Ruth Pereira

Introduction: Essential oils (EO), rich in bioactive metabolites with biocidal activity, present great potential for agricultural applications as new biopesticides. However, their high volatility and sensitivity to environmental conditions limits their application. To address these limitations, nanotechnology-based formulations have been developed, incorporating EO into natural clays such as montmorillonite (MMT). Due to its colloidal properties, high adsorption capacity, and modifiable surface, MMT serves as an effective carrier for stabilizing EO while controlling their release. Besides aiming to enhance EO efficacy, these MMT-based formulations also aim to minimize EO toxicity to non-target organisms. Materials and methods: In this study, the toxicity of Satureja montana EO (SM EO), of its dispersant agent Tween 20 ^® , of the MMT nanoclay and of the nanoclay-EO formulation was evaluated using aquatic ( Aliivibrio fischeri , Raphidocelis subcapitata , Lemna minor and Daphnia magna ), and terrestrial ( Folsomia candida and soil microbiota) non-target model organisms, following standard protocols. Results: Among the tested species, R. subcapitata and D. magna , exhibited the highest sensitivity, with D. magna showing an EC ₅₀ of 0.011 mg mL ^-1 and a complete growth inhibition being observed for R. subcapitata at concentrations ≥0.021 mg mL ^-1 , for the nanoclay-EO formulation. F. candida reproduction was also significantly reduced for all tested concentrations of the nanoclay-EO formulation. In contrast, it was observed a stimulatory effect on soil microbial activity particularly for dehydrogenase and acid phosphatase enzymes. Discussion: These findings suggest that the nanoclay-EO formulation did not reduce the toxicity of SM EO, and in some cases, may even raise ecotoxicological concerns, particularly for aquatic and soil invertebrates. This study highlights the importance of detailed ecotoxicological evaluations of biopesticide formulations based on plant-based and materials as essential oils, and other natural materials, as they cannot be assumed as safe compounds. To the best of our knowledge ecotoxicological data is limited for most of the EO including some that already in the market. Based on these results, the concentrations to be tested for efficacy against target organism (safe to non-target organism) should be lower than 0.007 mg mL ^-1 .

This chapter aims to contribute to a comprehensive view of environmental radiobiology and discuss the effects of different kinds of ionizing radiation on ecosystems. The impact of ionizing radiation was considered on both organisms and the abiotic environment, assessing the fate of radionuclides in abiotic compartments (e.g., the movement through atmosphere, hydrosphere, and lithosphere) and in the trophic chains, with implications for human and non-human biota. The available methodologies for estimating radiation dose to biota were also addressed as well as the associated challenges. This chapter also focused on the impacts of ionizing radiation exposure on non-human biota from microorganisms to vertebrates, as well as on the basic concepts related to environmental radiobiology and the molecular effects associated with the exposure to different types of ionizing radiation. The particular context of Naturally Occurring Radioactive Material (NORM) contamination was also tackled, as well as its effects on non-human biota.

Dithiocarbazates comprise an important class of Schiff bases with remarkable biological applications due to the imine group present in their structure. However, full exploitation of the biological activity of 3-methyl-5-phenyl-pyrazoline-1-(S-benzyldithiocarbazate) (DTC) is limited due to its easy degradation and poor solubility in aqueous solutions. The loading of DTC into mesoporous silica nanoparticles (MSiNPs) can be an excellent strategy to improve the solubility of DTC in the aqueous medium. Therefore, the main goal of the present work was to design MSiNP-DTC and to evaluate the success of the loading process by measuring its physicochemical properties and evaluating the environmental safety of the new DTC formulation using different aquatic organisms, such as the microalgae Raphidocelis subcapitata, the macrophyte Lemna minor, and the marine bacterium Aliivibrio fischeri. DTC, MSiNP, and MSiNP-DTC concentrations ranging from 8.8 to 150 mg L⁻¹ were tested for all the species, showing low toxicity against aquatic organisms. Loading DTC into MSiNPs caused a slight increase in the toxicity at the concentrations tested, only allowing for the estimation of the effect concentration causing a 20% reduction in bioluminescence or growth rate (EC₂₀). Therefore, despite the potential of MSiNPs as a drug delivery system (DDS), it is of utmost importance to assess its impact on the safety of the new formulations.

Lipid nanoparticles (LN) composed of biodegradable lipids and produced by green methods are candidates for the encapsulation of pesticides, potentially contributing to decreasing their release in the environment. From a safety-by-design concept, this work proposes LN for the encapsulation of insecticide active ingredients (AI). However, given the complexity of nanoparticles, ecotoxicological studies are often controversial, and a detailed investigation of their effects on the environment is required. Accordingly, this work aimed to produce and characterize LN containing the insecticide lambda-cyhalothrin (LC) and evaluate their safety to crops (Solanum lycopersicum and Zea mays), soil invertebrates (Folsomia candida and Eisenia fetida), and soil microbial parameters. The average particle size for LN-loaded with LC (LN–LC) was 165.4 ± 2.34 nm, with narrow size distribution and negative charge (−38.7 ± 0.954 mV). LN were able to encapsulate LC with an entrapment efficacy of 98.44 ± 0.04%, maintaining the stability for at least 4 months. The LN–LC showed no risk to the growth of crops and reproduction of the invertebrates. The effect on microbial parameters showed that the activity of certain soil microbial parameters can be inhibited or stimulated by the presence of LN at highest concentrations, probably by changing the pH of soil or by the intrinsic properties of LN.

Food production is increasing year by year, with modern agriculture occupying high-fertility soils

Strategies to minimize the effects of glyphosate (GLY), the most used herbicide worldwide, on non-target plants need to be developed. In this context, the current study was designed to evaluate the potential of nitric oxide (NO), provided as 200 µM sodium nitroprusside (SNP), to ameliorate GLY (10 mg kg⁻¹ soil) phytotoxicity in tomato plants. Upon herbicide exposure, plant development was majorly inhibited in shoots and roots, followed by a decrease in flowering and fruit set; however, the co-application of NO partially prevented these symptoms, improving plant growth. Concerning redox homeostasis, lipid peroxidation (LP) and reactive oxygen species (ROS) levels rose in response to GLY in shoots of tomato plants, but not in roots. Additionally, GLY induced the overaccumulation of proline and glutathione, and altered ascorbate redox state, but resulted in the inhibition of the antioxidant enzymes. Upon co-treatment with NO, the non-enzymatic antioxidants were not particularly changed, but an upregulation of all antioxidant enzymes was found, which helped to keep ROS and LP under control. Overall, data point towards the benefits of NO against GLY in tomato plants by reducing the oxidative damage and stimulating detoxification pathways, while also preventing GLY-induced impairment of flowering and fruit fresh mass.