Embed Size (px)
Citation preview
Journal of Coastal Research SI 39 713 - 717 ICS 2004 (Proceedings) Brazil ISSN 0749-0208
TESSLER, M. G.; FIGUEIRA, R. C. L.; MAHIQUES, M. M.; FUKUMOTO, M. M., and CIAPINA, E. M. P., 2006.Sedimentation rates and contamination levels by heavy metals at the shallow sedimentary columns from Santosestuary and bay, SP, Brazil. Journal of Coastal Research, SI 39 (Proceedings of the 8th International CoastalSymposium), 713 - 717. Itajaí, SC, Brazil, ISSN 0749-0208.
The coastal region off Santos (State of São Paulo, Southeastern Brazil), one of the most strategical Brazilian areas,where is placed the main port terminal has had an accelerated process of industrial and harbor improvement duringthe second half of the 20th century. An evolution of the depositional (sedimentary) processes in the context of thisaccelerated growth can be verified by sedimentation rates and the variation of heavy metal levels in the sedimentarycolumns from the upper estuary as well as in the Santos bay. The sedimentary changes were evaluated from theanalysis of the texture as well as the variations of the concentrations of the metallic elements (Pb, Cu, Zn and others).The sedimentation rates were obtained by 210Pb and 137Cs. The most representative sedimentary column from thearea of the Santos bay (core S2T3) presented a segmentation of the sedimentation between 10 and 14 cm of depth.The value obtained for the uppermost sequence is about 0.91 mm.y-1 while the lower sequence presented a highervalue rate (3.8 mm.y-1). This rate change represents a modification in the sedimentary pattern of the area, as onesequence of thin sandy sediments is replaced by the depositional of finer sediments (medium to fine silt). The highersedimentation rate values from the area of the upper estuary, 4.0 mm.y-1 to 210Pb (Barnabe Island), correspondes toan approximate time range of 100 years. For 137Cs the sedimentation rate is 5.6 mm.y-1 which representsapproximately the last 40 years. The increases of the concentration of the metallic elements in the sedimentarycolumns from these areas point to a change in the sedimentary dynamics and the concentration of the sedimentsstarting at 10 cm. From this, it was possible to develop a history of the contamination by levels over that area.
ADDITIONAL INDEX WORDS: Sedimentation rates, heavy metal levels, sedimentary processes.
ABSTRACT
Sedimentation Rates and Contamination Levels by Heavy Metals at the ShallowSedimentary Columns from Santos Estuary and Bay, SP, Brazil
M. G. Tessler†; R. C. L. Figueira‡; M. M. Mahiques†; M. M. Fukumoto† and E. M. P. Ciapina‡
INTRODUCTION
The coastal region of Sao Paulo State, namely the bay andestuary of Santos, contains the largest Brazilian marine harbor(Santos Harbor), where a continuous social and economicalgrowth happened along the second half of the twentieth century.
The intensification of an anthropogenic interference processon the area of the estuary and the bay of Santos (23º 58' 24º 04'S/ 46º 18' 046º 22' W) started with the construction of a newhighway between the plateau and Santos city (Anchietahighway), in the beginning of the 1940's, when the activities intourism and services increased.
The construction of an underground generating plant by theLight Company between 1956 and 1962 amplified the capacityof generating energy in this area, turning possible theinstallation of a petroleum refinery, a petrochemical complexand, later, a metallurgical complex (1959-1963), modifyingsignificantly the environmental and hydrodynamic conditionsof the estuary.
The amplification of the installed electric capacity led to anincrease in the flow of fresh water originating from the plateau,in the estuary. This water carried a considerable amount ofmaterial, rich in metallic and organic elements, and resultingfrom the industrial and urban activities in the areas of the upperestuary in suspension.
This period of fast growth (1950-1960), implicated not onlyin the amplification of the port area, but also in the need forcontinuous dredging of the navigable bed aiming the access ofheavy ships to the harbor as well as the access to areas of theupper estuary where exclusive wharfs were built to themetallurgical industry.
In the upper Santos estuary the fluvial waters coming fromthe rivers of Serra do Mar mountain chain go into the estuary,
especially in the harbor channel area, originating apredominance of an unidirectional flow to the bay.
and (1976) described the characteristicsof the fluvial flows of the upper estuary and demonstrated thatthe mangrove surrounding the estuary holds great part of thematerial transported by traction, releasing only the muddysuspension material to the channels.
The area of the medium estuary is a zone of influence for tidalcurrents supporting the movement caused by sea action fromSantos bay. (1991) relates that the contact betweenthe unidirectional fluvial and marine flows is vertical,corresponding to a break zone of transport energy of the system.
F LFARO PON ANO
YASSUDA
Ú Ç
† Department of GeologySao Paulo University, Sao Paulo05508-900, [email protected],[email protected],[email protected]
‡ CETEC/CCBSCruzeiro do Sul University, Sao Paulo08060-090, [email protected]
Journal of Coastal Research Special Issue 39, 2006,
Figure 1. Area of study and sampling.
The upper and medium estuary from Santos configures ageneral process of sedimentation, in a low energy environment,where muddy sedimentation predominates.
An evaluation of the depositional processes in the context ofthe intense sedimentary dynamics in the Santos estuary and bay,throughout the last 70 years, was developed using recentsedimentation rates obtained by gamma spectrometry ( Pb and
Cs) and by the variation of heavy metals levels along fourcores collected in the area of the bay (S2T3 and 6945) and in theupper estuary (Barnabe Island and Santa Rita Inlet). These areasare presented in Figure 1.
The cores were sliced every 2 cm, freeze-dried,homogenized and transferred to appropriate plastic pots to thecounting in the gamma-ray spectrometer, low background Gedetector, EG&G Ortec, GEM 60120 P model, with theresolution of 1.9 keV at 1332.40 keV photopeak of Co. The
methodology of analysis and data acquisition is described byFigueira et al. (1997) and (2001a, 2001b).
Chemical analysis of the heavy metals in the sediments wascarried out by CEIMIC Corporation laboratory. The sampleswere digested using EPA 3050A Method (USEPA, 1996) andanalyzed by Perkin Elmer Optima 4300 ICP-OES. Grain size of
METHODS
210
137
60
SAITO et al.
Tessler et al.
Figure 3. Sedimentation rate for the shallow sedimentarycolumn 6945. The values of Cs were corrected by mud level.137
Figure 2. Sedimentation rate for the shallow sedimentarycolumn S2T3. The values of Cs were corrected by mud level.137
Figure 4. Sedimentation rate for Barnabe Island shallowsedimentary column. The values of 137Cs were corrected bymud level.
Figure 5. Sedimentation rate for Santa Rita Inlet shallowsedimentary column. The values of Cs were corrected by mudlevel.
137
Journal of Coastal Research Special Issue 39, 2006,
714
18
16
14
12
10
8
6
4
2
0
1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5
(1964-65)
137Cs (Bq/kg)
De
pth
(cm
)
18
16
14
12
10
8
6
4
2
0
-10 0 10 20 30 40 50 60
S2T3
Sed. rate = (3.8 +- 8.5) mm/y
R2= 0.16
Sed. rate = (0.91 +- 0.37) mm/y
R2
= 0.593
210Pb
(unsupported)(Bq/kg)
Depth
(cm
)
22
20
18
16
14
12
10
8
6
4
2
0
0 1 2 3 4 5 6 7 8 9 10 11 12
6945
(1964-65)
137Cs (Bq/kg)
De
pth
(cm
)
(1964-65)
0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0
137Cs (Bq/kg)
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
0,0
De
pth
(cm
)
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
1 10 100 1000
Barnabe Island
Sed. rate = (4.0+-2.0) mm/y
R2= 0,419
210Pb
(unsupported)(Bq/kg)
Depth
(cm
)
22
20
18
16
14
12
10
8
6
4
2
0
1 10 100 1000
Santa Rita Inlet
Sed. rate = (1.49+-0,25) mm/y
R2
= 0.858
210Pb
unsupported(Bq/kg)
De
pth
(cm
)
14
12
10
8
6
4
2
0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0
(1964-65)
137Cs (Bq/kg)
De
pth
(cm
)
the collected sediments was obtained according to(1973).
In Santos bay the core S2T3 presents a significant change inthe sedimentary pattern in the interval between 10 and 14 cm ofdepth. The sedimentary sequence is constituted of muddysediments containing biogenic material.
The upper sedimentary sequence (top 10cm) presents asedimentation rate of 0.91 mm.y related to the radioactivedecay of Pb. The lower sequence presented a highervalue rate (3.8 mm.y ), with a precision error significantly
larger than the computed value. Cs analysis confirmed thechange in the sedimentation pattern in the range between 10 and14 cm. The sedimentary sequence presented a sedimentationrate of 4.0 mm.y (0.05 mm.y ) with a maximum value at 14 cmof depth, corresponding to 1964 and 1965, characterized as theperiod of larger emission of this radionuclide in the atmospherefrom nuclear tests on surface. Figure 2 shows the sedimentationrate for Pb and Cs in shallow sedimentary column S2T3.
The core 6945 presents mud contents varying from 21.7% (6cm of depth) to 43.2% (16 cm of depth). The sedimentation raterelated to Pb radionuclide was not determined in core 6945,once its radioactive decay column was homogenized, either byremobilization of sedimentary package or by percolation of
SUGUIO
RESULTS
-1
210
-1
137
-1 -1
210 137
210
Sedimentacion Rates and Contamination Levels by Heavy Metals
Figure 6. Levels of metals and mud for shallow sedimentary columns S2T3, 6945, Barnabe Island and Santa Rita Inlet.
Journal of Coastal Research Special Issue 39, 2006,
715
Tessler et al.
fluids along the column. However, no difficulty was presentedby Cs method (Figure 3) making possible to obtain asedimentation rate of 2.7 mm.y , with a maximum value ofradioactive fallout at 12 cm of depth.
The sedimentary sequences obtained in the cores of the upperestuary, Barnabe Island and Santa Rita Inlet, werehomogeneous, being constituted of muddy sediments, and asolid structure without the presence of bioturbations or shells.
In the upper estuary area, the Barnabe Island shallowsedimentary column presented a pattern of continuousradioactive decay for Pb, with a sedimentation rate value of4.0 mm.y (1.8 mm.y ). For Cs the rate was slightly higher 5.6mm.y (1.2 mm.y ), with the maximum emission being
detected at the 20-22 cm of depth (Figure 4).The rate obtained by the Pb technique for the Santa Rita
core was of 1.5mm.y (0.4 mm.y ); using the Cs technique thefound value was similar (1.7 mm.y-1) (Figure 5).
A homogeneous behavior of the metallic elements in thesampled shallow sedimentary columns of Santos bay, isobserved, along the basal sequences of the cores S2T3 and6945.Achange in the levels of some metals (Pb, Cu, Cr and Zn),that were normalized by Sc levels (UNEP, 1995), occur in thedirection on the top, presenting a little enrichment. The samplesdating, from sedimentation rate indicated that the highest levelsare related to the beginning of the 1950's, it was a period ofintense industrialization in Santos area.
137
-1
210
-1 -1 137
-1 -1
210
-1 -1 137
Figure 7 . Normalized metals values by Al and Sc for shallow sedimentary columns S2T3, 6945, Barnabe Island and Santa Rita Inlet.
Journal of Coastal Research Special Issue 39, 2006,
716
In the upper estuary area the levels of the metallic elements(Pb, Zn and Cu), normalized by Sc, on the top of theshallowsedimentary columns presented higher results thanSantos bay. Figures 6 and 7 present the levels of metals and thenormalized factor by Sc in the region studied.
Cs showed to be the most appropriate radionuclide toobtain the recent sedimentation rates for the studied cores. Thedifference between the results from Pb and Cs techniquesmay be due to the low content of mud along the sampledsequences. The increase of mud levels on the top of the cores,the presence of radioactive fallout of Cs in this depth and itslonger half-life (about 30 years) contributed to a more reliableanalysis.
The obtained values in the upper estuary sequences by Pband Cs techniques are in agreement. Sedimentation rates areslightly higher in Barnabe Island when compared to other areasof the upper estuary and Santos bay.
It was also observed that an enrichment of Pb, Cu and Znoccurred from 1950. This enrichment was more significant inthe upper estuary area (Barnabe Island and Santa Rita Inlet)than in Santos bay (S2T3 and 6945).
The sedimentation rates and the metallic elements valuesobtained along the cores of the upper estuary and the Santos bayallowed us to obtain a history of sedimentary deposition for theperiod of intense industrialization in Santos area.
This work was funded by Fundação deAmparo à Pesquisa noEstado de Sao Paulo (FAPESP) via grant numbers 99/12692-5,2000/10977-1, 01/10615-5 and 01/10704-8.
W. L. 1976. Sedimentação atual doestuário e baía de Santos : um modelo geológico aplicado aprojetos de expansão da zona portuária. In:
Rio deJaneiro,Associação Brasileira de Geologia de Engenharia. v.2, p. 67-90.
I. I. L. 1997. Instrumental analysis by gammaspectrometry of low level caesium-137 in marine samples.
(Goiânia,Brazil), pp. 329-337.
I. I.L. 2001a. Pb-210 and Cs-137 geochronologies in theCananeia-Iguape Estuary (São Paulo, Brazil).
, v.249, n.1, p.257-261.I. I.
L. 2001b. Geochronology of sediments in the Cananeia-Iguape Estuary and in southern continental shelf of SãoPaulo State, Brazil. , v.250, n.1,p.109-115.
K. Ed. Edgard Blucher,1973.
United Nations Environment Programme. 1995.Manual for the analyses of marine sediments and suspendedparticulate matter. Reference Methods for Marine PollutionStudies, n. 63.Amsterdam, Netherlands, 65p.
U.S. Environmental ProtectionAgency. 1996.Acid digestion ofsediments, sludges and soils. U.S. Environmental ProtectionAgency Publication, EPASW-846, 7p.
E. A. 1991. Modelo numérico do transporte desedimentos no canal principal do estuário de Santos. SãoPaulo, São Paulo: São Paulo University, Master´s thesis,121p.
.
.
.
.
.
CONCLUSIONS
ACKNOWLEDGEMENTS
LITERATURE CITED
137
210 137
137
210
137
F LFARO, V. J.; PON ANO,
FIGUEIRA, R. C. L.; SILVA, L. R. N.; FIGUEIREDO, A. M. G.;CUNHA,
SAITO, R. T. ; FIGUEIRA, R. C. L.; TESSLER, M. G.; CUNHA,
SAITO, R. T. ; FIGUEIRA, R. C. L.; TESSLER, M. G.; CUNHA,
SUGUIO,
UNEP -
YASSUDA,
Ú Ç
CongressoBrasileiro de Geologia de Engenharia, 1. Anais.
Proceedings of an International Conference
J. Radioanal.Nucl. Chem.
J. Radioanal. Nucl. Chem.
Introdução a Sedimentologia.
Sedimentacion Rates and Contamination Levels by Heavy Metals
Journal of Coastal Research Special Issue 39, 2006,
717
