Environ. Sei. Technol. 1989, 23, 314-320
timate the effect of the inherent maldistribution.
79-01-6;CH&C13, 71-55-6;CC12=CC12, 127-18-4;CC4, 56-23-5; CHBr,, 75-25-2;C02, 124-38-9.
Glossary a
C1 c2
A dP
D G H' HG HL HOL
H*OL 2:a
L m NOL
N*OL ReL S sa,sb UG UL
V
X
Y z
x
mass-transfer area inlet concentration of solute outlet concentration of solute absorption factor packing size diffusivity mass velocity of gas Henry's law constant based on volumetric concentrations height of a gas-phase transfer unit height of a liquid-phase transfer unit overall height of a transfer unit based on the liquid-phase HoL for uniform distribution gas film volumetric mass-transfer coefficient overall volumetric mass-transfer coefficient molar flow rate of liquid or mass velocity of liquid slope of equilibrium line on a y - x plot number of transfer units number of transfer units in local regions of the column Reynolds number for liquid stripping factor local value of the stripping factor superficial velocity of gas superficial velocity of liquid molar flow rate of gas liquid-phase concentration Vapor-phase concentration effective film thickness maldistribution parameter
Literature Cited (1) Gossett, J. M.; Cameron,C. E.; Eckstrom, B. P.; Goodman, C.; Lincoff, A. H. Air Force Eng. Service Lab. Report ESL-TR-85-18,June 1985. (2) Shenvood,T. K.; Holloway, F. A. L. Trans. Am. Inst. Chem. Eng. 1940, 36, 39. (3) Roberts, P. V.; Hopkin, G. D.; Munz, C.; Riojas, A. H. Environ. Sei. Technol. 1985, 19, 164. (4) Roberts, P. V.; Hopkin, G. D.; Munz, C.; Riojas, A. H.
OWRT Report, Dec 1982. ( 5 ) Onda, K.; Takeuchi, H.; Okumoto, Y. J. Chem. Eng., Jpn. 1968, 1, 56.
(6) Ball, W. P.; Jones, M. D.; Kavanaugh, M. C. J.-Water Pollut. Control Fed. 1984, 56, 127. (7) Cummins,M. D.; Westrick, J. J. R o c . ASCE Environ. Eng. Conf. 1983, 442. (8) Suzuki, M. J. Chem. Eng., Jpn. 1975, 8, 163. (9) Perry, R. H.; Green, D. W. Chemical Engineering Handbook, 6th ed.; McGraw-Hill: New York, 1984; pp 18-29.
(10) Shulman, H. L.; Ulrich, C. F.; Proulx, A. Z.; Zimmerman, J. 0. AIChE J. 1955, 1, 263. (11) Miyauchi, T.; Vermeulen, T. Ind. Eng. Chem. Fundam. 1963, 2, 113. (12) Hatton, T. A,; Woodburn, E. T. AIChE J. 1978,24, 187. (13) Buchanan, J. E. AZChE J. 1971,17, 746. (14) Cooper, C. M.; Christl, R. J.; Peery, L. C. Trans. Am. Inst. Chem. Eng. 1941,37, 979. (15) Hoek, P. J.; Nesselingh, J. A,; Zuiderweg, F. J. Chem. Eng. Res. Des. 1986, 64, 431. (16) Porter, K. E.; Templeman, J. J. Trans. Inst. Chem. Eng. 1968, 46,
86.
(17) Yuan, H.; Spiegel, L., Chem. Ing. Tech. 1982, 54, 774.
Received for review December 23, 1987. Accepted September
Registry No. CH2C12,75-09-2;CHC13,67-66-3;CHC1=CCl2,
15, 1988.
Natural Trace Metal Concentrations in Estuarine and Coastal Marine Sediments of the Southeastern United States Herbert L. Windom,",+ Steven J. Schropp,' Fred D. Calder,' Joseph D. Ryan,$ Ralph G. Smith, Jr.,t Louis C. Burney,' Frank G. Lewis,$ and Charles H. Rawllnsont Skidaway Institute of Oceanography, P.O. Box 13687,Savannah, Georgia 31416,and State of Florida Department of Environmental Regulation, 2600 Blair Stone Road, Tallahassee, Florida 32301
IOver 450 sediment samples from estuarine and coastal
marine areas of the southeastern United States remote from contaminant sources were analyzed for trace metals. Although these sediments are compositionally diverse, As, Co, Cr, Cu, Fe, Pb, Mn, Ni, and Zn concentrations covary significantly with aluminum, suggesting that natural aluminosilicate minerals are the dominant natural metal bearing phases. Cd and Hg do not covary with aluminum apparently due to the importance of the contribution of natural organic phases to their concentration in sediments. It is suggested that the covariance of metals with aluminum provides a useful basis for identification and comparison of anthropogenic inputs to southeastern US. coastal/estuarine sediments. By use of this approach sediments from the Savannah River, Biscayne Bay, and Pensacola Bay are compared.
Introduction Estuarine and coastal marine sediments are sinks for many materials transported from the land. Many sub'Skidaway Institute of Oceanography. t
State of Florida Department of Environmental Regulation.
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stances that occur naturally, such as trace metals and nutrients, may be mobilized as a result of natural processes as well as by man's activities and thus may become enriched in coastal and estuarine sediments. Before anthropogenic contributions to these sediments can be assessed, contributions due to natural processes must be estimated. The concentrations of trace metals in natural estuarine and coastal marine sediments are dominantly determined by inorganic detrital, rather than organic and nondetrital materials. The inorganic detritus is the result of chemical and physical weathering of the continents and is composed mostly of a limited number of silicate minerals, such as quartz, feldspars, micas, pyroxenes, amphiboles, and clay minerals, and smaller amounts of metal oxide and sulfide phases. In some coastal areas, such as those of Florida, carbonate minerals represent the major component of estuarine and coastal sediments. Of the materials contained in natural sediments, quartz, feldspars, and carbonates are relatively metal poor as compared to the other phases and thus serve to dilute sediment metal concentrations. Anthropogenic trace metal contributions to estuarine
0013-936X/89/0923-0314$01.50/0
0 1989 American Chemical Society
and coastal marine sediments are often introduced initially to the environment in solution and accumulate on fine grain suspended sediments and on inorganic and organic colloidal particles. Trace metal contaminants from anthropogenic sources may also be introduced in large particles. For most coastal areas natural trace metal concentrations can range over 2 orders of magnitude, causing confusion in data interpretation regarding anthropogenic loadings. This is particularly true in the coastal regions of the southeastern United States where natural estuarine and nearshore sediments are composed of trace-metal-poor phases (e.g., fine- to coarse-grain carbonates and quartz sands), and metal-rich phases in mixtures depending on local natural sources. The most important natural metal bearing phases in these sediments are the clay minerals smectite and kaolinite (I, 2). Since the metal-rich aluminosilicates (Le,, clays) are associated with the fine-grain fraction of sediments, the grain size distributions along with sediment source become the most important factors influencing natural metal concentrations. To assess anthropogenic contributions to coastal and estuarine sediments a number of approaches have been used to factor out the variability in natural trace metal concentrations. In most cases, the source of the natural material making up the sediment has been assumed to be constant so that emphasis has been placed on accounting for the “grain size effect”. Often analyses have been carried out on a specific size fraction to correct for natural variability ( 3 , 4 ) ,but this approach requires a separation step and results are often confusing since concentrations in a certain size fraction do not reflect the concentration in the total sediment. Many workers have used various geochemical approaches where the natural trace metal variability is normalized by the concentration of other elements. Such normalizers have included Fe (5),Sc, and Cs (6). The most basic geochemical approach, however, has been to use aluminum as a normalizer of trace metal concentrations since it has a high natural abundance and is not commonly associated with anthropogenic inputs. Examples of this approach include studies by Duce et al. (7) who compared metal to aluminum ratios in atmospheric dust samples to that of average crustal material to estimate the relative atmospheric enrichment of metals due to anthropogenic sources. Goldberg et al. (8)used metal to aluminum ratios to evaluate the pollution history recorded in sediments from the Savannah River estuary, and Trefry et al. (9) compared lead levels to those of aluminum in sediments of the Mississippi delta to assess the changes in relative amounts of lead pollution carried by the river over the past half-century. All of the above examples where aluminum or other “geochemical normalizers” have been used were relatively site specific and assumed that the natural sources of sediment were constant (5,6,8,9) or assumed that the metal to aluminum ratio of natural materials is that based on average crustal abundances (7) as reported by Turekian and Wedepohl (IO) or Taylor (12). For these studies the use of normalizers provides a good basis for calculating the relative importance of anthropogenic contributions to the sediments being studied. It is clear that similar approaches could be used to compare the relative importance of anthropogenic trace metal contributions to coastal/estuarine sediments on more regional scales such as the coast of the southeastern United States. For this purpose, however, it cannot be assumed that natural sources are similar throughout the region. It may be possible to overcome this
problem by assessing regional variations in the trace metal levels of natural sediments and selecting an appropriate geochemical normalizer to establish relationships between natural sediments from different areas within the region. This paper presents the results of trace metal analyses of natural sediments from southeastern U S . coastal environments which provide a basis for assessing regional variations. Aluminum concentration is used as a geochemical normalizer to establish the relationship between natural trace metal concentrations in sediments from different areas. Finally, an example is presented where this relationship is used to compare the relative importance of anthropogenic contributions to sediments from widely differing environments of the southeastern United States.
Sampling and Analytical Methodology During the past few years two projects have been underway that involved the collection of a large number of natural sediments for trace metal analysis. One project, addressing the basic trace metal geochemistry of nearshore sediments along the coasts of Georgia and South Carolina, was conducted by the Skidaway Institute of Oceanography. The other, conducted by the Florida Department of Environmental Regulation, attempted to evaluate the degree of trace metal contamination of coastal and estuarine sediments of that state. Although these two projects have different objectives, they both generated a large amount of data on trace metal concentrations in uncontaminated estuarine and nearshore sediments of diverse composition. Of the total number of sediment samples analyzed during these studies many were collected from natural areas by design. The major criterion for selection of sampling sites for natural sediments was based on their remoteness from any potential contaminant sources. Sediment samples from the coasts of Georgia and South Carolina (Figure 1)were collected along nearshore transects (labeled HH through GA4) by using stainless steel box cores. From these cores 340 sediment samples were collected; some were from various depths in the core and others were composites of various depths. Nonmetallic spatulas were used to collect samples, which were stored frozen in plastic bags until analysis. Samples of coastal and estuarine sediments of Florida (Figure 1) were collected by epoxy-coated Ponar grab sampler or by diver using cellulose acetate butyrate (CAB) cores to collect the upper ca. 10 cm from 103 stations. Each of the samples that were collected were homogenized with a nonmetallic spatula and stored frozen in plastic bottles. Samples collected from the Georgia and South Carolina coasts were analyzed at the Skidaway Institute of Oceanography. Samples from Florida were analyzed by Savannah Laboratory and Environmental Services, Inc., under contract to the Florida Department of Environmental Regulation. Data from the two projects are comparable because both laboratories used the same analytical techniques, intercalibrated, and carried out similar quality assurance programs. The laboratories’ analytical procedures involved a total sediment digestion technique. To accomplish this, sediment samples were oven dried at 80 “C and then weighed (250 mg) into 100-mL Teflon flasks. After addition of 10 mL of HNO, and 5 mL of HF, the samples were allowed to stand at room temperature for at least 2 h. Samples were then heated on a hot plate at ca. 120 OC after the addition of 3 mL of HC104. If upon complete evaporation of acid the residue was not white, additional HNO, (10 mL) was added and the sample reheated. In some cases additional HF and/or HC104were needed to produce a white or yellow/white residue. This Environ. Sci. Technol., Vol. 23, No. 3, 1989
315
Flgure 1. Sediment sampling stations.
residue was dissolved with 1.0 mL of concentrated HN03 and diluted to 10 mL with double distilled water. Samples were then analyzed with Perkin-Elmer 5000 atomic absorption spectrophotometers,employing a Zeeman furnace when necessary. Both laboratories routinely analyzed NBS Standard Reference Material 1646 (estuarine sediment) with each batch of sediment to assess daily performance. Any analyses that deviated by more than 2 standard deviations from the reported certified value for the standard were repeated.
Results and Discussion The results of trace metal analyses of sediments from the coasts of Georgia and South Carolina are plotted against aluminum in Figure 2. Each data point represents the mean of duplicate analyses. As discussed in the Introduction, it was assumed a priori that aluminosilicate minerals (Le., kaolinite and smectite) are the major natural 316
Environ. Sci. Technol., Vol. 23, No. 3, 1989
metal bearing phases in these sediments. The results appear to support this assumption since aluminum accounts for most of the variability of the other metals with the exception of cadmium. Clearly other phases such as iron oxides and organic matter could be important contributors to total natural metal concentrations in these sediments. The relatively close relationship between iron and aluminum, however, suggests that iron oxides are not important (i.e., iron is associated with aluminum in aluminosilicate phases). Total organic carbon (TOC) in these sediments ranges up to -2% and is generally highest in sediments with highest aluminum concentrations, which are the finer grain sediments. Nonetheless, the concentration of metals in the sediments covary with TOC at a far less significant level (e.g., the highest r2 is ca. 0.49 for zinc on TOC as compared to an rz of 0.7 for zinc on aluminum; Table I). The importance of natural organic phases to trace metal levels in the sediments can be estimated by using data
Table I. Comparison of Metal on Aluminum Regression Analysis to Natural Abundances”
GA/SC
Florida
m
b
r2
N
1.15
0.05
0.60 (0.13)
340
1.8 0.47 3.5 55 4.4 12
-1.4 -0.08 1.5 57 -3 -8
0.64 (0.39) 0,91 (0.45) 0.62 (0.21) 0.61 (0.13) 0.53 (0.21) 0.70 (0.49)
340 340 340 340 340 340
m 7.5
arsenic cobalt chromium copper iron lead manganese nickel zinc
9.5 2.5 0.48 3.2 46 2.9 12
b
r2
N
-0.7
0.77 (0.13)
103
4.0 2.2 0.07 2.3 27 2 1
0.81 (0.31) 0.61 (0.29) 0.88 (0.21) 0.69 (0.22) 0.50 (0.02) 0.68 (0.29) 0.83 (0.22)
103 103 103 103 78 103 103
metal:Alb crustal rocks soils 1.1
1.9 10 4.6 0.56 2.3 104 7.1
18
0.85 1.1 9.8 4.8 0.52 4.9 140 7.0 13
” In all calculations, iron and aluminum concentrations are in percent and the concentrations of the other metals are in ppm. Values are for the general equation M = m(A1) b. All regression curves are significant above the 95% confidence level. For comparison, the 9 values for the correlation between metal and TOC are given in parentheses; N = 264 for the GA/SC data set and N = 73 for the Florida data set. bData from Martin and Whitfield (15).
+
Table 11. Potential Contribution of Organic Phases to the Trace Metal Concentrations in Sediments
metal Cd co cu Fe
Hg
Mn Ni Pb Zn
M:C ratio, pg/g phytoplankton’ Spartinab 100 3 30 700 3 20 30 20 300
0.2 0.9 50 1900 4 2 7 4 200
max contrib: rg/g 2 0.06 0.6 38 0.06 0.4 0.6 0.4 6
“From Collier and Edmond (12) and Martin and Knauer (13). bFrom Windom et al. (14). CAssuminga maximum organic carbon concentration of 2% and using the natural source with the higher meta1:C ratio.
shown in Table 11. There are two potentially important natural sources of organic matter in coastal sediments of the southeastern United States: phytoplankton detritus and detritus of Spartina alterniflora, the dominant salt marsh species. The metal to carbon ratios of these materials can be used to estimate a maximum contribution of natural organic phases to the trace metal content of the sediment (Table 11). Comparing the results of Table I1 to those shown in Figure 2 demonstrates clearly that for all metals except cadmium (and perhaps mercury, see below) the contribution of the organic phase, even at its maximum concentration, would have an insignificant effect on total metal concentration. In the case of cadmium, the natural organic phases can represent a significant or, perhaps, the most important contribution to total concentations. This would etrplain the lack of a cadmium to aluminum relationship. It might be expected that cadmium concentrations would correlate with TOC or that a multiple regression of cadmium on TOC and aluminum would be significant. Experimental results by Collier and Edmond (12),however, have demonstrated that cadmium is rapidly released from phytoplankton detritus. This complex biogeochemistry suggests that the results shown in Figure 2 for cadmium are not surprising, For the metals that do correlate with aluminum, the relationship provides a useful method to normalize the relatively large range of observed natural metal levels in these sediments. In the case of the coastal sediments of Georgia and South Carolina, aluminum clearly accounts for most of the grain size effect. We were interested to see if aluminum might also provide a basis to normalize metal concentrations in Florida
estuarine and coastal sediments so that perhaps a regional picture of natural sediments might emerge. As mentioned above, these sediments are more heterogeneous, with respect to metal bearing phases, than those from the Georgia-South Carolina coast. In coastal and estuarine sediments of Florida, carbonates may be important, particularly along the southern coast. Results of the trace metal analysis of Florida sediments are plotted against aluminum in Figure 3. In this case each data point represents the mean of duplicate (67 cases) or triplicate (36 cases) analyses. Superimposed on the results, for metals common to both studies, are the 95% confidence bands from the Georgia-South Carolina data (Figure 2). With the exception of copper, the results for metals common to both studies show similar relationships to aluminum (Table I). In additipn, the Florida results suggests that arsenic and chromium also covary significantly with aluminum. The TOC concentrations in the Florida sediments ranged up to 10% . Here again the relationships between metals and TOC were considerably less significant than that between metals and aluminum (Table I). No significant relation was observed between cadmium and aluminum concentrations nor between mercury and aluminum in the Florida data. We believe that this is probably due, to a large degree, to the relative importance of organic phase contributions to overall metal concentrations as discussed above. The similarity between the metal on aluminum regression equations or the two studies (Table I) suggests a relatively constant composition (i.e., proportionality between metals) of the source area of natural metal bearing phases for southeastern U.S. estuarine and coastal sediments. To provide a more global perspective for our results, the slopes of these regression equations can be compared to the metal to aluminum ratios computed for average continental crustal rocks and for average continental soils (15). These comparisons (Table I) indicate that the metal composition of southeastern estuarine and coastal sediments is similar to expected continental sources with the exception that arsenic is enriched by a factor of -7 and copper, manganese, and nickel are depleted by a factor of -2. The higher arsenic concentrations are perhaps related to the relatively common phosphate deposits that occur throughout the region. The watersheds of the region are composed of deeply weathered soils that are apparently depleted somewhat with regard to copper, manganese, and nickel. On the basis of the results presented above, we propose that aluminum can be used to normalize sediment metal N
Environ. Scl. Technol., Vol. 23, No. 3, 1989 317
0.6
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data over a fairly large region of the southeastern U.S. coast for the purpose of evaluating anthropogenic inputs. This would facilitate comparisons of metal levels in sediments from differnt geographic regions, of different mineralogy and texture, and from different habitats. To demonstrate this we compare data on metal concentrations in sediments from different and widely separated areas of the region we have studied. We chose lead and zinc for the comparison since they are typically associated with non-point-source discharges from urban areas. The concentrations of these two metals for sediments collected from the Savannah River and adjacent salt marsh, Pensacola Bay, and Biscayne Bay are plotted against alumi318
Environ. Sci. Technol., Vol. 23, No. 3, 1989
num in Figure 4 with the confidence limits from Figure 2 superimposed. Data for the Savannah area were reported by Goldberg et al. (8) and are from two cores collected in the river and from a third core collected from a salt marsh nearby. Data for sediments collected from Biscayne Bay are from Ryan and Windom (16)and those from Pensacola Bay are from results of an unpublished study of the Department of Environmental Regulation of the State of Florida. The range in lead and zinc concentrations in sediments from the three areas are generally similar, although four samples from Pensacola Bay have obviously higher zinc concentrations than other sediments (Figure 4). When
70
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Aluminum % Aluminum % Figure 3. Metal concentration in estuarine and coastal sediments of Florida versus aluminum.
compared to the metal-aluminum trend based on natural sediments, however, contaminated sediments can be clearly distinguished from those that have natural metal levels. For example, many of the samples from Biscayne Bay appear to be contamihated by both lead and zinc. This is not surprising since extremely contaminated sediments occur in the Miami River, which has been identified as a source for the contaminated sediments in Biscayne Bay (16).
Some of the samples from cores taken in the Savannah River appear to be contaminated with lead, while all of the samples from the salt marsh core have natural levels. The contaminated samples are all from the upper 10 cm of the Savannah River cores. None of the sediments from the
Savannah area appear to be contaminated with zinc, although there appears to be a systematic downward shift in the zinc-aluminum relationship from that we observed. Goldberg et al. (8) ashed their samples before digestion, which may have led to a systematic volatization of zinc (17).
Finally, some of the sediments collected from Pensacola Bay appear to be contaminated with both lead and zinc. Those sediments that appear most contaminated (i.e., data lying farthest from the natural range) are in closer proximity to port facilities. Although the above is a relatively simple example, it shows the usefulness of comparing metal data from different areas to the metal-aluminum relationships deterEnviron. Sci. Technol., Vol. 23, No. 3, 1989
319
7 0 c Literature Cited
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3
v
-0
tU
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J
40 30 20 Biscayne Bay V Pensacola B a y 0 Marsh Core A 0 Savannah R i v e r Cores]
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mined for natural uncontaminated sediments collected throughout the region. The regression relationships observed for the Georgia-South Carolina sediments have also been employed by the NOAA Status and Trends Program to interpret metal contamination of East Coast sediments (18);thus the results reported here may have even wider application.
(1) Neiheisel, J.; Weaver, C. E. J. Sediment Petrol, 1967, 37, 1084-1 116. (2) Windom, H. L.; Neal, W. J.; Beck, K. C. J. Sediment. Petrol. 1971, 41, 497-504. (3) Ackermann, F.; Bergmann, M.; Schleichert, U. Enuiron. Technol. Lett. 1983,4, 317-328. (4) Forstner, U.; Salomons, W. Environ. Technol. Lett. 1980, 1, 494-505. (5) Trefrey, J. H.; Presely, B. J. In Marine Pollutant Transfer, Heath and Co.: Lexington, MA, 1976; p 39. (6) Ackermann, F. Environ. Technol. Lett. 1980, I, 518-520. (7) Duce, R. A.; Hoffman, G. L.; Ray, B. J.; Fletcher, I. S.; Walsh, P. R.; Hoffman, E. J.; Miller, J. M.; Heffter, J. L.; Wallace, G. T.; Fasching, J. L.; Piotrowicz, S. R. In Marine Pollutant Transfer,Heath and Co., Lexington, MA, 1976, p 77. (8) Goldberg, E. D.; Griffin, J. J.; Hodge, V.; Koide, M.; Windom, H. Environ. Sci. Technol. 1979,13, 588-594. (9) Trefrey, J. H.; Metz, S.; Trocine, R. P. Science 1985,230, 439-441, (10) Turekian, K. K.; Wedepohl, K. H. Geol. SOC.Am. Bull. 1961, 72, 175-192. (11) Taylor, S. R. Geochim. Cosmochim. Acta 1964, 28, 1273-1286. (12) Collier, R.; Edmond, J. Prog. Oceanogr. 1984,13, 113-199. (13) Martin, J.-H.; Knauer, G. A. Geochim. Cosmochim. Acta 1973,37, 1639-1653. (14) Windom, H. L.; Tenore, K. R.; Rice, D. L. Can. J . Fish. Aquat. Sci. 1982, 39, 191-196. (15) Martin, J.-M.; Whitfield, M. Trace Metals in Seawater; Plenum Press: New York and London, 1983; p 265. (16) Ryan, J. D.; Windom, H. L. Metals in Coastal Enuironments of Latin America; Springer-Verlag: Berlin, New York, 1988; p 47. (17) Bruland, K. W.; Bertine, K.; Goldberg, E. D. Environ. Sci. Technol. 1974,8, 425-432. (18) Progress Report and Preliminary Assessment of Findings of the Benthic Surveillance Project-1984. National Status and Trends Program for Marine Environmental Quality, NOAA, Office of Oceanography and Marine Assessment, Rockville, NY, 1987.
Acknowledgments We thank Anna Boyette and Suzanne McIntosh who drew all the figures and Dannah McCauley who typed the drafts of the manuscript. Registry No. Co, 7440-48-4; Cu, 7440-50-8; Fe, 7439-89-6; Pb, 7439-92-1; Mn, 7439-96-5; Zn, 7440-66-6; Ni, 7440-02-0; As, 7440-38-2; Cr, 7440-47-3; Hg, 7439-97-6; Cd, 7440-43-9; Al, 7429-90-5.
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Received for review September 30, 1987. Revised manuscript received May 4, 1988. Accepted September 23, 1988. Studies conducted on the Georgia-South Carolina sediments by the Skidaway Institute were supported by U S . Department of Energy Grant No. DE-FG09-86ER60435. Work on the Florida sediments was supported by a grant from the US.NOAA Office of Coastal Zone Management and the Florida Officeof Coastal Management, Department of Environmental Regulation.
