微咸水矿化度对土壤水盐运移的影响研究

日益短缺的淡水资源严重影响着工农业生产,开发、利用微咸水进行农田灌溉具有重要意义。本文通过微咸水室内一维垂直入渗试验,研究了钠吸附比（SAR）相同条件下,矿化度单一指标对土壤水盐运移特征的影响。结果表明土壤导水和持水能力随入渗水矿化度的增加而增大．矿化度大于3g／L时,增加幅度减小;土壤含盐量随入渗水矿化度的增加明显增大,矿化度大于3g／L时,土壤基本处于积盐状态;不同矿化度水入渗后5～40cm土层土壤浸提液SAR均小于入渗水钠吸附比8,但大于土壤浸提液初始钠吸附比。因此在此种土壤理化条件下,入渗水SAR为8h,矿化度为3g／L是土壤安全灌溉的上限。     

Mitigation of soil liquefaction using microbially induced desaturation

Soil liquefaction can cause disastrous consequences to buildings and human lives. Regular countermeasures against soil liquefaction are often overly expensive for normal buildings and structures. This could be the major reason that liquefaction induced damage is still widely encountered in large- and mid-size earthquakes in recent years. In this paper, a new method for the mitigation of soil liquefaction using the microbially induced soil desaturation is proposed and tested. The desaturation effect in soil is achieved by the generation of nitrogen gas produced from the microbial denitrification process. Some major issues related to this method are experimentally investigated. These include soil desaturation procedures, shapes and distribution of gas bubbles in soil, mechanical responses and liquefaction resistance of desaturated soils, and stability of gas in soils. The desaturation treatment of soils is made simply by introducing denitrifying bacteria and a desaturation solution into soil pores by mixing, flushing, or injection. The degree of saturation can be reduced as the microbial reaction proceeds. Experimental results show that the final degree of saturation is related to the initial nitrate concentration added to the soil: the higher the concentration of nitrate in the desaturation solution, the lower the degree of saturation that can be achieved. The existence of gas bubbles in soil is evidenced by computer tomography (CT) technology. The CT images reveal that gas is in the form of small pockets which has a size a little larger than the mean size of sand grains. It is shown in the shaking table tests that microbially induced desaturation can effectively improve the liquefaction resistance of soil by showing a much lower pore pressure generation, much smaller volumetric strain, and much smaller settlement of the structure in desaturated soil, as compared with those in saturated soil. Triaxial consolidated undrained tests reveal that the desaturation treatment of soil can improve the undrained shear strength of loose sand. The stability of gas is tested under hydrostatic and water flow conditions. The gas phase is stable under the hydrostatic condition, but unstable under water flow conditions. So measures ought to be taken to prevent steady flow in practice.     

几种水稻土对磷的吸附及解吸特性研究

水稻土对磷的吸附曲线与简单Ｌａｎｇｍｕｉｒ等温吸附方程基本吻合,土壤对磷的吸附及解吸能力主要受土壤物理性粘粒含量及土壤活性铁、活性铝含量的影响,而与土壤本身有效磷含量无关。同一种水稻土随吸附磷量的增加,其解吸率有增加的趋势     

Chelators effect on soil Cu extractability and uptake byElsholtzia splendens

Phytoremediation is emerging as a potential cost-effective solution for remediation of contaminated soils, and bioavailability of metal in the soil for plant uptake is an important factor for successful phytoremediation. This study aimed at investigating the ability of EDTA and citric acid for enhancing soil bioavailability of Cu and phytoremediation by Elsholtzia splendens in two types of soils contaminated with heavy metals [i.e. mined soil from copper mining area (MS), and paddy soil (PS) polluted by copper refining]. The results showed that addition of 2.5 mmol/kg EDTA significantly increased the H₂O extractable Cu concentration from 1.20 to 15.78 mg/kg in MS and from 0.26 to 15.72 mg/kg in PS, and that shoot Cu concentration increased 4-fold and 8-fold as compared to the control. There was no significant difference between the treatment with 5.0 mmol/kg EDTA and that with 2.5 mmol/kg EDTA, probably because that 2.5 mmol/kg EDTA was enough for elevating Cu bioavailability to the maximum level. As compared with the control, citric acid had no marked effect on both soil extractable Cu and shoot Cu concentration or accumulation. The results indicated that EDTA addition can increase the potential and efficiency of Cu phytoextraction byE. splendens in polluted soils. Project supported by the National Natural Science Foundation of China (No. 29977017) and the Science and Technology Ministry of China (No. 2002CB410804)     

浸水培养法测定土壤水溶硅的研究

选用石灰性及中性土壤 ,研究了浸水培养法测出的水溶性硅和 pH4.0醋酸一醋酸钠缓冲液浸提法测出的有效硅之间的关系 ,并试验了在 40℃下浸水培养法的浸水时间对水溶性硅的影响 ,结果表明 :土壤浸水培养一周 ,水溶硅的释放便趋于稳定 ,在酸性和中性土壤上 ,用两种方法测出的硅含量极显相关 (r=0 .95 14) ,而在石灰性土壤上水溶硅与有效硅无任何相关     

Evaluation of spatial and vertical variability of nitrogen and phosphorus in sewage-irrigated soil in Tongliao, China

The reuse of wastewater for the irrigation of farmlands is gaining popularity, and the nutrient leaching associated with wastewater irrigation is becoming a matter of concern. The variability of nitrogen and phosphorus fractions in wastewater-irrigated soil was investigated in both horizontal and vertical directions in Kongjiaxiang, Tongliao, Inner Mongolia, China. The results showed that wastewater irrigation resulted in the concentrations of available N and P being 40.36% and 66.49% higher, respectively, than those with groundwater irrigation. Different forms of N and P exhibited significantly different distribution patterns. Higher concentrations of NO3- and total available N, as well as of those of Ca-P and total available P were observed near wastewater irrigation channels. Ca-P has a spatial distribution pattern similar to that of available P. The concentrations of NO3- and NH4+ were the highest in top soil and decreased with depth. The complex interactions between nitrate leaching and nitrogen transformation processes (e.g., nitrification, denitrification, and mineralization) determined the vertical profile of NO3- . The significant amount of NH4+ loss inhibited its deep seepage. The Ca-bound compound contained more P than other inorganic fractions as a result of high Ca levels throughout the soil profile. The differences in the concentrations of Ca-bound P at different depths could be due to the upward flux or translocation of Ca from subsurface to surface soil and the sequestration of P.     

盐渍土水分下渗能力及水盐动态运移试验

为探究盐渍化土壤水分下渗规律、水分下渗能力及水盐动态运移过程,设计了土壤剖面分层定水头供水及土壤剖面变水头供水下渗实验。测定不同层位土壤水分下渗率、含水率、孔隙水溶液电导率及土壤体电导率等参数,进行入渗条件下水盐动态运移规律分析。试验结果表明:盐渍化土水分下渗规律可由积水入渗Kostiakov模型进行刻画;浅层0~40 cm土壤相对于深层40~60 cm土壤具有较强的拦截和贮存入渗水分能力;盐渍化土壤盐分变动带位于浅层0~40 cm,且20~40 cm深度的土壤盐分波动幅度较大,深层40~60 cm土壤孔隙水溶液盐分向下运移的通量与土壤体盐分对其的补充量达到动态平衡,水分下渗过程中深层土壤孔隙水盐分含量相对平稳。实验结果为盐渍土的防治提供参考。     

钾离子在粘性土中扩散运移的影响因素

为了研究日本九州地区的2种区域性土———有明粘土和赤土作为废弃物填埋场底部粘土衬垫层的适应性,做了一系列室内扩散试验.应用软件Pollute V6·3模拟计算了实验结果,反算出了钾离子的扩散系数.研究结果表明,有明粘土的扩散系数比赤土的扩散系数小,说明有明粘土有望能作为更合适的粘土衬垫材料.通过对比试验研究,发现在混合溶液的情况下,钾离子的扩散系数较在单一溶液的钾离子的扩散系数小.因此建议尽可能使用与现场淋滤液成分相近的混合溶液来做扩散试验,以求出扩散系数来作为废弃物填埋场的设计和性能评估参数.     

Study on a calibration equation for soil water content in field tests using time domain reflectometry

The crucial point in calibrating soil water content using the technology of time domain reflectometry (TDR) is to establish the relationship between the apparent dielectric constant and the water content. Based on a database, which included 45 kinds of soil samples and 418 data points from our own test data and relevant literature, an empirical calibration equation is proposed. Additionally, the influence of soil type, dry density of soil, compaction energy, pore fluid conductivity, and temperature on the calculated result for water content was also analyzed. Results show that the equation can offer an error of ±0.05 g/g for most soils encountered in geotechnical engineering. However, the estimation error given by the empirical equation becomes significant for soils with dry density less than 1.3 g/cm³, so the equation was modified to consider the influence of dry density. Both of the empirical equations can be used to test gravimetric water content using the TDR method conveniently and efficiently without calibration.     

Water and heat transport in hilly red soil of southern China： I. Experiment and analysis

INTRODUCTION Located in subtropical monsoon area, the redsoil region in western Zhejiang, China, is one of themain cash crop production bases of this province. Dueto the climate, the temporal and spatial distribution ofrainfall varies greatly in this region. Only 15 percentof rainfall occurs in summer (July, August and Sep-tember), while about 60 percent of rainfall occurs inspring (from March to June). The region suffersdrought in summer and waterlogging in spring. Theparent ma…     

Chelators effect on soil Cu extractability and uptake by Elsholtzia splendens

INTRODUCTIONPhytoremediation,thatuseofgreenplantstodecontaminateCuandotherheavymetalsinsoils,isanemergingtechniquewithadvantagesofbeinginsitu,cost-effectiveandenvironmentallysus-tainable(Chanyetal.,1997;Cunninghametal.,1997;Saltetal.,1998).Theavailabilityofmetalinthesoilforplantuptakeisoneimportantlimitationforsuccessfulphytoremediation(Blaylocketal.,1997).Forexample,lead(Pb)isoneofthemostimportantenvironmentalpollutants,haslimitedsolubilityinsoils,andisavailableforplantuptakeduetocompl…     

Chelators effect on soil Cu extractability and uptake by Elsholtzia splendens

Phytoremediation is emerging as a potential cost-effective solution for remediation of contaminated soils, and bioavailability of metal in the soil for plant uptake is an important factor for successful phytoremediation. This study aimed at investigating the ability of EDTA and citric acid for enhancing soil bioavailability of Cu and phytoremediation by Elsholtzia splendens in two types of soils contaminated with heavy metals [i.e. mined soil from copper mining area (MS), and paddy soil (PS) polluted by copper refining]. The results showed that addition of 2.5 mmol/kg EDTA significantly increased the H2O extractable Cu concentration from 1.20 to 15.78 mg/kg in MS and from 0.26 to 15.72 mg/kg in PS, and that shoot Cu concentration increased 4-fold and 8-fold as compared to the control. There was no significant difference between the treatment with 5.0 mmol/kg EDTA and that with 2.5 mmol/kg EDTA, probably because that 2.5 mmol/kg EDTA was enough for elevating Cu bioavailability to the maximum level. As compared with the control, citric acid had no marked effect on both soil extractable Cu and shoot Cu concentration or accumulation. The results indicated that EDTA addition can increase the potential and efficiency of Cu phytoextraction by E. splendens in polluted soils.     

三门峡黄河滩地土壤特性分析

本文对三门峡黄河滩地土壤进行了吸湿水含量、酸碱度、有效氮、有效磷和有机质含量分析。研究结果表明:河滩地种植黄豆可以改良土壤质地,调节PH值,增加土壤有效氮、有效磷和有机质含量,提高土壤肥力。     

Effect of land use on microbial biomass-C,-N and-P in red soils

Eleven red soils varying in land use and fertility status were used to examine the effect of land use on microbial biomass-C,-N and-P. Microbial biomass-C in the red soils ranged from about 68 mg C/kg to 225 mg C/kg, which is generally lower than that reported from other types of soil, probably because of low organic matter and high acidity in the red soils. Land use had considerable effects on the amounts of soilC _mic. TheC _mic was the lowest in eroded fallow land, followed by woodland, tea garden, citrus grove and fallow grassland, and the highest in vegetable and paddy fields. There was significant correlation betweenC _mic and organic matter content, suggesting that the influence of land use onC _mic is mainly related to the input and accumulation of organic matter. Microbial biomass-N in the soils ranged from 12.1 Nmg/kg to 31.7 Nmg/kg and was also affected by land use. The change ofN _mic with land use was similar to that ofC _mic. The microbial C/N ratio ranged from 5.2 to 9.9 and averaged 7.6. TheN _mic was significantly correlated with soil total N and available N. Microbial biomass-P in the soils ranged from 4.5 mg P/kg to 52.3 mg P/kg. The microbial C/P ratio was in the range of 4–23. TheP _mic was relatively less affected by land use due to differences in fertilization practices for various land use systems. Project (No. 40025104) supported by National Outstanding Youth Foundation of China     

One-dimensional coupled model for landfill gas and water transport in layered unsaturated soil cover systems

Cover systems are used to prevent water infiltration into a waste body. They also play an important role in controlling landfill gas transport from the waste body to the atmosphere. It is important to assess the flux of landfill gas at the surface of a cover system by considering the coupled effects of rainwater infiltration and gas transport in the cover soils. We have developed a 1D mathematical model for coupled transient gas and water transport in unsaturated cover soils. The coupled model was solved by the finite element method. Results obtained by the proposed model agreed well with experimental data. Based on the proposed solution, the influences of gas pressure, gas permeability, and the thickness of the cover soils on soil gas concentration profiles were investigated. The difference in soil gas concentration reached up to 31% as the thickness of cover increased from 1 to 2 m. Gas concentration at a depth of 0.2 m decreased by 6% as the amplitude of atmospheric gas pressure fluctuation increased from 20 to 100 Pa. The gas concentration increased by only 3% when gas permeability increased by a factor of 2 for a relatively long period of gas migration (e.g., 60 h) under the given conditions. Results suggest that both diffusion and advection should be considered when estimating gas transport in unsaturated cover soils. The numerical model can be used in the design of cover systems in relation to gas breakthrough time, breakthrough concentration, and flux.     

Effect of land use on microbial biomass-C, -N and -P in red soils

INTRODUCTIONTheimportanceofmicroorganismstosoilfer tilityandsoilqualityhasbeencommonlyaccept ed (Smithetal.,1 990 ;Brookes,1 995;Da lal,1 998;Wicketal.,1 998) .Soilmicrobialbiomassasanimportantmicrobialpropertyhasbeenextensivelystudiedsinceitisthelivingco…     

Computation of one-dimensional consolidation of double layered ground using differential quadrature method

The authors give the solution to the problem of one-dimensional consolidation of double-layered ground with the use of the differential quadrature method. Case studies showed that the computational results for pore-water pressure in soil layer agreed with those of analytical solution; and that in the computational results for the interface of soil layer also agreed with those of the analytical solution except for the small discrepancies during shortly after the start of computation. The advantages of the solution presented in this paper are that compared with the analytical solution, it avoids the cumbersome work in solving the transcendental equation for eigenvalues, and in the case of the Laplace transform solution, it can resolve the precision problem in the numerical solution of long time inverse Laplace transform. Because of the matrix form of the solution in this paper, it is convenient for formulating computational program for engineering practice. The formulas for calculating double-layered ground consolidation may be easily extended to the case of multi-layered soils. Project (No. RC9609) supported by the Zhejiang Provincial Natural Science Foundation of China     

Computation of one-dimensional consolidation of doublelayered ground using differential quadrature method

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Investigation of iodine concentration in salt,water and soil along the coast of Zhejiang,China

Objective: We aim to describe the environment iodine concentration in salt, water and soil along Zhejiang Province coast in the China foreland. It will be helpful for us to judge whether this area is insufficient in iodine and universal iodized salt is necessary or not. Methods: We collected iodized salt samples, drinking water samples (tap water in the towns, and well water or spring water in the villages), water samples from different sources (ditches, lakes, rivers) and soil samples through random sampling in June, 2005. Salt, water and soil iodine was detected by arsenic-cerium redox method. Statistical analysis was expressed as mean±SEMby Windows SPSS 13.0. Results: (1) The iodine concentration in salt was 27.9±4.33 mg/kg (n=108). (2) Seventy-five water samples were collected. The water iodine value was 0.6～84.8 μg/L (mean of 11.66 μg/L). The watershed along the Qiantang River has significantly higher iodine content than the water in Lin'an in mountain area (P＜0.01). The iodine content and mean iodine content of tap water, well or spring water and natural water sources were 4.30±2.43 μg/L (n=34), 23.59±27.74 μg/L (n=19)and 12.72±10.72 μg/L (n=22) respectively. This indicated that among environmental water sources, the ditch iodine content was the highest with river water iodine being the lowest (P＜0.01). (3) Soil iodine value was 0.11～2.93 mg/kg (mean of 1.32 mg/kg).Though there was no statistical difference of soil iodine in different districts (P=0.131), soil iodine content correlated positively with water iodine content. Conclusion: Iodine concentration in salt accords with national policy of adding iodine in salt. Foreland has more iodine in water than mountain area. The data reflected that water and soil iodine in foreland area was not high, which suggests universal iodized salt should be necessary. Environment iodine has relatively close association with pollution.     

低分子量有机酸对土壤磷素的活化效应

用室内培养法试验了草酸 ,柠檬酸和酒石酸对土壤磷的活化作用。结果表明 :有机酸对土壤磷的活化作用明显 ,三种有机酸的活化作用草酸 >柠檬酸 >酒石酸。活化作用随有机酸浓度提高而增强 ,试验的两种土壤培养96小时 ,土壤有效磷释放便基本达到最大值。在潮土上 ,草酸、柠檬酸、酒石酸处理土壤磷素最大释放率分别为 15 0 .9%、97.6 %和 2 3 .3 %。