Importance of Noncrystalline Hydroxide Phases in Sequential Extractions to Fractionate Antimony in Acid Soils

Abstract

Sequential extraction techniques have been used to make inferences about speciation of phosphorus (P) and to a lesser extent arsenic (As) in soils. However, sequential extraction studies on the less‐abundant group V element, antimony (Sb), are limited. In this work, a widely used P sequential extraction scheme was modified and used to extract P, As, and Sb from two acidic soils from the Macleay River floodplain, NSW, that were enriched with Sb (26.9 and 23.0 mg kg^?1). An ammonium oxalate–oxalic acid step was included in the extraction sequence to dissolve the noncrystalline iron (Fe) and aluminium (Al) hydroxide phase. It extracted 30 to 47% of Sb, indicating the importance of this fraction, which may be mobilized in the floodplain by acid sulfate soil processes and periodic waterlogging. The original method overestimated P, As, and Sb in the residual fraction (30–71%). Relative efficiency values of extracts for P, As, and Sb were compared, and inferences about phase distributions were made. The results suggest some potential in using extractions to assess bioavailability of Sb in soil.     

Potential for the alleviation of arsenic toxicity in paddy rice using amorphous iron-(hydr)oxide amendments

Abstract

A pot culture experiment was conducted to investigate the effects of amorphous iron-(hydr)oxide (Am-FeOH) amendments on arsenic (As) availability and its uptake by rice (Oryza sativa L. cv. BR28) irrigated with As-contaminated water. A rhizobag system was established using 3.5 L plastic pots, each containing one central compartment for plant growth, a middle compartment and an outside compartment. Three levels of laboratory-synthesized Am-FeOH (0, 0.1 and 0.5% w/w) were used to amend samples of the As-free sandy loam paddy soil placed into each compartment of the rhizobag system. The soils were submerged with a solution containing 5 mg L^?1 As(V). Two-week-old rice seedlings were planted in the central compartments and cultured for 9 weeks under greenhouse conditions. The addition of 0.1% Am-FeOH to the soil irrigated with As-contaminated water improved plant growth, reduced the As concentration in the plants and enhanced Fe-plaque formation on the root surfaces. Analysis of soil solution samples collected during the experiment revealed higher pH levels and lower redox potentials in the soils amended with Am-FeOH at the onset of soil submergence, but later the soil solution collected from the 0.1% Am-FeOH treatment was slightly acidic and more oxidized than the solution from the 0% treatment. This indicated active functioning of the roots in the soil treated with 0.1% Am-FeOH. The concentrations of As(III) in the soil solution collected from the central compartment were significantly reduced by the Am-FeOH amendments, whereas in the soil treated with 0% Fe, As(III) accumulated in the rhizosphere, particularly during the late-cultivation period. The improvement in plant growth and reduction in As uptake by plants growing in the Am-FeOH treated soil could be attributed to the reduction of available As in the soil solution, mainly as a result of the binding of As to the Fe-plaque on the root surfaces.     

不同色泽石粉的质量分析评估

为了在饲料生产中更安全、科学地使用石粉,试验检测了河南省南阳地区不同色泽的石粉中钙、镁、铅、氟和砷等几种金属的含量,结果表明:白石粉中钙含量最高,红石粉中镁含量最高,灰石粉中铅含量超标。由于南阳石粉不论其色泽如何价格均相同,所以白石粉的性价比更高,更适合用作饲料原料来获得更高的经济效益。     

毛头鬼伞子实体对重金属元素的富集特性

通过对毛头鬼伞(Coprinus comatus)产区中原辅材料中铅(Hg)、镉(Cd)、砷(As)、汞(Pb)4种重金属含量的检测和使用添加不同浓度重金属栽培材料的栽培试验,分析栽培原辅料中重金属含量对子实体中重金属含量的影响,为毛头鬼伞的安全生产提供参考。试验结果表明,除水之外的13个测试原辅材料样品中均含一定量的重金属元素;子实体中的重金属含量随着栽培材料中重金属元素含量的增加而呈上升趋势,子实体对覆土和对栽培基质中4种重金属元素的富集强弱分别为Hg>Cd>As>Pb和Hg>Cd>Pb>As,其中对覆土和栽培基质中重金属汞分别表现较弱和一定的富集作用。     

适于轻度Cd、As污染土壤种植的水稻品种筛选

对重金属具有高耐性、低富集的水稻品种可用于轻度重金属污染的水稻土。采用温室盆栽试验研究2种水稻土（红泥田和黄泥田）中Cd、As污染对9种水稻生长的影响,分析不同水稻品种对Cd、As富集能力的差异。结果表明,As污染处理下所有水稻品种的生物量均显著降低,在红泥田上,水稻生物量降低幅度为29.4%～54.3%;在黄泥田上,降低幅度为29.5～53.3%。不同水稻品种对As耐性有显著差异（P〈0.05）,晚粳9707（粳稻）生物量降幅较小,耐性较高;浙1500（籼稻）降幅较大,耐性较低。对于Cd污染处理,在2种类型土壤上9种水稻对Cd耐性差异不显著。不同水稻品种对土壤Cd、As的富集能力有显著差异（P〈0.05）。在2种类型土壤上,德农2000（杂交稻）和浙1500（籼稻）分别对As、Cd的富集系数最高,对As、Cd污染敏感;南粳32（粳稻）对Cd、As的富集系数均较低,对Cd、As污染不敏感。在9个水稻品种中,南粳32对Cd、As的富集能力最低,并且对As耐性较高,适合在Cd、As轻度污染的水稻土上种植。     

砒砂岩地区沙棘生态工程的土壤修复效果分析

本文以砒砂岩地区沙棘生态工程为研究对象,探讨沙棘生态修复工程实施对表层土壤理化性状的改良作用,初步研究结果表明：实施造林工程8年后,沙棘林地表层土壤的总孔隙度比荒坡地提高7.4%,土壤粘粒含量占49.15%,比荒地增加了75%;〉5mm的大团粒含量为43.38%,是荒地的2.99倍,有机质含量为13.92g/kg,是荒地的3.68倍;全氮、全磷、全钾的含量分别为荒地的1.72倍、1.13倍与1.36倍,有效氮、速效钾、速效磷含量分别为荒地的4.54倍、3.29倍与7.6倍。说明沙棘造林使造林区的土壤结构得到显著改善,沙棘生态修复工程的生态效益突出,可有效降低该地区降雨对土壤的侵蚀和地表径流的冲刷。     

物权法理念下森林资源他项权利探析

首先对我国森林资源他项权利的基本法律属性进行了分析,然后在对我国森林资源他项权利制度现状及所存的问题进行分析的基础上,提出了协调森林资源相关他项权利关系,增加森林资源使用权流转方式;强化森林资源他项权利的排他性、独立性以及将森林资源生态价值的使用和收益权,纳入森林资源他项权利体系等建议,以期进一步丰富和发展我国森林资源物权法律制度。     

氢化物发生-原子荧光光谱法同时测定土壤中的砷和锑

为了简便、快速地同时测定土壤样品中砷和锑的含量，样品用HNO3－HCl（1＋1）分解，在氢化物发生－原子荧光光谱法测定过程中，研究了不同介质、酸度、还原剂质量浓度对测定结果的影响。结果，砷、锑的回收率分别为95％－101％，91％－93．8％，砷、锑的检出限分别是0．36，0．41μg/L。用此方法测定土壤标准样品中的砷、锑含量，结果与标准值吻合。     

水泥厂对周边农田污染的影响调查

水泥厂在生产过程中产生的大气污染对周边环境影响较大。经调查发现水泥厂附近的小麦中氟含量超标较严重,还发现汞超标。建议开展排污企事业与农田的安全距离研究。     

酸性土壤有效砷提取方法研究

采用0.5mol·L-1NaHCO3(pH8.5),0.5mol·L-1NaH2PO4和0.1mol·L-1HCl等3种浸提剂,对福建省酸性水稻土和酸性菜地土壤有效砷的提取效果以及相关的提取条件进行了研究。结果表明,3种浸提剂所提取的土壤有效砷与作物可食用部分砷含量之间均存在显著相关,其中0.5mol·L-1NaH2PO4提取的有效砷与糙米和蔬菜地上部砷含量的相关性最高,相关系数分别是0.628和0.824,是三者中最佳的浸提剂。对NaH2PO4的提取条件的研究表明,在15∶1的液土比条件下以250r·min-1的速度振荡120min是最佳的酸性土壤有效砷的提取方法。