Presence of microplastics in water, sediments and fish species in an urban coastal environment of Fiji, a Pacific small island developing state

Microplastics (MP) in the marine environment are widely reported. However, MP occurrence in some geographical areas such as from Small Island Developing States (SIDS) is missing. The main aim of this study was to assess MP levels in the urban coastal environment of Suva, the capital of the Republic of Fiji. Microplastics were measured from surface water, sediments and fish gastrointestinal tracts (GI) from three sites adjacent to Suva. In addition, an evaluation on the contribution from the local sewage treatment plant to MP levels was undertaken. In general, low levels of MP in water and sediments were detected, but significant differences were observed among sites. The sewage treatment plant was shown to contribute to MP levels in sediment but not in water. Species ingestion of MP was high and associated with MP in sediments. Fibres and fragments were the predominant type of MP, and fifteen different polymers were detected, with higher percentages of polyethylene, latex and polypropylene. In conclusion, MP were found in Suva coastal environment and these MP were associated to land based human activities.

Reaction Mechanism and Mechanical Property Improvement of Poly(Lactic Acid) Reactive Blending with Epoxy Resin

Polylactic acid (PLA) was melt-blended with epoxy resin to study the effects of the reaction on the mechanical and thermal properties of the PLA. The addition of 0.5% (wt/wt) epoxy to PLA increased the maximum tensile strength of PLA (57.5 MPa) to 67 MPa, whereas the 20% epoxy improved the elongation at break to 12%, due to crosslinking caused by the epoxy reaction. The morphology of the PLA/epoxy blends showed epoxy nanoparticle dispersion in the PLA matrix that presented a smooth fracture surface with a high epoxy content. The glass transition temperature of PLA decreased with an increasing epoxy content owing to the partial miscibility between PLA and the epoxy resin. The Vicat softening temperature of the PLA was 59 °C and increased to 64.6 °C for 0.5% epoxy. NMR confirmed the reaction between the -COOH groups of PLA and the epoxy groups of the epoxy resin. This reaction, and partial miscibility of the PLA/epoxy blend, improved the interfacial crosslinking, morphology, thermal properties, and mechanical properties of the blends.

Measurement and daily consumption of microplastics in drinking water from a Small Island Developing State-Fiji: from freshwater to groundwater sources

The occurrence of microplastics (MPs) in drinking water has emerged as a significant source of this contaminant, posing an increased risk to human health. These MPs are now of extreme concern, especially on the possible harmful effects it may have on human health. This study is the first baseline MPs data in drinking water from Fiji. Raw, treated, tap, rain, ground, and bottled water were investigated for the presence of MPs and the ingestion rate by the different age groups. The analytical procedure was validated by determining recovery rates and analyses of blanks. The detection limit of the MPs was 10 µm, while fibers and particles ≥ 100 µm were analyzed on 100% of the filter area. The abundance of MPs in drinking water was source-dependent. Percentage removal of MPs from water treatment plants was 45-67%, resulting in the presence of 0.10 ± 0.03 to 2.90 ± 0.57 MPs L-1 in tap water. The presence of MPs in bottled, rain, and groundwater was in the range of 0 to 2.20 ± 0.41 MPs L-1. Fiber MPs predominated in all water sources except for bottled water. Main types of polymer identified were polyethylene, polypropylene, and poly(ethylene terephthalate). Estimated daily intake of MPs in tap water by children and adults were 0.0031-0.1813 and 0.0021-0.0829 MPs/kg bw/day, respectively. Information from this work in combination with information from the health sector will help to fully understand microplastic impact on human health and the actions that are required to mitigate it.

Towards sustainable microplastic cleanup: Al/Fe ionotropic chitosan hydrogels for efficient PET removal

Chitosan (CHI) was modified with iron and aluminum salts to create ionotropic beads, Fe-CHI and Al-CHI, for the removal of polyethylene terephthalate microplastics (PET-MP) from water. Infrared spectroscopy revealed reduced hydrogen bonding associated with N-H vibration of CHI (3500-3100 cm-1) due to the interaction with the metal ions, and absorption peaks between 500 and 916 cm⁻1 predominantly due to metal-oxygen stretching vibrations. The swelling behavior of the beads increased with temperature but decreased as pH and metal doping concentration increased. Conductivity and PET-MP removal efficiency improved with higher metal ion concentrations, with Al-CHI exhibiting greater swelling and conductivity compared to Fe-CHI. The highest efficiency for MP remediation was recorded at low pH levels. MP adsorption decreased with rising temperatures and varied with pH changes due to protonation and deprotonation reactions of CHI, along with the various cationic and anionic species formed by the metals. At pH 7, MP removal by Fe-CHI beads declined as the doping concentration increased, attributed to specific Fe species that emerged at this pH. The zeta potential measurements showed that both the beads and the MP were in an unstable range at low pH but shifted towards stability at higher pH levels. Re-adsorption efficiencies exceeded 70% for both low and high-doped Fe-CHI and Al-CHI beads when tested with ~ 40 MP/mL of MP suspension over three different cycles. Overall, the use of ionotropic CHI beads offers a promising, eco-friendly method for effectively reducing PET-MPs in water.