硫酸和硝酸对桂林毛村碳酸盐岩溶蚀的室内模拟
Laboratory simulation of the dissolution of carbonate rocks sampled from Maocun,Guilin by sulfuric acid and nitric acid
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摘要: 硫酸和硝酸对碳酸盐岩的溶蚀会减少岩溶碳汇量,但其定量关系有待进一步研究。文章根据野外水体中SO42-、NO3-浓度,在室内封闭条件下分别设计了碳酸(0.033 mol?L-1)、硫酸和硝酸(0.1~1.7 mmol?L-1)(CSN酸)及硫酸、硝酸(0.1~1.7 mmol?L-1)(SN酸)对碳酸盐岩的溶蚀实验,实验历时144 h。结果表明:CSN酸中泥晶灰岩和白云岩的溶蚀速率均大于SN酸的。CSN酸中,泥晶灰岩溶蚀速率总体均高于白云岩,平均值分别为1.34 mg?(cm2?d)-1和1.21 mg?(cm2?d)-1。而在SN酸中,二者溶蚀速率差别不大,平均值分别为0.92 mg·(cm2?d)-1和0.93 mg·(cm2?d)-1;HCO3-浓度与溶蚀速率结果对应,泥晶灰岩和白云岩在CSN酸溶蚀液中HCO3-平均值分别为1.43 mmol?L-1和1.33 mmol?L-1,而在SN酸中泥晶灰岩的HCO3-低于白云岩,平均值分别为0.33 mmol?L-1和0.39 mmol?L-1。CSN酸中HCO3-浓度随酸浓度的增大而减小,而SN酸中其浓度随酸浓度的增大而增大。当SO42-、NO3-浓度为0.1~0.3 mmol?L-1时,碳酸对白云岩的溶蚀作用占75.89%~58.64%,对泥晶灰岩的溶蚀作用占80.21%~59.06%,当SO42-、NO3-浓度大于0.44 mmol?L-1时,其溶蚀作用小于50%。当SO42-、NO3-浓度为0.0~0.2 mmol?L-1时,野外实测数据与模拟数据基本吻合;当浓度>0.2 mmol?L-1时,野外实测碳酸对碳酸盐岩的溶蚀比例高于模拟实验。研究结果进一步说明了硝酸和硫酸对碳酸盐岩溶蚀作用的显著影响,可为其他酸对岩溶碳汇影响提供参考。Abstract: The dissolution of carbonate rocks by sulfuric acid and nitric acid would reduce the amount of karst carbon sink, however, the quantitative relationship between these acids and carbon sink needs further study. Based on the concentrations of SO42-and NO3- in field water,this paper designed carbonic acid(0.033 mol?L-1 )+ sulfuric acid + nitric acid(0.1-1.7 mmol?L-1)(CSN acid)and sulfuric acid + nitric acid(0.1-1.7 mmol?L-1)(SN acid)dissolution experiment on carbonate rocks,and the experiment lasted 144 hours. The results show that the dissolution rates of micrite and dolomite in the CSN acid are both higher than that in the SN acid.In the CSN acid,the dissolution rate of micrite is generally higher than that of dolomite, with average values of 1.34 mg·(cm2?d)-1 and 1.21 mg·(cm2?d)-1, respectively. In the SN acid,the dissolution rates of micrite and dolomite have little difference,and their average values are 0.92 mg·(cm2?d)-1 and 0.93 mg·(cm2?d)-1, respectively. The HCO3- concentration corresponds to the result of the dissolution rate. The average HCO3- values generated by dissolution of micrite and dolomite in the CSN acid solution are 1.43 mmol?L-1 and 1.33 mmol?L-1, while the average values of HCO3- generated by dissolution of micrite and dolomite in the SN acid are 0.33 mmol?L-1 and 0.39 mmol?L-1. The concentration of HCO3- in the CSN acid decreases with the increase of acid concentration,while the concentration in the SN acid increases with the increase of acid concentration. When the concentration of SO42- and NO3- is 0.1-0.3 mmol?L-1, the dissolution rate of carbonic acid to dolomite accounts for 75.89 %-58.64%, and the dissolution rate of carbonic acid to micrite accounts for 80.21%-59.06%.When the concentrations of SO42- and NO3- are more than 0.44 mmol?L-1,the dissolution rate of carbonate rock by carbonate acid will be less than 50%.When the concentrations of SO42- and NO3- are 0.0-0.2 mmol?L-1, the field measured data is basically consistent with the simulated data. However,when the concentration of SO42- and NO3- is higher than 0.2 mmol?L-1,the field measured data is higher than the simulated data. These results indicate that nitric acid and sulfuric acid significantly affect the dissolution of carbonate rock,which could provide references for the effects of other acids on karst carbon sink.
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Key words:
- dolomite /
- micrite /
- mixed acid /
- dissolution rate /
- laboratory simulation /
- carbon sink amount
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