长三角地区农田土壤中新老碳的含量和组成特征研究  

Investigation on content and composition characteristics of labile carbon and recalcitrant carbon in farmland soils of Yangtze River Delta

作　　者：张婷[1] 李根[1] 杨忠芳[2] 季峻峰[1] 

机构地区：[1]南京大学地球科学与工程学院表生地球化学研究所,江苏南京210093 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地学前缘》2011年第6期125-133,共9页Earth Science Frontiers

基　　金：中国地质调查局项目"中国矿物碳汇潜力研究"(水[2011]01-15-08)

摘　　要：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。Soil carbon pool is one of the major concerns about farmland soil today. Soil carbon pool contains the recalcitrant carbon with turnover time of thousands of years, and the labile carbon with turnover time of hundreds of years. Effective separation and exploration of the two are essential for modeling precise SOC dynamics and assessing soil＇s carbon storage potential. In this study, 24 soil samples collected in Yangtze Riv- er Delta were selected for analysis. According to the difference in antioxidant capability, disodium peroxodisul- phate oxidation method was chosen to separate recalcitrant carbon and labile carbon, and then, the near-infrared （NIR） and mid-infrared （MIR） spectroscopy were applied to probe into SOM＇s composition changes before and after oxidation treatment as well as verify the effectiveness of the method and find the possible factors affecting the distribution of labile carbon and recalcitrant carbon. Carbon oxidized by Na2 S2O8 took up 64 %- 92% of total organic carbon （TOC）, manifesting that labile carbon accounted for 64%- 92 % of TOC while recalcitrant carbon accounted for 8 %- 36 % of TOC. Element analyses show that the ratio of labilecarbon to recalcitrant carbon in the south Yangtze River region is around 6 - 8, more stable than that in the north. Enrichment of Ca results in an increase in recalcitrant carbon content. When analyzing NIR spectrum, an overall rise of the samples＇ reflectivity after oxidation was detected, especially among the 400 - 600 nm band. According to the MIR spectrum, the group peaks having been reduced after Na2S2O8 treatment are mainly those of alkyl, carboxyl and amide, indicating that when compared with recalcitrant carbon, labile carbon contains lots of alkyl, carboxyt and amide, which can serve as the spectrum indication of labile carbon.

关 键 词：农田土壤 新碳 老碳 过硫酸钠氧化法 光谱 

分 类 号：P595[天文地球—地球化学]