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Diffuse reflectance infrared Fourier transform, surface-enhanced Raman and proton nuclear magnetic resonance spectroscopies were applied to investigate the structure of humic acids (HA) extracted from peat (P–HA), leonardite (Le–HA) and lignite (Li–HA) samples. The combined use of these techniques has shown a specific pattern of functional groups for each sample. P–HA was characterised by a greater content of oxygenate (COOH, C–OH in carbohydrates and phenols) and aliphatic groups. Le–HA and Li–HA showed a lower content of sugar-like components and polyethers. On the other hand, the aromatic structures were ubiquitous in all samples, although the different composition in Le–HA and Li–HA could be employed to identify and distinguish the HA in these two kinds of humic materials.

The role of soil organic matter in B adsorption and desorption processes in soil is not yet clearly understood. Adsorption/desorption isotherms of B were compared in three soils before and after organic‐matter removal by NaOCl. The amount of B adsorbed was considerably greater after the organic matter had been removed from the soil, and the release of B showed a hysteretic trend or, in any case, the hysteretic nature of the B release increased. An increase in oxalate‐extractable Fe and Al occurred after destruction of the organic matter. It is suggested that a portion of the Fe and Al oxides, as well as other possible adsorption sites, are generally coated or occluded by organic matter and become active only after removal of the organic matter.

The transport of bioavailable phosphorus (BAP) in agricultural runoff can accelerate the eutrophication of receiving water bodies. However, procedural and theoretical limitations of algal bioassays and chemical extractants have restricted widespread measurement of BAP. Thus, a simple method using iron oxide—impregnated paper (Fe‐oxide strips) as a sink for BAP in runoff samples has been developed. As the method has potential application for BAP extraction at one location and analysis at another, Fe‐oxide strips were sent to Bologna and Rome, Italy, for P extraction of runoff samples and BAP determined. These BAP estimates were not significantly different (p< 0.001) from values determined on duplicate strips returned to the USA for BAP analysis. The close agreement in BAP measured in Italian and U.S. laboratories indicates that the simplicity of the proposed method can give highly reproducible BAP estimates. Prepared Fe‐oxide strips may be sent to a location and BAP extracted using only a 100‐ to 500‐mL bottle in which a strip and runoff sample are shaken overnight. The Fe‐oxide strip may then be air‐dried and returned to an analytical laboratory for subsequent P removal and measurement. Storage of these strips for up to 60 d had no effect on the amounts of P released.

Soil samples were taken from the plots of an experimental field that had been treated continuously for 22 years with different residue and fertilizer applications (cereal residues, cattle manure, NH4NO3). The electrofocusing (EF) technique was used to characterize the humic substances extracted from these soils with 0.5 MNaOH. The EF patterns of the organic matter extracted from the soil which had received applications of cattle manure showed many bands focused in the typical pH gradient region of the most humified compounds. The EF patterns of the organic matter extracted from both unfertilized soil and from soils amended with straw appeared to be much less complex. The addition of NH4NO3did not affect the soil organic matter characteristics investigated with the EF technique. The results obtained show that electrofocusing is a promising technique for the characterization of humic substances and may well be particularly useful in the evaluation of differences that occur in the humic substances in soil due to residue and organic fertilizer applications.

Extraction procedures represent a crucial point in the study of the molecular structure of humic substances (HS). Although alkaline extractants such as NaOH plus Na4P2O7are usually employed for the extraction of the HS from soil and peat, little information concerning the interaction between extractants and humic acids is available. In this study, the results on the molecular structure of humic acids (HA) extracted and separated from a SphagnumIrish peat sample with an alkaline pyrophosphate solution (0.1 MNaOH + 0.1 MNa4P2O7) are reported. The HA were redissolved in 5 mMNaCl, fractionated in six cut‐off fractions (nominal molecular weight: HA >300, 100–300, 50–100, 20–50, 10–20, and 5–10 kDa) using a tangential ultrafiltration system. All samples were dialyzed against distilled water and then freeze‐dried. Fourier‐transform infrared (FT‐IR) and 31P nuclear magnetic resonance (NMR) spectroscopies were applied to characterize the incorporation of pyrophosphate (PP) in both the unfractionated HA and in the six HA fractions. Spectroscopic analyses showed that it was possible to assign a given pattern of bands to define the structure of phosphate: PP was present only in the unfractionated HA, whereas orthophosphate was present in both the high molecular weight and lower molecular weight fractions. The high concentration of phosphate found in the lower molecular weight HA fractions has been attributed to the presence of metals and the oxygenated groups of HA. The changes in the relative intensity of the bands attributed to oxygenated functional groups observed in the FT‐IR spectra could be assigned to the interaction of phosphate groups with metal cations, which are involved in a coordination complex with the oxygenated groups.

Results obtained with a dialysis membrane technique for the study of the sorption and desorption of herbicides by a fraction of the organic matter extracted from soil are reported. The humic acid (HA) fraction of a Typic Haplumbrept soil, extracted with 0.1 MNaOH plus 0.1 MNa4P2O7, was cut off at 5,000 Da. The water solution of HA>5,000was transferred to a 1,000-Da dialysis tube and inserted in a shaded flask containing a water solution of the herbicides (paraquat or linuron). The sorption of herbicide by the humic acid was determined by measuring at different time intervals (0, 0.5, 1, 2, 4, and 24 h) the decreasing concentration of the herbicide in the solution external to the dialysis tube. Measurement of the herbicide concentration was carried out spectrophotometrically in the λ = 200-300 nm UV region. The results obtained indicate that the procedure adopted can be useful to study the interactions between herbicide and fractions of soil organic matter with relatively large molecular sizes (>1,000 Da).

The use of isoelectric focusing (IEF) to characterize soil humic substances is a technique that appears to be of widespread interest. The use of carrier ampholytes permits the electrophoretie separation in the presence of a pH gradient, but until now the problem of interferences that could occur between the soil organic matter and the carrier ampholytes during the IEF separations have not been recognized. The commercial carrier ampholytes have different chemical structures; thus, interferences with soil humic substances could be different.

A given tolerance value on the declared nutrient content of fertilizers is permitted by some national laws. A statistical method to assess systematic exploitation of tolerance values by single nutrient fertilizer producers is proposed. Production of superphosphate was selected as the case study. The method was tested on a yearly production, on randomly selected samples, and on a generated series of samples; it was found to be simple and reliable. The method is theoretically expected to be more reliable than the Wilcoxon test recommended by French law for normal distributions; it appears to fit better than the Wilcoxon test to uneven production of fertilizers.

The objectives of the study were to test the electrofocusing technique to determine its suitability as a method for the characterization of organic fertilizers from a qualitative point of view and identification of the organic matrix in an unknown fertilizer; no laboratory methods for this purpose are presently available. Analytical electrofocusing (EF) is shown to fulfill these objectives and may be easily adopted as a routine manual procedure. A solution of sodium hydroxide was chosen as the extractant because it allows comparisons between various types of humified materials and permits the evolution of organic matter to be followed during “maturation” of the fertilizer itself. The organic fertilizers considered included many nitrogen-rich waste materials, mostly of animal origin. They are divided into different groups according to origin and EF profiles.

An enzymatic approach to assess the stability of organic matter extracted from organic fertilizers and amendments is proposed. The use of 0.1MNaOH plus 0.1MNa4P2O7previously 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 3NH2SO4; 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.

Fourier transform infrared (FT-IR), surface-enhanced Raman spectroscopy (SERS), and nuclear magnetic resonance (NMR) (1H and 13C) have been applied to the characterization of un fractionated and fractionated fulvic acids extracted from an Irish peat. Raman study of these compounds is possible on rough metallic surfaces, which enhance the Raman signal and quench the high fluorescence. The application of these spectroscopic techniques has provided important structural information concerning the aromaticity and the carboxylate and carbohydrate group contents in each fraction. In addition, a SERS study at different pH levels has revealed interesting interfacial behavior of these components based on electric charge and conformational changes.

The adsorption of several fractions of humic and fulvic acids on silver colloids was studied by means of surface-enhanced Raman spectroscopy. The short-range mechanism of this technique was applied in the determination of the chemical groups which are directly attached to the metallic surface. Adsorption of humic substances was found to be very sensitive to pH, to the electric charge of both the humic substances and the metallic surface, and to the size of the adsorbed macromolecules. From the obtained results, a model for the adsortion mechanism of these macromolecules is proposed on the basis of a conformational change and a variation of their electric charge on modifying the pH. FTIR spectra of some of the extracted fractions and SERS spectra ofo-,m-, andp- hydroxybenzoic acids, used as molecular models for humic substances, were also obtained in order to better attribute the SERS spectra of these humic substances.

A simple and useful analytical method is proposed for the characterization of blood meal fertilizer, a quality organic fertilizer commonly used in agriculture. Despite the agronomical and commercial importance of this organic fertilizer, Italian law does not indicate an analytical method for its identification in organic matrices. This situation is very unsatisfactory because unscrupulous producers could declare the presence of a quality organic fertilizer, such as blood meal, instead of a poorer fertilizer. In this work the heme group of the hemoglobin contained in blood meal was characterized spectrophotometrically and a calibration curve prepared using different concentrations of hemoglobin was used to determine the hemoglobin content in six blood meal samples. The method was successfully applied for the qualitative identification of hemoglobin in mixtures of organic and/or organic fertilizers with small amounts (3–10%) of blood meal.

Several samples of peat and leonardite (organic fossil material of vegetable origin) and of humic extracts from peat and leonardite were characterized using some humification parameters and isoelectric focusing (IEF). The HA/TOC and the humification rate (HR) show values lower than 60% for peat and higher than 70% for leonardite samples. These two parameters are useful to distinguish peat from leonardite, but unable to identify the organic materials in the humic extracts. Peat an leonardite samples and their humic extracts were characterized using IEF and evaluating the quantitative distribution of the bands of the profile. The group of bands in the range from pH 4.8 to 5.5 (region C) is characteristics in all samples. In particular, the relative area is less than 55% for peat and humic extracts from peat and higher than 60% for leonardite and humic extracts from leonadite.

Leather meal fertilizer was mixed with a soil (Typic Xerorthent) and incubated in the laboratory for one year at room temperature. Soil samples were collected periodically and analyzed in order to follow the transformation of the organic matter as well as the availability of Cr and certain plant nutrients. The results obtained showed intense mineralization during the first 60–120 days of the incubation period. The amount of humic acids (HAs) separated from the alkaline extracts showed that the humification level increased markedly after the first 60 days of incubation and, as shown by IEF analysis, organic compounds similar to the soil humic substances were formed. Variations in the amount of available nutrients were observed; only the extractable Cr increased during the first period of mineralization.

Leather meal is an important organic N fertilizer in Italy, but there is concern about the effect of the Cr it contains on the environment. Humification of leather meal, added to soil as granules, took approximately 300 days to reach completion, but as a powder took longer. Humification processes started immediately under aerobic conditions, and started after a lag of about 40 days under anaerobic conditions. EDTA-extractable and water-soluble Cr present in leather decreased sharply immediately after incorporation of fertilizers in soil; after 40 days of incubation, however, there was a pronounced increase, especially of EDTA-extractable Cr; thereafter there was a decrease. Chromium is continuously released from leather during the decomposition of organic matter and is then insolubilized. No detectable amounts of Cr(VI) have been found during the entire period of incubation; additions of Cr(VI) resulted in an immediate transformation to Cr(III). The release of Cr when leather is used as a fertilizer is of little agronomic or environmental significance.

We studied the effects of Pb pollution on soil dehydrogenase and phosphatase activity. Samples of four soils (Saxe, Podestà, Porto Teulada, and Sa Xia Manna) were collected from various locations in southwestern Sardinia, Italy. The soils, which differ mainly in heavy metal contents of pedologic origin (Cu, Zn, Cd, and Pb), were treated with Pb (0, 100, 500, 1000, and 5000 µg Pb g-1 soil) and incubated in the laboratory. Samples of the incubated soils were collected periodically (0, 1, 2, 4, 8, and 16 weeks) and the enzymes were measured. Soil dehydrogenase activity was influenced by both the Pb additions and variations in soil moisture content. Only the addition of 5000 µg Pb g-1 soil led to a significant decrease in dehydrogenase activity compared to the controls, while the other doses of Pb did not always result in a clear reduction in enzyme activity. Drying the soil led to a considerable reduction in dehydrogenase activity, sometimes so far as to render the differences found between the various treatments not statistically significant. Soil phosphate activity was also influenced by the Pb additions, but the effect of the variation in soil moisture content was less than that found for the dehydrogenase. After the 2nd week of incubation, the phosphate activity in the Podestà and Saxe soils had decreased proportionally to the increase in Pb content. At the end of the incubation period, in the Porto Teulada and Sa Xia Manna soils, a net reduction in phosphatase activity versus controls was found only at the highest Pb concentration. Although both enzyme activities were influenced by the Pb additions, the phosphate activity was less sensitive to variations in the soil moisture content and may thus be a more suitable indicator for soil pollution by Pb.

Fourier transform infrared spectroscopy (FT-IR), surface-enhanced Raman spectroscopy (SERS), and nuclear magnetic resonance (NMR) (1H, 13C, and 31P) have been applied to the study of fractions of humic acids in Irish peat. Owing to the high fluorescence of these materials, no Raman spectra have been obtained, up to now, for the characterization of humic acids. The SERS technique was employed for the first time in the study of these complex substances, demonstrating that very valuable information about the aromatic groups and the spacial conformation of these macromolecules in water solution can be obtained. The combined use of these techniques has evidenced an increase of oxygenated groups in those fractions containing humic acids with low molecular weight. The presence of a greater number of carboxylate and phenolic groups can explain the high concentration of metals and phosphate ions found in these fractions.

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.