Inappropriate nitrogen fertilizer application, either too much or at the wrong time, can lead to nitrate pollution in groundwater and the adjacent surface water bodies. Prior greenhouse investigations have examined the application of graphene nanomaterials, encompassing graphite nano additives (GNA), to curtail nitrate leaching within agricultural soils during lettuce cultivation. In order to understand the mechanism behind GNA's effect on nitrate leaching, we executed soil column experiments utilizing native agricultural soils, employing either saturated or unsaturated flow to mimic different irrigation conditions. To study the effects of temperature on microbial activity, we used two temperatures (4°C and 20°C) in biotic soil column experiments and varied GNA doses (165 mg/kg soil and 1650 mg/kg soil). In contrast, abiotic (autoclaved) soil column experiments employed a single temperature (20°C) and a single GNA dose (165 mg/kg soil). The results reveal a minimal impact of GNA on nitrate leaching in saturated flow soil columns, attributed to the relatively short hydraulic residence time of 35 hours. A 25-31% reduction in nitrate leaching was observed in unsaturated soil columns with prolonged residence times (3 days), compared to control soil columns without GNA. Correspondingly, nitrate retention within the soil column was found to be lowered at a temperature of 4°C compared to 20°C, implying a bio-mediated effect of GNA incorporation to reduce nitrate leaching rates. Soil-derived dissolved organic matter demonstrated an association with nitrate leaching, where nitrate leaching was lower in samples where higher dissolved organic carbon (DOC) levels were present in the leachate. In unsaturated soil columns, the addition of soil-derived organic carbon (SOC) only promoted greater nitrogen retention when GNA was simultaneously present. The results point toward a decrease in nitrate loss from soil treated with GNA, possibly due to enhanced nitrogen retention in the microbial biomass or the elevated emissions of nitrogen into the gaseous phase via the improved nitrification and denitrification pathways.
Electroplating procedures globally, including those in China, frequently utilize fluorinated chrome mist suppressants (CMSs). China's compliance with the Stockholm Convention on Persistent Organic Pollutants resulted in the phase-out of perfluorooctane sulfonate (PFOS) for widespread use as a chemical substance by March 2019, except for applications within closed-loop systems. Radioimmunoassay (RIA) From that time forward, diverse replacements for PFOS were devised, but a significant number still constitute part of the broader category of per- and polyfluoroalkyl substances (PFAS). This unique study, the first of its kind, meticulously collected and analyzed CMS samples from the Chinese market in 2013, 2015, and 2021, to comprehensively determine their PFAS constituent makeup. Products with a restricted range of PFAS targets were subject to a total fluorine (TF) screening procedure, supplemented by the examination of suspected and unidentified compounds. Our study's conclusions point to 62 fluorotelomer sulfonate (62 FTS) as the dominant substitute in the Chinese marketplace. Against expectations, the primary component of CMS product F-115B, an extended-chain variant of the common CMS product F-53B, was identified as 82 chlorinated polyfluorinated ether sulfonate (82 Cl-PFAES). Moreover, we discovered three novel PFAS replacements for PFOS, such as hydrogen-substituted perfluoroalkyl sulfonates (H-PFSAs) and perfluorinated ether sulfonates (O-PFSAs). We also found and evaluated six hydrocarbon surfactants, the key ingredients in PFAS-free products. Nevertheless, certain PFOS-containing CMS products persist within the Chinese marketplace. The stringent regulation of PFOS and the use of CMSs only within closed-loop chrome plating systems are essential to preventing its opportunistic misuse.
Treatment of electroplating wastewater, which contained various metal ions, involved the addition of sodium dodecyl benzene sulfonate (SDBS) and adjustment of pH, after which the resulting precipitates were examined using X-ray diffraction (XRD). The treatment process revealed the in-situ formation of organic anion-intercalated layered double hydroxides (OLDHs) and inorganic anion-intercalated layered double hydroxides (ILDHs), effectively removing heavy metals. To explore precipitate formation, SDB-intercalated Ni-Fe OLDHs, NO3-intercalated Ni-Fe ILDHs, and Fe3+-DBS complexes were synthesized through co-precipitation, with the goal of comparing them at different pH values. To characterize these samples, X-ray diffraction (XRD), Fourier Transform infrared (FTIR) spectroscopy, elemental analysis, and the determination of aqueous residual Ni2+ and Fe3+ levels were used. Examination of the outcomes revealed that OLDHs exhibiting high crystalline quality can be produced at pH 7, with ILDHs appearing subsequently at pH 8. Firstly, at a pH below 7, the formation of complexes involving Fe3+ and organic anions with an ordered layered structure occurs, and then, as the pH value elevates, Ni2+ is incorporated into this solid complex, thus initiating the formation of OLDHs. Nonetheless, Ni-Fe ILDHs did not manifest at a pH of 7. The solubility product constant (Ksp) for OLDHs was determined to be 3.24 x 10^-19, and for ILDHs, 2.98 x 10^-18, at a pH of 8. This implied that OLDHs may prove more readily formable than ILDHs. MINTEQ simulations of ILDHs and OLDHs' formation demonstrated that OLDHs may form more readily than ILDHs at pH 7. This study provides theoretical support for effective in-situ OLDH formation within wastewater treatment.
Utilizing a cost-effective hydrothermal route, this research synthesized novel Bi2WO6/MWCNT nanohybrids. Microbiological active zones Sunlight simulation was employed to study the photocatalytic performance of these specimens, specifically focusing on the degradation of Ciprofloxacin (CIP). By utilizing a range of physicochemical characterization techniques, a systematic investigation was undertaken of the prepared pure Bi2WO6/MWCNT nanohybrid photocatalysts. The structural/phase characteristics of Bi2WO6/MWCNT nanohybrids were elucidated by XRD and Raman spectroscopy. Using FESEM and TEM techniques, the placement and distribution of Bi2WO6 plate-shaped nanoparticles were visualized along the nanotubes. Analysis by UV-DRS spectroscopy demonstrated that the introduction of MWCNTs altered the optical absorption and bandgap energy of Bi2WO6. Incorporating MWCNTs into Bi2WO6 decreases its band gap energy from 276 eV to 246 eV. Under sunlight irradiation, the BWM-10 nanohybrid exhibited exceptional photocatalytic activity, resulting in a 913% degradation of CIP. BWM-10 nanohybrids exhibit enhanced photoinduced charge separation efficiency, as evidenced by the PL and transient photocurrent tests. The CIP degradation process is primarily attributable to the contributions of H+ and O2, as evidenced by the scavenger test. The BWM-10 catalyst's outstanding reusability and firmness were evident in its performance across four successive reaction cycles. Bi2WO6/MWCNT nanohybrids are expected to act as potent photocatalysts, proving beneficial for environmental remediation and energy conversion. This study presents a novel approach towards the development of a potent photocatalyst, aiming at the degradation of pollutants.
As a synthetic chemical pollutant, nitrobenzene is frequently found in petroleum byproducts, and is absent from the natural environment. Humans can suffer toxic liver disease and respiratory failure due to the presence of nitrobenzene in the surrounding environment. Electrochemical technology's effectiveness and efficiency are demonstrated in the degradation of nitrobenzene. The electrochemical treatment of nitrobenzene was examined in this study, with a focus on the influences of process parameters (electrolyte type, concentration, current density, and pH) and their unique reaction pathways. Consequently, chlorine availability significantly outweighs hydroxyl radical activity in the electrochemical oxidation process, making a NaCl electrolyte a superior choice for nitrobenzene degradation compared to a Na2SO4 electrolyte. Directly influencing nitrobenzene removal, electrolyte concentration, current density, and pH were the key factors in regulating the concentration and existence form of available chlorine. The electrochemical degradation of nitrobenzene, as determined through cyclic voltammetry and mass spectrometric analysis, demonstrated the operation of two key mechanisms. In the initial oxidation phase, nitrobenzene and other aromatic compounds are transformed into NO-x, organic acids, and mineralization products. In the second instance, the orchestrated reduction and oxidation of nitrobenzene to aniline generates N2, NO-x, organic acids, and mineralization byproducts. This study's results will foster a deeper understanding of the electrochemical degradation mechanism of nitrobenzene and the creation of effective treatments for nitrobenzene.
Increased soil nitrogen (N) levels induce changes in the abundance of N-cycle genes, ultimately affecting nitrous oxide (N2O) emissions, a process significantly influenced by N-induced soil acidification in forest ecosystems. Besides this, the level of microbial nitrogen saturation might influence microbial actions and nitrous oxide release. Quantifying the contributions of N-induced modifications to microbial nitrogen saturation, and N-cycle gene abundances, in relation to N2O emissions, is a rarely undertaken endeavor. read more Over the period 2011-2021, a temperate forest in Beijing was the site of an investigation into the underlying mechanisms responsible for N2O emissions from nitrogen additions (NO3-, NH4+, and NH4NO3, each applied at 50 and 150 kg N ha⁻¹ year⁻¹). The experimental data indicated an escalation in N2O emissions at both low and high nitrogen application rates, for each of the three treatment types when compared to the control group, over the entire experimental period. Nonetheless, N2O emissions exhibited a decrease in treatments with high concentrations of NH4NO3-N and NH4+-N compared to those receiving low N inputs over the past three years. Nitrogen (N) rate, form, and experimental duration all influenced the effects of nitrogen (N) on microbial nitrogen (N) saturation and the abundance of nitrogen-cycle genes.