Inhibition effect of magnetic field on nitrous oxide emission from sequencing batch reactor treating domestic wastewater at low temperature

This study aims to investigate the effect of a magnetic field on nitrous oxide(N_2O) emission from a sequencing batch reactor treating low-strength domestic wastewater at low temperature(10℃).After running for 124 days in parallel,results indicated that the conversion rate of N_2O for a magnetic field-sequencing batch reactor(MF-SBR) decreased by34.3% compared to that of a conventional SBR(C-SBR).Meanwhile,the removal efficiencies for total nitrogen(TN) and ammonia nitrogen(NH4-N) of the MF-SBR were 22.4% and 39.5% higher than those of the C-SBR.High-throughput sequencing revealed that the abundances of AOB(Nitrosomonas),NOB(Nitrospira) and denitrifiers(Zoogloea),which could reduce N_2O to N_2,were promoted significantly in the MF-SBR.Enzyme activities(Nir) and gene abundances(nos Z nir S and nir K) for denitrification in the MF-SBR were also notably higher compared to C-SBR.Our study shows that application of a magnetic field is a useful approach for inhibiting the generation of N_2O and promoting the nitrogen removal efficiency by affecting the microbial characteristics of sludge in an SBR treating domestic wastewater at low temperature.     

铁路次生噪声的区域分布规律与防治对策研究

铁路交通大大促进了城市化,城市化的发展必将造成铁路站点周边区域的人口密度、交通流量和土地使用等因素的改变,铁路站点周边区域环境质量的变化,同时造成周边区域的环境污染加剧,特别是环境噪声的增强,形成次生环境影响。对铁路站点周边区域次生环境影响程度、范围、主要控制因素的分析评价是在铁路建设环境影响评价工作中需要考虑的问题。笔者通过对北京站和西客站等北京地区主要铁路站点周边区域噪声水平的监测和测试,得到了铁路站点周边区域噪声环境水平的现状值分布特征,比较分析不同规模的铁路站点周边区域噪声水平的不同分带特征,将车站周边区域噪声水平的监测值与城市背景噪声值进行对比,得到了对车站周边区域次生噪声环境影响特征,明确了次生噪声环境影响的成因和控制因素,提出了铁路次生噪声环境影响的防治对策。     

瓦斯对煤尘爆炸特性影响的实验研究

瓦斯的存在对煤尘爆炸特性的理论计算和数值仿真的结果与实际数据有一定差距,因此,通过不同浓度瓦斯与煤尘共存条件下爆炸实验研究,得出了矿井瓦斯对煤尘的最低着火温度、最小点火能量、爆炸下限浓度、最大爆炸压力和最大爆炸压力上升速度等爆炸特性影响的规律即瓦斯对煤尘最低着火温度影响不大;瓦斯可使煤尘的最小点火能量减小,尤其是对难于点燃的煤尘;混合物的爆炸下限浓度随瓦斯浓度的增加而降低;混合物的最大爆炸压力上升速度由于瓦斯的存在而增强,而最大爆炸压力几乎没有变化。同时研究了瓦斯对无爆炸性煤尘的影响。实验研究的结论对于现场防止煤尘爆炸的发生具有指导意义。     

重金属单一污染对灯心草生长及重金属积累特性的影响

盆栽试验结果表明：在土壤环境质量标准低浓度设置范围内，Cd、Pb、Cu能够刺激灯心草的生长。而灿（地上部除外）、Zn在整个浓度设置范围内对灯心草的生长都表现出抑制作用。相对于地上部而言，各重金属对灯心草地下部生物量影响趋势不明显。单一污染条件下，各种金属对灯心草各项生长指标的抑制程度大小排序为：Zn〉As〉Cu〉Pb〉Cd。以灯心草生物量减产10％为依据，可以将土壤中Cd、Pb、Cu三种重金属临界值分别设定为10ms／ks、100mg／kg、100ms／ks。灯心草不适合在Zn污染的土壤中种植，土壤中As临界值则尚需作进一步的研究来确定。除Cd外，其余四种重金属均主要积累在灯心草根部。根据线性回归分析，Cd、Ph在灯心草地上部和地下部以及灿在灯心草地下部的积累量与土壤中对应各重金属添加量之间存在显著线性关系（P〈0．5）。     

Potential environmental fate of elsinochrome A,a perylenequinone toxin produced in culture by bindweed biocontrol fungus Stagonospora convolvuli LA39

The photosensitizing perylenequinone toxin elsinochrome A (EA) is produced in culture by the bindweed biocontrol fungus Stagonospora convolvuli LA39 where it apparently plays a pathogenicity related role. We investigated the fate of EA with reference to its stability under different temperature and light conditions. EA remained stable when boiled in water at 100^∘C for 2 h. Similarly, exposing EA to 3–27^∘C in the dark for up to 16 weeks did not affect its stability either in dry or in aqueous form. However, results from irradiation experiments indicate that direct photolysis may be a significant degradation pathway for EA in the environment. EA either in dry form or dissolved in water was degraded by different irradiation wavelengths and intensities, with degradation plots fitting a first order rate kinetics. EA degraded faster if exposed in aqueous form, and at higher quantum flux density (μmol s⁻¹ m⁻²). Sunlight was more effective in degrading EA than artificial white light and ultraviolet radiations (UV-A or UV-B). Exposing EA to natural sunlight, particularly, during the intense sunshine (1,420– 1,640 μmol s⁻¹ m⁻²) days of 30 July to 5 August 2004 in Zurich caused the substance to degrade rapidly with half-life under such condition only 14 h. This implies that should EA gets into the environment, particularly on exposed environmental niches, such as on plant surfaces through biocontrol product spray, or released from shed diseased leaves, it may have no chance of accumulating to ‘level of concern’. Furthermore, a toxicity assay using Trichoderma atroviride P1 as biosensor showed that photo-degraded EA was not toxic, indicating that no stable toxic by-products were left.     

目的地旅游系统隐性结构的分析

目的地系统是旅游系统中的一个重要子系统,组成这一系统的结构和要素有显性和隐性之分.从目的地旅游系统隐性结构要素的存在形式、功能表现等进行分析,旨在引起人们对隐性要素的关注,并进行有效的保护和合理的利用,实现旅游目的地的可持续发展.     

福州市道路交通安全现状分析

根据福州市2002年道路交通安全的现状，利用统计分析方法，对道路交通事故的成因、月份分布、事故形态及事故与道路类型等进行了分析和研究。与大多数城市相比，福州市道路交通事故的月份分布变化比较小；发生在路段上的交通事故比例较高，达到了83．1％；由人因造成的交通事故比例也比较高，达96．96％。针对福州市道路交通事故的特点与规律，本同时提出了改善福州市道路交通安全状况的若干具体措施。     

Ecological restoration as a strategy for conserving biological diversity

Though the restoration of disturbed ecosystems has so far played a relatively modest role in the effort to conserve biological diversity, there are reasons to suspect that its role will increase and that its contribution to the maintenance of diversity will ultimately prove crucial as techniques are further refined and as pristine areas for preservation become scarcer and more expensive.It is now possible to restore a number of North American communities with some confidence. However, it should be noted that many current efforts to return degraded lands to productive use, like attempts to reclaim land disturbed by mining, try only for rehabilitation to a socially acceptable condition and fall considerably short of actually restoring a native ecological community.Possible uses for restoration in the conservation of biodiversity include not only the creation of habitat on derelict sites, but also techniques for enlarging and redesigning existing reserves. Restoration may even make it possible to move reserves entirely in response to long-term events, such as changes in climate. Restoration in the form of reintroduction of single species to preexisting or restored habitat is also a critical link in programs to conserve species ex situ in the expectation of eventually returning them to the wild. And restoration provides opportunities to increase diversity through activities as diverse as management of utility corridors, transportation rights-of-way, and parks.     

污水生物处理中微生物的相互协作

从化学、物理和遗传信息三个不同水平,系统介绍了污水生物处理中微生物的相互协作关系,阐述了各个水平的协作机制、应用研究进展以及存在问题     

Treatment of biologically treated effluents from baker's yeast industry by membrane and ozone technologies

This paper presents pilot‐scale membrane treatment results performed on biologically treated effluents from fermentation industry and ozone oxidation on concentrates from the same membrane treatment system. The results obtained from the ultrafiltration (UF) and/or the reverse osmosis (RO) systems indicate that membrane treatment are very effective for COD, Color, NH₃‐N and conductivity removal. Ozone oxidation of the membrane concentrates was tested to increase biodegradability of the wastes. The initial ratios of Biochemical oxygen demand (BOD₅) to Chemical oxygen demand (COD) were increased significantly by applying chemicaloxidation with O₃ and O₃ + H₂O₂.