Earth Science Frontiers ›› 2011, Vol. 18 ›› Issue (6): 125-133.

• Article • Previous Articles     Next Articles

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

  

  1. 1. Institute of Surficial Geochemistry; School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China
    2. School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China
  • Received:2011-09-01 Revised:2011-10-30 Online:2011-11-25 Published:2011-12-05

Abstract:

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 River Delta were selected for analysis. According to the difference in antioxidant capability, disodium peroxodisulphate 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 Na2S2O8 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 labile carbon to recalcitrant carbon in the south Yangtze River region is around 68, 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 400600 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, carboxyl and amide, which can serve as the spectrum indication of labile carbon.

Key words: farmland soil, labile carbon, recalcitrant carbon, Na2S2O8 oxidation, spectrum

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