Search

In agriculture HS and HS-based products (solid and liquid) are generally used in plant nutrition: their role in increasing bioavailability of nutrients and biological activities is well supported in scientific literature. For a proper use of HS it’s fundamental to know their elemental composition as well as some basic features. In commercial products such data are often lacking. The main reason is that at national and especially at international level (EC Regulation n. 2003/2003) the specific rules, up to date, neglected HS. In fact, it must be kept in mind that even the recent European Regulation 2003/2003 (EC Regulation n. 2003/2003) has completely neglected organic and organic-based fertilizers and amendments. At the best the existing rules require the declaration of total content of organic and humic carbon (Ministerio de la Presidencia, 2005). Among others, the Italian Legislative decree 75/2010 (Decreto Legislativo 29 aprile 2010 n. 75) is one of the most advanced in Europe from this point of view (Table 1). The need of standardization and regulations of commercial humic and humic-based products is imperative in a modern agriculture and for a market globalization.

Energy crops are designed for biomass production to generate bioenergy. Their recent introduction in the Po Valley (North Italy) is connected to the mitigation of environmental effects of the intensive management. Intensive management has a dramatic impact on the soil ecosystem of the area, reducing soil organic matter, degrading soil structure and altering nutrient cycles by reducing microbial biomass, and thus compromising soil productivity. Soil organic carbon (SOC) content in the Emilia-Romagna region is the lowest in the Po Valley (

Il reimpiego dei sottoprodotti della vinificazione, consentito dalla scorsa vendemmia, va incontro a istanze di reddito e organizzative del viticoltore ma deve tenere conto anche delle caratteristiche fisico-chimiche di questo materiale, che sono in grado di influenzare l'equilibrio della microflora del terreno.

In the present study, the urban wastewater sludges were treated in two-phase separate anaerobic digesters. The first digester was used for hydrolysis, acidification and acetogenesis, whereas the second one was for methanogenesis The two series of digesters were fed with the same raw sludge and working in steady-state conditions. Sludge samples were taken daily from both digesters for analyses. Special focus was placed on characterization of organic matter using diffuse reflectance infrared transform spectroscopy (DRIFT), 13 C stable isotopic ratio, differential thermal (DTA) analyses. The composition of volatile (VFA) was also analyzed, by head-space solid phase microextraction combined with gas-chromatography and mass spectrometry (HS-SPME-GC-MS), and discussed. Valuable information about the phase of degradation or stabilization of sludges was obtained by means of these analytical techniques, suggesting the possibility of a more efficient recycling of urban wastewaters organic matter.

A survey of the role of organic vs. conventional on soil C sink/source was performed in 2007 in 8 typical organic vs. 8 conventional peach orchard farms located in Emilia-Romagna Region, Italy. Chemical analyses were carried out on top layer (0-15 cm depth). Determination included total (TOC), extracted (TEC) and humified (HA+FA) organic carbon, total nitrogen (TN) and isotopic signatures δ 13C and δ 15N. Principal component analysis (PCA) was carried using the following variables: TOC, TN, C/N, δ 13C, δ 15N. Conventional peach orchards showed lower values of all the parameters compared vs. organic orchards. PCA analysis has shown that in organic farms δ 13C and 15N are positively correlated with TOC and TN and δ 13C can be used for further discrimination concerning the type of fertilizer used. From the quantitative point of view an average increasing of TOC and HA+FA of 15.5 and 18.5%, respectively, was observed.

In this study, the distribution of the total (TOC) and humified (HA+FA) organic carbon (C) in a 16 years-old peach orchard was evaluated by comparing the row that is tilled and irrigated and the inter-row that is covered with perennial grass. The grass favoured the accumulation of TOC and humified C in the top layer (0-20 cm), indicating that the absence of tillage promoted the accumulation of humified compounds. In the deep layer (20-40 cm) the TOC content was higher in the row while the content of humic substances was similar. TG-DTA analysis pointed out structural variations related to the carbohydrates and aromatic compounds content in the humic fraction of the samples taken from both top and deep layers of the two soil management systems.

Long-term field experiments are crucial for studing the effects of different management practices on organic C storage capacity of agricultural soils. One of the most important pools of soil organic C (SOC) is that of the humic substances and in particular of humic acids (HA-http//ihss.gatech.edu/ihss2) that are complex macromolecules modified from plant compounds or newly synthesized during decomposition, that accumulate in soil. Because of their resistance to microbial degradation, they represent a crucial component of SOC where C tends to be stored for long periods and an important reservoir of nutrients. In the long-term field experiment at the Cadriano farm (Bologna University) different fertilization treatments have been compared for over thirty years on a continuous-wheat (used as a reference field) and a continuous-maize cropping. These two plant species have different C isotope composition because the C3 and C4 photosynthetic pathways differently fractionate against the heavier isotope of CO2-C, therefore the isotopic approach was used to quantify the C3 and C4-derived C in soil. In particular three fertilization treatments were compared: no fertilization (control) mineral fertilization and organic amendment, and the content of old C3 and new C4-derived C in soil and in the humic acids (HA) was determined. Moreover a structural characterization of HA was carried out with thermogravimetric (TG) and differential thermal analysis (DTA). After 36 years of continuous maize cropping the old C3-derived C similarly decreased in spite of the treatments. The new C4-derived C constantly increased with all the treatments, significant higher amounts compared the control were measured with the mineral, and even more with the organic treatment. In the HA the amount of C3-derived C decreased over the studied period in the control and in the mineral treatment, whereas it increased with the organic treatment. The amount of C4-derived C in the HA linearly increased over the studied period in all the treatments with the higher values measured for the mineral and organic one. TG-DTA data showed that the 36 years organic amendment caused in the HA an increase in aromatic compounds compared to the control and the mineral treatment.

Peat is the best substrate in growing media, but its rapid depletion needs at least a partial substitution. Composting of urban green wastes and agro-industrial by-products can produce good compost (Cm) for this purpose. Cm-based substrates are increasing in the market. However, physical and chemical characterization of Cm-based growing media is the first step for their proper use. This paper reports the results of the fractionation of the bulk organic matter (OM) of four growing media, containing increasing amount (v/v) of Cm [100% Peat; 80% Peat + 20% Cm (CP20); 40% Peat + 60% Cm (CP60); 100% Cm) into well-defined fractions: humic acid-like (HAL), non-humic fraction (NH) and dissolved OM (DOM) and their characterization by a combination of chemical, thermogravimetric (TG), differential thermal analysis (DTA), spectroscopic (Diffuse Reflectance Infrared Fourier Transform-DRIFT) and isotopic (δ 15N) techniques. TG-DTA of bulk growing media, HAL, NH and DOM showed significant differences among increasing Cm in Cm-based growing media. DRIFT spectra confirmed these differences. The N isotope ratio (δ 15N) of all the substrates increased with the amount of Cm in the substrate. The combination of chemical, TG-DTA, DRIFT and δ 15N techniques can be successfully applied for the chemical characterization of Cm based growing media with a good identification of different matrices.

The structural characterization of humic acids (HAs) is a focal point in understanding and establishing a relationship between their structure and biological properties. However, the complexity of HAs seriously limits the application of a single analytical technique. For a better understanding of HAs role in the environment, it is necessary to develop methods which can provide a complete characterization of HA structure. Humic acid extracted from the A horizon of a Chernozem (Boroll, USDA Soil Taxonomy) soil and their fractions (A, B and C+D) with different molecular size (MS) obtained by coupling size exclusion chromatography and polyacrylamide gel electrophoresis (SEC-PAGE) were investigated using thermal (TG-DTA), spectroscopic (DRIFT) and isotopic ( d 13C) analyses. Moreover, the molecular structure of the high temperature stable fraction (residues obtained by stopping the heating of the sample in TG-DTA apparatus at 400°C) was studied by DRIFT spectroscopy. The highest MS fraction (A) were characterized by the highest contents of aliphatic, carboxyl groups, carbohydrates and amino acids than the B and C+D fractions. Instead, the C+D fraction, that was 36% of HA (w/w), seems to be characterized by a higher content in aromatic compounds, in particular in benzoic derivatives, than the other fractions. A shift of δ 13C to more negative values was observed in the lowest MS fractions (B and C+D). The aromatic structure of A and B residues seems to be more complex than that of C+D residue.

The effect of organic fertilisation on the level of total organic carbon (TOC) in an 18-years old pear orchard (cv. Abate Fetel) was evaluated vs. a conventional pear orchard mineral fertilized (control). In both orchards soil samples (Typic Udochrept loamy soil) were taken at two depths (0-15 and 30-50 cm) along the row (tilled and mainly amended with compost) and in the inter-row space (grassed with different Graminaceae species in the organic orchard, bare in the conventional orchard). The area (elevation 20 m), located in Bologna province, Emilia-Romagna Region (Italy), is characterised by mean annual temperature 13.1 °C and rainfall around 750 mm. In the horizon 0-15 cm of the row an increase of about 14 tons ha-1 of TOC has been calculated after 18-years of cultivation and amendment compared to the control soil, which had received just mineral fertilisation. A significant increase of TOC (about 6.3 tons ha-1) was also measured in the top layer (0-15 cm) in the grassed inter-row, where this C sink is exclusively due to the cover crop. A survey of the role of organic vs. conventional farming on soil C sink/source is started in 2007 in 8 typical organic orchard farms located in Emilia-Romagna Region and it is still running.

Soil organic carbon (C) preservation in agroecosystems is crucial point to maintain soil fertility and productivity, and to reduce losses of CO2 in the atmosphere. Agricultural management practices can differently affect the level of soil organic C (SOC). In the present paper or chapter the results of a long-term field experiment (30 years) were investigated to evaluate the effect of mineral fertilization and organic amendments on soil organic C content and on the humic acids (HA) that represent the most important and stable reservoir of soil organic C. The effect of the plant species was also evaluated by comparing wheat and corn monocultures. The amount of corn-derived C in soil and HA at the end of the experiment was calculated by 13C natural abundance measurements. After 30 years of cultivation, the SOC significantly decreased in both unfertilized (Control) cropping systems, especially with continuous corn. Mineral fertilization (Min) and organic amendments (Org) always caused an increase in SOC, especially with Org treatment on continuous corn. The C always increased in HA, except in the unfertilized plots of corn monoculture. Again the highest increase was observed with Org treatment. The amount of corn-derived C in total organic C (TOC) increased in the following order: unfertilized < Min < Org treatments, ranging from 19 to 29%. The turnover time of the older C3-derived C increased in the same order ranging between 55 and 86 years in the Control and Org treatment, respectively. In the HA the proportion of corn-derived C was similar in the Control and Org treatment (26.4%), lower in the Min treatment (23.7%). Nevertheless if we consider the total amount of corn-derived C in soil and the proportion recovered in the HA, the highest was measured in the unfertilized control. In general a proportion ranging from 35% (Org) to 40% (control) of the total corn-derived C in soil was recovered as humic C, confirming the important role of this pool as a C reservoir in soil.

The chemical characteristics of soil organic matter (SOM) can be influenced by management and amendment practices which effects can be measured only after long-term experiment. In this long-term study of over 30 years, with a rotation wheat-corn, we compared the effects of adding cattle manure (CM) and crop residues (CR) wheat straw or corn-stalks after each crop, on humic substances (HS). Potentiometric titration, thermal analysis (TG-DTA), and spectroscopic methods such as diffuse reflectance infrared Fourier (DRIFT) and liquid nuclear magnetic resonance (13C NMR) spectroscopies were used in order to investigate humic acid (HA) structure. The amendment practices clearly influenced the humic C and the COOH groups content that only increased in CM treatment. The quality of this humic fraction was affected by the different agricultural practices, so that when the soil did not receive any amendment, the aromatic and carboxylic C decreased, whereas the aliphatic C increased as an effect of the crop rotation. With the amendments, in contrast, the aromatic C generally increased, this increase was mainly due to the incorporation of aromatic groups in the structure of HA, arising from the phenolic groups present in the lignin of the crop residues.

Humic substances are the most important fraction of soil organic matter both in natural and an-thropic systems. Their elemental composition and chemical structure, influenced by the kind of organic residues and environment in which they are formed, are fundamental to preserve the soil fertility. Recently, emphasis has been devoted also on their effect on carbon (C) sequestration. The aim of the present study was to examine the effect of amendment with cow manure and crop residues added consecutively over a period of 30 yrs on soil humic acids. Briefly, the experimen-tal design included plots amended over a 30-year period with cattle manure and crop residues constituted by wheat straw or corn-stalks (wheat and corn were the two crops regularly cropped in succession), using un-amended soil as the control. The samples were taken from the 0-40 cm horizon of a long-term field experiment located in the experimental farm of the Agricultural Sci-ence Faculty of the Alma Mater Studiorum University of Bologna, Italy. The humic acids were characterized using chemical and spectroscopic techniques such as diffuse reflectance infrared Fourier spectroscopy (DRIFT), surface enhanced Raman spectroscopy (SERS) and nuclear magnetic resonance (13C NMR). The results showed that the quality of humic fraction was affected by the different agricultural practices, so that when the soil did not receive any amendment, the aromatic and carboxylic C decreased, whereas the aliphatic C increased as possible effect of the crop rotation. With the amendments the aromatic C generally increased, but with crop residues this increase was mainly due to preservation of undecomposed lignin components derived from the crop-residues added to the soil. With manure the composition of humic acids appeared enriched in carboxylic groups, aromatic rings highly substituted and alkyl-C. These results indicate the key role played by amendment practices on soil humic substances formation and on the ability of humic substances to sequester C.

Dynamics of chemical and biological parameters in a three years project comparing conventional and organic farming in two Italian experimental sites The multidisciplinary research group of BIOGEA project on soil fertility curried out a three years study comparing organic and conventional soil management performed in two sites in growing areas representative of two Italian environments: North East-Ravenna, lat. 44° 25' 4'' N and South-East - Foggia , lat. 41° 28' 0'' N. Materials and methods. The study was carried out on a three years rotation system under organic and conventional management with two final crops: sugar beet and processing tomato. Upon completion of three-years project, chemical (TOC, TEC, HA+FA, Nmin and Ntot dynamics), and biological (TOC, TEC, HA+FA, Nmin and Ntot dynamics) parameters are discussed. Organic management in the adopted agronomic conditions has not significantly improved chemical and biological parameters if compared to conventional farming. However, the dynamics of the majour part of the evaluated chemico-biological parameters is slow in soil environment and therefore, three years is a too short period to draw definitive conclusions.

The purpose of the present study is to investigate, by means of thermogravimetric analysis (TG) and differential thermal analysis (DTA), diffuse reflectance infrared Fourier transform (DRIFT) and 2D nuclear magnetic resonance (NMR) spectroscopies, the structural features of the humic-like fraction (HLF) from olive pulp (OP), its effluents originated from the fermentation processes for hydrogen (EH2) and methane production (ECH4) and humic acid (HA) from soil amended with each of these materials. A considerable structural modification emerged between the HLF, in particular from the ECH4 effluent, which was characterised by a high content of polyphenolic and polypeptidic substances. The short-term amendment trial with OP and EH2 indicated that no chemical or structural changes in soil HA appeared. In contrast, the amendment with ECH4 substantially influenced the chemical and structural composition of soil HA. The structural interpretation performed by 2D NMR indicated the presence of aliphatic and aromatic protons while the sugar-like content and O–CH3 groups decreased with respect to the soil control HA. It emerges from this study that olive wastes contain stabilised humic-like material that may be recycled as an amendment in areas where olive trees are cultivated.

High amount of biomasses of agro-industrial and municipal origin can be properly transformed into organic compounds that can be used in agriculture as soil amendments, organic-based fertilisers, growing media and organic products with biostimulant activity. Amendments are particularly recommended in soils where the organic carbon content is very low (i.e. < 1.0%), i.e. in the Mediterranean soils, contributing to the natural closure of the nutrients cycle, to the increase in soil fertility and in carbon sink. A sustainable use of organic materials can be obtained only by a deep study of the quality of their organic and humified carbon. Up to date at European scale (EU at 27 Countries) the EC Reg. 2003/2003 only regulates mineral fertilizers, whereas organic, organic-based fertilizers and amendments are not included. This means that the control of organic-based fertilisers is devoted to each Member State and all the fertilisers made in the EU-27 can freely circulate from a country to another, abiding by the laws of the country of origin. In this respect the Italian law on fertilisers is advanced and many parameters have been settled in recent years. The paper reports some selected examples of official analytical methods used in Italy to characterize amendments, organic-based fertilisers, growing media and organic products with biostimulant activity recently settled by the Italian law of fertilisers (D.Lgs. 217/06).

Spectroscopic (DRIFT) and thermal (TG-DTA) analyses were carried out to investigate the structure of humic acids formed in different environments: a soil developed under Norwegian spruce (Picea abies, (L.) Karst) subalpine forests of north Italy and two kinds of coals (Sphagnum peat and leonardite-North Dakota). The samples taken from forest soil were classified in relation to vegetal cover at different old age (grassland, young and old forest). The thermal patterns and DRIFT spectroscopy showed different structural modifications can be ascribed to interaction between soil and vegetal cover. The main structural changes in grassland and both forests appeared in carbohydrates, aliphatics and aromatics content. Particularly different was the humic acid composition from old forest because it did not preserve any memory of molecules derived from plants. Similarly, the thermal and DRIFT analyses of humic acids from peat and leonardite showed considerable structural differences in relation to their formation ways. In leonardite the disappeared of all features of plant residues, contrary to peat, and the carbon skeletons containing aromatic units indicated an increase of humification rank.

In agricultural ecosystems the maintenance of soil organic carbon (SOC) depends on soil tillage, on the amount of crop residues after harvest, rhyzodeposition and on the addition of organic amendments. Mineralization and leaching of dissolved organic C are, on the contrary, the mechanisms mainly responsible for the C loss from the system. The balance between inputs and outputs can result in an accumulation or viceversa in a decline of SOC content depending on the agricultural managements. To better highlight the SOC dynamics, it’s also important to follow the fate and turnover of organic C contained in several components of SOC, in particular that of the humic substances which are considered important sink for organic C in soils. The effects of the agricultural management on SOC content and on the humic substances, can be appreciated only after long period of time, in long term field experiments. However, in order to study the turnover of SOC and to quantify the amount of new C which is being incorporated, a change in vegetation from C3 to C4 species is required. In this situation the C4-derived C entering in a C3 soil is quantified by the 13C natural abundance measurement technique. In the present study we present data from a 30 year field experiment where a monoculture of maize (Zea mays L. spp. mays) started in 1973 on a C3 soil. The change of SOC, total N, and humic fraction C was monitored in this field and in the reference site cultivated with wheat (Triticum durum L.). The maize-derived C entering the SOC and the humic substances during this period of time was quantified with the 13C natural abundance technique on the basis of the isotopic shift of the C4 field with respect to the C3 reference field. In spite of a decline of SOC content that was accompanied by a decline of total soil N, the amount of maize-derived C progressively increased accounting for about 10% and 19% of total SOC after 15 and 30 years of maize monoculture, respectively. The same trend was observed also for the humic fraction, in spite of a significant decrease of C, the portion of maize-derived C significantly increased after 15 and 30 years of maize accounting for 12% and 26%, respectively. The percentage of maize-derived C that was stored in the humic substances progressively increased throughout the experiment from 27% after 15 years, to 36% after 30 years, confirming the important role of the humic fraction in the storage of SOC.

Thermal analyses (TG-DTA), elemental composition and isotope analyses (13C and 15N) were performed on humic acids (HA) from peats (P), leonardites (Le) and lignites (L), in order to investigate their structure and the changes taking place during the humification process. Thermal analyses showed structural differences between HA samples in relation to their coalification rank. In particular the lignite HA were characterized by a more stable chemical composition at high temperatures. The delta 13C and delta 15N values can provide information on the biogeochemical processes involved in HA formation. In particular, peat HA were linked to anoxic environments that enable plant residues to persist in their structure. In contrast, leonardite and lignite HA formation seems to be governed by different biogeochemical processes from those responsible for peat diagenesis. However, the isotopic analyses did not provide any distinction between leonardite and lignite HA. On the basis of the data presented in this study, it may be concluded that TG-DTA and isotope ratio measurements are powerful tools for investigating the formation pathway of humic substances from

The humic substances (HS) are macromolecules involved in many chemical and biochemical processes of great importance for soil fertility and environmental equilibrium. The HS ensure a slow release of nutrients, a high soil quality and a less extent of green house gas emissions. The addition of organic matter to contaminated soils, especially those with organic pollutants (PAH, PCBs, LAS) has been recently employed successfully. For these reasons, the addition of biomasses more or less rich in humic-like compounds had become important to improve the quality of organic matter in exploited or contaminated soils. The aim of this study' was to characterize the organic matter of three contaminated soils located in North Italy, before and after the remediation with two different kind of compost. The soils analyzed came from a stone quarry, a landfill and from an industrial area in disuse. The samples extracted and separated in the two classical conventional fractions (humic and fulvic acids) have been investigated using some humification parameters and different analytical techniques: potentiometric titrations, spectroscopic (FT-IR) and thermal analysis (TG and DTA) were applied to obtain structural information. The results have shown a general increase in the organic matter in the soil samples amended with biomasses respect to untreated soils. In particular, thermal analysis reveals an increase of the second exotermic peak after the soil treatment due to the presence of organic matter more resistant to the degradation. DRIFT spectra confirm a structural change of the soil organic matter well correlated with the amendment type. Note: 'Research supported with funds provided by PRIN-Cofin 2002 (National Coord. P. Genevini).

Lo scopo del presente studio è stato quello di valutare, mediante tecniche diverse (CF-IRMS, DRIFT e SERS), il contenuto di carbonio organico (TOC) e la struttura molecolare delle sostanze umiche (SU) estratte da un suolo (Typic Udochrept) trattato per trent’anni con biomasse (Toderi et al., 1999). Le tesi considerate, inserite nell’ambito di prove di pieno campo in una rotazione biennale frumento/mais, hanno riguardato trattamenti con letame (L), liquame bovino (LB) e residui colturali (paglia o stocchi, P/S), oltre al controllo non trattato (C). Tutte le tesi considerate hanno ricevuto annualmente anche azoto minerale. Ciascuna tesi prevedeva 3 repliche a blocchi randomizzati. Al termine del trentennio tutte le tesi hanno mostrato variazioni statisticamente significative del TOC rispetto al controllo. Solo nel trattamento con L il TOC del suolo è risultato superiore al controllo, mentre è diminuito in tutte le altre tesi (LB, P/S). I valori del delta 13C (CF-IRMS) ottenuti sul TOC apparivano progressivamente meno negativi in tutti i trattamenti rispetto al controllo. Lo studio spettroscopico (DRIFT e SERS) delle SU estratte dai suoli ammendati ha mostrato una grande variabilità della struttura molecolare in relazione al tipo di trattamento. In particolare le SU della tesi L, hanno presentato un incremento dei gruppi ossigenati e aromatici. I risultati ottenuti hanno dimostrato che, nel lungo periodo, il contenuto di carbonio organico del suolo e le caratteristiche strutturali delle SU possono variare significativamente in funzione del tipo biomassa utilizzata.

L’obiettivo del presente lavoro è stato quello di studiare mediante l’analisi chimica, termogravimetrica - termico differenziale (TG-DTA) e spettroscopica (DRIFT) la struttura della frazione umica (HA) estratta da suoli forestali in località Paneveggio (Trento) al fine di ottenere informazioni sul processo di umificazione. A tale scopo gli HA sono stati estratti da 5 siti corrispondenti ai diversi stadi di sviluppo vegetativo del bosco: megaforbie, prato, rinnovazione, bosco giovane (alberi intorno a 30 anni) e bosco maturo (alberi di età oltre 150 anni). Il profilo termico di ciascun HA è risultato caratterizzato da tre picchi esotermici: il primo picco tra 327-319°C è attribuito alla decarbossilazione, alla decomposizione di ammine quaternarie e di carboidrati semplici; il secondo picco tra 434-451 °C è attributito alla combustione di steroli, acidi grassi, peptidi, fenoli, monomeri della lignina; ed in fine il terzo picco tra 524-519 °C è attribuito alla rottura degli anelli aromatici, aromatici alchilici, dimeri della lignina e composti contenenti N. In particolare gli HA provenienti dai siti con vegetazione di megaforbie o prato sono caratterizzati da un maggior contenuto di composti basso bollenti, come i carboidrati semplici; al contrario gli HA estratti dal bosco maturo presentavano un incremento di composti termicamente stabili attribuiti a sostanze aromatiche o dimeri della lignina. Un comportamento termico anomalo è invece risultato quello degli HA estratti dal sito rinnovazione dove il contenuto dei composti basso bollenti come i carboidrati semplici sono dominanti rispetto alla componente aromatica. Gli spettri DRIFT degli HA sono caratterizzati da una varietà di bande caratteristiche di strutture molecolari e di gruppi funzionali specifici per ciascun campione. In tutti gli spettri appariva una banda intorno a 1510 cm-1 che indicava la presenza nella struttura degli HA di composti aromatici derivati dalla decomposizione della lignina. I risultati ottenuti sono stati discussi in relazione alle differenze della composizione degli stadi di sviluppo vegetativo del bosco e del grado di umificazione.

The aim of the present work was to study a series of peats, leonardites and lignites humic acid samples using different (chemical, 13C isotopic ratio mass spectroscopy, thermal analysis (DTA), infrared Fourier transform and 1H nuclear magnetic resonance spectroscopies) techniques, in order to gain quali-quantitative information on humic substances structure and on the main structural changes that take place during the coalification process.