Environ. Sci. Technol. 1886, 20,457-463
Theis, T. L.; Singer, P. C. Environ. Sei. Technol. 1974,8, 569-573. James, H. R.; Birge, E. A. Trans. Wis. Acad. Sei. Arts Lett. 1938, 31, 1-154. Jones, B. F.; Bowser, C. J. In "Lakes: Chemistry, Geology, Physics"; Lerman, A., Ed.; Springer-Verlag: New York, 1978; Chapter 7.
(58) Nriagu, J. 0.;Dell, C. I. Am. Mineral. 1974, 59, 934-946.
Received for review October 28, 1983. Revised manuscript received May 10,1985. Accepted October 21,1985. Partial research support was provided by USEPAResearch Grant R805281 and by the private K A M Foundation.
Distribution of Chlorophenolics in a Marine Environment Tlan-Mln Xle,+ Katarlna Abrahamsson, Ellsabet Fogelqvlst, and Bjorn Josefsson" Department of Analytical and Marine Chemistry, Chalmers University of Technology and University of Goteborg, S-41296 Goteborg, Sweden
w The distribution of some chlorophenols, chloroguaiacols, and chlorocatechols, which were discharged from a sulfate pulp mill, were studied in the Gulf of Bothnia. These compounds were determined both in the water column and in the bulk sediments to understand their degradation pathways and accumulation patterns in the sea. Chloroform was used as a tracer to monitor the distribution and dilution of the effluent plume. The results showed that the transport of chlorophenolics was dominated by dilution and adsorption processes. Their behavior in the receiving water was correlated to the lipophilicity of the chlorophenolics, described by their partition coefficients in an octanol-water system (corrected for pH). A strong influence of bioactivity on the fate of chloroguaiacols and chlorocatechols was observed in sediments containing large amounts of organic carbon.
Introduction The release of industrially derived halogenated organic compounds into the aquatic environment is of great concern, mainly because of their toxicity, resistance to degradation, and tendency to bioaccumulate. The wood pulp industries, which use different chlorine bleaching processes, are one of the main sources of organic chlorinated compounds ( I and references cited therein). Chlorophenolic compounds have been found to be major constituents produced from lignin residues (2-6). Some of them are toxic and can be accumulated in living organisms (7-9). The transport and concentrations of some chlorophenols have been investigated in rivers, lakes, and estuaries (10-12). Recently, some chlorocatechols were determined in seawater and sediment close to pulp mills (13). Still, there is little known about the marine biogeochemistry of these types of compounds. Pulp mill effluent plumes are traditionally investigated by using artificially introduced tracers, such as radioactive bromide or dyes, e.g., rhodamine (14). Recently, Fogelqvist et al. utilized chloroform as a tracer substance in marine receiving waters (15). Chloroform is produced during chlorine bleaching in pulp mills in such a high concentration that it is possible, with this method, to monitor dilutions up to 10000 times. Chloroform determinations are simple and fast, thereby, a large recipient area can be investigated in a short time period to provide adequate statistical information. The adsorption of organic pollutants onto particles is mainly dependent on their lipophilicity, described by their log P values-the logarithm of the partition coefficient in Permanent address: Academy of Science of the Ministry of Light Industry, Beijing, China. 0013-936X186/0920-0457$01.50/0
the octanol-water system (16-19). The use of log P values to investigate the transportation of organic pollutants in a river has been reported (20). The log P concept is valuable in explaining the behavior of the chlorophenolic constituents discharged into the sea. It should be noticed that the log P values of the chlorophenolic compounds investigated are in the range 3-5, which are considerably lower than the corresponding values of other organic pollutants such as DDT, PCBs, and hydrocarbons (21). The biogeochemistry of chlorophenolics is therefore expected to be different. Investigations of the distribution of chlorophenolics in a relatively large area in a marine environment are rare, mainly due to the difficulty of analyzing large numbers of samples at low concentrations under the often complex hydrologic conditions (compared to rivers). The lipophilicity parameters of chlorophenolics(22,23), as well as the simple and sensitive GC methods for determiningtrace amounts of chlorophenolics in water and sediments, presented recently (24,25), offer the opportunity to conduct such investigations. The objective of this work was to establish the distribution pattern of different chlorophenolic compounds over a large marine recipient area, both in water and sediment, and compare this pattern with the effluent distribution pattern determined by using chloroform as a tracer.
Experimental Section Nature of the Sampling Area. The sampling area, located in the Gulf of Bothnia off the East Coast of Sweden, is characterized by several islands and skerries. This complicates the determination of a distribution pattern of the effluent. However, the following circumstances dominate the transport mechanism. The effluent (1m3/s) from the plant is mixed with seawater in a shallow receiving area. Into this pond seawater flows from the south and is pumped to the north at a rate of 20 m3/s. The effluent water, thus diluted 20 times, enters a bay surrounded by small islands. The seabed in the near recipient is dominated by transportation bottoms. However, accumulation of sediment takes place in patches all over the area. The sampling was performed on four occasions: (1) September 1982 (seawater and sediment); (2) March 1983 (effluent); (3) May 1983 (sediment); and (4) November 1983 (effluent, seawater, and sediment). Details of sampling locations, dates, and types are given in Figure 1. To avoid contamination artifacts or adsorptive losses, unfiltered water samples were used. Materials. The compounds measured were as follows: 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TrCP), 2,3,4,6-tetrachlorophenol(TeCP), pentachlorophenol
0 1986 American Chemical Society
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P
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Flgure 1. Sampling area and sampling stations: (A)water samples from September 1982; (0)water samples f r m November 1983: (0) sediment samples
(PCP), 4,5-dichloroguaiacol (DCG), 3,4,5- and 4,5,6-trichloroguaiacol (TrCG), tetrachloroguaiacol (TeGC), 3,4,5and 3,4,6-trichlorocatechol (TrCC), tetrachlorocatechol (TeCC), and chloroform. Bromotrichloromethane and acetylated 2,6-dibromopbenol and 3,4,5-trichlorophenoI were used as internal standards. Other chemicals used were acetic anhydride, sodium hydrogen carbonate, sodium carbonate, and sodium hydroxide. The solvents were acetone, hexane, and pentane. Chlorinated guaiacols and catechols were kindly supplied by J. S. Knuutinen. All chemicals were purchased as analytical grade quality. Pentane was purified by distillation until free of chloroform as shown by gas chromatographic tests. Double distilled water was used. Instrumentation. A Carlo Erba Fractovap 4160 and a Perkin-Elmer 3920 gas chromatograph were used. Both of them were equipped with a 63Nielectron capture detector, a split-splitless injector, and a Duran 50 glass capillary column (length 30 m, 0.3 mm i.d.) coated with OV-73 prepared according to the procedures of Grab (26). Analytical Methods. The determination of chloroform in water was performed according to Eklund et al. (27). One milliliter of pentane containing 50 Fg/L bromotrichloromethane was added to 100 mL of water sample in a volumetric flask. After the flask was shaken for 5 min, 1pL of the pentane extract was injected in the gas chromatograph. The determination of chlorinated phenolics in the water samples was performed according to Abrahamsson and Xie (24). A 9-g portion of NaHC03 was dissolved in a 100-mL sample, contained in a volumetric flask. After 0.5 mL of hexane containing acetylated 2,6-dibromophenol and 0.8 mL of acetic anhydride was added, the flask was shaken for 3 min. A Z-FL volume of the extract was injected in the gas chromatographin a splitless mode. For the effluent analysis only 5-mL samples were used. The three-phase extraction acetylation method for the determination of chlorinated phenolics in sediment samples was employed according to Xie (%). A 5-mL portion of 0.1 M Na2C03 solution was added to a 1-2 mL wet 458
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sediment sample in a screw-cap (Teflon-lined) glass tube. After the mixture was shaken for 10 min, 1mL of hexane containing acetylated 3,4,5-TrCP and 180 pL of acetic anhydride was added. The mixture was shaken for 5 min and centrifuged. The extract (2 FL) was then injected splitless in the gas chromatograph. The water content in the sediment was determined by heating a t 110 "C to constant weight. The organic content was estimated by the loss of weight on ignition at 475 "C for 5 h, according to Byers et al. (28). Before analysis the sediment samples were stored at a temperature of -20 "C.
Results and Discussion Distribution Pattern of Effluent Water. The plume of the bleaching effluent from the pulp mill was investigated with chloroform as a tracer. On four occasions, between July 1982 and November 1983, distribution patterns were determined, two of which are presented in Figure 2. The two isopleth maps are based on the seawater samples from 36 different stations. Figure 2a shows that on October 31,1983 the northeast effluent flow turns south into a gyre, due to the southbound main current. Between the sampling dates (October 31 and November 3,1983) a storm was blowing from the west, which shifted the gyre to the east (Figure 2b). Persistence of Chloroform. The use of chloroform as a tracer implies its persistence in the water. As the hydrolysis of chloroform in water of pH 7 and 7 "C has a half-life of loo0 years according to Hine and Ehrenson (29), the possibility of chemical breakdown is ruled out. The adsorption of chloroform to humic substances, iron hydroxide, and clay particles was studied by Helz and Hsu (30). They found no loss of chloroform from the water phase. Bioaccumulation of chloroform in organic tissues has been investigated by Pearson and McConnell(31) and Dickson and Riley (32) illustating that chloroform is only slightly bioaccumulated (2-25 times the seawater concentration on a dry weight basis). The log P value of chloroform (1.9) is low compared to the log P values of the chlorophenolics studied in this work (log P between 3 and 5) and of DDT and PCBs (log P between 5 and 6). A correlation between log P values and bioconcentrationhas been shown (33,34). Bacterial degradation of halogenated organic substances has been subject to investigations concerning the effect of biological treatment of sewage water by Thom and Agg (35)and by Tabak et al. (36). Chloroform was supposed to be biodegradable after some time of adaptation. Bouwer et al. (37)showed that such a degradation is possible under anaerobic conditions with methaneproducing bacteria, but they observed no degradation under aerobic conditions (38).The depletion of chloroform observed in an aerated lagoon by Voss (39)is possibly due to volatilization only. The persistence of chloroform when dissolved in seawater may therefore be limited by volatilization, which is determined by the Henry's law constant (H) and the mass transfer rate coefficient (K). Recently the Henry's law constant for chloroform was determined in seawater at different temperatures (40). The following relation was found In H = -3649/T + 10.63, where T i s the absolute temperature. Assuming a temperature of 7 "C in the water, H = 0.091. Mackay and Shiu ( 4 1 ) recommend a value of 0.101 with a relative standard deviation of 10%. This will give a mass transfer coefficient of 0.10&0.111 m/h calculated according to Dilling (42)or Liss and Slater (43). The flux (F),calculated from F = KC, where C is the concentration of chloroform in water, and assuming that the concentration in air is negligible, will give the following expression for the half-life ( t )in hours: t = L
A"
Flgure 2. Distribution panems of effluent water: (a)effluentplume in October 31. 1983; (b) effluentplume in November 3. 1983. The isopletes describe the concentration of chloroform in pglL.
In 2 / K , where L is the depth of the well-mixed layer. If the water is well-mixed to the bottom at 10 m, the half-life will he 62-64 h or 2.6-2.7 days. Current measurements in the area give 5 cm/s = 4.3 km/day, which means a 50% depletion of chloroform at least 11km away compared with the observed 1.9 km. Thus, volatilization is of minor importance in the depletion of chloroform.
The effects of the wind stress and the surface film thickness are difficult to estimate, and the air-sea exchange under natural conditions is not fully understood. The difficulties of modeling the air-sea exchange are discussed and demonstrated by Hasse and Liss (44) and by Holmen and Liss (45). In an investigation, in large tanks of seawater, of the fate of compounds similar to chloroform, the transfer rates were found to he 1order of magnitude lower than the estimated open-ocean ones (46). This could be due to a thicker surface film at the air-water boundary compared to the real ocean values. Chloroform has been compared to rhodamine as a tracer of bleachery effluents in a separate investigation in the Baltic Sea (47). In general, considering sampling and analytical uncertainties, no differences were observed in the distribution patterns established with chloroform as the naturally occurring tracer or with rhodamine added to the effluent. However, differences were observed just after a change in the weather, which created a well-mixed surface layer of about 2 m depth. A depletion of chloroform compared to rhodamine could then be noticed in the surface water down to a depth of 2-3 m. Investigation of Chlorinated Phenolics. Some determinations of chlorinated phenolic compounds have been made from the same water samples as chloroform. Table Ia,b show the results of water sample determinations from two different occasions. Table I1 shows the phenolic contents of the effluent a t the outlet from the plant measured on two different occasions. The contents of chlorophenolics in the sediments have also been determined. The sampling stations and the results are shown in Figure 1and Table 111,respectively. Chlorophenolics i n Water. The dilution patterns of the chlorophenolics differ from each other, indicating that other factors also play an important role. Their lipophilicity, measured by the log P, implies that they can be adsorbed onto organic particles suspended in the water. Since the phenolics are weak acids, their adsorption potentials are not only dependent on their lipophilicity but are also strongly influenced by the pH of the ambient water. Table IV lists the half-distances of some chlorophenolics together with their values of pK., log P, and log P.. Pais the partition coefficient that takes the phenolate ions into account at pH 7. The half-distance is the distance from station 831, a t which the Concentration of an individual chlorophenolic is reduced to half of its concentration. Data show that the half-distances of chlorophenolics are not related to their log P values, but to their log Pavalues. The half-distances increase as the log Pa values decrease, hecause the effluent contains a lot of large organic particles, mainly fibers, which adsorb chlorophenolics and rapidly sink to the bottom. This is supported by the high concentrations of chlorophenolics in the sediments near the source (Table 111). The distribution of pentachlorophenol (PCP) appears to be different from the other phenolics. After rapid dilution at the near recipient its concentration seems to he independent of the effluent plume. This may imply that the main source of PCP is not the factory investigated, which is possible since it is widely used as a fungicide and wood preservative. The concentrations of TeCG and 3,4,5-TrCG, at the most remote stations located in the northeast, such as stations 82% and 838, are slightly higher than expected. This might he a result of the influence of several pulp mills located in the north, not far from the area investigated. Environ. Sci. Technol.. VoI. 20, NO.
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Table I. Concentrations of Chlorophenolics in Seawater (ng/L) (a)
Station nr:depth
2,4-DCP
2,6-DCP
123 105 >2 21 31
40 34
1:l 1:3 2:2 2:4 3:2 3:4 4:2 4:4 5:2 5:5 6:2 6:5 7:2 7:3 7:5 8:2 8:5 9:2 9:5 10:2 10:5 . . 11:2 11:5 12:2 12:5 13:2 13:5 14:2 14:5 15:2 15:5 16:2 16:5 17:2 17:5 18:2 18:5 61:2 61:5
2,4,6-TrCP
2,3,4,6-TeCP
84 77 47 18 23 4 13 5 2 2 1
