Environmental Technology最新文献

The dramatic increase in carbon dioxide emissions is a major cause of global warming and climate change, posing a serious threat to human development and profoundly affecting the global ecosystem. Currently, carbon dioxide emissions prediction studies rely heavily on a large amount of data support, and the accuracy of predictions is greatly reduced when data are scarce. In addition, the inherent uncertainty, volatility, and complexity of CO2 emission data further exacerbate the challenge of accurate prediction. To address these issues, a novel hybrid model for CO2 emission prediction is proposed in this paper. A feature screening method is designed for effective and reliable feature selection from the perspective of algorithm stability, which can improve the prediction performance. In order to accurately predict periodic sequences with limited training samples, a least squares support vector machine is employed in this paper. In addition, the parameters of the prediction model are optimised using the improved sparrow search algorithm and enhanced by Sin chaos mapping, adaptive inertia weights and Cauchy-Gauss variables. An empirical study is conducted using Chinese carbon emission data as a case study, and the validity and superiority of the proposed model are verified through comparative experiments. The results show that the improved SSA has stronger global optimisation capability and faster convergence speed. In addition, in terms of prediction results, the hybrid model has the best consistency with the actual data, which significantly improves the prediction accuracy.

The rapid and stable monitoring of CO₂ emissions from point sources in localized regions remains a key challenge in energy conservation and emission reduction efforts. To address this challenge, the Gaussian plume model is adopted for the rapid prediction of carbon emission dispersion from multiple point sources, and an inversion model for carbon emission intensities is constructed based on the Simplex search algorithm. By incorporating elevation data, the Gaussian plume model is modified to adapt to undulating mountainous terrain, and the impacts of the Gaussian diffusion model on the CO₂ concentration diffusion of multiple point sources are analyzed under the conditions of the observation height, atmospheric stability and terrain correction. When the number of monitoring stations reach 10, the average inversion error ranges from 0.01 to 0.47% under various atmospheric conditions, together with an average inversion uncertainty in a range of [0.09%, 1.22%], indicating that enhancing the number of monitoring stations and selecting more stable atmospheric conditions can significantly improve the inversion accuracy of the carbon emission intensities from multiple point sources. This work provides a theoretical guidance for formulating the energy conservation and emission reduction policies together with monitoring and reducing the anthropogenic carbon emission.

In this study, biogenic CO₂ emissions, COD and other nutrients (i.e. TP, TN and $N{H}_4^{+}\text{-}N$) from aerobic treatment in municipal Wastewater Treatment Plants (WWTP) were quantified and reduced by phycoremediation using a mixotrophic co-cultivation of Chlorella vulgaris and activated sludge. It has been shown that the microalgae sludge consortium (A-ASR, R1) outperformed the normal-activated sludge system (ASR, R2). In fact, estimated biogenic CO₂ emissions with algae mark 1.20-fold higher removal, COD marks 1.40-fold higher removal, TP marks 1.70-fold higher removal, and $N{H}_4^{+}\text{-}N$ marks 1.40-fold higher removal, compared to normal activated sludge (ASR, R2). Meanwhile, due to aeration, $N{O}_3^{\text{-}}\text{-}N$ concentration increased in both reactors because some Ns were oxidized through nitrification. Furthermore, COD increased again during C. vulgaris stationary growth; thus, activated sludge addition every 4 days (optimal time) was implemented to maintain algae-bacteria balance. The results suggest that integrating the treatment of GHG emissions and water pollutants in a single, concurrent process can significantly enhance the sustainability and efficiency of wastewater treatment plants, which has not been explored comprehensively. Finally, by leveraging C. vulgaris capabilities for carbon and nutrients sequestration, this study can provide practical guidance for achieving carbon neutrality in a WWTP.

The removal of phosphorus from wastewater has consistently posed a major focus in the field of wastewater treatment. Microalgae-based phosphorus removal is widely acknowledged as an effective biological approach. However, ensuring the microalgae-mediated high phosphorus concentration removal remains a persistent challenge. In this study, a kind of multicellular microalgae, Klebsormidium sp., was used to explore its ability to remove phosphorus in high-phosphorus wastewater. The phosphorus removal rate by Klebsormidium sp. in highly concentrated (>20 mgP/L) wastewater can exceed 90%. To investigate the phosphorus absorption process, various nitrogen and phosphorus concentrations along with light conditions were employed. The results showed that 50% to 80% of the total phosphorus absorbed by microalgae entered the intracellular polymer. The phosphorus concentration and light intensity did not exert any significant effects on the absorption of phosphorus by microalgae. However, the nitrogen concentration and the light-to-dark ratio significantly influenced the storage of phosphorus by microalgae. At a nitrogen concentration over 300 mgN/L, phosphorus absorption by microalgae was inhibited. A higher light-to-dark ratio increased phosphorus transfer by microalgae, while the light duration exceeds 16 h inhibited it. Microalgae have emerged as promising materials for phosphorus removal in high-phosphorus sewage, the study offering potential solutions for a cleaner and more sustainable future.

To have a deep insight into the microscopic mechanism of N₂ formation during coal pyrolysis, the density functional theory was employed to compute and investigate the formation path of N₂. Seven-membered ring containing two pyridine nitrogen is selected as carbonaceous models. The results reveal that different dinitrogen active sites induce varied electron distribution on the surface of models. It makes varying energy barriers for the breakage of the C-N. In the pyrolysis process of R1 (two N atoms numbered 4 and 6) and R2 (two N atoms at positions 6 and 8), the energy barriers of the cleavage of the first N (the nitrogen first stripped in the structure) are 387.49 and 357.47 kJ/mol, respectively, and the energy barriers of the cleavage of the second N (the nitrogen stripped later in the structure) are 142.43 and 316.89 kJ/mol, respectively. However, different dinitrogen active sites have no effect on the main pyrolysis properties of the structure. Both of the two dinitrogen char models experienced the same process: the stripping of the first N atom and the formation of five-membered ring, the formation of dinitrogen five-membered ring, the stripping of the second N atom, the formation of C(NN) structure, N₂ desorption. According to the analysis of the reaction energy barriers, dinitrogen zigzag char model to N₂ is consistent with the experimental results.

Convenient and portable, sustained provision of safe drinking water is crucial for wilderness survival. In this study, a portable water collection bag utilising solar-driven interface evaporation technology has been developed. The water collection bag includes a plastic film, CB-PS microsphere evaporator, and a small vial. By placing on the water surface, the CB-PS microspheres float and absorb sunlight to quickly evaporate the surrounding water. The plastic film and vial make it easy and fast to collect clean and safe drinking water. The device boasts an impressive evaporation rate of 1.64 kg·m⁻²·h⁻¹ under 1 sun illumination. Moreover, the portable water collection bag can withstand harsh acidic and alkaline conditions, efficiently removing organic contaminants from wilderness water sources to meet drinking water standards. Importantly, it is designed for repeated use without any water evaporation rate decreasing. The portable water collection bag also exhibits strong resistance to salt, making it suitable for applications in desalinating seawater into freshwater.

Heavy metals (HMs) are hazardous contaminants with persistence and bioaccumulation, attracting widespread attention. Wastewater treatment plants (WWTPs) play vital roles in the pollution control of sewage, closely related to human health and the biological environment. Therefore, eight HMs in three typical WWTPs of Nanjing were determined in this study. The results revealed that Cr, Ni, Cu, and Zn were high-level HMs in all WWTPs. Notably, the highest contents of high-level HMs were found in electroplating WWTP (EWWTP) influent among three WWTPs, probably causing their higher removal (19.34-55.32%) during their primary treatment. In contrast, most HMs could be removed in the secondary treatment stage of municipal WWTP (MWWTP) and industrial WWTP (IWWTP) with the highest removal of As (72.00-85.81%). Analogously, nutrients were mainly removed during the secondary stage, with superior performance in MWWTP. A decrease in HMs removal was observed in the tertiary treatment of MWWTP and IWWTP compared to the secondary stage, while higher HMs removal (0.51-29.15%) was found in EWWTP except Hg. The highest content of HMs in sludge was Zn and Cr, which was more abundant in EWWTP than other WWTPs. The results of Illumina Miseq sequencing demonstrated the inhibition of microbial richness and diversity of EWWTP and IWWTP by industrial wastewater. Besides, alterations of microbial community structure and components were also observed owing to various influent sources. More similarity was found between EWWTP and MWWTP, in which the abundance of dominant genera, including Saccharimonadales (7.60-9.56%), Raineyella (5.06-7.38%), and Thauera (2.48-4.45%) was much higher than IWWTP.

To solve the urgent issue of electromagnetic (EM) wave radiation pollution and promote the resource utilisation of red mud (RM, a solid waste), Fe/C/ceramic composite EM wave-absorbing materials were constructed by recycling RM with raw coal (RC) through simple mechanical mixing and then carbothermal reduction between Fe₂O₃ in RM and carbon component in RC. It was found that the calcined temperature of 900 °C can be considered the optimal formation temperature for Fe. In addition, a tuneable EM wave absorption performance could be attained by regulating the mass ratio of RC to RM (denoted as M_RC:M_RM). When the M_RC:M_RM value reaches to 0.4:1 and 0.5:1, the composites exhibit more favourable performance. The composite with M_RC:M_RM of 0.4:1 showed the minimum reflection loss (RL_min) of -41.6 dB, accompanied by an effective absorption bandwidth (EAB) of 3.2 GHz when the simulating thickness was 2 mm. The composite with M_RC:M_RM of 0.5:1 possessed the maximum EAB of 4.2 GHz with the RL_min of -25.3 dB at a thickness of 1.5 mm. The satisfactory performance profits from good impedance matching and strong intrinsic attenuation capability. The former can be attributed to the regulatable EM parameters of the multicomponent system; the latter is mainly credited to the strong dielectric loss arising from the medium graphitised carbon, highly crystalline Fe, and plentiful defects and interfaces in the composites. This work not only provides a valid path to realise the economical preparation of microwave absorbents but also achieves the rational disposal of RM.

Polylactic acid (PLA) is the most promising bio-based alternative to traditional petrochemical plastics across diverse applications. In this study, the biodegradation performance of PLA plastic under two potential end-of-life scenarios: mesophilic and thermophilic anaerobic digestion (AD) were investigated. The biotic and abiotic influence factors were evaluated through short-time exposure experiments. The potential bacteria and archaea involved in PLA anaerobic biodegradation were identified by high-throughput 16S rRNA sequencing analysis. The results showed that PLA had different biodegradation performance at mesophilic and thermophilic digestion (the biogas yield: 36.70 ± 0.2vs 398.6 ± 1.1 mL/g VS). The increased temperature at thermophilic conditions improved the biodegradability of PLA, but an attack by microorganisms was more crucial for biodegradation. The bacteria engaged in PLA hydrolysis and acidification were closely associated with proteolytic microbes. Mesophilic biodegradation of PLA involved Clostridia (14.94%), Anaerolineae (22.6%) and acetoclastic Methanothrix (53.0%). Thermophilic biodegradation of PLA was mainly accomplished by syntrophic microbes, Clostridia (38.2%), Synergistia (18.99%) and Thermotogae (17.82%), in tandem with hydrogenotrophic Methanothermobacter (20.5%). The results provide some insights for understanding mechanisms governing PLA biodegradation under AD conditions.

ABSTRACTA shipborne detection device has been developed for the detection of heavy metal ions in offshore seawater, utilizing a mercury film electrode. The automatic determination of Cd²⁺ and Pb²⁺ ions in seawater can be conducted without any manual intervention. Waste solutions are collected in a recycling bag for subsequent treatment, thereby preventing environmental pollution. The accuracy, as well as the stability of the measurements, were thoroughly examined. The relative standard deviation for Pb²⁺ was determined to be 7.02% after conducting 10 repeated tests using a standard solution concentration of 5 μg L⁻¹ and the relative standard deviation of Cd²⁺ is 2.65%. Linear calibration curves have been established along with detection limits of 0.31 μg L⁻¹ for both Cd²⁺ and Pb²⁺ ions. Ultimately, this shipborne detection device was successfully employed for the in-situ determination of Cd²⁺ and Pb²⁺ ions in seawater.