Environ. Sci. Technol. 1990, 24, 1536-1541
Habibian, M. T.; O’Melia, C. R. J. Environ. Eng. Diu. (Am. SOC.Ciu. Eng.) 1975,101, 567. Yao, K.M. Ph.D. Dissertation; University of North Carolina at Chapel Hill, 1968. Spielman,L. A.;FitzPatrick, J. A. J . Colloid Interface Sci.
Prieve, D. C.; Ruckenstein, E. AIChE J. 1974,20, 1178. Rajagopalan, R.; Chu, R. Q. J. Colloid Interface Sci. 1982, 86,299.
Dukhin, S.S.;Lyklema, J. Langmuir 1987,3,94. Van Leeuwen, H. P.; Lyklema, J. Ber. Bunsenges. Phys.
1973,42,607.
Chem. 1987,91,288.
Yoshimura, Y.: Ueda, K.; Mori, K.; Yoshoka, N. Int. Chem.
Tomlinson, G. A. Philos. Mag. J . Sci. 1928,6,695. Krupp, H. Adu. Colloid Interface Sci. 1967,1, 111. Dahneke, B.J . Colloid Interface Sci. 1972,40, 1. Reerink, H.; Overbeek, J. Th. G. Discuss. Faraday SOC.
Eng. 1980,20,600.
J.; Wishart, A. J. Colloids Surf. 1980, 1, 313. Hirtzel, C. J.; Rajagopalan,R. Colloidal Phenomena; Noyes Publications: Park Ridge, NJ, 1985. Adamczyk, Z.; Czamecki,J.;Dabros, T.; van de Ven, T.G.M. Gregory,
Adu. Colloid Interface Sci. 1983,19,183. Wang, Z.Ph.D. Dissertation; Johns Hopkins University, 1985. Israelachvili, J. N. Chem. Scr. 1985,25,7. Elimelech,M. J. Chem. SOC.,Faraday Trans. 1990,86,1623. Elimelech, M.; O’Melia C. R. Langmuir 1990,6, 1153. Tobiason, J. E. Colloids Surf. 1989,39,53. Hull, M.; Kitchener, J. A. Trans. Faraday SOC.1969,65, 3093. Bowen, B.D.;Epstein, M. J . Colloid Interface Sci. 1979, 72,81. Derjaguin, B. V.; Muller, V. M. Dokl. Akad. Nauk SSSR (Engl. Transl.) 1967,176,738. Honig, E. P.; Roebersen, G. J.; Wiersema, P. H. J . Colloid Interface Sci. 1971,36,97.
1954,18,74.
Ottewill, R. H.; Shaw, J. N. Discuss. Faraday SOC.1966, 42,154.
Joseph-Petit, A. M.; Dumont, F.; Watillon, A. J . Colloid Interface Sci. 1973,43, 649.
Penners, N.H. G.; Koopal, L. K. Colloids Surf. 1987,28, 67.
Tobiason, J. E. Ph.D. Dissertation; Johns Hopkins University, 1987. Spielman,L. A.;Cukor, P. M. J. Colloid Interface Sci. 1973, 43,51. Received for review March 12,1990.Revised manuscript received June 1, 1990. Accepted June 20, 1990. We acknowledge the support of the U.S. Environmental Protection Agency under Research Grant R812760.
N-Chloramine Derivatization Mechanism with Dansylsulfinic Acid: Yields and Routes of Reaction James A. Jersey, E. Choshen, J. N. Jensen, and J. Donald Johnson”
Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27599-1400 Frank E. Scully, Jr.
Department of Chemical Sciences, Old Dominion University, Norfolk, Virginia 23508 At present, direct methods for analysis of chloramines are unavailable. Several approaches using derivatization-based methods for their anlaysis have been reported in the literature. One such method employs reaction of chloramines with dansylsulfinic acid to produce stable dansylsulfonamide products, which are analyzed by HPLC. This paper reports results of experiments examining the routes and yields produced during the dansylation of model chloramine solutions. Potential limitations of the method arise due to matrix effects, low yields for dilute chloramine concentrations, and a marked dependence of yield upon the composition of the chloramine pool. These limitations disallow quantitative application of the dansylation method to the analysis of chloramine mixtures.
Introduction When chlorine is used for water and wastewater disinfection, a wide variety of chloramines are formed (1-3). Some of these compounds may have important health implications ( 4 ) . There is little data, however, on the composition and chemistry of the organic chloramine fraction in water or wastewater. To a large extent the gaps in our knowledge regarding the significance and environmental fate of the chloramines is due to the lack of sensitive and selective methods for their analysis. Several researchers have proposed methods for analysis of chloramines that are based upon derivatization procedures and analysis of the resulting products by high-performance liquid chromatography (HPLC). The Scully et 1536
Environ. Sci. Technol., Vol. 24, No. 10, 1990
al. (5, 6 ) method is based upon derivatization of chloramines with dansylsulfinic acid to produce stable and highly fluorescent dansylated products. Unfortunately this derivatization proceeds indirectly through the formation and reaction of the dansyl chloride intermediate. Lukasewycz et al. (7) proposed a derivatization method based upon 2-mercaptobenzothiazole. Although the yields are somewhat higher and the kinetics faster than the dansylation method, this derivatization procedure also appears to proceed through an intermediate and thus may suffer problems similar to those of the dansylation method discussed below. Ammonia and glycine are both commonly found in wastewater (8) and upon chlorination are converted rapidly to their N-chloro derivatives (9). These compounds were selected as models for study of the routes and yields produced in derivatization of aqueous organic and inorganic chloramines with dansylsulfinic acid. The purpose of this paper is to clarify an assertion made in previous work of the dependence of product yields on relative kinetics (5). Specifically, kinetic and yield data from model compound solutions will be used to demonstrate limitations for quantitative application of the dansylation method to analysis of chloramine mixtures. Experimental Section
Materials. Amino acids and dansylated amino acid standards were obtained from Sigma Chemical Co. and used without further purification. Glassware contacting
0013-936X/90/0924-1536$02.50/0
0 1990 American Chemical Society
Table I. Molar Absorptivities for Monochloramine and N-Chloroglycine molar absorDtivitv. M-' cm-' 244 nm 280 nm monochloramine observed literature N-chloroglycine observed literature
'Reference
390 455' 415b
39 62' 40b
319 316' 300b
177 183a 230b
12. Reference 23.
the dansyl reagents and dansyl amino acids was silanized before use. Water was deionized by mixed-bed ion exchange, passed through an activated carbon bed, and glass distilled. Chloramines were synthesized by adding diluted sodium hypochlorite with stirring to buffered solutions (phosphate buffer 0.02 M, pH 7.0) containing the appropriate amine and left to sit for 0.5 h before use. In all experiments, the chlorine-to-nitrogen molar ratio was less than or equal to 1. Procedure for Spectrophotometric Measurements. Concentrations of N-chloroglycine and monochloramine in model solutions were determined spectrophotometrically by a method analogous to that described by Isaac and Morris (10). Since both species have characteristic absorbances (molar absorptivities) at the two wavelengths selected for study, simultaneous measurement of absorbance at each wavelength leads to two equations, which can be solved for the concentrations of the individual chloramine species. The two simultaneous equations used in this study are
where A244and Azso are the measured UV absorbances at 244 and 280 nm, respectively, L is the path length (cm), Cl and C2 are the concentrations of the two N-chloramines, and E, and E, are the measured molar absorptivities for N-chloramines 1 and 2 at the indicated wavelengths. Molar absorptivities of N-chloroglycine and monochloramine were determined with calibration curves prepared at 280 and 244 nm. Total chloramine concentrations of stock solutions used in constructing calibration curves were measured by amperometric titration (11). Molar absorptivities for N-chloroglycine and monochloramine are listed in Table I. A Cary Model 219 spectrophotometer with 1-cm quartz cells was used in all spectrophotometric measurements. Dansylation Procedure. The dansylation procedure followed was that reported by Scully and co-workers (5) with the exception of minor modifications. To 20-mL samples were added, in order 0.4 g of sodium bicarbonate, 20 mL of acetonitrile, one drop of 5 N sodium hydroxide, and 0.6 mL of a 0.01 M dansylsulfinic acid solution. The derivatization was allowed to proceed overnight in darkness. The pH of the derivatization matrix was measured to be 9.6 (f0.2). No additional sample treatment was needed prior to analysis by HPLC. Liquid Chromatography. The HPLC system used in these experiments consisted of a Water Associates Model 660 solvent programmer, two M-6000A pumps, and a Model U6K injector. Detection employed a Perkin-Elmer 650-10s fluorescence spectrophotometer (xenon lamp) with
0.016
1
NHzCl
0-0
4
P)
g
0.012
0
gu,
0.008
4
0.004
n
0.000 0
1
2
3
4
5
6
Time (hours) Figure 1. Measured absorbance at 445 nm during the dansylation of 5 X lo-' M monochloramine and N-chloroglycine.
excitation and emission wavelengths of 342 and 510 nm, respectively (12). For both wavelengths, the bandwidth was 10 nm. Detector operation under these conditions gave optimum sensitivity for detecting dansyl amino acids. A reverse-phase CIEcolumn (Zorbax ODS 4.6 mm i.d. X 25 cm length) and mobile-phase solvents of 0.025 M sodium acetate adjusted to pH 4.5 with acetic acid (solvent A) and acetonitrile (solvent B) were used. A linear gradient was employed with the following flow program: initial 90% A, 10% B; to 100% B in 1 h and 48 min. The flow rate was 1.0 mL/min for all separations. Dansylnorvaline was added to model solutions prior to HPLC analysis as an internal standard.
Results Yields, Reaction Rates, and Products. By use of commercial standards the HPLC fluorescence detector was calibrated to determine concentrations of dansylamide and dansylglycine in dilute solution. Solutions of N-chloroglycine (5 X M) and monochloramine (5 X M) were prepared (initial molar [N]:[Cl] = 1)and derivatized in the normal manner. Aliquots of each solution were removed at different time intervals to determine the yield of dansylamide and dansylglycine formed. As shown previously (5) 6-9 h was needed for the reaction to go to completion under the conditions used in these experiments. Dansylamide was produced in higher yields than dansylglycine. Large amounts of a chromatographically unidentified compound were found during the reaction of dansylsulfinic acid with either N-chloroglycine or monochloramine. Production of artifacts from the derivatization procedure has been reported previously (6, 13, 14). Production and Disappearance of Dansyl Chloride. Dansyl chloride was found to exhibit a local absorption maximum at 445 nm with a molar absorptivity of 31 M-' cm-'. Since dansyl chloride was the only compound within the derivatization matrix found to absorb significantly at this wavelength, the dansylation of 5 X M solutions of either monochloramineor N-chloroglycine was followed at this wavelength to monitor for the presence of the dansyl chloride intermediate. Results are plotted in Figure 1. For both of the chloramines examined, there is a fast accumulation of dansyl chloride followed by a slower decrease. The maximum amount of dansyl chloride produced from N-chloroglycine is less and peaks earlier than that produced from monochloramine. The hydrolysis of dansyl chloride in the dansylation matrix appears to be the main route of loss as shown in Figure 1. Loss rates were similar for the two experiments. In separate experiments examining the hydrolysis of dansyl chloride, rates were measured at two wavelengths and three Environ. Sci. Technol., Voi. 24, No. 10, 1990
1537
Table 11. Solution and Product Composition for Examining the Dansylation of Chloramine Mixtures
solution
Clz
A B
0.07
C
0.50 1.24
0.00
1.34 1.34
2.72 270
D E F a
precursor amine concn, M X NH, Gly Cl-NH2
0.84
13.4 13.4
0.00
Cl-Gly
0.00
Dans-Gly, M X IO"
dansylated product formation Dans-NHZ, yield,b % M X 10"
0.043 0.51
0.00
2.72 2.72 2.72 2.72
total Clz resid," MX
0.29 0.60 0.043
0.76
0.53
0.30
0.6
1.1 13
26 25
1.2 14
28
2.1 2.3
1.4 5.0 1.0
0.80 0.80
yield, %
6.6 3.4
26
Total chlorine residual measured by amperometric titration. *Yields are expressed as a percent of chlorinated starting material.
concentrations. The reaction was pseudo first order (constant hydroxide ion concentration) with an approximate observed rate constant of 2.7 (f1.6) X lo4 s-l at pH 9.6 (f0.2) and 25 (f3) "C. Reaction between Dansyl Chloride and the Parent Amine. The effect of dansyl chloride concentration upon the yield of dansylated product was examined by using glycine as a model compound under the standard derivatization conditions. The yields are strongly dependent on, but not proportional to the dansyl chloride concentration. For M glycine, the yield of dansylglycine was approximately 4% when dansyl chloride was present at M. The corresponding yield was only 0.2% when the initial amount of dansyl chloride was reduced to M. Thus, a 10-fold decrease in the amount of dansyl chloride (from to lo-, M) produced a larger (approximately 20 times) decrease in the amount of dansylglycine formed. Chlorination and Dansylation of Two-Component Solutions. Mixtures of amino acids in solution produce mixtures of chlorinated amino acids upon chlorination with the distribution being dependent upon pH, the chlorineto-nitrogen molar ratio, relative rates for chlorination of the amines, and the stability of the chlorinated products formed. N-Chloroglycine and monochloraminewere again selected as models to study the dansylation of chloramine mixtures. The results of this experiment are listed in Table 11. Upon chlorination of excess ammonia (solutions A and B) all of the total residual chlorine concentration is due to NH2C1. Dansylamide is formed in 25-26% yield at both levels of chlorination. Upon chlorination and dansylation of glycine solutions (solutions C and D), observed yields of 2 % were similar for both levels of chlorination. These yields are roughly one-twelfth of that observed for monochloramine in solutions A and B. When mixtures of ammonia and glycine were chlorinated, the concentrations of each chloramine were measured by UV spectrophotometry. Their sum compared well with the total residual chlorine concentration measured by amperometric titration. At the pH of this experiment (pH 7), monochloramine and N-chloroglycine have been shown to be stable (15). When the initial concentrations of glycine and ammonia were equal, but in excess of the added chlorine concentration (solution E), UV spectroscopy indicated 18 times more N-chloroglycine was formed than NH2Cl. This is consistent with the higher basicity of glycine and its faster rate of reaction with chlorine (9). Following derivatization, the yield of dansylamide (based on the actual amount of NH2C1 determined by UV spectroscopy) was greater than the yield of dansylglycine, as was the case in the pure solutions A-D. With a large excess of ammonia present (solution F) the same trend is observed, indicating that there is consistently an order of magnitude greater yield of the dansyl derivative of NH&l than N-chloroglycine over a broad range of concentration ratios. 1538
Environ. Sci. Technol., Vol. 24, No. 10, 1990
Table 111. Effect of Excess Monochloramine on Yield of Dansylgl ycine soln G H I
total added, M C12 NH3 1.0 2.0 11.0
X
Gly 1.0
1.0 10.0
1.0 1.0
yield" Dans-Gly, % 2.9 5.1 21
" Yield is expressed as a percent of the starting glycine concentration. In solution F, Table 11, the concentrations (by UV spectroscopy) of N-chloroglycine and monochloramineare within a factor of 2 even though the concentration of ammonia is about 2 orders of magnitude higher than the glycine concentration. Such an excess is not atypical of what might be encountered in wastewaters. The yield of dansylamide formed after derivatization of this solution is again an order of magnitude greater than the dansylglycine formed. In a separate experiment, mixtures of glycine and ammonia were chlorinated to the chloramine maximum (molar [Cl]:[N] = l), derivatized, and analyzed by HPLC. Results are listed in Table 111. In the presence of a 10-fold excess of monochloramine the yield of dansylglycine is greatly enhanced. In contrast to the results in Table 11, no excess free base ammonia or glycine is present in the solutions examined in Table 111. Discussion Mechanism. A mechanism for the dansylation of chloramines has been proposed by Scully et al. (5). The proposed mechanism consists of two steps: (1)the transfer of chlorine from the chloramine to dansylsulfinic acid to form dansyl chloride and the amine and (2) the reaction of dansyl chloride and an amine to form a dansylamine (Scheme I). As discussed below, the data in this paper support this two-step mechanism. The results plotted in Figure 1 show that the formation of dansyl chloride (k3+ k4) is competitive with its disappearance by reaction with amino compounds plus hydrolysis (k, + k, + k7). Previously, the first step in this mechanism (formation of dansyl chloride by nucleophilic attack of the dansylsulfinate ion on the chloramine chlorine, k, + kl) did not appear to be as important as the second step, the reaction of dansyl chloride with the free amine ( 5 , 6 ) .This led to the conclusion that the dansylation procedure would yield a distribution of identified products proportional to that formed upon chlorination. Since rates of chlorination increase with increasing basicity, the most basic amines in a mixture are most likely to be chlorinated (9, 16). Similarly, the most basic amines react fastest with dansyl chloride and thus are most likely to be dansylated (17-19). The present work demonstrates the importance of the first step of the proposed mechanism. Monochloramine (solutions A and B, Table 11) is dansylated in higher yields
Scheme I. Mechanism for the Dansylation of N-Chloramines by Reaction with Dansylsulf'inic Acid
C h l o r i n a t i o n H H+COO*
t
llHz
N H ,
t
k,
HOC I
HOC1
H i C O O -
d
N H C I
k 2
F o r m a t i o n
R e a c t i o n s
H,O
t
NH,CI
H,O
t
D a n s y l
o f
C h l o r i d e
D a n s y l
o f
C h l o r i d e
H
It-c-c 0 0 -
"
H-N
H C I
HZ
@
t
t
H C I
H H
C#'*C
H
Ik S 0 3 H I
than N-chloroglycine (solutions C and D) even though ammonia is a weaker base than glycine. This follows from the higher maximum yield of dansyl chloride formed from the reaction of dansylsulfinic acid with monochloramine (k4,Scheme I and Figure 1) than with N-chloroglycine (k3, Scheme I and Figure 1). Though the production of dansyl
chloride is continuous, the combined reactions of hydrolysis plus dansylglycine product formation result in consumption of dansyl chloride to insignificant levels within 6 h for 5 X lo4 M N-chloroglycine. The net result is termination of the production of detectable dansylglycine. By contrast, the higher concentration of dansyl Environ. Sci. Technol., Vol. 24, No. 10, 1990
1530
chloride formed by monochloramine continues reacting to give higher dansylamide yields. According to Scheme I, the pH dependence of the dansyl chloride reaction depends on three factors: the hydroxide concentration, the concentration of amino compounds present as the free base, and the rate constant for the reaction between each base and dansyl chloride (19,ZO). For monochloramine and N-chloroglycine, the derivatization matrix pH of 9.6 represented a compromise between dansyl chloride and the speed of its reaction with the amine and its unwanted loss to hydrolysis by hydroxide. Yield. It is important to note that we observed small yields for the dansylation of the chloraminesand especially the more basic N-chloramino acids. Although somewhat dependent on reaction conditions such as cosolvent and pH, yields for the dansylation of N-chloramino acids (Nchloro derivatives of glycine, alanine, leucine, norvaline, and phenylalanine) at concentrations of M were generally on the order of a few percent or less. The presence of a high concentration of monochloramine enhanced the yield of the dansyl derivative of N-chloroglycine (Table 111). This follows if the concentration of dansyl chloride intermediate was greatly increased by the large concentration of monochloramine present. The main reasons for the low yields at lod M chloramine are probably a combination of the low concentration of dansyl chloride intermediate formed (only one dansyl chloride molecule is formed for each molecule of chloramine present) and the relatively fast hydrolysis of dansyl chloride to dansylsulfonic acid at pH 9.6 and these amine levels. Gray (19) found the second-order rate constant for the reaction of dansyl chloride in 0.5% acetone/water at pH 9.8 and 22 "C with hydroxide to be 15 L M-' s-l, glycine 13 L M-' s-', and ammonia 0.5 L M-' s-l and about 8 times slower in 50% acetone. These kinetics agree well with our estimated hydroxide hydrolysis rate of 6.8 L M-' s-l in 50% acetonitrile in water at pH 9.6. From Figure 1 and measured rate constants, it can be seen the rates of disappearance of dansyl chloride depend primarily on hydroxide ion concentration and very little on which amine is reacting at low amine concentrations. The higher yields of dansyl derivatives for monochloramine than for N-chloroglycine seen in Table I1 are not consistent with the faster glycine dansyl chloride reaction rate (19), k5,Scheme I. The yield would seem to be more dependent on how much dansyl chloride forms. This is supported by the larger amount of dansyl chloride formed from monochloramine in Figure 1, the yields in Tables I1 and 111, and the kinetics. One could anticipate that the kinetics of formation of dansyl chloride from the chloramine of strongly basic glycine could be slower (9,16) so lower amounts of dansyl chloride should be seen in Figure 1. The higher concentration of dansyl chloride formed by monochloramine, k4, Scheme I, is more important than its rate of reaction, k6, so the yield with monochloramine is higher. Gray (19) similarly found that successful derivatization is most importantly influenced by absolute concentrations of dansyl chloride. It is known that the reaction rates of dansyl chloride with amines are strongly dependent on various experimental factors such as pH, temperature, and dielectric constant of the solvent (19,20). Attempts to change the pH, ionic strength, and ratio of water to acetonitrile of the dansylation mixture did not, however, result in significant improvements in yields. This might be expected from competitive effects such as amine base ionization and increasing hydroxide concentration, and solubility problems at higher ionic strength and lower water concentrations.
+
1540
Environ. Sci. Technol., Vol. 24, No. 10, 1990
Implications for the Derivatization of Drinking Water and Wastewater Chloramines. When a wastewater or drinking water is chlorinated to higher concentrations, the amount of total chloramines, organic and inorganic, will increase until the chloramine maximum of the water is reached. When this same water is derivatized with dansylsulfinic acid, the concentration of dansyl chloride intermediate formed increases in proportion to the total concentration of chloramines. This higher concentration of dansyl chloride can in turn react with any free amines that exist in solution. This situation potentially raises the yields of the dansyl derivatives of compounds such as the N-chloramino acids above that which would be produced from a single-component solution of the N-chloramino acid. Because yields are influenced by the level of dansyl chloride intermediate formed, yields of products across the breakpoint curve may not necessarily be directly proportional to the levels of chloramines present. High amounts of one unchlorinated amine may compete with another for dansyl chloride intermediate, while a high monochloramine concentration can cause the yields of other amines to be raised by increasing the production of dansyl chloride. Thus, the dansylation method can provide only qualitative identification of chlorinated amines in aqueous mixtures. Even qualitative results have higher confidence at the chloramine maximum where all amines are chlorinated. At low chlorine-to-nitrogen molar ratios the frequency of false positives could increase due to the problems discwed above. Amidic nitrogens such as those involved in peptide bonds, which are not likely to chlorinate under typical disinfection conditions (9), essentially show no reactivity toward dansyl chloride (19). Conclusions
This paper reports potential limitations or disadvantages of the derivatization of chloramines with dansylsulfinic acid due to matrix effects, low yields at dilute concentrations of chloramines, and a marked dependence of yield upon reaction conditions. In addition, the relative slowness of the derivatization procedure, requiring hours for complete derivatization, biases the method toward detection of the more stable chloramines. As evidence supporting the potential importance of this problem, half-lives for many of the N-chloroamino acids, an important component of the chloramine pool, are on the order of hours or less (21). Combined, these factors make precise quantification of N-chloramines in complex mixtures impossible. The method can, however, provide qualitative identifications. In waters chlorinated to a [Cl]:[N] molar ratio of 1, this method can provide for the unambiguous identification of N-chloramino acids by GC/MS analysis of their methylated dansyl derivatives (22). Acknowledgments
We thank Jeffrey T. Jewell for generation of preliminary data. Registry No. Monochloramine,10599-90-3;N-chloroglycine, 35065-59-9;water, 7732-18-5; dansylsulfinic acid, 71288-39-6. Literature Cited (1) Le Cloirec, C.; Martin, G. In Water Chlorination: Chemistry, Environmental Impact and Health Effects; Jolley, R. L., et al., Eds.; Lewis Publishers: Chelsa, MI, 1985; Vol. 5, pp 821-834. (2) Ram, N.; Malley, J. P., Jr. J. Am. Water Works Assoc. 1984, 76, 74-81. ( 3 ) National Research Council. Drinking Water and Health:
Disinfectant and Disinfectant By-Products; National
Environ. Sci. Technol. 1990. 2 4 , 1541-1548
Margerum, D. W.; Gray, E. T., Jr.; Huffman, R. P. In
Academy Press: Washington, DC, 1987; Vol. 7, pp 62-79. Reference 3, pp 194-195. Scully, F. E.,Jr.; Yang, J. P.; Mazina, K.; Daniel, F. B.
Organometals and Organometalloids: Occurrence and Fate in the Enuironment; Brinkman, F. E.,Bellama, J. M., as.; ACS Symposium Series 82; American Chemical Society: Washington, DC, 1978; pp 278-291. Rogne, 0. J. Chem. SOC.B 1971, 1855-1858. Strangeland,L. J.; Senatore, L.; Ciuffarin, E. J. Chem. Soc., Perkin Trans. 2 1972, 852-856. Gray, W. R. Methods Enzymol. 1972,25, 121-138. Seiler, N. In Methods of Biochemical Analysis; Glick, D., Ed.; John Wiley and Sons: New York, 1970; Vol. 18, pp 259-336. Issac, R. A.; Morris, J. C. In Water Chlorination: Enuironmental and Health Effects; Jolley, R. L., et al., Eds.; Ann Arbor Science: Ann Arbor, MI, 1983; Vol. 4, pp 63-75. Choshen, E.;Johnson, J. D.; Scully, F. E.,Jr.; Jersey, J. A,; Jensen, N.; Jewell, J. T. In Water Chlorination: Chemistry, Environmental Impact and Health Effects;Jolley, R. L., et al., Eds.; Lewis Publishers, Inc.: Chelsea, MI, 1990; Vol. 6, pp 751-761. Metcalf, W. S. J. Chem. SOC.1942, 148.
Enuiron. Sci. Technol. 1984, 18, 787-792. Scully, F. E.,Jr.; Bowdring, K. J. Org. Chem. 1981, 46, 5077-5081. Lukasewycz, M. T.; Bieringer, C. M.; Liukkonen, R. J.; Fitzsimmons, M. E.; Corcoran, H. F.; Lin, S.; Carlson, R. M. Enuiron. Sci. Technol. 1989, 23, 196-199. Pitt, W. W., Jr.; Jolley, R. L.; Scott, C. D. Environ. Sci. Technol. 1975,9, 1068-1073. Morris, J. C. In Principles and Applications of Water Chemistry; Faust, S . D., Hunter, J. V., Eds.; John Wiley and Sons: New York, 1967; pp 23-53. Isaac, R. A,; Morris, J. C. Environ. Sci. Technol. 1983,17, 738-742.
American Public Health Association, American Water Works Association, Water Pollution Control Federation. Standard Methods for the Examination of Water and Wastewater, 16th ed.; APHA, AWWA, WPCF: Washington, DC; 1985. Bayer, E.;Grom, E.;Kaltenegger, B.; Uhmann, R. Anal. Chem. 1976,48, 1106-1109. Neadle, D. J.; Pollitt, R. J. Biochem. J. 1965,97, 607-608. Seiler, N.; Schmidt-Glenewinkel,T.; Schneider, H. H. J. Chromatogr. 1973,84, 95-104. Johnson, J. D. In Water Chlorination: Environmental Impact and Health Effects; Jolley, R. L., Ed.; Ann Arbor Science: Ann Arbor, MI, 1978; Vol. 1, pp 37-63.
Received for review August 28,1989. Accepted May 5,1990. This work was supported by National Science Foundation Grant ECE-841425, Edward H.Bryan Contract Officer, and by Electric Power Research Institute Grant RP2300- 7. E.C. acknowledges the support of the Fulbright Program, administered by the Council for International Exchange of Scholars.
Historical Perspective on the Environmental Bioavailability of DDT and Its Derivatives to Gulf of Mexico Oysters J o d L. Sericano,” Terry L. Wade, Elliot L. Atlas, and James M. Brooks Geochemical and Environmental Research Group, Department of Oceanography, Texas A&M University, 833 Graham Road, College Station, Texas 77845 ~
~
~~
DDT and ita metabolites, DDD and DDE, were analyzed in 479 oyster samples from the Gulf of Mexico between 1986 and 1988 as part of the National Status and Trends “Mussel Watch” (NS&T) Program. DDT and/or its derivatives were found in every sample analyzed in concentrations ranging over 2 orders of magnitude. DDT accounted for 3 4 % of the total DDT burden in oysters. The remaining percentage was approximately equally distributed between DDD and DDE. After the first 3 years of the NS&T program, the geographical distribution of total DDT along the northern coast of the Gulf of Mexico has been well defined. Based on 3 years of data, there were only a few sites that had statistically significant monotonic changes in concentrations with time. However, when the present data set is compared to historical data for the Gulf of Mexico, a general decrease is observed. The rate of DDT disappearance, as monitored by Gulf of Mexico oysters, is comparable with its decline in other marine environments. Introduction
The National Oceanic and Atmospheric Administration’s (NOAA’s) National Status and Trends “Mussel Watch” (NS&T) Program is designed to monitor the current status and long-term effect of selected organic and inorganic environmental contaminants, e.g., chlorinated pesticides, polychlorinated biphenyls (PCBs), polynuclear aromatic hydrocarbons (PAHs), and trace metals, along the US. coasts by measuring their concentrations in bivalves and sediments over a number of years. The ultimate 0013-936X/90/0924-1541$02.50/0
goals of the NS&T program are to define the geographical distributions of contaminants, identify “problem” areas, and determine trends in concentrations. The rationale for the “Mussel Watch” approach using different bivalves, e.g., mussels, oysters, and clams, has been summarized by different authors (1-8) and its concept has been applied to many national (5,9) as well as international (7, 10,11) programs. Overviews of the initial results for the first years of the NS&T program have already been reported (12-15). A more complete data set and extensive interpretation of the chlorinated hydrocarbon data in oyster and sediment samples from the Gulf of Mexico is published elsewhere (16). This report focuses on DDT [1,1’-(2,2,2-trichloroethylidene)bis[Cchlorobenzene]]and its derivatives, DDD [l,l’-(2,2-dichloroethylidene)bis[4-chlorobenzene]] and [4-chloroDDE [ 1,l’-(2,2,2-trichloroethenylidene)bis benzene]], which, in spite of the ban of DDT in the United States in the early 1970s, have been reported to be present in sediments and marine animals from the Gulf of Mexico in numerous studies carried out over the past 15 years (17-29). DDT, DDD, and DDE concentrations in oysters resulting from the first 3 years (1986-1988) of the N O M S NS&T program for the Gulf of Mexico portion are presented here and compared to historical Gulf coastal-wide data sets (27, 29). Methods
Sampling. The site locations for the 1986, 1987, and 1988 samplings are shown in Figure 1. Samples were collected from three stations within each site over 2-3-
0 1990 American Chemical Society
Environ. Sci. Technol., Vol.
24, No. 10, 1990
1541
