模拟酸雨条件下石灰土-碳酸盐岩体系的碳汇效应

摘要

为揭示不同酸度降雨对石灰土-碳酸盐岩体系内岩溶碳汇效应的影响，以贵阳市花溪区历史降水量为参照，选取贵阳市青岩镇纯灰岩发育土壤与贵阳市花溪水库三叠纪大冶组纯灰岩为样本进行淋溶试验。测定了6个月时长内不同酸度降水﹑不同土壤深度下模拟石灰土-碳酸盐岩体系降水淋出液的 HCO-3﹑DOC含量和土壤呼吸速率，研究了模拟酸雨对石灰土-石灰岩体系碳汇的影响。结果表明：(1)在土壤深度10~50 cm 匀质状态的样本中，随着土壤厚度的增加，淋出液中 HCO-3含量逐渐增大﹑DOC含量逐渐减小﹑土壤呼吸速率逐渐增大，显示出土壤厚度对石灰土-碳酸盐岩体系的碳汇效应有着明显的影响；(2)在 pH=3.5~6.8的范围内，降水酸度的增强可以抑制岩溶作用与有机碳的溶解，并降低岩溶碳汇效应；(3)在日降水量90~230 mm 范围内，随着降水量的增大碳汇效应也会随之增强。%In order to investigate the influence of rainfall acidity on the carbon sink in a lime soil and carbonate rock system,a leaching test was conducted using lime soil sample developed in pure limestone in Qingyan town and a pure limestone sample of Triassic Daye formation from Huaxi reservoir,Guiyang,comparing to the historical precipitation in Huaxi district,Guiyang.The influence of simulated acid rain on lime soil and the limestone system carbon sink was studied by measuring the HCO-3 content,DOC in the leachates and the soil respiration rate in the lime soil and carbonate rocks system leached over six-months using a range of pre-cipitation acidities and at various depths in the soil.The results showed that,(1)in the homogeneous sample in the soil of 10-50 cm deep ,the content of HCO-3 increased with increased thickness of soil,however the DOC content decreased and the rate of soil respiration increased,indicating that soil thickness significantly affected the carbon sink in the lime soil and carbonate rock system;(2)for pH values ranging 3.5-6.8,the samples had significant differences in carbon emissions increasing precipitation acidity inhibited karstification and organic carbon dissolution,and the karst carbon sink effect decreased;(3)for a daily precipitation range of 90-230 mm,the carbon sink was enhanced with the increased precipitation.