原状水稻土土壤湿度高光谱特征及反演模型

室内高光谱遥感定量反演土壤湿度的相关研究,可以为利用星载或机载遥感数据源进行大尺度土壤水分监测提供理论基础;原状土土样相较于当前广泛使用的研磨土土样,能更好地保持土壤的原始光谱特性和持水性能。为了得到更可靠的土壤湿度光谱特征与更具有适用性的反演模型,利用ASD Field Spec 3光谱仪采集了江苏省金坛市竹林镇的62个原状水稻土土样12套不同湿度梯度的可见光-近红外反射光谱,通过反射率、相对反射率以及水分吸收峰特征参数探究原状湿土光谱特征;在此基础上,选择对土壤湿度变化响应明显的变量,采用偏最小二乘回归反演土壤湿度,并对比选出最佳反演模型。结果表明:(1)随着风干过程中土壤湿度的降低:土壤反射率整体先下降后上升,可见光波段在土壤湿度较低时存在误差;1450 nm和1950 nm吸收峰的位置向短波方向偏移,吸收峰深度、宽度和面积不断减小,2 200 nm处吸收峰右肩高度不断降低。(2)土壤水分吸收峰特征参数对土壤湿度响应明显;反射率和相对反射率与土壤湿度相关性较高的波段均出现在>1300 nm以后。(3)反射率(R)反演原状土湿度精度较低,R2val=0.752,RPD=1.81,经过数学形式和相对反射率(Rr)变换后,[lg(1/Rr)]'建模中R2val=0.820,RPD=1.99;基于水分吸收峰特征参数建立的模型R2val=0.800,RMSEP=62.70 g kg-1,RPD=2.29,最佳主成分数为3,是反演原状土土壤湿度的最佳建模变量。     

菲、芘在单一和复合污染条件下不同老化阶段的提取率及其生物有效性

研究了土壤中多环芳烃菲、芘在单一和复合污染条件下的老化过程,150天内观察到菲、芘的提取率随时间延长而逐渐减少,下降速率呈现初始较快、而后减慢的趋势;菲、芘的环糊精提取法的提取率随老化时间延长而下降的趋势要比索氏提取法明显。老化过程中复合污染土壤中芘的索氏法提取率略低于单一污染土壤中芘的提取率。在老化的后期,复合污染土壤中菲的环糊精法提取率略高于单一污染土壤中菲的提取率。利用蚯蚓作为测试生物,研究两种污染物的老化过程对其生物有效性的影响,发现表征其生物有效性的蚯蚓吸收率、生物富集系数(BCF)均随老化时间的延长而下降,此外,老化过程中复合污染条件下菲的生物有效性总是大于菲作为单一污染源时的生物有效性。对污染物的环糊精法提取率和蚯蚓吸收率作相关分析发现,单一污染土壤中菲和芘的环糊精提取法的提取率与蚯蚓吸收率均呈显著正相关。     

有机物覆盖地面对土壤物理因素影响的研究(Ⅰ)——有机物覆盖层下土壤湿度的变化

利用有机废弃物覆盖地面是在自然种植条件下调节土壤水分以促进作物生长的农业技术措施。以田间实验为基础，分析了在不同有机物覆盖层厚度下不同位置处土壤湿度的变化。与对照处理相比，有机物覆盖使覆盖带中部土壤表层的湿度显著提高，同时覆盖带具有显著的边缘效应。覆盖对土壤湿度的作用效果随着土壤深度的增加而减小，在２０ｃｍ土壤深处覆盖层对土壤湿度无显著的影响     

有机物覆盖地面对土壤物理因素影响的研究（I）——有机物覆盖层下…

利用有机废弃物覆盖地面是在自然种植条件下调节土壤水分以促进作物生长的农业技术措施。以田间实验为基础，分析了不同有机物覆盖层厚度下不同位置处土壤湿度的变化。与对照处理相比，有机物覆盖使覆盖带中部土壤表层的湿度显著提高，同时覆盖带具有显著的边缘效应，覆盖对土壤湿度的作用效果随着土壤深度的增加而减小，在２０ｃｍ土壤深处覆盖层对土壤湿度无显著的影响。     

土壤湿度对冬小麦光合速率的影响

本文通过盆栽及大田试验,对冬小麦开花灌浆期不同土壤湿度的小麦叶片光合速率测定得出:(1)土壤湿度在田间持水量的70%-85%时小麦光合速率最高,光合对土壤湿度的反应低湿较高湿更敏感;(2)土壤干旱可使小麦光合午休加重,适当灌溉可减小光合速率中午降低的程度;(3)土壤干旱后灌水,可明显提高小麦光合速率,以适宜土壤湿度下限时灌水效果最好.     

干湿循环对土壤斥水性的影响

处于地表的各类土壤总是处于不断的干湿循环过程,土壤性质也会因此而发生改变。本文通过试验对干湿循环过程中斥水性土壤的"斥水–亲水"特性展开研究,试验结果表明:干湿循环对斥水性土壤的接触角及斥水性有重要影响。在干湿循环过程中,增湿时的初始状态不同则其初始接触角会发生变化,土壤斥水性对初始状态的敏感性随着黏粒含量的增加而增大。干湿循环开始时,土壤越干则初始接触角越大。当黏土和黏壤土试样含水量减小时,增湿或脱湿过程中滴水穿透时间(waterdroppenetrationtime,WDPT)先增加后减小,在某一时刻达到峰值,试样含水量相同时,脱湿过程所对应的WDPT要明显小于增湿过程,两种类型的土样在干湿循环中均没有临界含水量。随着含水量的降低,壤质砂土的WDPT是不断增加的,且干湿循环过程中斥水性砂土并没有出现峰值,存在明显的临界含水量。     

土壤表现为朗伯体的土壤湿度临界值的确定方法初探——以黑土为例

多角度遥感中我们发现具有一定湿度的土壤表现为非朗伯体.而小于这个湿度时土壤则表现为朗伯体。本文以黑土土壤为例,通过对含水土壤偏振度的测量,建立偏振度与土壤湿度之间的数学模型,计算出偏振度为0时土壤湿度,这个湿度就是土壤表现为朗伯体和非朗伯体的湿度临界点,再通过实验验证我们得到的结论。     

2︰1和1︰1型黏土矿物胶体凝聚中Hofmeister效应的比较研究

土壤胶体是土壤具备肥力与生态功能的物质基础,土壤胶体凝聚与分散影响着土壤中一系列微观过程和宏观现象。采用动态光散射技术比较研究三种碱金属阳离子(Li+、Na+、K+)引发不同类型黏土矿物(2︰1型蒙脱石和1︰1型高岭石)胶体凝聚中的Hofmeister效应。研究发现,Li+、Na+、K+作用下蒙脱石、高岭石胶体的凝聚速率、临界聚沉浓度及活化能都存在明显差异,表现出强烈的Hofmeister效应。当电解质浓度为20 mmol·L–1时,K+引发蒙脱石胶体凝聚的速率为66.61 nm·min–1,远高于Na+、Li+引发蒙脱石胶体凝聚速率(5.93、4.41 nm·min–1);而与之对应的临界聚沉浓度则呈现K+(蒙脱石21.8 mmol·L–1、高岭石34.6 mmol·L–1)低于Na+(蒙脱石57.6 mmol·L–1、高岭石85.8 mmol·L–1)低于Li+(蒙脱石81.8 mmol·L–1、高岭石113.9 mmol·L–1)规律,胶体凝聚中活化能可合理解释此现象。电解质浓度为25 mmol·L–1时,Li+、Na+、K+引发蒙脱石、高岭石胶体凝聚的活化能分别为1.97 kT、1.43 kT、0 kT和2.94 kT、1.71 kT、0.49 kT,说明蒙脱石、高岭石胶体凝聚过程中Hofmeister效应序列均为Li+相似文献   

陕北黄土丘陵沟壑区旱地土壤水分动态

陕北黄土丘陵沟壑区早地土壤水分动态具有如下特征:(1)土壤入渗快、蒸发快。雨季时土壤湿度迅速增高,雨季过后土壤湿度骤降;即使在丰水年,到11月底时,雨季降水已基本损失殆尽。土壤在经过四个阶段的循环后,开春时其湿度仍保持在田间稳定湿度左右。(2)降水和蒸发同步。降水量最大的时段,正是蒸发强度最大的时段。(3)土壤蒸发时,水分整体移动性较强,在旱季0～2m土层上下层之间土壤湿度无明显差异,土壤湿度剖面比较均一。(4)作物耗水绝大部分或全部来自生育期降水,土壤对生育期内降水起调节和再分配作用。     

对硝基氯苯在土壤和腐殖酸上的长期吸附与多步解吸的研究

采用批量平衡实验法研究了对硝基氯苯（p-NCB）在土壤和腐殖酸上的长期吸附和多步解吸,比较了连续的多步解吸与一步解吸的差异。结果表明,随着吸附时间的增加吸附量均会有所增加,随吸附时间增加吸附等温线的非线性增强。p-NCB在液相和固相上的初始浓度对吸附速率有一定影响,低浓度比高浓度时达到平衡的速率要低。对于两种受试土壤,两次解吸得到的等温线均无法与吸附等温线重合,表现出很强的吸附不可逆性。而尽管p-NCB在腐殖酸上表现出明显的非线性吸附（n = 0.794）,但4次解吸后所得到的平衡位点与吸附所得的平衡位点基本落在同一条直线上,对数坐标下进行线性拟合的相关系数（R2）可达0.988,说明吸附过程是完全可逆的。     

土壤中有机污染物的老化及其环境意义

持久性有机污染物随着在土壤中时间的延长,其生物有效性和毒性会逐渐下降的现象被称为老化。老化对有机污染物的有效性和行为归趋有着重要的影响。本文对国外有关老化对有机污染物生物有效性和可浸提性的影响,老化的机理和影响因素,以及老化后有机污染物生物有效性评价方法的研究作了概述。指出老化作为土壤对有机污染物修复的一种自然修复过程,可降低有机污染物的潜在环境风险,具有重要的环境意义。     

Effect of Organic Matter on the Release Behavior and Extractability of Copper and Cadmium in Soil

Land disposal of organic waste materials may alter the heavy-metal status of the soil by affecting metal solubility or dissociation kinetics. The aim of this investigation was to study the influences of poultry manure and pistachio compost (at the rate of 300 g kg^?1) on release behavior and extractability of copper (Cu) and cadmium (Cd) in two soils of Iran. For release studies, samples after incubation were extracted with ethylenediaminetetraacetic acid (EDTA) at pH 7.0 with shaker for periods of 5 to 2880 min. Results showed that during the reaction periods, Cu and Cd release rates were rapid at first and then became slower until equilibrium was achieved. In the two soils, extractability of Cu increased with poultry manure treatment and decreased with pistachio compost treatment as compared to the control soil, and extractability of Cd decreased with both pistachio compost and poultry manure treatments as compared to the control soil.     

基于EPO算法去除水分影响的土壤有机质高光谱估算

野外进行土壤有机质的光谱快速预测时需考虑土壤含水量的影响。在室内设计人工加湿实验分别获取9个土壤含水量梯度(0~32%,间隔4%)的土壤光谱数据,分析土壤含水量变化对光谱的影响,再利用外部参数正交化法(external parameter orthogonalization,EPO)进行湿土光谱校正,并结合偏最小二乘回归和支持向量机回归分别建立土壤有机质预测模型。结果表明,土壤光谱反射率随着土壤含水量的增加呈非线性降低趋势,偏最小二乘回归模型的预测偏差比为1.16,模型不可用;经EPO算法校正后,各土壤含水量梯度之间的光谱差异性降低,能实现土壤有机质在不同土壤含水量梯度的有效估算,偏最小二乘回归和支持向量机回归模型的预测偏差比分别提高至1.76和2.15。研究结果可为田间快速预测土壤有机质提供必要参考。     

Interacting effects of cation saturation and drying, freezing, or aging on the extractability of nonylphenol and phenanthrene from a sandy soil

Purpose

The structure and properties of the soil organic matter and its interactions with solutes may be altered by changes in soil chemistry and by the aging of soil. The main objective of this study was to investigate the effect of long-term aging and cation saturation of soil on the extractability and degradability of two hydrophobic xenobiotics in soil. In addition, it was tested if drying or freezing of soils can accelerate the relevant aging processes.

Materials and methods

The sandy topsoil was treated by either 0.1?M NaCl, CaCl₂, AlCl₃ solutions or water and samples were sterilized by ??-radiation and spiked with ¹⁴C-labeled nonylphenol (NP) or phenanthrene (Phe) at 10???g?g^?1 of soil. Samples were then used in four parallel experimental setups: (1) 9?months of aging under sterile conditions, (2) inoculation by native original soil with further 7?months of aging (bioaging), (3) drying and wetting or (4) freezing and thawing of soils. After different time intervals, the extractability of xenobiotics with water, cyclodextrin, and ethanol was investigated.

Results and discussion

During 9?months of aging under sterile conditions a continuous decrease of NP and Phe extractability and an increase of the non-extractable fraction occurred. During the 7?months of biologically active aging, the mineralization of NP was lower than of Phe while more NP remained extractable than Phe. In comparison to the sterile aging, the bioaging led to a less formation of non-extractable residues of NP and Phe. The long-term sterile aging effects on NP-extractability were also achieved by short-term freezing and thawing of the soils, while aging of Phe was better mimicked by drying?Cwetting cycles. The effects of cation saturation of soils on xenobiotics extractability were less pronounced.

Conclusions

Sterile aging, bioaging, freezing, and thawing facilitate the formation of the non-extractable fraction of NP and Phe in the soils. Different cation treatments alter soil properties, but the effects on aging of NP and Phe in soils were negligible.     

The Effect of Contrasting Moistening Regimes on CO<Subscript>2</Subscript> Emission from the Gray Forest Soil under a Grass Vegetation and Bare Fallow

The effect of contrasting moisture regimes on the CO₂ emission from the gray forest soils (Haplic Luvisols (Loamic, Cutanic, Humic)) under a grass vegetation and bare fallow was studied in a field simulation experiment in June–September, 2015 (Moscow region). Two short soil droughts (53 and 34 days) and a long one (94 days) were simulated on plots isolated from precipitation. A variant with regular irrigation, where the soil moisture was maintained 60–70% of their water holding capacity, was used as a control. Over the whole observation period, the CO₂ emissions from the soils studied decreased by a factor of 1.8 compared to the control only in the variant with the grass vegetation under prolonged drought. During the first hours after irrigation of the dry plots, the soil respiration intensified due to the “Birch effect”. The magnitude of this effect was 84–104% in the soils under the grass vegetation and 114–133% in the fallow areas. Owing to this phenomenon, the total CO₂ emission from the soils subjected to two short droughts was equal to the CO₂ flux under regular moistening for the grass plots and exceeded it by almost 1.3 times for the fallow plots as compared to the control. However, the share of extra CO₂ flux induced by moistening of the dry soils did not exceed 8–10% of the total CO₂ emission over the whole observation period.     

Effects of Soil Drying on Soil pH and Nutrient Extractability

A sample set from a field experiment conducted at two sites, a commercial organic potato farm and a conventionally managed experiment station farm, was used to compare the extractability of nutrients in field-moist and air-dried soils. Standard soil characterization methods of the Maine Soil Testing Service were used to determine soil pH and extractable nutrient content. The data were analyzed with Systat using paired t-tests. Air drying decreased soil pH and increased extractability of calcium, micronutrients, and metals. Many of the observed changes were probably a result of increasing surface acidity with drying. Drying increased the extractability of inorganic phosphorus, probably because of disruption of aluminophosphate complexes, particularly in conventionally managed soils, which had received high amounts of inorganic phosphorus fertilizer. Drying also increased the extractability of complexed phosphorus, probably both organically and inorganically complexed phosphorus, and decreased the extractability of potassium, probably by enhancing potassium fixation in clay interlayers.     

Conservation of soil moisture by different stone covers on alpine talus slopes (Lassen, California)

This study reports on the influence of stone covers with different clast sizes on the soil moisture of alpine talus slopes in Lassen (California). Fifteen four-plot sets were sampled in the dry season (July 1990) in sandy areas and in talus covered with pebbles, cobbles, or blocks between 2740 and 2775 m. Three depths (0–5, 5–10, 10–15 cm) were sampled. Field moisture content increased gradually with depth in all soil profiles, and also in plots covered by increasingly larger rocks. Surface soils in sand areas were very dry, but under rocks had water contents 6 to 14 times greater. Differences among plots decreased with depth, but subsoil samples in sand were still drier than those beneath any stone cover at similar depths. Blocks were most effective in conserving moisture; water content below them was higher than even in deep (10–15 cm) sand soils. Soil temperatures were recorded in sand and under blocks for an 11-day period. Minima were not significantly different, but average maxima were 5.6°C lower under blocks than in sand, which reached highs 4.4°C lower than the air. Differences in soil moisture among talus types are ascribed to lower evaporation losses under stones, due to both disruption of capillarity by the coarse particles, which prevented water flow to the talus surface, and to their efficient reduction of maximum temperatures. An irrigation experiment was conducted at 2110 m on a steep talus on the Chaos Crags from July 18 to Aug. 2, 1993. Four 100×75 cm plots with the same surface types than at Lassen received 22.5 mm water; moisture content was then periodically sampled. Watering produced similar water distributions among soil depths and talus types to those in Lassen. Evaporation occurred quickly in bare soils due to high air and soil temperatures. The sand surface was already dry 2 days after watering, but stone-covered plots remained moist until day 15, when soils under blocks still retained 77–97% of the water content (percent by weight) at the start of the test.     

马铃薯淀粉渣对土壤保肥特性及玉米幼苗生长的影响

[目的]探究马铃薯淀粉渣对土壤保肥特性及玉米幼苗生长的影响,为马铃薯淀粉渣的利用提供依据。[方法]采用室内人工气候箱模拟自然环境和用淋洗管模拟田间淋洗的方法,测定沙壤土中施入0,1.00,5.00,10.00,20.00,30.00g/kg的马铃薯淀粉渣对土壤容重、土壤总孔隙度、土壤含水量;土壤淋洗出的硝态氮、铵态氮、速效磷和速效钾含量及玉米幼苗株高、茎粗和干鲜重等指标。[结果]马铃薯淀粉渣施用量为30g/kg时,土壤容重降幅达7.24%,土壤总孔隙度、土壤含水量升幅分别为10.15%,21.25%;土壤淋洗出的硝态氮、铵态氮、速效磷和速效钾含量降幅分别为97.13%,91.03%,63.85%和66.4%;玉米幼苗株高较对照降低8.90%,茎粗较对照增加25.53%,幼苗的干、鲜重分别比对照提高13.47%,15.79%。[结论]马铃薯淀粉渣施用量为30.00g/kg时,改善了土壤理化性状,增强了保肥能力,明显促进玉米幼苗干物质的积累。     

农田河道河岸土壤含水量变化特性分析研究

河岸土壤含水量是选择农田河道护岸植物的一个重要影响因素。根据2008年10月~2009年9月对宁波农村地区3条典型农田河道河岸土壤含水量的周年监测结果,同时结合同期的降水量数据和河道水位数据,开展宁波农村地区农田河道河岸土壤含水量的变化特征研究。结果表明:(1)农田河道河岸不同位置的平均土壤含水量顺序为位置3(常水位至洪水位河岸区域)>CK(岸边蔬菜地)>位置2(洪水位至岸顶河岸区域)>位置1(岸顶区域),岸顶及洪水位以上河岸区域的土壤相对干燥,而常水位至洪水位之间河岸区域相对湿润,但此区域土壤含水量变化幅度大,长期处于旱湿交替状态;(2)河岸位置1和位置2的土壤含水量与采样当地3日内的降水量之和存在显著相关关系,河岸位置3的土壤含水量与降水量相关性不显著,而与河道水位高低存着极显著相关关系。(3)农田河道河岸不同位置的护岸植物选种需根据土壤含水量变化特征进行确定。