Dissertation > Excellent graduate degree dissertation topics show

The Compositions and Structural Characteristics of Humic Substances and Their Evolution with Time in Luochuan Loess-paleosol, Shaanxi

Author: SunXuHui
Tutor: LiFuChun
School: Nanjing Agricultural College
Course: Soil
Keywords: loess paleosol soil organic carban humic substance clay minerals iron oxide minerals
CLC: S158
Type: Master's thesis
Year: 2012
Downloads: 11
Quote: 0
Read: Download Dissertation


Soil humic substance (HS) is a kind of dark macromolecule organic compound which is amorphous and complex. It’s the main part of soil organic matter and plays an extremely important role in soil. HS can not only provide various nutrients for plants, but also improve crop quality, and at the same time it gives great contribution to soil structure. HS is also helpful in reducing environmental pollution. Researches found that organic pollutants and harmful heavy metal ions can be absorbed well on some parts of HS. So research about the stability and transformation on HS is absolutely useful and important.It’s well known that clay particles and clay minerals can protect organic matter by some well researched way. Result is that the dominant factor and main way have not been fully understood, and there is less systematic research of HS evolution characteristics on a long time span. We studied the quantitative contants and structure properties of HS in17loess-paleosol profiles in Luochuan Shaanxi province by some physical, chemical and spectroscopy methods. The main results are as follows:(1) There are higher TOC in paleosols than in underlying loess. The average contents of TOC in S0-S8and L1-L8are2.12g/kg and1.54g/kg respectively. The contents of MOC are higher in paleosol than in loess, while StOC and COC are at the same level.(2) The unstable part of soil organic carbon is decomposed and the remaining is StOC in long buried soil. It takes140~250ka and330~410ka to reach a stable state in loess and paleosol respectively, because of the indifferent mineral composition, organic compositions and chemical structure.(3) The correlations between caly and TOC, COC are positive (r=0.46and0.54respectively), whereas these are poor between fine sand and TOC, COC.The correlations between Kaolinite and TOC, COC are positive (r=0.74and0.61respectively), while the contents of illite and montmorillonite are not related to TOC and COC. (4) Approximate order of the contents of HS component in paleosols is HM>HA>FA, whereas in loess it’s FA>HM>HA. And these HS components are decreasing both in loess and paleosols with the increasing of burial time.(5) Analysis between HS components and TOC components shows that the relationship between HA, HA+FA, HA+FA+HM and TOC are positive, r=0.89,0.94and0.96respectively. The HS that can be extracted takes93%of TOC on average.(6) HA, HA+FA and HA+FA+HM are related with kaolinite (r=0.62,0.57and0.65respectively). Complex HS components are relatived with Fep. These means the stability of soil organic matter is due to kaolinite and Fep.(7) There are more aliphatic structures and humification trend in HS in paleosols than in loess. HAs have more aromatic constituents and less carbonyl and aliphatic structures than FAs.

Related Dissertations

  1. Effect of Soil Erosion on Soil Quality in the Cultivated Slope Land on the Loess Plateau, China,S157.1
  2. Study on the Variation of Soil Clay Minerals and Influence Factors in Karst Regions under Different Rocky Desertification, Southwest China,X171
  3. Studies on Water and Soil Conservation in Lvliang Mountain Area during the Period of Collectivization,S157
  4. Characteristics of Natural Quercus Liaotungensis Communities and the Gap Effects on the Understory Regeneration in the Loess Plateau, China,S718.5
  5. Naturalized Development and Reproductive Characteristics of Caragana Korshinskill Population in the Gullied Loess Plateaus,S793.3
  6. Facing Loess, Bearing Heaven,I207.42
  7. The Analysis of Landscape Patterns and Their Scaling Effects in Small Watersheds of Loess Hilly Area,P901
  8. Study on the Root Distribution of Ziziphus Jujuba and the Relationship between the Distribution and Soil Water and Nutrients in Hillside Fields,S665.1
  9. Effects of Conservation Tillage on Soil Fertilization and Yield of Spring Maize on Dry Land,S513
  10. Analysis of Slope Stability of 3~# Line Loess Basement Dump in Yuanbaoshan Surface Coal Mine,TD824.8
  11. The Study of Strength in Unsaturated Loess Based on the Soil-water Characteristic Curve,TU43
  12. The Loess Slope and Inhiblt Sturcture interaction Mechanism Research,TU43
  13. Study on the Characteristics of Seismic Subsidence Loess in Guanzhong Area,TU444
  14. Study on the Planning and Design of Plant Landscaping for Plateau-Mountain Type Park in the Loess Plateau,TU986.5
  15. Research on Properties Determination of Dynamle Mechanlcs and Basic mechznics Properites for Remolded Loess,TU444
  16. Study on the Engineering Properties of Loess and the Stability of Loess Slope Along a Railway,U212.22
  17. A Research on the Spatial Evolution of the Rural Settlements on the Loess Hilly Region in the West Long,K928.5
  18. Analysis of Sedimentary Characteristics and Provenance of Surficial Sediments on the West South Yellow Sea,P736.21
  19. Study for the Earth Pressure and Side Friction Acted on the Open Caisson’s Wall in the Loess Region,TU432
  20. Collapsible loess drilling rammed pile reinforced soil compaction and applied research,TU473
  21. Experimental Study on Dynamic Shear Modulus and Damping Ratio of Loess under Complex Initial Stress States,TU411.8

CLC: > Agricultural Sciences > Agriculture as the foundation of science > Soil > Soil fertility (soil fertility )
© 2012 www.DissertationTopic.Net  Mobile