Responses of soil microbiome to copper-based materials (nano and bulk) for agricultural applications: An indoor-mesocosm experiment.

The foreseen increasing application of copper-based nanomaterials (Cu-NMs), replacing or complementing existing Cu-agrochemicals, may negatively impact the soil microbiome. Thus, we studied the effects on soil microbiome function and composition of nano copper oxide (nCuO) or copper hydroxide NMs in a commercial (Kocide®3000) or a lab-synthetized formulation (nCu(OH)2) or bulk copper hydroxide (Cu(OH)2-B), at the commonly recommended Cu dose of 50 mg(Cu)kg-1 soil. Microbial responses were studied over 28 days in a designed indoor mesocosm. On day-28, in comparison to non-treated soil (CT), all Cu-treatments led to a reduction in dehydrogenase (95% to 68%), arylsulfatase (41% to 27%), and urease (40% to 20%) activity. There was a 32% increase in the utilization of carbon substrates in the nCuO-treatment and an increased abundance of viable bacteria in the nCu(OH)2-treatment (75% of heterotrophic and 69% of P-solubilizing bacteria). The relative abundance of Acidobacteria [Kocide®3000, nCuO, and Cu(OH)2-B treatments] and Flavobacteriia [nCu(OH)2-treatment] was negatively affected by Cu exposure. The abundance of Cu-tolerant bacteria increased in soils treated with Kocide®3000 (Clostridia) and nCu(OH)2 (Gemmatimonadetes). All Cu-treated soils exhibited a reduced abundance of denitrification-related genes (0.05% of nosZ gene). The DTPA-extractable pool of ionic Cu(II) varied among treatments: Cu(OH)2-B > Kocide®3000 âˆ¼ nCuO>nCu(OH)2, which may explain changes on the soil microbiome composition, at the genera and OTU levels. Thus, our study revealed that Cu-materials (nano and bulk) influence the soil microbiome with implications on its ecological role. It highlights the importance of assessing the impact of Cu-materials under dynamic and complex exposure scenarios and emphasizes the need for specific regulatory frameworks for NMs.

Structural and Functional Shifts in the Microbial Community of a Heavy Metal-Contaminated Soil Exposed to Short-Term Changes in Air Temperature, Soil Moisture and UV Radiation.

The interplay between metal contamination and climate change may exacerbate the negative impact on the soil microbiome and, consequently, on soil health and ecosystem services. We assessed the response of the microbial community of a heavy metal-contaminated soil when exposed to short-term (48 h) variations in air temperature, soil humidity or ultraviolet (UV) radiation in the absence and presence of Enchytraeus crypticus (soil invertebrate). Each of the climate scenarios simulated significantly altered at least one of the microbial parameters measured. Irrespective of the presence or absence of invertebrates, the effects were particularly marked upon exposure to increased air temperature and alterations in soil moisture levels (drought and flood scenarios). The observed effects can be partly explained by significant alterations in soil properties such as pH, dissolved organic carbon, and water-extractable heavy metals, which were observed for all scenarios in comparison to standard conditions. The occurrence of invertebrates mitigated some of the impacts observed on the soil microbial community, particularly in bacterial abundance, richness, diversity, and metabolic activity. Our findings emphasize the importance of considering the interplay between climate change, anthropogenic pressures, and soil biotic components to assess the impact of climate change on terrestrial ecosystems and to develop and implement effective management strategies.

Locust bean milling-derived dust as a raw material for the development of biodegradable bioplastics with antioxidant activity.

BACKGROUND: Non-value agrifood byproducts are rich in biomolecules such as proteins and polysaccharides, and possess film-forming ability, motivating their use in the development of biodegradable plastics. This work studied the feasibility of using locust bean milling-derived dust (LBMD) as a source of biomolecules suitable for developing biodegradable plastics. RESULTS: LBMD is composed of 56% protein, 28% carbohydrate, 10% moisture, 6% lipid, and 2% ash. In addition, phenolic compounds are also present. The carbohydrates are mainly composed by (1 → 4)-mannose, (1 → 4,6)-mannose, and t-galactose glycosidic linkages. Depending on the LBMD concentration used, when employed in casting biodegradable plastics, LBMD yields transparent yellowish bioplastics with 90% elongation at break and surface water contact angles ranging from 60° to 90°. Additionally, LBMD-based bioplastics display antioxidant activity, inhibiting cationic 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals up to 61% in just 24 h. LBMD-based bioplastics are disintegrated when incubated on the soil surface for 34 weeks, perhaps acting as a soil nutrient. CONCLUSION: LBMD represents a potential source of biomolecules for producing transparent, flexible, water tolerant, antioxidant, and biodegradable bioplastics, opening up opportunities to implement a novel circular strategy to valorize this locust bean industry byproduct. © 2022 Society of Chemical Industry.

The effects of different temperatures in mercury toxicity to the terrestrial isopod Porcellionides pruinosus.

Climate changes and metal contamination are pervasive stressors for soil ecosystems. Mercury (Hg), one of the most toxic metals, has been reported to interact with temperature. However, compared to aquatic biota, little is known about how temperature affects Hg toxicity and bioaccumulation to soil organisms. Here, toxicity and bioaccumulation experiments were replicated at 15 °C, 20 °C, and 25 °C to understand how sub-optimal temperatures affect the toxicokinetics and toxicodynamics of Hg via soil. Genotoxicity and energy reserves were also assessed to disclose potential trade-offs in life-history traits. Results underpin the complexity of temperature-Hg interactions. Survival was determined mainly by toxicokinetics, but toxicodynamics also played a significant role in defining survival probability during early stages. The processes determining survival probability were faster at 25 °C: General Unified Threshold of Survival (GUTS) model identified an earlier/steeper decline in survival, compared to 20 °C or 15 °C, but it also approached the threshold faster. Despite potentiation of Hg genotoxicity, temperature promoted faster detoxification, either increasing toxicokinetics rates or damage repair mechanisms. This metabolism-driven increase in detoxification led to higher depletion of energy reserves and likely triggered stress response pathways. This work emphasized the need for comprehensive experimental approaches that can integrate the multiple processes involved in temperature-metal interactions.

Short-Term Responses of Soil Microbial Communities to Changes in Air Temperature, Soil Moisture and UV Radiation.

We analyzed the effects on a soil microbial community of short-term alterations in air temperature, soil moisture and ultraviolet radiation and assessed the role of invertebrates (species Enchytraeus crypticus) in modulating the community's response to these factors. The reference soil, Lufa 2.2, was incubated for 48 h, with and without invertebrates, under the following conditions: standard (20 °C + 50% water holding capacity (WHC)); increased air temperature (15-25 °C or 20-30 °C + 50% WHC); flood (20 °C + 75% WHC); drought (20 °C + 25% WHC); and ultraviolet radiation (UV) (20 °C + 50% WHC + UV). BIOLOG EcoPlates and 16S rDNA sequencing (Illumina) were used to assess the microbial community's physiological profile and the bacterial community's structure, respectively. The bacterial abundance (estimated by 16S rDNA qPCR) did not change. Most of the conditions led to an increase in microbial activity and a decrease in diversity. The structure of the bacterial community was particularly affected by higher air temperatures (20-30 °C, without E. crypticus) and floods (with E. crypticus). Effects were observed at the class, genera and OTU levels. The presence of invertebrates mostly resulted in the attenuation of the observed effects, highlighting the importance of considering microbiome-invertebrate interactions. Considering future climate changes, the effects described here raise concern. This study provides fundamental knowledge to develop effective strategies to mitigate these negative outcomes. However, long-term studies integrating biotic and abiotic factors are needed.

Toxicity of historically metal(loid)-contaminated soils to Folsomia candida under the influence of climate change alterations.

Global warming is drastically altering the climate conditions of our planet. Soils will be among the most affected components of terrestrial ecosystems, especially in contaminated areas. In this study we investigated if changes in climate conditions (air temperature and soil moisture) affect the toxicity of historically metal(loid)-contaminated soils to the invertebrate Folsomia candida, followed by an assessment of its recovery capacity. Ecotoxicity tests (assessing survival, reproduction) were performed in field soils affected by metal(loid)s under different climate scenarios, simulated by individually changing air temperature or soil moisture conditions. The scenarios tested were: standard conditions (20°C + 50% soil water holding capacity-WHC); increased air temperature (daily fluctuation of 20-30°C + 50% WHC); soil drought (20°C + 25% WHC); soil flood (20°C + 75% WHC). Recovery potential was assessed under standard conditions in clean soil. Increased temperature was the major climate condition negatively affecting collembolans performance (decreased survival and reproduction), regardless of metal(loid) contamination. Drought and flood conditions presented less pronounced effects. When it was possible to move to the recovery phase (enough juveniles in exposure phase), F. candida was apparently able to recover from the exposure to metal(loid) contamination and/or climate alterations. The present study showed that forecasted climate alterations in areas already affected by contamination should be considered to improve environmental risk assessment.

Biochar in soil mitigates dimethoate hazard to soil pore water exposed biota.

Soil contamination is a worldwide problem urging for mitigation. Biochar is a carbonaceous material used as soil amendment that can immobilize chemical compounds, potentially turning them unavailable for soil biota. The aim of our study was to evaluate biochar's capacity to immobilize dimethoate in soil and, therefore, decreasing the toxicity to soil organisms. Two biochar application rates (2.5% and 5% w/w) were chosen to assess dimethoate potential immobilization, looking at changes in its toxicity to the collembolan Folsomia candida and the plant Brassica rapa upon soil amendment. Complementarily, chemical analyses were performed on soil pore water. Results showed that biochar may sorb and decrease dimethoate concentrations in soil pore water, influencing dimethoate bioavailability and consequent toxicity. Contrary to dimethoate solo impact on collembolans (LC50 0.69 mg kg-1, EC50 0.46 mg kg-1), their survival rate and offspring production were not affected by dimethoate when biochar was applied, regardless of application rate (LC50 and EC50 > 1.6 mg kg-1). Shoot length, fresh and dry weights of B. rapa were less affected by dimethoate upon biochar addition (EC50 values increase for all endpoints). Our study shows that biochar may contribute to decrease dimethoate bioavailability and toxicity to soil porewater exposed organisms.

Effects of climate conditions on the avoidance behavior of Folsomia candida and Enchytraeus crypticus towards metal(loid)-contaminated soils.

Global climate changes are predicted for the 21st century. Alterations in soil contaminants' availability and soil invertebrates' behavior are expected, which may interfere with the avoidance capacity that invertebrates may have towards contaminated soils and, therefore, compromise their role in soil functioning. This study aimed to assess the individual effects of air temperature, ultraviolet (UV) radiation and atmospheric CO2 concentration on the avoidance behavior of the arthropod Folsomia candida and the soft-bodied oligochaete Enchytraeus crypticus towards metal(loid)-contaminated soils. Avoidance behavior was evaluated under distinct climate treatments (simulating increases in air temperature, UV radiation exposure or atmospheric CO2 concentration) and compared to the response obtained at the standard conditions recommended by ISO guidelines. Both soil invertebrate species behave differently under standard conditions, with F. candida not avoiding the contaminated soils while E. crypticus did. Increases in air temperature and exposure to UV radiation did not change F. candida behavior towards contaminated soils. However, high atmospheric CO2 concentration modified this pattern and induced avoidance towards contaminated soils. As for E. crypticus, contaminated soils were also avoided under the different climate treatments simulated. Thus, our study shows that, depending on the species and the climate factor, changes in climate conditions may alter soil invertebrates' behavioral pattern towards meta(loid)-contaminated soils.

Soil moisture influences the avoidance behavior of invertebrate species in anthropogenic metal(loid)-contaminated soils.

Water availability is paramount in the response of soil invertebrates towards stress situations. This study aimed to evaluate the effects of forecasted soil moisture scenarios on the avoidance behavior of two invertebrate species (the arthropod Folsomia candida and the soft-bodied oligochaete Enchytraeus crypticus) in soils degraded by different types of anthropogenic metal(loid) contamination (mining soil and agricultural soil affected by industrial chemical wastes). Different soil moisture contents (expressed as % of the soil water holding capacity, WHC) were evaluated: 50% (standard soil moisture conditions for soil invertebrates' tests); 75% (to simulate increasing soil water availability after intense rainfalls and/or floods); 40%, 30%, 25% and 20% (to simulate decreasing soil water availability during droughts). Invertebrates' avoidance behavior and changes in soil porewater major ions and metal(loid)s were assessed after 48 h exposure. Soil incubations induced a general solubilization/mobilization of porewater major ions, while higher soil acidity favored the solubilization/mobilization of porewater metal(loid)s, especially at 75% WHC. Folsomia candida preferred soils moistened at 50% WHC, regardless the soils were contaminated or not and the changing soil porewater characteristics. Enchytraeus crypticus avoided metal(loid) contamination, but this depended on the soil moisture conditions and the corresponding changes in porewater characteristics: enchytraeids lost their capacity to avoid contaminated soils under water stress situations (75% and 20-25% WHC), but also when contaminated soils had greater water availability than control soils. Therefore, forecasted soil moisture scenarios induced by global warming changed soil porewater composition and invertebrates capacity to avoid metal(loid)-contaminated soils.

The comet assay in Folsomia candida: A suitable approach to assess genotoxicity in collembolans.

The present study shows the comet assay technique being successfully applied for the first time to one of the most widely used soil organisms in standardized ecotoxicological tests, Folsomia candida, providing a step forward in assessing the genotoxicity induced by xenobiotics. Because collembolans have a high content of chitin, a new methodology was developed in which the heads of the collembolans were separated from the rest of the body, allowing the hemolymph to leak out. This procedure allows the cells to be released, and after lysis the genetic material is available for the comet assay. Among other key procedures, the use of 30 organisms (20- to 22-d-old adults) per replicate and the correct amount of cells with genetic material (translated as 10 µL of suspension) applied on the agarose gel were determinants for the success of the results obtained. The methodology was validated by exposing F. candida to a representative metallic element (cadmium) and a representative of organophosphates, the insecticide dimethoate, for a shorter time period of 10 d, compared with the 28 d for the International Organization for Standardization 11267 method. Within this method, the relatively low percentage of DNA damage (30%) observed in controls and the significant increase in terms of percentage of DNA damage for almost all the concentrations of dimethoate and Cd (reaching 52% and 56% of damage in the highest concentrations, respectively) confirmed the genotoxic effect of both compounds and validated this technique. The comet assay proved to be a sensitive technique to detect DNA strand breaks in collembolans' cells. Environ Toxicol Chem 2017;36:2514-2520. © 2017 SETAC.

Ultrathin phenyl-functionalized solid phase microextraction fiber coating developed by sol-gel deposition.

A new sol-gel application for the development of SPME fibers is described. Phenyltrimethoxysilane (PTMOS) and methyltrimethoxysilane (MTMOS) were the sol-gel precursors used at different proportions, together with different water contents, catalyst and reaction time. It was observed that obtaining a good film quality was determinant for a good extracting fiber performance. The film thickness ranged 0.2-1 microm and could not be increased by multi-coating processes. Apparently, a dense, non-porous microstructure was obtained. These coatings exhibited a strong hydrophobic character, as shown by the capability of extraction of long chain and apolar aromatic compounds, which, was comparable to that of the 100 microm polydimethylsiloxane (PDMS) and 65 microm carbowax-divinylbenzene (CW-DVB). The developed fiber has shown high thermal (350 degrees C) and organic solvent stability (ethanol, toluene and dichloromethane), thus bearing adequate characteristics to be associated to GC and potentialities that may also envisage suitability for HPLC. The new fibers may be useful for the microextraction of non-polar compounds, although at trace levels and in simple matrixes only, due to the susceptibility to competition.