M. Govi

Characterization of humified compounds by extraction and fractionation on solid polyvinylpyrrolidone.

Abstract New humification parameters are proposed for characterizing soils and organic fertilizers or amendments. They include an index, a degree and a rate of humification, all devised to assess the ratio between humified and non-humified materials. The separation of the two types of materials is essentially performed by extraction and fractionation on solid polyvinylpyrrolidone.

Use of insoluble polyvinylpyrrolidone and isoelectric focusing in the study of humic substances in soils and organic wastes

Abstract The use of insoluble polyvinylpyrrolidone and isoelectric focusing in the study of humic substances is reviewed. Chromatography on insoluble polyvinylpyrrolidone is widely used to characterize humic materials extracted from soils, organic fertilizers, soil amendments and organic wastes in order to evaluate their degree of humification. The isoelectric focusing technique is employed mainly to evaluate the stability of the organic matter in organic wastes before their use in agriculture.

Changes in organic matter during stabilization of compost from municipal solid wastes

Stabilization of the organic matter contained in two static piles of compost derived from municipal solid wastes was followed for 55 days during both winter and summer. The degree of humification, i.e. the ratio between the humified fractions and total extractable carbon, increased steadily in compost stabilized during winter, while the transformation was less obvious during summer composting. Electrofocusing analyses of the organic extracts from both winter and summer piles of compost from municipal solid wastes showed a definite trend in the humification processes, not only during winter but also during summer composting.

Determination of organic carbon in aqueous extracts of soils and fertilizers

Abstract A simple and accurate method for the routine determination of organic carbon in aqueous extracts of soils and fertilizers is described. Samples are oxidized for exactly 10 minutes with a mixture of 5 mL of 2N potassium dichromate plus 20 mL of concentrated sulphuric acid at 160 ± 2°C, and the excess dichromate is titrated either potentiometrically or manually with iron (II) sulphate. An appropriate correction factor (1.05) is suggested for aqueous extracts from humic acid.

Evaluation of heavy metals during stabilization of organic matter in compost produced with municipal solid wastes

The total content of six heavy metals (Cu, Zn, Pb, Cr, Ni and Cd), the Cd/Zn ratio and the zinc equivalent were determined for composts produced from municipal solid waste (MSW) both with and without the removal of inert components prior to the beginning of composting. For two of the composts, one produced by summer and the other by winter composting, the content of heavy metals and the degree of humification were monitored at regular intervals throughout the composting period, and the correlation between the solubility/extractability of the heavy metals with various extractants (H2O, KNO3, EDTA and DTPA) and the degree of humification was calculated. The total content of heavy metals increased appreciably during composting due in part to mineralization of the organic matter but also to the ‘purification’ of the compost (removal of inert materials such as plastic and glass) during the composting period. The solubility/ extractability of the various heavy metals in the summer and winter composts showed similar trends. High correlations between heavy metal content and degree of humification were found for all of the elements, with most of the extractants, for the winter compost, whereas for the summer compost this correlation was high only for Zn.

An enzymatic approach to the determination of the degree of stabilization of organic carbon in fertilizers.

An enzymatic approach to assess the stability of organic matter extracted from organic fertilizers and amendments is proposed. The use of 0.1M NaOH plus 0.1M Na4P2O7 previously suggested as a suitable extractant solution for soil organic matter was also found satisfactory for the extraction of organic matter from organic fertilizers and amendments, especially when the temperature was raised to 65°C. The presence of nonhumified compounds in the extracts from organic fertilizers may interfere considerably during fractionation of organic carbon. An enzymatic hydrolysis with lipase, lysozyme and pronase, added sequentially to the extracts, led to an appreciable reduction in the interference. The interference was further reduced by carrying out a successive acid hydrolysis with 3N H2SO4; in this case the DH values (percentage of humified fractions with respect to total extractable carbon) were reduced to less than 10% in all organic fertilizers, but remained higher than about 70% in organic amendments.

Evolution of organic matter in sewage sludge: A study based on the use of humification parameters and analytical electrofocusing

Abstract The degree of humification (DH), humification index (HI), and humification rate (HR) were determined for seventeen samples of sewage sludges and composts from sewage sludges. The same samples, extracted with 0·5 M NaOH, 0·1 M Na 4 P 2 O 7 , and 0·1 M Na 4 P 2 O 7 adjusted to pH 7, were analyzed with analytical electrofocusing (EF). The results clearly show that the organic matter changes much more quickly during composting than during the anearobic digestion. It was also found that the ability of the alkaline solutions to solubilize the organic complexes was greater the higher the apparent isoelectric point and the greater the reproducibility of the analytical electrofocusing data.

Influence of blood meal organic fertilizer on soil organic matter: A laboratory study

Abstract Blood meal is an organic nitrogen (N) fertilizer containing about 10–13% organic N. The fertilizer is mainly composed of hemoglobin which is characterized by the presence of a prosthetic group containing iron (Fe). Knowledge about the influence of blood meal on soil organic matter and soil fertility is now limited. In this work, blood meal was incubated in the soil for one year and the evolution of the organic matter was followed at time intervals by use of isoelectric focusing (IEF) and humification parameters. The mineralization of the total N and the availability of some mineral nutrients (Fe in particular) were also followed. The results show that only a part (about 75%) of the organic carbon (C) and of the organic N mineralized and that the remaining C was transformed into humified compounds. The availability of the Fe increased during the incubation, probably due to the progressive degradation of the prosthetic group and the successive chelation of the Fe from the humic substances.

Characterization of Organic Matter in Compost Produced with Municipal Solid Wastes: An Italian Approach

Stabilization of the organic matter of a static pile of compost from municipal solid wastes (MSW) under a forced-pressure ventilation composting system was followed for 55 days during winter season. The materials were analyzed according to the official methodologies required by Italian regulations regarding the quality of composts from MSW. The stabilization process of the organic matter was monitored using both the degree of humification (DH), i.e. the ratio between the humified fractions (HA + FA) and the total extractable carbon (TEC), and the electrofocusing technique (EF). The DH increased steadily in compost during stabilization process and converged asymptotically at the end of the period of composting. The EF analyses of the organic extracts of compost from MSW showed a definite trend in the humification process and confirmed the actual evolution of the organic matter composted.

Capillary electrophoresis of humic acid fractions

Abstract Capillary electrophoresis (CE) was used for the characterization of peat humic acid (HA) fractions of different molecular weight. The HA were precipitated from a 0.1M NaOH plus 0.1M Na4P2O7 peat extract acidified at pH < 2 with HCl. The HA fractions with different molecular weights were obtained using an ultrafiltration system. Using phosphate (pH 9) as running buffer, the peaks of the CE profiles were not well resolved, but using borate (pH 8.5) as the running buffer, the resolution of the peaks was improved. The highest resolution of the profiles was obtained using borate as the running buffer with the HA fractions of lower molecular weights. Using both phosphate and borate as the running buffer, the elution time for the HA fractions appeared at shorter times as the molecular size of the HA fractions decreased.