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Chemical and Molecular Heterogeneity of Humic Acids Repetitively Extracted from a Peat

^a State Key Lab. of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
^b Dep. of Civil, Architectural, and Environmental Engineering, Drexel Univ., Philadelphia, PA 19104

View larger version (11K): [in a new window]   Fig. 1. Plot of H/C vs. O/C atomic ratios for the eight humic acid fractions.

View larger version (22K): [in a new window]   Fig. 2. Fourier transform infrared spectra of the eight humic acid fractions.

View larger version (17K): [in a new window]   Fig. 3. Cross-polarization magic angle spinning (CPMAS) 13C-NMR spectra for the eight humic acid fractions.

View larger version (22K): [in a new window]   Fig. 4. Chromatograms of high performance size exclusion chromatography for the eight humic acid fractions.

View larger version (21K): [in a new window]   Fig. 5. Changes of H/C and O/C atomic ratios as a function of the peak area of the small-size humic acid (HA) subunit for the eight HA fractions. Symbols represent data points and lines are the best fits using linear regressions.

View larger version (22K): [in a new window]   Fig. 6. Changes of carboxylic and phenolic contents as a function of the peak area of the small-size humic acid (HA) subunit for the eight HA fractions. Symbols represent data points and solid lines are the best fits using linear regressions. The dotted line represents the linear fitting of the data excluding Fr6 through Fr8.

View larger version (15K): [in a new window]   Fig. 7. Changes of aromaticity as a function of the peak area of the small-size humic acid (HA) subunit for the eight HA fractions. Symbols represent data points and solid lines are the best fits using linear regressions.