Unlocking the potential of carbon dots in agriculture using data-driven approaches.

The utilization of carbon dots (CDs) in agriculture to enhance plant growth has gained significant attention, but the data remains fractionated. Systematically integrating existing data is needed to identify the factors driving the interactions between CDs and plants and strategically guide future research. Articles reporting on CDs and their effects on plants were searched based on inclusion and exclusion criteria, resulting in the collection of 71 articles comprising a total of 2564 data points. The meta-analysis reveals that the soil and foliar application of red-emitting bio-derived CDs at a low concentration (<10 ppm) leads to the most beneficial effects on plant growth. Random forest and gradient boosting algorithms revealed that the size and dose of CDs were important factors in predicting plant responses across multiple aspects (CDs properties, plant properties, environmental factors, and experimental conditions). Specifically, smaller sizes are more favorable to growth indicators (GI) below 6 nm, nutrient and quality (NuQ) at 3-6 nm, photosynthesis (PSN) below 7 nm, and antioxidant responses (AR) below 5 nm. Overall, our analysis of existing data suggests that CDs applications can significantly improve plant responses (GI, NuQ, PSN, and AR) by 10-39 %. To unlock the full potential of CDs, customized synthesis techniques should be employed to meet the specific requirements of different crops and climate condition. For example, we recommend the synthesis of small CDs (<7 nm) with emission peak values falling within the range of 405-475 and 610-670 nm to enhance plant growth. The global prediction of plant responses to CDs application in future scenarios have shown significant improvements ranging from 17 to 58 %, suggesting that CDs have widespread applicability. This novel understanding of the impact of CDs on plant response provides valuable insights for optimizing the application of these nanomaterials in agriculture.

Testing methods to estimate population size for wastewater treatment plants using census data: Implications for wastewater-based epidemiology.

In wastewater-based epidemiology (WBE), wastewater loads are commonly reported as a per capita value. Census population counts are often used to obtain a population size to normalise wastewater loads. However, the methods used to calculate the population size of wastewater treatment plants (WWTPs) from census data are rarely reported in the WBE literature. This is problematic because the geographical extents of wastewater catchments and census area units rarely align perfectly with each other and exist at different spatial scales. This complicates efforts to estimate the number of people serviced by WWTPs in these census area units. This study compared four geospatial methods to combine wastewater catchment areas and census area units to calculate the census population size of wastewater treatment plants. These methods were applied nationally to WWTPs across New Zealand. Population estimates varied by up to 73 % between the methods, which could skew comparisons of per capita wastewater loads between sites. Variability in population estimates (relative standard deviation, RSD) was significantly higher in smaller catchments (rs = -0.727, P < .001), highlighting the importance of method selection in smaller sites. Census population estimates were broadly similar to those provided by wastewater operators, but significant variation was observed for some sites (ranging from 42 % lower to 78 % higher, RSD = 262 %). We present a widely applicable method to calculate population size from census, which involves disaggregating census area units by individual properties. The results reinforce the need for transparent reporting to maintain confidence in the comparison of WBE across sites and studies.

Combining Outreach and Cross-sectional Research to Gather Children's Soil Values in Aotearoa New Zealand: Protocol for the Mixed Methods Soilsafe Kids Program.

BACKGROUND: Soil underpins most terrestrial systems; hence, its degradation should concern everyone. In 2021, Soilsafe Aotearoa surveyed the adult population of New Zealand about how they value soil, particularly values related to how they care about and are concerned about soil. Pursuant to this study, Soilsafe Kids (the outreach branch of Soilsafe Aotearoa) developed a combined research and outreach program to collect a supplemental data set of children's soil values, so both adults' and children's voices can be considered when understanding the implications of different practices and how to care for presently "uncared for" or neglected soils in the future. OBJECTIVE: The program not only asks primary school students about their soil values but also aims to teach them about soil from many disciplinary perspectives to enhance their understanding and awareness of soil, and, more broadly, for knowledge production. METHODS: Here we describe the research protocol used in this Soilsafe Kids program. This program uses surveys (in the form of worksheets), focus groups (introduced as group discussions), and art projects to learn what children think about soil in Tamaki Makaurau Auckland. We have received ethics approval from the University of Auckland's Human Participants Ethics Committee (reference number 23556) on March 25, 2022, for 3 years. RESULTS: We have begun recruiting participants and delivering the Soilsafe Kids program in schools across Tamaki Makaurau Auckland. Our data collection is ongoing with final student engagement in the first quarter of 2023. We expect to analyze data at the start of 2023 and to disseminate results later this year. CONCLUSIONS: Once this study is complete, we will disseminate the final results to the research community, stakeholders, and the local community through conference presentations, journal articles, hui (meetings), on our website, and in art exhibits. We note that although Tamaki Makaurau Auckland is home to the majority of people living in Aotearoa New Zealand, the Auckland region only represents a small portion of Aotearoa New Zealand's land, and findings are not generalizable to Aotearoa New Zealand as a whole. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/43390.

Formation of disinfection by-products from microplastics, tire wear particles, and other polymer-based materials.

Disinfection by-products (DBPs) are formed through the disinfection of water containing precursors such as natural organic matter or anthropogenic compounds (e.g., pharmaceuticals and pesticides). Due to the ever increasing use of plastics, elastomers, and other polymers in our daily lives, polymer-based materials (PBMs) are detected more frequently and at higher concentrations in water and wastewater. The present review provides a comprehensive and systematic analysis of the contribution of PBMs - including elastomers, tire waste, polyelectrolytes, and microplastics - as precursors of DBPs in water and wastewater. Literature shows that the presence of PBMs can lead to the leaching of dissolved organic matter (DOM) and subsequent formation of DBPs upon disinfection in aqueous media. The quantity and type of DBPs formed strongly depends on the type of polymer, its concentration, its age, water salinity, and disinfection conditions such as oxidant dosage, pH, temperature, and contact time. DOM leaching from elastomers and tire waste was shown to form N-nitrosodimethylamine up to concerning levels of 930 ng/L and 466,715 ng/L, respectively upon chemical disinfection under laboratory conditions. Polyelectrolytes can also react with chemical disinfectants to form toxic DBPs. Recent findings indicate trihalomethanes formation potential of plastics can be as high as 15,990 µg/L based on the maximum formation potential under extreme conditions. Our analysis highlights an overlooked contribution of DOM leaching from PBMs as DBP precursors during disinfection of water and wastewater. Further studies need to be conducted to ascertain the extent of this contribution in real water and wastewater treatment plants.

Global geological occurrence and character of the carcinogenic zeolite mineral, erionite: A review.

As with the six regulated asbestos minerals (chrysotile, amosite, crocidolite, anthophyllite, tremolite, and actinolite), the zeolite mineral, erionite, can exhibit a fibrous morphology. When fibrous erionite is aerosolized and inhaled, it has been linked to cases of lung cancers, such as malignant mesothelioma. Importantly, fibrous erionite appears to be more carcinogenic than the six regulated asbestos minerals. The first health issues regarding erionite exposure were reported in Cappadocia (Turkey), and more recently, occupational exposure issues have emerged in the United States. Erionite is now classified as a Group 1 carcinogen. Thus, identifying the geological occurrence of erionite is a prudent step in determining possible exposure pathways, but a global review of the geological occurrence of erionite is currently lacking. Here, we provide a review of the >100 global locations where erionite has been reported, including: 1) geological setting of host rocks; 2) paragenetic sequence of erionite formation, including associated zeolite minerals; 3) fiber morphological properties and erionite mineral series (i.e., Ca, K, Na); and 4) a brief overview of the techniques that have been used to identify and characterize erionite. Accordingly, erionite has been found to commonly occur within two major rock types: felsic and mafic. Within felsic rocks (in particular, tuffaceous layers within lacustrine paleoenvironments), erionite is disseminated through the layer as a cementing matrix. In contrast, within mafic (i.e., basaltic) rocks, erionite is typically found within vesicles. Nevertheless, aside from detailed studies in Italy and the United States, there is a paucity of specific information on erionite geological provenance or fiber morphology. The latter issue is a significant drawback given its impact on erionite toxicity. Future erionite studies should aim to provide more detailed information, including variables such as rock type and lithological properties, quantitative geochemistry, and fiber morphology.

Determining acceptance and rejection of nano-enabled agriculture: A case study of the New Zealand wine industry.

This paper gathers gatekeeper views and perceptions on nano-enabled viticulture in Aotearoa New Zealand. While the science of nanotechnology is indicated to offer improvements to conventional vineyard inputs and operations, its acceptability by potential users and consumers has an impact on the governance of nano-enabled agriculture. This governance takes place not just at the state level through regulation and policy, but also through corporate, and community sectors' use of branding and narratives about nanotechnology and nano-based agrichemicals, and the (non)consumption of nano-enabled products. This paper investigates the technical and market acceptability, or governance, of nanotechnology by elucidating the attitudes of industry gatekeepers towards wines grown with nanotechnology. This necessarily informs the 'market permissibility' of such technologies, and illuminates sensitivities, concerns, and consumer-based barriers to adoption. We conducted 15 semi-structured, key informant interviews and a thematic data analysis. Our results suggest a high level of technical acceptability, particularly if environmental sustainability benefits are made clear. Wine producers are interested in nano-solutions to labour, pest and disease, and cost of production issues. However, key actors in the production-consumption network of New Zealand wine have concerns about nano-enabled approaches. Regulatory approval and safety assurances are expected prior to adoption in food or wine. Respondents argue that consumer acceptability is less clear, and that thought leaders like wine writers, intermediaries and 'influencers' will be critical in shaping public opinion. This research highlights the potential risks of nanotechnology development and adoption.

Occurrence and fate of poly- and perfluoroalkyl substances (PFAS) in urban waters of New Zealand.

Information on the occurrence of PFAS in aquatic matrices of countries with no PFAS manufacturing, e.g., New Zealand, is limited. Also, the fingerprint of PFAS along an urban water cycle, following water path from wastewater treatment plant (WWTP) effluent to treated drinking water has not been widely assessed. Hence, 38 long-, short-, ultrashort-chain PFAS and fluorinated alternatives (including precursors) were monitored in this study by collecting composite samples from two urban WWTPs of New Zealand and grab samples from the water bodies receiving the WWTPs' effluents and a drinking water treatment plant, whose source water received the effluent of one of the studied WWTPs. ∑PFAS at concentrations 0.1 - 13 ng/L were detected in all wastewater samples, including influents and different treatment stages of the two WWTPs (WW1 and WW2). The fate of most PFAS was similar in the two WWTPs, despite large differences in WWTPs' PFAS loads in the influents, serving populations (1.6 vs 0.16 million), total capacities (300 vs 54 million liters per day), and designs (aerobic and anoxic secondary treatment vs aerobic only). The fate of PFAS in WWTPs appeared to be driven by a range of processes. For instance, a simultaneous increase (41.6%) in short-chain perfluorohexanoic acid (PFHxA) concentrations and decrease (49.7%) in precursor 6:2 fluorotelomer sulfonate (6:2 FTS) concentrations after secondary biological treatment suggested possible transformation of 6:2 FTS into PFHxA during the treatment. In contrast, the reason behind an average decrease of 35% in ultrashort-chain perfluoropropionic acid (PFPrA) concentrations after treatment was unclear, and further studies are recommended. The concentrations of a linear isomer of long-chain perfluorosulfonic acid (PFOS-L) decreased (48%) in the effluent, possibly due to its partitioning to sludge. Although the concentrations of PFAS in coastal waters suggested that the WW1 effluent is a potential source of PFAS, earlier dispersion model and no detection of PFAS in the receiving waters of WW2 implied that other sources, such as septic systems, peripheral industries, and the airport, could also be contributing to PFAS in coastal waters. The source of ultrashort-chain PFPrA (5.5 ng/L) detected in the treated drinking water produced from that river was unclear. The monitoring results confirm incomplete removal of PFAS in WWTPs, indicate a possible transformation of unknown precursors present in wastewater into short-chain perfluoroalkylcarboxylic acids (PFCAs) during biological treatment, and reveal a possible accumulation of perfluoroalkylsulfonic acids (PFSAs) in the sludge, overall suggesting the circulation of PFAS in urban water systems.

International Analysis of Sources and Human Health Risk Associated with Trace Metal Contaminants in Residential Indoor Dust.

People spend increasing amounts of time at home, yet the indoor home environment remains understudied in terms of potential exposure to toxic trace metals. We evaluated trace metal (and metalloid) concentrations (As, Cu, Cr, Mn, Ni, Pb, and Zn) and health risks in indoor dust from homes from 35 countries, along with a suite of potentially contributory residential characteristics. The objective was to determine trace metal source inputs and home environment conditions associated with increasing exposure risk across a range of international communities. For all countries, enrichments compared to global crustal values were Zn > Pb > Cu > As > Cr > Ni; with the greatest health risk from Cr, followed by As > Pb > Mn > Cu > Ni > Zn. Three main indoor dust sources were identified, with a Pb-Zn-As factor related to legacy Pb sources, a Zn-Cu factor reflecting building materials, and a Mn factor indicative of natural soil sources. Increasing home age was associated with greater Pb and As concentrations (5.0 and 0.48 mg/kg per year of home age, respectively), as were peeling paint and garden access. Therefore, these factors form important considerations for the development of evidence-based management strategies to reduce potential risks posed by indoor house dust. Recent findings indicate neurocognitive effects from low concentrations of metal exposures; hence, an understanding of the home exposome is vital.

Comprehensive framework for human health risk assessment of nanopesticides.

Nanopesticides are not only in an advanced state of research and development but have started to appear on the market. Industry and regulatory agencies need a consolidated and comprehensive framework and guidance for human health risk assessments. In this perspective we develop such a comprehensive framework by exploring two case studies from relevant product types: an active ingredient delivered with a nanocarrier system, and a nanoparticle as an active ingredient. For a nanocarrier system, three entities are tracked during the assessment: the nanocarrier-active ingredient complex, the empty nanocarrier remaining after the complete release of the active ingredient, and the released active ingredient. For the nanoparticle of pure active ingredient, only two entities are relevant: the nanoparticle and the released ions. We suggest important adaptations of the existing pesticide framework to determine the relevant nanopesticide entities and their concentrations for toxicity testing. Depending on the nature of the nanopesticides, additional data requirements, such as those pertaining to durability in biological media and potential for crossing biological barriers, have also been identified. Overall, our framework suggests a tiered approach for human health risk assessment, which is applicable for a range of nanopesticide products to support regulators and industry in making informed decisions on nanopesticide submissions. Brief summaries of suitable methods including references to existing standards (if available) have been included together with an analysis of current knowledge gaps. Our study is an important step towards a harmonized approach accepted by regulatory agencies for assessing nanopesticides.

Response of soil enzyme activity and bacterial community to copper hydroxide nanofertilizer and its ionic analogue under single versus repeated applications.

Nanosized agrochemicals like nanofertilizers are being applied to soils. Adverse impacts of nanofertilizers on soil microflora were reported in past studies, but only considering a single application. Repeated applications are however more likely to occur in agriculture. We investigated effects of single versus repeated applications of a copper hydroxide nanofertilizer formulation (NFF) on soil enzyme activity and bacterial community. One or three applications were performed within 21 days to achieve same final level of Cu in soil (48 mg(Cu)/kg: the recommended dose of NFF). Besides, the active ingredient (i.e., copper hydroxide nanotubes (NT)) and dispersing agent (DA) of NFF, and an ionic fertilizer (i.e., CuSO4) were examined. Fluorescein diacetate hydrolase (FDAse), N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and urease (URE) showed negligible changes in the activities between the control and DA treatment. Bacterial community abundance, composition and diversity exhibited similar phenomena. Exposures to copper hydroxide NFF and NT or CuSO4 enhanced the activities of FDAse and NAG, weakened the activity of URE, and showed negligible changes in the LAP activity irrespective of single and repeated applications. Concentrations of NO3--N and NH4+-N in soil were also affected by the application mode of NFF. More importantly, responses of soil bacterial community to copper hydroxide NFF were highly dependent on its application mode, whereas similar responses were observed in the CuSO4 treatment regardless of single or repeated applications. This study provided new insights into environmental risk of copper hydroxide NFF that were ignored in previous studies using a single exposure.

A review of the occurrence, transformation, and removal of poly- and perfluoroalkyl substances (PFAS) in wastewater treatment plants.

Poly- and perfluoroalkyl substances (PFAS) comprise more than 4,000 anthropogenically manufactured compounds with widescale consumer and industrial applications. This critical review compiles the latest information on the worldwide distribution of PFAS and evaluates their fate in wastewater treatment plants (WWTPs). A large proportion (>30%) of monitoring studies in WWTPs were conducted in China, followed by Europe (30%) and North America (16%), whereas information is generally lacking for other parts of the world, including most of the developing countries. Short and long-chain perfluoroalkyl acids (PFAAs) were widely detected in both the influents (up to 1,000 ng/L) and effluents (15 to >1,500 ng/L) of WWTPs. To date, limited data is available regarding levels of PFAS precursors and ultra-short chain PFAS in WWTPs. Most WWTPs exhibited low removal efficiencies for PFAS, and many studies reported an increase in the levels of PFAAs after wastewater treatment. The analysis of the fate of various classes of PFAS at different wastewater treatment stages (aerobic and/aerobic biodegradation, photodegradation, and chemical degradation) revealed biodegradation as the primary mechanism responsible for the transformation of PFAS precursors to PFAAs in WWTPs. Remediation studies at full scale and laboratory scale suggest advanced processes such as adsorption using ion exchange resins, electrochemical degradation, and nanofiltration are more effective in removing PFAS (~95-100%) than conventional processes. However, the applicability of such treatments for real-world WWTPs faces significant challenges due to the scaling-up requirements, mass-transfer limitations, and management of treatment by-products and wastes. Combining more than one technique for effective removal of PFAS, while addressing limitations of the individual treatments, could be beneficial. Considering environmental concentrations of PFAS, cost-effectiveness, and ease of operation, nanofiltration followed by adsorption using wood-derived biochar and/or activated carbons could be a viable option if introduced to conventional treatment systems. However, the large-scale applicability of the same needs to be further verified.

Is centrifugal ultrafiltration a robust method for determining encapsulation efficiency of pesticide nanoformulations?

Loading active ingredients on nanocarrier systems is becoming a common strategy for improving pesticide formulations. One of the most important properties of these nanoformulations is the proportion of pesticide associated with the nanocarriers (encapsulation efficiency, EE). EE is often determined by centrifugal ultrafiltration. However, the losses of active ingredient in the centrifugal ultrafiltration devices are typically not assessed, potentially leading to erroneous results. In this work, the losses of three pesticides (tebuconazole, terbuthylazine and chlorpyrifos) during centrifugal ultrafiltration have been systematically evaluated for nine different devices. Results suggest that centrifugal ultrafiltration is not suitable for determining the EE of compounds such as chlorpyrifos as 100% losses were observed on all the devices tested. Losses of tebuconazole and terbuthylazine were highly variable according to the type of membrane and the lowest losses were observed in the devices with hydrophilic regenerated cellulose membranes. Based on these results, we propose a correction factor and demonstrate its application to calculate the EE of two nanoformulations based on poly(ε-caprolactone) nanocarriers. The approach extends the applicability of centrifugal ultrafiltration to a wider range of pesticide nanoformulations. We also discuss the effect of dilution on EE and make recommendations to improve the characterisation of nanoparticles-based pesticide nanoformulations in the future.

Fate of Biodegradable Engineered Nanoparticles Used in Veterinary Medicine as Delivery Systems from a One Health Perspective.

The field of veterinary medicine needs new solutions to address the current challenges of antibiotic resistance and the need for increased animal production. In response, a multitude of delivery systems have been developed in the last 20 years in the form of engineered nanoparticles (ENPs), a subclass of which are polymeric, biodegradable ENPs, that are biocompatible and biodegradable (pbENPs). These platforms have been developed to deliver cargo, such as antibiotics, vaccines, and hormones, and in general, have been shown to be beneficial in many regards, particularly when comparing the efficacy of the delivered drugs to that of the conventional drug applications. However, the fate of pbENPs developed for veterinary applications is poorly understood. pbENPs undergo biotransformation as they are transferred from one ecosystem to another, and these transformations greatly affect their impact on health and the environment. This review addresses nanoparticle fate and impact on animals, the environment, and humans from a One Health perspective.

Sequestration and potential release of PFAS from spent engineered sorbents.

Per- and poly-fluoroalkyl substances (PFAS) have contaminated land and water at numerous sites worldwide that now require remediation. The most common approach for treating contaminated water currently relies on removal of PFAS by sorption. The spent sorbents loaded with PFAS can potentially be disposed of at landfills, provided the sorbed contaminants remain sequestered and certain risk criteria are met. Hence, it is essential that remediation sorbents (i) rapidly adsorb a large variety of PFAS under varying water chemistry conditions, and (ii) do not release the adsorbed PFAS in due course. This review aims at establishing the current state of knowledge about the potential release of PFAS that may occur during and after treatment. The scientific literature currently provides data for a very restricted range of long-chain PFAS. Our knowledge of the dynamics of PFAS adsorption processes on engineered sorbents is limited, and even less is known about their desorption processes. The sorption of PFAS can be strongly affected by changes in the solution pH, ionic strength and dissolved organic matter content, and the process is also subject to complex competition mechanisms in the presence of other PFAS as well as organic contaminants and inorganic salts. Several studies suggest that changes in one or several of these factors may trigger the release of PFAS from engineered sorbents. This phenomenon is more likely to occur for PFAS with shorter carbon chain lengths (

Transformations of Ag2S nanoparticles in simulated human gastrointestinal tract: Impacts of the degree and origin of sulfidation.

Engineered silver sulfide nanoparticles (e-Ag2S-NPs) are used in industry and can be released into the environment. Besides e-Ag2S-NPs, transformed silver sulfide nanoparticles (t-Ag2S-NPs) from silver nanoparticles are more likely to be the form that is widely distributed in the environment. Both e-Ag2S-NPs and t-Ag2S-NPs may be ingested and get into human gastrointestinal tract (GIT) through trophic transfer, posing a potential threat to human health. Nevertheless, knowledge of chemical stability of t-Ag2S-NPs and e-Ag2S-NPs in the human GIT is very limited. Herein e-Ag2S-NPs and a series of t-Ag2S-NPs with different degrees of sulfidation were selected as models for exposure to the simulated human GIT including mouth, stomach and small intestine phases under fed and fasted conditions. Silver ions were detected in the simulated saliva, gastric and small intestine fluids when t-Ag2S-NPs or e-Ag2S-NPs were incubated in the simulated GIT, but the amount (e.g., < 20 µg) of silver ion in each phase accounted for < 0.2‰ (w/w) of the silver added (i.e., 100 mg). Silver species of the residual particulate from each phase of the simulated GIT with t-Ag2S-NPs or e-Ag2S-NPs were thus analyzed through a developed analytical method that could selectively, successively and efficiently dissolve and quantify AgCl, Ag(0), and Ag2S in particulates. Both e-Ag2S-NPs and fully sulfidized t-Ag2S-NPs were shown to be highly stable in the simulated human GIT. Conversely, partially sulfidized t-Ag2S-NPs primarily underwent transformations in the mouth phase relative to stomach and small intestine phases regardless of fed or fasted status, wherein AgCl and Ag2S were observed besides Ag(0). The amount of Ag2S in the mouth phase negatively (r = -0.99, p < 0.001) correlated with the sulfidation degree of initial t-Ag2S-NPs. This work improved our understanding of potential transformations of t-Ag2S-NPs in the simulated human GIT, providing valuable information for future researches on evaluating health risks of ingested Ag2S-NPs.

Remediation of poly- and perfluoroalkyl substances (PFAS) contaminated soils - To mobilize or to immobilize or to degrade?

Poly- and perfluoroalkyl substances (PFASs) are synthetic chemicals, which are introduced to the environment through anthropogenic activities. Aqueous film forming foam used in firefighting, wastewater effluent, landfill leachate, and biosolids are major sources of PFAS input to soil and groundwater. Remediation of PFAS contaminated solid and aqueous media is challenging, which is attributed to the chemical and thermal stability of PFAS and the complexity of PFAS mixtures. In this review, remediation of PFAS contaminated soils through manipulation of their bioavailability and destruction is presented. While the mobilizing amendments (e.g., surfactants) enhance the mobility and bioavailability of PFAS, the immobilizing amendments (e.g., activated carbon) decrease their bioavailability and mobility. Mobilizing amendments can be applied to facilitate the removal of PFAS though soil washing, phytoremediation, and complete destruction through thermal and chemical redox reactions. Immobilizing amendments are likely to reduce the transfer of PFAS to food chain through plant and biota (e.g., earthworm) uptake, and leaching to potable water sources. Future studies should focus on quantifying the potential leaching of the mobilized PFAS in the absence of removal by plant and biota uptake or soil washing, and regular monitoring of the long-term stability of the immobilized PFAS.

Assessing the Impacts of Cu(OH)2 Nanopesticide and Ionic Copper on the Soil Enzyme Activity and Bacterial Community.

Nanopesticides are being introduced in agriculture, and the associated environmental risks and benefits must be carefully assessed before their widespread agricultural applications. We investigated the impacts of a commercial Cu(OH)2 nanopesticide formulation (NPF) at different agricultural application doses (e.g., 0.5, 5, and 50 mg of Cu kg-1) on enzyme activities and bacterial communities of loamy soil (organic matter content of 3.61%) over 21 days. Results were compared to its ionic analogue (i.e., CuSO4) and nano-Cu(OH)2, including both the commercial unformulated active ingredient of NPF (AI-NPF) and synthesized Cu(OH)2 nanorods (NR). There were negligible changes in the activity of acid phosphatase, regardless of exposure dose, whereas significant (p < 0.05) variations in activities of invertase, urease, and catalase were observed at a dose of 5 mg kg-1 or higher. Invertase activity decreased with an increasing bioavailable Cu concentration in soil under various treatments. In comparison to CuSO4, both Cu(OH)2 nanopesticide (i.e., NPF) and nano-Cu(OH)2 (i.e., AI-NPF and NR) caused a significant (p < 0.05) inhibition of urease activity, wherein a significant (p < 0.05) increase in the activity of catalase was observed, representing serious oxidative stress. Accordingly, NPF, AI-NPF, and NR differently affected soil bacterial abundance, diversity, and community compared to CuSO4, which could have resulted from the changes in the bioavailable Cu concentration as a result of the distinct nature of copper spiked (i.e., nano form versus salt). Moreover, minor differences in the soil enzyme activity and bacterial community were observed between NPF and AI-NPF, reflecting that the impact of the Cu(OH)2 nanopesticide was primarily attributed to the presence of nano-Cu(OH)2. In total, the impacts of nano-Cu(OH)2 on the soil bacterial community and enzyme activity tested in this study differed from CuSO4, shedding light on the environmental risks of the Cu(OH)2 nanopesticide in the long run.

Mineralisation and release of 14C-graphene oxide (GO) in soils.

Graphene-based nanomaterials (GNMs) have been touted as miracle materials due to their extraordinary properties that can benefit many industries, including in agriculture and for environmental remediation. While improvement in nutrient delivery and the ability to adsorb environmental contaminants have been demonstrated, what happens to GNMs in soil is a question that has not been addressed. The main aim of this study was to investigate their degradation in soil to have a better understanding of their environmental fate. Using radioisotope techniques, this study assessed the potential mineralisation and release of graphene oxide (GO), one of the most commonly used forms of graphene. Results revealed that the conversion of GO to carbon dioxide was negligible (<2%) in microbially-active soils. GO remaining in soil was also not readily released by water extractions. The lack of mineralisation and release is indicative of GO's high (bio)degradation stability which is likely due to its limited availability resulting from its rapid homo/hetero-aggregation. Over-all, the results provide new and important information on the environmental fate of graphene nanomaterials applied to soils.

Are Nanoparticles a Threat to Mycorrhizal and Rhizobial Symbioses? A Critical Review.

Soil microorganisms can be exposed to, and affected by, nanoparticles (NPs) that are either purposely released into the environment (e.g., nanoagrochemicals and NP-containing amendments) or reach soil as nanomaterial contaminants. It is crucial to evaluate the potential impact of NPs on key plant-microbe symbioses such as mycorrhizas and rhizobia, which are vital for health, functioning and sustainability of both natural and agricultural ecosystems. Our critical review of the literature indicates that NPs may have neutral, negative, or positive effects on development of mycorrhizal and rhizobial symbioses. The net effect of NPs on mycorrhizal development is driven by various factors including NPs type, speciation, size, concentration, fungal species, and soil physicochemical properties. As expected for potentially toxic substances, NPs concentration was found to be the most critical factor determining the toxicity of NPs against mycorrhizas, as even less toxic NPs such as ZnO NPs can be inhibitory at high concentrations, and highly toxic NPs such as Ag NPs can be stimulatory at low concentrations. Likewise, rhizobia show differential responses to NPs depending on the NPs concentration and the properties of NPs, rhizobia, and growth substrate, however, most rhizobial studies have been conducted in soil-less media, and the documented effects cannot be simply interpreted within soil systems in which complex interactions occur. Overall, most studies indicating adverse effects of NPs on mycorrhizas and rhizobia have been performed using either unrealistically high NP concentrations that are unlikely to occur in soil, or simple soil-less media (e.g., hydroponic cultures) that provide limited information about the processes occurring in the real environment/agrosystems. To safeguard these ecologically paramount associations, along with other ecotoxicological considerations, large-scale application of NPs in farming systems should be preceded by long-term field trials and requires an appropriate application rate and comprehensive (preferably case-specific) assessment of the context parameters i.e., the properties of NPs, microbial symbionts, and soil. Directions and priorities for future research are proposed based on the gaps and experimental restrictions identified.