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341.
缙云山4种森林植被土壤团聚体有机碳分布特征 总被引:7,自引:0,他引:7
以重庆市缙云山的竹林、阔叶林、针叶林和针阔叶混交林这4种亚热带森林植被为研究对象,分析不同林分下土壤团聚体及团聚体有机碳在0~20、20~40、40~60和60~100 cm土壤剖面上的分布规律.结果表明,阔叶林土壤 2 mm粒级团聚体含量、平均重量直径(MWD)、几何平均直径(GMD)及 0. 25 mm团聚体含量(R0. 25)均随土层深度的增加而降低,而其他林分在整个土层中则无明显规律.在各土层中,竹林以 2 mm粒级团聚体为主(30. 73%~53. 08%);阔叶林和混交林的2~0. 25 mm粒级团聚体含量较高,为36. 27%~44. 67%和48. 69%~52. 44%;针叶林的优势粒径为2~0. 25 mm和0. 053 mm.总体上,在各土层中,竹林团聚体的MWD、GMD、R0. 25值均高于其他林分,且其分形维数(D)低于其他林分,可见竹林的土壤团聚体稳定性较好.随着土层深度的增加,不同林分(除针叶林外)土壤团聚体有机碳含量逐渐降低,其中竹林团聚体有机碳含量最高,显著高于针叶林和混交林.就不同团聚体粒级而言,4种林分土壤团聚体有机碳在整个土壤剖面上无明显规律,但各土层均以2~0. 25 mm和0. 053 mm粒级团聚体有机碳含量较高.不同林分下土壤团聚体有机碳相对贡献率存在显著差异,其中针叶林中0. 053 mm粒级团聚体有机碳贡献率最高;竹林的 2 mm粒级团聚体有机碳贡献率高达27. 44%~53. 47%;而阔叶林和混交林则以2~0. 25 mm粒级团聚体有机碳贡献率最高.缙云山的4种林分中,竹林的土壤团聚体稳定性较好,而针叶林的较差;在各土层中,竹林土壤各粒级团聚体有机碳含量最高,针叶林最低. 相似文献
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N. A. Kuznetsova 《Russian Journal of Ecology》2003,34(4):248-254
Trends in the diversity of structural organization of soil animal communities are analyzed using an example of the taxocenes of springtails, small soil arthropods. Different methods for describing the structure of communities are considered. On the basis of parameters characterizing specialization and stability of communities, several patterns of their organization in springtails are distinguished. It is shown that the new approach offers new opportunities in forecasting community dynamics under the effects of natural and anthropogenic factors. 相似文献
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In an attempt to increase the range of analytical techniques able to monitor ultimate degradation stages of degradable, biodegradable, and bioresorbable polymers, capillary zone electrophoresis (CZE) was used to analyze tentatively oligomers formed during thermal condensation of lactic, glycolic, anddl-3-hydroxybutyric acids. The influence of the buffer and of capillary coating are discussed in terms of electroosmotic flow. Typical analyses were first performed using a 0.1M borate buffer (pH 8.9) with anodic injection. In the case of lactic acid, seven peaks were well separated, while only three peaks were observed for glycolic acid. A more complex situation was found fordl-3-hydroxybutyric acid oligomers. The first five peaks were split. The major component of each doublet was attributed to hydroxy-terminated oligomers, whereas the satellite peaks were assigned to oligomers bearing a C=C double bond at the noncarboxylic terminus. CZE of pH-sensitive lactic acid oligomers was also performed in 0.05M phosphate buffer (pH 6.8) with cathodic injection after physical coating of the fused-silica capillary with DEAE-Dextran. The buffer-soluble fraction present in lactic acid oligomers was extracted from a dichloromethane solution. Extracts issued from different batches of lactic acid condensates gave a constant water-solubility pattern whose cutoff was at the level of the decamer. CZE was also used to monitor thein vitro aging of aqueous solutions of these water-soluble oligomers. The lactyllactic acid dimer appeared more stable than higher oligomers, thus showing that ultimate stages of the degradation did not proceed at random. These physicochemical characteristics were used to complement the degradation pathway based on diffusion of oligomers duringin vitro aging of large size lactic acid plates made by compression molding. CZE data showed that lactic acid was the only component which was released in the aqueous medium during degradation.Presented by C.B. at the 4th International Workshop on Biodegradable Plastics and Polymers, October 11–14, 1995, Durham, NH, USA. 相似文献
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PM(10) concentration and chemical composition (ions and carbon compounds) at three sampling stations in Rome and in its surroundings was determined daily during a one-month field study, carried out during December 2003. PM concentration at the traffic station was considerably higher than at the urban background and semi-rural stations; elemental carbon was detected as one of the chemical components responsible for this increase. The difference in the concentration of sulphate and ammonium was negligible, as it was expected for secondary pollutants. A negative artefact in the determination of ammonium nitrate by means of heated automatic monitors was highlighted. The dilution properties of the lower atmosphere were traced by means of a natural radioactivity monitor. This parameter has been found to play an essential role in pollution buildup. A considerable increase in PM concentration was observed to coincide with periods of atmospheric stability. The main difference in PM composition between periods of high concentration and periods of "clean" air was found to be in the increase of ammonium nitrate concentration. 相似文献
350.
添加硫酸根对燃煤电厂V2O5基脱硝催化剂性能的影响 总被引:1,自引:0,他引:1
采用浸渍法分别制得活性物质V2O5的含量均为1%和SO2-4的含量不同的催化剂,并通过实验研究了添加SO-24对燃煤电厂SCR法脱硝技术中V2O5基催化剂活性和热稳定性的影响.在固定床反应器上,在NH3/NOx物质的量比为1.0和模拟烟气流量为72 L·h-1条件下,对几种催化剂的活性进行了测试,结果显示,当负载加入5.01%的SO2-4或使用含有8.91%的SO-24载体制备催化剂时,催化剂的活性提高最为显著;在TGA 92热重.差热分析仪上对这两种催化剂进行了热重实验,结果表明,添加的硫酸根对催化剂的热稳定性也有一定提高,且不会影响电厂SCR催化剂的使用. 相似文献