Mechanisms of arsenite elimination by Thiomonas sp. isolated from Carnoulès acid mine drainage

Weathering of the arsenopyrite-rich tailings of the Carnoulès abandoned mining site (Gard, France) results in the formation of acid mine waters heavily loaded with arsenic. Dissolved arsenic present in the seepage waters is precipitated within a few meters from the bottom of the tailing dam by microorganisms. From these effluents, we have isolated and characterized a Gram negative bacterium involved in this bioremediation process. This bacterium, which belongs to the Thiomonas genus, is very efficient in removing arsenite from contaminated acidic waters by oxidizing it to arsenate, which precipitates.     

Mechanisms of cadmium accumulation in rice grains and molecular breeding for its reduction

ABSTRACT

Cadmium (Cd) has an important impact on agriculture, as the excessive consumption of this element from contaminated food crops leads to toxicity in humans. Rice is the greatest source of dietary Cd intake in populations consuming rice as a staple food. Therefore, reducing the Cd concentration of rice grains for diminishing the potential risk of Cd for human health is a major challenge. This review summarizes the main achievements on Cd accumulation in rice by our research group. Using a positron-emitting tracer imaging system, we succeeded to visualize differences in real-time Cd dynamics from roots to panicles in rice varieties with different Cd accumulation abilities. Several loci or genes responsible for Cd accumulation in rice were found through quantitative trait loci (QTLs) analysis. Using the QTL qCdp7 responsible for efficiently extracting Cd from paddy soils, practical rice varieties for Cd-phytoextraction were developed by DNA marker-assisted breeding. A rice variety named ‘Koshihikari Kan No.1? carrying a mutant allele of OsNramp5 for reducing Cd concentration in rice grains was produced by mutant breeding with ion-beams, and breeding programs have been implemented to transfer this allele into many Japanese rice varieties by DNA marker-assisted breeding. Growing low-Cd varieties aerobically would be a feasible way to simultaneously reduce inorganic arsenic and Cd concentrations in rice grains. These results provide basis for reducing Cd concentration in rice through breeding new varieties.     

原子荧光法测定纸质食品接触材料中砷的不确定度评定

[目的]评定原子荧光法测定纸质食品接触材料中砷的不确定度。[方法]根据相关不确定度标准及规范要求,以测定一次性纸杯中砷含量为例对原子荧光法方法的测量不确定度进行评定。[结果]分析表明,影响测量结果的主要因素依次为拟合标准曲线的过程和重复测量;标准物质的不确定度次之;消解液的定容和样品称量的不确定度相比上述3项可以忽略。该法测得一次性纸杯中砷的含量为0.39 mg/kg,扩展不确定度为0.016 mg/kg(95%,k=2)。[结论]该评价过程及结果对日常检测中提高测量结果的准确性有一定的指导意义。     

硝酸体系消解-HG-AFS同时测定土壤中砷汞的研究

[目的]为了研究硝酸体系消解-HG-AFS同时测定土壤中砷、汞的分析方法。[方法]采用微波消解仪对土壤样品消解,优化最佳微波消解条件、硝酸体系等。应用双道原子荧光光度计,测定土壤中的砷、汞。[结果]砷和汞线性范围分别在0~150、0~3μg/L内线性关系良好;砷和汞检出限分别为0.60、0.02μg/L;砷和汞定量限分别为2.00、0.07μg/L;砷和汞加标回收率分别为92.8%~107.0%、92.8%~104.0%;砷和汞RSD分别为1.5%~3.5%、2.5%~3.0%。[结论]该方法操作简单,灵敏度高,重复性好,可作为同时测定土壤中砷汞的方法。     

三氧化二砷对蛋用小公鸡生长的影响

通过在日粮中添加不同剂量的三氧化二砷,研究了三氧化二砷对蛋用小公鸡生长的影响。其结果表明:小剂量(0.5,1ppm)时,促进生长;较大剂量(2,4,8ppm)时,抑制生长。     

几种蔬菜中砷含量及影响因素

[目的]为了研究蔬菜和土壤砷含量及其影响因素之间的关系。[方法]在云南省丘北县开展大田调查试验。[结果]蔬菜根、茎叶、果实中总砷平均含量分别为0.62、0.92和0.46 mg/kg,叶菜类、果菜类蔬菜各部位总砷含量分别为茎叶根,茎叶根果实。土壤中总磷和速效磷含量的平均值分别为13.49 g/kg和124.11 mg/kg,土壤中总砷和有效砷含量的平均值分别为28.24和7.11 mg/kg。土壤中磷含量(总磷和速效磷)和土壤中砷含量(总砷和有效砷)是影响蔬菜中砷含量的主要因素。土壤pH、CEC和有机质含量的平均值分别为6.9、10.32 cmol/kg和54.24 g/kg,在一定程度上影响蔬菜中砷含量。[结论]不同类型蔬菜对砷累积的主要部位是茎叶。影响蔬菜中砷累积的因素除土壤pH、CEC和有机质外,主要为土壤磷含量。     

pH和磷的交互作用对稳定化土壤砷释放的影响

以3种含Fe材料稳定化土壤(FeSO_4、FeS和Fe~0稳定化土壤)为研究对象,研究了不同pH和P的交互作用对As释放量的影响及其作用机理。结果表明,在pH=3条件下,随着时间的延长能够促进释放的As重新趋于稳定化,而pH=11时3种稳定化土壤中As的释放量显著增加,144 h后分别约为pH=3时的10.5、16和10倍。添加P时,在3种pH条件下都促进了稳定化土壤中As的释放,尤其在酸性条件下,相对于无P体系As的释放量增加最为明显。FeSO_4稳定化土壤中As的释放特征能用Elovich方程较好地描述,而双常数方程拟合FeS和Fe~0稳定化土壤效果更优。在pH=3条件下,3种稳定化土壤中As的释放量与Ca、Mg、Mn的溶出量呈(极)显著相关,而pH=11时FeSO_4和FeS稳定化土壤中As的释放量与SO_4~(2–)的溶出量呈(极)显著相关,表明在酸性条件下,稳定化土壤As的释放主要受Ca、Mg、Mn氧化物结合态As溶解的影响,而碱性条件下,FeSO_4和FeS稳定化土壤中As的释放可能与硫化物的溶解有关。     

高砷硫铁矿周边农田土壤砷分布及真菌群落结构特征研究

本文主要以高砷硫铁矿区周边农田中的真菌群落为研究对象,研究利用Miseq高通量测序技术系统的分析了矿区周边不同区域土壤中真菌的群落特征,对硫铁矿区周边土壤真菌群落的适应机制进行了探究分析。结果表明,(1)砷、铁复合污染土壤可促使土壤真菌丰富度降低,而对土壤真菌多样的影响则表现为先促进后抑制;(2)砷、铁复合污染抑制土壤中Ascomycota(子囊菌门)代谢,促进Basidiomycota(担子菌门)代谢,而对Zygomycota(接合菌门)则表现为低浓度促进,高浓度抑制,对Fusarium(镰刀菌属)、Pseudallescheria(假霉样真菌属)、Cryptococcus(隐球菌属)也呈现“低浓度促进、高浓度抑制”作用;(3)砷、铁的复合物污染使土壤中真菌群落结构产生了明显差异,环境因子对土壤环境真菌群落结构差异影响大小依次为有效砷、总砷、总铁。     

Use of water-treatment residue containing polysilicate-iron to stabilize arsenic in flooded soils and attenuate arsenic uptake by rice (Oryza sativa L.) plants

A pot experiment was conducted to examine how soil amendment with water-treatment residue (WTR) containing polysilicate-iron affected dissolved arsenic (As) in flooded soils and As uptake by rice plants (Oryza sativa L.). The WTR was applied at a rate of 0 (control), 5, 10 or 20 t ha^?1. Simple linear regression analyses showed significant negative relationships between the concentrations of dissolved As in soil solution and WTR application rates at all sampling times, probably due to adsorption of As onto ferrihydrite in the WTR. Compared to As concentrations in rice plants grown on control soil, the concentrations in plants grown on WTR-treated soils decreased by 20.1–41.6% in straw (stems and leaves), 19.8–31.7% in husk and 18.6–21.0% in grain. The regression analyses demonstrated that the concentration and content of As in rice are negatively correlated with WTR application rate. Total As content was 16.5–32.0% lower in rice shoots grown on WTR-treated soils than on control soil. The percentage of each As species in grain decreased in the following order: As(III) » dimethylarsinic acid » As(V). The application of WTR did not change the As speciation in grain. Silicon contents in shoot significantly increased with application of WTR, indicating the potency of WTR as a silicate fertilizer. Taken together, our results indicate that WTR containing polysilicate-iron promises to be a practical amendment for stabilizing As and attenuating As uptake by rice plants.     

石墨炉原子吸收法测定中药材中微量砷的研究

采用密闭容器高压消解样品,钯涂层石墨管平台技术、横向加热、纵向塞曼效应扣背景和基体改进剂相结合的方法测定中药材中微量砷。该法可消除基体带来的干扰,同时提高砷的灰化温度到1200℃,消除灰化损失的问题。采用纵向塞曼效应扣背景可消除光谱带来的干扰。该法回收率范围为：90．3％～101．7％,相对标准偏差（RSD）为3．7％。该法灵敏、准确、快速,干扰小,结果令人满意。