Mineralogical characteristics and photocatalytic properties of natural sphalerite from China

Different natural sphalerites have a range of photocatalytic properties that can potentially be exploited for environmental remediation purposes. To develop value in the exploitation of sphalerite, samples were collected from 19 ore deposits in China and characterized for their mineralogical and photocatalytic properties. X-ray diffraction (XRD) and electron probe micro analysis (EPMA) measurements indicated that all the natural sphalerites from various localities crystallized in cubic phases with various chemical compositions. The substitution of Fe for Zn ranged from 0.235% to 14.826% by weight, Mn from 0.004% to 4.868%, Cu from 0.009% to 5.529% and Cd from 0.133% to 1.576%. As Fe became more abundant, the color of natural sphalerite darkened, becoming almost black; and higher Fe content was associated with stronger visible light absorption. Photoluminescence spectra showed emission mainly related to S-vacancies and progressively decreasing fluorescence intensity with increasing Fe content. Tests of the photocatalytic degradation of methyl orange indicated that the sample with the highest Cd content but moderate Fe content had the highest photocatalytic activity. Specifically, the degradation of Methyl Orange (30 mg/L) attained 82.11% efficiency under visible light irradiation for 4 hr of natural sphalerite with 4.262% Fe and 1.576% Cd. Overall, the Fe content in sphalerite was found to contribute to the visible light absorption ability and the recombination rate of photo-generated electrons and holes, while substitution by Cd was observed to have a greater effect on the photocatalytic properties. These findings provide a scientific basis for the profitable utilization of base metal resources like sphalerite.     

凤眼莲、稻草和污泥制备生物炭的特性表征与环境影响解析

有机废弃物限氧热解制备生物炭可在减缓温室气体排放的同时改善土壤和水体环境质量,但同时生物炭在环境中的应用具有潜在生态毒理风险.因此,在将生物炭大规模应用于各类环境介质前,对其关键物理-化学性质进行系统分析与评价是极为必要的.本文选择对我国水生生态环境危害最大的入侵植物凤眼莲(Eichhornia crassipes)和我国产量最高的农业废弃物稻草,以及市政污水处理厂剩余污泥3种生物质前体,于250~550℃进行低温慢热解,对所制备生物炭的表面形貌、元素组成、矿物形态和一系列关键化学特性进行了全面表征与比较分析.在此基础上,深入探讨了此3类生物炭应用于土壤改良、重金属污染修复和水体富营养化控制的潜力与风险.结果表明,凤眼莲生物炭中K、Ca、Na、Mg含量最为丰富,指示其对于缓解土壤酸化具有重要应用价值,而其中P主要以AlPO_4晶体态存在,水溶性较低,这有利于降低此类生物炭引起水体富营养化的风险;水稻秸秆生物炭阳离子交换量(CEC)相对较高,达到33.7 cmol·kg~(-1),表明其在提高土壤保肥能力和降低重金属生物有效性方面具有较大潜力;SEM-EDX显示,凤眼莲生物炭和稻草秸秆生物炭均具有发达的束筒结构,可优先考虑用于改善土壤通气性;但是,部分生物炭中水溶性Cd、As含量超出安全阈值,表明对有机质前体和热解产物进行严格检测和筛选是实现生物炭在环境与农业中安全利用的必要环节.     

深溪沟电站大坝强震监测系统设计及应用

强震监测是大坝安全监测的重要内容之一,强震监测成果对大坝的安全性和稳定性分析有重要作用。本文根据水电站枢纽工程实际对深溪沟水库大坝强震监测系统设计开展研究,并对仪器的性能指标和数据采集处理分析软件进行了全面阐述。通过深溪沟水电站建设大坝强震监测系统的运行实践,大坝强震监测系统可以在地震发生后短时间内自动获取强震动加速度记录,储存地震波数据,并显示大坝坝体各测点的地震反应过程。强震监测结果进一步验证了设计烈度,为判定震后大坝安全性提供了支持。     

关于未来中国劳动力是否短缺的一个证明

迅速发生的人口转变现象对未来中国社会的各个方面影响深远,经济增长同样受到人口转变的影响.本文以1978-2004年为样本区间.按照2010、2020、2030年劳动力人口预测数,对未来经济增长的4种路径分别进行模拟.通过分析中国经济增长模式和内在源泉.我们发现在未来很长一段时间内,全要素生产率代表的技术进步、劳动力受教育水平的提高和制度变迁等其他因素,都会降低人口转变对未来经济增长可能的影响.由人口转变导致的劳动年龄人口减少不太可能对中国未来年均经济增长7.2%的目标构成较大瓶颈.而有可能的瓶颈应该是资本存羹能否继续维持目前这种高速增长、低效利用的状态.在未来的经济增长中,我们急需改变对资本投入的过度依赖.发挥技术进步和制度改革的力量,以减缓外部冲击对宏观经济的整体影响.     

Performance Enhancement of a Beta Type Rhombic Drive Stirling engine

ABSTRACT

Stirling engines maintain attraction because of their high energy conversion efficiencies. In this study, experimental comparison of a beta-type Stirling engine for two different rhombic-drive mechanisms was presented. In one of the rhombic mechanisms, spur gears were used and the gear shaft was supported in bearings from one side. In the other mechanism, two helical gears were placed on crankshafts and the crankshafts were supported in bearings from both sides. Rhombus lengths of the mechanisms were determined as 66 mm and 80 mm to provide same constant compression ratio of 2.5 for both configurations. Both mechanisms were used in the same beta-type Stirling engine having same cylinder, piston and displacer dimensions. Performance parameters of the engines were evaluated at different helium charge pressures (2–4 bar) and hot-end temperatures (400–600°C). The hot-end of the displacer cylinder was heated by a liquefied petroleum gas (LPG) burner. The engine power increased by 132%, friction losses and gear noses were reduced by supporting the rhombic-drive mechanism from both side and using helical gears. The maximum output torque and power of the engine were obtained as 13.14 Nm at 428 rpm engine speed and 663 W at 800 rpm engine speed, respectively, at 600°C hot-end temperature and 4 bar charge pressure.     

Mercury uptake by halophytes in response to a long-term contamination in coastal wetland salt marshes (northern Adriatic Sea)

Mercury (Hg) distribution in saltmarsh sediments and in three selected halophytes (Limonium narbonense, Sarcocornia fruticosa and Atriplex portulacoides) of a wetland system (Marano and Grado Lagoon, Italy) following a contamination gradient in sediments was investigated. The Hg uptake was evaluated at the root system level by calculating the enrichment factor (EF) and in the aboveground tissues by means of the translocation factor (TF). The related methylmercury (MeHg) concentrations in the halophytes were also investigated with regard to the location of the sites and their degree of contamination. Hg concentration in halophytes seemed poorly correlated both with the total Hg in rhizo-sediments and with the specific plant considered, supporting the evidence that the chemico-physical parameters of sediments could significantly affect metal availability for plants. Hg concentrations in roots increased with depth and were 20-fold higher than content measured in related rhizo-sediments (high EF). A low content of Hg is translocated in aboveground tissues (very low TF values), thus highlighting a kind of avoidance strategy of these halophytes against Hg toxicity. MeHg values were comparable between the two sites and among species, but the translocation from below- to aboveground plant tissues was more active.     

2种鼠尾草对模拟酸雨胁迫的耐受性比较及其生理机制研究

为探究2种具有较高药用和观赏价值的鼠尾草对酸雨的耐受性及其生理机制,以美丽鼠尾草(Salvia meiliensis S.W.Su)和贵州鼠尾草(S. cavaleriei Lévl.)为试验材料,分析了2种鼠尾草在不同pH(6.8、5.6、4.5、3.5和2.5)模拟酸雨胁迫下伤害等级、叶绿素含量、抗氧化酶活性以及丙二醛和有机渗透调节物质含量的变化。结果显示：模拟酸雨对美丽鼠尾草的伤害程度高于贵州鼠尾草;随pH的下降,2种鼠尾草叶片叶绿素a、b和总含量逐渐降低,但贵州鼠尾草叶片叶绿素a、b和总含量高于美丽鼠尾草,并以较高的叶绿素a/b适应模拟酸雨胁迫;2种鼠尾草在模拟酸雨胁迫下产生了适应性反应,表现为叶片可溶性糖、可溶性蛋白和脯氨酸含量以及超氧化物歧化酶和过氧化物酶活性的升高,但这一适应性反应被降低的过氧化氢酶活性严重削弱;模拟酸雨胁迫下,贵州鼠尾草叶片SOD、POD和CAT活性均高于美丽鼠尾草,叶片MDA含量低于美丽鼠尾草。研究表明,尽管美丽鼠尾草渗透调节能力很强,但其抗氧化酶活性、叶绿素含量和叶绿素a/b都低于贵州鼠尾草,使其膜脂过氧化程度较高、对光能的吸收和转化效率较低,是其对模拟酸雨的耐受性低于贵州鼠尾草的重要原因。