Metals from'Urban Runoff in Dated Sediments of a Very Shallow Estuary Erik R. Christensen'" and Jan Scherfig School of Engineering, University of California, Irvine, Calif. 92717
Minoru Koide Scripps Institution of Oceanography, University of California, La Jolla, Calif. 92037
Pollution sources for Newport Bay, California, are of a nonpoint nature. To assess the heavy metal pollution of sediments in Upper Newport Bay, receiving runoff from a watershed of 376 km2, a number of sediment cores are dated and analyzed for Cr, Mn, Fe, Co, Cu, Zn, and Pb. The sedimentation rate is determined to be about 1.8 cm/yr by three independent methods: Pb-210 dating of selected cores, correlation between long-term oscillations in rainfall and similar variations vs. depth of grain size and heavy metal content in cores from tidal flats, and estimation of the settleable solids budget. Vertical profiles of heavy metals in dated sediment cores indicate that Zn and P b are the only metals of those investigated that show clearly increased levels in the uppermost strata, deposited since about 1955, when urban development in the watershed began. The ecological impact of trace metals derived from urban runoff has feceived increasing attention during recent years because heavy metals, which may be present in runoff from industrialized or urbanized areas, can adversely affect living organisms in the receiving waters. Health hazards can arise either through direct human contact with contaminated waters or through groundwater infiltration and subsequent drinking water contamination. Most studies of water pollution have dealt with effluents from either sewage treatment or industry. These sources are easily identifiable and can be classified as point sources. With the advent of secondary treatment of these effluents, increasing concern for nonpoint source pollution has become justified. Nonpoint sources include urban, agricultural, and residential runoff as well as irrigation return flows and construction pollution. Urban runoff is created when storm water flushes streets and buildings and picks up solids, debris, and contaminants such as heavy metals ( 1 , Z ) . Typical sources are residues from automobile tires, oils, and exhaust gases. The quality of storm runoff is dependent on the intensity and duration of the storm. Other factors include climate, type of drainage area, and the length of the antecedent dry weather. Debris and contaminants that have been accumulated in a dry weather period are suddenly released during heavy rainfall. The quality of first flush storm runoff is often comparable to that of raw sewage. Later, the runoff becomes more dilute, and its quality may approach that of dry weather flow. Sediment core analyses can give valuable information on the history of metal pollution. Galloway ( 3 )investigated trace metal profiles in sediments adjacent to the Los Angeles County wastewater outfall. He found that the concentrations of Cu, Cr, Ag, Zn, Cd, and Pb in the upper strata of a sediment core were up to 64 times the natural levels in the deeper strata of the same core. Crecelius et al. ( 4 ) studied heavy metal enrichment in sediments due to industrial effluents in Puget Sound, Wash. In Newport Bay, pollution sources are of a nonpoint nature. Here one could expect to find correlations between periods of heavy rainfall and levels of typical urban runoff contami-
nants such as P b and Zn. The reason is that runoff is almost entirely induced by rainfall, although a certain low baseflow is present due to irrigation tail water, automobile washing, etc. The purpose of the present study is to evaluate the historical metal pollution (Cr, Mn, Fe, Co, Cu, Zn, and Pb) of sediments of an estuary in which the primary pollution source is urban and agricultural runoff. In the dating of sediment cores, special interest was focused on the question whether or not the Pb-210 technique, previously used successfully for inner basins off the coast of California ( 5 , 6 ) ,could be extended to a shallow (depth: 0-1.5 m), rapidly depositing estuary, in which tidal variations are appreciable. To find supporting dating evidence, an attempt was made to correlate long-term oscillations in rainfall with variations vs. depth of grain size and concentrations of metals in sediment cores. Description of Study A r e a
Newport Bay (Figure 1) is located in Orange County, California, 64 km southeast of Los Angeles. The bay is enclosed and receives more than 95% of the total freshwater input from two major streams: San Diego Creek (agricultural runoff), and Santa Ana-Delhi Ditch (urban and industrial runoff). Upper Newport Bay is a narrow estuarine inlet about 5.6 km long which drains a watershed of 376 km2. The main part of the bay is surrounded by high bluffs, which are almost vertical, rising to 30 m ab.ove the bay surface. The Upper Bay comprises about 4.0 km2 of water surface, tideland, and salt marshes (7).
NEWPORT BAY A S A N DIEGO C R E E K
B S A N T A A N A - D E L H I DITCH C B I G CANYON CREEK
1168
Environmental Science & Technology
A
'
D T H E NARROWS 1-15 S A M P L I N G S T A T I O N S
30' 12
36'
117'56'
Present address, Department of Civil Engineering, University of Wisconsin-Milwaukee, Milwaukee, Wis. 53201.
33'40'
-KILOMETERS
5 2'
Figure 1. Map of Newport Bay showing tributary channels and sampling stations 0013-936X/78/0912-1168$01.00/0 @ 1978 American Chemical Society
Table 1. Characteristics of Core Sampling Locations in Upper Newport Bay station no.
description (see Figure 1)
4
mouth of San Diego Creek mouth of Santa Ana-Delhi Ditch large homogeneous tidal mudflat, exposed at low tide channel between southern large island and west bank large homogeneous tidal mudflat, exposed at low tide tidal creek carrying water from San Diego Creek at low tide large homogeneous tidal mudflat, exposed at low tide. Sampling point between main dike and east dike, about 500 m northeast of main dike
5 6a 12 13 14 15
Environmental problems are associated with the inflow of contaminants such as heavy metals and silt from the two major channels, San Diego Creek and Santa Ana-Delhi Ditch. Core sampling in Upper Newport Bay was carried out according to the following criteria: it was desired to obtain samples directly from the mouths of the two major channels carrying fresh water into the bay with the intent of identifying specific metal pollution form the two channels, only undisturbed, nondredged locations should be considered, and sampling stations should be chosen on the basis of geographical representativeness to have a reasonably complete sampling in the Upper Bay. Characteristics of the sampling locations are listed in Table I.
Methods Sampling. Core samples of up to 40 cm length were collected on August 28, 1975, from stations 4,5, and 6a (Figure 1)using cast lucite tubes with an inner diameter of 4.6 cm and a length of about 2 m. Other core samples were taken on October 6 and November 5, 1976, from stations 12,13, 14, and 15. T o ensure cores undisturbed by the coring device, larger diameter tubes were used this time, Le., PVC tubes of 10 cm inner diameter. The tubes served as containers during transportation to the laboratory and subsequent freezing. All core sampling was carried out at low tide, wading, and using a raft for support. Dating Techniques. Three independent methods were used for the determination of sedimentation rates: Pb-210 dating, correlation between long-term oscillations in rainfall and grain size and concentration of metals in sediments, and estimation of the settleable solids budget. Frozen sediment cores were cut into 4- or 5-cm segments, thawed a t 5 "C for 24 h, and dried at 105 OC for 48 h. After drying and cooling to room temperature in a desiccator, the samples were gently crushed into a powder using a mortar and pestle. Sedimentation rates were determined for selected cores using the Pb-210 technique (5,8). Sieve analyses of selected cores were done in an attempt to
find correlation between years with heavy rainfall, grain size, and heavy metals such as lead. Storms result in deposition of larger particles and will presumably also give higher lead concentrations due to efficient lead removal from street surfaces and other areas. U S . standard sieves No. 16,32,42,60, 100,115,170, and 200 were used, and all samples were shaken automatically for 5 min. Settleable solids in storm waters were determined after more than one week's settling in a 1-L Nalgene bottle by decanting 90% of the water plus suspended solids, centrifuging the settleable solids with the 10% remaining water phase, decanting, drying the solids in a preweighed aluminum cup a t 105 OC for 24 h, and reweighing the aluminum cup. Metal Analyses. Of the metals investigated, Mn, Cu, Zn, and P b were determined by atomic absorption spectroscopy (AAS), whereas Cr, Fe, and Co were determined by neutron activation analysis (NAA). Finely divided sediment samples to be analyzed by NAA were transferred directly into vials and irradiated, while AAS required an acid digestion step prior to analysis. Digestion of sediments was performed essentially as described by Van Loon et al. (9).All trace metal determinations by AAS used a Perkin-Elmer Model 403 instrument, for which settings were determined from the recommendations in the instruction manual (IO). Interferences from background absorption were removed, for wavelengths below 300 nm, by means of the deuterium background corrector. All NAA determinations were carried out by means of the NAA equipment at the University of California at Irvine. Five-gram sediment samples were transferred to 7.4-mL polyethylene vials, which were irradiated for 2 h at 1012 n/ cm2/s, allowed to decay for 16 days to reduce the 24Naactivity to insignificant levels, and counted for 15 min with the Ge(Li) detector. NAA determinations of selected elements in the standard reference material, orchard leaves, gave results within 10% of the certified values.
Results a n d D i s c u s s i o n
Settleable Solids. Estimation of the settleable solids budget for the channels and the Upper Newport Bay can give an approximate indication of the overall sedimentation rate. The concentration of settleable solids and their heavy metals content at the storm of December 1976-January 1977 are given in Table 11. It is evident that water from Station 1 has the higher content of settleable solids. However, water from Station 2 generally has the higher concentrations of heavy metals. Based on the content of settleable solids, and the runoff volumes obtained by numerical integration of hydrographs supplied by Gietzen ( I I ) , the sedimentation rate can be estimated using the following main assumptions: extrapolation of results from the storm of December 1976-January 1977 to a yearly basis is valid; and the settleable solids will settle mainly in Upper Newport Bay (area = 2.51 km2),and only to a small extent in Lower Newport Bay (area = 3.15 km2). The first assumption is obviously an approximation, since
Table II. Settleable Solids and Their Heavy Metals Content as Determined by Atomic Absorption Spectroscopy at the Storm of December 1976-January 1977 date
weather conditions
siatlon no.
December 30, 1976
storm
January 6, 1977
storm
1 2 1 2
a
flow rate,a m3/s
2.86 6.03 26.6 18.0
settleable solids, g/L
Mn
Cu
ppm Zn
Pb
1.96 0.32 1.98 0.38
261 204 252 252
24 31 17 29
101 98 130 198
55 125 28 71
From Gietzen ( 11).
Volume 12, Number 10, October 1978 1169
Table 111. Mass Injection Rates of Settleable Solids into Upper Newport Bay Based on Data from the Storm of December 1976-January 1977
channel
av concn of settleable sollds, g/L
San Diego Creek Santa Ana-Delhi Ditch
1.97 0.35
aExampIe:(1.97 X
runoff VOI, m3
4.48 x 1.93 X
settleable
solids,' tonslyr
8.46 8.43
106
lo6
3.34 2.56
x x
104 103
X 4.48 X IO9 X 31.98)/8.46 = 3.34 X lo4 tons solids/yr from San Diego Creek, assuming a yearly rainfall of 31.98 cm ( 13).
the settleable solids content generally increases with increasing flow rate. However, from Table 11, this variation appears to be small in the range of flow rates considered. In the first assumption it is further implied that an “average” year includes about four typical storms like the one of December 1976-January 1977. Such a description reflects, however, adequately the actual rainfall pattern in the area. The second assumption is based on the observation that sediments in Upper Newport Bay consist of fine sand or coarse silt, whereas the deposits in Lower Newport Bay consist of fine silt or clay. Thus, the heavy load of solids settle in the Upper Bay, which acts as a large settling basin, and only the finest particles settle in the Lower Bay or are carried into the Pacific Ocean. This variation in grain size is generally valid for rivers and estuaries (12). Other assumptions in the present estimation of sedimentation rate are that the surface samples taken are representative of the total channel cross section, and that the bedload discharge is small relative to the total discharge of settleable material. From Table 111,the total mass injection of settleable solids is 3.60 X lo4tons/yr. This is in reasonable agreement with the more accurate value of 5.06 X lo4 tons for San Diego Creek, obtained by the U.S. Geological Survey (14) for the water year 1975. This year is comparable to the “average” year defined above in respect to total rainfall, discharge, and number of storms. Let us assume that 3.60 X lo4tons/yr of settleable solids are uniformly dispersed over the Upper Newport Bay area, i.e., the area north of the Coast Highway Bridge. Hence, the sedimentation rate of solids is 1.43 g/cm2/yr. The average density of a 40-cm-long core was found to be 1.42 g/cm3, of which 51.6% was solid sediment on a salt-free basis. Thus, the amount of solids was 0.73 g/cm3, indicating that the average sedimentation rate is 2.0 cm/yr with an estimated uncertainty of 1.0 cm/yr. This rate is within the range obtained by other investigators using the technique of laying a distinctive sand layer on the sediment surface, and then, after a period of time from 6 months to a year, taking cores and measuring the thickness of sediment above the sand layer (15). Pb-210 Dating. Dating by the Pb-210 method was attempted for core nos. 6a, 12,13,14. Core no. 12 gave the best determination. From Figure 2, the sedimentation rate for this core is 0.8 f 0.1 cm/yr. Core no. 14 shows a more scattered pattern of Pb-210 activity vs. depth with a sedimentation rate of about 1.8 f 0.4 cm/yr. For both cores, the uncertainty is mainly due to the uncertainty of supported Pb-210. Only four samples, instead of five, were processed for each of the core nos. 6a and 13 from the tidal flat. While the counting rate, on the average, did seem to decrease with depth, significant oscillations appeared to be superimposed on the values so that the data obtained were insufficient for an accurate determination of sedimentation rates. The oscillations observed appeared to be similar to those exhibited by the grain size and concentration of heavy metals, to be discussed later. 1170
rainfall, cm
Environmental Science & Technology
18cm 7-EqE 0.8crniyr
Core No.12 Corrected f o r supported Pb-210 activity = 0.4 dpm/g I
0
20
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Core No.14 Corrected f o r supported Pb-210 act i vit y = 0.42 d pm/g
01
0
20
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100
Figure 2. Pb-210 activities vs. depth for core nos. 12 and 14
ZINC 100
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-1940
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401
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Rainfallg r o i n s i z e dated
-1955
40
50
-1950
P b - 2 1 0 dated
50L
Figure 3. Zinc and lead in dated sediment cores from Upper Newport Bay
Results of zinc and lead analyses of cores are given in Figure 3. Similar graphs for Cr, Mn, Fe, Co, and Cu are included in the supplementary material. The cores have a length of between 35 and 50 cm, except no. 5, which is only 15 cm, since sandy layers below this depth made it difficult to retain a longer core. Core Nos. 4,5, and 6a. Of the metals considered in these cores, zinc and lead are remarkable due to a pronounced maximum for both metals a t a depth of about 12-22 cm, and a much higher lead concentration of core no. 5 than of the other two cores. Core no. 5 was taken at the mouth of the channel draining an urban area, so that the high lead content presumably is related to automotive use of leaded gasoline in the watershed. Another point of interest is the apparent, nonrandom oscillation with depth of the concentration of most of the metals in core no. 6a. A possible explanation for this pattern, together with the results of supporting sieve analyses,
will be discussed in the section describing correlation of rainfall with grain size and metal levels in selected cores. Core Nos. 12 and 14. As shown by the Pb-210 analysis, both of these cores are datable. Lead pollution cannot be observed until about the year 1955, when the intensive development of automobile traffic in the watershed began. The history of lead pollution shown here is in good agreement with the results of Bruland et al. (6) for San Pedro Basin, 40 km off the mouth of Newport Bay. Although the sedimentation rate of 0.9 mm/yr for San Pedro Basin is much less than for Newport Bay, the dated lead concentration profiles are similar, except that maximum values are higher in Newport Bay (45-50 ppm; core nos. 12 and 14) than in San Pedro Basin (37 ppm). Both of the core nos. 12 and 14 show elevated levels of zinc in the upper strata. For core no. 14, the zinc enrichment seems to have taken place concurrently with the lead enrichment. Zinc enrichment in core no. 1 2 (enrichment factor = 3.1, defined Volume 12, Number 10, October 1978
1171
years with heavy rainfall, carry larger sized grains. The sedimentation rate derived by this matching, using core no. 13, is 1.8 cm/yr (Figures 3 and 4) in good agreement with the rate of 1.8 f 0.4 cm/yr determined by the Pb-210 method for the adjacent core no. 14 (Figure 3). That maximum grain size can be correlated with maximum lead concentration for core nos. 13 and 15 could be explained by the cleansing action of large storms, such as the one of 1969, which tend to wash most available lead from street surfaces and other areas into Upper Newport Bay. It remains to be determined why concentrations of the other metals considered follow the variations with depth of grain size, so that metal levels are high a t maximum grain size and low at minimum grain. size. This unusual result may be uniquely related to the fact that the area is semiarid with runoff as the major source of metals. Another point that would require separate study is the question of why the metal concentrations have oscillating patterns vs. depth in tidal flats (core nos. 6a and 13) but only so to a small extent, if a t all, in a tidal creek (core no. 14) and not at all in the channel between the southern large island and the west bank (core no. 12).
Table IV. Metal Fluxes to Upper Newport Bay: Total and Atmospheric Input
element
Cr Mn Fe co cu Zn Pb a
concn Upper Newport Bay sediments, core no. 14, ppm
fluxes, pg/cm*/yr total Input. atmos Upper Newport Input, Bay, core Corona del no. 1 4 a Mar ( 1 6 )
78 380
100 490
44 000 13 40 160 49
57 000 17 52 210 -63
50.7 3.3 2.4
Assuming a sedimentation rate of 1.29 g solids/cm2/yr.
as the maximum level in the upper strata of a core divided by the natural level in the lower strata) is more difficult to follow in time, since this core has an enrichment factor of about 2 for other metals considered, Le., chromium, iron, and cobalt, all of which have nearly constant concentrations with depth in core no. 14. Copper has an enrichment factor higher than 2 in core no. 12, and may have elevated levels in core no. 14. A comparison of total metal fluxes (natural and anthropogenic) to Upper Newport Bay and atmospheric input to Corona del Mar is given in Table IV. The fluxes to the sediments of Upper Newport Bay are much higher than the atmospheric fluxes to Corona del Mar. This indicates that the metals are mainly derived from runoff. Based on natural levels of zinc (75 ppm) and lead (10 ppm) in the lower strata of core no. 14, and the corresponding higher levels in the uppermost strata, the anthropogenic fluxes can be estimated to be 50 pg Pb/ cm2/yr (80%) and 110 pg Zn/cm2/yr (55%), where the percentages are relative to the total fluxes. Core Nos. 13 and 15. Maxima for lead in these cores do not occur at top layers, but rather at a depth of 13-18 cm. Similar patterns were previously observed for core nos. 4 and 6a for both lead and zinc. While core no. 15 does not seem to have any characteristic patterns of metals vs. depth, except in the case of lead, core no. 13 from a tidal flat south of the main dike exhibits the oscillating structure of metals vs. depth, previously observed for core no. 6a from the same tidal flat. Correlation of Rainfall with Grain Size and Metal Levels in Selected Cores. T o explain the oscillating metal concentrations vs. depth found in cores nos. 6a and 13, the long-term rainfall pattern was investigated. This is logical since runoff is largely a consequence of rainfall. A record of rainfall for a precipitation station in the watershed is presented in Figure 4a (11). The four-year averaged rainfall shows a clearly oscillating pattern, which for core no. 13 can be correlated with oscillations of grain size and concentrations of a metal such as zinc. For core no. 15 the correlation only holds for the uppermost 15 cm. Below this depth the grain size remains fairly high for about 15 cm, and then drops to a low value. A possible explanation is that the 1969 storm (13)deposited an extraordinary thick sediment layer. Core no. 15 was taken from a location upstream of the main dike and may therefore have received considerably more material during the 1969 storm than core no. 13, which came from a location downstream of the main dike. By comparison of average grain size for core nos. 13 and 15 (Figure 4) it is clear that core no. 15 has the larger grains. This is consistent with the previously mentioned general observation that the grain size tends to decrease in the downstream direction of a river or an estuary. The correlation found between rainfall and grain size is reasonable, since large storms, occurring more frequently in 1172
Environmental Science & Technology
Conclusions The following conclusions can be made based on the present study: The overall sedimentation rate for Upper Newport Bay was estimated to be 2.0 f 1.0 cm/yr, based on data for the total mass injection of settleable solids, assuming that these solids settle mainly in Upper Newport Bay and only to a small extent in Lower Newport Bay. Pb-210 dating can be carried out for sediments in very shallow waters, or if exposed a t low tide for a brief period
,
10080 60 40
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,
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RAINFALL
AVERAGE SEASONAL
n
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STATION No. 61 (OCFCDI I R V I N E RANCH HOUSE
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Figure 4. Correlation between (a) Cyear-averapd rainfall in watershed, (b) grain size in core no. 13, (c) zinc concentration in core no. 13, and (d) grain size in core no. 15 (inches X 2.54 = cm)
(4) Crecelius, E. A., Bothner, M. H., Carpenter, R., Enuiron. Sci. Technol., 9,325-33 (1975). (5) Koide, M., Soutar, A., Goldberg, E. D., Earth Planet. Sei. Lett., 14,442-6 (1972). (6) Bruland, K. W., Bertine, K., Koide, M., Goldberg, E. D., Environ. Sci. Technol., 8,425-32 (1974). (7) Frey, H. W., Hein, R. F., Spruill, J . L., Report of the Natural Resources of Upper Newport Bay and Recommendations Concerning the Bay’s Development, Dept. of Fish and Game, State of California, 1970. (8) Koide, M., Bruland, K. W., Anal. Chim. Acta, 75,l-19 (1975). (9) Van Loon, J. C., Lichwa, J., Ruttan, D., Kinrade, J., Water, Air, Soil Pollut.. 2,473-82 (1973). (10) Perkin-Elmer Corp., Norwalk, Conn., Instruction Manual for Atomic Absorption Spectrophotometer, Model 403, 1973. (11) Gietzen, J. B., Orange County Flood Control District, private communication, 1977. (12) Leopold, L. B., Wolman, M. G., Miller, J. P., “Fluvial Processes in Geomorphology”, Freeman, San Francisco, Calif., 1964. (13) Gietzen, J. B., Franklin, E .J., Nestlinger, A. J., Mastrocola, N., Recht, W. J., Hydrological Data Report 1973-74 Season, Orange County Flood Control District, Santa Ana, Calif., 1974. (14) US.Geological Survey, Water R.esources Data for California, Water Year 1975, Vol 1, National Tech. Information Service, Springfield, Va., 1976. (15) Stevenson, R. E., Emery, K. O., “Marshlands a t Newport Bay, California”, Univ. of Southern California Press, Los Angeles, Calif., 1958. (16) Davidson, C. I., PhD thesis, California Institute of Technology, Los Angeles, Calif., 1977.
(depth: 0-1.5 m). However, at longer time exposure, which occurs for tidal flats, the data obtained were not sufficient for the determination of sedimentation rates. Rates determined by the Pb-210 technique were: 0.8 f 0.1 cm/yr for the channel between the southern large island in Upper Newport Bay and the west bank, and 1.8 f 0.4 cm/yr for a tidal creek 800 m north of the Narrows. Vertical profiles of heavy metals in dated sediment cores indicate that zinc and lead are the only metals of those investigated that show clearly increased levels in the upper strata, deposited since about 1955. The highest lead level (132 ppm) was found close to the mouth of the channel draining an urban area. Vertical profiles of heavy metals in sediment cores from the tidal flat south of the main dike show a clearly oscillating pattern, also shown by the average grain size. Thus, maximum concentration of a metal such as lead is associated by maximum grain size, indicating material carried by large storms. A plot of 4-year-averaged rainfall vs. time shows a similar oscillating pattern, so that maximum grain size can be matched with maximum rainfall. This strongly suggests a cause-effect relationship between patterns of rainfall and patterns of grain size and heavy metals. The sedimentation rate obtained for the tidal flat by this matching is 1.8 cm/yr in good agreement with the value of 1.8 f 0.4 cm/yr obtained by thePb-210 method for a tidal creek that runs through the flat. Acknowledgment
We thank V. P. Guinn and E. D. Goldberg for valuable comments on this work.
Literature Cited (1) Sartor, J. D., Boyd, G. B., Agardy, F. J., J. Water Pollut. Control Fed., 46,458-67 (1974). (2) Whiuule. W.. Jr.. Hunter. J . V.. ibid.. 49. 15-23 (1977). (3) Galloway, J., PhD thesis; University of’california, San Diego, Calif., 1972.
..
I
I
Received for review November 7, 1977. Accepted May 4, 1978. Work supported i n part by grants from Statens Naturvidenskabelige Forskningsrad, Otto Mtjnsteds Fond, Thomas B. Thriges Fond, Knud HQjgards Fond, and Handelsbankens Studierejselegat. Supplementary Material Available. Additional graphs for Cr, M n , Fe, Co, and Cu (Figure 3 ) will appear following these pages i n the microfilm edition of this volume of the journal (10 pages). Photocopies of the supplementary material from this paper only or microfiche (105 X 148 m m , 2 4 X reduction, negatives) containing all of the supplementary material for the papers in this issue may be obtained f r o m the Business Operations Office,Books and Journals Division, American Chemical Society, 1155 16th St., N . W., Washington, D.C. 20036. Remit check or money order for $6.50 for photocopy or $3.00 for microfiche, referring to code number ES&T-781168.
Assessment of Intermittently Chlorinated Heated Effluents on Survival of Adult Rainbow Trout ( S a h o gairdneri) at Power Generating Facilities lbrahim H. Zeitoun Department of Environmental Services, Consumers Power Co., Jackson, Mich. 49201 ~
Monthly 96-h bioassays were carried out from November 1975 to June 1976 at the J. H. Campbell Plant of the Consumers Power Co., Michigan, to determine the effects of intermittent chlorination on the survival of caged rainbow trout (Salrno gairdneri). The results indicated that eight covariates, which included total and free chlorine-exposure time integrations, dissolved oxygen supersaturation and temperature, contributed significantly to the mortalities exhibited among caged fish. Squared multiple correlation coefficients were used to determine the relative effects of these significant covariates on fish mortality since the individual function of these variables appeared to be additive. A maximum value of 0.3 mg/L TRCl per 54 min of exposure time was extrapolated as a safe concentration that would result in the same mortality rate as in controls which were not exposed to chlorine. Blood analysis indicated that chlorine was not the primary cause of the observed stress.
0013-936X/78/0912-1173$01.00/0
A matrix of algae, bacteria, fungi, and other organisms develops on the cooling surfaces of condensers of steam power plants that use natural waters for cooling. This biofouling reduces the flow of cooling waters and insulates the heat exchange’ surface, which reduces the efficiency of electrical generation and causes a considerable power loss. T o counteract the biofouling buildup, condensers are periodically chlorinated. Although chlorination is normally the most economical and practical means for controlling the fouling organisms ( I ) , the chlorinated effluents could produce localized effects on aquatic life in natural habitats ( 2 , 3 ) . The U S . Environmental Protection Agency ( 4 )limited the discharge of free available chlorine from power plants to a maximum concentration of 0.5 mg/L and an average concentration of 0.2 mg/L for not more than 2 h daily. Mattice and Zittel ( 5 ) used the available chlorine literature and extrapolated acute chlorine levels that would be considered safe for aquatic organisms. The acute toxicity threshold for freshwater organisms was approximated by a straight line connecting
@ 1978 American Chemical Society
Volume 12, Number 10, October 1978
1173
