Ernest S. Gladney”, Lawrence E. Wangen, David B. Curtis, and Edward T. Jurney University of California, Los Alamos Scientific Laboratory, P.O. Box 1663, Los Alamos, N.M. 87545
The boron content of coal and power plant process ashes is investigated. Calculation of mass balances suggests that a large fraction of the boron is being released to the atmosphere.
Table II. Mass Balance for BoronI at Two Coal-Fired Power Plants (Fraction-ppm)
Plant
Trace element emissions from industrial sources, especially coal-fired power plants, have been the subject of a number of recent studies (1-6). Mass balances on as many as 37 elements have been measured ( 4 ) , and in-stack particle size distributions have been determined for 34 elements ( I , 2). These measurements have been performed almost exclusively by instrumental neutron activation. Several potentially toxic elements (e.g., B, Cd, F, Pb) cannot be satisfactorily determined in power plant effluents by neutron activation. Among this group, boron is of particular interest. Coal-fired power plants are often constructed in rural, agricultural areas where social and economic factors are favorable. There is a growing literature (7-11) that suggests boron has a rather narrow range of tolerance in plants. Outside this concentration range it can have severe effects on vegetation. Concern about boron in agricultural fertilizers and pesticides is evident (12-15). Sources of airborne boron have not been carefully studied, but adverse effects of boron release from appliance manufacturing have been reported (7,16). This note reports an investigation of the behavior of boron during the combustion of coal a t two large coal-fired power plants. It includes a discussion of boron partitioning in coal and power plant process ashes. Experimental A complete description of the Chalk Point Electric Generating Station (Maryland) and of sampling techniques is given by Gladney ( I ) . Similar data for the Four Corners plant may be found in Wangen and Wienke (17). The thermal neutron prompt gamma-ray facility at the Los Alamos Omega West Reactor (18,19) was used for all boron determinations in the present work. The details of the analytical procedure may be found in ref. 18. Results and Discussion The 9-day average boron content of Chalk Point coal and process ashes is shown in Table I. Similar %day averages are given for the Four Corners plant. An approximate mass balance for an element may be determined in the following manner. The boron concentration in the feed coal is divided by the ash content (%) of the coal. This yields the “total possible in ash” boron concentration (i.e., as if the coal were ashed without loss of boron). The boron concentration in each pro-
Table I. Boron Concentrations in Power Plant Coals and Process Ashes (ppm) Plant
Chalk Point, Md. Four Corners, N.M. This work SWES (20) 1084
Coal
Bottom slag
Econornlzer
13 f 2
17 f 3
19 f 2
33 f 3
...
240f5 230
92f 1 120f 12 98 f 32 120
Environmental Science & Technology
...
Preclpltator fly ash
Chalk Point Four Corners
EconBottom omlzer slag ash
1.5
AccountPreclp- Account- Total able/ Itator able porslble total fly ash In ash In ash posalble
2.3
25
29
100
0.29
This
24
...
190
214
390
0.55
work SWES
24
...
180
204
415
0.49
cess ash is multiplied by the fraction of the total ash collected at that location. The sum of the latter figures should equal the boron concentration in the “coal ash” if all the boron is being collected in the plant (“Accountable in ash”). The ratio of the accountable boron to the total possible boron is the fraction of boron collected by the emission control system. The ash contents of coal burned at Chalk Point and Four Corners a t the time of sampling were 13 and 23.6%, respectively ( I , 20). Therefore, the coal ash boron concentrations are 100 and 390 ppm. Using process ash distributions of 9,12, and 75% for bottom, economizer, and precipitator fly ash, respectively a t Chalk Point (1)and 20,0, and 8096, respectively, at Four Corners (17),the data in Table I1 may be calculated. This excludes the 4% of ash released from the stack at Chalk Point. If the mass balance shown in Table I1 is correct, then boron becomes one of the most enriched elements in power plant emissions, in a class with Br, C1, Hg, Se, and As ( I ) . A similar depletion for boron in the process ashes with implied loss to the stack is seen in the Southwest Energy Study (17,ZO).The SWES data for boron content of coal are highly variable. Using the lowest error limit, one still calculates a loss of 30% of the boron. One in-stack cascade impactor sample set from Chalk Point was analyzed for boron. Only the filter stage showed a positive indication for boron: 0.4 Mg or 2.0 pg/m3 of stack gas. This provides a hint that the boron is condensing only on the smallest particles and that most of it is being emitted in the gas phase. It has been suggested that boric acid or boron halides would be the most probable volatile species in the emissions (21). Another study (22) provides data that indicate higher boron concentrations on stack particulates of 1 2 km and less. Float-sink data on organic affinities as studied in coals by the Illinois Geological Survey (IGS) (23) are also suggestive. Their conclusions break trace elements into three groups: organic: Ge, B, Be, Sb, Br; intermediate: Co, Ni, Cu, Cr, Se; and inorganic: Zn, Cd, Mn, As, Mo, Fe. Data indicated that most of the elements having high organic affinities (23) become preferentially enriched in the fly ash (1-6) and are emitted to the atmosphere. Our data support this for boron. However, significant quantities of As have also been measured leaving the plant (1-4, and IGS identifies this element as clearly inorganic associated. The more “volatile” material found in the coal, the higher the average boron concentration on a coal ash basis. Ray and Parker (24) report the following average coal ash boron concentrations (ppm): Anthracite, 90; low volatile bituminous, 123; medium volatile bituminous, 218; high volatile bituminous, 770; and lignite,
0013-936X/78/0912-1084$01,00/0 @ 1978 American Chemical Society
1020. The apparently large amounts of boron lost to the environment through stack emissions may be closely related to the organic association of boron in the coal. While these data are hardly definitive, they imply that coal-fired power plants are a significant source of atmospheric boron. These results indicate a need for more detailed studies of the behavior of boron during combustion and the effects, if any, of boron releases on agriculture.
Acknowledgment We thank Glen E. Gordon and William H. Zoller of the University of Maryland for supporting the collection of samples a t Chalk Point in 1973, and the staff of the Los Alamos Omega West Reactor for their assistance with the irradiations. Literature Cited (1) Gladney, E. S., PhD dissertation, University of Maryland, College
Park, Md., 1974. (2) Gladney, E. S., Small, J. J., Gordon, G. E., Zoller, W. H., Atmos. Enuiron., 10, 1071 (1976). (3) Kaakinen, J. W., Jorden, R. M., Lawasani, M. H., West, R. E., Enuiron. Sci. Technol., 9,862 (1975). (4) 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., ibid., p 973. (5) Lee, R. E., Crist, H. L., Riley, A. E., MacLeod, K. E., ibid., p 643. (6) Ragaini, R. C., Ondov, J. M., “Trace Contaminants from CoalFired Power Plants”, presented a t Int. Conf. on Environmental Sensing and Assessment, Las Vegas, Nev., 14-19 Sept. 1975. (7) Temple, P. J., Linzon, S. N., J. Air Pollut. Control Assoc., 26,499 (1976). (8) Eaton, F. M., J . Agric. Res., 69,237 (1944). (9) Bradford, G. R., “Boron”, in “Diagnostic Criteria for Plants and Soils”, H. D. Chapman, Ed., pp 33-61, University of California Press, Riverside, Calif., 1966.
(10) Neary, D. G., Schneider, G., White, D. P., Soil Sci. SOC. Am. Proc., 39,981 (1975). (11) Purfes, D., Mackenzie, E. J., Plant Soil, 40,231 (1974). (12) Melton, J. R., Hoover, W. L., Howard, P. A., J. Assoc. Off. Anal. Chem., 52,950 (1969). (13) Carlson, R. M., Paul, J. L., Soil Sci., 108,266 (1969). (14) Pickett, E. E., Pan, J.C-M., J. Assoc. Off. Anal. Chem., 56,151 (1973). (15) Pickett, E. E., Pan, J.C-M., Koirtyohann, S. R., ibid., 54, 796 (1971). (16) Jervis, R. E., University of Toronto, Toronto, Canada, private communication, 1974. (17) Wangen, L. E., Wienke, C. L., “A Review of Trace Element Studies Related to Coal Combustion in the Four Corners Area of New Mexico”, LA-6401-MS, Los Alamos Scientific Lab, July 1976. (18) Gladney, E. S.,Jurney, E. T., Curtis, D. B., Anal. Chem., 48,2139 (1976). (19) Jurney, E. T., Motz, H. T., Vegors, S. H., Nucl. Phys. A, 94,351 (1967). (20) Southwest Energy Study, Appendix J , Coal Resources, Southwest Energy Federal Task Force, PB-232106, Jan. 1972. (21) Duce, R. A., University of Rhode Island, private communication, 1977. (22) Lyons, W. S., “Trace Element Profiles Through a Coal-Fired Steam Plant”, Quarterly Progress Rep. for June-August, Internal Memorandum, ORNL, Oak Ridge, Tenn., Aug. 1971. (23) Gluskoter, H. J., Ruch, R. R., Miller, W. G., Cahill, R. A., Dreher, G. B., Kuhn, J. K., “Trace Elements in Coal: Occurrence and Distribution”, Illinois Geological Survey, Circular 499, pp 118,119,123, 1977. (24) Ray, S. S., Parker, F. G., “Characterization of Ash from CoalFired Power Plants”, Environmental Protection Agency, EPA-6001 7-77-010, Jan. 1977.
Receiued for review January 13, 1978. Accepted March 27, 1978. Work performed under the auspices of the Department of Energy. Sample collection a t Chalk Point supported by NSF-RANN Grant GI-36338X to the Uniuersity of Maryland.
Dispersion of Plutonium from Contaminated Pond Sediments Terry F. Rees*’, Jess M. Cleveland’, and W. Carl Gottschal12 Rockwell International, Atomics International Division, Rocky Flats Plant, P.O. Box 464, Golden, Colo. 80401
Sediment-water distributions of plutonium as a function of pH and contact time are investigated in a holding pond a t the Rocky Flats plant of the Department of Energy. Although plutonium has been shown to sorb from natural waters onto sediments, the results of this study indicate that under the proper conditions it can be redispersed a t pH 9 and above. Concentrations greater than 900 pCi Pu/L result after 34 h contact at pH 11or 12 and the distribution coefficient, defined as the ratio of concentration in the sediment to that in the liquid, decreases from 1.1X lo5 a t pH 7 to 1.2 X lo3 at pH 11. The plutonium is probably dispersed as discrete colloids or as hydrolytic species adsorbed onto colloidal sediment particles whose average size decreases with increasing pH above pH 9. About 5% of the total plutonium is dispersed at pH 12, and the dispersion seems to readsorb on the sediment with time. Consequently, migration of plutonium from the pond should be slow, and it would be difficult to remove this element completely from pond sediment by leaching with high pH solutions.
‘Present address, U S . Geological Survey, Lakewood, Colo. 2Present address, University of Denver, Department of Chemistry, Denver, Colo. 0013-936X/78/0912-1085$01 .OO/O
The behavior of plutonium in aquatic environments has received considerable attention because of nuclear weapons tests in the Pacific and concern about potential radioactive releases from nuclear energy facilities and waste burial sites. At the pH conditions found in natural waters, plutonium hydrolyzes (1-4) and sorbs onto bottom sediments (5-9). Little effort has been expended in determining in what form and how permanently the plutonium is fixed, even though changes in pH would be expected to change the character of both the plutonium and the sediment particles. In this paper we report on a study of the dispersion of plutonium from the sediments of a freshwater holding pond at the Rocky Flats Plant of the Department of Energy near Golden, Colo. This pond, known as B-1, was selected for study because it had measurable concentrations of plutonium in the sediment. This pond has been receiving treated sewage effluent since 1952 and laundry wastewaters from that date until late 1973. Most of the element now present in the sediment is believed to be from the latter stream, which was contaminated in the laundering of protective clothing used in a plutonium processing facility. Pond B-1 has a maximum depth of approximately 4 m and a volume of about 3 X lo6 L. The residence time for water in the pond is approximately 34 h (IO).Although the results reported here are specific to waters and sediments from Pond B-1, they should be a t least quali-
@ 1978 American Chemical Society
Volume 12, Number 9, September 1978
1085
