Environ. Sci. Technol. 1989, 23,333-340
of hydrazine. Atmospheric humidity and previous conditioning experiments play significant roles in altering the fluorocarbon-film surface and thus changing the behavior of hydrazine vapor in this type of chamber. Previous studies of the atmospheric chemistry of fuel hydrazines using fluorocarbon-film environmental chambers have failed to account for these noncatalytic effects and thus overestimated the rate constants for homogeneous oxidation reactions.
Development Office: Tyndall Air Force Base, FL, January 1978. (8) Stone, Daniel A. T h e Autoxidation of Monomethylhydrazine Vapor; ESL-TR-79-10, Air Force Engineering and Services Center: Tyndall Air Force Base, FL, April 1979. (9) Stone, Daniel A. T h e Vapor Phase Autoxidation of Un-
Registry No. Teflon FEP, 25067-11-2;MMH, 60-34-4; UDMH, 57-14-7; hydrazine, 302-01-2; water, 7732-18-5.
Services Center: Tyndall Air Force Base, FL, April 1980. (10) Pitts, J. N., Jr.; Tuazon, E. C.; Carter, W. P. L.; Winer, A. M.; Harris, G. W.; Atkinson, R.; Graham, R. A. Atmospheric
symmetrical Dimethylhydrazine and 50-Percent Unsymmetrical Dimethylhydrazine 50-Percent Hydrazine Mixtures; ESL-TR-80-21, Air Force Engineering and
-
Chemistry of Hydrazines: Gas Phase Kinetics and Mechanistic Studies; ESL-TR-80-39, Air Force Engineering
Literature Cited Schmidt, Eckart W. Hydrazine and I t s Derivatives; Wiley-Interscience: New York, 1984.
and Services Center: Tyndall Air Force Base, FL, August 1980. (11) Tuazon, E. C.; Carter, W. P. L.; Brown, R. V.; Atkinson, R.; Winer, A. M.; Pitts, J. N., Jr. Atmospheric Reaction Mechanisms of Amine Fuels; ESL-TR-82-17, Air Force Engineering and Services Center: Tyndall Air Force Base, FL, March 1982. (12) White, J. L. J . Opt. Soc. Am. 1942, 32, 285-288. (13) Horn, D.; Pimentel, G. C. Appl. Opt. 1971,10,1892-1898. (14) Fersht, A. R.; Jencks, W. P. J. Am. Chem. SOC.1970,92, 5432-5442. (15) Johnston, Harold S. Gas Phase Reaction Rate Theory; Ronald Press: New York, 1969; pp 329-332.
Hazards of Chemical Rockets and Propellants. Volume ZII Liquid Propellants; Hannum, John A. E., Ed.; Chemical Propulsion Information Agency, CPIA Publication 394, The Johns Hopkins University, Applied Physics Laboratory: Laurel, MD, September 1984. Bowen, E. J.; Birley, A. W. Trans. Faraday SOC.1951,47, 580-583. Winning, W. I. H. J . Chem. SOC.1954, 926-931. Moody, K. N. P b D . Dissertation, The University of Leeds, Leeds, England, 1985. Vernot, E. H.; MacEwen, J. D.; Geiger, D. L.; Haun, C. C. A m . Ind. Hyg. Assoc. J. 1967,28, 343-347. Stone, Daniel A. T h e Autoxidation of Hydrazine Vapor; CEEDO-TR-78-17, Civil and Environmental Engineering
Received for review February 12,1988. Accepted October 3,1988.
Acidic Deposition and Cistern Drinking Water Supplies Harvey Olem"
Olem Associates, 1000 Connecticut Avenue, N.W., Suite 202, Washington, D.C. 20036 Paul M. Berthouex
Department of Civil and Environmental Engineering, University of Wisconsin, Madison, Wisconsin
rn The water quality characteristics, including the trace elements Cd, Cu, Pb, and Zn, in rainwater cistern supplies representing an area receiving acidic deposition were compared to cistern water chemistry in a control area that does not receive a significant input of acidic deposition. Mean volume-weighted pH for bulk deposition was two pH units higher and SO4 was 50% lower in the control region. Rainwater was neutralized upon contact with cistern masonry in both regions, as indicated by a 1.5-unit increase in pH and an increase in calcium and alkalinity. While there seemed to be a clear difference in water quality for the two study regions, any difference in trace metals was marginal. Metal concentrations were below current drinking water limits in all but a few samples. Cistern water that remained in the home plumbing system overnight exceeded the proposed drinking water standard of 5 pg/L for lead in 18 homes in the region receiving acidic deposition and 10 homes in the control region. No relation between metal concentrations and roofing material, plumbing materials, or water stability indices could be found. ~~
Introduction
Very little information is currently available on the relationship between acidic deposition and drinking water supplies. McDonald (I) reviewed the direct and indirect effects of acidic deposition on human health and suggested 0013-936X/89/0923-0333$0 1.50/0
that users of small, private, rural water supplies sustain the greatest health risk because many of these waters are corrosive to plumbing systems and operators of these systems do not usually monitor water quality. It was mentioned, however, that no conclusive evidence exists linking acidic deposition to increased leaching of contaminants from drinking water systems. Several studies have documented elevated concentrations of Cd, Cu, Pb, Zn, and other constituents in shallow wells, springs, surface water supplies, and rainwater cisterns (2-11). Review articles on the subject have suggested that these results implicate acidic deposition (12-15), but no study to date has rigorously evaluated the relationship between acidic deposition and drinking water degradation because of the difficulty in determining whether acidic deposition leads to the increased levels of contaminants. Cisterns have received more attention than other individual water systems because these supplies receive rainwater directly. Water does not come in contact with soils and rocks that can alter its characteristics. Young and Sharpe (2)found that tap water remaining in the pipes of cistern systems overnight exceeded the current drinking water limit for P b in 9 of the 40 systems sampled. The leaching of contaminants from the plumbing system was attributed to acidic deposition, although there was no estimate of how much leaching would occur if rainfall had not been acidic. Other investigators (5, 6) also found
0 1989 American Chemical Society
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similar percentages of cistern waters exceeding drinking water limits in areas receiving acidic deposition. None of these studies, however, were designed to determine the precise role of acidic deposition. Gumbs and Dierberg (16) studied cistern systems of 40 homes on the island of St. Maarten, Netherlands Antilles. Although the study was not intended to provide information relating cistern water quality to acidic deposition, the results provide a comparative data set in an area not receiving acidic deposition. Even though their precipitation pH values were higher than those in acidic deposition areas, cistern water samples had observed values of pH, alkalinity, and calcium that were very close to those reported by others ( 5 , 6 ) . The investigators also found that the percentages of cistern tap water samples exceeding US. drinking water standards for Pb were similar to the results of other studies (2, 5 , 6). Although a direct comparison could not be made due to differences in methodologies, the results questioned whether acidic deposition caused increased leaching of contaminants from cistern systems. These questions led to the initiation of a comparative study to determine the role of acidic deposition in modifying the quality of cistern drinking water supplies. The water quality characteristics, including the trace elements Cd, Cu, Pb, and Zn, in rainwater cistern supplies representing an area receiving acidic deposition were compared to cistern water chemistry in an area that does not receive acidic deposition.
Experimental Methods Study Sites. Twenty-five homes were selected in an area of Kentucky and Tennessee (KT) where rainfall is acidic and where there are a relatively large number of rainwater cisterns. Another 25 homes were selected in St. Maarten, Netherlands Antilles (SM),which is not affected by acidic deposition. The possibility of sea salt influencing the results for cistern waters in SM was considered prior to selection of a control site. No inland location in the United States with minimal sea-salt influence could be found where cisterns were prevalent and deposition was not acidic. Rainwater cisterns are the primary source of domestic water in St. Maarten, and the rainfall is near neutral. Deposition quality and quantity in both areas were measured during a 3-month period prior to cistern water sampling. A bulk deposition collector was located at one of the cistern sites in each study region. Samples from these collectors simulated the combined wet and dry deposition falling on the home’s roof. Information was also obtained in the K T region from a nearby wet deposition collector operated by the Tennessee Valley Authority as part of the federally funded National Trends Network. These data were used to compare results of the more useful but more variable bulk collection method. Gages were set up next to the bulk and wet deposition collectors in the K T region to continuously record precipitation quantity. Precipitation amounts for SM were obtained from a nearby gage operated by the Netherlands Antilles government (17). Cistern supplies in each region were selected so the systems would be as similar as possible. Cistern water had to be derived entirely of precipitation and be in regular use, and cistern tank construction had to be masonry, the most common type encountered. In a typical cistern system, rainwater runoff from a roof is routed through gutters and downspouts directly to the cistern, or storage tank, where it remains until it is pumped through household plumbing as the need arises. The household piping in the sample from each region was as follows: SM had 334
Environ. Sci. Technol., Vol. 23, NO. 3, 1989
DEPOSITION
COLLECTION
STORAGE
PRECIPITATION
HOUSE ROOF
q3: CISTERN
DISTRIBUTION
CONSUMPTION
Figure 1. Locations of cistern system sampling points. Sampling points include (1) bulk deposition, (2) roof water, (3) cistern water, (4)cistern sediment, (5)running tap water, (6) standing tap water.
18 plastic, 5 copper, and 2 galvanized systems; K T had 5 plastic, 8 copper, and 12 galvanized. The pumps typically had a small galvanized pressure tank. Bulk Deposition Measurements. Bulk deposition samples were collected weekly at one cistern site in each study region from January through April 1986. For the same period, wet deposition samples were also collected weekly a t the KT study site. Continuous records of precipitation quantity were obtained, and gage calibrations were checked on a weekly basis. Sampling protocols outlined by the National Atmospheric Deposition Program were followed where appropriate (18). Installation and operation of bulk collectors followed protocols of Wiener (19). Additional protocols described by Lindberg (20) were employed because of the addition of trace metal analyses. Cistern and Tap Water Sampling. Samples were collected at four locations within the cistern systems as shown in Figure 1. Sampling was conducted immediately following the conclusion of weekly deposition sampling (in May). Field personnel questioned the homeowners prior to sample collection to obtain information about each system. They also instructed the homeowner regarding sample collection. Each homeowner was given sample bottles and written instructions to collect a standing cold water sample from the kitchen tap first thing in the morning prior to any other water use in the home that day. Field personnel then returned to the home to pick up the standing tap water sample and to collect the other samples. The homeowner’s procedure was checked and if the specified procedure had not been followed the home was resampled. The running water sample was collected from the same kitchen tap after allowing the water to run for 1 min. Preliminary tests had shown that this was sufficient time to flush out the standing water. Sampling of the cistern storage tank was performed by using a Teflon tubing pump
Table I. Laboratory Chemical Analyses
pH (air equilibrated) conductivity alkalinity acidity total dissolved solids Na, K C1, PO4, SO4, NO3 Cd, P b Cu. Zn, Ca, Ma
electrometric Wheatstone bridge meter microtitration with H2S04,Gran plot microtitration with NaOH, Gran plot total filtrable residue dried at 180 "C atomic absorption ion chromatography atomic absorption, graphite furnace ICP atomic emission
set a t -500 mL/min. Cistern water samples were collected at 0.5 m below the surface. Cistern sediment/water samples were collected by pumping a mixture of sediment and water at 1 cm above the cistern floor. Temperature, pH, and conductivity measurrements were made on all samples immediately upon collection. Ten percent of all samples were collected in duplicate for quality control purposes. Filtration and container blanks were obtained one time for every 10 samples collected. Sampling Roof-Cistern-Tap Water System Changes. In order to evaluate the changes in water characteristics between deposition and the cistern system, minor modification of the roof water collector was made at one home in Kentucky to sample a portion of roof water just before it entered the cistern storage tank. Ten monthly samples of roof water were collected and compared to corresponding bulk deposition and cistern waters at the same site. Cistern water, cistern sediment, standing tap water, and running tap water samples were also collected and analyzed. Laboratory Methods. Chemical constituents, chosen because they were present is significant quantities or anticipated to be important in the understanding of cistern water chemistry, were measured by the procedures indicated in Table I. Analyses were performed on unfiltered samples with the exception of major cations and anions (filtered through a 0 . 4 - ~ mpore size filter) and total dissolved solids (filtered through a glass fiber filter). Trace metals Cd, Cu, Pb, and Zn were analyzed on both filtered (0.4-pm) and unfiltered samples and the results are reported, respectively, as dissolved and total concentrations. Sampling handling and analyses were conducted according to standard methods (21) with appropriate modifications for low ionic strength waters (22). Analyses met prescribed holding times except for three bulk deposition samples from SM which were detained through U S . Customs. Ten percent of all samples were analyzed in duplicate and another 10% were analyzed after spiking the samples. Blanks and duplicates collected in the field were also analyzed. Calculations. Bulk and wet deposition results were volume-weighted and SO4 concentrations were corrected for sea-salt influence. For the sea-salt correction, it was assumed that all the Na is of marine origin and that no fractionation exists between SO4and Na, either in aerosol formation or when these ions are incorporated into marine-derived precipitation (23).
Results Rainfall Characterization. Results of chemical analysis of weekly deposition samples are summarized in Table I1 for the K T and SM sites. Comparison of mean volume-weighted chemistry shows that bulk deposition in SM was 2 pH units higher and had about half the SO4 (corrected for sea-salt contribution) deposition of the KT region. The results are consistent with comparisons made
Table 11. Mean Volume-Weighted Deposition Chemistry for Kentucky-Tennessee and St. Maarten Sites, January-April 1986
parameter PHn conductivity, pSJcm total dissolved solids, mg/L cations, pequiv/L H+ Ca Mg Na K anions, pequiv/L c1 PO4
so4
NO3 metals, pg/L Cd cu Pb Zn cationJanion ratio rainfall amount, cm
KentuckyTennessee wet bulk
St. Maarten
bulk
4.53 17.2 NAb
4.41 31.9 23.9
6.54 36.5 22.9
29.6 21.6 4.1 6.1 1.31
38.9 50.9 8.2 8.3 8.5
0.29 49.5 49.3 211 6.9
4.1 0.3 41.0 19.2
10.2 19.6 44.1 37.8
257 1.9 36.6 (23.7)c 8.2
NA NA NA NA 0.97 20.8
0.44 19 73 310 1.03 18.8
0.17 9 472 624 1.04 20.1
'Calculated from mean volume-weighted H+ concentration. NA means not available. Value in parentheses is corrected for sea-salt contribution. by Galloway et al. (24),who found SO4enriched 2-16 times in eastern North American precipitation relative to its concentration in more remote areas. Rainfall quantity, specific conductance, and total dissolved solids were remarkably similar between the two sites, although total ionic strength and ion distributions were much different. These comparisons support the initial hypothesis that the SM site could be used as a nonacidic deposition control. As expected, Na and C1 dominated deposition chemistry for SM while H+, Ca2+,S042-,and NO3- were dominant ions in bulk deposition at the KT site. Cation/anion ratios were within 5% of unity for all volume-weighted deposition results. Trace metals in bulk deposition were very different for the two sites. Concentrations of Cd and Cu in SM were about half the KT region, while Pb and Zn concentrations were considerably higher for SM. The Pb concentrations in deposition in SM were over 6 times those in KT, which may be due to the combined effects of the higher density of automobiles in SM and the exclusive use of leaded gasoline. A comparison of wet and bulk deposition collectors in the KT area showed little difference in SO1. All other major cations and anions, however, were considerably higher in the bulk samples, indicating the influence of dry deposition. Bulk collectors may have lower collection efficiencies for fine particle fractions, a common form of particulate SO1. The results confirm the usefulness of bulk collectors for estimating the quality of water at the roof surface. Water Quality Changes through Cistern System. A comparison of selected constituents for one KT home at the six sampling locations (Figure 1)is shown in Figure 2. The house had asphalt shingles and galvanized plumbing. The 40-m3 concrete cistern was 50 years old. Considerable variation in water quality occurred over the 10-month sampling period. The roof water was 1.5 pH units higher than bulk deposition due to neutralization upon contact with roof and gutter materials, and with N
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91
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Flgure 2. Changes in water chemistry at different points in a cistern system in Kentucky over a IO-month period. Sample locations include bulk deposition (BD), roof water (RW), cistern water, (CW), running tap water (RT), standing tap water (ST), and cistern sediment (CS).
materials that may have been on the roof or in the gutters. Stones in asphalt shingles may contribute substantially to neutralization. More neutralization took place in the cistern tank following contact with masonry, as evidenced by the substantial increase in alkalinity and the approximate 0.5 pH unit increase. Little additional changes occurred in tap water pH and alkalinity. Cistern sediment was quite variable in pH. Changes in Ca concentrations generally followed those of pH and alkalinity, increasing in roof water and further increasing in cistern and tap waters. The results show the substantial neutralizing capacity of the roof collection and cistern system. The metals Cd, Pb, and Zn generally decreased between the roof and the cistern and increased again in standing tap water. Cistern sediment was variable but was generally extremely high in these metals compared to concentrations in roof water and cistern water. Concentrations of Cu are not shown because they were at or near the analytical detection limit of 10 pg/L for the bulk deposition, roof water, and cistern waters. Cistern sediment, however, contained as much as 240 pg/L Cu and considerably more P b and Zn. The low concentrations of these metals in cistern water compared to deposition and roof water and relatively high values in sediment suggest that these metals are removed in the cistern by precipitation, sorption, and sedimentation, due to the reduced solubility at the increased pH levels. Cistern and Tap Water Quality. Descriptive statistics for constituents in cistern water samples from SM and KT are given in Table 111. Because the data were not symmetrically distributed about a mean value and some var336 Environ. Sci. Technoi., Voi. 23, No. 3, 1989
iables were censored at the analytical detectable limit, the median values with minimum and maximum values indicated are used for this summary description. Field pH, Na, and C1 were higher in SM than in KT. The elevated Na and C1 concentrations measured may be attributed to seawater spray. Considerable neutralization of rainwater occurred in the cisterns of both regions. The lower rainfall pH of the K T region is evident in the lower field pH of the cistern water. The laboratory (air-equilibrated) pH measurement seemed generally lower in K T than in SM, but the difference was not statistically significant. For all other parameters, the two regions were either equivalent or the K T region had the higher values. No statistical summary is given for tap waters because they were virtually identical with the cistern water with respect to pH, alkalinity, acidity, conductivity, total dissolved solids, cations, and anions. Total and dissolved Cd were higher in K T than SM (Table HI). Dissolved Cd concentrations were only slightly lower than total for both regions. A similar relationship was observed for dissolved and total Pb. Comparisons were based on testing the null hypothesis that the water quality was the same in the two regions by the t test, with significance tested at the 95% confidence level (25). An explanation and justification for using a t test on the censored metals data is given in the Discussion. The t test, like other statistical methods that compare averages, is robust with respect to deviations of the original data from normality because the averages tend to be normally distributed regardless of the parent distribution of the data. The t test, however, is not robust with regard
Table 111. Comparison of Cistern Water Chemistry for the Kentucky-Tennessee and St. Maarten Study Regions parameters field pH lab pH conductivity, pS/cm alkalinity, pequivll acidity, pequiv/L total dissolved solids, mg/L cations, pequivll H+ CS Mg Na K anions, pequiv/L
7.00 7.76
r!d ._
cu
Pb Zn cation/anion ratio
6.20 7.0
101 620 450 60
47.4 102 210 30
0.10 775 43.6 43.1 19.5
