宝鸡某场地污染土的分析评价

宝鸡某场地由于长期堆放食盐，造成地基上污染、通过勘察，查明了污染土层，进行了腐蚀性测试和评价，对场地污染区与非污染区土的物理力学性质指标进行了对比，并分析了土的污染机理，提出了防护措施。     

Modelling of soil temperature profiles using data from the pilot experiment at Anand

We present some preliminary results from a multi-layer soil temperature finite-difference model using the data set obtained during the pilot experiment on land surface processes at Anand. We hope that the present results will prove useful during the final field experiments scheduled for the coming monsoon season.     

Parameters of Land-Surface Processes for Gobi in North-West China

Using data from the intensive observation period (May–June 2000) of the NWC-ALIEX (The Field Experiment on Interaction between Land and Atmosphere in Arid Region of North-west China), the characteristics and mechanisms of some key land-surface process over Gobi in a typical arid region of north-west China are analyzed and several parameters of land-surface processes are calculated. The weighted mean of the surface albedo over a typical arid region of the Dunhuang Gobi is calculated using the relative reflection as a weighting factor, and its value is 0.255 ± 0.021. After removing the influence of precipitation, the mean soil heat capacity over a typical arid region of the Dunhuang Gobi is 1.12 × 10⁶ J m^-3 K^-1,which is smaller than that observed in the Heihe (China) River basin Field Experiment (HEIFE). The mean soil heat diffusivity and conductivity are about half of those observed in HEIFE.     

Space-time mapping of soil salinity using probabilistic bayesian maximum entropy

The mapping of saline soils is the first task before any reclamation effort. Reclamation is based on the knowledge of soil salinity in space and how it evolves with time. Soil salinity is traditionally determined by soil sampling and laboratory analysis. Recently, it became possible to complement these hard data with soft secondary data made available using field sensors like electrode probes. In this study, we had two data sets. The first includes measurements of field salinity (EC_a) at 413 locations and 19 time instants. The second, which is a subset of the first (13 to 20 locations), contains, in addition to EC_a, salinity determined in the laboratory (EC_2.5). Based on a procedure of cross-validation, we compared the prediction performance in the space-time domain of 3 methods: kriging using either only hard data (HK) or hard and mid interval soft data (HMIK), and Bayesian maximum entropy (BME) using probabilistic soft data. We found that BME was less biased, more accurate and giving estimates, which were better correlated with the observed values than the two kriging techniques. In addition, BME allowed one to delineate with better detail saline from non-saline areas.     

水泥搅拌桩与锚杆组合支护结构的力学参数研究

水泥搅拌桩--锚杆组合支护结构是一种新型的组合支护结构,笔者采用有限元方法进行各相关力学参数研究,分析了该组合支护结构的受力特性及变形性态.通过计算结果与实测数据的比较,表明本文所得结论对该组合支护结构的应用有一定的指导价值.     

深层水泥土搅拦桩在软土地基处理中的应用

通过对深层水泥土搅拌桩的加固机理及复合地基承载力性状的简要分析,根据国家现行规范,结合具体地基处理工程实例,对深层水泥搅拌桩在软土地区地基加固处理中的方案选择、设计、施工及检测中的常见技术要点作初步探讨。     

Vegetation dynamics during the late Pleistocene in the Barreirinhas region, Maranhão State, northeastern Brazil, based on carbon isotopes in soil organic matter

The study place is in the Barreirinhas region, Maranhão State, northeastern Brazil. A vegetation transect of 78 km was studied among four vegetation types: Restinga (coastal vegetation), Cerrado (woody savanna), Cerradão (dense woody savanna), and Forest, as well as three forested sites around Lagoa do Caçó, located approximately 10 km of the transect. Soil profiles in this transect were sampled for δ¹³C analysis, as well as buried charcoal fragments were used for ¹⁴C dating. The data interpretation indicated that approximately between 15,000 and ∼9000 ¹⁴C yr B.P., arboreal vegetation prevailed in the whole transect, probably due to the presence of a humid climate. Approximately between ∼9000 and 4000-3000 ¹⁴C yr B.P., there was the expansion of the savanna, probably related to the presence of drier climate. From ∼4000-3000 ¹⁴C yr B.P. to the present, the results indicated an increase in the arboreal density in the area, due to the return to a more humid and probably similar climate to the present. The presence of buried charcoal fragments in several soil depths suggested the occurrence of palaeofires during the Holocene. The vegetation dynamic inferred in this study for northeastern Brazil is in agreement with the results obtained in areas of Amazon region, based on pollen analysis of lake sediments and carbon isotope analysis of soil organic matter (SOM), implying than similar climatic conditions have affected these areas during the late Pleistocene until the present.     

Changes in soil organic carbon and other physical soil properties along adjacent Mediterranean forest, grassland, and cropland ecosystems in Turkey

Cultivation, overgrazing, and overharvesting are seriously degrading forest and grassland ecosystems in the Taurus Mountains of the southern Mediterranean region of Turkey. This study investigated the effects of changes on soil organic carbon (SOC) content and other physical soil properties over a 12-year period in three adjacent ecosystems in a Mediterranean plateau. The ecosystems were cropland (converted from grasslands in 1990), open forest, and grassland. Soil samples from two depths, 0–10 and 10–20 cm, were collected for chemical and physical analyses at each of cropland, open forest, and grassland ecosystems. SOC pools at the 0–20 cm depth of cropland, forest, and grassland ecosystems were estimated at 32,636, 56,480, and 57,317 kg ha⁻¹, respectively. Conversion of grassland into cropland during the 12-year period increased the bulk density by 10.5% and soil erodibility by 46.2%; it decreased SOM by 48.8%, SOC content by 43%, available water capacity (AWC) by 30.5%, and total porosity by 9.1% for the 0–20 cm soil depth (p<0.001). The correlation matrix revealed that SOC content was positively correlated with AWC, total porosity, mean weight diameter (MWD), forest, and grassland, and negatively with bulk density, pH, soil erodibility factor, and cropland. The multiple regression (MLR) models indicated that any two of the three ecosystems and one of the two soil depths accounted for 86.5% of variation in mean SOC values ((p<0.001).     

河南省土壤湿度年变化规律

利用河南省土壤墒情预报模型中建立的河南省台站土壤墒情数据库资料，对不同类型土壤湿度进行分析，从而确定不同类型土壤湿度差异、地下水对土壤湿度的影响及河南省土壤湿度的年变化规律。     

Mineralogical changes during thermal demagnetization of natural continental sandstones

We study the mineralogical changes suffered by specimens of natural miocene red and green continental sandstones (from Pozuelos Formation and Tiomayo Formation) cropping out in the Argentine Puna that increase their bulk magnetic susceptibility and change color when thermally treated. We hypothesize that on heating siderite, which is present in small quantities as cement in the studied sandstones, would oxidize and decompose into maghemite and/or magnetite. Subsequent heating to higher temperatures sometimes would bring about the conversion of maghemite and/or magnetite to hematite. Mössbauer spectroscopy proved to be a very valuable tool for the determination of the presence of siderite in small amounts in the studied samples. The present results show that further work is needed in order to fully understand the mineralogical changes suffered by continental sandstones during heating. The characterization of such changes occurred during laboratory routines is relevant, since they can help to better understand natural processes.