Influence of B-permeated goethite on soil B fraction and its availability to rape seedlings (brassica napus L.)

The purpose of the study was to determine the effect of boron (B)-permeated goethite on soil B fractionation and the availability of this B fraction to rape seedlings (Brassica napus L.). For this purpose, goethite and two kinds of B-permeated goethite were synthesized and their processes in soil were simulated. Plant availability of B adsorbed or occluded on goethite was investigated with rape seedling. Results found that both ad-B-goethite and oc-B-goethite significantly increased the water soluble B (WS-B), specifically adsorbed B (SPA-B), B occluded in amorphous iron (Fe) and aluminum (A1) oxides (AMO-B) and crystalline Fe and Al oxides (CRO-B) content in the soil, compared with ordinary goethite. Also the B-permeated goethites improved B content of the rape seedling and therefore enhanced the rape shoot and root dry weight. Correlation analysis demonstrated that water soluble B (WS-B) plays the most important role in rape B uptake and accumulation, moreover the specifically adsorbed B (SPA-B), nonspecifically adsorbed B (NSA-B), amorphous Fe and A1 oxides (AMO-B) was also significant correlated with the B content or B accumulation of the rape.     

氧化铁/水界面Cd吸附研究:CD-MUSIC模型模拟

以针铁矿和赤铁矿为研究对象,研究p H、Cd浓度等对不同类型氧化铁Cd吸附行为的影响,构建氧化铁Cd吸附的CD-MUSIC模型,并分析氧化铁表面Cd的形态分布特征。结果表明:氧化铁表面Cd吸附量和吸附密度均随p H升高、Cd浓度增大而增大。针铁矿对Cd的吸附量和吸附密度显著高于赤铁矿。CD-MUSIC模型能准确模拟Cd在氧化铁/水界面的吸附特征,拟合结果表明Cd主要以(Fe OH)2Cd+1、(Fe OH)2Cd OH0两种形态吸附在氧化铁表面,其在针铁矿和赤铁矿表面亲和常数(lg KCd)分别是7.3、12.8和6.1、11.0。Cd的形态分布受p H的影响显著,但几乎不受Cd浓度的影响。p H 5.0和7.0时,针铁矿的Cd形态分布与赤铁矿相似,(Fe OH)2Cd+1是主要吸附形态。p H 9.0时,针铁矿上超过80%的Cd以(Fe OH)2Cd OH0形态存在。赤铁矿上,Cd浓度较低时,(Fe OH)2Cd+1是主要吸附形态;随Cd浓度增大,(Fe OH)2Cd+1和(Fe OH)2Cd OH0所占比例均逐渐接近50%。     

植酸对碳酸盐绿锈转化的影响

为研究植酸（IHP）对绿锈转化过程及机制的影响，通过空气氧化法合成碳酸盐绿锈[GR1 （CO₃^2-）]，并利用X射线衍射、衰减全反射-傅里叶变换红外光谱、高分辨透射电子显微镜、扫描电子显微镜和能量色散X射线能谱对体系中的固体产物进行分析表征。研究表明：不存在IHP时GR1（CO₃^2-）在5 h左右完全转化为针铁矿，而存在IHP时GR1（CO₃^2-）的转化会受到抑制。在0~0.5mmol·L^-1的IHP浓度范围内，GR1 （CO₃^2-）的转化产物为针铁矿，而当IHP浓度高于1.0 mmol·L^-1时，GR1 （CO₃^2-）的转化产物为针铁矿和高铁绿锈。IHP对GR1（CO₃^2-）转化机制的影响与其浓度有直接关系，在低浓度IHP（0~0.5 mmol·L^-1）条件下，GR1（CO₃^2-）转化过程只涉及溶解-氧化-沉淀（DOP）机制；而高浓度IHP（1.0~5.0 mmol·L^-1）体系中，固态氧化（SSO）机制占主导地位，在其转化过程中，一部分GR1（CO₃^2-）通过溶解再沉淀机制转化为针铁矿，一部分GR1（CO₃^2-）通过原位脱质子反应转化为高铁绿锈。此外，在GR1 （CO₃^2-）转化过程中，IHP在GR1 （CO₃^2-）及其转化产物表面会形成内圈络合物和植酸（亚）铁沉淀。总体而言，IHP会抑制GR1 （CO₃^2-）的溶解再沉淀转化机制，阻碍针铁矿的结晶和晶体生长，且抑制作用与IHP浓度呈正相关。