Functional keystone taxa promote N and P removal of the constructed wetland to mitigate agricultural nonpoint source pollution.

Characterized by irregular spatial and temporal variations of pollutant loading and complex occurrence mechanisms, agricultural nonpoint source pollution (ANPSP) has always been a great challenge in field restoration worldwide. Returning farmlands to wetlands (RFWs) as an ecological restoration mode among various constructed wetlands was selected to manage ANPSP in this study. Triarrhena lutarioriparia, Nelumbo nucifera and Zizania latifolia monocultures were designed and the water pollutants was monitored. N. nucifera and Z. latifolia could reach the highest TN (53.28 %) and TP (53.22 %) removal efficiency, respectively. By 16s high-throughput sequencing of rhizosphere bacteria, 45 functional species were the main contributors for efficient N and P removal, and 38 functional keystone taxa (FKT) were found with significant ecological niche roles and metabolic functions. To our knowledge, this is the first study to explore the microbial driving N and P removal mechanism in response to ANPSP treated by field scale RFWs.

Molybdenum disulfide co-catalysis boosting nanoscale zero-valent iron based Fenton-like process: Performance and mechanism.

The conventional Fenton process has the drawbacks of low efficiency of Fe3+/Fe2+ conversion, low utilization of H2O2, and narrow range of pH. In this paper, molybdenum sulfide (MoS2) was used as a co-catalyst to boost the nanoscale zero-valent iron (nZVI) based heterogeneous Fenton-like process for the degradation of Rhodamine B (RhB). The catalytic performance, influences of parameters, degradation mechanism, and toxicity of intermediates were explored. Compared with the conventional like-Fenton process, the existence of MoS2 accelerated the decomposition of H2O2 and the RhB degradation rate constant of MoS2/nZVI/H2O2 reached more than six times that of nZVI/H2O2. In addition, the effective pH range of MoS2/nZVI/H2O2 was broadened to 9.0 with 84.9% of RhB being removed within 15 min. The co-catalytic system of MoS2 and nZVI was stable and had high reusability according to the results of four consecutive runs. Quenching tests and electron paramagnetic resonance (EPR) demonstrated that hydroxyl radical (·OH), superoxide anions (·O2-), and singlet oxygen (1O2) were all involved in MoS2/nZVI/H2O2. Compared with nZVI/H2O2 system, MoS2 not only increased the corrosion of nZVI but also accelerated the conversion of Fe3+/Fe2+. ECOSAR analysis suggested that the overall acute and chronic toxicity of the degradation products decreased after treatment. Hence, this MoS2 co-catalytic nZVI based Fenton-like process can be used as a promising alternative for the treatment of organic wastewater.

Enhanced elimination of Cr(VI) from aqueous media by polyethyleneimine modified corn straw biochar supported sulfide nanoscale zero valent iron: Performance and mechanism.

A novel polyethyleneimine modified corn straw biochar supported sulfide nanoscale zero-valent iron (S-nZVI@PBC) was developed to enhance Cr(VI) removal from aqueous media. The characteristics of morphology, chemical composition, and functional groups of S-nZVI@PBC, as well as its kinetics and mechanism for Cr(VI) removal were explored. Characterization verified S-nZVI was successfully loaded onto PEI modified biochar. The adsorption process was well represented pseudo-second-order model (R2 = 0.990) and Langmuir isotherm model (R2 = 0.962), indicating it was a monolayer chemical adsorption process. The Cr(VI) removal was affected by pH and achieved the maximum when pH = 3.0, which may be ascribed to the better corrosion of nZVI and release of Fe(II) from the S-nZVI@PBC in acidic condition. The primary mechanisms were adsorption, reduction, and co-precipitation. S-nZVI@PBC exhibited higher stability and reusability than nZVI, which makes it more promising in environmental application. Overall, S-nZVI@PBC is of great potential for treating Cr(VI)-containing wastewater.

Long-term effects of phytoextraction by a poplar clone on the concentration, fractionation, and transportation of heavy metals in mine tailings.

Mine tailings are one of main causes of diffused heavy metal pollution since the heavy metals in there may acquire mobility. The current knowledge of the processes at work in long-term phytoremediation by woody species remains insufficient. Through a 4-year field study, we evaluated the phytoextraction efficiency of Populus deltoides CL. 'Xianglin 90' grown on a mine tailing co-polluted by Cd, Cu, Cr, Ni, Pb, and Zn. The concentrations of Cd, Cu, Ni, Pb, and Zn in the rhizospheric soil were reduced by amounts ranging from 12.86 to 42.19% during the study period. Bioconcentration factors and translocation factors showed that the accumulation of Cd and Zn occurring in the shoots was the most effective. Combined with the considerable biomass produced by poplar, the extracted amounts of Cd and Zn could reach 0.61 g and 10.66 g plant-1, respectively, in which the shoots account for 77.3% (Cd) and 89.0% (Zn) of the overall extraction amounts. Acid-soluble Cd and Zn increased by 5.49% and 4.29%, respectively, in the rhizosphere compared to the bulk soil, indicating that poplar enhanced the mobility of Cd and Zn in the rhizosphere, which explained its ability for bioaccumulation and root-shoot translocation. Moreover, calculated time required to address the issue of Cd and Zn pollution was theoretically shortened by more than half from 2015 to 2019. This study brings new insights into the long-term effects of phytoextraction on the concentration, fractionation, and transportation of heavy metals and confirms the potential of poplar as a Cd and Zn remediation species.

Calcium peroxide eliminates grease inhibition and promotes short-chain fatty acids production during anaerobic fermentation of food waste.

Deterioration of anaerobic fermentation can occur with the presence of grease in food waste, but little information on eliminating this deterioration is currently available. In this study, it was found that the presence of 10 g/L grease decreased SCFAs production from 16.97 to 13.32 g COD/L and prolonged the optimal fermentation time to 7 days, but could be respectively recovered to 39.10 g COD/L and 4 days with 0.02 mg/g VS (volatile solids) calcium peroxide addition. Mechanism investigations indicated that calcium peroxide facilitated biodegradable organics release and improved grease degradation, thereby providing enough nutrients and better growth environments to microbes for SCFAs-producing, which could be further supported by the elevated enzymes activities responding to hydrolysis and acidification process. Further investigations revealed that among the main derivates of calcium peroxide, OH- and Ca2+ played vital role in SCFAs production promotion, O2- and OH radicals were the main contributors to grease degradation.

Characterization and mechanism of lead and zinc biosorption by growing Verticillium insectorum J3.

Verticillium insectorum J3 was isolated from a local lead-zinc deposit tailing, and its biosorption characteristics and reaction to the toxicities of different Pb(II) and Zn(II) concentrations were investigated. SEM, FTIR, a pH test and a desorption experiment were carried out to identify a possible mechanism. The biosorption of J3 presented an inhibition trend at low concentrations (25-75 mg L-1) and promotion at high concentrations (100-300 mg L-1). J3 absorbed Pb(II) prior to Zn(II) and produced alkaline substances, while mycelial and pellet morphology modifications were important for the removal of Pb(II) and Zn(II) under different stressful conditions (SEM results). Both intracellular accumulation and extracellular absorption may contribute to the removal of Pb(II) at lower concentrations (25-50 mg L-1), although mainly extracellular biosorption occurred at higher concentrations (75-300 mg L-1). However, Zn(II) bioaccumulation occurred at all concentrations assayed. Verticillium insectorum J3 may have evolved active defenses to alleviate the toxicity of heavy metals and proved to be a highly efficient biosorbent, especially for Pb(II) at high concentrations. This study is a useful reference for the development of biotreatment technologies to mitigate heavy metal waste.

How to Construct DNA Hydrogels for Environmental Applications: Advanced Water Treatment and Environmental Analysis.

With high binding affinity, porous structures, safety, green, programmability, etc., DNA hydrogels have gained increasing recognition in the environmental field, i.e., advanced treatment technology of water and analysis of specific pollutants. DNA hydrogels have been demonstrated as versatile potential adsorbents, immobilization carriers of bioactive molecules, catalysts, sensors, etc. Moreover, altering components or choosing appropriate functional DNA optimizes environment-oriented hydrogels. However, the lack of comprehensive information hinders the continued optimization. The principle used to fabricate the most suitable hydrogels in terms of the requirements is the focus of this Review. First, different fabrication strategies are introduced and the ideal characteristic for environmental applications is in focus. Subsequently, recent environmental applications and the development of diverse DNA hydrogels regarding their synthesis mechanism are summarized. Finally, the Review provides an insight into the remaining challenging and future perspectives in environmental applications.

An electrochemical DNA sensor based on a layers-film construction modified electrode.

This work developed a relatively inexpensive and layers-film construction electrochemical sensor for DNA recognition and its performance was investigated. The Fe(3)O(4) magnetic nanoparticles-cysteine were immobilized on the carbon paste electrode (CPE) surface using magnetic force. Multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (GNPs), and chitosan (Chi) were used successively to coat on the electrode surface. The thiolated capture probe was assembled and competitively hybridized with the target nucleic acid and biotinylated response probe. The electrochemical behavior was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. In addition, the sensor performance was also analyzed by introducing the notion of detection efficiency. The experimental results showed that although the electron transfer capability of the CPE is less strong than that of a metal electrode used in the DNA sensor, the materials modified on the CPE could significantly improve the performance. A detection limit of 1 nM of target DNA and a sensitivity of 2.707 × 10(3) mA M(-1) cm(-2) were obtained. Although the resulting detection limit was not remarkable, further experiments could improve it.

Oxalate production at different initial Pb²+ concentrations and the influence of oxalate during solid-state fermentation of straw with Phanerochaete chrysosporium.

The production of oxalate at different initial Pb(2+) concentrations during solid-state fermentation of straw with Phanerochaete chrysosporium was investigated. It was found that the maximal peak value of oxalate concentration (22.84 mM) was detected at the initial Pb(2+) concentration of 200 mg kg(-1) dry straw, while the minimum (15.89 mM) at the concentration of 600 mg Pb(2+)kg(-1) dry straw, and at moderate concentration of Pb(2+) the capability of oxalic acid secretion was enhanced. In addition, it was also found that more oxalic acid accumulation went together with better Pb(2+) passivation effect and higher manganese peroxidase (MnP) activity. The present findings will improve the understandings of the interactions of heavy metals with white-rot fungi and the role of oxalate in lignin degradation system, which could provide useful references for more efficient treatment of Pb-contaminated lignocellulosic waste.

Highly sensitive fluorescence quantification of picloram using immunorecognition liposome.

Picloram is a widely used chlorinated herbicide, which is quite persistent and mobile in soil and water with adverse health and environmental risks. A simple and efficient method with high sensitivity and good selectivity was developed in this work to analyze picloram. The aldehyde group functionalized quartz glass plate was used to catch picloram by Schiff base reaction, and reacted with the liposomes-labeled antibody. The fluorescein isothiocyanate (FITC) solution was encapsulated in the liposomes. After being released from the liposomes, the fluorescence of FITC was measured by a fluorimeter. It was found that the fluorescence intensity is linearly correlated to the logarithm of picloram concentration, ranging from 1.0 × 10(-4) to 100 ng mL(-1), with a detection limit of 1.0 × 10(-5) ng mL(-1). Picloram concentration in real wastewater samples were accurately measured by the proposed method and HPLC, the results of the two methods were approximately the same. The proposed method showed high sensitivity and good selectivity, and could be an efficient tool for picloram quantitative analysis.

Mycelial growth and solid-state fermentation of lignocellulosic waste by white-rot fungus Phanerochaete chrysosporium under lead stress.

Lignocellulosic biomass is an abundant renewable resource difficult to degrade. Its bioconversion plays important roles in carbon cycles in nature, which may be influenced by heavy metals in environment. Mycelial growth and the degradation of lignocellulosic waste by lignin-degrading fungus Phanerochaete chrysosporium under lead stress were studied. It was shown that P. chrysosporium could grow in liquid media with 400 mg L⁻¹ Pb(II), and mycelial dry weight was reduced by 54% compared to the control. Yellow mycelia in irregular short-strip shape formed in Pb-containing media, whereas the control showed ivory-white regular mycelial pellets. Two possible responses to Pb stress were: dense hyphae, and secretion from mycelia to resist Pb. During solid-state fermentation of straw, fungal colonization capability under Pb stress was positively correlated with the removal efficiency of soluble-exchangeable Pb when its content was higher than 8.2 mg kg⁻¹ dry mass. Carboxymethyl cellulase activity and cellulose degradation were inhibited at different Pb concentrations, whereas low Pb concentrations increased xylanase and ligninolytic enzyme activities and the hemicellulose and lignin degradation. Cluster analyses indicated that Pb had similar effects on the different microbial indexes related to lignin and hemicellulose degradation. The present findings will advance the understandings of lignocellulose degradation by fungi under Pb pollution, which could provide useful references for developing metal-polluted waste biotreatment technology.

[Research on sorption and transport characteristics of ligninolytic enzymes in different compost substances].

To understand the characteristics of ligninolytic enzymes sorption and transport in different compost substances, ligninolytic enzymes adsorption on soil, vegetable leaf, rice straw and chaff was comparatively studied through batch jar tests and relevant kinetics and isotherm equilibrium were discussed as well as a column experiment was performed to study the process of transport. The results showed that the sorption efficiency was depended on the sorts of substances. The adsorptive capacities of soil, vegetable leaf, rice straw and chaff to lignin peroxidase (LiP) were 1.22 U x g(-1), 1.27 U x g(-1), 1.13 U x g(-1), 1.22 U x g(-1) and to manganese peroxidase (MnP) were 5.09 U x g(-1), 4.88 U x g(-1), 4.43 U x g(-1), 3.95 U x g(-1), respectively. Comparing the kinetic models of LiP and MnP adsorption, the pseudo-second-order reaction model (R2 0.973-0.999 7) was the best of the models. Elovich equation was a bit better than pseudo-first-order kinetic which was the worst. The equilibrium data could be fitted well with Langmuir model while it could not satisfied with Freundlich model. The adsorptive saturation of soil, vegetable leaf, rice straw and chaff to LiP were 1.23 U x g(-1), 1.30 U x g(-1), 1.17 U x g(-1), 1.14 U x g(-1) and to MnP were 5.70 U x g(-1), 5.19 U x g(-1), 4.73 U x g(-1), 4.14 U x g(-1). LiP and MnP had good transport capability in straw and chaff to move to the deepest layer of 10 mL while remained in the superficial layers in soil and vegetable leaf.

Changes of microbial population structure related to lignin degradation during lignocellulosic waste composting.

Microbial populations and their relationship to bioconversion during lignocellulosic waste composting were studied by quinone profiling. Nine quinones were observed in the initial composting materials, and 15 quinones were found in compost after 50days of composting. The quinone species Q-9(H2), Q-10 and Q-10(H2) which are indicative of certain fungi appeared at the thermophilic stage but disappeared at the cooling stage. Q-10, indicative of certain fungi, and MK-7, characteristic of certain bacteria, were the predominant quinones during the thermophilic stage and were correlated with lignin degradation at the thermophilic stage. The highest lignin degradation ratio (26%) and good cellulose degradation were found at the cooling stage and were correlated with quinones Q-9, MK-7 and long-chain menaquinones attributed to mesophilic fungi, bacteria and actinomycetes, respectively. The present findings will improve the understandings of microbial dynamics and roles in composting, which could provide useful references for development of composting technology.

[Analysis of the effect of enzymes on microbial community metabolic profiles during composting using biolog method].

The effects of enzymes on organic material degradation and microbial communities metabolic profiles during composting process were studied using Biolog method, and together with cluster analysis and PCA. The results showed that, adding the enzyme solution in the composting could increase the degradation rate of organic material by 4.90%. The microbial community metabolic results of cluster analysis showed that when the enzyme solution was added into the compost, the carbon metabolic capability of intermediate metabolite was improved. The results of PCA indicated that when the enzyme solution was added, microbial communities enhanced the metabolic capability of miscellaneous, polymers, amino acids and amides carbon substrates, which results in the efficient degradation of organic substance. In addition, cluster analysis of each composting phase showed that the effects of the enzymes solution on microbial community metabolism were mainly observed on 6 d and 30 d, which promoted the composting process.

Degradation of lead-contaminated lignocellulosic waste by Phanerochaete chrysosporium and the reduction of lead toxicity.

Lead, as one of the most hazardous heavy metals to the environment interferes with lignocellulosic biomass bioconversion and carbon cycles in nature. The degradation of lead-polluted lignocellulosic waste and the restrain of lead hazards by solid-state fermentation with Phanerochaete chrysosporium were studied. Phanerochaete chrysosporium effectively degraded lignocellulose, formed humus and reduced active lead ions, even at the concentration of 400 mg/kg dry mass of lead. The highest lignocellulose degradation (56.8%) and organic matter loss (64.0%) were found at the concentration of 30 mg/kg of lead, and at low concentration of lead the capability of selective lignin biodegradation was enhanced. Microbial growth was delayed in polluted substrate at the initial stage of fermentation, and organic matter loss is correlated positively with microbial biomass after 12 day fermentation. It might be because Phanerochaete chrysosporium developed active defense mechanism to alleviate the lead toxicity. Scanning electron micrographs with energy spectra showed that lead was immobilized via two possible routes: adsorption and cation exchange on hypha, and the chelation by fungal metabolite. The present findings will improve the understandings about the degradation process and the lead immobilization pathway, which could be used as references for developing a fungi-based treatment technology for metal-contaminated lignocellulosic waste.

Composting of lead-contaminated solid waste with inocula of white-rot fungus.

The treatment of the simulated lead-contaminated solid waste by composting with white-rot fungus was studied at laboratory scale. The composting system without the inocula of white-rot fungus was prepared as control, and the composting of the uncontaminated solid waste with the inocula of white-rot fungus was carried out as the other control. The results indicated that the solid waste inoculated with white-rot fungus could be successfully processed. The final compost was mature with 70.5% of lead (Pb) in residual fraction and none in exchangeable fraction. Germination index reached 120%. All the results indicated that the bioavailability of Pb in compost was reduced and the potential harm of Pb in compost was alleviated by composting with the inocula of white-rot fungus.

[Application of white-rot fungi in composting lead-contaminated waste].

Simulative lead polluted wastes which containing unpolluted soil, household waste, straw, bran and lead nitrate were prepared. Inoculation of white-rot fungi and uninoculation in composting of lead-contaminated waste were studied. Change of chemical factor, biological parameter and biological toxicity analyses with time during the composting process were determined to study effect of heavy metal on composting process and probability of application of white-rot fungi in composting of metal-contaminated waste. The results show the composting of lead-contaminated waste inoculated white-rot fungi could be successfully processed, which lead to the reduction of the bioavailability of Pb in compost and alleviate the potential harm from heavy metal. Under this composting process, for the final compost, pH, water-soluble organic carbon/nitrogen, volatile solid, lignin and coarse fibre remained reached 7.9, 4.01, 36.1%, 22.4g, 30.1g, respectively. In addition, 63.38% of Pb in residual fraction and 0% of Pb in soluble-exchangeable fraction were found in final compost, and the germination index of final compost reached 121%.

Bioremediation of Pb-contaminated soil by incubating with Phanerochaete chrysosporium and straw.

The bioremediation of the simulated lead (Pb)-contaminated soils by incubating with Phanerochaete chrysosporium and straw was studied at laboratory-scale. The soil pH, Pb concentration, soil microbial biomass, microbial metabolic quotient, microbial quotient and microbial biomass C-to-N ratios were monitored. The above indicators were to study the stress of Pb on soil and the microbial effects during the bioremediation process. It was found that the soils treated with P. chrysosporium and straw showed a much lower concentration of soluble-exchangeable Pb, lower metabolic quotient and biomass C-to-N ratios (0mgkg(-1) dry weight soil, 1.9mg CO(2)-Cmg(-1) biomass carbon and 4.9 on day 60, respectively) and higher microbial biomass and microbial quotient (2258mgkg(-1) dry weight soil and 7.86% on day 60, respectively) compared with the controls. In addition, the kinetic parameters in the model based on logistic equation were calculated by the BIOLOG data. By analyzing those kinetic parameters some information on the metabolic capacity of the microbial community could be obtained. All the results indicated that the bioavailability of Pb in contaminated soil was reduced so that the potential stress of Pb was alleviated, and also showed that the soil microbial effects and the metabolic capacity of microbial community were improved.