Highly Efficient Electrosynthesis of Glycine over an Atomically Dispersed Iron Catalyst.

Glycine is a nonessential amino acid that plays a vital role in various biological activities. However, the conventional synthesis of glycine requires sophisticated procedures or toxic feedstocks. Herein, we report an electrochemical pathway for glycine synthesis via the reductive coupling of oxalic acid and nitrate or nitrogen oxides over atomically dispersed Fe-N-C catalysts. A glycine selectivity of 70.7% is achieved over Fe-N-C-700 at -1.0 V versus RHE. Synergy between the FeN3C structure and pyrrolic nitrogen in Fe-N-C-700 facilitates the reduction of oxalic acid to glyoxylic acid, which is crucial for producing glyoxylic acid oxime and glycine, and the FeN3C structure could reduce the energy barrier of *HOOCCH2NH2 intermediate formation thus accelerating the glyoxylic acid oxime conversion to glycine. This new synthesis approach for value-added chemicals using simple carbon and nitrogen sources could provide sustainable routes for organonitrogen compound production.

Repair of soft magnetic properties of wasted silicon steel and Co7Fe3 alloy deposition mechanism.

In order to repair the soft magnetic properties of wasted silicon steel, a theoretical process of co-depositing Co-Fe soft magnetic alloy on the surface of wasted silicon steel is proposed. The results show that the co-deposited Co-Fe alloy coatings can serve to repair the soft magnetic properties of wasted silicon as detected by the vibrating sample magnetometer, and the alloy coatings with Co7Fe3 as the main phase structure can provide surface protection for silicon steel. Subsequently, the mechanism of co-deposited Co-Fe alloys was investigated, and it was concluded that Co2+ and Fe2+ undergo a one-step two-electron co-deposition reaction, as studied using cyclic voltammetry. The chronoamperometric analysis and its fitting results indicated that the deposition of Co2+ and Fe2+ was a diffusion-controlled transient nucleation process, and the AC impedance indicated that higher voltages were favorable for the deposition of Co-Fe alloys but were accompanied by hydrogen precipitation reactions.

Electrochemical Mechanism of the Preparation of High-Purity Indium by Electrodeposition.

Indium is a crucial material and is widely used in high-tech industries, and electrodeposition is an efficient method to recover rare metal resources. In this work, the electrochemical behavior of In3+ was investigated by using different electrochemical methods in electrolytes containing sodium and indium sulfate. Cyclic voltammetry (CV), chronoamperometry (CA), and alternating current impedance (EIS) techniques were used to investigate the reduction reaction of In3+ and the electrocrystallization mechanism of indium in the indium sulfate system. The cyclic voltammetry results showed that the electrodeposition process is irreversible. The average charge transfer coefficient a of In3+ was calculated to be 0.116 from the relationship between the cathodic peak potential and the half-peak potential, and the H+ discharge occurred at a higher negative potential of In3+. The nucleation mechanism of indium electrodeposition was analyzed by chronoamperometry. The mechanism of indium at potential steps of -0.3 to -0.6 V was close to diffusion-controlled instantaneous nucleation with a diffusion coefficient of 7.31 × 10-9 cm2 s-1. The EIS results demonstrated that the reduction process of In3+ is subject to a diffusion-controlled step when pH = 2.5 and the applied potential was -0.5 V. SEM and XRD techniques indicated that the cathodic products deposited on the titanium electrode have excellent cleanliness and purity.

Phase Transformation Behavior of the Aluminosilicate Phase During High-Pressure Hydrothermal Reduction of High-Iron Red Mud.

One-step separation and recovery of sodium, aluminum and iron in high-iron red mud in a high-calcium alkaline hydrothermal system is realized by a high-pressure hydrothermal reduction process. The transformation behavior of the aluminasilica phase in high-iron red mud is mainly investigated. The results show that under the optimized conditions, a temperature of 290℃, a Na2O concentration of 240 g/L, a calcium to silicon ratio of 3.5, and a liquid-solid ratio of 5, the Na2O content in the transition slag is reduced to 0.12%, the dealkalization rate can reach 98%, and the alumina dissolution rate is 73%. When the starch-free reductant is added, the transition slag mainly consists of hematite and hydroandradite, and when the starch reductant is added (the addition amount is 1/4 that of ω(Fe2O3) in the red mud), all Fe2O3 in the transition slag is completely reduced to Fe3O4, and the main phases are magnetite and hydrogrossular.

The surgical outcomes and perioperative complications of bowel resection as part of debulking surgery of advanced ovarian cancer patients.

BACKGROUND: To review the utilization of bowel resection in ovarian cancer surgery in our institution. METHODS: All ovarian cancer patients who received bowel resection between 2006/01 and 2018/12 were identified. Postoperative morbidities were assessed according to the Clavien-Dindo classification (CDC). RESULTS: There were 182 patients in the anastomosis group and 100 patients in the ostomy group, yielding a total of 282 patients. The median age was 57 years, and most patients had high-grade serous histology (88.7%). Forty-nine (17.3%) patients received neoadjuvant chemotherapy. During the operation, 78.7% of patients had ascites, and the median volume was 800 mL. Extensive bowel resection (at least two-segment) and upper abdominal operation were performed in 29 (10.2%) and 69 (24.4%) patients, respectively. The rectosigmoid colon was the most commonly resected (83.8%) followed by right hemicolectomy (5.9%) and small bowel resection (2.8%). No macroscopic residual disease was observed in 42.9% of the patients, whereas 87.9% had residual disease ≤ 1 cm. Among the entire cohort, 23.0% (65/282) experienced different complications. Severe complications (CDC 3-5) accounted for 9.2% of complications and were mostly categorized as pleural effusion requiring drainage (3.5%) followed by wound dehiscence requiring delayed repair in the operating room (1.8%). Nine patients experienced anastomotic leakage (AL): one in the ostomy group with extensive bowel resection and eight in the anastomosis group. The overall AL rate was 4.2% (9/212) per anastomosis. CONCLUSIONS: The execution of bowel resection as part of debulking surgery in patients with newly diagnosed ovarian cancer resulted in a severe morbidity rate of 9.2%.

Transformation Behavior of Iron Minerals in High-Iron Red Mud During High-Pressure Hydrothermal Reduction.

Nowadays, the comprehensive utilization of red mud is still a difficult problem. Using starch as the reducing agent, the "high-pressure hydrothermal reduction method" is used to separate and recover sodium, aluminum, and iron in high-iron red mud in one step in an alkaline hydrothermal system. This article focuses on the hydrothermal reduction behavior of the iron ore phase. The results showed that starch formed a strong reduction system through degradation under alkaline hydrothermal conditions, in which Fe2O3 was first partially dissolved and reduced to form Fe[OH]+, then Fe[OH]+ further reacted with Fe2O3 to form Fe3O4. At a temperature of 260°C, a C/S (calcium to silicon ratio) of 3.5, a Na2O concentration of 250 g/L, Whigh-iron red mud/Wstarch = 10, the Fe reduction rate was 98.46%, and the transformation slag at a magnetic field strength of 1800 Gs resulted in a magnetic iron concentrate powder with a TFe grade of 65.75%.

Histone deacetylase 3 suppresses the expression of SHP-1 via deacetylation of DNMT1 to promote heart failure.

AIMS: Heart failure (HF) is a progressive disease with recurrent hospitalizations and high mortality. However, the mechanisms underlying HF remain unclear. The present study aimed to explore the regulatory mechanism of histone deacetylase 3 (HDAC3) and DNA methyltransferase 1 (DNMT1)/Src homology domain 2-containing tyrosine phosphatase-1 (SHP-1) axis in HF. METHODS: The HF rat models and hypertrophy cell models were established. The characteristic parameters of the heart were detected by echocardiography. A multichannel physiological signal acquisition system was used to detect the hemodynamic parameters. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of HDAC3, DNMT1, and SHP-1 mRNAs, while Western blot was applied to analyze the expression of proteins. Masson staining was used to analyze the degree of collagen fiber infiltration. TdT-mediated DUTP nick end labeling (TUNEL) staining was performed to analyze the apoptosis of myocardial tissue cells. Co-immunoprecipitation (co-IP) was conducted to study the interaction between HDAC3 and DNMT1. Flow cytometry was used to analyze the apoptosis. KEY FINDINGS: HDAC3 and DNMT1 were highly expressed in HF rat and hypertrophy cell models. HDAC3 modified DNMT1 through deacetylation to inhibit ubiquitination-mediated degradation, which promoted the expression of DNMT1. DNMT1 inhibited SHP-1 expression via methylation in the promoter region. In summary, HDAC3 modified DNMT1 by deacetylation to suppress SHP-1 expression, which in turn led to the development of cardiomyocyte hypertrophy-induced HF. SIGNIFICANCE: This study provided potential therapeutic targets for HF treatment.

LncRNA SNHG16 accelerates atherosclerosis and promotes ox-LDL-induced VSMC growth via the miRNA-22-3p/HMGB2 axis.

Long non-coding RNAs (LncRNAs) are essential regulators in the occurrence and development of AS. Here we aim to explore the underlying molecular mechanism of LncRNA SNHG16 in regulating ox-LDL-induced VSMC proliferation, migration and invasion. After constructing AS in vivo and in vitro models, the expressions of SNHG16, miR-22-3p, HMBG2, proliferation- and metastasis-related proteins were determined by qRT-PCR and Western blot assays. Detection of serological lipids, H&E and Masson staining analysis were conducted to evaluate the AS injury in mice. The effects of ox-LDL treatment on VSMCs were examined by CCK-8, wound scratch and Transwell Chamber assays. The targeted relationship was measured by luciferase reporter and RIP assays. The results showed that SNHG16 and high-mobility group box 2 (HMGB2) expressions were increased while miRNA-22-3p expression was decreased in AS mice and ox-LDL-stimulated VSMCs. Functionally, sh-SNHG16 restrained ox-LDL-induced VSMC growth and migration. SNHG16 suppressed miRNA-22-3p expression by direct binding. Furthermore, in ox-LDL-treated VSMCs, miRNA-22-3p mimic prevented proliferation, migration, and invasion. Further explorations showed that HMGB2 was a target of miRNA-22-3p, SNHG16 upregulated HMGB2 levels by acting as a competing endogenous RNA (ceRNA) of miRNA-22-3p. More importantly, sh-HMGB2 partially reversed the effects of sh-SNHG16 together with miR-22-2p inhibitor on ox-LDL-induced VSMC proliferation, migration and invasion. Collectively, SNHG16 accelerated atherosclerotic plaque (AP) formation and enhanced ox-LDL-activated VSMCs proliferation and migration by miRNA-22-3p/HMGB2 axis.

Chemical Composition and Source Apportionment of Wintertime Airborne PM2.5 in Changchun, Northeastern China.

This study presents field observations and laboratory analyses of wintertime airborne particulate matter (PM2.5) and its chemical components in the Changchun metropolitan area, the geographical center of northeastern China. Twenty-four hour PM2.5 filter samples were collected from 23 December 2011 to 31 January 2012 at four sites in the types of traffic, residential, campus, and a near-city rural village, respectively. Daily PM2.5 concentrations ranged from 49 to 466 µg m-3, with an arithmetic average of 143 µg m-3. Laboratory analyses showed that among all measured chemical species, mineral dust contributed the largest proportion (20.7%) to the total PM2.5 mass, followed by secondary inorganic aerosols (SIA, including SO42-, NO3- and NH4+), which constituted 18.8% of PM2.5 mass. Another notable feature of PM2.5 chemical composition was high halogen (Cl- and F-) loadings at all sites, which was likely due to emissions from coal combustion, plastic manufacturing, and glass melting. Among the four sampling sites, the suburban site exhibited the highest PM2.5 levels and extremely high Cl- and F- loadings due to residential wood burning and nearby industrial facilities lacking effective emission controls. Our results report one of the earliest observations of PM2.5 composition in this region, providing a baseline of aerosol profiles of aerosol before PM2.5 was routinely measured by environmental protection agencies in China, which could be useful for assessing long-term trends of air quality and effectiveness of mitigation measures.

Lycium barbarum polysaccharide protects against Homocysteine-induced Vascular smooth muscle cell proliferation and phenotypic transformation via PI3K/Akt pathway.

Lycium barbarum polysaccharide (LBP) is an alkaloid extracted from lycium barbarum. LBP is the active component of lycium barbarum used to treat hypertension, atherosclerosis and other cardiovascular diseases in Chinese traditional medicine. However, the underlying cellular and molecular mechanisms of LBP- mediated activity in vascular disease remain poorly understood. In the present study, we showed the protective effect of LBP in vascular smooth muscle cells. Our results indicate that LBP significantly reduces the proliferation of VSMCs caused by Homocysteine (Hcy) and inhibits the phenotypic transformation of VSMCs caused by Hcy, from contractile to synthetic. LBP inhibited the protein expression of PI3K and Akt caused by Hcy, and increased the expression of miR-145. The results indicate that LBP exhibits substantial therapeutic potential for the treatment of Hcy-induced VSMCs proliferation and phenotypic transformation through inhibition of PI3K/Akt signaling pathway.

Exendin-4 reverses high glucose-induced endothelial progenitor cell dysfunction via SDF-1ß/CXCR7-AMPK/p38-MAPK/IL-6 axis.

AIM: Exendin-4, a glucagon-like peptide-1 (GLP-1) analog, has been used for treating diabetes mellitus (DM). However, its effects on improving the dysfunction of high glucose (HG)-induced endothelial progenitor cells (EPCs) remain unclear. The present study explored the effects of Exendin-4 on improving dysfunction of EPCs and the underlying mechanism. METHODS: EPCs were isolated from SD rats and identified by flow cytometry. Next, the EPCs were treated by HG and high or low concentration of Exendin-4, and cell viability, migration and tube formation were, respectively, examined by performing MTT assay, wound-healing assay and tube formation assay. Interleukin-6 (IL-6) secretion was measured by enzyme-linked immunosorbent assay (ELISA). The protein expressions of relative stromal-derived growth factor-1ß (SDF-1ß), C-X-C chemokine receptor type 7 (CXCR7), AMP-activated protein kinase (AMPK), p38 and expressions of CXCR7 and IL-6 in EPCs were measured by Western blot. The cell behaviors of EPCs treated by HG and Exendin-4 with or without silencing of CXCR7 and IL-6 were detected. RESULTS: Exendin-4 reversed the inhibitory effects of HG on viability, migration and tube formation of EPCs and on SDF-1ß/CXCR7-AMPK pathway in EPCs in a dose-dependent manner. Moreover, Exendin-4 promoted the effects of HG on IL-6 level in EPCs through the promotion of p38-MAPK phosphorylation and reduction of cleaved caspase-3 protein expressions in EPCs. However, silencing of CXCR7 and IL-6 reversed the effects of Exendin-4 on cell behaviors, inactivated SDF-1ß/CXCR7-AMPK pathway and increased cleaved caspase-3 expression in EPCs. CONCLUSIONS: Exendin-4 could ameliorate HG-induced EPC dysfunction through regulating the production of IL-6 via SDF-1ß/CXCR7-AMPK/p38-MAPK axis.

Exendin-4 regulates endoplasmic reticulum stress to protect endothelial progenitor cells from high-glucose damage.

BACKGROUND: High glucose affects the function of endothelial cells by increasing oxidative stress. Studies have found that exendin-4 can improve wound healing in diabetic mice and mice with normal blood glucose. However, the mechanism of exendin-4 in endothelial progenitor cells under high-glucose condition has not been fully elucidated. METHODS: Diabetic mouse models were established to investigate the effects of exendin-4 on endothelial progenitor cells in diabetic mice. Serum superoxide dismutase (SOD) and malondialdehyde (MDA) were determined by WST-8 and thiobarbituric acid (TBA) colorimetry, respectively. Cell viability, apoptosis and reactive oxygen species (ROS) were detected by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and flow cytometry. Gene and protein expressions were determined by Quantitative reverse transcription PCR (qRT-PCR) assay and Western blot (WB). RESULTS: The results showed that in diabetic mice, exendin-4 did not affect blood glucose or body weight, moreover, it improved aortic diastolic function, increased SOD activity and down-regulated malondialdehyde (MDA) level in the mice. In addition, exendin-4 also increased endothelial progenitor cell (EPCs) viability and reduced cell apoptosis through inhibiting p38 MAPK pathway and reducing endoplasmic reticulum stress and ROS. CONCLUSION: Exndin-4 can alleviate diabetes-caused damage to mice, moreover, it reduced endoplasmic reticulum stress and ROS through inhibiting p38 MAPK pathway in MPCs cells under high-glucose condition, thus increasing cell viability and reducing cell apoptosis.

Study of the electrochemical recovery of cobalt from spent cemented carbide.

The massive accumulation of spent cemented carbide not only produces environmental pollution but also wastes resources such as tungsten and cobalt. To solve the problem, a low-temperature acid aqueous electrochemical method was used; cobalt was recycled on a stainless steel cathode, and at the same time, tungstic acid was enriched at a spent cemented carbide anode, achieving a high efficiency, low energy consumption, and low pollution separation and recovering spent cemented carbide. The transient electrochemical test results show the following: the reduction mechanism of cobalt is Co2+ (aq) + 2e- → Co(s). The nucleation mechanism is close to instantaneous nucleation. The electrodeposition is irreversible and controlled by the diffusion step. The average diffusion coefficient of Co(ii) is 2.16589 × 10-7 cm2 s-1. Electrodeposition experiments show that cobalt enters the electrolyte in the form of Co(ii) and is reduced to elemental cobalt on the stainless steel electrode, and tungsten carbide (WC) is oxidized to tungstic acid (H2WO4) under the oxidizing atmosphere of the anode and enriched in the anode area. The investigation provides favorable electrochemical conditions for the recovery and separation of other valuable metals from spent alloys.

Electronucleation mechanism of copper in wastewater by controlled electrodeposition analysis.

In order to improve the efficiency of copper deposition in wastewater containing the surfactant polyvinylpyrrolidone (PVP) and reveal the mechanism of copper crystals, a controlled electrodeposition process was developed using a low-cost stainless steel cathode and investigated using chronoamperometry (CA), electrochemical impedance spectroscopy (EIS) and infrared spectroscopy (IR). The theoretical analysis was verified by fitting them to experimental curves and calculating the kinetic parameters of the deposition process. The experimental results showed that Cu(PVP)2 was formed by the reaction between the C[double bond, length as m-dash]O bond of PVP and Cu2+. When powdered, reduction of Cu2+ in the Cu(PVP)2 structure was promoted, a positively-charged PVP-coating layer was formed on the surface of the copper crystal nuclei to inhibit the growth of the copper powder. At a potential of -0.2 V, the electrodeposition crystallization curve of copper changed from progressive nucleation to instantaneous nucleation. The kinetic parameters of the deposition process were calculated by fitting the experimental curves to verify the correctness of the theoretical analysis. The EIS tests showed that removing the powder reduced the resistance of the organic solvent (PVP) film on the electrode surface and the charge transfer resistance during copper deposition. According to particle size analysis, removing the powder could reduce the growth energy of copper powder on the electrode surface, increase the area of the active part on the electrode surface, increase the current efficiency of copper powder to 84.2%, and control dust. The size of copper powder reached up to around 900 nm.

Electrochemical Deposition and Nucleation/Growth Mechanism of Ni⁻Co⁻Y2O3 Multiple Coatings.

Ni⁻Co alloy and Ni⁻Co⁻Y2O3 multiple coatings refined with nano-Y2O3 particles were fabricated by ultrasonic-assisted electrochemical deposition in an acid sulfamate bath. Linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) techniques were applied to investigate the nucleation/growth process of composite coatings in co-deposition. The LSV results indicated that the incorporation of nano-Y2O3 particles with the Ni⁻Co matrix shifted the initial deposition potential to a more positive potential and decreased cathodic polarization. For both coatings, the nucleation/growth process approximately agreed with the Scharifker⁻Hill instantaneous nucleation model. Nucleation parameters, including active nucleation sites (N0) and nucleation rate (A) of the composite, were higher when the measured potential range was between −1.05 V (vs. SCE) and −1.20 V vs. SCE, when compared with the Ni⁻Co alloy, and the observed AFM images of the coatings were in good agreement with the calculated nucleation parameters (using the Marquardt⁻Levenberg algorithm) of experimental curves. EIS testing indicated that the charge transfer resistance of the composite was lower in electrodeposition. The incorporation of nano-Y2O3 particles in the matrix changed the preferred orientation of coatings and produced a more uniform and compact deposit layer with finer grains.

Microstructure and Antiwear Property of Laser Cladding Ni-Co Duplex Coating on Copper.

Ni-Co duplex coatings were cladded onto Cu to improve the antiwear properties of Cu products. Prior to laser cladding, n-Al2O3/Ni layers were introduced as interlayers between laser cladding coatings and Cu substrates to improve the laser absorptivity of these substrates and ensure defect-free laser cladding coatings. The structure and morphology of the coatings were characterized by scanning electron microscopy and optical microscopy, and the phases of the coatings were analyzed by X-ray diffraction. Their hardness was measured using a microhardness tester. Experimental results showed that defect-free composite coatings were obtained and that the coatings were metallurgically bonded to the substrates. The surface of the Ni-Co duplex coatings comprised a Co-based solid solution, Cr7C3, (Fe,Ni)23C6, and other strengthening phases. The microhardness and wear resistance of the duplex coatings were significantly improved compared with the Cu substrates. The average microhardness of the cladded coatings was 845.6 HV, which was approximately 8.2 times greater than that of the Cu substrates (102.6 HV). The volume loss of the Cu substrates was approximately 7.5 times greater than that of the Ni-Co duplex coatings after 60 min of sliding wear testing. The high hardness of and lack of defects in the Ni-Co duplex coatings reduced the plastic deformation and adhesive wear of the Cu substrates, resulting in improved wear properties.

[Folic acid prevents Bcl-2 hypomethylation in rats with hyperhomocysteinemia].

OBJECTIVE: To investigate the effects of folic acid on Bcl-2 gene methylation status in rats with hyperhomocystinemia induced by ingestion of excess methionine. METHODS: 36 healthy 6-week-old wistar male rats, weighing (160 +/- 10) g, after being fed adaptable for one week, were randomly divided into control group (n = 12), hyperhomocysteinemia group (n = 12), folic acid treatment group (n = 12). The control group was fed with AIN-93G diet. The hyperhomocysteinemia group was fed with high-methionion diet, consisting of AIN-93G diet plus 1.7% methionion. The folic acid treatment group was fed with high-methionion plus folic acid-rich diet, consisting of AIN-93G diet plus 1.7% methionion and 0.008% folic acid. After be maintained for 18 weeks on the previously described diets, the concentrations in the plasma Hcy and folic acid and Vit B12 were measured with the IMX assays. The thoracic aorta was harvested for immunohist Chemical analysis. The methylation status of Bcl-2 gene was determined by nest touch-down PCR combined MSP(methylation specific PCR). Real-time RT PCR was used to detect mRNA expression of arotic Bcl-2. RESULTS: The study showed the following: (a) A high methionine diet for 18 weeks is sufficient to induce hyperhom degree Cystinemia; Folic acid supplementation to the rats fed the high-methionine diet prevented an elevation homocysteine (Hcy) levels in the plasma (P < 0.01 ). (b) Compared with the control group, the Hhcy group had a elevating Bcl-2 expression by immunohistochemical analysis in aorta, along with Bcl-2 hypomethylation (P < 0.05) and increased Bcl-2 mRNA expression (P < 0.05 ). (c) Most important, after folic acid supplementation, the lowering of Hcy levels was accompanied by a marked decreased Bcl-2 expression by immunohistochemical analysis and Bcl-2 hypermethylation (P < 0.05) and reduced Bcl-2 mRNA expression (P < 0.05). CONCLUSIONS: Folic acid supplementation can prevents Bcl-2 hypomethylation in rats with hyperhomocysteinemia, resulting in a decreased Bcl-2 expression.

[CO2 fluxes in mire and grassland on Ruoergai plateau].

With closed chamber and GC technique, a comparative study was conducted on the CO2 fluxes in mire and grassland on Ruoergai plateau during the plant growth period in 2003-2005. The results showed that the mean value of the CO2 fluxes in the three years was 203.22 mg x m(-2) x h(-1) in mire and 323.03 mg x m(-2) x h(-1) in grassland, with the former being only about 60% of the latter. The perennially water-logging of mire limited the decomposition of plant residues, roots and organic substances, resulting in a lower CO2 flux in mire than in grassland. The seasonal changes of CO2 fluxes in mire and grassland were positively correlated with air temperature, the peak value being usually appeared in July or August, and the diurnal changes of the CO2 fluxes were also positively correlated with air temperature, the peak value being usually appeared between 11:00 and 17:00. The CO2 fluxes had a higher correlation with the soil temperature at the depth of 5 cm than at the depths of 10 cm and 15 cm.

Emission of CO2, CH4 and N2O from freshwater marsh in northeast of China.

The wetlands play an important role in carbon storage, especially at high latitudes, at which they store nearly one-third of global soil carbons. However, few studies have investigated the emissions of CO(2), CH(4) and N(2)O in the long-term, especially effects of freeze-thaw cycles on these gases emissions in freshwater marsh ecosystems. In this paper, we collected greenhouse gas emission data from a freshwater marsh area in China for 4 years, evaluated their release variables and speculated on their potential atmospheric impact. For this paper, we report on the CO(2), CH(4) and N(2)O emission rates recorded from June 2002 to November 2005 in the Sanjiang Plain of northeast China. We measured their interannual variations and fluctuations, as well as factors affecting their emissions, and estimated their regulation and freeze-thaw cycle impacts. Our results revealed obvious CO(2) and CH(4) emission fluctuations during the winter months, and during the freeze-thaw cycle, and a strong interannual variation during the growing season. Overall, we documented a close relationship between the CO(2) and CH(4) emissions, implicating some regulatory commonality. We determined that the marsh was a N(2)O sink during the winter, but a significant source of N(2)O during the freeze-thaw cycle as the temperature increased, especially in early summer. During the thaw-freeze period, the N(2)O levels were positively correlated with the water depth. Additionally, water depth greatly governed the interannual variation of the N(2)O emissions from the marshes during the thaw-freeze period.

[Characteristics of nitrous oxide flux in spring wheat field ecosystem in Sanjiang Plain of Northeast China].

With static-closed-chamber and GC (Agilent 4890), the nitrous oxide (N2O) flux in spring wheat field ecosystem in the Sanjiang Plain of Northeast China was continuously observed in situ from May 2004 to October 2006. The results showed that the N2O flux presented obvious seasonal and inter-annual variation, which was mainly related with precipitation and field water management. The diurnal variation of N2O flux had correlations with the air temperature and the temperature at 5 cm underground. Wheat field ecosystem was the strong sources of atmosphere N2O during plant growth season. The N2O flux decreased obviously in fallowing period, was weaker in freezing period, and increased slowly when soil thawing. The average N2O flux in wheat growth season was 0.190 mg x m(-2) x h(-1), the flux was 0.077 mg x m(-2) x h(-1) from after-reaping to before-freezing period, and 0.017 mg x m(-2) x h(-1) in freezing and thawing period.