Effects of cerium on growth and physiological mechanism in plants under enhanced ultraviolet-B radiation

Effect of cerium （Ce^3＋） on the growth, photosynthesis and antioxidant enzyme system in rape seedlings （Brassica juncea L.） exposed to two levels of UV-B radiation （T1： 0.15 W/m^2 and T2：0.35 W/m^2） was studied by hydroponics under laboratory conditions. After 5 d of UV-B treatment, the aboveground growth indices were obviously decreased by 13.2%-44. 1%（T1） and 21.4%-49.3% （T2）, compared to CK, and except active absorption area of roots, the belowground indices by 14.1%-35.6%（T1） and 20.3%-42.6% （T2）. For Ce＋UV-B treatments, the aboveground and belowground growth indices were decreased respectively by 4.1%-23.6%, 5.2% -23.3%（Ce＋T1） and 10.8%-28.4%, 7.0%-27.8%（Ce＋T2）, lower than those of UV-B treatments. The decrease of growth indices appeared to be the result of changes of physiological processes. Two levels of UV-B radiation induced the decrease in chlorophyll content, net photosynthesis rate, transpiration rate, stomatal conductance and water use efficiency by 11.2%-25.9%（T1） and 20.9%- 56.9%（T2）, whereas increase in membrane permeability and activities of antioxidant enzymes including superoxide dismutase（SOD）, catalase （CAT） and peroxidase （POD） by 6.9%, 22.8%, 21.5%, 9.5%（T1） and 36.6%, 122.3%, 103.5%, 208.9%（T2）, respectively. The reduction of the photosynthetic parameters in Ce＋UV-B treatments was lessened to 3.2%-13.8%（Ce＋T1） and 4.9%-27.6%（Ce＋T2）, and the increase of membrane permeability and activities of antioxidant enzymes except POD in the same treatments were lessened to 2.4%, 8.4%, 6.6%（Ce＋T1） and 30.1%, 116.7%, 75.4%（Ce＋T2）. These results indicate that the regulative effect of Ce on photosynthesis and antioxidant enzymatic function is the ecophysiological basis of alleviating the suppression of UV-B radiation on growth of seedlings. Furthermore, the protective effect of Ce on seedlings exposed to TI level of UV-B radiation is superior to T2 level.     

Ecological effects of crude oil residues on the functional diversity of soil microorganisms in three weed rhizospheres

Ecological effects of crude oil residues on weed rhizospheres are still vague. The quantitative and diversity changes and metabolic responses of soil-bacterial communities in common dandelion （Taraxacum officinale）, jerusalem artichoke （Silphiurn perfoliatum L.） and evening primrose （A colypha australis L.） rhizospheric soils were thus examined using the method of carbon source utilization. The results indicated that there were various toxic effects of crude oil residues on the growth and reproduction of soil bacteria, but the weed rhizospheres could mitigate the toxic effects. Total heterotrophic counting colony-forming units （CFUs） in the rhizospheric soils were significantly higher than those in the non-rhizospheric soils. The culturable soil-bacterial CFUs in the jerusalem artichoke （S. perfoliatum） rhizosphere polluted with 0.50 kg/pot of crude oil residues were almost twice as much as those with 0.25 kg/pot and without the addition of crude oil residues. The addition of crude oil residues increased the difference in substrate evenness, substrate richness, and substrate diversity between non-rhizospheric and rhizospheric soils of T. officinale and A. australis, but there was no significant （p〉0.05） difference in the Shannon＇s diversity index between non-rhizospheric and rhizospheric soils of S. perfoliatum. The rhizospheric response of weed species to crude oil residues suggested that S. perfoliatum may be a potential weed species for the effective plant-microorganism bioremediation of contaminated soils by crude oil residues.     

NH3-N在大连湾的水环境行为模拟研究

应用三维水质模型对大连湾中的主要污染物NH3-N的行为进行了模拟,对NH3-N浓度的时空变化规律以及其影响因素进行了研究,选择主要的模型参数进行了灵敏度分析。由空间分布的模拟结果可知,在大连湾,NH3-N浓度主要集中在排污口附近区域,灵敏度分析显示,在排污口区水体的扩散能力对NH3-N浓度的影响较大。由季节变化模拟结果可知,在湾顶部的排污口区NH3-N浓度显示明显的季节变化趋势。在湾中部和朝海边界的湾口区NH3-N浓度较低,变化平缓。模拟结果可以为大连湾的污染控制、水质规划和管理提供科学依据。     

藻类在大连湾的水环境行为数值模拟研究

应用三维水质模型对大连湾水体中的藻类碳浓度的时空变化规律以及其影响因素进行了研究,选择主要的模型参数进行了灵敏度分析。由空间分布的模拟结果可知,在大连湾,藻类主要集中在排污口附近区域。由季节变化模拟结果可知,在湾顶部的排污口区藻类生产显示明显的季节变化趋势,在夏季,主要受到磷酸盐浓度的限制。灵敏度分析显示,在排污口区水体的扩散能力对藻类生产的影响较大,在湾中部和湾口区主要受到磷酸盐负荷的影响。模拟结果可以为大连湾的污染控制、水质规划和管理提供科学依据。     

MODIS林火识别算法的验证分析

利用中国境内9起森林火灾事件对MODIS火点识别的理论算法进行验证分析．结果表明：MODIS火点识别的理论算法在中国境内是基本通用的．但受地域和季节变化的影响．应用时可能会遗漏个别低温闷烧的热点;利用火点亮温偏离统计均值标准差的关系来确定阁值．可以避免火点的遗漏;林火点在CH21和CH22上的值比较接近。一般有CH21-CH22〈20K。而噪声点在两个波段上的亮温差异比较大。根据以上知识．提出了改进MODIS林火热点识别算法的建议。     

地铁自动检票闸机对人员疏散的影响分析

本文采用计算机仿真技术,建立了地铁车站的疏散模型,获得了每个时刘的人员分布状态,找到了不利于人员疏散的”瓶颈”位置。同时指出了现有地铁站台疏散时间的计算方法的不足之处。通过模拟详细分析了地铁自动检票闸机对人员疏散的影响,模拟结果显示,地铁自动检票闸机的存在,降低了人员疏散的效率,在研制疏散预案以及现场指挥时需要审慎地考虑闸机的影响。文末就此提出了一些合理建议。     

近年来珠三角地区大气中痕量氟氯烃(CFCs)的浓度水平与变化特征

用预浓缩-GC/MS方法研究了珠江三角洲大气中的CCl3F、CFC-12、CFC-113和CFC-114等4种痕量氟氯烷烃气体。结果表明,2005年珠江三角洲背景点鼎湖山大气中CFC-12和CFC-11的年平均浓度高于全球本底站,说明珠三角地区还存在一定CFC-11和CFC-12的排放源;CFC-113浓度水平则与全球本底站点浓度接近,且CFC-113和CFC-114在广州城区与鼎湖山差别不显著,表明区内其排放源强度应很小。观测日内广州和鼎湖山大气中四种CFCs的日变化幅度均较小,无明显的昼夜变化规律。广州市CFCs总体呈夏秋高、冬春低的特征,与城区致冷设备高温季节使用频率较大有关;鼎湖山则呈冬春高、夏秋低的特征,主要受扩散作用和季风的影响。初步分析显示,从1997年到2005年,CFC-11、CFC-12和CFC-114浓度总体呈现先上升后缓慢降低的趋势,而CFC-113的浓度一直逐年下降。     

同位素及其在环境科学中的应用

介绍了同位索的一些基本概念,同位案在水循环、测定地下水年龄、判别地下水来源及古气候、古环境研究等领域中的应用．同时阐述了我国同位索水文学的发展现状、存在的问题及研究方向。     

孔隙水压力消散试验在尾矿坝安全施工中的应用

尾矿库设计的主要控制条件是坝体的稳定性。在尾矿坝施工中还需要考虑强度、渗水性等影响因素。以锡冶山尾矿坝工程为例,探讨了数值法在尾矿库坝体岩土孔隙水压力消散试验中的应用。对提高试验精度、减少试验开支、指导工程安全施工具有现实意义。     

考虑公众选择偏好的应急避难安置双阶段选址-分配模型

为使开放避难场所符合公众自行避难的实际情况,借鉴Huff模型量化公众选择行为,构建双阶段选址-分配模型,第1阶段确定开放避难场所位置,第2阶段将溢出容量的灾民二次分配到有剩余容量的避难场所,并利用改进粒子群算法进行求解。研究结果表明：双阶段选址-分配模型能够实现同一需求点灾民前往不同避难场所的过程,管理者干预政策能够使服务人数大幅度增加,避免资源浪费、灾民流离失所且二次分配情况主要依赖于第1阶段的结果。研究结果可为管理部门规划应急避难场所提供参考。