A technique for estimating one-dimensional diffusion coefficients in low-permeability sedimentary rock using X-ray radiography: comparison with through-diffusion measurements

The measurement of diffusive properties of low-permeability rocks is of interest to the nuclear power industry, which is considering the option of deep geologic repositories for management of radioactive waste. We present a simple, non-destructive, constant source in-diffusion method for estimating one-dimensional pore diffusion coefficients (D(p)) in geologic materials based on X-ray radiography. Changes in X-ray absorption coefficient (Deltamicro) are used to quantify changes in relative concentration (C/C(0)) of an X-ray attenuating iodide tracer as the tracer solution diffuses through the rock pores. Estimated values of D(p) are then obtained by fitting an analytical solution to the measured concentration profiles over time. Measurements on samples before and after saturation with iodide can also be used to determine iodide-accessible porosity (phi(I)). To evaluate the radiography method, results were compared with traditional steady-state through-diffusion measurements on two rock types: shale and limestone. Values of D(p) of (4.8+/-2.5)x10(-11) m(2).s(-1) (mean+/-standard deviation) were measured for samples of Queenston Formation shale and (2.6+/-1.0)x10(-11) m(2).s(-1) for samples of Cobourg Formation limestone using the radiography method. The range of results for each rock type agree well with D(p) values of (4.6+/-2.0)x10(-11) m(2).s(-1) for shale and (3.5+/-1.8)x10(-11) m(2).s(-1) for limestone, calculated from through-diffusion experiments on adjacent rock samples. Low porosity (0.01 to 0.03) and heterogeneous distribution of porosity in the Cobourg Formation may be responsible for the slightly poorer agreement between radiography and through-diffusion results for limestones. Mean values of phi(I) for shales (0.060) and limestones (0.028) were close to mean porosity measurements made on bulk samples by the independent water loss technique (0.062 and 0.020 for shales and limestones, respectively). Radiography measurements offer the advantage of time-saving for diffusion experiments because the experiment does not require steady-state conditions and also allows for visualization of the small-scale heterogeneities in diffusive properties within rocks at the mm to cm scale.     

Characterization of the Khamaseen (spring) dust in Jordan

During the spring each year, the Eastern Mediterranean is affected by Khamaseen dust cyclones sourced from the North African Sahara. In order to characterize Khamaseen dust in Jordan, we collected dust from ten localities during the spring of 2006. The collected dust was analyzed for grain size, mineralogy, and chemical composition. The dust is predominantly aluminosilicates (clay minerals and feldspars), quartz and carbonates with minor amounts of phosphate. The particles are mostly subrounded to subangular and generally between 5 and 20 μm in size. The majority of the elements analyzed have a natural abundance and distribution. However, several elements such as As, Cd, Cr, Cu, Pb, Se and Zn have higher than natural abundances due to anthropogenic enrichment by various enrichment factors. The analyzed dust samples are chemically homogenous, indicating a similar provenance and good mixing by the Khamaseen winds. The rare earth elements patterns are similar to those of the upper continental crust composition and average shale. Total amount of dust deposited on Jordan during the spring of 2006 is around 0.3 million tons.     

黄河三角洲浅层地下水位动态特征及其成因

为了解黄河三角洲地下水位动态特征及其成因,在野外调查、观测及资料收集的基础上,利用地学理论和数理统计方法,对该地区浅层地下水位时空变化及其对降雨的响应等进行了深入分析。结果表明:(1)黄河三角洲地区地下水位埋深较浅,一般在0.50～2.50 m,其中滨海地带普遍小于1.00 m。(2)区内黄河现行流路两侧的河成高地及滨海近岸的局部地区年内地下水位动态属基本稳定型,其地下水位动态成因类型属"渗入-径流"或"水文"型,而其它地区年内地下水位动态属震荡起伏型,且以"降-升-降"型为主,其地下水位动态成因类型属"渗入-蒸发"型。(3)总体上该地区年内地下水位以相对稳定的季节性变化为主,而年际地下水位处于动态平衡状态。黄河下游生态调度及"蓝黄"战略在区内叠加实施过程中应密切关注区域地下水位动态及其效应。     

南京北郊夏季大气颗粒物中有机碳和元素碳的污染特征

采用DRI Model 2001A热/光碳分析仪对2013年5~7月期间南京北郊大气气溶胶9级惯性撞击式分级Andersen采样器膜采样样品中有机碳(OC)和元素碳(EC)的质量浓度进行了分析.结果表明,南京北郊夏季EC、OC的平均浓度,在PM2.1(空气动力学直径≤2.1μm)中分别为(2.6±1.1)μg·m-3、(13.0±5.2)μg·m-3,在PM9.0(空气动力学直径≤9.0μm)中,分别为(3.4±1.7)μg·m-3、(20.3±7.3)μg·m-3.EC主要富集在超细颗粒物中,OC主要存在于细颗粒物中,EC的PM1.1/PM9.0比值和OC的PM2.1/PM9.0比值分别为0.62和0.64.EC和OC浓度的平均最高值都出现在≤0.43μm粒径段中,分别占PM9.0中的总元素碳的33.4%和总有机碳的21.1%.南京北郊夏季PM1.1、PM2.1和PM9.0中EC、OC的相关性较好,说明存在共同的一次污染源.通过OC/EC特征物比值的方法得到南京夏季碳质颗粒物的主要来源有机动车尾气排放、燃煤排放和地面扬尘排放.     

北京市黑碳气溶胶浓度特征及其主要影响因素

为探究北京市黑碳(black carbon,BC)气溶胶时空分布特征及其主要影响因素,对4个站点2019年的ρ(BC)、ρ(PM2.5)、ρ(CO)和φ(NOx)及同期气象因子进行比对分析.结果表明,背景区(BA)、城区(UA)、城区路边(UR)和外环路边(HR)的平均 ρ(BC)分别为(1.58±1.15)、(2.27±1.67)、(3.35±2.13)和(3.57±2.40)μg·m-3,o(BC/PM2.5)分别为(5.3±1.6)％、(6.0±2.3)％、(9.0±3.6)％和(8.1±3.5)％;除 UR 站点 ρ(CO)高于 HR 站点以外,4个站点的ρ(BC)、ρ(PM2.5)、ρ(CO)和ψ(NOx)由低到高排序均为:背景区＜城区＜城区路边＜外环路边,且采暖季是非采暖季的1.1～1.7倍;用最大频率法估算各站本底ρ(BC),UR站点最高,BA站点最低,分别为0.56 μg·m-3和0.19 μg·m-3;交通排放导致路边站点本底ρ(BC)、平均ρ(BC)和ω(BC/PM2.5)均高于其他站点.ρ(BC)日变化曲线呈双峰型结构,非采暖季早高峰时段(07:00～08:00)峰值较高,采暖季全天浓度高于非采暖季且凌晨时段(00:00～02:00)峰值较高,谷值均在午后(14:00～16:00)出现.4个站点的平均吸收埃斯特朗指数(AAE)为1.38、1.34、1.26和1.26,表明全市BC主要来自化石燃料燃烧;采暖季平均AAE为1.46,高于非采暖季的1.23,主要是由于采暖季生物质燃烧排放占比增加;非采暖季各站点AAE日变化曲线主要受机动车活动时间影响,一致呈凌晨低、午后高的分布特点,采暖季曲线各异.BC与PM2 5、CO、NOx、风速和相对湿度的Pearson相关系数(r)为0.86、0.81、0.69、-0.37和0.34;由于燃煤源作为4种污染物的共同来源贡献增加,采暖季较非采暖季| r |更高.4个站点的△BC/△CO值分别为3.1×10-3、3.5×10-3、3.9×10-3和4.1×10-3.一次污染过程中,城区站点BC以区域传输为主要来源,路边站点局地排放BC积累过程较明显,易发生颗粒物二次生成过程.     

火箭弹检测安全分析与防护

在分析火箭弹检测的特点和安全性特征的基础上,归纳了影响火箭弹检测安全性的主要因素.从安全性设计和安全性管理两个方面,提出了火箭弹检测设备的安全性的一般要求,并分析了火箭弹检测中安全防护的一般方法和设计措施.     

南京北郊大气臭氧周末效应特征分析

本研究根据2013-12-01~2014-11-30南京北郊臭氧(O_3)及其前体物(NO_x、CO、VOCs)的观测资料,分析了工作日与周末O_3、NO_x、CO和VOCs质量浓度变化的差异及成因.结果表明,南京北郊O_3具有明显的"周末效应":即工作日O_3质量浓度高于周末,前体物质量浓度的变化与之相反;O_3平均质量浓度分别为19.84μg·m~(-3)(冬季)、53.45μg·m~(-3)(春季)、57.17μg·m~(-3)(夏季)和40.43μg·m~(-3)(秋季),春季的周末效应较其它季节更为明显.NO_2/NO工作日与周末分别为3.63和3.46,工作日比周末高4.81%.工作日O_3累积时间更长,O_3累积速率更快,大气氧化性更强,是工作日O_3质量浓度高于周末的原因.VOCs、NO_x、NO和NO_2与O_3质量浓度的相关性均呈现出工作日大于周末的特点.     

NO2--N/NH4+-N及COD/NH4+-N对厌氧氨氧化耦合反硝化脱氮除碳的影响

采用序批式反应器-厌氧序批式反应器（SBR-ASBR）组合工艺处理常温低C/N比实际生活污水,通过调控SBR缺氧：好氧时间分别为80min：60min、120min：60min和150min：60min时,实现半亚硝化,将其出水直接泵入ASBR反应器中,考察不同进水NO₂^--N/NH₄⁺-N和COD/NH₄⁺-N对厌氧氨氧化耦合反硝化同步脱氮除碳的影响,并采用响应面法设计正交批次试验.结果表明：在NO₂^--N/NH₄⁺-N为1.55,COD/NH₄⁺-N为4.22时,出水NH₄⁺-N、NO₂^--N和COD的浓度分别为2.79,0.47,38.37mg/L,其去除率分别高达87.56%,98.45%和62.69%.ΔNO₂^--N/ΔNH₄⁺-N为2.23,生成的NO₃^--N的量比理论值小2.47mg/L,厌氧氨氧化和异养反硝化共同完成氮素去除,系统脱氮除碳性能最佳.当NO₂^--N/NH₄⁺-N和COD/NH₄⁺-N分别由0.84增加到1.55和3.24增加到4.22时,厌氧氨氧化和异养反硝化对脱氮贡献率分别由80.40%降至53.33%和19.60%增加到46.67%.NO₂^--N/NH₄⁺-N和COD/NH₄⁺-N对TN和COD去除的正交影响显著,均呈现正相关,R²分别为0.9243和0.9700.     

絮凝方式对藻类絮体形态、强度及气浮的影响

 采用聚合氯化铝(PAC)作为混凝剂,利用混凝-气浮法处理含有较高浓度铜绿微囊藻(MA)的富藻水,在恒速絮凝和降速絮凝2 种方式下,研究PAC-MA 絮体的形态及强度对气浮的影响.结果表明,在PAC 投加量及能耗相同的条件下,采用降速絮凝比恒速絮凝处理效果更好.在PAC 投加量(以Al₂O₃ 计)为5.6 mg/L、快速混合搅拌强度(G)和时间分别为500s^-1 和1min、2 级降速絮凝G 值分别为100s^-1 和20s^-1、回流比为10%条件下,当絮凝时间为6~10min 时处理效果较好,最佳絮凝时间为8min;不同的絮凝方式对PAC-MA 絮体形态及强度有着显著影响,2 种絮凝方式形成的絮体形态相似时,降速絮凝形成的絮体强度更大;絮体的形态和强度共同影响气浮处理效果.     

东南沿海地区钢质包装弹药的储存管理研究

为了进一步做好钢质包装弹药的保障工作,在分析东南沿海地区的气候环境的基础上, 着重从包装储存功能角度研究钢质包装材料的功能特点,并讨论了采用钢质包装对弹药储存工作带来的不利影响,最后提出了在东南沿海地区恶劣气候条件下钢质包装弹药的储存与管理措施。