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1.
The effects of pH andEh on release of nitrogen and phosphorus from sediments of West Lake under different conditions were investigated by simulation test. Results showed that the net flux of NH4 +-N release from sediments increased with pH, but NO3 −-N showed negative-going release at all tested pH levels. The net flux of NH4 +-N release from sediments was higher under anaerobic or aerobic condition of the overlying water, but only under aerobic condition would net release of NO3 −-N occur. It was also shown that phosphorus released was mainly in its inorganic form, higher pH and anaerobic conditions of overlying water greatly stimulated release of phosphorus. In situ measurement at several West Lake locations indicated that sediment resuspension induced by boat propeller stimulated nutrients release from sediment into overlying water. Project (No.294059) supported by National Natural Science Foundation of Zhejiang Province, China  相似文献   

2.
The reuse of wastewater for the irrigation of farmlands is gaining popularity, and the nutrient leaching associated with wastewater irrigation is becoming a matter of concern. The variability of nitrogen and phosphorus fractions in wastewater-irrigated soil was investigated in both horizontal and vertical directions in Kongjiaxiang, Tongliao, Inner Mongolia, China. The results showed that wastewater irrigation resulted in the concentrations of available N and P being 40.36% and 66.49% higher, respectively, than those with groundwater irrigation. Different forms of N and P exhibited significantly different distribution patterns. Higher concentrations of NO3- and total available N, as well as of those of Ca-P and total available P were observed near wastewater irrigation channels. Ca-P has a spatial distribution pattern similar to that of available P. The concentrations of NO3- and NH4+ were the highest in top soil and decreased with depth. The complex interactions between nitrate leaching and nitrogen transformation processes (e.g., nitrification, denitrification, and mineralization) determined the vertical profile of NO3- . The significant amount of NH4+ loss inhibited its deep seepage. The Ca-bound compound contained more P than other inorganic fractions as a result of high Ca levels throughout the soil profile. The differences in the concentrations of Ca-bound P at different depths could be due to the upward flux or translocation of Ca from subsurface to surface soil and the sequestration of P.  相似文献   

3.
In recent years, excessive use of chemical nitrogen (N) fertilizers has resulted in the accumulation of excess ammonium (NH 4 + ) in many agricultural soils. Though rice is known as an NH 4 + -tolerant species and can directly absorb soil intact amino acids, we still know considerably less about the role of high exogenous NH 4 + content on rice uptake of soil amino acids. This experiment examined the effects of the exogenous NH 4 + concentration on rice uptake of soil adsorbed glycine in two different soils under sterile culture. Our data showed that the sorption capacity of glycine was closely related to soils;’ physical and chemical properties, such as organic matter and cation exchange capacity. Rice biomass was significantly inhibited by the exogenous NH 4 + content at different glycine adsorption concentrations. A three-way analysis of variance demonstrated that rice glycine uptake and glycine nutritional contribution were not related to its sorption capacity, but significantly related to its glycine:NH 4 + concentration ratio. After 21-d sterile cultivation, the rice uptake of adsorbed glycine accounted for 8.8%;–22.6% of rice total N uptake, which indicates that soil adsorbed amino acids theoretically can serve as an important N source for plant growth in spite of a high NH 4 + application rate. However, further studies are needed to investigate the extent to which this bioavailability is realized in the field using the 13C, 15N double labeling technology.  相似文献   

4.

Objectives

To investigate the effects of different nitrate sources on the uptake, transport, and distribution of molybdenum (Mo) between two oilseed rape (Brassica napus L.) cultivars, L0917 and ZS11.

Methods

A hydroponic culture experiment was conducted with four nitrate/ammonium (NO3 ?:NH4 +) ratios (14:1, 9:6, 7.5:7.5, and 1:14) at a constant nitrogen concentration of 15 mmol/L. We examined Mo concentrations in roots, shoots, xylem and phloem sap, and subcellular fractions of leaves to contrast Mo uptake, transport, and subcellular distribution between ZS11 and L0917.

Results

Both the cultivars showed maximum biomass and Mo accumulation at the 7.5:7.5 ratio of NO3 ?:NH4 + while those were decreased by the 14:1 and 1:14 treatments. However, the percentages of root Mo (14.8% and 15.0% for L0917 and ZS11, respectively) were low under the 7.5:7.5 treatment, suggesting that the equal NO3 ?:NH4 + ratio promoted Mo transportation from root to shoot. The xylem sap Mo concentration and phloem sap Mo accumulation of L0917 were lower than those of ZS11 under the 1:14 treatment, which suggests that higher NO3 ?:NH4 + ratio was more beneficial for L0917. On the contrary, a lower NO3 ?:NH4 + ratio was more beneficial for ZS11 to transport and remobilize Mo. Furthermore, the Mo concentrations of both the cultivars’ leaf organelles were increased but the Mo accumulations of the cell wall and soluble fraction were reduced significantly under the 14:1 treatment, meaning that more Mo was accumulated in organelles under the highest NO3 ?:NH4 + ratio.

Conclusions

This investigation demonstrated that the capacities of Mo absorption, transportation and subcellular distribution play an important role in genotype-dependent differences in Mo accumulation under low or high NO3 ?:NH4 + ratio conditions.
  相似文献   

5.
The effects of salinity(50 mmol/L NaCl) and Cd(1 μmol/L CdCl2) as sole and combined on growth and photosyn-thetic parameters were studied using two soybean genotypes,Huachun 18 and NGB.The concentrations of Cd2 ,Zn2 ,Ca2 ,Mg2 ,K and Na were also determined in seeds and pods.Huachun 18 suffered a more serious decrease than NGB in net photosynthetic rate(Pn) in the treatments of salinity stress alone and combined stress(NaCl Cd),showing that it is relatively sensitive to salinity.The decrease in Pn caused by salt stress in Huachun 18 was mainly due to the reduced total chlorophyll content and photosynthetic efficiency(the ratio of variable fluorescence to maximal fluorescence,Fv/Fm),whereas the decease in NGB was mainly related to reduced stomatal conductance(Gs).The combined stress of both Na and Cd did not induce further decrease in photosynthesis and fluorescence in the two genotypes relative to salt or Cd stress alone.Greater change in the pod concentrations of Zn2 ,Ca2 ,Mg2 ,K and Na was detected under salt stress for Huachun 18 than for NGB.The results suggested that the interactive effect of NaCl-Cd on growth and nutrient uptake differs between the two soybean genotypes.  相似文献   

6.
Chemically processed Nb-doped SrTiO3 films and properties   总被引：1，自引：0，他引：1  
Homogeneous, crack-free SrNbxTi1−x O3 thin films on (110) silicon substrates were successfully fabricated by sol-gel processing. The optimum route and conditions were systematically investigated. Sr(OAc)2 glacial acctic acid solution, after being refluxed and reacted with tartrate, formed Sr(OAc)2(C4H6O6)2; Ti(OBu)4 formed Ti(OAc)4−x (AcAc)x after having the ligand partially exchanged with AcAc, while Nb(OC2H5)5 formed (OAc)2Nb(AcAc) (C4H6O6) by exchanging of ligand in glacial acetic acid with (CH3CO)2O. All the metal species after undergoing partial hydrolysis and polymerization with hydroxyl or oxygen, formed SrNbxTi1−x O13 cluster sol. Methyl cellulose (MCL) caused SrNbxTi1−x O3 sol to have polymeric structure and easily form films. SrNbxTi1−x O3 films with perovskite were subsequently formed after being annealed at 650∼750 °C for 60 min in 25% N2+75% H2 (volume ratio) atmosphere. Resistivity of the SrNb0.1Ti0.9O3 films at room temperature was 64 μω·cm, a particular T 2 temperature dependence of the resistivity, from 25 K up to room temperature, was observed. Project (No. 2002CB613305) supported by the National Basic Research Program (973) of China  相似文献   

7.
1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ｔｈｅｃｈｅｍｉｃａｌｅｆｆｅｃｔｓｏｆｕｌｔｒａｓｏｕｎｄａｒｅｄｕｅｔｏｈｉｇｈｐｒｅｓｓｕｒｅｐｒｏｄｕｃｅｄｄｕｒｉｎｇｖｉｏｌｅｎｔｃｏｌｌａｐｓｅｏｆｃａｖｉｔａｔｉｏｎｂｕｂｂｌｅｓ.Ｔｈｅｒｅａｃｔｉｏｎｓｄｏｎｏｔｔａｋｅ ｐｌａｃｅｈｏｍｏｇｅ ｎｅｏｕｓｌｙｉｎｔｈｅｓｏｌｕｔｉｏｎｂｕｔｉｎ”ｈｏｔｓｐｏｔｓ”ｗｈｅｒｅｃａｖｉ ｔａｔｉｏｎｂｕｂｂｌｅｓｐｕｌｓａｔｅｏｒｃｏｌｌａｐｓｅ .Ｄｕｒｉｎｇｔｈｅａｄｉａｂａｔ ｉｃｃｏｍｐｒｅｓｓｉｏ…  相似文献   

8.
Studies were initiated for two consecutive years to find out the effect of time of transplanting and seedlings hill^-l on the productivity of rice in Dera Ismail Khan district of North West Frontier Province （NWFP）, Pakistan. The experiment was laid out in a randomized complete block design with split plot arrangements. Main plots consisted of four transplanting dates viz. 20th and 27th of June and 4th and 1 lth of July while sub-plots contained 1, 2, 3 or 4 seedlings hill^-1. Among transplanting dates, June 20th planted crop gave highest paddy yield and net return with I seedling hill^-1. It explains that the use of more seedlings hill^-1 not only adds to cost but is also a mere wastage of natural resources. Based on research findings, we conclude that the use of I seedling hill^-1 is most appropriate for timely sowing otherwise 4 seedlings hill^-1 should be used to compensate for the yield gap in late transplanted rice.  相似文献   

9.
Objective: To investigate the influence of lead exposure on the immune function of lymphocytes and erythrocytes in preschool children. Materials and methods: A group of 217 children three to six years of age from a rural area were given a thorough physical examination and the concentration of lead in blood samples taken from each subject was determined. The indices of lymphocyte immunity (CD 3CD 4, CD 3CD 8, CD 4CD 8, CD-3CD 19) and erythrocyte immunity (RBC-C3b, RBC-IC, RFER, RFIR, CD35 and its average fluorescence intensity) of 40 children with blood lead levels above 0.483 μmol/L were measured and compared with a control group. Results: The blood lead levels of the 217 children ranged from 0.11 μmol/L to 2.11 μmol/L. The CD 3CD 4and CD 4CD 8 cells were lower (P＜0.01) and the CD 3CD 8 cells were higher in the lead-poisoned subjects than those in the control group (P＜0.05). CD 3 and CD-3CD 19 did not show significant differences. Although the RBC-C3b rosette forming rate was lower and the RBC-IC rosette forming rate was higher in the lead-poisoned group, this difference could not be shown to be statistically significant (P＞0.05). RFIR was found to be lower in the lead-poisoned group (P＜0.01). Compared with the control group, the positive rate of CD35 was not found to be significantly different in a group of 25 lead-poisoned children (P＞0.05), while the average fluorescence intensity was lower in the lead-poisoned group (P＜0.05). Conclusion: Lead exposure can result in impaired immune function of T lymphocytes and erythrocytes in preschool children.  相似文献   

10.
With InCl3·4H2O being used as raw materials, the precursor of nano-sized In2O3 powder was prepared by hydrolysis, peptization and gelation of InCl3·4H2O. After calcination, nano-sized In2O3 powder was obtained. The powder was characterized by thermo-gravimetric and differential thermal analysis (TG-DTA), X-ray diffractometry (XRD) and transmission electron microscopy (TEM), respectively. Calculation revealed that the mean crystalline size increased with increasing the calcination temperature, but crystal lattice distortion rate decreased with the increasing in the average crystalline size. This indicated that the smaller the particle size, the bigger the crystal lattice distortion, the worse the crystal growing. The activation energies for growth of nano-sized In2O3 were calculated to be 4.75 kJ·mol−1 at the calcination temperature up to 500°C; and 66.40 kJ·mol−1 at the calcination temperature over 600°C. TEM photos revealed that the addition of the chemical additive (OP-10) greatly influenced the morphology and size of In2O3 particles.  相似文献   

11.
INTRODUCTION Nitrogen oxide (NOx) is one of the main air pol- lutants found in the flue gases from chemical and power plants belching acid rain and photochemical smog. Over 90 percent of all man-made nitrogen ox- ides that enter our atmosphere are produced by the combustion of various fuels. Compared with the ad- vanced stage of SO2 gas removal technologies devel- opment, the removal of NOx gases is still in the initial stages of development as roughly 90 to 95 percent of NOx emitted i…  相似文献   

12.
Ammonium affects cell viability to inhibit root growth in Arabidopsis   总被引：1，自引：0，他引：1  
Ammonium (NH4 +) is an important form of nitrogen nutrient for most plants, yet is also a stressor for many of them. However, the primary events of NH4 + toxicity at the cellular level are still unclear. Here, we showed that NH4 + toxicity can induce the root cell death in a temporal pattern which primarily occurs in the cells of root maturation and elongation zones, and then spreads to the cells in the meristem and root cap. The results from the NH4 +-hypersensitive mutant hsn1 further confirmed our findings. Taken together, NH4 + toxicity inhibits primary root growth by inhibiting cell elongation and division and inducing root cell death.  相似文献   

13.
Understanding the pattern of phytoplankton and their dependence on water quality variables, can help the management of eutrophic lakes. The aim of this study was to determine water quality and environmental factors associated with cyanobacteria dominance and microcystin production in Qingshan Lake, a subtropical lake located in the headwater of the Taihu watershed, China. Water samples collected monthly from 10 study sites in Qingshan Lake were analyzed for the species distributions of freshwater algae and physico-chemical parameters including total nitrogen (TN), ammonia (NH4 +-N), nitrate (NO3 −-N), total phosphorus (TP), and chlorophyll a (Chl-a) from June, 2008 to May, 2009. Qingshan Lake was found to be eutrophic, based on the calculated trophic state index (TSI). The average TN of 4.33 mg/L during the study period exceeded the Surface Water Quality Standards of China. TP was significantly correlated with relative abundance of cyanobacteria and Microcystis biovolume, indicating its important role in regulating cyanobacteria. Microcystis, Anabaena, and Oscillatoria were dominant cyanobacteria in Qingshan Lake from June to November, 2008. Cyanobacteria dominance was regulated by water temperature and TP. Principal component analysis further indicated that microcystin production was most affected by water temperature, TP, and cyanobacteria biomass. Results suggest that the control of TP in summer can mitigate cyanobacteria dominance and microcystin production in Qingshan Lake, and close monitoring should be undertaken in summer.  相似文献   

14.
N-valeronitrile-N’-methylimidazolium hexafluorophosphate ([C 4 CNmim]+ PF 6),as a novel ionic liquid with polar nitrile functional group,was prepared.The structure of the ionic liquid was characterized by using IR and 1 H NMR.As a medium,the ionic liquid plays an important role in copolymerization of carbon monoxide (CO) with styrene (St).Some synthetic conditions were determined,including the usage of ionic liquid,palladium composite catalyst and methanol,CO pressure,reaction time and reaction temperature.The influence of these factors on catalytic activity was analyzed.The results show that the catalytic activity has reached 1 724.1 gStCO/(gPd·h) and the catalyst could be reused 5 times under the optimal condition:composite catalyst 0.015 mmol,ionic liquid 3 mL,methanol 0.75 mL,CO pressure 2MPa,reaction time 2 h and reaction temperature 70℃.This CO/St copolymerization within [C 4 CNmim]+ PF 6 system could facilitate ionic liquids with efficient and economical applications to polymeric materials.  相似文献   

15.
A series of Lil-xNaxV3O8 materials was prepared by solution reaction followed by calcination method and their electrochemical performances in 2 M LieSOa-water-ethanol solution as negative electrodes for aqueous electrolyte lithium ion battery were studied and compared each other. X-ray diffraction analysis revealed that partially substituting sodium for lithium in LiV3Os could increase the interlayer distances of （100） plane. Cyclic voltammetric experiments have demonstrated that the Li^＋ insertion and extraction kinetics of Li0.7Na0.3V3O8 is superior to that of LiV3O8. Charge/discharge results showed that the discharge specific capacity of Li0.7Na0.3V3O8 electrode is higher than that of LiV3O8 electrode.  相似文献   

16.
Let Γd2nbe the set of trees with a given diameter d having a perfect matching,where 2n is the number of vertex.For a tree T in Γd2n,let Pd+1be a diameter of T and q = d m,where m is the number of the edges of perfect matching inPd+1.It can be found that the trees with minimal energy in Γd2nfor four cases q = d 2,d 3,d 4,[d2],and two remarks aregiven about the trees with minimal energy in Γd2nfor2d 33q d 5 and [d2] + 1 q2d 33 1.  相似文献   

17.
纳米银对黄瓜和小麦的毒性效应研究   总被引：1，自引：0，他引：1  
研究目的：研究纳米银对黄瓜和小麦的毒性及在植物中的转运和分布,探讨其毒性机制,为纳米银的环境风险评估提供科学依据。创新要点：1.选取单子叶和双子叶植物为对象,比较研究纳米银对其萌发阶段和生长阶段的毒性效应及其影响因素;2.多数研究中的纳米银均有表面修饰,本研究选择无表面修饰的纳米银材料,排除表面活性剂的干扰因素;3.以络合剂半胱氨酸掩蔽解离出的银离子,探讨纳米银颗粒对植物毒性的贡献。研究方法：通过植物根长（图2）和生物量（图3）分别评价萌发和生长阶段纳米银的植物毒性。利用电感耦合等离子体质谱（ICP-MS）测定植物组织银元素的含量（图7）。通过组织切片,利用透射电镜（TEM）观察植物根中银的微观分布（图6）。通过在暴露介质中添加半胱氨酸掩蔽银离子来评价纳米银颗粒对植物毒性的贡献（图3和5）。重要结论：在较高暴露浓度情况下,纳米银和银离子对小麦和黄瓜都具有明显的毒性。但当纳米银浓度低于200 mg/L,银离子浓度低于5 mg/L时,两者均能促进黄瓜根系的生长。两种植物在营养生长阶段比萌发阶段对纳米银的毒性更敏感。纳米银暴露后,银首先积聚于植物的根,然后被转移到地上部。为评价纳米银释放的银离子的作用,我们测定了暴露后介质中银离子的浓度。在种子萌发阶段,黄瓜和小麦的暴露液中约0.03%和0.01%的纳米银溶解,而在营养生长阶段,溶解的纳米银达到0.17%和0.06%。半胱氨酸作为银离子的强络合剂,能够彻底消除纳米银对黄瓜和小麦的作用,说明纳米银的植物效应可能来自于其释放的银离子。  相似文献   

18.
Amorphous InGaZnO (a-IGZO) films were deposited on the corning eagle XG (EXG) glass substrates using magnetron sputtering method. The structure, surface morphology, electrical and optical properties of these films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), semiconductor parameter analyzer and spectrophotometry, respectively. The influence of oxygen flow on the electrical properties of IGZO thin films was studied, showing that increasing oxygen flow changes the resistivity with six orders of magnitude. The contact resistance of ITO/IGZO is 7.35×10−2 Ω·cm2, which suggests that a good ohmic contact exists between In2O3: Sn (ITO) and IGZO film.  相似文献   

19.
1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ｓｉｎｃｅｔｈｅ 90’ｓ ,ｔｈｅｆｅｍｔｏｓｅｃｏｎｄｌａｓｅｒｔｅｃｈｎｉｑｕｅｓｈａｖｅｂｅｅｎｕｓｅｄｔｏｓｔｕｄｙｖａｒｉｏｕｓｕｌｔｒａ ｐｒｏｃｅｓｓｗｉｔｈｉｎｍａｔｅｒｉａｌｓ,ｂｅｃａｕｓｅｏｆｉｔｓｈｉｇｈｔｉｍｅ ｒｅｓｏｌｕｔｉｏｎ .Ｉｎｃｈｅｍｉｃａｌｒｅａｃｔｉｏｎｓ ,ｃｈｅｍｉｃａｌｂｏｎｄｂｒｅａｋｉｎｇｏｒｂｏｎｄｆｏｒｍａｔｉｏｎｉｓｏｎｔｈｅｓｃａｌｅｏｆｆｅｍｔｏｓｅｃｏｎｄ (10 - 15ｓｅｃ ｏｎｄ) [1] .Ｗｉｔｈｆｅｍｔｏｓｅｃｏｎ…  相似文献   

20.
The thermolysis of urea-water solution and its product, HNCO hydrolysis is investigated in a dual-reactor system. For the thermal decomposition below about 1073 K, the main products are ammonia (NH3) and isocyanic acid (HNCO) whereas at higher temperatures the oxidation processes take effect and the products include a low concentration of nitric oxide (NO) and nitrous oxide (N2O). The gas HNCO is quite stable and a high yield of HNCO is observed. The ratio of NH3 to HNCO increases from approximately 1.2 to 1.7 with the temperature. The chemical analysis shows that H radical is in favor of HNCO hydrolysis by instigating the reaction HNCO+H·→·NH2+CO and high temperature has positive effect on H radical. The hydrolysis of HNCO over an alumina catalyst made using a sol-gel process (designated as γ-Al2O3) is investigated. The conversion of HNCO is high even at the high space velocities (6×105 h-1) and low temperatures (393–673 K) in the tests with catalysts, which enhances HNCO hydrolysis and raises the ratio of NH3 to HNCO to approximately 100. The pure γ-Al2O3 shows a better catalytic performance than CuO/γ-Al2O3. The addition of CuO not only reduces the surface area but also decreases the Lewis acid sites which are recognized to have a positive effect on the catalytic activity. The apparent activation energy of the hydrolysis reaction amounts to about 25 kJ/mol in 393–473 K while 13 kJ/mol over 473 K. The overall hydrolysis reaction rate on catalysts is mainly determined by external and internal mass-transfer limitations.  相似文献   

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