Humic Research Articles

Rejection of heavy metal ions in water by zeolite forward osmosis membrane

Water treatment of heavy metals using zeolite membranes in forward osmosis was demonstrated. A continuous Na-ZSM-5, aluminosilicate zeolite, crystal layer was synthesized on the outer surface of a porous tubular α-alumina support and used as the forward osmosis membrane. The rejection performances and fouling resistances of Na-ZSM-5 membrane were studied. Na-ZSM-5 membrane exhibited a high rejection performance of 99 % for various metal species (As(III), As(V), Se(IV), Se(VI), Cr(VI)). This superior rejection performance was achieved by combining the molecular sieving effect and electrostatic repulsion between the anions and the anionic framework of the zeolite. Na-ZSM-5 membrane exhibited a stable water flux in the presence of model foulants such as sodium alginate, humic acid, bovine serum albumin, and silica particles, suggesting that the membrane had excellent antifouling properties against both organic and inorganic foulants.

Novel integration of dual-modified Zr-MOFs and graphene oxide nanocomposites in polyethersulfone membranes: Enhanced permeability, selectivity, and fouling resistance

Designing and fabricating ultrafiltration membranes that possess relatively high permeability while simultaneously maintaining high rejection and improved antifouling properties continues to be a challenge. In this study, we investigated the integration of novel melamine modified Zr-based metal organic frameworks (Zr-MOFs) with nanosheets of graphene oxide (GO) and sulfonated graphene oxide (SGO). These composite materials were synthesized using the solvothermal process and subsequently coated onto the PES membrane surface using the vacuum-assisted dip-coating method. The stability enhancement of the topmost MOF composite layer adhering to the membrane surface is attributed to hydrogen bonding, π-π stacking, and van der Waals interactions. These effects are augmented by the incorporation of polar functional groups such as hydroxyl, carboxyl, sulfonate, and amine groups. The optimized composite membranes incorporating MOFs exhibit enhanced performance, with a permeability of 80.2 L/m2hbar, achieving a bovine serum albumin (BSA) rejection of ≥97.8 % and a humic acid (HA) rejection of 98.9 %. Moreover, a flux recovery ratio (FRR) of 89.5 %. To investigate the interactions among the incorporated components, molecular dynamics (MD) simulations were employed in a computational study. The simulations validated hydrogen bond formation and reinforced prior studies, demonstrating the potential of Zr-MOF compositions as effective hydrophilic nanoparticles. The overall results indicate a substantial enhancement in membrane performance and underscore the high potential for practical applications.

Co-doped NH2-UiO-66 for fast and effective adsorption of oxytetracycline: Kinetics, thermodynamics and mechanism

Novel type of micro mesoporous materials Co-doped NH2-UiO-66 had been successfully prepared. The properties of the material were understood through a series of characterization. When the dosage of Zr:Co is 2:1, the modified material showed specific surface area of 840.02 m2∙g−1, which is larger than the material without Co. Especially, the material was transformed from microporous NH2-UiO-66 to micro-mesoporous Co-doped NH2-UiO-66 through the adjustment of metal Co. The Co-doped nanocomposite was then applied to the adsorption of oxytetracycline. The effects of initial concentration, pH, humic acid and ionic strength on the adsorption were investigated. It was found that 50 mg∙L−1 oxytetracycline can be effectively adsorbed by Co-doped NH2-UiO-66 in pH 7. Further research showed that adsorption was pseudo-second-order kinetics and fitted Freundlich model with the maximum adsorption capacity 223.7 mg∙g−1. In addition, the adsorption equilibrium time was only 2 h, which is shorter than the adsorption time of most adsorbents. The mechanism of pore adsorption, π-π interaction, hydrogen bonds and electrostatic interactions was deeply discussed. In conclusion, Co-doped NH2-UiO-66 was a fast and effective absorbent for the removal of oxytetracycline in aqueous solution.

Microbial Fertilizing Products Impact on Productivity and Profitability of Organic Strawberry Cultivars

Poland is a major producer of various fruits, including strawberries. As growing consumer awareness of food quality, health, and wellbeing is increasing, farmers are receiving a new market opportunity for organic products of good quality. The integration of microbial solutions into agricultural practices can foster the transition of agricultural farms towards more resilient and sustainable production of quality food. The objective of this study was to assess the influence of novel microbial biopreparations (microbial fertilizing products) containing Bacillus sp., humic acids, and other organic compounds on the economic viability of three strawberry cultivars (‘Honeoye’, ‘Vibrant’, and ‘Rumba’) under organic farming conditions. This study was conducted in 2021 as a field experiment. Irrigated and non-irrigated strawberries were treated with five microbial fertilizing products (K2–K6). The single plot area was 16 m2, with a total of 144 plots. The adopted planting density of strawberries was 30,052 per hectare. K3 treatment was found to be the most universal microbial treatment in terms of positive impact on yields, with significant yield increase on both the non-irrigated (yield increase of 3.76 t·ha−1) and irrigated experiments (yield increase of 5.78 t·ha−1). The K4 treatment on the non-irrigated strawberries resulted in a yield increase of 4.96 t·ha−1, which at the same time had no effect on the yield of the irrigated experiment. On average, application of the K2–K6 combinations on the non-irrigated strawberries resulted in a yield increase from 13.4% (K2) to 33.5% (K4). The irrigated strawberries showed a yield increase from 3.9% (K4—non-significant yield increase) to as much as 36.1% (K3). The highest direct surplus for the non-irrigated strawberries was recorded for the K4 treatment (38,603 PLN·ha−1) and for K3 for the irrigated experiment (42,945 PLN·ha−1). The direct surplus for ‘Rumba’ and ‘Vibrant’ was higher than for ‘Honeoye’ on both the irrigated (22% and 53%, respectively) and non-irrigated (19% and 18%, respectively) experiments. The average profitability index for all tested non-irrigated and irrigated varieties improved when treated with microbial fertilizer products, with profitability indexes of 143.3–168.8% on the non-irrigated plantation and 129.2–169.7% on the irrigated plantation. The tested microbial fertilizing products proved to be valuable products to improve the productivity and economic effectiveness of organic strawberry production. At the same time, their use needs to be adapted to local plantation conditions.

La-Al modified Fe3O4 adsorbent for adsorption performance and mechanism of low P concentration in water

Adsorbents of LaAl hydroxide (oxygen) species have been widely used for removal of phosphate (P) from water, but fewer studies were conducted on the removal of low P concentration. This study firstly fabricated a new composite material of LaAl modified Fe3O4 by co-precipitation method applied for removal of low P concentration in water. Results showed that the optimal adsorbent performance was at a La/Al molar ratio of 2:1 and an optimum dosage of 0.1 g/L. P removal was >99 % with a low initial P concentration (2 mg/L), and the residual P was only 0.02 mg/L. La2-Al@Fe3O4 adsorbent was an irregular magnetic particle with a large specific surface area of 101.35 m2/g. Adsorption process primarily involved chemisorption and formation of multiple adsorption layers. The maximum adsorption capacity was 71.75 mg/g when the initial P concentration was 50 mg/L. Meanwhile, it showed good adsorption performance at pH 4.0–9.0, exhibited notable selectivity for P despite competing ions such as Cl−, HCO3−, SO42−, and NO3−, and was influenced by coexisting citric acid and humic acid. Also, La2-Al@Fe3O4 showed good reproducibility and maintained 85.6 % of the original adsorption capacity after five adsorption and desorption cycles. Additionally, P concentration could be reduced to below 0.02 mg/L in actual water, and La2-Al@Fe3O4 was friendly to the water environment based on the toxicity analysis of Chlorella vulgaris. The adsorption mechanism of P by La2-Al@Fe3O4 mainly involved electrostatic adsorption and ligand exchange. This novel adsorbent shows great potential for application in low P concentration water treatment.

Sustainable bioenergy potential of peat-moss derived hydrothermal aqueous phase: Insights into methane production and organic transformation

Achieving Sustainable Development Goal 7 (SDG-7) by exploring bioenergy production from peat-moss derived hydrothermal aqueous phase (HAPs) through anaerobic digestion (AD). This study investigated six combinations of hydrothermal conversion temperature (HCT) and residence time (HCRT). Methane yields varied significantly, with the highest (256 mL/g COD) achieved at 200 °C:4h, while the lowest (97 mL/g COD) was at 320 °C:4h due to formation of toxic and refractory organics. Microtox analysis showed acute toxicity > 98 % for all HAPs. Notably, higher HCT and HCRT led to more complex and diverse organic patterns, promoting the formation of humus-like substances, ester, alkane alcohols, and aromatics. GC–MS analysis revealed a 23 % increase in aldehyde and ketone compounds at 320 °C:4h. Continuous experiments confirmed 29 % COD removal efficiency at 320 °C:4h and identified 13 refractory organics, highlighting challenges in biodegradability. These findings provided valuable insights for optimizing AD processes, enhancing bioenergy production, and advancing sustainable energy solutions in alignment with SDG-7.

Artificially obtained humic-like substances from chicken manure and symbionts in in vitro and in situ improvement of oil degradation in soil

Artificially obtained humic-like substances from chicken manure and symbionts in in vitro and in situ improvement of oil degradation in soil

Adsorption of oxidized humic acid onto redox-inert mineral surfaces induces formation of hydroxyl radicals and carbon dynamics

The dark formation of hydroxyl radicals (·OH) from O2 activation by reduced humic substances at oxic-anoxic interfaces has been extensively documented. However, their generation in oxic subsurface environments is typically overlooked due to the scarcity of electron donors, especially in the presence of minerals. In this study, the formation of ·OH during the adsorption of oxidized humic acids (HA) onto redox-inert minerals was investigated under oxic and pH-neutral conditions. Batch experiment results demonstrated that the adsorption of oxidized HA onto aluminum (hydr)oxide and Fe-free clay minerals induces the formation of ·OH (e.g., 16/28 μmol/g C) without the addition of exogenous electron donors. In contrast, the interaction of oxidized HA alone with O2 did not result in measurable ·OH production. The enhanced electron-donating capacity (EDC) and humification of the whole HA (mainly in adsorbed state) were measured after adsorption. The surface-catalyzed polymerization of oxidizable polyphenols in HA is proposed as the plausible mechanism for the observed EDC enhancement, which in turn triggers O2 activation for ·OH production. Furthermore, substantial chemical alterations of lignins and condensed aromatics within HA were observed, producing more compounds exhibiting higher molecular weight, aromaticity, O/C ratio, and nominal oxidation state of carbon. It is indicated that the contribution of oxidative polymerization outweighs ·OH oxidation in the molecular transformation of adsorbed HA. Overall, our findings extend the understanding of HA-induced ·OH production from oxic-anoxic interfaces to the oxic zone and present a novel pathway for the abiotic transformation of recalcitrant organic matter in subsurface environments with extensive surface water-groundwater interactions.

Fouling of Reverse Osmosis (RO) and Nanofiltration (NF) Membranes by Low Molecular Weight Organic Compounds (LMWOCs), Part 1: Fundamentals and Mechanism.

Reverse osmosis (RO) and nanofiltration (NF) are ubiquitous technologies in modern water treatment, finding applications across various sectors. However, the availability of high-quality water suitable for RO/NF feed is diminishing due to droughts caused by global warming, increasing demand, and water pollution. As concerns grow over the depletion of precious freshwater resources, a global movement is gaining momentum to utilize previously overlooked or challenging water sources, collectively known as "marginal water". Fouling is a serious concern when treating marginal water. In RO/NF, biofouling, organic and colloidal fouling, and scaling are particularly problematic. Of these, organic fouling, along with biofouling, has been considered difficult to manage. The major organic foulants studied are natural organic matter (NOM) for surface water and groundwater and effluent organic matter (EfOM) for municipal wastewater reuse. Polymeric substances such as sodium alginate, humic acid, and proteins have been used as model substances of EfOM. Fouling by low molecular weight organic compounds (LMWOCs) such as surfactants, phenolics, and plasticizers is known, but there have been few comprehensive reports. This review aims to shed light on fouling behavior by LMWOCs and its mechanism. LMWOC foulants reported so far are summarized, and the role of LMWOCs is also outlined for other polymeric membranes, e.g., UF, gas separation membranes, etc. Regarding the mechanism of fouling, it is explained that the fouling is caused by the strong interaction between LMWOC and the membrane, which causes the water permeation to be hindered by LMWOCs adsorbed on the membrane surface (surface fouling) and sorbed inside the membrane pores (internal fouling). Adsorption amounts and flow loss caused by the LMWOC fouling were well correlated with the octanol-water partition coefficient (log P). In part 2, countermeasures to solve this problem and applications using the LMWOCs will be outlined.

The Effect of Szigetvár Medicinal Water on HaCaT Cells Exposed to Dithranol.

(1) Introduction: Topical dithranol is still commonly used today as an effective treatment for psoriasis. Dithranol treatment is often supplemented with balneotherapy, which has been shown to increase effectiveness and reduce side effects. The inorganic salts (sulfhide, selenium, zinc) are usually thought to be responsible for the effect. The antioxidant effect of the waters is thought to be behind the therapeutic effect, for which inorganic substances (sulfides, selenium, zinc) are thought to be responsible. The organic matter content of medicinal waters is also particularly important, as humic acids, which are often found in medicinal waters, have antioxidant effects. (2) Methods: In this short-term experiment, we aimed to test the possible protective effect of Szigetvár medicinal water and its organic matter isolate on HaCaT cells exposed to dithranol. Malondialdehyde levels were measured, and RT-qPCR was used to investigate the gene expression of selected cytokines relevant in the oxidative stress response (IL-6, IL-8, TNF-α, GM-CSF) and the expression of microRNA-21. (3) Results: Szigetvár medicinal water and the organic isolate prevented the increase in malondialdehyde levels caused by dithranol treatment. The cytokine gene expressions elevated by dithranol exposure were reduced by the treatment. (4) Conclusions: Szigetvár medicinal water and organic substances alone may have a protective effect on patients' healthy skin surfaces against dithranol damage. We also demonstrated that the organic compounds are also responsible for the protective effect.

Enhancing Mango Productivity with Wood Vinegar, Humic Acid, and Seaweed Extract Applications as an Environmentally Friendly Strategy

Enhancing Mango Productivity with Wood Vinegar, Humic Acid, and Seaweed Extract Applications as an Environmentally Friendly Strategy

Molecular insights into the binding mechanism of strontium and cesium on phyllosilicates with different expandability

The environmental fate of strontium (Sr) and cesium (Cs), as the critical radioactive fission products, have raised significant concerns regarding radioactive waste disposal and environmental protection. The current study investigated the distinction in the binding configurations of Sr2+ and Cs+ on various 2:1 phyllosilicate (illite, vermiculite, and montmorillonite) by combining batch adsorption, sequential extraction, and spectroscopic analyses. The results show that strontium adsorption is strongly influenced by pH as well as ionic strength, while there is no significant variability in strontium adsorption by different types of clay minerals. EXAFS analysis confirms the outer complexation of strontium on the planar sites of the clay minerals, i.e., Sr2+ is surrounded by ~8.0 O atoms, RSr-O ≈ 2.6 Å, and that process is mainly realized by ion exchange. In contrast, Cs+ adsorption was markedly influenced by the variety of clay minerals but less by pH and ionic strength, the presence of humic acid (HA) inhibited Cs+ adsorption. The inner-sphere complexation formed mainly at the frayed edge sites on illite, and interlayer sites on vermiculite and montmorillonite, was the dominant mechanism for Cs+ adsorption. In addition, the collapse of the interlayer space of vermiculite induced by Cs+ adsorption on the interlayer sites was responsible for the more stable and irreversible immobilization. The findings in present work highlighted the significance of prevailed mineral in governing environmental migration risk of radionuclides, the revealed adsorption mechanism and binding configuration of Sr2+ and Cs+ on typical phyllosilicates would be referable in constructing a reliable migration model of Sr2+ and Cs+ in natural media.

Understanding the Interactions of Nanoparticles and Dissolved Organic Matter at the Molecular Level by 1H 2D Multi-Exponential Transverse Relaxation NMR Spectroscopy.

The interaction between humic acid (HA) and engineered nanoparticles (NPs) is critical in environmental sciences, especially for understanding the behavior of NPs in natural waters. This study employs 1H 2D Multi-Exponential Transverse Relaxation (METR) NMR spectroscopy to examine the molecular-level interactions between Pahokee Peat humic acid (HA) and carboxyl-functionalized iron oxide nanoparticles (NPCOs). First, 1H 2D METR NMR spectroscopy allowed not only the identification of HA in terms of its chemical composition but also the separation of molecules with the same chemical shift values but different rates of molecular tumbling. Then, using solutions with varying NPCO concentrations (0, 10, 40, and 100 μM), we observed significant changes in the T2 relaxation times of HA components, indicating interactions between HA and NPCO. Analysis showed the biggest effect on two chemical shift regions, corresponding to lipids and carbohydrates, revealing that smaller molecules within these regions exhibit the most significant changes in T2 values upon the addition of NPCO. This suggests that these molecules are the initial sites of interaction, with the entire HA system being affected at higher NPCO concentrations. These findings highlight the utility of METR NMR spectroscopy in studying complex environmental mixtures and provide insights into the behavior of HA and NPs, essential for understanding the fate of NPs in the environment.

Dissolved organic matter-mediated adsorption behavior of benzophenones on functionalized covalent triazine frameworks

Adsorption is a highly efficacious technique for the remediation of organic micropollutants (OMPs). However, the presence of dissolved organic matter (DOM) frequently impedes adsorbent process, with insufficient attention given to this influence. This study systematically evaluates the adsorption performance of covalent triazine frameworks (CTFs) functionalized with electron-donating or electron-withdrawing groups for benzophenones (BPs). The adsorption capacities of SO3H-CTF, OH-CTF, and NH2-CTF for BPs were 512.11 μmol/g, 1356.27 μmol/g, and 1421.85 μmol/g, respectively. The adsorption mechanism is predominantly governed by π-π electron donor–acceptor (EDA) interactions, supplemented by hydrogen bonding, particularly in hydroxyl-containing BPs, with electrostatic interactions being relatively negligible. Functionalization with − OH and − NH2 groups increased the electron density in π-conjugated regions, enhancing BPs adsorption capacity, whereas − SO3H modification, due to its electron-withdrawing nature, acted as a π electron acceptor. Importantly, the mediating role of humic acid (HA) in the adsorption process was investigated. The CTF-BPs-HA ternary system can either inhibit/enhance π-π EDA interactions between π-electron donor/acceptor and BPs by adsorbing onto the CTF materials. The HA-mediated system primarily affects the film diffusion stage, with minimal impact on pore diffusion and inner surface adsorption. The oxygenated functional groups in HA slightly enhanced hydrogen bonding within the adsorption system, with negligible influence on electrostatic interactions. In the presence of HA, the overall adsorption capacity of SO3H-CTF decreased by 67.0 %, while that of OH-CTF and NH2-CTF increased by 120.9 % and 55.3 %, respectively. This study elucidates the electronic behavior modifications of functionalized CTFs during BPs adsorption and underscores the significant role of HA in interaction mechanisms, providing theoretical guidance for the design of advanced adsorbents to enhance pollutant removal efficiency.

A novel polysulfone ultrafiltration membrane constructed with the sandwich-like structure SGO-ZnO for ultra-easy water transport and enhanced anti-fouling

Fouling formation on membrane surfaces limits membrane-based separation performance in industrial activities such as wastewater recycling and desalination. Designing and preparing emerging materials capable of improving the balance between permeability and rejection remains a great challenge. A sandwich-like composite with loose and flat interlayers was produced by combining rigid zinc oxide (ZnO) nanoparticles with easily stackable, folded sulfonated graphene (SGO) and subsequently non-solvent-induced phase separation (NIPs) was employed to produce novel PSF ultrafiltration (UF) membranes with varying amounts of nanofiller of SGO-ZnO. The successful anchoring of ZnO on SGO was confirmed by FTIR, XRD, Raman spectroscopy and TGA. The produced membranes have been investigated using contact angle (CA), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The incorporation of ZnO suppressed the stacking and wrinkling of SGO, which increased the vertical interlayer paths and lateral bending paths. As a result, water molecules could freely pass through the extended channels of SGO, and with only 0.2 wt% of nanoparticles doped, the pure water flux was increased f from 229.2 L m−2h−1 to 601 L m−2h−1. Negatively charged impurities were selectively repelled due to electrostatic interactions with −SO3H, which resulted in the removal of BSA remaining above 98 %. In addition, the separation performance of the humic acid (HA)-simulated water sample, a common contaminant, was investigated using the designed modified membranes. The greatest HA rejection (98.33 %) was shown by the UF membrane. All these findings suggest that the addition of sandwich-like SGO-ZnO successfully overcomes the “trade-off effect” between permeability and selectivity in PSF membranes.

The Effects of Montmorillonite–Humic Acid Composite Particles on the Photolysis of Tetracycline in Water

Suspended particulate matter (SPM) is an important component of natural water bodies and can significantly influence the photolytic behavior of water pollutants. A comprehensive understanding of the photochemical behavior of water pollutants in natural waters requires consideration of the presence of SPM. In this study, montmorillonite–humic acid (MMT-HA) composite particles were synthesized to simulate SPM in natural waters and their effects on the photolysis of tetracycline (TC) were investigated. The results demonstrated that the presence of MMT-HA composite particles in water significantly enhanced the photolysis of TC, with the photolytic kinetics following a pseudo-first-order model. Electron spin resonance spectra and free radical quenching experiments indicated that the photoactive components (MMT and humic acids) in the composite particles induced the generation of reactive oxygen species under light exposure, further contributing to the enhanced photolysis of TC. Comparative analysis of the free radical signals and adsorption experiments revealed that the accelerated photolysis of TC was also related to the interfacial interaction between the MMT in the composite particles and the TC molecules. The formation of surface complexes between TC molecules and the negatively charged sites on the MMT surface facilitated light absorption and electron transfer, thereby accelerating the photolysis of TC. Photoproduct analysis indicated that the primary degradation pathways of TC in the composite particle systems included the addition of hydroxyl radicals to the aromatic ring, as well as demethylation, deamination and dehydration in the side chains. This study shows that SPM in water bodies can affect the photochemical behavior of pollutants and should be taken into account when assessing the phototransformation of pollutants in natural waters.

Sources and doses of biofertilizers in soybean and corn crops

The application of humic substances (SHs) can provide numerous benefits to the soil-plant system, such as greater absorption of nutrients and greater plant growth, resulting in productivity gains in several crops. In this context, the study aimed to evaluate the growth attributes, nutritional aspects and yield, as well as the chemical attributes of the soil after harvest, as a function of the application of biofertilizers containing fulvic and humic acids in the sowing furrow for soybean crops. and corn. The experiments were carried out in the municipality of Paracatu, Minas Gerais, in a randomized block design, in a 4x3+1 factorial structure, with four replications. The first factor formed by four sources of biofertilizers (Biof. 1, Biof. 2, Biof. 3 and Biof. 4), the second factor composed of three doses (2, 4 and 6 L ha-1), and the additional treatment as a control, totaling 13 treatments. Different results were observed between the sources and doses evaluated. For corn, biofertilizers affected the uptake of N, K, S and B and plant growth, as well as the P and Ca content in the soil, however, they did not affect the crop yield. For the soybean crop, the biofertilizers provided an increase in the absorption of N, S and Mg and an increase in the phosphorus content in the soil; however, they did not interfere in the variables of growth and crop yield. The long-term use of biofertilizers containing SHs can contribute to building soil fertility, and provide improvements to plant development and productivity.

Scallop farming impacts on dissolved organic matter cycling in coastal waters: Regulation of the low molecular weight fraction

To elucidate the impacts of scallop farming on the biogeochemical characteristics of low molecular weight (LMW, <1 kDa) dissolved organic matter (DOM), samples collected from a bay scallop mariculture area (MA) and its surrounding areas were determined for absorption and fluorescence spectroscopy after microfiltration and centrifugal ultrafiltration. The values of absorption coefficient a350 showed a spatial variation trend of inshore area (IA) > MA > non-mariculture area (NMA) for both bulk (<0.7 μm) and LMW fractions. Four fluorescent components, namely two protein-like components (tryptophan-like C1 and tyrosine-like C2) and two humic-like components (microbial humic-like C3 and terrestrial humic-like C4), were identified. Scallop farming influenced DOM transformation by altering phytoplankton abundance and promoting microbial degradation. In July, the net contributions of phytoplankton to the spectroscopy parameters of LMW-DOM in the surface seawater were 11.0% for a350, 4.3% for C1, 0.8% for C2, 0.6% for C3 and 3.0% for C4, respectively; the corresponding values of bulk DOM in the surface seawater were 24.3% for a350, 20.1% for C1, 5.9% for C2, 2.0% for C3, 2.9% for C4, respectively. Compared with NMA, the contributions of microbial degradation to a350 in MA's surface seawater increased by 9.0% for LMW-DOM and 6.9% for bulk DOM in July; however, the effects on different fluorescent components varied. In August, compared with NMA, the contributions of microbial degradation to spectroscopy parameters in the bottom water of MA decreased by 35.7% for a350, 6.3% for C2, 1.3% for C3, and 4.4% for C4 for LMW-DOM fraction; for bulk DOM, the corresponding contribution decreased by 10.8% for C1. These variations indicate that protein-like substances from scallop aquaculture are easily degraded into LMW substances, while humic-like substances degradation diminishes over time.

Effects of Humic Acid from Weathered Coal on Water-Stable Aggregates and Pore Structure of a Reclaimed Cambisol

To clarify the effects of weathered coal humic acid on water-stable aggregates and pore characteristics of reclaimed cambisol, this research analyzed the evolution characteristics of soil aggregates and pores. Effects of different humic acid dosages (0, 1%, 3%, and 5% by weight) and application period (1 year, 2 years, and 3 years) on soil aggregates and organic carbon components in soil water-stable aggregates were investigated. The results showed that it is advisable to have an addition of 5% weathered coal humic acid in reclaimed cambisol. The humic acid of weathered coal promoted the disintegration and transformation of water-stable aggregates and increased soil pore p &gt; 75 μm. At 3 years, the structure of reclaimed soil was the most stable, with more robust connected pores, and the irregular pores increased. The humic acid of weathered coal has the potential to be used as an effective organic amendment for improving the quality of reclaimed cambisol.

New insights into the spatial variability of microbial diversity and density in peatlands exposed to various electron acceptors with an emphasis on methanogenesis and CO2 fluxes.

Peatlands are vital in the global carbon cycle, acting as significant sinks for carbon and releasing methane (CH4) and carbon dioxide (CO2) into the atmosphere. However, the complex interactions between environmental factors and the microbial communities responsible for these greenhouse gas emissions remain insufficiently understood. To address this knowledge gap, a pilot-scale mesocosm study was conducted to assess the impact of different terminal electron acceptors (TEAs), including sulfate (SO4 2-), humic acid (HA), and goethite, on CH4 and CO2 emissions and microbial community structures in peatlands. Our results revealed that the addition of TEAs significantly altered the CH4 and CO2 emissions. Specifically, the addition of SO4 2- nearly doubled CO2 production while substantially inhibiting CH4 emissions. The combined addition of SO4 2- and HA, as well as HA alone, followed a similar pattern, albeit with less pronounced effects on CH4. Goethite addition resulted in the highest inhibition of CH4 among all treatments but did not significantly increase CO2 production. Community composition and network analysis indicated that TEAs primarily determined the structure of microbial communities, with each treatment exhibiting distinct taxa networks. Proteobacteria, Acidobacteria, Chloroflexi, and Bacteroidetes were the most abundant phyla across all mesocosms. The presence of methanotrophs, including Methylomirabilales and Methylococcales, was linked to the inhibition of CH4 emissions in these mesocosms. This study provides novel insights into the spatial variability of microbial diversity and density in peatlands under various TEAs, emphasizing the role of methanogenesis and CO2 fluxes in carbon cycling. Our findings enhance the understanding of carbon cycling in microbe-rich environments exposed to TEAs and highlight the potential for future studies to investigate the long-term effects of TEAs on microbial communities, enzymes, and carbon storage.