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251.
生态环境问题是当今许多大城市所面临的最主要问题之一.生态环境本身的多元性及交互作用,决定了生态环境保护的综合性与复杂性.它既涉及到自然科学,又涉及到社会科学;既需要定量的研究,也需要定性的研究;既包括实证的描述,也包括实义的分析和趋势的预测.以昆明为例,重点从城市规划的角度出发,定性地探索城市生态环境保护问题. 相似文献
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253.
Jung Sik Koh 《环境科学学报(英文版)》1993,5(3):269-278
The relationship between man-made CO2 emission and atmospheric CO2 concentration has been established. The factors that affect CO2 reduction allotment and the impacts on future energy demand and supply were discussed, in order to help energy policy makers both in developed countries and in developing countries for understanding the fundamental constraint on energy sector resulted from global warming related CO2 reduction, and hopefully in finding a common objective starting point to deal with global warming negotiation in energy sector, and to investigate the optimum stabilization goal and process acceptable to all sovereign countries that based on equity and applicability. 相似文献
254.
低pH对草鱼血液酸碱平衡的影响 总被引:4,自引:1,他引:4
研究了低pH(6.0—4.0)对草鱼血液酸碱平衡、p_(o2)及p_(co2)的影响,结果表明,低pH引起草鱼严重的酸血症.亚致死pH(6.0—5.0)时,血液酸碱平衡的影响主要表现为碱贮备[HCO_3]的丧失,血液pH的明显下降经机体缓冲调节可趋于稳定.致死低pH(4.0)时,血液pN和[HCO_3]下降均非常显著,并在96h内随酸化时间延长而日趋严重.仅在pH≤4.0的酸水中草鱼存在低氧症影响问题.草鱼是一种酸敏感性鱼类,为确保成鱼在天然水体的生存和繁育,水质pH至少应维持在6.0以上. 相似文献
255.
An amniocentesis was performed at 13.3 weeks' gestation for advanced maternal age. A mosaic sex chromosome pattern was found: of 50 cells examined, 34 had a 45,X karyotype. In 14 cells with a modal number of 46, a recognizable Y was substituted by a small non-fluorescent marker. C-banding identified the marker as an isodicentric in 12 cells. In two cells, the non-fluorescent marker appeared to be monocentric and looked like a non-fluorescent del (Yq), but could have been an isodicentric Y with inactivation of one of the centromeres. Two cells with a modal number of 47 showed two copies of the monocentric marker. Fluorescent in situ hybridization with an alpha satellite Y-specific centromeric probe confirmed the Y-chromosome origin of the markers and allowed for more accurate prenatal diagnostic information. 相似文献
256.
浦东新区大气气溶胶中碳颗粒的分布规律 总被引:11,自引:0,他引:11
采用元素相关性分析方法,找出浦东新区大气气溶胶中碳颗粒的污染源,确证该区大气中碳颗粒主要来自煤的燃烧。同时初步找出浦东新区大气中碳颗粒污染的时空分布和粒径分布规律,为改善浦东 新区大气污染状况提供依据。 相似文献
257.
In this paper, impacts of climate change on wheat development rate and production in the northern China are discussed. The results show that the temperature is a controlling factor of development rate but the precipitation is not. The higher the temperature is. the faster the development and the shorter development period will be. Without consideration to varieties and cropping system, meteorological yield of winter wheat would decrease 170.40, 134.25, 98.70 and 97.20 kg/hm2 in the north China and 13.97, 7.95, 39.60 and 19.80 kg/hm2 in the northwest China compared with that in 1950s, 1960s, 1970s and 1980s, respectively, when the CO2 concentration in the atmosphere is doubled. In drought and semi-drought regions, the spring wheat yield would drop with the temperature rise in and raise with the precipitation increase. The influence of temperature on weight of leaf and stalk is also remarkable. 相似文献
258.
采用加压活性炭生物膜法处理以对硝基甲苯磺酸盐为主的难降解的有机废水的研究,是在活性炭生物膜法处理有机废水基础上发展起来的新技术。本实验结果表明,在加压9.8×10~4Pa(1kgt/cm~2)的条件下,COD_(Cr)去除率为62%~70%,比常压活性炭生物膜法高20%~25%;其容积负荷Nv=1.7~2.9kgCOD/m~3·d,比一般活性污泥法高3~6倍。 相似文献
259.
260.
《环境科学学报(英文版)》2023,35(4):387-395
This study examined the effectiveness for degradation of hydrophobic (HPO), transphilic (TPI) and hydrophilic (HPI) fractions of natural organic matter (NOM) during UV/H2O2, UV/TiO2 and UV/K2S2O8 (UV/PS) advanced oxidation processes (AOPs). The changing characteristics of NOM were evaluated by dissolved organic carbon (DOC), the specific UV absorbance (SUVA), trihalomethanes formation potential (THMFP), organic halogen adsorbable on activated carbon formation potential (AOXFP) and parallel factor analysis of excitation–emission matrices (PARAFAC-EEMs). In the three UV-based AOPs, HPI fraction with low molecular weight and aromaticity was more likely to degradate than HPO and TPI, and the removal efficiency of SUVA for HPO was much higher than TPI and HPI fraction. In terms of the specific THMFP of HPO, TPI and HPI, a reduction was achieved in the UV/H2O2 process, and the higest removal rate even reached to 83%. UV/TiO2 and UV/PS processes can only decrease the specific THMFP of HPI. The specific AOXFP of HPO, TPI and HPI fractions were all able to be degraded by the three UV-based AOPs, and HPO content is more susceptible to decompose than TPI and HPI content. UV/H2O2 was found to be the most effective treatment for the removal of THMFP and AOXFP under given conditions. C1 (microbial or marine derived humic-like substances), C2 (terrestrially derived humic-like substances) and C3 (tryptophan-like proteins) fluorescent components of HPO fraction were fairly labile across the UV-based AOPs treatment. C3 of each fraction of NOM was the most resistant to degrade upon the UV-based AOPs. Results from this study may provide the prediction about the consequence of UV-based AOPs for the degradation of different fractions of NOM with varied characteristics. 相似文献