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土壤碳库问题是当前环境碳循环最关注的问题之一。土壤碳库中有滞留时间为千年尺度的老碳成分及百年尺度的新碳成分,有效区分二者并探索其成分对于建立精确的土壤有机碳(SOC)的动力学模型、评估碳库潜能十分必要。文中以长三角地区24个农田土壤样品为研究对象,依据不同碳库抗氧化能力,利用过硫酸钠法对其进行分离,并进一步用可见/近红外(Vis/NIR)、中红外(MIR)光谱等分析方法,探究了过硫酸钠处理前后土壤有机碳的组成变化。研究发现过硫酸钠氧化后TOC含量下降64%～92%,说明新碳占总有机碳(TOC)的64%～92%,老碳则占总有机碳的8%～36%。元素分析表明浙江地区的样点老碳含量总体高于江苏,碱性及钙盐较多的环境有利于老碳的富集。对比处理前后的土壤样品,发现氧化处理后样品在Vis/NIR光谱的所有波段反射率均上升,400～600nm波段最为显著。MIR光谱分析显示过硫酸钠处理主要使烷基、羧基及酰胺基等基团特征峰发生较大程度消减,表明相对老碳、新碳中含有大量羧基、酰胺基等基团,它们可以作为新碳的光谱指示。
The issue of soil carbon pool is one of the most concerned issues in the current carbon cycle of the environment. The soil carbon stocks have old carbon components with a thousand-year residence time and new carbon components at the hundred-year scale, effectively distinguishing between them and exploring their components for establishing accurate kinetic models for soil organic carbon (SOC) and for assessing potential for carbon stocks necessary. In this paper, soil samples of 24 farmlands in the Yangtze River Delta were selected as the research objects. According to the antioxidant capacity of different carbon pools, the soil samples were separated by sodium persulfate and further analyzed by Vis / NIR, MIR, Spectroscopy and other analytical methods to explore changes in soil organic carbon composition before and after sodium persulfate treatment. The results showed that the content of TOC decreased 64% -92% after the oxidation of sodium persulfate, indicating that the new carbon accounts for 64% -92% of the total organic carbon (TOC) and the old carbon accounts for 8% -36% of the total organic carbon. Elemental analysis showed that the old carbon content of samples in Zhejiang Province was generally higher than that of Jiangsu Province, and the environment with more alkaline and calcium salts was favorable for the enrichment of old carbon. Comparing the soil samples before and after the treatment, it was found that the reflectance of all samples in the Vis / NIR spectrum increased after the oxidation treatment, and the band of 400-600 nm was the most significant. MIR spectroscopy analysis showed that sodium persulfate treatment mainly reduced the peaks of alkyl groups, carboxyl groups and amido groups, which indicated that relative to old carbon, the new carbon contained a large number of carboxyl groups, amido groups and other groups, which could be used as new Spectral indication of carbon.