Composition and transformation of 1.4 nm minerals in cutan and matrix of alfisols in central China

Background, Aims, and Scope  Hydroxy interlayered vermiculite (HIV) and vermiculite are commonly referred to as 1.4 nm minerals. In the subtropical soils of central China, the concentration of vermiculites decreased while that of HIVs increased gradually from north to south as the intensity of soil formation or eluviation increases in the same direction. The cutans in these soils closely interact with air, roots, microbes, water and dissolved ions in soils. Cutans may therefore be expected to exert an important influence on the formation of 1.4 nm minerals relative to the matrix soils. However, little is known about the transformation of 1.4 nm minerals in Alfisols in central China. Here, we investigate the compositional differences of 1.4 nm minerals in cutans and matrix soils, and the probable transformation of vermiculite to HIV or vice versa when sodium citrate and sodium acetate are added to matrix Alfisols. Methods  Cutans and matrix soils were separated from three soils in the northern subtropical zone in China. The samples were analyzed for Fe, Mn, exchangeable cations, organic matter(O.M.), pH, and clay minerals. To 10 mL of matrix soil, suspensions containing about 250 mg (oven-dry weight) of clay was added with 5 mL of 0.4 mol/dm³ or 2 mol/dm³ of sodium citrate or sodium acetate solution and 5 mL of 0.2 mol/dm³ mixed solutions of CaCl₂, Mg(NO₃)₂ and KCl. After its pH was adjusted to 6.0, the mixture was ‘incubated’ for 120 or 210 days (more than one season or half a year) during which period it was shaken for 1 hour every day. The clay mineral composition of the samples was determined after incubation. Results  Both vermiculites and HIVs were present in matrix soils, but only vermiculties were detected in cutans. The addition of organic ligands (citrate and acetate) promoted the transformation of HIV to vermiculite. This transformation was obvious for the matrix soils that had been incubated with 0.5 mol/dm³ sodium citrate for 210 days while sodium acetate was less effective in this regard. The promoting effect of organic ligands is dependent on type and concentration as well as incubation time. This would suggest the reverse transformation occurred in the formation of cutans compared with a vermiculite-to-HIV transformation in the subtropical soils of central China from north to south. Discussion  The position and environment of cutans in the B horizon together with the pH, organic matter and exchangeable base status in cutans seem conducive to the co-existence of vermiculite and HIV in the soils, but only vermiculite is found in cutans. The transformation of HIV to vermiculite in incubation experiments could be divided into two steps: 1) Cheluviation of organic matter to the interlayer hydroxy-aluminums from HIVs. 2) Rebasification of hydrated cations into the interlayers of vermiculites. Conclusions  The clay minerals in cutans can interact with organic ligands and nutrient elements excreted by roots. Under conditions of frequent wetting and drying and high pH, and when the concentrations of exchangeable bases, iron-manganese oxides, clays, and organic matter are high, the exchangeable cations can be incorporated into the interlayers of HIV, thereby promoting the partial transformation of HIV to vermiculite in rhizosphere soils. Recommendations and Perspectives  Cutan is at the interface of material and energy exchange involved in physical, chemical and biochemical reactions in the rhizosphere. These factors strongly affect the compositions of cutans. HIVs in (upper or adjacent) matrix soils may transform to vermiculites during cutan formation in these special soil environments. ESS-Submission Editor: Jizheng (Jim) He (jzhe@rcees.ac.cn)     

中性氧化铝作为吸附剂对土霉素薄层层析的效果测定

通过以中性氧化铝为吸附剂，０．５％ＣＭＣ－Ｎａ为粘合剂，在展开剂分别为９５％乙醇－１ＮＨＣｌ、正丁醇－１ＮＨＣｌ、正丁醇－１ＮＨＣｌ－水、甲醇－１ＮＨＣｌ和甲醇－１ＮＨＣｌ－水中对土霉素的层析效果研究，结果表明：中性氧化铝在上述５种展开剂中均不能使土霉素达到有效分离。故不能用中性氧化铝单独作为吸附剂对土霉素进行层析分离。     

南方森林土壤溶解有机碳与土壤因子的关系

采用TOC-5000A总有机碳仪测定了福建主要森林类型土壤溶解有机碳(DOC)的含量，分析了土壤溶解有机碳与土壤因子的关系。结果表明：南方酸性森林土壤中，DOC与有机碳总量、全氮、全磷、碱解氮、有效磷和速效钾等养分因子之间呈极显著或显著的正相关关系，因而可以作为评价土壤肥力性状的生物学指标。土壤DOC与土壤中有机络合态铁、有机络合态铝和活性轻基铝之间呈权显著或显著的正相关。土壤中有机碳是影响土壤中铝和铁的溶出及迁移的一个重要因子。土壤DOC与pH值之间在一定的范围内呈权显著的负相关关系，因而土壤中铝的吸附、保持及溶解铝的排出受到溶液中DOC的强烈控制。土壤DOC与交换性铝之间无显著相关性。表2参14     

酚酸类物质对黄瓜幼苗生长及保护酶活性的影响

 以对羟基苯甲酸和苯丙烯酸为代表性酚酸类物质 ,研究其对黄瓜幼苗生长和保护酶活性的影响。结果表明 ,该 2种酚酸物质对黄瓜幼苗的生长有抑制作用 ,鲜重、株高、茎粗、叶面积均有减小 ,随处理浓度的增加抑制作用增强 ,苯丙烯酸比对羟基苯甲酸具有更强的抑制作用 ;与对照 (CK)相比 ,2种酚酸物质对过氧化物酶 (POD)活性的影响呈现出先升高、然后下降 ,最后低浓度处理有回升趋势而高浓度无回升趋势 ;对过氧化氢酶 (CAT)活性的影响则呈现出低浓度处理其活性先升高、然后下降、最后回升的变化趋势 ,高浓度处理首先表现为活性降低、然后略有升高、最后下降而无回升趋势 ;对超氧化物歧化酶 (SOD)活性的影响表现出首先高于CK ,然后逐渐下降低于CK ,最后低浓度处理逐渐回升趋于CK ,而高浓度处理无回升趋势。高浓度酚酸类物质使丙二醛 (MDA)含量增加     

土壤铝对林木根系的影响

采用孔洞根系生长法、进行铝对杉木和湿地松根系生长影响的研究，结果表明：土壤中加入铝离子后，活性铝含量明显增加，PH值下降；孔洞中根系生物量与对照比较，虽无明显差异，但均表现出铝毒害症，根中铝含量降低，但钙含量继续升高。这说明铝对杉木和湿地松根系有抑制作用，而钙对铝有拮抗作用。表3参7     

H2O2/NaOH改性玉米秸秆制备石油吸附剂的实验研究

本文采用H2O2/NaOH对玉米秸秆（RCS）进行改性来制备可吸附石油的生物质吸附剂（HNCS）。通过模拟实验,比较了不同改性时间的HNCS吸油量,发现改性14h的吸油量最大,达14.08g·g-1,而改性前RCS仅为4.33g·g-1,改性使得吸油量提高了325%,且吸油速率更快。通过扫描电子显微镜（SEM）、比表面积/孔隙度分析仪和傅里叶红外光谱仪（FT-IR）,对改性前后样品结构进行表征,同时采用洗涤剂法和硫酸法对纤维素、半纤维素、木质素含量进行测定,结果发现：改性后的HNCS表面更加粗糙,且出现大量的吸附孔隙,比表面积为7.14m·2g-1,表面亲水性官能团减少,纤维素含量增加而木质素含量减少。这说明吸油量和吸油速率受到吸附剂表面官能团、比表面积和孔隙/间隙的影响。     

Molecular Aspect of Al Tolerance in Crop Plants: Novel Al-Activated Malate Transporter Gene in Wheat Roots

Aluminum (Al) is a major element in the soil; 30–40% of arable land is acidic. Solubilized Al ion in acid soils inhibits root elongation. Intensive research on the Al tolerance mechanism has been conducted in the past few decades. Mechanism of Al tolerance can be classified into Al exclusion mechanism and intracellular tolerance mechanism. Efflux of organic acids from roots upon receiving the Al signal is the major Al exclusion mechanism. Efflux of organic acids through the channel in the plasma membrane was confirmed, and the gene specifically encoding malate transporter in Al-tolerant wheat was discovered recently. The regulatory mechanism in the efflux of organic acids upon protein phosphorylation may be operative. The production of reactive oxygen species (ROS) and their scavenging system are thought to be important in the intracellular tolerance mechanism.     

铝胁迫对小麦根尖细胞蛋白质及苹果酸分泌的影响

以一对近等位基因小麦品系(ET8和ES8)为材料,研究了铝胁迫条件下根系生长情况,根尖铝含量,根尖细胞质蛋白组分以及铝胁迫下两个小麦品系苹果酸分泌的差异。结果表明,小麦品系ET8的耐铝性明显高于ES8;而ET8根尖铝含量则明显低于ES8;50mol/L铝处理24h后ES8小麦的细胞质蛋白组成受到明显影响,而ET8则无明显影响。由于铝胁迫条件下ET8分泌的苹果酸的量明显高于ES8,因此可以认为,分泌的苹果酸一方面与铝结合使其无毒化;另一方面将铝排斥于根尖细胞外,从而阻止铝进入细胞质内对细胞产生毒害作用。     

铝、镉胁迫对空心菜生长及抗氧化特性的影响

为明确铝(Al)、镉(Cd)胁迫对空心菜植株生长、有害元素积累和抗逆生理代谢的影响,采用营养液培养试验,模拟酸性环境(p H值4.5),对空心菜幼苗进行Al、Cd单一及复合处理3周,测定相关指标。试验结果表明,与对照组相比,单独10μmol·L-1Al和0.5μmol·L-1Cd处理促进空心菜植株生长;高浓度Al(100μmol·L-1)、Cd(5μmol·L-1)胁迫导致植株根系和地上部Al、Cd大量积累,诱导叶片中超氧化物歧化酶(SOD)和过氧化物酶(POD)活性增强,丙二醛(MDA)含量增多;叶片叶绿素含量明显降低,植株生物量大幅下降。Al、Cd复合处理植株各器官有害元素含量均显著高于单一毒害处理,尤其是根系,并诱发更严重的植株生长抑制效应和氧化胁迫,表明Al、Cd对空心菜植株的生长抑制和氧化胁迫具有协同性。本试验研究结果可为Al、Cd复合污染酸性菜园蔬菜安全栽培提供理论指导。     

污泥衍生吸附剂对废水中酸性雪青的吸附特性研究

[目的]研究污泥衍生吸附剂对废水中酸性雪青的吸附特性.[方法]以污泥粉为原料,加入锯末,用氯化锌活化,高温热解制得一种污泥衍生吸附剂(碘值为462.36 mg/g),并研究了污泥衍生吸附剂对废水中酸性雪青的吸附特性.[结果]污泥衍生吸附剂对酸性雪青吸附动力学模型拟合结果表明,100、300、400 mg/L的酸性雪青溶液都符合假二级动力学模型,其R2都＞0.99; 100、300、400 mg/L的酸性雪青溶液到达平衡的时间分别是30、90、150 min,低浓度到达平衡的时间短,高浓度到达平衡时间长.根据热力学试验可以得出,其吸附过程在10、20、30℃下都可用Langmuir和Freundlich吸附模型很好地描述(其R2都＞0.99).根据其吸附过程与液膜扩散模型和颗粒内扩散模型的拟合情况,得到液膜扩散是其吸附过程的速率控制步骤,但不是唯一速率控制步骤,而颗粒内扩散并不是其过程的速率控制步骤.[结论]使用污泥衍生吸附剂吸附废水中酸性雪青具有可行性.