动态综合层次判别分析方法──以水土流失强度综合分析为例

随着遥感技术的发展,可获取的遥感信息越来越丰富,各种分类算法也层出不穷,然而在分类精度上却始终无法突破遥感数据本身的局限,而且不同的方法在判识的结果上往往有很大的不同。本文认为不同遥感信息、不同的判别分析方法,对不同的对象在不同的地表组合条件下其判别的能力是不同的,只有综合地运用这些不同的方法才可能在现有遥感资料的能力下提高分类精度。本文提出一种动态综合层次判别分析算法可将多种并行的分类算法综合在一起,取长补短,提高最后分类精度。通过在浙江省新昌县某地进行水土流失强度分析试验,取得了良好的效果。     

Foreword

The main objective of this special issue of the Bulletin of Earthquake Engineering is to bring to the earthquake engineering community the outcomes of the research project QUAKER (Quantification and Reduction of Seismic Risk through the Application of Advanced Geotechnical Engineering Techniques) financed by European Commission under contract EVG1-CT-2002-00064.     

Flow Characteristics of Microbubble Suspensions in Porous Media as an Oxygen Carrier

Microbubble suspensions were generated as an oxygen carrier for aerobic biodegradation, and their flow characteristics in porous media were investigated. Commercial surfactants including sodium dodecyl sulfate (SDS), and dodecylethyldimethylammonium bromide (DEDAB), saponin (a natural surfactant), and collagen (a protein hydrolysate) were examined as base materials for generating microbubble suspensions. Among them, 2×CMC (critical micellar concentration) of SDS, DEDAB, and saponin developed microbubble suspensions with the highest gas hold‐up and half‐drainage time. Visualization of the flow patterns in sand showed that the microbubble suspensions were separated into a liquid and gas phase directly after injection, showing much faster movement of liquid phase flow. The gas front of the microbubble suspensions flowed in a plug‐flow manner, particularly in cases of SDS and DEDAB. The experimental results from both homogeneous and heterogeneous cells confirmed that the microbubble flow could overcome the heterogeneity in porous media. However, the plug‐flow characteristics and flow propagation of the microbubble suspensions to the low‐permeability zone was accompanied by a large pressure drop, which needs to be considered for future field application.     

Hazardous Waste Pollution Prevention Using Clay with Admixtures

Landfill is the most commonly used method for disposal of waste materials since it is one of the least expensive methods. In order to dispose of any hazardous material to a landfill, a liner is used, which protects the underlying land and groundwater since it acts as a barrier to fluid movement. Of the various methods available for providing improved and more effective properties of landfills, methods involving the use of bentonite, cement, lime, gypsum, etc., have been explored in the laboratory. The aim is to overcome the problem and deficiencies of the existing liners. It is observed from the experimental results that the metal concentrations of the input waste solution can be reduced to 80–98% using a soil‐cement admixture, 60–95% using a soil‐gypsum mixture, 45–95% using a soil‐bentonite mixture, 50–90% for soil, 35–80% using a soil‐lime mixture, as liner materials. The permeation rate of different metals through the different soil‐admixture media depends on various factors. A simple mathematical treatment of the phenomenon related to the permeation of liquid through the admixture of the clay and other components has been developed. The experimental results show satisfactory agreement with the predictions.     

Impact of acid effluent from Kawah Ijen crater lake on irrigated agricultural soils: Soil chemical processes and plant uptake

Volcanogenic contamination of irrigation water, caused by effluent from the hyperacid Ijen crater lake, has severely affected the properties of agricultural soils in East Java, Indonesia. From a comparison of acidified topsoil with subsoil and with top- and subsoil in a reference area, we identified processes responsible for changes in soil and soil solution chemistry induced by acid irrigation water, with emphasis on the nutrients Ca, Mg, Fe, and Mn, and on Al, which may become phytotoxic under acid conditions in soils. Compositional data for bulk soil composition and selective extractions with 1 M KCl and 0.2 M acid ammonium oxalate are used in a mass balance approach to specify element fluxes, including uptake by rice plants. The results show that input via irrigation water has produced an increase in the total aluminum content in the affected topsoil, which is of the same order of magnitude as the increase in labile Al. High bioavailability of Al, as reflected by concentrations in KCl extracts, is consistent with elevated concentrations observed in rice plants. In contrast, and despite the high input via irrigation water, Ca and Mg concentrations have decreased in all measured soil fractions through dissolution of amorphous phases and minerals, and through competition of Al for adsorption sites on the exchange complex and plant roots. Strong leaching is also evident for Fe and especially Mn. In terms of the overall mass balance of the topsoil, plant uptake of Al, Ca, Fe, Mg and Mn is negligible. If the use of acid irrigation would be stopped and the soil pH were to increase to values above 4.5, the observed phytotoxicity of Al will be halted. However, crops may then become fully dependent on the input from irrigation water or fertilizer for essential elements, due to the previous removal from the topsoil through leaching.     

沈大高速公路两侧土壤重金属污染分布特征研究

对沈大高速公路沈阳、辽阳、鞍山、营口和大连段两侧土壤中铅、镉、锌、铬、镍和铜的含量进行测定。结果表明:在距路肩250 m范围内,各段土壤中铅、镉均有不同程度的累积,锌、铬、镍、铜污染不显著。土壤中铅、镉最大污染指数为3.34和2.42,污染较高值出现在距路肩50 m内,尤以20—40 m为高,除铅外其余重金属含量在距路肩150 m以外趋于背景值,但土壤中铅污染为250 m以外。     

模糊综合评价法在土壤环境质量评价中的应用实例

The soil environmental quality was evaluated by fuzzy comprehensive assessment method,which could decrease the gradual change and fuzz of soil environmental pollution.The soil environmental quality at five plots of sewage irrigation region in Fuxin was validated by fuzzy comprehensive assessment method.The results indicate that this assessment method is feasible.And the method can also detect the soil environmental grades scientifically.The effects of different pollution factors on soil environmental quality can be estimated,and the pollution grades can be divided and evaluated.The method can provide the base for soil environmental plan and pollution prevention and cure.     

Spatio-temporal analysis of potential aquifer recharge: Application to the Basin of Mexico

Regional estimates of aquifer recharge are needed in data-scarce regions such as the Basin of Mexico, where nearly 20 million people are located and where the Basin’s aquifer system represents the main water source. In order to develop the spatio-temporal estimates of aquifer recharge and to analyze to what extent urban growth has affected aquifer recharge, this work presents a daily soil water balance which uses different vegetation and soil types as well as the effect of topography on climatological variables and evapotranspiration. The soil water balance was applied on a daily time step in the Basin of Mexico for the period 1975–1986, obtaining an annually-lumped potential recharge flow of 10.9–23.8 m³/s (35.9–78.1 mm) in the entire Basin, while the monthly values for the year with the largest lumped recharge value (1981 = 78.1 mm) range from 1 m³/s (0.3 mm) in December to 87.9 m³/s (23.7 mm) in June. As aquifer recharge in the Basin mainly occurs by subsurface flow from its enclosing mountains as Mountain Block Recharge, urban growth has had a minimal impact on aquifer recharge, although it has diminished recharge in the alluvial plain.     

科尔沁沙地土壤微生物区系季节动态的初步研究

通过对流动沙丘、半固定沙地、固定沙地及其附近农田黄土和农田黑土中主要土壤微生物类群的好气型细菌、放线菌、丝状真菌和芽孢型杆菌不同季节数量的测定结果表明,微生物类群不同,所表现的季节变化有明显差异。放线菌和芽孢杆菌的生长高峰在春季,丝状真菌的高峰在夏季,好气型细菌的生长高峰出现在秋季。另外,土壤微生物的数量随土壤质地的不同也表现出显著变化,可划分为几种情形,即农田型、固定和半固定沙地型以及流动沙地型。