Carbon sink effect of simulated acid rain in lime soil and carbonate rock system

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 HCO3- 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 precipitation 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 HCO3- 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.