中国岩溶2025，Vol.44Issue(1)：124-135,146,13.DOI:10.11932/karst20250109
不同水体在大气环境中对碳酸盐岩溶蚀过程及溶解无机碳δ13C演变规律
Dissolution process of carbonate rocks by different types of water in atmospheric environment and δ13C evolution of dissolved inorganic carbon
摘要
Abstract
Carbonate dissolution is a geological process that occurs in the shallow surface environment of the Earth.Due to its geochemical characteristics—such as low temperature,openness,sensitivity,and biological participation—it leads to variability in the concentration of dissolved inorganic carbon(DIC)and its δ13C(δ13CDIC)values in karst water.In addition,although the global distribution of carbonate rocks(approximately 15.2％)is smaller than that of silicate rocks(approximately 41.8％),the rapid kinetics of carbonate weathering contributes to approximately 68％of DIC in large rivers all over the world.Therefore,exploring the effects of different types of water on the dissolution of carbonate rocks,changes in DIC concentration,and carbon isotope characteristics are of great significance.This study selects the Yaji Karst Experimental Site,a karst area in Southwest China characterized by acid rain,as the research object to conduct experimental investigations in the atmospheric environment.Additionally,this study examines the effects of atmospheric precipitation,soil water,and karst groundwater on this process.The effects of continuous soil CO2 input and aquatic photosynthetic plants are excluded.This study also explores the influence of hydrochemical components in different types of water on the dissolution of carbonate rocks under acid rain conditions.Besides,it examines the control of CO2 degassing and CO2 exchange at the water-gas interface on the evolution of δ13CDIC. The results indicate as follows,(1)Precipitation,along with its infiltration into the soil and subsequent exposure to the surface,still exert a significant dissolution effect on carbonate rocks,even in the absence of a continuous input of soil CO2 and aquatic photosynthetic plants.However,under the same conditions,karst pipelines/fissure water exert weak or no dissolution effects on carbonate rocks after its exposure to the surface.(2)As the soaking time increases,the dissolution amount of carbonate rocks per unit time gradually decreases,and ultimately transforms into calcite crystals,with the highest dissolution rate of approximately 19.7 mg(cm2·h)-1.Except for the precipitation soaking group,the concentrations of DIC in the other soaking solutions gradually decrease and tend to stabilize.Furthermore,the decrease in DIC in the karst groundwater soaking solution is greater than that in the soil leaching soaking solution.The δ13CDIC values increase progressively with longer soaking time,ranging from an initial value of-18.21 ‰ to-12.66 ‰,and reaching values between-5.79 ‰ and 3.11 ‰.Except for the precipitation soaking group,the CO2 partial pressure(pCO2)in the other soaking solutions rapidly decreases and tends to stabilize.The stable pCO2 level in each soaking solution is mainly observed:the pCO2 level in soil leaching soaking solution(1,000-3,000 ppmv)is higher than that in karst pipeline/fissure water soaking solution(1,000 ppmv)but is roughly comparable to that in precipitation soaking solution.The level of stable pCO2 in all soaking solutions is higher than that of atmospheric pCO2(approximately 420 ppmv),with the former being roughly two to eight times higher than the latter.(3)If water is in an open atmospheric system without continuous input of soil CO2 and without aquatic photosynthetic plants,when concentrations of SO42-exceed 29 mg·L-1 or concentrations of NO3-exceed 50 mg·L-1,the salt effect and ion pair effect produced by SO42-and NO3-can significantly increase the solubility of calcite and promote its dissolution.If the concentrations of SO42-and NO3-in water are high,the saturation index of calcite,calculated based on Ca2+and HCO3-concentrations,may not accurately reflect the dissolution/crystallization state of calcite.Therefore,the simultaneous effects of various ions in water on calcite dissolution/crystallization should be considered,including ion effects,salt effects,and ion pair effects.(4)After soil vadose water or karst pipeline/fissure water is exposed to the surface,CO2 in the water can complete the degassing process within a few hours.In the absence of a continuous input of soil CO2 and aquatic photosynthetic plants,pCO2 quickly reaches an equilibrium state and ceases to be the major factor controlling the dissolution/crystallization of calcite.The CO2 degassing effect significantly increases the δ13CDIC value,with an increase of up to+10.98 ‰.This results in a substantial discrepancy between the actual and theoretical contributions of soil or atmospheric CO2 to DIC.关键词
丫吉试验场/碳酸盐岩溶解/大气开放环境/溶解无机碳δ13C同位素/CO2脱气Key words
Yaji experimental site/carbonate rock dissolution/open atmospheric environment/δ13C of dissolved inorganic carbon/CO2 degassing分类
天文与地球科学引用本文复制引用
赵光帅,朱义年,谢银财,沈利娜,吴华英,李腾芳,黄奇波..不同水体在大气环境中对碳酸盐岩溶蚀过程及溶解无机碳δ13C演变规律[J].中国岩溶,2025,44(1):124-135,146,13.基金项目
国家自然科学基金联合基金(U21A2041) （U21A2041）
广西自然科学基金面上项目(2025GXNSFAA069711,2025GXNSFAA069865) （2025GXNSFAA069711,2025GXNSFAA069865）
中央引导地方专项(XZ202301YD0005C) （XZ202301YD0005C）
国家自然科学基金(42372294) （42372294）
中国地质调查局地质调查项目(DD20230081) （DD20230081）
