Download - Average of discharge from Ji-Paraná river (1978 to 2001) (Agência Nacional das Águas – ANA)
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Legend
Rivers
Amazônia
Rondônia
Basin of Ji-Paraná
COM-1
PB-1
COM-2
PB-2
JIP-1
JIP-2
JIP-3
JIP-4
JIP-5
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9°0'0"S 9°0'0"S
8°0'0"S 8°0'0"S
0 40 80 120 16020Kilometers
Legend
Sites
Rivers
Basin Ji-Paraná
Average of discharge from Ji-Paraná river (1978 to 2001)
(Agência Nacional das Águas – ANA)
0200400
600800
100012001400
160018002000
J F M A M J J A S O N D
Month
Dis
char
ge (
m3.s
-1)
pC
O2
(µat
m)
JJJ F MM AA S O N D
atm equilibrium tributaries Ji-Paraná
pCO
2 (
µat
m)
0
500
1000
1500
2000
F M A M J J S N D4.0
4.5
5.0
5.5
6.0
6.5pCO2 pH
Average COM-1 and PB-1
pH
Low waterHigh water
2.7
38,0 24,3
4,2
pC
O2 (
µa
tm)
Average JIP-2,3
pH
High water Low water
177,5166,8
24,2
240,5
pCO
2 (
µat
m)
Average JIP-1, 4, 5
High water Low water
156,9
84,124,4
185,9
CO2* (µM)
HCO3-(µM)
CO2* (µM)
HCO3-(µM)
pH
0
500
1000
1500
2000
2500
3000
3500
4000
F M A M J J S N D
5.0
5.5
6.0
6.5
7.0pCO2 pH
Machadinho
105,4
29,4 87,184,3
pCO
2 (
µat
m)
High water Low water
Pimenta Bueno -2
pCO
2 (
µat
m)
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
F M A M J J S N D
5.5
6.0
6.5
7.0
7.5
pCO2 pH
pHHigh water
177,2154,7
Low water
36,1
219,7
Base Saturation
( % ) Urupá
pH
0
2000
4000
6000
8000
10000
12000
F M A M J J S N D
5.0
5.5
6.0
6.5
7.0
7.5
8.0pCO2 pH
610,8
60,3
High water Low water
215,6
264,3
pCO
2 (
µat
m)
INTRODUCTION
OBJECTIVE
STUDYAREA
Fev/00
Mar/01
Abr/02
May/99
Jun/00
Jul/01
Sep/00
Nov/99
Dec/01
The partial pressures of dissolved CO2 (pCO2) in the Ji-Paraná and its tributaries are a
function of respiration and mineral weathering. Although rivers draining eutrofic soils
(Rolim, Urupá, Jarú and Pimenta Bueno-2) show the highest DIC concentrations and
outgassing (evasion) of CO2, pH changes lead to a pronounced seasonality in evasion.
The outgassing is higher during the rising water, because the dilution of ground water by
rain water, and probably also changes in metabolism, result in lower pH values, thus
increasing the partial pressures of dissolved CO2 (pCO2) and evasion process. In the
falling water, groundwater stay longer in contact with the substrate and weathering, which
consumes H+ and converts carbonic acid into bicarbonate, increases pH and lowers pCO2
and the evasion process.
The rivers draining distrofic soils (Comemoração, Pimenta Bueno-1, Preto e Machadinho)
show lower DIC concentrations and lower pH, and the potential evasion of CO2 is limited
by lower pCO2.
CONCLUSION
The influences of total dissolved inorganic carbon (DIC) concentrations and pH on potential outgassing from rivers
in Rondônia.Maria de Fátima F. L. Rasera1; Alex Vladimir Krusche1; Nei K. Leite1; Jeffrey E. Richey2; Anthony K. Aufdenkampe3
1 Universidade de São Paulo –CENA. Lab. de Ecologia Isotópica. Piracicaba/SP – Brasil [email protected] School of Oceanography, University of Washington, USA
3 Stroud Water Research Center - USA
Recent studies point to the importance of CO2 outgassing from rivers of the Amazon,
suggesting that a significant part of the carbon fixed by forest return to the
atmosphere through this pathway. Gas exchange between the atmosphere and
waters is a funcion of gaseous gradients across the air-water interface, and the water
pCO2 is strongly determined by the concentrations of dissolved inorganic carbon
(DIC) and pH, which, in turn, are a funcion of physical, chemical and biological
processes. This study focus on the influence of DIC concentrations and the pH on
potencial CO2 outgassing to atmosphere from rivers of the Ji-Paraná basin,
Rondônia.
METODOLOGY
RESULTS
River Water
Field
Laboratory FiltrationDissolved Inorganic
Carbon - ( DIC )
Calculated
Theoretical diffusion model :
F = D.(Cwater - k.Pair) / Z (Broecker, 1974)
Where:
D = gas- and temperature-specific diffusion coefficient;
Cwater = concentration of gas in the water;
k.Pair = concentration of gas in equilibrium with the atmosphere
Z = thicness of the boundary layer
Total Organic Carbon Analyser
(Shimadzu, 5000A)
Infrared gas analyser,
non dispersive
Thermodynamic equilibrium equations
[CO2*] = DIC .(10pH)2 .
(10pH)2+ k1.(10pH) + k1.k2
(Stumm & Morgan, 1996)
DIC
(µ
M)
pH
temperature
pH
pH meter
condutivity
Condutivity meterAdd Thymol
[pCO2] = [CO2*] k0
Acknowledgements
CO
2 e
vasi
on
(m
ol
CO
2.m
-2.d
-1)
AVERAGE
HIGH WATER
LOW WATER
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
COM1 COM2 PB1 PB2 J IP1 Rolim Urupá J IP2 J IP3 J aru Machad. J IP4 J IP5 Preto
* D/Z = K (exchange coeficient) = 1,2 m.d-1 (Richey et al, 2002)
SH 37.13
To expand the understanding of changes in pH and DIC concentrations in the Ji-
Paraná River Basin and its consequences for the outgassing of CO2.
