Long-neglected contribution of nitrification to NO emissions in the Yellow River.

Rivers play a significant role in the global nitrous oxide (NO) budget. However, the microbial sources and sinks of NO in river systems are not well understood or quantified, resulting in the prolonged neglect of nitrification. This study investigated the isotopic signatures of NO, thereby quantifying the microbial source of NO production and the degree of NO reduction in the Yellow River.

Unignorable enzyme-specific isotope fractionation for nitrate source identification in aquatic ecosystem.

Nitrate contamination in aquatic systems is a widespread problem across the world. The isotopic composition (δN, δO) of nitrate and their isotope effect (ε, ε) can facilitate the identification of the source and transformation of nitrate. Although previous researches claimed the isotope fractionations may change the original δN/δO values and further bias identification of nitrate sources, isotope effect was often ignored due to its complexity.

Effect of low temperature on contributions of ammonia oxidizing archaea and bacteria to nitrous oxide in constructed wetlands.

Constructed wetlands (CWs) have been widely used for ecological remediation of micro-polluted source water. Nitrous oxide (NO) from CWs has caused great concern as a greenhouse gas. However, the contribution of ammonia oxidation driven by ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) to NO emission, especially at low temperature, was unknown.

Using hierarchical stable isotope to reveal microbial food web structure and trophic transfer efficiency differences during lake melt season.

The microbial food web (MFW) is a material and energy source in lake water ecosystems. Although it is crucial to determine its structure and function for water ecological health, MFW changes during lake melt period have not been well studied. In this study, the MFW was divided into three categories by analyzing its structure and trophic transfer efficiency using hierarchical C/N stable isotopes and eDNA sequencing techniques, including the detrital food web (DFC, 15 %), classical grazing food web (CFC, 60 %), and mixed trophic food web (MFC, 25 %).

Distinct oxygen isotope fractionations driven by different electron donors during microbial nitrate reduction in lake sediments.

Microbial nitrate reduction can be driven by organic carbon oxidation, as well as by inorganic electron donors, such as reduced forms of sulfur and iron. An apparent inverse oxygen isotope fractionation effect was observed during nitrate reduction in sediment incubations from five sampling sites of a freshwater lake, Hongze Lake, China. Incubations with organic and inorganic electron donor additions were performed.

Archaeal and bacterial ecological strategies in sediment denitrification under the influence of graphene oxide and different temperatures.

As an emerging material, graphene oxide (GO) has been widely used in recent years and will inevitably enter into natural water bodies, and it may have an impact on lake microbial communities owing to its potential toxicity and denitrification-enhancing ability. This study simulated the effect of 0.1 g/L GO on denitrification in lake sediments under summer (28 °C) and winter temperatures (8 °C).

Electron beam-induced athermal nanowelding of crossing SiO amorphous nanowires.

Nanowelding of two crossing amorphous SiO nanowires induced by uniform electron beam irradiation at room temperature was demonstrated in an transmission electron microscope. It was observed that, under the electron beam irradiation, the amorphous nanowires became unstable driven by nanocurvature non-uniformly distributed over the nanowire surface centered around the crossing site of the nanowires. Such an instability of the nanowires could give rise to an athermal fast and massive migration of atoms nearby the surface centered around the crossing site, and thus the two crossing nanowires become gradually welded.

The promotion and inhibition effect of graphene oxide on the process of microbial denitrification at low temperature.

This study found that graphene oxide (GO) improved microbial denitrification at low temperatures (~12 °C), and the optimal concentration was 10 mg/L as the removal rate of NO-N increased by 17%. At the optimal concentration, GO improved the electron transport system activity of the microbes and enhanced the activity of nitrate reductase and nitrite reductase while exhibited low microbial toxicity. The addition of GO increased the content of tightly bound extracellular polymeric substances (EPS).

Microbial coupling mechanisms of nitrogen removal in constructed wetlands: A review.

Nitrogen removal through microorganisms is the most important pathway in constructed wetlands (CWs). In this review, we summarize the microbial coupling mechanisms of nitrogen removal, which are the common methods of nitrogen transformation. The electron pathways are shortened and consumption of oxygen and energy is reduced during the coupling of nitrogen transformation functional microorganisms.

Nanoinstabilities of CuO porous nanostructured films as driven by nanocurvature effect and thermal activation effect.

In this work, the instabilities at the nanoscale (i.e. nanoinstabilities) of triangular pyramids-like CuO porous nanostructured films (PNFs) are studied by heating treatments under different atmosphere and temperature.

CuO porous nanostructured films fabricated by positive bias sputtering deposition.

In this work, the authors fabricated CuO porous nanostructured films (PNFs) on glass slide substrates by the newly developed positive bias deposition approach in a balanced magnetron sputtering (MS) system. It was found that the surface morphology, crystal structure and optical property of the as-deposited products were greatly dependent on the applied positive substrate bias. In particular, when the substrate was biased at +50 and +150 V, both of the as-prepared CuO PNFs exhibited a unique triangular pyramids-like structure with obvious edges and corners and little gluing, a preferred orientation of (111) and a blue shift of energy band gap at 2.

Quantitative analysis of genetic associations in the biodegradative pathway of PAHs in wetland sediments of the Bohai coast region.

The present study characterized the distribution and sources of polycyclic aromatic hydrocarbons (PAHs) in 57 sediment cores collected from estuary and tidal flat wetlands in the Bohai coast region and investigated the molecular degradation mechanism of PAHs. The results showed that the PAH concentrations in estuary sediments were significantly higher than in tidal flat sediments. PAH patterns and pollutant sources were more complicated in estuary sediments.

Preparation and specific recognition of protein macromolecularly imprinted polyampholyte hydrogel.

Bovine serum albumin (BSA) imprinted polyampholyte hydrogels (PAHs) were prepared by free radical polymerization using acrylamide (Am) as structural monomer, N-isopropylacrylamide (NIPAm), [2-(methacryloyloxy)ethyl]trimethylammonium chloride (DMC) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as functional monomers and N,N'-methylenebisacrylamide (MBA) as crosslinker in aqueous solution. The morphology of imprinted hydrogels and non-imprinted hydrogels were characterized by scanning electron microscope (SEM). The adsorption and recognition properties were evaluated as functions of Am monomer concentration, NIPAm/Am molar ratio, crosslinking structure and charge density ratio etc.

In situ TEM observation of preferential amorphization in single crystal Si nanowire.

The nanoinstability of a single crystal Si nanowire under electron beam irradiation was in situ investigated at room temperature by the transmission electron microscopy technique. It was observed that the Si nanowire amorphized preferentially from the surface towards the center, with the increasing of the electron dose. In contrast, in the center of the Si nanowire the amorphization seemed much more difficult, being accompanied by the rotation of crystal grains and the compression of d-spacing.

Coalescence between Au nanoparticles as induced by nanocurvature effect and electron beam athermal activation effect.

The coalescence of two single-crystalline Au nanoparticles on surface of amorphous SiOx nanowire, as induced by electron beam irradiation, was in situ studied at room temperature in a transmission electron microscope. It was observed that along with shrinkage of the SiOx nanowire during irradiation, adjacent Au nanoparticles moved around and migrated close to each other. Once the two nanoparticles contacted with each other, a fast, massive atom transportation took place along their contact surface, where a neck region was created.

Atom Diffusion and Evaporation of Free-Ended Amorphous SiO Nanowires: Nanocurvature Effect and Beam-Induced Athermal Activation Effect.

Arresting effects of nanocurvature and electron beam-induced athermal activation on the structure changes at nanoscale of free-ended amorphous SiO nanowire were demonstrated. It was observed that under in situ uniform electron beam irradiation in transmission electron microscope, the near surface atoms at the most curved free end of the nanowire preferentially vaporized or diffused to the less curved wire sidewall. The processing resulted in an intriguing axial shrinkage and an abnormal radial expansion of the wire.

Removal of Cu(II) and Ni(II) ions from an aqueous solution using α-Fe₂O₃nanoparticle-coated volcanic rocks.

An adsorbent, volcanic rocks coated with α-Fe₂O₃nanoparticles, was prepared and utilized for the removal of Cu(II) and Ni(II) ions from an aqueous solution. Characterization of the coated volcanic rocks indicated that the α-Fe₂O₃nanoparticles were successfully and homogeneously distributed on the volcanic rocks, including penetration into rock pores. Batch experiments were conducted to investigate adsorption performance.

Intriguing surface-extruded plastic flow of SiOx amorphous nanowire as athermally induced by electron beam irradiation.

Nanoinstability and nanoprocessing of a SiOx amorphous nanowire at room temperature as induced by in situ electron beam irradiation in transmission electron microscopy are systematically investigated. It is demonstrated that in contrast to the crystalline nanowires where only the beam-induced ablation of atoms was observed, the amorphous nanowire herein can give rise to an arresting beam-induced surface-extruded plastic flow of massive atoms and surface migration of atoms in addition to the beam-induced ablation of atoms. Via the plastic flow and ablation, a new S-type deformed wire and the thinnest amorphous nanowire are elaborately created locally at nanoscale precision with a highly controllable manner depending on the beam current density, beam spot size, and beam position.

Assessment and sources of heavy metals in surface sediments of Miyun Reservoir, Beijing.

Heavy metals concentrations in surface sediments from Miyun Reservoir were determined to evaluate the pollution and identify the sources. The average content of metals in sediments from Miyun Reservoir followed the order Al>Fe>Ti>Mn>V>Zn>Cr>Ni>Cu>Pb>As>Cd>Hg, and the most mean values were lower than the globe average shale. Heavy metals concentrations at the inflow area of Baihe were higher than those at the inflow area of Chaohe.

Controllable fabrication of PS/Ag core-shell-shaped nanostructures.

In this paper, based on the previous steps, a facile in situ reduction method was developed to controllably prepare polystyrene/Ag (PS/Ag) core-shell-shaped nanostructures. The crucial procedure includes surface treatment of polystyrene core particles by cationic polyelectrolyte polyethyleneimine, in situ formation of Ag nanoparticles, and immobilization of the Ag nanoparticles onto the surface of the polystyrene colloids via functional group NH from the polyethyleneimine. The experimental parameters, such as the reaction temperature, the reaction time, and the silver precursors were optimized for improvement of dispersion and Ag coat coverage of the core-shell-shaped nanostructures.