Fulvic Fractions Research Articles

Spatiotemporal dynamics of dissolved organic matter in subtropical karst cave waters identified by optical properties

Natural dissolved organic matter (DOM) is ubiquitous in aquatic environments and is an essential component in the carbon cycle in karst areas. To improve understanding of the carbon cycle in karst caves with heterogeneous hydrological processes, we examined the spatiotemporal variability of DOM composition and further uncovered its source and fate. Results may also provide insights into the feedbacks of organic carbon to carbon sinks in karst regions. In this study, concentrations and compositions of DOM, partial pressure of aqueous carbon dioxide (pCO2), dissolved inorganic carbon, and other physicochemical parameters were investigated in a karst cave at Mahuang, Southwest China. Ultraviolet-visible absorption spectroscopy was coupled with multiple statistical analyses to identify the compositional variations and potential fates of DOM in cave waters. The results showed that DOM dynamics were regulated by both terrigenous and biogenic drivers under the control of meteorological conditions. With higher air temperature, precipitation, and microbial activity, fulvic fractions were consumed to generate CO2, leading to the accumulation of refractory DOM in cave waters and changing the hydrochemical features. When temperature and precipitation decreased, DOM was dominated by lignin fractions, which served as an indicator of terrestrial inputs and vascular plants, suggesting variation in the preferential fraction of biological consumption. In addition, different hydrological path patterns influenced DOM properties in cave waters due to differences in recharging, the leaching process, and subsurface reworking. Thus, hydrology could serve as an important constraint on the coupling between dissolved organic and inorganic carbon.

Evaluation of the simplified method of fulvic fractions extraction from peat and lignite

Due to numerous and valuable properties of humic substances, preparations produced from alternative organic materials have been widely used in agriculture, bioremediations, dietary supplements and others. In addition to well-known humic acids, fulvic acids (FA) are a valuable product with a wide range of applications. The aim of performed examinations was to assess the thermal and physicochemical properties of FA obtained from lignite and peat using simplified conventional and ultrasound-assisted methods. DSC coupled with TG and MS, 13C NMR, FTIR spectroscopy and differential pulse voltammetry has been used to examine extracted FA. Depending on the source of FA and the extraction method applied, their structure and properties differ. Obtained FA fractions varied for both tested raw materials in terms of analyzed carbon structures, and the highest discrepancy was observed for carbonyl groups (20.2 pp) in fractions obtained by conventional extraction. The use of the ultrasound-assisted extraction (UAE), in comparison with the traditional method, lowered the ratio of carbon in carbonyl groups by 8.4 pp and increased the ratio of aromatic and aliphatic carbon by 3.5 and 4.9 pp, respectively, for FA obtained from lignite. As for FA obtained from peat, the UAE effect appeared to be less impactful in terms of structural changes. Thermal analysis showed that the products were thermally stable up to 100 °C, and the simplified extraction resulted in the creation of mineral-organic structures that decomposed at unusually high temperatures. Simplifying the extraction process, by excluding inorganic purification and protonation of obtained FA fractions, greatly affects product quality and limits its possible application.

Humic fractions from Amazon soils: Lifetime study and humification process by fluorescence spectroscopy

The Amazon Forest is an important and primordial ecosystem, as it controls the dynamics of soil organic matter (SOM) and is considered one of the crucial carbon reservoirs in the world. Based on that, this study evaluated the molecular properties of humic (HA) and fulvic (FA) acid from Amazon soil, with and without Cu(II) ions, by Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) and Fluorescence Spectroscopy (FS). Fluorescence excitation-emission matrix (EEM) was obtained by FS, and EEM spectra were treated by canonical polyadic/parallel factor analysis (EEM-CP/PARAFAC). The results showed that the humification index (A465nm) determined by FS is directly dependent on fluorophores’ CII/CI ratio in these soils with depth (r = 0.89), especially for HA samples in deep horizons, which demonstrated that the CII consists more complex and humified structure of the SOM. The lifetime decay showed the presence of static quenching in the humic fractions. From the lifetime data provided by TRLFS and the different correlations with carbon content and A465nm, it can be suggested that the fluorescence suppression modifies the molecular properties of the humic fractions with the addition of Cu(II) ions, such as altering the mobility and availability of the metal in the complexation reactions in these Amazonian Spodosols, mainly for the fulvic fraction.

Fulvic Acid from Chestnut Forest as an Added Qualities to Spring Water: Isolation and Characterization from Fiuggi Waters

The aquifer of “mineral” water, historically known for its curative properties, is an identifying characteristic of the Anticolana valley. This area hosted a coppice chestnut forest for a long time. Under the forest, there is an important aquifer, historically renowned and widely recognized for preventing renal stone formation and or facilitating their expulsion. This mineral water pre- vents the formation of calcium oxalate and phosphate crystals in the kidney and promotes their dissolutions through soluble calcium complexes. The forest environment soil is particularly rich in humification products owing to the interaction of the rainwater–litter–soil system. The fulvic fraction is soluble in water under all pH conditions and enriches the water basin. We aimed to test these hypotheses and assess how the coppice chestnut forest is involved in fulvic acid production. Fulvic fractions isolated and purified from soil samples and mineral water (550 μg L−1) were analyzed by GC-MS, FTIR, and NMR. Data from different sources were compared, showing sufficient similarities to state that the fulvic acids isolated from the water come from the processes that take place between the stems and the chestnut litter. The chestnut forest provides enrichment to water quality, which is a distinctive piece of information in defining water enhancement strategies, establishing soil management and designating sustainable forest management.

Quantification of Humic and Fulvic Acids in Humate Ores, DOC, Humified Materials and Humic Substance-Containing Commercial Products

The purpose of this method is to provide an accurate and precise concentration of humic (HA) and/or fulvic acids (FA) in soft coals, humic ores and shales, peats, composts and humic substance-containing commercial products. The method is based on the alkaline extraction of test materials, using 0.1 N NaOH as an extractant, and separation of the alkaline soluble humic substances (HS) from nonsoluble products by centrifugation. The pH of the centrifuged alkaline extract is then adjusted to pH 1 with conc. HCl, which results in precipitation of the HA. The precipitated HA are separated from the fulvic fraction (FF) (the fraction of HS that remains in solution,) by centrifugation. The HA is then oven or freeze dried and the ash content of the dried HA determined. The weight of the pure (i.e., ash-free) HA is then divided by the weight of the sample and the resulting fraction multiplied by 100 to determine the % HA in the sample. To determine the FA content, the FF is loaded onto a hydrophobic DAX-8 resin, which adsorbs the FA fraction also referred to as the hydrophobic fulvic acid (HFA). The remaining non-fulvic acid fraction, also called the hydrophilic fulvic fraction (HyFF) is then removed by washing the resin with deionized H2O until all nonabsorbed material is completely removed. The FA is then desorbed with 0.1 N NaOH. The resulting Na-fulvate is then protonated by passing it over a strong H+-exchange resin. The resulting FA is oven or freeze dried, the ash content determined and the concentration in the sample calculated as described above for HA.

Humic Substances as Indicator of Degradation Rate of Chernozems in South-Eastern Poland

Unfavourable quantitative and qualitative changes of soil organic matter result from degradation processes, such as water erosion connected with intense arable land use. In order to take adequate preventive action, the proper indicators of soil quality or degradation are urgently needed. In particular, tests considering the soil organic matter quality seem to be beneficial for soil monitoring. In this paper, we performed organic matter fractionation using the Tyurin and IHSS procedures on eight profiles of chernozemic soils (non-degraded, eroded, forest and accumulative soils). The study conducted confirmed the applicability of using humic and fulvic fractions in order to determine the pedogenesis processes and degradation rates of chernozemic soils. For example, the HA/FA ratio was higher in non-eroded and accumulative soils, compared with eroded or forest profiles. These findings were supported by statistical discrimination performed on the mid-infrared spectra of humic acids extracted from the selected profiles. Groups of samples were divided into classes depending on land usage or degradation rate. Considering the results, fractions of humic substances can be recommended as useful tools for the assessment of soil transformation.

Humic fractions as indicators of soil organic matter responses to clear‐cutting in mountain and lowland conditions of southwestern Poland

AbstractClear‐cutting means forest removal (stems only) and is the most common type of forest harvesting but undoubtedly has a negative impact on the C budget in soils. This work aimed to describe responses of soil organic matter (SOM) in the mixed coniferous forest following the removal of trees under temperate climate conditions in lowland and mountain regions in southwestern Poland. Investigated soils are described as Brunic Arenosols derived from sand with an average content of total organic carbon (TOC) in the Oa‐horizons of 244 g·kg−1 in the lowland and Dystric Cambisols derived from gneiss; the average content of TOC in the Oa‐horizons in the mountain regions was 309 g.kg‐1. Analyzed soils were very acidic in the both regions (pH 2.7–3.5 in the topsoil). In the experiment, two replicated soil profiles were located on each site, both taken after clear‐cutting and without any harvesting. Humic fraction was isolated from Oa‐ and A‐horizons; differences between investigated objects were checked with a significance p < 0.05, (n = 16). Using the instrumental analysis, like electron paramagnetic resonance (EPR), proton nuclear magnetic resonance (1H NMR), and Fourier transformed infrared (FTIR) spectroscopy applied to isolated humic fractions, it has been found that clear‐cutting alters C cycling and accelerates decomposition in the forest floor, leading to loss of humic fractions in the investigated soils. In the mountain forests, the more labile, low‐molecular‐weight fulvic fraction decreased as the effect of harvesting practice by 30% in Oa‐horizon and by 54% in A‐horizon. The analysis of stable radicals by EPR showed a decrease in radical concentration observed for humic acids (HA) from mountain clear‐cut areas compared to the undisturbed forest. Results presented in this article have proved there is less aliphatic character of HA molecules from the lowlands, compared to the mountain forest as the effect of clear‐cutting. Changes in plant cover observed as a consequence of deforestation lead to the decrease in concentration of humic fractions with different solubility properties.

Waste Willow-Bark from Salicylate Extraction Successfully Reused as an Amendment for Sewage Sludge Composting

Due to the fact that compost is a valuable fertilizer that serves principally as a source of macronutrients, composting is one of the preferred methods of management of organic waste, including municipal sewage sludge. However, due to its high moisture content and low C/N ratio, sewage sludge cannot be composted alone. This study investigated the usefulness of waste willow-bark (WWB) (after salicylate extraction) as an amendment for municipal sewage-sludge composting in a two-stage system: an aerated bioreactor and a periodically turned windrow. Both organic matter (OM) removal and humification progress were monitored. It was found that the prepared feedstock (70% sewage sludge, 25% WWB, and 5% wood chips, w/w) enabled proper temperature profiles to be obtained, with a maximum temperature of 72.3 °C. The rate constant of OM degradation in the bioreactor was 0.25 d−1, almost 4-fold higher than that in the windrows. During composting, the concentrations of humic substances (HS), humic acids (HA), and the fulvic fraction (FF) changed. HS, HA, and FF formation proceeded according to 1. order kinetics, and their respective rates were 1.33 mg C/(g OM d), 1.03 mg C/(g OM d), and 0.76 mg C/(g OM d). However, in mature compost, FF predominated (ca. 70%) in HS. These results indicate that waste willow-bark, a product of salicylate extraction, can be successfully reused as an amendment during municipal sewage sludge composting. Both waste willow-bark reuse and sewage sludge composting are compatible with a circular economy.

Organic Matter Characterization and Phytotoxic Potential Assessment of a Solid Anaerobic Digestate Following Chemical Stabilization by an Iron-Based Fenton Reaction.

Digestates, a byproduct of the anaerobic bioconversion of organic wastes for the production of biogas, are highly variable in chemical and biological properties, thus limiting their potential use in agriculture as soil amendment. Using a lab-scale glass reactor, we aimed to assess the feasibility to chemically stabilize the solid fraction of an anaerobic digestate by applying a Fenton reaction under constant pH (3.0), temperature (70 °C), reaction time (8 h), and various combinations of H2O2 and Fe2+. In Fenton-treated samples, the phytotoxic potential (determined on a test plant), total phenols, and the bad smell odor index markedly declined, whereas total C and N remained unaltered. Thermogravimetric (TG) analysis and Fourier transform infrared (FT-IR) spectroscopy revealed contrasting changes in extracted humic and fulvic fractions being increased or depleted, respectively, in aromatic substances. Process feasibility and optimum conditions for an effective biomass stabilization were achieved with a H2O2/Fe2+ ratio between 0.02 and 0.03.

Susceptible soil organic matter, SOM, fractions to agricultural management practices in salt-affected soils

In the recent decades, soil salinity became the main human-induced soil degradation causes in Egypt’s Nile Delta Valley (ENDV) by affecting the stabilization processes of soil organic matter (SOM). However, soil organic carbon (SOC) is highly conserved by aggregating the stabilized organic molecules under sound agricultural management. In particular, labile SOM fractions assumed to be dually influenced by salinity and agricultural management practices other than the stabilized fractions. This work aimed to study various labile and stable SOM fractions that are more susceptible to the current agricultural practices in salt-affected soils of the ENDV area. Three different agro-ecological sites were studied: Eastern (EH, EM soils) and Western (WM, WL soils) Delta regions dominated by Vertic Torrifluvents, and Coastal region (NCH, NCM soils) dominated by Typic Calcitorrerts of high CaCO3 contents. Two different salinity levels were detected in each site; low in WL soils, medium in WM, NCM, and EM soils, and high in EH and NCH soils. The least values in EM, WL, and NCM soils were due to the recurrent legume applications. The carbon content of glomalin-related soil protein (GRSP) (C-GRSP) was positively correlated with SOC and water-extractable organic carbon (WEOC) fraction confirming the contribution of GRSP to the stabilization of SOM. The lower soil β-glucosidase, phosphatase, and protease enzymes activities were in those soils with larger salinity levels in each site as NCH < NCM, WM < WL, and EH < EM reflecting the effect of soil salinity and CaCO3 contents on soil metabolic activities. Extracted organic carbon (EOC) in both humic and fulvic fractions was higher in EH, WM, WL, and EM soils than in NCH and NCM soils. The chemical composition of SOM obtained by the pyrolysis gas chromatography showed that lignocellulosic and condensed aromatic structures in SOM increased significantly with CaCO3 and salinity. In conclusion, the considered SOM fractions such as WEOC, EOC, GRSP, C-GRSP, together with the pyrolytic results can be considered as significant indicators in the dynamic stability of SOM. Intercropping with legumes may increase the stability of SOM fractions in salt-affected soils of degraded lands. In calcareous soils, severe alteration in SOC conservation was observed and negatively influenced the active constituents of SOM.

Humic substances of differently matured composts produced from municipal solid wastes and biomass of energetic plants

Abstract The aim of the study was to assess the transformation of humic substances during composting of biomass of energetic plants and municipal solid waste. The type of the organic material to be composted and the type of technology used affect the course of the humic substances transformation and formation of compost maturity parameters. Compost produced from the mixture of energetic willow and hay biomass contained humic substances with higher share of low-molecular fractions and lower share of humic acids in total organic carbon than those produced from municipal solid wastes. Obtained results also showed that insoluble alkali fraction plays an important role in humification process by its convertion to a new humic substances. Share of humic and fulvic fractions in relation to the total organic carbon appears to be reliable indicator of composting as a process of enhancing organic matter humification.

Washing agents from sewage sludge: efficiency of Cd removal from highly contaminated soils and effect on soil organic balance

PurposeTo compare Cd removal from different soils with three washing agents recovered from sewage sludge (dissolved organic matter (DOM), soluble humic-like substances (HLS), soluble humic substances (SHS)). Also, to investigate how washing with these agents changes soil organic-matter composition (OM).Materials and methodsSandy clay loam (S1) and clay (S2) highly contaminated with Cd (300 mg kg−1) were washed with DOM, HLS, or SHS solutions at various pHs, and with various washing times and washing modes (single or double). Cd distribution and OM composition were determined (including content of humic substances (HS), fulvic fraction (FF), labile humic acids (L-HA), and stable humic acids (S-HA)).Results and discussionCd removal proceeded with pseudo-second-order kinetics. Equilibrium was reached in 30 min (S1) and 60 min (S2). DOM, HLS, and SHS removed 75–82% of Cd from S1, and 80–87% from S2. The most mobile fraction of Cd was removed after one wash. S2 retained more OM, including HS, than S1. Although washing did not change the HA/FF ratio in most variants, washing with DOM and HLS increased the percentage of L-HA in both soils. Washing with SHS increased S-HA content in both soils, but the percent content of S-HA was similar to that in the unwashed soil.ConclusionsDOM, HLS, and SHS derived from sewage sludge can effectively remediate clay and sandy clay soils highly contaminated with Cd. Washing with an SHS solution can increase the content of the most stable carbon forms (HA), which is beneficial for carbon sequestration in remediated soils.

Effect of barley straw and coniferous bark on humification process during sewage sludge composting

This study investigated how different amendments (barley straw, coniferous bark) influence organic matter (OM) removal kinetics and humification during sewage sludge composting. With bark, high temperatures, intensive OM degradation and humification were achieved later than with straw. The rate of OM degradation was lower with bark than with straw (15.18 g/kg OM·d vs 24.07 g/kg OM·d) and the time needed for intensive HS formation was longer with bark (140 days vs 60 days). The kinetic constants for humic substances (HS) and humic acids (HA) formation were lower with bark than with straw (kHS 0.025 d−1 vs 0.047 d−1, kHA 0.022 d−1 vs 0.044 d−1). With bark, however, the increase in HS concentration during composting (Cmax,HS) was higher (178 mg C/g OM vs 84 mg C/g OM), and the fulvic fraction predominated in HS (80%), whereas with straw, humic acids predominated (82% of HS).

Metodología para obtener ácidos húmicos y fulvicos y su caracterización mediante espectrofotometría infrarroja

&#x0D; &#x0D; &#x0D; Los extractos orgánicos en la actualidad tienen gran aceptación por los productores agrícolas fundamentalmente por su costo y aléxitodesusaplicacionesenloscultivos,conelfindeobtener un compuesto orgánico-mineral o humato como alternativa para eficientar los nutrientes a los cultivos, se recolectó un mineral fósil orgánico de una mina, en laboratorio se extrajeron las fracciones de ácido húmico (AH) y fúlvico (AF). Después se ajustó el pH de estos ácidos con fertilizantes químicos. Para los ácidos húmicos y fúlvicos se manejó un pH de 6, 7, 8 y 4, 6, 7 respectivamente y finalmente se solidificaron. Para la caracterización de los grupos funcionales de estos ácidos se utilizó un espectrómetro de luz infrarroja (IR). Los resultados muestran que ácidos húmicos y fúlvicos presentan grupos funcionales similares pero en cantidad diferente, la mezcla orgánico-mineral de AH y AF mostraron un comportamiento similar en adsorción del elemento incorporado, sin embargo el AH y AF ambos con pH 7 presentaron la mayor adsorción del Ca y Fe, esto se debe a que son compuestos pH dependientes y la capacidad de agrupamiento se debe a la reacción de intercambio catiónico dada por los radicales libres.&#x0D; &#x0D; &#x0D;

Weed control methods and coffee shrub residue effects on carbon stocks in a Latosol under conservation management practices

Weed control methods in coffee crops can significantly influence carbon (C) stocks of soil humic substances. The aim of this study was to evaluate C stocks in an experimental coffee crop submitted to conservation agriculture for weed control between coffee rows. The study was carried out in a very clayey Dystroferric Red Latosol, Londrina, Paraná state (23°21’30” S; 51°10’17” W), cultivated with cultivar Mundo Novo IAC 379-19. In 2008, the experiment was established as randomized block design with four replicates within split-split plot scheme. Seven weed control methods between coffee rows were considered (hand weeding; portable mechanical mower; herbicides application; two cover crops; weed check and spontaneous). In September 2013, coffee shrub pruning was conducted and residues were distributed along inter rows. The weed control methods were considered as the main-plot factor and sampling period (March 2014 and February 2015) as the split-plot. Soil samples were collected at the center of the inter rows at four depth increments. C stocks evaluation included total organic carbon determination by chromic acid wet oxidation. Humic substances were characterized by UV-Vis spectroscopy. Most of the considered weed control methods did not affect organic carbon storage in 0 – 40 cm layer, nevertheless led to increase at topsoil. In 2015, the humin fraction C stock was 54 % higher at superficial layer than subsequent depth, presenting 39 % average increase at the 2014/2015 interval. Although C stocks from humic and fulvic acids did not vary, more conjugated/condensed characteristic for the fulvic fraction was observed.

Floristic Composition and Carbon Sequestration of "Indikada Mukalana" Forest Reserve, Waga; A Lowland Wet Evergreen Forest in Sri Lanka

Tropical lowland wet zone forests hold the greatest plant diversity, promise high plant carbon stocks. This study examined plant and soil carbon stocks of Forest reserve, Waga, Sri Lanka. Five representative sampling sites (20x20 m) in the forest were used for floristic survey and soil core sampling. Chemical and physical properties of soil samples were analysed for five years during 2011 and during 2014 to 2017. Vegetation survey documented 17 common tree species belonging to 15 genera and 12 families. Of the recorded species, 10 were endemics and 7 were native species. There were two species belonging to Dipterocarpaceae (Diptrocarpus zeylanica and Hopea juncunda). The mean total % C showed a negative correlation (R2=0.42) ranges in value between 2.84% in 2011 and 2.16% in 2017. The soil C fractions were determined by Loss on Ignition (LOI) method and predominated by the fulvic fractions (68.88%) followed by the humic fractions (18.36%) and the free soil litter fractions (12.76%). The total ecosystem carbon in the Indikada Mukalana lowland wet zone forest was 625t C/ha (i.e. biomass C 573.57 tC/ha and soil C 51.68 tC/ha), which was comparatively higher than our previous studies conducted in a highland wet zone forest (361 tC/ha at Udawattakele forest reserve) and a dry zone forest (176 tC/ha at Sigiriya forest sanctuary). The above ground biomass carbon for the forest was 477.98 t C/ha and the below ground biomass was 95.6t tC /ha. The mean total N % showed a positive correlation (R2=0.84) ranges in value between 0.14% in 2011 and 0.18% in 2017. Soil pH in Waga forest was acidic (<5) over the five-year period due to accumulation of more organic acids due to decomposed litter. In conclusion, we recommend this study to further extend towards other land-use classes to understand carbon sequestration in associated land-use classes for providing carbon benefits through carbon conservation via sustainable land management practices. Keywords: Floristics, Carbon sequestration, Waga forest, Soil organic carbon

Quantification of Humic and Fulvic Acids, Macro- and MicroNutrients and C/N Ratio in Organic Fertilizers

ABSTRACTHumic substances are the main responsible for soil conditioning and are one of the major components of the composting product. However, there is still little information about their composition and mechanisms of activity. This study aimed to evaluate quantitatively the humic and fulvic fraction by size-exclusion liquid chromatography and the metal content by atomic absorption spectrometry. The chromatographic method used was efficient for humic and fulvic acids quantitation. Levels of 1.73 ± 0.03 and 1.6 ± 0.5 g kg−1 were found for chicken manure regarding humic and fulvic acids, respectively, and 5.1 ± 0.9 and 1.2 ± 0.1 g kg−1 for peat. The metal contents indicated the need of a mineral enrichment, because only the levels of iron reached the minimum recommended by legislation. It was also observed that evaluated organic fertilizers were in accordance with the specifications established by legislation in relation to carbon and total nitrogen and the pathogen levels.

New methodology to assess the quantity and quality of humic substances in organic materials and commercial products for agriculture

The traditional method to determine humic content (humic and fulvic acids) in commercial fertilizers, biostimulants, and organic materials is based on the oxidation of the organic carbon contained in the basic-soluble but acid-insoluble fraction (humic acids) and the basic-acid soluble fraction (fulvic acids) of their alkaline water extracts. This methodology, merely operational, makes it impossible to distinguish if the quantified carbon corresponds to substances with “humic” chemical nature or to non-humic organic matter but with similar solubility properties to those of humic matter. The aim of this work is to develop a new methodology that not only quantifies the humic content in commercial products (and raw materials) but also assesses the humic quality of the quantified organic matter. To this end, humic and fulvic (-like) fractions have been isolated/purified from several humic and non-humic materials and characterized by means of elemental analysis and UV-visible, fluorescence, and infrared spectroscopies, and these data have been used to perform a discriminant analysis (DA). The model obtained from the DA is able to discriminate humic and fulvic fractions from apparently humic or fulvic ones and provides discriminant classification functions that have proven to successfully predict the “humic quality” of the fractions isolated from commercial products, after their elemental and spectroscopic characterization. Therefore, the combination of the fractionation, characterization, and evaluation by the DA is proposed as an effective methodology for quantifying and assessing the quality of the humic content claimed in the labels of commercial products.

FRACTIONAL COMPOSITION OF HUMUS IN SELECTED FOREST SOILS IN THE KARKONOSZE MOUNTAINS

This paper describes the fractions of humus compounds present in the organic and mineral horizons of the forest soils in the area of the Karkonosze Mountains. Soil profiles that represented the mountain Podzols and Dystric Cambisol were located on the northern slope along an altitude gradient from 890 to 1255 m a.s.l. Two soils were located under the spruce forest, and one in the subalpine meadow. Soil samples were taken both from the surface organic layers (the ectohumus layer) and from the mineral horizons. Fractionation of humus compounds was made using the modified Turin method. The soils had the texture of loamy sand and sandy loam, an acidic or strongly acidic reaction, low base saturation, and the predomination of aluminum among exchangeable cations. A significant increase in the fulvic fraction (Ia) with depth in the soil profiles was observed that confirmed the high mobility of this fraction in the acid mountain soils, higher in the forest soils, and lower in the meadow soils. The content of fraction I decreased generally with depth in the soil profile; however, a secondary increase was observed in an illuvial Bh horizon of the Podzols. Fulvic acids predominated over the humic acids and this predominance increased with depth in the soil profile. The ratio of the humic to the fulvic acids in fraction I in the ectohumus horizons was influenced by the composition of a biomass inflow. TheCHA:CFA ratio had the highest values under a spruce forest compared to a mixed stand and a subalpine meadow. In the surface horizons of the forest soils, a predominance of humic over fulvic acids was always observed, while in the subalpine meadow soils, the fulvic acids predominated over the humic acids in all soil horizons. Based on this study, it can be stated that the vegetation type and the dominant soil-forming process rather than simply climate factors influence the fractional composition of humus in the mountain soils of the Karkonosze Mountains.

Assessment of Fulvic Acid-Like Fractions during Tannery Waste Composting

Changes in the structural composition of fulvic acids were followed during composting of tannery solid waste after neutralization of its acidity by ammonium or by lime. Different techniques (elemental analysis, Fourier transform infrared (FTIR), 13C-NMR spectroscopy) were applied. During both trials of composting, a decrease of carbon and increase of oxygen occurred, which originated from strong microbial oxidation and preservation of some structures during composting. In fact, Nuclear Magnetic Resonance (NMR) spectra showed the preservation of anomeric or tannin structures around 105 ppm. The infrared (IR) spectral data showed a decrease in the intensity of COO− group bands (1623 and 1399.5 cm−1); this is correlated with a decrease of fulvic acid levels. The variations observed in NMR spectra could be explained by the involvement of COO− groups of certain structures in polycondensing to form humic acids. The fulvic acids remain composed of less polycondensed structures with a –COOH extremity, as supported by a decrease of the C/H ratio. In contrast, in the trial with addition of ammonia a slight increase in N content occurred, a decrease in absorbance in the 1730–1000 cm−1 regions compared to the absorbance around 3400 cm−1, and a strong decrease of carboxyl carbon in the 13C-NMR spectra.