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581.
水体表面微层的环境化学研究 总被引:3,自引:1,他引:3
水体表面微层是大气和水体间的界面,其物理、化学和生物特性可影响水体中各种物质的存在形式及最终归缩。本文总结了近几十年的参考文献,对表面微层的采样及各类物质的表面微层的行为做了系统的论述,指出了研究的难点和今后的发展方向。 相似文献
582.
The evolution of activated sludge settleability and its relationship to membrane fouling in a submerged membrane bioreactor were studied at a lab-scale equipment fed with synthetic wastewater. It was found that sludge volume index (SVI) gradually increased and the sludge settleability was reduced, which was caused by the propagation of filamentous bacteria. With increasing SVI, the average increasing rate of trans-membrane pressure increased, the stable filtration period was shortened, and the two stages (smooth stage and accelerating stage) of the trans-membrane pressure were more obvious. At the same time, the increasing rate of trans-membrane pressure at the smooth stage decreased and the rate at the accelerating stage increased with SVI, respectively. The observation by using scanning electronic microscopes showed the cake layer with loose structure and large thickness formed on the membrane surface due to the appearance of filamentous bacteria and high SVI in sludge. Influence of the sludge settleability on the trans-membrane pressure was related to the structure and thickness of the cake layer on the membrane. 相似文献
583.
Weiguo Luo Shihe Wang Juan Huang Lu Yan Jun Huang 《Frontiers of Environmental Science & Engineering》2007,1(3):316-319
To determine the impact of photosynthesis and transpiration on nitrogen removal in wetlands, an artificial wetland planted with reeds was constructed to treat highly concentrated domestic wastewater. Under different meteorological and hydraulic conditions, the daily changes of photosynthesis and transpiration of reeds, as well as nitrogen removal efficiency were measured. It was found that net photosynthesis rate per unit leaf area was maintained on a high level (average 19.0 μmol CO2/(m2·s)) from 10:00 to 14:00 in July 2004 and reached a peak of 21.1 μmol CO2/(m2·s) when Photon Flux Density was high during the day. Meanwhile, TN and NH4 +-N removal efficiency rose to 79.6% and 89.6%, respectively—the maximum values observed in the test. Correlation coefficient analysis demonstrated a positive correlation among photon flux density, net photosynthetic rate, transpiration rate, and TN and NH4 +-N removal efficiency. In contrast, there was a negative correlation between stomatal conductance and TN and NH4 +-N removal efficiency. Results suggest that the photosynthesis and transpiration of wetland plants have a great impact on nitrogen removal efficiency of wetlands, which can be enhanced by an increase in the photosynthesis and transpiration rate. In addition, the efficiency of water usage by reeds and nitrogen removal efficiency could be affected by the water level in wetlands; a higher level boosts nitrogen removal efficiency. 相似文献
584.
X.G. Lin R. Yin H.Y. Zhang J.F. Huang R.R. Chen Z.H. Cao 《Environmental geochemistry and health》2004,26(2):119-128
A survey was done recently in Jiaxing city of Zhejiang Province in the Yangtze River Delta to compare the differences of soil microbiological properties among paddy soils with different land use including continuous open-field vegetable cultivation (OFVC), plastic-greenhouse vegetable cultivation (PGVC) and traditional rice–wheat rotation (RWR). The soil types included are percolating, permeable and waterlogged paddy soils. The results indicate that the microbial flora was markedly changed as the land use changed for all the three soil types. In continuous vegetable cultivation soils, especially in PGVC soils, the bacteria amounts decreased dramatically, but the fungal and actinomyce amounts increased as compared with RWR soils. The dehydrogenase activities decreased significantly in vegetable soils, especially in PGVC soils as compared with RWR soils. The microbial biomass C and the total phospholipid contents (TPL) in vegetable cultivation soil greatly decreased as compared with RWR soils. Biolog analysis indicated that the kinds of carbon sources that could be metabolized by native microbes in PGVC soils greatly decreased as compared with OFVC soils and RWR soils, revealing that microbial diversity had decreased since land use change. The activities of some soil enzymes including urease, invertase and phosphase were all lower in OFVC soils than those in RWR soils, and those in PGVC soils were the lowest. The degradation of microbiological activities in continuous vegetable cultivation soils, especially in PGVC soils, as compared with RWR soils might have been caused by soil acidification and accumulation of salts due to overuse of both organic and inorganic fertilizers in vegetable cultivation. 相似文献
585.
原子吸收分光光度法测定植株中钙、镁的几种样品前处理方法的比较 总被引:1,自引:0,他引:1
本文比较了原子吸收分光光度法测定植株中钙、镁的三种样品前处理方法:干友化法、1mol/LHCl振荡提取法(振荡法)和1mol/LHCl静止浸泡提取法(浸泡法).结果表明,振荡法和浸泡法对钙的测定结果平均分别为干灰化法的101%和92.0%,对镁的测定结果平均分别为103%和97.6%.振荡法和浸泡法与干灰化法之间不存在显著性差异(α=0.05),它们之间有极显著的正相关性(相关系数在0.99以上).因此,在大批量样品的常规分析中,1mol/LHCl提取法可代替干灰化法. 相似文献
586.
我国人口增长方式的转变与可持续发展 总被引:4,自引:0,他引:4
本文探讨了人口增长的不同方式对可持续发展的影响,分析了我国可持续发展中存在的人口障碍,并提出建议以促进我国人口增长方式向有利于可持续发展方向转变。 相似文献
587.
本文阐述英国及中国中小学环境教育状况,并结合中国的实际,借鉴英国的环境教育经验,提出中国学校环境教育进一步发展的实质性建议. 相似文献
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590.
Mei Li Yao Zhang Chenglei Pei Jinwen Zhang Chunlei Cheng Xiufeng Lian Mubai Chen Bo Huang Zhong Fu Zhen Zhou 《环境科学学报(英文版)》2023,35(2):806-822
The real-time detection of the mixing states of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs in ambient particles is of great significance for analyzing the source, aging process, and health effects of PAHs and nitro-PAHs; yet there is still few effective technology to achieve this type of detection. In this study, 11 types of PAH and nitro-PAH standard samples were analyzed using a high performance-single particle aerosol mass spectrometer (HP-SPAMS) in lab studies. The identification principles ‘parent ions’ and ‘mass-to-charge (m/z) = 77’ of each compound were obtained in this study. It was found that different laser energies did not affect the identification of the parent ions. The comparative experiments of ambient atmospheric particles, cooking and biomass burning emitted particles with and without the addition of PAHs were conducted and ruled out the interferences from primary and secondary organics on the identification of PAHs. Besides, the reliability of the characteristic ions extraction method was evaluated through the comparative study of similarity algorithm and deep learning algorithm. In addition, the real PAH-containing particles from vehicle exhaust emissions and ambient particles were also analyzed. This study improves the ability of single particle mass spectrometry technology to detect PAHs and nitro-PAHs, and HP-SPAMS was superior to SPAMS for detecting single particles containing PAHs and nitro-PAHs. This study provides support for subsequent ambient observations to identify the characteristic spectrum of single particles containing PAHs and nitro-PAHs. 相似文献