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Zhang M.,CAS Wuhan Institute of Hydrobiology | Zhang M.,Jiangxi Academy of Environmental science | Wang Z.,American Hach Company | Xu J.,CAS Wuhan Institute of Hydrobiology | And 4 more authors.
Chemosphere | Year: 2011

The heavy bloom of cyanobacteria is a disastrous consequence of freshwater eutrophication, and the bloom is highly toxic due to its secondary metabolites called microcystins (MCs). The release of organic substances from dense blooms causes an increase in NH4+ and decrease in oxygen in lake water. In the present study, the dynamics of physio-biochemical responses of five aquatic macrophytes to MCs and NH4+ stresses in Meiliang Bay were evaluated. The bay is one of the most seriously eutrophized areas dominated by the toxic cyanobacteria of Lake Taihu, China. The results demonstrate that aquatic macrophytes in Meiliang Bay are subjected to successive external stresses. From January to May, they are subjected to high NH4+ stress (>0.56mgL-1), whereas from June to September or during dense blooms, the macrophytes experience both MC proliferation and moderate NH4+ toxicity (>0.3mgL-1). In August, high NH4+ stress occurs along with hypoxia stress, whereas from September to December, the macrophytes experience moderate NH4+ stress, causing a serious imbalance in C-N metabolism and oxidative stress. Between the two aquatic plant life forms, floating-leaved plants are more resistant to the stresses of eutrophication than are submersed plants. Elevated MCs in the water column can aggravate oxidative stress and suppress the soluble protein contents of aquatic plants. High NH4+ in the water causes severe C and N imbalance in submersed macrophytes because of considerable carbon consumption for free amino acid synthesis. The superoxide dismutase activities of submersed macrophytes are suppressed by low light penetrating the eutrophic water, which might impair the antioxidative function of the plants. The findings of this study provide mainly field evidence that reveals the physical, chemical, and biological stresses on aquatic plants in bloom-prevailed eutrophic lakes. © 2010 Elsevier Ltd. Source

Zhu G.,CAS Wuhan Institute of Hydrobiology | Zhu G.,Henan Normal University | Cao T.,CAS Wuhan Institute of Hydrobiology | Zhang M.,Jiangxi Academy of Environmental science | And 2 more authors.
Hydrobiologia | Year: 2014

Decline of submersed macrophytes has occurred in eutrophic lakes worldwide. Little is known about effects of nutrient enrichment on biomechanical properties of submersed macrophytes. In a 30-day experiment, Myriophyllum spicatum was cultured in aquaria containing two types of sediment (mesotrophic clay vs. fertile loam) with contrasting water NH4 + concentrations (0 vs. 3.0 mg L-1 NH4-N). The plant growth, shoot and root morphology, stem biomechanical properties, and stem total nonstructure carbohydrates content (TNC) were examined. The NH4 +-enriched water, particularly combined with the fertile sediment, caused adverse effects on M. spicatum as indicated by reductions in the growth, stem biomechanical properties (tensile force, bending force and structural stiffness), and TNC content. These results indicate that increased sediment fertility and water NH4 +-enrichment made the plant more fragile and vulnerable to hydraulic damage, particularly for the upper stem, implying that M. spicatum was prone to uprooting and fracture by hydraulic force, and the broken fragment from parent shoot of M. spicatum might have low-survival potential due to its low-TNC content. This may be a mechanical aspect for the decline of submersed macrophytes and makes it more difficult to restore submersed vegetation in the eutrophic lakes. © 2014 Springer Science+Business Media Dordrecht. Source

Zhu P.,Hohai University | Li H.-M.,Jiangxi Academy of Environmental science
Journal of Molecular Structure | Year: 2011

A novel 2D layer complex [Mn(TPA)Cl(H2O)]n (1) has been synthesized by two methods through the reaction of MnCl2 and TPC or TPA under hydrothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, infrared spectrometry (IR), powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA), where heterocyclic carboxylic acid ligand TPA = 2-(5-(pyridin-2-yl)-2H-tetrazol-2-yl)acetic acid, TPC = 2-(5-(pyridin-2-yl)-2H-tetrazol-2-yl)acetonitrile. The distorted octahedral Mn(II) centers are bridged by carboxylic O atoms resulting in the formation of a 1D chain. Then the 1D chains are connected with each other through TPA ligands into a 2D (3,3)-connected topology framework. The H-bonding interactions extend the complex into a three-dimensional network, and such weak interactions further stabilized the complex. Furthermore, solid-state fluorescence spectrum of complex 1 exhibits intense broad emissions at 396 nm at room temperature, which is red-shifted by 21 nm relative to that of free ligand TPA. © 2011 Elsevier B.V. All rights reserved. Source

Liu X.,Huazhong University of Science and Technology | Li S.,Huazhong University of Science and Technology | Li M.,Huazhong University of Science and Technology | Li M.,Jiangxi Academy of Environmental science
Plasma Science and Technology | Year: 2013

A simple negative ion mobility spectrometer (IMS) is designed and used to investigate the factors that influence the number and efficiency of electrons generated by the needle-ring pulsed corona discharge electron source. Simulation with Ansoft Maxwell 12 is carried out to analyze the electric field distribution within the IMS, and to offer the basis and foundation for analyzing the measurement results. The measurement results of the quantities of electrons show that when the drift electric field strength and the ring inner diameter rise, both the number of effective electrons and the effective electron rate are increased. When the discharge voltage becomes stronger, the number of effective electrons goes up while the effective electron rate goes down. In light of the simulation results, mechanisms underlying the effects of drift electric field strength, ring inner diameter, and discharge voltage on the effective electron number and effective electron rate are discussed. These will make great sense for designing negative ion mode IMS using the needle-ring pulsed corona discharge as the electron source. Source

Cao T.,CAS Wuhan Institute of Hydrobiology | Ni L.,CAS Wuhan Institute of Hydrobiology | Xie P.,CAS Wuhan Institute of Hydrobiology | Xu J.,CAS Wuhan Institute of Hydrobiology | Zhang M.,Jiangxi Academy of Environmental science
Freshwater Biology | Year: 2011

Increased ammonium concentrations and decreased light availability in a water column have been reported to adversely affect submersed vegetation in eutrophic waters worldwide. We studied the chronic effects of moderate enrichment (NH 4-N: 0.16-0.25mgL -1) on the growth and carbon and nitrogen metabolism of three macrophytes (Ceratophyllum demersum, Myriophyllum spicatum and Vallisneria natans) under contrasting light availability in a 2-month experiment. The enrichment greatly increased the contents of free amino acids and nitrogen in the shoot/leaf of the macrophytes. This indicates that was the dominant N source for the macrophytes. Soluble carbohydrate contents remained relatively stable in the shoot/leaf of the macrophytes irrespective of the treatments. Under ambient light, the starch contents in the shoot/leaf of C. demersum and M. spicatum increased with enrichment, whereas V. natans did not exhibit any change. The starch contents decreased in C. demersum, increased in M. spicatum and remained unchanged in V. natans after the combined treatment of enrichment and reduced light. The enrichment did not affect the growth of the three macrophytes under the ambient light. However, it did suppress the growth of C. demersum and M. spicatum under the reduced light. The results indicate that a moderate enrichment was not directly toxic to the macrophytes although it might change their viability in eutrophic lakes in terms of the carbon and nitrogen metabolism. © 2011 Blackwell Publishing Ltd. Source

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