Plant Organic Matter Research Articles

Natural and anthropogenically driven change of organic carbon burial rate in two alpine lakes from the southeastern margin of the Tibetan Plateau

The rate of organic carbon (OC) burial in lakes depends considerably on natural and anthropogenic factors. Delineating how and to what extent potential drivers shape a lake’s OC burial rate is crucial for anticipating OC sequestration under future environmental change scenarios. Alpine lakes provide valuable opportunities for studying the influence of climate warming and atmospheric nitrogen (N) deposition on OC burial in lakes, owing to the lack of human activities in their catchments; however, this aspect has not been sufficiently documented. Here, the OC burial rate was reconstructed in two alpine lakes (Heihai and Jiren) from the southeastern margin of the Tibetan Plateau over the past ∼ 160 years, and the associated drivers were identified by resolving the temporal trends in organic matter (OM) input from specific sources to lake sediments via paleolimnological methods. The results demonstrated a consistently low OC burial rate (6.21–10.86 g m−2 yr−1) in Lake Heihai. The low hydrogen index (HI), moderate Paq, and high long-chain n-alkane flux revealed that submerged macrophytes and terrestrial plants are major contributors to the sequestrated OC. The notable decrease in the OC burial rate after 1980 was hypothesized to be caused by regional climate warming during this period because a greater export of terrestrial materials under such a climate can inhibit light penetration, diminishing submerged macrophyte productivity and OM input. In contrast, the synchronous input of higher amounts of terrestrial plant OM was largely degraded owing to the increased water temperature and the intensification of water column stratification. In Lake Jiren, a notably high OC burial rate (13.82–46.75g m−2 yr−1) was observed. The high HI, Paq, and short-chain n-alkane flux showed that phytoplankton and submerged macrophytes were the major contributors to the sequestrated OC. The two-phase increase in the OC burial rate in this lake, including a slow increase after 1947 and a rapid increase after 1983, might have resulted from strengthening aquatic primary productivity and OM input, driven by anthropogenic intensification of nutrient emissions, especially reactive N, from highly urbanized areas and the subsequent long-term atmospheric transport and deposition of these materials over the lake basin. A comparative analysis of the results between the two lakes suggested that atmospheric N deposition has a stronger influence on the OC burial than climate warming. These drivers affect the OC burial rate by altering aquatic productivity rather than the terrestrial OM input. This study provides a basic for predicting future OC burial scenarios in warmer climates with more intense anthropogenic N emissions.

Recovery of plant nutrients from human excreta and domestic wastewater for reuse in agriculture: a systematic map and evidence platform

BackgroundAchieving a more circular and efficient use of nutrients found in human excreta and domestic (municipal) wastewater is an integral part of mitigating aquatic nutrient pollution and nutrient insecurity. A synthesis of research trends readily available to various stakeholders is much needed. This systematic map collates and summarizes scientific research on technologies that facilitate the recovery and reuse of plant nutrients and organic matter found in human excreta and domestic wastewater. We present evidence in a way that can be navigated easily. We hope this work will help with the uptake and upscaling of new and innovative circular solutions for the recovery and reuse of nutrients.MethodsThe systematic map consists of an extension of two previous related syntheses. Searches were performed in Scopus and Web of Science in English. Records were screened on title and abstract, including consistency checking. Coding and meta-data extraction included bibliographic information, as well as recovery pathways. The evidence from the systematic map is embedded in an online evidence platform that, in an interactive manner, allows stakeholders to visualize and explore the systematic map findings, including knowledge gaps and clusters.ResultsThe evidence base includes a total of 10 950 articles describing 11 489 recovery pathways. Most of the evidence base is about recovery technologies (41.9%) and the reuse of recovered products in agriculture (53.4%). A small proportion of the evidence base focuses on the characteristics of recovered products (4.0%) and user acceptance and perceptions of nutrient recovery and reuse (0.7%).ConclusionsMost studies we mapped focused on nutrient recovery from ‘conventional’ systems, that is, from centralized sewer and wastewater treatment systems that produce biosolids and a treated effluent. While we also found substantial research on nutrient recovery from source-separated urine, and to some extent also on nutrient recovery from source-separated excreta (notably blackwater), the body of research on nutrient recovery from source-separated feces was relatively small. Another knowledge gap is the relative lack of research on the recovery of potassium. More research is also needed on user acceptance of different recovery technologies and recovered products.

A thermal conductivity model for alpine meadow soils on the Tibetan Plateau and validation analysis

Under the background of global warming, natural disasters such as landslides and mudslides are becoming more frequent on the Tibetan Plateau. It is important to study the thermal behavior of alpine meadow soils, which are widely distributed on the Tibetan Plateau due to the high altitude and extreme climate. In this paper, a quantitative mathematical model of thermal conductivity for alpine meadow soils is presented, which successfully describes the influence of plant roots and organic matter on the thermal behavior of alpine meadow soils. A series of thermal conductivity experiments are carried out on thirty alpine meadow soils collected from Nangqian district, located east of Tibetan Plateau, China. The results of the proposed model are compared with the experimental measured data to validate the model efficiency and satisfactory agreement is achieved. Furthermore, Root mean square error (RMSE) and bias are also used to evaluate the performance of the proposed model and other available models. The results of the validation analysis show that the proposed model, with an RMSE of 0.041 W m−1 K−1 and a bias of 0.005 W m−1 K−1, provides reliable and accurate estimated values of thermal conductivity for alpine meadow soils. This study is beneficial for understanding the thermal behaviors of soil-root system on the Tibetan Plateau.

Autumn sunlight promotes aboveground carbon loss in a temperate mixed forest

BackgroundPhotodegradation of plant litter plays a pivotal role in the global carbon (C) cycle. In temperate forest ecosystems, the exposure of plant litter to solar radiation can be significantly altered by changes in autumn phenology and snow cover due to climatic change. How this will affect litter decomposition and nutrient dynamic interacting with forest canopy structure (understorey vs. gaps) is uncertain. In the present study, we conducted a field experiment using leaf litter of early-fall deciduous Betula platyphylla (Asian white birch) and late-fall deciduous Quercus mongolica (Mongolian oak) to explore the effect of change in autumn solar radiation on dynamics of litter decomposition in a gap and understorey of a temperate mixed forest.ResultsExposure to the full-spectrum of not only significantly increased the loss of mass, C, and lignin, but also modified N loss through both immobilization and mineralization during the initial decomposition during autumn canopy opening, irrespective of canopy structure and litter species. These effects were mainly driven by the blue-green spectral region of sunlight. Short-term photodegradation by autumn solar radiation had a positive legacy effect on the later decomposition particularly in the forest gap, increasing mass loss by 16% and 19% for Asian white birch and Mongolia oak, respectively.ConclusionsOur results suggest that earlier autumn leaf-fall phenology and/or later snow cover due to land-use or climate change would increase the exposure of plant organic matter to solar radiation, and accelerate ecosystem processes, C and nutrient cycling in temperate forest ecosystems. The study provides a reference for predictive research on carbon cycling under the background of global climate change.

Different responses of oxygen and hydrogen isotopes in leaf and tree-ring organic matter to lethal soil drought.

The oxygen and hydrogen isotopic composition (δ18O, δ2H) of plant tissues are key tools for the reconstruction of hydrological and plant physiological processes and may therefore be used to disentangle the reasons for tree mortality. However, how both elements respond to soil drought conditions before death has rarely been investigated. To test this, we performed a greenhouse study and determined predisposing fertilization and lethal soil drought effects on δ18O and δ2H values of organic matter in leaves and tree rings of living and dead saplings of five European tree species. For mechanistic insights, we additionally measured isotopic (i.e. δ18O and δ2H values of leaf and twig water), physiological (i.e. leaf water potential and gas-exchange) and metabolic traits (i.e. leaf and stem non-structural carbohydrate concentration, carbon-to-nitrogen ratios). Across all species, lethal soil drought generally caused a homogenous 2H-enrichment in leaf and tree-ring organic matter, but a low and heterogenous δ18O response in the same tissues. Unlike δ18O values, δ2H values of tree-ring organic matter were correlated with those of leaf and twig water and with plant physiological traits across treatments and species. The 2H-enrichment in plant organic matter also went along with a decrease in stem starch concentrations under soil drought compared with well-watered conditions. In contrast, the predisposing fertilization had generally no significant effect on any tested isotopic, physiological and metabolic traits. We propose that the 2H-enrichment in the dead trees is related to (i) the plant water isotopic composition, (ii) metabolic processes shaping leaf non-structural carbohydrates, (iii) the use of carbon reserves for growth and (iv) species-specific physiological adjustments. The homogenous stress imprint on δ2H but not on δ18O suggests that the former could be used as a proxy to reconstruct soil droughts and underlying processes of tree mortality.

APPLICATION OF MICROBIOMORPHIC AND TOTAL PHOSPHORUS ANALYSES TO THE ARCHAEOLOGICAL STUDY OF THE SREDNY ZELENCHUK TEMPLE, NIZHNY ARKHYZ HILLFORT

The article presents the results of the first geoarchaeological study of the materials of Christian burials identified in the interior of the Middle Zelenchuk temple of the 10th century in the Nizhne-Arkhyz ancient settlement (Republic of Karachay-Cherkessia). The results of microbiomorphic (phytolith) and total phosphorus content analyses allowed us to reveal previously unknown features of the funeral rites of the multicultural and multi-ethnic Christian population of one of the largest cities of the North Caucasus in the Middle Ages. The differences in funerary practices between the 11th and 13th centuries became evident when studying even a small group of funerary complexes in which people of the same social group – representatives of the social elite of Western Alania – were buried. The geoarchaeological study showed an abundance of plant and animal organic matter in the burials. The complex analysis of archaeological materials and data obtained during the microbiomorphic study allowed us to conclude that members of the urban Christian community had several burial traditions: in stone boxes (tombs), in wooden frames, and a mixed ritual when a wooden structure was placed in a stone box. The presence of wooden bark particles in the burials seems to be related not so much to the material from which the burial structures were made as to the presence in the graves of bark or bast objects (bast caskets or boxes, birch bark amulets, toys, etc.). The tradition known from pagan Alanian burials of placing the head of the deceased on a “stone cushion” (more typical for male burials) was preserved in early Christian burials. In one of the four women’s graves studied, the analysis showed the presence of a “hay pillow.” Probably, before the burial, a ritual of washing the deceased was performed, as evidenced by the presence of diatoms and sponge spicules in the samples.

Thermo-Mechanical, Structural, and Biodegradability Properties of Water Hyacinth and Sheep Wool Fiber Reinforced Hybrid Polypropylene Composites

Hybrid fiber reinforcements can incorporate a wider array of qualities than single fiber reinforcement. Instead of synthetic fibers, applying plant and animal-based organic materials as reinforcement in polymer matrix offers certain benefits, such as low price, greater availability, and better biodegradability. In the present study, water hyacinth fiber and sheep wool fiber reinforced polypropylene hybrid composites were fabricated at three different (5, 10, and 15 wt.%) fiber loading. The effect of fiber loading on thermo-mechanical, structural, and biodegradability properties was subsequently investigated. The manufacturing process of the composite material was carried out with utmost consideration for biodegradability, since polypropylene, the primary constituent, is not inherently biodegradable. The insertion of fibers into the polypropylene matrix showed variance in properties of different aspects. The tensile strength of the composites displayed a downward trajectory (from 25 to 10 MPa) with a 15% increase in fiber loading due to voids, and fiber dispersion, while impact strength exhibited an opposite trend (from 25 to 32 J/m). Except for hardness, all the mechanical properties degraded slightly after the employment of the reinforcement. Fourier transform infrared spectroscopic analysis revealed the movement of typical peaks and the appearance of new peaks demonstrating the bonding between the fiber and the matrix. Thermogravimetric analysis showed that the thermal degradation temperature of the composites improved at maximum fiber loading. On the other hand, the goal of achieving biodegradability has been succeeded by the implementation of a combination of plant and animal-based fibers as biodegradability of the manufactured composites thrives with increasing fiber content for the presence of cellulosic bonds, as evident from the FTIR spectrum. Even though some properties of the hybrid composite declined slightly with increasing fiber loading, the other characteristics, including service temperature and biodegradability experienced a prospective advancement. Hence, the 15% fiber-loaded composite was found to be a potential candidate in terms of slightly high temperature and environment-friendly applications.

Effects of Biochar and Municipal Solid Waste Compost on Soil Physical Quality and Productivity Index Under Sorghum Cultivation Irrigated with Saline Water

ABSTRACT Amending soil with different materials is gaining acceptance as an effective and inexpensive technique for reclamation of salt-affected soils. The main idea of this study was to investigate the effects of biochar, compost of municipal solid waste and different water salinities level on soil physical quality (SDexter) and soil productivity index (SPI). The treatments were as followed: Control: Soil without biochar or compost and irrigated with tap water, S1: Soil without biochar or compost and irrigated with saline water (EC = 4.5 dS m−1), S2: Soil without biochar or compost and irrigated with saline water (EC = 9 dS m−1), B: Soil amended with 1.5%w/w biochar and irrigated with tap water, B+S1: Soil amended with 1.5%w/w biochar and irrigated with saline water (EC = 4.5 dS m−1), B+S2: Soil amended with 1.5%w/w biochar and irrigated with saline water (EC = 9 dS m−1), C: Soil amended with 1.5%w/w compost and irrigated with tap water, C+S1: Soil amended with 1.5%w/w compost and irrigated with saline water (EC = 4.5 dS m−1), C+S2: Soil amended with 1.5%w/w compost and irrigated with saline water (EC = 9 dS m−1). Soil water characteristic curve (SWCC), Field capacity (FC), Plant wilting point (PWP), Plant available water (PAW), Dexter’s index of soil physical quality (SDexter) and SPI were examined in a greenhouse experiment. The SPI was calculated by integrating the effects of six soil quality indices: plant available water, organic matter (OM), Electrical conductivity (EC), pH, Bulk density (BD) and Root weighting factor (RF) for all treatments were calculated. The results showed that the B treatment had a slightly higher effect on SWCC. The applied B and C treatments caused insignificant increase in PAW relative to the control. In addition, application of biochar or compost to soil significantly increased the SDexter. The application of C treatment had insignificantly higher value of SDexter compared to other treatments. Compared with the control, SPI was significantly higher for the B and C treatments. Overall, the application of biochar/compost minimized the destructive effects of saline irrigation water and improved the quality of the salt-affected fine-textured soil.

Fungal biodeterioration and preservation of cultural heritage, artwork, and historical artifacts: extremophily and adaptation.

SUMMARYFungi are ubiquitous and important biosphere inhabitants, and their abilities to decompose, degrade, and otherwise transform a massive range of organic and inorganic substances, including plant organic matter, rocks, and minerals, underpin their major significance as biodeteriogens in the built environment and of cultural heritage. Fungi are often the most obvious agents of cultural heritage biodeterioration with effects ranging from discoloration, staining, and biofouling to destruction of building components, historical artifacts, and artwork. Sporulation, morphological adaptations, and the explorative penetrative lifestyle of filamentous fungi enable efficient dispersal and colonization of solid substrates, while many species are able to withstand environmental stress factors such as desiccation, ultra-violet radiation, salinity, and potentially toxic organic and inorganic substances. Many can grow under nutrient-limited conditions, and many produce resistant cell forms that can survive through long periods of adverse conditions. The fungal lifestyle and chemoorganotrophic metabolism therefore enable adaptation and success in the frequently encountered extremophilic conditions that are associated with indoor and outdoor cultural heritage. Apart from free-living fungi, lichens are a fungal growth form and ubiquitous pioneer colonizers and biodeteriogens of outdoor materials, especially stone- and mineral-based building components. This article surveys the roles and significance of fungi in the biodeterioration of cultural heritage, with reference to the mechanisms involved and in relation to the range of substances encountered, as well as the methods by which fungal biodeterioration can be assessed and combated, and how certain fungal processes may be utilized in bioprotection.

Carbon pools in the steppes of the Republic of Tyva (Russia)

The purpose of this work is to determine the reserves of carbon of plant matter (CPM) and carbon of soil organic matter (CSОM) in steppe ecosystems and agrocenoses of the Republic of Tuva, to assess the carbon cycle over the past 100 years due to changes in land use. The data obtained by us showed that in the territory of Tuva, until 1910, undisturbed vegetation was characterized by a natural mode of use. The replacement of natural ecosystems in agrocenoses since 1950 has led to a change in the carbon budget. Steppe ecosystems suffered the greatest carbon losses. The current supply of plant organic matter (POM) is 2–3 times less than the past. The carbon pool is decreasing from the forest steppe to the dry steppes. As in the Krasnoyarsk Territory and Khakassia, in Tuva a large proportion of carbon in agrocenoses is contained in soil organic matter. Since 1990 the reduction of arable land and the restoration of natural cover has begun. Currently, there is an accumulation of plant organic matter (POM) and a slow increase in the stock of soil organic matter (SОM), although at the local level, but it is the most effective way to mitigate the effects of the greenhouse effect.

From rust to riches: phytochemically assisted synthesis of superparamagnetic Fe3O4 nanoparticles with Au for SERS sensing

This work introduces a synthesis of SERS-active AuFe3O4 using organic plant matter as a substitute for typical ecotoxic reagents. The nanoparticles demonstrate high SERS enhancement with a simple liquid-phase sample of an organothiol.

Accelerating peat fiber decomposition by bacteria Pseudomonas taiwanensis and its impact on the physical properties and shear strength of fibrous peat in Palangkaraya

Peat soil is formed through the accumulation of undecomposed plant organic matter, resulting in a high fiber content that leads to poor physical properties and low shear strength. Consequently, peat soil is identified as problematic and detrimental in infrastructure construction. One proposed method to improve its physical properties and enhance shear strength is biological soil stabilization through biotechnology, with bioaugmentation as an environmentally friendly alternative. The objective of this research is to accelerating the decomposition of peat fiber by Pseudomonas taiwanensis bacteria, thereby accelerating soil compaction and improving its physical properties and shear strength. The subject of this research is fibrous peat soil in Bereng Bengkel Village, Palangkaraya, Central Kalimantan. From the experimental results, it was found that the addition of 15% Pseudomonas taiwanensis bacteria to fibrous peat can significantly improve the physical properties and shear strength. Thus, Pseudomonas taiwanensis bacteria can be used as an environmentally friendly alternative to improve the geotechnical properties of fibrous peat.

Organic Geochemical Evaluation of the Black Shale interbeds Within the Lithological Succession of the Al Aziziyah Formation, NW Libya

The samples under investigation represent the black shale in interbeds within the Al Aziziyah Formation, located in the NW part of Libya and were analysed using geochemical techniques method and a variety of organic geochemical parameters. The aim of this study is to assess the type of organic matter, thermal maturity, and environment of deposition, based on biomarker distributions and Rock-Eval pyrolysis. The Gas chromatograms of the saturated hydrocarbon fractions of the study samples display a smooth high-end member distribution of the n- n-alkanes extending beyond nC34. The sample displayed evidence of biodegradation as suggested by the presence of the loss of some of the lower molecular weight n-alkanes. The predominance of high molecular weight n-alkane in the study sample suggests a significant input of higher land plant organic matter into these sediments. Geochemical (Rock-Eval, Tmax. values ranging from 416-4390C typical of immature range). Another related feature of these rocks extracted is the presence of a high relative abundance of gammacerane, indicating an anoxic marine hypersaline source depositional environment. The relatively high abundance of common land-plant-derived biomarkers, such as oleananes, is a clear indication of major terrigenous input to the source of these extractable organic matters. The high abundance of C24 tetracyclic terpanes could be associated with higher land-plant, algae, or microbial sources, thereby suggesting a mixed source input. TOC valued < 0.5 wt.%, in the analyzed samples can be considered as a poor source rock generative potential. Based on this study, it can be said that the interbedded shales of the Al Aziziyah Formation seem to have received substantial amounts of land-derived organic matter that has been transported into an open marine subtidal depositional setting had prevailed and was deposited in a photosynthetic-organisms dominated environment (thereby suggesting a mixed source input).

Interdisciplinary research of ash heap sediment near Stepnoye settlement (Chelyabinsk Oblast)

An ash heap is defined as a specific object at an archaeological site, usually in the form of a separate hillock containing a layer of finely-dispersed greyish-yellow or ash-coloured soil. The existing assumptions about the formation and functional pur-pose of ash heaps, as special archaeological objects found near the Bronze Age pastoral settlements, have so far been poorly supported by scientific data. At the ash heap near the Sintashta fortified settlement of Stepnoye, Chelyabinsk Oblast, for the first time, large-scale and comprehensive studies were carried out on the structure of these deposits, their granulometric and geo-chemical composition, in combination with the analysis of plant macroremains, paleoparasites, microbiomorphic and palynologi-cal complexes, indicative bacterial groups, and keratinophilic fungi. Judging by the archaeological materials, it is patently obvi-ous that this was a multifunctional object that developed over many centuries and played different roles at different stages. The results of the conducted analyses showed that the 45 cm thick “ash” horizon in the Stepnoye ash heap contains a significant proportion of a fine sand fraction, and not a silty fraction. An increase in the biophilic elements (predominantly calcium, as well as phosphorus and sulphur), accumulated mainly in the organic matter of faunal origin, was noted in the upper bench of the ash layer. However, the high concentration of phytoliths in the “ashy” deposits indicates that the layer was formed mainly as a result of the accumulation of a large amount of plant organic matter. The absence of charcoal and the scarcity of charred macro-remains indicate that the deposited organic material was not burnt but decomposed naturally. The increased content of sapro-trophic bacteria in the “ashy” layer also supports the natural decomposition of an organic matter. The composition of the phyto-lithic and pollen spectrum of the “ashy” horizon is not typical for the steppe of the south of Western Siberia, since it is dominated by a group of mixed herbs with elements of a ruderal flora, and not by cereals. All the data supports the hypothesis that the ash heap is the result of regular practice of cleaning of the floor and interiors of the buildings of the fortified settlement of Stepnoye. This is evidenced by the increase in the number of keratinophilic fungi, which decompose wool and hair and therefore accumu-late in the occupational layer of the structures. Based on the results of the study, the hypotheses that the Stepnoye ash heap is a place of consolidated ash removal or composting of stable manure were rejected.

Chemical characteristics and valuation of sewage sludge from four different wastewater treatment plants.

Sewage sludge contains plant nutrients and organic matter in its composition, making it a potential partial substitute for mineral fertilizers if it meets environmental, agronomic, and sanitary standards. The objective was to evaluate the content of nutrients and heavy metals in the sludge generated in four wastewater treatment stations (WWTPs) in Rio de Janeiro state and assess its potential value and usefulness. The samples of 19 batches from the WTTPs Alegria, Barra da Tijuca, Ilha do Governador, and Sarapuí were analyzed. The WWTPs differ in methods and processes used for treating sewage and sludge. The total contents of C, N, P, K, Ca, Mg, Fe, Al, Na, Co, Mn, As, Ba, Cd, Cr, Cu, Ni, Se, Pb, and Zn were evaluated, as well as the ratio C/N, pH, organic matter content, and electrical conductivity. The grouping of sludge samples was assessed using principal components (PCA) and cluster analysis. The economic valuation of sludge was conducted utilizing the substitute goods method, which compared the sludge's N-P-K contents with the prices of consolidated nutrient sources. All the evaluated sludge batches exhibited concentrations of heavy metals below the limits allowed by Brazilian law, along with high levels of nutrients and organic matter. Considering the chemical characteristics, all evaluated materials showed potential for agricultural use, but it is crucial to evaluate the microbiological characteristics of sludge batches before agriculture application. PCA and cluster analysis demonstrated that sludge samples from the same WWTP clustered close to each other, demonstrating higher similarity among themselves than with samples from other WWTPs. The sludge had an average added value of U$ 88.46 per megagram, considering the total contents of N, P, and K in its composition. Land application of sewage sludge can reduce the need to purchase mineral fertilizers, thereby supporting the feasibility of reusing this material in the agricultural sector.

Enzyme adaptation in Sphagnum peatlands questions the significance of dissolved organic matter in enzyme inhibition

Peatlands store a large proportion of global soil carbon in the form of peat because decomposition of plant organic matter is slow. In Sphagnum-dominated peatlands, dissolved organic matter (DOM) is traditionally considered an important inhibitor of hydrolytic enzymes due to the polyphenolic polymers it contains. Interestingly, the acidic character of the polymers in such DOM has never been tested for its enzyme-inhibitory properties. We raised two principal hypotheses: (1) not only the polyphenolic but also the acidic character of DOM inhibits the activity of extracellular enzymes in Sphagnum-dominated peatlands; (2) environmental, peat-extracted enzymes will show adaptation to their environment.We tested the inhibition of commercial acid phosphatase and cellobiohydrolase, and environmental phosphatase and β-glucosidase by following dissolved substances: (1) polyphenol-free polycarboxylates from Sphagnum cell walls, i.e. sphagnan, (2) environmental DOM (peat-DOM) containing polymers of polyphenolic–polycarboxylate nature, (3) tannic acid (carboxyl-free polyphenolic oligomer) and (4) monomeric phenolic acids.Sphagnan strongly inhibited commercial acid phosphatase, to a similar extent as peat-DOM and more strongly than tannic acid and a polycarboxylate from another moss (Leucobryum glaucum). Monomeric phenolic acids were weak inhibitors. Commercial cellobiohydrolase was only partially inhibited by sphagnan or peat-DOM. Environmental phosphatase and β-glucosidase were consistently slightly inhibited by tannic acid, but not by sphagnan or peat-DOM. Inhibition of commercial phosphatase by sphagnan and peat-DOM was counteracted by a polycation chitosan, indicating the electrostatic nature of carboxylate-mediated inhibition.Our results question the polyphenol-mediated enzyme inhibition in Sphagnum-dominated peatlands as (1) the DOM had a strong inhibitory potential due to its polycarboxylates; nevertheless, (2) the peat microbial communities exhibited enzyme resistance to both polyphenol and polycarboxylate polymers in peat-DOM.

Study of efficient catalytic electrode for hydrogen evolution reaction from seawater based on low tortuosity corn straw cellulose biochar/Mo2C with porous channels

Porosity and channel structure has important effects on the performance of hydrogen evolution reaction (HER) of nanostructured electrocatalysts in acid solution and seawater. Mesopore usually helps to enhance the reaction kinetics and mass transfer, while the macroporous channel structure also affects the electrocatalyst. Traditional graphene materials do not have such structure. Therefore, this paper designs a method to synthesize Mo2C composite nanomaterial in situ on corn straw biochar, inspires by the natural channel structure of conducting water, salt and organic matter in plants. Characteristic characterization shows that the material also has a large number of mesoporous and vertical distribution of large porous channel structure, through the decrease of tortuosity and porosity, ensure the catalyst surface electrolyte transport and hydrogen timely escape, alleviate the process of metal ion precipitation blocking pore channel, so as to improve the rate of hydrogen evolution reaction. The results shows that the overpotential of the catalyst was 48 mV and 251 mV under 10 mA cm−2 acidic electrolyte and simulated seawater electrolyte, respectively. This method provides new ideas for the design of efficient electrocatalysts for seawater decomposition, then the HER performance in alkaline and neutral environments needs to be further explored.

Inactivation of dried cells and biofilms of Listeria monocytogenes by exposure to blue light at different wavelengths and the influence of surface materials.

Antimicrobial blue light (aBL) in the 400-470 nm wavelength range has been reported to kill multiple bacteria. This study assessed its potential for mitigating an important foodborne pathogen, Listeria monocytogenes (Lm), focusing on surface decontamination. Three wavelengths were tested, with gallic acid as a photosensitizing agent (Ps), against dried cells obtained from bacterial suspensions, and biofilms on stainless-steel (SS) coupons. Following aBL exposure, standard microbiological analysis of inoculated coupons was conducted to measure viability. Statistical analysis of variance was performed. Confocal laser scanning microscopy was used to observe the biofilm structures. Within 16 h of exposure at 405 nm, viable Lm dried cells and biofilms were reduced by approx. 3 log CFU/cm2 with doses of 2,672 J/cm2. Application of Ps resulted in an additional 1 log CFU/cm2 at 668 J/cm2, but its effect was not consistent. The highest dose (960 J/cm2) at 420 nm reduced viable counts on the biofilms by 1.9 log CFU/cm2. At 460 nm, after 800 J/cm2, biofilm counts were reduced by 1.6 log CFU/cm2. The effect of material composition on Lm viability was also investigated. Irradiation at 405 nm (668 J/cm2) of cells dried on polystyrene resulted in one of the largest viability reductions (4.0 log CFU/cm2), followed by high-density polyethylene (3.5 log CFU/cm2). Increasing the dose to 4,008 J/cm2 from 405 nm (24 h), improved its efficacy only on SS and polyvinyl chloride. Biofilm micrographs displayed a decrease in biofilm biomass due to the removal of biofilm portions from the surface and a shift from live to dead cells suggesting damage to biofilm cell membranes. These results suggest that aBL is a potential intervention to treat Lm contamination on typical material surfaces used in food production. IMPORTANCE Current cleaning and sanitation programs are often not capable of controlling pathogen biofilms on equipment surfaces, which transmit the bacteria to ready-to-eat foods. The presence of native plant microbiota and organic matter can protect pathogenic bacteria by reducing the efficacy of sanitizers as well as promoting biofilm formation. Post-operation washing and sanitizing of produce contact surfaces might not be adequate in eliminating the presence of pathogens and commensal bacteria. The use of a dynamic and harmless light technology during downtime and close of operation could serve as a useful tool in preventing biofilm formation and persistence. Antimicrobial blue light (aBL) technology has been explored for hospital disinfection with very promising results, but its application to control foodborne pathogens remains relatively limited. The use of aBL could be a complementary strategy to inactivate surfaces in restaurant or supermarket deli settings.

Is the Direct Soil Application of Two-Phase Olive Mill Waste (Alperujo) Compatible with Soil Quality Protection?

In Spain and other Mediterranean countries, significant quantities of semi-solid olive mill waste are generated, which should be preferentially applied to agricultural soils to close nutrient cycles. However, two-phase olive mill waste (termed alperujo in Spanish) is known to pose risks to soil quality and plant production when applied to soil in large quantities. Alperujo has high contents of polyphenol substances, which can inhibit microbial growth and are also phytotoxic in nature. However, when applied in appropriate quantities and following specific methods, it is possible that the practice may not pose any risks, and this requires evaluation. As a waste management option, direct application of alperujo can supply plant nutrients and organic matter to degradation-prone Mediterranean soils. In order to validate this circular economy fertilization and soil protection strategy, an 18-month field experiment was undertaken, applying moderate quantities of alperujo on permanent crop groves throughout the Spanish region of Valencia. Eleven experimental parcels with permanent crops managed by farmers were identified to test two scenarios: a single application of 10 t/ha, and a second application of 10 t/ha after 10 months. Soil chemical parameters were assessed at 0, 6, 10, and 18 months. Soil organic carbon, total Kjeldahl nitrogen, pH, electrical conductivity, nitrates, and polyphenol contents were modified by alperujo application, but these effects were highly transient in nature, with generally no lasting effects after 4–6 months for either application scenario. Also, qualitative evaluations carried out by farmers revealed few effects, although some reductions in erosive processes and improvements in plant vigor were noted. As such, based on the measured parameters, it is concluded that the direct soil application of alperujo olive mill wastes at low application rates did not lead to any lasting detrimental effects on soil quality or compromise the productivity of permanent crops in this Mediterranean region.

Age-Dating of Foliage and Soil Organic Matter: Aligning 228Th:228Ra and 7Be:210Pb Radionuclide Chronometers over Annual to Decadal Time Scales.

The 228Th:228Ra ratios of foliage and organic soil horizons evolve with time following a predictable radioactive decay law and thus provide a new chronometer for absolute age-dating of plant and soil organic matter. Preferential uptake of 228Th (t0.5 = 1.9 years) and 228Ra (t0.5 = 5.9 years) by canopy tree species, ferns, and mosses, drives disequilibrium in the 232Th-228Ra-228Th radioactive decay series within forest vegetation and organic soils. With examples from northeastern USA, we verify a new 228Th:228Ra age model by demonstrating its concordance with the fallout radionuclide chronometer 7Be:210Pb in the 0 to 5-year time frame [R2 = 0.87, RMSE = 0.5 years]. At our locality, canopy tree species assimilate 228Th with a typical initial ratio (228Th:228Ra)0 ∼ 0.3, but in several instances, both deciduous and coniferous tree species show a preference for Th over Ra with (228Th:228Ra)0 exceeding 5. While the 228Th:228Ra system is restricted to organic soil horizons, concordance of 228Th:228Ra with established 7Be:210Pb and 241Am bomb-pulse chronometers establishes a coherent age-dating system of soil organic matter based on three independent chronometers and five particle reactive metals, and spanning 0-200 years in time scale that encompasses both organic and mineral soils to depths of up to 30 cm. Concordance indicates that these metals all follow common processes of organometallic colloid formation and migration and, in conjunction with 14C, may open new opportunities to understand soil pedogenic processes that regulate the storage of carbon and atmospheric metals such as Pb and Hg.