细化搜索
结果 4651-4660 的 8,010
Characterizing variations in dissolved organic matter (DOM) properties in Nansi Lake: a typical macrophytes-derived lake in northern China 全文
2021
Nansi Lake is the largest lake along the eastern route of China’s South-to-North Water Diversion Project (SNWDP). It is divided into the upper lake and the lower lake by a dam. By using UV-Vis spectroscopy, synchronous fluorescence (SF) spectroscopy, excitation-emission matrix and parallel factor analysis (EEM-PARAFAC), spatial, and temporal differences in the properties of dissolved organic matter (DOM) were found in the 2 areas of Nansi Lake under different hydrological conditions. A total of 5 fluorescence components were obtained by EEM-PARAFAC, which included 3 humic-like components (C1–C3) and 2 protein-like components (C4 and C5). On the spatial scale, the fluorescence intensities (Fₘₐₓ) of humic-like substances and the ratio of the fluorescence intensity of humic-like components to the total fluorescence intensity (%Fₘₐₓ) and degree of humification (HIX) in the upper lake were higher than those in the lower lake. This indicated the strong contributions of terrestrial sources to the upper lake, while DOM properties in the lower lake were more endogenous than those in the upper lake. On the temporal scale, protein-like substances played a more important role in DOM properties in April (Fₘₐₓ=0.72±0.03 in the upper lake and 1.84±0.13 in the lower lake) and July (Fₘₐₓ=1.10±0.05 in the upper lake and 1.49±0.04 in the lower lake) than in October. This result might be related to the water transfer of the eastern route of the SNWDP and to the death of submerged plants. However, the contents of humic-like substances (ranging from 55.61±1.23% to 66.56±0.58% for the upper lake and 29.98±1.56% to 61.98±0.99% for the lower lake) and degree of humification (from 2.23±0.06 to 3.10±0.05 for the upper lake and 1.06±0.05 to 2.62±0.08 for the lower lake) in Nansi Lake showed an increasing trend from April to October. In addition, significant correlations and good linear relationships between humic-like components, a₂₅₄, and DOC in the 3 months reflected the continuous contribution of humic-like substances to DOM properties in Nansi Lake. Rapid changes in the fluorescence signal were largely dependent on changes in water quality. The fluorescence signal could be a tool for the management of water quality in Nansi Lake.
显示更多 [+] 显示较少 [-]Experimental investigation on solar-powered ejector refrigeration system integrated with different concentrators 全文
2021
The objective of the work is to analyse and to improve the efficiency of solar-powered ejector refrigeration system integrated with flat-plate collector and Scheffler concentrator. The Scheffler concentrator of 2.7 m² and flat-plate collector of 5 m² collecting area are coupled with the storage tank of 15 l capacity. The developed system was designed for a potential replacement of conventional 1-ton room air conditioner with much reduced electrical energy consumption. The system was built based on two key subsystems namely ‘Scheffler concentrator-based vapour system’ and ‘ejector-based cooling system’. The pilot effort showed promising results with the probability of energy-saving potential as near 70 to 80% over conventional air conditioners.
显示更多 [+] 显示较少 [-]Simulating reference crop evapotranspiration with different climate data inputs using Gaussian exponential model 全文
2021
Jia, Yue | Wang, Fengchun | Li, Pengcheng | Huo, Shuyi | Yang, Tao
Obtaining accurate data on reference crop evapotranspiration (ET₀) is important for agricultural water management. A novel Gaussian exponential model (GEM) was developed in this study to predict ET₀ with limited climatic data. The GEM was further compared with the M5 model tree (M5T), extreme learning machine (ELM), and boosted trees (BT) model under local and regional scenarios. Daily meteorological data during 1997–2016 from four stations in Northeast China were used to develop and validate the model. The results showed that the models considering solar radiation and relative humidity demonstrated considerably higher accuracy than those using other inputs. The GEM demonstrated higher accuracy among the four machine learning models for different stations. The accuracy of GEM under local scenarios was higher than that under regional scenarios with the root mean square error (RMSE) reducing by 0.025–0.046 mm/d, relative root mean square error (RRMSE) reducing by 0.879–2.022%, coefficient of efficiency (Eₙₛ) increasing by 0.008–0.026, the coefficients of determination (R²) increasing by 0.008–0.026, and mean absolute error (MAE) reducing by 0.015–0.033 mm/d. The GEM considering solar radiation had the highest accuracy with the global performance indicator (GPI) of 1.876. It can also be seen from the Taylor diagrams that the GEM has the the lowest standard deviation and mean square error and the highest correlation coefficient with the standard values. In general, the GEM considering solar radiation had the lowest error and the highest consistency and could be recommended for ET₀ simulation for Northeast China.
显示更多 [+] 显示较少 [-]Experimental study on the characteristics of train-induced vibration in a new structure of metro depot 全文
2021
Chen, Yanming | Feng, Qingsong | Liu, Qinjie | Jiang, Jian
In order to improve the utilization rate of expensive and very limited urban land, a new structure system, underground metro depot, has been developed and applied in several cities in China. The underground metro depot, which is built underground, can be multiple stories, and allows other developments on top, has become increasingly popular in recent years. Since there are other developments on top, the vibration induced by the trains frequently entering and exiting the depot cannot be ignored. To better understand the characteristics of the train-induced vibration in the underground metro depot, a series of field tests were conducted on a two-story underground depot which is the largest underground metro depot in Asia. The results show that the main frequency components of vibration source are between 50 and 200 Hz and the level of that in the first floor underground is larger than that in the second floor underground due to the train floor structure interaction when the train running on the first floor underground. The vibration in the top platform decreases linearly with the distance from the measuring point to the center line of the track. When the train is running on the track at the edge area, the linear attenuation rate was about 0.2dB/m. It is easy to excite the vibration mode of the floor structure when the train is running on the first floor underground, so the vibration in the top platform induced by the train running on the first floor underground was much larger than the train running on the second floor underground. In the future design, if the underground depot has more than one floor, the structural dynamic behavior of over-track buildings induced by the train running on the floor slab underground should be the focus. The throat area has many rail joints and turnouts which can lead to a larger vibration level, the level easy to exceed the limit given for human vibration comfort. If developments are proposed on top of the throat area, the vibration level should be carefully checked in the area within 30 m from the track to avoid potential later vibration problem.
显示更多 [+] 显示较少 [-]Heavy metal phytoremediation potential of the roadside forage Chloris barbata Sw. (swollen windmill grass) and the risk assessment of the forage-cattle-human food system 全文
2021
Madanan, Minisha Thalikulangara | Varghese, George Kuttiparichel | Shah, Irfan Khursheed
This study presents the assessment of the risks incidental to the growth of the common tropical grass species Chloris barbata Sw. (swollen windmill grass) on road margins contaminated with Pb and Cd. Pot experiments were first carried out to quantify the Pb and Cd accumulation potential of the plant species in various plant parts as a function of the metal concentration in soil. C. barbata was found to be a hyperaccumulator for Cd (BCF>1, for aerial parts) and an excluder of Pb (BCF<1, for aerial parts). As the plant was found to accumulate Pb in its roots with TF<1, it can be considered a phytostabilizer of Pb. The mathematical relationship developed between soil concentrations of Pb and Cd and their corresponding concentrations in aerial parts were used in combination with the concentrations of these heavy metals reported in roadside soils to obtain estimates of their accumulation in the forage and consequently in the animal organs. Risk to the consumers of offal was estimated. It was found that the consumption of kidney meat was riskier than the consumption of liver meat. Furthermore, it was seen that despite the nearly two order less concentrations of Cd in roadside soils compared to Pb, it was posing a higher risk. For the median concentrations of Pb reported in roadside soils and cattle feeding exclusively on C. barbata growing on roadside soils, the HQ exceeded 1 for weekly consumption of kidney meat above 650 g. For median Cd concentrations, consumption of kidney meat above 230 g/week resulted in HQ>1. The scenario considered for risk assessment is significant for India, where stray grazing of cattle on road margins is common and offal offers a cheap source of animal protein for the economically poor.
显示更多 [+] 显示较少 [-]Variation of dissolved organic matter during excess sludge reduction in microbubble ozonation system 全文
2021
Sun, Zhiyi | Wang, Yuxiang | Chen, Xiaoliang | Zhu, Nanwen | Yuan, Haiping | Lou, Ziyang
Sewage sludge is the major by-product of wastewater treatment plants, and about 30% readily biodegradable organic matters might be reused through the mass reduction process, which could be also reduced the disposal fee. In this study, the microbubble ozonation (MB-O₃) was employed to improve the oxidation efficiency for sludge solubilization. At 160 mgO₃/gSS, the maximum mixed liquor suspended solids (MLSS) reduction ratio was 37.5% and the protein and polysaccharide contents increased to 31.6 and 138.6 mg/L, respectively. It was proposed that aromatic protein and soluble microbial in sludge were oxidized preferentially by MB-O₃, and the dissolved organic matter (DOM) fractions (mainly humic-acid-like substances) exhibited low degradability according to the variations of fluorescence excitation-emission spectrum coupled with fluorescence regional integration. MB-O₃ could enhance the settleability, but deteriorate sludge dewaterability at low dosage (< 160 mgO₃/gSS) due to a reduction in particle size from 61.7 to 47.5 μm. MB-O₃ has a good performance on the mass reduction of sludge through the improvement of the radical generated.
显示更多 [+] 显示较少 [-]Approaches to prevent and control Campylobacter spp. colonization in broiler chickens: a review 全文
2021
Abd El-Hack, Mohamed E. | El-Saadony, Mohamed T. | Shehata, Abdelrazeq M. | Arif, Muhammad | Paswan, Vinod K. | Batiha, Gaber El-Saber | Khafaga, Asmaa F. | Elbestawy, Ahmed R.
Campylobacter, Gram-negative bacteria, is the most common cause of acute bacterial enteritis in human beings, both in developing and developed countries. It is believed that poultry, in particular broiler chickens, is the main host of human infection with Campylobacter. Handling and consumption of contaminated chicken meat are the usual modes of transmission. Prevention and reduction of Campylobacter colonization in poultry farms will cut off the road of infection transmission to humans throughout the food chain. With the incidence of antibiotic resistance and with growing concern about superbugs, the search for natural and safe alternatives will considerably increase in the coming years. In this review, we will discuss the prevalence and risk factors of Campylobacter colonization in broiler chickens and sources of infection. This review also provides extensive and recent approaches to prevent and control Campylobacter colonization in broiler chickens, including biosecurity measures, natural feed/drinking water additives with antimicrobial properties, bacteriocins, bacteriophages, antimicrobial peptides, and vaccination strategies to prevent and control the incidence of human campylobacteriosis.
显示更多 [+] 显示较少 [-]Natural dye from Caesalpinia sappan L. heartwood for eco-friendly coloring of recycled paper based packing material and its in silico toxicity analysis 全文
2021
Nathan, Vinod Kumar | Rani, Mary Esther
The uses of natural dyes are getting popularized due to the increased awareness regarding the toxicity of many chemical colorants. The chemical colorants are being replaced by the natural colorants for the various industrial applications. The plant-based natural colorants are considered eco-friendly and toxic free. In the present study, we report a natural dye from the heartwood of Caesalpinia sappan suitable for paper based packing materials. This forms the first report on the study of natural dye obtained from the heartwood of C. sappan on paper material. The extracted dye had a good photostability and able to make imprints on recycled paper bags. Moreover, a significant inhibition of bacterial growth was observed at a higher dye concentration of 100 μg mL⁻¹ against P. aeruginosa which was higher than the standard antibiotics. Growth inhibition was also observed in case of B. subtilis (22 ± 0.17 mm) and K. pneumonia (21 ± 0.53 mm) at 100 μg mL⁻¹. The dye could be used in making medicated packing materials and have many other bio-potential which was validated through in silico toxicity analysis. The application of such natural dyes in paper material value addition will help in a cleaner and sustainable process during paper recycling.
显示更多 [+] 显示较少 [-]Ecotoxicological risk assessment of pentachlorophenol, an emerging DBP to plants: evaluation of oxidative stress and antioxidant responses 全文
2021
Ranjan, Jyoti | Joshi, Vayam | Mandal, Tamale | Mandal, Dalia Dasgupta
Chlorophenols are not only noticed in an effluvium of industries but also can emerge from the water treatment plants for domestic supply which poses a high threat for crop production and human health. Therefore, research on their risks to ecosystem and human health via ecotoxicological tests to derivate permissible environmental contaminant concentrations is necessary. The chlorophenols produced in the course of chlorination of potable water is an outcome of natural carboxylic acids/organic material and those chlorophenols occurred as emerging disinfection byproducts (EDBPs). Among chlorophenols, pentachlorophenol (PCP) has been recently identified as one of the important EDBPs. The main objective was to evaluate the PCP-induced genotoxicity and the oxidative damage in two plant species, i.e., Allium cepa and Vigna radiata. Genotoxicity of PCP was examined at three selected concentrations based on EC₅₀ (half-maximal effective concentrations) values in both the plants along with the defense mechanism. EC₅₀ value for A. cepa and V. radiata was 0.7 mg/L and 35 mg/L. Root length inhibition, DNA laddering, lipid peroxidation, H₂O₂ content, and antioxidant enzymatic assays evaluated revealed a dose-dependent response. PCP influenced defense enzyme glutathione peroxidase (GPX) and ascorbate peroxidase (APX) action in both plants and showed deprivement of catalase (CAT) with the increase of PCP concentrations. PCP-invaded toxicity management by these plants implied that A. cepa is more sensitive than V. radiata regarding PCP-induced toxicity.
显示更多 [+] 显示较少 [-]Oil field–produced water treatment: characterization, photochemical systems, and combined processes 全文
2021
Hollanda, Luana Rabelo | Santos, Samuel Brito Ferreira | Faustino, Júlia Gabriela Araújo Arruda | Dotto, Guilherme Luiz | Foletto, Edson Luiz | Chiavone-Filho, Osvaldo
Produced water, a mixture of inorganic and organic components, comprises the largest effluent stream from oil and gas activities. The removal of contaminants from this wastewater is receiving special attention of the researchers since most of them are persistent and difficult to remove with simple techniques. Several technologies from conventional to advanced oxidation processes have been employed to treat produced water. However, the achievement of greater efficiency may be conditioned to a combination of different wastewater treatment techniques. Hereupon, the present paper discusses three important aspects regarding produced water treatment: analytical methods used for characterization, relevant aspects regarding photochemical systems used for advanced oxidation processes, and combined techniques for treating oil field wastewaters. Analytical methods employed for the quantification of the main species contained in produced water are presented for a proper characterization. Photochemical aspects of the reaction systems such as operating conditions, types of irradiation sources, and technical details of reactors are also addressed. Finally, research papers concerning combined treatment techniques are discussed focusing on the essential contributions. Thus, this manuscript aims to assist in the development of novel techniques and the improvement of produced water treatment to obtain a high-quality treated effluent and reduce environmental impacts.
显示更多 [+] 显示较少 [-]