Deborah P. Mangrich b , Sonia M. Menezes c and Betania F.
Humic acids HA extracted from two coals of different ranks, from their regenerated samples and from a nitrated sample, were characterized by elemental analysis and by infra-red FTIR , solid state 13 C nuclear magnetic resonance NMR and eletronic paramagnetic resonance EPR spectroscopies. NMR results showed that both samples were more aromatic and less carboxylic than common soil HA. Those characteristics may limit the coal HA efficiency as an appropriate soil conditioner and fertilizer. The regeneration process did not produce major alterations in the coal HA, except a decrease of the free radical content as determined by EPR spectroscopy.
Probably, the regeneration conditions and time were not adequate to oxidize the samples. The obtained FTIR spectra were much alike, except that from the nitrated sample, where the absorption band at cm -1 confirms the presence of nitrated groups. Introduction The soil organic matter has a vital role in maintaining soil quality. Additionally, an increase in the aromaticity degree of HA with the coal rank is also reported. The main objectives of this study are: 1 to characterize HA from different coal samples through appropriate chemical and spectroscopic techniques e.
The fifth studied sample LN was obtained by nitrating the sample LO with concentrated HNO 3 at room temperature soil:solution ratio Humic acids isolation The humic acid extraction was based on Swift. L -1 HCl; the acid supernatant was separated by centrifugation 10 minutes, rpm and discarded.
This procedure was repeated three times. After the acidic pretreatment, the samples were extracted with 30 mL of 0. L -1 NaOH under mechanical shaking during 3 h. The alkaline extract was separated by centrifugation and stored in a polyethylene flask.
Register for a free account
This procedure was performed three times. The HA was separated by precipitation with 0.
L -1 HCl added to the extract until pH 2 was reached. The dried samples were maintained in a dissiccator with silica gel before further analysis. Elemental analysis The HA elemental composition was determined by a Perkin Elmer elemental analyzer and the content of O was calculated by difference of mg.
The band assignments were made according to Mangrich et al. The following experimental conditions were employed: 1 13 C-MAS: a resonance frequency of The abundance of each carbon type was estimated by integration of the respective spectral region. The region ppm to ppm was not integrated because the MAS rotation was limited to Hz.
- OECD Economic Surveys 2000-2001: France.
- Nonlinear Partial Differential Equations with Applications.
- Blessing Your Spirit.
- Improving Schools and Governing Bodies: Making a Difference.
The areas of the EPR peaks were calibrated with that corresponding to the EPR signal of a "weak pitch" reference of known free radical content obtained from Bruker. Results and Discussion Elemental composition The elemental composition and elemental ratios of the humic acids are listed in Table 1. The increase in the molecular condensation and in the carbon reduction along the coalification development usually reported for bulk coal samples, 9,10,11 was not verified for the coal humic acids in the present study.
It seems that the coal rank did not affect their HA chemical composition. HA with such composition as that verified in the present study are expected to be quite stable with respect to mineralization process.
This feature is probably more related to the lower effectiveness of the purification process rather than to the regeneration or to the coal rank. The intensity decrease of the peak at cm -1 suggests that nitration occurred at the expenses of the carboxylic groups, while the intensity increase of the band at cm -1 is probably due to the contribution of the bending of the C-N group, that also absorbs in this region. All five HA presented a much higher aromatic and lower carboxylic contents than those obtained for an Australian brown coal HA 8 and those usually reported for soil HA, 1,21 but are in the range of the values verified for Spanish coal HA.
THE APPLICATION OF MULTIDIMENSIONAL NMR TO THE STUDY OF SOIL HUMIC SUBSTANCES
This result may be associated to the preservation of carbohydrate-like structures in the low rank coal HA. Analogous to the infrared spectroscopy, no changes in the chemical composition and structure of the humic acids due to coal regeneration in pile were evidenced by the NMR data. The book will primarily be of interest to soil scientists and to ecological and environmental scientists. People in the fields of forest science, agronomy, analytical and environmental chemistry, water science, environmental engineering, and coal science will also find this publication worthy of their attention.
Chapter 2 Humus in World Soils. Chapter 4 Dissolved Humus in Soil Waters.
Chapter 5 Humus and Soil Conservation. Chapter 6 Microorganisms and Humus in Soils. Chapter 7 Humus and Enzyme Activity. Chapter 8 Organisms and Humus in Soils.
- Insiders Guide to Graduate Programs in Clinical and Counseling Psychology: 2006/2007 Edition?
- Account Options!
- Dogs and Demons: Tales from the Dark Side of Japan.