There is increasing concern about the environmental behaviors of microplastics (MPs), in particular fine MPs (FMPs), such as their concentrations, sources, size distributions, and fragmentation by weathering in waters. However, there is little information about size distributions of MP polymer types and their relationships to their sources. Here, we analyzed concentrations, compositions, and size distributions of 18 polymer types of MPs of >20 μm by micro-Fourier transform infrared spectroscopy with a novel pretreatment method in surface waters at five sites from the headwaters to the mouth of a Japanese river, and in influent and effluent from a sewage treatment plant (STP). The microplastic concentrations ranged from 300 to 1240 particles/m³ in surface waters. Cluster analysis identified two primary sources of MPs: residential wastewater at the headwater site and non-point sources from urban areas at downstream sites; concentrations of chemical contaminants from STPs were much higher at the downstream sites. The median particle sizes (D₅₀) of MPs increased in urban areas at the downstream sites and were larger than those in influent and effluent. These results imply the release of larger MPs from non-point sources in urban areas. The size distributions of each polymer and all MPs could be fitted significantly to the Weibull distribution function. Values of D₅₀, shape parameters, and scale parameters estimated from the functions were useful indicators for evaluating size distributions in detail. A significant positive correlation of D₅₀ with the tensile strengths of virgin polymers among 13 dominant polymers detected in the surface water suggests that the fragmentation properties of each polymer are influenced by its physical strength. Multidimensional analysis with concentrations, polymeric compositions, and size distributions of MPs, including FMPs, could provide useful information about their sources and their environmental behaviors.

To enable and/or facilitate analysis of microplastics from environmental samples, a purification process is required to reduce the organic matter content. The development of such process has as one main concern, besides achieving efficient organic matter reduction, the preservation of the microplastics. In this study, a three-step method for sewage sludge purification was proposed employing sodium dodecyl sulfate and hydrogen peroxide. The effects of the purification method on seven polymers (LLDPE, HDPE, PP, PS, PET, PA66 and SBR) were evaluated in terms of mass change, surface characteristics, mechanical properties, thermal properties and functional groups change. It was also assessed how the polymers were affected by the purification chemicals without the presence of sewage sludge. The purification process led to changes in all tested plastics, but in different intensities. LLDPE, HDPE, PP, PS and PET did not suffer considerable degradation. PET was more affected by hydrolysis than oxidation. On the other hand, the integrities of PA66 and SBR were noticeably affected. The effects of the purification process were considered to be due to the plasticizer behavior of water and oxidation on PA66 and loss of filler and oxidation on SBR. For both polymers there was a reduction on the tensile strength of around 50–60% after the purification, indicating they could be prone to fragmentate into smaller pieces along the process. After purification, PA66 also started to decompose at a temperature around 10 °C lower comparing to virgin samples. Except for SBR, the presence of sewage sludge and its oxidation was more harmful to the polymers than the purification chemicals without the presence of sewage sludge. This study serves as an evaluation of the effects of the purification process on the degradation of microplastics and a methodology for such assessment when designing a purification process.

Abandoned gillnets in the marine environment represent a global environmental risk due to the ghost fishing caused by the nets. Degradation of conventional nylon gillnets was compared to that of nets made of polybutylene succinate co-adipate-co-terephthalate (PBSAT) that are designed to degrade more readily in the environment. Gillnet filaments were incubated in microcosms of natural seawater (SW) and marine sediments at 20 °C over a period of 36 months. Tensile strength tests and scanning electron microscopy analyses showed weakening and degradation of the PBSAT filaments over time, while nylon filaments remained unchanged. Pyrolysis-gas chromatography/mass spectrometry revealed potential PBSAT degradation products associated with the filament surfaces, while nylon degradation products were not detected by these analyses. Microbial communities differed significantly between the biofilms on the nylon and PBSAT filaments. The slow deterioration of the PBSAT gillnet filaments shown here may be beneficial and reduce the ghost fishing periods of these gillnets.

Polyvinyl chloride (PVC) is the third one after polyethylene and polypropylene in the production demand. It intends to grow further, causing an increase in the risk of health and ecological problems due to environmental accumulation and incineration. In the present study, we determined the biodegradative abilities of marine bacteria for PVC. Three potential marine bacterial isolates, T-1.3, BP-4.3 and S-237 (Vibrio, Altermonas and Cobetia, respectively) were identified after preliminary screening. They led to active biofilm formation, viability and protein formation on the PVC surface. The highest weight loss (1.76%) of PVC films was exhibited by BP-4.3 isolate after 60 days of incubation. Remineralization of PVC film was confirmed by CO₂ assimilation assay. Change in surface topography was confirmed by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The functional group peak intensity was decreased for the terminal chlorine group at the region 1000–1300 cm⁻¹, which indicated the dechlorination. Thermogravimetric, tensile strength and contact angle analysis showed a decline in the mechanical properties and a rise in PVC film's hydrophilic nature after biodegradation. These results demonstrated promising evidence of PVC degradation by marine bacteria.

Polyethylene is a commonly used polymer in plastic products and is often found as marine litter. Nevertheless there is limited knowledge about what happens to the material when it ends up in the sea. Polyethylene films were therefore thermally oxidised to four different levels of degradation. The films were then placed in stainless-steel cages in the sea off the Swedish west coast for 12 summer weeks. Subsamples were analysed with respect to biofouling, degradation and buoyancy. All levels showed a continued oxidation in the field. The pre-degraded films started fragmenting and the non-degraded films showed a decrease in tensile strain. All levels showed increased biofouling with higher presence of filamentous algae and bryozoans on pre-degraded materials. The density (kg·m−3) of the films was seen to increase slightly, and the apparent density for the pre-degraded films (density of the films with biofilm) showed a strong increase, which resulted in sinking.

Contamination by microplastic particles and fibres has been observed in sediment and animals sampled from the Firth of Clyde, West Scotland. In addition to microplastics released during clothes washing, a probable source is polymer ropes in abandoned, lost and discarded fishing and recreational sailing gear. The fragmentation of polypropylene, polyethylene, and nylon exposed to benthic conditions at 10m depth over 12months was monitored using changes in weight and tensile properties. Water temperature and light levels were continuously monitored. The degree of biofouling was measured using chlorophyll a, the weight of attached macroalgae, and colonising fauna. Results indicate microplastic fibres and particles may be formed in benthic environments despite reduced photodegradation. Polypropylene, Nylon, and polyethylene lost an average of 0.39%, 1.02%, and 0.45% of their mass per month respectively. Microscope images of the rope surface revealed notable surface roughening believed to be caused by abrasion by substrate and the action of fouling organisms.

Demand for particleboards keeps increasing and as such more trees are fell for its production, engendering deforestation. For the purpose of reducing falling of trees, this study, focused on recycling of waste paper in the development of paperboard as alternative to particleboards used for furniture and interior household applications. Kenaf fiber (KF) was blended at varying proportions of 0, 1, 2, 3, 4, and 5 wt.% with 20 wt.% constant cement and 20 wt.% constant coconut shell powder while the remaining was paper pulp. Board specimen developed were cured for 14, 28, and 90 days and mechanical properties were examined. Results obtained showed that fiber dosage improved bond strength and screw holding strengths as compared with the control mix. Similarly, modulus of rupture was enhanced with KF loading as compared with control mix while 1 to 3 wt.% KF spawned enhancement of modulus of elasticity. However, 4 and 5 wt.% KF led to a reduction in the modulus. Infusion of the fiber enhanced tensile strength from 1 to 3 wt.% content. 14-day and 28-day curing periods were observed to improve properties while the 90-day curing period is detrimental to all properties. Optimization via signal-to-noise ratio revealed an optimum mix of 2 wt.% obtained for fiber and an optimum curing duration of 28 days.

Cold recycling techniques emerged in road construction to recycle deteriorated pavements as bases and surfaces. A detailed review is carried out in the current study on the design, evaluation, performance, and advances in the emulsified asphalt-treated bases (EATB). The mix-design of EATB is a complex procedure in which the performance is based on optimizing water, additives, and emulsified asphalt contents. This paper covers the design methods, compaction characteristics, curing periods, additive contents, strength development, strength parameters, determination of the optimum emulsified asphalt content, and finally, the performance evaluation of EATB. From the detailed review, indirect tensile strength (ITS) is the most influencing parameter considered in the mix design of the EATB. Maximum dry density, Marshall Stability, and ITS are considered as primary performance indicators of the EATB. Modulus, rutting, and fatigue being consider secondary performance indicators. Overall, the recycled bases using emulsified asphalt proved sustainable and economical compared with the natural aggregates (NA).

Concrete is one of the most important materials that are used in the construction industry all around the world. A larger part of the capacity in concrete is generally employed by the coarse aggregate. Due to the tremendous use of coarse aggregate in the construction industry, the material is getting degraded. In order to preserve the natural material, we are in search of an alternate material that can be used in concrete instead of the original one. So in this research work, it has been attempted to study the mechanical behaviour of lightweight concrete when we use waste coconut shell as coarse aggregate inside concrete. To improve the strength of the concrete, we also use the sisal fibres in various proportions ranging between 1 and 5% in accordance to the binder weight. After the mechanical property tests such as the compression test, spilt tensile strength, flexural test, modulus of elasticity test, and impact resistant test were conducted, finally it was concluded that there was increment in the compression strength up to 5%, and tensile strength was increased to 17% and elastic modulus to 7% when the fibre content used was 3%. Thus, with the use of these waste materials, it was found that the concrete’s strength gets increased and it leads to the formation of sustainable concrete thus reducing the pollution in the environment.

The production of cement contributes to 10% of global carbon dioxide (CO₂) pollution and 74 to 81% towards the total CO₂ pollution by concrete. In addition to that, its low strength-to-weight ratio, high density and thermal conductivity are among the few limitations of heavy weight concrete. Therefore, this study was carried out to provide a solution to these limitations by developing innovative eco-friendly lightweight foamed concrete (LFC) of 1800 kg/m³ density incorporating 20–25% palm oil fuel ash (POFA) and 5–15% eggshell powder (ESP) by weight of total binder as supplementary cementitious material (SCM). The influence of combined utilization of POFA and ESP on the fresh state properties of eco-friendly LFC was determined using the J-ring test. To determine the mechanical properties, a total of 48 cubes and 24 cylinders were prepared for compressive strength, splitting tensile strength and modulus of elasticity each. A total of 24 panels were prepared to determine the thermal properties in terms of surface temperature and thermal conductivity. Furthermore, to assess the environmental impact and eco-friendliness of the developed LFC, the embodied carbon and eco-strength efficiency was calculated. It was determined that the utilization of POFA and ESP reduced the workability slightly but enhanced the mechanical properties of LFC (17.05 to 22.60 MPa compressive strength and 1.43 to 2.61 MPa tensile strength), thus satisfies the ACI213R requirements for structural lightweight concrete and that it can be used for structural applications. Additionally, the thermal conductivity reduced ranging from 0.55 to 0.63 W/mK compared to 0.82 W/mK achieved by control sample. Furthermore, the developed LFC showed a 16.96 to 33.55% reduction in embodied carbon and exhibited higher eco-strength efficiency between 47.82 and 76.97%. Overall, the combined utilization of POFA and ESP as SCMs not only enhanced the thermo-mechanical performance, makes the sustainable LFC as structural lightweight concrete, but also has reduced the environmental impacts caused by the disposal of POFA and ESP in landfills as well as reducing the total CO₂ emissions during the production of eco-friendly LFC.