Soil Profile Concentration Distributions of Antimony and Bismuth across Southeastern Missouri (USA)

Recent research has suggested that increased industrial and technological utilization of antimony and bismuth necessitates greater research to determine the soil and water chemistry and the environmental risks associated with these elements. The near-total soil profile concentrations of antimony and bismuth were determined for key soil series across southeastern Missouri. The antimony concentrations ranged from 0.65 to 0.08 mg kg−1, whereas the bismuth soil profile concentrations ranged from 0.92 to 0.03 mg kg−1. Most pedons showed antimony concentrations ranging from 20 to 30 mg kg−1, whereas bismuth concentrations were commonly 10 to 20 mg kg−1. For soils having argillic horizons, antimony and bismuth concentrations were greater for the illuvial horizons than the eluvial horizons, whereas Entisols, Inceptisols, and one Vertisol showed rather uniform antimony and bismuth concentrations, features paralleling the soil texture distribution. Both antimony and bismuth showed significant correlations with iron.

Effect of Lanthanum on Quantity of Major Microorganism Groups in Yellow Cinnamon Soil

Different accumulations of La in yellow cinnamon soil were simulated as results of long term application of rare earth elements and dosage response curves of three major soil microorganism groups and three physiological groups were obtained. La accumulated from 5%～50% of adsorption capacity(ADC) had inhibitory effects on the total number of bacteria in soil. La accumulated below 30% ADC stimulated the growth of actinomycetes with the highest effect at 20% ADC. The total number of fungi was strongly stimulated by La up to 50% ADC with the highest effect at 30% ADC. The aerobic cellulolytic bacteria and celluloloytic fungi were stimulated by La below 10% ADC and up to 50% ADC, respectively. La above 10% ADC had very strong inhibitory effects on soil ammonifiers.

3D finite element analysis on pile-soil interaction of passive pile group

The interaction between pile and soft soil of the passive pile group subjected to soil movement was analyzed with three-dimensional finite element model by using ANSYS software. The soil was assumed to be elastic-plastic complying with the Drucker-Prager yield criterion in the analysis. The large displacement of soil was considered and contact elements were used to evaluate the interaction between pile and soil. The influences of soil depth of layer and number of piles on the lateral pressure of the pile were investigated, and the lateral pressure distributions on the (2×1) pile group and on the (2×2) pile group were compared. The results show that the adjacent surcharge may result in significant lateral movement of the soft soil and considerable pressure on the pile. The pressure acting on the row near the surcharge is higher than that on the other row, due to the "barrier" and arching effects in pile groups. The passive load and its distribution should be taken into account in the design of the passive piles.

Effect of Cultivation on Spatial Distribution of Nematode Trophic Groups in Black Soil

Geostatistics combined with GIS was applied to assess the spatial distribution of nematode trophic groups following two contrasting soil uses in the black soil region of Northeast China. Two plots, one with fallow for 12 years and the other cultivated, were marked on regular square grids with 2-m spacing. Soil samples were collected from each sampling point, nematodes were extracted from these samples and classified into four trophic groups: bacterivores, fungivores, plant parasites, and omnivores/predators. The numbers of total nematodes and trophic groups analyzed had normal distributions on both fallow and cultivated plots. The absolute abundances of total nematodes and trophic groups were observed to be much more homogeneous on cultivated plot than on fallow one. Geostatistical analysis showed that the densities of total nematodes and trophic groups on both fallow and cultivated plots exhibited spatial dependence at the sampled scale and their experimental semivariograms were adjusted to a spherical or exponential model, except those of bacterivores and fungivores on cultivated plot. The spatial distribution of nematode trophic groups was found to be different for the two land uses, indicating that cultivation changed the native condition for soil nematode activities.

Nitrogen additions inhibit nitrification in acidic soils in a subtropical pine plantation: effects of soil pH and compositional shifts in microbial groups

Plantation forests play a pivotal role in carbon sequestration in terrestrial ecosystems, but enhanced nitrogen(N) deposition in these forests may affect plantation productivity by altering soil N cycling. Hence,understanding how simulated N deposition affects the rate and direction of soil N transformation is critically important in predicting responses of plantation productivity in the context of N loading. This study reports the effects of N addition rate(0, 40, and 120 kg N ha^(-1) a^(-1)) and form(NH_4Cl vs. NaNO_3) on net N mineralization and nitrification estimated by in situ soil core incubation and on-soil microbial biomass determined by the phospholipid fatty acid(PLFA) method in a subtropical pine plantation. N additions had no influences on net N mineralization throughout the year. Net nitrification rate was significantly reduced by additions of both NH_4Cl(71.5) and NaNO_3(47.1%) during the active growing season, with the stronger inhibitory effect at high N rates. Soil pH was markedly decreased by 0.16 units by NH_4Cl additions. N inputs significantly decreased the ratio of fungal-to-bacterial PLFAs on average by 0.28(49.1%) in November. Under NH_4Cl additions, nitrification was positively related with fungal biomass and soil pH. Under NaNO_3 additions,nitrification was positively related with all microbial groups except for bacterial biomass. We conclude that simulated N deposition inhibited net nitrification in the acidic soils of a subtropical plantation forest in China,primarily due to accelerated soil acidification and compositional shifts in microbial functional groups. These findings may facilitate a better mechanistic understanding of soil N cycling in the context of N loading.

Shake table test of soil-pile groups-bridge structure interaction in liquefiable ground

This paper describes a shake table test study on the seismic response of low-cap pile groups and a bridge structure in liquefiable ground. The soil profile, contained in a large-scale laminar shear box, consisted of a horizontally saturated sand layer overlaid with a silty clay layer, with the simulated low-cap pile groups embedded. The container was excited in three E1 Centro earthquake events of different levels. Test results indicate that excessive pore pressure （EPP） during slight shaking only slightly accumulated, and the accumulation mainly occurred during strong shaking. The EPP was gradually enhanced as the amplitude and duration of the input acceleration increased. The acceleration response of the sand was remarkably influenced by soil liquefaction. As soil liquefaction occurred, the peak sand displacement gradually lagged behind the input acceleration; meanwhile, the sand displacement exhibited an increasing effect on the bending moment of the pile, and acceleration responses of the pile and the sand layer gradually changed from decreasing to increasing in the vertical direction from the bottom to the top. A jump variation of the bending moment on the pile was observed near the soil interface in all three input earthquake events. It is thought that the shake table tests could provide the groundwork for further seismic performance studies of low-cap pile groups used in bridges located on liquefiable groun.

Indigenous Knowledge on Soil Classification of Ethnic Groups in Luang Prabang Province of the Lao PDR

The objectives of this study were to demonstrate ethno-scientific elicitation techniques in retrieving indigenous knowledge at village-level, and to document the indigenous soil classification systems of different ethnic groups in Luang Prabang province in the Lao PDR. The study area comprised three villages – Nambo, Huaymaha and Thapo, in the Phonxay district of Luang Prabang province. Three ethnic groups were covered by the study – Hmong, Khmu and Lao Loum. All three ethnic groups used soil color as main criteria for soil classification. However, even within the same ethnic group, sometimes different villages have differences in the way they classify soils; this was apparent for the Hmong ethnic group in the villages of Huaymaha and Nambo. A significant difference of the Lao Loum ethnic group from the other two, was the emphasis used in classifying soil types according to their water holding capabilities. In contrast, the Khmu and Hmong classified many soil types in relation to their rock content (‘with rock’ or ‘pure rock’ sometimesbeing used). The results of the study suggest that the ethnic groups classify the soils in relation to their potential for different types of agricultural production.

Dragload and Downdrag Performances of Inclined Pile Group Embedded in Consolidating Soil

The performance of inclined pile group embedded in consolidating soil under surcharge load was investigated by experiment in comparison with vertical pile group and single pile under the same conditions; dragload, downdrag, and layered soil settlement were measured. A three-dimensional numerical model was built via FLAC3D software, and verified by the experimental results. Influence factors, such as consolidation time, pile spacing, and pile tilt angle were analyzed. The results show that dragload of inclined pile group increases with the increase of consolidation time and pile spacing or the decrease of pile tilt angle. Downdrag of inclined pile group increases with the increase of consolidation time, pile spacing and pile tilt angle.

泥炭土腐殖酸环境室内模拟试验研究

为能提供一种贴合天然环境的泥炭土腐殖酸环境,通过在冲洪积黏性土中掺入胡敏酸(Humic Acid, HA)试剂和富里酸(Fulvic Acid, FA)试剂人工制备泥炭土试样,并将试样浸泡在富里酸液中来模拟泥炭土腐殖酸环境。采用腐殖酸含量检测试验、扫描电镜(Scanning Electron Microscope, SEM)、X射线衍射(X-Ray Diffraction, XRD)、X射线荧光光谱(X-Ray Fluorescence spectroscopy, XRF)和无侧限抗压强度(qu)试验来评估模拟效果及可行性。结果表明,在pH值为6.0的浸泡液中浸泡90 d后,试样中富里酸实测质量分数超过了初始掺量,而胡敏酸的实测质量分数相较于初始掺量表现出波动性。试样中孔隙随着腐殖酸掺量的增加而逐渐发育连通,试样所含的原生矿物主要为石英和云母,主要元素为O、Si、Al和Fe。通过与天然泥炭土环境对比分析,揭示了模拟的腐殖酸环境在微观特征上与天然腐殖酸环境具有相似性。宏观力学试验结果表明,模拟试样的qu随腐殖酸掺量的增加而降低,对比分析显示模拟试样的力学性能与天然泥炭土的力学性能接近。以上结果表明,采用所提出的方法可以模拟出与天然泥炭土环境相近的泥炭土腐殖酸环境。

种植模式对当归根际土壤真菌群落与功能类群的影响

再植障碍问题限制了当归产业健康发展。为了建立高效种植方式,在甘肃渭源县设置5种种植方式[A:豌豆-小麦-当归;B:豌豆-蒙古黄芪-当归;C:豌豆-马铃薯-当归;D:豌豆-当归-当归(对照);E:豌豆-休耕-当归],采挖期通过Illumina Hisqe 2500高通量测序平台测定了不同种植模式下当归根际土壤真菌ITS1变异区的基因序列,分析不同种植方式对当归根际土壤真菌群落和功能差异性的影响。结果表明:(1)5种种植方式下当归根际真菌多样性差异不大,较对照D处理,A、B、C和E处理的Chao1指数、Ace指数和Shannon指数较低,Simpson指数较高。(2)5种种植方式下当归根际土壤真菌群落隶属于11门167属,其中,子囊菌门(Ascomycota)、被孢菌门(Mortierellomycota)、担子菌亚门(Basidiomycota)和壶菌门(Chytridiomycota)为优势门;被孢霉属(Mortierella)、四枝孢属(Tetracladium)为优势属。(3)冗余度分析发现:在门水平影响土壤真菌群落结构组成的主要因子为速效钾、电导率、pH值,在属水平影响土壤真菌群落结构组成的主要因子为有机质、pH值、二氧化碳呼吸速率。(4)FUNGuild预测表明:植物病原体和木质腐生真菌功能群的相对丰度较高。综上所述,不同作物轮作较当归连作,降低了当归根际土壤真菌群落的相对丰度和多样性,有利于根际土壤真菌群落向有益的方向发展。

Numerical Study of Piles Group under Seismic Loading in Frictinal Soil—Inclination Effect

Recent devastating earthquakes in some countries, such as Pakistan, Turkey, Algeria and China, call to the mind the high risk exposure of Lebanon which is located over an active seismic zone. Many experts shared the view that major seismic event may occur in Lebanon in the future. Moreover, many earthquakes, of low magnitudes between three and four, have been registered in Lebanon during 2008. These events have increased the anxiety of Lebanese people because of the poor quality of the constructions and their behavior under moderate or severe earthquake events. The efficient way to minimize seismic effects, material and human losses, is the prevention. The system piles-foundation is an appropriate way and widely used to ensure the stability of constructions when subjected to seismic excitation. It seems necessary to study the interaction of pile-foundation-pile-cap-structure in the case of non linear soil behavior and the interface pile-soil. The study will be also conducted by using measures recorded during real earthquakes for example in Turkey (Kocaeli, 1999). In this paper, we present a numerical modeling of the interaction of using FLAC3D software. According to soil behavior and pile inclination, parametric studies are also performed. The analysis of the results could give the better piles group configuration in order to minimize the seismic effect on the structures.

1ZL-7.2型联合整地机的研制

整地作业可将犁耕后的土壤进行碎土、平整,为播种环节创造良好的作业条件,联合整地机在新疆已被广泛应用。近年来大中马力拖拉机保有量逐年增加,为提高整地作业幅宽和效率,研制了一款与大马力拖拉机相配套的联合作业机,开发了新型合金材料的耐磨耙片。作业幅宽为7.2 m,机架可以进行折叠便于运输。田间试验表明,该型机具作业效果良好,故障率低,操作简单、方便。

3种混交林造林初期土壤真菌群落结构特征

土壤微生物是参与陆地生态系统生物地球化学循环过程的重要成员。造林可以显著影响土壤微生物群落结构与功能,但造林初期驱动的土壤理化因子变化对土壤微生物结构与功能的影响尚不清楚。通过分析由珍稀乡土树种组成的三种新造混交林(BB:银杏Ginkgo biloba⁃桢楠Phoebe zhennan;CB:香椿Toona sinensis⁃红豆杉Taxus wallichiana⁃桢楠Phoebe zhennan;MB:鹅掌楸Liriodendron chinense⁃乐昌含笑Michelia chapensis⁃香椿Toona sinensis⁃玉兰Yulania denudata)表层(0—20 cm)土壤真菌群落组成、功能类群及其土壤理化因子,并以草灌化未造林地作对照(CK),研究土壤真菌群落结构和功能对不同林型造林初期的响应。结果表明:(1)不同林型土壤真菌群落丰富度、多样性指数高于CK,表现为MB>BB>CB>CK,主要受到土壤孔隙度、水解性氮的影响。(2)土壤真菌门水平优势类群在不同处理间无显著差异,其中子囊菌门占绝对优势,MB中的被孢霉门相对丰度显著高于CK(P<0.05)。与CK相比,球囊菌门与Leptodiscella相对丰度在各林型中均降低。(3)通过非度量多维尺度(NMDS)与置换多元方差(Adonis)分析表明,造林初期,造林土壤真菌群落结构与CK存在显著差异(P<0.01)。冗余分析(RDA)分析表明全钾、水解性氮、土壤容重及土壤碳氮比是影响真菌群落指示种的主要土壤理化因子;被孢霉门与水解性氮、碳氮比、全氮、非毛管孔隙度、含水率均呈正相关,与全钾呈负相关。(4)真菌群落主要以腐生营养型为主,病理营养型次之;造林后腐生营养型真菌相对丰度降低,而土壤腐生菌的相对丰度在BB与MB处理中反而显著增加(P<0.05);MB处理中动物病原菌的相对丰度显著增加(P<0.05);真菌优势功能类群主要受到土壤pH、土壤孔隙度、土壤碳氮比(C/N)、土壤有机质、全氮、全钾的影响。造林初期土壤真菌群落结构与功能类群发生了显著改变,阔阔混交林较针阔混交林变化更加明显,其中多种阔叶树混交林病原菌相对更高。

软土地层基坑群模型试验相似材料研制及应用

针对基坑群连续开挖存在的耦合效应问题,首先确定相似材料配比方案,通过正交试验得出合理的配比材料,进而设计基坑群模型试验来研究两侧基坑叠加作用影响下车站基坑的围护结构和土体表层变形.研究结果表明:满足该软土地层相似常数的土层材料配比为(石英砂∶滑石粉∶双飞粉∶膨润土∶水=0.27∶0.27∶0.232∶0.058∶0.17);基坑群开挖时由于相邻墙体引起的墙后土拱效应叠加导致坑间土体水平应力降低,围护结构受力和变形量减小,坑间土体沉降量增大;基坑间距是支护结构变形的主要影响因素,两侧基坑间距位于1H~2H之间(H为基坑深度),接近1倍开挖深度一侧的叠加影响大于接近2倍开挖深度一侧.

青藏高原高寒草甸地上植物功能群去除对土壤线虫群落的影响

土壤线虫对高寒草甸生态系统功能有重要的指示作用,植物功能群丧失对土壤线虫群落的影响尚不清楚。本研究在青藏高原东部的高寒草甸生态系统中设置对照、保留豆科、保留禾状草、保留非豆科杂类草和去除所有植物功能群5个处理的地上部植物功能群去除实验,以探究植物功能群损失对土壤线虫群落的影响。结果显示:(1)去除植物功能群地上部对植物根系生物量和土壤线虫总密度影响不显著。(2)去除植物功能群地上部对线虫不同营养类群相对丰度影响显著。保留豆科处理下,食细菌线虫相对丰度整体最高,而植物寄生线虫相对丰度最低;保留杂类草处理下,植物寄生线虫相对丰度整体最高,而食细菌线虫相对丰度最低。(3)非度量多维尺度分析(NMDS)结果表明,去除不同植物功能群会导致土壤线虫类群产生差异,对土壤线虫群落结构产生显著影响。

无锡市区土体工程地质层组划分及其应用

无锡市区地处太湖冲湖积平原区,第四纪松散沉积物较厚,城市建设多以土体为载体,土体结构质量关系到工程建设的成本和周期,但长期以来无锡市区土体工程地质层组划分并无统一标准,地层代号编码混乱,严重降低了工程地质资料的可重复利用率。为提高无锡市区工程地质资料的通用性,使其利用价值最大化,文章基于大量地质钻孔和土体参数测试数据,对比区域地层资料,综合考虑研究区沉积演化特征、土体物质组成及工程特性等因素,采用绘制工程地质剖面的方法建立地层层序结构和编码规则,将无锡市区100 m以浅的土体划分为9个工程地质层组和27个工程地质亚层。利用土体参数的离散性和三维地质结构模型分析了该工程地质层组划分方案的合理性,并探讨了该划分结果在优势持力层的选择、地下空间开发利用适宜性评价和浅层地热能开发利用中的应用。结果显示,该土体工程地质层组划分方案能准确地反映无锡市区100 m以浅的土体结构,划分方案合理正确。

亚热带4种林分土壤真菌群落结构及功能

【目的】探究亚热带地区不同林分类型土壤变化特征及真菌群落结构和功能差异,为该地区人工林和次生林的营林管理及土壤养分研究提供理论参考。【方法】利用高通量测序技术,对亚热带典型人工林杉木和马尾松,以及次生林甜槠和针阔混交林的土壤真菌群落结构、功能差异及其与土壤理化性质的相互关系进行分析。【结果】4种林分的土壤优势真菌门类群为担子菌门和子囊菌门,优势真菌科为红菇科与蜡伞科。土壤真菌群落的α多样性表现为杉木人工林>马尾松人工林>混交林>甜槠林;群落的β多样性在4种林分中存在显著差异。对于真菌功能群,杉木林与其他3种林分的土壤真菌的优势营养模式具有显著差异。杉木林以腐生营养型为主,其次为共生营养型,病理营养型比例最低;而马尾松林、甜槠林和混交林主要以共生营养型为主,其次是腐生营养型,病理营养型比例最低。在以共生营养型为主的林分中,马尾松林的真菌共生营养型相比阔叶林和混交林减少,而病理营养型增加。土壤pH、速效钾(AK)及铵态氮(NH+4)是影响土壤真菌群落结构和功能的主要因素。【结论】不同林分类型土壤真菌群落结构和功能特征差异明显,并与土壤因子密切相关。

基于土壤线虫群落成熟度指数的拉沙山土壤生态系统稳定性评价及可行性研究

土壤生态系统被誉为是生物圈的能量储存介质,稳定健康的土壤生态系统是维持陆地生态系统生产力的关键,但系统内部各种生物作用和复杂过程很难直接观测,很难利用陆地生态系统的评价体系评价其稳定性。近年来土壤线虫群落成熟度指数作为土壤生态系统稳定性的指示类群被广泛认可和利用,拟通过拉沙山区域13个固定大样地中的52个样方的土壤线虫成熟度指数对区域土壤生态系统稳定性进行评价,并对评价的可行性进行验证。采用宏基因技术共获取线虫扩增子序列变体(Amplicon Sequence Variant, ASV)963个,隶属于2纲10目41科67属,群落结构以食细菌线虫和捕食-杂食类线虫为主,群落以K—策略者(c-p 3—5)生活类群为主导。研究结果表明,土壤线虫的成熟度指数均值为3.24±0.32,评价结果认为拉沙山区域土壤生态系统整体较为稳定,且土壤线虫成熟度指数在空间上不存在统计差异(P>0.05)。通过利用样地监测获得的人为干扰强度与利用土壤线虫成熟度指数所评价出的结果呈现显著的负相关关系(P<0.05),表明稳定性较低的样地其人类活动干扰也较大;同时对土壤线虫成熟度指数的评价结果与样地地表生态系统现状验证结果显示,在中海拔的区域主要因其河谷较深,同时两侧山体陡峭且时有塌方发生导致土壤生态系统的不稳定且土壤线虫成熟度指数偏低,评价结果与实际地表生境状态相符,所以利用土壤线虫成熟度指数评价区域大样地是可行的,该研究为未来区域的土壤生态系统健康评价完善提供了新的指标。

不同生态类群蚯蚓对凋落物源碳在土壤团聚体中的分配的影响

[目的]通过研究不同生态型蚯蚓作用下凋落物源碳在土壤中的转化与分配规律,揭示凋落物源碳在土壤中的去向,为深入探究蚯蚓对杨树人工林土壤固碳增汇潜力的影响提供理论依据和数据支撑。[方法]应用脉冲标记法标记富集^(13)C的杨树幼苗叶片;接种3种不同生态型蚯蚓,通过室内短期培养试验(室温25℃,培养120 d),研究不同生态型蚯蚓作用下凋落物源碳在粗大团聚体(d>2 mm)、细大团聚体(2 mm≥d>0.25mm)、微团聚体(0.25 mm≥d>0.053 mm)和粉-黏团聚体(d≤0.053 mm)4个粒径级别的水稳性团聚体中的分配。[结果]接种蚯蚓后,显著促进了凋落物源碳向土壤中的并入与分配,土壤δ^(13)C值显著提高,单独接种表栖型蚯蚓提升的幅度最低,表栖型和表-内栖型共同作用提升的幅度最高;不同粒级土壤水稳性团聚体的δ^(13)C值在蚯蚓的作用下均显著升高;4种土壤团聚体的δ^(13)C值,都是粉-黏团聚体的最低,粗大团聚体和细大团聚体中最高,接种赤子爱胜蚓对凋落物向土壤团聚体中并入作用效果低于接种皮质远盲蚓和威廉环毛蚓。[结论]120 d的短期培养内,不同生态型蚯蚓作用显著促进凋落物源碳向土壤中的并入与分配,更是显著增加了凋落物源碳在粗大团聚体和细大团聚体中的积累,且在表-内栖型蚯蚓和深栖型参与作用下,更显著提高了凋落物源碳向团聚体中的分配。建议可以在林业生产经营过程中适当增加林木凋落物残体的施用,同时考虑不同生态型蚯蚓之间的协同和竞争作用,接种多种类型蚯蚓以改善或增强蚯蚓调节林业生态系统中土壤有机碳(SOC)动态的潜能,加速土壤中外源有机质向土壤中的并入与分配。

虹吸排水法处理软土地基的水位与沉降计算模型

软土具有渗透性差、承载力低等特性,软土地基的处理一直是岩土工程中的一大难题。利用虹吸免动力排水的特点,可将虹吸排水法应用于软土地基处理中,达到改善土体性质的目的。本文针对虹吸排水法独特的定降深降水模式,先基于离散化的Theis井流模型以及非线性的分层总和法,构建了以孔隙率为核心、渗透系数与压缩模量随固结情况改变的水位与沉降动态计算模型,并与数值模拟结果对比,然后从土体渗透系数、排水板间距以及场地大小3个方面对虹吸排水法处理软土地基的效果进行了分析。结果表明:数值模拟结果验证了计算模型的可靠性,对于浙江沿海不同渗透系数的土体,虹吸排水法均可起到良好的排水固结作用;调整排水板间距可对排水固结时间以及地下水位线起到显著控制作用;排水带来的附加应力随着场地面积的增大向土体深处延伸,对于面积50 m×50 m大小的场地,有效影响深度可达到地表以下27.31 m,远远超出虹吸扬程的极限。在实际的大面积软土地基处理中,虹吸排水法可发挥更好的作用。