自制土壤渗水性监测仪创新实验教学

2022年新版《义务教育科学课程标准》指出,要培养学生的核心素养,其中科学思维是关键和核心。笔者在教学教科版科学四年级上册《比较不同的土壤》一课时,发现该课在探索土壤渗水性这一活动时,因实验材料差异性、实验装置的粗陃和观察的局限性,易对实验结果产生混淆甚至是错误判断。故尝试自制土壤渗水性监测仪,规范了实验材料的使用,明确了实验方法,借助传感器检测将定性指标细化为定量指标,同时增加了从其他角度来观察渗水性,希望逐步培养学生的推理论证和创新思维能力。在实操实验的基础上还引入了理想模型来进行实验或原理的讲解,将土壤间较为细微的差异放大并得到直观呈现,帮助学生进入更深层的思考,更概括、更深刻地理解实验现象产生的原因和本质,逐步培养学生的探究实践能力。

季节性冻融土壤的冻融特点和减渗特性的研究

本文基于季节性冻土地区冻融期间自然冻融土壤的大田入渗试验，分析了田间耕作土壤的冻融特点；讨论了冻融土壤的减渗特性；探讨了冻融土壤的减渗机理。研究结果表明：在不同的冻融阶段，土壤冻层的形态、厚度、层数和层位不同，对入渗水流的控制和影响，不同；冻结土壤的减渗特性随冻融阶段的变化而变化；冻结条件下，土壤导水率的减小是其入渗能力减小的根本原因，而土壤液态水的相变是土壤导水率减小的根源所在。研究结果对于季节性冻土地区大田冻融土壤入渗规律的更深入的研究具有理论价值，对指导季节性冻土区冬春灌溉确定节水灌溉技术参数具有实际意义。

透水沥青路面在我国湿热多雨地区城市道路应用的可行性研究

在渗水性良好的土壤上构筑大面积透水沥青路面可大幅度降低排水系统建构成本,解决我国城市道路行车安全,广场、居民区、城市道路排水难,城市自来水紧张,江河污染等技术难题。开展透水沥青路面的研究,解决湿热多雨地区的集料与沥青的匹配性、土壤渗水性与透水基层和透水面层的相匹配空隙率的设计和实施以及路面的吸音和高温稳定性等问题,以保证路面的耐久性和长期路用性能,对我国制定透水路面设计和施工规范具有参考价值。

黄丘区不同地类的降雨入渗试验

采用加拿大倒“L”型人工模拟降雨装置，在野外试验研究了黄土丘陵沟壑区几种坡面治理措施在暴雨下的入渗特征，取得了不同地类的降雨入渗过程线和拟合公式，同时印证了用双环法所得入渗曲线与降雨人渗过程有较大差异的结论。从而为提高小流域综合治理措施标准，建立土壤侵蚀数学模型提供了科学依据。

Effect of Salt Solution on Characteristics of Soil Infiltration

[Objective] The aim was to study the effect of salt solution on characteristics of soil infiltration, and to provide references for the further studies on the effect of water quality on soil infiltration characteristics and its mechanism. [Method] With the NaCl, CaCl2 solutions as the main test materials, the effect of different water quality and salt solution concentration on soil infiltration was studied under one-dimensional vertical ponded water infiltration at laboratory. [Result] The solution concentration could affect the infiltration performance. The trends of the infiltration rates, cumulative infiltrations and wetting front migration distances were all 50 mg/L 100 mg/L 10 mg/L. At the same concentration, the effect of NaCl solution on soil infiltration characteristics was more significant than CaCl2 solution： in the same time, cumulative infiltration and wetting front migration distance of NaCl solution were greater than CaCl2 solution; compared with NaCl solution, CaCl2 solution took longer time to infiltrate the same amount of water. The dynamic changes of infiltration rate, wetting front and cumulative infiltration were well fitted to the Philip model. [Conclusion] This study only conducted indoor experiment to the infiltration of salt solutions, involving in low concentration and small range. Although it provided some references for the study on the effect of water quality on soil infiltration characteristics and its mechanism, studies in larger areas and with bigger concentrations are demanding.

河滩地板栗丰产栽培技术总结

华北石质低山的沟谷两侧，有不少河滩地，其特点是下层河卵石多，沙质表层土，20cm以下为沙石层，土壤渗水性强，抗旱能力差。我们结合三北防护林工程建设，进行了河滩地板栗丰产栽培试验。

Effect of Irrigation Water Quality on Soil Hydraulic Conductivity

The effect of irrigation water quality on unsaturated hydraulic conductivity (HC) of undisturbed soil in field was studied.Results show that within the operating soil suction range (0-1.6 KPa) of disc permeameters,the higher the electric conductivity (EC) of irrigation water,the higher the soil HC became.The soil HC doubled when EC increased from 0.1 to 6.0ds m^-1.High sodium-adsorption ratio(SAR) of irrigation water would have an unfavorable effect on soil HC.Soil HC decreased with the increasing of SAR,especially in the case of higher soil suction.An interaction existed between the effects of EC and SAR of irrigation water on soil HC.The HC of unsaturated soil dependent upon the macropores in surface soil decreased by one order of magnitude with 1 KPa increase of soil suction.In the study on the effect of very low soluble salt concentration (EC=0.1 ds m^-1 of irrigation water on soil HC,soil HC was found to be lowered by 30% as a consequence of blocking up of some continuous pores by the dispersed and migrated clay particles.Nonlinear successive regression analysis and significance test show that the effects of EC and SAR of irrigation water on soil HC reached the extremely significant level.

Effect of Sulphur in Rainfall, Irrigation Waterand Perco colating Water on Soil Sulphur in Jiangxi Province

Ten rainfall and irrigation water-collecting posts were set up in different ecotype districts of JiangxiProvince, China, to quarterly measure S content in rainfall and irrigation water. A rainwater chemicalcomposition- collecting device was used to collect the sulphur in rainfall land the amount of sulphur adsorbedon the resin column in the device was determined. The soil percolating water was gathered using 6 lysimeters,built up according to the profile sequence of the red soil derived from red sandstone and the red soil derivedfrom Quaternary red clay, separately. On the lysimeters peanuts, soybean and radish were grown in rotation.Two treatments were designed: without S addition and with S addition at a rate of 14 kg S ha-1. The SO24contents in rainfall, irrigation water and soil percolating water were determined by the turbidimetry.The results in 1997 showed that the average annual S content in rainwater was 28.13 kg S ha-1, theaverage S content in irrigation water was 1.7 mg S L-1 , and the average content of in soil percolationwater was 2.30 kg S ha-1 year-1 and 4.70 kg S ha-l year-1 in treatments without and with sulphurapplication, respectively. In Jiangxi Province, apart from the losses by runoff and leaching, the sulphur inrainfall available to crops is 7.3 kg S ha-1 year-1 and additional S application is required. When rice isgrown , however, irrigation water can supply 6.9 kg S ha-1, which, along with the sulphur in rainfall, canalmost meet the S requirement of one cropping of rice.

An Improved Frequency Domain Technique for Determining Soil Water Content

For many years a soil water content sensor with low cost, reliability and sufficient accuracy has been desirable. Thus, an improved measurement method based on the frequency domain (FD) principle for determining soil water content was considered. Unlike other measurement principles, a new measurable index, η, which was independent of the output impedance and the amplitude of the oscillator while relying on the electrical impedance of a multi-pin probe, was pro- posed. Moreover, a model for processing the impedance of the multi-pin soil probe was developed, and several important electrical parameters for establishing their operating ranges applicable to this probe were evaluated. In order to confirm the theoretical analysis, an experiment was conducted with a 4-pin probe. Using the developed model, the relationship between the proposed index η and soil volumetric water content was shown to be linear (R2 = 0.9921). Thus, as the measurable index, η seemed satisfactory.

Water and Heavy Metal Transport in Roadside Soils

Roads with very high traffic loads in regions where soils are low in both pH and sorption capacity might be a source of percolation water loaded with heavy metals. Looking at some "worst case" scenarios, this study focused on the input of traffic related pollutants and on Pb, Cd, Cu, Zn, Ni and Cr concentrations in the soil matrix and soil solution, respectively. The analysis also included pH and electrical conductivity and at some sites DOC. The investigations were carried out on sandy soils with more or less low pH values at four motorway sites in Germany. The average of daily traffic was about 50 000 up to 90 000 vehicles. Soil pore water was collected in two soil depths and at four distances from the road. The pH in general decreased with increasing distance from the roadside. The elevated pH near the roadside was presumably caused by deposition of dust and weathering residues of the road asphalt, as well as by infiltration of salt that was used during winter time. At these road sites, increased heavy metal concentrations in the soil matrix as well as in the soil solution were found. However, the concentrations seldom exceeded reference values of the German Soil Protection Act. The soil solution concentrations tended to increase from the road edge to 10 m distance, whereas the concentration in the soil matrix decreased. Elevated DOC concentrations corresponded with elevated Cu concentrations but did not substantially change this tendency. High soil water percolation rates were found near the roads. Thus, even low metal concentrations of percolation water could yield high metal loads in a narrow area beside the road.

A Dynamic Model for Simulating Atmospheric, Surface and Soil Water interactions in Hillslope of Loess Area Under Natural Conditions and Its Application

The mechanism of atmospheric, surface and soil water interactions (water transformation) in hillslope under natural conditions was analyzed, and a dynamic model was developed to simulate infiltration, overland flow and soil water movement during natural rainfall in hillslope, by bringing forward concepts such. as rainfall intensity on slope and a correction coefficient of saturated soil water content for soil surface seal. Some factors, including slope angle, slope orientation and raindrop inclination, which affect the rainfall amount on slope, were taken into account while developing the dynamic model. The effect of surface seal on infiltration and water balance under a boundary condition of the second kind was also considered. Application of the model in a field experiment showed that the model simulated precisely the infiltration, overland flow and soil water movement in hillslope under natural rainfall conditions.

Field and Numerical Tests of the Two-Ponding Depth Procedure for Analysis of Single-Ring Pressure Infiltrometer Data

The two-ponding depth （TPD） analysis procedure of single-ring infiltrometer data can yield invalid results, i.e., negative values of the field-saturated soil hydraulic conductivity or the matric flux potential, denoting failure of the two-level run. The objective of this study was to test the performance of the TPD procedure in analyzing the single-ring infiltrometer data of different types of soils. A field investigation carried out in western Sici]y, Italy, yielded higher failure rates （40%） in two clay loam soils than in a sandy loam soil （25%）. A similar result, i.e., fine-textured soils yielding higher failure rates than the coarse-textured one, was obtained using numerically simulated infiltration rates. Soil heterogeneity and reading errors were suggested to be factors determining invalid results in the field. With the numerical data, allowing a less generic definition of soil heterogeneity, invalid TPD results were occasionally obtained with the simultaneous occurrence of a high random variation （standard deviation ≥ 0.5） and a well developed structural correlation for saturated hydraulic conductivity （correlation length 〉 20 cm）. It was concluded that a larger number of replicated runs should be planned to characterize fine-textured soils, where the risk to obtain invalid results is relatively high. Large rings should be used since they appeared more appropriate than the small ones to capture and average soil heterogeneity. Numerical simulation appeared suitable for developing improved strategies of soil characterization for an area of interest, which should also take into account macropore effects.

Effects of the conversion of natural tropical rainforest to monoculture rubber plantations on soil hydrological processes

Rubber plantations have increased signifcantly under unprecedented economic growth in tropical areas,which leads to soil degradation and thereby alters soil hydrological processes.However,our understanding of how forest conversion affects soil hydrological processes remains unclear.Here,we collected soil samples from secondary forests(SF)and rubber plantations(RP)to determine the soil hydrological characteristics.We found the topsoil(0-20 cm)water retention in SF was higher than that of RP but displayed the contrast pattern in a deeper soil layer(20-60 cm).Meanwhile,the soil infltration rates among the two vegetation types decreased signifcantly with infltration time,with higher stable soil infltration rates in SF than those in RP.Moreover,soil properties were also impacted by the forest conversion,such as the topsoil capillary porosity(CP)and total porosity(TP)in SF were higher than those of RP but contrasted in a deep soil layer.In comparison,the topsoil bulk density(BD)in SF was lower than that of RP,but contrasted in the deep soil layer and reached a signifcant level in the 0-10 and 40-50 cm(P<0.05).Overall,the soil water retention was mainly determined by the CP,which could explain 31.56%of the total variance in soil water retention,followed by TP(26.57%)and soil BD(26.47%),whereas soil texture exerts a weak effect on soil water retention.Therefore,we can conclude that the conversion of tropical rainforest into rubber plantations may accelerate soil erosion owing to its lower topsoil water retention and soil infltration rates.