The ubiquity of microplastics in aquatic and terrestrial environments and related ecological impacts have gained global attention. Microplastics have been detected in table salt, drinking water, and ...air, posing inevitable human exposure risk. However, rigorous analytical methods for detection and characterization of microplastics remain scarce. Knowledge about the potential adverse effects on human health via dietary and respiratory exposures is also limited. To address these issues, we reviewed 46 publications concerning abundances, potential sources, and analytical methods of microplastics in table salt, drinking water, and air. We also summarized probable translocation and accumulation pathways of microplastics within human body. Human body burdens of microplastics through table salt, drinking water, and inhalation were estimated to be (0–7.3)×104, (0–4.7)×103, and (0–3.0)×107 items per person per year, respectively. The intake of microplastics via inhalation, especially via indoor air, was much higher than those via other exposure routes. Moreover, microplastics in the air impose threats to both respiratory and digestive systems through breathing and ingestion. Given the lifetime inevitable exposure to microplastics, we urgently call for a better understanding of the potential hazards of microplastics to human health.
Human exposure to perfluorochemicals (PFCs) has attracted mounting attention due to their potential harmful effects. Breathing, dietary intake, and drinking are believed to be the main routes for PFC ...entering into human body. Thus, we profiled PFC compositions and concentrations in indoor air and dust, food, and drinking water with detailed analysis of literature data published after 2010. Concentrations of PFCs in air and dust samples collected from home, office, and vehicle were outlined. The results showed that neutral PFCs (e.g., fluorotelomer alcohols (FTOHs) and perfluorooctane sulfonamide ethanols (FOSEs)) should be given attention in addition to PFOS and PFOA. We summarized PFC concentrations in various food items, including vegetables, dairy products, beverages, eggs, meat products, fish, and shellfish. We showed that humans are subject to the dietary PFC exposure mostly through fish and shellfish consumption. Concentrations of PFCs in different drinking water samples collected from various countries were analyzed. Well water and tap water contained relatively higher PFC concentrations than other types of drinking water. Furthermore, PFC contamination in drinking water was influenced by the techniques for drinking water treatment and bottle-originating pollution.
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•Neutral PFCs are dominant in indoor air and dust.•Dietary PFC exposure is mostly through fish, shellfish and meat consumption.•Well water and tap water contain relatively higher PFC concentrations than other types of drinking water.
Sludge disposal such as land application is suspected as a significant source of microplastic (MP) pollution in the environment. To examine such a hypothesis, the present study was conducted to ...investigate the occurrence of MPs in sludge by analyzing 79 sewage sludge samples collected from 28 wastewater treatment plants (WWTPs) in 11 Chinese provinces. MP concentrations in the sludge samples ranged from 1.60–56.4 × 103 particles per kilogram of dry sludge, with an average of 22.7 ± 12.1 × 103 particles per kilogram of dry sludge. Thereinto, the sludge-based MP contents were greater in eastern China than in western China and varied during different months. Their colors and types were mainly white (59.6%) and fibers (63%), respectively. Microscope Fourier Transform infrared spectroscopy revealed that most of MPs belonged to polyolefin, acrylic fibers, polyethylene and polyamide. Some WWTP parameters, such as servicing area, proportion of industrial wastewater, secondary treatment and sludge dewatering may have affected MP concentrations in sludge. Based on the total sludge production in China, the average amount of sludge-based MPs entering into natural environmental was estimated to be 1.56 × 1014 particles per year. The findings confirmed that sewage sludge discharge is an important source of MP pollution in the environment. Further evaluation of the associated environmental hazards with MPs is deemed necessary.
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•Microplastics (MPs) in 79 sludge samples from 28 WWTPs in China were investigated.•Average MP concentration of the samples is 22.7 ± 12.1 × 103 particles kg−1 dry sludge.•MP concentrations in sludge are greater in eastern China than in western China.•Some WWTP parameters may have affected MP concentrations in sewage sludge.•About 1.56 × 1014 MP particles from Chinese sludge enter into environment per year.
Occurrence of microplastics (MPs) in the environment has attracted great attention as it has become a global concern. This review aims to systematically demonstrate the role of marine microplastic as ...a novel medium for environmental partitioning of chemicals in the ocean, which can cause toxic effects in the ecological environment. This review assimilated and analyzed available data published between 1972 and 2017 on the interaction between MPs and selected chemicals. Firstly, the review analyzes the occurrence of chemicals in MPs and outlines their distribution patterns. Then possible mechanisms of the interaction between MPs and organic chemicals and potential controlling factors were critically studied. Finally, the hazards of MPs and affiliated organic chemicals to marine organisms were shortly summarized.
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•The toxic chemicals found in microplastics were outlined with detailed analysis.•The interaction mechanisms between chemicals and microplastics were analyzed.•The potential effects of microplastics on marine organisms were summarized.
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•CMC-FeS@BC was synthesized combining the advantages of biochar, CMC, and FeS.•57% of Cr(VI) removal was due to reduction and 43% was ascribed to sorption.•External mass transfer ...model adequately represents Cr(VI) sorption kinetics.•Isotherm data of Cr(VI) were simulated adequately by Redlich-Peterson model.
A novel biochar supported nanoscale iron sulfide (FeS) composite (CMC-FeS@biochar) combining the advantages of biochar, carboxymethyl cellulose (CMC), and FeS was synthesized and tested for Cr(VI) removal efficiency and mechanisms. FeS particles were effectively soldered onto the surface of biochar through OH, CC, OCO, CO, and SiO functional groups. The composite at a mass ratio of FeS:CMC: biochar=1:1:1 displayed an enhanced Cr(VI) adsorption capacity of 130.5mg/g at pH 5.5 compared to 38.6mg/g for FeS and 25.4mg/g for biochar. Surface sorption and reduction were the dominant removal mechanisms. At the equilibrium Cr(VI) concentration of 13.4mg/L, 57% of Cr(VI) removal was attributed to reduction and 43% was ascribed to surface sorption. The adsorption kinetic data were adequately simulated with pseudo second-order kinetic model and mass transfer model, suggesting that sorption kinetics were the combination of chemisorption and external mass transfer. The Redlich-Peterson model fitted better than the Langmuir and Freundlich models in simulating the adsorption isotherm data, again suggesting a hybrid chemical reaction-sorption process. The Dubinin–Radushkevich isotherm model resulted in an adsorption energy of 10.0kJ/mol, implying a chemisorption between Cr(VI) and CMC-FeS@biochar. The present study demonstrated the promise of CMC-FeS@biochar composite as a low-cost, “green”, and effective sorbent for removal of Cr(VI) in the environment.
FeS-coated iron (Fe/FeS) magnetic nanoparticles were easily prepared, characterized, and applied for Cr(VI) removal in simulated groundwater. TEM, XRD, and BET characterization tests showed that FeS ...coating on the surface of Fe0 inhibited the aggregation of Fe0 and that Fe/FeS at a S/Fe molar ratio of 0.207 possessed a large surface area of 62.1m2/g. Increasing the S/Fe molar ratio from 0 to 0.138 decreased Cr(VI) removal by 42.8%, and a further increase to 0.207 enhanced Cr(VI) removal by 63% within 72h. Moreover, Fe/FeS inhibited the leaching of Fe, reducing the toxicity of the particles. Mechanistic analysis indicated that Fe0, Fe2+, and S2− were synergistically involved in the reduction of Cr(VI) to nontoxic Cr(III), which further precipitated as (CrxFe1-x)(OH)3 and Cr(III)-Fe-S. The process of Cr(VI) sorption by Fe/FeS (S/Fe=0.207) was fitted well with a pseudo-second-order kinetic model, and the isotherm data were simulated by Langmuir isotherm model with a maximum sorption capacity of 69.7mg/g compared to 48.9mg/g for Fe0. Low pH and initial Cr(VI) concentration favored Cr(VI) removal. Continuous fixed bed column studies showed that simulated permeable reactive barriers (PRB) with Fe/FeS was considerably effective for in situ removal of Cr(VI) from groundwater. This study demonstrated the high potential of Fe/FeS for Cr(VI) immobilization in water, groundwater, and soil.
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•FeS coated on Fe0 surface, effectively inhibited Fe0 aggregation, and formed Fe/FeS•Increasing S/Fe molar ratio from 0.138 to 0.207 enhanced Cr(VI) removal by 63%•Fe/FeS inhibited the leaching of Fe, reducing the toxicity of the particles•Fe/FeS removed aqueous Cr(VI) mainly by adsorption, reduction, and precipitation•Fe/FeS effectively removed Cr(VI) through batch and column tests
The occurrence of microplastics (MPs) in the environment has been gaining widespread attention globally. MP-colonizing microorganisms are important links for MPs contamination in various ecosystems, ...but have not been well understood. To partially address this issue, the present study investigated biofilm formation by microorganisms originating from lake water on low-density polyethylene (LDPE) MPs using a cultivation approach and the surface-related effects on the MP-associated microbial communities using 16S rRNA high-throughput sequencing. With the addition of nonionic surfactants and UV-irradiation pretreatment that changed the surface properties of LDPE MPs, more microorganisms were colonized on LDPE surface. Microbial community analysis indicated that LDPE MPs were primarily colonized by the phyla Proteobacteria, Bacteroidetes and Firmicutes, and the surface roughness and hydrophobicity of MP were important factors shaping the LDPE MP-associated microbial community structure. Half of the top 20 most abundant genera colonizing on LDPE were found to be potential pathogens, e.g., plant pathogens Agrobacterium, nosocomial pathogens Chryseobacterium and fish pathogens Flavobacterium. This study demonstrated rapid bacterial colonization of LDPE MPs in lake water microcosms, the role of MPs as transfer vectors for harmful microorganisms in lake water, and provided a first glimpse into the effect of surface properties on LDPE MP-associated biofilm communities.
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•Investigated bacterial colonization of LDPE MPs in lake water microcosms.•Surfactant addition and UV-pretreatment enhanced biofilm colonization of LDPE MPs.•LDPE MP-associated biofilm communities affected by the surface properties of MP.•Half of the top 20 most abundant genera colonized on LDPE were potential pathogens.•Pathogens colonized on LDPE MPs also affected by the surface properties of MP.
Environmental lake water bacteria including potential pathogens can rapidly colonize LDPE MPs, and the surface properties of LDPE MPs affect MP-associated biofilm communities.
An increasing number of reports have been published concerning microplastic (MP) pollution in aquatic environments. Methods used in these studies continue to be updated and lack standardization, so ...that an up-to-date review pertaining methods for MP research is needed. This critical review examines the analytical methods, including sampling, identification, and quantitation, for MP research. Samples are generally collected from water, sediment, and biota gastrointestinal tract. Manta nets or trawls are prevalently used in surface water sampling, while direct shoveling or box-corer grab are commonly applied in sediment sampling. Microplastics in biota are generally obtained by dissecting organisms and separating livers, gills, and guts. Density separation is frequently chosen to separate MPs from sample matrices. Chemical digestion can dissolve other organic materials and isolate MPs for further identification. Visual sorting should be combined with chemical composition analysis to better identify the polymer type. Pyrolysis or thermal decomposition gas chromatography coupled with mass spectrometry, Fourier transform infrared spectroscopy, and Raman spectroscopy are currently the main technologies for MP identification. Units prevalently used to express MP abundance in water, sediment, and biota are “particles per m
3
,” “particles per m
2
,” and “particles per individual,” respectively. As MP abundances often varied with the methods used, we recommend that analytical protocols of MPs should better be standardized and optimized. Despite the important progress in analysis of MPs, detection technologies for identifying nano-sized plastic particles are still lacking, and therefore should be developed swiftly.
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•Stratified EPS fractions extracted from Geobacter biofilms using three methods.•Ultrasound-based extraction method led to higher EPS yield and less cell lysis.•Ultrasound-based ...method extracted more redox-active proteins.•EET function of TB-EPS and total EPS positively related with protein content.
Extracellular polymeric substances (EPS) play crucial roles in promoting biofilm formation and contribute to electrochemical activities of biofilms in bioelectrochemical systems (BES). In this study, three stratified EPS fractions were extracted from Geobacter biofilms using EDTA-, ultrasound- and heating-based protocols and characterized with chemical, spectral and electrochemical analyses. Results suggested that, for Geobacter biofilms, ultrasound-based extraction protocol was more effective in EPS yield (62.1–66.5 mg C/g dry cell) than EDTA method, and had less cell lysis than heating method. The extraction methods greatly affected the proteins composition in the extracted EPS, indicated by the varied ratios of tryptophan/tyrosine protein-like substances. Electrochemical measurements demonstrated a good correlation between protein concentration and extracellular electron transfer function for both tightly-bound EPS and total EPS. This is the first study to extract and characterize stratified EPS fractions from Geobacter biofilms, and helpful for better understanding the function of EPS in BESs predominated by Geobacter.
Plastic pollution derived from the disposal of plastic bags in the environment is clearly evidenced. However, little attention has been directed towards plastic waste derived from plastic dog poop ...bags (DPBs), which are widely used and can never be recycled. Herein, we raise concerns about the contribution of DPBs to plastic pollution in the environment. Combining the weight of each DPB, the number of bags daily used for a dog, and the number of pet dogs around the world, we estimated the number of annual consumed and disposed DPBs at more than 415 billion, or equivalently 0.76–1.23 million tons of plastics based on various weights of different DPBs. Although plastic waste produced by DPBs only accounts for a small fraction (0.6%) of the total plastic waste generation, the extremely short life cycle of DPBs has made them a non-negligible source of plastic pollution in the environment.
•Approximately 0.76–1.23 million tons of global dog poop bags (DPBs) are disposed annually.•Plastic waste produced by DPBs accounts for 0.6% of total plastic waste generation in mass.•Disposed DPBs is a non-negligible source of plastic pollution in the environment.
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