The influences of graphene oxide and nitrification inhibitor on vegetable growths and soil and endophytic bacterial communities: Double-edge sword effects and nitrate risk controls

Soil enzyme activities and bacterial communities respond to co-exposure of butyl benzyl phthalate and TiO2 nanomaterials: Earthworm-mediated effects

Phthalic acid esters (PAEs) are widely used due to their advantageous properties, which enhance the durability, flexibility, and transparency of plastic products. Nanomaterials are also commonly used in plastic additives and agricultural fertilizers. However, both are easy to fall off, diffuse, and release into the environment during production, use, and disposal. The adsorption and transportation of PAEs by nanomaterials may jointly affect soil health. However, less attention is paid to the soil microorganisms caused by co-exposure between PAEs and nanomaterials, especially mediated by earthworms. The present study investigated the effects of BBP (1 mg kg-1) and nTiO2 (1 mg kg-1), alone and in combination, on soil enzyme activities, microbial composition, and bacterial community diversity, with and without mediation by the earthworm Metaphire guillelmi. Results showed that co-exposure to BBP and nTiO2 activated enzyme activities in earthworm-mediated soil. Both contaminants, individually and combined, altered the composition, distribution, diversity, and complexity of the soil bacterial community mediated by earthworms. Bacteroidetes, Proteobacteria, and Actinobacteria were the dominant phyla. However, the complexity of soil bacterial community networks decreased. The findings highlight the importance of considering co-exposure and soil fauna mediation when evaluating the ecological impacts of emerging contaminants and fill the lack of ecotoxicity data on the co-exposure of PAEs and nanomaterials, thus promoting the design and synthesis of safer and more efficient nanomaterials.

Enhancing pakchoi cabbage yield and quality but reducing human-disease risk of bacterial community from wastewater irrigation by combined nanoscale zerovalent iron and nitrification inhibitor

It was indispensable to seek effective and feasible measures to alleviate the adverse effects of wastewater irrigation. Nanoscale zerovalent iron (nZVI) and soil nitrogen management might enhance the vegetable yield and quality but mitigate the potential human-disease risks from wastewater irrigation. This study selected the nZVI and nitrification inhibitor as experimental objects. The planted pakchoi cabbage was irrigated with the tap water and wastewater and treated with nZVI and 3, 4-dimethylpyrazole phosphate (DMPP), respectively, the pakchoi cabbage yield and quality, soil enzyme activity and abiotic property, and human-disease risk of bacterial community were quantified. Compared with the control, the nZVI significantly enhanced the pakchoi cabbage yield by 51.5% but reduced the pakchoi cabbage nitrate content by 52.6% under wastewater irrigation condition. The nZVI alone had double-edged sword effects of increasing the pakchoi cabbage yield, reducing the pakchoi cabbage nitrate content and soil human-disease risk but inhibiting the system multifunctionality and soil bacterial community diversity and stability, under wastewater irrigation condition. The nZVI diminished human-disease risk via increasing the soil Firmicutes and Verrucomicrobiota ratios, and the extra DMPP could mitigate the negative effects of nZVI by increasing soil enzyme activity and stimulating soil Acidobacteria ratio. The combinations of nZVI and DMPP could not only enhance the pakchoi cabbage yield and quality but also reduce the human-disease risk of soil bacterial community from wastewater irrigation.

Antagonistic Effect of Microplastic Polyvinyl Chloride and Nitrification Inhibitor on Soil Nitrous Oxide Emission: An Overlooked Risk of Microplastic to the Agrochemical Effectiveness

Microplastics are widely persistent in agricultural ecosystems and may affect soil nitrous oxide (N2O) emissions. Nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) is applied to decelerate nitrification and reduce soil N2O emission. Nevertheless, the interactive effects of nitrification inhibitors and microplastics on soil N2O emissions have not been investigated. Sole DMPP, polyvinyl chloride (PVC), and polystyrene (PS) substantially reduced agricultural soil N2O emission rates by 25.93%, 69.04%, and 73.89%, respectively. Nevertheless, PVC and DMPP had antagonistic effects on the N2O emission rates. The observed reductions in N2O emissions could be attributed to variations in soil oxygen availability, electron transport system activities, and Firmicutes, nap, and GDH genes. Moreover, the DMPP, PVC, and PS alone or copresences significantly enhanced the soil ecosystem multifunctionality (EMF). The findings shed light on the role of microplastics in soil N2O emission, EMF, and the microbial community, expanding the understanding of microplastics' effects on agrochemical effectiveness.

Tradeoffs among yield, cadmium bioavailability, nitrous oxide emission and bacterial community stability: Effects of iron-modified woody peat and nitrification inhibitors on soil-vegetable systems

Cadmium (Cd) pollution leads to soil degradation, decreases crop yield and affects human health through the food chain. Iron-modified woody peat (IMP) is an organic passivation material that significantly affects the migration of heavy metals in soil. Nitrification inhibitors are widely used to reduce greenhouse gas emissions. This study investigated the effects of the IMP and nitrification inhibitors dicyandiamide (DCD) and 3, 4-dimethylpyrazole phosphate on Cd content and form, crop yield, nitrous oxide (N2O) emission and bacterial communities in soil-lettuce systems. The simultaneous additions of IMP and DCD substantially reduced the soil available Cd content by 22.6 % and significantly promoted the lettuce yield by 42.9 %. Lettuce yield was significantly and negatively correlated with soil available Cd (correlation coefficient = -0.52). The simultaneous applications of IMP and nitrification inhibitors stimulated N2O emission risk by enhancing the soil NH4+-N contents and the relative abundances of Firmicutes, which could also decrease soil bacterial community stabilities. Therefore, tradeoffs among yield, Cd bioavailability, N2O emission and bacterial community stability should be comprehensively considered when evaluating the combined performances of IMP and nitrification inhibitors.

Application of waste eggshells elevates phytoremediation efficiency of Pb-Zn mine-contaminated farmland and mitigates soil greenhouse gas emissions: A field study

Remediating heavy metal (HM)-contaminated farmlands and sequestering soil carbon for emission reduction have been prominent topics in environmental research in recent years. However, few studies have looked into the soil greenhouse gas (GHG) impacts of growing hyperaccumulators in composite HM-contaminated farmland, as well as agronomic measures to remediate soil HMs while mitigating GHG emissions. To investigate fertilization measures to improve phytoremediation efficiency and mitigate GHG emissions, S. photeinocarpum was planted with three different fertilization measures on farmland contaminated by lead-zinc (Pb-Zn) mines (1200 kg ha-1 eggshell, 125 kg ha-1 28-homobrassinolide, and 16.7 kg ha-1 mineral potassium fulvic acid) during its growth period. The findings are as follows: Eggshell application significantly enhanced the translocation factor (TF) of Pb, Zn, and cadmium (Cd) from the roots to the shoots of Solanum photeinocarpum. Moreover, eggshells notably increased the bioaccumulation factor (BCF) of Cd and Pb in plant shoots by 120.75% and 159.09%, respectively. Regarding GHG emissions, the combined application of eggshells and 28-homobrassinolide substantially lowered the global warming potential (GWP) of the soil. Correlation analyses revealed that eggshell application increased the relative abundance of the Gemmatimonadota bacterial phylum in the soil, facilitating Pb and Cd migration from the roots to shoot tissues in S. photeinocarpum. Eggshell use inhibited nitrate nitrogen (NO3--N) transformation into nitrous oxide (N2O) by the Myxococcota bacterial phylum and reduced N2O release from the soil. The application of low-cost eggshells can achieve a win-win situation of soil HM remediation and GHG emission reduction, as well as provide simple and scalable management measures for HM-contaminated farmland.

Metabolomic and microbiomic resilience of Hong Kong oysters to dual stressors: Zinc oxide nanoparticles and low salinity

Zinc oxide nanoparticles, increasingly used in industrial and consumer products, and low salinity, exacerbated by climate change-induced alterations in precipitation patterns, represent significant environmental pressures in estuarine and coastal environments. This study advances previous research on their impacts on Hong Kong oysters (Crassostrea hongkongensis) by integrating metabolomics of hepatopancreas and gills with intestinal microbiomics. Employing advanced multi-omics integration methods, our analysis reveals novel insights into metabolic resilience under combined stress conditions. This resilience is characterized by coordinated, organ-specific adjustments in energy metabolism (d-glucose 1-phosphate in hepatopancreas, cytidine in gills), antioxidant defenses (glutathione, meso-2,6-diaminoheptanedioate, pimelic acid in hepatopancreas; indole, 3-(3-hydroxyphenyl)propanoic acid in gills), immune function (l-glutamine, ergocalciferol in hepatopancreas; argininosuccinic acid in gills), and membrane stability (lanosterin in hepatopancreas, allantoin in gills). Notably, under dual stressors, we observed a previously undescribed stabilization of microbial alpha diversity and certain phyla, an absence of distinctive biomarkers, and certain metabolic activity stabilization within the intestinal microbiota. These findings suggest robust compensatory mechanisms that maintain physiological homeostasis and microbial balance under stress, contrasting with primarily negative impacts reported in previous studies. Integration of metabolomic and microbiomic data revealed coordinated responses between microbial community changes and metabolic adjustments, particularly in osmoregulation, energy metabolism and antioxidant defenses, under dual stressors. This comprehensive approach provides a more realistic model of environmental challenges, revealing sophisticated adaptive strategies in Hong Kong oysters. Our study offers critical insights for understanding bivalve resilience, informing conservation strategies, and managing marine ecosystems in the face of increasing anthropogenic pressures.

Dicyandiamide Applications Mitigate the Destructive Effects of Graphene Oxide on Microbial Activity, Diversity, and Composition and Nitrous Oxide Emission in Agricultural Soil

The widespread production and utilization of graphene oxide (GO) raise concerns about its environmental release and potential ecological impacts, particularly in agricultural soil. Effective nitrogen (N) management, especially through nitrification inhibitors like dicyandiamide (DCD), might mitigate the negative effects of GO exposure on soil microbes via N biostimulation. This study quantified changes in soil physicochemical properties, nitrous oxide (N2O) emissions, microbial activity, biomass, and community after treatments with GO and DCD. The GO exposure significantly reduced bacterial 16S rRNA gene abundance and the biomass of major bacterial phyla. It also stimulated pathways linked to human diseases. However, DCD application alleviated the negative effects of GO exposure on soil bacterial biomass. While DCD application significantly reduced soil N2O emission, the GO application tended to hinder the inhibiting performance of DCD. Our findings highlight the hazards of GO exposure to soil microbes and the potential mitigation strategy with soil N management.

Asymmetries among soil fungicide residues, nitrous oxide emissions and microbiomes regulated by nitrification inhibitor at different moistures

Carbendazim residue has been widely concerned, and nitrous oxide (N2O) is one of the dominant greenhouse gases. Microbial metabolisms are fundamental processes of removing organic pollutant and producing N2O. Nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) can change soil abiotic properties and microbial communities and simultaneously affect carbendazim degradation and N2O emission. In this study, the comprehensive linkages among carbendazim residue, N2O emission and microbial community after the DMPP application were quantified under different soil moistures. Under 90% WHC, the DMPP application significantly reduced carbendazim residue by 54.82% and reduced soil N2O emission by 98.68%. The carbendazim residue was negatively related to soil ammonium nitrogen (NH4+-N), urease activity, and ratios of Bacteroidetes, Thaumarchaeota and Nitrospirae under 90% WHC, and the N2O emission was negatively related to NH4+-N content and relative abundance of Acidobacteria under the 60% WHC condition. In the whole (60% and 90% WHC together), the carbendazim residue was negatively related to the abundances of nrfA (correlation coefficient = -0.623) and nrfH (correlation coefficient = -0.468) genes. The hao gene was negatively related to the carbendazim residue but was positively related to the N2O emission rate. The DMPP application had the promising potential to simultaneously reduce ecological risks of fungicide residue and N2O emission via altering soil abiotic properties, microbial activities and communities and functional genes. ENVIRONMENTAL IMPLICATION: Carbendazim was a high-efficiency fungicide that was widely used in agricultural production. Nitrous oxide (N2O) is the third most important greenhouse gas responsible for global warming. The 3, 4-dimethylpyrazole phosphate (DMPP) is an effective nitrification inhibitor widely used in agricultural production. This study indicated that the DMPP application reduced soil carbendazim residues and N2O emission. The asymmetric linkages among the carbendazim residue, N2O emission, microbial community and functional gene abundance were regulated by the DMPP application and soil moisture. The results could broaden our horizons on the utilizations DMPP in decreasing fungicide risks and N2O emission.

Effects of Graphene-Based Nanomaterials on Microorganisms and Soil Microbial Communities

The past decades have witnessed intensive research on the biological effects of graphene-based nanomaterials (GBNs) and the application of GBNs in different fields. The published literature shows that GBNs exhibit inhibitory effects on almost all microorganisms under pure culture conditions, and that this inhibitory effect is influenced by the microbial species, the GBN's physicochemical properties, the GBN's concentration, treatment time, and experimental surroundings. In addition, microorganisms exist in the soil in the form of microbial communities. Considering the complex interactions between different soil components, different microbial communities, and GBNs in the soil environment, the effects of GBNs on soil microbial communities are undoubtedly intertwined. Since bacteria and fungi are major players in terrestrial biogeochemistry, this review focuses on the antibacterial and antifungal performance of GBNs, their antimicrobial mechanisms and influencing factors, as well as the impact of this effect on soil microbial communities. This review will provide a better understanding of the effects of GBNs on microorganisms at both the individual and population scales, thus providing an ecologically safe reference for the release of GBNs to different soil environments.

Core Soil Microorganisms and Abiotic Properties as Key Mechanisms of Complementary Nanoscale Zerovalent Iron and Nitrification Inhibitors in Decreasing Paclobutrazol Residues and Nitrous Oxide Emissions

Agrochemical residues and nitrous oxide (N2O) emissions have caused considerable threats to agricultural soil ecology. Nanoscale zerovalent iron (nZVI) and nitrification inhibitors might be complementary to each other to diminish soil agrochemical residues and N2O emissions and enhance soil bacterial community diversities. Compared to the control, the nZVI application declined soil paclobutrazol residues by 5.9% but also decreased the bacterial community co-occurrence network node. Combined nZVI and Dicyandiamide applications significantly decreased soil N2O emission rates and paclobutrazol residues but promoted Shannon diversity of the bacterial community. The increased soil pH, ammonium nitrogen, and Actinobacteriota could promote soil paclobutrazol dissipation. The nZVI generated double-edged sword effects of positively decreasing paclobutrazol residues and N2O emissions but negatively influencing soil multifunctionalities. The nZVI and Dicyandiamide could be complementary to each other in diminishing soil agrochemical residues and N2O emission rates but promoting soil bacterial community diversities simultaneously.