Levels and distributions of polychlorinated biphenyls in sewage sludge of urban wastewater treatment plants

Concentrations of polychlorinated biphenyls (PCBs) have been measured in sewage sludge samples from 8 urban wastewater treatment plants in Beijing, China. The PCB congeners were analyzed by isotope dilution high resolution gas chromatography/high resolution mass spectrometry method. The concentration of PCBs ranged from 65.6 to 157 ng/g dry weight (dw), with a mean value of 101 ng/g dw. The dioxin-like PCB WHO-TEQs (World Health Organization-Toxic Equivalents) of the sludge were lower than 1 pg /g dw. Conse...     

城市中水回用于火电厂循环冷却水系统的应用研究

火电厂循环冷却水系统利用中水水源实现城市中水大规模回用,对缓解水资源短缺、减轻水体污染具有现实的意义。阐述了城市中水回用火电厂循环冷却水系统的现状、中水深度处理,提出ABFT＋机械澄清池工艺弥补了传统深度处理工艺的不足,介绍其原理、特点及成功应用实例。     

燃煤火电厂石灰石-石膏湿法烟气脱硫系统日常运行环保监督考核方法探讨

从二氧化硫总量减排环保监督管理的实际出发,结合日常监督工作的实例,分析影响烟气脱硫效率的因素,找出脱硫系统容易出现的故障,提出对脱硫系统日常监督考核的重点,探索建立烟气脱硫系统监督考核方法。     

辽宁省主要自然保护区外来入侵植物的调查分析

通过野外实地调查,对辽宁省的4个国家级自然保护区外来入侵植物的种类数量和分布现状进行了调查分析。结果表明,老铁山、鸭绿江口、医巫闾山、九龙川4个自然保护区内的外来入侵植物分别为27,10,7和6种,总计16科36种。依据保护区内外来入侵植物的特点和生态影响,提出了一些有效的管理措施和防治建议。     

RIP-N模型对官厅水库库滨带去氮效应的流域尺度模拟分析

以官厅水库库滨带为研究对象,构建适用于流域尺度岸边带去氮负荷估算的生态水文模型——RIP-N(Riparian-Nitrogen)模型,对官厅水库库滨带2007年3~9月间岸边带去氮效应进行分析.同时,在延庆水保站开展田间尺度的野外模拟实验,结合室内外试验分析和以往研究成果,对模型模拟结果进行验证.RIP-N模型包括土壤化学过程模拟和植物生长过程模拟.前者包括土壤反硝化模拟、硝化模拟和氨挥发模拟;后者包括植物净第一性生产力(net primary productivity,NPP)模拟、植物生产力分配模拟和植物营养元素吸收模拟.结果表明:①RIP-N模型模拟值与实验值的决定系数大于0.5,证明该模型在空间尺度模拟上的有效性及模拟结果的可靠性;②模型模拟结果表明官厅水库库滨带流域3~9月对N的总去除量为5.91×103t;③RIP-N模型对官厅水库库滨带去氮环境效益分析表明,当前库滨带土地利用格局中,滩地、林地和草地是去污效果较好的土地利用类型,3~9月对流域的去N量占流域总去N量的76.5%,在非点源污染防治中起到"汇"的作用;但是研究区中专属湿地的"汇"作用表现不明显,3~9月去N量仅占流域总去N量的5.9...     

Rheum palaestinum (desert rhubarb), a self-irrigating desert plant

The rare plant Rheum palaestinum (Polygonaceae) is a perennial hemicryptophyte that grows during the rainy winter in desert mountainous areas in Israel and Jordan that receive an average annual rainfall of ca. 75 mm. It produces between one and four large round leaves that are tightly attached to the ground and form large rosettes of up to 1 m². These leaves differ markedly from the typical small leaves of most desert plants. Moreover, they have a unique 3D morphology resembling a scaled-down mountainous area with well-developed steep drainage systems, raising the question which selective agents were involved in their evolution. We propose that the large leaves collect rainwater that then infiltrates the soil surrounding the root. We measured the seasonal course of leaf growth, examined the area of wet soil surrounding the root after actual and simulated rain, and modeled the water harvesting capacity using the plant leaf area and the weekly precipitation. We show that even in the slightest rains, water flows above the veins to the leaf’s base where it irrigates the vertical root. A typical plant harvests more than 4,100 cm³ of water per year, and enjoys a water regime of about 427 mm/year, equivalent to the water supply in a Mediterranean climate. This is the first example of self-irrigation by large leaves in a desert plant, creating a leaf-made mini oasis. All authors contributed equally to this paper.     

Phytoplankton community structure and environmental parameters in aquaculture areas of Daya Bay, South China Sea

Environmental characteristics and phytoplankton community structure were investigated in two aquaculture areas in Dapeng Cove of Daya Bay, South China Sea, between April 2005 and June 2006. Phytoplankton abundance ranged between 5.0 and 8877.5 cells/mL, with an average of 751.8 cells/mL. The seasonal cycle of phytoplankton were demonstrated by frequent oscillations, with recurrent high abundances from late spring to autumn and a peak stage in late winter. Diatoms were the predominant phytoplankton group, accounting for 93.21% of the total abundance. The next most abundant group was the dinoflagellates, which made up only 1.24% of total abundance. High concentrations of Alexandrium tamarense (Lebour) Balech with a maximum of 603.0 cells/mL were firstly recorded in this area known for high rates of paralytic shellfish poisoning (PSP) contamination. Temperatures and salinities were within the suitable values for the growth of phytoplankton, and were important in phytoplankton seasonal fluctuations. The operation of the Daya Bay Nuclear Power Station (DNPS) exerts influences on the phytoplankton community and resulted in the high abundances of toxic dinoflagellate species during the winter months. Dissolved inorganic nitrogen (DIN) and dissolved silicate (DSi) were su cient, and rarely limited for the growth of phytoplankton. Dissolved inorganic phosphorus (DIP) was the most necessary element for phytoplankton growth. The enriched environments accelerated the growth of small diatoms, and made for the shift in predominant species from large diatom Rhizosolenia spp. to chain-forming diatoms such as Skeletonema costatum, Pseudo-nitzschia spp. and Thalassiosira subtilis.     

A simple formula for calculating the ionization potential of two-electron ions

The ionization potential of one-electron ions can be calculated from a well-known simple equation, but no such equation has been available for calculating the ionization potential of multi-electron ions. I report here an equation that accurately gives the ionization potential of helium-like (i.e., two-electron) ions as a function of the atomic number, the relative difference from experimental values being below 1% for all ions for which reliable experimental data were found (Z = 3–29). The equation also predicts the stability of the negative hydrogen ion (the hydride ion), H⁻, although with twice too large a value for the ionization potential.     

乙烯装置裂解炉操作的危害分析及对策

分析识别乙烯装置裂解炉操作中的危害因素,制定了确保裂解炉安全运行的对策.     

土壤修复与重金属回收中的超临界二氧化碳萃取技术

针对应用于污染土壤修复、重金属回收以及核废料处理领域的超临界二氧化碳萃取技术,重点阐述了该技术的国内外研究进展和最新动向,分析了超临界二氧化碳萃取用于上述领域与传统工艺相比的技术优势,并指出了今后应该着力解决的关键问题。