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1.
A basic investigation of boron in discharged fly ash by coal fuel thermal power plants in several worldwide locations was carried out. Eight kinds of fly ash sample were prepared from eight coal fuel thermal power plants. Two of the fly ash samples were used to examine the relationship between the concentration of boron in fly ash and the particle size. When the particle size of fly ash is smaller, there is a possibility that it will be released into the air and spread over a wide area in the environment. However, it has become apparent that fly ash of smaller particle size has a higher concentration of boron and a higher enrichment factor. In other fly ash samples, the boron contents were examined and leaching tests were carried out. There is acidic fly ash as well as alkaline fly ash that contains larger amounts of acidic or basic salts. On alkaline fly ash, when the concentration of boron bound to Fe-Mn oxide is low; it has become apparent that leaching boron is increased in a solution with lower pH of approximately 4 which is nearly the pH of acid rain.  相似文献   

2.
The nickel species in the feed coals and ash by-products from seven Canadian power plants (including one with a fluidized bed combuster) burning local subbituminous and bituminous coals with sulfur contents ranging from 0.22 to 3.6% have been examined using nickel XANES spectroscopy. XANES spectroscopy of Ni in coal and coal derived ash is complicated by a poor signal : noise ratio due to fluorescence of the much more abundant iron in the coal. Nevertheless, it has proved possible to show that the Ni environment in coals varies from largely oxidic species to mixtures of Ni-containing oxide and sulfide species. The nickel in one oxidized coal appears to be present as nickel sulfate. Nickel in all bottom and fly ash samples examined appears also to be present largely in oxygen anion environments. With the exception of one fly ash sample, for which the Ni exhibited spectral features similar to those for Ni(2+) in spinel or oxide phases, the nickel in the bottom and fly ash samples appears to exist largely as Ni(2+) in environments similar to those reported for Ni in silicate glasses. The data obtained indicate that the presence of potentially carcinogenic nickel sulfides in ash by-products from combustion of these coals is unlikely.  相似文献   

3.
The attenuation of arsenic in groundwater near alkaline coal fly ash disposal facilities was evaluated by determining the uptake of arsenic from ash leachates by surrounding alkaline soils. Ten different alkaline soils near a retired coal fly ash impoundment were used in this study with pH ranging from 7.6 to 9.0, while representative coal fly ash samples from two different locations in the coal fly ash impoundment were used to produce two alkaline ash leachates with pH 7.4 and 8.2. The arsenic found in the ash leachates was present as arsenate [As(V)]. Adsorption isotherm experiments were carried out to determine the adsorption parameters required for predicting the uptake of arsenic from the ash leachates. For all soils and leachates, the adsorption of arsenic followed the Langmuir and Freundlich equations, indicative of the favorable adsorption of arsenic from leachates onto all soils. The uptake of arsenic was evaluated as a function of ash leachate characteristics and the soil components. The uptake of arsenic from alkaline ash leachates, which occurred mainly as calcium hydrogen arsenate, increased with increasing clay fraction of soil and with increasing soil organic matter of the alkaline soils. Appreciable uptake of arsenic from alkaline ash leachates with different pH and arsenic concentration was observed for the alkaline soils, thus attenuating the contamination of groundwater downstream of the retired coal fly ash impoundment.  相似文献   

4.
The concentration of As, Cr and Ni and their speciation (As3+;5+, Cr3+;6+ and Ni0;2+) in milled coal, bottom ash and ash collected by electrostatic precipitator (ESP) from a coal fired-power plant in western Canada were determined using HGAAS, ICP-AES and XANES. The chemical fractionation of these elements was also determined by a sequential leaching procedure, using deionized water, NH4OAC and HCI as extracting agents. The leachate was analyzed by ICP-AES. Arsenic in the milled coal is mostly associated with organic matter, and 67% of this arsenic is removed by ammonium acetate. This element is totally removed from milled coal after extraction with HCI. Arsenic occurs in both the As3+ and the As5+ oxidation states in the milled coal, while virtually all (>90%) of the arsenic in bottom ash and fly ash appears to be in the less toxic arsenate (As5+) form. Both Ni and Cr in the milled coal are extracted by HCI, indicating that water can mobilize Ni and Cr in an acidic environment. The chromium is leached by water from fly ash as a result of the high pH of the water, which is induced during the leaching. Ammonium acetate removes Ni from bottom ash through an ion exchange process. Chromium in milled coal is present entirely as Cr3+, which is an essential human trace nutrient. The Cr speciation in bottom ash is a more accentuated version of the milled coal and consists mostly of the Cr3+ species. Chromium in fly ash is mostly Cr3+, with significant contamination by stainless-steel from the installation itself.  相似文献   

5.
Indraprastha Power Station (IPP Stn) and Rajghat Power House (RPH), owned by Delhi Electric Supply Undertaking, are both coal-fired power stations located on Ring Road in New Delhi. Ash content of the coal used ranges between 38–47%. The ash is collected in electrostatic precipitators which have an efficiency of 99.3% (IPP station), and 99.7% (RPH). There are instances of major dust pollution around the power stations from fly ash dispersal. The main method of disposal of fly ash from the power stations is by mixing with water, the resultant slurry is pumped through pipes to ash disposal ponds. The supernatant from these ponds is discharged into River Yamuna. Field studies have revealed large quantities of fly ash being deposited into the river. Local populations of Eichhornia crassipes have reduced dramatically between 1987–1995, with a marked reduction in the year 1994–1995. Field studies, conducted in January, 1995 have investigated the impact of fly ash dispersal in the Delhi region with particular reference to metal contamination. Elemental concentrations for a range of elements are determined by ICP-AES in fly ash and top soils along four transects from the power stations up to a distance of 8 km. The effects of fly ash leachates from the ash settling ponds on the river are determined by analyzing river overbank soils and vegetation for their elemental contents. It is concluded that fly ash dispersal from the stacks are a source of alkali, alkaline-earth and to some extent heavy metals in soils in the vicinity of the power stations, and enrichment of elements in river overbank soils are a result of discharge of fly ash leachates from ash disposal ponds. However, the impact from both these sources of metal contamination is not large enough to give cause for concern. Marked reduction in populations of Eichhornia crassipes downstream of the river where it receives leachates from the ash disposal ponds are attributed to turbidity of the ash pond leachates and metal toxicity. Elemental enrichment in the floodplain soils, as a result of fly ash particle deposition during monsoons, may enhance the horticultural value of these soils as is shown by a healthy cultivated crop of Brassica juncea.  相似文献   

6.
Synthesis and characterization of zeolites prepared from industrial fly ash   总被引:1,自引:0,他引:1  
In this paper, we present the possibility of using fly ash to produce synthetic zeolites. The synthesis class F fly ash from the Stalowa Wola SA heat and power plant was subjected to 24 h hydrothermal reaction with sodium hydroxide. Depending on the reaction conditions, three types of synthetic zeolites were formed: Na-X (20 g fly ash, 0.5 dm3 of 3 mol?·?dm?3 NaOH, 75 °C), Na-P1 (20 g fly ash, 0.5 dm3 of 3 mol?·?dm?3 NaOH, 95 °C), and sodalite (20 g fly ash, 0.8 dm3 of 5 mol?·?dm?3 NaOH?+?0.4 dm3 of 3 mol?·?dm?3 NaCl, 95 °C). As synthesized materials were characterized to obtain mineral composition (X-ray diffractometry, Scanning electron microscopy-energy dispersive spectrometry), adsorption properties (Brunauer-Emmett-Teller surface area, N2 isotherm adsorption/desorption), and ion exchange capacity. The most effective reaction for zeolite preparation was when sodalite was formed and the quantitative content of zeolite from X-ray diffractometry was 90 wt%, compared with 70 wt% for the Na-X and 75 wt% for the Na-P1. Residues from each synthesis reaction were the following: mullite, quartz, and the remains of amorphous aluminosilicate glass. The best zeolitic material as characterized by highest specific surface area was Na-X at almost 166 m2?·?g?1, while for the Na-P1 and sodalite it was 71 and 33 m2?·?g?1, respectively. The ion exchange capacity decreased in the following order: Na-X at 1.8 meq?·?g?1, Na-P1 at 0.72 meq?·?g?1, and sodalite at 0.56 meq?·?g?1. The resulting zeolites are competitive for commercially available materials and are used as ion exchangers in industrial wastewater and soil decontamination.  相似文献   

7.
Fly ash is a by-product of coal-fired electricity generation plants. Its utilization and disposal is of utmost importance. Using onion (Allium cepa) root tip system, the present study was carried out to evaluate the potential toxic and genotoxic effects of fly ash, collected from a thermal power plant in West Bengal, India. Prior to testing, the collected fly ash sample was mixed with sand in different proportions. Allium bulbs were allowed to germinate directly in fly ash and after five days the germinating roots were processed for the Allium test. Additionally, the Allium test was adapted for detecting DNA damage through comet assay. The results from the Allium test indicate that fly ash at 100% concentration inhibits root growth and mitotic indices; induces binucleated cells as a function of the proportion, but is not toxic at very low concentration. In the comet assay, a statistical increase for DNA strand breaks was found only at higher concentrations. The sample was analyzed by flame atomic absorption spectrometer for Zn, Pb, Cu, Ni, Cd and As, whose presence could partly be responsible for the toxicity of fly ash. The study concludes that the classical Allium test can give a more comprehensive data when done in combination with the comet assay, which is faster, simpler and independent of mitosis. Also when fly ash is used for other purposes in combination with soils, it should be judiciously used at very low concentrations in order to protect the ecosystem health from any potential adverse effects.  相似文献   

8.
The chromium species leaching from a coal combustion fly ash landfill has been characterized as well as a novel approach to treat leachates rich in hexavalent chromium, Cr(VI), by using another natural waste by-product, acid mine drainage (AMD), has been investigated during this study. It is observed that as much as 8% (approximately 10 microg g(-1) in fly ash) of total chromium is converted to the Cr(VI) species during oxidative combustion of coal and remains in the resulting ash as a stable species, however, it is significantly mobile in water based leaching. Approximately 1.23 +/- 0.01 microg g(-1) of Cr(VI) was found in the landfill leachate from permanent deposits of aged fly ash. This study also confirmed the use of AMD, which often is in close proximity to coal combustion by-product landfills, is an extremely effective and economical remediation option for the elimination of hexavalent chromium in fly ash generated leachate. Speciated isotope dilution mass spectrometry (SIDMS), as described in EPA Method 6800, was used to analytically evaluate and validate the field application of the ferrous iron and chromate chemistry in the remediation of Cr(VI) runoff.  相似文献   

9.
Use of lignite in power generation has led to increasing environmental problems associated not only with gaseous emissions but also with the disposal of ash residues. In particular, use of low quality coal with high ash content results in huge quantities of fly ash to be disposed of. The main problem related to fly ash disposal is the heavy metal content of the residue. In this regard, experimental results of numerous studies indicate that toxic trace metals may leach when fly ash contacts water. In this study, fly ash samples obtained from thermal power plants, namely Soma and Tunçbilek, located at the west part of Turkey, were subjected to toxicity tests such as European Committee for standardization (CEN) and toxicity characteristic leaching (TCLP) procedures of the U.S. Environmental Protection Agency (U.S. EPA). The geochemical composition of the tested ash samples from the power plant show variations depending on the coal burned in the plants. Furthermore, the CEN and TCLP extraction results showed variations such that the ash samples were classified as `toxic waste' based on TCLP result whereas they were classified as `non-toxic' wastes based on CEN results, indicating test results are pH dependent.  相似文献   

10.
Although many leaching methods have been used for various purposes by research groups, industries, and regulators, there is still a need for a simple but comprehensive approach to leaching coal utilization by-products and other granular materials in order to estimate potential release of heavy metals when these materials are exposed to natural fluids. A serial batch characterization method has been developed at the National Energy Technology Laboratory that can be completed in 2–3 days to serve as a screening tool. The procedure provides an estimate of cumulative metals release under varying pH conditions, and leaching the sample at increasing liquid/solid ratios can indicate the rate at which this process will occur. This method was applied to eight fly ashes, adapted to the acidic or alkaline nature of the ash. The leachates were analyzed for 30 elements. The test was run in quadruplicate, and the relative standard deviation (RSD) was used as a measure of method reproducibility. RSD values are between 0.02 and 0.70, with the majority of the RSD values less than 0.3. The serial batch leaching procedure was developed as a simple, relatively quick, yet comprehensive method of estimating the risk of heavy metal release from fly ash when it is exposed to natural fluids, such as acid rain or groundwater. Tests on a random selection of coal fly ashes have shown it to be a reasonably precise method for estimating the availability and long-term release of cations from fly ash.  相似文献   

11.
Assessment of oxidative stress levels and tissue concentrations of elements in plants growing wild on fly ash basins is critical for realistic hazard identification of fly ash disposal areas. Hitherto, levels of oxidative stress markers in plants growing wild on fly ash basins have not been adequately investigated. We report here concentrations of selected metal and metalloid elements and levels of oxidative stress markers in leaves of Cassia occidentalis growing wild on a fly ash basin (Badarpur Thermal Power Station site) and a reference site (Garhi Mandu Van site). Plants growing on the fly ash basin had significantly high foliar concentration of As, Ni, Pb and Se and low foliar concentration of Mn and Fe compared to the plants growing on the reference site. The plants inhabiting the fly ash basin showed signs of oxidative stress and had elevated levels of lipid peroxidation, electrolyte leakage from cells and low levels of chlorophyll a and total carotenoids compared to plants growing at the reference site. The levels of both protein thiols and nonprotein thiols were elevated in plants growing on the fly ash basin compared to plants growing on the reference site. However, no differences were observed in the levels of cysteine, reduced glutathione and oxidized glutathione in plants growing at both the sites. Our study suggests that: (1) fly ash triggers oxidative stress responses in plants growing wild on fly ash basin, and (2) elevated levels of protein thiols and nonprotein thiols may have a role in protecting the plants from environmental stress.  相似文献   

12.
Fly ash from coal combustion contains trace elements which, on disposal or utilisation, may leach out, and therefore be a potential environmental hazard. Environmental conditions have a great impact on the mobility of fly ash constituents as well as the physical and chemical properties of the fly ash. Existing standard leaching methods have been shown to be inadequate by not representing possible disposal or utilisation scenarios. These tests are often criticised on the grounds that the results estimated are not reliable as they are not able to be extrapolated to the application scenario. In order to simulate leaching behaviour of fly ash in different environmental conditions and to reduce deviation between measurements in the fields and the laboratories, it is vital to study sensitivity of the fly ash constituents of interest to major factors controlling leachability. pH, liquid-to-solid ratio, leaching time, leachant type and redox potential are parameters affecting stability of elements in the fly ash. Sensitivity of trace elements to pH and liquid to solid ratio (as two major overriding factors) has been examined. Elements have been classified on the basis of their leaching behaviour under different conditions. Results from this study have been used to identify leaching mechanisms. Also the fly ash has been examined under different standard batch leaching tests in order to evaluate and to compare these tests. A Leaching Test Framework has been devised for assessing the stability of trace elements from fly ashes in different environments. This Framework assists in designing more realistic batch leaching tests appropriate to field conditions and can support the development of regulations and protocols for the management and disposal of coal combustion by-products or other solid wastes of environmental concern.  相似文献   

13.
Aerosol samples were collected during the scientific expedition to Mt. Bogda in July-August, 2009. The major inorganic ions (Na(?+?), NH??, K(?+?), Mg(2?+?), Ca(2?+?), Cl(?-?), SO2??, and NO??) of the aerosols were determined by ion chromatography. SO2??, NO??, and Ca(2?+?) were the dominate ions, with the mean concentrations of 0.86, 0.56, and 0.28 μg m?3, respectively. These mean ion concentrations were generally comparable with the background conditions in remote site of Xinjiang, while much lower than those in ürümqi. Morphology and elemental compositions of 1,500 particles were determined by field emission scanning electron microscopy equipped with an energy dispersive X-ray spectrometer. Based on the morphology and elemental compositions, particles were classed into four major groups: soot (15.1%), fly ash (4.7%), mineral particles (78.9%), and little other matters (0.8% Fe-rich particles and 0.5% unrecognized particles). Presence of soot and fly ash particles indicated the influence of anthropogenic pollutions, while abundance mineral particles suggested that natural processes were the primary source of aerosols over this region, coinciding with the ionic analysis. Backward air mass trajectory analysis suggested that ürümqi may contribute some anthropogenic pollution to this region, while the arid and semi-arid regions of Central Asia were the primary source.  相似文献   

14.
This study evaluates the behaviour of total Cr and Cr (VI) during coal combustion in two Spanish power stations. The content and distribution of Cr in the feed coal and combustion wastes was determined and the Cr contents were normalized using enrichment factor indexes. The speciation of Cr in the fly ash fractions from the different hoppers of the electrostatic precipitators was established and the possibility that the Cr (VI) might lixiviate when ashes are disposed of at landfill sites was assessed. Differences in the distribution and behavior of Cr in the two power stations were observed. According to European directive 1999/31/CEE, soluble Cr(VI) in the fly ashes studied would be unlikely to pose an environmental or health risk when the ash is disposed of.  相似文献   

15.
Fly ash (FA) from coal-burning industries may be a potential inorganic soil amendment; the insight of its nutrient release and supply to soil may enhance their agricultural use. The study was conducted to assess the ability of fly ash (a coal fired thermal plant waste) to reduce soil fertility depletion and to study bioaccumulation of mineral nutrients in Jatropha curcas grown on soils amended with fly ash. Fly ash was amended to field soil at six rates (0, 5, 10, 20, 40, and 70 % w/w) on which J. curcas was grown. After 8 months of growth, the height of jatropha plants was significantly increased at 5 and 10 % FA-amended soil, whereas, biomass significantly increased at 5, 10, and 20 % FA-amended soil compared to control soil (0 % FA). Leaf nutrients uptake, followed by stems and roots uptake were highly affected by fly ash amendment to soil. Most of nutrients accumulation were increased up to 20 % fly ash and decreased thereafter. The results of available nutrient analysis of soil revealed that availability of nitrogen, potassium, sulfur, copper, iron, mangnese, and zinc declined significantly at higher levels of fly ash amendments, whereas, availability of phosphorus increased at these levels. However, pH, organic carbon, and available boron were not influenced significantly by fly ash amendment to soil. Microbial biomass C, N, and ratio of microbial-C to organic C were significantly reduced at 20 % fly ash and higher amounts. This study revealed that J. curcas plants could gainfully utilize the nutrients available in fly ash by subsequently amending soil.  相似文献   

16.
The weathering of coal combustion products (CCPs) in a lotic environment was assessed following the Tennessee Valley Authority (Kingston, TN) fly ash release of 2008 into surrounding rivers. Sampled materials included stockpiled ash and sediment collected from 180 to 880 days following the release. Total recoverable concentrations of heavy metals and metalloids in sediment were measured, and percent ash was estimated visually or quantified by particle counts. Arsenic and selenium in sediment were positively correlated with percent ash. For samples collected 180 days after the release, total concentrations of trace elements downstream of the release were greater than reference levels but less than concentrations measured in stockpiled ash. Total concentrations of trace elements remained elevated in ash-laden sediment after almost 2.5 years. A sequential extraction procedure (SEP) was used to speciate selected fractions of arsenic, copper, lead, nickel, and selenium in decreasing order of bioavailability. Concentrations of trace elements in sequentially extracted fractions were one to two orders of magnitude lower than total recoverable trace elements. The bulk of sequentially extractable trace elements was associated with iron-manganese oxides, the least bioavailable fraction of those measured. By 780 days, trace element concentrations in the SEP fractions approached reference concentrations in the more bioavailable water soluble, ion exchangeable, and carbonate-bound fractions. For each trace element, the percentage composition of the bioavailable fractions relative to the total concentration was calculated. These SEP indices were summed and shown to significantly decrease over time. These results document the natural attenuation of leachable trace elements in CCPs in river sediment as a result of the loss of bioavailable trace elements over time.  相似文献   

17.
Investigations of the existing chemical forms and the concentrations of arsenic (As), selenium (Se) and antimony (Sb) in samples of fly ash obtained from six coal-fired power stations in various countries were carried out. The concentration of As was found to vary from 5.4 to 22.3 mg kg(-1), and the most common mode of occurrence of As in the fly ashes is in association with carbonates or Fe-Mn oxides. The concentrations of Se and Sb ranged from 2.3-5.2 and 1.0-3.9 mg kg(-1), respectively. The dominant chemical forms of Se and Sb in the fly ashes were as extractable species. Also, water-soluble As, Se and Sb in the fly ashes were extracted, and the chemical species of As, Se and Sb in the extract determined using HPLC-ICP-MS. This was done as the potential release of soluble As, Se and Sb through leaching of fly ash is of environmental concern. The most abundant form of As in the extract was the low toxicity As(V). The main species of Se was Se(IV), although it was found that the ratio of Se(VI) to Se(IV) in acidic fly ashes is higher than in alkaline fly ash samples. Antimony was mostly present as Sb(III).  相似文献   

18.
The exposure of paving workers to polycyclic aromatic hydrocarbons (PAH) during stone mastic asphalt (SMA) paving and remixing was evaluated. The effects on the workers' PAH exposure were also evaluated during the use of an industrial by-product, coal fly ash (CFA), instead of limestone as the filler in the SMA. The PAH exposure was measured by personal air sampling and by analysing the levels of urinary naphthols, phenanthrols and 1-hydroxypyrene (1-OHP) in the workers' pre- and post-shift urine samples. The respiratory PAH exposure of the paving workers (geometric mean (GM) 5.7 microg m(-3)) was about ten-fold that of the traffic controllers (GM 0.43 microg m(-3)). The levels of PAH metabolites were significantly higher (p < 0.05) in the post-shift urine samples than in the pre-shift urine samples, and the levels of metabolites in the post-shift urine of paving workers were significantly higher than in that of the controls (p < 0.01). Urinary 1-naphthol correlated well with the airborne concentrations of the two- to three-ring PAHs (r = 0.544, p = 0.003) and naphthalene (r = 0.655, p < 0.001), when non-smoking paving workers were tested. A good correlation was observed between urinary 1-OHP and the airborne concentrations of the four- to six-ring PAHs (r = 0.524, p = 0.003) as well as total PAHs (r = 0.575, p = 0.001). The concentrations of 1-OHP and phenanthrols in the urine of the pavers were significantly higher (p < 0.01) during remixing than during SMA paving. The CFA in the asphalt had no effect on the airborne PAH exposure or on the concentrations of the PAH metabolites in the paving workers' urine.  相似文献   

19.
研究比较了M12半自动净化法与手工净化法应用于二噁英检测的效果。结果显示,采用高分辨气相色谱-高分辨质谱法(HRGC-HRMS)检测飞灰样品中的二噁英,手工净化法的回收率要优于M12半自动净化法的回收率,但M12半自动净化法除2种单体外,其余单体回收率均满足对二噁英的分析要求,且2种净化方法所得二噁英的总毒性当量结果相近,证明手工净化法与HRGC-HRMS联用检测飞灰中二噁英的效果较好,但M12半自动净化法也能够满足HRGC-HRMS检测二噁英的净化要求。应用酶联免疫法检测飞灰样品中二噁英的总毒性量,当样品中二噁英浓度较高时,M12半自动净化法和手工净化法净化测得结果与基准值一致性较好;当样品中二噁英浓度较低时,手工净化法检测结果与基准值差别较大,表明酶联免疫法更适合用M12半自动净化法进行净化。  相似文献   

20.
Airborne particles in fugitive emissions have been measured at a slagging fixed-bed coal-gasification pilot plant using lignite. Sampling was conducted during shutdown operations and opening of the gasifier following an aborted startup. Aerosol collected with a Sierra high-volume impactor was subjected to analysis by gas chromatography, mass spectrometry, and scanning electron microscopy; aerosol collected with an Andersen low-volume impactor was subjected to flameless atomic absorption analysis. The data show that the bulk of the trace organic material is associated with small particles: these data are similar to data on ambient air reported in the literature. Particle morphologies resemble those of fly ash from coal combustion, including smooth spheres, vesicular spheres, and crystalline material. Trace element size distributions are bimodal and resemble data for ambient air. Pb-containing particles are generally submicron, while particles containing Al, Fe, and other crustal species are mostly of supermicron size. Aluminum-based aerosol enrichment factors calculated from the lignite composition show that the composition of the aerosol resembles that of the coal, with the exception of modest enrichments of Mg, Na, As, and Pb in the submicron size range. Aerosol enrichment factors based on the earth's crustal composition are somewhat greater than those based on coal composition for several elements, suggesting potential errors in using crustal enrichment data to investigate chemical fractionation during aerosol formation.  相似文献   

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