Fate Of Micro Research Articles

A review on the fate of micro and nano plastics (MNPs) and their implication in regulating nutrient cycling in constructed wetland systems

This review discusses the micro-nano plastics (MNPs) and their interaction with physical, chemical and biological processes in a constructed wetland (CW) system that is typically used as a nature-based tertiary wastewater treatment for municipal as well as industrial applications. Individual components of the CW system such as substrate, microorganisms and plants were considered to assess how MNPs influence the CW processes. One of the main functions of a CW system is removal of nutrients like nitrogen (N) and phosphorus (P) and here we highlight the pathways through which the MNPs influence CW's efficacy of nutrient removal. The presence of morphologically (size and shape) and chemically different MNPs influence the growth rate of microorganisms important in N and P cycling, invertebrates, decomposers, and the plants which affect the overall efficiency of a CW treatment system. Certain plant species take up the MNPs, and some toxicity has been observed. This review focuses on two significant aspects: (1) the presence of MNPs in a significant concentration affects the efficiency of N and P removal, and (2) the removal of MNPs. Because MNPs reduce the enzyme activities in abundance and overproduction of ROS oxidizes the enzyme active sites, resulting in the depletion of proteins, ultimately inhibiting nitrogen and phosphorus removal within the substrate layer. The review found that the majority of the studies used sand-activated carbon (SAC), granular-activated carbon (GAC), rice straw, granular limestone, and calcium carbonate, as a substrate for CW treatment systems. Common plant species used in the CW include Phragmites, Arabidopsis thaliana, Lepidium sativum, Thalia dealbata, and Canna indica, which were also found to be dominant in the uptake of the MNPs in the CWs. The MNPs were found to affect earthworms such as Eisenia fetida, Caenorhabditis elegans, and, Enchytraeus crypticus, whereas Metaphire vulgaris were found unaffected. Though various mechanisms take place during the removal process, adsorption and uptake mechanism effectively emphasize the removal of MNPs and nitrogen and phosphorus in CW. The MNPs characteristics (type, size, and concentration) play a crucial role in the removal efficiency of nano-plastics (NPs) and micro-plastics (MPs). The enhanced removal efficiency of NPs compared to MPs can be attributed to their smaller size, resulting in a faster reaction rate. However, NPs dose variation showed fluctuating removal efficiency, whereas MPs dose increment reduces removal efficiency. MP and NPs dose variation also affected toxicity to plants and earthworms as observed from data. Understanding the fate and removal of microplastics in wetland systems will help determine the reuse potential of wastewater and restrict the release of microplastics. This study provides information on various aspects and highlights future gaps and needs for MNP fate study in CW systems.

Unraveling the in vivo fate of inhaled micro- and nanoplastics with PET imaging

Microplastics and nanoplastics have become ubiquitous environmental pollutants. The threat these plastics pose to human health has fueled research focused on their pathophysiology and toxicology, yet many of their fundamental properties — for example, their in vivo pharmacokinetics — remain poorly understood. In this investigation, we have harnessed positron emission tomography (PET) to track the in vivo fate of micro- and nanoplastics administered to mice intratracheally and intravenously. To this end, 1 μm and 20 nm diameter amine-functionalized polystyrene particles were modified with an isothiocyanate-bearing variant of desferrioxamine (DFO) and radiolabeled with the positron-emitting radiometal [89Zr]Zr4+. Both radioplastics — [89Zr]Zr-DFO-PS1000 and [89Zr]Zr-DFO-PS20 — were produced in ∼95% radiochemical yield and found to be >85% stable to demetallation over one week at 37 °C in human serum and simulated lung fluid. The incubation of [89Zr]Zr-DFO-PS1000 and [89Zr]Zr-DFO-PS20 with MH-S cells revealed that the majority of the former were phagocytosed by alveolar macrophages within 4 h, while the latter largely evaded consumption. Finally, the in vivo behavior of the radioplastics was interrogated in mice upon intravenous and intratracheal administration. PET imaging and biodistribution experiments revealed that the intravenously injected plastics accumulated primarily in the liver and spleen, yielding hepatic radioactivity concentrations of 101 ± 48 %ID/g and 92 ± 22 %ID/g at 168 h post-injection for [89Zr]Zr-DFO-PS1000 and [89Zr]Zr-DFO-PS20, respectively. In contrast, the mice that received the radioplastics via intratracheal installation displayed the highest uptake in the lungs at the end of one week: 4 ± 2 %ID/g for [89Zr]Zr-DFO-PS1000 and 32 ± 6 %ID/g for [89Zr]Zr-DFO-PS20. Ultimately, this work illustrates the critical role that the route of exposure plays in the bioaccumulation of plastic particles, reveals that size dramatically influences the pulmonary retention of inhaled particles, and underscores the value of PET imaging as a tool for studying the pharmacokinetics of environmental pollutants.

Variability of Micro- and Macro-Elements in Anaerobic Co-Digestion of Municipal Sewage Sludge and Food Industrial By-Products.

The main aim of this study was to evaluate the effect of the addition of selected industrial food wastes on the fate of micro- and macro-elements within an anaerobic digestion process (AD), as well as define the relationship between their content and AD efficiency. Orange peels, (OP), orange pulp (PL) and brewery spent grain (BSG) were used as co-substrates, while municipal sewage sludge (SS) was applied as the main component. The introduction of co-substrates resulted in improvements in feedstock composition in terms of macro-elements, with a simultaneous decrease in the content of HMs (heavy metals). Such beneficial effects led to enhanced methane production, and improved process performance at the highest doses of PL and BSG. In turn, reduced biogas and methane production was found in the three-component digestion mixtures in the presence of OP and BSG; therein, the highest accumulation of most HMs within the process was also revealed. Considering the agricultural application of all digestates, exceedances for Cu, Zn and Hg were recorded, thereby excluding their further use for that purpose.

The fate of plastic litter within estuarine compartments: An overview of current knowledge for the transboundary issue to guide future assessments.

Plastics can enter biogeochemical cycles and thus be found in most ecosystems. Most studies emphasize plastic pollution in oceanic ecosystems even though rivers and estuaries are acknowledged as the main sources of plastics to the oceans. This review detected few studies approaching the transboundary issue, as well as patterns of estuarine gradients in predicting plastic distribution and accumulation in water, sediments, and organisms. Quantities of plastics in estuaries reach up to 45,500 items m-3 in water, 567,000 items m-3 in sediment, and 131 items per individual in the biota. The role of rivers and estuaries in the transport of plastics to the ocean is far from fully understood due to small sample sizes, short-term approaches, sampling techniques that underestimate small plastics, and the use of site-specific sampling rather than covering environmental gradients. Microfibres are the most commonly found plastic type in all environmental matrices but efforts to re-calculate pathways using novel sampling techniques and estimates are incipient. Microplastic availability to estuarine organisms and rising/sinking is determined by polymer characteristics and spatio-temporal fluctuations in physicochemical, biological, and mineralogical factors. Key processes governing plastic contamination along estuarine trophic webs remain unclear, as most studies used "species" as an ecological unit rather than trophic/functional guilds and ontogenetic shifts in feeding behaviour to understand communities and intraspecific relationships, respectively. Efforts to understand contamination at the tissue level and the contribution of biofouling organisms as vectors of contaminants onto plastic surfaces are increasing. In conclusion, rivers and estuaries still require attention with regards to accurate sampling and conclusions. Multivariate analysis and robust models are necessary to predict the fate of micro- and macroplastics in estuarine environments; and the inclusion of the socio-economic aspects in modelling techniques seems to be relevant regarding management approaches.

In vitro localisation and degradation of few-layer MoS2 submicrometric plates in human macrophage-like cells: a label free Raman micro-spectroscopic study

Monitoring the uptake, micro-environment and fate of micro or nano scaled particulate materials in cells is of paramount importance for the emerging fields of toxicology and medicine. Such particulate materials are known to interfere with colorimetric assays and many such assays record only a single end-point. Therefore, there is a need for a label-free, cost effective technique with little or no inference from the particulate materials.Raman micro-spectroscopy was used to simultaneously interrogate the integrity of few-layer MoS2 submicrometric plates in human macrophage-like cells, in vitro, as well as the biochemical characteristics of the local micro-environment in which they are encompassed. Firstly, the degradation profile of MoS2 plates induced by hydrogen peroxidase was established using UV–vis absorption and Raman micro-spectroscopy. Raman micro-spectroscopic maps interrogated all aspects of the cell, including the nucleus, cytoplasm and perinuclear region, and the location/distribution of MoS2 was monitored as a function of time (4, 24 and 72 h). Whereas only pristine MoS2 was detectable after 4 and 72 periods, degradation in vitro was confirmed following a 24 h incubation. Analysis of the MoS2 micro-environments revealed the presence of both phosphatidyl lipidic vesicles and enzymatic regions containing lysozyme, the former being most associated with the MoS2 degradation. There was an increase and saturation of cytosolic neutral lipids detected following a 24 h incubation with MoS2, which reduces following a prolonged incubation of 72 h. This study reveals that macrophage-like cells perform degradation of the material in vitro within lipidic vesicles subsequent to phagocytosis, which manifest as an increase in the production of lipid bodies as a mechanism of defense following exposure to industrial grade MoS2.

Predictors of Bubble Formation and Type Obtained With Pneumatic Dissection During Deep Anterior Lamellar Keratoplasty in Keratoconus

To identify predictors of bubble formation and type during big-bubble deep anterior lamellar keratoplasty (BB-DALK) performed in keratoconus at different stages of severity. Retrospective Cohort Study. Setting: University Magna Græcia (Catanzaro, Italy); Study Population: Consecutive keratoconus patients undergoing BB-DALK from September 2014 to February 2019. Keratometric astigmatism, mean keratometry value (K-mean), highest keratometry value (K-max), thinnest point, anterior segment optical coherence tomography (AS-OCT)-based stage of ectasia. Rate of bubble formation and type; number and fate of micro-/macroperforation; conversion to mushroom keratoplasty (MK); comparison of parameters in patients with bubble formation vs failure and in type 1 vs type 2 bubble; areas under the curves (AUC) of preoperative parameters for distinguishing between bubble types. Pneumatic dissection succeeded in 113 of 155 eyes (72.9%), with 100 type 1 bubbles (88.4%), 11 type 2 (9.8%), and 2 mixed-type (1.8%). Microperforations were managed conservatively in type 1 bubbles; macroperforations occurring in both types of bubbles required conversion to MK. Preoperative K-mean and K-max values were significantly higher in eyes in which bubble formation succeeded (respectively, P= .006 and P < .013). Type 1 bubbles formed in eyes with significantly lower age, K-mean, and AS-OCT stages and higher pachymetric values (always P < .029). Age had the highest diagnostic power for discrimination between bubble types, followed by AS-OCT stage, pachymetry, K-mean, and astigmatism (respectively, AUC= 0.861, 0.779, 0.748, 0.700, 0.670). Older age and advanced stages of keratoconus were predictors of type 2 bubble formation during BB-DALK that was associated with an increased risk of complications.