Envlron. Scl. Technol. 1982, 16, 582-587
Organic Contaminants in Groundwater near an Underground Coal Gasification Site in Northeastern Wyoming Daniel H. Stuermer,* Douglas J. Ng, and Clarence J. Morris Environmental Sciences Division, Lawrence Livermore National Laboratory, University of California, Livermore, California 94550
Three groundwater samples collected near two underground coal gasification (UCG) sites 15 months after the end of gasification were analyzed for dissolved organic contaminants. The contaminants consisted of phenols, aromatic carboxylic acids, aromatic hydrocarbons, ketones, aldehydes, pyridines, quinolines, isoquinolines, and aromatic amines. Concentrations ranged up to about 50 ppm with large variations both in the relative concentrations of acidic, neutral, and basic constituents and in the concentrations of individual compounds. Naphthalene, oxylene, 2-methylpyridine, and o-cresol were consistently present in high concentrations and were identified as UCG contaminant-indicator compounds that appear to be particularly useful for monitoring purposes. A simplified method of analysis for these compounds was developed. ~~
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Introduction Underground coal gasification (UCG) is being considered as an alternative method for the extraction of energy from coal that is not feasible to mine because of economical or environmental constraints. One environmental concern associated with UCG technology is the contamination of local ground water with leachates of the residual ash that remains in the gasification cavity and with organic and inorganic vapors that escape to the surrounding underground formation. These concerns have stemmed in part from study results of large-scale UCG projects conducted in the Soviet Union during the late 1950s and early 1960s that have shown groundwater contaminants resulting from these projects to be widespread (1) and persistent (2). More recently, UCG experiments in the United States have been conducted, and groundwater contamination near these sites has also been observed. Examples include discovery of phenols in water near the Pricetown I UCG test in West Virginia (3),inorganic and organic contaminants in the ground water at two UCG experimental sites in lignite coals near Fairfield, Texas (4,5), and contamination in ground water at the Hoe Creek UCG sites in northeastern Wyoming (6-8). In both laboratory studies (9-12) and field studies (5, 7,12,13) it has been observed that sorption of contaminants on aquifer substrates is an important mechanism that acts to decrease the concentration of contaminants in groundwater over time. However, certain contaminants are not sorbed sufficiently to alleviate the concern for their transport in groundwater aquifers, and it is important to define which contaminants these are. Mattox and Humenick (5) have sampled ground water from the burn cavity at a UCG site near Fairfield, Texas, shortly after the completion of gasification and 1 year later. Their results show a decrease in organic contaminant concentration and a change in composition over this time period and suggest that phenols and low molecular weight aromatic hydrocarbons persist in solution while less soluble components such as three-, four-, and five-ring aromatic hydrocarbons are removed by sorption. We have observed a similar change in concentration and composition over time in the neutral organic contaminants in groundwater 582
Environ. Sci. Technol., Vol. 16, No. 9, 1982
from several wells near the Hoe Creek UCG experiment no. 2 (12). Our purpose here is to describe in detail the composition of organic constituents that were observed 15 months after the completion of gasification in groundwater samples from two aquifers near two different UCG experiments at the Hoe Creek site in northeastern Wyoming. The wells sampled have consistently shown the highest total organic contaminant concentration in the respective aquifers and, therefore, represent the main source for organic contaminantsthat could be transported by groundwater flow. The 15-month samples were selected because the concentration and compositional changes observed early after gasification (12) have nearly stabilized and the compositions observed are representative of samples from other contaminated wells. Studies of the concentration and compositional changes with time and distance at the Hoe Creek site for both organic and inorganic contaminants are underway; however, results of these studies will be the subject of a future publication. Descriptions of the UCG process and the Hoe Creek experiments have been previously published (14, 15).
Experimental Section The map of the Hoe Creek UCG experiment site in Figure 1shows the locations of experiment no. 1, no. 2, and no. 3 burn cavity boundaries and the position of the sampling wells. Groundwater samples were collected from two wells approximately 5 m outside the Hoe Creek experiment no. 2 burn cavity boundary; one well (WS-10) was completed in the Felix no. 1 coal seam aquifer and the other well (WS-6) was completed in the Felix no. 2 coal seam aquifer. A third water sample was collected from well W-la completed in the Felix no. 1coal seam aquifer approximately 5 m outside the Hoe Creek Experiment no. 3 burn cavity boundary. All three wells had consistently shown high organic contamination. A control sample was collected from a well (WS-14) completed in the Felix no. 1 coal seam aquifer approximately 95 m outside the Hoe Creek Experiment no. 2 burn cavity. The water samples discussed here were collected 15 months after completion of the respective UCG experiment. The samples were collected through permanent downhole centrifugal pumps after pH, redox potential (Eh), conductivity, and temperature had stabilized in the pump effluent. This procedure helped to ensure that the water sampled was representative of the aquifer (16). The water samples for organic analysis (approximately1800 mL) were filtered directly out of the wellhead through Schleicher and Schuell (Keene, NH) type 25 glass-fiber filters into precleaned 2-L glass bottles with Teflon-lined closures. The samples were preserved with 100 mL of CH2C12(Burdick and Jackson, Glendale, CA) and stored in the dark at 0-4 "C to prevent biological degradation and adsorption of organic solutes until extracted and analyzed at Lawrence Livermore National Laboratory (LLNL). At LLNL the samples were extracted and fractionated into acidic, basic, and neutral organic components (Figure
0013-936X/82/0916-0582$01.25/0
0 1982 American Chemical Society
Table I. Percent Recovery and Standard Error of Analysis of Spiked Replicate Groundwater Samplesa standard compound % recovery error 3 90 2-methylpyridineb 3 83 ethylbenzene 2 85 p-xylene 3 102 2,6-dimethylpyridine 2 85 o-xyleneb 2 101 2-ethylpyridine 2 86 n-propylbenzene 2 86 1-ethyl-3-methylbenzene 2 78 aniline 3 76 2-aminotoluene 2 30 phenol 4 66 o-cresolb 2 83 naphthalene
Hoe Creek II burn cavity
Hoe Creek I burn cavity
'-la
\()
a The concentration of spiked compounds ranged from Compounds selected as indicators 250 to 1000 ppb. for UCG contamination in groundwater in the simplified extraction procedure.
Hoe Creek Ill burn cavity
+------
Site boundary line
ZOO feet
-F
Flgure 1. Hoe Creek UCG experiment site wlth the location of Experlment no. 1, no. 2, and no. 3 burn cavity boundaries and the relathre location of wells W S 4 , WS-IO, W-la, and WS-14. Well WS-6 was completed in the Felix no. 2 coal seam aquifer while all other wells were completed In the Flex no. 1 coal seam aquifer.
11 ADJUST TO PH 1.5 2) EXTRACT 3X w i CH2C12
-+
WASH 2X w/ 0 01 N HCI 11 A D J U S T T O p H 1 2 21 EXTRACT 3X w/ CH,CI,
+EXTRACT 3X w/ 0.01 N KOH
w/ 0.01 N HCI
-+WASH -4WASH
I 1
2X w/ CH2CIZ+-
2X w/ CHzCIz+-
11 ADJUST TO PH 12 21 EXTRACT 3X w/ CHZCIZ
ti
- -
I
DISCARD
Flgure 2. Liquid-llqukl extractlon scheme for the isolation of acldlc, neutral, and basic organic constituents from groundwater samples.
2). Generally, the water (1800 mL) and solvent (100 mL) in the sample bottle were transferred to a 5-L separatory funnel, acidified to pH 1.5 with purified HC1, and extracted with CH2C12(three times with 100 mL each) to obtain the acidic and neutral compounds. The water was then adjusted to pH 12.5 with purified KOH and extracted with CHZCl2(three times with 100 mL each) to obtain the basic compounds. The acidic compounds were recovered from the acid-neutral extract by back extracting with aqueous 0.01 N KOH (three times with a 1:l solvent ratio) and then adjusting the pH of the solution to 1.5 with HC1 and extracting with CH2CI2(three times with a 1:l solvent ratio).
The actual scheme, shown in Figure 2, is more complex because back extraction of the individual fractions is required to obtain sufficient purity for detailed chemical characterization. The individual fractions were concentrated to an appropriate volume by rotary evaporation (15 "C) followed by evaporation under a stream of cold, pure nitrogen. Care was taken to avoid concentration of the sample to dryness and the consequent loss of volatile constituents. The samples were analyzed without derivatization directly by gas chromatography with a Hewlett-Packard Model 5880 gas chromatograph equipped with a capillary injector system at 270 OC and a flame ionization detector (FID) at 280 "C. The column was an SP2100 fused-silica, wall-coated open tubular (WCOT) column 0.25 mm in diameter and 25 m long. The column oven was held at 35 OC for 5 min, temperature programmed at 3 "C/min to 260 "C, and then held at that temperature for 20 min. The data were collected, integrated, and calculated on a Hewlett-packard Model 3350 laboratory automation system. Concentrations of individual compounds were determined by using response factors obtained by injection of standards of the same compound class. Compounds were identified by combined gas chromatography and mass spectrometry (GC-MS) on a Hewlett-Packard Model 5985 GC-MS system. Gas chromatography columns and conditions were identical with those described above. Individual structures were determined by comparison of mass spectra obtained by 70-eV electron impact and gas chromatography retention times with those of standard compounds. Three replicate filtered samples from well WS-14 that contained none of the standard compounds were spiked with a standard mixture of acidic, basic, and neutral compounds at concentrations of 250-1000 ppb each. The samples were extracted by following the scheme in Figure 2. The recovery of the standard compound and the standard error is presented in Table I. The precision based on these values is 7% or less, and the recovery ranges from approximately 30% for phenol to 100% for the alkylpyridines. The methyl substitution on phenol (i.e., o-cresol) has a marked affect on recovery, increasing the value to 65%. For this reason, o-cresol instead of phenol was chosen in the simplified extraction scheme as an indicator compound for the presence of UCG contaminants in groundwater. A simplified method was developed for monitoring purposes and compared to the rather complex extraction Envlron. Sci. Technol., Vol. 16, No. 9, 1982
583
,c T # m e i m # n0l
10
20
30
40
50
T m- Irr n
0
Temp1 Cl 35
35
80
125
110
Flgure 3. Oas chromatogram of the acidic constltuents Isolated from well WS-10. Peak numbers refer to the compounds identified In Table 11.
Tern0
10
20
30
40
50
C 35
35
80
125
170
Flgure 5. Gas chromatogram of the basic constituents isolated from well 1-A. Peak numbers refer to the compounds identified in Table IV.
Table 11. Acidic Compounds Identified in Groundwater Samples concentration, ppb peak no.
Time I m n / 0
Tempi
Cl 35
10
35
40
20
50
80
125
170
Flgure 4. Gas chromatogram of the neutral constituents isolated from well WS-6. Peak numbers refer to the compounds aentlfled in Table 111.
scheme described above. The water sample (1800 mL) was adjusted to pH 8.4-8.6 by the addition of saturated aqueous sodium bicarbonate and liquid-liquid extracted with CHzClz(three times with 100 mL each). An internal standard of 1-chloronaphthalene was added, and the extract was concentrated and then analyzed by either gas chromatography or GC-MS. The gas chromatography analysis provided either estimation of the total extractable organic compounds present by using an average FID response factor or, if sufficient resolution was obtained, estimation of specific organic compound concentrations. The GC-MS analysis allowed estimation of specific compounds even in poorly resolved mixtures by integration of specific characteristic fragment ions. This technique could be used for quantitative concentration determination of specific compounds by spiking the water sample with deuterated isomers of the compounds of interest prior to extraction and analysis by GC-MS. However, we have used this technique only as a qualitative tool to be followed by more detailed analyses of certain samples of special interest. Results and Discussion Exemplary gas chromatograms of the acidic, neutral, and basic components isolated from groundwater are presented in Figures 3-5, respectively. The peak numbers refer to peak identities in Tables 11-IV, respectively. Ambiguous determinations of isomers are indicated either by not specifying the position of alkyl substituents or by giving the known information followed by the word isomer. These tables also present quantitative information on the concentration of the compounds in all three wells. None of these compounds was observed in the control sample (WS-14) above the 0.5-ppb detection limit. 584
Envlron. Scl. Technol., Vol. 16, No. 9, 1982
compound
well well well WS-6 WS-10 W-la
1 phenol 6.5 10200 870 2 o-cresol 63 6600 950 9.6 16000 1300 3 m- and p-cresol 4 2-ethylphenol 20 1100 130 29 5 dimethylphenol isomer 3200 330 6 3-ethylphenol 9.1 3100 280 22 7 dimethylphenol isomer 560 220 780 63 8 3,4-dimethylphenol 7.1 0.5 26 NDa 9 C,-phenol isomer 10 C,-phenol isomer 1.5 53 8 11 C,-phenol isomer 2.0 56 12 1 2 C,-phenol isomer 2.0 ND 9 3.8 130 ND 1 3 C,-phenol isomer 23 7.0 110 1 4 C,-phenol isomer 130 34 1 5 C,-phenol isomer 0.5 1 6 methylethylphenol isomer 1.5 59 ND 16 860 320 17 benzoic acid 1 8 methylethylphenol isomer 4.3 150 12 5.6 320 17 1 9 dimethylbenzaldehyde isomer 14 490 41 20 toluic acid isomer 7.4 64 24 21 dimethylbenzaldehyde isomer 4 1.8 110 22 dimethylacetophenone isomer total of reported compounds 234.2 44098 4647 20 4 detection limit for analysis 0.3 Compound not detected. ~
The acidic compounds observed in the three wells are a rather simple mixture of phenols with minor amounts of aromatic carboxylic acids, aldehydes, and ketones (Table 11). Both the total concentration of acids and the relative concentrations of individual compounds are extremely variable, but the same components are present in all samples. The neutral compounds consist mainly of alkyl-substituted benzenes, indans, and naphthalenes with smaller amounts of ketones, thiophenes, and furans (Table 111). The total concentration of neutral compounds in the three water samples ranges only from 5300 to 9000 ppb, a surprisingly narrow range compared to an approximately 200-fold range for the acidic components. In addition, the relative concentrations of individual components in these mixtures are more consistent than that of the acidic constituents. The basic fraction consists almost entirely of alkylsubstituted pyridines, quinolines, and isoquinolines with small amounts of aniline isomers (Table IV). Very low concentrations of basic compounds were observed in well WS-6 in comparison to wells WS-10 and W-la. It appears
Table 111. Neutral Compounds Identified in Groundwater Samples concentration, ppb peak well well well no. compound WS-6 WS-10 W-la 1 methylpentanone isomer 2 hexanone isomer 3 toluene 4 cyclopentanone 5 mixture (2-methylthiophene t 3-hexanone) 6 hexanone isomer 7 2-methylcyclopentanone 8 3-methylcyclopentanone 9 ethylbenzene 10 m- and p-xylene 11 dimethylthiophene isomer 1 2 dimethylcyclopentanone isomer 1 3 dimethylthiophene isomer 1 4 o-xylene 1 5 isopropylbenzene 1 6 n-propylbenzene 17 trithiapentane isomer (C,H,S,) 18 1-eth yl-3-met h yl benzene 1 9 1-ethyl-4-methylbenzene 20 C,-thiophene isomer 21 1,3,5-trimethylbenzene 22 C,-thiophene isomer 23 1-ethyl-2-methylbenzene 24 trimethylthiophene isomer 25 C,-benzene isomer 26 C,-benzene isomer 27 1,2,4-trimethylbenzene 28 C,-benzene isomer 29 trimethylthiophene isomer 30 1,2,3-trimethylbenzene 3 1 indan 32 indene 33 diethylbenzene isomer 34 methylpropylbenzene isomer 35 n-butylbenzene 36 dimethylethylbenzene isomer 37 methylpropylbenzene isomer 3 8 diethylthiophene isomer 39 C,-benzene isomer 40 dimethylethylbenzene isomer 41 dimethylbenzene isomer 42 methylbenzofuran isomer 43 C,-benzene isomer 44 dimethylethylbenzene isomer 45 tetramethylbenzene isomer 46 C,-benzene isomer 47 methylindan isomer 48 methylindan isomer 49 tetramethylbenzene isomer 50 naphthalene 51 benzothiophene 52 dimethylindan isomer 53 dimethylindan isomer 54 dimethylindan isomer 55 dimethylbenzofuran isomer 56 C,-benzene isomer 57 dimethylindan isomer 58 2-methylnaphthalene 59 1-methylnaphthalene 60 biphenyl 61 1-ethylnaphthalene 62 dimethylnaphthalene isomer 6 3 dimethylnaphthalene isomer 64 dimethylnaphthalene isomer 6 5 dimethylnaphthalene isomer 66 2-ethylnaphthalene 67 acenaphthene 6 8 dibenzofuran isomer 69 pentamethylindan isomer 70 trimethylnaphthalene isomer 71 fluorene 72 trimethylnaphthalene isomer total reported compounds detection limit for analysis a Compound not detected.
10 21 420 13 NDa
37 67 170 180 29
21 66 740 37 23
ND 12 8 400 830 29 ND 36 590 27 87 ND 250 140 27 88 13 220 26 ND ND 460 ND 21 450 400 190 29 28 47 42 33 ND 150 49 41 30 190 20 43 9 110 260 160 1800 63 41 31 44 22 23 52 3 20 210 43 29 56 31 52 27 22 25 17 14 18 15 17 8981 5
41 230 110 92 240 60 26 53 260 59 160 19 45 31 23 14 17 61 53 18 70 88 47 9 110 430 100 110 34 27 15 12 110 52 29 56 16 74 20 43 24 87 120 75 740 50 25 18 20 10 12 30 130 97 25 17 38 20 46 23 27 39 25 16 19 18 18 5316 5
22 66 31 250 440 34 10 45 360 19 70 28 140 110 27 59 13 150 24 ND ND 300 ND 17 280 240 36 29 39 51 36 27 33 54 42 33 11 72 15 30 19 110 110 84 380 28 29 24 32 32 23 65 130 82 27 17 30 36 33 22 21 15 10 10 17 8
12 5536 5
Table IV. Basic Compounds Identified in Groundwater Samples concentration, ppb well well well peak W-la WS-6 ws-10 no. compound 49 0.82 53 1 pyridine 57 0.88 6 1 2 2-methylpyridine 34 0.69 51 3 3- and 4-methylpyridine 20 0.10 14 4 2,6-dimethylpyridine 11 7.1 0.34 5 2-ethylpyridine 12 9.6 0.24 6 2,4-dimethylpyridine 3.5 2.9 0.03 7 dimethylpyridine isomer 7.5 0.18 10 8 3-ethylpyridine 1.6 1.6 NDa 9 4-ethylpyridine 7.0 0.03 2.9 1 0 2-methyl-6-ethylpyridine 1.4 1.1 ND 11 3,5-dimethylpyridine 36 ND 1 2 aniline 0.35 1.8 0.06 1 3 C,-pyridine isomer 1.0 1.3 ND 1 4 C,-pyridine isomer 1.1 1.3 0.02 1 5 C,-pyridine isomer 0.84 0.78 ND 1 6 C,-pyridine isomer 0.37 ND 1.5 17 C,-pyridine isomer 1.0 0.24 18 C,-pyridine isomer 1.2 1.2 0.03 1.5 1 9 C,-pyridine isomer 0.52 0.66 0.03 20 C,-pyridine isomer ND ND 1.2 21 C,-pyridine isomer 0.22 ND 0.75 22 C,-pyridine isomer 0.47 2.3 0.06 23 C,-pyridine isomer 0.9 24 C,-pyridine isomer 1.7 0.06 0.3 0.05 25 C,-pyridine isomer 0.97 0.37 1.4 0.06 26 0-and p-toluidine 9.2 27 m-toluidine 3.3 1.5 ND 28 C,H,,N isomer 0.49 ND 11 29 C,- and C,-pyridine isomers ND 1.9 0.73 30 tetrahydroquinoline isomer ND 1.1 1.1 31 methyltetrahydroquinoline ND 2.0 5.6 isomer 32 methyltetrahydroquinoline ND ND 3.0 isomer 3 3 methyltetrahydroquinoline ND ND 1.9 isomer 34 C,H,N isomer ND 2.0 1.8 3 5 quinoline and isoquinoline 0.45 7.1 14 36 methylquinoline isomer 0.17 0.2 2.8 37 methylquinoline isomer 0.48 8.0 0.2 38 methylquinoline isomer 0.4 1.7 0.15 39 methylquinoline isomer ND 1.4 0.12 40 dimethylquinoline isomer 0.13 1.2 1.7 41 dimethylquinoline isomer ND 0.12 2.0 total reported compounds 5.54 240.98 327.56 detection limit for analysis 0.02 0.5 0.2 a Compound not detected.
that many of the same basic compounds are present in all three samples although several of the peaks identified in wells WS-10 and W-la are below the detection limit or absent in well WS-6. The fact that many of the same compounds are observed in all three water samples suggests that the composition is controlled by partitioning of organic compounds between the water and the aquifer substrate. We and others (5) have analyzed tar samples collected from process streams during the UCG experiments and find them to contain much more complex mixtures of organic constituents with a much greater molecular weight range than the groundwater samples. The pyrolysis products that are deposited in the aquifers are probably of similar nature to the tars observed in the process stream. Our data on the composition of neutral compounds in the groundwater collected shortly after gasification show a much more complex mixture than is observed at 15 months (12). However, it appears that only those compounds that are sufficiently water soluble and not strongly sorbed are observed in the Envlron. Scl. Technol., Vol. 16,No. 9, 1982 585
ground water after 15 months. It is interesting to note the striking similarity between the composition of the neutral fraction of these groundwater samples and that of water equilibrated with petroleum (17, 18), again suggesting water solubility and partitioning as the controlling mechanism. The reasons for the wide variation both in the relative amounts of acidic, neutral, and basic compounds and in the relative composition of the same fraction in different water samples are not clear. Variations in process conditions, aquifer substrate composition, or groundwater flow patterns may all contribute to differences in the composition of the deposited contaminants. Biological degradation may also play a role in altering the composition of the organic contaminants in the groundwater. Although there are variations in both total and relative concentrations of these contaminants in the various aquifers, we feel that the principal constituents of our samples, which have had 15 months to stabilize since deposition, may be of long-term environmental concern. The compounds observed in these samples may be the contaminants of aquifers in the vicinity of not only this but perhaps other UCG sites. We therefore developed a comparatively rapid analytical scheme based on our findings of the composition of contaminants in these groundwater samples. The indicator compounds that we selected are naphthalene, o-xylene, 2-methylpyridine, and o-cresol because (1)they are always present in the samples as major constituents, (2) they are normally well resolved in the gas chromatograms, and (3) they are, therefore, more easily quantitated. Since the pK, of o-cresol is 10.2 and the pKb for 2-methylpyridineis 5.97, liquid-liquid extraction at pH 8.6 (bicarbonate buffer) will allow efficient extraction of both these compounds as well as the aromatic hydrocarbons o-xylene and naphthalene. The addition of an internal standard (such as 1-chloronaphthalene used here) allows convenient calculation of concentration using relative response factors. We compared the concentration values for these four indicator compounds obtained by the acid-base-neutral fractionation scheme and the direct bicarbonate extraction scheme both by FID gas chromatography and GC-MS analysis. Integration of single ion chromatograms in GCMS can provide an advantage in distinguishing specific compounds in more complex mixtures. Molecular ion traces were used in this comparison. Agreement in quantitation between the two extraction schemes was 19% or better for all compounds by both gas chromatography and GC-MS analysis. The time savings is over 5-fold for the bicarbonate extraction scheme followed by either gas chromatography or GC-MS analysis. Several other compounds could be quantitated by using the simplified extraction scheme, although obtaining pure mass spectra for positive identification of most constituents will still require acidbase-neutral separation because of the complex composition of the sample.
Conclusions We have identified 135 compounds produced by UCG activities that have persisted in the local groundwater for 15 months. These compounds consist of aromatic acidic, neutral, and basic compounds of low molecular weight that probably represent the water-soluble component of a more complex organic mixture deposited in the aquifer. We have identified a few compounds that can be used as indicators of UCG contamination in monitoring operations and have developed and tested a rather simple procedure 586
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for extraction and analysis of these compounds.
Acknowledgments We are pleased to acknowledge the continued support and cooperation provided by Warren Mead and Francis Wang. Darrel Gravis provided important contributions to our field sampling efforts. Support is provided by the Division of Health and Environmental Research (DOE/ ASEV).
Literature Cited (1) Klimentov, P. P. Izv. Vyssh. Uchebn. Zaved., Geol. Razved. 1963, 4, 106-19. (2) Kononov, V. I. In “Gidrogeotermicheskie Usloviia Verkhnikh Chastei Zemnoi Kory”; Akademiia Nauk SSSR, Geologicheskii Institut, Moscow, 1964; UCRL-Trans-10812, pp 35-51. (3) Werner, E.; Rauch, H. W.; Eli, R. N.; Gillmore, D. W. “Some Environmental Effects of the Pricetown I Underground Coal Gasification Test in West Virginia, U.S.A.”; Proceedings of the 6th Underground Coal Conversion Symposium, Afton, OK, 1980; pp V20-V32. (4) Humenick, M. J.; Mattox, C. F. Water Res. 1978,12,463-69. (5) Mattox, C. F.; Humenick, M. J. In Situ 1980, 4, 129-51. (6) Mead, S. W.; Wang, F. T.; Stuermer, D. H.; Raber, E.; Ganow, H. C.; Stone, R. “Implications of Ground-Water Measurements at the Hoe Creek UCG Site in Northeastern Wyoming”; Lawrence Livermore National Laboratory, Livermore, CA, 1980; UCRL-84083. (7) Mead, S. W.; Wang, F. T.; Stuermer, D. H. “Ground-Water Effects of the UCG Experiments a t the Hoe Creek Site in Northeastern Wyoming”; Lawrence Livermore National Laboratory, Livermore, CA, 1981; UCRL-85468. (8) Campbell, J. H.; Pellizzari, E.; Santor, S. “Results of a Groundwater Quality Study Near an Underground Coal Gasification Experiment (Hoe Creek I)”; Lawrence Livermore Laboratory, Livermore, CA, 1978; UCRL-52404. (9) Henry, J. F.; Mckinley, M. D. “Groundwater Contamination from In-Situ Coal Gasification: Laboratory Studies”; Proceedings of the 2nd Annual Coal Gasification Symposium, Lakeview Inn and Country Club, Morgantown, WV, 1976; pp 105-18. (10) Humenick, M. J.; Novak, A. E. In Situ 1978, 4, 329-52. (11) Wang, F. T. “The Sorptive Property of Coal”; Proceedings of the 5th Underground Coal Conversion Symposium, Alexandria, VA, 1979; pp 403-7. (12) Stuermer, D. H.; Ng, D. J.; Morris, C. J.; Cotton, A. “Distribution of Neutral Organic Reaction By-products in the Groundwater at an Underground Coal Gasification Site”; Lawrence Livermore Laboratory, Livermore, CA, 1979; UCRL-52847. (13) Drever, J. I.; McKee, C. R. In Situ 1980,4, 181-206. (14) Aiman, W. R.; Thorsness, C. B.; Hill, R. W.; Rozsa, R. B.; Cena, R. J.; Gregg, D. W.; Stephens, D. R. “The Hoe Creek I1 Field Experiment on Underground Coal Gasification, Preliminary Results”; Lawrence Livermore Laboratory, Livermore, CA, 1978; UCRL-80592. (15) Hill, R. W.; Thorsness, C. B.; Cena, R. J.; Aiman, W. R.; Stephens, D. R. Proceedings of the 6th Annual Underground Coal Conversion Symposium, 1980; pp 46-57. (16) Gravis, D. G.; Stuermer, D. H . Water Res. 1980,14,1525-7. (17) Stuermer, D. H.; Spies, R. B.; Davis, P. H. Mar. Environ. Res. 1981, 5 , 275-86. (18) Zurcher, F.; Thuer, M. Environ. Sci. Technol. 1978 12, 838-43.
Received for review October 13, 1981. Revised manuscript received May 3, 1982. Accepted May 21, 1982. Work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. This document was prepared as a n account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees makes any warranty,
Environ. Sci. Technol. 1982, 16, 587-593
express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise does not neces-
sarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the Univeristy of California. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government thereof and shall not be used for advertising or product endorsement purposes.
Laboratory Study of Sulfuric Acid Spill Characteristics Pertaining to Maritime Accidents Ignatlus N. Tang," Wing T. Wong,f and Harry R. Munkelwitz Department of Energy and Environment, Brookhaven National Laboratory, Upton, New York 11973
Michael F. Flessner United States Coast Guard, Department of Transportation, Washington, D.C. 20590
Concentrated sulfuric acid and oleums are routinely transported in bulk quantities on U.S. and international waterways. It is conceivable that, in the event of an accident, an acid spill could occur with consequences detrimental to both man and the environment. In the present paper, several acid-spill scenarios are briefly described, and the results from laboratory experiments designed to simulate the two most important types of acidspill accidents are reported. In the first case, the convective mixing of concentrated sulfuric acid with water is shown to be governed by the buoyancy force arising from changes in acid concentration and released heat of dilution. In the second case, experiments with oleums have resulted in the formation of dense clouds of acid aerosols well within the respirable particle size range. Introduction Concentrated sulfuric acid and oleum are among the most potentially hazardous chemicals routinely transported in bulk quantities on US.and international waterways. Although these chemicals are normally contained in cargo compartments sealed against gas and water leakage, the rupture of one or more of these compartments during a marine accident could conceivably bring about the abrupt release of tons of acid into water. The large amount of heat generated from acid-water mixing could cause both water and the absorbed sulfur trioxide in oleum to vaporize, thus forming an acid mist in the atmosphere. This acid mist would pose an immediate danger to anyone directly involved in the accident and, under adverse meteorological conditions, even threaten the safety of the nearby public as well. Furthermore, depending upon the magnitude and location of a specific spill, the water temperature and acidity could be significantly altered long enough to destroy marine life in the release vicinity. There have been, in the past, several documented marine accidents involving sulfuric acid cargo vessels. The most recent acid-spill accident, known as the case of the MT Big Mama ( l ) ,occurred at dawn on August 18, 1976. A tank barge loaded with approximately 1060 tons of 20% oleum capsized while being towed in the lower Chesapeake Bay. All of the cargo was lost into the Bay during a time period of 30-60 min. The towboat personnel later recalled that they observed a tremendous reaction under the capsized barge, which produced great quantities of steam and Present address: New Jersey Institute of Technology, Department of Chemical Engineering and Chemistry, Newark, NJ 07102. 0013-936X/82/0916-0587$01.25/0
vapor. In fact, it was noted that the barge itself was lifted 4 f t upward in the water for an estimated 30 min before sinking. Fortunately, the accident took place in a remote deep-water region of the Bay and no apparent damage was reported except for a rather extensive but localized fish kill sighted by the first Coast Guard boat crew arriving on the scene. In the present paper, several acid-spill scenarios are briefly described. The results from laboratory experiments designed to simulate two different types of acid spill accidents are presented. The first series of experiments deal with the convective mixing of concentrated sulfuric acid released instantaneously into still water. A mathematical model is developed that adequately describes the dispersion of the acid mass as a function of time and distance. Since dimensionless parameters are used, the model is suitable, in principle, for predicting the consequences of large-scale acid-spill accidents. The second series of experiments were designed to measure the quantities of sulfuric acid aerosols that could become airborne during instantaneous surface spills of oleum. The particle-size distributions of the acid aerosols formed in the spill experiments were also determined. Sulfuric Acid Spill Scenarios For simplicity in describing the acid-spill scenarios, the following two broad classes of accidents are considered: class I, accidents during which no appreciable amount of acid aerosols are produced; class 11, accidents in which the major safety hazards are associated with acid aerosol formation. In all cases, of course, a large amount of heat is liberated from acid-water mixing, especially during the very early stage of the spill. Thus, the class I accidents involve only the convective mixing of acid with water, resulting from either a quick discharge of concentrated sulfuric acid into deep water, such as might be the case of a capsized barge with all hatches blown open, or a gradual leak through a hole of finite size developed, say, in a minor collision mishap. The third possibility is the spill of an oleum cargo well underwater as in the case of the MT Big Mama described above. In all cases, the released acid mass tends to sink quickly in water because of the high density of the acid. Vigorous turbulent mixing takes place over the advancing front, resulting in entrainment of the ambient fluid. The acid-containing region initially grows extremely fast by this entrainment process. As the volume becomes larger and the density differences smaller, the advancing speed of the acid mass as a whole slows down accordingly.
0 1982 American Chemical Society
Environ. Sci. Technoi., Vol. 16, No. 9, 1982
587
