Long-term effects of amendment with liquid swine manure on proton binding behavior of soil humic substances.
The acid-base properties of humic acids (HAs) and fulvic acids (FAs) isolated from liquid swine manure (LSM), soils amended with either 90 or 150 m(3)ha(-1)year(-1) of LSM for 7 years, and the corresponding unamended control soil were investigated by a current potentiometric titration method. The non-ideal competitive adsorption (NICA)-Donnan model for proton binding by two classes of binding sites (i.e., carboxylic- and phenolic-type groups) was fit to titration data, and a set of fitting parameters was obtained for each HA and FA sample. The NICA-Donnan model was shown to describe with a great degree of accuracy the behavior of experimental titration datasets, and highlighted important differences in the acid-base properties of the HAs and FAs examined. When compared to the unamended soil HA and FA, LSM-HA and LSM-FA, had smaller acidic functional group contents, larger proton binding affinities of both carboxylic- and phenolic-type groups, smaller heterogeneity of carboxylic-type groups, and smaller, in the case of HA, or similar, in the case of FA, heterogeneity of phenolic-type groups. Amendment with LSM caused a decrease of acidic functional group contents and a slight increase of proton binding affinities of carboxylic- and phenolic-type groups of soil HAs and FAs. Further, LSM application induced a decrease of the heterogeneity of carboxylic-type groups, whereas appeared not to affect substantially the heterogeneity of phenolic-type groups of LSM-amended soil HAs and FAs. These effects were more evident for HAs than for FAs and tended to slightly increase with increasing LSM amendment rate.
Plaza
César
C
Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Científicas, Serrano 115 dpdo, Madrid, Spain. c.plaza@ccma.csic.es
Hernández
Diana
D
Fernández
José M
JM
Polo
Alfredo
A
D000143:Acids / Q000737:chemistry; D000818:Animals; D005243:Feces; D005308:Fertilizers; D006812:Humic Substances; D011522:Protons; D012989:Soil Pollutants / Q000737:chemistry*; D013552:Swine; D013997:Time Factors
D000143:Acids; D005308:Fertilizers; D006812:Humic Substances; D011522:Protons; D012989:Soil Pollutants