土壤有机/无机胶体凝聚的光散射研究

有机/无机复合体是土壤中最重要的物质形态。本文在不同浓度的CaCl2作用下,对黄壤、胡敏酸、黄壤/胡敏酸混合胶体的凝聚动力学和凝聚体结构特征进行了研究,结果表明:黄壤、胡敏酸、黄壤/胡敏酸混合胶体的凝聚与否均强烈地依赖于体系电解质CaCl2浓度,其临界絮凝浓度(Critical flocculation con-centration,CFC)分别为1.38 mmol L-1、45 mmol L-1、15 mmol L-1。当CaCl2浓度高于CFC时,3种胶体的凝聚均表现为快速的扩散控制团簇凝聚(Diffusion limited cluster-cluster aggregation,DLCA)机制,形成分形维数分别为1.45、1.76、1.46的疏松凝聚体;当CaCl2浓度低于CFC时,3种胶体的凝聚过程对电解质浓度非常敏感,表现为慢速的反应控制团簇凝聚(Reaction limited cluster-cluster aggregation,RLCA)机制,形成分形维数高至1.58、1.86、1.56的相对紧实的凝聚体。凝聚速率越快,形成的凝聚体越疏松。在悬液中黄壤胶体自凝聚形成的结构很疏松,但是非常不稳定,而胡敏酸自凝聚体的结构非常稳定。胡敏酸的参与没有改变黄壤胶体凝聚体的结构性质,但显著促进所形成的凝聚体结构的稳定。     

Na~+、Ca~(2+)及Na~+-Ca~(2+)混合离子对胡敏酸胶体稳定性的影响

以胡敏酸为研究对象,通过光散射技术比较土壤中常见盐基离子(Na~+、Ca~(2+)和Na~+-Ca~(2+)混合三种电解质)不同浓度条件下胡敏酸胶体凝聚动力学过程,明确不同价态离子界面行为和陪补离子效应对胡敏酸分散稳定性和凝聚体结构的影响。结果发现,Na~+和Ca~(2+)对胡敏酸胶体聚沉能力的差异远远大于舒尔策-哈迪(Schulze-Hardy)规则中因其化合价不同所引起的差异;Na~+-Ca~(2+)混合体系中Ca~(2+)主导凝聚过程,且Na~+-Ca~(2+)混合与Ca~(2+)两种离子体系中凝聚现象的差异随离子浓度的降低而增大;混合离子体系中Na~+作为陪补离子,其陪补离子效应对临界聚沉浓度、颗粒间活化能和胡敏酸凝聚体结构均有一定影响,尤以对凝聚体的结构特征影响显著;Na~+-Ca~(2+)混合体系中胡敏酸凝聚体的结构紧实程度介于单纯离子体系之间,因此可通过调节溶液中的离子组成实现对凝聚体结构紧实程度的调控。上述结果表明,Ca~(2+)对胡敏酸的聚沉不仅依赖于静电作用,还有Ca~(2+)在强电场中的极化诱导其与胡敏酸表面含氧官能团之间发生的共价键和桥键的贡献;此外,陪补离子Na~+与Ca~(2+)在胡敏酸胶体表面的竞争吸附抑制了Ca~(2+)对胡敏酸的聚沉作用,从而形成紧实程度适中的结构体。研究结果为探究胶体界面反应及土壤胶体凝聚机制提供新的思路和理论。     

恒电荷土壤及可变电荷土壤与离子间相互作用的研究 Ⅰ.共存离子对NO3-吸附的影响

研究了我国典型3种可变电荷土壤和4种恒电荷土壤在陪伴阳离子分别为K+、Na+、Ca2+时和1mmolL-1KCl、K2SO4支持电解质中NO-3的吸附.结果表明,NO-3吸附量随pH的增加而减小.在添加相同浓度NO-3时,3种可变电荷土壤对NO-3的吸附量顺序为Ca(NO3)2＞KNO3＞NaNO3＞KNO3+KCl＞KNO3+K2SO4;在初始NO-3浓度0.5～5mmolL-1的范围内,吸附量随浓度变化的关系符合Langmuir等温吸附式.由此求出与NO-3吸附结合能有关的常数(K)在不同共存离子存在下数值较小且差异不大,因此认为不同陪伴阳离子和不同伴随阴离子对NO-3吸附的电性机理影响不大,只是改变了土壤表面的正电荷数量从而使吸附量发生变化.4种恒电荷土壤对NO-3的吸附量通常很小,其中在Ca(NO3)2介质中较在其他介质中稍大,最大吸附量仅为1.5mmolkg-1左右,约为可变电荷土壤的1/10,且在浓度较低时常观察到负吸附.     

不同盐基离子对黑土胶体zeta电位及凝聚过程的影响

以黑土胶体为研究对象,比较黑土胶体在不同浓度的四种盐基离子Na+、K+、Ca2+、Mg2+体系中的zeta电位、颗粒凝聚动力学过程和平均凝聚速率,明确不同离子界面行为对黑土胶体zeta电位和凝聚过程的影响。研究发现土壤胶体较高的颗粒密度(0.61 g L-1)更有利于获得稳定的zeta电位值;二价阳离子与一价离子相比,因其有更强的压缩双电层能力而引起zeta电位的降低和较强的土壤胶体凝聚过程;同价离子对zeta电位和土壤胶体聚沉影响的差异表现为离子浓度同为200 mmol L-1时,黑土胶体在K+体系中的凝聚速率是Na+体系中的7.65倍,离子浓度同为4 mmol L-1时,黑土胶体在Ca2+体系中的凝聚速率是Mg2+体系中的2.79倍。除了其自身体积的差异还与离子在表面强电场中的极化作用有关。不同盐离子受土壤表面附近电场的强烈影响,在土壤胶体表面固-液界面上被诱导极化,从而易引起胶体zeta电位的不同。该研究为表征土壤胶体表面性质及胶体凝聚过程和团聚体形成理论研究提供基础。     

不同pH下有机酸对针铁矿和膨润土吸附Cd2+、Pb2+的影响

用平衡吸附法研究了不同pH下,三种有机酸(乙酸、酒石酸和柠檬酸)对针铁矿和膨润土等温吸附Cd2 、Pb2 的影响。结果表明:在加入的Cd2 、Pb2 浓度分别小于0.2 mmol L-1和4.0 mmol L-1时,针铁矿和膨润土吸附平衡体系的pH随加入重金属浓度的增加而降低,膨润土体系的pH降低更明显。在有机酸作用下,pH对针铁矿和膨润土吸附Cd2 、Pb2 的影响差异显著。3酒石酸>乙酸,其对膨润土吸附的影响差异不明显。     

用悬液Wien效应研究Na+、K+、NH4+、Ca2+、Zn2+和Cd2+阳离子与红壤黏粒间的相互作用及能量关系

采用悬液Wien效应法研究了Na+、K+、NH4+、Ca2+、Zn2+和Cd2+阳离子与红壤黏粒间的相互作用及能量关系。结果表明,在试验条件下,红壤黏粒与阳离子Na+、K+、NH4+、Ca2+、Zn2+和Cd2+的平均结合自由能分别为:4.50、7.35、7.15、9.12、9.84和9.63 kJ mol-1。含Ca2+悬液的电导率随场强增加而递增最快,含Na+和NH4+悬液的电导率随场强增加而增加最慢,而含K+、Zn2+和Cd2+的悬液电导率的增速相近、介于其间。红壤悬液中不同阳离子的解离速率顺序为Ca2+>K+>Zn2+=Cd2+>Na+=NH4+。在低场强(15～80 kV cm-1)下,不同阳离子的平均吸附自由能ΔGad没有差异。在场强100 kV cm-1以上,二价阳离子的ΔGad明显大于单价阳离子,不同阳离子间ΔGad的大小顺序为NH4+≤Na+>K+=NH4+>Ca2+>Zn2+=Cd2+,Na+离子平均解离度的递增速率(场强增加1kV cm-1所引起的解离度增量)最大,为0.000 427 cm kV-1,其次是Ca2+离子,为0.000 221 cm kV-1,其余阳离子为0.000 12～0.000 14 cm kV-1。     

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   

阴离子对可变电荷土壤吸附铜离子的影响机理

根据NO-3、Cl-和SO24-对可变电荷土壤和恒电荷土壤吸附Cu2+的影响的比较,探讨了阴离子对可变电荷土壤吸附Cu2+的影响机理。结果表明,当3种阴离子的浓度相同时,在SO24-体系中铁质砖红壤对Cu2+的吸附率较在NO3-和Cl-体系中大得多,而在浓度相同的3种阴离子体系中,黄棕壤对Cu2+的吸附率相差不大。在离子强度相近的NaCl体系中,砖红壤对Cu2+的吸附率相近。在3种阴离子体系中,随着pH升高,砖红壤对Cu2+的吸附率均增大;但在NO-3体系和Cl-体系中Cu2+的吸附率相近;而在SO24-体系中Cu2+的吸附率最大。随着Na2SO4浓度的增大,铁质砖红壤和砖红壤对Cu2+的吸附率减小。但在0.005 mol L-1和0.05 mol L-1Na2SO4体系中,Cu2+的吸附率大于在不含Na2SO4的体系中者。而在0.5 mol L-1Na2SO4体系中,Cu2+吸附率小于在不含Na2SO4体系中者。在3种浓度的Na2SO4体系中,黄棕壤对Cu2+的吸附率均小于在不含Na2SO4体系中者。总之,阴离子可通过离子强度、专性吸附和形成离子对影响土壤对Cu2+的吸附。在可变电荷土壤中,阴离子对Cu2+吸附的影响机理较在恒电荷土壤中复杂得多。     

陪伴离子对土壤胶体吸附Cu2+和Pb2+的影响

采用表面络合模式研究了不同陪伴离子对陕西 4种典型土壤胶体吸附Cu2 、Pb2 的影响。结果表明 :在各阴离子体系 ,同一土壤胶体对Cu2 、Pb2 吸附百分数达到 5 0 %时对应的pH(pH50 )值呈现 :Cl->SO2 - 4>草酸根 >柠檬酸根 >NO- 3的趋势 ,表面络合常数logKintM 的大小次序与此相反 ;专性吸附特征值 (n值 )反映了吸附过程专性吸附与电性吸附比例的大小 ,其值大小表现为 :NO- 3>Cl- >SO2 - 4>草酸根 >柠檬酸根的趋势     

恒电荷土壤及可变电荷土壤与离子间相互作用的研究Ⅲ Cu2+和Zn2+的吸附特征

研究了3种典型可变电荷土壤和4种典型恒电荷土壤在不同pH和不同浓度下单纯及共存体系中Cu2 和Zn2 的吸附及其影响因素。结果表明,两类土壤对Cu2 或Zn2 的吸附量均随平衡浓度增加而增大,符合Langmuir吸附等温式;当Cu2 、Zn2 浓度一定时,pH升高使Cu2 、Zn2 吸附量增大,但当pH >5时,Cu2 、Zn2 吸附量随pH变化甚微,出现一个接近最大吸附量的“平台”。当添加Cu2 、Zn2 浓度相同,但二种离子的总浓度不同时,平衡液的Cu2 /Zn2 浓度比均小于1,说明两类土壤对Cu2 的吸附选择性大于Zn2 ,且这种趋势不因pH和离子浓度而改变。当Cu2 、Zn2 共存时,使可变电荷土壤的Zn2 吸附量减小约70 % ,是恒电荷土壤降低量的约1.5倍;可变电荷土壤吸附一个Cu2 或Zn2 时所释放H 的平均数,明显大于恒电荷土壤者,说明可变电荷土壤对Cu2 及Zn2 的吸附中专性吸附的比例较恒电荷土壤大     

外来种互花米草对江苏省潮间带生物地球化学过程的影响研究

Spartina alterniflora Loisel, a species vegetating in intertidal flats along the eastern coast of the United States, was introduced in China almost 30 years ago and has become an urgent topic due to its invasiveness in the coastal zone of China. The impacts of this alien species S. alterniflora on intertidal ecosystem processes in the Jiangsu coastland were investigated by comparing the sediment nutrient availability and trace element concentration characteristics in a mud flat and those of a four-year old Spartina salt marsh that had earlier been a mudflat. At each study site, fifteen plots were sampled in different seasons to determine the sediment characteristics along the tidal flats. The results suggested that Spartina salt marsh sediments had significantly higher total N, available P, and water content, but lower pH and bulk density than mudflat sediments. Sediment salinity, water content, total N, organic C, and available P decreased along a seaward gradient in the Spartina salt marsh and increased with vegetation biomass. Furthermore, the concentrations of trace elements and some metal elements in the sediment were higher under Spartina although these increases were not significant. Also, in the Spartina marsh, some heavy metals were concentrated in the surface layer of the sediment. The Spartina salt marsh in this study was only four years old; therefore, it is suggested that further study of this allen species on a longer time frame in the Jiangsu coastland should be carried out.     

土壤有机矿质复合体研究——Ⅱ.土壤各级团聚体中有机矿质复合体的组成及其氧化稳定性

土壤团聚体的形成是一个复杂的过程,而大团聚体(直径大于0.25毫米)形成过程则更为复杂。以往,许多研究者认为有机矿质复合体是大团聚体形成的基础。但是在具体地探索那些和大团聚体形成有关的有机矿质复合体的实质,如有机质的数量,有机物质的种类,有机矿质复合体的类型等等问题时,现有的资料仍然是不充分的。不同研究者的结果并不很一致,有一些结论甚至是相互矛盾的。从而影响这一成果在生产上的广泛应用。     

施用生物质炭对黑土腐殖质组成及水稳性团聚体分布的影响

为探究生物炭对土壤腐殖质组成和团聚体特征的影响，以东北黑土区植烟土壤为研究对象，设置了3个处理，2019-2020年连续施用低量生物炭5t/hm2（C1）；高量生物炭25t/hm2（C2）和不施生物炭（CK），分析了不同用量生物炭对土壤腐殖质组分及水稳性团聚体分布的影响，并利用傅里叶红外光谱(FTIR)和13C核磁共振光谱(13C-NMR)对土壤胡敏酸化学结构进行表征。结果表明：C1和C2处理分别使富里酸减少了16.90%和40.85%，胡敏酸含量显著增加了14.86%和33.78%，胡敏酸在腐殖酸中所占比例（PQ值）也显著增加；FTIR和13C-NMR分析表明，C2处理的土壤胡敏酸的2920/1620值降低了11.82%，脂族C/芳香C比值降低了13.04%，表明高量生物炭使胡敏酸芳构化程度增强，脂肪结构比例降低；生物炭的添加促使土壤大团聚体（>0.25mm）比例增加，C2处理提升大团聚体的作用更显著。结合相关性分析发现，胡敏酸含量与2~0.25mm大团聚体含量显著正相关，胡敏酸分子的脂肪族官能团特征与>2mm粒级团聚体显著正相关。此外，C1和C2处理显著提高了烟叶产量。从而表明，生物炭能提升土壤腐殖质中胡敏酸含量和结构，有利于土壤大团聚体形成，提高土壤固碳潜力，对作物有一定的增产效果。     

Observation of specific ion effects in humus aggregation process

Specific ion effects play a vital role in a variety of colloidal and interfacial processes. However, few studies have reported the specific ion effects in the humus aggregation process, which strongly influence the transport and fate of environmental pollutants. In this study, soil humus colloids were prepared and characterized, and the specific ion effects on humus aggregation in electrolyte solutions were investigated at a variety of concentrations and p H values using dynamic light scattering methods. Activation energy(?E), which is known to reflect the dynamics and stability of a colloidal system, was used to quantitatively characterize the specific ion effects. The results showed that given ?E value of 2.48 × 10~3 J mol~(-1) at p H 3.0, the electrolyte concentrations were 91.6, 58.2, 3.8, and 0.8 mmol L~(-1) for Na~+, K~+, Mg~(2+), and Ca~(2+), respectively, thus indicating significant specific ion effects in the humus aggregation process. Most importantly, decreasing the electrolyte concentrations increased the differences in the ?E value between two cation species with the same valence(i.e., ?EN_a-?E_K and ?E_(Mg)-?E_(Ca)), while increasing the p H increased the magnitude of ?E_(Mg)-?E_(Ca). However, the classic Derjaguin,Landau, Verwey, and Overbeek(DLVO) theory and the double layer theory, as well as the currently widely used ionic hydration and dispersion effects, failed to predict the experimentally observed increase in the specific ion effects with decreasing electrolyte concentrations in a quantitative sense. These results have implications for the necessity of involving specific ion effects for a better understanding of humus aggregation and interactions in aqueous and soil systems.     

Der Einfluß der natürlichen organischen Substanzen auf die Metallverteilung zwischen Boden und Bodenlösung in einem sauren Waldboden

The influence of organic matter in the translocation of metals between soil and soil solution of an acid forest soil Water extracts were prepared from soil samples which were collected from a soil profile showing very little variation in the texture down to a depth of 120 cm and thus only little translocation of clay in the soil profile. The aim of the study was to describe the distribution between soil and soil solution of several metals like Cu, Pb, Cd, Zn, Al and Mn as a function of humic substances, electrolyte concentration and pH. From the experimental results the following hypothesis on the reaction mechanisms involving metals and humus derived substances has been deduced. The metals Cu, Fe, Al and Pb are mobilized through complexation by soluble humus substances in addition to the usual pH dependent desorption and dissolution of hydroxides. This mobilization determines the solution concentration of Cu and Fe at pH > 3.7 and Al and Pb at pH > 4.2. Al, Fe and Pb are complexed selectively by high molecular weight humus derived substances which undergo adsorption on soil mineral surfaces. Cu interacts with low molecular weight humus derived substances which are not easily adsorbed by the mineral surfaces. Zn, Cd and Mn primarily undergo sorption and are thus controlled by pH and electrolyte concentration of solutions because their complexation with humus derived substances seems to be weak or nonexistant. It is further postulated that the humus derived substances mobilize Al³⁺ and Fe³⁺ ions. By this, other metals like Cd, Zn, Mn, Ca and Mg can occupy the free exchange sites.     

快速湿润过程中钾和钙离子浓度对土壤团聚体稳定性的影响

为探索土壤团聚体稳定性对电解质的响应情况,该文研究湖北省2种土地利用方式下(林地、耕地)的3种类型土壤(黄褐土、黄棕壤、棕红壤)团聚体,在不同浓度(0、0.005、0.01、0.02、0.05、0.08、0.10、0.20 mol/L)电解质(KNO_3、Ca(NO_3)_2)溶液中快速湿润时的稳定性和破碎过程。结果表明:1)浓度低于0.1 mol/L时,团聚体稳定性随电解质浓度增大而减小;2)团聚体稳定度AS随湿润时间呈双指数衰减,与纯水相比,棕红壤和林地黄褐土的破碎过程受电解质溶液影响尤为显著,黄褐土和耕地黄棕壤在电解质溶液中迅速全部破碎;3)初始阶段团聚体破碎能量与土壤粉粘比和有机质含量呈负相关,与铁铝氧化物含量呈正相关。总之,团聚体稳定性随电解质溶液浓度增大而减小,且相对于纯水,团聚体在电解质溶液中破碎更快。     

钙离子通过调节抗氧化酶活性保护NaCl对菊芋的毒害

The ameliorative effect of external Ca^2＋ on Jerusalem artichoke （Helianthus tuberosus L.） under salt stress was studied through biochemical and physiological analyses of Jerusalem artichoke seedlings treated with or without 10 mol L^-1 CaCl2, 150 mmol L^-1 NaCl, and/or 5 mmol L^-1 ethylene-bis（oxyethylenenitrilo）-tetraacetic acid （EGTA） for five days. Exposure to NaC1 （150 mmol L^-1） decreased growth, leaf chlorophyll content, and photosynthetic rate of Jerusalem artichoke seedlings. NaC1 treatment showed 59% and 37% higher lipid peroxidation and electrolyte leakage, respectively, than the control. The activities of superoxide dismutase （SOD）, peroxidase （POD）, and catalase （CAT） were decreased by NaCl, indicating an impeded antioxidant defense mechanism of Jerusalem artichoke grown under salt stress. Addition of 10 mmol L^-1 CaCl2 to the salt solutions significantly decreased the damaging effect of NaC1 on growth and chlorophyll content and simultaneously restored the rate of photosynthesis almost to the level of the control. Ca^2＋ addition decreased the leaf malondialdehyde （MDA） content and electrolyte leakage from NaCl-treated seedlings by 47% and 24%, respectively, and significantly improved the activities of SOD, POD, and CAT in NaCl-treated plants. Addition of EGTA, a specific chelator of Ca2＋, decreased the growth, chlorophyll content, and photosynthesis, and increased level of MDA and electrolyte leakage from NaCl-treated plants and from the control plants. EGTA addition to the growth medium also repressed the activities of SOD, POD, and CAT in NaCl-treated and control seedlings. External Ca2＋ might protect Jerusalem artichoke against NaC1 stress by up-regulating the activities of antioxidant enzymes and thereby decreasing the oxidative stress.     

盐生植物海蓬子对不同形式的氮源的响应

Salt-affected soils are agricultural and environmental problems on a global scale. Plants suffer from saline stresses in these soils and show nitrogen (N) deficiency symptoms. However, halophytes grow soundly under saline conditions. In order to clarify the N nutrition of the halophyte Salicornia bigelovii, it was grown at several N levels (1, 2, 3, and 4 mmol L^-1), supplied in the form of NO₃^- or ammonium (NH₄⁺), under high NaCl conditions (200 mmol L^-1). NH₄⁺-fed plants showed better growth than NO₃^--fed plants at 1-3 mmol L^-1 N, and plants in both treatments showed the same growth at 4 mmol L^-1 N. Nitrogen contents in NO₃^--fed plants increased with the N concentrations in solution; competitive inhibition of NO₃^- absorption by Cl^- was observed under lower N conditions. In addition, shoot dry weight was significantly correlated only with shoot N content. Therefore, growth of NO₃^--fed plants was regulated by N absorption. Inc ontrast, N contents of shoots in NH₄⁺-fed plants did not change with N concentration. Shoot Na content decreased with increasing N concentration, while K content increased. Dry weight was highly correlated only with K content in NH₄⁺-fed plants. These observations indicated that growth of NH₄⁺-fed plants was mainly regulated by K absorption.