Degradation Of Organic Matter Research Articles

Response of different plants to ecological floating bed-microbial fuel cells: Decontamination and power generation

Screening suitable plants that can facilitate decontamination and sustainably harvest electricity plays a crucial role in phyto-power integrated with bioelectrochemical systems (BES). Here, four plant-integrated microbial fuel cell (PMFCs) were assembled to assess decontamination and power generation performance within micro-contaminated water. The results demonstrated the Hydrocotyle vulgaris L.-MFC exhibited exceptional performance, achieving optimal removal rates of 53.17% for COD, 88.35% for TN, 80.51% for NO3−-N, 98.56% for NO2−-N, and 99.89% for NH4+-N, respectively. The same tendency is observed for power generation performance. It is attributed that plant introduction could enhance the enrichment of the exoelectrogen in the rhizosphere. Furthermore, the dominant functional bacteria such as Proteobacteria, Actinobacteriota, Firmicutes, Bacteroidota and Chloroflexi contributing to nitrogen cycle, autotrophic denitrification, and organic matters degradation were observed in PMFCs significantly more than that of single MFC. The present study could provide brandnew technique reference for micro-polluted water remediation in real-world scenarios.

Evaluation of fate of organic matter in sediment through microcosm experiments

AbstractLaboratory microcosm experiments help to understand the degradation pattern of different sources derived from organic matter (OM) at the sediment–water interface and relate it to field processes. Microcosm experiments were carried out for 65 days to assess the degradation of organic materials such as diatoms, zooplankton, and mangrove leaves using source‐specific fatty acid (FA) biomarkers. The viable bacterial population in the microcosm sediment was low on day 1, but on day 3, it increased substantially by two to threefold in all the treatments. An increase in the bacterial population resulted in a decrease in the FAs specific to organic materials during the initial incubation phase (10 days), suggesting the degradation of organic materials derived from different sources. The FAs specific to diatoms showed faster degradation when compared to zooplankton and mangrove‐specific FAs. The degradation of FAs was influenced by the nature of the source material, unsaturation of FAs, and the sediment type. Sandy sediment facilitated higher degradation of diatom and zooplankton‐specific FAs, whereas mangrove‐specific FAs showed higher degradation in silty‐clay sediment. Thus, bacterial community composition coupled with the habitat characteristics, the OM composition, and the grain size of the sediment, influenced the degradation of FAs. The degradation of mangrove‐specific long‐chain FAs was ~1.11–2.5 times higher when spiked with plankton‐derived labile OM from mixed sources, which otherwise took a longer time for degradation pointing toward co‐metabolism (priming effect), which could play a significant role in the cycling of terrestrial plant‐derived OM in an estuarine ecosystem.

88 Ruminal degradation profiles of dry matter, organic matter, and crude protein of finishing diets with different levels of inclusion of dried distiller’s grains plus solubles and soybean meal

Abstract The objective of this study was to estimate the ruminal degradation profile of dry matter (DM), organic matter (OM), and crude protein (CP) in concentrate-based diets with different levels of inclusion of dried distiller’s grains plus solubles (DDGS) and soybean meal (SBM). Red Angus steers [n = 4; body weight (BW) = 360 ± 9 kg] with ruminal, duodenal, and ileal cannulas, were used in a 4 × 4 latin square. Diets (TMR) consisted of dry-rolled corn (70%), hay (10%), liquid supplement (5%), and test ingredients (15%). Treatments were (DM basis): 1) 15.0% DDGS (CON); SBM in replacement of 50% of DDGS (SBM50); SBM in replacement of 75% of DDGS (SBM75), and SBM in replacement of 100% of DDGS (SBM100). Each period lasted 18-d, consisting of a 7-d diet adaptation followed by an 11-d collection period. An in situ ruminal incubation of each TMR was performed from d 8 to 11 of each period. Ingredients were weighed separately, maintaining their proportion in the TMR. Air-dried TMR sample (6 g, 2 mm grind) was ruminally incubated in a nylon bag (Ankom, 10 × 20 cm) using the same steer from the in vivo study. Samples were incubated for 0, 2, 4, 8, 16, 24, 48, and 72 h. The number of bags varied as a function of the incubation time to guarantee enough residual samples after incubation, where more bags per sample were incubated for the longer incubation times relative to the shorter incubation times (72 and 48 h, n = 5; 24 h, n = 4; 16 h, n = 3; 8 h and 4 h, n = 2; 2 h and 0 h, n = 1). DM, OM, and CP degradation were estimated by using the following model: Yt = a + b × (1 − e(−kd × t)), The NLIN procedure of SAS 9.4 was used and restricted and full models were compared by a likelihood ratio test. Rumen degradable protein (RDP) of each TMR was calculated as follows: RDP = a + b + [kd/(kd + kp)], where kp was 0.05 h−1). There were no differences (P ≥ 0.47) on the fractions a, b, and kd, or RDP (55%) between treatments for DM, OM, and CP. According to our analysis, approximately 13 h of incubation is necessary to accurately estimate the RDP content of the TMR. The NASEM (2016) adopts 35 and 75% of RDP for DDGS and SBM, respectively, based on fixed incubation time of 16 h. Most studies have evaluated degradation profiles of individual feed and not TMR; however, animals are fed complete diets, made up by feedstuff that vary in physical characteristics, nutrient composition, and consequently RDP. In this study, the similar degradation profiles between diets suggest that RDP of complete diets differs from that of individually assayed ingredients.

Characteristics of microplastics and their effects on phthalates and microbial activity in greenhouse soil after long-term planting

As an exogenous pollutant, the microplastics accumulated in soil could alter microbial activity. The use of plastic mulch in greenhouse vegetable planting not only enhances vegetable yield and quality, but also leads to the formation and accumulation of microplastics in the soil over time. It is essential to determine the characteristics of microplastics and microorganisms in soils with varying years of planting is crucial for ensuring vegetable quality and quantity. Therefore, this study investigated the abundance and particle size of microplastics, the concentration of phthalates (PAEs), and the dynamics of soil microbial activity in greenhouse soils with different planting years (5, 10, 15, 20, 25, and 30 years). Results showed that microplastics increased in abundance, particle size, and PAEs concentration as planting years progressed. Specifically, the abundance of microplastics rose from 70.0±8.7 to 224.0±10.4 items/kg, with the proportion of microplastics sized 0-2 mm increasing from 14.02 to 69.11%, and the total PAEs concentration in the soil escalating from 0.31 to 1.89 mg/kg. Additionally, Bacteroidetes and Actinobacteria levels increased, correlating with organic matter degradation. Metabolic pathway linked to degradation were enriched according to KEGG analysis. Correlation analysis revealed that microplastics notably decreased soil pH, creating an acidic environment that boosted urease activity and the relative abundance of Nitrospirae. This study sheds light on the accumulation characteristics of microplastics and their impact on soil microbial activity following prolonged planting.

Demo-scale up-flow anaerobic sludge blanket reactor coupled with hybrid constructed wetlands for energy-carbon efficient agricultural wastewater reuse in decentralized scenarios

The impact of climate change on water availability and quality has affected agricultural irrigation. The use of treated wastewater can alleviate water in agriculture. Nevertheless, it is imperative to ensure proper treatment of wastewater before reuse, in compliance with current regulations of this practice. In decentralized agricultural scenarios, the lack of adequate treatment facilities poses a challenge in providing treated wastewater for irrigation. Hence, there is a critical need to develop and implement innovative, feasible, and sustainable treatment solutions to secure the use of this alternative water source. This study proposes the integration of intensive treatment solutions and natural treatment systems, specifically, the combination of up-flow anaerobic sludge blanket reactor (UASB), anaerobic membrane bioreactor (AnMBR), constructed wetlands (CWs), and ultraviolet (UV) disinfection. For this purpose, a novel demo-scale plant was designed, constructed and implemented to test wastewater treatment and evaluate the capability of the proposed system to provide an effluent with a quality in compliance with the current European wastewater reuse regulatory framework. In addition, carbon-sequestration and energy analyses were conducted to assess the sustainability of the proposed treatment approach. This research confirmed that UASB rector can be employed for biogas production (2.5 L h−1) and energy recovery from organic matter degradation, but its effluent requires further treatment steps to be reused in agricultural irrigation. The AnMBR effluent complied with class A standards for E. coli, boasting a concentration of 0 CFU 100 mL−1, and nearly negligible TSS levels. However, further reduction of BOD5 (35 mg L−1) is required to reach water quality class A. CWs efficiently produced effluent with BOD5 below 10 mg L−1 and TSS close to 0 mg L−1, making it suitable for water reuse and meeting class A standards. Furthermore, CWs demonstrated significantly higher energy efficiency compared to intensive treatment systems. Nonetheless, the inclusion of a UV disinfection unit after CWs was required to attain water class B standards.

Inactivation of Microcystis aeruginosa using piezoelectric T-BaTiO3/Ag3PO4-PVDF composite photocatalyst: Characterization, performance and mechanism

To mitigate the profound impact of Microcystis aeruginosa algal bloom outbreaks on aquatic ecosystems and human health, a piezoelectric T-BaTiO3/Ag3PO4-PVDF composite photocatalyst (T-BTO/AP-PVDF) was successfully synthesized in this study. The catalyst inactivated 97.12% of Microcystis aeruginosa within 4 h by the combined effect of ultrasound and sunlight, and the inactivation rate remained above 88% after five cycles of reuse, which exhibits excellent inactivation effectiveness and stability. Under the conditions of piezo-photocatalytic, the analysis of the physiological properties of algal cells showed that T-BTO/AP-PVDF produced a large amount of •OH, which were active species that could effectively inactivate the algal cells and promote the degradation of organic matter, thus preventing the occurrence of secondary pollution. The composite photocatalysts were characterized using XRD, SEM, XPS, FTIR, PFM, and WCA. Combined with the results of quenching experiments, possible mechanisms for the inactivation of Microcystis aeruginosa by T-BTO/AP-PVDF were proposed. The application results in actual water bodies further proved that T-BTO/AP-PVDF is a new method for effectively inhibiting cyanobacterial bloom outbreaks and shows promising potential for application.

Enhanced electro-catalytic activity of TNTs/SnO2-Sb electrode through the effect mechanism of TNTs architecture

The TiO2 nanotubes arrays/SnO2-Sb (TNTs/SnO2-Sb) electrode is successfully fabricated using the solvothermal synthesis technique. Various architectures of TNTs are constructed by varying the anodization voltage and time, aiming to investigate their impact on the structural and electrochemical properties of the SnO2-Sb electrode. The anodization voltage is identified as the primary influencing factor on the morphology and surface hydrophilia of TNTs arrays, which is evidenced by scanning electron microscopy (SEM) and contact angle testing. In contrast, the effect of anodization time is relatively small. SEM, X-ray diffraction (XRD), linear sweep voltammograms (LSV), and electrochemical impedance spectroscopy (EIS) results indicate that the morphology and crystal size of the catalytic coating, as well as the oxygen evolution potential of the electrode, are influenced by the pore size of TNTs arrays. The influencing mechanism of enhanced electrochemical activity by adjusting the architecture of TNTs arrays is investigated using X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and hydroxyl radicals (·OH) generation test. The results reveal a higher concentration of oxygen vacancies on the sample with a compact and smaller particle coating, indicating the presence of more adsorbed oxygen species. Consequently, this enhances the generation capacity of active radicals for organic matter degradation. The electrode featuring TNTs arrays with a length of 950 nm and a pore diameter of 100 nm exhibits the most effective remediation of phenol-containing wastewater, achieving approximately 92% ± 4.6% removal after a duration of 2 h.

Composting Dairy Manure with Biochar: Compost Characteristics, Aminopyralid Residual Concentrations, and Phytotoxicity Effects

Aminopyralid (2-pyridine carboxylic acid, 4-amino-3, 6-dichloro-2-pyridine carboxylic acid) is an auxin herbicide that has been used widely to control broadleaf weeds in pasture and hay fields. With no post-application withdrawal time, aminopyralid absorbed into forage material can contaminate compost feed stocks such as hay, grass bedding material, and manure. Composts derived from such feed stocks raises concerns about after-effect injuries to sensitive crops by residual aminopyralids. Biochar (BC) additive may affect the composting process and immobilizes organic pollutants. This study examined the effect of composting dairy manure/sawdust 1:1 mixture containing 10 ppb (wet) of aminopyralid with 0%, 2%, 4%, and 10% (w/w) BC levels on chemical and biological characteristics of compost, residual aminopyralid concentration, and intensity of plant injury to tomato (Lycopersicon esculentum L.) plants after composting in 140 L plastic rotary drum reactors for two 6-month cycles. Biochar addition decreased organic matter degradation and intensified reduction in residual aminopyralid levels in a dose-dependent manner. Composting with BC concentrated more N, P, and K, caused mild plant injuries, and increased the above ground biomass compared to the no BC incorporation. Addition of BC for composting aminopyralid-contaminated dairy manure can increase the phyto safety level of compost while enhancing the key fertilizer values.

Enhanced response of soil respiration to experimental warming upon thermokarst formation

AbstractAs global temperatures continue to rise, a key uncertainty of terrestrial carbon (C)–climate feedback is the rate of C loss upon abrupt permafrost thaw. This type of thawing—termed thermokarst—may in turn accelerate or dampen the response of microbial degradation of soil organic matter and carbon dioxide (CO2) release to climate warming. However, such impacts have not yet been explored in experimental studies. Here, by experimentally warming three thermo-erosion gullies in an upland thermokarst site combined with incubating soils from five additional thermokarst-impacted sites on the Tibetan Plateau, we investigate how warming responses of soil CO2 release would change upon upland thermokarst formation. Our results show that warming-induced increase in soil CO2 release is ~5.5 times higher in thermokarst features than the adjacent non-thermokarst landforms. This larger warming response is associated with the lower substrate quality and higher abundance of microbial functional genes for recalcitrant C degradation in thermokarst-affected soils. Taken together, our study provides experimental evidence that warming-associated soil CO2 loss becomes stronger upon abrupt permafrost thaw, which could exacerbate the positive soil C–climate feedback in permafrost-affected regions.

Assessing the consequences of recent climate change on World Heritage sites in South Greenland

In the Arctic region, microbial degradation poses a significant threat to the preservation of archaeological deposits, actively consuming irreplaceable cultural and environmental records. In this study we assess the potential effects of the last 40 years of climate change on organic archaeological deposits within the UNESCO World Heritage area Kujataa in South Greenland. We use the dynamic process-oriented model, CoupModel to simulate soil temperatures and soil moisture contents at four archaeological sites in the area. The results show that the organic deposits have experienced a substantial warming the last 40 years, which combined with decreasing soil moisture contents creates a dangerous combination that can accelerate the degradation of organic materials. Currently, there are 583 archaeological sites registered within the area. Our findings highlight that the current climatic conditions are not conducive to organic preservation. The greatest risk of degradation lies within the relatively dry continental inland areas of the study region, where all Norse Viking Age settlements are situated. However, even at the "cold" and "wet" outer coast, the combined effects of rising summer temperatures and declining soil moisture levels may already be exerting a noticeable impact.

Ultrathin Sulfur‐Doped g‐C3N4 Nanosheets Controlled by Steam Activation for Enhanced Visible‐Light Photocatalytic Performance

AbstractGraphite carbon nitride (g‐C3N4) has garnered considerable attention due to its excellent photocatalytic properties for the degradation of organic matter in wastewater treatment. Herein, sulfur‐doped g‐C3N4 nanosheets (CN−S‐X) were successfully synthesized via physical steam activation using thiourea and urea as precursors. Comprehensive characterizations demonstrate that the enhanced photocatalysis is attributed to the ultrathin structure, highly active site, vacancy defects, and high specific surface area due to the synergy of S doping and steam activation. The as‐prepared CN−S‐25 photocatalyst exhibits a desirable degradation efficiency of 95.4 % for methylene blue dye with a high degradation rate of 2.65×10−2 min−1 under visible‐light irradiation, which are 2.1 and 5.52 times those for bulk g‐C3N4, respectively as well as good reusability and stability. This study provides a simple and promising strategy to regulate the nanostructure of g‐C3N4 for highly efficient photocatalytic degradation of organic pollutants.

Soil Fertility and Bacterial Community Composition in Response to the Composting of Biochar-Amended Chicken Manure

Amidst the burgeoning expanse of the poultry sector, the escalation of chicken manure production has ensued, potentially exacerbating ecological contamination. However, the application of chicken manure is bound to transmute the habitat of edaphic microorganisms, precipitating an alteration in the soil’s microbial consortium. The composting of biochar-amended chicken manure and wood chips (biochar composting products, BCPs) was used to improve Chinese cabbage (Brassica campestris L.) production and regulate soil properties and bacterial community structure. On the 40th day of Chinese cabbage growth, soil and Chinese cabbage were collected for laboratory analysis. The effects of different proportions of BCPs (0, 1%, 3%, 5% and 7% biochar) on soil fertility, enzyme activity, the microbial community and the growth of Chinese cabbage were studied under facility conditions. The results showed that the growth performance and quality of Chinese cabbage were significantly increased with increasing BCP ratios. Soil fertility indicators including pH, AN, AP, AK and SOM were significantly increased, except for the pH value in the 1% BCP group. The activities of phosphatase, catalase and urease were increased for all groups of BCP treatment. The soil microbial community response was significantly different, and the application of 5% and 7% BCPs reduced the abundance, diversity and evenness of soil bacteria. Chinese cabbage growth performance was positively correlated with an increase in BCP supplemental levels in the range of 3–5%. Also, the abundance, diversity and uniformity of the soil microbial community were improved in the 3% BCP treatment group. Therefore, the dominant bacterial phyla were Bacteroidetes, Actinobacteriota, Gemmatimonadota, Myxococcota, Bdellovibrionota and Firmicutes, especially the Bradyrhizobium of Proteobacteria. BCP treatment reduced the degradation of soil organic matter. In addition, it also improved the relative abundance of sequences associated with improving soil fertility. Collectively, these findings offer insights for the re-evaluation of application management strategies for BCP organic fertilizers.

Synergistically electronic interacted PVDF/CdS/TiO2 organic-inorganic photocatalytic membrane for multi-field driven panel wastewater purification

Solar-driven wastewater purification technology is a promising candidate to solve the hazards of water contaminants. However, it is difficult for most of particulate photocatalysts to maintain durable photoactivity due to its micro/nano size. Herein, a synergistically electronic interacted membrane catalyst with large extending area and high pollutant capture capacity was processed based on a highly active CdS/TiO2 heterojunction and ferroelectric polyvinylidene fluoride for achieving highly efficient Cr6+-to-Cr3+ (CTC) reduction (1.6×10−2 min−1) and synchronous decomposition of organic matters (methylene blue (1.2×10−2 min−1) and bisphenol A (0.6×10−2 min−1)) under simulated sunlight (SSL, 74.1 mW·cm−2) irradiation following a durably steady photoactivity even being recycled for 20 times, which effectively avoided the hazards of secondary pollution. Subsequently, a tailor-made panel wastewater purification system was first built based on this membrane catalyst to drive CTC reduction and synchronous organic matter degradation, and high-efficiency purification performance was presented on this panel system under multi-field drive of light-activation and piezoelectric polarization. This work provides an insight for photocatalytic wastewater purification through membrane catalyst assisted panel technology.

Sediment microbial fuel cell with biochar-modified cathode for remediation of black-odorous water sediments and analysis of microbial community

Sediment microbial fuel cells (SMFCs) generate electricity through microbial degradation of organic matter in sediments, and the cathode catalyst used for the oxygen reduction reaction is a key factor affecting the performance of SMFCs. To improve power production in SMFCs and remediate black-odorous water sediments, this study modifies the cathode carbon felt of the SMFC system with Enteromorpha prolifera (EP) biochar with high N and P content. The study demonstrated that the SMFC system with the modified cathode carbon felt (C-800℃/CF) exhibited superior power generation capabilities, achieving a maximum power density of 219.44 mW·m−2. Over 25 days of operation, the anode biofilm effectively degraded around 78.15% of total organic carbon, 79.55% of acid volatile sulfide, 74.78% of total nitrogen, 80.58% of ammonia nitrogen, and 77.46% of total phosphorus in the sediment. In addition, microbial community analysis showed that functional bacteria Thiobacillus, Acidaminobacter, Sulfurimonas, Bacteroidetes_vadinHA17, and Sideroxydans were the dominant genera in the anode biofilm.

Photocatalytic peroxydisulfate activation for dissolved organic matter degradation in eutrophic lake water using S-scheme BiVO4/g-C3N4 3D/2D heterojunction under visible light

Large amounts of carbon are stored primarily in dissolved organic matter (DOM), which plays an important indicator of lake eutrophication. However, removing DOM from eutrophic lakes remains a major challenge. Herein, a novel S-scheme flower-like microsphere BiVO4/nanosheet g-C3N4 3D/2D heterojunction was successfully constructed using a two-step method for DOM degradation of real eutrophic lake water in the presence of peroxydisulfate (PDS). 1.0-BiVO4/g-C3N4/PDS exhibited highly efficient photocatalytic performance with an 87.8 % removal rate of DOM for 60 min, which was 5.3 and 8.9 times higher than BiVO4/PDS and g-C3N4/PDS, respectively. Sulfate radical (·SO4−), hydroxyl radical (·OH) and singlet oxygen (1O2) were mainly responsible for DOM degradation in the 1.0-BiVO4/g-C3N4/PDS system, and the transformation pathway of 1O2 was emphatically analyzed. In addition, the changes of fluorescence components in DOM were detected using synchronous fluorescence spectra, second derivative spectra, and two-dimensional correlated spectroscopy analysis. Humic-like fluorescence, fulvic-like fluorescence, and protein-like substances were removed higher than 85.30 %, 73.02 %, and 67.23 % by the 1.0-BiVO4/g-C3N4 catalyst activating the PDS under visible light (VL), respectively. When the toxicity of catalytically treated eutrophic lake water was estimated by growth inhibition of Escherichia coli, the biotoxicity of DOM decreased continuously in the BiVO4/g-C3N4/PDS/VL coupling process. Theoretical calculations and photoelectrochemical tests suggested that the BiVO4/g-C3N4/PDS catalytic activity enhancement was attributed to the S-scheme mechanism and hybrid advanced oxidation process. It is expected that this work can provide new insight into DOM degradation in eutrophic lake water by the heterogeneous photocatalysis combined with the PDS activation system.

Degradation of phenol by Cu-Ni bimetallic-doped sludge biochar as a fenton-like catalyst: Mechanistic study and practical application

In this study, the sewage sludge was converted into sludge biochar (SBC) and doped with Cu-Ni bimetal to synthesize a novel composite catalyst (Cu-Ni@SBC) for the activation of H2O2 for phenol degradation. Characterization results showed that the Cu-Ni bimetal was successfully doped into the SBC and led to the formation of a porous structure with abundant cavities, resulting in a larger specific surface area and higher adsorbed oxygen content. Mechanism analysis revealed a valence state conversion cycle between Cu0-Cu(II), Ni(III)-Ni(II) and Cu-Ni which made Cu-Ni@SBC have higher electron transfer performance. Response surface methodology was applied to determine the optimal preparation and reaction conditions, under which the Fenton-like system composed of Cu-Ni@SBC and H2O2 removed 100 % of phenol and mineralized 69.1 % of TOC from simulated wastewater. In addition, the experimental results showed that the Cu-Ni@SBC material had a relatively wide pH adaptation range (4–8), and the removal efficiency of phenol could reach 76.4 % after 5 cycles of experiments, and the catalytic inhibition rates of the two common coexisting anions, HCO3– and Cl-, were 17.1 % and 0 %, respectively. The results of practical application revealed that the phenol removal efficiency reached 90.44 % and the pollutant mineralization rate could reach 58.5 % within 90 min, which proved that the catalyst was suitable for the advanced degradation of organic matter in coal chemical wastewater. Therefore, Cu-Ni@SBC can be considered as a promising Fenton-like catalyst, and the process method is also of some guiding significance for the treatment of coal chemical wastewater.

Conversion of Natural Soil to Paddy Promotes Soil Organic Matter Degradation in Small-Particle Fractions: δ13C and Lipid Biomarker Evidence

The stabilization mechanism of soil organic matter (SOM) has received considerable attention. It is widely accepted that mineral sorption/protection is important for SOM stabilization. However, it remains unclear which organic carbon component is beneficial for mineral protection. We collected soil samples from a paddy field (TP) to compare with natural soil (NS). To illustrate the behavior of different SOM pools and their protection by particles, we separated the soils into different particle-size fractions and then removed the active minerals using an acid mixture (1 M HCl/10% HF). The different carbon pools were analyzed using stable carbon isotopes and lipid biomarkers. Our study showed that acid treatment evidently increased the extractability of free lipids, usually over 60%, which confirmed the predominant role of minerals in SOM protection. For NS, the δ13C values increased with decreasing soil particle sizes and soil depths, indicating that 13C-enriched SOM was selectively preserved. However, this trend disappeared after cultivation, which was mainly attributed to the combined effects of the input of 13C-depleted fresh SOM and decomposition of the preserved 13C-enriched SOM. Meanwhile, based on the degradation parameters of the overall lipid biomarkers, SOM showed higher degradation states in clay and silt fractions than in the sand fraction before cultivation. It is possible that the small particle-size fractions could selectively absorb highly degraded SOM. The clay-associated SOM showed a low degradation state, but its carbon content was low after cultivation. We propose that the previously protected SOM was degraded after cultivation and was replaced by relatively fresh SOM, which should be carefully monitored during SOM management.

Fenton reaction in the process of “Laser + Fe” mode excited plasma for Rhodamine B degradation

The spectral emission of laser-induced plasma in water has a broadband continuum containing ultraviolet light, which can be used as a novel light source for the degradation of organic compounds. We studied the degradation process of the organic dye Rhodamine B (RhB) using plasma light source excited by the “Laser + Fe” mode. Spectral analysis and reaction kinetics modelling were used to study the degradation mechanism. The degradation process using this light source could be divided into two stages. The initial stage was mainly photocatalytic degradation, where ultraviolet light broke the chemical bond of RhB, and then RhB was degraded by the strong oxidising ability of ·OH. As the iron and hydrogen ion concentrations increased, the synergistic effect of photocatalysis and the Fenton reaction further enhanced the degradation rate in the later stage. The plasma excited by the “Laser + Fe” mode achieved photodegradation by effectively enhancing the ultraviolet wavelength ratio of the emission spectrum and triggered the Fenton reaction to achieve rapid organic matter degradation. Our findings indicate that the participation of the Fenton reaction can increase the degradation rate by approximately 10 times. Besides, the impact of pH on degradation efficiency demonstrates that both acidic and alkaline environments have better degradation effects than neutral conditions; this is because acidic environments can enhance the Fenton reaction, while alkaline environments can provide more ·OH.

Short-term effects of a simulated massive river flood and its recovery on sediment biogeochemistry of a Mediterranean lagoon

ABSTRACT Strong rainfalls and river floods are becoming increasingly frequent and intense in southern Europe. Mediterranean coastal lagoons, due to their hydrological characteristics, could mitigate the consequences of such events, whose effects on sediment biogeochemistry are poorly studied, yet. To provide insights on this, we investigated short-term changes in organic matter quantity, composition, nutritional quality, degradation rates, and turnover time in a lagoonal benthocosm. Both flooding and recovery phases increased the sedimentary organic load and turnover time, whereas phytopigment contents and C degradation rates were not affected. The biochemical composition varied during both phases, with an increase in carbohydrate and lipid after the flooding, and an increase in protein and chlorophyll-a after its recovery. Our results suggest that even sudden changes in salinity caused by floods and their recovery can increase sedimentary organic loads, with minor effects on their nutritional quality. The observed effects of the flooding persist in the short-term also after the recovery of the salinity, when the substrates are pre-eminently of heterotrophic origin. Our results suggest that extreme, even if short-lasting, episodic events of flooding and recovery can severely alter the benthic trophic status of coastal lagoons, having possible effects on benthic trophodynamics.

An evaluation of the effectiveness of sumac and molasses as additives for alfalfa silage: Influence on nutrient composition, in vitro degradabilityandfermentation quality.

This study investigated the effects of sumac and molasses on nutrient composition, in vitro degradabilityandfermentation quality of alfalfa silage. Alfalfa was ensiled in quadruplicate in vacuum jars untreated group (A) or after the following treatments: sumac group at 10% (AS), molasses group at 5% (AM), and sumac (10%) and molasses (5%) group (ASM). Silos (n = 64) were stored for 0, 21, 45or 60 days. The results showed that dry matter (DM) contents of the AS, AMandASM groups were statistically higher than the control group (p < 0.001). Only on the 21st day of fermentation the crude ash content of the AS group was found to be significantly higher than the other groups (p < 0.05). In vitro, DM and organic matterdegradation values of the AMS group increased significantly (p < 0.001). A significant decrease in alfalfa silage's pH values was determined with sumac and molasses additives (p < 0.001). The ammonia nitrogen (NH3-N) values of the control, AS, AMandASM groups at Day 60 were determined as 9.08%, 7.22%, 7.00%and 6.81%respectively (p < 0.05). The water-soluble carbohydrate (WSC) values of all groups on the 60th day were significantly decreased compared to the 0th day (p < 0.001). When the groups were evaluated within themselves, there was a statistically significant difference between the 0th and 60th day lactic acid values. The acetic acid content of the A group on the 60th day was found to be significantly higher than the other groups (p < 0.01). There was a significant decrease in propionic acid levels on Days 21, 45and60 compared to Day 0 of fermentation (p < 0.001). The highest butyric acid (BA) level was determined in the A group on the 21st, 45thand60th days of fermentation (p < 0.05). In conclusion, sumac prevents proteolysis depending on its tannin content. It improves silage fermentation positively thanks to its organic acid content, while the molasses additive is effective in silage fermentation, mainly depending on the WSC level. However, it was determined that neither additive could reduce the silage pH to the appropriate value ranges due to the low doses, and they could not mainly prevent the formation of BA.