盐胁迫下转Bt基因棉的K+、Na+转运及SOD活性的变化

通过对转Bt基因棉(苏抗103)和受体棉(苏棉12)在不同浓度盐胁迫条件下的钾钠离子的转运、累积分布以及它们SOD活性和H2O2含量变化的比较,证明了Bt抗虫基因的导入一方面导致棉花植株地上部钾累积增多,根部钾含量降低,从根往地上部的钾转运能力增强,而且根吸收能力也有增强趋势;然而另一方面,受盐胁迫时转Bt基因棉对钾的向上运输选择性减弱,地上部钠积累偏多,盐耐性减弱;SOD活性受盐胁迫影响,下降显著,超氧自由基的清除能力可能受到影响。结果表明,与常规棉有所不同,转Bt基因棉可能不太适宜在盐碱土壤上种植。     

无源蓄冷控温运输箱设计与试验

针对蓄冷运输箱信息化程度低、控温时间短、控温困难等问题,设计了一款集控温、远程监控、定位、故障诊断等功能于一体的蓄冷运输箱。以脐橙为试验对象,结合能耗模型,对蓄冷控温箱控温性能进行了研究。结果表明,箱内各截面温度不均匀系数分别为0.38、0.47、0.78,温度极差最大值为2.8℃,均匀性较好;当蓄冷剂用量为180 kg,预冷脐橙660 kg,在外部环境平均温度26.39℃的条件下,总控温时长为122 h,风机共执行控温21次,且随着蓄冷量减少,风机开启控温所用时间呈指数上升趋势,决定系数不小于0.928 0;结合能耗模型分析得出,该箱体在广州夏季高温环境下可控温5 d以上,能够满足远距离运输要求。     

富贵竹切口保鲜及贮运研究

通过大量实验筛选出适合富贵竹切口的保鲜液,冬季宜采用配方12,夏季宜采用配方5进行处理。处理液B对防治脚部黄化及促根效果极显著。加工后的富贵竹成品货柜运输的最佳温度为15￣16℃,配合含1.0mg/L6-BA 1‰托布津的保水剂包根处理,可极显著降低贮运中的损失率。研究成果在生产中成功应用。     

蓄水坑灌条件下复水对水氮运移规律的影响

为了明确灌后复水(降水)对土壤中水氮分布的影响以及选择合理的灌施方式,通过室内模型试验,研究了在蓄水多坑肥灌条件下不同降水量(30.624,37.334,43.56 mm)所对应单坑不同复水量(140.1,228.7,400.5 mm)和不同复水时间(灌后1,5,10 d)对土壤水氮运移的影响.研究结果表明:复水后土壤含水率增大,复水量为228.7 mm及以上时,30~80 cm深度范围内土壤含水率均达到田间持水率的80%以上,且复水量越大或复水时间间隔越短,复水后水分分布越均匀;硝态氮在湿润锋处积累明显,复水后坑壁附近土壤硝态氮质量浓度降低,硝态氮质量浓度峰值向远处推进,复水量越大或复水时间间隔越短,硝态氮推进越远且向深处迁移越明显;复水后铵态氮质量分数在近坑处降低,在距坑较远处增加,但变化幅度均不大,复水量越大,或复水时间间隔越短,对铵态氮质量浓度影响越大,复水后土壤铵态氮分布越均匀.     

基于分形理论的马铃薯干燥过程水分输运特征分析

基于马铃薯内部结构的异质性和分布随机性,利用分形特性模拟了在干燥过程中的水分输运过程。结果发现结合收缩和分形现象的模型呈无收缩现象连续介质模型更接近实验值,且分形模型的内部压力分布没有出现像连续模型呈比例逐层下降的现象。包括收缩的分形模型与孔的连通性、孔隙率、面积分形维数和孔最小最大直径比值成正比,与迂曲分形维数和迂曲度成反比。     

北京市南水北调受水区垃圾场地下水污染预测

根据南水北调供水方案,南水北调进京10年后,受水区内垃圾场将会被地下水浸泡,如不采取防治措施,会对含水层水质造成严重污染。以北京西郊为研究区,利用Visual Modflow软件中的MODFLOW模块和MT3DMS模块分别建立了地下水水流模型和溶质运移模型,对研究区内污染物运移规律进行预测。预测结果表明,10a后氯离子(Cl-)、硝酸盐氮(NO2-3)和总硬度(THD)3种离子的最高浓度和被污染的面积均增大,预测结果可作为调整地下水开采与调蓄方案和垃圾场防渗规划设计的依据。     

横坡垄作下土壤湿润速率对褐土坡面侵蚀特征的影响

不同土壤湿润速率和侵蚀类型下团聚体破碎存在较大差异,进而诱发坡面侵蚀特征变化。横坡垄作特有的侵蚀过程可能改变土壤湿润速率对坡面侵蚀特征的影响效应。以褐土横垄为研究对象,基于室内模拟降雨试验,研究5个土壤湿润速率下(10、20、30、60、90 mm/h)不同侵蚀阶段的产流产沙和团聚体迁移规律。结果表明,细沟间阶段径流量随土壤湿润速率的增大而增加,而细沟阶段不同土壤湿润速率间的径流量无显著差异。2个阶段内,侵蚀量均随土壤湿润速率的增大而增加,与土壤湿润速率10 mm/h相比,20、30、60、90 mm/h速率下的侵蚀量分别显著增加25.16%~115.51%、95.02%~144.34%、151.03%~164.49%、249.42%~398.91%。细沟间阶段,土壤湿润速率的变化仅改变了产沙过程,而细沟阶段产流产沙过程均随土壤湿润速率发生了改变。主要迁移粒级-微团聚体流失所增加的细沟间和细沟侵蚀阶段分别主要来自2~5 mm和0.25~0.5 mm团聚体的破碎,而相应控制这2个粒级破碎的关键土壤湿润速率分别为20 mm/h和10 mm/h。不同阶段下迁移团聚体平均重量直径由大到小依次为细沟阶段、湿润处理后、细沟间阶段。     

设施条件下膜孔灌土壤水氮运移分布特性研究

在室内进行了模拟设施条件下膜孔灌灌施硝酸钾肥液试验,分析测定了灌后不同时间的土壤含水量和硝态氮质量分数。研究表明,土壤含水率和硝态氮质量分数随着灌后时间延长逐渐减小,土壤水分和硝态氮在灌后1d内存在明显减少现象,灌后5d土壤硝态氮反硝化作用加强;土壤含水率和硝态氮存在耦合现象,二者分布趋势基本相同,以膜孔中心为最大,远离膜孔中心逐渐减小。     

Fine-earth translocation by tillage in stony soils in the Guadalentin, south-east Spain: an investigation using caesium-134

Tillage erosion is increasingly recognised as an important soil erosion process on agricultural land. In view of its potential significance, there is a clear need to broaden the experimental database for the magnitude of tillage erosion to include a range of tillage implements and agricultural environments. The study discussed in this paper sought to address the need for such data by examining tillage erosion by a duckfoot chisel plough in stony soils on steep slopes in a semi-arid environment. Results of the investigation of coarse fraction (rock fragment) translocation by tillage in this environment have been presented elsewhere and the paper focuses on tillage translocation and erosion of the fine earth. Tillage translocation was measured at 10 sites, representing both upslope and downslope tillage by a duckfoot chisel plough on five different slopes, with tangents ranging from 0.02 to 0.41. A fine-earth tracer, comprising fine earth labelled with ¹³⁴Cs, was introduced into the plough layer before tillage. After a single pass of the plough, incremental samples of plough soil were excavated and sieved to separate the fine earth from the rock fragments. Translocation of the fine-earth tracer was established by analysing the ¹³⁴Cs content of the samples of fine earth. These data were used to establish translocation distances for each combination of slope and tillage direction. Translocation distances of the fine earth were not significantly different from translocation distances of the coarse fraction. For all sites, except uphill on the 0.41 slope, translocation distances were found to be linearly related to slope tangent. The soil flux due to tillage for each site was calculated using the translocation distance and the mass per unit area of the plough layer. For slopes with tangents <0.25, the relationship between soil flux and tangent was linear and the soil flux coefficient derived was 520–660 kg m⁻¹ per pass. This is much larger than the coefficients found in other studies and this high magnitude is attributed to the non-cohesive nature and high rock fragment content of the soil in this investigation. A second contrast with previous studies was found in non-linearity in the relationship between soil flux and tangent when steeper slopes were included. This was a product of variation in plough depth between the steepest slopes and the remainder of the study area. On the basis of the study it is suggested that an improved understanding of tillage erosion may be obtained by considering the dual processes of tillage detachment (mass per unit area of soil subject to tillage) and tillage displacement (equivalent to translocation distance per pass) in assessing, comparing and modelling tillage translocation. An improved model is proposed that recognises the complexity of soil redistribution by tillage, provides a framework for process-based investigation of the controls on tillage fluxes, and allows identification of potential self-limiting conditions for tillage erosion.     

Oxidation of methane in the rhizosphere of rice plants

Oxidation of CH₄ in the rhizosphere of rice plants was quantified using (1) methyl fluoride, a specific inhibitor of CH₄ oxidation, and (2) measuring changes in plant-mediated CH₄ emission after incubation under air, N₂, or 40% O₂. No significant rhizospheric CH₄ oxidation was observed from rice plants in the ripening stage. CH₄ emission from rice plants 1 week before panicle initiation increased by 40% if CH₄ oxidation in the rhizosphere was blocked. The growth stage of the rice plant is an important factor determining the rhizospheric CH₄ oxidation. Fluctuation of rhizospheric CH₄ oxidation during the growing season may help to explain the observed seasonal CH₄ emission patterns in field studies. Measurements from four rice varieties showed that one variety, Pokkali, had higher rhizospheric CH₄ oxidation. This was probably because Pokkali was in an earlier growth stage than the other three varieties. Both in the early and in the late growth stages, incubation under N₂ caused a much stronger CH₄ flux than inhibition of CH₄ oxidation alone. Apparently, N₂ incubation not only blocked CH₄ oxidation but also stimulated methanogenesis in the rhizosphere. Incubation under a higher O₂ atmosphere (40% O₂) than ambient air decreased the CH₄ flux, suggesting that increasing the oxidation of the rice rhizosphere may help in reducing CH₄ fluxes from rice agriculture. The O₂ pressure in the rhizosphere is an important factor that reduces the plant-mediated CH₄ flux. However, inhibition of methanogenesis in the rhizosphere may contribute more to CH₄ flux reduction than rhizospheric CH₄ oxidation.