Silvia Ceppi

Differential scanning potentiometry: surface charge development and apparent dissociation constants of natural humic acids.

Humic acids (HA) are the main components of soil organic matter which can form complexes with metal ions and other soil and/or water contaminants. Here, we focus on their acid-base properties. HA were extracted from two different soils (Tipic Ustifluvent and Entic Haplustoll) with different vegetation. In this study we use a simple method, differential scanning potentiometry (DSP), to determine HA buffer capacity distribution, apparent dissociation constant values and surface charge development.

CHARACTERIZATION OF HUMIC ACIDS ORIGINATED FROM ARGENTINEAN COMPOST AND SOIL BY CAPILLARY ELECTROPHORESIS AND MASS SPECTROMETRY

Humic acids (HAs) extracted from different organic compost and soil from Argentina have been characterized by capillary electrophoresis (CE) and mass spectrometry. The chemical properties of HAs show changes depending on their origin (compost, soil). Capillary electrophoresis analyses were carried out using a background electrolyte consisting of boric acid, TRIS and EDTA (BTE). BTE was also modified with cyclodextrins. After optimization of BTE, the best results were obtained when b-cyclodextrin was used. Under optimized separation conditions, the characteristics CE fingerprints of compost derived HAs (CHAs) were studied. CE fingerprints show differences in the composition of the different CHAs. Mass spectra obtained by laser desorption ionization time of flight mass spectrometry show differences between the CHAs and HAs extracted from Argentinean soil. A comparison with the soil standard HAs (International Humic Substances Society) was made. CHAs show mostly compounds in the mass spectra with low m/z values. The typical patterns exhibited in soil HAs of different origin are present in the Argentinean soil HA, i.e. groups of peaks around mass-to-charge (m/z) 800

Characterization of humic acids derived from rabbit manure treated by composting-vermicomposting process

The aim of this work was to evaluate, through different analytical techniques, the evolution of some chemical and physicochemical properties of humic acid (HA)-like fraction extracted from an organic amendment, like rabbit manure, handle with composting followed by vermicomposting process, in comparison with soil HA, in order to reach an appropriate criterion to evaluate the maturity of an organic amendment. The raw material used was rabbit manure treated with composting followed by vermicomposting process. Soil and organic amendments were analyzed by chemical properties. The HA was extracted from the amendments samples and from an Entic Haplustol and analyzed the chemical and physicochemical characteristics by several analytical methods. Through these analytical techniques was possible to follow the evolution of the HA-like fraction during this stabilization-maturation process Through the composting followed by vermicomposting process the HA-like fraction are evolving toward more stable and complex macromolecule resembling native soil HA.

Fire Impact on Several Chemical and Physicochemical Parameters in a Forest Soil

Cordoba is a Mediterranean State, with semiarid climate, dry autumn and winter, in which the wild fire can take place, especially at the end of dry season. Forest fires happen frequently in the mountain zones of the province of Cordoba, Argentina, which are located at west and south-west region. The vegetation, in the south-west zone, are principally Pinus halepensis Mill.; Pinus elliottii implanted and the native vegetation cover is Stipa caudata, Piptochaetium hackelii, P. napostaense y Briza subaristata, between others. Taxonomically the soil corresponds to an Ustorthent. In the west area the native vegetation is principally Acacia caven, Festuca hieronymi, Stipa, Poa stukerti, between others. The soil is an Argiustoll. Forest wild fires constitute a serious environmental problem, not only due to the destruction of vegetation but also because the degradation that may be induced in a soil as a consequence of the change produced in its properties. Wild fire can strongly modify the abiotic and biotic characteristics of soil, altering its structure, chemical and physicochemical properties, carbon content and macronutrient levels. The degree of the alteration produced depends on the frequency and intensity of fire, all these modifications being particularly important in the surface horizons. Organic matter is a key factor for forest soil. It has a direct and /or an indirect influence on all physical and chemical characteristics of the soil. While low severity fires, such as those prescribed for forest management, have been reported to have transient but positive effect on soil fertility, severe wildfire result in significant losses of soil organic matter, and nutrient, and deterioration of the overall physical-chemical properties of soil that determine its fertility, such as porosity, structure among others (Certini, 2005). Fire may directly consume part or all of the standing plant material and litter as well as the organic matter in the upper layer of the soil. One of the most important soil change, during the burning is the alteration in the organic matter content therefore, the nutrient contained in the organic matter are either more available or can be volatilized and lost from the site. The soluble nutrient would be loss for erosion or leaching if they are not immediately absorbed by plants or retained by soil. Humic substances are one of the most important fractions of the organic matter and are considered the most abundant organic component in nature and largely contribute to soil structuring and stability, to its permeability for water and gases, to its water holding

The influence of heating temperature on the physical and chemical properties of soils with different parent materials and anthropogenic uses

Although natural and controlled fires are common in natural environments of the Province of Cordoba (Argentina), the effects on the physical and chemical soil properties are not well known. Warming effects were studied in two representative soil parent materials located in the piedmont of the Sierra Chica, Cordoba, Argentina. The aim of this study was to quantify the changes caused by different heating temperatures (100 °C and 500 °C), under laboratory conditions, on physical and chemical properties of two soils with different granulometric compositions and anthropic uses. The soils were classified as Udic Haplustoll, fine loamy (alluvial soils) and Udic Argiustoll, fine silty (loessoides soils). The depth analyzed corresponded to the upper 5 cm of the surface horizon. The physical property was granulometric composition (clay, silt and sand content) and the chemical properties: pH, oxidizable carbon (Cox), total nitrogen (Nt), cation exchange capacity (CEC), exchangeable cations (Ca+2, Mg+2, Na+, K+), extractable phosphorus (Pe) and electrical conductivity (EC). These analyses included both unheated samples (control) and those heated at different temperatures. Cox, pH, EC and CEC showed similar behavior at the different heating temperatures, despite the parent materials and the soil use conditions. Cox, pH, Nt and CEC could statistically explain the differences in edaphic properties at the temperatures analyzed. At 300 °C statistically significant differences were recorded for the analyzed soil parameters, and at 500 °C changes difficult to reverse due to the inorganic colloidal fraction collapse and the decrease (90%) of the organic fraction were found.