多种工况下尾矿坝稳定性分析

尾矿坝的稳定性是评价一座尾矿库安全的重要指标,然而尾矿坝的坝高、坡比以及尾矿渣的不同状态是影响尾矿坝稳定性的重要影响因素。在分析尾矿坝稳定性影响因素的基础上,通过FLAC3D软件内嵌的强度折减法计算分析了同种条件下某尾矿坝的坝高、坡比对尾矿坝稳定性的影响,计算并对比了尾矿渣在自然和饱水状态下尾矿坝的安全系数。结果表明:在相同坝高下,坡比对稳定性影响较大,而在相同坡比下,坝高对稳定性影响相对较小;饱水状态下的尾矿渣更容易使尾矿坝体发生破坏。     

基于风险沟通的城市居民应急宣教培训体系构建——以北京市海淀区为例

针对资源与需求不匹配的实践难题,依据风险感知与风险沟通理论,对城市居民应急宣教培训问题进行了研究。调查数据来自于北京市海淀区的1444份有效问卷。按照个性特征、灾害、社区等维度划分居民类型,在城市居民的风险感知、培训意愿和培训偏好三个方面开展分析。研究发现:城市居民风险感知状况存在差异、应急培训意愿强烈的参与意愿、应急培训偏好呈现复杂性。在此基础上提出应急宣教培训体系构建思路:一是从需求调研与专家库和师资库建设方面科学制定应急宣教培训计划;二是从组织机构、常态机制、内容体系、软硬件建设等方面开展标准化的应急宣教培训活动;三是适应社会化趋势创新应急宣教培训方式,适时开展政府购买服务,强化家庭教育和学校教育,并探索引入第三方机构测评等。     

三种观测标准的霾日与空气污染日对比分析

目前气象观测业务和空气污染分析中存在对霾日统计的分歧,甚至出现空气污染日无霾的现象,对霾观测标准的科学划分,显得非常重要和紧迫。利用2013—2015年廊坊市气象观测站能见度、相对湿度、霾人工观测资料和廊坊市环保局AQI、PM25浓度等气象环保资料,对目前观测业务和空气污染分析中常用的三种霾观测、统计方法进行了对比分析。分析发现:目前廊坊气象观测站所依据的记录霾天气现象的标准,与实际大气污染相趋甚远,不能反映实际的空气污染状况,建议国家及省级相关部门及早根据实际情况,更新霾观测标准,更好地为当前大气污染的防治工作提供客观依据。     

基于FTA-AHP模型的动车组列车火灾风险分析

采用事故树分析(FTA)与层次分析(AHP)相结合的方法对动车组列车火灾风险进行分析,并求得各指标层对目标层的影响权重,同时还将单独的FTA方法与FTA-AHP方法进行了比较,总结出FTA-AHP方法的优点,解决了在动车组列车火灾风险分析中的什么是重点的问题。结果表明:对动车组列车火灾风险影响较大的因素依次为,列车材料耐火等级、火灾报警系统、防火巡查、电气系统的安全状况、消防设施的维护等,必须首先从这些因素入手来控制动车组列车火灾风险。     

基于SWAT模型的三峡库区香溪河非点源氮磷负荷模拟

三峡水库蓄水后,水动力条件改变下营养盐的过量输入导致部分支流库湾水华现象及水体富营养化问题严重.本文以香溪河为研究示范区,基于GIS平台建立流域下垫面空间数据库,以氮磷为研究对象,应用SWAT模型对流域三大主要水系及涉及35个子流域进行2000-2009年径流、营养盐输出模拟研究,并对实测数据和模拟结果进行分析,结果表明:径流模拟结果校验阶段的效率系数0.65和0.86,确定系数是0.78和0.91,模拟效果较好,径流和营养盐负荷受降雨影响呈正相关关系,在丰水年和丰水季节较大,2000-2009年期间TN和TP年均负荷分别是2640.64和300.01 t,在2007年达到最大值,分别是3475.96和399.20 t,在2005年为最小值,分别是2036.72和226.44 t,TN和TP负荷的贡献率高岚水系＞古夫水系＞南阳水系,支流TN和TP输出强度空间差异较大,空间分布差异系数分别是0.34和0.58,TN最大值和最小值是29.39 kg·hm-2·a-1和3.86 kg·hm-2·a-1,TP最大值和最小值分别是4.90 kg·hm-2·a-1和0.54 kg·hm-2·a-1.     

电子供体对地下水中高氯酸盐生物去除的影响研究

通过静态实验,考察了电子供体类型及用量对厌氧条件下微生物去除地下水中高氯酸盐的影响.结果表明,电子供体醋酸盐和H₂的加入,可以明显提高ClO₄^-的去除率,驯化后的微生物去除ClO₄^-的速率比未加入电子供体时提高约1.4~3倍.Monod动态模型能很好地拟合两种电子供体环境下ClO₄^-的微生物去除过程,分别以醋酸盐和H₂作为电子供体时,基质半饱和常数K_s为12.6 mg·L^-1和2.2 mg·L^-1,最大比基质消耗速率V_m为0.45 d^-1和0.08 d^-1.动力学参数表明,本实验条件下,异养型混合菌去除ClO₄^-的效果明显优于自养型混合菌;在少数受高浓度ClO₄^-污染的地下水环境中,为了提高ClO₄^-的去除速率只有通过增加菌体浓度或提高微生物酶的活性来实现.随着电子供体醋酸盐用量增加,ClO₄^-的(比)消耗速率逐渐增大.当初始CH₃COO^-与ClO₄^-的比例为3.80 mg(COD)/mg(ClO₄^-)时,比消耗速率v最大(0.27 d^-1).     

碳源对厌氧氨氧化脱氮性能影响的试验研究

分别研究了无机碳源和有机碳源对厌氧氨氧化反应脱氮性能的影响。接种稳定运行的复合式UASB厌氧氨氧化反应器污泥至ASBR反应器进行批式试验,考察不同碳酸氢钠浓度及COD浓度条件下的氮素转化情况,研究碳源对厌氧氨氧化脱氮效果的影响。厌氧氨氧化反应适宜的进水碳酸氢钠浓度为1.5～2.0 mg/L,超过30 mg/L时有机碳源的存在对厌氧氨氧化反应产生抑制作用,COD浓度超过60 mg/L时反应器表现出反硝化特性。无机碳源对厌氧氨氧化反应的影响表现在提供充足碳源和调节反应器pH的综合作用,较高浓度的COD对厌氧氨氧化反应具有抑制作用。     

Adsorption of lead on multi-walled carbon nanotubes with different outer diameters and oxygen contents: Kinetics, isotherms and thermodynamics

The effects of different outer diameters and surface oxygen contents on the adsorption of heavy metals onto six types of multi-walled carbon nanotubes (MWCNTs) were investigated in an aqueous solution and lead was chosen as a model metal ion. The results indicated that the percentage removal and adsorption capacity of lead remarkably increased with decreasing outer diameter due to larger specific surface area (SSA). The SSA-normalized maximum adsorption capacity (qm /SSA) and SSA-normalized adsorption coefficient (Kd /SSA) were strongly positively correlated with surface oxygen content, implying that lead adsorption onto MWCNTs significantly increases with the rise of oxygen content and decreases with decreasing SSA. The calculated thermodynamic parameters indicated that adsorption of lead on MWCNTs was endothermic and spontaneous. When the oxygen content of MWCNTs increased from 2.0% to 5.9%, the standard free energy (△ G0 ) became more negative, which implied that the oxygenated functional groups increased the adsorption affinity of MWCNTs for lead. Through calculation of enthalpy (△ H0 ), G0 and free energy of adsorption (Ea ), lead adsorption onto MWCNTs was recognized as a chemisorption process. The chemical interaction between lead and the phenolic groups of MWCNTs could be one of the main adsorption mechanisms due to highly positive correlations between the phenolic groups and K d /SSA or q m /SSA.     

Sulfur speciation and bioaccumulation in camphor tree leaves as atmospheric sulfur indicator analyzed by synchrotron radiation XRF and XANES

Analyzing and understanding the effects of ambient pollution on plants is getting more and more attention as a topic of environmental biology.A method based on synchrotron radiation X-ray fluorescence and X-ray absorption near edge structure spectroscopy was established to analyze the sulfur concentration and speciation in mature camphor tree leaves (CTLs),which were sampled from 5 local fields in Shanghai,China.Annual SO2 concentration,SO42-concentration in atmospheric particulate,SO42-and sulfur concentration in soil were also analyzed to explore the relationship between ambient sulfur sources and the sulfur nutrient cycling in CTLs.Total sulfur concentration in mature camphor tree leaves was 766-1704 mg/kg.The mainly detected sulfur states and their corresponding compounds were +6 (sulfate,include inorganic sulfate and organic sulfate),+5.2 (sulfonate),+2.2 (suloxides),+0.6 (thiols and thiothers),+0.2 (organic sulfides).Total sulfur concentration was strongly correlated with sulfate proportion with a linear correlation coefficient up to 0.977,which suggested that sulfur accumulated in CTLs as sulfate form.Reduced sulfur compounds (organic sulfides,thiols,thioethers,sulfoxide and sulfonate) assimilation was sufficed to meet the nutrient requirement for growth at a balanced level around 526 mg/kg.The sulfate accumulation mainly caused by atmospheric sulfur pollution such as SO2 and airborne sulfate particulate instead of soil contamination.From urban to suburb place,sulfate in mature CTLs decreased as the atmospheric sulfur pollution reduced,but a dramatic increase presented near the seashore,where the marine sulfate emission and maritime activity pollution were significant.The sulfur concentration and speciation in mature CTLs effectively represented the long-term biological accumulation of atmospheric sulfur pollution in local environment.     

Factors influencing the contents of metals and As in soils around the watershed of Guanting Reservoir, China

Topsoil samples from 61 sites around the Guanting Reservoir,China,were measured for Cu,Zn,Cr,Ni,Cd,Pb and As concentrations.The mean concentrations of Cu,Zn,Cr,Ni,Cd,Pb and As were 16.8,59.4,37.8,18.3,0.32,20.1 and 8.67 mg/kg dry weight,respectively.Factors that influence the dynamics of these metals in soils around the watersheds of Beijing reservoirs were examined.The influence of atmospheric deposition,land use,soil texture,soil type and soil chemical parameters on metal contents in soils was investigated.Atmospheric deposition,land use and soil texture were the important factors affecting heavy metal residues.Soil type and soil chemical parameters were also involved in heavy metal retention in soils.The data provided in this study are considered crucial for reservoir remediation,especially since the Guanting Reservoir will serve as one of the main drinking water sources for Beijing in the foreseeable future.