含硫酸盐还原菌土壤中阴极保护对Q235钢腐蚀的影响

利用交流阻抗测试技术、扫描电镜及表面能谱、微生物分析等方法，研究了阴极保护对土壤中Q235钢硫酸盐还原菌腐蚀的影响.30天的实验结果表明，在相同的阴极极化电位下，有菌土壤中Q235钢所需要的阴极极化电流密度均大于灭菌土壤，有菌土壤中Q235钢的平均腐蚀速率均大于灭菌土壤.随着阴极极化电位负移的增大，有菌及灭菌土壤中Q235钢试件周围土壤逐渐呈碱性，有菌土壤中Q235钢试件周围土壤中硫酸盐还原菌数量逐渐减少，当阴极极化电位为-1050 mV时，Q235钢试件周围土壤中硫酸盐还原菌仍能够存活.     

在不同Cl-含量土壤中硫酸盐还原菌对Q235钢腐蚀的影响

利用交流阻抗测试技术、扫描电镜及表面能谱分析、失重法、微生物分析等方法，研究了在同一类型不同Cl-含量的土壤中，硫酸盐还原菌对Q235钢腐蚀的影响规律.136天的试验结果表明：随着土壤中Cl-含量的增大，Q235钢腐蚀速率也增大，当Cl-含量增大到0.5%时，腐蚀速率达到最大；随后腐蚀速率随着土壤中Cl-含量的增大而减小，当土壤中Cl-含量高于1%时，接菌土壤与灭菌土壤中Q235钢腐蚀速率相差不大.在土壤中Cl-含量低于1%时，接菌土壤中Q235钢腐蚀速率明显大于灭菌土壤的腐蚀速率；点蚀速率在不同Cl-含量的土壤中的变化规律与腐蚀速率的变化有所不同，点蚀速率基本随着土壤中Cl-含量的增加而增大.而且接菌土壤中的点蚀速率大于灭菌土壤的点蚀速率. TG174.5  硫酸盐还原菌； 含Cl-土壤； Q235钢； 微生物腐蚀 2003-01-13 2003-05-08     

考虑禁锢空气影响的层状土壤Green-Ampt入渗模型及试验验证

为考虑土壤孔隙中禁锢空气对入渗水流的阻滞作用,引入饱和度系数Sa（Sa小于1）来量化湿润区的饱和程度,建立了改进的层状土壤Green-Ampt入渗模型（MGAM）,并提出了由土壤物理特性参数估算Sa的计算公式。为检验MGAM的适用性,分别在室内长土柱和田间进行层状土壤的积水入渗试验,并采用MGAM、传统的Green-A...     

Residual phosphate fertilizer compounds in soils

A variety of P compounds can accumulate in soils as residues of fertilizer and may influence soil test versus plant yield relationships. This work evaluates specific chemical extractants for their capacity to identify such Al, Fe and Ca phosphates in soils as a basis for increasing the precision of yield prediction. Aluminium phosphate, iron phosphate, calcium phosphate (apatite) and P sorbed onto gibbsite, goethite and calcite were added to four Western Australian lateritic soils. These soils were then subjected to sequential selective extraction using a modified Chang and Jackson procedure in order to evaluate the selectivity of these extractants for the different forms of P with the sequence of extraction: 1 M NH₄Cl, 0.5 M NH₄F, 0.1 M NaOH + 1 M NaCl, citrate-dithionite-bicarbonate (CDB), 1 M NaOH and 1 M HCl. The results show that the procedure is not sufficiently specific and thus might be of little value for estimating the forms and amounts of residues of phosphate rock fertilizers in soils.     

SMC的制造工艺及成型技术

针对SMC在汽车工业中的应用,介绍了该塑料的材料选择、制造工艺、成型技术和急需研究开发的课题。     

NO and N2O emissions from savanna soils following the first simulated rains of the season

Data on the emissions of oxides of nitrogen from the soil during the early part of the wet season are reported for nutrient-rich and nutrient-poor sandy soils at Nylsvley, South Africa. The emissions of NO_x and N₂O following the first wetting event of the season are elevated relative to subsequent events. The observed high emission rates (76 ng N-NO m^-2 s^-1) are partially attributed to the sandiness of the soil, which permits NO to diffuse out of the soil rapidly. The pulse of high emissions following wetting is maintained for approximately 72 hours, thereafter continuing at around 20 ng NO m^-2 s^-1 while the soil remains moist. The initial pulse is suggested to be due to the accumulation of a substrate pool during the dry period, coupled with an inability of plants and microbes to use it effectively during the first few days after wetting. There were no significant differences in the peak or subsequent emission rates for either NO or N₂O between two sites of differing nitrogen mineralisation potentials. N₂O emissions averaged 8% of NO_x emissions. The enhanced emissions of NO_x which follow the first wetting after a prolonged dry period do not make a very large contribution to the annual gaseous N emission budget, but could be a significant contributor to the high tropospheric ozone levels observed over southern Africa in springtime.     

层状土壤条件下地下滴灌水氮运移模型及应用

基于土壤水分运动的动力学方程和溶质运移的对流-弥散方程,考虑地下滴灌灌水器流量随时间的变化,建立了层状土壤地下滴灌施用硝酸铵(NH4NO3)条件下水氮运移的数学模型。利用均质砂土(S)、均质壤土(L)、上砂下壤(SL)和砂土夹层(LSL)四种土壤的试验数据对模型进行了验证。结果指出,考虑土壤中灌水器流量随时间变化可稍改善土壤含水率和硝态氮的模拟精度。利用验证后的数学模型研究了灌水器流量(1.1、1.75和2.6L/h)、灌水器与犁底层相对位置对地下滴灌水氮分布的影响,模拟结果表明灌水器流量对含水率分布的影响不明显,但灌水器流量的增大可明显增加20~40cm土层硝态氮含量;灌水器与犁底层相对位置对水氮分布影响显著,灌水器位于犁底层中(埋深25cm)土壤表层干土层较薄、水氮向下运移深度较小,有利于减小土壤蒸发和避免水氮淋失。     

考虑变形非线性影响的有限土体土压力计算模型

分析了墙后有限土体的破坏模式及位移特征。对墙后土体梯形滑动楔体进行分区处理,分别采用薄层单元法建立了极限状态土压力强度一阶微分方程,导出了有限土体极限土压力理论公式。在此基础上,考虑土压力的非极限状态与极限状态的关联性,建立了土体位移与土压力的关系式,提出了考虑土体位移非线性影响的有限土体土压力计算模型。该模型可考虑围护结构挠曲变形等非线性位移对土压力发挥的影响,且参数简单物理意义明确。与试验实测数据对比表明,该方法相比规范方法更接近于实测值,可供相关设计计算参考。     

Energy flux characteristics of seismic waves at the interface between soil layers with different saturations

Based on the multiphase poroelasticity theory describing the propagation of waves in the unsaturated fluid-saturated porous medium, the reflection and transmission coefficients of the seismic waves at the interface between soil layers with different saturations are obtained. Our unsaturated model consists of a deformable skeleton in which two compressible and viscous fluids (i.e., water and gas) flow in the interstices. Three compressional waves (i.e., P1, P2, and P3 waves) and one shear (i.e., S wave) wave exist in the unsaturated soils. The expressions for the energy ratios of the various reflected and transmitted waves at the interface during the transmission and reflection processes are presented in explicit forms accordingly. At last, numerical computations are performed and the results obtained are respectively depicted graphically. The variation of the energy ratios with the incident angle, wave frequency and saturation degrees of the upper and lower soil layers is illustrated in detail. The calculation results show that the allocation of incident seismic waves at the interface is influenced not only by the angle and frequency of the incident seismic waves, but also by the saturations of the upper and lower soil layers. It is also verified that, at the interface, the sum of energy ratios of the reflected and transmitted waves is approximately equal to unity as was expected. This study is of importance to several fields such as geotechnical engineering, seismology, and geophysics.     

Zinc equilibria in submerged sodic soils as influenced by application of amendments

In a pot culture experiment, the effect of gypsum (50% of soil requirement), pyrites (equivalent to gypsum), farmyard manure (0.5 g per 100g soil) and Zn (10mg Zn kg^–1 soil) on Zn equilibria in Ghabdan and Langrian series of sodic soils was studied. The equilibrium soil solutions collected anaerobically after 1, 14, 28, 42, 56, 70 and 84 days of submergence were analysed for pH, EC, HCO₃ and Zn. Submergence markedly decreased soil solution pH and Zn up to 14 days and thereafter, the former slightly increased and the latter continued to decrease. Addition of amendments decreased soil solution pH in the order gypsum, pyrites and farmyard manure (FYM) and increased Zn concentration in the order FYM, gypsum and pyrites. The values of Zn potential (pZn + 2pOH) were within the range of pKsp for Zn(OH)₂-Zn²⁺ (aq) from 16 to 84 days of submergence in Ghabdan soil and from 9 to 42 days of submergence in Langrian soil, where later it shifted to ZnCO₃-Zn²⁺ (aq) system. Addition of FYM, pyrites and gypsum shortened the period of predominant existence of Zn(OH)₂-Zn²⁺ (aq) system to 40, 30 and 12 days in Ghabdan soil and 30, 20 and 6 days in Langrian soil respectively. After these periods the system was saturated with respect to ZnCO₃-Zn²⁺ (aq) except gypsum treatment where Zn-soil (unknown solid phases) -Zn²⁺ (aq) system controlled the solubility of Zn after 38 and 28 days of submergence of Ghabdan and Langrian soil respectively.