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Butyltin Species and Inorganic Tin in Water and Sediment of the Detroit and St. Clair Rivers
J. Great Lakes Res. 11(3):320-327 Internat. Assoc. Great Lakes Res., 1985
BUTYLTIN SPECIES AND INORGANIC TIN IN WATER AND SEDIMENT OF THE DETROIT AND ST. CLAIR RIVERS
R. James Maguire, Richard J. Tkacz, and David L. Sartor
Environmental Contaminants Division National Water Research Institute Department of the Environment Canada Centre for Inland Waters Burlington, Ontario L7R 4A6 ABSTRACT. Water and sediment samplesfrom 29 locations in the Detroit and St. Clair rivers were analyzed for the highly toxic tri-n-butyltin (Bu 3Sn+) species and for the less toxic di-n-butyltin (Bu2Sn2+) and n-butyltin (BuSn 3+) species and inorganic tin. In general, locations sampled in the St. Clair River were less contaminated with butyltin species than those in the Detroit River. Inorganic tin and BuSn3+ were detected in over 90% of all subsurface water samples, while Bu2Sn 2+ and BU3Sn+ were detected in 45 and 28% of the same samples, respectively. The highest concentration of BU3Sn + in subsurface water, 5.9 x 1rF10 mol Sn/L, was at the mouth of the Ecorse River, a tributary of the Detroit River. The three butyltin species and inorganic tin were also detected in 23-46% of all sediment samples. The highest concentrations ofBU3Sn+ in sediment werefound close to the mouths of the River Rouge, another tributary ofthe Detroit River, and the Ecorse River, and were 6.2 x 1rF7 and 1.7 x 1rF 7 mol Sn/kg dry weight, respectively, for the top 2 em of sediment. ADDITIONAL INDEX WORDS: Toxic substances, trace metals, industrial wastes.
Studies on the environmental persistence of butyltin and phenyltin compounds indicate that abiotic degradation generally occurs, as does biological degradation, through mechanisms of sequential dealkylation (e.g., Maguire et al. 1983) or dearylation (Soderquist and Crosby 1980); therefore, the series PhnSn(4-n)+ , CYnSn(4-n)+ and BunSn(4-n)+ (where in each case n < 4), OctnSn(4-n)+ (where n ~ 2), and MenSn(4-n)+ (where n ~ 4) may be present in the Canadian environment. The last series includes tri- and tetramethyltin, which are not released per se to the environment, since methylation of tin and methyltin compounds has been demonstrated in natural water-sediment mixtures (Chau et al. 1981, Guard et al. 1981). Our work deals with the aquatic environmental occurrence and persistence of butyltin compounds. Samples collected in 1981 at 30 locations in Ontario revealed, for the first time in Canada, the presence of methyltin and butyltin species, and inorganic tin, in some waters (Maguire et al. 1982)
INTRODUCTION Organotin compounds are used in three main ways, viz., as stabilizers for poly(vinyl chloride), as catalysts in the production of polyurethane foams, and as biocides (Zuckerman et al. 1978). The main organotin species which are likely to be released to the environment in Canada are triphenyltin (Ph3Sn +), tricyclohexyltin (CY3Sn +), tri-n-butyltin (Bu3Sn+), di-n-butyltin (BuzSnz+), di-n-octyltin (OctzSnz+), and dimethyltin (MezSnz+) (Thompson et al. 1985). Triphenyltin and tricyclohexyltin compounds are insecticides. Tri-n-butyltin compounds are used mainly as antifouling agents in paint for ships, boats, and docks, as slimicides in cooling towers, and in lumber preservation. Di-n-butyltin compounds are used as poly(vinyl chloride) stabilizers, as are dimethyltin compounds, and as catalysts in a number of industrial processes. Di-noctyltin compounds are used as stabilizers in some food wrappings. 320
BUTYLTIN SPECIES AND INORGANIC TIN IN WATER AND SEDIMENT and sediments (Maguire 1984). In general, the occurrence of inorganic tin was widespread, methyltin species were found in harbours or areas of industrial activity, and butyltin species were found mainly in harbours and other areas of heavy boating or shipping traffic. In addition, tri-nbutylmethyltin and di-n-butyldimethyltin were found in the sediments of some harbours, indicating that butyltin species can be methylated in aquatic environments. This article reports the extent of butyltin species contamination of water and sediment in the Detroit River (23 locations sampled in June 1983) and the St. Clair River (6 locations sampled in October 1983). For brevity, the tri-n-butyltin, di-n-butyltin, and n-butyltin species are referred to in this article as though they existed only in cationic form (e.g., Bu3Sn +), since there is evidence that at least some organotin species exist in water as cations (e.g., Tobias 1966, Maguire et al. 1983). We were more interested in debutylation reactions than in cation hydrolysis or the identity of the counter ion, mainly because the toxicity of butyltin compounds in general decreases with decreasing number of butyl groups (Davies and Smith 1980). EXPERIMENTAL METHODS Water and sediment samples were collected from small boats which had not been painted with antifouling paint. Materials Bis (tri-n-butyltin) oxide (97%), tri-n-butyltin chloride (97070), di-n-butyltin dichloride (96.5%), n-butyltin trichloride (95%), and metallic tin (99.99%) were from Ventron (Danvers, MA). Tropolone (2-hydroxy-2,4,6-cYcloheptatrien-l-one) was from Aldrich (Milwaukee, WI). All organic solvents were pesticide grade from Caledon Laboratories (Georgetown, Ont.). All mineral acids were reagent grade, but the HCI was washed with 1% wIv tropolonelbenzene to remove inorganic tin. The Grignard reagent n-pentylmagnesium bromide was prepared from commonly available chemicals. All butyltin compounds were purified by passage in benzene or hexane through a 60 x 1.5 cm Ld. column of activated silica gel and were pure, as judged by gas chromatography of their npentyl derivatives (cf. below) with flame photometric, flame ionization, and electron capture detectors.
321
Determination of Butyltin Species and Inorganic Tin in Water Eight litres of subsurface water (0.5 m) were collected in amber glass bottles and the contents were acidified to pH 1 and stored at 4°C until extraction. Analyses of the unfiltered water samples for butyltin species (Bu3Sn +, BU2Sn2+, and BuSn3 + ) and inorganic tin (Sn (II) and Sn (IV» (Maguire and Huneault 1981) involved extraction with 0.5% (w Iv) tropolonelbenzene, derivatization of the extract with n-pentylmagnesium bromide, silica gel column clean up, and determination of the Bun Pe4-nSn derivatives by gas chromatography• atomic absorption spectrophotometry (MagUIre and Tkacz 1983). Considering that a fairly specific detector for tin was used in the analyses, identities of the BunPe4_n Sn species were deemed to be confirmed by co-chromatography with authentic standards on two column packing materials of widely varying polarity. In the quantitation of the analytes, use was made of appropriate reagent blanks. The results reported in this article are above the limit of quantitation, which is defined (Keith et al. 1983) as the reagent blank value plus ten times its standard deviation. In our case, this was equivalent to stating that a chromatographic peak was not accepted as real unless it was at least 2.5 times as large as any corresponding peak in the reagent blank. Recoveries of the butyltin species and Sn(lV) spiked at 10-6 - 10-5 mol Sn/L in acidified water were 96-103 % (Maguire and Huneault 1981), and the limit of quantitation for each of the Bu Pe Sn species is about 3 x 10- 11 mol Sn/L. At ;i~ locations in the St. Clair River, 4-litre samples of the surface microlayer were obtained with a rotating drum sampler similar to that described by Harvey (1966). The drum sampler is estimated to collect the top 60 J.'m of the water column. The surface microlayer samples were analyzed in the same way as the subsurface water samples. Determination of Butyltin Species and Inorganic Tin in Sediment Sediment samples were analyzed by the method of Maguire (1984) which is briefly described here. Sediment samples were collected with an Ekman dredge, the top 2 cm were scraped off in.to glass jars, and the sediment was kept fr<,lzen until analysis. The sediment was freeze-dned, stones and other debris were removed, and the sediment was
322
MAGUIRE et ale
passed through a 850-pm sieve after being ground by mortar and pestle. Ten g of dry sediment was refluxed for 2 hr with 0.25 g of tropolone in 100 mL of benzene. The mixture was filtered, and the filtrate was derivatized, cleaned up, and analyzed as described above. An estimate of the organic matter content of the sediments was made by heating separate portions at 375°C to constant weight. Recoveries of the butyltin species and Sn (IV) spiked at 10-7 - 10-3 mol Sn/kg dry weight were quantitative. The limit of quantitation for each of the Bun Pe4_n Sn species in sediment is about 10-8 mol Sn/kg dry weight (Maguire 1984). Although Sn (IV) was the only inorganic tin species for which recoveries were determined in spiking experiments, the inorganic tin in the environmental samples is reported as "total recoverable inorganic tin" since it has been shown that hydride derivatization of either Sn (II) or Sn (IV) yields SnH4 (Brinckman et al. 1983), and thus any Sn (II) that may be present in our samples may similarly be pentylated to tetrapentyltin.
RESULTS AND DISCUSSION Tables 1 and 2 show concentrations of butyltin species and inorganic tin in water and sediment, respectively, of the Detroit River. The locations are shown in Figure 1. Table 1 shows that Bu3Sn+ and Bu2Sn2 + were detected in about one third of the subsurface water samples from the Detroit River, while BuSn3 + and inorganic tin were detected in almost all of the samples. The aqueous concentrations of all the butyltin species and inorganic tin are in general similar to those reported for some other locations in Ontario (Maguire et al. 1982). Since the toxicity of butyltin compounds decreases with decreasing number of butyl groups (Davies and Smith 1980), the Bu3Sn + concentrations are of most interest. The highest concentration of Bu3Sn + in water was at the mouth of the Ecorse River (site 0311), and was about 40/0 of the Lq~ value of 1.5 x 10-8 mol Sn/L for rainbow trout yolk sac fry (Seinen et al. 1981). As noted above, Bu3Sn+ is used as an anti-
TABLE 1. Concentrations (mol Sn/L) of butyltin species and total recoverable inorganic tin (TRIT) in unfiltered subsurface water of the Detroit River. * Location 0399 0379 0386 0370 0381 0353 0352 0346 0330 0314 0311 0280 0269 0257 0255 0224 0223 0231 0214 0213 0212 0210 0203
BU2Sn2+
BU3Sn+ 6.90 x 10-
11
2.14 x 10-10
3.4 x 10- 11 3.79x10- 1O 3.19x10- 1O 5.86 x 10- 10
4.29 X 5.58 x 3.86 x 6.01 X
10-11 10-10 10-10 10- 10
3.10x 10-10 3.45 x 10-11
8.15 x 10-10 4.29 X 10-11
2.07 x 10-10
3.43 X 10- 10
BuSn3 +
TRIT
9.66x 1.14 x 3.98 X 5.68 x 2.27 x 1.70 x
10
1010-10 10- 10 10-11 10- 10 10- 10
6.22 x 3.36 X 2.48 X 1.68 X 1.09 X 5.46 X
10-9 10- 10 10-8 10- 10 10-9 10-9
1.70 X 2.27 X 1.70 X 1.70 X 2.84 x 1.14 x
10- 10 10- 10 10- 10 10-10 10-10 10-10
5.04 X 6.81 X 4.20 X 5.88 X 1.18 X 2.52 X
10-9 10-9 10- 10 10-10 10-9 10-10
2.84 x 10-10 1.70 x 10-10 3.41 X 10-10 2.27 X 10- 10 1.70 x 10- 10 1.70 x 10- 10 1.14 x 10- 10 5.68 x 10- 11 1.14x 10-10
1.43 X 6.72 x 1.68 X 1.93 X 2.52 x 5.88 X 2.52 X 3.95 X 5.04 x
10-9 10-10 10-9 10-9 10-10 10- 10 10-10 10-9 10-10
*Locations are shown in Figure la, band c; blank means below limit of quantitation, which was about 3 x 10- 11 mol Sn/L for each species; areal standard deviation of chromatographic peaks on triplicate injection was < 15070.
BUTYLTIN SPECIES AND INORGANIC TIN IN WATER AND SEDIMENT fouling agent in boat and dock paint, as a lumber preservative, and as a slimicide in cooling towers. Although most of the locations in the Detroit River at which Bu3Sn + was detected in water are close to ship berths or marinas, it is interesting to note that the second highest concentration of Bu3Sn + was in the middle of the river north of Fighting Island (site 0330). The Bu2Sn2 + detected in subsurface water of the Detroit River could be introduced from the use of dibutyltin compounds as poly(vinyl chloride) stabilizers, or it could be a degradation product of Bu 3Sn + which is perhaps more likely since it was found at most of the locations at which Bu3Sn + was detected. Monobutyltin compounds do not appear to be used commercially, so the BuSn3+ species in water is most likely a degradation product of Bu2Sn2 +. In contrast to our earlier study (Maguire et al. 1982), BuSn3+ was frequently detected in subsurface water, and its presence at any particular location suggests introduction of either Bu2Sn2 + or BU3Sn + , or both, at that location
or upstream. The inorganic tin detected in subsurface water may be present naturally, may be introduced in inorganic form, and/or may be a degradation product of organotin compounds. Table 2 shows that Bu3Sn + and Bu2Sn2 + were detected in the top 2 cm of sediment at about half of the sampling locations in the Detroit River, while BuSn3+ and inorganic tin were detected in about one quarter of the samples. The concentrations in sediment of all the butyltin species and inorganic tin are in general similar to those reported for some other locations in Ontario (Maguire 1984). The highest concentrations of Bu3Sn + were found close to the mouth of the River Rouge (site 0346) and at the mouth of the Ecorse River (site 0311) (6.1 x 10-7 and 1.6 x 10-7 mol Sn/kg dry weight, respectively). Although the biological availability, hence toxicological significance, of sediment-associated Bu3Sn + has yet to be established, the water and sediment results combined indicate these two locations as the most likely of all locations sampled in the Detroit River
TABLE 2. Concentrations (mol Sn/kg dry weight) of butyltin species and total recoverable inorganic tin (TRIT) in top 2 cm of sediment of Detroit River. * 070 Organic Location
0399 0379 0386 0370 0381 0353 0352 0346 0330 0314 0311 0280 0269 0257 0255 0224 0223 0231 0214 0213 0212 0210 0203
Matter
BU2Sn2+
BU3Sn+
BuSn3 +
TRIT
2.84 x 10-8
1.49 X 10-6
0.8 no sediment
0.7 6.4 no sediment
0.9 0.4 12.1 14.2 1.9 8.6 3.0 5.8 5.4 4.5 2.8 5.5 0.9 1.8 3.1 5.7 5.9 8.3
6.1xlO-7 7.56x 10-8 1.59 x 10-7
1.97 X 10-7
4.14 x 10-8
3.00 X 3.00 x 1.54 X 3.43 X 1.89 X
4.48 x 10-8 2.41 x 10-8 1.03 x 10-7 1.72 x 10-8 3.lOx 10-8 6.90 x 107.59 x 10-8 8
323
10-7 10-8 10-7 10-8 10-7
3.98 X 10-8
1.13 X 10-6 1.68 X 10-7 1.01 X 10-7
8.58 x 10-8
4.54 X 10-8
6.72 X 10-8
3.43 x 10-8 1.11 X 10-7 8.15 X 10-8
1.14xlO-7
9.09 X 10-8
*Locations are shown in Figure la, band c; blank means below limit of quantitation, which was about 10-8 mol Sn/kg dry weight; areal standard deviation of chromatographic peaks on triplicate injection was < 15070; 070 organic matter of the sediments was estimated by heating at 375°C to constant weight.
324
MAGUIRE et ale
/r
~.' .;.
~ .~~'~ ... L.AKE 51 CL.A . IR .•: ,....
• • • 0379
... · .••.•• 0399 .
..
V
. .•.•••
/
~4 <:::J
.~~
~
0311
1L Is.
l
WINDSOR
~AAoomiA
DETROIT
\
1000 _ 2000
4000
2000 metres sOoo feet
~~~
Z~sG~ ~, 0352
~~IVER ~ .. 0346
ROUGE
PT. HENNEPIN
,
? o
1qoo
2qoO
metres
2000 4000 eOoo feet
FIG. I. Map ofDetroit River showing sampling locations; la is upper reach, Ib is middle reach, and lc is lower reach.
at which one might expect chronic toxic effects in sensitive organisms. As with the water samples, the BuzSnz+ species was detected in sediment at most of the locations at which Bu 3Sn + was detected, which again suggests that it is a degradation product of Bu3Sn + rather than being introduced to the river itself. With regard to BuSn3 + and inorganic tin in sediments, essentially the same comments apply as for the water samples. There was no correlation of concentration of butyltin species and inorganic tin with percent organic matter.
No organotin species other than the butyltin species were detected in Detroit River water or sediment. Tables 3 and 4 show concentrations of butyltin species and inorganic tin in water and sediment, respectively, of the St. Clair River. The locations are shown in Figure 2. In general, the subsurface water and sediment concentrations of all the butyltin species and inorganic tin are similar to those reported earlier for other locations in Ontario (Maguire et al. 1982, Maguire 1984), and
BUTYLTIN SPECIES AND INORGANIC TIN IN WATER AND SEDIMENT
325
SARNIA
• ?
0255
.. /v'.~. . ~ GIBRAl.~.:r. •. •. •. A .•. . .••R . '•. •.'•'••. • '•• . .
~ ...
,
•
·0223
~.·0224 . ->
",',
Is.
' .•.•..•.• C••. . E.LERQN
••....
, BAR POINT 0214.
.0213 0212.
0210.
f Lake Erie o !
I
1000 20'00
4000
2Km !
• Sampling Stations 2000 metre 6000 feet
FIG. Ie. Lower reach of Detroit River.
are similar to those reported above for the Detroit River. Table 3 also shows concentrations of the butyltin species and inorganic tin in the surface microlayer, as sampled with a rotating drum sampler. We have previously found very high concentrations of butyltin species in surface microlayers relative to subsurface waters (Maguire et al. 1982). Because the nature of the surface microlayer is profoundly affected by turbulence and the presence of both natural and anthropogenic surface-
FIG. 2. Map of St. Clair River showing sampling locations.
active material, however, we are inclined to view concentrations of toxic substances in the microlayer as being extremely variable with time. Therefore, quite apart from its implications for surfaceswelling biota, a contaminated microlayer serves as an imperfect indicator of subsurface water contamination. In the case of the St. Clair River samples, the microlayer results suggest that Bu3Sn + may be present in subsurface water below its detection limit at locations 1 and 2.
326
MAGUIRE et ale
TABLE 3. Concentrations (mol Sn/L) ofbutyltin species and total recoverable inorganic tin (TRIT) in both unfiltered surface microlayer and unfiltered subsurface water of the St. Clair River. * BU2Sn2+
BU3Sn+ Location
Microlayer
1 2 3 4 5 6
3.45 x 102.76 X 10-10
Subsurface
Microlayer
Subsurface
4.29 X 104.29 X 10-11 4.29 xlO- il 4.29 X 10- 11
4.29 X 10-
11
11
BuSn3 + 11
5.58 X 10- 10 4.29x 10- 11 8.58 X 10-11 1.29 X 10-10
Microlayer
TRIT
Subsurface
Microlayer
Subsurface
1.14xlO-
1.91 X 1.83 X 1.93 X 9.24 X 5.04 X 5.88 X
1.68 X 1.26 X 2.18 X 1.68 X 1.09 X 5.29 X
7.39 X 1.14 x 1.70 X 2.27 X
1O
10-10 10-10 10- 10 10- 10
1010-8 10-9 10- 10 10- 10 10- 10 8
10-9 10-9 10-9 10-10 10-9 10-9
*Locations are shown in Figure 2; blank means below limit of quantitation, which was about 3 x 10- 11 mol Sn/L for each species; areal standard deviation of chromatographic peaks on triplicate injection was less than 15070.
TABLE 4. Concentrations (mol Sn/kg dry weight) of butyltin species and total recoverable inorganic tin (TRIT) in top 2 em of sediment of St. Clair River. * 0J0 Organic
Location
Matter
1 2 3 4 5 6
0.12 0.38 0.29 no sediment 0.20 0.24
BuSn3 +
TRIT
5.86 X 10-8 3.45 X 10-8 3.30xl0-6 2.95 X 10-7
*Locations are shown in Figure 2; blank means below limit of quantitation, which was about 10-8 mol Sn/kg dry weight; areal standard deviation of chromatographic peaks on triplicate injection was less than 15%; organic matter content of the sediments was estimated by heating at 375°C to constant weight.
ACKNOWLEDGMENTS We thank G. A. Bengert, G. D. Bruce, Y. K. Chau, M. E. Comba, G. G. LaHaie, and R. F. Platford for help with the sampling, and A. Mudroch for determining the organic matter contents of some of the sediments.
REFERENCES Brinckman, F. E., Jackson, J. A., Blair, W. R., Olson, G. J., and Iverson, W. P. 1983. Ultratrace speciation and biogenesis of methyltin transport species in estuarine waters. In Trace Metals in Sea Water, eds. C. S. Wong, E. Boyle, K. W. Bruland, J. D. Burton, and E. D. Goldberg, pp. 39-72. N.Y.: Plenum Press. Chau, Y. K., Wong, P. T. S., Kramar, 0., and Bengert, G. A. 1981. Methylation of tin i~ the aquatic envi-
ronment. In International Conference on Heavy Metals in the Environment, Amsterdam, Sept. 1981, proceed. pub!. by World Health Organization, pp. 641-644. Davies, A. G., and Smith, P. J. 1980. Recent advances in organotin chemistry. Adv. Inorg. Chem. Radiochem. 23:1-77. Guard, H. E., Cobet, A. B., and Coleman, W. M., III. 1981. Methylation of trimethyltin compounds by estuarine sediments. Science 213:770-771. Harvey, G. W. 1966. Microlayer collection from the sea surface: a new method and initial results. Limnol. Oceanogr. 11:608-613. Keith, L. H., Crummett, W., Deegan, J., Jr., Libby, R. A., Taylor, J. K., and Wentler, G. 1983. Principles of environmental analysis. Anal. Chem. 55:2210-2218. Maguire, R. J. 1984. Butyltin compounds and inorganic tin in sediments in Ontario. Environ. Sci. Technol. 18:291-294.
BUTYLTIN SPECIES AND INORGANIC TIN IN WATER AND SEDIMENT ____ , and Huneault, H. 1981. Determination of butyltin species in water by gas chromatography with flame photometric detection. J. Chromatogr. 209:458-462. ____ , and Tkacz, R. J. 1983. Analysis ofbutyltin compounds by gas chromatography. Comparison of flame photometric and atomic absorption spectrophotometric detectors. J. Chromatogr. 268:99-101. ____ , Chau, Y. K., Bengert, G. A., Hale, E. J., Wong, P. T. S., and Kramar, O. 1982. Occurrence of organotin compounds in Ontario lakes and rivers. Environ. Sci. Technol. 16:698-702. ____ , Carey, J. H., and Hale, E. J. 1983. Degradation of the tri-n-butyltin species in water. J. Agric. Food Chem. 31:1060-1065. Seinen, W., Helder, T., Vernij, H., Penninks, A., and Leeuwangh, P. 1981. Short term toxicity of tri-nbutyltin chloride in rainbow trout (Salmo gairdneri Richardson) yolk sac fry. Sci. Total Environ. 19:155-166. Soderquist, C. J., and Crosby, D. G. 1980. Degradation
327
of triphenyltin hydroxide in water. J. Agric. Food Chem.28:111-117. Thompson, J. A. J., Pierce, R. C., Sheffer, M. G., Chau, Y. K., Cooney, J. J., Cullen, W. R., and Maguire, R. J. 1985. Organotin compounds in the aquatic environment: scientific criteria for assessing their effects on environmental quality. National Research Council of Canada Associate Committee on Scientific Criteria for Environmental Quality, NRCC Publ. No. 22494, Ottawa, Ontario, Canada, KIA OR6. Tobias, R. S. 1966. Sigma-bonded organometallic cations in aqueous solutions and crystals. Organometal. Chem. Rev. 1:93-129. Zuckerman, J. J., Reisdorf, R. P., Ellis, H. V., III, and Wilkinson, R. R. 1978. Organotins in biology and the environment. In Organometals and Organometal/oids, Occurrence and Fate in the Environment, eds. F. E. Brinckman and J. M. Bellama, pp. 388-422, American Chemical Society, Washington, D.C., ACS Symp. Ser. No. 82.
BUTYLTIN SPECIES AND INORGANIC TIN IN WATER AND SEDIMENT OF THE DETROIT AND ST. CLAIR RIVERS
R. James Maguire, Richard J. Tkacz, and David L. Sartor
Environmental Contaminants Division National Water Research Institute Department of the Environment Canada Centre for Inland Waters Burlington, Ontario L7R 4A6 ABSTRACT. Water and sediment samplesfrom 29 locations in the Detroit and St. Clair rivers were analyzed for the highly toxic tri-n-butyltin (Bu 3Sn+) species and for the less toxic di-n-butyltin (Bu2Sn2+) and n-butyltin (BuSn 3+) species and inorganic tin. In general, locations sampled in the St. Clair River were less contaminated with butyltin species than those in the Detroit River. Inorganic tin and BuSn3+ were detected in over 90% of all subsurface water samples, while Bu2Sn 2+ and BU3Sn+ were detected in 45 and 28% of the same samples, respectively. The highest concentration of BU3Sn + in subsurface water, 5.9 x 1rF10 mol Sn/L, was at the mouth of the Ecorse River, a tributary of the Detroit River. The three butyltin species and inorganic tin were also detected in 23-46% of all sediment samples. The highest concentrations ofBU3Sn+ in sediment werefound close to the mouths of the River Rouge, another tributary ofthe Detroit River, and the Ecorse River, and were 6.2 x 1rF7 and 1.7 x 1rF 7 mol Sn/kg dry weight, respectively, for the top 2 em of sediment. ADDITIONAL INDEX WORDS: Toxic substances, trace metals, industrial wastes.
Studies on the environmental persistence of butyltin and phenyltin compounds indicate that abiotic degradation generally occurs, as does biological degradation, through mechanisms of sequential dealkylation (e.g., Maguire et al. 1983) or dearylation (Soderquist and Crosby 1980); therefore, the series PhnSn(4-n)+ , CYnSn(4-n)+ and BunSn(4-n)+ (where in each case n < 4), OctnSn(4-n)+ (where n ~ 2), and MenSn(4-n)+ (where n ~ 4) may be present in the Canadian environment. The last series includes tri- and tetramethyltin, which are not released per se to the environment, since methylation of tin and methyltin compounds has been demonstrated in natural water-sediment mixtures (Chau et al. 1981, Guard et al. 1981). Our work deals with the aquatic environmental occurrence and persistence of butyltin compounds. Samples collected in 1981 at 30 locations in Ontario revealed, for the first time in Canada, the presence of methyltin and butyltin species, and inorganic tin, in some waters (Maguire et al. 1982)
INTRODUCTION Organotin compounds are used in three main ways, viz., as stabilizers for poly(vinyl chloride), as catalysts in the production of polyurethane foams, and as biocides (Zuckerman et al. 1978). The main organotin species which are likely to be released to the environment in Canada are triphenyltin (Ph3Sn +), tricyclohexyltin (CY3Sn +), tri-n-butyltin (Bu3Sn+), di-n-butyltin (BuzSnz+), di-n-octyltin (OctzSnz+), and dimethyltin (MezSnz+) (Thompson et al. 1985). Triphenyltin and tricyclohexyltin compounds are insecticides. Tri-n-butyltin compounds are used mainly as antifouling agents in paint for ships, boats, and docks, as slimicides in cooling towers, and in lumber preservation. Di-n-butyltin compounds are used as poly(vinyl chloride) stabilizers, as are dimethyltin compounds, and as catalysts in a number of industrial processes. Di-noctyltin compounds are used as stabilizers in some food wrappings. 320
BUTYLTIN SPECIES AND INORGANIC TIN IN WATER AND SEDIMENT and sediments (Maguire 1984). In general, the occurrence of inorganic tin was widespread, methyltin species were found in harbours or areas of industrial activity, and butyltin species were found mainly in harbours and other areas of heavy boating or shipping traffic. In addition, tri-nbutylmethyltin and di-n-butyldimethyltin were found in the sediments of some harbours, indicating that butyltin species can be methylated in aquatic environments. This article reports the extent of butyltin species contamination of water and sediment in the Detroit River (23 locations sampled in June 1983) and the St. Clair River (6 locations sampled in October 1983). For brevity, the tri-n-butyltin, di-n-butyltin, and n-butyltin species are referred to in this article as though they existed only in cationic form (e.g., Bu3Sn +), since there is evidence that at least some organotin species exist in water as cations (e.g., Tobias 1966, Maguire et al. 1983). We were more interested in debutylation reactions than in cation hydrolysis or the identity of the counter ion, mainly because the toxicity of butyltin compounds in general decreases with decreasing number of butyl groups (Davies and Smith 1980). EXPERIMENTAL METHODS Water and sediment samples were collected from small boats which had not been painted with antifouling paint. Materials Bis (tri-n-butyltin) oxide (97%), tri-n-butyltin chloride (97070), di-n-butyltin dichloride (96.5%), n-butyltin trichloride (95%), and metallic tin (99.99%) were from Ventron (Danvers, MA). Tropolone (2-hydroxy-2,4,6-cYcloheptatrien-l-one) was from Aldrich (Milwaukee, WI). All organic solvents were pesticide grade from Caledon Laboratories (Georgetown, Ont.). All mineral acids were reagent grade, but the HCI was washed with 1% wIv tropolonelbenzene to remove inorganic tin. The Grignard reagent n-pentylmagnesium bromide was prepared from commonly available chemicals. All butyltin compounds were purified by passage in benzene or hexane through a 60 x 1.5 cm Ld. column of activated silica gel and were pure, as judged by gas chromatography of their npentyl derivatives (cf. below) with flame photometric, flame ionization, and electron capture detectors.
321
Determination of Butyltin Species and Inorganic Tin in Water Eight litres of subsurface water (0.5 m) were collected in amber glass bottles and the contents were acidified to pH 1 and stored at 4°C until extraction. Analyses of the unfiltered water samples for butyltin species (Bu3Sn +, BU2Sn2+, and BuSn3 + ) and inorganic tin (Sn (II) and Sn (IV» (Maguire and Huneault 1981) involved extraction with 0.5% (w Iv) tropolonelbenzene, derivatization of the extract with n-pentylmagnesium bromide, silica gel column clean up, and determination of the Bun Pe4-nSn derivatives by gas chromatography• atomic absorption spectrophotometry (MagUIre and Tkacz 1983). Considering that a fairly specific detector for tin was used in the analyses, identities of the BunPe4_n Sn species were deemed to be confirmed by co-chromatography with authentic standards on two column packing materials of widely varying polarity. In the quantitation of the analytes, use was made of appropriate reagent blanks. The results reported in this article are above the limit of quantitation, which is defined (Keith et al. 1983) as the reagent blank value plus ten times its standard deviation. In our case, this was equivalent to stating that a chromatographic peak was not accepted as real unless it was at least 2.5 times as large as any corresponding peak in the reagent blank. Recoveries of the butyltin species and Sn(lV) spiked at 10-6 - 10-5 mol Sn/L in acidified water were 96-103 % (Maguire and Huneault 1981), and the limit of quantitation for each of the Bu Pe Sn species is about 3 x 10- 11 mol Sn/L. At ;i~ locations in the St. Clair River, 4-litre samples of the surface microlayer were obtained with a rotating drum sampler similar to that described by Harvey (1966). The drum sampler is estimated to collect the top 60 J.'m of the water column. The surface microlayer samples were analyzed in the same way as the subsurface water samples. Determination of Butyltin Species and Inorganic Tin in Sediment Sediment samples were analyzed by the method of Maguire (1984) which is briefly described here. Sediment samples were collected with an Ekman dredge, the top 2 cm were scraped off in.to glass jars, and the sediment was kept fr<,lzen until analysis. The sediment was freeze-dned, stones and other debris were removed, and the sediment was
322
MAGUIRE et ale
passed through a 850-pm sieve after being ground by mortar and pestle. Ten g of dry sediment was refluxed for 2 hr with 0.25 g of tropolone in 100 mL of benzene. The mixture was filtered, and the filtrate was derivatized, cleaned up, and analyzed as described above. An estimate of the organic matter content of the sediments was made by heating separate portions at 375°C to constant weight. Recoveries of the butyltin species and Sn (IV) spiked at 10-7 - 10-3 mol Sn/kg dry weight were quantitative. The limit of quantitation for each of the Bun Pe4_n Sn species in sediment is about 10-8 mol Sn/kg dry weight (Maguire 1984). Although Sn (IV) was the only inorganic tin species for which recoveries were determined in spiking experiments, the inorganic tin in the environmental samples is reported as "total recoverable inorganic tin" since it has been shown that hydride derivatization of either Sn (II) or Sn (IV) yields SnH4 (Brinckman et al. 1983), and thus any Sn (II) that may be present in our samples may similarly be pentylated to tetrapentyltin.
RESULTS AND DISCUSSION Tables 1 and 2 show concentrations of butyltin species and inorganic tin in water and sediment, respectively, of the Detroit River. The locations are shown in Figure 1. Table 1 shows that Bu3Sn+ and Bu2Sn2 + were detected in about one third of the subsurface water samples from the Detroit River, while BuSn3 + and inorganic tin were detected in almost all of the samples. The aqueous concentrations of all the butyltin species and inorganic tin are in general similar to those reported for some other locations in Ontario (Maguire et al. 1982). Since the toxicity of butyltin compounds decreases with decreasing number of butyl groups (Davies and Smith 1980), the Bu3Sn + concentrations are of most interest. The highest concentration of Bu3Sn + in water was at the mouth of the Ecorse River (site 0311), and was about 40/0 of the Lq~ value of 1.5 x 10-8 mol Sn/L for rainbow trout yolk sac fry (Seinen et al. 1981). As noted above, Bu3Sn+ is used as an anti-
TABLE 1. Concentrations (mol Sn/L) of butyltin species and total recoverable inorganic tin (TRIT) in unfiltered subsurface water of the Detroit River. * Location 0399 0379 0386 0370 0381 0353 0352 0346 0330 0314 0311 0280 0269 0257 0255 0224 0223 0231 0214 0213 0212 0210 0203
BU2Sn2+
BU3Sn+ 6.90 x 10-
11
2.14 x 10-10
3.4 x 10- 11 3.79x10- 1O 3.19x10- 1O 5.86 x 10- 10
4.29 X 5.58 x 3.86 x 6.01 X
10-11 10-10 10-10 10- 10
3.10x 10-10 3.45 x 10-11
8.15 x 10-10 4.29 X 10-11
2.07 x 10-10
3.43 X 10- 10
BuSn3 +
TRIT
9.66x 1.14 x 3.98 X 5.68 x 2.27 x 1.70 x
10
1010-10 10- 10 10-11 10- 10 10- 10
6.22 x 3.36 X 2.48 X 1.68 X 1.09 X 5.46 X
10-9 10- 10 10-8 10- 10 10-9 10-9
1.70 X 2.27 X 1.70 X 1.70 X 2.84 x 1.14 x
10- 10 10- 10 10- 10 10-10 10-10 10-10
5.04 X 6.81 X 4.20 X 5.88 X 1.18 X 2.52 X
10-9 10-9 10- 10 10-10 10-9 10-10
2.84 x 10-10 1.70 x 10-10 3.41 X 10-10 2.27 X 10- 10 1.70 x 10- 10 1.70 x 10- 10 1.14 x 10- 10 5.68 x 10- 11 1.14x 10-10
1.43 X 6.72 x 1.68 X 1.93 X 2.52 x 5.88 X 2.52 X 3.95 X 5.04 x
10-9 10-10 10-9 10-9 10-10 10- 10 10-10 10-9 10-10
*Locations are shown in Figure la, band c; blank means below limit of quantitation, which was about 3 x 10- 11 mol Sn/L for each species; areal standard deviation of chromatographic peaks on triplicate injection was < 15070.
BUTYLTIN SPECIES AND INORGANIC TIN IN WATER AND SEDIMENT fouling agent in boat and dock paint, as a lumber preservative, and as a slimicide in cooling towers. Although most of the locations in the Detroit River at which Bu3Sn + was detected in water are close to ship berths or marinas, it is interesting to note that the second highest concentration of Bu3Sn + was in the middle of the river north of Fighting Island (site 0330). The Bu2Sn2 + detected in subsurface water of the Detroit River could be introduced from the use of dibutyltin compounds as poly(vinyl chloride) stabilizers, or it could be a degradation product of Bu 3Sn + which is perhaps more likely since it was found at most of the locations at which Bu3Sn + was detected. Monobutyltin compounds do not appear to be used commercially, so the BuSn3+ species in water is most likely a degradation product of Bu2Sn2 +. In contrast to our earlier study (Maguire et al. 1982), BuSn3+ was frequently detected in subsurface water, and its presence at any particular location suggests introduction of either Bu2Sn2 + or BU3Sn + , or both, at that location
or upstream. The inorganic tin detected in subsurface water may be present naturally, may be introduced in inorganic form, and/or may be a degradation product of organotin compounds. Table 2 shows that Bu3Sn + and Bu2Sn2 + were detected in the top 2 cm of sediment at about half of the sampling locations in the Detroit River, while BuSn3+ and inorganic tin were detected in about one quarter of the samples. The concentrations in sediment of all the butyltin species and inorganic tin are in general similar to those reported for some other locations in Ontario (Maguire 1984). The highest concentrations of Bu3Sn + were found close to the mouth of the River Rouge (site 0346) and at the mouth of the Ecorse River (site 0311) (6.1 x 10-7 and 1.6 x 10-7 mol Sn/kg dry weight, respectively). Although the biological availability, hence toxicological significance, of sediment-associated Bu3Sn + has yet to be established, the water and sediment results combined indicate these two locations as the most likely of all locations sampled in the Detroit River
TABLE 2. Concentrations (mol Sn/kg dry weight) of butyltin species and total recoverable inorganic tin (TRIT) in top 2 cm of sediment of Detroit River. * 070 Organic Location
0399 0379 0386 0370 0381 0353 0352 0346 0330 0314 0311 0280 0269 0257 0255 0224 0223 0231 0214 0213 0212 0210 0203
Matter
BU2Sn2+
BU3Sn+
BuSn3 +
TRIT
2.84 x 10-8
1.49 X 10-6
0.8 no sediment
0.7 6.4 no sediment
0.9 0.4 12.1 14.2 1.9 8.6 3.0 5.8 5.4 4.5 2.8 5.5 0.9 1.8 3.1 5.7 5.9 8.3
6.1xlO-7 7.56x 10-8 1.59 x 10-7
1.97 X 10-7
4.14 x 10-8
3.00 X 3.00 x 1.54 X 3.43 X 1.89 X
4.48 x 10-8 2.41 x 10-8 1.03 x 10-7 1.72 x 10-8 3.lOx 10-8 6.90 x 107.59 x 10-8 8
323
10-7 10-8 10-7 10-8 10-7
3.98 X 10-8
1.13 X 10-6 1.68 X 10-7 1.01 X 10-7
8.58 x 10-8
4.54 X 10-8
6.72 X 10-8
3.43 x 10-8 1.11 X 10-7 8.15 X 10-8
1.14xlO-7
9.09 X 10-8
*Locations are shown in Figure la, band c; blank means below limit of quantitation, which was about 10-8 mol Sn/kg dry weight; areal standard deviation of chromatographic peaks on triplicate injection was < 15070; 070 organic matter of the sediments was estimated by heating at 375°C to constant weight.
324
MAGUIRE et ale
/r
~.' .;.
~ .~~'~ ... L.AKE 51 CL.A . IR .•: ,....
• • • 0379
... · .••.•• 0399 .
..
V
. .•.•••
/
~4 <:::J
.~~
~
0311
1L Is.
l
WINDSOR
~AAoomiA
DETROIT
\
1000 _ 2000
4000
2000 metres sOoo feet
~~~
Z~sG~ ~, 0352
~~IVER ~ .. 0346
ROUGE
PT. HENNEPIN
,
? o
1qoo
2qoO
metres
2000 4000 eOoo feet
FIG. I. Map ofDetroit River showing sampling locations; la is upper reach, Ib is middle reach, and lc is lower reach.
at which one might expect chronic toxic effects in sensitive organisms. As with the water samples, the BuzSnz+ species was detected in sediment at most of the locations at which Bu 3Sn + was detected, which again suggests that it is a degradation product of Bu3Sn + rather than being introduced to the river itself. With regard to BuSn3 + and inorganic tin in sediments, essentially the same comments apply as for the water samples. There was no correlation of concentration of butyltin species and inorganic tin with percent organic matter.
No organotin species other than the butyltin species were detected in Detroit River water or sediment. Tables 3 and 4 show concentrations of butyltin species and inorganic tin in water and sediment, respectively, of the St. Clair River. The locations are shown in Figure 2. In general, the subsurface water and sediment concentrations of all the butyltin species and inorganic tin are similar to those reported earlier for other locations in Ontario (Maguire et al. 1982, Maguire 1984), and
BUTYLTIN SPECIES AND INORGANIC TIN IN WATER AND SEDIMENT
325
SARNIA
• ?
0255
.. /v'.~. . ~ GIBRAl.~.:r. •. •. •. A .•. . .••R . '•. •.'•'••. • '•• . .
~ ...
,
•
·0223
~.·0224 . ->
",',
Is.
' .•.•..•.• C••. . E.LERQN
••....
, BAR POINT 0214.
.0213 0212.
0210.
f Lake Erie o !
I
1000 20'00
4000
2Km !
• Sampling Stations 2000 metre 6000 feet
FIG. Ie. Lower reach of Detroit River.
are similar to those reported above for the Detroit River. Table 3 also shows concentrations of the butyltin species and inorganic tin in the surface microlayer, as sampled with a rotating drum sampler. We have previously found very high concentrations of butyltin species in surface microlayers relative to subsurface waters (Maguire et al. 1982). Because the nature of the surface microlayer is profoundly affected by turbulence and the presence of both natural and anthropogenic surface-
FIG. 2. Map of St. Clair River showing sampling locations.
active material, however, we are inclined to view concentrations of toxic substances in the microlayer as being extremely variable with time. Therefore, quite apart from its implications for surfaceswelling biota, a contaminated microlayer serves as an imperfect indicator of subsurface water contamination. In the case of the St. Clair River samples, the microlayer results suggest that Bu3Sn + may be present in subsurface water below its detection limit at locations 1 and 2.
326
MAGUIRE et ale
TABLE 3. Concentrations (mol Sn/L) ofbutyltin species and total recoverable inorganic tin (TRIT) in both unfiltered surface microlayer and unfiltered subsurface water of the St. Clair River. * BU2Sn2+
BU3Sn+ Location
Microlayer
1 2 3 4 5 6
3.45 x 102.76 X 10-10
Subsurface
Microlayer
Subsurface
4.29 X 104.29 X 10-11 4.29 xlO- il 4.29 X 10- 11
4.29 X 10-
11
11
BuSn3 + 11
5.58 X 10- 10 4.29x 10- 11 8.58 X 10-11 1.29 X 10-10
Microlayer
TRIT
Subsurface
Microlayer
Subsurface
1.14xlO-
1.91 X 1.83 X 1.93 X 9.24 X 5.04 X 5.88 X
1.68 X 1.26 X 2.18 X 1.68 X 1.09 X 5.29 X
7.39 X 1.14 x 1.70 X 2.27 X
1O
10-10 10-10 10- 10 10- 10
1010-8 10-9 10- 10 10- 10 10- 10 8
10-9 10-9 10-9 10-10 10-9 10-9
*Locations are shown in Figure 2; blank means below limit of quantitation, which was about 3 x 10- 11 mol Sn/L for each species; areal standard deviation of chromatographic peaks on triplicate injection was less than 15070.
TABLE 4. Concentrations (mol Sn/kg dry weight) of butyltin species and total recoverable inorganic tin (TRIT) in top 2 em of sediment of St. Clair River. * 0J0 Organic
Location
Matter
1 2 3 4 5 6
0.12 0.38 0.29 no sediment 0.20 0.24
BuSn3 +
TRIT
5.86 X 10-8 3.45 X 10-8 3.30xl0-6 2.95 X 10-7
*Locations are shown in Figure 2; blank means below limit of quantitation, which was about 10-8 mol Sn/kg dry weight; areal standard deviation of chromatographic peaks on triplicate injection was less than 15%; organic matter content of the sediments was estimated by heating at 375°C to constant weight.
ACKNOWLEDGMENTS We thank G. A. Bengert, G. D. Bruce, Y. K. Chau, M. E. Comba, G. G. LaHaie, and R. F. Platford for help with the sampling, and A. Mudroch for determining the organic matter contents of some of the sediments.
REFERENCES Brinckman, F. E., Jackson, J. A., Blair, W. R., Olson, G. J., and Iverson, W. P. 1983. Ultratrace speciation and biogenesis of methyltin transport species in estuarine waters. In Trace Metals in Sea Water, eds. C. S. Wong, E. Boyle, K. W. Bruland, J. D. Burton, and E. D. Goldberg, pp. 39-72. N.Y.: Plenum Press. Chau, Y. K., Wong, P. T. S., Kramar, 0., and Bengert, G. A. 1981. Methylation of tin i~ the aquatic envi-
ronment. In International Conference on Heavy Metals in the Environment, Amsterdam, Sept. 1981, proceed. pub!. by World Health Organization, pp. 641-644. Davies, A. G., and Smith, P. J. 1980. Recent advances in organotin chemistry. Adv. Inorg. Chem. Radiochem. 23:1-77. Guard, H. E., Cobet, A. B., and Coleman, W. M., III. 1981. Methylation of trimethyltin compounds by estuarine sediments. Science 213:770-771. Harvey, G. W. 1966. Microlayer collection from the sea surface: a new method and initial results. Limnol. Oceanogr. 11:608-613. Keith, L. H., Crummett, W., Deegan, J., Jr., Libby, R. A., Taylor, J. K., and Wentler, G. 1983. Principles of environmental analysis. Anal. Chem. 55:2210-2218. Maguire, R. J. 1984. Butyltin compounds and inorganic tin in sediments in Ontario. Environ. Sci. Technol. 18:291-294.
BUTYLTIN SPECIES AND INORGANIC TIN IN WATER AND SEDIMENT ____ , and Huneault, H. 1981. Determination of butyltin species in water by gas chromatography with flame photometric detection. J. Chromatogr. 209:458-462. ____ , and Tkacz, R. J. 1983. Analysis ofbutyltin compounds by gas chromatography. Comparison of flame photometric and atomic absorption spectrophotometric detectors. J. Chromatogr. 268:99-101. ____ , Chau, Y. K., Bengert, G. A., Hale, E. J., Wong, P. T. S., and Kramar, O. 1982. Occurrence of organotin compounds in Ontario lakes and rivers. Environ. Sci. Technol. 16:698-702. ____ , Carey, J. H., and Hale, E. J. 1983. Degradation of the tri-n-butyltin species in water. J. Agric. Food Chem. 31:1060-1065. Seinen, W., Helder, T., Vernij, H., Penninks, A., and Leeuwangh, P. 1981. Short term toxicity of tri-nbutyltin chloride in rainbow trout (Salmo gairdneri Richardson) yolk sac fry. Sci. Total Environ. 19:155-166. Soderquist, C. J., and Crosby, D. G. 1980. Degradation
327
of triphenyltin hydroxide in water. J. Agric. Food Chem.28:111-117. Thompson, J. A. J., Pierce, R. C., Sheffer, M. G., Chau, Y. K., Cooney, J. J., Cullen, W. R., and Maguire, R. J. 1985. Organotin compounds in the aquatic environment: scientific criteria for assessing their effects on environmental quality. National Research Council of Canada Associate Committee on Scientific Criteria for Environmental Quality, NRCC Publ. No. 22494, Ottawa, Ontario, Canada, KIA OR6. Tobias, R. S. 1966. Sigma-bonded organometallic cations in aqueous solutions and crystals. Organometal. Chem. Rev. 1:93-129. Zuckerman, J. J., Reisdorf, R. P., Ellis, H. V., III, and Wilkinson, R. R. 1978. Organotins in biology and the environment. In Organometals and Organometal/oids, Occurrence and Fate in the Environment, eds. F. E. Brinckman and J. M. Bellama, pp. 388-422, American Chemical Society, Washington, D.C., ACS Symp. Ser. No. 82.