anionic TCP, the fit of the data was not completely satisfactory. According to the Langmuir theory of adsorption, the parameter b (see Equations l and 2) should be constant. In this b,C,) in the denominator of Equation 1 case the term (Z should be much less than unity a t very low concentration and adsorption should take place without competition. However, this was not the case a t p H 5.2, 7.0, and 9.1. In all instances, the term ( b l C l + b&2) was significant relative to unity; as the value of C, decreases, the corresponding value of bi increases causing the entire denominator in Equation 1 to remain greater than unity. The parameter b is proportional to exp(-AHIRT) where AH is the adsorption energy. Adsorption energy varies with surface coverage; high-energy sites are occupied first with subsequent adsorption occurring a t increasingly lower energy sites as the surface coverage increases. The net result is significant competition between sorbates even a t very low concentration. Evaluation of the competitive effects of commercial HA, soil FA, and leaf F A showed that the presence of these materials decreased the capacity of carbon for chlorophenol too, and that each of the materials competed somewhat differently. When the findings on competitive adsorption between chlorophenols and humic substances are considered, it is apparent that any testing to determine the best carbon and design criteria for a given application should be done using the specific water to be treated. Such factors as the nature and concentration of competing organic materials and the pH, among others, play a major role in determining the removal one can expect of a certain component. Acknowledgment
The assistance of P. Boening, J. McCreary, and N. Wood with portions of this study is also acknowledged.
L i t e r a t u r e Cited ( 1 ) Burtschell, R. H., Rosen, A. A,, Middleton, F. M., Ettinger, M. B.,
J . A m . Water Works Assoc., 51,205-14 (1959). (2) Lee, G. F., in “Principles and Applications of Water Chemistry”, Faust, S.J., and Hunter, J . V., Eds., Wiley, New York, N.Y., 1967. (3) Korenman, Y., J . Appl. Chem. U S S R (Engl. Trans/.),47,2134-7 (1974). (4) U S . Environmental Protection Agency, “Methods for Organic Pesticides in Water and Wastewater”, National Environmental Research Center, Cincinnati, Ohio, 1971. (5) Leenheer, J . A., Huffman, E. W. D., Jr., J . Res. U.S. Geol. Suru., 4,737-45 (1976). (6) Snoeyink, V. L., McCreary, J. J., Murin, C. J.,“Activated Carbon Adsorption of Trace Organic Compounds”, Report EPA-600/277-223, U.S. Environmental Protection Agency, Cincinnati, Ohio, 1977. (7) Zogorski, J. S., Faust, S. D., “Removal of Phenols from Polluted Waters”, New Jersey Water Resources Research Institute, Rutgers University, 1974. (8) Ward, T. M., Getzen, F. W., Enuiron. Sci. Technol., ‘4, 64-7 (1970). (9) Gauntlett, R. B., Packham, R. F., in Proc. Conference on Activated Carbon in Water Treatment, University of Reading, Water Research Association, Medmenham. England, 1973. (10) Zogorski, J. S., Faust, S. D., J . Enciron. Sci. Health, A l l ( 8 & 9), 501-15 (1976). (11) Butler, J. A. V., Ockrent, C., J . Phys. Chem., 34, 2841-59 (1930). (12) Langmuir, I. J. A m . Chem. Soc., 40,1361-403 (1918). (13) Jain, J . S., Snoeyink, V. L., J . Water Pollut. Control Fed., 45, 2463-79 (1973) (14) Radke, C. J., Prausnitz, J. M., AIChE J., 18,761-8 (1972). (15) Wershaw, R. L., Burcar, P. J., Goldberg, M. C., Enuiron. Sci. Technol., 3, 271-3 (1969). Received for reuiew April 17, 1978. Accepted October 3, 1978. T h e partial support o f the EPA, Grant No. R803473, for this study is gratefully acknowledged. The contents do not necessarily re//ect the views and policies of the EPA, houeuer, and the mention of trade names and commercial products does not constitute endorsement.
Growth and Element Uptake of Woody Plants on Fly Ash David H. Scanlon” and J. Carroll Duggan’ Division of Forestry, Fisheries, and Wildlife Development, Tennessee Valley Authority, Norris, Tenn. 37828
Pulverized coal ash stored a t the John Sevier Power Plant, Rogersville, Tenn., was tested as a substrate for eight woody plant species. Concentrations of As, B, Cd, Cr, Cu, Hg, K, N, Ni, P, P b , Se, and Zn were measured in plant foliage in the second and third growing seasons on fly ash and a soil control, and were compared with concurrent analyses of the substrates. B, Ni, and Se appeared more available to plants of all species when grown on fly ash, while uptake of As and Hg varied by species. Cr and P b showed no increases in foliar concentration in plants grown on fly ash as compared with soil. Mean survival of plants on fly ash was 53%, ranging from 12 to 84% depending on species. Application of 10 cm of subsoil over the fly ash resulted in no improvement in plant performance. Nitrogen-fixing species appeared best adapted for use in fly ash stabilization. Difficulties in disposal of fly ash resulting from pulverized coal combustion a t electric power plants are of increasing concern. About 62 million tons of fly ash were collected in the Present address, Tennessee Valley Authority, Division of Energy Research, Chattanooga, Tenn. 37401.
United States in 1976 ( I ) , up from 40 million in 1974 ( 2 ) ,and with a renewed emphasis on coal utilization, collections may increase rapidly during the next decade. While approximately 20% of the fly ash collected in 1976 was utilized ( I ) , mostly in concrete, asphalt products, and road stabilization, the remainder was stored in dewatering ponds or landfills. Ash placed in disposal areas must be stabilized and covered to prevent wind and water erosion and concomitant environmental problems. Establishment of vegetation is often an effective means of stabilizing solid wastes. However, a review of the literature reveals relatively few studies dealing with establishment of vegetation directly on fly ash and information on plant growth and chemical relationships on the substrate is limited. Differences in response have been reported for plant species growing on fly ash as with the plant A t r i p l e x h a s t a t a var. deltoidea which was observed to rapidly colonize on bare ash where other species failed ( 3 ) .When A t r i p l e x was compared in ash pot culture studies with barley ( H o r d e u m uulgare), only the barley exhibited numerous element toxicity symptoms ( 3 ) . Yellow sweet clover ( M e l i l o t u s o f f i c i n a l i s ) , observed vigorously growing on landfilled fly ash with a pH of 4.5, was compared with clover grown on an isolated gravel bank and found to have higher concentrations of most elements ana-
This article not subject to U.S. Copyright. Published 1979 American Chemical Society
Volume 13, Number 3, March 1979
311
Table 1. Composition of John Sevier Fly Ash in Disposal Area at Initiation of Test a malor element
dry wt, %
major element
dry wl, %
Si02 A1203
52.8
Na20 K20 Ti02
0.3 2.9 1.4 0.9
b o 3
CaO MgO a
26.8 12.7 1.4 1.2
so3
Loss on ignition, 5.2%; pH 5.6 (range 4.0-7.6); fineness, % through 16
mesh, 82.
lyzed ( 4 ) .Tall fescue (Festuca arundinacea cv. Ky. 31) and white sweet clover (Melilotus a l b a ) were grown successfully on fly ash of pH ranging from 6.5 to 7.5 ( 5 ) .Other herbaceous plant studies have involved the effect of fly ash used as a soil amendment on plant toxicity and element uptake in tests of agricultural crops including cabbage (Brassica oleracea) (6), alfalfa (Medicago satiua) and corn (Zea m a y s ) (7), barley, beets (Beta uulgaris), and kale (Brassica oleracea acephala) (8).
Using woody plants, 19 species were tested in pots using two types of fly ash and only boxelder (Acer negundo), green ash (Frasinus pennsyluanica var. lanceolata), and white poplar (Populus alba) resulted in good survival and growth (9).European black alder (Alnus glutinosa) and Virginia pine (Pinus uirginiana) were successfully established on a dewatered settling pond of pH 6.5 to 7.5 fly ash, although initial pine growth was much slower than the alder (4). On 12-year-old, sluiced bottom ashes (pH 8.9-9.2), planted loblolly pine (Pinus t a e d a ) , sycamore (Platanus occidentalis), and sweetgum (Liquidambar styraciflua) had good survival, and tissue analyses indicated no element toxicity problems (10).
Although the above work demonstrates the feasibility of establishing some species directly on fly ash, information is needed on species variability in growth and toxic element uptake on different types of fly ash. Therefore, this study was undertaken to evaluate the performance of eight species of trees and shrubs planted in acidic fly ash in a dewatered disposal area. Concurrent analyses of metallic elements and plant nutrients were made on the fly ash and plants growing thereon to determine trends in uptake and possible toxic effects on the plants.
Experimental TVA's John Sevier Steam Plant is located in eastern Tennessee on the south bank of the Holston River 5 km southeast of Rogersville. Fly ash produced there is sluiced into settling ponds approximately 300 m from the plant. The experimental site is located on a north-facing, 20% slope of mounded ash in a completed section of the disposal area. An analysis of the major elements in the ash as sampled just prior to plot establishment is shown in Table I. The experimental design included four adjoining 24.4 m X 48.8 m blocks on the slope of mounded fly ash, with two blocks located in upslope positions and two on the lower slope. A 10-cm cover of gravelly clay subsoil was applied on two blocks, one in each of the slope positions. In each of the four blocks, 16 seedlings from each of 8 woody plant species were randomized in four, four-plant replications using 3 m X 3 m spacing. A fifth block planted as an experimental control was located 200 m away on a graded and turfed area developed on a level subsoil fill of gravelly clay loam with a pH of 7.4. The species tested included European black alder (Alnus glutinosa), sweet birch (Betula lenta), sycamore (Platanus occidentalis), sawtooth oak (Quercus acutissirna), cherry 312
Environmental Science € Technology i
olive (Elaeagnus multiflora ouata), autumn olive (E. u m bellata), silky dogwood (Cornus a m o m u m ) , and gray dogwood (C. racemosa). These were selected for their general ability to grow under adverse conditions and provide wildlife habitat and aesthetic improvement. One-year-old seedlings were grown in the TVA Norris nursery and bare rooted plants were hand planted in early April 1975. During the previous fall the experimental blocks were seeded with tall fescue, ryegrass (Lolium perenne), yellow sweet clover, and sericea lespedeza (Lespedeza sericea), fertilized with 200 k g h a of 10-10-10,and mulched with oat (Auena sativa) straw to provide initial erosion control. Evaluations of the test were made following the second and third growing seasons. Survival percentages and total heights were recorded to evaluate establishment success and were tested by analysis of variance. Foliage samples were collected in 1976 and 1977 during the last week in August. Small sizes of the plants and some low survival made it necessary to combine samples from the replicates which precluded analysis of variance tests. Samples were taken from the dominant shoots of all surviving plants of a species in a given block using fully developed leaves. Foliage samples were washed, thoroughly mixed, dried in a forced air oven at 40 "C for 13 h, and finally milled to pass through a 2-mm screen. Samples of fly ash and also subsoil from the control plot were collected concurrently with the foliage samples using four subsamples per test block. On the two blocks with 10 cm of subsoil covering the fly ash, the soil was scraped away to permit collection of ash samples below. All collections were made a t a depth of about 15 cm. Samples were dried in a forced air oven a t 40 "C and then screened through a 16 mesh before analysis. In the third growing season, fruits were produced by only the European black alder, cherry olive, and autumn olive, but only cherry olive in block 4 was in sufficient quantity to provide a sample for chemical analysis. Fruits were prepared for analysis by removing the seeds before drying and milling. All samples were analyzed by the Analytical Laboratory in the Fundamental Research Branch of TVA. Arsenic was distilled as AsCl3 and determined spectrophotometrically as the heteropoly blue complex. Boron was determined spectrometrically by the azomethine-H procedure as proposed by Wolf ( I 1 ). Selenium was determined fluorometrically using the reagent 2,3-diaminonaphthalene and the method proposed by Ihnat (12).A modified version of the vanadomolybdate method as described by AOAC (13) was used to determine phosphate. Flame atomic emission spectrometry was used to determine potassium. Cadmium, chromium, copper, nickel, lead, and zinc were determined by atomic absorption spectrometry by flame or graphite furnace atomization according to the methods described by the instrument manufacturer ( 1 4 ) .Mercury was determined by flameless atomic absorption spectrometry according to Hatch and Ott ( 1 5 ) after digestion of the samples following the techniques suggested by Barrett (16).
Results At the end of three growing seasons approximately half the shrub and tree seedlings planted on fly ash were living. Table I1 presents the survival percentages by species and treatment. Analysis of variance showed highly significant differences among species and among treatments. Two Elaeagnus species, cherry olive and autumn olive, had the best survival followed by sawtooth oak and the shrub dogwoods. Survival of sycamore and European alder was moderate to low on the four fly ash blocks while most sweet birch failed to survive on subsoil or fly ash. Comparison of treatments shows no overall improvement
Table II. Mean Percentage Survival after Three Growing Seasons plants grown on fly ash disposal area effect of soil cover a effect of slope location a without 10-cm cover upslope downslope
a
100' 91 78 ns 69 cherry olive 94 ns 62 84 72 ns autumn olive 91" 62 66 ns 38 sawtooth oak 72 ns 44 62 53 ns silky dogwood 66 ns 47 62 50 ns gray dogwood 66 19 28 56 ns sycamore 47 ns 19 28 38 ns European alder 19 ns 9 16 ns 6 sweet birch "t" test results indicated as: *, significance at 5% level: ns, not significant at 5% level.
all test plantsa fly ash area control area fly ash substr. soil substr.
84 78 64 58 56 42 33 12
100" 88 ns 62 ns 81 69 ns 62 ns 38 ns 12 ns
Table 111. Mean Total Heights in Centimeters after Three Growing Seasons plants grown on fly ash disposal area effect of slope location a effect of soil cover a without 10-cm cover upslope downslope
European alder cherry olive autumn olive sycamore silky dogwood gray dogwood sawtooth oak sweet birch a
214 234 185 55 56 49 64 66
197 ns 176* 160 ns 91 ns 80 ns 54 ns 62 ns 80 ns
"t" test results indicated as: * , significance at 5%
210 ns 238 176 ns 68 ns 70 ns 51 ns 60 n s 88 ns
195 172 172 85 61 51 61 51
all test Dlants a control area fly ash area fly ash substr. sol1 substr.
206 205 174 74 66 51 60 73
338 ns 220 ns 145' 141" 135" 135' 74 ns 77 ns
level; ns, not significant at 5 % level
in plant survival by the addition of 10 cm of subsoil over fly ash. Upslope and downslope locations had more impact on survival than subsoil cover. Initially high acidic (pH 4.0) conditions and greater moisture stresses of the upslope blocks likely were responsible for higher mortalities there. Mean total heights attained by the eight species in 3 years are shown in Table 111. All species, but particularly the shrub dogwoods and sycamore, showed stem dieback and sprouting under the extreme conditions of moisture stress and winter severity experienced during the test period. Therefore, heights were measured on the dominant leader or sprout of each plant. Vigorous initial height growth appeared to give some species an advantage in competition with groundcover species, and thus the alder, cherry olive, and autumn olive showed better growth on fly ash than the other species. Analysis of variance showed height differences among species to be highly significant while treatment effects on total heights were not statistically significant. Results of elemental analysis of fly ash, subsoil, and foliage of seven plant species are presented in Table IV. Although analyses of fly ash and fly ash grown foliage were determined for each of four treatment blocks, differences among blocks were relatively small so results shown are means of four blocks. In comparisons of the elements in fly ash and subsoil substrate, it is notable that all elements except zinc analyzed consistently higher in fly ash. The followup analyses of fly ash showed decreased contents of As, B, Cu, Hg, Pb, and Se while Cd, Cr, K, Ni, P, and Zn increased. Foliar analyses indicated substantially elevated levels of B, Ni, and Se for all seven species grown in fly ash. Increased levels of As were detected only in sycamore and silky dogwood, while Cr and P b showed no increases in plants grown on fly ash. There appeared to be some accumulation of Hg in plant tissue and levels were slightly higher in fly ash grown plants. Levels of Cd, Cu, and Zn generally were comparatively higher in foliage from fly ash than from subsoil. Most notable in the foliar comparisons are the high accumulations of B and Se in tissue grown on fly ash.
Results of the one fruit analysis of cherry olive from fly ash block 4 (Table V) indicate levels of As, B, Hg, Ni, Pb, and Se in fruit to be lower than those in comparable leaf tissue. Levels of Cd, Cr, and Cu were slightly increased in fruit, while Zn levels were the same.
Discussion Experimental results indicate that two Elaeagnus species, autumn olive and cherry olive, can be successfully established on acidic to neutral fly ash disposal areas. These species appeared exceptionally adaptable to adverse site conditions and generally showed no visual toxicity or element imbalance symptoms. European black alder showed rapid growth after rather poor survival. This species appeared more site selective and sensitive to moisture 'stress, since an earlier study ( 4 ) showed good survival of alder on a level ash pond site. However, because it is a soil nitrogen-fixer like the Elaeagnus species, European black alder should be strongly considered for inclusion in shrub and tree mixtures planted on ash disposal sites. Sawtooth oak survived well although, typical of oak species, early growth has been slow. Further growth evaluations are required, but conditionally the species appears to have potential on acid to neutral fly ash. Sycamore and the shrub dogwoods showed fair to moderate survival but also dieback and poor early growth. Although evaluations of growth must be continued, the inclusion of sycamore, which performed well on alkaline ash ( I O ) , and silky dogwood, the more site-flexible species, appears warranted on a trial basis. Sweet birch, though an invader on coal strip mines, was found unsuitable for establishment on fly ash. The application of 10 cm of subsoil to fly ash before revegetation appeared to reduce wind erosion but did not significantly improve survival or growth of woody plants. Growth of herbaceous vegetation on the subsoil-covered blocks showed no improvement over that on fly ash; however, the subsoil used as cover was relatively heavy and infertile. If a good quality topsoil had been available and used, herbaceous and possibly woody vegetation on the treated blocks might have shown Volume 13, Number 3, March 1979 313
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Table IV. Elements in Foliage of Woody Plants in Second and Third Seasons on Fly Ash and Subsoil (Parts per Million) fly ash a
subsoll element
2nd
3rd
2nd
2nd
2nd
3rd
4 695
