Showing papers by "Chao Liu published in 2021"

Carbonized polyaniline activated peroxymonosulfate (PMS) for phenol degradation: Role of PMS adsorption and singlet oxygen generation

Abstract: N-doped carbonaceous materials are promising efficient catalysts for peroxymonosulfate (PMS) activation In this study, the high-efficient N-doped carbon materials were prepared by direct carbonization of polyaniline (PANI) at 700 °C–1000 °C It was optimized that the CPANI-9 (carbonized polyaniline prepared at 900 °C) exhibited excellent catalytic performance to activate PMS for phenol degradation, which was efficient over a wide pH range (pH 35∼9) In the CPANI-9/PMS system, the PMS adsorption/activation was identified as the key step determining the reaction rate The quenching experiments and electron paramagnetic resonance demonstrated that the non-radical pathway was dominant in phenol degradation and singlet oxygen (1O2) was the main active specie Graphitic N, pyridinic N, defects and ketonic groups (C O) were identified as catalytic sites Interestingly, only the presence of PO43− greatly decreased the phenol degradation rate and PMS decomposition The CPANI-9/PMS system could also degrade effectively various organic pollutants, indicating that it had potential practical application

Activation of peroxydisulfate by V-Fe concentrate ore for enhanced degradation of carbamazepine: Surface ≡V(III) and ≡V(IV) as electron donors promoted the regeneration of ≡Fe(II)

Abstract: V-Fe concentrate ore was applied to activate peroxydisulfate (PDS) for carbamazepine (CBZ) degradation. The excellent performance of V-Fe concentrate ore was mainly ascribed to the quick electron transfer from surface ≡V(III) and ≡V (IV) to ≡Fe(III) for ≡Fe(II) regeneration, which was confirmed by XPS and XAS analyses. This accelerated ≡Fe(II) regeneration could thus lead to quick formation of HO , SO4 −, O2 − and effective degradation of CBZ. The degradation rate of CBZ could be also expressed by a kinetic model, i.e., −d[CBZ]/dt = (0.83 mM-0.55 min-1(g/L)-0.65) [CBZ]0.29[PDS]1.26[V-Fe]0.65. Combined with the measured intermediates and the results of DFT calculation, CBZ degradation pathway was proposed systematically. Moreover, this catalyst displayed excellent recyclability and general applicability for a broad substrate scope. This study suggests low valent vanadium makes crucial contributions to the high activity of V-Fe-based catalysts, and improves the understanding of electron transfer mechanism between V and Fe in PDS activation process.

Degradation of benzophenone-4 by peroxymonosulfate activated with microwave synthesized well-distributed CuBi2O4 microspheres: Theoretical calculation of degradation mechanism

Abstract: Well-distributed CuBi2O4 microspheres prepared by microwave-assisted co-precipitation method and subsequent calcination treatment were used to activate peroxymonosulfate (PMS) for benzophenone-4 (BP-4) degradation. Uniformly distributed active sites, hydroxyl groups, and the cycle of Cu(I)/Cu(II) on the surface of CuBi2O4 microspheres effectively facilitated PMS activation to generate SO4 −, OH and 1O2, but 1O2 was not the dominant reactive oxygen species. The degradation mechanism of BP-4 was proposed through theoretical calculations and intermediates identification that the first and dominant step of BP-4 oxidation with SO4 −/ OH is radical addition reaction rather than single electron transfer. It breaks through previous reports that reaction between SO4 − and electron-rich aromatic organics is mainly via single electron transfer. Ecotoxicity assessment by ECOSAR program indicated that the presence of Cl− did not increase the toxicity of intermediates because generated chlorinated intermediates are hydrophilic.

Estimation of Urban Ecosystem Services Value: A Case Study of Chengdu, Southwestern China

Abstract: Research on the service values of urban ecosystems is a hot topic of ecological studies in the current era of rapid urbanization. To quantitatively estimate the ecosystem service value in Chengdu, China from the perspectives of natural ecology and social ecology, the technologies of remote sensing (RS) and geographic information system (GIS) are utilized in this study to extract the land use type information from RS images of Chengdu in 2003, 2007, 2013 and 2018. Subsequently, a driver analysis of the ecosystem services of Chengdu was performed based on socioeconomic data from the last 16 years. The results indicated that: (1) from 2003 to 2018, the land utilization in Chengdu changed significantly, with the area of cultivated lands, forest lands and water decreasing remarkably, while the area of construction lands dramatically increased. (2) The ecosystem services value (ESV) of Chengdu decreased by 30.92% in the last 16 years, from CNY 2.4078 × 1010 in 2003 to CNY 1.6632 × 1010 in 2018. Based on a future simulation, the ESV is further predicted to be reduced to CNY 1.4261 × 1010 by 2033. (3) The ESV of Chengdu showed a negative correlation with the total population, the urbanization rate and the per capita GDP of the region, indicating that the ESV of the studied region was inter-coupled with the socioeconomic development and can be maintained at a high level through rationally regulating the socioeconomic structure.

A Survey of Remote Sensing and Geographic Information System Applications for Flash Floods

Abstract: Flash floods are among the most dangerous natural disasters. As climate change and urbanization advance, an increasing number of people are at risk of flash floods. The application of remote sensing and geographic information system (GIS) technologies in the study of flash floods has increased significantly over the last 20 years. In this paper, more than 200 articles published in the last 20 years are summarized and analyzed. First, a visualization analysis of the literature is performed, including a keyword co-occurrence analysis, time zone chart analysis, keyword burst analysis, and literature co-citation analysis. Then, the application of remote sensing and GIS technologies to flash flood disasters is analyzed in terms of aspects such as flash flood forecasting, flash flood disaster impact assessments, flash flood susceptibility analyses, flash flood risk assessments, and the identification of flash flood disaster risk areas. Finally, the current research status is summarized, and the orientation of future research is also discussed.

Optimal segmentation scale selection and evaluation of cultivated land objects based on high-resolution remote sensing images with spectral and texture features

Abstract: As the remote sensing technology develops, there are increasingly more kinds of remote sensing images available from different sensors. High-resolution remote sensing images are widely used in the detection of land cover/land change due to their plenty of characteristics of a specific feature in terms of spectrum, shape, and texture. Current studies regarding cultivated land resources that are the material basis for the human beings to survive and develop focus on the method to accurately obtain the quantity of cultivated land in a region and understand the conditions and the trend of change of the cultivated land. Pixel-based method and object-oriented method are the main methods to extract cultivated land in remote sensing field. Pixel-based method ignores high-level image information, while object-oriented method takes the image spot after image segmentation as the basic unit of information extraction, which can make full use of spectral features, spatial features, semantic features, and contextual features. Image segmentation is a key step of object-oriented method; the core problem is how to obtain the optimal segmentation scale. Traditional methods for determining the optimal segmentation scale of features (such as the homogeneity-heterogeneity method, the maximum area method, and the mean variance method), in which only the spectral and geometrical characteristics are considered, while the textural characteristics are neglected. Based on this, the Quickbird and unmanned aerial vehicle (UAV) images obtained in Xiyu Village, Pengzhou City, Sichuan Province, China, were selected as experimental objects, and the texture mean and spectral grayscale mean method (MANC method based on GLCM), which comprehensively considered the spectrum, shape, and texture features, was proposed to calculate the optimal segmentation scale of cultivated land in the study area. The error segment index (ESI) and centroids distance index (CDI) were adopted to evaluate image segmentation quality based on the method of area and position differences. The experimental results show that the MANC method based on GLCM can obtain higher segmentation precision than the traditional methods, and the segmentation results are in good agreement with the cultivated land boundary obtained by visual interpretation.

Combined impact of organic matter, phosphorus, nitrate, and ammonia nitrogen on the process of blackwater.

Abstract: Blackwater events are frequently reported over the world and become a serious environmental problem. However, the mechanisms of blackwater occurrence are not fully understood yet. This study simulated the process of blackwater with the combined pollution in an orthogonal experiment, which had 4 factors (TOC, TP, NH4+-N, and NO3--N) and 4 levels (None, Low, Middle, and High). Results showed that the process of water condition changes was divided into two parts, which were "exogenous" and "algae-derived" blackwater, and the influence of four different pollutants on the occurrence of the blackwater was ranked as follows: TOC > TP > NO3--N > NH4+-N. With the increase of organic matter addition, the anaerobic condition in water was prolonged and the concentration of Fe2+ had a significant increase. In addition, under the None phosphorus condition, the descent rates of DO and COD in the water were reduced, and the algae bloom was obviously deferred. Moreover, the addition of organic matter or phosphorus changed the microbial community structure and led to different water processes. Particularly, only on the condition of the high content of TOC and phosphorus, the diversity of sulfate-reducing bacteria (e.g., Pseudomonas, Paludibacter, and Bacteroides) increased significantly, which accounted for 51.4%, causing the significant production of S2- in the water. Water's lack of phosphorus showed a low rate of decomposition of organic matter, which might be the result of a considerable increase in the abundance of aerobic Trichococcus and Malikia. This study shows that organic matter and phosphorus have synergistic effect on blackwater occurrence. In the treatment of blackwater, the exogenous pollutant control should reduce the discharge of organic pollutants, and endogenous control should focus on phosphorus abatement and reduce nitrogen control.

Response of Plant Rhizosphere Microenvironment to Water Management in Soil- and Substrate-Based Controlled Environment Agriculture (CEA) Systems: A Review.

Abstract: As natural agroecology deteriorates, controlled environment agriculture (CEA) systems become the backup support for coping with future resource consumption and potential food crises. Compared with natural agroecology, most of the environmental parameters of the CEA system rely on manual management. Such a system is dependent and fragile and prone to degradation, which includes harmful bacteria proliferation and productivity decline. Proper water management is significant for constructing a stabilized rhizosphere microenvironment. It has been proved that water is an efficient tool for changing the availability of nutrients, plant physiological processes, and microbial communities within. However, for CEA issues, relevant research is lacking at present. The article reviews the interactive mechanism between water management and rhizosphere microenvironments from the perspectives of physicochemical properties, physiological processes, and microbiology in CEA systems. We presented a synthesis of relevant research on water-root-microbes interplay, which aimed to provide detailed references to the conceptualization, research, diagnosis, and troubleshooting for CEA systems, and attempted to give suggestions for the construction of a high-tech artificial agricultural ecology.

N/Fe/Zn co-doped TiO2 loaded on basalt fiber with enhanced photocatalytic activity for organic pollutant degradation

Abstract: To avoid the loss of catalytic material powder, a loaded catalytic material of TiO2 with basalt fiber as the carrier (TiO2@BF) was synthesized by an improved sol–gel method. The TiO2@BF was doped with different contents of N, Fe and Zn elements and was used to degrade rhodamine B (RhB) under ultraviolet light. The physical characterization analysis indicated that the co-doping of the N, Fe and Zn elements had the effects of reducing grain size, increasing sample surface area, and narrowing the electronic band gap. The electronic band gap of nitrogen–iron–zinc co-doped TiO2@BF (N/Fe/Zn_TiO2@BF) was 2.80 eV, which was narrower than that of TiO2@BF (3.11 eV). The degradation efficiency of RhB with N/Fe/Zn_TiO2@BF as a photocatalyst was 4.3 times that of TiO2@BF and its photocatalytic reaction was a first-order kinetic reaction. Quenching experiments suggested that the reactive species mainly include photoinduced holes (h+), superoxide radicals (˙O2−) and hydroxyl radicals (˙OH). In brief, this study provides a prospective loaded catalytic material and routine for the degradation of organic contaminants in water by a photocatalytic process.

LAI scale effect research based on compact airborne spectrographic imager data in the Heihe Oasis

Abstract: As one of the key parameters for characterizing crop canopy structure, Leaf Area Index (LAI) has great significance in monitoring the crop growth and estimating the yield. However, due to the nonlinearity and spatial heterogeneity of LAI inversion model, there exists scale error in LAI inversion result, which limits the application of LAI product from different remote sensing data. Therefore, it is necessary to conduct studies on scale effect. This study was based on the Heihe Oasis, Zhangye city, Gansu province, China and the following works were carried out: Airborne hyperspectral CASI (Compact Airborne Spectrographic Imager) image and LAI statistic models were adopted in muti-scale LAI inversion. The overall difference of muti-scale LAI inversion was analyzed in an all-round way. This was based on two aspects, “first inversion and then integration” and “first integration and then inversion”, and on scale difference characteristics of three scale transformation methods. The generation mechanism of scale effect was refined, and the optimal LAI inversion model was expanded by Taylor expansion. By doing so, it quantitatively analyzed the contribution of various inversion processes to scale effect. It was found that the cubic polynomial regression model based on NDVI (940.7 nm, 712 nm) was the optimal model, where its coefficient of determination R2 and the correlation coefficient of test samples R reached 0.72 and 0.936, respectively. Combined with Taylor expansion, it analyzed the scale error generated by LAI inversion model. After the scale effect correction of one-dimensional and two-dimensional variables, the correlation coefficient of CCD-LAI (China Environment Satellite HJ/CCD images) and CASI-LAI products (Compact Airborne Spectro graphic Imager products) increased from 0.793 to 0.875 and 0.901, respectively. The mean value, standard deviation, and relative true value of the two went consistent. Compared with one-dimensional variable correction method, the two-dimensional method had a better correction result. This research used the effective information in hyperspectral data as sub-pixels and adopted Taylor expansion to correct the scale error in large-scale and low-resolution LAI product, achieving large-scale and high-precision LAI monitoring.