A review on decoding the cellular and ecological risks of polypropylene microplastics

Hazard assessment of airborne and foodborne biodegradable polyhydroxyalkanoates microplastics and non-biodegradable polypropylene microplastics.

Internal interaction between chemically-pretreated polypropylene microplastics and floc growth during flocculation: Critical effect on floc properties and flocculation mechanisms

Microplastic pollution is globally recognised as a serious environmental threat due to its ubiquitous presence related primarily to improper dumping of plastic wastes. While most studies have focused on microplastic contamination in the marine ecosystem, microplastic pollution in the soil environment is generally little understood and often overlooked. The presence of microplastics affects the soil ecosystem by disrupting the soil fertility and quality, degrading the food web, and subsequently influencing both food security and human health. This study evaluates the growth and biodegradation potential of the Antarctic soil bacteria Pseudomonas sp. ADL15 and Rhodococcus sp. ADL36 on the polypropylene (PP) microplastics in Bushnell Haas (BH) medium for 40 days. The degradation was monitored based on the weight loss of PP microplastics, removal rate constant per day (K), and their half-life. The validity of the PP microplastics’ biodegradation was assessed through structural changes via Fourier transform infrared spectroscopy analyses. The weight loss percentage of the PP microplastics by ADL15 and ADL36 after 40 days was 17.3% and 7.3%, respectively. The optimal growth in the BH media infused with PP microplastics was on the 40th and 30th day for ADL15 and ADL36, respectively. The infrared spectroscopic analysis revealed significant changes in the PP microplastics’ functional groups following the incubation with Antarctic strains.

Reeds (Phragmites australis) modulate the impacts of microplastics on carbon and nitrogen metabolisms in wetland soil.

Microplastic (MP) pollution is a growing concern and various methods are being sought to alleviate the level of pollution worldwide. This study investigates the biodegradation capacity of MPs by indigenous microorganisms of raw water from Tehran drinking water treatment plants. By exposing polypropylene (PP) and polyethylene (PE) MPs to selected microbial colonies, structural, morphological, and chemical changes were detected by scanning electron microscope (SEM), cell weight measurement, Fourier transform infrared (FTIR), Raman spectroscopy test, and thermal gravimetric analysis (TGA). Selected bacterial strains include Pseudomonas protegens strain (A), Bacillus cereus strain (B), and Pseudomonas protegens strain (C). SEM analysis showed roughness and cracks on PP MPs exposed to strains A and C. However, PE MPs exposed to strain B faced limited degradation. In samples related to strain A, the Raman spectrum was completely changed, and a new chemical structure was created. Both TGA and FTIR analysis confirmed changes detected by Raman analysis of PP and PE MPs in chemical changes in this study. The results of cell dry weight loss for microbial strains A, B, and C were 13.5, 38.6, and 25.6%, respectively. Moreover, MPs weight loss was recorded at 32.6% for PP MPs with strain A, 13.3% for PE MPs with strain B, and 25.6% for PP MPs with strain C.

Adsorption mechanism of two pesticides on polyethylene and polypropylene microplastics: DFT calculations and particle size effects

The widespread application of micro-plastics (MP) and their release in the open environment has become a matter of worldwide concern. When interacting with contaminants such as heavy metals in the soil ecosystem, MPs can result in detrimental effects on the soil environment and plant growth and development. However, information based on the interaction between MPs and heavy metals and their effects on terrestrial plants is still limited. Keeping this in mind, the present study was conducted to explore the single and combined toxicity of polypropylene (PP) MPs (13 and 6.5 μm) and cadmium (Cd) on germination indices; root and stem growth; fresh and dry weight; and anti-oxidative enzyme activities of rice (Oryza sativa L.) seedlings. Our results indicated that a single application of PP MP and Cd on rice seedlings inhibited most of the germination indicators, while their co-occurrence (PP + Cd) showed a reduction in the overall toxicity to some extent. A single application of both the contaminants significantly inhibited root length, stem length, fresh weight and the activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) enzymes in rice seedling, while no significant effect on dry weight was observed. The combined toxicity of both PP and Cd revealed that 13 μm PP + Cd had an antagonistic effect on the growth of rice seedlings, while 6.5 μm PP + Cd showed a synergistic effect. The present study revealed that smaller PP MP particles (6.5 µm) prominently affected plant growth more as compared to larger particles (13 µm). Our work reported the combined effect of PP MP and Cd on the germination and growth of rice for the first time. This study can provide the basis for future research on the combined effects of different types and sizes of MPs and heavy metals on the terrestrial ecosystem.

Exposure to polypropylene microplastics via diet and water induces oxidative stress in Cyprinus carpio

Plastic films are essential in modern livestock and crop production. According to the Plastics Europe Report 2022, Light Polyethylene (LDPE) and Polypropylene (PP) are the primary plastic material demand in the agricultural sector. Especially for crop production, plastic mulching films cover arable soil to increase temperature, reduce evaporation, and prevent weed growth. However, mechanical and environmental weathering removes microplastics from the mulch film and can stock in the soil. Additionally, sewage sludge and compost use in agriculture lead to further microplastic contamination. Obviously, microplastic input to soils is critically high, but an accurate quantification is still lacking. This is partly caused by challenges in detection and analysis of microplastic in soils. First, it is challenging to extract microplastic from a matrix of organic and inorganic particles of similar size. Second, the well-established spectroscopic methods (e.g., Raman and FTIR) for detecting microplastics in water samples are sensitive to soil organic matter, and they are very time-consuming. Eliminating very stable organic particles (e.g., lignin) from soil samples without affecting the microplastic to be measured is another challenge. Hence, a robust analytical approach to detect microplastic in soils is needed. In this context, we developed a methodological approach that is based on a high-throughput (25 g soil sample) density separation scheme for measurements in a 3D Laser Scanning Confocal Microscope (Keyence VK-X1000, Japan) and subsequently using a Machine-Learning algorithm to classify and analyze microplastic in soil samples. Our aim is to develop a method for a fast screening of microplastic particle numbers in soils while avoiding the use of harmful substances (e.g., ZnCl2) or prolonged organic carbon destruction. For method development, we contaminate three different soil types (sandy soil: 86.6% sand, 9.7% silt, 3.7% clay, 0.58% organic carbon; silty loam: 6% sand, 59% silt, 25% clay, 1.3% organic carbon analysis and loamy sand: 72% sand, 18% silt, 10% clay, 0.9% organic carbon) with transparent LDPE, black LDPE and PP microplastic in three different size ranges (< 50, 50 – 100 and 100 – 250 µm). Moreover, we test our method on microplastic fibers (PP, 1000 µm). The separated microplastic plus organic particles and some small mineral particles were scanned using a 3D Laser Scanning Confocal Microscope. For each sample, the 3D Laser Scanning Confocal Microscope generates three different main outputs: color, laser intensity, and surface characteristics with a pixel size of 2.72 µm. Based on these data outputs, a Machine-Learning algorithm distinguishes between the mineral, organic, and microplastic particles. It was found that color changes of microplastics due to soil contact challenge the classification but can be compensated by surface characteristics that become an essential input parameter for the detection. The presented methodological approach provides an accurate and high-throughput microplastic assessment in soil systems, which is critically needed to understand the boundaries of sustainable plastic application in agriculture.

Effects of microplastics and excessive nitrogen pollution on oat growth and soil nitrogen cycling.

Objectives : Recently, microplastics (MPs) is observed at surface water in worldwide because of massive use of plastics. Since MPs have a large specific surface area, they could provide adsorption sites to water contaminants such as Levofloxacin (LVF). LVF is one of widely used antibiotics and is detected in surface water. Therefore, the aim of this study is to evaluate adsorption trend of LVF on polypropylene (PP) and polyethylene(PE) microplastics in aqueous solution.Methods : For kinetic adsorption experiment, 0.02 g of PP and PE MPs were placed in glass vials and mixed with LVF solution (10 mg/L) for 1-48 hours. And the experimental data was fitted to pseudo-first order and pseudo-second order. For isotherm adsorption experiment, initial LVF concentrations were varied from 1 to 25 mg/L for 24 hours and the results were applied to Langmuir and Freundlich models. The Thermodynamic adsorption experiment was conducted in the temperature range of 298-318 K. Each cations (Na+, Ca2+, Cu2+, Cr3+, Pb3+) and LVF solution were both reacted with the MPs to determine effect of LVF adsorption when cations were coexistence.Results and Discussion : Based on the FT-IR analysis, it was confirmed that the prepared PP and PE MPs were consisted of the respective single polymer. The kinetic experiment results showed that LVF adsorption on PP and PE MPs reached equilibrium at 24 hours with adsorption capacities of PP (0.748 mg/g) and PE (0.801 mg/g) MPs, respectively. Kinetic data of PP MPs was well fitted to the pseudo-first order (R2=0.986) model, while the data of PE MPs was described well by the pseudo-second order (R2=0.992) model. The results of the isotherm experiments were explained well by the Freundlich model (R2>0.97), indicating that multilayer adsorption occurred in both MPs. The thermodynamic experiments showed that LVF adsorptions on each MPs were exothermic reaction and physical adsorption process. Cations can inhibit the adsorption of LVF to the MPs.Conclusion : This study shows that LVF could be adsorbed to PP and PE MPs in aqueous solution and its adsorption capacity can be changed according to the various factors: characteristics of polymer, reaction time, initial concentration of LVF, temperature, and coexistence of cations.

Transport of polyethylene and polypropylene microplastics under the action of agricultural chemicals: Role of pesticide adjuvants and neonicotinoid active ingredients

Plastic particles with a diameter of 5 mm or less are called microplastics. Microplastics are one of the primary sources of pollution in the environment. It has been proven that microplastics are also carriers of heavy metals, but there are few studies on their adsorption mechanism. In this study, the adsorption of Pb, Cu, Cd, and Zn by polypropylene (PP) microplastics was analyzed and discussed. The morphology of PP was observed by scanning electron microscopy (SEM), the surface elemental composition of PP was determined by X-ray photoelectron spectroscopy (XPS), and the functional groups of PP were analyzed by Fourier transform infrared spectroscopy (FTIR). The results showed that the adsorption behavior of microplastics to different heavy metals could be balanced in 32 hours. Kinetics experiments showed that the adsorption process could be fitted well by a two-stage dynamic model, and the adsorption of Pb and Cu by PP is greater than that of Cd and Zn. The Freundlich model has the best fitting effect on Pb for the adsorption isothermal results. The Langmuir model showed that the process is favorable for adsorption. The adsorption of mixed heavy metals by microplastics showed that when the concentration of the mixed adsorption mass was low, the presence of a coexistence system promoted the adsorption of Zn and Cu by microplastics. With an increasing concentration, the adsorption of 4 heavy metals by microplastics is inhibited.

Adsorption behaviour of accelerated UV aged PET and PP microplastics towards Pb(II) under varying pH, temperature, and salinity conditions.

Microplastics (MPs) exposed to environmental weathering, particularly UV radiation, undergo significant modifications to their surface properties, thereby enhancing their potential to adsorb and transfer pollutants such as heavy metals (HMs). This study examines the adsorption behavior of zinc (Zn(II)) onto virgin and UV-aged polyethylene terephthalate (PET) and polypropylene (PP) MPs subjected to up to 30 days under UV exposure. The aging process altered the morphological and physicochemical characteristics of the MPs as evidenced by characterization, which revealed the increased surface roughness, cracking, and enhanced hydrophilicity. Surface chemistry changes were further analyzed using FTIR and XRD; revealing the development of new functional groups like carbonyl (C = O) and hydroxyl groups (OH) in association with improved crystallinity indicates the emerging new active adsorption sites. Batch adsorption experiments were conducted under varying aging durations (0 to 30 days) and contact time (0 to 48 h). Results showed that UV aging significantly enhanced Zn(II) adsorption capacity for PET and PP, with adsorption equilibrium reached at 24 h. Kinetic data best fit the PSO model (R2 > 0.95) indicating chemisorption as the dominant mechanism, while the isotherms more closely confirmed to the Langmuir model, suggesting homogeneous monolayer adsorption. This research highlights the understanding of the adsorption behavior of MPs and takes the effect of UV aging into account.