| In order to reveal the reclamation affect the components of chongming dongtan soil organic carbon,this study selected the chongming dongtan 92 levee,98 levee and 2016 dike reclamation district as the study area,through the analysis of chongming dongtan reclamation district within 0?100 cm depth of soil physical and chemical properties,total organic carbon(TOC),active organic carbon(LC)and inert spatial distribution characteristics of organic carbon content(RC)and organic carbon composition structure,combined with the feature of infrared spectroscopy of soil reclamation on chongming dongtan soil organic carbon composition,the results showed that:(1)The particle size,moisture content,pH,conductivity and total nitrogen content of all soil samples in the study area were 5.29?37.02 m,13.29?44.84%,7.29?8.95,0.08?0.75 2ms and 0.26?6.73g/kg,respectively.The mean values of soil particle size,moisture content,pH,conductivity and total nitrogen at 0?100cm depth were 16.97±2.95 m,29.75±3.88%,8.44±0.25,0.32±0.07 2ms and 0.80±0.42 g/kg,with significant peaks at some depths.(2)The soil TOC content of all samples in the study area ranged from 0.62 to 43.74 gC/kg,with an average value of 6.86±3.68 gC/kg,slightly lower than that in the surface sediments of chongming dongtan salt marsh wetland.The overall characteristics of the vertical distribution of TOC content 0?100cm show that it fluctuates and decreases with the increase of depth,and obvious TOC peaks may appear at some depths.The TOC content of soil under different land use types has little difference.Among them,the soil TOC content in vegetable fields was slightly higher than that in other land use types,and the distribution range and average value of soil TOC content were 3.35?24.42 g C/kg and 7.25±5.02g C/kg,respectively.The distribution range of soil LC content in the study area was 0.01?26.06g C/kg,with an average value of 2.60± 1.90g C/kg.There are significant differences in the vertical distribution characteristics of LC content in different column samples.The overall characteristics of the vertical distribution in 0?100cm show that it fluctuates and decreases with the increase of depth,and obvious TOC peaks may appear in some depths.Land reclamation and tillage resulted in the decrease of soil LC content,and the LC/TOC ratio of different land use methods was the highest,reaching 63.43±6.73%.The distribution range of soil RC content in the study area was 1.065?17.68g C/kg,with an average value of 5.22± 1.43g C/kg.The proportion of soil RC in total organic carbon ranged from 0.08 to 98.89%,with an average value of 60.42± 18.46%.The RC/TOC ratio of watermelon field was slightly higher,at 62.77±31.33%.(3)In the study area,the variation trend of soil infrared spectra at different depths of the same column sample showed obvious similarity,and soil absorbance was positively correlated with soil organic carbon content.After acid hydrolysis,soil active organic carbon(LC)was dissolved during acid hydrolysis,so the soil organic carbon content(RC)of acid hydrolysis was lower than that of original soil(TOC)on the whole,and the soil absorbance in each depth range of soil was also lower than that of original soil on the whole.The distribution of absorbance of different functional groups on the depth of soil samples in different column samples showed that the absorbance of polysaccharides was higher and that of aromatic compounds and aliphatic compounds were similar.Compared with the absorbance of different functional groups in the original soil samples,the absorbance of soil polysaccharides hydrolyzed by acid showed an overall trend of decreasing,while the absorbance of aromatic compounds and aliphatic compounds remained basically unchanged.After the acid hydrolysis of the original soil of each column sample,the soil dissolved the soil active organic carbon(LC)in the acid hydrolysis process,and the polysaccharides were also acidic,so the polysaccharide absorbance of the soil at all depths was lower than that of the original soil as a whole. |
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