含岩屑紫色土水力特性及饱和导水率传递函数研究

紫色土中存在的岩石碎屑会对土壤的水力性质如饱和导水率、水分特征曲线产生显著影响。以两种不同母质发育的土壤(紫色页岩和紫色泥岩)为研究对象,设置0.25~2、2~5、5~10 mm三个岩屑粒径水平,0、30%、50%、70%、100%五个岩屑含量水平,采用压力膜仪法和定水头法分别测定水分特征曲线和土壤饱和导水率。利用BP神经网络,选择特定输入变量建立土壤饱和导水率传递函数PTF1和PTF2(PTF1的输入变量为岩屑含量、岩屑粒径、初始土壤容重和机械组成,PTF2的输入变量为岩屑含量、岩屑粒径、初始土壤容重、机械组成、进气压力值和S指数(土壤水分特征曲线拐点处斜率的绝对值))。结果表明:添加岩屑极大提高了土壤饱和导水率和S指数,并且随岩屑含量的增加而增加,相比之下,进气压力值随岩屑含量增加而减小,饱和导水率也随岩屑粒径的增加而增加,岩屑粒径从0.25~2 mm增加至5~10 mm,饱和导水率平均提高了2.3倍。岩屑粒径对进气压力值和S指数影响较小。PTF1和PTF2的几何平均数、几何标准偏差、均方根误差以及AIC指数分别为1.27、5.57、0.16、2.94和1.17、1.70、0.06、–53.28,PTF2的相关值均小于PTF1,表明PTF2模型的预测效果更好。综上所述,岩屑的存在显著影响了紫色土的水力特性,使饱和紫色土导水能力增加而保水能力减弱,利用神经网络所构建的传递函数PTF2可很好地实现含岩屑土壤饱和导水率的预测。     

科尔沁沙地土壤水分扩散率比较研究

利用水平土柱入渗法对科尔沁沙地的草地、固定沙丘和流动沙丘0~20 cm土层的土壤水分扩散率(D(θ))与土壤体积含水量(θ)之间的关系进行了测定,并建立了D(θ)和波尔兹曼参数(λ)与θ的定量关系。结果表明:(1)不同类型沙地0~20 cm土壤湿润峰迁移速率以草地的最小,其次为固定沙丘,而流动沙丘的最大,平均值分别为0.38、0.70和1.45 cm min-1;而且三类沙地土壤湿润峰迁移速率随入渗距离呈对数形式递减;(2)随着土壤体积含水量θ的增加,波尔兹曼参数λ逐渐减小,而且当θ达到某一临界值之后,λ急剧减少;(3)三类沙地D(θ)以草地和固定沙丘的较低,平均值分别为1.44和1.43 cm2min-1,而流动沙丘的较高,平均值为2.88 cm2min-1;土壤水分扩散率与土壤体积含水量的关系符合经验公式D(θ)=aebθ;(4)对科尔沁沙地土壤水分扩散率影响较大的土壤理化性质主要是有机质含量和粘粉粒含量。     

草原露天矿区劣质土壤水平扩散特征与模拟

为探究草原露天矿区不同类型土壤的水平扩散特征,以内蒙古鄂尔多斯市伊旗武家塔矿区的原状土、矿山堆积土和生态改造土3种不同立地类型的土壤为对象,通过土壤质地、扩散率、含水率等测试试验,采用HYDRUS-1D软件,对原状土、矿山堆积土和生态改造土入渗特性进行数值模拟,分析各因素对矿区土壤入渗规律的影响,探讨草原露天矿区不同类型土壤水平扩散过程的影响及变化规律。结果表明,在一维水平入渗运动条件下,原状土、堆积土、生态改造土3种不同粒径土壤的湿润锋运移距离与时间曲线整体呈现相似变化,随着入渗时间的增加,湿润锋运移距离呈现先快速增加,后缓慢推进趋势。同一种土壤类型条件下,土壤的湿润锋到达土柱最末端所需时间与土层深度呈反比关系,随着土层深度的增加,所需时间逐渐减少,且平均扩散速率更快;在同一入渗时间下,湿润锋运移距离与土层深度呈正比关系,随着土层深度增加,湿润锋运移距离也相应增大。Boltzmann参数(λ)随着土壤含水率的增加而逐渐减小,各土壤的λ～θ关系曲线随土壤含水率的增加呈现下降趋势。当θ达到某一临界值之后,λ急剧减少,原状土、堆积土和改造土各土层θ临界值略有差异,原状土各土层的θ临界值为0...     

压砂条件下灰钙土地区农田土壤水分垂直入渗特征研究

为探讨压砂条件下灰钙土水分垂直入渗特征,采用土柱模拟法,分别研究了压砂厚度、砂石粒径、土壤初始含水率及灌水量,对压砂条件下水分累计入渗量和土壤湿润锋的影响。结果表明:压砂条件下,土壤水分累计入渗量与入渗时间可以用正相关幂函数拟合。累计入渗量随着压砂厚度的增加呈增加趋势,入渗速率增加值的临界点是压砂厚度为15 cm;当砂石粒径为4.75 ~ 20 mm,明显促进水分垂直入渗过程,而砂石粒径20 ~ 40 mm及2 ~ 4.75 mm的处理,水分入渗速率变慢;土壤初始含水率增加,明显促进土壤水分垂直入渗;而灌水量从59 mm增加至177 mm时,有效促进水分入渗和湿润锋运移过程,但继续增加灌水量入渗过程则无显著性变化。     

辽西低山丘陵区坡地砾石含量及粒径对土壤入渗性能的影响

基于室内土柱模拟试验对比分析辽西低山丘陵区坡地不同粒径及砾石含量的土壤入渗规律,并采用4种模型分析了含砾石土壤对传统土壤入渗模型的适用性。结果表明:粒径一定时,随砾石含量的增加土壤累积入渗量减少,随累积入渗量的增加土柱湿润锋变化速率由小变大;砾石含量小于20%时,湿润锋前进到一定深度下,土壤累积入渗量随粒径的增加而增大;当砾石含量增大到一定值时,砾石含量相同直径不同的土壤累积入渗量与湿润锋随时间的变化基本无差异。累积入渗量与湿润锋推进距离呈良好的线性关系。利用Green-Ampt模型、通用模型、Horton模型和Kostiakov模型对入渗率与入渗历时的关系进行拟合,其中砾石含量为5%时,Horton模型拟合效果最好,砾石含量为10%~30%时通用模型适用性更强,Horton模型拟合效果最差,其他模型拟合效果因砾石含量及粒径等因素的不同而异。     

残膜对土壤水分水平运动的阻滞作用

为探明不同残膜量对土壤水分水平运动过程的影响规律,设置6个残膜量水平,分别为0,80,160,320,640,1 280kg/hm~2,采用室内水平土柱吸渗法,分析残膜对水平湿润锋运移、累积入渗量、Boltzmann系数和土壤水分扩散率的影响。结果表明:水平湿润锋运移速率、土壤含水率和累积入渗量均随残膜量增加而减小,残膜量≥160kg/hm~2时,水平湿润锋运移速率和累积入渗量大幅降低;残膜对土壤水分水平运动的阻滞系数与残膜量呈正相关关系,残膜阻滞系数的最大增长率出现在80~160kg/hm~2残膜量区间,高达251.15%;随残膜量的增加,阻滞作用较强区域距离入渗点的距离增大,Boltzmann系数和水分扩散率则逐渐减小,土壤基质势对水分水平运动的驱动作用和土壤持水能力逐渐减弱;混有残膜的土壤水分水平运动过程,仍符合土壤水分扩散率单一参数模型和Kostiakov入渗模型。残膜是一种难降解持续性污染物,会降低水平湿润锋运移速率、累积入渗量和土壤水分扩散率,对土壤水分水平运动的阻滞作用随残膜增多而增强。     

重庆紫色母岩及土壤As、Hg环境地球化学基线研究

为了掌握紫色土类中As和Hg在不同发育阶段土壤中元素含量的理论值(基线值),在重庆市合川区系统采集侏罗系沙溪庙组(J2s)紫色母岩及其不同发育程度的各土种样品,利用土壤"钛值"法测定和验证土壤发育程度;通过对土壤全量As、Hg的测定,采用标准化方法,建立紫色土类中灰棕紫泥土属As、Hg的环境地球化学基线模型。结果表明:侏罗系沙溪庙组(J2s)紫色母岩发育的土壤As、Hg的环境地球化学基线均表现为随土壤发育加深而轻度累积,As基线值大小顺序为母岩石骨子土半沙半泥土大眼泥紫黄泥,而Hg的基线值大小顺序为母岩石骨子土半沙半泥土紫黄泥大眼泥;Hg在土壤发育过程中的富集程度约大于As;深度发育土中As和Hg的化学基线值分别为5.94 mg kg-1、29.0μg kg-1,可作为重庆地区中性紫色土亚类、灰棕紫泥土属土壤污染评价的参考。     

红壤丘陵区不同盖度生物结皮对水分入渗的影响

为探究不同盖度生物结皮对入渗特征的影响,在红壤丘陵区咸宁选取第四纪黏土发育土壤(S型)和泥质页岩发育土壤(N型)上的生物结皮,设计6个盖度水平(裸地,1%~20%,20%~40%,40%~60%,60%~80%,80%~100%),使用微型圆盘入渗仪(mini disk)测定土壤入渗过程,探究入渗过程的影响因素,同时采用3种常见的入渗模型对入渗过程进行拟合,并评价模型适用性。结果表明:(1)相对于裸地,生物结皮发育提高土壤有机质和黏粒含量,增加结皮厚度和生物量,降低砂粒含量。(2)第四纪黏土发育土壤水分入渗特征随生物结皮盖度的增加而逐渐降低,初始入渗速率、稳定入渗速率、平均入渗速率、非饱和导水率的变化范围分别为0.25~1.55,0.13~0.91,0.17~1.11,2.04~8.48 mm/min。泥质页岩发育土壤除40%~60%盖度砾石含量较高,土壤水分入渗也随盖度的增加而逐渐减小,80%~100%盖度的初始、平均和稳定入渗率较裸地分别降低91.14%,87.64%和91.30%,生物结皮的存在阻碍土壤水分入渗。冗余分析表明,对于第四纪黏土发育土壤,生物量(54.30%)对其入渗特征的解释度最高,泥质页岩发育土壤则为盖度(39.30%)和砾石含量(34.00%)。(3)Horton模型、Kostiakov模型、Philip模型3种主流入渗模型中Horton模型拟合效果最优。研究结果可为揭示湿润区生物结皮水分运移规律提供科学参考。     

不同植烟年限对土壤团聚体稳定性的影响及其相关因素分析

通过野外调查、取样和室内分析,对凉攀地区不同植烟年限的土壤团聚体稳定性及其有机碳含量等相关影响因素进行研究。结果表明:水稳性团聚体在植烟0~5 a期间被显著破坏,红壤、紫色土和水稻土团聚体MWD值分别下降68%、64%和52%;非水稳性团聚体的破坏集中在植烟3~5 a期间,3种土壤团聚体MWD值依次分别下降31%、9%和17%。有机碳含量影响团聚体水稳定性,尤以水稻土和紫色土表现显著。有机碳主要分布在5 mm和0.25 mm粒径团聚体中,随植烟年限的增加,紫色土和水稻土各粒径团聚体有机碳含量显著降低,且5 mm和0.25 mm粒径团聚体下降最明显,各粒径团聚体中有机碳分布越均匀。烤烟不宜连作,连作紫色土和水稻土烟地(田)可增施有机肥,保护土壤团聚体。     

聚丙烯酰胺对盐渍化土壤水分垂直入渗特性的影响

为了探明聚丙烯酰胺(PAM)对盐渍化土壤水分入渗性能及变化过程的影响,通过室内模拟入渗试验,比较分析了不同盐分含量、不同PAM掺量处理的盐渍化土壤水分的入渗速率、累计入渗量及湿润锋等的动态变化。结果表明:(1)经PAM处理的盐渍化土壤入渗速率随PAM浓度的增大而显著减小;(2)对于重度盐渍化土壤,PAM掺量的多少对累计入渗量的影响不显著,而非盐渍化土壤、轻度盐渍化及中度盐渍化土壤均随着PAM浓度的增大而显著减小;(3)对于盐分含量不同的土壤,在同一PAM处理水平下,入渗速率、累计入渗量及湿润锋总体呈现随着盐分增加而减小的趋势;(4)土壤含水率随着PAM掺量及盐分含量的增加而增加的趋势,而对于重度盐渍化土壤PAM施用量之间的差异同样不显著。     

喀斯特地区不同层次土石混合介质对土壤水分入渗过程的影响

桂西北喀斯特地区土壤中常常含有土石隔层,分析其对土壤水分入渗过程的影响有助于深入研究该区水循环机理和促进植被恢复重建进程。通过室内模拟土柱试验,研究了不同土石隔层碎石粒径(5～20,20～40 mm)及土石隔层(土石质量比为1:1)位置(上层(0～20 cm),中层(10～30 cm),下层(20～40 cm))对土壤水分入渗过程的影响。结果表明,碎石粒径为5～20 mm时,土石隔层位于中层时土壤累积入渗量最大。碎石粒径为20～40 mm时,土石隔层位于下层时土壤累积入渗量最大。当土石隔层位置一定时,碎石粒径较小有利于土壤水分入渗;粒径为5～20 mm的土石隔层土壤稳定入渗速率最大,且达到稳定入渗的时间最短,但土层隔层位于下层时均质土壤及不同粒径土壤的稳定入渗速率无显著差异。土石隔层位置和隔层碎石粒径对初始入渗速率没有显著影响;土石隔层位于上层时,土石隔层的存在缩短了水分入渗运移过隔层的时间。土石隔层位于中层时,隔层碎石粒径为20～40 mm时水分入渗到达隔层及运移过隔层的时间最长。土石隔层位于下层时,隔层碎石的存在缩短了水分入渗到达隔层及运移过隔层的时间。Kostiakov入渗模型与Philip方程都可以较好地描述含土石隔层土壤的入渗过程,但Kostiakov入渗模型模拟效果更好。     

土石混合介质水分入渗特性试验研究

土壤中碎石的存在改变了土壤结构和土壤水分运动规律.为研究碎石含量和碎石粒径对土石混合介质水分入渗特性的影响.利用垂直一维积水入渗试验资料对其进行分析.结果表明:土石混合介质的累积入渗量和湿润锋推进速度均小于细土,碎石含量对累积入渗量和湿润锋的影响存在一个转折点.该转折点因粒级不同而不同;碎石含量对含水量剖面的影响表现为含水量随含石量增加而下降;碎石粒径只对混合介质本身的物理特性有影响,对水分入渗无明显影响.     

三峡库区碎石含量对紫色土容重和孔隙特征的影响

土壤容重和孔隙分布特征是土壤重要的基本物理性质,但有关含碎石土壤的物理性质以及碎石含量对土壤结构影响的研究尚不多见。三峡库区紫色土中存在大量的碎石,为了深刻了解和评价土壤中碎石对容重与大孔隙形成的可能作用,通过野外调查、典型土样采集和室内分析实验,探讨了三峡库区典型土地利用类型下土壤中的碎石体积含量以及不同粒径碎石的基本物理性质及其对土壤容重和孔隙特征的影响。结果表明:土壤中碎石的孔隙度和饱和含水率随着碎石粒径的减小而增大,小碎石本身具有一定的持水、供水性能;碎石含量对土壤的总容重、细土容重有显著影响,随着碎石含量的增加,土壤的总容重逐渐增加,而细土容重与碎石含量呈线性负相关关系,土壤中碎石的存在有利于改善土壤的结构;土壤孔隙分布特征与碎石含量密切相关,随着碎石含量的提高,土壤总孔隙度和毛管孔隙度呈减少趋势,而非毛管孔隙度即大孔隙呈增加趋势,碎石的存在有利于改善土壤的透水性能。本研究为山区农用地灌溉与水分管理提供了科学依据。     

Effects of rock fragments on physical degradation of cultivated soils by rainfall

To understand better the role of rock fragments in soil and water conservation processes, the effects of rock fragments in maintaining a favourable soil structure and thus also in preventing physical degradation of tilled soils was studied. Laboratory experiments were conducted to investigate the effects of rock fragment content, rock fragment size, initial soil moisture content of the fine earth and surface rock fragment cover on soil subsidence by rainfall (i.e. change in bulk density by one or more cycles of wetting and drying). A total of 15 rainfall simulations (cumulative rainfall, 192.5 mm; mean intensity, 70 mm h⁻¹) were carried out. Before and after each rainfall application the surface elevation of a 19-cm thick plough layer was measured with a laser microrelief meter. In all experiments, the bulk density of the fine earth increased with applied rainfall volume to reach a maximum value at about 200 mm of cumulative rainfall. From the experimental results it was concluded that the subsidence rate decreased sharply for soils containing more than 0.50 kg kg⁻¹ rock fragments, irrespective of rock fragment size. Fine earth bulk densities were negatively related to rock fragment content beyond a threshold value of 0.30 kg kg⁻¹ for small rock fragments (1.7–2.7 cm) and 0.50 kg kg⁻¹ for large rock fragments (7.7 cm). Initial soil moisture content influenced subsidence only in the initial stage of the experiments, when some swelling occurred in the dry soils. Surface rock fragment cover had no significant effect on subsidence of the plough layer. Therefore, subsidence of the plough layer in these experiments appears to be mainly due to changing soil strength upon drainage rather than the result of direct transfer of kinetic energy from falling drops. The relative increase in porosity of the fine earth as well as the absolute increase in macroporosity with rock fragment content will cause deeper penetration of rainfall into the soil, resulting in water conservation. Therefore, crushing of large rock fragments into smaller ones is to be preferred over removal of rock fragments from the plough layer.     

非常规水水质对红壤水分运移参数的影响及其过程模拟

为了探究非常规水水质对亚热带红壤水分运移参数的影响,采用蒸馏水(CK)、再生水(RW)、稀释2,4,6倍再生水(RW-D2、RW-D4、RW-D6)和生活污水(_(WW))等6种不同水质的非常规水模拟红壤水分入渗过程,利用水平土柱吸渗法测定红壤湿润锋运移速率和水分扩散度,应用压力膜仪法测定了土壤水分特征曲线并且借助van Genuchten(VG)模型提取了相应的土壤残余含水量θ_r、土壤饱和含水量θs、α和n等特征参数值。结果表明:不同水质入渗下红壤湿润锋运移速率、水分扩散度均存在着一定差异,湿润锋运移速率由快到慢分别为V_(CK)≈V_(RW-D2)V_(RW-D6)≈V_(RW-D4)V_(WW)V_(RW);在同一含水率下D_(RW-D6)(θ)D_(RW-D4)(θ)D_(WW)(θ)D_(RW-D2)(θ)D_(CK)(θ)D_(RW)(θ)。不同水质处理对VG模型参数变化率的影响程度不同,对α的影响最大,对θ_r的影响最小。因此,非常规水灌溉会降低红壤入渗速率、持水性能以及抗旱能力。     

重金属迁移与土壤性质的关系

Cu, Zn, Pb and Hg runoff from yellow limestone soil and purple soils and the relationships between the mobility of the heavy metals and the soil characteristics were studied in laboratory using a rainfall simulator. The results showed that the concentrations of soluble Zn in surface runoff were significantly negatively correlated with the contents of < 0.002 mm particles and CEC of the soils, indicating that Zn was mostly adsorbed by clays in the soils. The contents of Cu and Hg in surface runoff were positively related to their contents in the soils. The amounts of Cu, Zn, Pb and Hg removed by surface runoff were influenced by the amounts of soil and water losses and their contents in the soils, and were closely related to the contents of soil particles 1~0.02 mm in size.     

Water-facilitated dispersal of inoculant Bradyrhizobium japonicum in soils

Summary Studies were performed to assess the influence of percolating water and an advancing wetting front on the transport of Bradyrhizobium japonicum in sand and silt loam soils, and to assess the influence of clay content on water-facilitated dispersal of these bacteria in a sand amended with various amounts of kaolin. The data obtained showed that movement of B. japonicum in soil was dependent upon water movement and that both percolating water and an advancing wetting front readily transported bacteria in coarse-textured soils. Percolation with the equivalent of 10 cm of rainfall dispersed B. japonicum throughout 40-cm columns containing sand and silt loam soils. Percolation with 5 cm of water was sufficient to disperse B. japonicum throughout 20-cm columns of these soils but did not transport these bacteria below the surface 4 cm of a sand amended with 12% kaolin. Our finding that cells of B. japonicum are readily transported by an advancing wetting front indicates that non-saturated flow of soil water contributes to dispersal of inoculum in soils.     

Anthropic pedogenesis of purple rock fragments in Sichuan Basin,China

Considerable amounts of rock fragments are found in many “Purple soils” developed from purple rocks in the Sichuan basin of southwestern China. We describe the effects of anthropic pedogenetic processes on purple rock fragments associated with soil amelioration by determining changes in rock fragment size distribution, transformation of P and K of purple rocks into soils, and the complexing of purple rock particles (soil mineral particles) with organic matter during anthropic pedogenesis of “Purple soils” in Sichuan basin of southwestern China. The pedogenetic capacity of rock fragments can be expressed by the content of < 2.0 mm particles as weathered products of rock fragment disintegration. The pedogenetic capacity of the purple rocks studied ranges from 0.3% to 6.2% under natural conditions. The rates of P and K transformed from purple rocks are closely associated with the pedogenetic capacity of rock fragments(r = 0.891^??; 0.961^??, n = 16). Digging (simulated by sieving) and crop planting facilitate pedogenesis of purple rock fragments and their mineral nutrient transformations. The soil mineral particles preserve 18%–36% of the organic carbon added as corn straw. The organic carbon is complexed after corn straw is mixed with < 1.0 mm soil mineral particles for 1 year. The improvement of newly reclaimed purple soils is enhanced by the complexing effect of organic substances with purple rock particles. The pedogenesis of purple rock in Sichaun basin can be accelerated by anthropic activity, such as tillage, crop planting, fertilization, and land reclamation.     

拉巴豆在不同土壤上的结瘤效应、饲用品质

选择重庆市4种具有代表性的土壤（灰棕紫泥两种、红棕紫泥和灰岩黄壤各一种）,接种促生根瘤菌,研究了拉巴豆的结瘤性能、生长情况、光合速率、营养品质及矿质养分等。结果表明,在微酸性和酸性灰棕紫泥土壤上,拉巴豆的生长、生理、光合、产量和品质显著优于灰岩黄壤和红棕紫泥。在微酸性灰棕紫泥（pH 6.14）和灰岩黄壤（pH 6.45）上,接种根瘤菌能形成根瘤,但在酸性灰棕紫泥（pH 4.09）和碱性红棕紫泥（pH 7.50）上,形成根瘤极少或不形成根瘤,说明土壤酸碱度过高和过低均抑制根瘤形成。接种根瘤菌形成根瘤之后,不同程度地改善了拉巴豆氮、磷营养,提高了其净光合速率,促进了生长,增加了生物量,改善了品质。拉巴豆生物量,氮、磷吸收量,收获后土壤有效氮、磷含量与根瘤重量呈显著正相关,故根瘤重量可反映根瘤活性。此外,在微酸性灰棕紫泥土壤中,拉巴豆的根瘤数量虽然比灰岩黄壤少53.32%,但根瘤体积较大,根瘤重量为灰岩黄壤上的1.66倍,接种效应总体上优于灰岩黄壤。所以,在重庆市的拉巴豆栽培中,选择微酸性和酸性灰棕紫泥,并接种根瘤菌有益于高产优质。