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131.
Hematite (Fe2O3) chemical reduction into FeO and Fe3O4 by releasing O2 at high temperatures is considered one of the generally accepted mechanisms for processing waste minerals and clay into lightweight
aggregate construction materials. In many case studies, this mechanism has not been strictly confirmed. To verify whether
hematite can effectively release O2 at 1,000–1,260°C, a material containing hematite, simulating waste sediments from a Taiwanese reservoir, was shaped into
pellets and fired into lightweight aggregates at high temperatures for 20 min and studied with various techniques. As revealed
by the X-ray absorption near-edge structure technique, almost all the hematite remained as Fe(III) in the pellets when fired
at 1,000–1,260°C, implying a negligible release of O2 leading to the creation of pores. This finding shows that the generally accepted mechanism for lightweight aggregate formation
associated with hematite decomposition into FeO, Fe3O4, and O2 is invalid. Furthermore, Fe(III)-containing composites were formed in the fired pellets. Although firing at 1,000°C can trigger
the decomposition of the components K2CO3, Na2CO3, and CaCO3 with a release of CO2, the sintering reaction was seemingly too weak to encapsulate the gases effectively. For pellets fired at 1,050–1,150°C,
pores grew in size because the sintering reaction sufficed to generate a glassy phase that could better encapsulate gases. 相似文献
132.
Izabela Polowczyk Anna Bastrzyk Tomasz Koźlecki Wojciech Sawiński Piotr Rudnicki Adam Sokołowski Zygmunt Sadowski 《Environmental geochemistry and health》2010,32(4):361-366
The aim of this work is to investigate the application of fly ash adsorbent for removal of arsenite ions from dilute solution
(100–1,000 ppm). Experiments were carried out using material from the “Turów” (Poland) brown-coal-burning power plant, which
was wetted, then mixed and tumbled in a granulator to form spherical agglomerates. Measurements of arsenic adsorption from
aqueous solution were carried out at room temperature and natural pH of fly ash agglomerates, in either a shaken flask or
circulating column, to compare two different methods of contacting solution with adsorbent. Adsorption isotherms of arsenic
were determined for agglomerated material using the Freundlich equation. Kinetic studies indicated that sorption follows a
pseudo-second-order model. Preferable method to carry out the process is continuous circulation of arsenite solution through
a column. 相似文献
133.
Monitoring of day-active butterflies by water pan traps method over the period 2001–2012 was conducted on a gradually overgrowing habitat in Ko?ick? kotlina basin (Slovakia). Totally, 1457 individuals of 57 species of butterflies were caught and evaluated. Monitoring revealed significant changes in the butterfly community which might be a consequence of a gradual overgrown of the study area. During the research, 12 butterfly species have disappeared from the study area. The monitoring provided results which point to the necessity of appropriate management for conservation of rare and protected butterfly species. 相似文献
134.
Co-contamination of arsenic and fluoride in the groundwater of unconsolidated aquifers under reducing environments 总被引:1,自引:0,他引:1
The co-contamination of arsenic (As) and fluoride (F−) in shallow aquifers is frequently observed worldwide, and the correlations between those contaminants are different according to the redox conditions. This study geochemically explores the reasons for the co-contamination and for the redox-dependent correlations by investigating the groundwater of an alluvial aquifer in Korea. Geochemical signatures of the groundwater in the study area show that the As concentrations are enriched by the reductive dissolution of Fe-(hydr)oxides, and the correlations between As and F− concentrations are poor comparatively to those observed in the oxidizing aquifers. However, F− concentrations are strongly dependent on pH. Desorption/adsorption experiments using raw soils and citrate-bicarbonate-dithionite treated soils indicated that Fe-(hydr)oxides are the important As and F− hosts causing the co-contamination phenomenon. The weaker correlation between F− and As in reducing aquifers is likely to be associated with sulfate reduction, which removes As from groundwater without changing the F− concentration. 相似文献
135.
Kamila Kočí Ivana Troppová Miroslava Edelmannová Jakub Starostka Lenka Matějová Jaroslav Lang Martin Reli Helena Drobná Anna Rokicińska Piotr Kuśtrowski Libor Čapek 《Environmental science and pollution research international》2018,25(35):34818-34825
Lanthanum-modified TiO2 photocatalysts (0.2–1.5 wt% La) were investigated in the methanol decomposition in an aqueous solution. The photocatalysts were prepared by the common sol-gel method followed by calcination. The structural (X-ray diffraction, Raman, X-ray photoelectron spectroscopy), textural (N2 physisorption), and optical properties (diffuse reflectance spectroscopy, photoelectrochemical measurements) of all synthetized nanomaterials were correlated with photocatalytic activity. Both pure TiO2 and La-doped TiO2 photocatalysts proved higher yields of hydrogen in comparison to photolysis. The photocatalyst with optimal amount of lanthanum (0.2 wt% La) showed almost two times higher amount of hydrogen produced at the same time as in the presence of pure TiO2. The photocatalytic activity increased with both increasing photocurrent response and decreasing amount of lattice and surface O species. It has been shown that both direct and indirect mechanisms of methanol photocatalytic oxidation participate in the production of hydrogen. Both direct and indirect mechanisms take part in the formation of hydrogen. 相似文献
136.
Koç C 《Environmental monitoring and assessment》2008,146(1-3):397-409
In this study, the characteristics, benefits, and effects of the environment and ecology project, which has been implemented in Turkey for the first time to restore the natural life that has been spoilt and the ecological balance of Lake Bafa located in Great Meander Basin, are searched. Moreover, the water samples taken from the stations that were spotted in the lake have been analyzed for the physical and chemical changes taking place in water quality before and after the project. The water cycle occurring as a result of giving water that was raised in Great Meander River by the Rubber regulator, which is the most important element of the project, through the Serçin inlet and feeder channel; and draining the saline and low-quality water to the river bed of the Great Meander, will improve the water quality, the natural life, and the ecological balance of the lake in time. Thanks to the water given to the lake within the scope of project, the salinity of the lake water decreased from 25,500 to 22,500 mmhos cm???1. The electrical conductivity, Na?+?, Mg?+?2, Ca?+?2, Cl???, $\text{CO}_\text{3} ^{-\text{2}}In this study, the characteristics, benefits, and effects of the environment and ecology project, which has been implemented in Turkey for the first time to restore the natural life that has been spoilt and the ecological balance of Lake Bafa located in Great Meander Basin, are searched. Moreover, the water samples taken from the stations that were spotted in the lake have been analyzed for the physical and chemical changes taking place in water quality before and after the project. The water cycle occurring as a result of giving water that was raised in Great Meander River by the Rubber regulator, which is the most important element of the project, through the Ser?in inlet and feeder channel; and draining the saline and low-quality water to the river bed of the Great Meander, will improve the water quality, the natural life, and the ecological balance of the lake in time. Thanks to the water given to the lake within the scope of project, the salinity of the lake water decreased from 25,500 to 22,500 mmhos cm( - 1). The electrical conductivity, Na+, Mg+2, Ca+2, Cl(-), CO3(-2), HCO3(-), and the amount of the organic substances were found as over the appropriate values for fishery. Besides, the decreases in the amounts of NO3(-), HN3(-) and PO4(-3) affect the living beings in the lake negatively. In addition, the measures to take are specified, so that the natural life of the Lake and the ecological balance can renew themselves within a short time. 相似文献
137.
Effect of reservoir flushing on downstream river water quality 总被引:1,自引:0,他引:1
The effect of short-term reservoir flushing on downstream water quality in the Geum River, Korea was studied using field experiments and computer simulations. The reservoir release was increased from 30 to 200 m(3)/s within 6 h for the purpose of this experiment. The flushing discharge decreased the concentrations of soluble nitrogen and phosphorus species considerably, but the experimental results revealed a negative impact on organic forms of nutrients and biochemical oxygen demand (BOD). A dynamic river water quality model was applied to simulate the river hydraulics and water quality variations during the event. The model showed very good performance in predicting the travel time of flushing flow and the variations of dissolved forms of nitrogen and phosphorus constituents. However, it revealed a limited capability in simulating organic forms of nutrients and BOD because it does not consider the re-suspension mechanism of these constituents from sediment during the wave front passage. 相似文献
138.
In this study, a model experiment in a long road tunnel employing the longitudinal ventilation system with a ventilation shaft is carried out during a fire accident to determine the optimum exhaust airflow rate through the ventilation shaft. The appropriate operation of the shaft fan according to the position of fire is investigated, and the optimum exhaust airflow rate for prevention of smoke spreading through the tunnel is determined based on the entire exhaust of both smoke and airflow generated by fire and jet fan operation, respectively. As a result of using the amount of smoke, the critical air velocity produced by jet fans, the effective cross-sectional area of a tunnel and the correction factor, a formula for exhaust airflow rate is drived. In addition, a correction factor (α = 1.1) for the thermal expansion caused by heat of a 20 MW fire is determined theoretically and experimentally. It is expected that this study will contribute to plan the shaft operation for the emergency ventilation as well as provide the preliminary data to design the airflow rate of shaft. 相似文献
139.
Chen YL Chang JE Lai YC Ko MS 《Journal of the Air & Waste Management Association (1995)》2012,62(5):587-593
The purpose of this study was to investigate the effects of sintering atmosphere (oxidizing and reducing) on the polymorphs of dicalcium silicates (Ca2SiO4, C2S) and on the chromium leaching of the belite-rich clinkers made from a chromium-bearing sludge. This sludge was generated in an electroplating factory, and in addition to chromium, it contained nickel, copper and zinc. In the clinker production, air was used as the oxidizing atmosphere, and carbon monoxide, which was produced by burning graphite with an insufficient amount of oxygen, was employed as the reducing atmosphere. Dicalcium silicates were substantially formed under both kinds of sintering atmosphere, but there was some nonhydraulic gamma-C2S in the clinkers produced under the oxidizing atmosphere. In addition, the amount of gamma-C2S decreased with the chromium-bearing sludge addition, whereas that of beta-C2S increased. The clinkers produced under the reducing atmosphere had less residual chromium, a finding that shows that more chromium was evaporated. However, the reducing atmosphere can decrease the proportion of hexavalent chromium (Cr(VI)) in the resulting clinkers. For other heavy metals, the residual amounts of nickel and copper generally increased with the sludge addition, but zinc was absent in most of the clinkers produced under the reducing atmosphere. This implies that the evaporation of zinc is much more significant than that of the other heavy metals under a reducing atmosphere. In the leaching tests, the concentrations of nickel, copper, and zinc were below the detection limits in all the leachates. In terms of chromium, the total leaching concentration was highly related to Cr(VI). The clinkers produced under the oxidizing atmosphere had high leaching concentrations of chromium, and thus failed to meet the regulatory limit. In contrast, the reducing atmosphere was effective in decreasing the chromium leaching, and it therefore makes the resulting cement clinkers more environmentally sound. 相似文献
140.
Kocí V Ocelka T Dragoun D Vit M Grabic R Sváb M 《Environmental science and pollution research international》2007,14(2):94-101
Background, Aim and Scope
The article is focused on dioxin, furan, PCB and organochlorine pesticide monitoring in the surface waters of the Central
European, protected natural reserve Krivoklatsko, under the UNESCO programme Man and Biosphere. Persistent compounds are presently
transported via different means throughout the entire world. This contamination varies significantly between sites. This raises
the question of what constitutes the naturally occurring background levels of POPs in natural, unpolluted areas, but which
are close to industrialised regions. Information of real background POP contamination can be of high value for risk assessment
management of those sites evidently polluted and for the defining of de-contamination limits.
Preserved areas should not be seen as isolated regions in which the impacts of human activities and natural factors are either
unexpected or overlooked. Every ambient region, even those protected by a law or other means, are still closely connected
to neighbouring human developed and impacted areas, and are therefore subject to this anthropogenic contamination. These areas
adjacent to natural reserves are sources of diverse substances, via entry of air, water, soil and/or biota. After an extended
period of industrial activities, organochlorine pollutants, even those emitted in trace concentrations have reached detectable
levels. For future research and for the assessment of environmental changes, present levels of contamination would be of high
importance. This work publishes data of the contamination with organochlorine pollutants of this natural region, where biodiversity
and ecological functions are of the highest order.
Materials and Methods:
Semipermeable membrane devices (SPMDs) were utilised as the sampling system. SPMDs were deployed in two small creeks and one
water reservoir selected in the central part of the Krivoklatsko Natural Reserve, where it could be expected that any possible
contamination by POPs would be lowest. The exposed SPMDs were analysed both for chemical contents of POPs and for toxicity
properties. The chemical analyses of dibenzo-dioxins, dibenzo-furans, PCBs and OCPs were analysed by GC/MS/MS on GCQ or PolarisQ
(Thermoquest). Toxicity bioassays were performed on the alga Desmodesmus subspicatus, bacteria Vibrio fischeri and crustacean
Daphnia magna. All toxicity data were expressed as the effective volume Vtox. Vtox is a toxicity parameter, the determination
of which is independent of SPMD deployment time and pre-treatment dilution (unlike, for example, the EC50 of the SPMD extract).
Results:
The following chemical parameters were monitored: 1) tetra, penta, hexa and hepta dibenzo-p-dioxins and furans; 2) all those
detectable from tri- through deca-polychloriated biphenyls (PCBs) and 3) a group of organochlorine pesticides: hexachlorobenzene
and isomers of hexachlorocyclohexane, DDE, DDD and DDT. The concentrations of dioxins and furans on the assessed sites varied
from under detection levels up to 7 pg.l-1; PCBs were detected in a sum concentration up to 2.8 ng.l-1; and organochlorine
pesticides up to 346 pg.l-1. The responses of bioassays used were very low, with the values obtained for Vtox being under
0.03 l/d.
Discussion:
Toxicity testing showed no toxicity responses, demonstrating that the system used is in coherence with the ecological status
of the assessed sites. Values of Vtox were under the critical value – showing no toxicity. The PCA of chemical analysis data
and toxicity responses resulted in no correlations between these two groups of parameters. This demonstrated that the present
level of contamination has had no direct adverse effects on the biota.
Conclusions:
The concentration values of six EPA-listed, toxic dioxins and sums of tetra-hepta dioxins; nine EPA toxic dibenzofurans and
the sums of tetra-hepta bibenzofurans are presented together with all tri-deka PCBs and organochlorine pesticides (alfa-,
beta-, gama-, delta-HCH, HCB, opDDE, ppDDE, opDDD, ppDDD, opDDT, ppDDT). These values represent possible current regional
natural background values of these substances monitored within the Central European region, with no recorded adverse effects
on the freshwater ecosystem (up until the present time).
Recommendations and Perspectives:
Assessment of dioxins, furans and other organochlorine compounds within natural reserves can be important for the monitoring
of human-induced impacts on preserved areas. No systematic monitoring of these substances in areas not directly affected by
industry has generally been realised. There is a paucity of data of the presence of any of these substances within natural
regions. Further monitoring of contamination of both soil and biota by dioxins and furans in preserve regions is needed and
can be used for future monitoring of man-made activities and/or accidents.
Semipermeable membrane devices proved to be a very good sampling system for the monitoring of trace concentrations of ambient
organochlorine compounds. Toxicity evaluation using the Vtox concept demonstrated that those localities assessed expressed
no toxicity. 相似文献