重金属在根际中的化学行为——Ⅱ.土壤中吸附态铜解吸的根际效应

用第四纪红壤性水稻土(QP)、淀浆白土(WP)、第四纪红土(QR)和赤红壤(LR)研究了土壤中吸附态铜的解吸的根际效应。结果表明,吸附态铜可分为0.1M KNO_3解吸的易解吸态铜和0.1MHCl解吸的难解吸态铜。随吸附量增加,易解吸态铜百分数增加,而难解吸态铜百分数下降。易解吸态铜在根际土中的量小于非根际土中的量,各土壤的根际效应依次为:QP>WP>LR>QR;其平均解吸百分数则为:QR>LR>WP>QP。难解吸态铜的量为根际土大于非根际土,各土壤的根际效应为:WP>LR>QP>QR,其平均解吸百分数依次为QP>WP>LR>QR。根际中铜吸附的增加主要是因为难解吸态铜的增加。     

碳酸钙对土壤镉吸附及解吸的影响

采用等温吸附法,并以1mol/L KNO3进行解吸试验,研究CaCO3对3种土壤镉吸附和解吸的影响。结果表明,3种土壤的原状土样对镉吸附总趋势为：栗钙土＞棕壤＞淋溶褐土,均符合Langmuir方程、Frenudlich方程和Temink方程,其中以Freumdlich方程最佳。镉的专性吸附量表现为栗钙土＞淋溶褐土＞棕壤。添加CaCO3使3种土壤中镉的吸附量增加,增加幅度棕壤为4％－11％,淋溶褐土2％－11％,栗钙土2％－8％。外界加入的镉浓度越高,增加幅度越大。Freundlich方程（lgX=lgK lgC/n）拟合的参数结果表明：加入CaCO3后,K和n值均下降;Langmuir方程中镉最大吸附值增加,吸附平均常数减小。可以推测,CaCO3的存在之所以能够使土壤体系吸附镉能力增加,除CaCO3本身的吸附作用增加,吸附平衡常数减小。可以推测,CaCO3的存在之所以能够使土壤体系吸附镉能力增加,除CaCO3本身的吸附作用外,还可能影响反应体系的平衡系数。加入CaCO3,土壤对镉的专性吸附明显增加,尤其以棕壤专性吸附的镉最多,淋溶褐土其次,而栗钙土增加较少,栗钙土去除CaCO3后,镉的吸附减少了2.0%-26.0%,土壤专性吸附的镉减少4.0%-38.2%。3种土壤镉的解吸能力表现为：棕壤＞淋溶褐土＞栗钙土。添加CaCO3,土壤镉的解吸量下降。去除CaCO3后,栗钙土匐解吸量明显增加。     

不同污染负荷土壤中镉和铅的吸附－解吸行为

采用一次平衡法,对3种不同污染负荷土壤Cd2 和Pb2 的吸附-解吸行为进行了比较.结果表明,低污染负荷土壤对Cd2 和Pb2 的吸附能力高于高污染负荷土壤.3种土壤对Cd2 的吸附等温线与Freundlich方程有较好的拟合性,Pb2 的等温吸附过程可用Langmuir方程与Freundlich方程来描述.双常数方程是描述这3种不同污染负荷土壤中Cd2 和Pb2 吸附动力学行为的最优模型,其次为Elovich方程,最差模型是一级动力学方程.Pb2 的解吸滞后现象较Cd2 明显.高污染负荷土壤的吸附态Cd2 、Pb2 解吸率高于低污染负荷土壤,Cd2 、Pb2 解吸量与其初始吸附量之间的关系符合二次幂方程.3种土壤Cd2 、Pb2 的解吸速率随重金属初始浓度的增加而增加,随解吸时间的延长而降低.     

超积累植物东南景天根际可溶性有机质对土壤锌吸附解吸的影响

采用盆栽和模拟试验研究了锌超积累植物东南景天根际土壤可溶性有机质(DOM)对土壤锌吸附解吸的影响.结果表明: 采用矿山土壤种植锌超积累植物东南景天后,根际土壤水溶性锌和乙酸铵提取态锌含量显著降低,而非根际土壤有效锌无明显变化.与不种植东南景天的对照土壤相比,根际土壤pH值降低了0.3个单位,有机质和DOM含量分别提高13.6%和20.9%.东南景天根际DOM对土壤锌吸附解吸的影响方式和程度与土壤类型有关.与对照DOM相比,在矿山土、黄筋泥和黄松土中,添加根际DOM使锌的最大吸附量(X_m)分别降低了17.8%、21.9%和27.7%,而非根际DOM对锌的最大吸附量没有影响.在3种供试土壤中添加根际DOM促进了锌的解吸,其中以黄松土最明显.东南景天根际DOM能降低土壤锌吸附容量,减少土壤对锌的吸附,促进吸附态锌的解吸,从而提高了根际锌的生物有效性.     

河口湿地植物活体-枯落物-土壤的碳氮磷生态化学计量特征

碳(C)、氮(N)、磷(P)生态化学计量比是生态系统过程及其功能的重要特征.以闽江河口的芦苇(Phragmites australis)和短叶茳芏(Cyperus malaccensis var.brevifolius)湿地为对象,开展植物活体-枯落物-土壤系统的C、N、P季节动态研究.结果表明:芦苇和短叶茳芏植物活体、枯落物和土壤年均C、N、P含量为C＞N＞P,两种湿地系统C、N含量均为植物活体和枯落物高于土壤,但与土壤P含量大小关系因植物构件差异而不同;芦苇和短叶茳芏植物活体、枯落物和土壤的C、N、P生态化学计量比表现为C∶P＞C∶N＞N∶P;芦苇湿地C∶N为枯落物＞植物活体＞土壤,短叶茳芏为植物活体＞枯落物＞土壤,而C∶P和N∶P均为枯落物＞植物活体＞土壤;C、N、P化学计量比可以反映湿地C、N、P交换过程和植物群落的生态功能.     

茶树根际土壤磷的解吸特性

为了探明茶树根际土壤磷的释放过程与供应机制,采用外源磷吸附培养方法,研究了不同母质、不同种植年限茶树根际土壤磷的解吸过程与特性,并用最小二乘法进行最优函数拟合.结果表明:茶树根际土壤与非根际土壤磷的解吸过程有明显的差异.茶树根际土壤的磷解吸能力极显著高于非根际土壤;与非根际土壤相比,根际土壤的平均有效磷含量、平均解吸率和平均β值(单位吸附量中的解吸量)分别高出5.49 mg.kg-1、1.7%和24.4%.不同成土母质发育的茶树根际土壤磷解吸能力为花岗岩风化物>第四纪红色粘土>板页岩风化物.随着种植年限的延长,3种母质茶树根际土壤的有效磷与磷解吸能力均有不同程度地提高.     

干湿交替对半干旱区沙地樟子松人工林土壤C和N矿化速率影响

在干旱/半干旱地区,土壤干湿交替是非常普遍的自然现象。近年来,随着极端降水和极端干旱气候事件增加,干湿交替对土壤C和N循环过程影响受到广泛重视。本研究以我国北方半干旱地区科尔沁沙地樟子松人工林为对象,模拟土壤干湿交替对土壤C和N矿化速率影响及其延时效应。结果表明,土壤呼吸CO2释放速率随土壤干旱化增加不断降低,干旱土壤重新湿润后,土壤呼吸速率能够迅速恢复到初始水平。与恒湿处理相比,干湿交替变化能够降低土壤呼吸CO2释放累积量和土壤硝态氮含量;而干湿交替处理土壤呼吸CO2释放累积量、土壤硝态氮含量和净硝化速率均显著高于恒干处理。在干湿交替结束后延时期间,土壤呼吸CO2释放速率、累积释放量对干湿交替变化表现出延时性,而土壤净硝化速率在不同处理间差异不显著。研究表明,土壤水分是影响半干旱地区沙地樟子松人工林土壤C和N循环的重要环境因子,且土壤C和N矿化速率对土壤干湿交替变化的延时响应存在差异。     

氮添加对沙质草地氨挥发及硝态氮淋溶的影响

采用密闭室法和离子交换树脂袋法,研究了科尔沁沙质草地不同处理(水添加、氮添加、水氮添加)氧挥发的损失量和硝态氮的淋溶量.结果表明:氮添加处理和水氮添加处理显著促进了氨挥发(P＜0.05),最大氨挥发速率显著高于对照;氮添加处理和水氮添加处理的氨挥发累积量为111.80和148.64 mg·m-2,分别占氮添加量的1.1％和1.5％;水氮同时添加条件下,氨挥发累计量显著高于氨添加处理(P＜0.05),水添加处理和对照相比没有显著差异(P＞0.05);水氮添加处理显著增加了土壤深度20 cm处的硝态氮淋溶量(P＜0.05),氮添加处理和水氮添加处理的硝态氮淋溶量分别是对照的1.96和4.22倍,然而在土壤深度40 cm处各处理硝态氮淋溶量差异不显著(P＞0.05);可见,氮添加和水氮添加均促进了土壤的氧挥发,对硝态氮的淋溶没有显著影响.     

南方稀土采矿恢复地土壤稀土元素含量及植物吸收特征

通过野外取样调查和室内ICP-MS测定,研究了福建省长汀县稀土矿治理地土壤和主要植物中稀土元素的含量、分布以及转移特征.结果表明:稀土矿治理地的土壤养分含量较低;土壤中稀土元素的含量为507.40～841.37 mg· kg-1,高于对照地土壤的含量.稀土矿治理地土壤中稀土元素主要为交换态,其含量占总量的61％～98％.稀土矿治理地土壤中稀土元素从原来偏单一的交换态转变为多种形态共存,其中有机态含量显著升高.植物根、茎、叶中稀土元素含量分别为40.27～986.01、5.14 ～ 206.58、6.81 ～ 2364.51mg·kg-1.稀土元素在植物各器官中含量水平除芒萁为叶＞根＞茎,其他植物均表现为根＞叶＞茎.根据不同植物吸收和积累稀土元素的差异,可将矿区治理地植物分为富集型和根部囤积型植物.芒萁属于富集型植物,桉树、高羊茅、宽叶雀稗、木荷和油茶属于根部囤积型植物.     

不同Hg浓度下水稻中Hg的分布累积特征

利用土壤盆栽实验方法,研究了土壤中Hg的形态分布,以及不同Hg浓度下,水稻不同生长时期各组织中Hg的分布规律和累积特征.土壤Hg存在的形态为:有机结合态＞残渣态＞＞氧化态＞＞溶解与可交换态≈特殊吸附态,在水稻的生长过程中,土壤中的Hg呈现从残渣态向有机结合态转化的趋势,有机结合态Hg平均占比为61.7％,是土壤Hg最重要的存在形态.Hg在水稻不同部位的浓度分布呈现W根＞W叶＞W茎＞W穗＞W籽粒,分析表明,水稻根、茎和籽粒中的Hg与土壤各形态Hg浓度呈显著或极显著正相关,但在水稻生长后期叶片中Hg与土壤Hg浓度的相关性不显著,叶片Hg与大气Hg进行交换起主要作用,改变了累积状况.随着土壤Hg浓度的增加和生长期的延长,根对Hg的束缚能力逐渐增加,根部Hg累积量增大,所占比例上升,而茎和叶的累积量相对稳定.     

择伐干扰对小兴安岭阔叶红松林土壤磷吸附解吸的影响

以小兴安岭地区阔叶红松林经过轻度、中度和强度择伐干扰后形成的天然林以及未经干扰的原始林(对照)林地表层(0～10 cm)土壤为对象,对土壤磷素的最大吸附量、吸附强度、最大缓冲容量、最大解吸量、平均解吸率和易解吸磷量等指标进行测定,研究不同干扰强度导致土壤磷吸附解吸的规律性变化,分析择伐干扰对阔叶红松林土壤磷吸附解吸特征的影响.结果表明: 各林地土壤磷最大吸附量为1383.93～1833.34 mg·kg^-1,中度和强度干扰林地显著高于轻度干扰林地和原始林地;磷吸附强度为0.024～0.059 L·mg^-1,强度和轻度干扰显著增加了林地土壤磷吸附强度;最大缓冲容量为35.68～97.97 L·kg^-1,强度干扰林地土壤的最大缓冲容量最高.择伐干扰显著降低了林地土壤的供磷潜力.各样地土壤磷最大解吸量、平均解吸率和易解吸磷量分别为526.32～797.54 mg·kg^-1、14.7%～25.5%和1.79～5.41 mg·kg^-1,林地土壤磷素释放能力随干扰强度的增加显著降低.择伐干扰通过降低林地土壤磷的供应及释放能力改变了阔叶红松林土壤磷吸附与解吸特征.     

Effect of Irrigation Water Quality on the Leaching and Desorption of Phosphorous from Soil

Knowledge of the rate of decrease of nutrients from soils resulting from poor water quality application is essential for long-term planning of crop production while minimizing the impact on groundwater quality. In this study, we examined the effect of Ca²⁺ concentration of irrigation water on phosphorus (P) leaching and kinetic release in columns of sandy soil. Phosphorous sorption in the presence of CaCl₂ solutions with Ca²⁺ concentrations of 3, 5, 10, and 15 mM CaCl₂ was determined to understand the transport and leaching of P in the sandy soil. The geochemical Visual MINTEQ was used to calculate saturation indices. A considerable number of leachate samples contained P at concentrations that could cause eutrophication. Total P leached from soil due to application of different CaCl₂ solutions ranged from 1.7 to 1.8 kg ha^?1 after 20 pore volumes had passed through the soil. Comparison of the leaching experiments results with the kinetic desorption data indicated that leaching removed on average 50 times less P than cumulative P desorbed by successive extractions with different CaCl₂ solutions. Leaching in presence of different CaCl₂ solutions was controlled by rate-limited dissolution of calcium hydroxyappatite and ß-tricalcium phosphate.     

Comparative study on EUF and other methods of soil analysis for the determination of available potassium in soils from Northern Greece

Summary Twenty-one representative soils from Northern Greece could be grouped into three categories based on the EUF-K curves which displayed marked differences in the magnitude of K release by the soils employed. The cumulative K desorption by EUF within 35 min and the cumulative K-uptake values of ryegrass (10 cuts) were found to be correlated (r=0.87***). Although this correlation is rather close, the K dynamics of a soil can be better characterized by the course of the K-desorption curves. Because the quotient EUF-K-80°C/EUF-K-20°C can give information on the course of K desorption it is therefore sufficient in routine investigations to know the EUF-K-20°C contents and the numerical values of the quotients EUF-K-80°C/EUF-K-20°C.The EUF procedure does not only indicate the close relationship between K extracted and K uptake by plants, but it can also provide information on other nutrients in the same soil sample. With this extra information it was possible to explain why in some of the analysed soils K uptake was low despite high K availability, the reason being that P availability was not optimal in one of the experimental soils and that the Mn concentration of the soil solution was too high in another. At equal K availability the K uptake was also dependent on the amount of EUF-extractable N.     

Reversibility of phosphorus sorption by ferruginous nodules

Ferruginous nodules sorb significant amounts of available soil and fertiliser phosphate. The effect of this sorption on phosphorus availability of an agricultural soil was tested by sequential extraction and by exhaustive cropping with millet (Pennisetum typhoides) in a greenhouse trial following fertilisation of the original soil containing 70% nodules and of prepared samples containing various mixes of separated soil fines and nodules. Phosphorus sorption maxima by the soil fines and nodules were 190 mg kg⁻¹ and 380 mg kg⁻¹ respectively. Samples of fines and nodules which had sorbed 110 and 194 mg kg⁻¹ were submitted to 8 successive extractions with 0.01 M KCl, after which P desorption amounted to 117 mg kg⁻¹ and 103 mg kg⁻¹ respectively. Hysteresis between sorption and desorption was negligible for the soil fines and increased with increasing nodule content of the samples. In the greenhouse experiment, P uptake at the first cropping was highest in the soil fines at all levels of phosphorus applied. Subsequent croppings, however, showed higher P uptake in the concretionary soils. These results indicate a higher initial P release from the soil fines with cropping followed by an earlier exhaustion of phosphorus. At the end of the greenhouse experiment, yields were low in spite of the large quantities of P still remaining in the soils. Phosphorus fractionation showed that, of the P left in the soil after cropping 20% was in labile, 29% in Fe or Al-associated, and 51% in low-availability forms.     

退耕还湖后湿地土壤对磷的吸附解吸特性

以安徽菜子湖区不同退耕年限(3、5、9和11年)湿地为研究对象,以相邻油菜地和原始湿地为对照(共6个样地),研究退耕还湖后湿地土壤对磷的吸附解吸特性变化.结果表明: 退耕湿地土壤对磷的等温吸附曲线与Langmuir和Freundlich吸附方程拟合程度均达极显著水平(P<0.01);6个样地土壤对磷的最大吸附量(X_m)、吸附常数(K)和最大缓冲容量(MBC)范围分别为478～1074 mg·kg^-1、0.14～0.61和68.6～661.5 mg·kg^-1,且退耕湿地的这些参数均随着退耕年限的延长而升高,但未达到原始湿地水平;6个样地土壤磷的平均解吸率为6.2%～14.6%,且退耕湿地土壤磷解吸率随着退耕年限的延长呈先增高后降低的趋势,但均显著高于原始湿地.表明随着退耕年限的增加,湿地土壤对外源磷的固持能力不断增强,而土壤有机质和粘粒含量是影响湿地土壤对外源磷固持能力的重要因子.     

Kinetics of zinc desorption from soils

Summary The kinetics of zinc desorption by DTPA were investigated in several soils. The rate of desorption of soil zinc and adsorbed zinc was rapid initially and gradually declined with time. The desorption reaction can be described by a two constant rate equation, C=At^B. The rate of zinc desorption in soil containing freshly adsorbed zinc was considerably higher than soil zinc, possibly due to the higher solubility and zinc concentration on the surfaces of soil particulate matter. The amount of zinc desorbed by DTPA, however, continued to decrease with increasing aging time. Elevated temperature further enhanced zinc aging and reduced zinc extractability. Recrystallization of adsorbed zinc in soil which subsequently increased the bonding strength of adsorbed zinc, could be responsible for the reduction of zinc desorption by DTPA.Contribution from the Department of Agronomy and Range Science, University of California, Davis, Ca.     

An investigation of the anion-exchange resin method for soil phosphate extraction

Summary The anion-exchange resin method for soil-phosphate extraction was investigated on 4 different soils under varying experimental conditions. The variables were: (a) the type of anion-exchange resin, (b) the anionic form of the resin, (c) the ratio between the amounts of resin, soil, and water, and (d) the time of shaking. The amount of P extracted was dependent on the anionic form of the resin. For resins in the chloride form both the amount of P extracted psr soil unit and the pH of the soil suspension varied with the type of resin and the soil-water ratio. Resins in the bicarbonate form stabilized the system, so that the amount of P extracted and the suspension pH were almost independent of the type of resin and the soil-water ratio. The results indicated that the rate-determining step in the overall process of P transport from the soil phase through the water phase to the resin phase is the P desorption from the soil phase to the water phase, provided the resin is added in excess. The rate of this P desorption is dependent on the chemical composition of the water phase, which in turn is governed by the type of soil, the soil-water ratio, the time of shaking and the anionic form of the resin. In a final experiment a resin was used in the chloride- and the bicarbonate form, respectively, for extraction of phosphate from 34 soils. The available P of these soils had been determined 15 years before in a pot experiment with ryegrass and by different laboratory methods². The degree of correlation between the ryegrass P uptake and the P. determined by the laboratory methods decreased according to the following order: resin (bicarbonate form), resin (chloride form), 0.5M sodium bicarbonate, L value, E value, ammonium lactate solution, sodium zeolite, 0.01M calcium chloride, phosphate potential, and 0.1M sulphuric acid. It is recommended that resins in the bicarbonate form should be used for both routine as well as more advanced analyses of the ability of soils to supply phosphate to plants. A final procedure for the analysis is given in the paper.     

土壤保肥-供肥机理及其调节Ⅲ.棕壤型菜园土的N素保持与供应

对辽宁省北部、中部及南部棕壤型菜园土15对肥、瘦地N素保持与供应性能的研究表明,绝大多数肥地及其各粒级微团聚体的全N量、NH₄⁺吸附与解吸量均大于瘦地及其各相应粒级微团聚体的,而NH₄⁺解吸率则相反。除了大粒级微团聚体外,肥、瘦地及其小粒级微团聚体全N储量与NH₄⁺吸附与解吸性能均有显着差异。肥、瘦地微团聚体的NH₄⁺吸附与解吸量均随粒径的增大而降低,解吸率则随之升高。NH₄⁺吸附与营养物质或酶活性等大多没有显着的线性相关关系;肥地及各粒级微团聚体NH₄⁺解吸与土壤有机质及其结合形态、全N含量、脲酶与磷酸酶活性等呈显着线性正相关,瘦地及其各相应粒级微团聚体的与营养物质含量和酶活性均无显着线性相关关系。     

百花湖消落带土壤磷释放的模拟研究

为探讨贵州省百花湖(水库)消落带土壤磷的释放状况,采用实验室模拟法研究了不同消落带土壤和环境条件变化对百花湖消落带土壤磷释放的影响,分析磷的释放量与磷赋存形态的关系。结果表明:未淹的黄壤释磷量最大,砂石壤最低;温度升高,土壤中磷的释放强度随之增大;扰动上覆水比静置条件下更有利于磷的释放;酸性和碱性条件下土壤磷的释放量略高于中性条件,且碱性条件下最高;厌氧条件比好氧条件更能加速磷释放;不同形态磷与土壤磷释放量有不同程度相关,其中有机磷(OP)与磷的释放极显著相关;与铁铝结合态磷(Fe/Al-P)和钙结合态磷(Ca-P)显著性相关。     

烟气脱硫石膏对滨海农耕土壤磷素形态组成的影响

为探明不同烟气脱硫石膏施用量对滨海农耕土壤中的全磷、有效磷、无机磷组分等的影响,通过田间试验的方式,分别在试验区土壤中施加0t/hm~2、15t/hm~2、30t/hm~2、45t/hm~2烟气脱硫石膏。研究结果表明:与对照组相比,各处理组的土壤全磷含量无显著差异,而土壤中的有效磷和渗滤液中的可溶性磷含量则随着烟气脱硫石膏施入量的增加而降低;施入烟气脱硫石膏后农耕土壤中无机磷含量显著增加,其中又以磷酸钙盐含量的增加为主,磷酸钙盐中的Ca2-P、Ca_8-P和Ca_10-P含量分别增加了30.8%—68.9%、35.2%—66.3%和7.3%—17.8%。烟气脱硫石膏的施用促进了植物的生长发育,有效磷的降低和无机磷组分中磷酸钙盐的增加并未影响到植物对磷素的吸收。因此,烟气脱硫石膏能有效地固定滨海农耕土壤中的溶解态磷,控制土壤过量磷素向水体迁移,降低附近水体富营养化发生的机率,保障区域水体生态系统环境安全。