Micro/nano-plastics (MNPs) have been found within many environments and organisms including humans, making them a significant and growing concern. Initial research into the potential detrimental effects these MNPs both from acute and chronic exposure has been ongoing but still requires substantially more data to clarify. This research presents the response of nano-polystyrene (NPS) on Raphidocelis subcapitata, a freshwater alga, under an existing acute toxicity test along with additional analytical techniques to try identifying possible sources of toxicity. R. subcapitata cells were exposed for 72 h to a concentration range of 0-100 mg/l NPS. Growth Inhibition (GI) testing showed the R. subcapitata demonstrated statistically distinct reductions in growth over 72 h at all NPS exposure concentrations while not suffering culture collapse. By the 100 mg/l NPS exposure the R. subcapitata has suffered almost a 33.7% reduction in cell concentration after 72 h compared to control samples. Confocal imaging showed the NPS wasn't permeating into the algal plasma membrane or individual organelles but agglomerated onto the algal cell wall. The agglomeration was irregular but increased in total surface area covered as NPS concentration increases. UV-Vis fluorimetry testing produced a linear response of emission intensities to algae exposed to the 0-100 mg/l range of NPS. However, comparisons of emission intensity values of algae exposed to NPS to emission intensities of pure NPS at identical concentrations showed consistent intensity reduction. This response further indicated NPS agglomerating within the media and onto the alga cells seen from confocal imaging. Finally, Raman spectroscopy on R. subcapitata attempted to distinguish the key 1001 cm^-1 peak or other crucial identifier peaks of polystyrene from overall Raman spectra. This was not successful as emissions from algal component (e.g. phenylaniline) completely suppressed the signal region.

Nano-plastic (NP) usage is increasing across many industries; however, the risks posed from waste production or their accidental release into the environment have not been well investigated. Additionally, the resulting effects on the organisms within various environments based on NP exposure have not been thoroughly investigated. To contribute to this information, our current study focused on using an OECD test with additional validation tests to replicate the effects of a specific NP entering the freshwater environment. The current research analysed the potential toxicological, developmental and reproductive effects caused by fluorescent nano-polystyrene spheres (NPS) in juvenile (neonate) freshwater planktonic crustaceans, Daphnia magna. D. magna neonates were exposed for 24 h to a concentration range of 0–100 μg mL⁻¹ of 100 nm diameter NPS as a mortality/immobility (MI) test. MI testing showed that the D. magna exhibited significant NPS consumption at all concentrations; however, adverse effects only occurred after exposure to 30 μg mL⁻¹. The resulting EC₅₀ for the NPS MI testing was 86.3 1 μg mL⁻¹. Florescence imaging showed that the NPS were isolated to the D. magna intestines, even with exposure to a low concentration, producing a distinct emission, with no distinguishable NPS present in the other organs. UV-vis fluorimetry displayed an indirect relation between the initial consumption of NPS and increase in NPS exposure. The fluorimetry results showed an increase in NPS uptake up to 30 μg mL⁻¹, and then a decrease since D. magna slowed consumption, and further increase after 100 μg mL⁻¹. This indicated a change in the ratio of NPS within the intestines of Daphnia, which is independent to the exposure concentration. Raman spectroscopy analysis of the control D. magna produced a consistent emission spectrum, but with large FWHM peaks from its organic structures. The NPS-exposed D. magna clearly produced a clear and sharp peak attributed to a pure polystyrene signal following careful Z-mapping, which was not detected in the control samples. The results clearly present the successful Raman detection of the styrene signal from the NPS-exposed D. magna without significant pre-processing of the neonates.

The presence of sub-micron-sized plastics in the environment has been increasing, with the possible risks of these particles remaining relatively unknown. In order to assess the toxicity of these particles, 100 nm diameter green fluorescent nano-polystyrene spheres (NPS) (20–60 mg/L) were exposed to zebra mussels (Dreissena polymorpha) to investigate the mortality, clearance rate and stress-related biomarker responses. D. polymorpha were collected and analysed with standard OECD toxicological tests and biomarker analysis to detect both physical and biochemical responses after exposure to NPS. The toxicity of the NPS to D. polymorpha was low, with 60 mg/L NPS causing a mortality rate of 11.1% at 96 h which was statistically significant compared to the 4.2% control. No statistical change could be found for the condition factor (k_c) of D. polymorpha after NPS exposure. Clearance rates in D. polymorpha using R. subcapitata algae showed NPS-exposed mussels had a reduction of filtering efficiency of up to 30.5%. Bioassay testing shows a mixed but undeniably negative response from the D. polymorpha to the NPS, notably a significant rise in DNA Strand Breaks (DSB) and Metallothionein (MT) responses for high NPS concentrations. Additionally, Lipid Peroxidation (LPO) and Ferric Reducing Antioxidant Power (FRAP) assay tests showed a significant increase in response from the higher (>40 mg/L) concentrations of NPS exposure. Although Glutathione S-Transferase (GST) assay showed no statistical change from the control for all NPS-exposed samples, an increase of 20% had occurred for 60 mg/L NPS. Overall, a minimal toxic response from D. polymorpha to the NPS exposure below 40 mg/L was seen. After 40 mg/L NPS, mussels presented more acute toxicity in terms of mortality, along with reduced algal clearance rates and anincrease in biomarker response. This study revealed a clear induction of oxidative stress and DSB in the digestive gland of zebra mussels following exposure to nano-polystyrene. While these findings provide valuable insights into the potential harmful effects of nanoplastics in freshwater bivalves, further studies are necessary to help understand the level of threat plastic pollution may pose to the health of freshwater ecosystems.

A crop pretreatment with silicon was combined with passive modified atmosphere packaging (PMAP) in a thermoformed recycled PET packaging format as a novel approach to minimize the quality degradation in mushrooms. This study was aimed to evaluate the effects of (a) two preharvest treatments, namely preharvest control (PHTC) and preharvest silicon treatment (PHTS) and (b) four packaging lid formats, namely PMAP1: a single hole of 1.1 mm size, PMAP2: two holes of 0.53 mm size, PMAP3: three holes of 0.53 mm size, and PMAPC: OMNI-PW micro perforated cling film as a control on the quality and shelf life of mushrooms during five days of storage at 4 °C and 99.9% RH. The results of the analysis of variance showed that packaging type, storage days, and the double interaction effects of storage days × packaging type had significant effects (p < 0.0001) on the changes in O₂, CO₂, colour L* and a* values, ΔE, total soluble solids (TSS), and the density of mushrooms. Density, electrolyte leakage (EL), and TSS were significantly affected by the double interaction effects of preharvest treatment × packaging type. Overall, PMAP1, PMAP2, and PMAP3 resulted in lower O₂ + higher CO₂ within packages compared with the conventional control. A preharvest silicon treatment had little overall effect. PMAP 1, 2 and 3 had a significantly lower ΔE (=better quality) after 5 days storage compared to PMAPC which had the highest ΔE (lowest quality) overall. PMAP1 and PMAP2 had the lowest EL values compared to PMAP3 and PMAPC. PMAP1, PMAP2, and PMAP3 all gave better TSS levels and density compared to PMAPC. Notably, this study proved that a perforation-mediated MAP design for mushrooms packaged in a thermoformed recycled PET packaging format maintained improved CO₂, lowered O₂, and reduced EL while maintaining TSS and the density of the mushrooms during the storage period.

This research builds a mathematical modelling to assess food waste production when designing sustainable packaging solutions integrated with an agricultural intervention in kale production. The model utilizes experimental data obtained from simulated retail and distribution storage conditions to assess the probability of the product to be found out of technical specification and becoming waste. The packaging design was made using a system of differential equations describing the gas exchanges inside the packaging. The waste was estimated fitting linear mixed effect models to the postharvest experimental data, accounting for the variability between and within groups. A field experiment with kale treated with silicon during growth as a bio stimulant was used with the aim to make the product more resilient to packaging conditions. The Kale was then packaged in polylactic acid and oriented polypropylene for postharvest testing. Technological thresholds that indicate out-of- specification product were used to estimate the percentage of product that would likely end up as food waste. In total 7.2% of the product was found to be out of specification with the PLA film after 7 days. Silicon treatment was able to reduce this value to negligible, demonstrating the ability of agricultural interventions to facilitate sustainable packaging and reducing food waste in horticultural products.