Contamination,chemical speciation and vertical distribution of heavy metals in soils of an old and large industrial zone in Northeast China

Heavy metal pollution of soils has become a major concern in China as a consequence of rapid urbanization and industrialization in recent years. However, the evaluation on soil heavy metal pollution in Shenyang, the largest heavy industrial base city in China, has not yet been conducted. In this study, accumulation, chemical speciation, and vertical distribution Cu, Zn, Pb and Cd in soils were studied and pollution condition was assessed in Tiexi Industrial District of Shenyang, the largest and oldest industrial zone in Northeastern China. The results showed that in topsoil, the average concentration of total Cu, Zn, Pb, and Cd was 209.06, 599.92, 470.19 and 8.59 mg kg⁻¹, respectively, much higher than the national threshold limit. The values of pollution index and integrated pollution index showed that the pollution level was Cd > Cu > Zn > Pb, and Cd, Cu and Zn belong to heavy pollution level. The residual, Fe and Mn oxide-bound, and organic-bound species accounted for about 90%, while carbonate-bound and exchangeable species accounted for about 10%. This study indicates that the soils in the industrial zone were widely and extremely polluted by multi-heavy metals as a result of long-term industrial activities.     

冻结方式对冻土试样制备的影响

冻土试样的制备是进行冻土试验最为基础而重要的工作,其中土样在冻结过程中受到的影响直接关系到试样内部状况.为研究冻结方式对粉质粘土含水量和干密度分布的影响,采取不同的冻结方式即单向冻结和多向冻结方法,对比分析不同状态下兰州黄土和北麓河粘土冻结试样各部位含水量与干密度的分布状况.结果表明:试样内含水量和干密度的分布程度取决于土的类型、饱和状态和冻结方式,具体为:非饱和兰州黄土在多向冻结情况下,可以取得比单向冻结更加均匀的冻结试样;饱和兰州黄土冻结试样无论是单向冻结还是多向冻结都较为均匀;北麓河粘土无论饱和与否,均以单向冻结为好.     

基于块克里金的土壤水分点观测向像元尺度的尺度上推研究

土壤水分是陆面水文过程的一个重要分量,土壤水分的地面点观测与卫星观测的尺度是不匹配的,用点观测数据进行遥感反演结果的验证或者融合这两种观测都需要开展点观测数据向卫星像元尺度的尺度上推研究.土壤水分时空异质性的分析和描述是进行尺度上推的基础,地统计方法是描述连续随机变量空间结构的经典方法.应用块克里金法分别将黑河寒区遥感试验阿柔试验区2008年4月1日与L波段微波辐射计同步的地面液态含水量和含冰量点观测数据经过尺度转换,得到与遥感像元相匹配的像元平均估计值和标准差,可用于该天L波段微波辐射计土壤液态含水量和含冰量反演结果的真实性检验,估计结果充分利用了像元临近位置的观测,得到了比直接的采样平均更合理的块估计结果,对块克里金估计值与采样平均值进行比较,发现两种结果趋势是一致的,块克里金法提供了更为合理的块估计结果,土壤水分空间结构的时间变异、小尺度的土壤特性的变化和测量误差都会对估计结果带来一定的不确定性.     

利用CT扫描对粗砂土中甲烷水合物形成过程中水分迁移特征的分析

多孔介质中甲烷水合物的形成及分解实验研究,对于了解多年冻土中天然气水合物的赋存有重要意义.通过X射线扫描系统对粗砂土中甲烷水合物的形成及分解过程中反应釜内水分的空间变化进行分析,结果表明:粗砂土中甲烷水合物的形成和分解过程中,CT数在反应釜内有明显的空间变化特征,且这个空间变化特征与甲烷水合物在粗砂土中形成、分解过程中水分的迁移是密切相关的.通过对不同阶段CT扫描所获得图像CT值的空间变化特征进行分析,可以看出:在甲烷水合物的生成过程中,反应釜内下半部分的水分会向上半部分迁移,以弥补上半部分水分的不足;在甲烷水合物分解过程中,分解所释放出来的水分会由反应釜上半部分向下半部分回迁,最终达到自然分布.     

Effect of Soil Parameters on Dynamic Cone Penetration Indices of Laterite Sub-grade Soils from India

The focus of this study was on correlating the effect of grain-size, maximum dry-density (MDD), field moisture content, and the void ratios on penetration measured using the dynamic cone penetrometer (DCP) for laterite soils blended with fines. Tests were performed on soil samples compacted to MDD for moulding water contents set to the optimum moisture content (OMC), dry of OMC, and wet of OMC un-soaked condition. The results indicated that an increase in the fines-content caused a decrease in the MDD, and an increase in the OMC and the DCP penetration. Regressions were developed correlating various parameters.     

Stabilization of Expansive Clays Using Granulated Blast Furnace Slag (GBFS) and GBFS-Cement

Expansive clays undergo swelling when subjected to water. This can cause damage, especially to light weight structures, water conveyance canals, lined reservoirs, highways, and airport runways unless appropriate measures are taken. In this study, granulated blast furnace slag (GBFS) and GBFS-cement (GBFSC) were utilized to overcome or to limit the expansion of an artificially prepared expansive soil sample (sample A). GBFS and GBFSC were added to sample A in proportions of 5–25% by weight. The effects of these stabilizers on grain size distribution, Atterberg limits, swelling percentage and rate of swell of soil samples were determined. GBFS and GBFSC were shown to successfully decreasing the total amount of swell while increasing the rate of swell.     

Statistical Distributions of Hydraulic Conductivity from Reliability Analysis Data

This paper describes a first-order reliability-based analysis to identify the best-fit probability distributions for hydraulic conductivity. The analysis involved the use of existing hydraulic conductivity model developed from laboratory data and applied to lateritic soils, considering variations in soil parameters. Plots of reliability indices versus coefficients of variation were first made for hydraulic conductivity as well as for initial degree of saturation, plasticity index and clay content, considering three compactive efforts and log-normally distributed hydraulic conductivity. The traditional two-parameter log-normal distribution was compared to four alternative distributions: normal, gamma, Gumbel (extreme value type I-EVT-I) and Weibull (extreme value type III-EVT-III). The analysis showed that the Weibull and normal are the best-fit probability distributions for the hydraulic conductivity based reliability data. Hydraulic conductivities predicted from reliability analysis were used to demonstrate the possibility of applying the results obtained in this research by practising engineers. Experimentally-determined hydraulic conductivities were shown to be in good agreement with predicted values.     

利用主被动微波数据联合反演土壤水分

在黑河中游干旱区水文试验的基础上,以临泽站为研究区域,探讨主被动微波数据联合反演土壤水分的方法。针对ALOS/PALSAR数据,使用AIEM理论模型计算地表的同极化后向散射系数,Oh半经验模型描述交叉极化散射特征,通过对大量后向散射模拟数据的分析,建立裸露地表粗糙度计算模型;利用模拟数据分析地表辐射亮温随土壤水分和粗糙度的变化规律,在此基础上构建NN模型结合粗糙度计算结果和辐射计飞行数据反演研究区域的土壤水分。地面同步测量数据的验证结果表明,该方法充分发挥了主被动微波数据各自的优势,同时避免了主被动协同过程中的尺度问题,为流域尺度的土壤水分监测提供了一种新的有效途径。     

四套土壤湿度再分析数据在中国西北东部—华北—江淮地区的适用性研究

基于1992~2010年全国778个农业气象站土壤湿度观测资料、ERA-Interim、JRA55、NCEP-DOE R2和20CR土壤湿度再分析资料,通过平均差值、相关系数、差值标准差、标准差比四个参数,利用Brunke排名方法和EOF(Empirical Orthogonal Function)分析,对四套土壤湿度再分析资料在中国西北东部—华北—江淮区域的适用性进行了分析。主要结论如下:不同季节的平均偏差空间分布上,JRA55资料同观测数据的平均偏差在±0.08m~3 m~(-3)之间,春、夏季西北东部JRA55土壤湿度偏小,ERA-Interim、NCEP-DOE R2、20CR资料较观测数据偏湿,华北南部、江淮地区平均偏差小于西北东部、华北北部。在年际变化上,各个季节ERA-Interim资料同观测资料最为接近,能稳定地再现西北东部、华北、江淮地区土壤湿度干湿变化趋势,反映出重要的旱涝年。整体而言,四套再分析资料中ERA-Interim资料同观测资料接近,JRA55、NCEP-DOE R2资料次之,20CR资料最差。     

塔里木河中游输水堤防的修建对地下水化学特征的影响

通过对塔里木河中游输水堤防修建后,沙子河口、乌斯满和阿其河口三个断面地下水化学特征自2001—2003年的时空变化的监测与分析,初步揭示了在输水堤防影响下地下水化学特征变化的初步规律,结果表明：在空间上,沙子河口断面地下水化学变化规律完全被颠倒过来,乌斯满断面,地下水化学变化规律受输水堤防的影响不十分明显,但地表积盐严重,阿其河口断面,则呈现复杂的变化;在时间上,丰枯期地下水化学特征的正常变化规律在沙子河口被彻底改变,在乌斯满和阿其河口呈现出复杂变化。由于地下水循环具有潜在性和迟滞性,要彻底揭示在输水堤防影响下地下水化学特征时空变化的规律,需要进一步跟踪监测研究。