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Changes in the Humic Acid Fraction of Soil Resulting from Sludge Application
Author(s) -
Boyd Stephen A.,
Sommers Lee E.,
Nelson Darrell W.
Publication year - 1980
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1980.03615995004400060009x
Subject(s) - humic acid , chemistry , amendment , decomposition , organic matter , environmental chemistry , sewage sludge , soil water , organic chemistry , sewage treatment , environmental engineering , biology , fertilizer , political science , law , ecology , engineering
Humic acids (HA) extracted from sludge, soil, and sludge‐amended soil were characterized by elemental and functional group analyses and visible and infrared spectroscopy. Humic acid extracted from a Chalmers soil appeared to be similar to an average HA (Schnitzer, 1978). Humic acid extracted from Chicago sludge, as compared to the average HA and Chalmers HA, had a lower C/H ratio, increased N content, decreased total acidity and carboxyl content, and a lower absorptivity. With respect to the average HA and Chalmers HA, the sludge HA appeared to be a more aliphatic, N‐enriched polymer with decreased amounts of carboxyls and phenolic hydroxyls. Proteinaceous materials associated with the sludge HA appeared to be the major source of N enrichment. In general, HA's extracted from the sludge‐amended soil had increased N contents, lower C/H ratios, lower values of total acidity and phenolic hydroxyl, somewhat lower values of CO 2 H groups, and lower absorptivities as compared to HA from soil not receiving sludge amendment. Sludge organic matter was apparently recovered in HA extracted from soil 2 and 14 months after sludge application. The association of sludge‐borne proteinaceous and aliphatic materials with the sludge and sludge‐amended soil HA fractions was indicated by increased amide and C‐H stretch infrared absorptions as well as by the increased N contents and decreased C/H ratios. The observation of proteinaceous materials associated with HA extracted from sludge‐amended soil as long as 14 months after application suggested these proteinaceous materials were resistant to decomposition, possibly as a result of their incorporation into the HA structure. Fatty acids may be associated with HA's extracted from sludge and sludge‐amended soil through esterification to phenolic hydroxyls.