Pedotransfer functions to assess adsorbed phosphate using iron oxide content and magnetic susceptibility in an Oxisol

Adsorbed phosphate in soils can be chemically extracted; however, this process is both time‐consuming and not cost‐effective if large numbers of samples have to be analysed. Indirect assessment of adsorbed phosphate by pedotransfer functions (PTFs) can help optimize fertilizer strategies. This study aimed to evaluate the spatial variability of adsorbed phosphate (P_ads), iron oxides and magnetic susceptibility (MS) in oxisols and to calibrate PTFs to predict P_ads. A total of 308 soil samples were collected from Hapludox and Eutrudox soils formed from sandstone in Brazil. The contents of clay (196–607 g/kg), iron oxides (40–165 g/kg), MS (1.2–29 × 10^?6 m³/kg) and P_ads (327–842 mg/kg) were in the range of typical values for these highly weathered soils. This study showed that the attributes studied were spatially dependent. Geomorphic surfaces enabled understanding of spatial variability and helped to develop a more efficient sampling scheme to calibrate PTFs. Moreover, the adsorbed phosphate in these oxisols could be predicted by a PTF using iron oxides and MS as predictors. The MS attribute enabled the most accurate prediction (concordance coefficient = 0.95, root‐mean‐square error = 46 mg/kg and relative improvement in root‐mean‐square error = ?4.12) of spatial variability through PTF compared to other predictors.     

中国黄土高原黄土-古土壤序列的红度对古气候的指示意义

Comparisons of red ratings (RR) with Fe_d, Fe_d/Fe_t, clay content, and magnetic susceptibility (x) of two loess-paleosol sequences at Luochuan and Lingtai on China's Loess Plateau were conducted to study the possible relationship between RR and pedogenic degrees of the two loess-paleosol sequences, and to discuss whether the RR could become new paleo-climatic indicators. Results showed that the RR of the two loess-paleosol sequences had positive, highly significant (P < 0.01) correlations with: 1) citrate-bicarbonate-dithionite (CBD) extracted iron (Fe_d), 2) ratios of CBD extracted iron to total iron (Fe_d/Fe_t), 3) clay (< 2 μm), and 4) magnetic susceptibility (x). This suggested that the RR of these loess-paleosol sequences could indicate degrees of loess weathering and pedogenesis and were potential paleo-climatic proxies. The strong correlations of RR to Fe_d and x also implied that during pedogenic processes, pedogenic hematite in loess and paleosols were closely related to the amount of total secondary iron oxides and pedogenic ferrimagnetic minerals (predominantly maghemite).     

几种可变电荷土壤中氧化铁类型与磷吸附特性

应用Ｘ射线衍射和化学分析等手段研究了红壤，砖红壤和黄棕壤中氧化铁类型及其与磷吸附和解吸的关系。结果表明：（１）黄棕壤中的氧化铁是针铁矿型，砖红壤和红壤是以赤铁矿为主，棕红壤是以针铁矿为主的针－赤混合型。（２）针铁矿的ＭＣＤ值一般小于赤铁矿的ＭＣＤ值，前者的比表面积大，后者的小。砖红壤中的赤铁矿晶体薄，红壤中的原。（３）针铁矿型氧化铁的磷吸附量明显高于针－赤混合型氧化铁的磷吸附量，并随粘粒中Ｇ／Ｇ（     

赤铁矿用于生物质化学链气化氧载体的反应性能

在鼓泡流化床反应器上以Ar气为流化介质,研究了反应温度、时间对天然铁矿石氧载体的化学反应特性的影响,并对其物理性质进行了表征。试验表明,氧载体与生物质热解产物的反应性随着温度的升高而逐渐增强,气化产物中H2、CO的含量随着温度的升高而逐渐增加,CH4、CO2的含量随着温度的升高而逐渐降低;随着反应时间的增加,氧载体活性逐渐下降,合成气中热解气含量逐渐升高。铁矿石热重试验表明,在惰性氛围下(Ar),氧载体不会释放晶格氧。利用X射线衍射、扫描电子显微镜分析了反应前后氧载体颗粒的化学成分及微观形貌,分析表明,Fe2O3的还原产物主要是FeO,天然铁矿石氧载体随着温度的增加,其颗粒表面的结焦现象越明显。试验结果表明将天然铁矿石用于生物质化学链气化过程是可行的。     

Desorption Characteristics of Three Mineral Oxides and a Non-crystalline Aluminosilicate for Supplying Phosphate in Soilless Root Media

The objective was to evaluate phosphate desorption characteristics of synthetic hematite, goethite, and allophane and commercial alumina after loading at maximum adsorbed phosphate levels to determine their potential to release phosphate at a constant, low level to sustain plant growth in soilless media and reduce phosphate leaching. Desorption isotherms were measured at pH 6.4 ± 0.1 using a continuously stirred-flow reactor. The time period during which dissolved phosphate was maintained within the range of 5–0.2 mg·L^?1 phosphate-P decreased in the order: allophane (12.4 d) > alumina (4.6 d) > goethite (3.6 d) > hematite (1.9 d). Allophane released the most phosphate during the desorption process (40% of maximum adsorbed phosphate; 12.7 mg?g^?1) followed by alumina and goethite (19–20%; ≈2.5 mg?g^?1) and lastly hematite (5%; 0.1 mg?g^?1). Allophane demonstrated the greatest potential as a phosphate-charged source for soilless root media, in amount and duration of phosphate release.     

颗粒级配技术的超高密度水泥浆体系研究

为实现缅甸A地区浅层高压气、低温超高密度的油气井的固井,根据紧密堆积理论的颗粒级配原理,在室内建立了紧密堆积颗粒级配模型,通过在单位体积水泥浆内增加固相颗粒,尽量降低水泥浆的水灰比,实现水泥浆体系密度的增加和水泥浆性能的改善。根据颗粒级配模型,利用室内优选出的加重剂铁矿粉的不同粒度颗粒进行了级配加重试验,利用复配后的加重剂所配置的高密度紧密堆积水泥浆体系性能优良,现场固井质量优良,验证了所建立的紧密堆积模型的可靠性。同时,开发和优选了适合高密度水泥浆的外加剂体系,完成了国内首次密度为2.80g/cm3的超高密度水泥浆体系的研制,加有纤维的高密度水泥浆体系具有良好的防漏堵漏功能。     

Occurrence and Origin of Crystalline Iron Oxides in Paddy Soils Derived from Red Earth

红壤性水稻土晶态氧化铁主要为针铁矿，并伴随少量的赤铁矿．红壤性水稻土中针铁矿的铝同晶替代量明显低于其母土（红壤），而针铁矿的晶胞参数ｂ和ｃ则是红壤性水稻土高于其母土．红壤性水稻土中赤铁矿的铝同晶替代量和晶胞参数ａ则与其母土相似．．据此认为红壤性水稻土中赤铁矿来源于母土；而针铁矿部分来源于母土，部分是由原有的赤铁矿和针铁矿的还原产物重新结晶形成的．随着水稻土的发育，赤铁矿逐渐下降，最后消失；针铁矿则相对增加，同时针铁矿中铝替代量也逐渐下降     

Experiments on reduction roasting and bio-dephosphorization of high-phosphorus oolitic hematite

Experiments are carried out on high-phosphorus oolitic hematite in western Hubei, using the method of reduction roasting and low intensity magnetic separation, and Aspergillus niger is used to do the research of bioleaching dephosphorization on concentrate.The orthogonal test results show that the descending order of factors influencing concentrate grade is calcinations temperature, roasting time, reduction ratio, grinding grain.The best condition for reduction roasting and low intensity magnetic separation is calcinations temperature 900 ℃, roasting time 25 min, reduction ratio 6%, and grinding grain -0.074mm95.08%.On these conditions, concentrate grade is 57.25% and recycling rate is 90.20%.Aspergillus niger has a strong removal capability on phosphorus in concentrates.After 8 days of microbiological leaching, removal of phosphorus is 79.68% with lower pulp density, and the percentage of phosphorus is reduced to 0.17% from 0.85%, which provides the foundation of application on dephosphorization by microorganism.     

Mineralogical composition of iron oxides in red- and yellow-colored soils from Southern Japan and Yunnan,China

Six soil samples from the Bt2 horizon of red- and yellow-colored soils collected in Southern Japan and Yunnan, China, were used in this study. Detailed mineralogical studies by differential X-ray diffraction analysis showed the presence of hematite in association with goethite in the red-colored soils, whereas no hematite was detected in the yellow-colored soils. Among the samples studied, the increase in the hematite contents was as follows: Terra rossa-like/Red-Yellow soil in Kikai Island, Red soil in Toyota City, Lateritic Red soil in Minami-Daito Island and Lateritic Red soil in Yunnan, China. Since Lateritic Red soil and Lateritic Yellow soil are distributed adjacently on the Pleistocene raised coral reef terrace in Minami-Daito Island, having a fairly similar soil temperature regime, soil pH, soil organic matter and iron oxide contents, the difference in the soil color between the two soils may be caused by the difference in the hydrologic conditions.     

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%。