(4) Anderson, R. V., Bull. Enuiron. Contam. Toxicol., 18, 492 (1977). (5) Manly, R., George, W. O., Enuiron. Pollut., 14,139 (1977). (6)Mathias, J., Cummings, T. C., J . Water Pollut. Control Fed., 45, 1573 (1973). ( 7 ) Foster, R. B., Bates, J. M., Enciron. Sei. Technol., 12, 1958 (1978). (8) Heit, M., Tan, Y. L., USDOE Report, Environmental Quarterly EML-353, New York, 1979. (9) Braunstein, H. M., Copenhaver, E. D., Pfuderer, H. A,, ORNL Report FIS-95, 1977. (10) Williams, S. L., Aulenbach, D. B., Clesceri, N. L., Proceedings of Conference 750929, USERDA Report 42, 1977. (11) Smith, R. M., Doctoral Thesis, Rensselaer Polytechnic Institute, Troy, N.Y., 1977. (12) Gogolak, C. V., Miller, K. M., USDOE Report EML-332, New York, 1977. (13) Leland. H. V., Luoam, S. N., Wilkes, D. J., J . Water Pollut.
Control Fed., 50, 1469 (1978). (14) Heit, M., USERDA Report HASL-320, New York. 1977. (15) Bertine, K. K., Goldberg, E. D., Science, 173, 223 (1971). (16) Frost, D. V., Fpd. Proc., Fed. A m . Soc. Exp. Biol., 26, 208 (1967). (17) Peterson, P. J., Butron, M. A. S., Gregson, M. G., Nye, S.M., Porter, E. K., in “Proceedings Trace Substances in Environmental Health X”, Columbia, Mo., 1976. (18) Hart, C. W., Fuller, S. L. A , , “Pollution Ecology of Freshwater Invertebrates”, Academic Press, New York, 1974, Chapter 8, pp 215-57, (19) National Academy of Sciences. “Particulate Polycyclic Organic Matter”, Washington, D.C., 1972, Chapter 2, pp 4-12. (20) Rose, F. L., Harshberger, J. C., Science, 198,1280 (1977). (21) Harley, J . H., USERDA Report HASL-300, New York. updated annually, 1972. Receiued for reuieu Octobpr 1, 1979. Accepted January 22, 1980.
NOTES
Coal Tar Coatings of Storage Tanks. A Source of Contamination of the Potable Water Supply Katherine Alben Environmental Health Center, Division of Laboratories and Research, New York State Department of Health, Albany, N.Y. 12201
Samples of water exposed to surfaces coated with a commercial coal tar have been analyzed for polycyclic aromatic hydrocarbons by gas chromatography-mass spectrometry. Concentrations of representative compounds total several hundred micrograms per liter in leachate from test panels freshly coated with coal tar and tenths of a microgram per liter in leachate from a 5-year-old storage tank coated with the same material. Coal tar is a complex mixture of polycyclic aromatic hydrocarbons (PAH), which includes a number of toxic substances listed as priority pollutants by the Environmental Protection Agency (11. These compounds are ubiquitous at low levels in the human environment. Concern for their presence in waste effluents is partially motivated by the desire t o limit contamination of drinking water. However, such reasoning is in conflict with the accepted use of coal tar to prevent corrosion in water distribution systems. In New York State, coal tar is commonly applied to steel storage tanks and to cement-lined ductile iron,pipes used in water distribution (2).T o determine the potential for contamination of water by commercial coal tar materials, samples of water exposed to coal tar coated surfaces have been analyzed by gas chromatography-mass spectrometry (GC-MS). Thus, this paper focuses on a specific aspect of water contamination during the process of supply and distribution, which is currently under scrutiny ( 3 ) .
Experimental Samples. Two types of samples were taken for analysis. Forty-liter field samples were collected in duplicate at the inlet a n d outlet of a 12 000-gal (45 400 L) storage tank. The tank interior had a commercial coal tar coating which was 5 years old but which still appeared in good condition. Similarly, 40-L laboratory samples were prepared from tap water exposed to test panels coated with the same coal tar as used on the storage tank. Blank t a p water samples were run as a control. T h e test panels were prepared according to the manufacturer’s specifications: cold rolled steel was sand blasted to remove mill scale, cleaned in distilled water followed 468
Environmental Science & Technology
by acetone to remove dirt and grease, given one coat of the manufacturer’s surface primer, dip coated in coal tar a t 240 “C, and cured by drying in open air for 1week. The test panels were then immersed in tap water a t room temperature. The ratio of volume to panel surface area was 4 gal/ft2 (160 L/m2), a value representative of storage tanks in New York State. After immersion for 1week, the test panels were removed. Procedures. Neutral organic compounds were extracted from the water samples by adsorption on a lipophilic resin, XAD-2, which has been shown to adsorb neutral organic compounds from water with high efficiency ( 4 ) . The XAD resin was precleaned by extraction in a Soxhlet apparatus with acetone, methanol, and dichloromethane for several days each. T h e water sample was pumped through a 1-pm glass fiber filter t o remove particulates and then through a column of XAD-2 resin (1.2 cm X 10 cm long). Masterflex peristaltic pumps were used to control the flow rate at 80 mL/min. After extraction, three 10-mL volumes of dichloromethane were used to elute organics adsorbed on the resin; the solvent extract was dried with sodium sulfate and concentrated, first in a Kuderna-Danish apparatus attached to a Snyder column, then in a stream of dry nitrogen. For confirmation, duplicate water samples from the storage tank were also extracted by liquid-liquid partitioning. T h e water samples were mixed overnight with 2 L of dichloromethane, and then set in a cold room a t 5 “C while the layers separated; the solvent extract was concentrated in the same manner as described for the XAD-2 solvent extract. Apparatus. Experimental data were taken using two different GC-MS systems: An AEI MS-30 double beam instrument with electrostatic and magnetic focusing, operated a t a resolution of 1000, was scanned from 30 to 600 amu every 5 s. The i n s t r u m p t was interfaced by a membrane (200 “C) to a 1.8m X 3 mm i.d. glass column packed with 3% SP 2250. The column was programmed from 40 “C (5 min) to 250 “C (30 min) a t 6 “C/ min. A Finnigan 4000 electric quadrupole, operated a t unit mass separation, was scanned from 45 to 600 amu every 2 s. T h e instrument was interfaced by a jet separator (250 “C) to a 30 m X 0.3 mm i.d. SF-96glass capillary column. The column
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@ 1980 American Chemical Society
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~
Table 1. Integrated MS Peak Areas for Compounds Identified in Storage Tank Samples ion abundance compound
base peak
influent
effluent
effluentlinfluent
naphthalene 2-methylnaphthaler~e 1-methylnaphthalene dimethylnaphthalenes fluorene phenanthrene, anthracene f luoranthene pyrene benz[ alanthracene, chrysene, triphenylene
128 142 142 156 166 178 202 202 228
36 572 12 013 9 213 15 377 14 916 111 794 18 105 4 422
250 582 53 624 35 350 61 574 300 645 1 208 920 427 254 121 955 20 346
6.8 4.5 3.8 4.0 20 11 23 28
Table II. Concentrations of Polycyclic Aromatic Hydrocarbons Found in Leachate Samples compound
166 I56
.. ..
142 I28
n
200
400
600
1
800
1000
Before storage
Ii, w - - 7 - - Y v -
2 00
400
6:40
13:20
600 2O:OO
,. 1000
26:40
33:20
0.004
0.025
0.001 0.019 0.003
0.021 0.210 0.081
0.002 -
0.071
0.029
0.41
56 27 22 13 29 125 27 29 328
1200 SCAN tank
MASS
RIC
800
naphthalene 2-methylnaphthalene 1-methylnaphthalene dimethy.lnaphthalene fluorene phenanthrene, anthracene fluoranthene pyrene total
concentrations, pglL storage tank influent effluent test panels
,A
I
1200 SCAN 40:OO TIME
Figure 1. XAD-2 extracts of water samples taken before and after the storage tank. Parent ion mass chromatograms are: naphthalene, 128; methylnaphthalenes, 142; dimethylnaphthalenes, 156; fluorene, 166; phenanthrene and anthracene combined, 178; fluoranthene and pyrene, 202; benz[ alanthracene, chrysene, and triphenylene combined, 228; internal standard at 23.20 min is diisobutyl phthalate
was programmed from 40 "C (2 min) to 200 "C (30 min) a t 6 'C/min. Both systems are linked to a Nova 3 computer for acquisition and processing of data.
Results a n d Discussion Typical results obtained by GC-MS analysis of the storage tank samples are shown in Figure 1, for data acquired on the Finnigan 4000 system. A number of PAHs are found; their peak areas, taken from the parent ion mass chromatograms, are tabulated in Table I. Concentrations of specific PAH compounds in storage tank effluent are increased 5 to 30 times, compared to the influent. Essentially the same results are obtained for storage tank samples extracted by lipophilic adsorption and liquid-liquid partitioning. GC-MS analyses of the leachate from the test panels reveal higher levels of PAH
contamination (negligible levels were found in the blank controls). Concentrations of specific compounds found in the leachate from the test panels are given in Table 11, together with values calculated for the storage tank samples. As part of this experiment, the particulates collected on the 1-Fm filter were also extracted in a Soxhlet apparatus using dichloromethane. Although parent PAHs were found in the particulate extract, their concentrations were more than 1000-fold lower than in the XAD-2 extract. Since the bulk of the contaminants found were extracted by adsorption on a macroreticular resin, they are thought to be physically dissolved in the water, rather than suspended as particulates, which would be collected by filtration. The qualitative composition of leachate samples from the storage tank and the test panels reflects the composition of the commercial coal tar and is affected to a lesser extent by the solubilities of individual compounds. Concentrations of the compounds found in both leachate samples are noted to be well below their solubilities in water ( 5 ) .Concentrations of PAHs extracted from the commercial coal tar in a Soxhlet apparatus using dichloromethane are given in Table 111. Whether in the coal tar or leachate samples, the most abundant compound is typically phenanthrene; its isomer anthracene is not resolved, but is considered to be a minor constituent based on the relative solubilities of the two compounds and analyses of coal tar reported in the literature ( 5 , 6). Relative to phenanthrene, the other PAHs are less abundant. However, the composition of the leachate from the test panels is weighted in favor of the more soluble compounds naphthalene and fluorene, whereas the leachate from the storage tank is biased in favor of the less soluble compounds fluoranthene and pyrene. This means that with continued exposure the coal tar surface becomes comparatively depleted in the more water-soluble compounds. Correspondingly, leachate from aged surfaces is enriched in the less water-soluble compounds. The large amounts of specific PAHs (several hundred miVolume 14, Number 4, April 1980
469
Table 111. Concentrations of Polycyclic Aromatic Hydrocarbons Found in Commercial Coal Tar concn, mg/g
compound
naphthalene fluorene phenanthrene, anthracene fluoranthene pyrene
0.15 1.2
25 20 19
~~
crograms per liter total) found in the leachate from the test panels, compared to the small amounts (tenths of a microgram per liter) found in the leachate from the storage tank, are also interpreted to indicate the difference in age and exposure of the coal tar surfaces. Residence time for storage tank samples a t the time of collection is estimated to have been about 1 day, compared to 7 days for the test panels. In conclusion, PAHs from commercial coal tar coatings of storage tanks can leach into the water supply, which was the main purpose of this study. These results corroborate analyses by the EPA of leachate trom a storage tank in Pascagoula, Miss. ( 7 ) .However. little information on this subject is found in the literature. Only one of the compounds discussed in this paper. fluoranthene, is among the six PAHs designated by the World Health OrganiLation t o indicate a health hazard from contamination of drinking water: 0.2 pg/L is t h e maximum recommended total concentration for these six PAHs in drinking water (8).With respect to this proposed standard, the levels of fluoranthene and other compounds reported are considered significant. However, all of these compounds are generally acknowledged to have low or negligible carcinogenic activity. No conclusion can be made concerning levels of other PAHs of toxicological interest not reported in this paper, for want of standards to optimize recoveries and GC-MS conditions a t the time of analysis. The diversity of PAHs encoun-
tered in coal tar leachate and the effects of chlorination will be discussed in a subsequent paper (9). The appropriate use of materials such as coal tar in the water supply system is brought to question. The PAH compounds found in leachate samples may in part account for increased mutagenicity levels associated with water distribution ( I O ) . However, a more complete chemical analysis is needed for a representative number of distribution systems, differing in age and design. Hopefully, the results presented in this paper will encourage the acquisition of an adequate data base to fully evaluate the potential health hazard from the use of coal tar materials in the water supply.
Literature Cited (1j U.S. Environmental Protection Agency, “Sampling and Analysis Procedures for Screening of Industrial Effluents for Priority Pollutants”, Environmental Monitoring and Support Laboratory, Cincinnati, Ohio, April 1977. ( 2 ) New York State Department of Health, Division of’ Sanitary Engineering, “Engineering Sanitation Manual, NY State”, Albany, N.Y., 1978rpp 1--12. ( 3 ) U.S. Food and Drug Administration and Environmental Protection Agency, Fed. fiegist., 4 4 , 4 2 775 (July 20, 1979). (4) Junk, G., Richard, J.,Greiser, M., Witiak, D., Witiak, J., Arguello, M., Vick, R., Svec, H.. Fritz, J.,Calder, G., J . Chromatogr., 99, 745 (1974). ( 5 ) hlay, W., Wasik, S., Freeman, D., Anal. Chem., 50,997 (1978). 16) Liiinskv. is’.. Domskv. I.. Mason. G.. Ramahi. H.. Safari. T.. Anal. Chem , i5,952 (19633: ( 7 ) McClanahan. M., EPA LVater S u.~_ u.l vBranch, Atlanta, Ga., private communication, 1977. (8) World Health Organization, “European Standards for Drinking LVater”, 2nd ed.. WHO, Geneva, 1970. (9) Alben, K., manuscript submitted for publication in Anal.
Chem.
(10) Schwartz. D., Saxena, J., Kopfler. F., Environ Sci. Technol , 13, 1138 (1979).
Receiced for revieic October 26, 1979. Accepted January 18, 1980
NO, Influence on Sulfite Oxidation and Scaling in LimeILimestone Flue Gas Desulfurization (FGD) Systems Harvey S. Rosenberg” and Henry M. Grotta Battelle Columbus Laboratories, 505 King Avenue, Columbus, Ohio 43201
A laboratory-scale scrubbing system was used to perform semibatch experiments with slaked lime slurries and simulated flue gas to determine the influence of NO, on the solid-phase oxidation of sulfite to sulfate. I t was found that N O acts as an inhibitor and NO2 acts as a promoter of the oxidation of CaS03. NO present a t the same concentration as NO2 is unable to significantly inhibit the oxidative influence of NOz; however, a t a n NO/N02 mole ratio of about 12:1, the promotive action of NO2 is offset and the total oxidation is no greater than it would be without NO, present. Above a mole ratio of about 20:1, the oxidation of sulfite appears to be minimized. Oxidation inhibition merits consideration as a method to avoid sulfate scaling in lime/limestone flue gas desulfurization systems. Crystallization of calcium sulfite or sulfate on scrubber surfaces was the main problem in early lime/limestone flue gas desulfurization (FGD) systems and continues to be a major consideration although considerable improvement has been made. Sulfite scaling can be controlled in lime systems by keeping the p H of the entering liquor below 9. In practice, sulfite scaling seldom occurs in limestone scrubbing because t h e p H is lower and because sulfite supersaturates to such a 470
Environmental Science & Technology
degree that crystallization does not occur until t h e slurry reaches the reaction tank. However, sulfate scaling is much more difficult to control. Unlike sulfite, the decrease in p H down through the scrubber does not help hold sulfate in solution. Thus, if there is a considerable amount of sulfite oxidation in the scrubber, sulfate crystallization can occur. Various approaches have been taken to avoid sulfate scaling ( I ) such as seeding the scrubbing slurry with gypsum ( C a S 0 ~ 2 H z 0 crystals ) to reduce the sulfate supersaturation by providing sites for sulfate nucleation. The gypsum content of the scrubbing slurry can also be increased by oxidizing the sulfite to sulfate a t some point in the scrubber loop. The latter approach has the added advantage of providing a scrubber waste t h a t is easier to dewater and handle for disposal. However, a n alternative approach to avoid sulfate scaling t h a t merits consideration because of its simplicity and reliability is to prevent sulfate formation by inhibiting the oxidation of sulfite. Many methods and additives have been proposed to inhibit the oxidation of sulfite in SO2 scrubbers. Such additives include magnesium oxide ( Z ) , thiosulfate ( 3 ) ,and hydroquinone ( 4 ) .Graefe e t al. ( 5 )discuss the effects of NO, on sulfite oxidation in, principally, sulfite/bisulfite scrubbers. NO,, which is always present in flue gas, is characterized as a n oxidation 0013-936X/80/0914-0470$01 .OO/O
@ 1980 American Chemical Society
