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261.
ABSTRACTThe effects of the flooding and initial Eh of sediments on the sorption of uranium onto the sediments were analysed by flooding and static experiments. The changes in uranium species with Eh and kinetic and thermodynamic characteristics of the uranium sorption onto the sediments were investigated. The flooding experiment indicates that the initial Eh of the sediment gradually decreased with the increase in flooding time. Based on the redox potential in the flooding experiment, simulation results obtained using the geochemical simulation software PHREEQC show that the concentration of U (VI) decreased. In contrast, the concentrations of U (III), U (IV), and U (V) gradually increased. The pseudo-second-order kinetic model well fitted the experimental data, which shows that the sorption was mainly chemical sorption. The thermodynamic parameters suggest that the entropy and enthalpy under the used conditions were positive and that ΔGθ was negative. A thermodynamic analysis shows that the sorption was endothermic and spontaneous. These results are useful for the understanding of the sorption mechanism and migration of uranium onto the sediment under different initial sediment redox potentials and provide a good theoretical foundation for radioactive pollution remediation. 相似文献
262.
文章论述了水务特许经营准入竞争方式的内涵及相关政策规定,并对协议、竞争性谈判、招募、公开招标及拍卖五大类准入竞争方式进行了分析,归纳了准入竞争方式和水务项目本身特性间的匹配关系。 相似文献
263.
264.
Combined amendment reduces soil Cd availability and rice Cd accumulation in three consecutive rice planting seasons 总被引:1,自引:0,他引:1
Wenjun Yang Shilong Wang Hang Zhou Min Zeng Jingyi Zhang Fang Huang Shiping Shan Zhaohui Guo Hongwei Yi Zhiguang Sun Jiaofeng Gu Bohan Liao 《环境科学学报(英文版)》2022,34(1):141-152
The scientific application of stabilized materials has been considered an effective method for the in situ remediation of Cd-contaminated soil. This study aimed to investigate the persistence of the effect of a combined amendment of limestone and sepiolite(LS) on soil Cd availability and accumulation in rice grown in a mildly Cd-contaminated paddy field(0.45 mg/kg of Cd) over three consecutive rice seasons. 1125–4500 kg/ha of LS was applied to the soil before the first rice planting season and 5... 相似文献
265.
Yu-San Han Yu-Liang Sun Yi-Fen Liao I-Chiu Liao Kang-Ning Shen Wann-Nian Tzeng 《Marine Biology》2008,155(6):613-621
The Japanese eel has dramatically declined in Asia since the 1970s. Over the past two decades, glass eel productivity in Taiwan has decreased, but is highly variable among each year catch, though the cause for this is unknown. The impact of both population decline and instability on genetic diversity, however, is unknown. In this study, we investigated changes in allele frequencies of Japanese eel recruitment events over the past 20 years using six polymorphic microsatellite DNA loci. Specimens of glass eels were collected yearly from a single location in northern Taiwan from 1986 to 2007. Overall genetic differentiation among all samples was very low but significant (FST = 0.002, P = 0.002), and only 2 out of 120 pairwise tests were significant. The relationship between genetic and temporal distance showed a slight but insignificant correlation (R2 = 0.03, P = 0.0504). There were no overall significant differences in allelic richness (P = 0.35) or genetic heterozygosity (P = 0.73) among annual recruitment events. No apparent loss of genetic diversity and occurrence of a genetic bottleneck for eel populations were observed. Estimates of the effective population size (Ne) generally exceeded 500, although confidence intervals were very wide. While El Niño /Southern Oscillation (ENSO) events had little impact on genetic diversity, they may account for the annual fluctuation in glass eel catch. These results indicate long-term stability of genetic diversity in the Japanese eel with little evidence for sweepstakes recruitment. 相似文献
266.
267.
广州市莲塘村风水林群落特征及植物多样性 总被引:10,自引:0,他引:10
风水林是极具南方地域特色的植被景观与物种储存库,是接近地带性植被特性的一种群落类型.研究风水林,对丰富和发展环境科学、生态科学、林业科学和园林科学,具有重要意义.本研究在广州市莲塘村村后风水林设立了样带、标准地和样方,对其乔木层、灌木层和草本层植物进行详细调查,结果表明,该区共有植物73种,隶属于33个科57个属.其植物种类丰富,以茜草科、樟科、大戟科、壳斗科、莎草科、桃金娘科植物占优势.该群落具有南亚热带常绿阔叶林群落的典型群落结构,垂直结构分层现象明显,层次清晰.文章对树种丰富度、Shannon-Winner指数、Simpson多样性指数、种间相遇机率以及均匀度等多样性指标的研究表明:该群落具有较大的物种丰富度,植物多样性较高,物种分布均匀,不同种之间相遇几率较大,其生物多样性各项指标远远大于尾叶桉人工纯林.该风水林群落是目前广州市保存较完好的具有典型地带特色的少数自然林之一,它的研究成果对以后生态公益林造林有极大的参考价值. 相似文献
268.
Tim Futing Liao 《中国人口.资源与环境(英文版)》2012,(2):67-77
Two opposing intellectual traditions and their contem-porary developments regarding the relations among population, available resources, and quality of life as reflected in economic growth are reviewed. What is at issue is whether population growth is detrimental to or beneficial for economic development. Neither of the extreme views gives a complete picture of the interplay among population, resources, and quality of life. Following previous literature on the topic, this paper establishes a more balanced approach that considers the function linking population and quality of life not constant but variable and regards the limitedness of resources as not absolute but relative to regions and societies. The proposed approach is more flexible in better explaining the relation between population and economic growth. China is examined as a case in point to shed light on the interaction of population growth, economic development, and available resources, and its recent post-economic reform experiences showcase the appropriateness of the synthetic approach. 相似文献
269.
Zhu Feng Chen Lan Qian Zhengmin Liao Yuxue Zhang Zhen McMillin Stephen Edward Wang Xiaojie Lin Hualiang 《Environmental science and pollution research international》2021,28(28):37195-37203
Environmental Science and Pollution Research - There are relatively few studies that focus on the health effects of exposure to size-specific particles on respiratory mortality in China. We aimed... 相似文献
270.
Watering techniques and zero-valent iron biochar pH effects on As and Cd concentrations in rice rhizosphere soils, tissues and yield 总被引:1,自引:0,他引:1
Md Shafiqul Islam Yali Chen Liping Weng Jie M Zulqarnain Haider Khan Zhongbin Liao Abdoul Salam Issiaka Abdoul Magi Yongtao Li 《环境科学学报(英文版)》2021,33(2):144-157
Zero-valent iron amended biochar (ZVIB) has been proposed as a promising material in immobilizing heavy metals in paddy fields. In this study, the impacts of pH of ZVIB (pH 6.3 and pH 9.7) and watering management techniques (watering amount in the order of CON (control, 5/72)>3/72>1–3/72>3/100>1/72, with 5/72, for example, representing irrigation given to 5 cm above soil surface in 72 hr regular interval) on As and Cd bioavailability for rice and its grain yield (YieldBR) were investigated in a pot experiment. Brown rice As (AsBR) content was irrelative to the watering treatments, while significantly decreased (>50%) with the addition of both ZVIB materials. The diminutions of brown rice Cd (CdBR) content as well as the YieldBR were highly dependent on both the soil amendment materials’ pH and watering amount. Among all the watering treatments, 3/72 treatment (15% less irrigation water than the CON) with ZVIB 6.3 amendment was the optimum fit for simultaneous reduction of AsBR (50%) and CdBR contents (19%) as well as for significant increment (12%) of the YieldBR. Although high pH (9.7) ZVIB application could also efficiently decrease As and Cd contents in brown rice, it might risk grain yield lost if appropriate (e.g. 3/72 in our study) watering management technique was not chosen. Therefore, ZVIB would be an environmentally friendly option as an amendment material with proper selection of watering management technique to utilize As and Cd co-contaminated arable soils safely for paddy cultivation. 相似文献