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土壤无机碳去除是土壤有机碳(C)准确定量的前提。研究以华北半湿润区石灰性土壤土壤为对象,采用不同浓度HCl和不同酸化时间对土壤进行处理,并用碳氮元素分析仪法(“燃烧法”)和Walkley-Black湿氧化法(“湿氧化法”)测定土壤有机碳。研究结果表明,3 M酸化后的农田土壤有机碳浓度低于0.5 M和1 M。燃烧法测得的土壤有机碳浓度随酸化时间延长无明显变化,而对于湿氧化法,土壤经过12 h酸化后,土壤有机碳浓度开始显著降低。对于0~5 cm土壤,燃烧法测得有机碳结果高于湿氧化法(p<0.05),而对于5~10 cm和10~20 cm土壤有相反的结果。鉴于湿氧化法的低氧化性和土壤中可能存在的Cl-干扰,造成土壤有机碳的低估或高估,燃烧法对于土壤有机碳的准确更为可靠。对于华北半湿润区农田土壤,0.5 M和1 M浓度HCl和2 h的酸化处理能够较彻底的去除土壤中无机碳。
Soil inorganic carbon removal is the prerequisite for accurate quantification of soil organic carbon (C). Soil samples from calcareous soils in semi-humid areas of North China were used to treat the soils with different concentrations of HCl and different acidification times. The soil samples were analyzed by carbon-nitrogen elemental analyzer method and Walkley-Black wet oxidation method. “Wet Oxidation Method”) to determine soil organic carbon. The results show that 3 M acidified farmland soil organic carbon concentrations below 0.5 M and 1 M. Soil organic carbon concentration measured by combustion method showed no significant change with the prolongation of acidification time, but after 12 h of acidification, soil organic carbon concentration began to decrease significantly. For 0-5 cm soil, the organic carbon obtained by the combustion method was higher than the wet oxidation method (p <0.05), but had opposite results for the 5-10 cm and 10-20 cm soils. In view of the low oxidation of wet oxidation and possible Cl-interference in soil, resulting in the underestimation or overestimation of soil organic carbon, the combustion method is more reliable for the accuracy of soil organic carbon. For farmland soils in semi-humid areas of North China, acid treatments at concentrations of 0.5 M and 1 M HCl and 2 h could remove soil inorganic carbon more thoroughly.