Microplastics Research Articles

Behavior and flow of microplastics during sludge treatment in Japan.

Microplastic (MP) pollution is a growing public and scientific concern. In urban environments, wastewater treatment plants (WWTPs) are major sources of MPs. This study sampled sludge and separated water from each sludge treatment unit in two WWTPs in Osaka, Japan. Analyzing method for MPs in sewage sludge was optimized, ultrasonic pretreatment and double digestion were introduced into the analyzing method of MPs in sewage sludge, recovering test of standard MPs proved its high efficiency. Then MPs larger than 100 μm were extracted and analyzed, their size and type were recorded, the MP concentration was calculated, and the MP flow in the sludge treatment system was estimated. MPs were detected at every step of the sludge treatment process, and 13 types of MPs were identified. The MP concentration in sludge ranged from 81 ± 48 to 6470 ± 1490 particles/kg dry sludge (DS). In the separated water, MP concentrations were much lower, ranging from 0 to 1740 ± 794 particles/kg DS. During the thickening and dewatering processes, nearly all MPs were transferred into thickened or dewatered sludge; only 5-10 % of MPs returned to the primary sedimentation pond with the separated water. The most common types of MPs were PMMA, PE, and PS. No significant differences in MP type distributions were observed among sampling batches; however, significant differences in a few types of MPs were detected between treatment units, which requires further investigation. All detected MPs were smaller than 1000 μm; larger MPs might have been removed in the grit chamber before reaching the primary or secondary sedimentation ponds. Overall, the particle size distribution did not substantially change during sludge treatment.

Analysis and Risk Evaluation of Soil Microplastics in the Rohingya Refugee Camp Area, Bangladesh: A Comprehensive Study

The global concern over the pollution-induced by microplastics (MPs) has intensified due to its adverse effects on the environment, particularly in terrestrial ecosystems, where it poses potential threats to soil quality and resident species. However, there is a noticeable research gap regarding soil MPs in dumping sites, specifically within the Rohingya Refugee Camp (RRC), the world's largest humanitarian crisis located in Bangladesh. The main objective of this study is to assess soil MPs' abundance, spatial distribution, and inherent risks in the RRC. The investigation involved extracting MPs from ten soil sampling sites in Kutupalong RRC, home to Rohingya refugees who sought refuge in Bangladesh following the 2017 ethnic atrocities in Northern Rakhine State, Myanmar. Stereomicroscopy and Fourier transform infrared spectroscopy were employed for identification purposes. The concentration of MPs in the study area varied from 67 to 126 (items/kg) (dry weight), with a mean concentration of 103.80 ± 20.671 (items/kg). MPs with sizes <0.5mm constituted the majority at 83%, with fragments (68%) being the prevailing shape, and transparent (63%) as the most abundant color. Predominant polymers included polyethylene (53%) and polypropylene (46%). Negative correlations were observed between MP abundance and pH and moisture content (p<0.05), while a positive correlation was found between MP abundance and organic matter. PCA results suggested that human-induced inappropriate waste and air deposition are the primary sources of soil MP pollution. Contamination factor values suggested moderate pollution with MPs in the study area. According to the geo-accumulation index (Igeo), the area was classified as pollution grade II, signifying 'uncontaminated to moderately contaminated.' However, pollutant load index and potential ecological risk index indicated Hazard Level-I and Pollution Grade-I, respectively. This study illuminates the contamination scenario with MPs, underscoring concerns for eco-environmental safety and providing crucial data for future investigations into MPs in terrestrial dumping habitats.

Prediction of vertical transport of microplastics: Shape- and aging-dependent drag models

The prediction of vertical transport of microplastics (MPs) is essential for understanding their multidimensional transport, fate, and environmental risks, but drag models applicable to aging MPs are currently understudied. In this study, pristine and UV-aged polyethylene terephthalate (PET) and polystyrene (PS) MPs were used for settling experiments. Combining physicochemical properties and transport data, a shape-dependent drag model based on the Corey shape factor was optimized with average errors of 9.73% and 10.42% and coefficients of determination of 0.6878 and 0.8359 for predicting the settling terminal velocities (ut) for PET and PS MPs, respectively. Meanwhile, aging-dependent drag models were constructed by incorporating the carbonyl index as functional forms of the newly defined aging index, which can be used to differentiate the effects of shape and aging characteristics on the vertical transport of MPs. These aging-dependent models showed better predictive abilities with average errors of 3.97% and 4.56% in predicting ut for PET MPs, and of 5.89% and 6.91% for PS MPs. Additionally, the drag models in this study improved applicability to predict vertical transport of environmentally-collected weathered MPs. With the continuous improvement of the transport database of diverse MPs, this study is expected to provide scientific support for predicting the environmental behaviors of MPs and formulating targeted pollution control strategies.

Chronic exposure to polystyrene microplastics induces renal fibrosis via ferroptosis

With the increasing prevalence of microplastics (MPs) in the environment, human health has become a growing concern. After entering the human body, MPs accumulate in the kidneys, indicating that the kidneys are their major target organs. This study investigated nephrotoxicity associated with MPs, with a specific focus on polystyrene (PS) MPs and amino-functionalized polystyrene (PS-NH2) MPs. Although previous studies have documented the nephrotoxic effects associated with short-term exposure to MPs, the mechanisms of kidney toxicity caused by chronic long-term exposure to MPs remain largely unclear. In animal models, mice were exposed to MPs (10mg/L) at concentrations that are accessible to humans, administered via drinking water over a period of six months. These findings indicate that MPs can induce renal fibrosis by facilitating the onset of inflammation and accumulation of a substantial number of inflammatory cells. Our in vitro study showed that long-term exposure to MPs (60μg/mL) induced ferroptosis in renal tubular epithelial cells via ferritinophagy and secreted TGF-β1, leading to renal fibroblast activation. Conversely, the application of Fer-1, a ferroptosis inhibitor, prevents ferroptosis in renal epithelial cells and reverses the activation of renal fibroblasts. Our study identified a novel toxicity mechanism for renal fibrosis induced by MPs exposure, offering new insights into the detrimental effects of environmental MPs on human health.

The influence of water conservancy project on microplastics distribution in river ecosystem: A case study of Lhasa River Basin in Qinghai-Tibet Plateau

Water conservancy projects affect the migration, suspension, and deposition of microplastic (MP). However, its impact on MP pollution of river ecosystem remains elusive. Herein, we investigated the MP characteristics and the influence of water conservancy projects on MPs in the Lhasa River Basin of the Qinghai-Tibet Plateau, China. The results demonstrated that the MPs concentration in surface water decreased from upstream to downstream, as more MPs in surface water were settling down and stored in reservoir sediments in the midstream. It is postulated that reservoir sedimentation of MPs occurs at a greater rate due to the barrier effect of reservoirs, steady hydrodynamics, and weak salinity-induced buoyancy. To evaluate the ecological risk of the Lhasa River Basin, the pollution load index, the polymer hazard index, and the potential ecological risk index were analyzed. The upstream exhibits elevated polymer hazard index values (>100), and the potential ecological risk index values in the Lhasa River Basin showed ecological risk similar to those of pollution load index values. This research represents the initial exploration of MP distribution within the entire Lhasa River basin, providing a foundational framework for investigating the impact of water conservancy projects on MP migration.

Investigation of Microplastic Contamination in the Gastrointestinal Tract of Fish: A Comparative Study of Various Freshwater Species

The aqueous environment has been reported to be seriously threatened by the pollution of microplastics (MPs), which has been confirmed in numerous studies affecting various aquatic habitats. Despite this, few investigations exist on MP contamination in fish of specific regions. Thus, the current study aims to determine MP concentrations in the fish species of the Chhota Nagpur zone of eastern India. From August to September 2023, fish samples were collected from 10 km distance between two locations of Subarnarekha and Kharkai river banks through fishermen. Microplastics were found in the gastrointestinal tract of 45 fish of 8 species out of 48 samples. Of these species, six species were secondary consumers, while the remaining two were primary consumers. The average amount of microplastics consumed by each fish (n = 48) was 3.0 ± 1.8. A total of 144 microplastics were found in collected samples of fish species. Among the analyzed sample of MPs, 69.4% were fibers, films were (22.3%), and (8.3%) were fragments. The least contaminated species was T. ilisha (0.8 ± 0.7 particles/ind.), while L. rohita had the highest microplastic contamination (4.5 ± 1.7 particles/ind.). The present study found a negative correlation of - 0.83 between MP consumption and the mean body weight of fish. Similarly, a negative correlation of - 0.5 was found between the length of fish and MP intake. Polyamide (nylon), polypropylene, polyvinyl chloride, polycarbonate, polyethylene terephthalate, and polyethylene polymers were found. The size of MPs ranged from 45-355 μm and mainly were fibers. They were also predominantly blue and black. Polyamide and polyvinyl chloride were the common MP types in every specimen. The possible sources of MPs were fishing nets, ropes, and packaging material. This investigation points to MP contamination in aquatic ecosystems and particular species. It provides advanced knowledge of MP pollution, sources, and effects on regional ecosystems and public health.

Differential photoaging behaviors of different colored commercial polyethylene microplastics in water: The important role of color characteristics

Upon entering the environment, plastics would undergo photoaging and forming microplastics (MPs). However, information on the photoaging behavior of colored MPs and how the color characteristics (wavelength, lightness, and saturation) influence their photoaging process is still lacking. Thus, attention was paid to comparing the photoaging process of transparent and five-colored MPs. To reveal the degree of photodegradation and photooxidation, physicochemical changes (e.g., surface morphology, functional groups, and the leaching of intermediates) of transparent and five-colored MPs were explored. Photodegradation rates and photooxidation degrees ranked transparent > yellow > red ≈ orange > green > blue. However, transparent and five-colored MPs exhibited a different photoaging sequence and eluted different photodegradation products from each other. Pearson correlation analysis was used to describe the relationships between color characteristics (wavelength, lightness, and saturation) and their photoaging properties, and the results indicated that MPs (yellow, red, and orange) with longer color wavelength, higher lightness, and lower saturation are more susceptible to UV light than MPs with shorter color wavelength, lower lightness and higher saturation (green and blue). The findings demonstrate that the photoaging process of colored MPs is correlated to their color characteristics, highlighting the important role of color in MPs' environmental fate.

Microplastic and antibiotics in waters: Interactions and environmental risks.

Antibiotics (ATs) are ubiquitously detected in natural waters worldwide, and their tendency to co-migrate with microplastics (MPs) post-adsorption leads to heightened environmental risk. Research on the adsorption of ATs on MPs and their subsequent effects on the environmental risks is gaining significant attention globally. This adsorption process predominantly occurs through hydrophobic forces, hydrogen bonds, and electrostatic interactions and is influenced by various environmental factors. The interaction between MPs and ATs exhibited varying degrees of efficiency across different pH levels and ionic strengths. Furthermore, this paper outlines the environmental risks associated with the co-presence of MPs and ATs in aquatic environments, emphasizing the potential effect of MPs on the distribution of antibiotic resistance genes (ARGs) and related environmental risks. The potential hazards posed by MPs and ATs in aquatic systems warrant serious consideration. Future research should concentrate on the adsorption of ATs/ARGs on MPs under real environmental conditions, horizontal gene transfer on MPs, as well as biofilm formation and agglomeration behavior on MPs that needs to be emphasized.

Meta-analysis shows that microplastics affect ecosystem services in terrestrial environments

To date, the understanding of the risks and impacts of microplastics (MPs) on terrestrial ecosystems remains limited, primarily due to most studies focusing on single ecosystem service. This study addressed this gap by conducting an integrative meta-analysis of 128 studies to explore the multifaceted impacts of MPs on various ecosystem services, including plant productivity, soil carbon (C) sequestration, microbial biodiversity, soil fertility, microbial biomass, and enzyme activity. We found that MPs reduced plant productivity service by 14.5%, microbial biodiversity service by 3.4%, and soil fertility service by 8.2%, while soil C sequestration service increased by 12.2%. No significant effects were observed on microbial biomass and enzyme activity services. Additionally, MPs of different types and shapes influenced the ecosystem services differently, with fiber, fragment, and round-shaped MPs decreasing the plant productivity service by 22.0%, 14.6%, and 12.7%, respectively. Correlation analysis revealed intricate relationships between MPs properties and the ecosystem services. Our findings also revealed complex interdependencies among the ecosystem services induced by MPs application. We observed that the plant productivity service was negatively correlated with the soil C sequestration service, but positively correlated with microbial biodiversity, microbial biomass, and enzyme activity services. Together, our study emphasized the need for targeted research to develop mitigation strategies addressing the multifaceted effects of MPs to terrestrial ecosystems.

Sublethal effects of microplastic and oil co-exposure on biological rates and lipid profiles of keystone Arctic copepods

Microplastics (MPs) and petroleum hydrocarbons are contaminants of emerging concern in the Arctic, but little is known about their co-exposure effects. In this study, we present the first assessment of the sublethal impacts resulting from combined exposure to microplastics and oil in three key Arctic copepod species. Specifically, we investigated the effects of a 5-day exposure to oil alone (1μLL-1) and in combination with MPs (polyethylene microspheres, 20μm, 20MPmL-1) and dispersant (Corexit 9500, 0.05μLL-1) on the biological functions and lipid profiles of the planktonic copepods Metridia longa, Calanus finmarchicus, and Calanus glacialis. Exposure to oil alone caused a significant reduction (34-58%) in fecal pellet production, but neither microplastics nor dispersant increased the negative effect of oil on fecal pellet production. C. glacialis and C. finmarchicus exposed to the studied pollutants for 5 days produced eggs with delayed hatching and lower hatching success. The highest hatching inhibition (50%) was observed in eggs of C. glacialis exposed to oil plus MPs and dispersant for five days. This indicates that maternal transfer of oil components to eggs negatively affects embryonic development and hatching. Lipid content and fatty acids profiles varied among the studied copepod species but were not affected by the tested pollutants after five days of exposure. By microscopical observation of fecal pellets, ingestion of small oil droplets and MPs was confirmed in all species, but the estimated ingestion of MPs was low (<25MPs cop-1 d-1, <0.2% of total offered MPs) suggesting avoidance of MP consumption in copepods. Our results indicate that virgin MPs did not increase the toxicity of oil to the studied Arctic copepods under co-exposure conditions, and dispersants can slightly increase certain adverse effects of oil (hatching). However, environmentally relevant concentrations of oil alone can negatively impact Arctic keystone copepods and potentially the biological carbon pump. These findings emphasize the need to reduce petrogenic pollution and the risk of oil spills in the sensitive Arctic ecosystem.

Uptake, removal and trophic transfer of fluorescent polyethylene microplastics by freshwater model organisms: the impact of particle size and food availability.

As an emerging contaminant, microplastics (MPs) are widely distributed in freshwater ecosystems and pose potential threats to aquatic organisms, attracting significant attention from both the scientific community and the general public. However, there is still uncertainty regarding the mechanisms of MPs transfer within aquatic biota and how particle size and food availability influence their transport patterns. In this study, zebrafish (Danio rerio) were selected as a model organism to investigate the uptake and elimination of fluorescent polyethylene (PE) MPs under different exposure scenarios (waterborne or trophic transfer, with or without food) and varying particle sizes (ranging from 10-300 μm at concentrations of 0.1, 2, and 300 mg/L). Additionally, water fleas (Daphnia magna) were provided as prey for the fish. The dynamic accumulation of PE-MPs sized between 10-20 μm at a concentration of 25 mg/L by daphnia was also determined along with its impact on animal feeding behavior. The results demonstrated that both organisms were capable of ingesting PE-MPs during exposures lasting up to 24 hours for daphnia and up to 72 hours for zebrafish. Furthermore, rapid elimination rates were observed within just 30 minutes for daphnia and between 6-12 hours for zebrafish. The presence of food reduced MPs uptake and removal by daphnia but significantly increased MP elimination by fish. Zebrafish showed a preference for ingesting larger-sized MPs that they could easily recognize; however, trophic transfer from daphnia to fish was found to be the primary route of ingestion specifically for PE-MPs sized between 10-20 μm. The findings suggest that while fish directly ingest fewer invisible MPs from the water column, they still accumulate these particles through predation on contaminated prey organisms. Therefore, it is imperative to prioritize the ecological risks associated with the transfer of MPs from zooplankton to fish.

Spray paint-derived microplastics and incorporated substances as ecotoxicological contaminants in the Neotropical Bumblebee Bombus atratus

While bumblebees may be exposed to microplastics (MPs), the effects on them are not well studied. Therefore, in this research, we assessed the cytotoxicity of pristine and photodegraded spray paint-derived MPs on the midgut, Malpighian tubules, and hepato-nephrocitic system cells of Bombus atratus workers exposed to 50mg.L-1 MPs for 96hours. Histological and histochemical analyses revealed that pristine MPs caused subtle cellular changes, while the exposure to photodegraded MPs led to significant vacuolization, nuclear condensation, and pyknosis. These effects are possibly linked to the release of potentially toxic elements (PTEs) like Copper, Manganese, and Iron from photodegraded MPs, which exceeded Brazil's CONAMA safety limits. Photodegraded MPs also reduced body weight, disrupting homeostasis and potentially decreasing bumblebee’s fitness. These findings highlight the importance of studying the toxicity of environmentally realistic MPs, as plastic composition and weathering significantly influence their harmful effects.

Effect of polyethylene microplastics on soil organic carbon pool dynamics in the soil-rhizosphere-alfalfa system

The effect of microplastics (MPs) on soil organic carbon (SOC) has become a growing concern. However, most studies have focused on the effect in a single soil system, and little is known about how MPs affect the soil carbon pool in the soil-plant system. In this study, a 90-day pot experiment was conducted with different concentrations (0%, 0.5%, 1%, and 5% w/w) and exposure times (30d, 60d, and 90d) of polyethylene microplastics to investigate their effects on SOC pools. The results showed that MPs increased particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) pools, while decreasing microbial biomass carbon (MBC). Initially, MPs increased POC by disguise and their effects on enzyme activities and C degradation genes, and indirectly increased MAOC by affecting dissolved organic carbon (DOC) levels (via soil pH) and stimulating enzyme activities. However, as alfalfa rapidly grew from the branching to the flowering stage, plants inputted C into the POC pool via rhizodeposition, while activating and absorbing the MAOC pool for growth through roots, resulting in an increase in POC and a decrease in MAOC. Moreover, plants had priming effects on soil MBC, enzyme activities, and C degradation genes, further influencing SOC pools. Overall, MPs affected plant growth and soil carbon pools by altering soil properties, while plants in turn influenced soil organic carbon pools and the impact of MPs on soil properties. This study provides deeper insights into the effect of MPs on SOC dynamics in the soil-rhizosphere-plant system.

Polystyrene microplastics induce activation and cell death of neutrophils through strong adherence and engulfment

Ingested microplastics (MPs) can accumulate throughout whole body, which may induce the dysfunction of immune system. However, it remains unclear how MP exposure affects innate immune responses at the cellular level. We found that mouse neutrophils strongly bind and then engulf polystyrene MPs. This interaction leads to proinflammatory state of neutrophils and eventually results in apoptotic cell death through toll-like receptor signaling pathway in a bacteria-recognition mimetic manner. Moreover, our data verified that orally administered polystyrene MPs reach various organs in mice, where they are interacted with and endocytosed by neutrophils. We confirmed that human neutrophils also strongly bind and internalize polystyrene MPs. Additionally, RNA sequencing analysis of polystyrene MPs-exposed human neutrophils showed the upregulation of cell death-related function. Therefore, the accumulated MPs may exacerbate inflammatory immune response by disrupting neutrophil function. These results provide novel insight into the adverse responses of neutrophils induced by MP exposure.

Exposure to microplastics contaminated with pharmaceuticals and personal care products: Histological effects on Ucides cordatus

Pharmaceuticals and personal care products (PPCPs) are known to interact with microplastics (MPs) in aquatic environments, with substances such as the antimicrobial triclosan (TCS) and the synthetic hormone 17α-ethinylestradiol (EE2) being prevalent. These persistent contaminants are linked to toxic effects in aquatic organisms. This study aimed to investigate histological and morphometric changes in the gills of Ucides cordatus exposed to microplastics alone and microplastics contaminated with PPCPs. The experimental design included four treatment groups: 1) control (C), 2) virgin microplastics (MP), 3) microplastics fortified with triclosan (MPT), and 4) microplastics fortified with 17α-ethinylestradiol (MPE), with exposure durations of 3 or 7 days. Significant differences were observed in the histopathological indices for treatments with PPCP-fortified microplastics at 3 days (MPT and MPE) and 7 days (MPT). Notable pathologies included necrosis, fibrosis, and circulatory disorders. Exposure duration was significantly associated with morphometric changes, including secondary lamellar width in MPT and secondary lamellar length in MPE. These findings indicate that exposure to microplastics contaminated with PPCPs may impair the osmoregulatory and respiratory functions of Ucides cordatus.

The synchronized dynamic release behavior of microplastics during farmland soil erosion process

Microplastics (MPs) are widespread in farmland soil. However, the risks associated with their loss through soil erosion remain unknown. This study investigates the occurrence and behavior of MPs in farmland soil in a southeastern coastal area of China, focusing on their synchronized dynamic release during soil erosion scenarios. The results showed that the abundance of MPs in the tested farmland soil ranged from 2.40×104 to 1.04×105 items·kg-1. MPs predominantly appear as fragments and particles, with sizes concentrated between 30-100 μm. During the process of soil erosion, characterized by rapid soil subsidence, the amount of MPs released into water bodies initially decreases, averaging a reduction of 1.08×104 items·kg-1. This is followed by an average increase of 1.89×104 items·kg-1. The competition between the adsorption, collision, and sedimentation of soil particles and the desorption and release of settled particles, determines this behavior. This pattern is strongly related to the physicochemical properties and mechanical composition of the soil. Deep learning predictions revealed that, without external influences, 49.42% of MPs in farmland soil could be synchronously released into water bodies during erosion. The analysis shows that MPs exhibit dynamic behavior in time and space, posing serious threats to aquatic ecosystems. Controlling soil erosion in farmland is crucial for the source management of MP migration.

Unveiling the optical and molecular characteristics of aging microplastics derived dissolved organic matter transformed by UV/chlor(am)ine oxidation and its potential for disinfection byproducts formation

The investigations into the existence and behavior of microplastics (MPs) in water environment were widely conducted, while the characteristics of dissolved organic matter derived from MPs (MPs-DOM) during advanced oxidation have garnered comparatively little attention. In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was employed along with multiple statistical analyses to gain a deeper understanding of the conversion of MPs-DOM in UV/chlor(am)ine advanced oxidation processes (AOPs). The diverse treatments exhibited varying degrees of augmentation in both aging and fragmentation of MPs with the order of UV/Cl2 > UV > UV/NH2Cl. The fragmentation degree of MPs upon two UV-based AOPs (UV-AOPs) was dependent on their monomer chemical structure. The highest TOC values of three MPs-DOM were observed after UV/Cl2 AOP and the lowest after UV/NH2Cl AOP. Polyvinyl chloride (PVC) displayed a greater release of MPs-DOM under varying leaching conditions. UV/Cl₂ AOP favored the reaction with saturated MPs-DOM, while UV/NH₂Cl AOP reduced unsaturated MPs-DOM, alleviating disinfection byproducts (DBPs) formation after chlorination. The precursors generated by UV/Cl₂ AOP owned lower H/C, higher modified aromatic index (AImod), and lower molecular weight (MW) products after chlorination. PVC-DOM with fewer CH₂ groups was more reactive. -H₂O, +O and -CH₂ reactions dominated in PVC-DOM (CHO compounds), while -2H, +O, -CH₂ did in PVC-DOM (CHON compounds). The dominant chlorine addition/substitution reactions occurred in PVC-DOM treated by UV/Cl₂ AOP, identifying 195 Cl-DBPs with 220 precursor-product pairs. Mass difference analyses showed that +2H and +O reactions were the most frequent of the 24 reaction types. Environmental ImplicationMicroplastics derived dissolved organic matters (MPs-DOM) transformed into disinfection byproducts (DBPs) under advanced oxidation processes (AOPs), heightening environmental risks. In this study, Fourier transform ion cyclotron resonance mass spectrometry was employed to gain a deeper understanding of MPs-DOM conversion in UV/chlor(am)ine AOPs. MPs fragmentation and fluorescent components varied with monomer chemistry and polymers. UV/Cl₂ AOP reacted with saturated MPs-DOM. UV/NH₂Cl AOP reduced unsaturated MPs-DOM, alleviating DBPs formation. DBPs precursors generated by UV/Cl₂ AOP owned higher modified aromatic index, lower H/C and molecular weight. Unveiling the MPs-DOM transformation during AOPs can mitigate the negative environmental impacts of MPs and their derivatives.

Multiple effects of submerged plants on microplastics-heavy metals redistribution and combination in the hyporheic sediment

Submerged plants (SP) in the hyporheic sediment (HS) dynamically alter the spatial distributions of heavy metals (HMs) and microplastics (MPs). In this study, we examined the redistribution and combination of HMs and MPs in the HS surrounding the SP (SSP) and non-nearby the SP (NSP) in the Weihe River Basin. The strong bioconcentration capacity of SP directly caused a decrease of HMs in the SSP (Bioconcentration Factors: SSP>NSP, 1.07>1.00). Algal proliferation at high nutrient concentrations strengthened the interception of MPs by SP (SSP-MPs >NSP-MPs, 495>315 items/kg). The significant correlation between SSP-HMs and SSP-MPs indicates the formation of MPs-HMs. The concentration of SSP-HMs was greater than NSP-HMs (Mn (462.95>437.66mg/kg)>Zn (63.46>60.51mg/kg)>V (53.98>50.67mg/kg)>Pb (21.98>18.47mg/kg)>As (18.36>15.65mg/kg). This finding implies that the MPs trapped by the SP indirectly contribute to elevating SSP-HMs, which showed higher pollution risk (Nemerow Pollution Index: 1.37>1.22; Contamination Factor: V, 0.87>0.82, Zn, 0.95>0.90, As, 1.61>1.41, Pb, 0.98>0.88). Furthermore, SP can reduce NSP contamination by proactively collecting pollutants into SSP, endangering the integrity of rivers through the ingesting of hydrobiont. Our study provides theoretical suggestions for the application SP to improve ecological health in complex environment.

Response of Soil Heavy Metal Forms and Bioavailability to the Application of Microplastics across Five Years in Different Soil Types

Microplastics (MPs) potentially alter physicochemical and transformation of heavy metals (HMs) in soils, which may depend on the specific characteristics of soil types. However, the dynamical and long-term mechanisms remain to be elucidated. A five-year incubation experiment was conducted to evaluate the influence of MPs on the chemical speciation of Pb, Ni, Cu, Cr, Cd, and As in the meadow, tidal, cinnamon, saline-alkali, and brown soils. From the first year to the fifth year, the clay value of the meadow, tidal, cinnamon, and saline-alkali soils was increased by 31.35%, 9.63%, 30.12%, and 33.12%, respectively; the pH values of the cinnamon and saline-alkali soils were increased by 15.02% and 15.86%, respectively. Besides, speciation distribution results suggested that the application of MPs reduces the liable available (LB) form (F2–water soluble and F3–ion exchangeable) of HMs and increases the potentially available (PB) form (F5–minerals and F6–organic-bound fraction) of HMs in all soils. Compared with other forms, F2 HMs fraction was the most responsive to MPs. Furthermore, the average bioconcentration factor (BCF) of Cr and Pb decreased by 73.75% and 70.41% in soils, respectively. Interestingly, soil type showed more impact on the form of HMs, which is associated with the different physicochemical parameters of soils, while time displayed more impact on the bioavailability of HMs. Moreover, our results suggest that soils with higher clay content and pH values (such as cinnamon and saline-alkali soils) may mitigate the bioavailability of HMs more effectively in the presence of MPs, while soils with lower clay content may be more vulnerable to HMs contamination over time. This work highlights the importance of long-term monitoring of the impact of MPs on HMs dynamics for effective mitigation of soil contamination risks. Our study provides valuable guidance for soil remediation strategies and environmental quality management across different soil types.

Enhancing the content of phycoerythrin through the application of microplastics from Porphyridium cruentum produced in wastewater using machine learning methods

Microalgae can produce secondary metabolites like phycoerythrin (Phy). The effects of some microplastics (MPs), wastewater (WW), and light intensity (LI) parameters, including complex data sets, on Phy concentration from Porphyridium cruentum were investigated using machine learning methods in this study. Also, the deep learning (DL) model was developed to get the maximum phy concentration from the dataset. The dataset (232 data groups), including a feature set, polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), WW, LI, and an output variable, Phy, were randomly divided into training and test sets to create and evaluate the models. The highest experimental and predicted Phy concentrations were 52.3 mg/g and 58.32 mg/g in a scenario with 15% WW, 80 mg/L PE, PP, PS, and PVC, and a LI of 175 μmolm−2 s-1, respectively. The Pearson correlation coefficient (r) indicates a positive correlation between Phy and the variables PE (r = 0.35), PVC (r = 0.69), PP (r = 0.27), PS (r = 0.29), and LI (r = 0.22). However, variables such as WW (r = -0.05) have a weak correlation, and while PVC and PE showed the most significant effect on Phy concentration, WW had the lowest effect. Furthermore, LIME (local interpretable model-agnostic explanations) and SHAP (shapley additive explanations) provided us with important results for interpreting the random forest regression (RF) and DL models' predictions, respectively. The LIME and SHAP analyses suggest that the system with more PVC has a higher predicted Phy value. For WW, the reverse is true; higher WW values result in lower Phy predictions. Researchers were given the model explainability decision tree (DT) structure to study reactants' effects on output (Phy). In conclusion, the dye industry can use microalgae to treat WW contaminated with MPs while also producing high amounts of Phy using a DL model.