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 15,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the plant drug collected at different localities in Slovakia and Bohemia in the same vegetation period of one year, the content of Mn and Zn were determined. The AAS method was employed after mineralization of the drug by the dry method (without mineralizing additives) and subsequent dissolution of the ash in a HCl solution. The content of both metals in the samples substantially differed (Mn: 24.7-2095.5 mg/kg, Zn: 46.5-362.0 mg/kg of the dried drug). The content of the ash, which was within the limits of the standard, excludes excessive pollution by dust fall-out. The birch tree most probably absorbs and cumulates Mn and Zn from the soil.
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PMID:[Mn and Zn content in the plant drug from Folium betulae grown in various locations]. 1095 57

An extraction process with saponins was evaluated for removing heavy metals from MSW (municipal solid waste) incinerator fly ashes. Two different fly ashes, A and B, were treated on a laboratory scale with three triterpene-glycoside type of saponins, M, Q, and T, in the pH range 4-9. The results were compared with those of the HCI and EDTA treatment. The treatment with saponins extracted 20-45% of Cr from the fly ashes. Saponins were also effective in extracting Cu from fly ash A attaining 50-60% extraction. Saponin T extracted 100% of Pb from fly ash A at pH around 4. The extraction of Zn with the saponin treatment was similar to that of the HCl treatment. Further, Cr, Cu, Pb, and Zn were fractionated by sequential extraction to investigate the effect of saponins on each fraction. Extraction behavior of other elements during the saponin treatment was also studied. The leaching test on the residues received after the saponin treatment showed that the fly ashes were successfully detoxified to meet the landfilling guideline.
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PMID:Extraction of heavy metals from MSW incinerator fly ash using saponins. 1105 96

In the de-novo synthesis and formation of PCDD/PCDF, the transfer of inorganic chlorine to the carbonaceous material of fly ash plays an important role. Here, copper acts as a catalyst in the chlorination reaction. In experiments in the range of 250-350 degrees C under helium, we determined the stoichiometry of the chlorination reaction with model systems. Therefore, it was necessary to develop a method to quantify the copper(II) and copper(I) ions. In a combination of solid electron paramagnetic (spin) resonance spectroscopy (EPR) for Cu(I), and X-ray fluorescence spectroscopy (XRFA) analysis for Cu (total), we found a way for the quantification of copper(I) and (II). With these experiments, we can show that the chlorination reaction is relatively fast and comes to a stop under helium, after the copper(II) is reduced. The ratio between the organic chlorine formed and copper(II) reduced is, at the end of the reaction, 0.5, which is in agreement with the following reaction: 2CuCl2 + R-H-->2CuCl + R-Cl + HCl.
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PMID:The role of copper(II) chloride in the formation of organic chlorine in fly ash. 1121 82

Certain volcanoes constitute the world's largest sources of SO2, HCl, and HF emissions and contribute significantly to regional acid deposition. However, the impact of volcanic acid emissions to nearby ecosystems remain poorly documented. In this paper, the spatial pattern of acid dry depositions was monitored within 44 km of Masaya Volcano, Nicaragua, with a network of sulfation plates. Measured SO2 deposition rates were <2-791 mg m(-2) day(-1). The plates also collected the dry deposition of HCI at rates of <1-297 mg m(-2) day(-1). A similar deposition velocity Vd (gas transfer) of 1.6 +/- 0.8 cm/s was calculated for SO2 and HCl above the plate surfaces. Quantities of SO2 and HCI deposited daily within the area surveyed amounted to 1.5 x 10(8) g and 5.7 x 10(7) g, respectively, which correspond to about 10% of the total SO2 and HCl released by the volcano. These depositions may generate an equivalent hydrogen flux ranging from <1 to 30 mg m(-2) day(-1). Our results demonstrate that volcano emissions can dramatically affect acid deposition downwind and in turn cause extreme acid loading of the local ecosystems. This study opens exciting prospects for investigating the sensivity of volcanic ash soils to acid inputs.
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PMID:Dry deposition and heavy acid loading in the vicinity of Masaya Volcano, a major sulfur and chlorine source in Nicaragua. 1134 58

A review of the scenarios for the Cretaceous/ Tertiary (K/T) boundary event is presented and a coherent hypothesis for the origin of the event is formulated. Many scientists now accept that the event was caused by a meteorite impact at Chicxulub in the Yucatan Peninsula, Mexico. Our investigations show that the oceans were already stressed by the end of the Late Cretaceous as a result of the long-term drop in atmospheric CO2, the long-term drop in sea level and the frequent development of oceanic anoxia. Extinction of some marine species was already occurring several million years prior to the K/T boundary. The biota were therefore susceptible to change. The eruption of the Deccan Traps, which began at 66.2 Ma, coincides with the K/T boundary events. It erupted huge quantities of H2SO4, HCl, CO2, dust and soot into the atmosphere and led to a significant drop in sea level and marked changes in ocean temperature. The result was a major reduction in oceanic productivity and the creation of an almost dead ocean. The volcanism lasted almost 0.7 m.y. Extinction of biological species was graded and appeared to correlate with the main eruptive events. Elements such as Ir were incorporated into the volcanic ash, possibly on soot particles. This horizon accumulated under anoxic conditions in local depressions and became the marker horizon for the K/T boundary. An oxidation front penetrated this horizon leading to the redistribution of elements. The eruption of the Deccan Traps is the largest volcanic event since the Permian-Triassic event at 245 Ma. It followed a period of 36 m.y. in which the earth's magnetic field failed to reverse. Instabilities in the mantle are thought to be responsible for this eruption and therefore for the K/T event. We therefore believe that the K/T event can be explained in terms of the effects of the Deccan volcanism on an already stressed biosphere. The meteorite impact at Chicxulub took place after the onset of Deccan volcanism. It probably played a regional, rather than global, role in the K/T extinction.
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PMID:Multiple factors in the origin of the Cretaceous/Tertiary boundary: the role of environmental stress and Deccan Trap volcanism. 1154 26

An integrated approach for the simultaneous reduction of major combustion-generated pollutants from power plants is presented along with a simplified economic analysis. With this technology, the synergistic effects of high-temperature sorbent/coal or sorbent/natural gas injection and high-temperature flue gas filtration are exploited. Calcium-based (or Na-based, etc.) sorbents are sprayed in the post-flame zone of a furnace, where they react with S- and Cl-containing gases to form stable salts of Ca (or Na, etc.). The partially reacted sorbent is then collected in a high-temperature ceramic filter, which is placed downstream of the sorbent injection point, where it further reacts for a prolonged period of time. With this technique, both the likelihood of contact and the length of time of contact between the solid sorbent particles and the gaseous pollutants increase, because reaction takes place both in the furnace upstream of the filter and inside the filter itself. Hence, the sorbent utilization increases significantly. Several pollutants, such as SO2, H2S, HCl, and particulate (soot, ash, and tar), may be partially removed from the effluent. The organic content of the sorbents (or blends) also pyrolyzes and reduces NOx. Unburned carbon in the ash may be completely oxidized in the filter. The filter is cleaned periodically with aerodynamic regeneration (back pulsing) without interrupting furnace operation. The effectiveness of this technique has been shown in laboratory-scale experiments using either rather costly carboxylic salts of Ca or low- to moderate-cost blends of limestone, lime, or sodium bicarbonate with coal fines. Injection occurred in the furnace at 1150 degrees C, while the filter was maintained at 600 degrees C. Results showed that 65 or 40% SO2 removal was obtained with calcium formate or a limestone/coal blend, respectively, at an entering calcium-to-sulfur molar ratio of 2. A sodium bicarbonate/coal blend resulted in 78% SO2 removal at a sodium-to-sulfur molar ratio of 2. HCl removal efficiencies have been shown to be higher than those for SO2. NOx reductions of 40% have been observed with a fuel (coal)-to-air equivalence ratio, phi, around 2. The filter has been shown to be 97-99% efficient in removing PM2.5 particulates. Calculations herein show that this integrated sorbent/filter method is cost-effective, in comparison with current technologies, on both capital cost ($/kW) and levelized cost ($/ton pollutant removed) bases, if a limestone/coal mixture is used as the sorbent for fossil fuel plants. Capital costs for the filter/sorbent combination are estimated to be in the range of $61-$105/kW for a new plant. Because current technologies are designed for removing one pollutant at a time, both their cost and space requirements are higher than those of this integrated technique. At the minimum projected removal efficiencies for HCl/SO2/NOx of about 40%, the levelized costs are projected to be $203-$261/ton of combined pollutant SO2/HCl/NOx and particulates removed from coal-fired power plants.
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PMID:Economics of an integrated approach to control SO2, NOX, HCl, and particulate emissions from power plants. 1202 92

The strontium, lithium and calcium contents have been determined in 87 samples of five kinds of milk-fermented products, as well as in 93 samples of ten kinds of marine smoked fish. The samples were purchased on the local market. The representative samples were dry ashed in quartz crucibles and the ash was treated with suitable amounts of conc. HCl and a few drops of conc. HNO3. The obtained sample solution was then used for the determination of Sr, Li and Ca by the flame atomic absorption spectrometry (AAS) method. Ca and Li were determined using the air-acetylene flame and Sr with nitrous oxide-acetylene flame, according to the manufacturer's recommendations. The contents of Sr in the fermented milk products ranged from 0.21 to 0.79 (mean 0.44 +/- 0.07) and in the marine smoked fish from 0.02 to 4.63 (mean 1.16 +/- 0.24) mg/kg of the edible form of both products. Li contents in the milk products ranged from 0.01 to 0.50 (mean 0.07 +/- 0.04) and in the smoked fish from 0.00 to 0.58 (mean 0.11 +/- 0.08) mg/kg. The calcium was highest in the milk products and ranged from 1,010 to 2,020.0 (mean 1,377 +/- 143) mg/kg. In the smoked fish calcium varied strongly and ranged from 40 to 1,052 (mean 303 +/- 53) mg/kg of the edible form. The calculated average ratio of strontium to calcium (mg Sr/1 g Ca) in the milk beverages and yogurts amounted 0.32 and in the smoked fish was 12 times as high and amounted 3.84. The main purpose of this work was to present Ca, Sr and Li together. This is justified because Sr and to some extent also Li are able to modulate Ca metabolism and vice versa.
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PMID:Content of strontium, lithium and calcium in selected milk products and in some marine smoked fish. 1210 23

The spray dryer system was conventionally employed to remove the SOx, NOx, and HCl in the flue gas. However, the removal efficiency of acid gas in the practical incineration flue gas, which contains dust, heavy metals, and acid gas itself, was seldom mentioned in the literature. The alkaline sorbents possess large specific surface that was a main factor on the adsorption of heavy metals and acid gas. Therefore, the primary objective of this study was focused on the effect of different additives on the removal efficiency of acid gas and heavy metals (Cr, Cd and Pb). The mass and element size distribution of heavy metals in fly ash under different additives were also investigated. The results indicated that the removal efficiency of HCl in the spray dryer system was higher than 97.8%. The effects of additives on the removal efficiency of HCl, however, were undistinguished. In the desulfurization process, the highest removal efficiency was 71.3% when the additive of amorphous SiO2 was added in the spray dryer system. The removal efficiency was 66.0% with the additive of CaCl2 and 63.1% without any additives, respectively. It was also found that the spray dryer system could decrease the concentration of metal in fly ash but increase the amount of fly ash. In addition, amorphous SiO2 in the alkaline sorbent tended to increase the adsorption of heavy metal on reactant, because it could enhance the dispersion of alkaline sorbent.
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PMID:Effects of different additives on the performance of spray dryer system during incineration process. 1211 21

This paper evaluates an elementary reaction mechanism for Hg0 oxidation in coal-derived exhausts consisting of a previously formulated homogeneous mechanism with 102 steps and a new three-step heterogeneous mechanism for unburned carbon (UBC) particles. Model predictions were evaluated with the extents of Hg oxidation monitored in the exhausts from a pilot-scale coal flame fired with five different coals. Exhaust conditions in the tests were very similar to those in full-scale systems. The predictions were quantitatively consistent with the reported coal-quality impacts over the full range of residence times. The role of Cl atoms in the homogeneous mechanism is hereby supplanted with carbon sites that have been chlorinated by HCl. The large storage capacity of carbon for Cl provided a source of Cl for Hg oxidation over a broad temperature range, so initiation was not problematic. Super-equilibrium levels of Cl atoms were not required, so Hg was predicted to oxidize in systems with realistic quench rates. Whereas many fundamental aspects of the heterogeneous chemistry remain uncertain, the information needed to characterize Hg oxidation in coal-derived exhausts is now evident: complete gas compositions (CO, hydrocarbons, H2O, O2 NOx, SOx), UBC properties (size, total surface area), and the ash partitioning throughout the exhaust system are required.
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PMID:A mechanism for mercury oxidation in coat-derived exhausts. 1218 87

The objective of this research was to evaluate the reaction characteristics of CaOH2, HCl and SO2 in the flue gas emitted by a laboratory incinerator. The amount of sulfur retained in the residues (including the spray dryer ash and baghouse ash) was also evaluated in this study. The experimental parameters included HCl concentration (500-2000 ppm), SO2 concentration (500-2000 ppm), relative humidity (40-80% RH), and the addition of CaCl2 (30 wt.%). The results indicated that an HCl concentration of 500-2000 ppm did not affect HCl removal efficiency in the spray dryer at 150 degrees C and 45+/-5% RH. On the other hand, increase in SO2 concentration from 500 to 2000 ppm enhanced SO2 removal at 150 degrees C and 75+/-5% RH. Moreover, increase in removal efficiency of SO2 was more obvious when the relative humidity was greater than 80%. When the flue gas contained both HCl and SO2 simultaneously, the removal efficiency of SO2 could increase from 56.7 to 90.33% at HCl concentration of 236 ppm. However, when the concentration of HCl exceeded 535 ppm, the removal efficiency of SO2 decreased with increasing concentration of HCl. The removal efficiency of SO2 could be increase to 97.7% with the addition of CaCl2.
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PMID:Reaction characteristics of Ca(OH)2, HCl and SO2 at low temperature in a spray dryer integrated with a fabric filter. 1242 43


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