tide influence on hydrochemical parameters in two coastal regions of ...
TIDE INFLUENCE ON HYDROCHEMICAL PARAMETERS IN TWO COASTAL REGIONS OF SÃO PAULO (BRAZIL) UNDER DIFFERENT ENVIRONMENTAL OCCUPATIONS Vitor Gonsalez Chiozzini1, Kátia Leite Agostinho 2, Ricardo Delfim 3, Elisabete de Santis Braga 4 Abstract ⎯ This study observes the changes in the hydrochemical parameters in function of the tide influence in two coastal environments at São Paulo-Brazil: i) Southern sector (Cananéia region), with hydrological properties strongly associated to tide currents, pluvial inputs and where the salinity reaches high values; ii) Northern sector (Iguape region), submitted to erosion process, agricultural and urban occupation showing lightly sea tide influence due to an enormous fluvial input across the Valo Grande Channel. Both regional sectors belong to same coastal system constituted by estuaries and lagoons forming an estuarine-lagoon complex. The observations were performed in a wet period under spring tide influence increasing the environmental answers in terms of salinity and dissolved nutrient variations. Index Terms ⎯ Hidrochemistry, nutrients, estuaries.
INTRODUCTION Estuaries are classically defined by [13] and [5] as “semienclosed coastal water body, free connected with the ocean, within which sea water is measurably diluted by fresh water resultant from the continental drainage”. This definition does not clearly include tides influence, fundamental and determining phenomenon for the hydrodynamical processes of these ecosystems. [7] adapted this definition and describes estuaries as an “extension of the river until the limit of the tide”, adding this way the spatial extent of these areas. There are many others definitions, but, any of them can delimitate in a satisfactory way this space within all processes that occur. Estuaries are considered critical transition zones between land, limnological environments and marine habitats [11]. These areas are considered biologically more productive than the marine system. The fresh water discharge and tides force daily changes. The turbulent mixture associated to tides can generate sudden changes of temperature, salinity, turbidity, pH and bioactive elements concentration [9].
This work aims to study the differences in the characteristics of the water body in regions under influence of different forms of historical and economic development, revealed in its own occupation of the land area in Northern and Southern sectors of the estuarine-lagoon complex of Cananéia and Iguape.
MATERIAL AND METHODS Study Area Cananeia-Iguape system (Figure 1) represents a large part of the South Coast of São Paulo State. The region is constituted by a group of small estuaries and tide channels, with some coast lagoons that form a lagoon-estuarine complex. This complex presents 4 principal water bodies: Trapandé Bay, Mar de Cubatão, Mar de Cananéia and Mar Pequeno; and two main barriers: Barra de Cananéia and Barra de Icapara, being separated from the ocean by an island called Ilha Comprida. The drain Basin that feeds the system with fresh water has approximately 23,350 km2 and it is mainly compounded by Ribeira do Iguape river. After the construction of the artificial channel Valo Grande on its Northern portion (Iguape region), a big amount of the Ribeira River flow was diverted to the Mar Pequeno, contributing to the input of fresh water, terrestrial particulate material, nutrients and contaminants to this area. This channel originally was constructed with 4 meters wide and 2 meters deep, but the carriage of terrestrial material from its bed and its banks under the river flood circumstances widened the channel, and, currently it has been around 250 meters wide and 5m deep [14]. Thus, the entire region began to undergo a strong process of siltation, which was highlighted by the growth of sedimentary facies and deposition of fine sediments, besides changes of their ecological characteristics[4]. In its Southern portion (Cananéia region), this system suffers a weak anthropic impact. The disposal of untreated sewage in water bodies and consequently the
1 Vitor Gonsalez Chiozzini - Technician, Instituto Oceanográfico da Universidade de São Paulo - Praça do Oceanográfico, 191 – Cidade Universitária, São Paulo / Brasil, CEP 05508-120, [email protected] 2 Kátia Leite Agostinho - Master student, Instituto Oceanográfico da Universidade de São Paulo - Praça do Oceanográfico, 191 – Cidade Universitária, São Paulo / Brasil, CEP 05508-120, [email protected] 3 Ricardo Delfim - Master student, Instituto Oceanográfico da Universidade de São Paulo - Praça do Oceanográfico, 191 – Cidade Universitária, São Paulo / Brasil, CEP 05508-120, [email protected] 4 Elisabete de Santis Braga, PhD Professor, Instituto Oceanográfico da Universidade de São Paulo - Praça do Oceanográfico, 191 – Cidade Universitária, São Paulo / Brasil, CEP 05508-120 [email protected] Acknowledgement to CNPq INCT-TMCO – Proc. 573.601-2008/9 for the financial support
© 2010 SHEWC
July 25 - 28, 2010, São Paulo, BRAZIL Safety, Health and Environment World Congress 97
estuary itself flowing into the sea is an unwanted action to be monitored. The situation is worse in summer, time due to population increase and high precipitation [3]. Tidal effects are more efficient in this sector, causing a constant renew of water in the region. Several studies present the estuarine-lagoon complex of Cananéia-Iguape as euthrophic system, naturally rich in nutrients [10]-[15]-[12]-[4]-[1]-[2]. Studies done by several authors when Valo Grande was closed [10]-[15]-[12]-[4] found values of dissolved inorganic phosphate in the Northern part of the system around 0.5 μmol.L-1. When Valo Grande was opened, highest values of this nutrient were observed reaching 5,0 μmol.L-1 [2], suggesting a hypertrophication process.
The water temperature was measured in situ using protected reversing thermometers, calibrated in Celsius degrees and packed in cartridges with auxiliary thermometers aggregates to the sampler bottle. This thermometers reading presented precision of ±0,02 oC. Salinity Samples for salinity determination were stored in ambar flasks of 250 ml. For its determination, an inductive method was used with the support of a Beckman RS10, salinometer with precision of ± 0,005. This analysis was done according to [8] recommendations. Nitrite The evaluation of nitrite levels in the samples is based on the method described by [16], using a Bran-Luebbe – Auto Analyzer II equipment. The precision offered by this method is 0,02 μmol.L-1 of N-NO2. Nitrate Samples were analyzed following the method described by [16], using a Bran-Luebbe – Auto Analyzer II equipment, with copper-cadmium column for nitrate reduction to nitrite. By the difference obtained in the analyze of nitrite that was done on the same time and from the same sample, we have the real value of nitrate concentration. The precision offered by this method is 0,02 μmol.L-1 of N-NO3.
FIGURE 1. STUDY AREA
Sampling Fix stations were set in two regions of distinct characteristics in the system: i) Iguape region, which is under the influence of a massive discharge of freshwater from Valo Grande ii) Cananéia region, hydrochemical properties strongly associated to tidal currents. During the summer period (February, 2009), water samples were collected at spring tide (to better highlight the effects provided by tide action) every 2 hours, contemplating the rainy period. The temperature reading and the sample to determinate salinity were obtained together with the Nansen Sampler of Hydrobios® while water samples for nutrients analyses were collected from a Van Dorn type sampler and kept under refrigeration until arrive at the laboratory where were filtered, for this Whatman GF/F glass microfiber filters were used. The filtered material was put in high quality polyetilene flasks and stored in -20°C until analysis time. Analytical Procedures Temperature
© 2010 SHEWC
N-ammoniacal The samples to N-ammoniacal were collected from the sampler and packed in glass flasks, where it was made the immediate addition of reagents .The analysis procedure was described by [16], and offers a precision of 0,05 μmol.L-1 of N-NH3/NH4+, without having to be made any correction to balance the salt effect Determinations were made using a Milton Roy Genesys II spectrophotometer. Phosphate The assessment of phosphate levels are based on the method described by [8], using a Milton Roy Genesys II spectrophotometer for the measurements.
RESULTS AND DISCUSSION Cananéia, temperature values were between 28.20 and 30.70°C, characterizing the summer period. Salinity levels ranged from 18.0 to 30.4. Is remarkable the increasing levels of salinity in response to the entry of sea water into the system during the rising tide. Temperature values were between 28.20 and 30.70°C. Thermohaline characteristics show a slight stratification during quilting tide, more evident over minimum tide oscillating, suggesting that, in the most dynamic events turbulent mixing process occur canceling the stratification. (Figure. 2a and 2c). Concentrations of nitrate in Cananéia remained, between 0.51 and 5.53 µmol.L-1, respectively and were
July 25 - 28, 2010, São Paulo, BRAZIL Safety, Health and Environment World Congress 98
synchronized to the maximum and minimum salinity, indicating the dilution of this parameter caused by the entry of sea water, poor in nutrients, into the system. Nitrite concentrations variations were between 0.21 e 0.73 µmol.L1, showing the same pattern of nitrate dilution by seawater. These can be considered low values, indicating that there is no accumulation of intermediate product in the organic matter degradation process (Figure. 2a and 2e).
(e) 1.6
1.2
1.2
0.0 b sal
s temp
(f)
b temp
(c)
b n‐amm
s nitrate
28.0 27.5
1.0
27.0
29
0.5
26.5
28
0.0
26.0
(g)
b nitrate
N-amm. (µmol.L-¹)
(µmol.L-¹)
6 4 2 0 b nitrite
s phosphate
b phosphate
nitrite (µmol.L-¹)
1.0 0.5
s n‐amm
b n‐amm
s nitrate
b nitrate
4
17.0
3
16.5
2
16.0
1
15.5
0
15.0
(h)
1.5 (µmol.L-¹)
b temp
1.5
8
s nitrite
s temp
31
10
(d)
b sal
2.0
30
s n‐amm
s sal
32
(Sal)
s sal
35 30 25 20 15 10 5 0
s nitrite
b nitrite
0.8
s phosphate
b phosphate 1.8
0.6
1.7
0.4
1.6
0.2
1.5 1.4
0.0
0.0 8:25
10:30
12:23
14:22
16:20
18:20
20:00
7:50
9:15
11:20
13:10
15:15
(°C)
0.4
0
(b)
(Sal)
0.8
0.4
17:15
nitrate (µmol.L-¹)
0.8
phosphate (µmol.L-¹)
(m)
1.6
(°C)
(m)
(a)
N-ammoniacal values were between 0.48 and 7.70 µmol.L-1. High levels were associated to ebb tide indicate a botton influence of the recent degradation of organic matter. Phosphate values oscillated between 0.09 and 1.08 µmol.L-1, being possible to observe the large influence of continental contribution to the abundance of this compound in the region.
19:34
hours
hours
FIGURE. 2 TEMPORAL VARIATION IN THE CONCENTRATION OF HYDROCHEMICAL PARAMETERS AGAINST THE TIDE. DIAGRAMS A) TO D) FOR THE FIX STATION OF CANANÉIA: A) VARIATION OF THE TIDE, B) FLUCTUATIONS IN SALINITY AND TEMPERATURE, C) VARIATION OF N-AMMONIACAL AND NITRATE, D) CHANGES IN CONCENTRATIONS OF NITRITE AND PHOSPHATE. DIAGRAMS E) TO H) FOR THE FIX STATION OF IGUAPE: E) VARIATION OF THE TIDE, F) FLUCTUATIONS OF SALINITY AND TEMPERATURE, G) CHANGES IN THE LEVELS OF N-AMMONIACAL AND NITRATE, H) CHANGES IN CONCENTRATIONS OF NITRITE AND PHOSPHATE. In Iguape, due to Valo Grande channel, there is a strong predominance of water from the Ribeira river reaching the estuarine system. Because of this large amount of fluvial water it can be noticed that the tide influence in hydrochemical parameters is very tenuous. Such characteristics can be observed by thermohaline conditions,
© 2010 SHEWC
which remained virtually constant throughout the sampling period: the salinity ranged between 0.04 and 1.70 while the temperature oscillated from 26.5 to 29.9ºC (Figure. 2b and 2d). Another evidence of the strong performance of fluvial water in this portion of the estuary is the high concentration
July 25 - 28, 2010, São Paulo, BRAZIL Safety, Health and Environment World Congress 99
of nitrate. These concentrations remained constant during the entire sample period, and much more significant than those found in the fixed station of Cananéia (Figure. 2f and 2e), since there is no dilution by seawater. Concentrations of nitrite were between 0.2 e 0.3 µmol.L-1 what is common to a healthy fresh water ambient. Phosphate concentration ranged from 1.4 to 1.7 µmol.L-1, and also were much more significant than those found in Cananéia sector.
CONCLUSIONS The Southern part of the estuarine-lagoon complex of Cananéia-Iguape suffers a huge influence of the tidal variation, keeping the conditions of a stratified estuary, like the dilution of a big part of fluvial parameters with the adjacent sea water, in response to the tidal increase. It can be noticed a large exportation of N-ammoniacal in the part of the complex which is located Cananéia city. This parameter has two sources contributing to a complex interpretation that include an origin from organic matter degradation and also is an intermediate of denitrification process increase when there is oxygen limitation, normally near the bottom and also when the organic matter is elevated demanding environmental attention. To the northern part, the termohaline stratification becomes more tenuous locating predominantly fluvial characteristics, as observed in phosphate and nitrate levels (higher than values found in southern part). The nutrient concentrations observed in this study showed an important disruption in the biogeochemical characteristics in the Northern part of the system due to the anthropic interference in relation to the Cananéia region that rest on more natural and protected conditions, representing a typical estuarine system.
[6]
CETESB 2007, Relatório de qualidade das Águas Interiores no Estado de São Paulo – 2006, 334p.
[7]
Dyer, K. R., Estuaries: a physical introduction John Wiley and Sons, London, 1973, 140 p.
[8]
Grasshoff et al., Methods of Sea Water Analysis, Sec. Edition. Weinhein. Willey-Vch Verlag, 1983, 407p.
[9]
Hedges, J. I. & Keil, R. G., Organic geochemical perspectives on estuarine processes: sorption, reactions and consequences. Marine Chemistry, v.65, 1999, p.55-65.
[10] Kato, K., Chemical Investigations on the Hidrographical System of Cananéia Lagoon, Boletim do Instituto Oceanográfico, v.15 (1), 1966, p.1-12. [11] Levin, L. A. et al., The function of marine critical transition zones and the importance of sediment biodiversity, Ecosystems, v. 4, 2001, p.430-451. [12] Miyao, S. Y. et al., Características físicas e químicas do Sistema Estuarino-Lagunar de Cananéia-Iguape. Boletim do Instituto Oceanográfico, São Paulo, v.34,1986, p.03-36. [13] Pritchard, D., Estuarine circulation patterns, Proc. Amer. Soc., v.81, 1955, p.1-11. [14] Teles, A. E. S. S., A evolução geológica quaternária e a influência do Valo Grande na dinâmica sedimentar da área de Iguape, São Paulo, Dissertação de Mestrado – Instituto Oceanográfico da Universidade de São Paulo,1997, 98p. [15] Tommasi, L. R., Projeto Valo Grande, Relatório Parcial para o Secretário de Obras e Meio Ambiente, 1984, 30p. [16] Treguer, P. & Le Corre, P., Manuel d'analyse des sels nutritifs dans l''eau de mer, Lab. Océanogr. Chimique, Univ. Brétagne Occident. Brest, 1975.
REFERENCES [1]
Aguiar, V. M. de C., Variação Espacial e Temporal das Características Biogeoquímicas do Fósforo e do Chumbo e Transporte de Propriedades no Sistema Estuarino de Santos/S. Vicente e na Porção Sul do Complexo Estuarino-Lagunar de Cananéia- Iguape, Tese de Doutorado, Universidade de São Paulo, Instituto Oceanográfico, 2005, 243pp.
[2]
Barrera-Alba, J. J. et al., Influence of allochthonous organic matter on bacterioplancton biomass and activity in a eutrophic, subtropical estuary, Estuarine Coastal Shelf, v.82, 2009, p.84-94.
[3]
Braga, E. S. & Chiozzini, V. G., Nutrientes dissolvidos no Complexo Estuarino-Lagunar de Cananéia –Iguape: Influência do Valo Grande no setor sul (1992 e 2005), Oceanografia e Mudanças Globais, Brazilian Journal of Oceanography. Proceedings do III SBO, 2008, p.573-582.
[4]
Braga, E. S., Nutrientes dissolvidos e produção primária do fitoplâncton em dois sistemas costeiros do estado de São Paulo, 2 vols, Tese de Doutorado. Universidade de São Paulo. Depto de Oceanografia Geológica, 1995.
[5]
Cameron, W. M. & Pritchard, D. W., Estuaries, M. N. Hill, The Sea vol. 2, John Wiley and Sons, New York, 1963, p.306 - 324.
© 2010 SHEWC
July 25 - 28, 2010, São Paulo, BRAZIL Safety, Health and Environment World Congress 100
INTRODUCTION Estuaries are classically defined by [13] and [5] as “semienclosed coastal water body, free connected with the ocean, within which sea water is measurably diluted by fresh water resultant from the continental drainage”. This definition does not clearly include tides influence, fundamental and determining phenomenon for the hydrodynamical processes of these ecosystems. [7] adapted this definition and describes estuaries as an “extension of the river until the limit of the tide”, adding this way the spatial extent of these areas. There are many others definitions, but, any of them can delimitate in a satisfactory way this space within all processes that occur. Estuaries are considered critical transition zones between land, limnological environments and marine habitats [11]. These areas are considered biologically more productive than the marine system. The fresh water discharge and tides force daily changes. The turbulent mixture associated to tides can generate sudden changes of temperature, salinity, turbidity, pH and bioactive elements concentration [9].
This work aims to study the differences in the characteristics of the water body in regions under influence of different forms of historical and economic development, revealed in its own occupation of the land area in Northern and Southern sectors of the estuarine-lagoon complex of Cananéia and Iguape.
MATERIAL AND METHODS Study Area Cananeia-Iguape system (Figure 1) represents a large part of the South Coast of São Paulo State. The region is constituted by a group of small estuaries and tide channels, with some coast lagoons that form a lagoon-estuarine complex. This complex presents 4 principal water bodies: Trapandé Bay, Mar de Cubatão, Mar de Cananéia and Mar Pequeno; and two main barriers: Barra de Cananéia and Barra de Icapara, being separated from the ocean by an island called Ilha Comprida. The drain Basin that feeds the system with fresh water has approximately 23,350 km2 and it is mainly compounded by Ribeira do Iguape river. After the construction of the artificial channel Valo Grande on its Northern portion (Iguape region), a big amount of the Ribeira River flow was diverted to the Mar Pequeno, contributing to the input of fresh water, terrestrial particulate material, nutrients and contaminants to this area. This channel originally was constructed with 4 meters wide and 2 meters deep, but the carriage of terrestrial material from its bed and its banks under the river flood circumstances widened the channel, and, currently it has been around 250 meters wide and 5m deep [14]. Thus, the entire region began to undergo a strong process of siltation, which was highlighted by the growth of sedimentary facies and deposition of fine sediments, besides changes of their ecological characteristics[4]. In its Southern portion (Cananéia region), this system suffers a weak anthropic impact. The disposal of untreated sewage in water bodies and consequently the
1 Vitor Gonsalez Chiozzini - Technician, Instituto Oceanográfico da Universidade de São Paulo - Praça do Oceanográfico, 191 – Cidade Universitária, São Paulo / Brasil, CEP 05508-120, [email protected] 2 Kátia Leite Agostinho - Master student, Instituto Oceanográfico da Universidade de São Paulo - Praça do Oceanográfico, 191 – Cidade Universitária, São Paulo / Brasil, CEP 05508-120, [email protected] 3 Ricardo Delfim - Master student, Instituto Oceanográfico da Universidade de São Paulo - Praça do Oceanográfico, 191 – Cidade Universitária, São Paulo / Brasil, CEP 05508-120, [email protected] 4 Elisabete de Santis Braga, PhD Professor, Instituto Oceanográfico da Universidade de São Paulo - Praça do Oceanográfico, 191 – Cidade Universitária, São Paulo / Brasil, CEP 05508-120 [email protected] Acknowledgement to CNPq INCT-TMCO – Proc. 573.601-2008/9 for the financial support
© 2010 SHEWC
July 25 - 28, 2010, São Paulo, BRAZIL Safety, Health and Environment World Congress 97
estuary itself flowing into the sea is an unwanted action to be monitored. The situation is worse in summer, time due to population increase and high precipitation [3]. Tidal effects are more efficient in this sector, causing a constant renew of water in the region. Several studies present the estuarine-lagoon complex of Cananéia-Iguape as euthrophic system, naturally rich in nutrients [10]-[15]-[12]-[4]-[1]-[2]. Studies done by several authors when Valo Grande was closed [10]-[15]-[12]-[4] found values of dissolved inorganic phosphate in the Northern part of the system around 0.5 μmol.L-1. When Valo Grande was opened, highest values of this nutrient were observed reaching 5,0 μmol.L-1 [2], suggesting a hypertrophication process.
The water temperature was measured in situ using protected reversing thermometers, calibrated in Celsius degrees and packed in cartridges with auxiliary thermometers aggregates to the sampler bottle. This thermometers reading presented precision of ±0,02 oC. Salinity Samples for salinity determination were stored in ambar flasks of 250 ml. For its determination, an inductive method was used with the support of a Beckman RS10, salinometer with precision of ± 0,005. This analysis was done according to [8] recommendations. Nitrite The evaluation of nitrite levels in the samples is based on the method described by [16], using a Bran-Luebbe – Auto Analyzer II equipment. The precision offered by this method is 0,02 μmol.L-1 of N-NO2. Nitrate Samples were analyzed following the method described by [16], using a Bran-Luebbe – Auto Analyzer II equipment, with copper-cadmium column for nitrate reduction to nitrite. By the difference obtained in the analyze of nitrite that was done on the same time and from the same sample, we have the real value of nitrate concentration. The precision offered by this method is 0,02 μmol.L-1 of N-NO3.
FIGURE 1. STUDY AREA
Sampling Fix stations were set in two regions of distinct characteristics in the system: i) Iguape region, which is under the influence of a massive discharge of freshwater from Valo Grande ii) Cananéia region, hydrochemical properties strongly associated to tidal currents. During the summer period (February, 2009), water samples were collected at spring tide (to better highlight the effects provided by tide action) every 2 hours, contemplating the rainy period. The temperature reading and the sample to determinate salinity were obtained together with the Nansen Sampler of Hydrobios® while water samples for nutrients analyses were collected from a Van Dorn type sampler and kept under refrigeration until arrive at the laboratory where were filtered, for this Whatman GF/F glass microfiber filters were used. The filtered material was put in high quality polyetilene flasks and stored in -20°C until analysis time. Analytical Procedures Temperature
© 2010 SHEWC
N-ammoniacal The samples to N-ammoniacal were collected from the sampler and packed in glass flasks, where it was made the immediate addition of reagents .The analysis procedure was described by [16], and offers a precision of 0,05 μmol.L-1 of N-NH3/NH4+, without having to be made any correction to balance the salt effect Determinations were made using a Milton Roy Genesys II spectrophotometer. Phosphate The assessment of phosphate levels are based on the method described by [8], using a Milton Roy Genesys II spectrophotometer for the measurements.
RESULTS AND DISCUSSION Cananéia, temperature values were between 28.20 and 30.70°C, characterizing the summer period. Salinity levels ranged from 18.0 to 30.4. Is remarkable the increasing levels of salinity in response to the entry of sea water into the system during the rising tide. Temperature values were between 28.20 and 30.70°C. Thermohaline characteristics show a slight stratification during quilting tide, more evident over minimum tide oscillating, suggesting that, in the most dynamic events turbulent mixing process occur canceling the stratification. (Figure. 2a and 2c). Concentrations of nitrate in Cananéia remained, between 0.51 and 5.53 µmol.L-1, respectively and were
July 25 - 28, 2010, São Paulo, BRAZIL Safety, Health and Environment World Congress 98
synchronized to the maximum and minimum salinity, indicating the dilution of this parameter caused by the entry of sea water, poor in nutrients, into the system. Nitrite concentrations variations were between 0.21 e 0.73 µmol.L1, showing the same pattern of nitrate dilution by seawater. These can be considered low values, indicating that there is no accumulation of intermediate product in the organic matter degradation process (Figure. 2a and 2e).
(e) 1.6
1.2
1.2
0.0 b sal
s temp
(f)
b temp
(c)
b n‐amm
s nitrate
28.0 27.5
1.0
27.0
29
0.5
26.5
28
0.0
26.0
(g)
b nitrate
N-amm. (µmol.L-¹)
(µmol.L-¹)
6 4 2 0 b nitrite
s phosphate
b phosphate
nitrite (µmol.L-¹)
1.0 0.5
s n‐amm
b n‐amm
s nitrate
b nitrate
4
17.0
3
16.5
2
16.0
1
15.5
0
15.0
(h)
1.5 (µmol.L-¹)
b temp
1.5
8
s nitrite
s temp
31
10
(d)
b sal
2.0
30
s n‐amm
s sal
32
(Sal)
s sal
35 30 25 20 15 10 5 0
s nitrite
b nitrite
0.8
s phosphate
b phosphate 1.8
0.6
1.7
0.4
1.6
0.2
1.5 1.4
0.0
0.0 8:25
10:30
12:23
14:22
16:20
18:20
20:00
7:50
9:15
11:20
13:10
15:15
(°C)
0.4
0
(b)
(Sal)
0.8
0.4
17:15
nitrate (µmol.L-¹)
0.8
phosphate (µmol.L-¹)
(m)
1.6
(°C)
(m)
(a)
N-ammoniacal values were between 0.48 and 7.70 µmol.L-1. High levels were associated to ebb tide indicate a botton influence of the recent degradation of organic matter. Phosphate values oscillated between 0.09 and 1.08 µmol.L-1, being possible to observe the large influence of continental contribution to the abundance of this compound in the region.
19:34
hours
hours
FIGURE. 2 TEMPORAL VARIATION IN THE CONCENTRATION OF HYDROCHEMICAL PARAMETERS AGAINST THE TIDE. DIAGRAMS A) TO D) FOR THE FIX STATION OF CANANÉIA: A) VARIATION OF THE TIDE, B) FLUCTUATIONS IN SALINITY AND TEMPERATURE, C) VARIATION OF N-AMMONIACAL AND NITRATE, D) CHANGES IN CONCENTRATIONS OF NITRITE AND PHOSPHATE. DIAGRAMS E) TO H) FOR THE FIX STATION OF IGUAPE: E) VARIATION OF THE TIDE, F) FLUCTUATIONS OF SALINITY AND TEMPERATURE, G) CHANGES IN THE LEVELS OF N-AMMONIACAL AND NITRATE, H) CHANGES IN CONCENTRATIONS OF NITRITE AND PHOSPHATE. In Iguape, due to Valo Grande channel, there is a strong predominance of water from the Ribeira river reaching the estuarine system. Because of this large amount of fluvial water it can be noticed that the tide influence in hydrochemical parameters is very tenuous. Such characteristics can be observed by thermohaline conditions,
© 2010 SHEWC
which remained virtually constant throughout the sampling period: the salinity ranged between 0.04 and 1.70 while the temperature oscillated from 26.5 to 29.9ºC (Figure. 2b and 2d). Another evidence of the strong performance of fluvial water in this portion of the estuary is the high concentration
July 25 - 28, 2010, São Paulo, BRAZIL Safety, Health and Environment World Congress 99
of nitrate. These concentrations remained constant during the entire sample period, and much more significant than those found in the fixed station of Cananéia (Figure. 2f and 2e), since there is no dilution by seawater. Concentrations of nitrite were between 0.2 e 0.3 µmol.L-1 what is common to a healthy fresh water ambient. Phosphate concentration ranged from 1.4 to 1.7 µmol.L-1, and also were much more significant than those found in Cananéia sector.
CONCLUSIONS The Southern part of the estuarine-lagoon complex of Cananéia-Iguape suffers a huge influence of the tidal variation, keeping the conditions of a stratified estuary, like the dilution of a big part of fluvial parameters with the adjacent sea water, in response to the tidal increase. It can be noticed a large exportation of N-ammoniacal in the part of the complex which is located Cananéia city. This parameter has two sources contributing to a complex interpretation that include an origin from organic matter degradation and also is an intermediate of denitrification process increase when there is oxygen limitation, normally near the bottom and also when the organic matter is elevated demanding environmental attention. To the northern part, the termohaline stratification becomes more tenuous locating predominantly fluvial characteristics, as observed in phosphate and nitrate levels (higher than values found in southern part). The nutrient concentrations observed in this study showed an important disruption in the biogeochemical characteristics in the Northern part of the system due to the anthropic interference in relation to the Cananéia region that rest on more natural and protected conditions, representing a typical estuarine system.
[6]
CETESB 2007, Relatório de qualidade das Águas Interiores no Estado de São Paulo – 2006, 334p.
[7]
Dyer, K. R., Estuaries: a physical introduction John Wiley and Sons, London, 1973, 140 p.
[8]
Grasshoff et al., Methods of Sea Water Analysis, Sec. Edition. Weinhein. Willey-Vch Verlag, 1983, 407p.
[9]
Hedges, J. I. & Keil, R. G., Organic geochemical perspectives on estuarine processes: sorption, reactions and consequences. Marine Chemistry, v.65, 1999, p.55-65.
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© 2010 SHEWC
July 25 - 28, 2010, São Paulo, BRAZIL Safety, Health and Environment World Congress 100
