土壤水与地下水溶质运移联合模型

土壤水溶质运移模型着重解决入渗与蒸发条件下盐份在非饱和含水层中的垂向运移问题 ,地下水溶质运移模型着重解决盐份在饱和含水层中的横向运移问题 ,它们都不能全面描述区域盐份迁移的规律。分别建立地下水、土壤水的溶质运移模型子系统 ,耦合集成并进行联合运行是理想的解决方案。     

一种溶质运移数学模型的应用研究

土壤中溶质运移的过程、规律和机理是土壤溶质运移研究的主要内容。本文的目的是对模拟非饱和介质中水分和溶质迁移的二维数值模型SWMS－2D进行研究和验证。以硝酸盐形式存在的溶解氮是地下水中最常见的污染物，将硝态氮视为土壤溶质，考虑其根系吸收、生物固持、吸附、解吸、硝化和反硝化等作用，土壤表面即上边界条件用大气边界条件描述，下边界条件定为第一类边界条件，在田间条件下对模型作了检验。     

滴灌施肥条件下土壤水氮运移数值模拟

为了研究滴灌施肥条件下土壤水、氮的运移分布规律,本文通过室内土柱滴灌水氮入渗试验,研究了滴灌结束时及再分布过程中土壤水、氮的运移变化规律;同时用HYDRUS软件建立了土柱滴灌水氮入渗的几何模型,用来模拟滴灌土壤水氮运移过程。对试验及模拟中12个观测点测得的土壤含水率、土壤铵态氮、硝态氮质量浓度进行对比分析,结果表明：土壤含水率模拟值与实测值的相对误差变化在10%以内;土壤铵态氮、硝态氮质量浓度的模拟值与实测值变化范围在20%以内。滴灌结束时土体剖面内土壤含水率随距滴头距离的增大而减小,再分布72 h土层25~30 cm土壤含水率增大到0.2 cm³·cm^-3,120 h后土体剖面内土壤含水率较滴灌结束时下降了18%。土壤铵态氮质量浓度主要分布于距滴头20 cm的范围;24 h土壤铵态氮质量浓度最大,且随着时间的推移逐渐减小,到120 h时减少了40%;各观测点24 h至120 h土壤硝态氮质量浓度随着时间的推移逐渐增大,且硝态氮质量浓度在滴头20 cm的范围内由0.442 mg·cm^-3增加到1.2 mg·cm^-3。各观测点24 h土壤硝态氮质量浓度在空间分布上差异不大,其中观测点1,3,6,8,5的土壤硝态氮质量浓度分别为0.437,0.467,0.451,0.482 mg·cm^-3和0.447 mg·cm^-3,差值均小于0.05 mg·cm^-3;48 h后土体剖面内土壤硝态氮质量浓度空间分布随离滴头距离的增加而减小,垂直方向上从距滴头5 cm的观测点1到距滴头25 cm的观测点8减少了53%。依据研究结果,可用数值模型模拟滴灌施肥条件下土壤水氮运移的变化规律。     

干旱区稳定蒸发条件下土壤盐溶质迁移的动态预测

<正> 1.导言土壤盐碱化是世界干旱区共同性的问题,也是人类遇到的最古老的环境问题。近30年来,迫于人口压力和食物需求,许多容易开发的土地均已得到利用,人们正在将注意力转向干旱区。由于干旱区自身的特征,土地开发和盐渍化防治,在强烈蒸发条件下土壤盐溶质浓度目标C(Z,t)及迁移预测已成为近代土壤—水环境研究热点之一,成为中国北     

灌水量对包气带水分运移与滞留影响过程研究

包气带水是支持植被生长的关键因子,也是联系地表水与地下水、以及补给地下水的重要水源,为了解地表灌溉量和历时对包气带水分运移和滞留过程的影响,在陕西省泾惠渠试验站开展了夏玉米和冬小麦畦灌试验,应用实测数据和Hydrus-1D模型模拟包气带0~6 m土壤水分运移滞留过程,并对其水分平衡进行定量分析计算,结果表明:不同的灌水量、进水流量和灌溉历时会引起明显土壤水分运移滞留变化。夏玉米模拟期采用大流量、快速灌溉,剖面底部的渗漏量大,占地表总入水量的24.88%;冬小麦模拟期灌溉流量小、历时长,底部渗漏量小,占地表灌溉量的2.29%;夏玉米试验期内蒸发蒸腾量大于冬小麦,分别占地表总入水量的32.32%和27.33%,棵间蒸发量占蒸发蒸腾量的比例分别为18.15%和16.92%;夏玉米与冬小麦试验期内包气带土壤水分滞留比例分别为42.8%和70.38%,灌溉进水流量和历时是控制包气带水分滞留和进入地下水的关键因素。     

干旱沙区滴灌条件下水盐运移过程试验研究

通过田间滴灌试验，研究了在不同滴头出水流量条件下干旱沙地土壤水分，盐分运移与分异过程，并调查作物的根系分布，结果表明，微灌系统仅给作物根际分布区以内的小面积土壤供水，并未使整个土表面均匀湿润，对于大多数农田而言，其优点是有限的湿润表面积能够限制杂草生长，减少土壤表面无效蒸发，但干旱区潜在蒸发量大，滴灌条件下水分运移的过程将引起和支配耕作层盐分的移动的重新分配，当水盐混合溶液（无机肥料溶液：N：P：K．＝12：6：6）在3种处理中（0．3L／h,0.8L/h,2.0L/h)由滴头流动至根系湿润区内，水分，养分被作物根系吸收，部分水分直接蒸发至大气后，过剩盐分将留存下来，并在土体表面和土体内湿润边界层逐渐积聚，形成高盐分聚集区，由作物根系分布特点看出，处理I，处理Ⅲ有利于提高根系单位土体分布密度，处理Ⅱ次之。     

地下水浅埋区盐碱地滴灌条件下土壤盐分运移研究

综述了国内外地下水浅埋条件下土壤盐分运移机理研究,滴灌条件下盐碱地土壤盐分运移机理研究,土壤盐分运移模型研究的相关研究成果,为滴灌技术在改造和利用地下水浅埋盐碱土地资源的应用提供了思路,为预报土壤盐碱化提供科学依据,并为地下水浅埋盐碱土滴灌条件下土壤盐分运移规律的进一步研究提出一些建议,认为地下水浅埋区盐碱地滴灌条件下土壤盐分运移规律的研究仍是今后土壤科学的研究重点.     

蒸发条件下氟在浅层水—土系统中的二维运移特征

文中利用渗流槽对强蒸发条件下氟在浅层水-土系统中的二维运移过程进行了试验模拟,对氟在水-土系统中的运移规律和影响因素进行了研究。结果表明:氟在水-土系统的二维运移是一个缓慢的渐进过程,土壤对氟元素的吸附特性和渗流场水动力条件是影响氟在水-土系统中运移的重要因素。水动力条件控制着氟运移的主方向,并与土壤的吸附作用一起影响着氟的运移速率。此外,蒸发浓缩作用是浅层高氟地下水区包气带低氟土壤高氟化的主要原因。文中为进一步研究浅层水-土系统中氟的运移及氟在浅层土壤中的富集特征提供了理论基础,具有一定的借鉴价值。     

覆膜畦灌条件下不同灌溉定额对饲用甜高粱农艺性状及生物产量的影响

为探索西北旱区饲用甜高粱最佳灌溉定额和节水效果,进行了覆膜畦灌条件下饲用甜高粱需水规律及优化灌溉制度试验,研究了不同灌溉定额(2 400、3 000、3 600、4 200、4 800 m~3·hm~(-2))条件下,饲用甜高粱生育期土壤水分变化情况、农艺性状及生物产量变化。结果表明,甜高粱生育期0~100 cm土层含水量随生育期的延长呈先降低后升高的趋势,灌水定额对土壤水分分布的影响发生在播后62 d。当灌溉定额小于2 400 m~3·hm~(-2)时,严重影响甜高粱长势,植株表现为矮小,茎秆增粗,干物质累积量降低。随灌溉定额的降低,甜高粱茎秆汁液的含糖量呈提高的趋势。甜高粱生物产量的增加是由于株高(R~2=0.97)、LAI(R~2=0.81)、茎节数(R~2=0.59)等因素共同作用的结果。从节水和增加生物量角度而言,畦灌条件下,甜高粱在全生育期灌水4次,灌水定额为900 m~3·hm~(-2),灌溉定额为3 600 m~3·hm~(-2)的灌溉制度最优。     

不同施肥条件下地膜小麦增产效应的研究

1998年～1999年在渭北旱原不同施肥条件下进行地膜小麦增产效应研究,结果表明施肥可以显著提高覆膜冬小麦的水分利用率[1.9～3.9kg/(mm     

尿素对浑水水肥一体化滴灌滴头堵塞的影响

为确定水肥一体化灌溉过程中,尿素对滴头堵塞的影响,分别配置了3种泥沙浓度(1.0、1.5 g·L~(-1)和2.0 g·L~(-1)),3种肥料质量浓度(1%、2%和3%),进行了间歇灌水堵塞试验,分析了滴头流量和排出泥沙量。结果表明:施加尿素对浑水滴灌具有缓解滴头堵塞的作用,在一定的尿素浓度范围内,施肥浓度越大,减缓作用越明显;施肥浓度对滴头的堵塞形式和主要堵塞物淤积位置的影响很小。滴头出流泥沙含量随灌水次数的增加呈现先快速增加,后逐渐变缓并趋于下降的趋势。施加尿素提高了滴头泥沙输送能力,施肥浓度越大,滴头输送泥沙的能力越大,泥沙排出率越大。浑水中施加尿素具有减缓滴头堵塞,延长滴头有效灌水次数的作用,当含沙量为2.0g·L~(-1)时,尿素浓度为1%,2%和3%的水肥一体化滴灌有效灌水次数比未添加尿素的可分别提高11%,89%和100%。可尝试通过尿素水肥一体化滴灌,缓解黄河水滴灌滴头堵塞危险,提高滴灌系统使用效率。     

灌水和施肥对温室滴灌施肥番茄生长和品质的影响

本研究目的在于分析滴灌施肥技术下,不同水肥耦合模式对温室番茄的生长和品质的影响。试验选取番茄惠玉0806为试材,设100%ET₀(I₁),75%ET₀(I₂),50%ET₀(I₃) 3个水分水平,外加高肥〔F₁(N 480 kg·hm^-2、P₂O₅ 240 kg·hm^-2、K₂O 300 kg·hm^-2)〕,中肥〔F₂(N 360 kg·hm^-2、P₂O₅ 180 kg·hm^-2、K₂O 225 kg·hm^-2)〕,和低肥〔F₃(N 240 kg·hm^-2、P₂O₅ 120 kg·hm^-2、K₂O 150 kg·hm^-2)〕3个肥料水平,共9个处理。结果表明：水肥条件的高低与株高及茎粗成正相关,I₂F₂处理其产量、干物质累积量和灌溉水利用效率均最高,依次为102 042.3 kg·hm^-2、37.19×10³ kg·hm^-2和37.3 kg·m^-3。对番茄品质而言,其灌水量和施肥量之间表现出明显的耦合交互作用,I₂F₂处理其番茄Vc含量(27.05 mg·100g^-1)、番茄红素含量(71.53 μg·g^-1)均最高,糖酸比(9.57)显著低于其余处理,其可溶性固形物含量(7.3%)较最高值I₃F₁低24.7%。综上分析,中水中肥(I₂F₂)模式,在高产的同时,其品质总体优于其它处理,极端水肥措施均不利于番茄生长及品质的提高。     

Numerical simulations of flow and sediment transport within the Ning-Meng reach of the Yellow River,northern China

Effective management of a river reach requires a sound understanding of flow and sediment transport generated by varying natural and artificial runoff conditions. Flow and sediment transport within the Ning-Meng reach of the Yellow River(NMRYR), northern China are controlled by a complex set of factors/processes, mainly including four sets of factors:(1) aeolian sediments from deserts bordering the main stream;(2) inflow of water and sediment from numerous tributaries;(3) impoundment of water by reservoir/hydro-junction; and(4) complex diversion and return of irrigation water. In this study, the 1-D flow sediment transport model developed by the Yellow River Institute of Hydraulic Research was used to simulate the flow and sediment transport within the NMRYR from 2001 to 2012. All four sets of factors that primarily control the flow and sediment transport mentioned above were considered in this model. Compared to the measured data collected from the hydrological stations along the NMRYR, the simulated flow and sediment transport values were generally acceptable, with relative mean deviation between measured and simulated values of 15%. However, simulated sediment concentration and siltation values within two sub-reaches(i.e., Qingtongxia Reservoir to Bayan Gol Hydrological Station and Bayan Gol Hydrological Station to Toudaoguai Hydrological Station) for some periods exhibited relatively large errors(the relative mean deviations between measured and simulated values of 18% and 25%, respectively). These errors are presumably related to the inability to accurately determine the quantity of aeolian sediment influx to the river reach and the inflow of water from the ten ephemeral tributaries. This study may provide some valuable insights into the numerical simulations of flow and sediment transport in large watersheds and also provide a useful model for the effective management of the NMRYR.     

滴灌条件下青海春油菜需水需肥规律

在青海省西宁市北郊二十里铺镇,采用"3414"肥料设计和不同梯度灌水量进行大田滴灌春油菜需水需肥规律研究。结果表明,滴灌施肥条件下,春油菜产量达到2 443.5~3 132.0 kg·hm-2,各施肥处理比无施肥对照增产了0.8%~29.2%,氮、磷、钾肥的肥料利用效率达到50.9%、22.5%、56.7%。滴灌方式水分利用率达到4.0kg·hm-2·mm-1以上,比大水漫灌提高了42.1%~61.4%。滴灌土壤含水量苗期盛花期角果期;0~60 cm土层土壤含水量苗期随着土层深度的增加而增加,中后期随着土层深度的增加先上升后下降。距滴头5 cm土壤含水量最低值小于距滴头15 cm土壤含水量最低值。根据试验结果得出滴灌肥最大产量施肥量为N 138 kg·hm-2,P2O561.5 kg·hm-2,K2O 57 kg·hm-2,最大产量可达3 000 kg·hm-2。设置滴灌土壤含水量下限为苗期55%、始花期60%、盛花期65%和角果期55%的水分管理具有较好的水分高效利用效果。     

不同地表覆盖对枣树树干液流特征的影响

为探究不同地表覆盖模式对枣树树干液流特征的影响,基于不同地表覆盖模拟试验,应用热扩散探针技术对枣树主要生长季(2013年6月—9月)树干液流进行定位监测,分析枣树枝全覆盖(WJBM)、枣树枝半覆盖+白三叶生草(JBM+SWC)、白三叶全生草覆盖(WCC)、清耕(CC)4种处理树干液流速率变化规律及其对环境因子的响应。结果表明:晴天各处理树干液流速率日变化均呈典型"几"字形宽峰曲线;阴天则均呈多峰波浪曲线,且变化趋势基本一致。阴天4种处理日均树干液流速率皆低于晴天,降低量分别为48.45%(WJBM)、41.94%(JBM+SWC)、45.59%(CC)、62.51%(WCC)。同一天气条件下,WJBM和JBM+SWC两处理树干液流速率均居于较高水平,WCC则较低。晴天,WCC与WJBM、JBM+SWC两处理均差异极显著(P0.01),与CC则差异显著(P0.05),WJBM与CC差异显著(P0.05);阴天,WCC与WJBM、JBM+SWC均存在显著差异(P0.05)。不同地表覆盖下枣树树干液流速率月变化规律基本相似,各处理均表现为8月份月平均树干液流速率最高,分别为0.0984 cm·min~(-1)(WJBM)、0.1032 cm·min~(-1)(JBM+SWC)、0.0723 cm·min~(-1)(CC)、0.0538 cm·min~(-1)(WCC),9月份则最低。4种处理月平均树干液流速率和0~70 cm土层平均土壤体积含水量整体表现为:WJBMJBM+SWCCCWCC。不同处理枣树蒸腾速率(Tr)均与空气相对湿度(RH)呈负相关,与光合有效辐射(PAR)、空气温度(Tair)、风速(Vwind)呈正相关,PAR是影响各处理枣树蒸腾最主要的环境因子。     

Field leaching of pesticides at five test sites in Hawaii: modeling flow and transport

BACKGROUND: Physically based tier‐II models may serve as possible alternatives to expensive field and laboratory leaching experiments required for pesticide approval and registration. The objective of this study was to predict pesticide fate and transport at five different sites in Hawaii using data from an earlier field leaching experiment and a one‐dimensional tier‐II model. As the predicted concentration profiles of pesticides did not provide close agreement with data, inverse modeling was used to obtain adequate reactive transport parameters. The estimated transport parameters of pesticides were also utilized in a tier‐I model, which is currently used by the state authorities to evaluate the relative leaching potential. RESULTS: Water flow in soil profiles was simulated by the tier‐II model with acceptable accuracy at all experimental sites. The observed concentration profiles and center of mass depths predicted by the tier‐II simulations based on optimized transport parameters provided better agreements than did the non‐optimized parameters. With optimized parameters, the tier‐I model also delivered results consistent with observed pesticide center of mass depths. CONCLUSION: Tier‐II numerical modeling helped to identify relevant transport processes in field leaching of pesticides. The process‐based modeling of water flow and pesticide transport, coupled with the inverse procedure, can contribute significantly to the evaluation of chemical leaching in Hawaii soils. Copyright © 2011 Society of Chemical Industry     

回流滴灌系统泥沙输移及抗堵塞性能研究

为探究在传统支状滴灌系统末端设置回流管后滴灌系统毛管主流流速增加后回流滴灌系统的输沙排沙潜力及其抗堵塞性能,通过周期滴灌实验分析回流滴灌系统的灌水均匀系数以及滴头堵塞情况,并对毛管内沉积泥沙分布特点和系统各部分输沙排沙所占比重进行分析。实验结果表明:0.035 m·s~(-1)回流、0.05 m·s~(-1)回流滴灌系统的灌水均匀系数、滴头堵塞数量均明显优于支状滴灌系统。回流流速为0.05、0.035、0.015 m·s~(-1)三种回流系统中毛管沉泥量依次增加,但均低于支状滴灌系统的毛管泥沙沉积数量,同时四种回流滴灌系统均表现为沿水流方向毛管内沉泥量逐渐增加。支状滴灌系统、0.015 m·s~(-1)回流、0.035 m·s~(-1)回流、0.05 m·s~(-1)回流系统回流排沙量分别为0、1.59、4.30、7.52 kg,表明回流管具有良好的输沙排沙能力。     

Solute transport characteristics of a deep soil profile in the Loess Plateau,China

Understanding solute transport behaviors of deep soil profile in the Loess Plateau is helpful for ecological construction and agricultural production improvement. In this study, solute transport processes of a deep soil profile were measured by a conservative tracer experiment using 25 undisturbed soil cores(20 cm long and 7 cm diameter for each) continuously sampled from the surface downward to the depth of 500 cm in the Loess Plateau of China. The solute transport breakthrough curves(BTCs) were analyzed in terms of the convection-dispersion equation(CDE) and the mobile-immobile model(MIM). Average pore-water velocity and dispersion coefficient(or effective dispersion coefficient) were calculated using the CDE and MIM. Basic soil properties and water infiltration parameters were also determined to explore their influence on the solute transport parameters. Both pore-water velocity and dispersion coefficient(or effective dispersion coefficient) generally decreased with increasing depth, and the dispersivity fluctuated along the soil profile. There was a good linear correlation between log-transformed pore-water velocity and dispersion coefficient, with a slope of about 1.0 and an average dispersivity of 0.25 for the entire soil profile. Generally speaking, the soil was more homogeneous along the soil profile. Our results also show that hydrodynamic dispersion is the dominant mechanism of solute transport of loess soils in the study area.     

Movement of pesticides to surface waters from a heavy clay soil

A field experiment at Cockle Park, Northumberland on a clay loam soil (Dunkeswick series) cropped with winter wheat investigated the effects of drainage and season of application on pesticide movement. Isoproturon, mecoprop, fonofos and trifluralin were applied in two consecutive seasons at normal agricultural rates to three hydrologically isolated plots each of 0.25 ha. Two of the plots were mole-drained and the third was an undrained control. Surfacelayer flow and drainflow from each plot were monitored at 10-min intervals. Samples of flow were analysed for pesticides to evaluate transport of applied chemicals from the site. Despite widely differing properties (K_oc 20–8000 ml g^?1, t_1/2 10–60 days), all four pesticides were found in surface-layer flow and mole drainflow from the site. Maximum concentrations of pesticides in flow ranged from 0.1 to 121 μg litre^?1 (aqueous phase) and < 0.2 to 48 μg litre^?1 (particulate phase). Over two contrasting seasons, total losses of pesticides in flow followed total amounts of flow and were approximately four and five times larger, respectively, in 1990/91 than in 1989/90. The maximum loss occurred from the undrained plot and was 2.8 g isoproturon (0.45% of that applied). Total losses of autumn-applied pesticides from an undrained plot were up to four times greater than losses from a mole-drained plot. Mole drainage decreased movement of pesticides from this slowly permeable soil by reducing the amount of surfacelayer flow. Maximum concentrations of mecoprop and isoproturon in drainflow were 10–20 times larger following spring application than after application in autumn. Bypass flow down soil cracks was an important process by which pesticide was lost from the site, with transport to the drainage system via mole channels (55 cm depth) after less than 0.5 and 6.7 mm net drainage in the two winters.     

Fate and transport of glyphosate and aminomethylphosphonic acid in surface waters of agricultural basins

BACKGROUND: Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops and is heavily used on soybeans, corn and cotton. Glyphosate is used in almost all agricultural areas of the United States, and the agricultural use of glyphosate has increased from less than 10 000 Mg in 1992 to more than 80 000 Mg in 2007. The greatest intensity of glyphosate use is in the midwestern United States, where applications are predominantly to genetically modified corn and soybeans. In spite of the increase in usage across the United States, the characterization of the transport of glyphosate and its degradate aminomethylphosphonic acid (AMPA) on a watershed scale is lacking. RESULTS: Glyphosate and AMPA were frequently detected in the surface waters of four agricultural basins. The frequency and magnitude of detections varied across basins, and the load, as a percentage of use, ranged from 0.009 to 0.86% and could be related to three general characteristics: source strength, rainfall runoff and flow route. CONCLUSIONS: Glyphosate use in a watershed results in some occurrence in surface water; however, the watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff and a flow route that does not include transport through the soil. Copyright © 2011 Society of Chemical Industry