Probing Hg evasion from surface waters of two Chinese hyper/meso-eutrophic reservoirs

Measurements of water/air exchange flux of gaseous elemental mercury (GEM) were conducted in a hyper-eutrophic reservoir and a meso-eutrophic reservoir in southwest China in both warm and cold seasons by using a dynamic flux chamber (DFC) method coupled with an automatic gaseous Hg analyzer. Both strong diurnal and seasonal variations of GEM fluxes were observed. The diurnal cycle of the GEM flux was more pronounced during sunny days compared to cloudy and rainy days, which highlights the effect of solar intensity on the GEM flux. GEM fluxes in warm seasons were considerably higher (2.5 to 4.1 times higher) than in cold seasons, which was attributed to the combined factors including meteorological factors, water quality parameters and water Hg concentrations. Clear variation in GEM fluxes was observed between the two reservoirs. Mean GEM fluxes in the hyper-eutrophic reservoir (WJD) (3.2-20.1 ng m⁻² h⁻¹) were significantly higher than those in the meso-eutrophic reservoir (SFY) (0.6-4.4 ng m⁻² h⁻¹). Evasion of Hg played a distinct role in the mass balance of Hg in the two reservoirs. In WJD, evasion was the second most important mechanism for Hg losses from the reservoir (17.5% of the total losses); whereas in SFY, loss of Hg via volatilization constituted an extremely little portion to the total losses of Hg (0.8%).     

层状土中污染物的一维扩散解析解

扩散是污染物在填埋场细颗粒土质衬里中迁移的主要方式,同时土质衬里存在着成层的情形。在建立了污染物在层状土中的一维扩散模型的基础上,通过分离变量法得到了解析解。基于该解析解,编制了相应的计算程序。通过与有限差分法对比,证明了该解析解的正确性及有效性。算例分析了不同衬里的放置顺序对污染物扩散的影响,虽然两种情况下土层的浓度剖面不同,但两者的击穿曲线是一致的。该解析解可用于对试验数据的拟合、对复杂数值模型的检验以及为垃圾填埋场衬里系统的初步设计提供参考。     

Factors influencing the temporal diffusion of broadband adoption: evidence from Oklahoma

This paper examines the shifting influence of household characteristics and telecommunications infrastructure on the residential broadband adoption decision for Oklahoma residents between 2003 and 2006. In particular, the spread of wired telecommunications infrastructure (namely cable Internet and Digital Subscriber Lines (DSL)) is examined, along with the effect that this diffusion has had on broadband access rates. The data indicates that the gap in broadband access rates between rural and urban areas has remained relatively constant over this period despite increased levels of cable and DSL throughout the state. In addition, an inter-temporal decomposition shows that the increasing levels of infrastructure are not the dominant cause of higher broadband rates over time. Instead, shifting returns to specific characteristics (namely income) are found to be the primary contributors.     

Spatial distribution of total Hg in urban soils from an Atlantic coastal city (Aveiro, Portugal)

The aim of this study was to investigate the levels and the spatial distribution of total Hg concentrations in soils from the urban area of Aveiro (Portugal) in order to assess the impact of industrial activities and identified Hg emission sources in these urban soils. For this purpose, soils were collected in 25 sampling points (at two depths) within the urban perimeter and in places considered representative of the main green areas of the city. A median concentration of 0.091 mg kg(-1) (dry weight) was obtained, regardless the depth. Aveiro was considered a low polluted city in terms of total Hg and no direct effects of emissions of Hg from industrial activities nearby could be detected in these urban soils. Despite of the low values obtained, high variability (range of approximately 0.5 mg kg(-1)) was observed in the results. Such was considered to be related to characteristic features of soils in urban settings and to the behaviour of Hg in the urban environment.     

有限土体刚性挡墙平动模式被动土压力试验研究

经典的库仑或朗肯土压力理论无法适用有限土体情况下的土压力问题。利用研制的土压力试验模型装置,进行了一组不同填土宽度的刚性挡墙平动模式室内模型试验,采用微型土压力盒量测从静止状态到被动极限状态的水平土压力分布的变化,利用颗粒图像测速技术研究土体内滑裂面发展规律。试验结果表明:半无限土体情况下的被动土压力大小、分布和合力作用点与库仑被动土压力较为接近。而有限宽度情况下移动挡墙上各深度的被动土压力值均大于库仑被动土压力,且土体宽度越窄,挡墙的被动极限位移有增大趋势,挡墙下部的被动土压力增大更明显,土压力分布的非线性程度愈高,被动土压力系数越大,被动土压力合力作用点明显往墙底移动。随着填土宽度的减小,填土表面的隆起愈明显,滑裂面的倾角略有增大。当移动挡墙达到或接近极限状态时,固定边界上的水平土压力随填土宽度的减小而逐渐增大,甚至接近库仑被动土压力。     

Lake sedimentary evidence of phosphorus,iron and manganese mobilisation from intensively fertilised soils

A study of historical P inputs to Friary Lough, Co. Tyrone, Northern Ireland used a multi-sediment core approach. One of the sediment cores taken from the littoral zone at 2.5m water depth showed exceptionally high P, Fe and Mn concentrations below 20 cm sediment depth. Concentrations increased to 14 mg Pg(-1), 238 mg Feg(-1) and 35 mg Mng(-1) in the sediment profile and compared with deep basin maxima of 7 mg Pg(-1), 70 mg Feg(-1) and 2 mg Mng(-1) in surface sediments at 8.5m water depth. It is proposed that the high concentrations in the littoral zone core are due to post-depositional intrusion of chemical-rich local groundwater from soils in adjacent fields that are excessively fertilised with organic slurry. Soil analyses showed Olsen-P concentrations in these fields up to 125 mgkg(-1) at the soil surface (0-7.5 cm) and 39 mgkg(-1) in the sub-soil at 20 cm depth. We suggest that the mobilisation of P, Fe and Mn is due to leaching following P saturation and/or the loss of P absorbing chemicals due to prolonged reduction and complexing in wet soils. Further work will explore this relationship and the nature of the hydrological pathways through soil.     

热强化有机污染物自土中挥发过程的试验与理论研究

为了研究热强化条件下有机污染物自土中挥发去除规律及挥发过程的影响因素,设计了室内挥发模型试验,研究了不同温度、不同初始污染物浓度的挥发去除规律。研究结果表明,有机污染物自土中的挥发过程曲线可分成三个阶段:快速挥发期,稳定增长期和平衡挥发期;另外,初始污染物浓度越大,自由相污染物分子的比例越高,挥发速率越大;温度由40℃升高至80℃时,砂土的平均挥发速率提高了4.0～4.8倍;综合考虑拟合方程的相关性发现,有机污染物自土中的挥发去除过程符合一级动力学模型。     

Experimental investigations of blast-induced consolidation of loess soils

A method of consolidating loess soils by the detonation of horizontal explosive charges situated in two tiers at a distance of 3–4 m with respect to depth is proposed. Test results for a different alternation of the detonation of horizontal charges in the upper and lower tiers are cited. The saving generated by the method adopted is indicated. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 6, pp. 9–13, November–December, 1994.     

软土蠕变特性试验研究

针对广州南沙原状软土进行了一系列室内试验研究,包括三轴压缩试验、三轴蠕变试验和一维固结试验,系统地探讨了软土的蠕变变形特性。结果表明:软土的蠕变特性与多种因素有关,包括土体的初始固结度、土层排水条件、加荷比等;次固结系数与固结压力的关系取决于土体的先期固结压力和试验中的加荷比。     

Experimental studies on curling development of artificial soils

Soil curling is an important phenomenon associated with volume changes induced by increasing soil suction upon desiccation. The study of soil behaviors associated with drying in soils (e.g. soil shrinkage, desiccation cracks and curling) has received increasing attention over the last few years, which has been mainly driven by the forecast climate change that will warm up our planet. There are significant gaps in the current knowledge related to the factors that control the development of curling deformations in soils. For this, the curling phenomenon is investigated through laboratory desiccation tests on different mixtures of artificial soils. The effects of soil grain size distribution, mineralogy, soil microstructure, and soil water content on the curling deformation are analyzed. Digital photos were taken at regular time intervals during the tests to understand the volume changes in the soil samples during drying. It is found that soil fabric and soil water content have significant effects on curling scenario. It is observed that the percentage of sand particles and the initial water content play a critical role in the development of soil curling. Samples of pure clayey minerals experienced shrinkage without or with minor curling during drying.     

Experimental assessment of an innovative process for simultaneous PAHs and Pb removal from polluted soils

This paper tests a soil washing process using flotation in its effectiveness for the removal of both polycyclic aromatic hydrocarbons (PAHs) and Pb from three polluted soils (soils A, B and C). The optimal flotation conditions were defined as: pulp density = 10%, Cocamidopropylhydroxysultaine (CAS) = 0.2% ww^− 1, [NaCl] = 5.5 M, pH = 3, flotation time = 15 min, air flow rate = 3 l min^− 1, stirring speed = 1800 rpm and temperature = 20 °C. Under these conditions, successive flotation stages (n), decreased the contaminant content to below permitted levels (up to 90% PAHs and Pb removal). Thus, a more contaminated matrix required the addition of a growing number of successive flotation stages to lower contamination levels below legal thresholds. While PAHs were distributed within the solid fractions of the process, Pb was mainly present in the liquid fractions. Electrodeposition allowed a total recovery of Pb after 60 min using a 2A electrical current.     

矿物掺合料抗氯离子扩散性能的试验研究

按照德国Aachen工业大学建筑材料研究所（ibac）采用的氯离子电迁移快速试验方法（RCM）测定混凝土中氯离子非稳定态快速迁移的扩散系数.试验结果表明：氯离子的扩散系数随粉煤灰、硅灰和高炉矿渣的掺量增加而降低,同时氯离子的扩散系数还与掺合料的种类有关,抗氯离子渗透能力依次为SF＞SG＞FA.分析并研究了粉煤灰、硅灰和高炉矿渣对混凝土抗氯离子渗透性能的影响.     

Experimental studies of the long-term deformability of clayey soils

Conclusions 1. Standard methods of determining the strain characteristics of a soil, e.g., GOST 12374-66, do not make it possible to evaluate to the fullest extent their yielding properties, which are governed by the rheological character of the deformation.2. The strain characteristics of soils (overall-compression modulus, stiffness coefficients of the foundation bed), which are determined from soil tests conducted in accordance with GOST 12374-66 may exceed their limiting long-term values obtained with consideration given to rheological properties by several factors (in our case, by a factor of 3.4).The use of stiffness coefficients on the high side for the design of buildings raised on nonuniformly deformable foundation beds (underexcavated sites, soils prone to slump-type settlement) leads to overdesigned structures. For these cases, therefore, it is recommended that the rheological characteristics of the soils be determined experimentally.3. For comparability of the rheological characteristics of soils determined from plate tests and on small specimens, it is necessary to assign consistent criteria for displacement stabilization, e.g., criteria that are interrelated over the depth of an equivalent layer.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 30–33, January–February, 1978.     

非饱和重塑土的干燥收缩试验研究

基质吸力和净平均应力的增大均可引起土体的压缩变形。针对砂土、粉土、黏土和软土4种不同类型土体,结合试样收缩曲线和土水特征曲线分析了土体干燥过程中基质吸力和孔隙比的关系。试验结果表明:土体干燥收缩过程中随着基质吸力的增大试样不断发生收缩,当基质吸力增大到某特定值时,基质吸力的增大对试样收缩变形无明显影响,称此基质吸力为缩限吸力。屈服吸力s0和缩限吸力ss将试样收缩过程分为弹性阶段、弹塑性阶段和缩限阶段3个阶段。并且不同类型土体的缩限吸力不相同,缩限吸力值与土体的塑性指数密切相关。在干燥收缩过程中,当试样的饱和度减小到90%时试样完成了绝大部分收缩,当试验饱和度达到70%时土样的孔隙比基本保持不变。     

粗粒土回弹特性试验研究

对2种粗粒土4种级配料进行了卸载–再加载的三轴固结排水剪试验,比较分析其强度变形特性与单调加载三轴试验条件下特性的差异。重点研究不同试验粗粒料的回弹模量取值规律,分析了回弹模量与初始模量、围压和应力水平等之间的关系。结果表明,围压对回弹模量影响较大而应力水平的影响相对较小;粗粒土的回弹模量约为初始模量的2.5～5.0倍,比目前对黏土等认识的1.5～3.0倍明显大。试验结果为邓肯–张模型等非线性弹性模型甚至弹塑性模型的回弹模量的合理取值提供了重要试验依据。     

滑坡滑带土非饱和蠕变特性试验研究

在库水位变动及降雨入渗作用下,一方面,滑坡土体在饱和与非饱和状态之间转化,土体强度和变形具有非饱和土的特性; 另一方面,滑坡变形发展大都经历了一个时间过程,具有流变特性,因此,考虑吸力（含水率）作用的非饱和土蠕变特性对于水作用下的坡体长期稳定性研究具有非常重要的意义 。 以 三峡库区 某大型滑坡滑动带土为研究对象,开展了一系列非饱和三轴蠕变试验 ,给出了不同偏应力荷载,不同基质吸力条件下的蠕变试验曲线。试验结果表明,同一偏应力荷载下,随着吸力逐渐减小,蠕变变形及蠕变速率均不断增加,且随偏应力荷载的增加增幅更大。在此基础上,建立了各级吸力水平下滑动带土的 Mesri 蠕变模型,即剪应力–应变关系采用双曲线模型,应变–时间关系采用幂函数。接着,通过建立吸力与 Mesri 模型参数 — 初始排水切线模量 之间的函数关系,构建了滑动带土的应力–吸力–应变–时间模型。最后,通过该模型的预测值与试验值的对比分析,发现模型能较合理地预测滑坡滑动带土的蠕变特性。     

纤维石灰土工程性质的试验研究

为了解决石灰改良引发的填筑土脆性破坏的问题,本文提出了将分散的聚丙烯纤维丝掺入到石灰土中的设想,并对不同纤维和石灰掺量的6组土样分别进行了无侧限抗压试验、剪切试验、膨胀率试验和收缩试验。试验结果表明,纤维的掺入不仅提高了石灰土的强度,而且还增强了石灰土的塑性,使其破坏形式从脆性破坏转变为塑性破坏。此外,在胀缩性方面,纤维的掺入减小了石灰土的膨胀性,但增加了收缩性。研究表明,纤维的强抗拉性是导致石灰土工程性质改变的主要因素。因此,纤维和石灰的混合掺入可以为填筑土工程性质的改良提供一个更加有效的方法。