Principal component analysis to assess the efficiency and mechanism for enhanced coagulation of natural algae-laden water using a novel dual coagulant system

A novel dual coagulant system of polyaluminum chloride sulfate (PACS) and polydiallyldimethylammonium chloride (PDADMAC) was used to treat natural algae-laden water from Meiliang Gulf, Lake Taihu. PACS (Al_n(OH)_mCl_3n-m-2k(SO₄)_k) has a mass ratio of 10 %, a SO₄ ^2?/Al₃ ⁺ mole ratio of 0.0664, and an OH/Al mole ratio of 2. The PDADMAC ([C₈H₁₆NCl]_m) has a MW which ranges from 5?×?10⁵ to 20?×?10⁵ Da. The variations of contaminants in water samples during treatments were estimated in the form of principal component analysis (PCA) factor scores and conventional variables (turbidity, DOC, etc.). Parallel factor analysis determined four chromophoric dissolved organic matters (CDOM) components, and PCA identified four integrated principle factors. PCA factor 1 had significant correlations with chlorophyll-a (r?=?0.718), protein-like CDOM C1 (0.689), and C2 (0.756). Factor 2 correlated with UV₂₅₄ (0.672), humic-like CDOM component C3 (0.716), and C4 (0.758). Factors 3 and 4 had correlations with NH₃-N (0.748) and T-P (0.769), respectively. The variations of PCA factors scores revealed that PACS contributed less aluminum dissolution than PAC to obtain equivalent removal efficiency of contaminants. This might be due to the high cationic charge and pre-hydrolyzation of PACS. Compared with PACS coagulation (20 mg L^?1), the removal of PCA factors 1, 2, and 4 increased 45, 33, and 12 %, respectively, in combined PACS–PDADMAC treatment (0.8 mg L^?1?+?20 mg L^?1). Since PAC contained more Al (0.053 g/1 g) than PACS (0.028 g/1 g), the results indicated that PACS contributed less Al dissolution into the water to obtain equivalent removal efficiency.     

The use of biomass production and allometric models to estimate carbon sequestration of <Emphasis Type="Italic">Jatropha curcas</Emphasis> L. plantations in western Burkina Faso

The topic of carbon sequestration in plants has received much attention recently due to concerns about global climate change, which is being exacerbated by deforestation. In the early days of the global bioenergy boom, the private sector and non-government organizations enthusiastically promoted the planting of Jatropha curcas L. as a key candidate shrub species for the production of bioenergy in West Africa. This study investigates the aboveground biomass production and carbon sequestration potential of J. curcas, which is already widely cultivated for the production of oil seeds, biodiesel and biokerosene. The specific objective is to use a destructive method to develop allometric prediction equations of the aboveground biomass production of J. curcas plantations. 38 J. curcas shrubs were harvested and weighed in order to estimate biomass production. These data were used to develop allometric equations for the estimation of wood, leaf and total aboveground biomass production. The best-fit models found for estimating shrub component biomass and total aboveground biomass production were of the power form. All of the regression equations relating the prediction of leaf biomass, wood biomass and total aboveground biomass with J. curcas diameter at 20 cm above the ground (D) were statistically significant (p < 0.001) and also presented the highest goodness of fit (high R ²). The aboveground biomass carbon content was estimated using the ash method. Carbon content in leaves and wood was, respectively, 48 and 54 %. The current established allometric equations can be helpful to provide a rapid estimation of the aboveground biomass and C stock for J. curcas biofuel projects in semi-arid conditions.     

奇特的极地景观

神秘莫测的南极南极大陆是最高大,最冷酷,最纯洁,最美丽,最神秘莫测,最桀骜不驯的。南极真是高得出奇,有2350米。犹如一个巨人。然而它又是最低的大陆。南极大陆上的本特莱冰下槽谷,在海平面以下2500多米．比北冰洋的平均深度还要深两倍多呢!这是由于在巨大冰盖的重压之下,大陆地壳产生了向     

基于可靠度约束的高层建筑结构优化设计

本文以文献中提出的结构体系可靠度分析的最弱失效模式法为基础,充分考虑结构体系的造价和结构的损失期望与结构体系可靠度的关系,以及结构构件的可靠度约束,提出了结构体系目标可靠度的优化决策方法;基于优化决策的结果,提出了结构体系的最优设计准则;最后,依所提出的最优设计准则,实现了高层建筑基于构件和结构可靠度约束的结构优化设计。     

±660kV直流输电系统故障对系统稳定性的影响

为验证宁夏电网±660 kV直流输电系统双极闭锁后安稳装置控制策略的正确性及安稳装置切机后对系统稳定性的影响,采用电力系统全数字实时仿真系统(Advanced DigitalPower System Simulator,ADPSS)进行故障仿真,仿真过程中,安稳装置动作可靠,系统保持稳定运行。仿真结果表明:安稳装置动作后,直流系统附近各线路电压在短暂波动后均恢复平稳,线路无过载现象。     

330/220kV电磁环网解环前后暂态稳定特性分析

为保证宁夏电网 330/220 kV 电磁环网解环后电网的安全稳定运行,运用电力系统分析综合程序(Power System Analysis Software Package,PSASP),对电磁环网解环前后电网在三级稳定标准涉及的各种故障形式下进行暂态稳定计算,对比分析解环前后系统电压与频率波动以及功角阻尼比的变化。计算结果表明:330/220kV 电磁环网解环对于宁夏电网的暂态稳定特性影响不大,解环后不会增加暂态失稳事故风险,解环条件一旦具备,应该及时实施解环。     

高寒地区道路工程的生态效应及其生态恢复研究进展

高寒地区道路施工等基础设施建设对高寒地区会造成巨大的生态破坏,生态恢复问题亟待解决.围绕目前的焦点问题:道路施工对高海拔生态系统造成的显著变化将对区域环境产生何种影响?退化生态系统的结构与功能恢复潜力如何?,本文介绍了道路施工建设对原生植被、植物个体生态、种群生态、群落生态、沿线景观生态系统的影响,通过国内外学者关于高原道路生态环境效益的研究,对生态效应评价方法和水土流失研究规律进行阐述,分析了道路生态恢复治理措施的构建规律,指出目前需要加强的研究有:道路建设过程中的生态恢复基础研究,生物多样性和生态系统恢复力在道路工程生态恢复中的作用研究.     

企业实施循环经济的战略探讨

本文从循环经济的原则出发,根据国际实践以及中国实行循环经济的实际情况,提出了企业实现循环经济发展的四种战略：清洁生产和全过程污染控制战略、企业生产者责任延伸战略、产业链拓展战略和废弃物综合利用战略,为企业进行循环经济建设提供一定的指导和参考作用。     

Characterization of the pesticide chlordane in estuarine river sediments

Sediments are increasingly recognized as both carrier and potential source of contaminants in aquatic environments. This study investigated the characteristics and spatial distribution of total chlordane and its three most abundant compounds, including alpha-chlordane, gamma-chlordane, and trans-nonachlor, in sediments from the Cedar and Ortega rivers, Florida, USA, using geographic information system (GIS)-based kriging analyses and field measurements. Kriging analysis showed that two areas, one from the Cedar River area and the other from the northern end of the Ortega River area, were contaminated. The maximum concentrations of total chlordane, gamma-chlordane, alpha-chlordane, and trans-nonachlor in the sediments were, respectively, 101.8, 20.1, 26.3, and 19.2 microg/kg. A plot of total organic carbon (TOC)-normalized chlordane concentrations showed that effects of grain size on sediment chlordane contamination were negligible. A principal axis analysis further revealed that a linear correlation existed between alpha-chlordane and total chlordane as well as between gamma-chlordane and total chlordane, whereas no correlation existed between trans-nonachlor and total chlordane. Comparison of total chlordane concentration with Florida Sediment Assessment Guidelines showed that the Cedar River and the northern end of the Ortega River had total chlordane concentrations above the probable effect level (4.79 microg/kg), which could pose a potential risk to aquatic life.