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Carbonate System and Partial Pressure of CO2 in the Subtropical Jiulongjiang River, China: A Discussion on Controlling Mechanisms (Vol.42, No.3) TEXT SIZE: A A A

QI Di1, ZHAI Wei-dong2, *, CHEN Neng-wang1, WU Jie-zhong1

 (1. College of Environment and Ecology, Xiamen University, Xiamen 361102, China; 2. National Marine Environmental Monitoring Center, Dalian 116023, China) 

Abstract: The authors investigated the distributions of surface water dissolved oxygen (DO), pH, dissolved inorganic carbon (DIC) and total alkalinity (TAlk) and calculated the partial pressure of CO2 (pCO2) in the Jiulongjiang River, a subtropical river in Fujian Province, China. The average values of DO% and pH were 67±18% and 7.08±0.12 in the dry season, and 57±12% and 7.22±0.11 in the flood season. The lowest values of DO% and pH were 10% and 6.88 in the dry season, and 35% and 6.98 in the flood season. The average DIC was 1027±620 µmol/kg in the dry season and 820±340 µmol/kg in the flood season. TAlk was 885±570 µmol/kg in the dry season. TAlk was mainly controlled by the geological background and chemical weathering in the watershed. However, most of free CO2 was associated with aerobic respiration in water columns and anaerobic processes in the sediments. Aqueous pCO2 in the Jiulongjiang River was  3470±1640 µatm on average in the dry season and 3590±1410 µatm on average in the wet season, respectively. Based on data analyses between supersaturated CO2 and apparent oxygen utilization, it was concluded that the in-situ aerobic respiration accounts for 66-94% of the supersaturated CO2 in the Jiulongjiang River, and the remaining supersaturated CO2 may come from denitrification in the sediments.

Key words: riverine pCO2; carbonate system; respiration; Jiulongjiang River

EARTH AND ENVIRONMENT Vol. 42, No.3, Tot No.299, 2014, Page 286-296

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