YAN Hui, LI Zhong-xuan, CHEN Jie 

( College of Urban Planning and Environment Science, Xuchang University, Xuchang 461000, China) 

Abstracts: TheHuaxi River, one of the tributaries of the Wujiang River, had been monitored for one year to determine the DIC concentrations and δ13CDIC. The results showed that DIC ranges from 1.73 to 4.53 mmol/L, and δ13CDIC varies from -9.6 ‰ to -3.6 ‰, reflecting the main control of carbonates, negative correlation between δ13CDIC and DIC indicated that the decomposition of organic matter and biological activities of the river also have an important influence on the DIC pool. Groundwater recharge and the dissolution of atmospheric CO2 in the winter led to higher δ13CDIC and DIC concentrations. With the onset of spring, enhancement of photosynthesis would cause an increase in δ13CDIC , a decrease in DIC concentrations, and the highest δ13CDIC value. During the summer, the decomposition of organic matter is a predominant control on shifts in the DIC pool, δ13CDIC reaches the lowest value, and due to the dilution effect of rainfall makes the DIC concentrations at the lower level. During the late summer, photosynthesis and elevated CO2 escape would cause an increase in δ13CDIC and a decrease in DIC concentrations. Decomposition of organic matter in the autumn would lead to a negative shift of δ13CDIC, accompanied by an increase in DIC concentrations.

Key words: dissolved inorganic carbon; carbon isotope;decomposition of organic matter; Huaxi River

EARTH AND ENVIRONMENT Vol. 39, No.3, Tot No.285, 2011, Page 300-304