滑坡勘查中的高密度电阻率法异常特征

以某滑坡区为例,使用高密度电阻率法对滑坡区的异常特征进行了研究,并对获取的视电阻率断面进行了地形校正.结果表明,对于沉积岩地区滑坡,滑坡体与滑床间存在明显的电性差异,根据经过地形改正的滑坡区视电阻率异常特征和断面,更清晰和直观显示了滑坡体的纵横向展布、主滑动面的位置与埋深,进而可圈定滑坡体的规模,从而为滑坡治理提供可靠的地球物理依据.     

地震现场数据共享标准化研究及其标准起草

标准化被普遍认为是保证信息更有效处理、交换、管理以及消除技术壁垒的最有效手段.信息共享标准是为规范信息共享的行为而制订的,是实现信息共享的"软"环境.通过对地震现场信息共享标准化研究,概述了这一标准制定的过程、总体内容框架安排的一些考虑以及存在问题,讨论了地震现场信息共享标准分类与编码体系、数据交换格式、元数据、数据字典及数据质量控制等与信息共享标准相关的一些问题.     

西安市地面沉降成因机理中的若干问题探讨

针对西安市区的地质环境和地面沉降特征,总结国内外与此相关的研究成果,重点从土层渗流与变形特性、地面沉降和地裂缝的关系、下部地层压密与地面变形关系以及开采地热资源对地面沉降的影响等几个方面分析西安市区地面沉降研究的现状及存在的问题,并针对这些问题提出了几点建议.     

Transport of Sr2+ and SrEDTA2- in partially-saturated and heterogeneous sediments

Strontium-90 has migrated deep into the unsaturated subsurface beneath leaking storage tanks in the Waste Management Areas (WMA) at the U.S. Department of Energy's (DOE) Hanford Reservation. Faster than expected transport of contaminants in the vadose zone is typically attributed to either physical hydrologic processes such as development of preferential flow pathways, or to geochemical processes such as the formation of stable, anionic complexes with organic chelates, e.g., ethylenediaminetetraacetic acid (EDTA). The goal of this paper is to determine whether hydrological processes in the Hanford sediments can influence the geochemistry of the system and hence control transport of Sr(2+) and SrEDTA(2-). The study used batch isotherms, saturated packed column experiments, and an unsaturated transport experiment in an undisturbed core. Isotherms and repacked column experiments suggested that the SrEDTA(2-) complex was unstable in the presence of Hanford sediments, resulting in dissociation and transport of Sr(2+) as a divalent cation. A decrease in sorption with increasing solid:solution ratio for Sr(2+) and SrEDTA(2-) suggested mineral dissolution resulted in competition for sorption sites and the formation of stable aqueous complexes. This was confirmed by detection of MgEDTA(2-), MnEDTA(2-), PbEDTA(2-), and unidentified Sr and Ca complexes. Displacement of Sr(2+) through a partially-saturated undisturbed core resulted in less retardation and more irreversible sorption than was observed in the saturated repacked columns, and model results suggested a significant reservoir (49%) of immobile water was present during transport through the heterogeneous layered sediments. The undisturbed core was subsequently disassembled along distinct bedding planes and subjected to sequential extractions. Strontium was unequally distributed between carbonates (49%), ion exchange sites (37%), and the oxide (14%) fraction. An inverse relationship between mass wetness and Sr suggested that sandy sediments of low water content constituted the immobile flow regime. Our results suggested that the sequestration of Sr(2+) in partially-saturated, heterogeneous sediments was most likely due to the formation of immobile water in drier regions having low hydraulic conductivities.     

Characteristics and driving factors of marsh changes in Zhalong wetland of China

Zhalong National Nature Reserve in the northeast of China is a large wetland and a habitat of hundreds species of fauna and flora. The rare red-crowned crane is one kind of endangered birds in it. Recently, Zhalong wetland is shrinking and it encounters many problems including occasional fires, bad water quality, human activities, etc. In order to find out a proper way to protect and restore the wetland, this study, using a geographic information system, the global positioning system and remote sensing techniques, analyses the spatial characteristics of the changes in marsh landscape pattern and examines the driving factors for these changes. Data sources include 8 Landsat Thematic Mapper satellite images of Zhalong area in the period of 1986–2002 and the investigation information on site. Based on the analysis of changes of marsh area and annual precipitation during the 16 years, it is found that there is a close correlation between annual precipitation and marsh area. It means that climate is one of driving factors of marsh pattern changes. To understand influences of other kinds of land uses on marsh spatial distribution in Zhalong wetland, this paper analyses the relationship between marsh and different kinds of land uses, such as water surface, residential area, farmland, salina land and grass land, respectively. According to the patch analysis theory, a fragmental index and a fractal dimension of the marsh are calculated with perimeter-area method. The results indicate that the marsh pattern is affected by human activities significantly. In addition, the location alteration of marsh centroid point over the 16 years is studied. The movement trace of marsh centroid point is concerned with different hydrological situation in different areas of the wetland. In summary the characteristics of the marsh landscape pattern evolution during the 16 years are affected by multiple driving factors. The main driving factors are climate, human activities, distribution of other kinds of land uses and hydrological situation in different areas.     

Survey of heavy metal pollution and assessment of agricultural soil in Yangzhong district, Jiangsu Province, China

We investigated concentrations of Hg, Cd, Pb, Zn, Cu, As, Ni, and Cr in samples of soil, cereal, and vegetables from Yangzhong district, China. Compared to subsoils, the sampled topsoils are enriched in Hg, Cd, Cu, Pb, Zn, and As. High levels of Cd and Hg are observed in most agricultural soils. Concentrations of Cr and Ni show little spatial variation, and high Cu, Pb, and Zn contents correspond well to areas of urban development. High As contents are primarily recorded at the two ends of the sampled alluvion. The contents of Cd, Hg, and total organic carbon (TOC) increase gradually to maximum values in the upper parts of soil profiles, while Cr and Ni occur in low concentrations within sampled profiles. As, Pb, Cu, and Zn show patterns of slight enrichment within the surface layer. Compared to data obtained in 1990, Cd and Hg show increased concentrations in 2005; this is attributed to the long-term use of agrochemicals. Cr and Ni contents remained steady over this interval because they are derived from the weathering of parent material and subsequent pedogenesis. The measured As, Cu, Pb, and Zn contents show slight increases over time due to atmospheric deposition of material sourced from urban anthropogenic activity. Low concentrations of heavy metals are recorded in vegetables and cereals because the subalkaline environment of the soil limits their mobility. Although the heavy metal concentrations measured in this study do not pose a serious health risk, they do affect the quality of agricultural products.     

Effects of potassium alkalis and sodium alkalis on the dechlorination of o-chlorophenol in supercritical water

Effects of potassium alkalis and sodium alkalis on the dechlorination of o-chlorophenol (o-CP) in supercritical water (SCW) were studied in this paper under the conditions of 450 degrees C and 25 MPa. Experimental results indicated that the dechlorination of o-CP can be accelerated significantly by all alkalis investigated. The dechlorination of o-CP proceeded mainly via two pathways: hydrodechlorination and hydrolysis. Both of the two pathways can be promoted by alkalis, and the dechlorination of o-CP can be accelerated by both the cations and hydroxide ion dissociated from alkalis. The overall dechlorination of o-CP can be accelerated by cations via promoting the hydrodechlorination pathway, while, hydroxide ion via promoting the hydrolysis pathway. In addition, the hydrodechlorination can be accelerated faster by sodium alkalis than that by potassium ones, while, the hydrolysis can be promoted faster by potassium alkalis. This difference may be caused by the different charge density between potassium ion and sodium ion, and the different solubility and dissociation constant between potassium alkalis and sodium alkalis in SCW. Dechlorination of o-CP with addition of alkalis prior to supercritical water oxidation (SCWO) process not only can avoid the reactor corrosion caused by the generated hydrochloric acid in direct SCWO of o-CP, but also can reduce the formation of toxic chlorinated byproducts compared with direct SCWO process or SCWO of o-CP with addition of alkali.     

Source apportionment of polycyclic aromatic hydrocarbons in surface soil in Tianjin, China

Principal component analysis and multiple linear regression were applied to apportion sources of polycyclic aromatic hydrocarbons (PAHs) in surface soils of Tianjin, China based on the measured PAH concentrations of 188 surface soil samples. Four principal components were identified representing coal combustion, petroleum, coke oven plus biomass burning, and chemical industry discharge, respectively. The contributions of major sources were quantified as 41% from coal, 20% from petroleum, and 39% from coking and biomass, which are compatible with PAH emissions estimated based on fuel consumption and emission factors. When the study area was divided into three zones with distinctive differences in soil PAH concentration and profile, different source features were unveiled. For the industrialized Tanggu-Hangu zone, the major contributors were cooking (43%), coal (37%) and vehicle exhaust (20%). In rural area, however, in addition to the three main sources, biomass burning was also important (13%). In urban-suburban zone, incineration accounted for one fourth of the total.     

长江沉积物中痕量氯代酚类化合物的测定

本文利用同位素稀释质谱法对长江南京段沉积物中１８种氯代酚进行了分离鉴定,结果表明,沉积物中ＣＰｓ的含量以五氯苯酚为主,     

铅锌尾矿废弃地的化学性质研究

凡口铅锌尾矿废弃地的不同区位及不同深度的尾矿中铅锌含量存在着较大的差异 ,总锌为 70 3～ 19657mg/ kg、总铅 10 4 13～ 94 988mg/ kg。正常尾矿中 ,有效态锌含量达到 151.6～ 84 1.7mg/ kg,有效态铅含量很低 ( 0 .75～ 2 .50 mg/ kg) ,有机质、总氮、有效磷及速效钾等营养物质缺乏。当尾矿酸化后 ,p H降低 ,有效态 Pb、Zn含量升高 ,有效锌达到 175.8～ 2 82 8.0 mg/ kg,有效铅含量最高为 10 0 .0 mg/kg,而有机质、总氮和有效磷为零 ,使尾矿更加贫瘠。在尾矿库的边缘区位和尾矿表面的覆盖土壤区位 ,基质中营养物质含量增加 ,但是营养状况的改善又引起了有效态的 Pb、Zn含量升高。