岩溶试片的岩性差异对估算岩溶速率和碳通量的影响

研究岩性差异对溶蚀速率的影响有助于提高溶蚀试片法估算岩溶碳汇强度的精确度。本文以贵州省普定县为研究区，将埋放地的主要基岩类型（石灰岩与白云岩）制成标准尺寸的试片，并将其埋设于不同土地利用类型和土壤深度下，经过4个水文年的监测后将估算的结果与前人在同一区域使用标准溶蚀试片的研究结果进行对比分析，结果表明:（1）在相同气候和土壤环境条件下，岩性对溶蚀试片的溶蚀速率有显著影响，且溶蚀速率与岩石中CaO含量呈正相关关系，与MgO含量呈负相关关系；（2）石灰岩与白云岩试片溶蚀速率的差异程度受土地利用及埋放深度的调控，整体上石灰岩溶蚀速率比白云岩溶蚀速率大14%；（3）不同岩性试片估算的岩溶碳汇强度相差较大，标准溶蚀试片估算的结果比埋放地基岩试片估算的结果高。故使用溶蚀试片法估算区域岩溶碳通量时应考虑埋放地基岩的岩性，或者对基于标准溶蚀试片的估算结果进行校正，才能准确反映区域尺度真实的岩溶碳通量大小。 

Effects of rock tablet lithology difference on estimation of rock dissolution rate and carbon flux

Under the control of subtropical humid monsoon climate, karstification is very strong in the karst area of southern China. At the same time, a lot of researches indicate that the carbon sink formed by karstification in southern China may be an important part of the global missing carbon sink. At present, there are many research methods to estimate the intensity of karst carbon sink. The carbonate rock tablet test is one of the main traditional research methods to estimate the karst carbon flux. The main principle of this method is based on the chemical reaction of water-CO₂-carbonate rock. The specific operation is to bury the carbonate rock test piece with the same size under the soil, then take them out and weigh them after a certain time, use the dissolution amount of rock tablets to calculate the dissolution rate and karst carbon flux in study area. Finally, the regional karst carbon sink can be estimated according to"point by area". In the study of estimating karst carbon sink in China, previous scientists used pure limestone from Rongxian formation of Devonian System in Guilin. However, the geological background of different regions is quite different, and the composition and structure of bedrock are different, so that the estimation results of standard carbonate rock tablets (pure limestone) may be also different from the actual dissolution amount of local bedrock tablets, resulting in great uncertainty in the estimation of karst carbon sink in the region. Based on this, in this study, we chose Puding county, Guizhou Province as the study area. The main bedrock types (limestone and dolomite) of this place are made into standard size rock tablets, and buried them in the typical land use types (secondary forest, shrub, grassland, dry land and paddy field) in the study area. After monitoring for four hydrological years, the dissolution rate and karst carbon flux were calculated, then compared them with the previous research results using the standard carbonate rock tablet (pure limestone) in the same study area, and the following results are obtained; (1) Under the same climatic conditions and soil environmental conditions, lithology has a significant impact on the dissolution rate of carbonate rock tablets, and the dissolution rate has a positive correlation with CaO content in the rock tablets and a negative correlation with MgO content in the rock tablets; (2) The difference of dissolution rate between limestone and dolomite is controlled by land use types and soil depths. Without considering the influence of environmental factors, on the whole, the dissolution rate of limestone is 14% higher than that of dolomite; (3) The karst carbon sink intensity estimated by different lithology carbonate rock tablets varies greatly. The estimated result of standard limestone tablets is higher than that of local tablets in this study. Therefore, when using the carbonate rock tablet method to estimate the regional karst carbon flux, we should consider the lithology of the bedrock where the rock tablet is buried, or correct the estimation results based on the standard carbonate rock tablet, so as to accurately obtain the real karst carbon flux on the regional scale.