soil organic carbon analysis techniques

Download Soil organic carbon analysis techniques

Post on 25-May-2015

362 views

Category:

Technology

3 download

Embed Size (px)

TRANSCRIPT

  • 1. By Group VI

2. Forms of carbon (1) elemental (2) inorganic (3) organic In most soils (with the exception of calcareous soils) the majority of C is held as soil organic carbon (SOC). 3. more accurately known as the carbon stored within soil. is a complex and varied mixture of materials is part of the soil organic matter (SOM) used as an indicator of SOM presence in a soil or sediment) is an essential part of any site characterization. 4. soil organic matter (SOM) is used to describe the organic constituents in the soil soil organic carbon refers to the C occurring in the soil in SOM. 5. Soil carbon is stored in a number of fractions with widely varying chemistry and stability. These soil carbon fractions can be converted to the greenhouse gas carbon dioxide, and comprise: rapidly decomposable raw pieces of plants and microorganisms that lasts for days or weeks 6. Measuring carbon in soils is increasingly important world-wide due to its conversion to the greenhouse gas, carbon dioxide Managing global climate change. 7. QUALITATIVE METHODS SEMI-QUANTITATIVE METHODS QUANTITATIVE TECHNIQUES 8. Two methods nuclear magnetic resonance (NMR) spectroscopy diffuse reflectance infrared Fourier transform (DRIFT) 9. Measuring the characteristic energy absorbed and re-emitted or dispersed by atomic nuclei Advantage no extraction of organic matter is needed. However, these are expensive and time-consuming 10. Carbon compounds are identified by assignment of the main infrared absorption bands to the bonds being stretched or deformed at that particular frequency.Both inorganic and organic forms rapid and inexpensive 11. Two primary methods: loss-on-ignition hydrogen peroxide digestion 12. heated destruction of all organic matter in the soil or sediment. ceramic crucible (or similar vessel) 3500 and 440oC 13. through oxidation. concentrated hydrogen peroxide (30% or 50%) Temperature: 900C 14. no universal conversion factor Conversion factors ranges 1.724 to as high as 2.5 15. destructive non-destructive techniquesThe destructive techniques the most common techniques 16. Three basic principles wet oxidation followed by titration with ferrous ammonium sulfate or photometric determination of Cr3+ wet oxidation followed by the collection and measurement of evolved CO2 dry combustion at high temperatures in a furnace with the collection and detection of evolved CO2 17. Wet Chemistry Techniques for the determination of Total Organic Carbon. Two phases: sample extraction sample quantitation. 18. Dry Chemistry Techniques Two phases: sample combustion sample quantitation CO2 is quantitated by titrimetric, gravimetric, manometric, spectrop hotometric, or gas chromatographic techniques. are typically cited as total carbon techniques 19. This technique: Involves inelastic neutron scattering and bears mentioning can be performed in situ. is based on the detection of 4.44 MeV gamma rays that result from the bombardment of carbon atoms with 14 MeV neutrons and the subsequent emission of gamma rays from the excited carbon. The gamma rays are then detected, quantified, and converted to % C content. Drawbacks is currently under development requires a radioactive neutron generator be used and taken to the field for analysis 20. Near-infrared (NIR) and Laser Induced Breakdown Spectroscopy (LIBS) 21. rapid and non-destructive involves diffusereflectance measurement in the near infrared region 1000 - 2500 nm depend on the number and type of chemical bonds in thematerial being analysed 22. to predict various soil properties including C and N content in soils Is recognized as a practical indicator tool to measure soil health and their basic characteristics 23. is based on atomic emission spectroscopy A laser pulse is focused on a (soil) sample, creating high temperatures and electric fields that break all chemical bonds and vaporize it into a white-hot gas of atomic ions known as micro plasma The resulting emission spectrum is then analyzed using a spectrometer covering a spectral range from 190 to 1,000 nm. 24. Root respiration is a direct release of photo synthetically-fixed C, root exudation is a process through which photosynthetic allyfixed C enters the C pool in the soil. 25. 14Clabeling is used to investigate microbial respiration of root exudates. 26. a Plexiglas chamber, an air supply and dispensing system, 14C02 generating and infrared gas analyzer loop two air mixing fans

Recommended

View more >