盐碱土团聚体的有机碳含量分布

盐碱土团聚中有机质的分布直接关系着土壤的肥力及其利用情况。本文通过干筛法从盐碱土中分离出〉1mm,1～0.25mm,0.25～0.1mm,〈0.1mm粒级的团聚体,研究了盐碱土中团聚体有机碳的含量分布,结果表明,盐碱土团聚体中碳含量较低,肥力差,土壤结构中1～0.25mm粒级的碳含量和腐殖质碳含量均最高,是有利于盐碱土肥力储存的粒级,该结果将为盐碱土改良及相关研究提供新的数据参考。

添加微量液体石蜡对超粗钨粉配炭及碳化效果的影响

以超粗钨粉为原料,液体石蜡为湿润剂,采用双锥混合的方式使石蜡均匀分布到钨粉表面,再以此混合物添加粉状炭黑进行球磨配炭,通过对不同石蜡添加量和碳量分布均匀性进行分析,探讨添加石蜡对配炭效果和总碳含量的影响。样品在相同工艺条件下进行碳化,对最终产品碳化钨的质量进行对比分析,探讨了添加微量液体石蜡对超粗钨粉碳化效果的影响。结果表明:添加微量液体石蜡可以使钨粉配炭后炭黑分布更均匀,同时还可以避免在碳化前装舟时钨炭分离,在压制时更容易成形,钨炭结合更紧密,提高了碳化效率和质量,能够生产晶粒粗大的纯碳化钨;液体石蜡在高温下会分解产生活性炭,并与钨结合而增加总碳含量,在定碳时需要予以平衡;添加过多的液体石蜡会导致炭黑聚集和碳化钨粒度下降。综合考虑,当石蜡含量为0.5‰~3‰时效果最佳。

钨粉配炭混合新工艺的研究

采用双锥混合器和立式高速搅拌混合器进行钨粉配炭,研究了双锥混合+搅拌混合配炭新工艺各项参数对W+C混合料质量的影响,用极差分析法对W+C混合料碳量分布均匀性进行分析。结果表明,采用双锥混合+搅拌混合新工艺生产的W+C混合料碳量均匀性优于传统的球磨混合工艺。双锥混合器运转速度12r/min时,填充率50%和混合时间5h,双锥正、反向交替运转,搅拌混合4min可生产碳量均匀性好的W+C混合料。

Products of carbothermic reduction of Fe-Cr-O and Fe-Cr-Ni-O systems

The reduction behaviors and characteristics of products of the Fe-Cr-O system （FeCr2O4 and Fe2O3＋Cr2O3） and Fe-Cr-Ni-O system （Fe2O3＋Cr2O3＋NiO） under various conditions were studied. The results show that more Fe-Cr or Fe-Cr-Ni solution and less residual carbon content were obtained at higher temperatures and lower initial molar ratio of C to O （nC：nO）. The degree of reduction was highly dependent on both time and temperature, and the residual carbon content greatly increased with increasing nC：nO at each temperature. The products generated during the carbothermic reduction of the Fe-Cr-O system were examined using X-ray diffraction （XRD）. A scanning electron microscope （SEM） coupled with energy dispersive spectrometer was used to observe the microstructure and the distribution of elements in the various phases of the final reduction products of the Fe-Cr-O and Fe-Cr-Ni-O.

Dynamics of profiles and storage of carbon dioxide in broadleaved/Korean forest in Changbai Mountain

CO2 concentrations at different heights in a broadleaved/Korean forest (with a mean height of 26 m) were measured with infrared gas analyzer IRGA (model 2250D, LI-COR Inc. and LI-COR, 820) from Aug. to Oct. of 1999, Apr. to Jul. of 2000, and from Aug. 2002 to Sept. 2003. Based on the collected dada, the diurnal and seasonal dynamics of profiles and storage of carbon dioxide in the forest were analyzed. The diurnal CO2 profiles showed that the vertical distribution of CO2 concentration were different for daytime and nighttime, and the CO2 concentration was highest close to forest floor, no matter at daytime and nighttime. The seasonal profiles of CO2 showed that stratification in the canopy was evident during growth season. CO2 concentrations at different heights (60 m to 2.5 m) had a little change in March, with a difference of 10 mmolmol-1, but had a significant change in July, with a difference of 60 mmolmol-1. In July, there also existed a greater gradient of CO2 concentrations at canopy (22, 26 and 32 m), with a difference of 8 mmolmol-1. The calculated total storage (ΔC/Δt ) of CO2 in the air column with height of 40 m beneath eddy covariance instrument was negative, and made a little contribution to NEE.

Spatial pattern of soil carbon and nutrient storage at the Alpine tun-dra ecosystem of Changbai Mountain, China

In August 2003, we investigated spatial pattern in soil carbon and nutrients in the Alpine tundra of Changbai Moun-tain, Jilin Province, China. The analytical results showed that the soil C concentrations at different depths were significantly (p<0.05) higher in Meadow alpine tundra vegetation than that in other vegetation types; the soil C (including inorganic carbon) concentrations at layer below 10 cm are significantly (p<0.05) higher than at layer of 1020 cm among the different vegetation types; the spatial distribution of soil N concentration at top surface of 0-10 cm depth was similar to that at 1020 cm; the soil P concentrations at different depths were significantly (p<0.05) lower at Lithic alpine tundra vegetation than that at other vegetation types; soil K concentration was significantly (p<0.05) higher in Felsenmeer alpine tundra vegetation and Lithic alpine tundra vegetation than that in Typical alpine tundra, Meadow alpine tundra, and Swamp alpine tundra vegetations.. However, the soil K had not significant change at different soil depths of each vegetation type. Soil S concentration was dramatically higher in Meadow alpine tundra vegetation than that in other vegetation types. For each vegetation type, the ratios of C: N, C: P, C: K and C: S generally decreased with soil depth. The ratio of C: N was significantly higher at 010 cm than that at 1020 cm for all vegetation types except at the top layer of the Swamp alpine tundra vegetation. Our study showed that soil C and nutrients storage were significantly spatial heterogeneity.

The Vertical Distribution Law of Underground Biomass of Reed

[Objective]The aim of this study was to reveal the relationship between the reed and salinity in severely salinized area,so as to making clear the vertical distribution of underground biomass of reed.[Method]Field investigation and sampling method were used to get the mass accurate data of underground biomass of reed.further its vertical distribution was analyzed using combined statistical and ecological method.Moreover,the C/N ratio was obtained by measuring the contents of organic carbon and nitrogen in reed wetland soil.The correlation model among organic carbon,nitrogen of reed wetlands and C/N were finally analyzed.[Result]Total underground biomass of reed population is concentrated at 10 to 40 cm underground soil layer.Thick root plays crucial role in the composition of reed total biomass,Overall change of organic carbon and total nitrogen shows a declining trend.The content of organic carbon and nitrogen in soils becpmes stable below 50 cm from the surface.The content of organic carbon in soil is positively correlated with total nitrogen in soil at significant level.[Conclusion]These results provided theoretical basis for revealing underground biomass of reed in salinized area of arid region.

Effects of Land Cover on Soil Organic Carbon Stock in a Karst Landscape with Discontinuous Soil Distribution

Land cover type is critical for soil organic carbon （SOC） stocks in territorial ecosystems. However, impacts of land cover on SOC stocks in a karst landscape are not fully understood due to discontinuous soil distribution. In this study, considering soil distribution, SOC content and density were investigated along positive successional stages （cropland, plantation, grassland, scrubland, secondary forest, and primary forest） to determine the effects of land cover type on SOC stocks in a subtropical karst area. The proportion of continuous soil on the ground surface under different land cover types ranged between 0.0% and 79.8%. As land cover types changed across the positive successional stages, SOC content in both the 0-20 cm and 20-50 cm soil layers increased significantly. SOC density （SOCD） within O-lOO cm soil depth ranged from 1.45 to 8.72 kg m^-2, and increased from secondary forest to primary forest, plantation, grassland, scrubland, and cropland, due to discontinuous soil distribution. Discontinuous soil distribution had a negative effect on 8OC stocks, highlighting the necessity for accurate determination of soil distribution in karst areas. Generally, ecological restoration had positive impacts on SOC accumulation in karst areas, but this is a slow process. In the short term, the conversion of croplandto grassland was found to be the most efficient way for SOC sequestration.

Labile Organic Matter Content and Distribution as Affected by Six-year Soil Amendments to Eroded Chinese Mollisols

Labile organic carbon （LOC） is a fraction of soil organic carbon （SOC） with rapid turnover time and is affected by soil fertilization. This investigation characterized the SOC content, LOC content and LOC distribution in the treatment plots of surface soil erosion at five levels （0-, 5-, 10-, 20- and 30-cm erosion）. The soil had received contrasting fertilizer treatments （i.e., chemical fertilizer or chemical fertilizer ＋ manure） for 6 years. This study demonstrated that both SOC and various LOC fractions contents were higher in the plots with fertilizer ＋ manure than in those with fertilizer alone under the same erosion conditions. The SOC and LOC contents de- creased as the erosion depth increased. Light fraction organic carbon, particulate organic carbon, easily oxidizable organic carbon （KMnO4-oxydizable organic carbon）, and microbial biomass carbon were 27% 57%, 37%-7%, 20%-25%, and 29%-33% higher respectively in the fertilizer ＋ manure plots, than in the fertilizer alone plots. Positive correlations （p 〈 0.05） between SOC content and different fractions contents were observed in all plots except the correlation between total SOC content and water-soluble organic carbon content in the different fertilization treatments. Obviously, fertilizer ＋ manure treatments would be conducive to the accumulation of LOC and SOC in the Black soil of Northeast China.

Effects of Propionate on Streptolydigin Production and Carbon Flux Distribution in Streptomyces lydicus AS 4.2501

To achieve higher antibiotic streptolydigin productivity through metabolic regulation, propionate was fed during the fermentation of Streptomyces lydicus AS 4.2501. The effects of propionate feeding on streptolydigin production and intracellular fluxes were investigated. The highest streptolydigin production yield of 95.10mg·L-1 was obtained when 2mmol·L-1 of sodium propionate was added at 60h of cultivation into shake-flask culture. This yield is 23.06% higher when compared to that of a batch culture without propionate supplementation. It was also found that when propionate was added, much more organic acids were excreted. Metabolic flux analysis was per-formed and it demonstrated that the carbon fluxes of the pentose phosphate pathway and the anaplerotic reaction were significantly increased after propionate feeding. The carbon flux from pyruvate to acetyl-CoA was determined to be 24.7, which was 12.27% higher than that in the batch culture. This study indicated that the glu-cose-6-phosphate and pyruvate nodes were potential bottlenecks for increasing streptolydigin productivity. Potential targets and strategies that could be manipulated through genetic and process engineering to increase the production of streptolydigin were also suggested.

In-situ Polymerization-modification Process and Foaming of Poly（ethylene terephthalate）

Most of traditional linear poly(ethylene terephthalate)(PET)resins of relatively low molecular mass and narrow molecular mass distribution have low melt strength at foaming temperatures,which are not enough to support and keep cells.An in-situ polymerization-modification process with esterification and polycondensation stages was performed in a 2 L batch stirred reactor using pyromellitic dianhydride(PMDA)or pentaerythritol(PENTA)as modifying monomers to obtain PETs with high melt strength.The influence of amounts of modifying monomers on the properties of modified PET was investigated.It was found that the selected modifying monomers could effectively introduce branched structures into the modified PETs and improve their melt strength.With increasing the amount of the modifying monomer,the melt strength of the modified PET increased.But when the amount of PENTA reached 0.35%or PMDA reached 0.9%,crosslinking phenomenon was observed in the modified PET.Supercritical carbon dioxide(ScCO2)was employed as physical foaming agent to evaluate the foaming ability of modified PETs.The modified PETs had good foaming properties at 14 MPa of CO2pressure with foaming temperature ranging from 265°C to 280°C.SEM micrographs demonstrated that both modified PET foams had homogeneous cellular structures,with cell diameter ranging from 35μm to 49μm for PENTA modified PETs and38μm to 57μm for PMDA modified ones.Correspondingly,the cell density had a range of 3.5×107cells·cm 3to 7×106cells·cm 3for the former and 2.8×107cells·cm 3to 5.8×106cells·cm 3for the latter.

The spatial distribution of commuting CO_2 emissions and the influential factors:A case study in Xi'an,China

As the transport sector is a major source of greenhouse gas emissions, the effect of urbanization on transport CO2 emissions in developing cities has become a key issue under global climate change. Examining the case of Xi＇an, this paper aims to explore the spatial distribution of commuting CO2 emissions and influencing factors in the new, urban industry zones and city centers considering Xi＇an＇s transition from a monocentric to a polycentric city in the process of urbanization. Based on household survey data from 1501 respondents, there are obvious differences in commuting CO2 emissions between new industry zones and city centers： City centers feature lower household emissions of 2.86 kg CO2 per week, whereas new industry zones generally have higher household emissions of 3.20 kg CO2 per week. Contrary to previous research results, not all new industry zones have high levels of CO2 emissions; with the rapid development of various types of industries, even a minimum level of household emissions of 2.53 kg CO2 per week is possible. The uneven distribution of commuting CO2 emissions is not uniformly affected by spatial parameters such as job-housing balance, residential density, employment density, and land use diversity. Optimum combination of the spatial parameters and travel pattern along with corresponding transport infrastructure construction may be an appropriate path to reduction and control of emissions from commuting.

Vertical Distribution of Soil Carbon, Nitrogen, and Phosphorus in Typical Chinese Terrestrial Ecosystems

Characterization of the vertical distribution of soil organic carbon(C), nitrogen(N), and phosphorus(P) may improve our ability to accurately estimate soil C, N, and P storage. Based on a database of 21 354 records in 74 long-term monitoring plots from 2004 to 2013 in the Chinese Ecosystem Research Network(CERN), we built fitting functions to quantify the vertical distribution of soil C, N, and P(up to 100 cm depth) in the typical Chinese terrestrial ecosystems. The decrease of soil C, N, and P content with depth can be well fitted with various mathematical functions. The fitting functions differed greatly between artificial(agriculture) and natural(desert, forest, and grassland) ecosystems, and also differed with respect to soil C, N, and P content. In both the artificial and natural ecosystems, the best fitting functions were exponential functions for C, quadratic functions for N, and quadratic functions for P. Furthermore, the stoichiometric ratios of soil C, N, and P were ranked in descending order: grassland > forest > agriculture > desert, and were also associated with climate. This study is the first to build the fitting functions for the profile distribution of soil C, N, and P in China at a national scale. Our findings provide a scientific basis to accurately assess the storage of C, N, and P in soils at a large scale, especially for the integrative analysis of historical data.

Mapping carbon distribution in 35SiMn steel by energy-filtered transmission electron microscopy

In this study,the three-windows method,the jump-ratio method and the R-map method in energy-filtered transmission electron microscopy(EFTEM) have been applied to mapping carbon distribution in 35SiMn steel after a quenching-partitioning treatment.The carbon contamination is successfully suppressed by using EFTEM and plasma-cleaning TEM samples.Compared to the three-windows method and the jump-ratio method,the R-map method provides carbon distribution with less noises,and is insensitive to changes in sample thickness.We have demonstrated that the R-map method is a better way for carbon mapping in middle-carbon steel without the influence of carbon contamination.