due to the accumulation of solid products, and this retardation may depend on the conversion raised to a power greater than unity.
Acknowledgment
Conclusions The rate of sorption of NO on various calcines of limestone and dolomite has been measured, the majority of the results referring to the more active of the two limestones employed. Chalk was the most active, but the activity was directly related to the surface areas of the calcines employed. On this basis, the two particular dolomites employed in this study were not the most reactive, and for practical purposes a coarse grained limestone might prove most effective. The order of reaction in NO was of first order, and a t low conversions a zero order dependence on the solid calcine may be assumed. However, a t high utilization of the calcines, the nitrate formed has a pronounced retarding effect on the sorption rate, but this can be accommodated by an empirical dependence on the nitrate loading. The activation energy and preexponential factor for the absorption have been measured. The value of the activation energy obtained, 22.6 kcal/gmol, suggests that the data were obtained in the chemical control region and confirms that the precautions taken to eliminate mass transfer resistances in the system were adequate.
Literature Cited
We acknowledge with gratitude the provision of stone samples by the British Quarrying and Slagging Federation. (1) Borgwardt, R. H., Enuiron. Sci. Technol., 4,59 (1970). (2) Pigford, R. L., Sliger, G., Ind. Eng. Chern. Process Des. Deu., 12, 85 (1973). (3) Coutant, R., Simon, R., Campbell, B., Barrett, R. E., Final Rep., “Investigation of Reactivity of Calcined Limestone and Dolomite for Capturing SO2 from Flue Gas”, to NAPCA, Contract CFA 70-111, Battelle Laboratories, Oct. 1, 1971. (4) James, N. J., Hughes, R., paper presented a t 2nd Int. Conf. on Control of Gaseous Sulphur and Nitrogen Compound Emission, Salford University, Salford, England, 1976. (5) Jonke, A. A., “Reduction of Atmospheric Pollution by Fluidized Bed Combustion”, Monthly Rep. No. 8, Argonne National Laboratory, Lemont, Ill., Mar. 1969. (6) Robinson, E. B., Bishop, J. W., Harvey, W. T., Jr., Ehrlich, S., Preprint 45C, 64th Nat. Mtg. AIChE, New Orleans, La., Mar. 1&20, 1969. (7) Crynes, B. L., Maddox, R. N., Chern. Technol., 502 (Aug. 1971). (8) Snell, F. D., Ettre, L. S., “Encyl. of Ind. Chem. Anal.”, Interscience, New York, N.Y., 1972. (9) Ruthven, D. M., Chern. Eng. Sci., 23,759 (1968). (10) Weisz, P. B., Hicks, J. S., ibid., 17, 265 (1962).
Received for review January 24, 1977. Accepted July 11,1977.
National Survey of Elements and Radioactivity in Fly Ashes Absorption of Elements by Cabbage Grown in Fly Ash-Soil Mixtures A. Keith Furr and Thomas: F. Parkinson Office of Occupational Health and Safety, and Nuclear Reactor Laboratory, Virginia Polytechnic Institute, Blacksburg, Va. 24061
Roger A. Hinrichs Physics Department, State University College, Oswego, N.Y. 13126
Darryl R. Van Campen US. Plant, Soil and Nutrition Laboratory, U S . Department of Agriculture, Cornell University, Ithaca, N.Y. 14853 Carl A. Bache, Walter H. Gutenmann, Leigh E. St. John, Jr., Irene S. Pakkala, and Donald J. Lisk’ Pesticide Residue Laboratory, Department of Food Science, Cornell University, Ithaca, N.Y. 14853
An analytical survey of 45 elements was conducted in fly ashes from 21 states by use of several instrumental methods. A high degree of correlation was found between the concentrations of pairs of chemically similar elements in the fly ashes and between the magnitude of gamma emission of the fly ashes and their respective concentrations of Th or U. Cabbage was grown to maturity in potted soil amended with 7% (w/w) of the various fly ashes. The concentrations of As, B, Mo, Se, and Sr in the cabbage showed a high degree of correlation with those in the respective fly ashes in which the plants were cultured.
present (2-5) such as selenium which can be absorbed from it by plants (2),foraging animals ( 6 ) ,and aquatic species (7). Furthermore, the presence of radionuclides in a limited number of fly ash samples has been reported (8). An analytical survey of the elemental content of fly ashes produced in this country has not been published. In the work reported, fly ashes from 2 1 states were analyzed for 45 elements and gamma emission by use of several instrumental methods. Cabbage grown on potted soil amended with the fly ashes was analyzed for these elements for possible correlation between the magnitude of element absorption by the crop and the element content of the respective fly ash.
Approximately 40 million tons of fly ash were collected in the United States in 1974, an increase of 15% over that produced in 1973 ( I ) . About 8.5% of this total was utilized in concrete and asphalt products and road stabilization ( I ) , the remainder being trucked to landfills or piped to settling ponds. Since fly ash typically contains nutrient elements, its use as a soil amendment in agriculture has been investigated to a limited extent (2). Numerous toxic elements may also be
Experimental In 1975 a description of our proposed study was sent to coal-burning power plants in 29 states with a request that they participate and return a representative sample of their fly ash to us for analysis. The power plants that participated and the data they provided pertaining to their fly ashes are listed in Table I. The fly ashes were mixed in a lucite twin shell blender and subsampled for analysis. Nondestructive neutron activation analysis for 36 elements
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was conducted by the procedure described earlier (9).Gallium was determined by charged-particle induced x-ray fluorescence by use of a proton energy of 1.95 MeV and a Si (Li) x-ray detector with a resolution of 200 eV. Calibration of the system was made with NBS standards of coal fly ash. The determination of selenium was accomplished by a modification of the method of Olsen ( 1 0 )employing wet digestion of the sample and measurement of the fluorescence of piazselenol resulting from reaction of selenium with 2,3diaminonaphthalene. Boron was determined by the curcumin spectrophotometric procedure ( I 1 ) . Cadmium, lead, and zinc were determined by conventional stripping voltammetry with a Princeton Applied Research Corp. Model 174 polarographic analyzer (12). Nickel was determined by furnace atomic absorption with a Perkin-Elmer Model 303 spectrophotometer equipped with an HGA-2000 furnace. Mercury was determined by flameless atomic absorption analysis following combustion of 0.5 g of the dry sample (to which 0.3 g by weight of powdered ashless cellulose was added to support combustion) by use of an oxygen flask (13).Fluorine was not determined on a total basis in fly ash. Rather, its concentration was determined with the Orion specific fluoride ion electrode in an equilibrate resulting from addition of 5 g of fly ash to 20 mL of distilled water and allowing the mixture to stand for 30 min. The method of Peech et al. ( 1 4 ) was used for the determination of pH. Gamma emission was measured with a Packard gamma scintillation spectrometer equipped with a Model 9012 multichannel analyzer. Total gamma radiation in the range of 5-505 keV was integrated and recorded for each sample over a period of 1000 s. A study was made to determine if a crop grown on fly ashamended soil would absorb elements in proportion to their concentration in the fly ash. Of the 23 ashes obtained for analysis (Table I), only 15 were supplied in sufficient quantity for plant growth studies. The soil used was a Tee1 silt loam, pH 7.2, and with an exchange capacity of 13.9 meq/100 g. The soil was air dried, sifted through a 2-mm screen, and mixed by quartering. Seven percent w/w of the various fly ashes was mixed with portions of the soil by quartering. For each power station, 10 kg of the respective fly ash-soil mixture was used to fill two 9-in. plastic pots (5 kg/pot). The pH values of the resulting fly ash-soil mixtures ranged from 7.1 to 7.8. The crop grown was "Green Winter" cabbage (Brassica oleracea uar. capitata). One cabbage plant was grown to maturity in each of the two pots representing a given power station. Cabbage grown in pots containing the soil alone served as controls. The plants were fertilized weekly with Hoaglands solution prepared from reagent-grade potassium nitrate and potassium dihydrogenphosphate (15).All plants were watered equally and at the same time daily, care being taken to avoid splashing soil on the aerial portions of the plants. At maturity the crops were harvested with only the edible leaf head portion collected for analysis. Prior to analysis the leaves were rinsed with distilled water to remove any adhering dust. The respective replicated cabbage heads grown on fly ash from a particular power station were combined and subdivided in a food cutter. The plant material was mixed, freeze dried, milled to a powder, again mixed, and subsampled for analysis. Elemental analyses were performed for the respective elements by the methods indicated in Table I1 except for several elements. Prior to analysis of B, Cd, Pb, and Zn the cabbage sample was dry ashed at 475 "C. These elements were then determined by the methods described. After dry ashing the plant sample nickel was isolated by chelation and determined by furnace atomic absorption analysis (16).Arsenic was determined by dry ashing ( I 7) the samples, distilling arsine and analysis by the silver diethyldithiocarbamate spectrophotometric procedure (18). Fluorine was determined with the specific ion electrode following combustion of 0.25 g of the Volume 11, Number 13, December 1977
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dried, pelleted cabbage sample in a 1-L polypropylene oxygen-filled flask containing 20 mL of distilled water as the absorbing solution. Results and Discussion The results of analysis of the fly ashes are listed in Table 11. The concentration of fluorine being that in an aqueous extract of the fly ashes would obviously vary according to the ratio of the volume of water to weight of fly ash and time of equilibration. The concentrations of elements in fly ashes may vary widely. The elemental composition of fly ashes depends on the composition of the parent coal and conditions during coal combustion and ash collection. As pointed out by Bowen (191, a large number of elements are accumulated by coal but not by every coal seam. Many rare elements tend to concentrate a t the boundaries of coal seams, but the reasons for this are not understood (20). Most importantly, the pathways of elements during combustion of coal in power plants vary considerably, some largely volatilizing through the stack while others deposit in the fly ash trapped above or remain in the slag below (3).The efficiency of electrostatic precipitators for trapping fly ash would also expectedly vary, and those which more efficiently trap finer fly ash particles would tend to yield an ash higher in the concentration of many elements ( 5 ) . Nevertheless, examination of the data in Table I1 indicates that certain pairs of chemically similar elements tended to occur in the fly ashes at related concentrations. Table I11 lists these element pairs and the correlation coefficient ( r )for their paired concentrations in each of the fly ashes studied. Although not similar chemically, the rare earths and actinides such as cerium and uranium, respectively, are known to occur geologically together in monazite and may also in coal. Notably all of the fly ashes showed gamma emission significantly above background. The gamma spectrum of each fly ash showed two significant peaks occurring between 54 and 107 and between 206 and 255 keV. No siginficant gamma radiation was observed in the energy spectrum from 400 keV to 8 meV. No attempt was made to identify specific radionuclides. Eisenbud and Petrow (8)have reported on the presence of isotopes such as Ra-226, Ra-Zz8, Th-Z28, Th-232, and U-238 in coal fly ash. In this regard, a high degree of correlation was found between the concentrations of either T h or U in the fly ashes and the magnitude of their respective gamma emissions (Table 111). Table IV lists the elements which showed a high degree of
Table 111. Correlation Coefficients for Pairs of Elements Whose Concentrations in Fly Ashes Varied Similarly Correlation coefla Element pairs
(I)
As, Sb 0.63 Ca, Mg 0.78 Cd,Zn 0.95 Ce, U 0.72 CI,Br 0.77 Co, Ni 0.62 Rb, K 0.79 Sm, Ce 0.9 1 Sm, Yb 0.94 Sr, Ba 0.84 Sr, Ca 0.80 U, Th 0.52 Th, cpmb 0.60 U, cpm 0.90 a All values of r were highly significant (1 % level). * Gamma radiation(counts per minute per gram) above background.
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correlation between their concentration in the cabbage and that in the respective fly ash added to the soil in which it was grown. The increase in selenium concentration in the crops was roughly proportional to the rate of application when fly ash was mixed with the soil at rates of 5 or 10%on a dry weight basis (2). As compared to the element content of control cabbage, many of the other elements showed higher concentrations in the cabbage grown in the soil mixed with the fly ashes in this study. The range of concentrations (ppm, dry wt) of these other elements determined in the cabbages grown in the soil amended with the various fly ashes was as follows: As (35.1-71.5), Au (0.001-0.006), Ba (19-105), Br (10.8-34.1), Ca (19500-50800), Ce (0.2-2.21, C1 (5700-9960), Co (0.4-LO), Cr (0.4-2.4), Cs (0.03-0.4), Cu (2.0-22), F (2.2-7.8), Fe (70-352), Hf (0.1-0.5), I (0.1-1.2), K (15 700-35 700),La (0.00-0.30), LU (0.00-O.l), Mg (2180-92601, Mn (18.8-77.3), Mo (0.5-32.8), Na (926-4390), Ni (0.3-3.2), Pb(l.l-3.0), Rb (5-58), Sb (0.7-54), Sc (0.01-0.04), Sm (0.04-0.3), Sn (0.7-31.6), T a (0.04-0.4), T h (0.1-0.8), Ti (4.7-26.7), V (0.02-0.41, W (0.21.71, Yb (0.01-0.3), and Zn (31-82). As, B, Ca, Cu, Fe, Hg, I, K, Mg, Mo, Ni, and S b were shown earlier (2) to increase in concentration in various vegetable crops grown on soil amended with 10% (w/w) fly ash from Milliken Station in Lansing, N.Y. (Table I). Enhancement of crop absorption of elements such as Ca, Cr, K, Mg, Mo, Rb, Se, and Sr would be expected at neutral to slightly alkaline p H of the growth media. Conversely, crop absorption of elements such as As, B, Cd, Co, Cu, F, Fe, Pb, Mn, Ni, Sn, and Zn would expectedly be depressed in this pH range. Measurement of gamma emission in the cabbage samples showed no significant radiation above background. The practical use of fly ash as a soil amendment would require careful monitoring. As an example, in many areas of the world, soils are deficient in selenium, an essential element for animals and man. Plants should ideally contain from about 0.05 to 0.1 ppm (dry wt) of Se to meet dietary needs. Fly ash can be used as a soil amendment to increase the selenium content of a variety of crops, and this increase is roughly proportional to the rate of fly ash application (2). Furthermore, this increase is reflected in plants grown successively on the same fly ash-amended soil (2).The work reported here indicates that fly ashes from several sources can be used to increase the Se content of cabbage. Selenium, however, has a very narrow permissible concentration range in feeds to meet essential animal needs. High concentrations ( 5 ppm) in rations are toxic to livestock (21).The magnitude of selenium absorption by plants grown on fly ash-amended soils will depend on the Se content of the fly ash, the rate of application, the soil type and its pH, the plant species, and other factors. Additions of high rates of fly ash to soil might therefore affect element availability to plants by altering soil pH. Although elements such as Cr, F, Hg, and P b tend to be fixed in soils in forms unavailable to plants, the concentration of other elements possibly increasing in plants as a result of fly ash amendments such as arsenic and molybdenum which are toxic to animals (22) would also have to be considered. Although strontium is not highly toxic to mammals (23), its accumulation in the bones of animals foraging on plants containing it would be possible. To control toxic element uptake by plants, the rates of application of fly ash would probably fall far below those which would considerably affect soil physical properties ( 2 4 ) . The use of fly ash as a soil amendment would therefore require preliminary field plot studies to determine a safe rate of application of a given fly ash on a particular soil for growing a specific crop continuously or as part of a crop rotation. Acknowledgment The authors thank H. Gene Knight, George J. Doss, William
~~
Table IV. Specific Elements Whose Concentrations in Cabbage Correlated with That in Respective Fly Asha in Which It Was Cultured Fly ash source
Colorado Delaware Georgia Iowa Kentucky Massachusetts Minnesota Montana New Hampshire New Mexico site 1 New Mexico site 2 New York Ohio South Carolina South Dakota Control (soil only)b
pH of fly ash-soil medium
7.7 7.0 7.5 7.6 7.0 7.6 7.4 7.8 7.1 7.7 7.5 7.0 7.1 7.2 7.4 7.2
As
ppm (dry weight) In cabbage B MO Sa
Sr
115 2.7 0.7 310 29 33 1.3 120 26 10 0.5 84 105 11 0.3 150 23 11 3.7 90 18 2.7 0.4 80 145 9.6 1.1 420 93 4.9 0.2 490 81 13.8 0.8 130 23 0.5 0.2 63 135 8.4 0.2 130 20 3.9 1.3 83 16 13.6 1.4 36 28 27.1 1.3 97 70 4.6 0.7 220 0.0 21 0.03 0.05 43 Correlation coeff ( r ) c - d 0.81 0.78 0.69 0.74 0.83 a The growth media consisted of 7 wt % of the respective fly ash added to Tee1 silt loam soil (see text). Total element concentration (ppm, dry wt) in the soil itself was As (0.0).B (6.0),Mo (lS), Se (0.3), and Sr (78). Correlation between the concentration of the element in cabbage and that in the respective fly ash (see Table 11) upon which it was grown. Values of r for each element are highly significant (1 % level).
A. House, and Helen L. Arnold for their assistance during this investigation.
Literature Cited (1) National Ash Assoc. and Edison Electric Inst., Ash a t Work, 7,
3 (1975). (2) Furr, A. K., Kelly, W. C., Bache, C. A., Gutenmann, W. H., Lisk, D. J., J. Agric. Food Chem., 24,885 (1976). (3) Klein, D. H., Andren, A. W., Carter, J. A., Emery, J. F., Feldman, C., Fulkerson, W., Lyon, W. S., Ogle, J. C., Talmi, Y., Van Hook, R. I., Bolton, N., Enuiron. Sci. Technol., 9,973 (1975). (4) Block, C., Dams, R., ibid., p 146. (5) Davison, R. L., Natusch, D.F.S., Wallace, J. R., Evans, C. A., Jr., ibid., 8, 1107 (1974). (6) Furr, K., Stoewsand, G. S., Bache, C. A., Gutenmann, W. A., Lisk, D. J., Arch. Enuiron. Health, 30,244 (1975). (7) Gutenmann, W. H., Bache, C. A., Youngs, W. D., Lisk, D. J., Science, 191,966 (1976). (8) Eisenbud, M., Petrow, H. G., ibid., 144,288 (1964). (9) Furr, A. K., Lawrence, A. W., Tong, S.S.C., Grandolfo, M. C., Hofstader, R. A., Bache, C. A., Gutenmann, W. H., Lisk, D. J., Enuiron. Sci. Technol., 10,683 (1976). (10) Olsen, 0. E., J. Assoc. Off. Anal. Chem., 52,627 (1969). (11) Greweling, H. T., “The Chemical Analysis of Plant Tissue”, Mimeo no. 6622, Cornel1 Univ., Ithaca, N.Y., 1966. (12) Gajan, R. J., Larry, D., J. Assoc. Off. Anal. Chem., 55, 727 (1972). (13) Bache, C. A., Gutenmann, W. H., St. John, L. E., Jr., Sweet, R.
0.1 1.8 0.7 0.6 1.1 0.0 0.2 0.0 1.7 0.2 0.2 0.6 0.3 1.4 0.6
D., Hatfield, H. H., Lisk, D. J., J . Agri. Food Chem., 21, 607 (1973). (14) Peech, M., Olsen, R. A., Bolt, G. H., Soil Sci., Soc. Am. Proc., 17, 214 (1953). (15) Hoagland, D. R., Arnon, D. I., “The Water-Culture Method for Growing Plants Without Soil”, Calif. Agr. Exp. Sta. Circular No. 347.1950. (16) Zachariasen, H., Anderson, I., Kostol, C., Barton, R., Clin. Chem., 21.562 (1975). (17) Evans, R. J., Bandemer, S. L., Anal. Chem., 26,595 (1954). (18) Fisher Scientific Co., “Reagents of Choice for Arsenic in Parts per Billion”, Tech. Data Bull. TD-142, Nov. 1960. (19) Bowen, H.J.M., “Trace Elements in Biochemistry”, Academic Press, New York, N.Y., 1966. (20) Bethell, F. V., Bull. Br. Coal Util. Res. Assoc., 26,401 (1962). (21) Ehlig, C. F., Allaway, W. H., Cary, E. E., Kubota, J., Agron. J., 60,43 (1968). (22) Browning, E., “Toxicity of Industrial Metals”, Butterworths, London, England, 1969. (23) Christensen, H. E., Luginbyhl, T . T., Carroll, B. S., Registry of Toxic Effects of Chemical Substances, 1975, USHEW, NIOSH, Rockville, Md. (24) Jones, C. C., Amos, D. F., “Physical Changes in Virginia Soils Resulting from the Additions of High Rates of Fly Ash, paper presented at the 4th Int. Fly Ash Symp., St. Louis, Mo., Mar. 2 6 2 6 , 1976. Received for review December 13, 1976. Accepted J u l y 28,1977.
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