Search

Exposure to oxygen and aerobic biological activity during drought periods alters the availability of terminal electron acceptors (TEA) in the peat catotelm layer. We investigated the changes in the electrochemical and chemical characteristics of humic acids (HA) induced by subjecting air-dried sphagnum peat to biological oxidation or reduction during a 90-day incubation experiment. Structural modifications of HAs from anaerobically (HAred) and aerobically (HAox) incubated peat were investigated by ATR-FTIR, UV-vis, and EEM fluorescence spectroscopy. Number and strength of acid groups were characterized by titration, while changes in redox properties were characterized by cyclic voltammetry and quantified by coulometry with mediated electrochemical oxidation (MEO). Exposure to oxygen had small effects, but compared to anaerobic incubation, decreased by 20% the capacity of HA to reduce the radical ion of 2,2'-Azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS·-), passing from 2.77 ± 0.13 mmole- gHA-1 in HAred to 2.21 ± 0.10 mmole- gHA-1 in HAox. Pseudo-first-order electron transfer kinetic constants were 13.3 ± 1.2 s-1 for HAox and 16.7 ± 1.4 s-1 for HAred. Alterations in the hydrological status of the catotelm have minor effects on the actual in situ availability of organic TEA, but if coupled to intensified biological activity they may result in significant variations of greenhouse gases emissions. [ABSTRACT FROM AUTHOR]

The Cananéia-Iguape estuarine–lagoon complex (São Paulo state, Brazil) is a natural laboratory to study metal binding by humic substances (HS) in subtropical settings. This transitional environment is evolving into a freshwater environment due to water input from the Ribeira River, funneled through the Valo Grande Canal (Iguape). Past mining activities in the Ribeira River basin and maritime traffic are suspected to be potential sources of trace metals in the system. In this study, the trace metal contents of Free Humic Acids (FHA), Bound Humic Acids (BHA), and Fulvic Acids (FA) extracted from sedimentary organic matter were investigated. Moreover, the sources of HS were traced using their stable carbon isotope compositions and C/N ratios. The results suggested a mixed marine–terrestrial source of FHA, BHA, and FA. Copper and Cr were the most abundant trace metals bound to HS. On average, Cu showed concentrations of 176, 115, and 37.9 μg g−1 in FHA, BHA, and FA, respectively, whereas Cr showed average concentrations of 47.4, 86.3, and 43.9 μg g−1 in FHA, BHA, and FA, respectively. Marine FHA showed the highest binding capacity for trace metals, whereas terrestrial FA derived from the decay of mangrove organic matter showed the lowest binding capacity. [ABSTRACT FROM AUTHOR]

Conversion of conventional farming (CF) to organic farming (OF) is claimed to allow a sustainable management of soil resources, but information on changes induced on dissolved organic matter (DOM) are scarce. Among DOM components, dissolved humic substances (DHS) were shown to possess stimulatory effects on plant growth. DHS were isolated from CF and OF soil leacheates collected from soil monolith columns: first in November (bare soils) and then in April and June (bare and planted soils). DHS caused an enhancement of nitrate uptake rates in maize roots and modulated several genes involved in nitrogen acquisition. The DHS from OF soil exerted a stronger biostimulant action on the nitrate uptake system, but the first assimilatory step of nitrate was mainly activated by DHS derived from CF soil. To validate the physiological response of plants to DHS exposure, real-time RT-PCR analyses were performed on those genes most involved in nitrate acquisition, such as ZmNRT2.1 , ZmNRT2.2 , ZmMHA2 (coding for two high-affinity nitrate transporters and a PM H+-proton pump), ZmNADH:NR , ZmNADPH:NR , and ZmNiR (coding for nitrate reductases and nitrite reductase). All tested DHS fractions induced the upregulation of nitrate reductase (NR), and in particular the OF2 DHS stimulated the expression of both tested transcripts encoding for two NR isoforms. Characteristics of DHS varied during the experiment in both OF and CF soils: a decrease of high molecular weight fractions in the OF soil, a general increase in the carboxylic groups content, as well as diverse structural modifications in OF vs. CF soils were observed. These changes were accelerated in planted soils. Similarity of chemical properties of DHS with the more easily obtainable water-soluble humic substance extracted from peat (WEHS) and the correspondence of their biostimulant actions confirm the validity of studies which employ WEHS as an easily available source of DHS to investigate biostimulant actions on agricultural crops. [ABSTRACT FROM AUTHOR]

The ability of the simultaneously extracted metals/acid volatile sulfides (∑SEM/AVS) index to ascertain environmental risk from potentially toxic elements in calcareous saltmarsh soils was tested using structural equation modeling. This technique allows the detection of both direct and indirect relationships among AVS, SEM, and other soil variables, representing results in a graphical view. The dataset included 90 soil samples from 21 different sites belonging to 6 different saltmarshes and featured a wide range of soil chemicophysical properties. Variables included in the a priori model were hydroperiod, pH, soil redox potential, labile organic carbon, carbonates, total iron, and total amount of potentially toxic elements (PTEs). The best optimized model pointed out the main soil properties that affect AVS accumulation and SEM speciation in these soils. Effect plots of AVS and SEM calculated with the partial linear mixed‐effects models included in the piecewise structural equation modeling showed a significant and positive influence of pH and carbonates on AVS and a highly significant effect of carbonates and labile organic carbon on SEM. Single SEM components were also considered separately, to define the potential contributions of labile organic carbon or carbonates as alternative binding phases. Simultaneously extracted Cu, Ni, and Zn were preferentially bound to carbonates, followed by labile organic carbon, whereas Pb and Cd were easily bound to labile organic carbon. Environ Toxicol Chem 2019;38:2688–2697. © 2019 SETAC [ABSTRACT FROM AUTHOR]

Monitoring of biogenic sulfide is important because acid volatile sulfides (AVS) represent a reactive pool responsible for immobilization of toxic metals. We propose a new sulfide paper sensor method for semiquantitative determination of AVS in which developed color is compared to a reference chart. The method was validated against the ion‐selective microelectrode and the purge‐and‐trap methods. For fieldwork, readings should fall within 1 to 10 μmoles S2–. Considering that the volume of soil used ranged between 1 and 16 cm3, the corresponding soil sulfides concentration range spans from 0.06 to 10 mmoles S2– cm−3. The sulfide paper sensor method is highly suitable for field screening and has sensitivity levels comparable to laboratory methods. Environ Toxicol Chem 2018;37:3025–3031. © 2018 SETAC [ABSTRACT FROM AUTHOR]

Born in Trento (Italy, 2003) for the purpose of standardising vocabulary and units of humus form classification, after publishing a first synthetic classification e-book (Zanella et al. 2011) they do not cover all site conditions in the European area. Although having basic concepts and general lines, the European (and North American, Canadian, the Humus group decided to use its classification for handling global change (Zanella and Ascher-Jenull 2018). The process is detailed in many scientific articles published in three Special Issues (Humusica 1, 2 and 3) of the journal Applied Soil Ecology. Conceptually, the whole of Humusica answers three crucial questions: A) What is soil? Soil is a biological ecosystem. It recycles dead structures and implements mineral material, furnishing more or less re-elaborated organic, mineral and organic-mineral elements to support living organisms. Article chapters: 1. Essential vocabulary; 2. Soil covers all the Earth's surfaces (soil as the seat of processes of organic matter storage and recycling); 3. Soil may be involved in the process of natural evolution (through organisms' process of recycling biomass after death). B) If soil has a biogenic essence, how should it be classified to serve such managerial purposes as landscape exploitation or protection? A useful classification of soil should consider and propose useful references to biologically discriminate soil features. Article chapters: 4. Soil corresponds to a biogenic structure; 5. TerrHum, an App for classifying forest humipedons worldwide (a first attempt to use a smartphone as a field manual for humus form classification). C) How can this soil classification be used for handling the current global change? Using the collected knowledge about the biodiversity and functioning of natural (or semi-natural) soil for reconstructing the lost biodiversity/functioning of heavily exploited or degraded soils. Article chapters: 6. Agricultural soils correspond to simplified natural soils (comparison between natural and agricultural soils); 7. Organic waste and agricultural soils; 8. Is traditional agriculture economically sustainable? Comparing past traditional farm practices (in 1947) and contemporary intensive farm practices in the Venice province of Italy. [ABSTRACT FROM AUTHOR]

Iron (Fe) sources available for plants in the rhizospheric solution are mainly a mixture of complexes between Fe and organic ligands, including phytosiderophores (PS) and water-extractable humic substances (WEHS). In comparison with the other Fe sources, Fe-WEHS are more efficiently used by plants, and experimental evidences show that Fe translocation contributes to this better response. On the other hand, very little is known on the mechanisms involved in Fe allocation in leaves. In this work, physiological and molecular processes involved in Fe distribution in leaves of Fe-deficient Cucumis sativus supplied with Fe-PS or Fe-WEHS up to 5 days were studied combining different techniques, such as radiochemical experiments, synchrotron micro X-ray fluorescence, real-time reverse transcription polymerase chain reaction and in situ hybridization. In Fe-WEHS-fed plants, Fe was rapidly (1 day) allocated into the leaf veins, and after 5 days, Fe was completely transferred into interveinal cells; moreover, the amount of accumulated Fe was much higher than with Fe-PS. This redistribution in Fe-WEHS plants was associated with an upregulation of genes encoding a ferricIII-chelate reductase (FRO), a Fe2+ transporter (IRT1) and a natural resistance-associated macrophage protein (NRAMP). The localization of FRO and IRT1 transcripts next to the midveins, beside that of NRAMP in the interveinal area, may suggest a rapid and efficient response induced by the presence of Fe-WEHS in the extra-radical solution for the allocation in leaves of high amounts of Fe. In conclusion, Fe is more efficiently used when chelated to WEHS than PS and seems to involve Fe distribution and gene regulation of Fe acquisition mechanisms operating in leaves. [ABSTRACT FROM AUTHOR]

A technology for remediation of mine tailings, based on air oxidation of added Fe(II) in solution, was tested by chemical extraction and growing pea (Pisum sativum) plants in a greenhouse experiment. Tailings, from a mine site (Cave del Predil, Italy) with high content of Pb and Zn, were saturated with a 0.5M FeSO4 solution and then air-dried. The acidity released by Fe(II) oxidation was successively neutralized by Ca(OH)2. This treatment was repeated 6 times. Cd, Cu, Ni, Mn, Pb and Zn mobility was assessed by Ca(NO3)2 extraction, and their bio-available fraction either by DTPA-extraction or by plant test. Mobility of Cd, Pb and Zn decreased at the end of 6 cycles by 48, 66 and 67%, respectively, whereas Cu, Mn and Ni were below detection limits. In treated mining tailings, DTPA-extractable Cu, Pb and Zn after 6 cycles of treatment showed a marked decrease of 50, 65 and 38%, respectively. Conversely, extractable Mn and Ni, although present at very low concentrations, slightly increased their bioavailability, and that of Cd did not change significantly. Pea dry matter yield increased significantly after 4 and 6 treatment cycles. Metal concentration in plant tissue at the end of 6 cycles showed a decrease for Cd (53%), Cu (9%), Mn (8%), Pb (35%) and Zn (26%), but a slight increase for Ni. [ABSTRACT FROM AUTHOR]

In membrane treatment of wastewater containing proteins, humic acid influences the rate and extent of fouling. Cations may increase the tendency of foulants to precipitate due to the changes in intermolecular electrostatic interactions. In this paper, we investigated the effect of cations, including ionic charge and size of hydrated ion, on ultrafiltration of the solutions containing the mixture of HA and bovine serum albumin (BSA). All experiments were carried out in an Amicon batch stirred cell using Amicon XM50, XM300, YM 100 ultrafiltration membranes with molecular weight cut-offs of 50 kDa, 300 kDa and 100 kDa, respectively, and Sartorius microfiltration membranes with a nominal pore size of 0.2 μm. Humic substances were extracted from a commercial sample of sphagnum peat from Northern Ireland (Bulrush). In the presence of Ba2+ cations, the HA rejection in the solutions containing HA and BSA was higher compared to the solutions containing Na+ cations. Unlike monovalent cations, divalent cations interact specifically with natural organic matter (NOM) and form metal humic complexes. The binding of divalent cations with natural organic matter is responsible for the development of a dense layer on the membrane surface. Metal cations may also act as a bridge between humic acid and protein. These phenomena result in a higher deposition of substances on the membrane surface leading to lower flux and higher rejection in the presence of divalent metal cations. In addition to the charge, the size of cation plays a role in the deposition process. The solutions containing MgCl2·6H2O are characterizing by higher flux and lower rejection compared to the solution containing BaCl2·2H2O at all ultrafiltration membranes. This phenomenon may be attributed to the size of Mg2+ and Ba2+ ions. [ABSTRACT FROM AUTHOR]

Climate change has strong impacts on soil conservation and agricultural productivity, with severe consequences on smallholders in developing countries, but virtually no research has been carried out so far on this issue. Therefore, it is necessary to foster the implementation of participatory projects to help communities deal with new difficulties. Sustainable soil management can reduce and even reverse land degradation, helping farmers to adapt to climate change effects. Progress toward sustainability cannot be implemented in small rural communities regardless of local knowledge, which can be addressed using participatory techniques. To this purpose the choice and use of indicators is essential to carry out correct assessments of soil vulnerability integrating local and technical knowledge. The purpose of this review was to study how the problem of building a set of integrated indicators to assess soil quality has been addressed so far and which participatory techniques have been more successfully employed, analyzing studies carried out in rural communities of developing countries. We found out that there is a lack of participated studies dealing with environmental issues. Those that do so address them only indirectly, being centered on present agricultural problems. The studies rarely feature a collaboration with social science experts, consequently the use of participatory techniques lacks protocols and a standardized nomenclature to help in the transfer and generalization of experiences. Women are rarely involved and nearly exclusively in African countries: this could be related to social and cultural conditions, but needs more attention. Different aspects need to be improved to help the implementation of a successful approach in future projects. This review provides a tool to facilitate future interdisciplinary research on integration of local and scientific knowledge and will help to devise more successful strategies to tackle the challenges posed by climate change to smallholders in developing countries. [ABSTRACT FROM AUTHOR]

The "Soil Continuum Model" questions the occurrence of any independent natural process of secondary synthesis that generates compounds structurally distinct from plant or microbial metabolites. This review shows that a vast volume of interdisciplinary scientific evidence supports the formation of relevant non-pre-existing complex molecules exhibiting various types of structures. These molecules form during degradation and decay of biological cell components. The spontaneous abiotic and enzymatically catalysed reactions of components of organic residues and of their oxidative decomposition products suggested by state-of-the-art studies are indeed those proposed by most of the classical descriptions of humification. The review also highlights the chemically active role of pedofauna, explaining why the apparently harsh conditions of alkaline extraction of HS cannot be considered un-natural. Many insects and larvae feeding on foliage of plants with a high content of tannins have a midgut pH above 9. Albeit, reducing conditions are often maintained to avoid oxidation, peroxidases are active in the intestinal tract and pass on to feces. Polyphenols are then immediately enzymatically oxidized to their reactive quinone form, once feces are excreted and exposed to oxygen. Implications of our current knowledge on the reactivity of plant components in soil are discussed in relation with the present state of the art research on humic substances. Contrary to claims by the "Soil Continuum Model" theory, complimentary modern approaches need to be used to understand the complexity of soil organic matter. • Secondary synthesis of humic substances does not require energy investments. • Non pre-existing complex molecules are produced by phenoloxidases and peroxidase. • Strongly alkaline conditions are present in the mid-gut of pedofauna. • Large molecular weight HS are theoretically possible. • All current, different but complementary, approaches need to be maintained, [ABSTRACT FROM AUTHOR]

An obituary for soil scientist David Jenkinson is presented.

Abstract: The aim of this study was to measure and compare methane oxidation rates of arable and grassland soils that received 7.5tha−1 y−1 of noncontaminated aerobically treated sewage sludge for ten years. Arable soils showed generally lower methane oxidation rates (from 6 to 15∗10−3 h−1) than grassland soils (from 26 to 33∗103 h−1). Oxidation rate constants (k) of soils amended with sewage sludge were remarkably close to their respective untreated controls, but a soil, that had received a tenfold sewage sludge application (i.e. 75tha−1 y−1), showed a statistically significantly higher k-value. Laboratory addition of up to 1000mgPbg−1 soil to this soil did not cause any significant change in methane oxidation, but caused a decrease from 13.9 to 10.9×10−3 h−1 in the control soil. Addition of Zn was much more toxic than Pb, with a significant decrease at 300μgg−1 soil rate and an almost complete inhibition at 1500μgg−1 soil rate. Higher resistance was evident of sewage sludge treated soil in comparison to control soil, for both biomass C and CH4 oxidation activity. [Copyright &y& Elsevier]

Abstract: Prions, are proteinaceous particles recognized as the agents of a class of neurodegenerative disorders, called transmissible spongiform encephalopathies (TSE), or prion diseases. Epidemiological data suggest that TSE-contaminated environments may serve as source of infectivity, but there is no information about adsorption of prions onto soil. We carried out experiments by mixing, healthy, or scrapie-infected hamster brains homogenates with three types of soil suspended in different buffers: (i) two saline buffers, i.e., phosphate buffer solution (PBS) and CaCl2 solution; (ii) a mix of nondenaturing detergents, i.e., Triton X-100 and sodium deoxycholate (DOC) solution; (iii) a non-ionic detergent, i.e., lauryl maltoside; (iv) two anionic detergents, i.e., Sarkosyl or sodium dodecyl sulphate (SDS); and (v) a chaotropic agent, i.e., urea. The unbound prion proteins were detected in the supernatants (after centrifugation of soil suspension) by Western blotting. Results clearly demonstrate that both the no infectious (PrPC) and infectious (PrPSc) forms are adsorbed by all soils. Only 1% sodium dodecylsulphate (SDS) partially impeded the association of PrPC, but not that of PrPSc with the sandy loam soil. Agents with different interacting properties towards hydrophilic and/or hydrophobic domains failed to extract PrPSc from sediments of soil–brain homogenate mixtures. The strong interaction of PrPSc with soil favors the accumulation of prions in soils, especially if amended with prion-containing organic fertilizers and/or whenever TSE-affected animal carcasses, placenta, and excreta in general are buried or laid at the soil surface. [Copyright &y& Elsevier]

Terms and concepts have been defined in Humusica 1, article 1 and the functioning of humus systems has been discussed in Humusica 1, article 2. Here a short overview of the matter, showing humus systems in their environment, is provided for beginners, before making field investigations. The present work is intended as a part of the field manual (HUMUSICA 1 and 2), an illustrated, easy-to-use application tool for humus systems classification, helpful even for not (yet) expert pedologists. The present article gives also a fast look at the classification, sharing Terrestrial, Histic, Aqueous and Para humus systems, every group being defined by its characteristics set in synthetic tables, and suggests a step-by-step approach allowing everyone to classify and investigate humus systems and forms. [ABSTRACT FROM AUTHOR]

The article is structured in six sections. A first portion is dedicated to the state of the art concerning climatic change and agriculture. Internet available IPCC maps and cartographic documents made by scientific Centres of research were used for illustrating forecasted climatic changes. In Sections 2 and 3 , bibliographic evidences were collected for supporting a vegetation and soil co-evolution theory. Humus, soil and vegetation systems are presented at planet level in many synthetic maps. In Sections 4 , 5 and 6 the authors discussed the human influence on the soil evolution during the Anthropocene. It appears that humans detected and used the Mull humus systems all over planet Earth for crop production and pasture. Human pressure impoverished these humus systems, which tend to evolve toward Amphi or Moder systems, losing their natural biostructure and carbon content. [ABSTRACT FROM AUTHOR]

Land application of sewage sludge (SS) is a convenient way of disposal compared to incineration or landfill, but can result in accumulation of potentially toxic elements (PTE) in agricultural soils. The environmental risk associated with PTE accumulation in soils that received several SS applications depends mainly on soil pH and SS treatments. We studied the effects of addition to soil of SS treated and untreated with FeCl 3 on the biological availability of Zn, Ni, Cd and Cu to oilseed rape ( Brassica napus ). The plants were grown on an acid and a neutral soil in a greenhouse incubation experiment. The following treatments were carried out: (i) unamended control soil, (ii) sewage sludge amended soils kept bare throughout the experiment and (iii) sewage sludge amended soil planted with oilseed rape. Amended soils received either untreated SS or FeCl 3 treated SS at a rate equivalent to 75 t d.w. ha −1 y −1 . Plant growth was enhanced by addition of both untreated SS and FeCl 3 treated SS, but the latter produced a lower shoot dry matter than untreated SS, particularly in the acid soil. Evaluation of biological availability of PTE was performed by three different methods: plant shoot analysis, single DTPA-extraction, and sequential fractionation procedure (SEP) in soil. After 50 days, accumulation of PTE was considerably larger in plant shoots grown on the acid soil and amended with FeCl 3 treated sludge. Conversely, the FeCl 3 treated SS reduced Cd, Ni and Zn accumulation in shoots in the neutral soil in comparison to untreated SS. Copper was generally unaffected by SS treatment in both soils. Plants significantly decreased the DTPA-extractability of Cd, Ni and Zn in both soils that received FeCl 3 treated SS, but they did not change it in soils that received untreated SS. These different behaviors may be explained by the different mechanism involved in metals stabilization in the two soils: adsorption on Fe and Mn oxides in the neutral soil, precipitation and organic complexation in the acid soil. The chemical flocculation treatment of waste water with FeCl 3 and addition to soils reduces PTE availability in neutral soils amended with SS, but markedly increases their solubility and bio-availability in acid soils. Therefore, the application of SS obtained from flocculation with FeCl 3 should be restricted to neutral or calcareous soils. [ABSTRACT FROM AUTHOR]

Abstract: The persistence of prions, the causative agents of transmissible spongiform encephalopathies, in soil constitutes an environmental concern and substantial challenge. Experiments and theoretical modeling indicate that a particular class of natural polyanions diffused in soils and waters, generally referred to as humic substances (HSs), can participate in the adsorption of prions in soil in a non-specific way, mostly driven by electrostatic interactions and hydrogen bond networks among humic acid molecules and exposed polar protein residues. Adsorption of HSs on clay surface strongly raises the adsorption capacity vs proteins suggesting new experiments in order to verify if this raises or lowers the prion infectivity. [Copyright &y& Elsevier]

Background: Sclerotinia sclerotiorum (Lib.) de Bary cause a deleterious disease on sunflower plants. Oxalic acid is the main pathogenicity factor of S. sclerotiorum . Two dimensional gel electrophoresis and mass spectrometry have been used in several studies to investigate molecular changes that occur in the plants in response to S. sclerotiorum infection. Comparing responses of resistant and susceptible lines upon pathogen infection provided novel information regarding defense mechanisms against this necrotrophic pathogen., Objectives: The present study reports proteome changes of partially resistant and susceptible sunflower lines under pathogen's culture filtrate treatment, resulting in the characterization of up- and down- regulated proteins., Material and Methods: Sunflower partially resistant and susceptible lines with two true leaves were exposed to fungus culture filtrate. The stems of treated and untreated plants were sampled at 24, 48 and 72 hours after treatment for two-dimensional electrophoresis. Twenty spots showed more than 1.5-fold change in abundance were subjected to MALDI/TOF-TOF MS for further analysis., Results: The identified proteins were categorized into several classes including carbohydrate and energy metabolism (25%), cellular metabolic process (15%), stress response (15%), plant cell wall biogenesis (10%), photosynthesis (10%), protein metabolism (10%), unknown function (10%) and redox homeostasis (5%)., Conclusions: Our proteomic investigation demonstrates an increase in the expression of proteins only in partially resistant line, such as proteins involved in carbohydrate metabolism and plant defense responses (malate dehydrogenase and peroxidase), metabolic process (adenosine kinase), regulating cell redox homeostasis (disulfide isomerase) and lignin biosynthetic process (laccase). Moreover, the expression of pyrroline-5-carboxylate reductase, involved in proline biosynthesis, was significantly changed in both sunflower lines in response to pathogen culture filtrate. Proteins which were only up-regulated in the partially resistant lines might have a significant role in mediating the defense against Sclerotinia and could be considered for enhancing resistance against this devastating pathogen., (Copyright: © 2021 The Author(s); Published by Iranian Journal of Biotechnology.)