作者机构:
[Fang, Xin; Xiong, Liwei] Hunan City Univ, Sch Municipal & Geomat Engn, Yiyang 413000, Peoples R China.;[Li, Shenxin; Zou, Bin] Cent South Univ, Sch Geosci & Infophys, Changsha 410083, Peoples R China.
通讯机构:
[Bin Zou] S;School of Geosciences and Info-Physics, Central South University, Changsha 410083, China
关键词:
air pollution;AOD;spatial-temporal variations;environmental modeling;population exposure
摘要:
Abstract: Fine particulate matter (PM2.5), which can cause adverse human health effects, has been proven as the first air pollutant in China. In situ observations with ground-level monitoring and satellite-based concentrations have been used to analyze the variations in PM2.5. However, variation analyses based on these two kinds of measurement have mainly focused on the concentration itself and ignored the effects on the population. Therefore, this study not only investigated these two kinds of measurements, but also performed weighted population analyses to study the variations in PM2.5. Firstly, daily models of timely structure adaptive modeling (TSAM) were constructed to simulate satellite-derived PM2.5 levels from January 2013 to December 2016. Secondly, population-weighted concentrations were calculated based on TSAM-derived PM2.5 surfaces. Finally, observed, TSAM-derived, and population-weighted concentrations were used to analyze the variations in PM2.5. The results showed the different importance of various input parameters; AOD had the highest rank. Additionally, TSAM models demonstrated good performance, fitting R ranging from 0.86 to 0.91, and validating R from 0.82 to 0.89. According to the air quality standard in China, TSAM-derived PM2.5 showed that the increase in area lower than Level II was 29.03% and the increase in population was only 14.81%. This indicates that the air quality exhibited an overall improvement in spatial perspective, but some areas with high population density showed a relatively low improvement due to uneven distributions in China. The population-weighted PM2.5 concentration could better represent the health threats of air pollutants compared with in situ observations. Keywords: air pollution; AOD; spatial–temporal variations; environmental modeling; population exposure
摘要:
The synthesis of CuO-TiO2 hybrid nanostructures using the sol-gel method, as well as their characterization as photocatalysts for photodegradation of p-nitrophenol (PNP) in industrial wastewater under sunlight irradiation, were presented in this paper. According to SEM and XRD investigations, the CuO-TiO2 hybrid nanostructure had a mixture of monoclinic structure CuO and anatase phase TiO2, indicating that the CuO-TiO2 hybrid nanostructure was successfully synthesised using the sol-gel method. Optical band gap values for CuO, TiO2, and CuO- TiO2 were determined to be 1.64, 3.02, and 2.10 eV, respectively. Electrochemical tests revealed that CuO-TiO2 has a longer electron lifetime, a higher separation efficiency, and a faster diffusion rate. After 75, 65, and 50 minutes of sunshine irradiation, full elimination of 200 mL of 10 mg/l PNP was obtained employing the photocatalytic activity of TiO2, CuO, and CuO-TiO2, respectively. These findings support CuO-high TiO2's photocatalytic activity when exposed to sunlight, owing to the synergistic effect of CuO and TiO2 in forming a CuO-TiO2 heterojunction with efficient separation of photo-generated electrons and holes, which improves electron transport. After 35, 90, and 150 minutes of UV irradiation, 100% treatment of 5, 30, and 100 mg/L of PNP was obtained, respectively. The CuO-practical TiO2's photocatalytic removal capacity was tested for degradation of a 200 mL 5 mg/L PNP solution generated from genuine industrial wastewater, demonstrating CuO-efficient TiO2's photocatalytic activity for PNP removal from real industrial wastewater.
摘要:
Soil pollution by potentially toxic elements (PTEs) is a serious threat to human health and ecosystem function. Soil washing using EDTA is one of the permanent disposal options available to remove PTEs from soil. Based on published studies, this paper summarized the current progress of remediation techniques using EDTA to mobilize and remove PTEs from contaminated soils. Firstly, the key factors to control EDTA washing were discussed, such as the concentration of EDTA, the pH of the washing solution, the washing time, multiple washing, and the liquid/solid ratio. Afterwards, the complicated changes in soil properties after washing were discussed. The change of soil properties is inevitable, so some measures need to be taken to reduce the damage to the soil by washing. Finally, the current improvements were summarized for the problems existing in the EDTA washing process. EDTA could be used in combination with other agents such as other chelating agents, reducing agents, acid compounds, and surfactants to improve efficiency of EDTA washing. The purpose of this paper is to provide a reference for further research and practical application of remediation of PTEs contaminated soil by EDTA washing. [GRAPHICS] .
摘要:
Diclofenac (DCF), as a typical representative of PPCPs, has potential ecotoxicity to the water environment. In this study, ultrasound (US) enhanced ferrous sulfide (FeS)-activated persulfate (PDS) technology (US/FeS/PDS) was used to degrade DCF. By comparing the degradation effects of US, US/PDS, FeS/PDS and US/FeS/PDS systems on DCF, this study confirmed the synergy and strengthening effects of US. The influences of single-factor experimental conditions on the US/FeS/PDS system were investigated and optimized. The FeS catalysts before and after the reaction were characterized and analyzed by X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The heterogeneous reaction proceeded on the surface of FeS, and a small part of FeS(2) was formed on FeS surface. During the reaction, the proportion of S(2-) on the catalyst surface decreased from 51% to 44%. Correspondingly, the proportion of S(x)(2-) increased from 21% to 26%. It indicated that S(2-) was oxidized into S(x)(2-) in the reaction, and the loss electrons of S(2-) caused the reduction of Fe(3+) to Fe(2+)on the FeS surface, which promoted the cycle between Fe(2+) and Fe(3+) in turn. Furthermore, SO(4)(-) and ‧OH were the main active free radicals, of which the contribution rate of ‧OH was about 34.4%, while that of SO(4)(-) was approximately 52.2%. In US/FeS/PDS, the introduction of US could promote the dissolution of iron on the FeS surface. US contributed to the formation of a redox power motor between S(2-)S(x)(2-) and Fe(2+)-Fe(3+), which continuously decomposed PDS to generate sufficient active SO(4)(-) and ‧OH radicals, thereby efficiently and continuously degrading DCF. Finally, the related mechanism of DCF degradation by US/FeS/PDS was summarized. Overall, US/FeS/PDS can not only efficiently degrade and remove DCF, but also has potential application value in organic pollution removal and wastewater purification.
关键词:
Exergy;Solid waste;Gasification;Updraft;Downdraft;Fixed bed
摘要:
The most commonly used for gasification of village-level solid waste is the fixed-bed gasifier, but there is no reasonable method to evaluate the gasification process. This paper attempts to find a gasifier that is most suitable for gasification of village-level solid wastes through exergy analysis method. Based on experimental data from literature, the exergy efficiencies and LHV(Low Heat Value) of product gas from updraft and downdraft fixed bed gasifier are studied in this paper. The results show that the updraft fixed bed gasifier has higher exergy efficiency, and the gas produced by the downdraft fixed bed gasifier has a higher heating value. Air gasification has higher exergy efficiency than steam gasification and pure oxygen gasification. The highest exergy efficiency at a gasification temperature of about 1000 degrees C and ER (Equivalence Ratio) value in the range of 0.33-0.36. The volatile content of gasification raw materials is higher, and the gasification efficiency is higher. Through the research of this paper, a new path to reasonably evaluate the gasification process is obtained. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
作者机构:
[杨仙; 肖宇锋] College of Resources, Environment and Safety Engineering, Hunan University of Science and Technology, Xiangtan;411201, China;[黎永索] School of Municipal and Geomatics Engineering, Hunan City University, Yiyang;413000, China;[陈娟] School of Information and Electrical Engineering, Hunan University of Science and Technology, Xiangtan
通讯机构:
[Chen, J.] S;School of Information and Electrical Engineering, China
作者机构:
[Xue, Yun; Liu, Fen-Liang; Zhang, Wei] Hunan City Univ, Sch Municipal & Surveying Engn, Yiyang 413000, Peoples R China.;[Xue, Yun] Cent South Univ, Key Lab Metallogen Predict Nonferrous Met & Geol, Changsha 410083, Peoples R China.;[Wen, Yi-Min] Guilin Univ Elect Technol, Sch Comp Sci & Informat Secur, Guilin 541004, Peoples R China.;[Duan, Zhong-Man] Hunan Prov Nat Resources Affairs Ctr, Changsha 410004, Peoples R China.
通讯机构:
[Xue, Yun] H;[Xue, Yun] C;Hunan City Univ, Sch Municipal & Surveying Engn, Yiyang 413000, Peoples R China.;Cent South Univ, Key Lab Metallogen Predict Nonferrous Met & Geol, Changsha 410083, Peoples R China.
关键词:
spectral absorption characteristics;chlorophyll-a;Dongting Lake
摘要:
The envelope removal method has the advantage of suppressing the background spectrum and expanding the weak absorption characteristic information. However, for second-class water bodies with a relatively complex water quality, there are few studies on the inversion of chlorophyll a (Chl-a) concentration in water bodies that consider the spectral absorption characteristics. In addition, the current research on the inversion of the Chl-a concentration was carried out under the condition of sample concentration equilibrium. For areas with a highly variable Chl-a concentration, it is still challenging to establish a highly applicable and accurate Chl-a concentration inversion model. Taking Dongting Lake in China as an example, this study used high-concentration samples and spectral absorption characteristics to invert the Chl-a concentration. The decap method was used to preprocess the high-concentration samples with large deviations, and the envelope removal method was used to extract the spectral absorption characteristic parameters of the water body. On the basis of the correlation analysis between the water Chl-a concentration and the spectral absorption characteristics, the water Chl-a concentration was inverted. The results showed the following: (1) The bands that were significantly related to the Chl-a concentration and had a large correlation coefficient were mainly located in the three absorption valleys (400-580, 580-650, and 650-710 nm) of the envelope removal curve. Moreover, the correlation between the Chl-a concentration and the absorption characteristic parameters at 650-710 nm was better than that at 400-580 nm and 580-650 nm. (2) Compared with the conventional inversion model, the uncapped inversion model had a higher R-P(2) and a lower RMSEP, and was closer to the predicted value of the 1:1 line. Moreover, the performance of the uncapped inversion model was better than that of the conventional inversion model, indicating that the uncapped method is an effective preprocessing method for high-concentration samples with large deviations. (3) The predictive capabilities of the ER_New model were significantly better than those of the R_New model. This shows that the envelope removal method can significantly amplify the absorption characteristics of the original spectrum, which can significantly improve the performance of the prediction model. (4) From the inversion models for the absorption characteristic parameters, the prediction models of A(650-710 nm)_New and D650-710 nm_New exhibited the best performance. The three combined models (A(650-710 nm)& D650-710 nm_New, A(650-710 nm)& NI_New, A(650-710 nm)& DI_New) also demonstrated good predictive capabilities. This demonstrates the feasibility of using the spectral absorption feature to retrieve the chlorophyll concentration.