The CO2 system in rivers of the Australian Victorian Alps: CO2 evasion in relation to system metabolism and rock weathering on multi-annual time scales

Abstract: The patterns of dissolved inorganic C (DIC) and aqueous CO2 in rivers and estuaries sampled during summer and winter in the Australian Victorian Alps were examined. Together with historical (1978-1990) geochemical data, this study provides, for the first time, a multi-annual coverage of the linkage between CO2 release via wetland evasion and CO2 consumption via combined carbonate and aluminosilicate weathering. delta C-13 values imply that carbonate weathering contributes similar to 36 of the DIC in the rivers although carbonates comprise less than 5 of the study area. Baseflow/interflow flushing of respired C3 plant detritus accounts for similar to 50 and atmospheric precipitation accounts for similar to 14 of the DIC. The influence of in river respiration and photosynthesis on the DIC concentrations is negligible. River waters are supersaturated with CO2 and evade similar to 27.7 x 10(6) mol/km(2)/a to similar to 70.9 x 10(6) mol/km(2)/a CO2 to the atmosphere with the highest values in the low runoff rivers. This is slightly higher than the global average reflecting higher gas transfer velocities due to high wind speeds. Evaded CO2 is not balanced by CO2 consumption via combined carbonate and aluminosilicate weathering which implies that chemical weathering does not significantly neutralize respiration derived H2CO3. The results of this study have implications for global assessments of chemical weathering yields in river systems draining passive margin terrains as high respiration derived DIC concentrations are not directly connected to high carbonate and aluminosilicate weathering rates. (C) 2010 Elsevier Ltd. All rights reserved.