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461.
A study on the leaching behaviour of trifluralin, lindane and aldicarb in three different types of soil was performed using soil column method. Leaching of trifluralin was not much influenced by soil types. Organic matter content showed an apparent influence on the leaching of lindane and aldicarb. Leaching depth of the pesticide was found to be negatively related to the organic matter content of the soil under study. It was also found that hydrophobic property of the pesticide increased the tendency of adsorption of the chemical to soil particles and hence reduced its leaching tendency. Thus, the leaching depths of the three pesticides in each of the three soils were observed in the order: aldicarb >lindane> trifluralin. Leaching behaviour of the three pesticides was also predicted based on the adsorption coefficients of the chemicals. For trifluralin and lindane, the predicted results were considerably in line with the results of the experiment. 相似文献
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高职数学教学必须加强数学思想方法的教学 总被引:1,自引:0,他引:1
代伟 《中国环境管理干部学院学报》2008,18(4):109-111
数学思想方法是数学知识的核心,是数学的精髓和灵魂,是研究数学理论和运用数学解决实际问题的指导思想。本文针对目前高职数学教学中存在的数学思想方法教学重视不够以及教法上随意性的现状,提出通过加强数学史和基本数学思想方法的介绍,以及倡导“问题解决”的教学模式来提高学生的数学素养。 相似文献
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长期单施NK肥条件下几种典型土壤磷的演化 总被引:3,自引:0,他引:3
为探讨我国典型土壤长期单施氮钾肥对土壤全磷和Olsen-P磷的影响,研究了不同气候条件、不同耕作制度下,7种典型土壤类型长期定位试验单施氮钾肥下土壤全磷和Olsen-P变化及其影响因素.结果表明,在长期单施氮钾肥条件下,除杭州水稻土全磷含量稳定在1.0g·kg-1左右外,其余6种耕作土壤全磷含量和土壤Olsen-P均呈显著下降趋势,全磷含量下降幅度在13.6%~44.9%之间;土壤Olsen-P下降速率比全磷高几倍,Olsen-P下降有一定阈值,这一阈值大约为5 mg·kg-1.土壤全磷含量与土壤Olsen-P含量呈极显著直线相关关系.因此,长期单施氮钾肥在很大程度上减少了土壤磷素养分库. 相似文献
469.
Shumei Jiang Xiang Li Long Zhang Wei Sun Shikun Dai Lianwu Xie Yonghong Liu Kyung Jin Lee 《Marine Biology》2008,153(5):945-952
The study describes the diversity of actinobacteria isolated from the marine sponge Iotrochota sp. collected in the South China Sea. Species and natural product diversity of isolates were analyzed, including screening
for genes encoding polyketide synthases (PKS) and nonribosomal peptide synthetase (NRPS), and 16S rRNA gene restriction fragment
length polymorphism (RFLP). PKS and NRPS sequences were detected in more than half of the isolates and the different “PKS-I–PKS-II–NRPS”
combinations in different isolates belonging to the same species indicated a potential natural product diversity and divergent
genetic evolution. The phylogenetic analysis based on 16S rRNA gene sequencing showed that the isolates belonged to genera
Streptomyces, Cellulosimicrobium, and Nocardiopsis. The majority of the strains tested belonged to the genus Streptomyces and one of them may be a new species. To our knowledge, this is the first report of a bacterium classified as Cellulosimicrobium sp. isolated from a marine sponge.
Key Laboratory of Marine Bio-recourses Sustainable Utilization (LMB-CAS), Guangdong Key Laboratory of Marine Materia Medica
(LMMM-GD), South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, People’s Republic of China. 相似文献
470.
Junming Xu Jianchun Jiang Weidi Dai Yu Xu 《Process Safety and Environmental Protection》2012,90(4):333-338
Direct liquefaction of lignocellulosic waste (sawdust) has been conducted in hot-compressed ethanol at temperatures from 150 to 250 °C. It was found that polyols such as glycerol, glycol and polyethylene glycol (PEG) promoted liquefaction process assisted with hot ethanol treatments seemed promising for production of bio-oils from lignocellulosic materials. Effects of different solvents and catalysts on liquefaction of sawdust were investigated. The results showed that the optimum operating condition for catalytic liquefaction is at 250 °C, 1 h of reaction time using glycerol and ethanol as solvent where operating at this condition realized the highest conversion of sawdust which is 97.8%. After reaction, the liquified product was separated by vacuum distillation. Two fractions were obtained, namely light oil and heavy oil. The properties and compositions of these two fractions were characterized in terms of Fourier transform infrared spectroscopy (FT-IR), gas chromatography–mass spectrometry (GC–MS), size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR). 相似文献