Influence of expanded polystyrene size on deformation characteristics of light weight soil

Deformation characteristics of light weight soil with different EPS (expanded polystyrene) sizes were investigated by consolidation tests.The results show that the confined stress-strain relation curve is in S shape,which has a good homologous relation with e-p curve and e-lgp curve,and three types of curves reflect obvious structural characteristics of light weight soil.When cement mixed ratio and EPS volume ratio are the same for different specimens,structural strength decreases with the increase of EPS size,but compressibility indexes basically keep unchanged within the structural strength.The settlement of light weight soil can be divided into instantaneous settlement and primary consolidation settlement.It has no obvious rheology property,and 90% of total consolidation deformation can be finished in 1 min.Settlement-time relation of light weight soil can be predicted by the hyperbolic model.S-lgt curve of light weight soil is not in anti-S shape.It is proved that there is no secondary consolidation section,so consolidation coefficient cannot be obtained by time logarithm method.Structural strength and unit price decrease with the increase of EPS size,but the reducing rate of the structural strength is lower than that of the unit price,so the cost of mixed soil can be reduced by increasing the EPS size.The EPS beads with 3-5 mm in diameter are suggested to be used in the construction process,and the prescription of mixed soil can be optimized.

Effects of soil moisture and light intensity on ecophysiological characteristics of Amorpha fruticosa seedlings

We investigated the combined effects of soil moisture and light intensity on the growth, development and ecophysiological characteristics of one-year old Amorpha fruticosa seedlings. Soil moisture and light intensity influenced the ecophysiological characteristics of Amorpha fruticosa seedlings. Soil moisture resulted in the decreases of growth rate, individual size, net photosynthetic rate, transpiration rate, leaf water loss rate （WLR）, and biomass accumulation of plant parts, and led to increased leaf water saturation deficit （WSD）. Under water stress, more photosynthetic products were allocated to root growth. With decreasing light intensity, net photosynthetic rate, transpiration rate, chla/b, water saturation deficit, water use efficiency, water loss rate and biomass accumulation declined, while Chla, Chlb, Chla＋b and carotenoids （Car） increased and more photosynthetic products were allocated to stem and leaf growth. Maximum growth vigor, net photosynthetic rate and total biomass accumulation in Amorpha fruticosa seedlings was recorded at 75 80% soil water-holding capacity and 100% light density in greenhouse environments.

Relationship between light and heavy fractions of organic matter for several agricultural soils in China

Although numerous studies about the nature and turnover of soil organic matter（SOM） in light and heavy fractions（ LFOM and HFQM, respectively） have been made, little information is available in relation to the relationship between LFQM and HFOM, and no attempts have been made to quantify a general relationship between LFQM and HFQM for agricultural soils under field condition. Qur hypothesis is there may be an inherent relationship between LFQM and HFQM for agricultural soils under certain unaltered management practices for a long period, to this end, we therefore studied typically soils taken from different parts in China by using a simple density fractionation procedure. The results indicated that LFQM was positively correlated with LFOM/HFOM ratio for three typical soils. This information will be of particular use not only in deepening our understanding of the dynamics of SQM fractions but also in evaluating the potential of agricultural soils to sequestrate C under different management practices in a long term.

Correlations between Light Rare Earth Elements in Soil and Navel Orange Tree System in Gannan Area

The total content of light rare earth elements( LREEs) in the soil of navel orange orchards of Gannan area is greater than that of heavy rare earth elements( HREEs). Appropriate content of LREE can not only promote the growth of navel oranges,and it is also conducive to human health. On the basis of exploring the correlations between the content of LREE in the soil of navel orange orchards of Gannan area and the contents of LREE in navel orange leaves and fruit,the influence mechanism of LREEs on the quality of navel oranges was revealed. In this study,with two Newhall navel orange orchards with different soil LREEs background levels in Xinfeng County as the research object,the changes in the content of LREE( lanthanum,La; cerium,Ce; praseodymium,Pr; neodymium,Nd) in leaves and fruit of navel orange at different growth stages were analyzed using Inductively Coupled Plasma-Mass Spectrometry( ICP-MS),and the correlations between the content of LREE in the soil,navel orange leaves and navel orange fruit were studied. The results showed that the contents of the four kinds of LREEs in the soil ranked as Ce > La > Nd > Pr,and there were significant differences among them( P < 0. 01). Navel orange leaves and fruit have selective and heterogenic absorption for LREEs. At different growth stages,La showed the highest accumulation amount in the leaves and fruit of navel orange; and the content of LREE in the leaves of navel orange increased first and then decreased,while that in the fruit of navel orange showed continuous decrease. During the migration of LREEs from soil to leaves to fruit,the content of LREE decreased rapidly as the migration distance increased. The accumulation amount of LREE in navel orange was positively correlated with the content of LREE in the soil. The correlation between the content of LREE in the leaves and fruit of navel orange was greatest. Among the four kinds of LREEs,the correlation of La was greatest,followed by Ce,indicating that the accumulation amount of LREE in the navel orange body was affected by the element types.

Accumulation of soil organic carbon during natural restoration of desertified grassland in China's Horqin Sandy Land

China＇s Horqin Sandy Land,a formerly lush grassland,has experienced extensive desertification that caused considerable carbon（C） losses from the plant-soil system.Natural restoration through grazing exclusion is a widely suggested option to sequester C and to restore degraded land.In a desertified grassland,we investigated the C accumulation in the total and light fractions of the soil organic matter from 2005 to 2013 during natural restoration.To a depth of 20 cm,the light fraction organic carbon（LFOC） storage increased by 221 g C/m2（84%） and the total soil organic carbon（SOC） storage increased by 435 g C/m2（55%）.The light fraction dry matter content represented a small proportion of the total soil mass（ranging from 0.74% in 2005 to 1.39% in 2013）,but the proportion of total SOC storage accounted for by LFOC was remarkable（ranging from 33% to 40%）.The C sequestration averaged 28 g C/（m2·a） for LFOC and 54 g C/（m2·a） for total SOC.The total SOC was strongly and significantly positively linearly related to the light fraction dry matter content and the proportions of fine sand and silt＋clay.The light fraction organic matter played a major role in total SOC sequestration.Our results suggest that grazing exclusion can restore desertified grassland and has a high potential for sequestering SOC in the semiarid Horqin Sandy Land.

Effects of Caragana microphylla plantations on organic carbon sequestration in total and labile soil organic carbon fractions in the Horqin Sandy Land, northern China

Afforestation is conducive to soil carbon（C） sequestration in semi-arid regions. However, little is known about the effects of afforestation on sequestrations of total and labile soil organic carbon（SOC） fractions in semi-arid sandy lands. In the present study, we examined the effects of Caragana microphylla Lam. plantations with different ages（12-and 25-year-old） on sequestrations of total SOC as well as labile SOC fractions such as light fraction organic carbon（LFOC） and microbial biomass carbon（MBC）. The analyzed samples were taken from soil depths of 0–5 and 5–15 cm under two shrub-related scenarios： under shrubs and between shrubs with moving sand dunes as control sites in the Horqin Sandy Land of northern China. The results showed that the concentrations and storages of total SOC at soil depths of 0–5 and 5–15 cm were higher in 12-and 25-year-old C. microphylla plantations than in moving sand dunes（i.e., control sites）, with the highest value observed under shrubs in 25-year-old C. microphylla plantations. Furthermore, the concentrations and storages of LFOC and MBC showed similar patterns with those of total SOC at the same soil depth. The 12-year-old C. microphylla plantations had higher percentages of LFOC concentration to SOC concentration and MBC concentration to SOC concentration than the 25-year-old C. microphylla plantations and moving sand dunes at both soil depths. A significant positive correlation existed among SOC, LFOC, and MBC, implying that restoring the total and labile SOC fractions is possible by afforestation with C. microphylla shrubs in the Horqin Sandy Land. At soil depth of 0–15 cm, the accumulation rate of total SOC under shrubs was higher in young C. microphylla plantations（18.53 g C/（m^2·a）; 0–12 years） than in old C. microphylla plantations（16.24 g C/（m^2·a）; 12–25 years）, and the accumulation rates of LFOC and MBC under shrubs and between shrubs were also higher in young C. microphylla plantations than in old C. microphylla plantations. It can be concluded that the establishment of C. microphylla in the Horqin Sandy Land may be a good mitigation strategy for SOC sequestration in the surface soils.

Soil organic carbon pool along different altitudinal level in the Sygera Mountains, Tibetan Plateau

Labile organic carbon（LOC） is one of the most important indicators of soil organic matter quality and dynamics elevation and plays important function in the Tibetan Plateau climate. However, it is unknown what the sources and causes of LOC contamination are. In this study, soil organic carbon（SOC）, total nitrogen（TN）, microbial biomass carbon（MBC）, microbial biomass nitrogen（MBN） and LOC were analyzed based on different soil horizons and elevations using turnover time in an experimental site（3700 m to 4300 m area） in Sygera. SOC and LOC in higher-elevation vegetation types were higher than that of in lower-elevation vegetation types. Our results presented that the soil microbial biomass carbon（SMBC） and soil microbial biomass nitrogen（SMBN）were positively correlated with SOC. The content of easily oxidized carbon（EOC）, particulate organic carbon（POC） and light fraction organic carbon（LFOC） decreased with depth increasing and the content were the lowest in the 60 cm to 100 cm depth.The total SOC, ROC and POC contents decreased with increasing soil horizons. The SOC, TN, MBC and MBN contents increased with increasing altitude in the Sygera Mountains. The MBC and MBN contents weredifferent with the changes of SOC（p＆lt;0.05）,meanwhile, both LFOC and POC were related to total SOC（p＆lt;0.05）. The physical and chemical properties of soil, including temperature, humidity, and altitude,were involved in the regulation of SOC, TN, MBC,MBN and LFOC contents in the Sygera Mountains,Tibetan Plateau.

刚性挡土墙后轻量土静止土压力特性模型试验研究

为了研究轻量土对挡土结构物的减压机理,通过开展大比尺刚性挡土墙模型试验,采用重物堆载的方式在填土表面施加均布荷载,分析重塑黄土和轻量土作为墙后填土时的静止土压力分布规律。结果表明:轻量土在养护阶段的静止土压力随着时间增长而逐渐增大,但增幅逐渐降低。重塑黄土和轻量土的静止土压力随着填土深度增加近似线性增大,并且静止土压力随着加载而逐渐增大,其中重塑黄土的增幅明显偏大。对比重塑黄土和轻量土的静止土压力,发现轻量土具有明显的减压作用,且填土表面均布荷载越大,轻量土的减压效果越好。重塑黄土和轻量土的静止土压力系数均不是常数,其中重塑黄土静止土压力系数为0.34~0.78,轻量土静止土压力系数为0.22~0.55。当填土表面作用均布荷载时,传统理论在计算重塑黄土静止土压力方面适用性较高,但轻量土计算误差较大。结合模型试验以及传统理论,提出了适用于轻量土的静止土压力修正公式,对比发现其相对误差总体上介于1.01%~23.13%。通过模型试验和理论计算揭示了轻量土的静止土压力特性,对于完善轻量土土压力理论具有重要意义。

Conventional tillage improves the storage of soil organic carbon in heavy fractions in the Loess Plateau, China

Soil labile organic carbon （C） plays an important role in improving soil quality. The relatively stable fractions of soil organic C （SOC） represent the bulk of SOC, and are also the primary determinant of the long-term C balance of terrestrial ecosystems. Different land use types can influence the distribution patterns of different SOC fractions. However, the underlying mechanisms are not well understood. In the present study, different fractions of SOC were determined in two land use types： a grazed grassland （established on previously cultivated cropland 25 years ago, GG） and a long-term cultivated millet cropland （MC）. The results showed that C concentration and C storage of light fractions （LF） and heavy fractions （HF） presented different patterns along the soil profiles in the two sites. More plant residues in GG resulted in 91.9% higher LF storage at the 0-10 cm soil depth, further contributed to 21.9% higher SOC storage at this soil depth; SOC storage at 20-60 cm soil depth in MC was 98.8% higher than that in GG, which could be mainly attributed to the HF storage 104.5% higher than in GG. This might be caused by the long-term application of organic manure, as well as the protection from plough pan and silt- and clay-sized particles. The study indicated that different soil management practices in this region can greatly influence the variations of different SOC fractions, while the conventional tillage can greatly improve the storage of SOC by in- creasing heavy fractions.

北京山区黄栌叶片水分和光能利用效率季节变化及影响因子

未来气候变化将影响光合环境资源供给,尤其是水分和光能。为深入了解植物对气候变化的适应性,使用LI-6800便携式光合仪,于2021年5-10月份(完全展叶期)测定了北京山区广布灌木黄栌(Cotinus coggygria)叶片的光响应曲线,分析其水分利用效率(WUE=最大净光合速率[P_(nmax)]/气孔导度[g_(s)])和光能利用效率(LUE)的季节变化特征及影响因子。结果显示:黄栌叶片WUE在5-6月份呈下降趋势,7-10月份比较稳定;LUE在5-7月份呈上升趋势,8-10月份比较稳定。WUE和LUE的生长季平均值分别为98.25μmol/mol和0.06 mol/mol,变异系数分别为22%和17%,两者呈负相关(R^(2)=0.86;P<0.01)。环境因子中,WUE和LUE主要受土壤含水量(SWC)影响,WUE随SWC增加呈线性降低趋势,而LUE随SWC增加呈线性增加趋势。SWC每增加0.1 m^(3)/m^(3),P_(nmax)和g_(s)分别线性增加4.23μmol m^(-2)s^(-1)和0.07 mol m^(-2)s^(-1),即g_(s)对SWC变化的敏感性比P_(nmax)高。光合有效辐射(PAR)对WUE和LUE的影响不显著。生物因子中,比叶面积(SLA)是影响WUE和LUE的主要因子,WUE随SLA上升而上升,LUE随SLA上升而下降。叶氮含量(LNC)与WUE和LUE均不显著相关。SWC和SLA双因子线性回归模型均可以较好模拟WUE和LUE的季节变化,解释度分别为91%和71%,且其中SWC的标准回归系数较大,说明SWC是影响WUE和LUE变异的主导因子。结果表明SWC是限制黄栌叶片WUE和LUE的主要环境因子,SLA是调控WUE和LUE的关键生物因子,其中SWC起主要调控作用。研究结果利于深入了解北京山区灌木生态功能对未来气候变化的响应。

不同植被恢复类型下土壤碳含量对光伏组件遮阴的响应

【目的】探究云南石漠化脆弱区光伏场区不同植被恢复类型下,土壤微生物量碳(MBC)、可浸提有机碳(EOC)及总碳(TC)含量对光伏组件遮阴的响应特征,以期为石漠化脆弱区光伏电站退化土地生态恢复中的植被选型优化提供科学依据。【方法】2021年10月,在云南省昆明市东川光伏电站内,选取黄金菊(Euryops pectinatu)和红花檵木(Loropetalum chinense var.rubrum)2种人工建植植被样地,分别在每个样地的光伏板间(IP)、前檐(FP)、后檐(RP)、板下(UP)设置4个平行采样带,并以未受电站建设干扰的场外草地(以黄茅(Heteropogon contortus)为优势物种群落)样地作为对照(CK),测定2种植被恢复类型下光伏场区不同位置的光照强度以及表层(0~20 cm)的土壤温度、土壤碳(TC、MBC、EOC)含量以及土壤理化性质(pH、电导率、含水量),并分析光照强度、土壤温度、土壤碳含量以及土壤理化性质间的相关性。【结果】光伏场区不同位置的光照强度在07:00-19:00差异明显,且光照强度由大到小表现为对照>板间>前檐>后檐>板下,其中对照、后檐及板下位置的光照强度日变化均呈单峰变化,而板间和前檐位置的日变化均呈双峰变化趋势。场外的土壤温度明显高于光伏场区内,光伏场区不同位置的土壤温度差异较小。植被类型和光伏场区不同位置的光照异质性对土壤碳含量均有显著影响。在黄金菊样地,场区不同位置的土壤微生物量碳含量均较对照显著升高,其中前檐位置的土壤微生物量碳含量最高;在红花檵木样地,除了板间位置的土壤微生物量碳含量较对照显著降低外,其他位置均显著升高。2种植被恢复类型下不同位置土壤pH与对照无显著差异,土壤含水量和电导率均显著高于对照。相关性分析结果表明,光照强度与土壤微生物量碳含量和土壤含水量呈显著负相关,与可浸提有机碳含量、电导率、土壤温度呈显著正相关;土壤含水量与土壤可浸提有机碳和总碳含量均呈显著负相关(P<0.05)。【结论】在石漠化脆弱区的光伏场区,光伏组件遮阴与植被恢复均有利于提高土壤微生物量碳含量,但对可浸提有机碳和总碳含量的影响有一定差异,其中黄金菊样地的土壤可浸提有机碳和总碳含量明显高于对照。若短期内想达到较好的恢复效果,应优先选用黄金菊进行植被恢复。

冻融循环作用下不同路基材料力学特性对比研究

为探究寒区路基新型材料泡沫轻质土强度特性,完成了不同湿密度下的泡沫轻质土路基的冻融强度损伤试验。并将新型路基材料泡沫轻质土和传统路基材料水泥改良土进行对比发现:水泥改良土在冻融前期强度会大幅下降,但是在冻融循环5次左右,抗压强度会有回升趋势;而泡沫土从冻融开始到结束始终随冻融循环次数增加抗压强度缓慢下降。强度损失方面,2种路基材料的强度损失速率不同,水泥改良土抗压强度下降速率比泡沫轻质土更快。泡沫轻质土损失率随循环次数变化波动较小,相较为稳定。冻融循环对水泥改良土损失率影响离散型较大。

泥鳅扰动对稻田土壤孔隙水中砷的影响

为探究不同养殖密度(低密度、中密度、高密度)泥鳅扰动对土壤孔隙水中砷(As)含量的影响,采集湖南浏阳稻田表层土,以泥鳅为扰动生物,对泥鳅扰动土壤孔隙水中As含量变化进行研究,为进一步开展土壤-水环境中As循环研究提供基础数据。结果表明:泥鳅扰动后,土壤pH随时间先升高后降低,扩散层变宽,并逐渐向深层土壤扩散,泥鳅组土壤pH表现为:中密度组>低密度组>高密度组,低密度组和中密度组土壤溶解氧(DO)显著高于对照组和高密度组(P<0.05),中密度组土壤DO略高于低密度组,推测中密度组的扰动能力较其他密度组强;土壤-水界面pH和DO梯度变化明显,低密度组和中密度组土壤-水界面DO变化梯度较高密度组大,分层现象明显,各处理土壤体系DO表现为:土壤上覆水>土壤-水界面>土壤;泥鳅扰动促进了As由土壤向土壤上覆水迁移释放,显著增加了土壤上覆水As含量,其中低密度组促进效果较中密度组和高密度组显著;各处理土壤孔隙水As含量随时间逐渐减小(淹水期除外),从土壤深处向土壤-水界面迁移,总体呈现为土壤表层小于深层,泥鳅扰动能显著减少土壤孔隙水As含量,尤其对低密度组和中密度组土壤孔隙水As含量减少具有一定促进作用,同时也促进了土壤中As向土壤-水界面迁移释放;第7天时,泥鳅组土壤孔隙水As含量变化最显著,贯穿于整个土壤深度,低密度组As含量显著小于中密度组和高密度组,说明低密度组促进效果较中密度组和高密度组显著,这与土壤上覆水结果一致。研究表明,泥鳅扰动显著减少了土壤孔隙水As含量,其中低密度组和中密度组对不同深度土壤孔隙水As含量减少具有一定的促进作用,同时也促进了土壤中As向土壤-水界面迁移释放。

超细铁尾矿气泡混合轻质土优化设计研究

目的:为了实现超细铁尾矿在气泡混合轻质土中的高效利用,以最优力学性能为目标,进行了配合比优化设计。方法:基于BBD响应面曲面法,以尾矿掺量15%~30%、泡沫掺量4%~6%、水料比0.4~0.6为变量,以7 d和28 d抗压强度为响应值,设计了17组配合比,并分析了组成因素间的相互作用对抗压强度的影响程度。结果:泡沫掺量对超细铁尾矿气泡混合轻质土抗压强度影响最为显著,其次是水料比和尾矿掺量;从两因素交互作用上看,尾矿掺量和泡沫掺量交互作用对抗压强度影响最为显著;通过对回归模型的极值求解,当尾矿掺量为34.19%、泡沫掺量为4.34%、水料比为0.45时,超细铁尾矿气泡混合轻质土具有最优的力学性能。结论:经优化设计后的超细铁尾矿气泡混合轻质土可满足填筑工程技术要求。

桩托式路基形变特征现场试验研究

针对高填软土路基易滑塌失稳,提出了桩托式路基结构,并通过现场监测试验研究了桩托式路基的沉降变形特征。结果表明:1)封闭效应影响下,桩托式路基横断面内沉降形状呈现明显的“沉降盆”特征;2)路基竖向变形主要由地基沉降和轻质土路基自身的收缩变形两部分组成。

泡沫轻质土在深厚软土地基路堤中的应用探讨

以某软弱下卧层上的填方路堤为对象,阐述了应力补偿原理,并利用有限元软件模拟分析了换填泡沫轻质土道路的沉降及应力变化规律。分析结果表明:利用传统路基填筑材料修筑路堤时路基的沉降和差异沉降均较大,对软弱下卧层产生较大的附加应力,道路容易产生裂缝;利用泡沫轻质土换填处治软弱下卧层时,路基沉降和软弱下卧层顶竖向附加应力均随换填深度的增加而逐渐减小。综合考虑道路处治效果和耐久性等因素,拟推荐换填4 m方案为该填方道路的处治方案。

泡沫轻质土对高速公路改扩建新旧路基差异沉降的影响分析

依托某高速公路改扩建工程,研究新型材料泡沫轻质土作为填筑材料在路基工程中的应用效果。通过FLAC3D数值仿真软件,建立新旧路基模型,模拟新筑路基的沉降变化值,新建路基累计沉降值与距路基中心距离呈先增大后减小的趋势,距离路基中心12.5m处的沉降最大。对涵顶填土沉降在泡沫轻质土作用下的变化值进行了分析,阐述了泡沫轻质土的施工关键技术。

泡沫轻质土与水泥土搅拌桩在厚软土桥头路基处理中的应用

泡沫轻质土具有重量轻、固化后自立、耐久性高等优点,应用泡沫轻质土是目前解决道路改扩建路基处理、管线开挖回填处理、软土地基处理和桥头路基不均匀沉降等工程问题的有效措施。针对厚软土地基桥头路基处理,文中结合实际工程案例,分析了泡沫轻质土材料在厚软土桥头路基处理中的设计和应用,阐明了泡沫轻质土的特性和正台阶填筑设计施工方法。结果表明,采用泡沫轻质土进行厚软土桥头路基处理对控制地基不均匀沉降具有显著效果。

泡沫轻质土路基变形特性及施工工艺

在对泡沫轻质土的基本特性进行分析的基础上,以广连高速公路为例,对泡沫轻质土施工工艺(包括施工准备、路基垫层施工、分层分块施工、浇筑方法、纵横坡调整以及施工后养护)进行详细介绍,提出更为高效的填充方法。该填充方法值得在高速公路路基处理。

光照、磷和AMF对白车轴草生长的影响

外来植物成功入侵受非生物因素与生物因素的共同调控。本研究以典型入侵植物白车轴草(Trifolium repens L.)为研究对象,通过三因素两水平正交实验,探究光照(L)、磷(P)和丛枝菌根真菌(Arbuscular mycorrhizal fungi,AMF)及其交互作用对其生长的影响。结果显示:(1)高光照、高磷和接种AMF均显著提高白车轴草的生物量及生长速率,且接种AMF对生物量的促进作用随着光照的增加而增强,低磷条件下AMF对总生物量和相对生长速率的促进效应更明显;(2)高光照降低比叶面积;高磷和接种AMF显著增加叶片数和总叶面积,在高光强下尤为明显;(3)高光照可显著提高根表面积、根直径和根质量分数,但降低细根占比和比根长。高磷显著降低根质量分数。不接种AMF时,高磷增加根表面积与根直径,降低细根长占比;但接种AMF后,高磷则降低根表面积与根直径,增加细根长占比。AMF显著降低根质量分数和比根长。研究结果表明,三种因素对白车轴草的生长具有显著影响,且磷和AMF对其生长及地上性状的影响与光照强度相关,AMF对其地下性状的影响与磷浓度相关。