This study presents the performance of a hybrid constructed wetland (Bp(VF + HF)₂:₁) system which consists of an unsaturated vertical flow (VF) unit followed by a saturated down-flow unit simulating horizontal flow (HF) with HF/VF area ratio of 0.5 and influent bypass to the HF unit. Treating synthetic wastewater simulating municipal wastewater, optimum total nitrogen (TN) removal (57%) was reached at 39% bypass and surface loading rate (SLR) of 33 g BOD₅/m² day and 9.7 g TN/m² day (overall system). On the other hand, treating actual municipal wastewater, the system reached 63% TN removal at 30% bypass and SLR of 18 g BOD₅/m² day and 4.7 g TN/m² day. Surface removal rates reached 5.5 and 3.0 g TN/m² day for synthetic and municipal wastewater. Surface nitrification rate in the VF unit was in the range of 5.0–7.4 and 3.6–3.8 g N/m² day for synthetic and municipal wastewater, respectively, indicating a large effect of wastewater characteristics on the nitrification process. Infiltration rate in the VF unit remained high and far from clogging risk. Overall greenhouse gas emissions were 0.11 (N₂O) and 0.41 (CH₄) g/m² day which corresponded to emissions factors (relative to total organic carbon and TN influent) of 0.7% (N₂O) and 3.6% (CH₄). Compared with a similar system with a different HF/VF area ratio of 2.0, organic matter and nitrogen removal efficiency was similar, but surface removal rates were about 3 times higher.

Plant height is among the most important agronomic traits influencing crop yield. Wheat lines carrying Rht genes are important in plant breeding due to their both higher yield capacity and better tolerance to certain environmental stresses. However, the effects of dwarf-inducing genes on stress acclimation mechanisms are still poorly understood. Under the present conditions, cadmium stress induced different stress responses and defence mechanisms in the wild-type and dwarf mutant, and the mutant with the Rht-B1c allele exhibited higher tolerance. In the wild type after cadmium treatment, the abscisic acid synthesis increased in the leaves, which in turn might have induced the polyamine and proline metabolisms in the roots. However, in the mutant line, the slight increment in the leaf abscisic acid content accompanied by relatively high salicylic acid accumulation was not sufficient to induce such a great accumulation of proline and putrescine. Although changes in proline and polyamines, especially putrescine, showed similar patterns, the accumulation of these compounds was antagonistically related to the phytochelatin synthesis in the roots of the wild type after cadmium stress. In the dwarf genotype, a favourable metabolic shift from the synthesis of polyamine and proline to that of phytochelatin was responsible for the higher cadmium tolerance observed.

Energy saving and emission reduction are the most concerned issues in the world. Objective and accurate prediction of carbon emissions can provide reference and early warning for the implementation of the government’s environmental strategy. Based on the traditional grey Verhulst model, this paper analyzes the main causes of its errors, introduces the extrapolation method to optimize the background value, and uses particle swarm optimization algorithm to optimize its parameters. In order to evaluate the performance of the models, six commonly statistical evaluation indicators are used to compare the new model with other optimization models and grey universal models, and the effect of the new model is basically better than other models. Finally, it is applied to the prediction of carbon dioxide emission of three kinds of coal in China. The results show that the increase of carbon dioxide related to raw coal slows down in 2016–2020, while the increase of carbon dioxide related to clean coal and other washed coal is 12.7097% and 19.2024%, respectively. Therefore, in order to prevent a strong rebound in carbon emissions, China should increase efforts to save energy and reduce emissions, and reduce energy consumption, especially coal consumption.

In this study, a new reuse process of the coarse fraction of basic oxygen furnace (BOF) sludge based on iron recovery by the ferrous sulfate production was proposed. This study was based on three main steps: (i) characterization of the steel waste, (ii) evaluation and optimization of the recycling process, and (iii) characterization of ferrous sulfate produced. Acid leaching was used to solubilize the iron for obtaining ferrous sulfate heptahydrate. The ferrous sulfate crystallization was performed by adding anhydrous ethanol (EtOH). A multivariate optimization for iron leaching and ferrous sulfate precipitation in the same solution was employed. This optimization consisted of screening steps using a full factorial design followed by optimization. The coarse fraction of BOF sludge was predominantly composed of iron in metallic form (82.5%, dry weight). The sulfuric acid concentration and leaching time had significant effects on Fe(II) solubilization. The desirability function predicted the following optimized conditions: 20% (v/v) sulfuric acid solution, 200 min of leaching time, 7.00 g of waste, and 110 mL of anhydrous EtOH, producing 19.60 g of ferrous sulfate heptahydrate (yield of 70.8%). The characterization of ferrous sulfate was performed by X-ray diffraction, scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The characterization of the ferrous sulfate produced evidenced the effectiveness of the optimized process condition. Graphical abstract

To promote the application of microbially induced mineralization technology in the field of coal dust suppression, two urease-producing bacteria were co-cultured, with the aim to define the influence of different culture conditions on the growth and urease activity of the bacteria. According to the results, when S. pasteurii and B. cereus CS1 were inoculated in succession at a volume ratio of 1:1 and an interval of 14 h, the mixed bacteria achieved optimal growth and had the highest urease activity; when the initial pH value of culture medium was 9 and the urea and Ca²⁺ concentrations in the substrate were uniformly 0.1 mol/L, the growth and urease activity of the mixed bacterial culture reached their peaks. SEM-EDS and XRD results indicated that, regardless of the specific urease-producing bacteria used (single urease-producing bacteria or the mixed urease-producing bacteria), their mineralization products were uniformly vaterite-type and calcite-type calcium carbonate; FTIR and thermogravimetric analysis also confirmed their mineralization products as calcium carbonate. By spraying the bacterial inoculants with a corresponding calcium source and urea on pulverized coal, it was found that the bacteria successfully survived and caused pulverized coal to be consolidated. In particular, the mixed bacterial inoculant manifested a stronger consolidation effect, with a wind erosion–induced mass loss of less than 20 g/(m²•h). We provide experimental support for the field of microbial coal dust suppression.

The xonotlite was synthesized from eggshell waste and modified with toluene diisocyanate (TDI). The xonotlite and amidoxime-modified xonotlite were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). FTIR revealed that the amidoxime group was successfully grafted onto the xonotlite. Factors affecting adsorption such as solution pH, adsorbent dose, contact time, and initial concentrations were set up to improve the adsorption performance. The adsorption of Cu (II) on all the adsorbents was well-described by the Freundlich model and pseudo-second-order model. The amidoxime-modified xonotlite showed rapid removal efficiency and reached equilibrium in 45 min at the pH of 5. The maximum adsorption capacities for Cu (II) (713.2 mg/g) on the modified xonotlite were 35.8% higher than that on the unmodified xonotlite. The existence of competing ions like K(I) and Na(I) had little effect on the Cu(II) removal efficiency. Therefore, the modified xonotlite could be used as a feasible adsorbent for the removal of Cu (II) in treating wastewater.

Microbe-assisted phytoremediation provides an eco-friendly and cost-effective approach to reclaim Cd- and Pb-contaminated soils. In this work, incubation and pot experiments were established to investigate the effect of Streptomyces pactum (Act12) combined with compost on soil physicochemical properties, enzymatic activities, and thereby acted on phytoextraction of Cd and Pb by using potherb mustard (Brassica juncea Coss.). The addition of Act12 and compost increased EC (7.2%), available phosphorus (P) (14.9%), available potassium (K) (17.0 folds), DOC (37.7%), OM (2.8 folds), urease (49.8%), dehydrogenase (2.2 folds), and alkaline phosphatase (23.0 folds) of soil, while reduced pH (7.7%) compared with control. Significant decrease of available Cd and Pb uptake was observed after adding compost and Act12 by 29.1% and 32.2%. Presence of compost and Act12 enhanced the biomass by 3.98 folds and 1.83 folds in shoots and roots of plant. Results showed the assimilation of Cd and Pb in shoots was increased by 103.8% and 48.7% due to the increased of biomass. Meanwhile, the rhizosphere effect of soil microorganisms increased the uptake of Cd (60.4%) and Pb (19.2%) in roots. These findings suggested that Act12 joined with compost-strengthened potherb mustard phytoremediation of Cd- and Pb-polluted soils, which may provide new insights into the clean-up of mining-contaminated soils in field practice.

Using the quantile GARCH model estimators to gauge the bidirectional risk magnitude and the Granger causality test in risk distributions to detect the existence of risk spillovers, this paper explores the extreme risk spillovers of China’s regional carbon markets to local listed firm’s stock returns. From the perspectives of macro region level and micro firm level, the findings are outlined as follows. First, among the top three active carbon trading pilots (Hubei, Guangdong, and Shenzhen), Hubei pilot exhibits significant “low risk and high profit” features. Second, the predominant risk spillover effects to local listed firms are heterogeneous across pilots. Specifically, Hubei pilot is dominated by “up-to-down” effect, and Guangdong pilot is dominated by “down-to-down” effect, while Shenzhen pilot has no predominant effect. The heterogeneous risk spillover performance may be caused by the regional divergence in economic development, industry structure, and cap setting concerning each pilot. Third, the risk transmission performance from carbon allowance price to local listed firm’s stock returns depends on the firm’s belonging sector. That is, environment-related firms, either environment-friendly firms or pollution-intensive firms, are more susceptible to carbon markets’ risks compared with environment-unrelated firms. This paper supplies novel information on the risk transmission from carbon markets to local economic entities, which proves valuable not only for firms to improve risk aversion ability but also for policy-makers to perfect carbon markets’ mechanism.

Organophosphorus insecticides toxicity is still considered a major global health problem. Malathion is one of the most commonly used organophosphates nowadays, as being considered to possess relatively low toxicity compared with other organophosphates. However, widespread use may lead to excessive exposure from multiple sources. Mechanisms of MAL toxicity include inhibition of acetylcholinesterase enzyme, change of oxidants/antioxidants balance, DNA damage, and facilitation of apoptotic cell damage. Exposure to malathion has been associated with different toxicities that nearly affect every single organ in our bodies, with CNS toxicity being the most well documented. Malathion toxic effects on liver, kidney, testis, ovaries, lung, pancreas, and blood were also reported. Moreover, malathion was considered as a genotoxic and carcinogenic chemical compound. Evidence exists for adverse effects associated with prenatal and postnatal exposure in both animals and humans. This review summarizes the toxic data available about malathion in mammals and discusses new potential therapeutic modalities, with the aim to highlight the importance of increasing awareness about its potential risk and reevaluation of the allowed daily exposure level.

Goethite is an effective adsorbent for hexavalent chromium (Cr(VI)). Oxalic acid and other organic acids will affect the release, immobilization, and bioavailability of Cr(VI) in nature on the mineral surface. Mn(II) can accelerate the reduction of Cr(VI) with oxalic acid. Herein, the effects of oxalic acid and Mn(II) on the mobilization and transformation of adsorbed Cr(VI) on the surface of goethite were investigated in this study. The results revealed that Mn(II) could increase the adsorption of Cr(VI) by increasing the positive charge on the surface of goethite. The complexation of oxalic acid with the surface of goethite caused the adsorbed Cr(VI) to be released into the solution. Moreover, oxalic acid could undergo redox with adsorbed Cr(VI) through electron conduction on the surface of goethite, thereby resulting in the transformation of adsorbed Cr(VI) to Cr(III). During the reaction in the presence of oxalic acid, the concentration of Cr(III) increased from 0 to 13.9 mg/L. In addition, Mn(II), oxalic acid, and Cr(VI) could form unstable ester-like species in the solution, which accelerated the reduction of Cr(VI) to Cr(III). These findings of this study may enrich our understanding of the behaviors of Cr(VI) in the coexistence of goethite, oxalic acid, and Mn(II).