Acid–base properties of humic substances from composted and thermally-dried sewage sludges and amended soils as determined by potentiometric titration and the NICA-Donnan model

• Published in: Chemosphere (Oxford) Vol. 69; no. 4; pp. 630 - 635
• Main Authors: Fernández, José M., Plaza, César, Senesi, Nicola, Polo, Alfredo
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.09.2007; Elsevier
• Subjects: Acid–base properties; agricultural soils; Agronomy. Soil science and plant productions; Benzopyrans - chemistry; binding sites; Biological and medical sciences; biosolids composts; carboxylic-type groups; drying; Fertilizers; Fulvic acids; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; heat treatment; Humic acids; Humic Substances; Hydrogen-Ion Concentration; Micronutrients fertilization; Models, Chemical; NICA-Donnan model; Osmolar Concentration; phenolic-type groups; potentiometers; potentiometric titration; Proton affinity distribution; Protons; Sewage; Sewage sludge; Soil; soil amendments; Soil-plant relationships. Soil fertility. Fertilization. Amendments; thermally-dried sewage sludge; titration; Titrimetry; NICA-Donnan model; Proton affinity distribution; Humic acids; Acid–base properties; Fulvic acids; Sewage sludge; Organic matter; Waste utilization; Heat treatment; Organomineral fertilizers; Waste treatment; Cultivated soil; Physical chemistry; Determination; Modeling; Organic acids; Environmental engineering; Humus; Distribution function; Soil science; Chemical properties; Mathematical model; Physicochemical method; Acid-base properties; Soil chemistry; Compost; Proton affinity; Physical dressing; Property of soil; Soil management; Fertilizers; Composting; Analysis method; Acidobasicity; Distribution; Potentiometric method; Humic substance; Measurement method; Fulvic acid; Computing method; Chemometrics; Humic acid; Physicochemical properties; Electrochemical titration; Organic amendment; Drying
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2007.02.063

The acid–base properties of humic acids (HAs) and fulvic acids (FAs) isolated from composted sewage sludge (CS), thermally-dried sewage sludge (TS), soils amended with either CS or TS at a rate of 80 t ha −1 y −1 for 3 y and the corresponding unamended soil were investigated by use of potentiometric titrations. The non-ideal competitive adsorption (NICA)-Donnan model for a bimodal distribution of proton binding sites was fitted to titration data by use of a least-squares minimization method. The main fitting parameters of the NICA-Donnan model obtained for each HA and FA sample included site densities, median affinity constants and widths of affinity distributions for proton binding to low and high affinity sites, which were assumed to be, respectively, carboxylic- and phenolic-type groups. With respect to unamended soil HA and FA, the HAs and FAs from CS, and especially TS, were characterized by smaller acidic functional group contents, larger proton binding affinities of both carboxylic- and phenolic-type groups, and smaller heterogeneity of carboxylic and phenolic-type groups. Amendment with CS or TS led to 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. These effects were more evident in the HA and FA fractions from CS-amended soil than in those from TS-amended soil.