Characterization of the Different Organic Matter from Soils and Sediments

The humic acid (HA) and nonhydrolyzable carbons (NHC) were isolated from three river sediment samples (1, 2, 3) from the rivers in the Tongzhou district of Beijing and four soil samples(4, 5, 6, and 7) from the surface soils in the vicinity area of Tianjin near Bohai Bay, respectively. The isolated HA and NHC fractions were also characterized using elementary analysis, X-ray photoelectron spectroscopy (XPS), solid state C-13 cross-polarization and magic angle spinning nuclear magnetic resonance spectroscopy (C-13 NMR), and Fourier transformed infrared spectroscopy (FTIR). The results showed that NHC had lower H/C and O/C atomic ratios than HA from the same source. The sum of surface O-containing groups accounted for 7. 6%similar to 10.7% and 40. 9%similar to 46. 7% in NHC and HA samples, respectively. C-13 NMR and FTIR spectra of the NHC samples revealed a large contribution of alkyl carbon and aryl carbon. In addition, the NHCs isolated from soils had higher content of aromatic carbon than the NHC form river sediments. Systematic characterization showed that the NHC samples were more condensed and hydrophobicity than the HA samples.