Paper Number: 522
Comparison of Atmospheric CO2 Consumption of Carbonate Rock Weathering with Silicate Rock One in the Pearl River Basin, China
JIANG Zhongcheng, QIN Xiaoqun， ZHANG Liankai, HUANG Qibo, LIU Pengyu
(Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004,Guangxi, China; Key Laboratory of Karst ecosystem and treatment of rocky desertification, Ministry of Land and Resources, Guilin 541004, Guangxi, China)
Abstract: Atmospheric CO2 can be absorbed and dissolved in water among karst processes. This process occurs not only in carbonate environments but also in lithological terrain globally. Few analyses, to date, have demonstrated how much atmospheric CO2 can be absorbed in different lithologies in a river basin. Here, using the Pearl River basin of China as an example, we examine variations in weathering rates to assess the importance of carbonate rock weathering for atmospheric CO2 fixation. Chemical and strontium isotopic analysis results of water samples collected from 11 stations in the Pearl River quarterly over one year reveal that independent of lithology (carbonate or silicate) HCO3-、Ca2+、Mg2+ become the main ionic compositions of the river and geological carbon sink processes operate across the river basin. The river ion stoichiometric and flux calculation show that, the carbonate rock weathering rate and atmospheric CO2 consumption are 28 mm/Ka and 540 x 103 mol/km2/a respectively, which are ~11 and 7 times of that which occurs under silicate rock weathering; carbonate rocks provide the main atmospheric CO2 sink in the basin. Under ideal climate and geological conditions, mean rock weathering rates and atmospheric CO2 fixation in the Pearl River basin can reach 30 mm/Ka and 620 x 103mol/km2 respectively. The atmospheric CO2 consumption value is about 2.6 times of the average value of 60 assessed rivers in the world.
Key words: carbonate rock weathering; silicate rock weathering; atmospheric CO2 sink; the Pearl River basin, China