RECLAMATION OF COAL REFUSE WITH A PAPERMILL SLUDGE AMENDMENT1 by
RS. Li and W. LeeDaniels2

~ Reclamation ofcoal mfuaeis difficultdueto the harshgrowing conditions resulting from the refuse’sunfavorablechemical andphysicalproperties.This researchpm- focused on the utilization potential of apapermillsludgeproducedbytheMeadPaperCompanyin K@ksP@ Term.,which ~~i~ PritilY of a mi~ ofwastewoodfiber,lime, kaoliq and tracesoffly ash. A field experimentwas initiatedin 1992. Loading rateswereO,112,224 Mg M-l forthe paperrnillsludgeand O,112,224, and336 kg lur’forN. Ourresultssuggest thatthe N-fertilizer additions gave a short-term boost to biomass production suppressed legume gmwtlL and resulted in a higher yield and thicker vegetation cover in the first year. From the second year OIL however, the vegetation on the papermill sludge plots was superior to that on the Osludge plots across all N ratea, suggesting that papermill sludge did not lead to excessive Nimmobilization as expected. By contributing organic matter, acid-neutralization potential, and light color, the paperrnill sludge significantly improved the refuse ~ increased the available P, increased the water holding capacity, and decreased the refuse temperatm during the summeF all ofwhich were beneficial to establishment and maintenance ofvegetation. The addition of papermill sludge also improved leachate quality. Thus, a proper combination ofN-fertilizer and papermill sludge, for example, 112kg ha_lN and 112Mg hd sludge, is recommended in addition to balanced P and K fertilization.
Additional Key Words: Revegetatiou nitrogen immobilization, acidity, water holding capacity.

The safe disposal ofpapermill sludge and other paper making residuals is a challenging problem. Currently, the majority ofwastes are disposed ofin landfills. Nevertheless, these alternatives are becoming
more expensive and pose substantial threats to water quality ifdeaign standards are not strictly met and maintained over the lifetime ofthe disposal fwility. llms, there is considerable interest in the pulp and paper industry over whether (and which @ their waste residurds can be successfully and safely land-applied. This research program was implemented to determine ifa paperrnill sludge product could be successfully utilized to reclaim coal processing waste materials in southwest Virginia.

lPaper presented at the 1997 National Meeting ofthe American Society for Surfke Mining and Reclamation, Austin, Texas, May 10-15, 1997.
2Ren-sheng Li is a Senior Research Associate and W. Lee Daniels is Associate Professor in the Dept. of Crop and Soil Environmental Sciences, Virginia Tech Blacksburg, VL 240614)404. Coal 

## refuse disposal areas cover thousanda of
acres in Virginia alone, and tend to be quite difficult to revegetate or stabilize without topsoil covers or significant surface amendments. The revegetation of coal refhse is limited by low soil water holding capacity, high summer heat loads, and variable levels of soil acidity (Stewart and Daniels, 1992). The refuse from coal preparation is low in organic matter, quite coarse textured, and is generally characterized by poor physical and chemical properties. On many coal refuse piles, revegetation potential is strongly limited by potential acidity and resultant low pH and high salt content ofthe refuse. A number ofAppalachian refuse piles are non-acid forming in ovemll reaction chemi~, but still suffer from the physical limitations to plant growth discussed above, particularly ifthey are to be direct-seeded without topsoil covers.
A considerable amount greenhouse and field research has been conducted to date on the utilization of papermill sludge on natural and disturbed lands. These studies have shown that appropriate rates ofpapermill sludge as a topical amendment have the potential to greatly improve the water holding and aggregation of raw mine spoils and refuse, supply plant nutrients, and decrease acidity. These numerous benefits have led to

277better plant growthand greater vegetative cover,

particularlywhen combinedwith appropriate fertilization strategies (Owusu-GyimaandRoy, 1991; Del Roaario, 1990: Feagley et al., 1994alxBellamy, et al., 1995; Dollar, et al., 1972; WatsonandHoithdq 1985; Cline and Chong, 1991; Pichtel, et al., 1994).
The specific objectivesofthis studywere:
1. To characterizethe chemical andphysical propertiesofapapermillby-product material that was available for utilization in the central Appalachian regiom and to determine its suitability for land application.

2. To determine the optimal loading rates for the product when used as a surface amendment for direct revegetation ofcoal refhse.
3. To measure the amendment’s influence on coal refuse leachate quality, and to determine the extent ofpH buffering over multiple seasons.

The papermill sludge generated by Mead Paper Co. in Kingsport (acquired by Willamette Paper in 1995) was particularly attractive for this use since it is
a mixture ofprimarily waste wood fiber (600A)and lime (25%), with minor amounts ofkaolin clay (10%) and fly ash (5?40).

The material is a non-biological water tm.atment sludge, is finely groundj and can be easily land-applied with manure spreadem or through conventional hydro-seeders. For the balance ofthis paper, we will refer to this material as lime-fiber mulch since that term best describes its properties and potentially beneficial role in mined land reclamation. Papermill waste materials can contain dioxins that are aby-product ofthe bleaching process. There is currently considerable public and agency debate over the environmental and human health risks associated with dioxins (Olson et al., 1988; Owusu-Gyima and Roy, 1991; Baker, 1994). Fo-tely, due to process changes at the Kingsport plant in the early 1990’s,the dioxin (TCDD) levels in this product were below detection (< 0.3 ppt) when this research experiment
was installed. However, a considerably less toxic daughter isomer (TCDF) was detectable at <5 ppt. Plot cmitrwh
The experimental ~ 45 m by 90 Q was located on the Pine Branch coal refuse pile operated by the Westmoreland Coal Company in Wise County, Virginia. This site was chosen because our earlier lE@OIUd Coldwaste research program (Stewart and Daniels, 1992) indicated that Pine Branch was close to the regional median for potential acidity. The area where this particular experiment was installed was near neutral in pm however, but was very coarse in texture and black on the surhce. Noticeable salt accumulations
were also apparent at the time ofplot installation. Thus, while this location is somewhat atypical ofApprdachian coal refuse with regard to acidity, it still posed a severe challenge for revegetation due to water stress coupled with severe N and P limitations. Other studies (lhniels et al., 1989; Stew@ 1990) at this and other refuse piles in the region have established that once potential acidity has been neutralized, N and P are the principal growth limiting nutrients, and that micro-nutrient deficiencies
are rare.
This experiment was a randomized complete block design with three replications and two main experimental factors. The first experimental fhctor was lime-fiber mulch applied at three rates: O, 112 and 224 Mg ha-l. The second factor evaluated was fertilizer-Nat four applied levels, O, 112,224 and 336 kg hd as ammonium nitrate. All plots also received 336 kg ha-lP and 112kg ld K with the initial fertilization based upon earlier research by Daniels et al. (1989). In March, 1992, the area was graded with abulldozer and the individual field plots were laid out and sampled for soil analyses.

In May 1992, lime-fiber mulch from Mead’s Kingsport plant was trucked to the Pine Branch refhse pile. A front-end loader was used to measure (by loader bucket) and spread the lime-fiber mulch at the appropriate rate on each plot. The weight/density/water content relationships for this material were determined in the lab the weekbefore spreading. The lime-fiber mulch was immediately chisel-plowed to incorporate it into the refuse surface. On June 9, 1992, the entire area was seeded with 17kg hd German millet (Sekwia itaiica) asa summer cover crop. The appropriate amounts offefilizer were applied to each plotjust before seeding. The millet was hamested on September 8, 1992, and these plots were then seeded with the reclamation species mix are given in Table 1. On April 13, 1993, N-fertilizer was again applied on each plot at one-half the rate applied in 1992.

278Table 1.The seedmixture used in 1992. Variety Purity(%) Ger.(%) KY-3 1 Tallfeseue Festuca arundinacea Schreber 49.00 85 AmIud ryegrass Lofium muMjlbrum 9.78 90 Redtop Agrostis afba 1.96 90 Alsike clover Trifofiumhybridum 7.91 90 Alta-swede Red clover Trz~oEitm

pratense 9.95 90 Birdsfoot trefoil Lotim comidatus 1.92 85 Yellow sweetclover A4efifoti offxinah 17.72 90

To monitorthe effkztsofthe surfhce treatmentson leaehate quality, zero-tensionlysimeters
wereinstalled underfourplots In October, 1992. Lysimeterswem installed undertwo treatedplots (224 Mg lid mulch+ 336 kg hd N), andtwo controlplots (OMg ha-lmulch+ Okg hd N). The lysimeterswere made ofa 0.4 m length ofsmoothbore0.24 m (diam) ABS plastic pipe with afitted endeap.The lysimeter
was plumbedwith a plastic tubeto evaeuateleaehate. One endofthetube was fixed tothebottom of lysimeterandwas screenedwith 80 mesh nylon sieve clotlLandotherend was broughtto the surfhee.A hole
was excavated in the refusewith a shovel (separating the top layerof- from deeperret%se) andthe lysimeterwas putinto the hole, with a ten-em layer of
coarse sand in the bottom ofthe lysimeter. Refuse was then paeked around and in the lysimeter with the top layer ofrefuse returned back over the top ofthe lysimeter and returned to original grade.

l&XhiWk Leaehates were pumped up monthly fkom eaeh lysimeter with a vacuum pump. The pH was measured on-site immediately and subsamplea were taken into a 250-ml plastic bottle for later laboratmy analyses. In the laboratory, the turbid samples were filtered through a #42 filter paper before analysis. Conductance was measumd with a conductivity meter and then we acidified these samples with HN03 to prepare them for fbrther analysis. The leachate sampleswere subsequently analyzed for. Al, CILFe, -. - Iv@ S, ZIL and CabyICPand/orAA speetroseopy.
Refuse samples
were taken at randomffom the aurfaee15 em ofeach plotbefo~ treatmentswere applied. The mulch was also sampledbeforeapplicationto develop weight/volume relationshipsas discussed earlier. Vegetationperformancewas evaluatedfor eaeh plotby estimatingthe percentagegroundcover, the species composition andthevigor ofgrowtheach spring, summer,andfhll. 13aeh

fhll in September,standing biomass samplesweretakenfrom eaeh plot randomly by handclipping to groundlevel within two 0.25 mz quadrata. Theplanttissuewas oven-driedat 65°C for 48 hoursandweighed. The planttissue was subsequentlygroundto determinenutrientand heavy metallevels. Soil samples were excavatedbeneath the biomass sampling quadratsto a 15-em depthwith a shovel. Soil sampleswem air-driedand passedthrough a 2-mm sieve to separatefine soil ilom coarse fragments.All analyses wereperformedon the fine-soil fkaetion.Soil samples were analyzedforpm waterretentio%andheavymetals. Soil pHwas determinedin a 1:1 soil:waterslurrywith a glass-calomel electrodepHmeter (McLemL1982). Waterretention was determined by the method of Klute (1982). Total analysis ofthe original lime-fiber mulch material and a combined sample ofthe untreated refuse was determined by ICP and AA spectroscopy after high temperature HF digestion

279(Hmtstein et al., 1973). The Neutralization potential of

the lime-fiber mulch material was estimated by treating the sample with an excess ofHC1followed by back titration with NaOH (Sobek et al., 1978). Total N
was measured calorimetrically after KjelW digestion (Bremner and Muhmney, 1982). Plant available P was analyzed with 0.5M NaHCOj method (Olsen and Sommers, 1982). Total P was determined with the perchloric acid digestion method (Olsen and Sommers, 1982).

Physical and chemical conditions ofthe soil
are critical for vegetation grow@ and the reclamation ofcoal refbse generally is not successfd without topsoiling or heavy use of amendments. For comparative purposes, the total elemental content of the lime-fiber mulch material and the raw refuse from Pine Bmnch are given in Table 2. The mulch material
as applied was 29°AC and very high in Ca derived from its waste lime content which led to a high neutralization potential (197 tons linwlthousand tons material). The Pine Branch refbse averages around 19% C due to its carbonaceous nature (Stew@ 1990).
Previous studies have shown that heavy metal bioaccumulation is generally not a problem for applications ofpapermill sludge because ofthe low concentrations applied and the lack ofuptake or toxic effects in sensitive crops like tomatoes, cucumbers and peppers (Ritter et al., 1992; Cline and Chong, 1991; and Bellamy et al., 1995). In general, the lime-fiber mulch material applied at Pine Branch was similar to or lower than the host refhse in heavy metals and should pose no long term heavy metal loading concerns, particularly when the pH buffering ofthe lime component is taken into account. Thus, this waste Ptiuct appeWs

veryattractive as a mine soil amendment particularly for acid-forming materials. In
one application%wood fiber residues are added to work
as a surf’ mulching agent and organic matter amendmen4 lime is added to neutralize acidity and buffer soil solution pm and a smaller amount ofclay and ash are added to aid with water retention and to slow the rate ofwater percolation down away from the rooting zone.
Lab analyses indicated that addition oflimefiber mulch not only increased and stabilized the soil pELbut also increased the available P levels in the soil (Figs. 1 and 2). This portionofthe Pine Branch refuse pile was moderate in pH before the plots were establish perhaps due to earlier lime additions by the company. In 1992, the pH ofthe refuse was around 6.5 with a large amount ofpoint to point variation. Lime fiber mulch additions increased pH to 7.0 to 7.8, but by 1993, the pH ofrefuse from control plots had decreased somewhat most likely due to oxidation oftrace pyrites due to incorporation disturbance.

It appeared that due to its high neutralization potential, the lime-fiber material neutralized acidity and/or inhibited the pyrite oxidatiorL and reduced the volubility of Fe (Backes et al., 1986). Pichtel and Dick (1991) report that organic materials can serve as inhibitors to reduce acid production from pyrite by preventing Fe-oxidation and by removing soluble Fe from solution. The effects ofLiming and inhibition probably worked together by raising soil pH and reducing Fe and Al levels. This combined effect should also increase the availability ofP, since at low pH, P is immobilized mainly by Fe and Al (see discussion of soil leachate properties). The average extractable P increased (p< 0.05) from 4.9 to 21.3 mg kgi with addition oflime-fiber mulch.
Adverse soil water conditions including seasonal waterlogging and drought are common problems during reclamation (Rimmer, 1982). Our monthly field observations indicated that waterlogging and runoff occurred only on the untreated refhse plots in the winter and after heavy storm events in summer. In contrast, there was no waterlogging and/or runoff observed on the lime-fiber mulch plots due to improved infiltration and water holding capacity (WHC). Without lime-fiber mulch the average WHC
was 87 g kg-l; with treatment it increased to 175 and 230 g kg-lwith the addition of 112 and 224 Mg M’ lime-fiber mulck respwtively (Fig. 3). Figure 4 indicates that the increase in WHC occurred mostly in the low tension portion (or readily available) ofthe
curve.
The surface temperature ofbare coal waste is very high in the summer, reaching as high as 75°C (Deely and Borden, 1973; Lee et al., 1975), a level lethal to plants. Our field measurements indicate that the lime-fiber mulch effectively moderated the surface temperature (Fig.5, p < 0.05). This temperature buffering is most likely due to the combined effects of direct mulching, improved vegetative cover, soil albedo effkxts(lighter), and improved soil WHC.

280Table 2, Elemental analysis ofcoal refuse andlime-fibermulchmaterials.

Sample Neutralization

potential To~ N% To~ PA c% Si% A1’?40 Fe% CaYO
refhae

------------------ 0.27 0.016 19.0 22.2 9.1 3.0 2.3 sludge 197

tons lime (1000 tijl 0.14 0.030 29.2 9.5 5.0 2.6 7.9

Sample Mg?? % c% ~ PbP N% CrW c%

0.8 112.0 26.0 1026 15.8 29.8 83.8 6.4 sludge 0.3 98.7 47.3 1213 24.0 33.7 103.4 2.5

8.0

7.!5

x Q 7>0

6.5

6.0 NOMO

N, ~N2M0N3M0NOM, 1- 1-

,M, N2M1 N3M1NOM2N1M2N2M2 N3M2

Figure 1. Soil pH in 1992 and 1993. No: no N fertilizer; Nl: 112kg N ha-l; N2: 224kg N ha-l; N3: 336kg N ha-l; Ma: no .&-& ~~ch; M<: 112 Mg ha-l sludge m~ch; Mm:224 Mg ha-l sludge mulch; SOilsamples taken on”March 1992, and on At. 1993 before and after applic~tion of papermill sludge. Values are means (n= 3) with standard errors.



### 281—

30



### 25

5 

## 0

Treatment Figure2. Available Pin 1993. Sludge:Lime-fibersludge; NO:noN fertilize~ Nl: 112kgN ha-l; N2: 224kg N ha-l; N3: 336kgN ha-l; M : no sludgemulch; Ml: 112Mgha-l sludgemulch; M2: 224 Mgha-l sludge mulch; Sod samplestakenon &t. 1993, and valuesaremeans(n=3)withstandard errors.

0.30



### 0.25

0.05



### 0.00 N M NM NM N M N M N, M, N2M1N3M, NOM2N,M2N2M2N3M2



### ooio 203004 Treatment Figure 3. 

### Soilwaterholdingcapacities(-O. OIMpato -1.5Mpa)in 1993. N : noN fertilizer; N : 112kgN ha-l; N2: 224kgN ha-l; N3: 336kgN ha-l; MO: no sludgemulch; Ml: 112Mg#a-l sludgemulch; I/f2:224 Mg ha-l sludgemulch. Soil samplestakenon Oct.1993,andvalues aremeans(n= 3) with standarderrors.

282f
: : 0 NOMO 

# 4 0 N2M0 T N2M1

o N2M2

.................................

0.0 1

0.0 0.5 1.0 1.5 saturation wilting (-O.OIMpa) 

### Soil water potential (Mpa) (-1 .5Mpa) Figure 4. Soil moisture potential curves for samples taken in 1993. N : no N fertilizer; N : 112kg N ha-l; N2: 224kg N ha-l; N3: 336kg N ha-l; MO:no sludge mulch; Ml: 112&g ha-l sludge mulck; M2: 224 Mg ha-l sludge mulclq

32 I
30 ] 

# -T ~ depth: 2.5cm

~ 

### depth: 10cm

20

18



### Treatment Figure 5. Effkets of treatment on soil temperature. NO:no N fertilizer; N1: 112kg N ha-l; N2: 224kg N ha-l; N3:336kg N ha-l; MO:no sludge mulch; Ml: 112 Mg ha-l sludge mulch; M2: 224 Mg ha-l sludge mulch; Temperatures measured on Aug. 18, 1994, and values are means (n = 3) with standard errors.


### 283Biomass yield and overallplantperformance

arethe most commonly employed indicatorsof revegetationsuccess. Total standingbiomassyields in the fall of 1992, 1993 and 1994 areshown in Fig. 6. In 1992, standingyields were determinedon the German millet covercroponly. In 1992, therewere signitlcant effects due to N-fertilizer rate, but no differences among mulch treatments. Millet is known to have a strong N-fertilizer response, and both the raw lime-fiber mulch and the raw refuse are quite Ndeficient. Thus, in 1992, the millet biomass accumulation appeared to be driven primarily by fertilily with no obvious effkctfrom the mulching treatment, In f- the mulched treatments appeared to be less vigorous than the ummdched plots. We attribute this to (1) the fact that the millet is adapted to hot summer conditions, (2) our relatively late spring seeding date, and (3) that the wet summer of 1992 may have negated any positive mulching effects.
The mixed gradlegume stand was established in the fall of 1992, and by the fall of 1993 it had established avigorous and nearly complete cover over the better performing treatments. Both N and mulch application rates influenced (p=O.01)yields in 1993 (Fig. 6), andworkedwell in combimtion. Variation ofbiomass productionwithin eachtreatment was less in 1993 than thatin 1992 andthe total vegetative productionwas consistently improvedby mulch and moderateN application. Theapplicationof lime-fiber mulch increasedoverallplantcoveracross all N ratesin 1993 (Fig. 7), and provided almost complete vegetative cover when combined with moderate N rates. Increasing the mulch rate from 112 to 224 Mg ha-l did not appear to improve vegetation performance, however. The composition ofthe vegetation varied (p< 0.05) in response to N rate across all mulch treatments. In general, the higher the N application the less the legume component and the greater the grass component (Fig. 7). Nitrogen fertilizer applications clearly increased the total vegetative cover but had the tendency to suppress legume grow@ which is a commonly observed phenomenon in mixed stands. Increasing the fertilizer beyond 112kg ha_] did not appear to improve total biomass production. This indicates that the application oflime-fiber mulch material does not lead to excessive N-fertilizer immobilization by soil microbial decompose as we had feared. Apparently, the C substrate within the mulch is either extremely resistant to microbial attack or has already been significantly degraded in the water treatment process at the mill. Regardless ofthe reason, it does not appear that heavy N applications will be Mcessa@ for this product to be successfully utilized in mine reclamation.
The overall evaluation ofvegetative cover shown in Figure 7 was made in October 1993, integrates both total ground cover and plant vigor, and therefore varies somewhat from the percent cover evaluation for each treatment. Based on the overall evaluation data it is clear that the NW (no N, no mulch) plot performance was poor (grade <2.5); while the NIIv$(112 kg ha-lN, no mulch) and the N&41 (no N, 112Mg ha_*

mulch) resulted in fair vegetation performance with grades of 3.3 and 2.7, respectively. Treatments that combined lime-fiber mulch and N fertilizer generated thick and vigorous vegetation (Fig. 7), reinforcing our finding that a combimtion ofthe lime-fiber mulch and N fertilizer appears to be a very successful treatment for direct seeding ofthis coarse coal refbse material. The data in Figure 7 also indicate that the ratio oflegume/grass can be regulated by the rate ofN fertilizer, particularly when the lime-fiber mulch is utilized. This effixt was particularly pronounced in the highest mulch rate treatments. Apparently, increasing N-fertilizer in this situation decreases the competitive advantage held by the N-iIxing legume and leads to a higher gradlegume ratio in the mixed stand.
The yield data from 1994 indicate that the N treatment effectbecame some negative, and only the lime-fiber mulch effect continued ~ be positive and significant (Fig. 8, p < 0.01). We also detected a trend oflower 1994yields with increasing N fertilizer applied. As discussed earlier, N-fefizer had the tendency to depress legume community establishment therefore, the legume component clearly decnased with increasing N rate (Figs. 7 and 8). In a short period oftime, the N fkomthe original fertilization is lost through leaching, uptake, gaseous loss, etc.. Subsequently, those plots which lack the N-fixation capability ofthe legumes, become Ndeficient for grass production and hence their lower yields over time.
The overall plant performance respond patterns varied behveen 1993 and 1994. In 1993, there
were three performance peaks that corresponded to the high rate ofN across the three high lime-fiber mulch rates (Fig. 7). This pattern indicated that both the N fertilizer and lime-fiber mulch were playing an important role in vegetation performance. However, in 1994, the performance appeared as a stair-step

284‘1 8000

10000

n y 

# 2 8000

2000

0 

# k

N3M2 

### Treatment Figure 6. Biomass yield as influenced by lime fiber mulch and N application. N : no N fertilizer N : 112kg N ~-l; N : 224kg N ~-l; N : 33&g N ha-l; M : no sludge mulch; Ml: 112 Mg%a-1 sludge mulch; hz: 224 5 Mg ha-~sludge mulch; val~es are means (n = 3 with standard errors.

40

20

0 

# Ilii3

Total cover% 

### ,0..

- 0 .X2 t 5 Lqmw% ,p-.--a .- 

### -Q t ---e -- -. )

Treatment Figure 7. Vegetation cover% and performance evaluation in 1993. N : no N fertilizer; N : 112kg N ha-l; N2: 224kg N ha-l; N3: 336kg N ha-l; MO:no sludge mulch; Ml: 112 ~g ha-l sludge mulck; M2: 224 Mg ha-l sludge mulch. *2: POOL3: fti, 4: good; 5: exeellent. Field survey ofvegetation on Oct. 5,1993, and values are means (n=3) with standard errors shown.



### 28540

20

0 5

4
al 0 % SE

e
: 2

NOMO NtMo N2Mo N3Mo NOM, N1M1N2MI N3M1 NOM2N1M2 N2M2 N3M2 1 

### Treatment Figure 8. vegetation cover YO and performance evaluation in 1994. N.: no N fertilizay N.: 112kg N ha-l; N2: 224kg N ha-l; N3: 336kg N ha-l; MO:no sludge mulch; ha-l sludge mulch. *2: poor; 3: faiq 4: good; 5: excellent. and values are means (n=3) with standard errors shown.

pattern. The overall performance increasedstrongly with increasing mulch rate,indicating thatthe mulch contributedthe majorityofthe positive impacton vegetation performance.Itwas notablethatthe higher rateof N appmredto have a negative effect on performanceto some extent (Fig. 8). Thevegetation performancein the groupwith no lime-fibermulch (NM, N1~, Nz~, andN$Q was poor,andhadan averagegradeof 2.2. The vegetation forthe N~l

- (112 I@ id lime-fiber mulch) performedwell andits averagegradewas 3.9. TheNM groupas a whole (224 Mg ha-llime-fiber mulch) exhibited excellent vegetation performance with a grade of4.9. During the three years ofthis study (1992- 1994), the yields increased over time on the plots with Oor low rates of N fertilizer application across all lime-fiber mulch treatments (Fig. 6; seeplots ofNW, N]Iv&N&fl, NIM1,NW, N1~). Simultaneously, the yields were decreasing on plots receiving high rates of N fertilizer and no lime-fiber mulch (Groups ofNJ%, NM). This result is consistent with other studies that have shown that a single application ofN can have a major et%ct on the initial growth ofnon-leguminous vegetation but little effect on establishment ofa selfM1: 11] Mg ha-l sludge mtdch; M2: 224 Mg Field survey of vegetation on Oct. 21, 1994,

sustaining grass cover on coal waste (Davison and JefFerie$ 1%6; Bloomfield et al., 1982). Therewas no doubtthatlime-fibermulch improvedboth physical and chemical properties ofcoal refbse, supplied a better condition for plant grcm@ and led to more vigorous vegetation growth and associated higher yields over multiple seasons.

The leachate data from the lysimeters at Pine Branch suggested that with lime-fiber mulch application the pH ofthe leachates were relatively stable. The pH varied from 6.5 to 7.2 with an average of7.2, well within the range suitable for vegetative growth (Table 3) and minimal heavy metal volubility. In cent.n@ without lime-fiber mulch applicatio~ The pH ofleachates was lower (5.9) with greater variation (4.5 to 6.9). As mentioned earlier, the levels of soluble Fe, Al were controlled by p~ which in turn determined the level of available P. Lime-fiber mulch treatment reduced the concentration ofheavy metal in leachate (Table 3); Mn, Zn and Cu levels were lower and more stable than untreated controls. The improvement in leachate metal content presumably

286Table 3. Average leachateproperties under control andlime-fibermulchplots fiwmDecember, 1992to July, 1994 (n=20)

. Treatment Mean STDError Miximum Maximum OMg ha-*Mulch 5.88 0.11 4.46 6.90 pH 224 Mg ha-lMulch 7.23 0.06 6.53 7.59

0 Mg ha”lMulch 0.09 0.09 0.04 EC(S m“’) 0.16

224 Mg ha”’Mulch 0.08 0.01 0.04 0.14
0 Mg ha-iMulch 1.41 0.50 0.02 8.05 Fe(mg ~’) 224 Mg ha-lMulch 0.08 0.02 0.02 0.48

0 Mg ha-’Mulch 6.64 3.99 0.00 75.94 Al(mg ~’) 224 Mg ha-iMulch 0.11 0.02 0.00 0.34

0 Mg ha-*Mulch 1.12 0.51 0.05 9.80 Mn(mg ~’) 224 Mg ha-*Mulch 0.09 0.04 0.00 0.55

0 Mg ha”lMulch 0.47 0.27 0.00 5.19 Zn(mg ~’) 224 Mg ha-lMulch 0.04 0.02 0.00 0.48

0 Mg ha-]Mulch 0.07 0.05 0.00 1.00 Cu(mg ~1) 224 Mg ha-lMulch 0.01 0.00 0.00 0.04

0 Mg ha-lMulch 190.61 27.03 49.26 471.75 Ca(mgl-’) 224 Mg ha-’Mulch 203.24 22.33 89.07 438.50

0 Mg ha-’Mulch 210.99 43.58 49.33 861.70 S(mg k’) 224 Mg ha-iMulch 144.54 25.93 20.33 452.70

287wouldbenefit deeperwaterqualityin the reiise pile,

but the overall eiTeetofthis surficial treatment on net pile discharge desewes further study.
The specific conductance of soil leachates is proportional to ionic strength, and is increased dramatically by pyrite oxi&tion products. Conductance values may also increase due to lime and fertilizer dissolution products. Inmost cases, the EC ofleachates obswved under the lime-fiber mulch was lower than that ofcontrol overtime due to the buffering action of the lime-fiber mulch material (Table 3). The Ca levels in leachates varied from 50 to 370 mg 11(Fig. 9), while other cations ranged from O-16 mg 11for control and O-0.5 mg 1-1 for the lime-fiber mulch treatment (’Table3), respectively. Taken together with Table 3, these data indicate that Ca was the dominant cation in leachates. The solution sulfate (S) levels under lime-fiber mulch deemased with time, and were generally lower than that ofcontrols (Fig. 9). Over time, the S levels for both control and mulch treatments varied between 50 and 400 mg 11,which
was similar to that of Ca. The Ca and S rose and fell along with each other (Fig. 9); correlation coefficients (r) betsveen S and C!a

were 0.96 for both control and lime-fiber mulch, indicating that they are controlled by
a emrunon solid phase mineral, most likely a complex gypsum salt (Stewart and Daniels, 1992).

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### Date Figure 9. Leachate Ca and S in immediate surface (0.45m in depth) from January 8,1992 to July 21, 1994.

288Application ofN-fertilizer in combination

with lime-fiber mulch can greatly improve the establishment and growth ofvegetation when it is di~-seeded onto coal refuse. Nitrogen fertilizer alone improved millet establishment and gave a short-term boost to biomass production but lime-fiber applications led to even higher biomass production by btiering the soil pH and improving soil physical conditions over the long term. The combination ofNfertilizer and lime-fiber mulch resulted in the highest mixed stand vegetative cover and production in 1993, and the ratio of grass to legume was regulated by the rate ofN fertilizer. The combined mulch and fertilizer treatments produced ground covers greater than 90’% at the end ofthe second growing season. During the third growing season (1994), there was a positive effect from lime-fiber mulch coupled with a significant negative effkct of the high N-rate on vegetation due to the suppression of legumes in earlier years. Application oflime-fiber mulch onto coal rei%seis not only beneficial to revegetation objectives, but appears to improve leachate quality as well. With the application oflime-fiber mulch the leachates were higher in pH and lower in toxic metals, which could reduce the chance ofgroundwater contamination with heavy metals and moderate the impact ofdischarged waters on the environment. Surface treatment ofan entire pile with a reasonable loading rate ofthis product could efk?ctivelycharge all waters percolating through the pile surface with alkahnity. Whether or not this would have any significant impact on whole-pile discharge water quality deserves fhrther study.

In ~j the lime-fiber mulch material appears to have outstanding potential as a soil amendment for coal refuse in the ctntral Appalachians. Due to ita lime content we ako presume that this product would have great utility in treating acid-forming materials as well. From both a short and a long-term perspective, a proper combination ofN fertilizer (112 kg IM-*) with lime-fiber mulch (112 Mg hd) is recommended for the reclamation ofcoal refuse materials.

This has been a cooperative effort among Virginia Tech Mead Paper Company, and the Powell River Project. In particular, we appreciate the field assistance ofKen Roddenberry and Steve Sutphin of Westmoreland Coal Company, Dave Bryer ofMead Paper, and Ron Ails and Bany Stewart from Virginia Tech. In 1995, the Mead Kingsport papermill fhcility
was acquired by Willamette Paper.

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