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231.
以县(市)作为研究单元,采用综合指数法,分别计算山东半岛城市群1986、2008年经济社会发展综合指数,通过比较各单元经济社会发展综合指数的变化,研究了20世纪80年代以来山东半岛城市群地区空间极化的特点;采用面板数据模型,定量探讨了山东半岛城市群地区空间极化的影响因素。研究表明:山东半岛城市群地区经济活动有明显的经济中心指向、沿海指向,空间发展依然以极化为主,新的发展极已经出现,但分布在区域的边缘地带,带动作用不大;大都市区整体规模加剧膨胀,核心和外围地区出现极化和反极化现象;东部地区出现网络化发展的雏形。原有经济基础、产业结构转换能力和经济全球化水平是改革开放以来山东半岛城市群地区空间极化的主要影响因素 相似文献
232.
Distribution characteristics of organochlorine pesticides in surface and vertical sediments from the Zha Long Wetland, China 总被引:1,自引:0,他引:1
Liu G Li J Yin L Liu L Qi H Wu Y 《Environmental science and pollution research international》2011,19(7):2681-2689
Introduction
The Zha Long Wetland, the first water bird conservation area in China, lies on the northern bank of the Song Nen Plain with an area of 2,100 km2. In many areas of the Zha Long Wetland, water pollution has led to a decrease in the wetland??s ecological function, vegetation degradation, a decrease in the number of bird species, and the depletion of fish resources.Materials and methods
The sediments used in this study were collected from the surface sediment of seven sites and from different depths in three types of marshes in the Zha Long Wetland in northeast China in late October 2006. The levels and distribution patterns of 17 organochlorine pesticides (OCPs; ??-HCH, ??-HCH, ??-HCH, ??-HCH, p,p??-DDE, p,p??-DDD, p,p??-DDT, endosulfan I, endosulfan II, endosulfan sulfate, heptachlor, heptachlor epoxide, aldrin, dieldrin, endrin, endrin aldehyde, and methoxychlor) in surface sediments as well as hexachlorocyclohexane (HCH) and 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) in vertical sediments were investigated.Results and discussion
The concentrations of HCHs, DDTs, endosulfans, heptachlors, aldrin, and methoxychlor in surface sediments ranged from 10.44 to 41.97 ng/g, nd (undetectable levels) to 211.88 ng/g, nd to 69.89 ng/g, nd to 28.10 ng/g, 9.81 to 623.83 ng/g, and from nd to 3.99 ng/g, respectively. The highest levels of OCPs were detected in Tangtugangzi at a total concentration of 727.72 ng/g, where the dominant compound was endrin at a concentration of 483.04 ng/g. In the vertical sediments, the HCHs and DDTs were in the ranges of nd?C136.00 and nd?C214.06 ng/g, respectively.Conclusions
Different distributions of HCHs, DDTs, and other OCPs indicated that they originated from different contamination sources. Composition analyses in surface sediments indicated recent OCP usage or discharge at some sample sites in the Zha Long Wetland. 相似文献233.
234.
A new Vis-Fe0-H2O2-citrate-O2 system comprising zero-valent iron, hydrogen peroxide, citrate anion and aeration at circumneutral pH under visible irradiation was studied. 21 μmol L−1 of Rhodamine B (RhB) was chosen as the substrate to be tested. Experiments were conducted under conditions of 2.9 mmol L−1 of H2O2, 12.6 g of Fe0 and 1.0 mmol L−1 of citrate at pH 7.5. Results showed that, in 1 h reaction, 54% of RhB was removed with corresponding 26% of COD reduced. Meanwhile, the amount of released dissolved irons from Fe0 surface was found to be at a very low level as <5.4 μmol L−1. Extinguishing tests with isopropanol suggested that RhB oxidation by hydroxyl radicals was the main process taken place in Vis-Fe0-H2O2-citrate-O2 system, which accounted for 75% of substrate removal in 3 h reaction. Control and factor influencing experiments showed that the prohibitive extents of individual factor importance on RhB removal followed a decreasing order of Fe0 > H2O2 > citrate > Vis > O2. This study showed an excellent system that could remove refractory organic compounds from water in laboratory researches, and also provided a good idea to reduce secondary contamination by dissolved irons in future investigations. 相似文献
235.
研究了混凝一气浮工艺对不同分子量区间三卤甲烷生成势(trihalomethanes formation potential,THMFP)的去除效果及絮体形态对THMFP去除效果的影响。结果表明,混凝一气浮工艺以去除大分子量区间THMFP为主,对小分子量区间THMFP的去除效果较差。UV254值与THMFP值的线性相关系数为0.9449,UV254值可以较好地反映THMFP的含量。絮体的分形维数为1.17~1.2时,孔隙率较大,可增加絮体对THMFP的活性吸附空间,且絮体相对密度较小,可增强同向絮凝作用,增加絮体和THMFP的接触概率,有利于气浮对THMFP的去除。 相似文献
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239.
Utilization of municipal solid waste incineration (MSWI) fly ash in ceramic brick: product characterization and environmental toxicity 总被引:4,自引:0,他引:4
In this study, municipal solid waste incineration (MSWI) fly ash was used as a blending in making ceramic brick based on its characterization and an orthogonal test was performed to determine the optimal mixture ratio of the materials. Besides, the fired bricks made in accordance with the optimal mixture ratio were characterized for performance, phase transformation, microstructure, leaching toxicity of the heavy metals in accordance with GB/T 2542-92 (Detection methods for bricks analysis, China) and by means of XRD, SEM and leaching toxicity analysis. It was found that the optimal mixture ratio of materials (MSWI fly ash:red ceramic clay:feldspar:gang sand) was 20:60:10:10 by mass, and the optimal sintering temperature was 950 °C. Leaching results of heavy metals from sintered bricks were reduced considerably in comparison with those from green bricks prior to sintering process. The results as a whole suggested that utilization of MSWI fly ash in ceramic brick constituted a potential means of adding value. 相似文献
240.
Zhou Qin Wang Leyang Xu Qi Zhao Yuan 《Environmental science and pollution research international》2019,26(21):21321-21328
Environmental Science and Pollution Research - The oil-water separation is a popular issue and the removal of oil from bulk water is also meaningful especially in oil spill incident, which not only... 相似文献