خيارات البحث
النتائج 4451 - 4460 من 6,558
A novel sorbent based on Ti-Ca-Mg phosphates: synthesis, characterization, and sorption properties النص الكامل
2020
Maslova, Marina | Mudruk, Natalia | Ivanets, Andrey | Shashkova, Irina | Kitikova, Natalia
This work focuses on the synthesis procedure of a new sorbent based on a TiCaMg phosphate. The synthesis strategy includes stepwise interaction between solid precursors and phosphorus-containing agents. The solid precursors were ammonium titanyl sulfate and calcined dolomite, which were used as titanium, calcium, and magnesium sources. The effect of the nature and concentration of phosphoric agent on the sorbent composition and properties has been investigated using elemental analysis, TG, XRD, IR spectroscopy, BET, and SEM techniques. The novel sorbent has been demonstrated to be a composite material consisting of the following components: TiO(OH)H₂PO₄·H₂O, Ti(HPO₄)₂·H₂O, CaHPO₄·2H₂O, MgНPO₄·3H₂O, and NH₄MgPO₄·6H₂O. The ratio between these phases in the composite depends on synthesis conditions. The optimal conditions, ensuring full conversion of Ti, Ca, and Mg containing in the initial precursors into the final product, have been found. The sorption properties of the obtained composite sorbent towards Co²⁺, Cs⁺, and Sr²⁺ cations and their radionuclide analogues have been studied. The obtained data has indicated that the purification effect was based on both precipitation and ion exchange mechanism. The combined action of the individual components of the composite sorbent ensures its high sorption capacity towards different cations in a wide pH range. The new sorbent shows high sorption ability towards radionuclides in multicomponent liquid radioactive waste (LRW) systems, and the distribution coefficient of the studied radionuclides was found to be 10⁵ mL g⁻¹. The presence of different types of functional groups in the composite sorbent allows realizing the one-step purification process of LRW that, in turn, simplifies the sorption system design.
اظهر المزيد [+] اقل [-]Effects of indoor plants on air quality: a systematic review النص الكامل
2020
Han, Ke-Tsung | Ruan, Li-Wen
No study has comprehensively reviewed the effects of indoor plants on air quality; therefore, this study systematically reviewed quantitative empirical research on these effects in both English and Chinese. The information sources were the Web of Science and WanFang Data Knowledge Service Platform electronic databases. Only journal articles reporting quantitative empirical research were selected. The eligibility criteria included studies with (1) interventions of any indoor plant, excluding biofilters that combine power facilities and vegetation, (2) comparators included within the same experimental treatment or between different experimental treatments, (3) air quality effects objectively measured using any instrument, and (4) any study design. Both authors screened 95 journal articles and compiled information according to (1) intervention (plant species, foliage, or medium), (2) scientific family name of each plant, (3) study design (experiment, field experiment, or survey), (4) air quality (e.g., temperature, humidity, negative ions, radiation, and dust), (5) pollutants, (6) research environment, (7) ventilation (types and rates), (8) climate (lighting, temperature, and humidity), (9) exposure duration, (10) sampling frequency or period, and (11) number of replications. The primary effects of the potential of the indoor plants on air quality were reduced pollutant levels (particularly formaldehyde, benzene, and toluene removal), followed by increase in humidity and decrease in temperature. In addition, including various plant species could improve the effects of indoor vegetation on ameliorating air quality and microclimate conditions.
اظهر المزيد [+] اقل [-]Identification of the heavy metal pollution sources in the rhizosphere soil of farmland irrigated by the Yellow River using PMF analysis combined with multiple analysis methods—using Zhongwei city, Ningxia, as an example النص الكامل
2020
Zhang, Min | Wang, Xueping | Liu, Chang | Lu, Jiayu | Qin, Yuhong | Mo, Yunkan | Xiao, Pengjun | Liu, Ying
In recent years, with the frequent occurrences of heavy metal (HM) pollution in agriculture, the problem of HM pollution in farmland soil, especially in the areas irrigation by the Yellow River, has been attracted increasing attention because of the complex sources of pollution. Qualitative identification of pollution sources and quantification of their contributions to HMs in soil are the key links in the prevention and control of HM pollution. The contents of 11 heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sn, V, and Zn) in the rhizosphere soil of the Ningxia irrigation area were determined by inductively coupled plasma mass spectrometry (ICP-MS). Multiple methods were used for source identification, including positive matrix factorization (PMF) analysis combined with multiple other analyses (single factor index method (Pi), coefficient of variation(CV), correlation analysis(CA), enrichment factor(EF), and principal component analysis(PCA)). The results showed that (1) the over-standard rates of As, Cd, Cr, Mn, Pb, Sn, and Zn in the study area were 100%, of which Cd was seriously polluted, while As, Zn, and Sn were moderately polluted. (2) The HM contributions from irrigation and silt soil formed by the Yellow River sediment were the highest (42.45%), followed by the smelting industry and traffic pollution (16.06%). (3) The contribution of agricultural pollution to HMs in the region was 15.54%, in which As was mainly from pesticides and Cd was mainly from fertilizers.
اظهر المزيد [+] اقل [-]Co-processing of the MSWI flue gas in a lab-scale coal-fired drop-tube furnace النص الكامل
2020
Coal-fired power plants are characterized by high combustion temperature and well-equipped air pollution control devices. The trace organic pollutants in the municipal solid waste incineration (MSWI) flue gas would be completely destroyed if the MSWI flue gas was injected into the high temperature area of a coal-fired boiler. In this study, the emission characteristics of common gas pollutants, heavy metals, and dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in both flue gas and bottom ash when the MSWI flue gas was injected into a lab-scale coal-fired drop-tube furnace were investigated. After co-processing, the concentrations of NOx, SO₂, CO, and all heavy metals in the flue gas emitted from the coal-fired drop-tube furnace did not change a lot. However, the concentration of HCl in the flue gas from drop-tube furnace increased after coupling the MSWI flue gas. Moreover, the I-TEQ values of the PCDD/Fs in the flue gas and bottom ash after coupling the MSWI flue gas were 0.037 ng I-TEQ/Nm³ and 0.63 ng I-TEQ/g, respectively. The main formation pathways of PCDD/Fs in the flue gas of drop-tube furnace were suggested to be de novo synthesis and precursor synthesis. Furthermore, the effects of oxygen content and temperature on the formation of PCDD/Fs were also studied. The reduction efficiencies of the total amount of PCDD/Fs in the flue gas from the co-processing system were more than 60%, and even reached 90%. Therefore, co-processing of the MSWI flue gas in coal-fired power plants might be an environmentally friendly technology.
اظهر المزيد [+] اقل [-]Assessment of the air pollution emission reduction effect of the coal substitution policy in China: an improved grey modelling approach النص الكامل
2020
In recent years, the Chinese government has proposed a policy to replace coal use with natural gas and electricity in the northern region to reduce the air pollution caused by the large consumption of coal. In order to assess the air pollution reduction effect of the coal substitution policy in Liaoning Province, this paper proposes a data grouping grey model with a fractional order accumulation (FDGGM (1,1)). The empirical analysis results show that the new grey model can predict the monthly coal consumption more accurately than the traditional DGGM (1,1) model. The MAPEs of the training set in the FDGGM(1,1) and DGGM(1,1) models are 4.58% and 5.48%, and the MAPEs of the test set are 23.89% and 33.78%, respectively. And the policy achieves a great success based on the FDGGM(1,1) model. During the policy implementation period (from January 2015 to December 2018), the coal consumption in Liaoning Province decreased by 27.2501 million tons, while the emissions of CO₂, SO₂ and NOₓ fell by 0.714, 0.2316 and 0.2017 million tons, respectively. The results also provide a necessary support to the further implementation of the coal substitution policy.
اظهر المزيد [+] اقل [-]Removal of ochratoxin A from liquid media using novel low-cost biosorbents النص الكامل
2020
Ground shells of almonds (ALM), hazelnuts (HAZ), walnuts (WAL), and chestnuts (CHE), coconut fiber (COC), spent coffee grounds (COF), and clementine peel (CLE) were used to remove ochratoxin A (OTA) from both water and an ethanol/water mixture (14:86, v/v). Other very efficient adsorbents like wood biochar (BC) and hydrochar (HC) and a humic acid (HA) were also adopted as a comparison. In batch experiments, sorption of OTA from water followed the trend BC (100% removed) > HA > CLE > COC > HC > COF > ALM > HAZ > CHE > WAL (8% removed), whereas sorption of OTA from ethanol/water mixture (14:86, v/v) onto only the raw materials was COC (54% removed) > CLE > HAZ > ALM > COF > CHE > WAL (0.4% removed). The desorption of the toxin from all materials in water was rather low. Afterwards, sorption kinetics and isotherms of OTA onto CLE, COC, and COF were performed. The three materials adsorbed OTA in about 2 h according to a pseudo-second-order kinetic model, thus indicating the occurrence of a chemisorption mechanism. Equilibrium sorption data of OTA onto CLE followed preferentially the Freundlich model, whereas those on COC and COF fitted well both Freundlich and Langmuir isotherms (r > 0.996). The values of Freundlich sorption constants, KFₐdₛ, for CLE, COC, and COF were 313, 202, and 98 L kg⁻¹, respectively. OTA desorption from each of the three materials showed hysteretic effects. Overall findings of this work suggest that raw plant wastes could be effectively used as biosorbents to abate the level of OTA in liquid media.
اظهر المزيد [+] اقل [-]Chemical characterization of mountain forest soils: impact of long-term atmospheric deposition loadings (Czech–Polish–German border region) النص الكامل
2020
Havelcová, Martina | Machovič, Vladimír | Novák, František | Lapčák, Ladislav | Mizera, Jiří | Hendrych, Jiří
The composition of lipids in soil offers clues to soil degradation processes due their persistency and selectivity in soil, and close relation to long-term processes in the ecosystem, thanks to their role in cell membranes of organisms. Organic solvent-extractable compounds were recovered from soils collected at two sites differing in the degree of forest damage. Gas chromatography/mass spectroscopy and Fourier transform infrared spectroscopy were applied in order to characterize solvent-extractable lipids. Raman spectroscopy was also applied as it provides distinct advantages for determining the structural order of carbonaceous materials. The organic matter measurement techniques were combined with an established simultaneous multi-element measurement technique. Variations in individual soil horizons from the sites were reflected in the crystallinity of epicuticular waxes, presence of long-chain aliphatic hydrocarbons, concentrations of n-alkanes, saturated and unsaturated fatty acids, dicarboxylic acids, and in the content of aromatic structures, hydroxyl, ester, and carboxylic acid groups. The results are explained by differently transformed organic matter. The concentrations of elements in the soils were also affected by atmospheric depositions, including higher accumulations of arsenic and antimony, and lower contents of natural nutrients. These data have potential to be used as sensitive biogenic indicators of ecosystem damage by long-term atmospheric depositions.
اظهر المزيد [+] اقل [-]Silicon application improved the yield and nutritional quality while reduced cadmium concentration in rice النص الكامل
2020
Li, Na | Feng, Aixuan | Liu, Na | Jiang, Zhenmao | Wei, Shiqiang
Silicon (Si) is an essential nutrient for rice, but its effects on the yield and quality of rice under heavy metal stress remain uncertain. In this study, two typical paddy soils (acidic and calcareous purple soils) in the western region of Chongqing were selected for field plot experiment, with the purpose of understanding the effects of Si implementation methods on grain yields and cadmium (Cd) uptake, transport, and accumulation in the grain of a hybrid rice (Oryza sativa L, Changliangyou 772). Four treatments were set for the purposes including soil-based Si application, foliar spray of Si alone, foliar spray of selenium (Se)–containing Si fertilizer, and a control without Si application, respectively. The results indicated that the Si applications reduced Cd contents in brown rice by 11.45~51.85% in the slightly Cd-contaminated acidic purple soil (pH = 4.77, soil total Cd content 0.413 mg kg⁻¹) and 26.93~43.77% in the purple calcareous paddy soil (pH = 7.77) with similar Cd-polluting levels. It is worth noting that the Cd content of conventional fertilized rice exceeds the Chinese National Food Safety Standard limit (0.2 mg kg⁻¹, GB2762-2017) in the slightly Cd-contaminated acidic purple soil, and foliar spray treatments showed most effective effects that meets the safety threshold standard. Soil-based Si application reduced Cd accumulation in rice grains mainly by inhibiting the translocation of Cd from stem to the rice grain or root to stem, while foliar sprays of Si mainly by inhibiting the translocation of Cd from stem to brown rice. Si applications increased the rice yield by 17.15 to 25.45% in calcareous paddy soil with foliar spray being the best, while no significant yield increase was found in acidic paddy soil. Si and Se-containing Si fertilizer improved the nutritional quality of rice grain as indicated by the increases of Se, Si, and protein contents and the significant decreases of Cd contents in the rice grains. The comprehensive effects in improving the rice quality follow the order of foliar spray of Se-containing Si fertilizer > foliar spray of Si alone > soil-based Si application. Thus, foliar spray Si-containing fertilizer could be helpful in increasing rice yield while reducing the Cd uptake in rice grains, which might be a feasible approach in controlling Cd entry into the human body via crops.
اظهر المزيد [+] اقل [-]Analysis of asymmetries in the nexus among clean energy and environmental quality in Pakistan النص الكامل
2020
Usman, Ahmed | Ullah, Sana | Ozturk, Ilhan | Chishti, Muhammad Zubair | Zafar, Syeda Maria
This study examines the short-run and long-run asymmetric effects of clean energy consumption on carbon emission in Pakistan, over the annual time period 1975–2018, by using a non-linear ARDL approach. The findings of the study confirm the existence of asymmetries, in the nexus between the clean energy consumption and carbon emission in the short and long run. The findings of non-linear model confirm that carbon emission responded contrary to positive shocks of energy variables as compared with their negative shocks. Asymmetric findings recommend that positive and negative shocks of the alternative and nuclear energy and combustible and waste energy have affected differently. Although, short- and long-run results suggest an insignificant positive and negative relationship between electric power consumption and carbon emissions. Therefore, more taxation of non-renewable energy and clean energy supports are suggested for the Pakistan economy. We concluded that Pakistan has potential in clean energy which will improve environmental quality in the near future.
اظهر المزيد [+] اقل [-]Ca, Cu, and Li in washed and unwashed specimens of needles, bark, and branches of the blue spruce (Picea pungens) in the city of Ankara النص الكامل
2020
Cetin, Mehmet | Sevik, Hakan | Cobanoglu, Oguzhan
The use of certain types of plants to determine the accumulation of HMs (heavy metals) has yielded quite consistent results in the research fields. Many researches have focused on particular types of HMs due to their common presence in the air (Pb, Cd, Ni, Co, Cr to name a few). However, it is equally as important to shed light on other types of HMs and the scale of their existence in our atmosphere, hence this paper. Blue spruce (Picea pungens) tree organs were used in an experiment to calculate the recent concentration of HMs. The research concentrates on Ca, Cu, and Li elements in the washed and unwashed needles, branches, and barks, and these organs were evaluated depending on the organ age. The study results showed that the concentration of the elements subjected to the research changed depending on the organ, washing status and organ age, and that the lowest concentrations of Ca and Cu elements were obtained in the barks in general. In relation to the organ age, it was found that there was an increase in the concentration of Ca with age, and that the concentration of Li element was inversely proportional to age.
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