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Fig. 18.43 Effect of sewage effluent organic matter on infiltration in a sandy loam soil. a Total
organic carbon (TOC) versus penetration depth; b polysaccharides versus penetration depth,
c fulvic acid (FA) versus penetration depth, and d humic acid (HA) versus penetration depth
(modified after McKinley and Siegrist 2010 ). Copyright 2010 Soil Science Society of America.
Reprinted with permission
The studies of Adani and Tambone ( 2005 ) and Adani et al. ( 2006 ) on sewage
sludge and compost disposal on soils provide additional information on their effect
on soil-HA composition. Comparison between diffuse reflectance infrared Fourier
transform spectroscopy (DRIFT) spectra of HA extracted from sludge (Fig. 18.45 a)
and compost (Fig. 18.45 b) contaminants, and from soils before and after their
contamination, show changes in the soil HA after long-term contamination. Humic
acid extracted from sludge-contaminated soil (ST-HA) showed a higher content of
aliphatic fractions, a similar content of O-aliphatic-C and/or N-aliphatic-C, and a
lower content of aromatic carbons than HA from untreated soil (SU).
Humic acid extracted from compost-contaminated soil (CM-HA) shows no
relevant absorption bands at 830-1,100 cm -1 assigned to carbohydrates but
exhibits bands at 1,038 and 1,231 cm -1 assigned to lignin. IR spectra show also
the presence of aliphatic carboxylic acid and of amide groups. Most of the car-
boxyl groups in the CM-hHA are amide form, whereas free COOH groups pre-
vailed in soil-HA.
The effect of annual addition of composed sewage sludge on the alteration of
soil HA was studied by Fernandez et al. ( 2009 ). In a field experiment, the authors
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