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911.
Dong Yuxiang 《中国减灾(英文版)》2002,(3)
TheNorthTibetanPlateau ,ortheQiangtangPlateau ,asthemainbodyoftheQing hai TibetanPlateauwhichisoneofthethreemajordistributionareasofdesertificationinChi na ,hasawell preservednaturalecosystemcharacterizedbyhigh altitudegrassland ,isanim portantareaforstudyi… 相似文献
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Koarashi J Amano H Andoh M Iida T Moriizumi J 《Journal of environmental radioactivity》2002,60(3):249-261
To realize the dynamical behavior of 14C among exchangeable carbon reservoirs in terrestrial environment, a method for in situ determination of 14CO2 flux at soil-atmosphere interface and a high flow rate CO2 sampler were developed. This method allowed us to collect integrated quantity of CO2 for determining 14C activity over an extended time period under environmental conditions with minimal site disturbance. The 14CO2 flux from ground surface was estimated to be 1.59 x 10(-5) Bq m (-2) S (-1) in a forest floor with the method. The specific activities of 14C in environmental materials such as some biological and air samples were also determined in the vicinity of the place, where the flux measurement was made, to discuss the behavior of 14C in the forest ecosystem. The results indicated that fresh pine needles had a similar 14C specific activity to the atmospheric CO2 at the same height due to its fairly rapid equilibrium, 14C specific activity in the atmospheric CO2 has a concentration gradient near the ground surface and, at least in this site, CO2 with high 14C specific activity was generated by decomposition of soil organic matter which may be accumulated in soil as a result of former nuclear weapons tests. 相似文献
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Oh CJ Lee SO Yang HS Ha TJ Kim MJ 《Journal of the Air & Waste Management Association (1995)》2003,53(7):897-902
This study was carried out to recover valuable metals from the printed circuit boards (PCBs) of waste computers. PCB samples were crushed to smaller than 1 mm by a shredder and initially separated into 30% conducting and 70% nonconducting materials by an electrostatic separator. The conducting materials, which contained the valuable metals, were then used as the feed material for magnetic separation, where it was found that 42% of the conducting materials were magnetic and 58% were nonmagnetic. Leaching of the nonmagnetic component using 2 M H2SO4 and 0.2 M H2O2 at 85 degrees C for 12 hr resulted in greater than 95% extraction of Cu, Fe, Zn, Ni, and Al. Au and Ag were extracted at 40 degrees C with a leaching solution of 0.2 M (NH4)2S2O3, 0.02 M CuSO4, and 0.4 M NH4OH, which resulted in recovery of more than 95% of the Au within 48 hr and 100% of the Ag within 24 hr. The residues were next reacted with a 2 M NaCl solution to leach out Pb, which took place within 2 hr at room temperature. 相似文献
914.
社区防灾减灾对策的复杂性科学问题 总被引:1,自引:1,他引:0
杨军 《防灾减灾工程学报》2003,23(3):105-115
"社区研究"已有约150年的历史,社区的防灾减灾对策是一个综合性的科学问题。充分发挥社区的防灾减灾功能十分必要,确立社区防灾减灾最优对策在中国的现代化建设和可持续发展战略中具有重要意义。利用复杂性科学的理论和模型来处理社区的防灾减灾对策问题,是系统科学或复杂性科学中的一个有意义的发展方向。本文提出并分析了社区防灾减灾对策研究中的4个问题,即如何界定社区防灾减灾应急管理的角色和方向;何为防灾减灾安全社区;如何预警突发性灾难事件;社区防灾减灾系统是如何自组织的。本文引入复杂性科学理论对社区的防灾减灾对策进行了研究,讨论了复杂性科学应用于社区防灾减灾对策的理论框架。 相似文献
915.
This study was conducted to investigate the effects of temperature and time on the mechanisms of phosphorus removal in swine manure during aeration. Removal of soluble orthophosphates significantly increased with aeration time and temperature. Successive significant ortho-P removals were observed between days one and nine but no significant additional removals were recorded thereafter. Removals were significantly higher at temperatures of 20 and 25 degrees C than at temperatures of 5, 10, and 15 degrees C and ranged between 22.9 to 31.0%. Insoluble inorganic phosphorus also changed significantly with aeration time and temperature and with a similar trend as soluble orthophosphates. The pH of the manure explained 92 and 87% of the content of insoluble inorganic phosphorus at lower temperatures (5, 10, 15 degrees C) and at higher temperatures (20, and 25 degrees C), respectively. Organic phosphorus and aerobes growth patterns were similar to that of soluble orthophosphates removal. The rapid growth of aerobes was most probably the principal factor behind a rapid soluble ortho-P removal above 15 degrees C. The contribution of inorganic phosphates to the removal of soluble orthophosphates was approximately 61% while that due to organic P was approximately 35%. Precipitation was found to be the principal mechanism governing removal of soluble ortho-P in swine manure during aeration treatments. 相似文献
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本文从我国石油能源短缺和汽车尾气污染环境加剧的背景出发,详细分析了目前主要的各种新能源汽车的特点及在我国发展的前景,最后得出乙醇汽车应是我国发展新能源汽车的最佳选择的结论。 相似文献