THE IMPACT OF HUMAN ACTIVITIES TO δ13CDIC OF KARST GROUNDWATER AND CARBON SINK IN THE UPPER AND MIDDLE REACHES OF WUJIANG RIVER
Quantitative evaluation of the impact of human activities to karst carbon sink not only helps to improve the estimation accuracy of karst carbon sinks,but also is significant for the current research on global climate change.The Wujiang River,the largest river in Guizhou Province,is a tributary of the Yangtze River with a highest proportion of carbonate.Recently,with the fast population proliferation and rapid economic growth,the drainage basin is intensively interfered by anthropogenic activities and shows an increasing SO42-and NO3-concentration.For investigating the hydrochemical characteristics and the main influencing factors,the hydrochemistry and Carbon isotope in dissolved inorganic carbon (DIC) from 42 and 26 karst groundwater samples were sampled and analyzed during the rainy (July,2013) and dry (October,2013) seasons,respectively,from the Upper and Middle reachesof Wujiang River.The contribution of atmospheric/soil CO2 (CO2ATM-SOIL) to the total HCO3-(CO2ATM-SOIL/ total HCO3-) were calculated using the stoichiometry method.The results showed that the advantage cations of groundwater and surface water were Ca2+ and Mg2+,which accounted for more than 55％,and the advantage anions were HCO3-and SO42-,accounting for more than 85％.The concentrations of Ca2+ and Mg2+ exceeded the equivalent concentrations of HCO3-,which the excess of Ca2+ and Mg2+ cations were compensated by SO42-+NO3-.The δ13CDIG of karst groundwater in the rainy and dry seasons,ranged from-14.19‰ to-8.27‰ and from-12.98‰ to -9.09‰,respectively,with a more depleted value in rainy season.A good positive correlation between δ13CDIC value and [SO24-+NO3-]/[HCO3-] indicated that sulphuric and nitric acid might play a relatively important role in carbonate weathering and has an important influence on δ13CDIC value.The average contribution of atmospheric/soil CO2 (CO2ATM-SOIL) to the total HCO3-(CO2ATM-SOIL/total HCO3-) is 33.83％ for rainy season,and 35.84％ for post-rainy reason,which corresponds to a mean decrease of 16.17％ and 14.16％ compared to natural environmental conditions (50％),respectively.As a consequence,in study area,the equal deficit of soil CO2 uptake by carbonate weathering reach 32.34％ and 28.32％ when nitric and sulfuric acids were involved in.
karst carbon sinkC isotope of dissolved inorganic carbon (δ13CDIC)sulfuric acidnitric acidupper and middle reaches of Wujiang River
NETL
NSTL
万方数据
维普
