黄土区不同施肥对土壤颗粒及微团聚体组成的影响

采用野外采样与室内分析方法,运用颗粒体积分形理论,研究了15年长期不同施肥处理对黄土区农田土壤颗粒组成、 微团聚体分布及有机碳的影响。结果表明,施肥处理对020 cm土层影响较大,不同施肥处理土壤颗粒及微团聚体的优势粒级均为0.02~0.05 mm。有机肥（M）、 磷肥（P）、 有机肥和氮肥配施（MN）、 有机肥、 氮肥和磷肥配施（MNP）处理可显著提高020 cm土层0.1~0.2 mm土壤颗粒的百分含量,有机肥和磷肥配施（MP）以及MNP处理有利于该土层大粒径土壤微团聚体的形成。氮肥和磷肥配施（NP）处理的土壤分散率最大,M处理最小。不同施肥处理土壤颗粒体积分形维数差异不显著。相关性分析表明, 020 cm及2040 cm土层土壤颗粒体积分形维数与粘粒（0.002 mm）和细粉粒 （0.002~0.02 mm） 呈极显著正相关,与粗粉粒 （0.02~0.05 mm） 和细砂粒 （0.05~0.2 mm）极显著负相关; 土壤团聚度与0.05 mm各粒径土壤团聚体显著或极显著负相关,与 0.05 mm各粒径土壤团聚体显著或极显著正相关。020 cm土层土壤有机碳与0.01~0.05 mm各粒径土壤团聚体显著或极显著负相关,与0.1~0.5 mm各粒径土壤团聚体极显著正相关。     

老冲积黄壤微团聚体对As(Ⅴ)与P竞争吸附—解吸特性

土壤微团聚体是土壤的最基本结构单元,不同粒径微团聚体的理化性质的差异不同使得重金属离子在各粒径微团聚体中的吸附—解吸能力大小不同。以名山河流域老冲积黄壤为研究对象,将其划分为4个粒径(2~0.25mm,0.25~0.053mm,0.053~0.002mm,0.002mm)。采用批培养法研究原土及不同粒径微团聚体对As(Ⅴ)与P的竞争吸附—解吸特性。结果表明:原土及不同粒径微团聚体对As(Ⅴ)、P的吸附—解吸特性相似,等温吸附均符合Langmuir和Freundlich方程,但Langmuir方程拟合效果最佳;动力学吸附均符合伪一级方程和伪二级方程,但伪二级方程拟合效果更好。原土及各粒径微团聚体对As(Ⅴ)、P的吸附均以专性吸附为主,非专性吸附为辅。原土及不同粒径微团聚体对As(Ⅴ)、P的最大吸附量不仅与粒径大小有关,与土壤有机质、CEC、游离氧化铁含量呈正相关。由于0.002mm粒径的土壤比表面积大,有机质、CEC、游离氧化铁含量高,故其对As(Ⅴ)、P有最大吸附能力和最高初始吸附速率。As(Ⅴ)、P在各粒径微团聚体上解吸量与其吸附量呈指数关系。当As(Ⅴ)与P共存时,明显互相抑制对方的吸附,促进对方的解吸。As(Ⅴ)与P在0.002mm粒径土壤中存在的竞争吸附—解吸能力最小。     

汶川震区不同植被下土壤组成及其分型特征

目前关于植被恢复对震区土壤颗粒、团聚体、微团聚体粒径分布的影响研究很少,故本文以植被恢复下汶川震区土壤为研究对象,采用土壤粒径分形维数的计算方法,研究了植被恢复类型下对土壤组成及分形特征的影响。结果表明:震区土壤风干团聚体以5mm的大粒径团聚体为主,湿筛后,土壤团聚体粒径分布中0.25mm粒径的团聚体为优势粒径,与对照样地相比,裸地、草地、灌木、经果林和玉米类型样地的土壤水稳性团聚体的MWD分别减小74.88%,40.30%,40.73%,46.98%和47.65%。震区土壤微团聚体组成以1~0.25mm粒径为优势粒级,0.25~0.05mm为粒径次优势粒级,该震区土壤微团聚体变化范围为2.327~2.853,呈现如下规律:玉米经果林灌木裸地草地对照样地;震区土壤颗粒分形维数与土壤砂粒(1~0.05mm)呈负相关性(D=2.926~0.002 X_(砂粒)),与土壤粉粒(0.05~0.002mm)呈显著负相关性(D=3.05~0.008 X_(粉粒),p0.01),与土壤黏粒(0.002mm)呈极显著正相关性(D=2.595+0.009 X_(黏粒),p0.01)。震区土壤遭受的扰动较大,导致震区土壤碎石含量增多,土壤微团聚体和土壤颗粒分形维数增大,通过对震区土壤结构特征的研究,可为震区灾后治理提供参考。     

柠檬酸对蒙山茶园土壤微团聚体吸附-解吸Cu2+的影响

以蒙山茶园土为对象,运用平衡液吸附法以及NaNO3溶液解吸法探讨了柠檬酸对原土及各粒径土壤微团聚体吸附-解吸Cu2+的特性,以期明确柠檬酸对土壤吸附解吸铜的过程中产生的影响。结果表明,加入柠檬酸后,随着Cu2+浓度的增加,原土和各粒径土壤微团聚体对Cu2+的吸附有所增加,吸附量大小顺序为:(0.002mm)(0.053~0.002)mm原土(2~0.25)mm(0.25~0.053)mm,与土壤微团聚体中游离氧化铁、阳离子交换量以及有机质含量大小顺序一致;柠檬酸对Cu2+的吸附既有促进作用又有抑制作用,低浓度(0~1mmol/L)的柠檬酸促进土壤微团聚体对Cu2+的吸附,而高浓度(1mmol/L)的柠檬酸则降低其吸附,吸附量在柠檬酸浓度为0.5mmol/L时达到最大;Langmuir、Freundlich、Temkin 3种方程对其等温吸附过程的拟合均达到了极显著水平(p0.01),其中以Langmuir方程的拟合效果最佳,说明加入柠檬酸后的原土及各粒径土壤微团聚体对Cu2+的吸附以单层吸附为主;随着铜浓度的上升,土壤微团聚体对Cu2+的易解吸率不断增加,柠檬酸的进一步加入使得土壤微团聚体对Cu2+的解吸率上升,而解吸大小顺序与吸附顺序相反。     

基于REE示踪的土壤团聚体破碎转化路径定量表征

土壤团聚体破碎转化路径是坡面侵蚀过程研究的难点问题之一。目前团聚体破碎转化路径的定量表征仍不明晰,一定程度上限制了土壤侵蚀过程中泥沙分选搬运机制的深入研究。基于大样带调查选取6种不同质地的典型农耕地土壤为研究对象,结合稀土元素(Rare Earth Elements,REE)示踪方法,综合分析不同粒径土壤团聚体(5~2,2~1,1~0.5,0.5~0.25,<0.25 mm)和不同径流扰动周期(24 h,7天)对REE吸附和解吸能力的影响,探究REE示踪不同粒径土壤团聚体破碎转化的可行性,定量表征了土壤团聚体破碎转化路径。结果表明:REE与土壤团聚体的实际吸附浓度低于施放浓度,2~1,1~0.5,0.5~0.25,<0.25 mm土壤团聚体的REE吸附浓度与黏粒含量呈显著正相关(P<0.05);径流扰动影响对吸附于土壤团聚体的REE解吸作用十分微弱,解吸浓度仅占REE实际吸附浓度的0.001%~0.139%。5~2,2~1,1~0.5,05~0.25,<0.25 mm土壤团聚体经过湿筛后向各粒径转化的路径基本相同,向<0.25 mm微团聚体转化为土壤团聚体破碎的主要路径。相较于粉粒、黏粒含量较高的土壤团聚体,砂粒含量较高的土壤团聚体向1~0.5,0.5~0.25 mm粒径的转化贡献率整体偏低。基于REE示踪得到的>0.25 mm各粒径团聚体质量整体被低估,低估范围为-27.96%^-11.08%;而<0.25 mm团聚体质量则被高估,高估范围为3.65%~22.73%。基于各粒径土壤团聚体的REE量化值建立了校正关系,可将计算相对误差降低至0.04%~16.24%。     

草海不同石漠化程度土壤分形特征研究

基于土壤粒径分形维数的计算方法,对草海不同石漠化程度土壤颗粒、微团聚体、团聚体粒径分布的分形维数进行了研究。结果表明:石漠化地区土壤颗粒分形维数与土壤粉粒(0.001~0.05mm)呈极显著负相关(r=-0.963**,P0.01),与土壤黏粒(0.001mm)呈极显著正相关(r=0.995**,P0.01);土壤微团聚体主要以0.01mm的大粒级微团聚体为主,其分形维数与大粒级(0.01mm)微团聚体表现出呈极显著的负相关(r=-0.964**,P0.01);土壤风干团聚体5mm粒级的含量达到70%以上。湿筛后,5mm土壤团聚体含量减少,其余粒级有不同程度的增加,其中0.25mm的增幅最大。石漠化程度的加剧,使土壤黏粒含量逐渐增多,土壤颗粒、土壤微团聚体分形维数逐渐增大。通过对草海地区石漠化土壤结构特征的研究,可为草海地区石漠化治理、草海湿地的保护提供参考。     

名山河流域水稻土微团聚体对砷(As~(5+))的吸附-解吸特性

以名山河流域典型水稻土为研究对象,通过模拟试验,采用平衡液吸附法及NaCl解吸剂解吸法研究全土及不同粒径微团聚体(2~0.25mm,0.25~0.053mm,0.053~0.002mm,0.002mm)对砷(As5+)的吸附解吸特征,同时研究了土壤微团聚体对砷(As5+)热力学与动力学吸附解吸过程的特征。结果表明:水稻土及不同粒径微团聚体对砷(As5+)的吸附量随时间、浓度的增加而逐渐趋于平衡,动力学吸附以Elovich方程拟合最佳,热力学吸附以Freundlich方程拟合最佳;动力学吸附量随时间逐渐降低,在600min达到吸附动态平衡;热力学吸附量随时间逐渐增加,初始砷(As5+)浓度达到160mg/L后几乎处于吸附动态平衡,吸附过程分为快速和慢速2个阶段;砷的动力学、热力学吸附均以专性吸附为主,非专性吸附为辅;根据解吸难易程度分为易解吸与难解吸,各粒径微团聚体易解吸率大小依次为:(0.25~0.053mm)(2~0.25mm)原土(0.053~0.002mm)(0.002mm),与有机质、游离氧化铁、CEC含量的大小呈正相关,难解吸率大小与之呈负相关。     

长期不同施肥处理下黄泥土原土和团聚体颗粒组的菲含量变化

研究了太湖地区长期不同施肥处理下黄泥土团聚体颗粒组的组成、有机C含量,以及菲的分布和溶出特点.结果表明,不同施肥处理下,团聚体颗粒组均以0.25 ～ 0.02 mm所占比例最高,其质量分数范围为38.3% ～ 43.6%,而黏粒组所占比例最低仅为7.9% ～ 11.7%.另外,施用猪粪和秸秆可大幅度提高2.00 ～ 0.25 mm颗粒组所占的比例.而不同施肥处理下2.00 ～ 0.25 mm颗粒组的有机C含量最高,介于20.57 ～ 28.32 g/kg,并且施用猪粪和秸秆可提高原土和团聚体颗粒组的有机C含量.施肥处理对团聚体颗粒组的菲含量也有较大影响,以化肥区菲含量最高,其次为无肥区,常规区和秸秆区最低.而不同施肥处理下,菲在团聚体颗粒组中的分布具有相似的特征,主要分布在＜0.002 mm和2.00 ～ 0.25 mm两个颗粒组.长期施肥处理对原土和团聚体颗粒组菲的溶出无显著影响,在电解质作用下菲均无溶出.因此,长期不同施肥处理在影响团聚体颗粒组的组成、有机C含量的同时,也可对黄泥土团聚体颗粒组中的菲分布有着显著的影响.     

有机物料对稻田土壤团聚体及有机碳分布的影响

通过连续5年定位试验,以紫云英、秸秆和商品有机肥等有机物料还田的稻田土壤为对象,研究有机物料还田后不同物理分组下土壤组成特点和有机碳变化特征。结果表明,稻田土壤团聚体主要分布在2~0.25mm与0.25~0.053mm粒级,团聚体颗粒有机碳含量随着粒径的减小而减少。有机物料还田可提高0.25~0.053mm和0.053mm粒级团聚体有机碳的含量,紫云英、秸秆、商品有机肥等有机物料可通过提高土壤微团聚体有机碳含量而增加土壤碳库。有机物料施用增加土壤轻组组分颗粒含量,减少重组组分颗粒含量,有助于土壤轻组组分的形成。稻田土壤轻组颗粒有机碳含量与0.25mm和0.053mm团聚体颗粒有机碳含量呈显著相关,与2~0.25mm团聚体颗粒有机碳含量呈极显著相关。稻田土壤施用紫云英、秸秆和商品有机肥等有机物料,可有效提高土壤微团聚体和轻组成分颗粒含量,增加土壤微团聚体和轻组有机碳含量,改变稻田土壤有机碳库组成特征。     

华北土石山区坡面溅蚀和片蚀泥沙颗粒特征研究

基于野外人工模拟降雨试验,研究3种降雨强度(35,65,100mm/h)、2种坡度(5°,15°)和3种植被盖度(0%,30%,80%)条件下,溅蚀和片蚀泥沙颗粒的粒径动态分布特征,及其与降雨强度、坡度和植被覆盖度的关系,揭示表层土壤团聚体在侵蚀过程中的破碎机制。结果表明,2种侵蚀方式下的泥沙颗粒主要集中在0.1~0.002mm粒级范围内,显著高于其它粒级颗粒含量。在溅蚀泥沙颗粒中0.1~0.05mm粒级颗粒含量较高,而片蚀泥沙颗粒中0.02mm粒级颗粒含量较高,溅蚀泥沙颗粒的平均重量直径均大于片蚀泥沙颗粒。对比泥沙颗粒粒径的变化特征,溅蚀泥沙颗粒中粗砂粒(2~0.25mm)和细砂粒(0.25~0.05mm)含量逐渐减少,粉粒(0.05~0.02mm)和粘粒(0.002mm)含量逐渐增加,而片蚀泥沙颗粒中砂粒(2~0.05mm)含量呈增加趋势,粘粒(0.002mm)含量呈减小趋势。2种侵蚀方式下不同粒径泥沙颗粒与坡面径流深和径流量的相关性分析表明,泥沙颗粒粒径分布与地表产流过程密切相关。同时,雨滴击溅侵蚀泥沙颗粒的分形特征与侵蚀土壤的相对机械破碎指数有关,能够有效预测侵蚀过程中降雨和径流对坡面土壤团聚体的分选特征。     

土壤不同粒径有机无机复合体对丁草胺的吸附特性

为了解土壤不同粒径组分对农药吸附-解吸行为的影响和吸附贡献率,以及不同粒径组分中有机无机组分的结合方式和复合程度如何影响有机质对农药的吸附,选取我国6个省区的7种理化性质差别较大的土壤,并采用物理方法提取该7种土壤的三个粒径有机无机复合体(黏粒:0.002mm;粉粒:0.02~0.002 mm;砂粒:0.05~0.02 mm)为研究材料,采用批量平衡法研究丁草胺在不同土壤和不同粒径有机无机复合体固/液界面的分配规律。同时,定量计算土壤各粒径组分对丁草胺的吸附贡献率,并从有机无机复合体角度探讨不同粒径组分中总有机碳(TOC)对丁草胺的吸附特性。结果表明:土壤黏粒组分对丁草胺具有最大的吸附量和较小的解吸率,而砂粒组分对丁草胺则具有较小的吸附量和最大的解吸率。土壤黏粒、粉粒和砂粒组分对丁草胺的吸附贡献率分别为36.7%~72.4%、21.7%~50.5%和10%。TOC是影响各粒径组分对丁草胺吸附的主要原因,但其影响程度受各粒径组分中TOC的理化性质以及其与无机矿物的复合程度控制。     

Association of the Fungicide Propiconazole with Size Fractionated Material from a Silty Clay Soil – S.E. Norway

Eroded soil material may be an important transporting agent for pesticides that are strongly sorbed to soil. The abilityof the fungicide propiconazole to interact with colloidal andparticulate materials has been studied by means of sorptionand desorption experiments. Size separation of silty clay soilfrom Mørdre, Norway and subsequent characterization showedthat different size fractions of soil possessed different physical and chemical properties and, therefore, different capacity to associate with propiconazole. A large part of the soil organic carbon was associated with coarser material (2–0.02 mm), which also showed higher affinity towards propiconazole than for smaller size fractions (<20 and <2 μm). Similar K _oc values (2306 and 2244) for the size fractions <2 and <20 μm indicate that organic carbon played a dominant role in the sorption of propiconazole. Furthermore, organic carbon associated with these size fractions seemed to have similar properties withrespect to binding of propiconazole. Although, poor in organiccarbon (0.4%), the smallest size fraction (<2 μm) had higher sorption capacity for propiconazole compared to the medium size fraction (<20 μm). Higher sorption for the smallest size fraction (<2 μm) is probably due to higherspecific surface area, cation exchange capacity and content of Fe/Al oxides (free, organically bound and amorphous oxides) than the other size fractions. Results from the desorption experiments indicate that a part of propiconazole associates with sites in the soil material that resist desorption. Fluvialsediments originating from propiconazole treated fields may, therefore, represent potential reservoirs of propiconazole.Treatment with H₂O₂ modified the sorption/desorptioncharacteristics of the soil beyond that which could be expectedsimply by the removal of organic material. The pH values for all the size fractions decreased, and the specific surface areaof the medium sized fraction (<20 μm) increased from 14 to 19 m² g^-1 after the treatment with H₂O₂,probably due to disruption of the aggregate structure. Carrying out fractionation and separation procedures, it is important to be aware of physical and chemical changes that areintroduced during the different steps. An effort should be made to develop fractionation methods that keep the original characteristics of the soil material as intact as possible.     

中国土壤颗粒研究 Ⅲ.赣中丘陵旱地红壤及其各级颗粒的理化特性

赣中丘陵第四纪红色粘土上发育的旱地红壤中粘土矿物的细粘粒(<0.001毫米)部分以高岭石和蛭石为主,并有一定量的水云母和夹层矿物。各级颗粒的化学组成中,随颗粒由粗到细,SiO₂的含量大体上也由高到低;Fe₂O₃的含量则是砂粒级稍稍超过粉粒级,后一情况与作者过去对太湖地区两种水稻土(白土和黄泥土)研究的结果相似。供试红壤粒径<0.005毫米的颗粒才显示抗压强度,而上述水稻土从<0.05毫米的颗粒就开始有抗压强度。同前所试水稻土一样,在供试红壤中,粒径<0.002毫米的颗粒开始表现出可塑性及膨胀性。     

The phenanthrene‐sorptive interface of an arable topsoil and its particle size fractions

Sorption of organic chemicals in soil is affected by the properties and availability of surfaces. These surfaces are composed of diverse mineral, organic and biological components, forming a soil's ‘biogeochemical interface’. Phenanthrene was used to probe the hydrophobic sorptive capacity of the interface of an arable soil. Batch sorption experiments were carried out with the bulk soil as well as the fine (0.2–6.3 µm) and coarse (6.3–63 µm) particle size fractions of two arable topsoil samples with different organic matter (OM) contents from a Eutric Cambisol. The specific surface area (SSA) of the bulk soil and particle size fractions was determined by BET‐N₂ and EGME sorption. OM composition was characterized by solid‐state ¹³C NMR spectroscopy. No clear relationship was found between phenanthrene sorption and SSA. We conclude that phenanthrene probes a specific fraction of the soil interface that is not well represented by the traditional methods of SSA detection such as BET‐N₂ and EGME sorption. The sorption behaviour of phenanthrene may therefore provide a useful additional tool to characterize the specific affinity of the soil biogeochemical interface for hydrophobic molecules. Sorption capacity for phenanthrene increased after particle‐size fractionation, indicating that the reduced availability of the interface caused by the aggregated structure is important for the sorptive capacity of a soil. This should be considered when projecting data obtained from extensively treated and fractionated samples to the actual interaction with biogeochemical interfaces as they are present in soil.     

Dissolved organic matter sorption by mineral constituents of subsoil clay fractions

The retention of dissolved organic matter in soils is mainly attributed to interactions with the clay fraction. Yet, it is unclear to which extent certain clay‐sized soil constituents contribute to the sorption of dissolved organic matter. In order to identify the mineral constituents controlling the sorption of dissolved organic matter, we carried out experiments on bulk samples and differently pretreated clay‐size separates (untreated, organic matter oxidation with H₂O₂, and organic matter oxidation with H₂O₂ + extraction of Al and Fe oxides) from subsoil horizons of four Inceptisols and one Alfisol. The untreated clay separates of the subsoils sorbed 85 to 95% of the dissolved organic matter the whole soil sorbed. The sorption of the clay fraction increased when indigenous organic matter was oxidized by H₂O₂. Subsequent extraction of Al and Fe oxides/hydroxides caused a sharp decrease of the sorption of dissolved organic matter. This indicated that these oxides/hydroxides in the clay fraction were the main sorbents of dissolved organic matter of the investigated soils. Moreover, the coverage of these sorbents with organic matter reduced the amount of binding sites available for further sorption. The non‐expandable layer silicates, which dominated the investigated clay fractions, exhibited a weak sorption of dissolved organic matter. Whole soils and untreated clay fractions favored the sorption of ”︁hydrophobic” dissolved organic matter. The removal of oxides/hydroxides reduced the sorption of the lignin‐derived ”︁hydrophobic” dissolved organic matter onto the remaining layer silicates stronger than that of ”︁hydrophilic” dissolved organic matter.     

中国土壤颗粒研究 Ⅱ.太湖地区黄泥土型水稻土及其各级颗粒的理化特性

对太湖平原地区高产的黄泥土型水稻土的全土(<1毫米)及7个粒级(1—0.25,0.25—0.05,0.05—0.01,0.01—0.005,0.005—0.002,0.002—0.001和<0.001毫米)共8个土样,进行测定。结果表明:黄泥土粘粒部分(<0.002毫米)的粘土矿物,主要由水云母、高岭和蒙脱组成。粗粘粒级(0.002—0.001毫米)和细粘粒级(<0.001毫米)中粘土矿物的分配有明显差异;砂粒级(1—0.05毫米)中除了主要的石英外,还含有少量“铁锰砂”,所以该粒级中的SiO₂含量较粉粒级(0.05—0.002毫米)的低,而Fe₂O₃的含量则相反,容积磁化率也较高;可塑性和膨胀性都是在<0.002毫米时才始现。上述特点与作者过去所研究的白土型水稻土类似。但是,与国内外报道的几种旱地土壤的资料有所不同。     

Retention of copper by a calcareous soil and its textural fractions: influence of amendment with two agroindustrial residues

Metal availability in soils is strongly related with sorption processes and the possible association of the metal ions with a particular particle-size fraction. Therefore, studies of metal retention by a soil will be aided if retention by different size fractions is also studied. Sorption of copper on a calcareous soil and its textural fractions was studied in batch assays. The soil was amended over 3 years with two agroindustrial residues, a composted olive mill sludge and vinasse. Sorption of Cu on the calcareous soil was very large (110 mmol kg⁻¹) and was enhanced by both amendments. Metal retention by the clay fraction of the unamended soil was less than that of the whole soil, but increased dramatically after amendment with olive mill sludge. This was caused by the larger calcite content in this fraction as well as the increase in organic matter content. The amount of Cu sorbed was very large in the silt fraction, again because of the carbonate content of this fraction (300–460 g kg⁻¹). Copper sorption decreased dramatically after removal of carbonate. Copper retention tended to be enhanced by organic amendments. This was particularly evident in the silt fraction, as a consequence of the organic matter accumulation in this fraction.
Copper sorption on the calcareous soil and its silt fractions (unamended and amended) was irreversible. By contrast, desorption was measurable from all the carbonate-free samples (both whole soil and textural fractions), although in all cases a large hysteresis was observed. We conclude that carbonate was the main component responsible for the lack of reversibility.     

稻草与生石灰添加介导的温室内土壤团聚体稳定性及碳分布特性

土壤中稳定的团聚体为碳的固定提供良好的物理保护,同时土壤中的碳又会促进团粒结构的形成,二者相辅相成,但在长期稻草和生石灰添加介导的设施内土壤中二者如何变化,却少见报导。以长期施肥定位试验为依托,采用湿筛法研究了施用鸡粪(M)的基础上,配施稻草(R)和生石灰(Ca)对设施土壤团聚体组成、稳定性及碳分布的影响,以不施肥(CK)为对照。结果表明:(1)在鸡粪基础上加入稻草(MR)或生石灰(MCa),与单施鸡粪(M)相比,0.25mm团聚体含量分别增加了123%和37%;稻草和生石灰同时添加可显著增加5~2mm大团聚体含量,较MR、MCa、M分别提高12%,59%,141%。(2)在鸡粪基础上施入稻草或生石灰均可增加MWD、GMD、R_(0.25),提高团聚体的稳定性,其中MR处理最高,MRCa处理次之,二者均显著高于MCa、M、CK处理。(3)在鸡粪基础上加入稻草或生石灰,均可提高土壤全碳含量,其中MRCa处理最高,较MR、MCa、M分别增加20%,40%,55%;稻草和生石灰同时施入可显著增加5~2mm大团聚体中碳含量;加入生石灰可增加0.5~0.25mm团聚体中碳含量;施入稻草或生石灰均可显著增加0.25mm团聚体中的碳对土壤全碳的贡献。(4)土壤全碳含量与5~2,2~1,1~0.5mm团聚体含量呈显著正相关,与0.25mm微团聚体含量呈显著负相关;MWD、GMD、R_(0.25)均与0.25mm团聚体含量呈显著正相关,与0.25mm微团聚体含量呈显著负相关。设施土壤在施入鸡粪的基础上同时加入稻草和生石灰,可改善土壤结构,提高土壤碳水平,有利于缓解设施生产中因长期连作所导致的土壤结构劣变问题。     

Zinc sorption–desorption by sand,silt and clay fractions in calcareous soils of Iran

Zinc sorption–desorption by sand, silt and clay fractions of six representative calcareous soils of Iran were measured. Sand, silt and clay particles were fractionated after dispersion of soils with an ultrasonic probe. Zinc sorption analysis was performed by adding eight rates of Zn from 6 to 120 μmol g^?1. For the desorption experiment, samples retained after the measurement of Zn sorption were resuspended sequentially in 0.01 M NaNO₃ solution and shaken for 24 h. Results indicated that Zn sorption by soil fractions increased in the order clay > silt > sand, and correlated negatively with CaCO₃ content and positively with cation exchange capacity (CEC) and smectite content. Results indicated that for all fractions, the Langmuir equation described the sorption rates fairly well. In contrast to sorption, Zn desorption from soil fractions increased in the order sand > silt > clay, and correlated positively with CaCO₃ content, CEC and smectite content. Results showed that parabolic diffusion and two constant equations adequately described the reaction rates of Zn desorption. In general, for all soils studied, the coarser the particle size, the less Zn sorption and more Zn desorption, and this reflects much higher risk of Zn leaching into groundwater or plant uptake in contaminated soils.