Humic acids 852 INDEX

Fig. 6. Relationship between the log Koc for phenanthrene sorption and the polarity index of humic acids and humin, sequentially extracted from a soil. F-l, F-4, F-7, and F-9 are the first, fourth, seventh, and nineth extracted humic acids, respectively. 0.005, 0.05, and 0.5 ig mL 1 are selected liquid-phase equilbrium concentration of phenathrene (Kang and Xing 2005).

Fig. 7. Relationship between polarity index, (N+0)/C, and the Koc of a-Naphthol sorption to peat, black shale, and humic acids (HA) from different horizons of a soil. Modified from Chen et al. (1996).

Fig. 8.47 Phenanthrene adsorption-desorption hysteresis observed for Lachine and Chelsa humic acid aggregate the hysteresis index is given by n. Reprinted from Huang W, Peng, P. Yu, Z. and Fu J (2003) Effects of organic matter heterogeneity on sorption and desorption of organic contaminants by soils and sediments. Appl Geochem 18 955-972. Copyright 2003 with permission of Elsevier...

SOM, soil organic matter HS, humic substances DH, degree of humification HAC, humic acid C FAC, fulvic acid C TEC, total extractable C HR, humification rate HI, humification index NHC, nonhumified C TOC, total organic C HA, humic acid FA, fulvic acids UV-Vis, ultraviolet-visible FT-IR, Fourier transform infrared NMR, nuclear magnetic resonance ESR, electron spin resonance EEM, excitation-emission matrix. 

Figure 16.44. Correlation between the humification index determined by LIF spectroscopy (Huf) in whole soil samples and the humification index /t465 (Milori et al., 2002) determined by conventional fluorescence in the corresponding humic acid samples. The indexes are expressed as arbitrary units (a.u.) (Milori et al., 2006).

Ash (%) Pyrophosphate Index —OCR, (%) Carbon %) Humic Acids Fulvic Acids... 

These data indicate that the tendency to distribute into the DOM varies both with the nature of the compound and the DOM. The soil humic acid was a more effective receptor and the magnitude of the Adom was directly related to the octanol-water partition coefficient, Aqw, which is also an index of a compound s tendency to distribute into a hydrophobic environment. Experiments with 1,2,3-trichlorobenzene (log Aqw = 4.14) and lindane (log = 3.70) did not give the same degree of solubility enhancement. Note that the distribution constant for DDT based on organic carbon, A[Pg.32]

In soils and clays the most generally present biopolymers that naturally occur in the adsorbed state on mineral and clay particles are humic substances , or humic acids these are decomposition products of lignin, whidi is the major non-cellulosic polymer in wood and other plant debris. Humic acids (also called allomelanins (Merck Index, 1989)) are for the greater part polyphenolic compounds, usueJly anionic polyelectrolytes, which can complex metal ions, and are surface active and thus capable, upon adsorption onto mineral particles, to enhance their suspension stability in aqueous media (Chheda and Grasso, 1994). 

Faced with this complexity, the proposal of a maturity index from UV spectrophoto-metric data supposes considering the evolution of the whole spectrum. The first step is the identification of the particular experimental spectra that permit explaining any other spectrum as a linear combination of these reference spectra [24]. This procedure is the semi-deterministic one, presented in Chapter 2 and already applied in the previous applications. These spectra are automatically selected from the set of a great number of spectra of raw extracts of composts (including humic and fulvic acids) or related to a gel chromatographic fraction. Four reference spectra have been selected from the spectra bank, corresponding respectively to the spectra of (Fig. 18) ... 

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