沙尘天气对环境空气中PM_(10)影响分析

利用2002年沈阳市沙尘天气时的环境监测资料和气象资料进行分析得出浮尘天气时环境空气中PM10浓度最大,空气污染最严重,空气中的尘主要来源于我国西北沙漠地区;沙尘暴出现频率低,持续时间短,但强度大,空气中PM10主要来源科尔沁沙漠、省内荒漠地带及本市地表沙尘;扬沙天气污染相对较轻,空气的PM10以本地地表尘为主。     

Experimental investigation on effect of an absorber plate covered by a layer of sand on the efficiency of passive solar air collector

A passive flat-plate solar air collector was constructed in the laboratory of New and Renewable Energy in Arid Zones, Ouargla University, South East Algeria. The absorber of the passive flat-plate solar air collector was laminated with a thin layer of local sand. This acted as a thermal packed bed with a collecting area of 0.5 m² (1 m × 0.5 m). Three series of experiments were performed. The first consisted of choosing the best sand brought from three different places of the Algerian desert. The second consisted of studying the effect of the thickness of the sand layer on the daily efficacy of the collector. The influence of the sand diameter was investigated in the third series. The experimental results showed that: All collectors covered with sand had higher efficiency than those without. It was noticed that, for a fixed mass of sand (given thickness of the sand layer), the improvement of the collector was inversely proportional to the sand particle diameters. The maximum efficiency approximates 62.1% for a particle diameter 0.063 mm, compared to 41.71% for a diameter 0.250 mm.The efficiency of the collector for a fixed particle diameter increases with the increase in the thickness of the sand layer. The collector with thickness sand layer 0.84 mm gave the best efficiency of 46.14% compared to 27.8% for 0.28 mm of thickness sand layer.     

科尔沁沙地和浑善达克沙地流动沙丘中土壤微生物学特征比较

通过对科尔沁沙地和浑善达克沙地流动沙丘中0～10 cm和>10～20 cm层土壤中微生物数量和生物量碳的比较表明:土壤微生物三大类群(细菌、放线菌和真菌)数量和微生物生物量碳均表现为浑善达克沙地 > 科尔沁沙地,其中两大沙地真菌数量差异显著,细菌和放线菌数量差异不显著,微生物生物量碳差异显著;两大沙地土壤微生物数量和生物量碳在不同土壤层次均表现为>10～20 cm 层高于 0～10 cm层,其中微生物三大类群数量差异均不显著,微生物生物量碳差异显著. 土壤性质的差异导致两大沙地流动沙丘中微生物数量和生物量碳略有不同. 细菌和真菌数量与土壤有机碳和土壤全氮呈显著正相关,与土壤水分含量和pH呈显著负相关,微生物生物量碳与土壤有机碳和土壤全氮呈显著正相关. 两大沙地土壤微生物与土壤养分的层化比率均小于1,科尔沁沙地中微生物数量、生物量碳和土壤养分的层化比率均大于浑善达克沙地,可以推断两大沙地的流动沙丘处于退化状态,而且浑善达克沙地退化速度更快.      

黄土与砂土液化特性的对比──土液化与减灾防灾

基于系统的试验 ,总结已有成果 ,研究了饱和黄土和砂土液化在液化机理、液化判别标准、影响液化的因素、孔压和应变的发展等方面的异同之处。研究表明 ,由于在液化机理上存在差异 ,导致二者动荷载下的孔压和应变发展特点有显著差别 ;同一因素对二者液化性状的影响可能相似 ,也可能不同 ;在动三轴液化试验中 ,黄土和砂土均可采用初始液化作为液化的判别标准。     

Experimental study and modeling of the transfer of zinc in a low reactive sand column in the presence of acetate

Nowadays, it is necessary to understand and identify the reactions governing the fate of heavy metals introduced into the environment with low complexing organic compounds, particularly when they are transferred through soils in urban areas. In this work the concomitant influence of pH and acetate on the fate of zinc on siliceous sand was studied in batch and non-saturated column experiments. Total zinc concentrations varied between 2 and 20 mg/l, and total acetate concentrations were fixed at 22, 72, 132, and 223 mM to obtain solution pHs of 4, 5, 6 and 7, respectively. Natural sand (diameter, 0.3-2 mm), mainly constituted of silica, was used. In batch adsorption experiments, zinc adsorption is insignificant at pH 4, low and linear at pH 5, and increasingly nonlinear, of the Langmuir type, at pH 6 and 7 indicating near-saturation conditions of surface sites at these high pH values. In column experiments, Zn retardation increases and the maximum outlet concentration of Zn decreases with rising pH and acetate concentrations. Previous column tracer experiments revealed the occurrence of regionalized water transport in the column. Modeling these data was based on a non-electrostatic approach. Batch and column data modeling was based on the PHREEQC code that allows concomitant resolution of chemical speciation and regionalized water transport. The speciation calculation indicates that the ZnAcetate+ species is the dominant Zn species in the solutions used. Batch experimental curves are correctly modeled assuming the formation of the three surface species triple bond SiOZn+, triple bond SiOH-Zn Acetate+ and triple bond SiO-Zn(Acetate)2-. The column data could be adequately modeled assuming a two-region water transport and the formation of the same three species with the same thermodynamic constants determined in the batch experiments. The hypothesis of the modeling leads to a slight overestimation of the quantities of zinc eluted (10%) at pH 6 and 7, mostly in the desorption phase. These results show that the methodology used facilitates the correct modeling of both batch and transport experiments and formulation of the hypothesis on the interactions between the low reactive sand and a complex solution.     

西北地区沙尘暴引发的荒漠化问题

从西北地区继1993～1995年连续3a出现沙尘暴之后，1996年甘肃和内蒙古西部的阿盟等地再次遭到沙尘暴的袭击入手，分析了沙尘暴发生的原因，指出它归根结底是荒漠化的直接后果。概述了荒漠化的状况及危害，并分析了其成因。     

沈阳市北部地区风沙危害及防治对策

荒漠化是当今世界严重的环境与社会经济问题。沈阳市北部康平、法库两县均被列为国家防沙、治沙重点县。本文阐述了康平、法库两县风沙危害现状及发展趋势 ,提出了风沙危害的防治对策。     

内蒙古是北京地区沙尘天气的主要沙尘源

本文就内蒙古西部地区生态环境恶化现状、生态环境恶化的原因、沙尘暴发生情况及对北京等地区的影响进行了分析探讨，并就如何改善内蒙古西部地区生态环境提出建议。     

城市污泥对不同质地土壤保水效果研究

利用城市污泥滞水性强的特性可开发污泥作为保水剂的新功能。通过土培实验,在砂土、壤土和粘土中加入不同质量的污泥,研究污泥对不同质地土壤的保水效果。结果表明:在充分供水条件下,添加污泥能显著提高3种质地土壤的持水能力,土壤中添加20%的污泥后,砂土、粘土和壤土初始含水率分别增加11.2%、8.7%和8.8%;在3种质地土壤中添加污泥均可增大土壤的保水性,使水分蒸发减慢,且污泥添加量越多,土壤含水率越大;土壤累积失水量主要受到土壤中含水量的影响,也和不同质地土壤自身的蒸发量有关;在150 g土壤中添加10 g污泥,对砂土保水性提高不大,对壤土保水性提高最大,随着添加污泥量的增多,污泥对砂土的保水效果提高最明显。研究表明:开发污泥做为保水剂是可行的,这为污泥的资源化利用提供了新的途径,也为复合保水剂的研制提供了新的廉价材料,对于污泥治理及农业节水都有重要意义。     

Properties of steel foundry electric arc furnace dust solidified/stabilized with Portland cement

Electric arc furnace dust from steel production is generated in considerable amounts worldwide and needs to be treated as hazardous waste. The aim of this study was to investigate the properties of electric arc furnace dust solidified/stabilized by using Portland cement. Mortar and paste samples were prepared with varying waste-to-binder ratios between 0% and 90%. A comprehensive experimental program was designed including XRF characterization, setting time, unconfined compressive strength, and toxicity characteristics leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), and acid neutralization capacity (ANC) tests. The results were evaluated in order to determine if the solidified /stabilized product can be disposed of at a landfill site with domestic waste or at a segregated landfill. The effect of using sand on S/S performance was also investigated. The results indicated that the solidification /stabilization process using PC helps the heavy metals to be bound in the cement matrix, but the TCLP leaching results exceeded the EPA landfilling limits. The SPLP leaching results conformed to the limits implying that the waste or S/S products can be disposed of at a segregated landfill; however the low ANC of the S/S products reveals that there may be leaching in the long-term. The sand used in the mortar samples adversely affected the S/S performance, causing higher heavy metal leaching levels, and lower pH levels in the leachate after the TCLP extraction than those measured in the leachate of the paste samples.