Search Results (21)

The efficient characterization of compost quality is essential for optimizing its application in agriculture and soil improvement. In this study, a correlation-based approach was employed to evaluate relationships between physicochemical properties, structural features, and reactivity indicators of compost extracts—fulvic acid-like (FA-L), humic acid-like (HA-L), and dissolved organic matter (DOM)—and their respective bulk composts. The goal was to identify key compost parameters that can serve as reliable predictors of humic substance composition and bioactivity, thereby reducing reliance on labor-intensive humic substance extractions. A comprehensive set of elemental, spectroscopic (UV-vis, ATR-FTIR, ¹H-NMR), and thermal (TGA-DSC) analyses were conducted to assess the composition and stability of the extracts. Strong correlations were found between compost oxidation state (C_oxi/C), cation exchange capacity (CEC), thermal stability, and the structural characteristics of humic substances-like (HS-L) fractions, suggesting that direct compost characterization can effectively predict humic substance reactivity and agronomic potential. The findings also align with a previously developed Compost Quality Index (CQI), reinforcing the functional role of humic substances in soil fertility and nutrient retention. By establishing a simplified yet robust compost assessment framework, this study advances the potential for efficient, cost-effective evaluation methodologies for compost quality. Full article

Phosphorus (P) retention in soils in the presence of organic matter (OM) has been, for years, a topic with no clear conclusions. Considering the important ecological functions of peatlands, the objective of this study is to examine the role of OM transformation in relation to P status in Histosols in the Oder Valley (Poland). Basic physical and chemical properties and the following P forms were determined in the organic horizons of 5 soil profiles from two habitats (eutrophic and dystrophic): total (Pt) and organic P (P_o), available P (P_M3), easily soluble P (P_CaCl2), water-soluble P (P_W), and fraction of P_o in humic (P_o_HA) and fulvic (P_o_FA) acids after extraction with 0.5 mol L⁻¹ NaOH. The results were statistically verified in both examined habitat groups separately. The higher values of mobile P forms were found in the upper organic horizons released from OM constituents as a result of their decomposition. The role of OM in P retention was strongly related to the activity of humic substances (HS): a higher P_o percentage (6.9–99.4% of P_o) was observed in dystrophic, whereas a lower (9.3–28.6% of P_o) was observed in eutrophic Histosols. Humic acids played a dominant role in P retention compared to fulvic acids in most peat horizons, especially at pH < 5. The role of HA and FA in P retention was clearly dependent on forms found only in eutrophic Histosols. The important role of FA in P retention during OM transformation was confirmed by negative correlations between P_o_FA and macronutrient ratios in both soil groups. The results confirm the variable role of OM in P retention, depending on soil environmental conditions and OM type (peat and moorsh). This may have important applications not only in areas of natural importance, for which the release of mobile P forms may be a threat, but also in agricultural areas where, for a change, we struggle to increase P availability. Full article

There has not been enough research conducted on the effect of land use on the composition of humus in Arenosols. This long-term study (1995–2022) aimed to determine the differences in the formation of humic compounds in the natural and agricultural ecosystems of Arenosols. Soil samples were collected from six plots at two soil depths (0–15 and 15–25 cm), with four replicates. Conclusions were reached based on the results of the accumulation of humic substances (HSs) and their qualitative fractional composition, C/N ratio, humification degree (HD), and the optical properties of the humus substances. Afforestation, after 27 years, significantly increased (+6.7 g kg⁻¹) the soil organic carbon (SOC) and influenced the qualitative composition of HS: HA + FA 79.3% of the SOC. Grassland cultivation showed faster (+3.8 g kg⁻¹) SOC sequestration, a higher HA/FA ratio, and an increased HD. Arenosols may be used in crop rotation with approximately 40% leguminous plants to maintain a stable humus balance. Additionally, the effects of mineral fertilisers on the humification processes and humus quality of +2.59 g kg⁻¹ SOC, +1.27 g kg⁻¹ humin in crop rotation, +3.26 g kg⁻¹ SOC, and 2.82 g kg⁻¹ humin in a grass cultivation field were established. For SOC accumulation and a larger humus amount of a better quality, it is recommended that an Arenosol is used, as it is suitable for use in perennial cut grasslands, natural grasslands, and pine afforestation. Full article

This study aims to investigate if high-resolution dissolved organic matter (DOM) data, obtained from water by chromatographic analyses, enable us to assess whether seasonal climate change and anthropogenic activities in the catchment area have an impact on the ecosystem’s sustainability. More specifically, the changes in the molecular properties of heterogeneous DOM from the hypertrophic River Vääna, Estonia, during the winter and spring seasons have been examined. The chromatographic HPLC method (HPLC-SEC), combined with UV-Vis spectroscopic detection, was used to characterize and fractionate DOM. Changes in several chromatographic/molecular parameters were investigated. The microbial-derived low-molecular-mass aromatic and heterocyclic compounds, humic substances (HS), and protein-like (PL) components were identified in the DOM. The HS to PL fractions ratio has been found to reflect the seasonal climatic change and can be applied as a potential environmental indicator. The River Vääna’s water was evaluated as sustainable, and even an anthropogenic impact was revealed. The results point out the usefulness of HPLC-SEC together with UV-Vis spectroscopy detection for climate change-related DOM studies in real environmental conditions. Full article

The aim of this study was to assess the transformation of organic matter in organic soils undergoing a phase of secondary transformation, based on a new method of nitrogen compound fractionation. Laboratory tests were carried out for 31 layers of muck (after secondary transformation) and peat (parent material of the soil) of drained organic soils (peat). The new method consists of sequential extraction in the following steps: (1) 0.5 M K₂SO₄ (extraction at room temperature); (2) 0.25 M H₂SO₄ (hot hydrolysis) (3) 3.0 M H₂SO₄ (hot hydrolysis); and (4) concentrated H₂SO₄ (mineralization of the post-extraction residue). As a result of the extraction process, the following fractions (operating forms) were obtained: mineral nitrogen (Nmin), dissolved organic nitrogen (N-DON), readily hydrolyzing organic nitrogen (N-RH), non-readily hydrolyzing organic nitrogen (N-NRH), and non-hydrolyzing organic nitrogen (N-NH). The study demonstrates the usefulness of the applied method for assessing the degree of secondary transformation of drained organic soils. The obtained results of nitrogen fractionation indicate the significant dynamics of nitrogen forms’ transformations and a significant relationship between these forms and soil properties. Nitrogen transformation processes during the secondary transformation process after dehydration resulted in an increase in the share of N-DON (on average: 1.47% of N_org for the peat layers and 2.97% of Norg for the muck layers) and in an increase in the share of N_RHON (on average: 20.7% of Norg for the peat layers and 33.5% of Norg for the muck layers). The method of sequential nitrogen fractionation used in our study allowed us to define an index determining the degree of transformation of organic matter in peat after drying. We defined it as the ratio of readily hydrolyzable forms (the fraction is very variable in the secondary transformation process) to non-readily hydrolyzable forms (relatively stable fraction in the secondary transformation process): N-RH/N-NRH. The average value of this index was significantly lower in the peat layers (0.64 on average) than in the muck beds (1.04 on average). The value of this index is significantly correlated with soil properties: bulk density (R² = 0.470); general porosity (R² = 0.503); total carbon content (TC) (R² = 0.425); total carbon to total nitrogen ratio (TC/TN) (R² = 0.619); and share of carbon of humic substances (C-HS) (R² = 0.466). We believe that the method of sequential nitrogen fractionation may be useful for other soils and organic materials. Full article

In urban areas, because of anthropopressure, the transformation of the soil cover can lead to the complete destruction of the natural layout and properties of these soils. The object of this study was to determine the quantity and quality of soil organic matter (SOM) originating in the topsoil horizons of the central part of Wroclaw (SW of Poland). Fractional composition of SOM and humic substances (HS) analysis were performed. Elemental composition and CP MAS ¹³C NMR spectra for the humic acids (HA) were determined, and α (aromaticity) and ω (oxidation) ratios were calculated. Total organic carbon content ranged from 22.39 to 66.1 g kg^–1, while that of total nitrogen ranged from 2.09 to 4.6 g kg¹. In most analysed urban soils, the highest share in SOM was found for residual carbon (CR), while HA of low maturity was the predominant group over FA. CP MAS ¹³C NMR spectroscopy of HA molecules indicated the structure of the samples was dominated by compounds with low aromaticity cores and considerable contents of aliphatic components. In urban soils, efforts should be made to enhance organic matter transformation into more matured and stable forms via, e.g., compost application and chemical treatments, and lawn maintenance should be very strictly controlled and limited. Full article

As increasing soil organic matter is considered one of the main strategies for reducing desertification in Europe, the production and use of high-quality composts has gained importance during the last decade. It is undisputed that the quantity and quality of humic substances (HS) and their fractions, i.e. fulvic acids (FA) and humic acids (HA) in compost are considered important indicators of compost maturity and chemical stability. Other important aspects are concentrations of macro- and micronutrients and heavy metals (HMs) that are introduced to the soil with mature compost. In this light, this study assessed the detailed characteristic of compost from municipal sewage sludge. Moreover, kinetic of organic matter (OM), and nitrogen transformations, therein nitrogen loss, were analysed. OM degradation proceeded according to first-order kinetics. In the bioreactor, the rate constant of OM removal and the rate of OM removal were 0.134 d⁻¹ and 12.6 mg/(g d.m.d), respectively. In the windrow, these constants were 5.2-fold and 16.7-fold lower, respectively. In mature compost, the concentration of HS equaled 240.3 mg C/g OM (1.65-fold higher than in the feedstock) and the concentrations of HA and FA were 120.7 mg C/g OM and 119.6 mg C/g OM, respectively. In FA predominated those with a molecular weight in the range of 10–30 kDa (47.2%), FA with a molecular weight >100 kDa accounted for only 14.4%. In HA, however, fraction with the highest molecular weight (>100 kDa) accounted for more than half (51.2%), while the share of HA with a molecular weight <10 kDa was only 6.8%. During composting, nitrogen loss was observed, which resulted from NH₃ rather than N₂O emission. In mature compost, organic nitrogen predominated (17.82 g/kg d.m.; ca. 92% of the overall nitrogen). The final concentrations of ammonia nitrogen and nitrate nitrogen were 0.23 and 1.12 g/kg d.m., respectively. The compost met the Polish requirements for the content of HMs (the HMs concentrations were as follows: Cd 1.85 mg/kg d.m., Pb 12.16 mg/kg d.m., Ni 11.05 mg/kg d.m., Cr 24.14 mg/kg d.m., Cu 104.24 mg/kg d.m., Zn 854 mg/kg d.m., Hg 0.12 g/kg d.m.). Full article

Anthropogenic pollutants that accumulate in bottom sediments may pose a serious threat to the aquatic environment and humans. The aim of the study was to determine the ecological risk related to the contamination of sediment with heavy metals and the relationship between the accumulation of heavy metals and various granulometric fractions and humic substances in the bottom sediments of small retention reservoirs located in catchments of varying anthropopressure. The research objects were five small dam reservoirs located in south-eastern Poland. The sediments of the reservoir exposed to the greatest anthropopressure from the catchment area posed a serious threat to aquatic organisms feeding at the bottom. The bottom sediments of the remaining reservoirs showed a low level of potential toxicity (or non-toxicity). The observed relationship between the enrichment of sediments with organic matter (OM) and the increased risk of their ecotoxic impact on aquatic organisms was determined by excessive exposure to heavy metal contamination. The sand content did not appear to have a clear effect on the metal accumulation, although it was associated with enrichment in OM. Due to diverse environmental conditions, it was not possible to unequivocally confirm that the accumulation of heavy metals in the sediments of small retention reservoirs directly depends on the content of organic matter and humic substances, but such relationships were observed in most of the objects. Full article

The Yeongsan River estuary was divided into freshwater and seawater zones by a sea dike constructed at its mouth in 1981. The freshwater zone, which flows through a metropolitan area, is eutrophic, causing frequent algal blooms with an expected increase in the concentration of refractory organic compounds such as humic substances (HS). Herein, the in situ freshwater zone phytoplankton community size and taxonomic composition were investigated in response to the addition of humic acids (HA) using seasonal mesocosm experiments. Phytoplankton (chlorophyll a) were fractionated into nano-(<20 µm) and net-size (>20 µm) classes and identified by species or genus. Their response to HA treatment was examined by repeated measures analysis of variance (RM-ANOVA). With the addition of HA, the concentrations of total and nanosized chlorophyll a increased significantly (p < 0.05), whereas that of net-sized chlorophyll a did not change significantly through the seasons. The abundance of Stephanodiscus sp. (diatoms) also increased significantly when this genus dominated the phytoplankton community. This suggests that the management of HS may be crucial in mitigating algal blooms in estuaries, such as in the Yeongsan River estuary, that are subjected to anthropogenic disturbances by engineered structures. Full article

Humic substances (HSs) have been researched for a long time and still manage to surprise humanity today. According to the latest research, in addition to their previously well-known effects, they also have antioxidant properties. However, this previous research does not examine the difference in the antioxidant effect of the fractions extracted/produced in different processes; they do not consider the light absorption of the HSs, which falsifies analysis based on the measurement of color change over time. In the present work, HS fractions were obtained from leonardite, the extraction processes can also be implemented on an industrial scale. The fractions were characterized by elementary analysis, UV–Vis and FT-IR spectroscopies, to prove that our self-extracted samples have similar characteristics to the International Humic Substances Society (IHSS) standard samples. The different methods of HS fractionation affected the elemental composition, and the spectral characteristics. The antioxidant effect was investigated using the DPPH method to screen the antioxidant efficiency of humic, fulvic, and himatomelanic acids. In addition, we compared our results with the IHSS standard samples to obtain a more comprehensive picture of the antioxidant effect of HSs extracted in different ways according to the DPPH method. Based on our results, the extraction method affects not only the physico-chemical properties but also the free radical scavenging activity of the fractions. Full article

Results of efficiency of obtaining humic substances (HSs) from peat in traditional alkaline extraction (TAE) and ultrasound-assisted alkaline extraction (UAAE) are presented. The influence of the duration of the process and ultrasound intensity on the efficiency of extraction of humic acids (HAs) and fulvic acids (FAs) extraction was determined. The composition of the fulvic acid fraction was examined depending on the type of eluent used. Fulvic acids were divided into fractions using columns packed with DAX-8 resin. For this process, 0.1 M NaOH and 0.5 M NH₃∙H₂O were used as eluents. For the quality assessment of specific fulvic acids fractions, spectroscopic methods (UV-Vis and FTIR) were used. Ultrasound had a positive effect on HS extraction efficiency, especially in increasing the amount of a desired hydrophobic fraction of fulvic acids (HPO). However, a negative effect of the excessive prolongation and ultrasound intensity (approximately 400 mW∙cm⁻²) on the extraction efficiency of HPO eluted with 0.1 M NaOH solution was observed. Using peat as a raw carbon material for the HS extraction process can be used as an alternative industrial application of peat. UAAE may be considered as an alternative method to TAE, which provides a higher efficiency in HS isolation from peat. Full article

Humic substances (HS) are the most important natural biostimulant of plants. However, the relationship between their structure and biological activity in plants is still not well recognized. The objective of this paper was to assess the influence of molecular fractions of humic acids (HA) (HA < 30 kDa and HA > 30 kDa) on reducing negative effects of drought stress in soybean (Glycine max (L.) Merr.) seedlings of Progres and Nawiko cultivars. Drought stress was induced in laboratory conditions by the addition of polyethylene glycol 6000 (PEG 6000) to make a water potential of −0.5 MPa. HA were extracted according to the International Humic Substances Society procedure, and then were separated into two molecular fractions by membrane filtration. The following physiological and biometric parameters were determined: chlorophyll content, photosynthesis activity, electrical conductivity, fresh and dry mass of overground and roots, and plant length. The enzyme activity and ion contents were also measured. Differences in response to drought stress with the addition of HA < 30 kDa and HA > 30 kDa or not to the Hoagland’s solution were observed among studied cultivars. Drought stress caused a decrease in the most physiological parameters and increase in peroxidase activity in the case of both studied cultivars. However, the results of biometric measurements showed that the Progres cultivar appears to have better tolerance to drought stress. The significant influence of water deficit on most macroelement content in dry matter leaves of both studied cultivars was not observed, while its effect on microelement uptake by soybean plants was concluded. In the case of the Progres cultivar, the results showed a significant decrease in microelement content in the dry matter of leaves, whereas in the leaves of Nawiko cultivar there was a significant increase. The influence of HA > 30 kDa and HA < 30 KDa fractions on physiological features of both studied cultivars was varied. HA > 30 kDa fraction better up-regulated the antioxidant defense system. Unfortunately, no effect of either HA fraction on the macro- and micronutrients uptake system of both studied cultivars was observed. Full article

Increasing agricultural productivity and, in particular, the productivity of livestock is one of the primary tasks in the present stage of development of society. This involves rational feeding and the use of biologically active substances, including humic preparations that activate the digestive and metabolic processes in the animal, promoting the transformation of feed nutrients in assimilable form, raising daily milk production and weight gain, and can play an important role in solving this urgent problem. The applications of humic substances in animal husbandry are diverse, but their use as feed additives is not developed sufficiently, and in the EU countries it is not sanctioned. Researchers in different countries have shown that humic substances in animals operate on the cellular and subcellular level, as they do in plants. Low molecular weight fractions HS enter the cell and are involved in metabolic processes, contributing to the optimization of inorganic ion passage through the intestinal wall, thereby promoting the absorption of minerals necessary for normal functioning of the organism. That is how the stimulating influence of humic substances on separate systems and on the organism as a whole is manifested. Humic substances formed from various natural materials are currently being tested in various branches of animal husbandry (cattle, pig breeding, poultry farming, fish farming, fur farming), and all the information received presents convincing evidence of the high efficiency of the humates. Such materials as peat and brown coal, vegetable waste, and vermicompost can act as a source of humic substances. However, in each case, more research is needed, specifying the dosage and schedule of their use. Full article

Five sample-preparation techniques were compared to quantify 31 elements in coal humic substances (HS) by ICP–AES from the viewpoints of complete isolation and speciation of elements. They include, for bulk composition, preparation of an aqueous colloidal HS solution followed by direct injection of the sample without decomposition and ashing followed by metaborate fusion; for element speciation, preparation of an aqueous colloidal HS solution followed by centrifugation and direct analysis without decomposition for water-soluble species; treatment with boiling nitric acid; and microwave-assisted treatment with nitric acid at 250 °C for acid-isolated species. The results of analysis significantly depend on the selected method of sample preparation due to specific features of HS, the simultaneous presence of many inorganic components in wide concentration ranges, and a significant fraction of the organic matrix; therefore, the total mineral composition of HS, both macro- and microcomponents, requires a combination of decomposition methods. Full article

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. Full article