Environ. Sci. Technol. 1907, 21,920-922
to remove mutagenic artifacts on filters and thereby reduce concomitant interference.
(12) Rappoport, S. M.; Wang, Y. I. Y.; Wei, E. T. Environ. Sei. Technol. 1980, 14, 1505-1509. (13) Claxton, L. D.; Kohan, M.; Austin, A,; Evans, C. T h e Ge-
netic Bioassay Branch Protocol for Bacterial Mutagenesis Including Safety and Quality Assurance Procedures;
Literature Cited
Ames, B. N.; McCann, J.; Yamasaki, E. Mutat. Res. 1975, 31, 347-363. Merller, M.; Alfheim, I. Atmos. Environ. 1980, 14, 83-88. Commoner, B.; Madyastha, P.; Bronsdon, A.; Vithayathil, A. J . Toxicol. Environ. Health 1978, 4, 59-77. Daisey, J. M.; Kneip, T. J.;Hawryluk, I.; Mukai, F. Environ. Sei. Technol. 1980,14, 1487-1490. Teranishi,K.; Hamada, K.; Watanabe, A. Mutat. Res. 1978, 56, 273-290. Tokiwa, H.; Morita, K.; Takeyoshi, A.; Takahashi, K.; Ohnishi, Y. M u t a t . Res. 1977, 48, 237-248. Pitts, J. N.; Grosjean, D.; Mischke, T. M. Toxicol. Lett. 1977, I, 65-70. Alink, G. M.; Smit, H. A.; van Houdt, J. J.; Kolkman, J. R.; Boleij, J. S. M. M u t a t . Res. 1983, 116, 21-34. Alfheim, I.; Lofroth, G.; Mdler, M. E H P , Environ. Health Perspect. 1983, 47, 227-238. Huisingh, J.; Bradow, R.; Jungers, R.; Claxton,L.; et al. In Application of Short-Term Bioassays to the Fractionation and Analysis of Complex Environmental Mixtures; Waters, M. D., Nesnow, S., Huisingh, J. L., Sandhu, S. S., Claxton, L., Eds.; Plenum: New York, 1979; pp 381-418. Ohnishi, Y.; Kachi, K.; Sato, K.; Tahara, I.; Takeyoshi, H.; Tokiwa, H. Mutat. Res. 1980, 77, 229-240.
Health Effects Research Laboratory, U.S. Environmental Protection Agency: Research Triangle Park, NC, 1981. (14) Stead, A.; Hasselblad, V.; Creason, J.; Claxton, L. Mutat. Res. 1981, 85, 13-27. (15) Alfheim, I.; Lindskog, A. Sei. Total Enuiron. 1984, 34, 203-222. (16) Krishna, G.; Nath, J.; Whong, W.-Z.; Ong, T. Mutat. Res. 1983, 124, 113-128. (17) Pitts, J. N.; Van Cauwenberghe, K. A.; Grosjean,D.; Schmid, J. P.; Fitz, D. R.; Belser, W. L.; Knudson, G. B.; Hynds, P. M. Environ. Sei. Res. 1979, 15, 353-379. (18) Merller, M.; Alfheim, I. M u t a t . Res. 1983, 116, 35-46. (19) Hoffman, D.; Norpoth, K.; Wickramasinghe, R. H.; Muller, G. Zbl. Bakt. Hyg. I . Abt. Orig. B 1980, 171, 388-407. Received for review March 28,1986. Revised manuscript received December 1,1986. Accepted April 27,1987. This paper has been reviewed by the Health Effects Research Laboratory, U S . Environmental Protection Agency, and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.
Determination of Mercury in River Water, Rain, and Snow Eiji Uchino,+Tsuneo Kosuga, Shlgekl Konishi, and Masakichi Nishimura * Deparrment of Chemistry, Faculty of Fisheries, Hokkaido University, Hakodate, Japan
For river water, even when a sample is not apparently polluted, addition of an oxidant and the heating process are confirmed to be necessary to determine the total Hg. Ten milliliters of concentrated HzS04and 10 mL of 0.5% KMn04 are added to a 1-L river water sample a t sampling, and the solution is heated for 4 h a t 100 "C. The Hg concentration in a river sample containing H2S04and KMnO, is unchanged for a t least 10 days. For rain and snow, when acidification and the addition of a preserving agent were made after the collection of rain or the melting of snow, 20-90% of Hg in a rain or snow sample was lost during the collection of rain or the melting of snow, mainly owing to adsorption on the wall of a vessel. Therefore, to obtain a correct Hg value, H2S04and KMn04 must be added to the receiving vessel prior to the collection of rain or the melting of snow. At the end of the collection or melting, the concentrations of HzS04 and KMn04 are adjusted to 0.2 M and 0.005%, respectively.
Natural water contains different kinds of species of Hg. Therefore, different concentration values of Hg may be obtained by different pretreatments of a natural water sample. Determinations of the so-called total Hg in river waters have been reported, e.g., with ultraviolet irradiation techniques (1,Z),1-month storage with addition of HzS04 and NaCl ( 3 ) , and digestion with strong acid-K2Cr207, -K2SZO8,or -KMn04 (4-9). Sometimes, such a pretreat*Address correspondence to this author at his present address: Evergreen Maruyama 703, Kita 19, Nishi 24, Sapporo, Japan 064. +Presentaddress: Hokkaido Institute of Public Health, Kita 19, Nishi 1 2 , Sapporo, Japan 060. Environ. Sci. Technol., Vol. 21, No. 9, 1987
Water Sample no. of
Hg found (mean f SD),
determinations
ng/L
5
0.8 f 0.3
H2S04,no
6
1.6 f 0.3
C
10 mL of concd H2S04and 10 mL of 0.5% KMnO,,
6
3.7 f 0.4
D
5
7.1 f 0.8
E
10 mL of concd H2S04and 10 mL of 0.5% KMnO,, heating for 4 h 25 mL of concd "OB, 20 mL of 5% KMnO,, and 20 mL of 5% K2SzO8, heating for 4 h
6
6.6k 0.6
F
10 mL of concd H2S04and
6
6.9 k 1.2
method
A
added to 1-L sample 10 mL of concd HN03, no
heating B
10 mL of concd
heating no
heating
10 mL of concd "OB,
River W a t e r
920
Table I. Comparison of Various Pretreatments for a River
heating for 4 h
ment has been omitted by the addition of only HNOBor HC1 when river water seems to be unpolluted. For an example, variations in Hg concentration in a river water sample determined by different chemical pretreatments and the stability of Hg in a treated sample are described in this paper. River samples were collected from the Akagawa River, which is so unpolluted that it is a source of city water. Variation of Mercury Concentration in a River Sample by Different Pretreatments. six different pretreatments described in Table I were each given to a
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Chemical Society
Table 11. Stability of Hg in a River Water Sample Pretreated with H2S04and KMnO, days after sampling 0 5 10 30
no. of determinations
Table 111. Loss of Mercury during Collection of Rain or Melting of Snow
determined Hg (mean f SD),” dg/L 4.2 f 0.5
4.3 f 0.5 4.7 f 0.9 3.4 f 0.3
Each solution was heated for 4 h before the Hg measurement.
river water sample. Reagents for pretreatment were added immediately after the river water was aliquoted into bottles. Without heating or after heating for 4 h in a steam bath, the solution was transferred into a reduction bottle, and the Hg was measured. The analytical procedure is as detailed elsewhere (10). Add SnC1, to the pretreated river water sample. Pass N2 through the solution, and collect the vaporized Hg on gold metal particles in a quartz tube. Heat the metal in an infrared-lamp furnace, and introduce the released Hg vapor into an absorption cell by passing N2. Determine the Hg by using an atomic absorption spectrophotometer. When KMnO, and/or K2S20swere used, NH,OH.HCl was added prior to the addition of SnC12. In all cases, a blank of the used reagents was determined (11) and subtracted. As shown in Table I, different Hg values were obtained by different pretreatments. The addition of HNO, or HzS04 only (methods A and B) gave fairly low values compared to those of method D in which the sample was treated with H,SO, and KMnO, and heated for 4 h. Two reasons may be considered for this difference. (1) Acidification only is not sufficient to prevent adsorption loss of Hg onto the walls of the sample bottle (12). (2) River water, even if unpolluted, contains several kinds of Hg species; i.e., some Hg is readily reduced to metallic Hg by Sn(II), but a large portion of Hg is reduced with difficulty, and it is decomposed only by strong oxidation. Methods D-F showed no significant differences in the Hg values a t a 95% confidence level. The value determined by any of these three methods can be called the “total” Hg because the three methods all involve very strong oxidation processes, and the good agreement of the Hg values among the methods can be taken as evidence of complete decomposition. For the total Hg, the overnight oxidation with KMnO, at room temperature has been adopted (7,9), but Nishi and Hiromoto (7) noted that such treatment was insufficient for heavily polluted waters. Sakamoto and Kamada reported results of the oxidation with KMnO, and heating for 2 h in a boiling water bath (8). In our experiments, heating for 3 and 4 h showed the same values while heating for 2 h showed lower values. Stability of Hg in a River Water Sample Pretreated with H2S04 and KMnO,. A total of 10 mL of concentrated HZSO, and 10 mL of 0.5% KMnO, was added to 1-L river water samples (method D), and they were stored. After several days the solutions were heated for 4 h, and the Hg concentrations were measured. Table I1 shows that no significant differences were found a t a 95% confidence level between the values determined 0,5, and 10 days after the sampling, but the samples stored for 30 days showed lower values. These results indicate that measurement of Hg in river water samples treated with H2S04 and KMnO, a t sampling can be performed within 10 days.
Rain and Snow According t o our experience, 40% of the mercury in a 0.5 ppb mercury solution is lost during a 1-day storage
sample rain rain rain snow snow snow
Hg found (H2S04and KMnO, added), ng/L A (after B (before sampling) sampling) 25 13 21 7
I 12
loss of Hg, % [(B - A)/B X 1001
30 32 90 64 48 60
17
59 71 89 85 80
period even in a solution acidified with HzS04(12),mainly due to adsorption of mercury onto the wall of the container. It is possible that trace amounts of mercury are more rapidly lost in a solution that is not acidified and contains no salts, such as rainwater and melted snowwater. Loss of Mercury during Collection of Rain or Melting Snow. Determinations of mercury have so far been carried out in rain samples acidified after collection or snow samples acidified after melting. As stated above, however, this may lead to a lower value of mercury owing to adsorption loss onto the wall of a receiving vessel during the collection of rain or the melting of snow. Two experiments were made. (A) Rain was collected in a glass bottle through a large polyethylene funnel ($, 24 cm), or snow was melted in a beaker held in a hot-water bath. Then, 9 M H2S04 was added to make a 0.2 M solution, and a 0.1% KMn0, solution was added to make a 0.005% solution. (B) A total of 10 mL of 0.1% KMnO, solution and 4 mL of 9 M HzS04was taken into a receiving glass bottle or a glass beaker prior to the collection of 200-500 mL of rain or the melting of a similar amount of snow. After the collection or melting, the solution was adjusted to 0.005% KMn0, and 0.2 M H2S04concentration by the addition of more KMn0, and HzS04,if necessary. One milliliter of 10% NH20H-HC1solution was added, and the mercury was determined by the method above. Table I11 shows the differences between methods A and B. The experiment indicates that 1 7 4 9 % of the mercury is lost by the time H2S04and KMnO, are added after the collection or melting. Therefore, if acidification and the addition of a preserving agent are made after the collection of rain or the melting of snow, a false and lower value for mercury will be obtained. To obtain the correct mercury value, the addition of H$04 and KMn0, should be made before the collection or melting, as in method B. Registry No. Hg, 7439-97-6; H20, 7732-18-5.
Literature Cited (1) Goulden, P. D.; Afghan, B. K. Technical Bulletin No. 27; Department of Energy, Mines, and Resources: Ottawa, Canada, 1970. (2) Fitzgerald, W. F.; Lyons, W. B. Nature (London)1973,242, 452-453. ( 3 ) Matsunaga, K. J p n . J . Lirnnol. 1976, 37, 131-134. (4) Chau, Y. K.; Saitoh, H. &‘roc.-Conf. Great Lakes Res. 1973, 16, 221-232. (5) Carron, J.; Agemian, H. Anal. Chirn.Acta 1977,92,61-70. (6) Bureau of International Technologie du Chlore Anal. Chirn. Acta 1979,109, 209-228. (7) Nishi, S.; Horimoto, Y. Special Technical Publication No. 573; American Society for Testing and Materials: Philadelphia, PA, 1975; pp 25-29. (8) Sakamoto, H.; Kamada, M. Nippon Kagahu Kaishi 1981, 32-39. Environ. Sci. Technol., Vol. 21, No. 9, 1987
921
Environ. Sci. Technol. 1987, 21, 922-924
(9) Omang, S. H. Anal. Chim. Acta 1971,53, 415-420. (10) Nishimura, M.; Matsunaga, K.; Konishi, S. Bunseki Kagaku 1975, 24, 655-658. (11) Uchino, E.; Konishi, S.; Nishimura, M. Bunseki Kagaku 1978,27, 457-459.
(12) Matsunaga, K.; Konishi, S.; Nishimura, M. Environ. Sei. Technol. 1979, 13, 63-65.
Received for review February 4, 1986. Revised manuscript received September 11, 1986. Accepted November 13, 1986.
CORRESPONDENCE Comment on “Airborne Dioxins and Dibenzofurans: Sources and Fates”
Table I. Dioxin Deposition Data for Chicago 1
SIR: Recent correspondence in this journal ( I , 2) has addressed the problem of determining the source and fate of airborne dioxins and dibenzofurans (3). That congener-selective processes appear to be acting on particulates emitted from incinerators may be construed from the dioxin data presented by Crummett (5),relating to soil in the vicinity of an incinerator sited in Chicago. Table I shows that, whereas total dioxins peak a t about 800 ft from the stack, the ratio of the hepta- to the octachloro congener exhibits an exponential decay; while the total deposition a t 400 ft is 400 times the deposition at 100 ft, the ratio of H7CDD/OCDD for the former is lower by a factor of 2. If the dioxin transformation mechanism operated after the dioxins were deposited onto the soil, then it might be expected that a t some point the deposition rate would exceed the transformation rate, resulting in a Gaussian distribution of the congener ratio that mirrored the pattern for total deposition ( 4 ) . If the validity of the exponential shift in the ratio is accepted, then the observations of Crummett suggest that this mechanism must be operating on the particles while they are in free-fall, the shift in congener ratio becoming a function of free-fall time. This transformation process may be due to one or a combination of thermochemical, physicochemical, or photolytic mechanisms-the above discussion suggests that changes to incinerator emissions occur after the material has left the stack. A t this stage it is not possible to assess whether, under these circumstances, the contact time between HC1 vapor and the dioxins is sufficient to produce changes in the relative ratios of congeners, as a result of chemical reaction. Turning to photolysis, Nestrick et al. (6) have shown that the photodegradation of polychlorodibenzo-p-dioxins (PCDDs) on glass surfaces and in solution is isomer specific. Therefore, environmental samples might be expected to produce isomer patterns related to isomer photostability. This does not appear to be the case (7). Alternatively, a nonisomer-specific photodegradation mechanism may be operating on the dioxins (8). Differential settling of fly ash particles may also contribute to the shift in ratios (7). Thermal equilibration is another candidate mechanism that could explain the congener ratios measured by Hites and co-workers (2, 9) on airborne particulates ( 4 ) . It is interesting to note that the volatility of octachlorodibenzodioxin (OCDD), relative to the other congeners, gives ratios of 0.0005,0.0025,0.01,and 0.125 for OCDD/T4CDD, OCDD/P5CDD, OCDD/HGCDD, and OCDD/H7CDD, respectively, which is in agreement with the background ratios postulated by Townsend (10) and with the data of Czuczwa and Hites (9). The adsorption/desorption pro922
Environ. Sci. Technol., Vol. 21, No. 9, 1987
distance from stack, f t
PCDD in soil, PPt
H,CDD/OCDD
100 200 400 1000
60 1280 25 640 10 040
0.34 0.24 0.15 0.17 ~
~~~
cesses relating to thermal equilibration are under investigation. The vapor pressure data of Rordorf (11) indicate that this parameter is not markedly isomer specific and that the congeners follow parallel paths. The relative volatilities can therefore be considered as independent of temperature; a change in temperature would only affect the rate a t which the equilibrated composition is attained, isomer patterns remaining relatively stable and unaltered. In view of the seemingly ubiquitous pattern of congener ratios in environmental samples, a strict interpretation of the similarity with congener patterns in human adipose tissue would be that this is the manifestation of a set of all-pervasive, congener-specific mechanisms that operate on dioxins in the environment, irrespective of their source, and ultimately resulting in this “background” ratio. For this reason, Eitzer and Hites’ contention (2) that combustion is the only source of significant size and ubiquity to account for PCDD and polychlorodibenzofuran (PCDF) patterns in humans cannot be sustained on a comparison of congener ratios alone. The size of the source can vary from district to district-in Canada, for example, chlorophenols are considered to be a source of input, equivalent to, or perhaps greater than, municipal and industrial incinerators (12, 13). Dioxin congeners in chlorophenol products are also generally biased toward OCDD (13). Samples of sewage sludge and river sediments analyzed by Hagenmaier et al. (14) show the same congener patterns as in the work of Hites and co-workers,but an examination of the isomer distribution suggested a strong link with dioxin input from pentachlorophenol, rather than from combustion. Hagenmaier et al. estimate that the amount of total PCDD/PCDF released into the environment by the open application of pentachlorophenol in Germany is a t least 100 times higher than that emitted from the 41 waste incineration plants. Graham e t al. (15) support the theory that diet (specifically animal products) is the major proximate source of dioxins found in humans and that airborne particulates provide one link in the chain between the ultimate source and man. Czuczwa and Hites (9) maintain that “air particulates contain a large fraction of combustion particulates”-hence the identification of combustion as the major source of dioxins, on the basis that congener ratios in humans and in particulates were similar. Whether or not the fraction of combustion particulates is sufficiently
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