Biochar is frequently applied for the reduction of mercury (Hg) migration in soil; however, most of the studies only focused on the adsorption capacity evaluation of fresh biochar. We investigated the Hg adsorption capacities of biochar prepared from wheat straw, corn straw, and sunflower seed shells. Biochar aging was simulated via natural aging, high-temperature aging, and freeze-thaw aging. The adsorption capacities of all the aged biochar were increased, and wheat straw biochar and seed shells biochar treated with high-temperature aging (wBC-Ha500 and sBC-Ha600) and corn straw biochar treated with freeze-thaw aging (cBC-Fta500) showed an observable improvement on the equilibrium adsorption amounts. The kinetics of the fresh biochar samples fitted the pseudo-first-order kinetic model and the pseudo-second-order kinetic model, while the kinetics of the aged biochar samples fitted the pseudo-second-order kinetic model. Biochar adsorption capacity increased with higher initial concentrations and increasing temperatures. Elemental analysis, Fourier-transform infrared spectroscopy (FT-IR) spectra, cation-exchange capacity (CEC), surface area (SA), zeta potential, and X-ray photoelectron spectroscopy (XPS) showed that the aging mechanism consisted of hydroxylation and carboxylation caused by the functional groups on the biochar surface. According to the different climatic zones in China, wheat straw biochar and seed shell biochar are suitable for the tropical zone and the subtropical zone, while corn straw biochar is more suitable for the cold and the mid-temperate zones.

Solutions with 0.65 mM of the antituberculosis drug isoniazid (INH) in 0.050 M Na₂SO₄ at pH 3.0 were treated by electro-Fenton (EF) and UVA photoelectro-Fenton (PEF) processes using a cell with a BDD anode and a carbon-PTFE air-diffusion cathode. The influence of current density on degradation, mineralization rate, and current efficiency has been thoroughly evaluated in EF. The effect of the metallic catalyst (Fe²⁺ or Fe³⁺) and the formation of products like short-chain linear aliphatic carboxylic acids were assessed in PEF. Two consecutive pseudo-first-order kinetic regions were found using Fe²⁺ as catalyst. In the first region, at short time, the drug was rapidly oxidized by ●OH, whereas in the second region, at longer time, a resulting Fe(III)-INH complex was much more slowly removed by oxidants. INH disappeared completely at 300 min by EF, attaining 88 and 94% mineralization at 66.6 and 100 mA cm⁻², respectively. Isonicotinamide and its hydroxylated derivative were identified as aromatic products of INH by GC-MS and oxalic, oxamic, and formic acids were quantified by ion-exclusion HPLC. The PEF treatment of a real wastewater polluted with the drug led to slower INH and TOC abatements because of the parallel destruction of its natural organic matter content.

Urban streams are degraded through multiple mechanisms, including severely altered flow regimes, elevated concentrations of waterborne contaminants, removal of riparian vegetation and the loss of a mosaic of heterogeneous aquatic habitats. Engineering of urban stream reaches using concrete is a widespread and extreme case of deliberate alteration of flow regimes and concomitant habitat simplification. To assess the effect of such engineering practices on stream ecosystems, we compared aquatic macroinvertebrate communities from concrete-lined engineered urban reaches, non-engineered urban reaches with natural substrates and reference reaches flowing through minimally disturbed forested subcatchments and with natural substrates, in the Sydney metropolitan region, Australia. The communities from all urban reaches were impoverished and distinctly different from more diverse communities in forested reference reaches. Despite low aquatic habitat heterogeneity, engineered urban reaches had very high abundances of Diptera and some other tolerant taxa. Diptera and/or Gastropoda were dominant in non-engineered urban reaches. Multivariate community structures were dissimilar between the urban reaches and forested reference reaches and between non-engineered and engineered urban reaches. However, the low family-level richness and SIGNAL scores in both urban reach types indicated they were severely ecological impaired, whether engineered or not. Most macroinvertebrate taxa in the regional pool that were hardy enough to inhabit urban reaches with natural substrates were also present in nearby concreted reaches. The results add weight to the growing evidence that in urban landscapes, regional-scale changes in water quality and flow regimes limit the establishment of diverse macroinvertebrate communities, which cannot be addressed through the provision of increased reach-scale habitat heterogeneity.

Wastewater from a limestone-gypsum wet desulfurization system cannot be directly reused or discharged due to its high suspended matter content and complex water composition. Desulfurization wastewater evaporation in flue gas is an effective way to dispose wastewater. Multicomponent soluble chlorine salts exist in the desulfurization wastewater. During the evaporation, chlorine enters into the flue gas due to volatilization, which accelerates the enrichment rate of the Cl⁻ concentration in the desulfurization slurry and leads to an increase in wastewater production. This study explored the chlorine migration of various chlorine salt solutions and typical desulfurization wastewater at high temperature during the evaporation process of concentrated wastewater by a laboratory-scale tube furnace and a pilot-scale system. Results showed that when NaCl-evaporated substance was heated, the chlorine ion hardly volatilized. For the evaporated substances of CaCl₂ and MgCl₂ solutions, some of the crystal water was lost, and hydrolysis occurred to generate gaseous HCl. NH₄Cl was easily sublimed, and the decomposition temperature was lowest. A pilot study on spray evaporation of desulfurization wastewater in flue gas showed that the particle size of the evaporated product increased and the main particle size was within 2.5–10 μm with increasing flue gas temperature. Increasing the mass ratio of gas to liquid significantly reduced the particle size of the atomized particles, thereby reducing the average particle size of the evaporated particles. The HCl concentration increased with increasing flue gas temperature. When the flue gas temperature was 350 °C, the concentration of HCl was 40 ppm, and the escape rate of chlorine in the desulfurization wastewater was approximately 30% using typical wastewater from a limestone-gypsum wet desulfurization system.

Stable Hg(II)-containing flue gas has been successfully simulated by the plasma oxidation of Hg(0), and an effective solution for Hg(0) mercury fumes was obtained by combining the plasma with a ceramic nanomaterial. Characterization tests showed that the ceramic nanomaterial was mainly composed of silicon dioxide (SiO₂) with other minor constituents, including potassium mica (KAl₃Si₃O₁₁), iron magnesium silicate (Fe₀.₂₄Mg₀.₇₆SiO₃) and dolomite (CaMg(CO₃)₂). The nanomaterial had many tube bank structures inside with diameters of approximately 8–10 nm. The maximum sorption capacity of Hg(II) was 5156 μg/g, and the nanomaterial can be regenerated at least five times. During the adsorption, chemical adsorption first occurred between Hg(II) and sulfydryl moieties, but these were quickly exhausted, and Hg(II) was then removed by surface complexation and wrapped into Fe moieties. The pseudo-first-order kinetic model and the Langmuir equation had the best fitting results for the kinetics and isotherms of adsorption. This work suggests that the ceramic nanomaterial can be used as an effective and recyclable adsorbent in the removal of gaseous Hg(II).

Aerosol samples of PM₂.₅ and PM₁₀ were collected every 6 days from March 2012 to February 2013 in Huangshi, a typical industrial city in central China, to investigate the characteristics, relationships, and sources of carbonaceous species. The PM₂.₅ and PM₁₀ samples were analyzed for organic carbon (OC), elemental carbon (EC), char, and soot using the thermal/optical reflectance (TOR) method following the IMPROVE_A protocol. PM₂.₅ and PM₁₀ concentrations ranged from 29.37 to 501.43 μg m⁻³ and from 50.42 to 330.07 μg m⁻³, with average levels of 104.90 and 151.23 μg m⁻³, respectively. The 24-h average level of PM₂.₅ was about three times the US EPA standard of 35 μg m⁻³, and significantly exceeds the Class II National Air Quality Standard of China of 75 μg m⁻³. The seasonal cycles of PM mass and OC concentrations were higher during winter than in summer. EC and char concentrations were generally highest during winter but lowest in spring, while higher soot concentrations occurred in summer. This seasonal variation could be attributed to different seasonal meteorological conditions and changes in source contributions. Strong correlations between OC and EC were found for both PM₂.₅ and PM₁₀ in winter and fall, while char and soot showed a moderate correlation in summer and winter. The average OC/EC ratios were 5.11 and 4.46 for PM₂.₅ and PM₁₀, respectively, with individual OC/EC ratios nearly always exceeding 2.0. Higher char/soot ratios during the four seasons indicated that coal combustion and biomass burning were the major sources for carbonaceous aerosol in Huangshi. Contrary to expectations, secondary organic carbon (SOC) which is estimated using the EC tracer method exhibited spring maximum and summer minimum, suggesting that photochemical activity is not a leading factor in the formation of secondary organic aerosols in the study area. The contribution of SOC to OC concentration for PM₂.₅ and PM₁₀ were 47.33 and 45.38%, respectively, implying that SOC was an important component of OC mass. The serious air pollution in haze-fog episode was strongly correlated with the emissions of pollutants from biomass burning and the meteorological conditions.

In the present study, the electrocatalytic degradation of triazine herbicide metamitron using Ti/PbO₂-CeO₂ composite anode was studied in detail. The effects of the current density, initial metamitron concentration, supporting electrolyte concentration, and initial pH value were investigated and optimized. The results revealed that an electrocatalytic approach possessed a high capability of metamitron removal in aqueous solution. After 120 min, the removal ratio of metamitron could reach 99.0% in 0.2 mol L⁻¹ Na₂SO₄ solution containing 45 mg L⁻¹ metamitron with the current density at 90 mA cm⁻² and pH value at 5.0. The reaction followed the pseudo-first-order kinetics model. HPLC and HPLC-MS were employed to analyze the degradation by-products in the metamitron oxidization process, and the degradation pathway was also proposed, which was divided into two sub-routes according to the different initial attacking positions on metamitron by hydroxyl radicals. Therefore, the electrocatalytic approach was considered as a very promising technology in practical application for herbicide wastewater treatment.

As potassium ferrate(VI) is an important kind of water treatment agent which has a high efficiency in algal removal, its effects on the cell substance are rarely discussed. The changing of the protein and enzyme was analyzed here to deeply understand the oxidation of Fe on the protein in the algae. The result of the research showed the inactivation on growth and the biochemical process of the algal cell were all inhibited by Fe, including the function of the photosynthesis system. During the process, SOD (superoxide dismutase), CAT (catalase), POD (peroxidase), and GST (glutathione S-transferase) played cooperative roles to prevent the injury on the cells from destructive oxidation stress. The lipid peroxidation strengthened the defense system. The damage was intensified with the increase of ferrate concentration.

Biogas reactors are now a common part of wastewater treatment systems. The quality of produced biogas is the result of many factors, mainly the input substrate and microbial composition of the bioreactor. The aim of this research was to evaluate the microbial community of the Modřice biogas reactor together with the possible changes in biogas composition. The key microbial groups and their content in anaerobic digester were identified by sequencing techniques. The most dominant group were sulphate-reducing (45%), followed by methanogenic (19%), acetate (6%) and hydrogen-producing (11%) microorganisms. The remaining microorganisms were identified only to their order (19%). Phylogenetic trees were constructed to show evolutionary relationships of detected microorganisms. The volume of methane in biogas content was 60%, which corresponds with literature data regarding sewage digesters. None of the detected impurities have crossed the safe limits and their volume remained stable during the measurement period. Despite sulphate-reducing bacteria being the dominant group, their produced hydrogen sulphide (H₂S) was detected only in a small quantity (2.43–7.46 ppm) and had no inhibitory effect on the methane production. The mechanism of inhibition by H₂S and the perspective of its biological removal were discussed. Application of phototrophic sulphur bacteria, especially Chlorobiaceae and Chromatiaceae family, and the creation of new photobioreactor systems can be a promising pathway for hydrogen sulphide treatment in biogas plants.

This article studies the price competition and cooperation in a duopoly that is subjected to carbon emissions cap. The study assumes that in a departure from the classical Bertrand game, there is still a market for both firms’ goods regardless of the product price, even though production capacity is limited by carbon emissions regulation. Through the decentralized decision making of both firms under perfect information, the results are unstable. The firm with the lower maximum production capacity under carbon emissions regulation and the firm with the higher maximum production capacity both seek market price cooperation. By designing an internal carbon credits trading mechanism, we can ensure that the production capacity of the firm with the higher maximum production capacity under carbon emissions regulation reaches price equilibrium. Also, the negotiation power of the duopoly would affect the price equilibrium.