The pollution of farm soils by the plasticizer dibutyl phthalate (DBP) should be researched owing to the extensive use of plastic film. We investigated the influence of DBP on microbial communities and enzyme activities in rhizosphere and non-rhizosphere soil during the different growth stages of wheat and determined the response through simulations. The results indicated that protease, polyphenol oxidase, and β-glucosidase activity in soil decreased with increasing DBP dosage, while dehydrogenase, urease, and acid phosphatase activities increased. Moreover, the effects of DBP on soil enzyme activity gradually weakened with DBP degradation. Dibutyl phthalate has a certain inhibitory effect on the activity, diversity, and heterogeneity of microorganisms in soil. In addition, DBP can increase the utilization of amines and carboxylic acids and decrease the utilization of carbohydrates and amino acids by soil microorganisms. According to the Gaussian and molecular docking analysis, we considered that monobutyl phthalate and DBP could affect the utilization of amino acids by Proteobacteria. The enzyme activity, microbial activity, and heterogeneity of rhizosphere soil were higher than those of non-rhizosphere soil. Microbial carbon source utilization in rhizosphere and non-rhizosphere soils depends on wheat growth, soil type, and DBP dosage. Owing to the widespread presence of DBP in agriculture, negative effects of phthalic acid esters should be considered in relation to soil quality and food safety in future.

A pot experiment was carried out on brown soil polluted by dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) to investigate the effects of biochar (BC) derived from corn straw and Fe–Mn oxide modified biochar composites (FMBC) on the bioavailability of DBP and DEHP, as well as ecosystem responses in rhizosphere soil after wheat ripening. The results indicate that the application of BC and FMBC significantly increases soil organic matter, pH, available nitrogen (AN), Olsen phosphorus, and available potassium (AK); reduces the bioavailability of DBP and DEHP; enhances the activities of dehydrogenase, urease, protease, β-glucosidase, and polyphenol oxidase; and decreases acid phosphatase activity. No changes in richness and diversity, which were measured by Illumina MiSeq sequencing, were observed following BC and FMBC application. The bacterial community structure and composition varied with DBP/DEHP concentrations and BC/FMBC additions in a nonsystematic way and no significant trends were observed. In addition, FMBC exhibited better performance in increasing soil properties and decreasing the bioavailability of DBP and DEHP compared with BC. Hence, the FMBC amendment may be a promising way of developing sustainable agricultural environmental management.

To study the effects of long-term mining activities on the agricultural soil quality of Mengnuo town in Yunnan province, China, the heavy metal and soil enzyme activities of soil samples from 47 sites were examined. The results showed that long-term mining processes led to point source heavy metal pollution and Pb, Cd, Zn and As were the primary metal pollutants. Polyphenoloxidase was found the most sensitive soil enzyme activity and significantly correlated with almost all the metals (P < 0.05). Amylase (for C cycling), acid phosphatase (for P cycling) and catalase (for redox reaction) activities showed significantly positive correlations (P < 0.05) with Pb, Cd, Zn and As contents. The correlations between soil enzymes activities and Cd, Pb and Zn contents were verified in microcosm experiments, it was found that catalase activity had significant correlations (P < 0.05) with these three metals in short-term experiments using different soils under different conditions. Based on both field investigation and microcosm simulation analysis, oxidoreductases activities (rather than a specific enzyme activity) were suggested to be used as “core enzyme”, which could simply and universally indicate the heavy metal pollution degrees of different environments. And hydrolases (for C, N, P and S recycling) could be used as a supplement to improve correlation accuracy for heavy metal indication in various polluted environments.

Nutrient loading is a leading cause of global seagrass decline, triggering shifts from seagrass- to macroalgal-dominance. Within seagrass meadows of Xincun Bay (South China Sea), we found that nutrient loading (due to fish farming) increased sediment microbial biomass and extracellular enzyme activity associated with carbon cycling (polyphenol oxidase, invertase and cellulase), with a corresponding decrease in percent sediment organic carbon (SOC), suggesting that nutrients primed microorganism and stimulated SOC remineralization. Surpisingly, however, the relative contribution of seagrass-derived carbon to bacteria (δ13Cbacteria) increased with nutrient loading, despite popular theory being that microbes switch to consuming macroalgae which are assumed to provide a more labile carbon source. Organic carbon sources of fungi were unaffected by nutrient loading. Overall, this study suggests that nutrient loading changes the relative contribution of seagrass and algal sources to SOC pools, boosting sediment microbial biomass and extracellular enzyme activity, thereby possibly changing seagrass blue carbon.

Seagrass meadows are experiencing worldwide declines mainly because of nutrient enrichment, which always result in macroalgae bloom and consequently periodic collapse and decomposition. However, effects of macroalgae decay on the sediment organic carbon (SOC) sequestration capacity remain unknown. Depending on the macroalgae biomass in eutrophic seagrass meadows of South China Sea, we carried out a laboratory chamber experiment to investigate the sediment labile organic carbon (OC) compositions and the influencing SOC transformation enzyme activity variations of seagrass meadows in response to common macroalgae bloom species (Cladophora spp.) decomposition. Although the dehydrogenase and β-glucosidase activities were not affected by macroalgae decomposition, the macroalgae decomposition significantly elevated the salt-extractable carbon (SEC) content, SEC/SOC, levels of invertase and polyphenol oxidase activities, and the CO₂ release. Overall, this study indicates that macroalgae decomposition stimulates the SOC transformation, and therefore, it is not benefit for SOC sequestration within seagrass meadows of the South China Sea.

A combined process comprised of electro-Fenton and bioslurry (EF–bioslurry) was developed at lab scale for remediating a real coking plant soil with an initial polycyclic aromatic hydrocarbons (PAHs) content of 3605 mg/kg. Sodium citrate was used as a complexant to keep the iron in solution at near-neutral pH conditions for increasing the reaction rate. The appropriate order of application was to perform EF process followed by bioslurry, which was evaluated through analysis of degradation characteristics of individual processes. The optimum EF duration was assessed through an analysis of the induced changes in PAHs degradation and bacterial counts. The optimum application time of EF process was determined to be 24 h. The removal of PAHs was 95.2% for EF–bioslurry after 40 days, and the efficiency was increased by almost 150%, compared with the individual bioslurry treatment. The EF reaction caused significant cell death and high inhibition to polyphenol oxidase (PPO) activity of soil. The bacterial activity and counts in the slurry recovered rapidly after EF oxidation through the addition of raw soil (2%, w/w). Therefore, the combined process of EF–bioslurry process may be an efficient and promising approach for the remediation of highly organic-contaminated soil.

Diesel spills may considerably damage the sensitive coastal wetlands along Huangpu River, Shanghai, China. In this experiment, Cyperus rotundus, a dominant coastal marsh plant, was cultured in diesel-contaminated soils at concentrations of 0, 1000, 5000, 10,000, 15,000 and 20,000 mg kg⁻¹ to investigate its phytoremediation potential. In this study, plant biomass, removal characteristic of diesel, redox potential, and activities of urease, dehydrogenase, and polyphenoloxidase in soils were determined after 50-day pot experiments. The results demonstrated that soils planted with Cyperus rotundus had significantly less diesel than did unplanted soils. The residual concentrations of alkanes in soils at 10,000 mg kg⁻¹ after 50 days showed that 52.9–92.0 % of Fraction a (C₁₄–C₁₉) and 47.8–64.4 % of Fraction b (C₂₀–C₂₇) were removed in unplanted soils, while more than 90 % of both Fractions a and b were removed in planted soils. The peak value of urease and dehydrogenase activities was at 15,000 mg kg⁻¹ of diesel-contaminated concentration; however, the peak value of polyphenoloxidase activity appeared at 10,000 mg kg⁻¹. It was deduced that the diesel concentration between 10,000 and 15,000 mg kg⁻¹ might be a limit which Cyperus rotundus could tolerate diesel pollution.

The novelty of the present research is conducting a new method in the systemic resistance of plant diseases by using distinct marine extracts. The ability of two octopus extracts to reduce the wilt disease caused by Fusarium oxysporum was observed. The applied methods are soaked roots (SR) and foliar shoots (FS). The antioxidant enzyme activities, percent disease index (PDI), and growth parameters were measured. In vitro antifungal potential of the octopus extracts against F. oxysporum was examined. The obtained result shows that SR extracts reduced PDI. Additionally, all the tested treatments promoted the growth and photosynthetic pigments of the infected plants. SR (in ethanolic extracts) was the most prominent inducer which offered a high advancement in the total soluble protein contents. Also, SR (in methanolic extracts) was the most suitable inducer which provided a very necessary development not only in the total phenol but also in the peroxidase (POD) and polyphenol oxidase (PPO) activities. GC-MS investigation of the octopus extracts exhibited that the compounds which possess antifungal activity were furoscrobiculin B and/or eugenol. They demonstrated a notable antifungal potential against F. oxysporum with a maximum activity of 38.5 and 12.7 mm ZOI after the treatment with the ethanolic and methanolic extract, respectively. FTIR results illustrated the functional group of the compound responsible for the antifungal activity. Additionally, an atomic absorption result reveals that there are traces of metals detected such as Pb, Ag, Cu, Zn, and Mg. The antifungal activity was decreased as the concentrations were reduced. Accordingly, the present extracts may be used as the vital agents in the agricultural field to restrain the plant pathogenic fungi, especially F. oxysporum from a proliferation.

The present study demonstrates the development of polyphenol oxidase (PPO) biosensor for the detection of catechol using strontium copper oxide (SrCuO₂) and polypyrrole nanotubes (PPyNT) matrix. The SrCuO₂ micro-seeds, a perovskite compound, are synthesized by co-precipitation under pH 8.0. The as-synthesized micro-seeds are characterized by scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction spectroscopy (XRD). The proposed sensor is fabricated on pencil graphite (P-Gr) by successive deposition of PPyNT, SrCuO₂, and PPO enzyme. The developed PPO/SrCuO₂/PPyNT/P-Gr sensor is characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) techniques. The PPO/SrCuO₂/PPyNT/P-Gr displayed excellent electrocatalytic activity towards the oxidation and detection of catechol. The as-developed sensor showed sensitive response ascribing to limit of detection (LOD) of 0.15 μM and sensitivity of 15.60 μA μM⁻¹ cm⁻². The fabricated sensor exhibited excellent repeatability and longer shelf life. The proposed biosensor finds its application within the broad linear range of 1–50 μM. Real sample analysis of mineral water, tap water, and domestic wastewater using developed sensor showed acceptable recovery. Hence, the biosensor endeavors its application in environmental monitoring and protection.

The toxic impacts of CuO nanoparticles (NPs) on the marine phytoplankton Nannochloropsis oculata were evaluated by measuring a number of biological parameters. Exposure to different concentrations of CuO-NPs (5–200 mg/L) significantly decreased the growth and content of chlorophyll a of N. oculata. The results showed that CuO-NPs were toxic to this microalga with a half maximal effective concentration (EC50) of 116.981 mg/L. Exposure to CuO-NPs increased the hydrogen peroxide (H₂O₂) content and induced the membrane damages. Moreover, the concentration of phenolic compounds was increased, while the levels of carotenoids were markedly decreased in comparison to the control sample. The activity of catalase (CAT), ascorbate peroxidase (APX), polyphenol oxidase (PPO) and lactate dehydrogenase (LDH) enzymes significantly was increased in response to CuO-NPs treatments. These results indicated that CuO-NPs stimulated the antioxidant defense system in N. oculata to protect the cells against the oxidative damages. The Fourier-transform infrared spectroscopy (FTIR) analyses showed that the main functional groups (C=O and C–O–C) interacted with CuO-NPs. The images of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the cell membrane damage and the change of cell wall structure which may be contributed to the nanotoxicity. These findings may provide additional insights into the mechanisms of cytotoxicity induced by CuO-NPs.