Subsequent Decomposition Research Articles

Novel oxygen vacancies-rich 3D porous ZnO for highly sensitive 3-hydroxy-2-butanone biomarker gas sensors

Listeriosis can cause human death via infection by Listeria monocytogenes (LMs) with a high fatality rate of 20–30 %. Detection of 3-hydroxy-2-butanone (3H-2B) biomarker of LMs can achieve estimation of LMs content, which is of great significance for human health. Exploring porous metal oxide semiconductors (MOSs) with rich vacancies towards 3H-2B sensing is quite promising for achieving this goal. Herein, we report a highly sensitive 3H-2B sensor based on novel 3D porous ZnO with rich oxygen vacancies which was facilely obtained by sacrificing Zn foam in oxalic acid and subsequent thermal decomposition. The ZnO sensor displays ultrahigh sensor response of Ra/Rg = 328@5 ppm, super-low detection limit of 0.001 ppm, excellent cycling stability and selectivity and good linear response at 120 °C, showing great potential for precise detection of 3H-2B biomarker. The porous structure and increased oxygen vacancies contribute greatly to the adsorption of active oxygen species therefore the sensing reactions on ZnO surface, which accounts for the high sensing performance. Our work provides an ingenious strategy to produce novel 3D ZnO with rich oxygen vacancies as well as new insights for boosting the detection of LMs.

Theoretical and modeling studies on the kinetics of diethylamine dehydrogenation and subsequent isomerization and decomposition reactions

Theoretical and modeling studies on the kinetics of diethylamine dehydrogenation and subsequent isomerization and decomposition reactions

Temperature and pressure effects on the decomposition mechanisms of 2,6-diamino-3,5-dinitropyrazine-1-oxide crystal: ab initio molecular dynamics study.

The decomposition process of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) crystal at high temperatures (2500 and 3390K) and detonation pressure of 33.4 GPa coupled with temperatures were studied by ab initio molecular dynamics simulations. The results show that the initial decomposition mechanism of LLM-105 is the same under different conditions. The product analysis indicates that high temperature is conducive to the formation of N2 and CO2, but inhibited the formation of H2O. It is found that the formation mechanism of H2O is the same under different conditions, which involves the reaction between OH radical and H radical. Although the detailed processes of the formation of N2 are different, they all involve the reaction between nitrogen-containing fragments, and its core is the formation of intermediates with R1-NN-R2 structure. The core of the formation of CO2 under different conditions is to form the intermediate R1-CO-R2 with carbonyl structure, and then generate the fragment with -OCO- structure, and finally generate CO2. This research may provide new insights into the initiation and subsequent decomposition mechanisms of energetic materials under extreme conditions. The LLM-105 supercell was constructed using the Materials Studio 7.0 package. AIMD simulations were performed in the CASTEP package. AIMD simulations adopted NVT and NPT ensemble, and the temperature was controlled by Nosé thermostat, while the pressure was controlled by Andersen barostat. Besides, DFT calculations were carried out at the B3LYP/6-311 + G(d,p) level using the Gaussian 09 package.

Mutual Transformations of Polysulfide Chromophore Species in Sodalite-Group Minerals: A DFT Study on S6 Decomposition.

It is known that various polysulfide species determine the color of sodalite-group minerals (haüyne, lazurite, and slyudyankaite), and that heating induces their transformations and color change, but the mechanisms of the transitions are unknown. A prominent example is the decay of cyclic S6 molecule. Using density-functional simulations, we explore its main decay pathways into the most probable final reaction products (the pairs of radical anions S3⋅-+S3⋅- and S2⋅-+S4⋅-). It was found that the most favorable reaction path involves initial capture of one electron by the S6 molecule, which greatly facilitates its decay of S6 and leads to the opening of the S6 cycle, and subsequent decomposition of the thus formed chain radical anion, with a limiting energy barrier of ~0.4 eV. Neutral polysulfide molecules capture one electron with a significant energy reduction. The radical anions Sn⋅- (n=2-6) are the most stable ones among corresponding species with the same n values and different charges. The capture of the second electron by S6⋅- occurs with a huge energy barrier (~2 eV). The results of the DFT calculations are in agreement with experimental data on the products of thermal conversions of extra-framework S-bearing groups in sodalite-group minerals.

Engineering Porosity-Tuned Chitosan Beads: Balancing Porosity, Kinetics, and Mechanical Integrity.

Chitosan, a cationic natural polysaccharide derived from the deacetylation of chitin, is known for its solubility in diluted acidic solutions, biodegradability, biocompatibility, and nontoxicity. This study introduces three innovative methods for preparing various types of porous chitosan beads: solvent extraction, surfactant extraction, and substance decomposition. These methods involve the integration and subsequent extraction or decomposition of materials during the synthesis process, eliminating the need for additional steps. We used state-of-the-art characterization techniques to analyze and evaluate the chemical and physical properties of the beads, such as Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and three-dimensional (3D) computed tomography (CT) scanning. The 3D CT scans visualized and measured the porosity of different bead types, ranging from 68.4% to 39.3%. This study also evaluated the mechanical properties of the particle beads under compressive forces in both wet and dry conditions, highlighting the influence of porosity on their mechanical integrity and compression pressure behavior. The adsorptive properties of these chitosan beads were studied using methylene blue as a model pollutant, emphasizing the importance of balancing porous structure, surface area, kinetics, and structural integrity. This study paves the way for the development of environmentally sustainable polymeric beads, highlighting the crucial need to balance porosity, surface area, and structural integrity to optimize their effectiveness in real-world applications.

One-step inverse generation network for sparse-view dual-energy CT reconstruction and material imaging

Objective. Sparse-view dual-energy spectral computed tomography (DECT) imaging is a challenging inverse problem. Due to the incompleteness of the collected data, the presence of streak artifacts can result in the degradation of reconstructed spectral images. The subsequent material decomposition task in DECT can further lead to the amplification of artifacts and noise. Approach. To address this problem, we propose a novel one-step inverse generation network (OIGN) for sparse-view dual-energy CT imaging, which can achieve simultaneous imaging of spectral images and materials. The entire OIGN consists of five sub-networks that form four modules, including the pre-reconstruction module, the pre-decomposition module, and the following residual filtering module and residual decomposition module. The residual feedback mechanism is introduced to synchronize the optimization of spectral CT images and materials. Main results. Numerical simulation experiments show that the OIGN has better performance on both reconstruction and material decomposition than other state-of-the-art spectral CT imaging algorithms. OIGN also demonstrates high imaging efficiency by completing two high-quality imaging tasks in just 50 seconds. Additionally, anti-noise testing is conducted to evaluate the robustness of OIGN. Significance. These findings have great potential in high-quality multi-task spectral CT imaging in clinical diagnosis.

Characterization of low-pressure gaseous plasma radiation and its usage for inactivation of waterborne viruses

Water disinfection is a critical treatment step for removing harmful organisms from contaminated water sources. Vacuum ultra-violet (V-UV) radiation, generated by a low-pressure gaseous plasma discharge, consists of photons with high enough energy to break molecular bonds. In this work, we constructed and characterized a low-pressure capacitively coupled gaseous plasma and used it as a V-UV radiation source to inactivate MS2 bacteriophage, a surrogate for human enteric viruses. The treatment system allows for variation of gas composition inside the sample chamber and the modulation of V-UV radiation intensity. Both were used to separate the actual germicidal contribution of V-UV radiation from producing germicidal species by using virus inactivation to determine efficiency. OH* radical production was determined through the terephthalic acid chemical probe, which showed that when air was present in the sample chamber, it resulted in the highest OH* production and the best inactivation of MS2. Furthermore, we showcase that the OH* production rate was wavelength dependent and that ozone, generated by plasma treatment in the gas phase, leads to hydroxy terephthalic acid degradation, allowing us to determine better the actual OH* production rate with different treatment regimes. Lastly, by adding an OH* scavenger to the liquid, we were able to elucidate it as the primary inactivation agent in this setup while also providing evidence of its production in the bulk liquid by the transport and subsequent decomposition of the longer-lasting ozone molecule. This study demonstrates, for the first time, the applicability of low-pressure plasma radiation as a water treatment method.

Implementation of generative artificial intelligence technologies in creative activities: development of a structural model of design thinking

The subject of the study is systemic changes in the methodology of design thinking, taking place under the influence of the development and spread of generative artificial intelligence (AI) technologies in design and other creative industries. The purpose of the work is: analysis of modern research on the impact of generative AI technologies on creative industries, design and on design thinking; development of a structural model of design thinking to further explore the evolution of the methodology. The following tasks are set in the article: to analyze modern scientific publications regarding the essence, structure and content of design thinking; review research on the benefits and challenges of using generative AI in design processes; to develop a model that allows identifying and describing changes in key components of the design thinking methodology arising under the influence of widespread adoption of generative AI technologies. During the research, the following methods were used: analysis and synthesis of the content of technical, economic, philosophical, linguistic, historical scientific and methodical research on the problems of forming the conceptual apparatus of the design-thinking methodology and the use of generative AI in design processes; comparative-historical, retrospective methods; structural and logical analysis. The following results were achieved: the actualized need for a comprehensive research approach to analyze the multifaceted impact of AI technologies on design; the key advantages and challenges associated with the integration of AI into creative processes are identified; a structural model of presentation of the design-thinking methodology was developed in the form of four interconnected structural layers with subsequent decomposition of each of the layers into constituent elements. The conclusions highlight the depth and multifaceted nature of the changes taking place in design and other creative industries under the influence of generative AI and need further in-depth research. The developed structural model of the design-thinking methodology allows to decompose the complex creative process to a certain extent, laying the foundation for a comprehensive analysis of the evolution of the methodology and the systematic introduction of generative artificial intelligence technologies into design processes.

Living and decaying roots as regulators of soil aggregation and organic matter formation—from the rhizosphere to the detritusphere

In dryland ecosystems, typically characterized by sparse vegetation and nutrient scarcity, pioneer plants exert a critical role in the build-up of soil carbon (C). Continuous root-derived C inputs, including rhizodeposition and structural root litter, create hotspots of increased microbial activity and nutrient availability where biogeochemical processes, such as soil aggregation and the accumulation and stabilization of organic matter (OM), are promoted. Our study aims to disentangle the effects of root C inputs on soil aggregate formation, microbial community structures, and on the fate of OM—both before and after plant death, i.e., during the transition from rhizosphere to detritusphere. This was realized in a two-phase incubation approach, tracing the natural and undisturbed transition from growth to subsequent decomposition of a pioneer plant-root system (Helenium aromaticum) in a semi-arid topsoil and subsoil. We quantified water-stable aggregates, investigated the fate and composition of OM separated into particulate and mineral-associated OM fractions (POM and MAOM), and observed successional changes in the root-associated microbiome. Our results underscore the significance of roots as vectors for macroaggregation within the rhizosphere in both topsoil and subsoil, associated with a particularly strong increase in fungal abundance in the subsoil. In topsoil, we identified root legacy effects in the detritusphere, as root-induced macroaggregation persisted after plant death, a phenomenon not observed in subsoil. These root legacy effects were accompanied by a clear succession towards gram + bacteria, which appeared to outcompete fungi during root decomposition. The increased availability of decaying litter surfaces further facilitated the protection of particulate OM via the occlusion into aggregates. Overall, to gain a holistic understanding of plant-microbe-soil interactions, we emphasize the need for more studies that span over the full temporal dimension from living to dying plants in intact soil systems.

Stable nature of [BH4]− ions in deliquescence thin-film NaBH4 and humidity control of their decomposition toward hydrogen supply and storage application

In this study, we investigated the deliquescence of NaBH4 thin films under atmospheric conditions toward their hydrogen supply application. Upon exposed to air, the film deliquesced along with generating hydrogen due to the decomposition of [BH4]- ions, but the decomposition rate was slow enough for a sizable amount of [BH4]- ions remained stable in the deliquesced film. As a result, a reversible deliquescence-recrystallization cycle in the NaBH4 thin film could be achieved through control of humidity. Molecular dynamics simulations suggested that Na+ and [BH4]- ions tended to neighbor each other with almost the same intra-distance as that in the crystal. A kind of such local ordered structures in deliquesced NaBH4 may prevent an excess hydration and subsequent decomposition of [BH4]- ions and is responsible for the stability of [BH4]- ions, enabling the reversible deliquescence-recrystallization cycle. These combined experimental and theoretical insights offer new perspectives on controlling hydrogen release from borohydrides based on humidity conditions in the thin film form.

Green process for Polyurethane: From CO2 to isocyanate

Polyurethane, a highly versatile and widely used polymer, has garnered significant interest as a candidate material for CO2 incorporation to address climate change. Nevertheless, research into alternative production methods for isocyanate, a key monomer in polyurethane production, remains insufficient, despite the heavy reliance of the conventional approach on phosgene, a highly toxic material. This study proposes a sustainable process for synthesizing methylene diphenyl diisocyanate (MDI). The proposed process involves the production of syngas from CO2, followed by syngas separation via a hydrogenation reaction, oxidative carbonylation of amine to form dicarbamate, and subsequent thermal decomposition to yield MDI. The syngas separation via the hydrogenation reaction eliminates the need for an additional separation process by simultaneously separating reaction products and preparing a reactant for the subsequent step. Moreover, the introduction of a Pd/TiO2 catalyst and a new reactant introduction strategy significantly reduces side reactions during oxidative carbonylation, thereby enhancing the overall yield. Process modeling and a life cycle assessment demonstrated substantial environmental advantages over the conventional MDI manufacturing process, highlighting the potential of this approach as a greener alternative.

Тионирование 4-((4-оксо-4H-хромен-3-ил) метилен)-2-фенилоксазол-5(4H)-она с применением реагента LAWESSON’S

Analysis of periodicals has showed that there is no information on the behavior of hybrid heterocyclic systems containing several pharmacophore fragments based on oxazol-5(4H)-ones and chromen-4(4H)-ones in reactions with thionizing reagents under various conditions. The interaction of 4-((4-oxo-4H-chromen-3-yl)methylene)-2-phenyloxazol-5(4H)-one with Lawesson’s reagent (LR) (2,4-bis-[pmethoxyphenyl]) has been studied for the first time – 1,3- dithiaphosphetane-2,4-disulfide) under conditions of thermal activation of the reaction mixture and the use of a closed reactor in the environment of non-polar solvents. Lawesson’s reagent is used as a mild thioniation agent. The scheme of the interaction has been discussed. Initially, it is assumed that the Lawesson reagent (LR) molecule dissociates into the particles of ylide structure, then the interaction with the carbonyl group of the chromen-4-one fragment of the initial substrate takes place, resulting in the formation of a spirocyclic intermediate, the subsequent decomposition of which produces the final product. It has been established that the use of a closed reactor makes it possible to reduce the transformation time and achieve an increase in the yield of the target product compared to the conventional type of activation of the reaction mixture. It has been shown that under the chosen conditions the transformation proceeds with the preservation of the oxazol-5(4H)-one ring. The composition and structure of the resulting compound have been established on the basis of complex data from elemental analysis, IR and NMR spectroscopy.

A locally solvent-tethered polymer electrolyte for long-life lithium metal batteries

Solid polymer electrolytes exhibit enhanced Li+ conductivity when plasticized with highly dielectric solvents such as N,N-dimethylformamide (DMF). However, the application of DMF-containing electrolytes in solid-state batteries is hindered by poor cycle life caused by continuous DMF degradation at the anode surface and the resulting unstable solid-electrolyte interphase. Here we report a composite polymer electrolyte with a rationally designed Hofmann-DMF coordination complex to address this issue. DMF is engineered on Hofmann frameworks as tethered ligands to construct a locally DMF-rich interface which promotes Li+ conduction through a ligand-assisted transport mechanism. A high ionic conductivity of 6.5 × 10−4 S cm−1 is achieved at room temperature. We demonstrate that the composite electrolyte effectively reduces the free shuttling and subsequent decomposition of DMF. The locally solvent-tethered electrolyte cycles stably for over 6000 h at 0.1 mA cm−2 in Li | |Li symmetric cell. When paired with sulfurized polyacrylonitrile cathodes, the full cell exhibits a prolonged cycle life of 1000 cycles at 1 C. This work will facilitate the development of practical polymer-based electrolytes with high ionic conductivity and long cycle life.

High efficiency separation of bastnaesite (REFCO3) and monazite (REPO4) in mixed rare earth concentrate by heating under N2 and leaching with HCl/AlCl3

Bayan Obo mixed rare earth (RE) concentrate is one of the most significant rare earth mineral resources worldwide. However, the concentrated sulfuric acid roasting method, which is commonly used to treat ores, generates pollutants such as waste gas, wastewater, and leach residue, resulting in the squandering of the associated resources. This paper introduces a green process involving selective mineral phase transformation (MPT) by heating, followed by leaching to separate bastnaesite and monazite in a mixed RE concentrate to facilitate their subsequent decomposition or extraction. The effects of the MPT conditions on rare earth extraction were investigated. During the MPT process, bastnasite decomposed into REOF, which is more easily leached, whereas monazite remained unchanged. Under suitable conditions, the leaching efficiency of REOF reached 93.7%, while that of monazite (REPO4) was only 3.2%. Furthermore, the content of monazite in the leach residue was 91.2%. Compared to the mixed RE concentrate, numerous cracks and pores were generated on the surface and inside the MPT products. Furthermore, the total pore volume and specific surface area significantly increased, which made the reaction between the MPT products and hydrochloric acid more efficient. Thus, the MPT process facilitated the leaching of bastnasite and its separation from monazite.

Nanoscale Al precipitation in the Si phase in AlSi10Mg alloy during electron beam powder bed fusion

Additive manufacturing of Al alloys has garnered attention in the aerospace and automobile industries. This is the first study on the formation of nanoscale Al precipitates in the Si phase of an AlSi10Mg alloy during electron beam powder bed fusion (EB-PBF). Spherical Si particles were homogeneously dispersed in the Al matrix, highlighting the difference from the laser beam PBF (LB-PBF) microstructures. Nanoscale Al phase was formed with a crystallographic orientation relationship with the surrounding Si phase: (111)Si//(111)Al and [11¯0]Si//[11¯0]Al. The formation of Al nanoprecipitates was attributed to an interplay between non-equilibrium solidification, wherein excess Al was dissolved in the Si particles, and the subsequent decomposition of the supersaturated Si phase during high-temperature exposure owing to the preheating procedure. To the best of our knowledge, such formation of Al nanoparticles has not been reported in AlSi10Mg produced through conventional processing or LB-PBF. Thus, the unique thermal history of EB-PBF provides novel opportunities for microstructural evolution, which may be beneficial for the development of novel Al-based alloys.

Highly efficient nickel recovery from industrial wastewater via synergistic electrodeposition and electrocatalytic oxidation technique

This study was conducted to address water pollution concerns entwined with electroless nickel plating (ENP) industry. Its principal endeavor centers on the development and application of an innovative single-compartment technique to proficiently treat spent ENP baths. The research demonstrated the recovery of Nickel (Ni) from wastewater through synergistic interactions between electrocatalytic oxidation and electrodeposition processes. Electrochemical tests used a direct current power supply in constant current mode, with the positive pole on IrO2/Ti mesh and negative pole on stainless steel. Zero-valent nickel recovered on the electrodes was conclusively identified via SEM, XRD, and EDS analyses. This work carefully examined the impact of initial pH, initial Ni ion concentration, and current density (CD) on electrochemical recovery efficiency. The findings suggest that higher current densities positively influence the Ni recovery ratio. Additionally, through meticulous experiments, the viability of this approach for treating spent ENP baths has been confirmed. An impressive 98.88% recovery of Ni was achieved under specific conditions: CD 4.5 mA cm−2, experimental time 180 min, pH 4.5, electrodes spacing 1.5 cm, temperature 55 °C, and a dilution factor 10 times. The study demonstrated the process for Ni recovering from ENP wastewater through direct oxidation and subsequent decomposition, leading to liberation of free Ni ions. The recovered substance, identified as zero-valent nickel, adheres to the electrodes. The method employed in this research is described by its cost-effectiveness, user-friendliness, and low energy consumption. As a result, this study makes valuable contributions to both wastewater remediation and the sustainable utilization of Ni resources.

Adaptive Online Decomposition of Surface EMG Using Progressive FastICA Peel-Off.

This study presents a method for adaptive online decomposition of high-density surface electromyogram (SEMG) signals to overcome the performance degradation during long-term recordings. The proposed method utilized the progressive FastICA peel-off (PFP) method and integrated a practical double-thread-parallel algorithm into the conventional two-stage calculation approach. During the offline initialization stage, a set of separation vectors was computed. In the subsequent online decomposition stage, a backend thread was implemented to periodically update the separation vectors using the constrained FastICA algorithm and the automatic PFP method. Concurrently, the frontend thread employed the newly updated separation vectors to accurately extract motor unit (MU) spike trains in real time. To assess the effectiveness of the proposed method, simulated and experimental SEMG signals from abductor pollicis brevis muscles of ten subjects were used for evaluation. The results demonstrated that the proposed method outperformed the conventional method, which relies on fixed separation vectors. Specifically, the proposed method showed an improved matching rate by 3.63% in simulated data and 1.98% in experimental data, along with an increased motor unit number by 2.39 in simulated data and 1.30 in experimental data. These findings illustrated the feasibility of the proposed method to enhance the performance of online SEMG decomposition. As a result, this work holds promise for various applications that require accurate MU firing activities in decoding neural commands and building neural-machine interfaces.

UV photolysis of oxalyl chloride: ClCO radical decomposition and direct Cl2${\rm Cl}_2 {\rm }$ formation pathways

AbstractOxalyl chloride, , is widely used as a photolytic source of Cl atoms in reaction kinetics studies. photolysis is typically assumed to produce Cl atoms with an overall yield of 2 via three‐body dissociation, , followed by fast subsequent ClCO unimolecular decomposition of either the energetically excited fragment, , or the thermalized ClCO radical, . However, a study by Huang et al. (J. Phys. Chem. A 121 (2017) 2888–2895) found that UV photolysis of at directly yields with a photolysis quantum yield of . This new product pathway may complicate the use of as a clean source of Cl atoms and challenges the previously accepted photodissociation scheme. The purpose of the present work was 2‐fold. Firstly, the unimolecular decomposition of and ClCO radicals has been investigated in / gas mixtures after UV photolysis at and . Cl atoms were captured by added in excess such that concentration‐time profiles of HCl measured by means of mid‐infrared frequency modulation spectroscopy reflect the temporally separated Cl formation pathways. The low‐pressure thermal ClCO decomposition rate constant was determined to be at , which is in very good agreement with previously reported literature values. Secondly, the photolysis quantum yield of direct formation from photofragmentation was studied with time‐of‐flight mass spectrometry using a photoelectron photoion coincidence setup. Calibrated concentration‐time profiles were recorded and analyzed using kinetic simulations accounting for both direct and secondary formation of from photolysis and reactions involving Cl, ClCO, and , respectively. Direct formation could be confirmed, where wavelength‐dependent quantum yields of , , and at , , and were determined. Complementary quantum‐chemical calculations of the potential energy diagram for ground‐state photodissociation reveal a low‐lying energy barrier for the formation of phosgene, . We suggest that subsequent and Cl formation from energetically excited may actually play a role for the overall photodissociation of .

The effect of dead standing (marcescent) biomass on litter decomposition in herbaceous flora is governed by plant functional group

Abstract In autumn, temperate herbs begin to senesce and gradually shed their litter. However, surprisingly large amounts of dead biomass remain standing, that is, marcescent. The consequences of marcescence for the decomposition of biomass once it finally reaches the soil are largely unknown. Here, we aimed to determine whether marcescence affects subsequent litter decomposition in the organic layer to such an extent that its mass loss and chemistry are distinguishable from those of directly shed biomass. We further aimed to disentangle the role of plant functional traits and groups (forbs vs. grasses) concerning the marcescence effect on decomposition. To this end, we sampled the living, marcescent and shed senescent biomass of 39 herbaceous plant species grown in a common garden experiment, determined plant functional traits and incubated the marcescent and shed plant tissues in the field in an allochthonous organic layer for 6 months. We determined the mass loss, C and N contents, chemical composition and microbial community structure of the decomposed tissues. Our results show that marcescent tissues decomposed more slowly than directly shed tissues (mass loss 37.3% vs. 63.2% for forbs, 43.5% vs. 45.5% for grasses), likely due to more favourable conditions for decomposition in the organic layer. These were reflected in a significantly higher microbial colonization of shed (~333 and 708 μg biomass C g−1 for forbs and grasses, respectively) than marcescent tissue (~189 and 543 μg biomass C g−1 for forbs and grasses, respectively) even after 6 months in the organic layer. Moreover, higher relative contributions of aliphatics and polyphenolics in shed tissues indicated a more advanced stage of decomposition. Notably, marcescent tissues of forbs, with a more complex growth architecture (being composed of stems [marcescent] and leaves [shed]), decomposed substantially more slowly than directly shed tissues. In contrast, differences in decomposition between marcescent and shed tissues of grasses, with a more uniform growth architecture, were substantially less pronounced. These findings highlight that marcescence in the temperate herbaceous flora can strongly affect litter decomposition and thus C and nutrient cycling through temperate ecosystems, but that the extent to which marcescence affects decomposition depends on plant functional group.

Dynamic Changes of Dissolved Organic Matter Derived from Algal Decomposition and the Environmental Effects in Eutrophic Lakes

The global occurrences of lake eutrophication have led to algal bloom and the subsequent algal decomposition, releasing high amounts of algae-derived dissolved organic matter (DOM) into the lake water. Algae-derived DOM could regulate the quantity and composition of DOM in lake water and further impact the biogeochemical cycles of multiple elements. In this study, the dynamic changes in the quantity and quality of DOM during algal decomposition under different eutrophic scenarios (e.g., from oligotrophication to severe eutrophication) were monitored, and the corresponding environmental effects (e.g., microbial responses and greenhouse gas emissions) caused by algal decomposition were further explored. The results showed that algal decomposition significantly increased the DOM levels, bioavailability, and intensities of fluorescent components in the water. The total DOM levels gradually decreased, whereas the average molecular weight increased along the decomposition process. Furthermore, unsaturated hydrocarbon and aliphatic compounds were preferentially utilized by microorganisms during algal decomposition, and some refractory molecules (e.g., lignin, condensed hydrocarbons, and tannin with high O/C values) were synchronously generated, as evidenced by the results from ultra-high-resolution mass spectrometry. The dominant bacterial species during algal decomposition shifted from Proteobacteria (46%) to Bacteroidetes (42%). In addition, algae addition resulted in 1.2-5 times the emissions of CO2 and CH4 from water, and the emission rates could be well predicted by the optical index of a254 in water. This study provides comprehensive perspectives for understanding the environmental behaviors of aquatic DOM and further paves the ways for the mitigation of lake eutrophication.