NITROGEN NUTRIENT MECHANISM IN SECONDARY SUCCESSION PROCESS OF THE MIXED BROAD-LEAVED/ KOREAN PINE (PINUS KORAIENSIS) FOREST

Chemical and biochemical analysis methods were used to monitor the vedations of nitrogen nutrient among the dominance trees species in secondary succession process of the mixed broad - leaved/Korean pine forest on Changbai Mountains, Northeast China. Amounts of total nitrogen, anunonium and NRA in soils of virgin broad-leaved/Korean pine forest which is in climax were higher than those of secondary birch forests those are in succession Stage. The amount of nitrate was in the other hand. In climax, dominance trees species are tolerant mesophytic trees such as Pinus Koraiensis, Tilia amurensis, Acer mono and also Fraxinus mandshurica, they are all ammonium + nitrate adapted species, but they show a preference for the anunonium rather than those of the pioneer trees species in secondary birch forest, such as Populus davidiava and Betula platyphylla. Because they have more ammonium in their leaves and roots, especially Pinus koraiensis. Populus davidvana and Betula plaaphlla are intolerant trees, amounts of nitrate and total nitrogen is higher in their leaves and roots and also NRA in their leaves, so they preference for the nitrate rather than the others.In secondary birch forest, the regeneration trees species adapt their nitroggn nutrient to the variation of nitrogen nutrient situation in soil, finally they could survival well and the secondary birch forest would succession to climax. In climax, dominance trees species adapt their Nitrogen nutrient to the situation in soil and there are not strong competition in nitrogen nutrient among them, so they can coexist well and keep the climax as stable vegetation.

Characterization of mechanical properties and microstructures of spark plasma sintered and cryo-rolled AA2024−Y composites

The relationship between the microstructure and mechanical properties of the spark plasma sintered AA2024 Y composites subjected to cryo-rolling was investigated. Yttrium addition enhances the mechanical properties of the composites by promoting grain refinement and precipitation. However, there is a clear trend of initial increase and later decrease in the properties. Also, it is observed that 0.3 wt.% of yttrium is the optimum amount of reinforcement content to obtain the highest mechanical properties. To further improve the tensile strength of the composites, cryo-rolling was performed on the composites under standard cryogenic conditions by several passes up to a reduction of 25%. The mechanical properties and the corresponding microstructures of composites after cryo-rolling were correlated. The SEM and TEM microstructures reveal that the samples exhibit dual size grains, i.e., nanograins are formed as sub-grains within the actual grain. Due to the grain size reduction and the increase in the dislocation density, the tensile properties are remarkably improved compared to those of the composites before cryo-rolling. The highest mechanical properties like hardness, YS and UTS are found to be 153 HV, 539 MPa and 572 MPa, respectively, with a reasonable ductility in the composite with 0.3 wt.% Y.

Reactive Precipitation of Procaine Benzylpenicillin

The reactive precipitation process of procaine benzylpenicillin is reviewed, while such secondary processes as ageing, agglomeration, breakage, and the effects of operation parameters on crystal size are emphasized. In the reactive precipitation the ageing of particles has a little effect on the process, while the greater effect comes from the agglomeration and breakage of particles, furthermore, the mixing has also notable influence on the product size. All of these provide the bases for further study on reactive precipitation.

Intensified wintertime secondary inorganic aerosol formation during heavy haze pollution episodes(HPEs) in Beijing,China

Air pollution in China is complex,and the formation mechanism of chemical components in particulate matter is still unclear.This study selected three consecutive heavy haze pollution episodes(HPEs)during winter in Beijing for continuous field observation,including an episode with heavy air pollution under red alert.Clean days during the observation period were selected for comparison.The HPE characteristics of Beijing in winter were:under the influence of adverse meteorological conditions such as high relative humidity,temperature inversion and low wind speed;and strengthening of secondary transformation reactions,which further intensified the accumulation of secondary aerosols and other pollutants,promoting the explosive growth of PM_(2.5).PM_(2.5)/CO values,as indicators of the contribution of secondary transformation in PM_(2.5),were approximately 2 times higher in the HPEs than the average PM_(2.5)/CO during the clean period.The secondary inorganic aerosols(sulfate nitrate and ammonium salt)were significantly enhanced during the HPEs,and the conversion coefficients were remarkably improved.In addition,it is interesting to observe that the production of sulfate tended to exceed that of nitrate in the late stage of all three HPEs.The existence of aqueous phase reactions led to the explosive growth sulfur oxidation ratio(SOR)and rapid generation of sulfate under high relative humidity(RH>70%).

Flocculation behaviors of a novel papermaking sludge-based flocculant in practical printing and dyeing wastewater treatment

In our previous studies,several papermaking sludge-based flocculants(PSBFs)were synthesized from wood pulp papermaking sludge.The structure-activity relationships of the PSBFs have been investigated in simulated dye wastewater treatment,but their efficiencies in practical printing and dyeing wastewater(PPDW)treatment are unknown.Herein,an PSBF was prepared,and its performance is discussed in comparison to polyaluminium chloride(PAC)and polyacrylamide(PAM)in PPDW treatment.The PSBF was used in three ways:as an independent flocculant,as a PAC aid,or used to treat the effluent of the PAC system.The results indicated that adding PSBF alone produced similar color and chemical oxygen demand(COD_(Cr))removals as the PAC system alone,but PSBF performed better than PAC when the pH of PPDW was higher than 7.0.Adding PSBF as a PAC aid improved the color,COD_(Cr)and turbidity removals,but the elimination efficiencies were slightly lower than those of the PAC+PAM system.However,when PSBF was used as a flocculant to treat the effluent of the PAC system(PAC→PSBF),the effluent qualities were enhanced.Compared with the PAC system,the color and COD_(Cr)removals of PAC→PSBF system increased by 16.21%and 13.26%,respectively.The excitation and emission matrix fluorescence results indicated that PSBF removed tryptophan-like pollutants more efficiently than PAC.Considering the pH requirements of the subsequent bioreactor treatment in practice,the PAC→PSBF system were also investigated at the PPDW pH level of 7.0.Its maximum removal efficiencies of color,COD_(Cr)and turbidity were 90.17%,32.60%and 82.50%,respectively.

Contents Variation Analysis ofγ-Amino Butyric Acid in Semen sojae praeparatum Fermentation Using Online Pre-Column Derivatization-HPLC

This paper reported the contents variation analysis ofγ-amino butyric acid(GABA)in Semen sojae praeparatum(SSP)which is a famous traditional Chinese medicine.High performance liquid chromatography(HPLC)was used and GABA was derivatized by online pre-column derivatization with o-phthalaldehyde(OPA).To validate this method,the precision,stability,repeatability and recovery were discussed.In the concentration range from 0.0125 to 0.400 mg/m L,the calibration curve for GABA was linear and the regression equation was obtained with correlation coefficient(R2)of 0.9999.Relatively high levels of GABA exist in SSP and the content changes of GABA at different time points during the fermenting process were detected.At the"yellow cladding"stage,GABA level was very low or even undetectable;the"secondary fermentation"stage witnessed a rapid increase of GABA content to 1.39-5.52 mg/g,which remained stable after 18 days of"secondary fermentation".This study demonstrated that GABA was generated at the"secondary fermentation"stage,revealing the significance and rationality of the"secondary fermentation"stage in the fermenting process of SSP.On the other hand,it suggested the downside of taking soy isoflavones as the only measurement in existing quality assessment and optimization approach for the fermenting process of SSP.