厌氧水稻土中水溶性As(Ⅲ)和As(Ⅴ)的测定方法研究

针对现行土壤污染物环境标准和分析方法都是用总砷表示,而对水溶性砷研究较少的现状,选择蠕动注射方法添加还原剂KBH4-NaOH溶液,通过控制样品溶液pH,对As( )和As( )进行了分步还原,用硝酸银-聚乙烯醇-乙醇溶液作吸收液来吸收还原生成的AsH3,分光光度法在400nm波长下测定吸收液的吸光度,求算As( )和As( )含量。用这种方法对模拟环境砷污染水样和厌氧水稻土中As( )和As( )的测定进行了研究。结果表明,砷质量浓度为0～0.5mg/L时,吸光度和砷质量浓度符合朗伯-比尔定律,标准溶液测定的相对误差为-3.60%～2.20%,检测限为0.6μg;环境水样测定的As回收率为97.14%～103.4%,与Ag-DDC标准方法比较无显著差异;水稻土中总砷和As( )的回收率分别为98.36%～102.8%及56.02%～65.34%;对22种无机离子的干扰试验测定表明,在容许量内无干扰。     

Soluble Mn(III) in suboxic zones

Soluble manganese(III) [Mn(III)] has been thought to disproportionate to soluble Mn(II) and particulate Mn(IV)O2 in natural waters, although it persists as complexes in laboratory solutions. We report that, in the Black Sea, soluble Mn(III) concentrations were as high as 5 micromolar and constituted up to 100% of the total dissolved Mn pool. Depth profiles indicated that soluble Mn(III) was produced at the top of the suboxic zone by Mn(II) oxidation and at the bottom of the suboxic zone by Mn(IV)O2 reduction, then stabilized in each case by unknown natural ligands. We also found micromolar concentrations of dissolved Mn(III) in the Chesapeake Bay. Dissolved Mn(III) can maintain the existence of suboxic zones because it can act as either an electron acceptor or donor. Our data indicate that Mn(III) should be ubiquitous at all water column and sediment oxic/anoxic interfaces in the environment.     

arrA is a reliable marker for As(V) respiration

Arsenate [As(V)]-respiring bacteria affect the speciation and mobilization of arsenic in the environment. This can lead to arsenic contamination of drinking water supplies and deleterious consequences for human health. Using molecular genetics, we show that the functional gene for As(V) respiration, arrA, is highly conserved; that it is required for As(V) reduction to arsenite when arsenic is sorbed onto iron minerals; and that it can be used to identify the presence and activity of As(V)-respiring bacteria in arsenic-contaminated iron-rich sediments. The expression of arrA thus can be used to monitor sites in which As(V)-respiring bacteria may be controlling arsenic geochemistry.     

阴离子黏土吸附砷酸根离子热力学研究

利用共沉淀水热法制备镁铝阴离子黏土材料,研究了其水溶液对砷酸根[As（V）]离子的吸附热力学及其机理。结果表明：在303～333 K和试验浓度范围内,阴离子黏土对水中As（V）的吸附平衡数据符合Langmuir和Freundlich吸附等温方程。阴离子黏土对水中As（V）的吸附是吸热过程;根据热力学函数关系计算出As（V）在阴离子黏土上的吸附焓为2.85 kJ/mol,吉布斯吸附自由能改变量为-6.64～-5.90 kJ/mol,吸附自由能的变小是As（V）在阴离子黏土上吸附的推动力,吸附熵变为29.38 J/（mol.K）。     

142Nd evidence for early (>4.53 Ga) global differentiation of the silicate Earth

New high-precision samarium-neodymium isotopic data for chondritic meteorites show that their 142Nd/144Nd ratio is 20 parts per million lower than that of most terrestrial rocks. This difference indicates that most (70 to 95%) of Earth's mantle is compositionally similar to the incompatible element-depleted source of mid-ocean ridge basalts, possibly as a result of a global differentiation 4.53 billion years ago (Ga), within 30 million years of Earth's formation. The complementary enriched reservoir has never been sampled and is probably located at the base of the mantle. These data influence models of Earth's compositional structure and require revision of the timing of global differentiation on Earth's Moon and Mars.     

氢化物发生-原子荧光光谱法同时测定食品中的砷锑铋硒

[目的]在食品中准确测量砷、锑、铋、硒这些元素。[方法]利用双道氢化物发生-原子荧光光谱法,采用硝酸+高氯酸(4∶1)对样品进行一次性消化,利用同一样品溶液,通过对试验条件的筛选以及仪器参数的优化,对食品中砷、锑、铋、硒进行双道同时测定。[结果]砷、锑、铋、硒4种元素的检出限均能满足食品的检验,通过对国家标准物质的测定以及加标回收试验,验证了该方法是准确可靠的。[结论]该方法的建立减少了试剂消耗,降低了劳动强度,提高了分析效率。     

The importance of threading dislocations on the motion of domain boundaries in thin films

Thin films often present domain structures whose detailed evolution is a subject of debate. We analyze the evolution of copper films, which contain both rotational and stacking domains, on ruthenium. Real-time observation by low-energy electron microscopy shows that the stacking domains evolve in a seemingly complex way. Not only do the stacking boundaries move in preferred directions, but their motion is extremely uneven and they become stuck when they reach rotational boundaries. We show that this behavior occurs because the stacking-boundary motion is impeded by threading dislocations. This study underscores how the coarse-scale evolution of thin films can be controlled by defects.     

有机酸对As(Ⅴ)在土壤中老化的影响

为了明确不同类型有机酸对土壤中砷释放及迁移转化等行为的影响,应用模拟试验方法,研究了添加乙酸、草酸、柠檬酸和腐植酸对砷在第四纪红壤中老化的影响。研究结果表明,在温度为25℃、湿度为最大田间持水量70%条件下,有机酸类型对砷在第四纪红壤中老化过程的影响不显著,但有机酸添加量对培养期间土壤有效态和结合态砷的含量具有显著影响。当乙酸的添加量为50、100 mg·kg~(-1)时,对As(Ⅴ)在土壤中的老化均有抑制作用;添加量达到200 mg·kg~(-1)时,对As(Ⅴ)的老化具有促进作用。而草酸和柠檬酸的添加量为50 mg·kg~(-1)时,对As(Ⅴ)的老化具有促进作用;添加量为100、200 mg·kg~(-1)时均抑制As(Ⅴ)的老化。腐植酸对外源砷在土壤中的老化具有抑制作用,且其对砷老化的影响远大于其他类型有机酸。当添加量在50~200 mg·kg~(-1)时,乙酸和草酸对土壤中专性吸附态砷含量有显著影响;添加量为50、100 mg·kg~(-1)时,柠檬酸和腐植酸对弱结晶水合铁铝氧化物结合态砷均有显著影响;添加量为200 mg·kg~(-1)时,乙酸、柠檬酸和腐植酸对结晶水合铁铝氧化物态砷影响显著。综上,在本试验条件下,As(Ⅴ)在第四纪红壤上老化不受有机酸类型的影响,而受有机酸添加量的影响。     

Mixed-phase oxide catalyst based on Mn-mullite (Sm, Gd)Mn2O5 for NO oxidation in diesel exhaust

Oxidation of nitric oxide (NO) for subsequent efficient reduction in selective catalytic reduction or lean NO(x) trap devices continues to be a challenge in diesel engines because of the low efficiency and high cost of the currently used platinum (Pt)-based catalysts. We show that mixed-phase oxide materials based on Mn-mullite (Sm, Gd)Mn(2)O(5) are an efficient substitute for the current commercial Pt-based catalysts. Under laboratory-simulated diesel exhaust conditions, this mixed-phase oxide material was superior to Pt in terms of cost, thermal durability, and catalytic activity for NO oxidation. This oxide material is active at temperatures as low as 120°C with conversion maxima of ~45% higher than that achieved with Pt. Density functional theory and diffuse reflectance infrared Fourier transform spectroscopy provide insights into the NO-to-NO(2) reaction mechanism on catalytically active Mn-Mn sites via the intermediate nitrate species.     

Accumulation of Mn(II) in Deinococcus radiodurans facilitates gamma-radiation resistance

Deinococcus radiodurans is extremely resistant to ionizing radiation. How this bacterium can grow under chronic gamma radiation [50 grays (Gy) per hour] or recover from acute doses greater than 10 kGy is unknown. We show that D. radiodurans accumulates very high intracellular manganese and low iron levels compared with radiation-sensitive bacteria and that resistance exhibits a concentration-dependent response to manganous chloride [Mn(II)]. Among the most radiation-resistant bacterial groups reported, Deinococcus, Enterococcus, Lactobacillus, and cyanobacteria accumulate Mn(II). In contrast, Shewanella oneidensis and Pseudomonas putida have high iron but low intracellular manganese concentrations and are very sensitive. We propose that Mn(II) accumulation facilitates recovery from radiation injury.     

原子荧光光度法中湿法消解、微波消解前处理法测定土壤中总汞、总砷的比较

采用微波消解对土壤样品进行前处理,同时与湿法消解作比较,采用AFS-930型双道原子荧光光度计测定2种土壤标准物质中总砷、总汞的含量。对2种前处理方法所得的待测液进行5个平行测定,测定值均在其证书标准值范围内,微波消解样品前处理所得的测定结果比湿法消解的更令人满意。     

河南省主要土类土壤耕层砷(As)含量的调查

抽样调查了河南省分布的主要土类耕层土壤100个土样.对其土壤类型、质地、有机质含量、pH值进行了测定,并用王水-高氯酸消解、电感耦合等离子体发射光谱仪对土壤样品中的砷舍量进行了测定.结果表明,主要土类中砷含量平均值大小顺序为砂姜黑土＞潮土＞黄褐土＞黄棕壤＞红黏土＞褐土,砷含量平均分别为10.75 H培/kg,9.92mg/kg,7.40mg/kg,4.89mg/kg,5.34mg/kg,4.89 mg/kg,均低于国家土壤环境质量标准(GB 15618-1995)中规定的砷含量≤25 mg/kg.     

被污染土壤砷的化学形态与含量变化分析研究

采用连续提取法对土壤中砷的化学形态进行分析研究,比较加入不同改良剂时砷的各种形态含量的变化。结果表明,在加入改良剂时,土壤中5种形态的砷含量均有所改变,易于被植物吸收的可交换态砷的含量均有下降;在分别加入氧化钙和碳酸钠固体时,可交换态砷含量分别下降42．11％和70．10％,但以碳酸盐形态存在的砷含量却升高646．01％和618．78％;实验发现加入8-羟基喹啉时,易于被植物吸收的可交换态和碳酸盐结合态砷的含量下降值最大,显示出较好的砷污染改良效果。     

添加钝化剂对污泥堆肥处理中重金属(Cu,Zn,Mn)形态影响

利用污泥和稻草进行高温堆肥,研究不同钝化剂包括粉煤灰、磷矿粉、沸石和草炭对污泥堆肥中重金属（Ｃｕ,Ｚｎ,Ｍｎ）形态的影响。试验表明：从对交换态重金属的钝化效果来说,草炭、粉煤灰、磷矿粉是３种有效的钝化剂。在实际生产及应用中,考虑到作为钝化剂原料的来源、价格及处理费用等问题,选择粉煤灰、磷矿粉作为钝化剂是切实可行的。粉煤灰和磷矿粉的合适的加入比例分别是２５％和２０％。     

Open Framework Structures Based on Sex2- Fragments: Synthesis of (Ph4P)[M(Se6)2] (M = Ga, In, TI) in Molten (Ph4P)2Sex

Polychalcogenide compounds with open polymeric frameworks are rare, and they represent a class of compounds in which microporosity might be achieved. Microporous frameworks that are not oxide-based are now attracting interest because of the combination of catalytic and electronic properties they may simultaneously possess. Three new compounds that may be forerunners to such materials have been discovered and are reported here. The reaction of gallium (Ga), indium (In), and thallium (TI) metal with (Ph(4)P)(2)Se(5) (Ph, phenyl) and an excess of elemental selenium (Se) in a sealed, evacuated Pyrex tube at 200 degrees C yielded small red crystals of (Ph(4)P)[Ga(Se(6))(2)] (I), (Ph(4)P)[In(Se(6))(2)] (II), and (Ph(4)P)[TI(Se(6))(2)] (III), respectively. The [M(Se(6))(2)](-) (M = Ga, In, TI) ions form a two-dimensional, open framework filled with Ph(4)P(+) ions. The [M(Se(6))(2)](n)(n-) structure consists of tetrahedral M(3+) centers and bridging Se(6)(2-) ligands, leading to an extended structure in two dimensions. These layers stack perfectly one on top of the other giving rise to one-dimensional channels running down the c axis that are filled with Ph(4)P(+) cations. These cations are situated in the layers, as opposed to between the layers, and the whole structure can be viewed as a template. Compound II shows remarkable thermal stability and melts congruently at 242 degrees C. Upon cooling to room temperature it gives a glassy phase that recrystallizes upon subsequent heating to 160 degrees C.     

微波消解-ICP-oaTOF-MS法检测烟田土壤中Cr· As·Cd· Hg· Pb的研究

[目的]研究烟草土壤中几种重金属元素含量的测定方法。[方法]采用微波密闭消解-电感耦合等离子体直角加速飞行时间质谱(ICP-oaTOF-MS)法,分析了烟田土壤中Cr、As、Cd、Hg、Pb 5种元素含量。同时,研究了影响其测量的主要因素,确定了最佳测定条件。[结果]Cr、As、Cd、Hg、Pb检出限分别为0.090、0.130、0.083、0.090、0.093μg/L,回收率为90.67%～100.62%,RSD低于5%。[结论]与其他方法相比,所建立的方法具有简便、快速、准确、灵敏度高、检测限低等优点,特别是对一些浓度低达ng/L级的超痕量组分的检测,但高质量的丰度灵敏度要差一些,可用于烟叶重金属检测、质量控制。     

火焰原子吸收分光光度法与甲醛肟法测定水中锰的方法比较

通过检出限研究、考核样测定、精密度和准确度试验,分析实验室采用甲醛肟分光光度法测定水中锰含量的可行性。测定7个水样,每个水样3次重复,采用方差分析（F检验）,明确火焰分光光度法与甲醛肟分光光度法测定水中锰含量的差异显著性。结果表明,甲醛肟分光光度法测定水中锰的实验室检出限为0.009 7mg/L;用火焰原子吸收分光光度法和甲醛肟分光光度法测定考核样,结果分别为0.493及0.502mg/L,均在考核样锰含量的不确定度范围内。在P〈0.05时,2种方法测定水中锰的结果无差异显著性。     

As胁迫对二年生三七生长、根部As含量和根系分泌物的影响

通过大田试验,研究不同As处理浓度(As5+:0、20、80、140、200、260mg/kg)下,二年生三七绿果期生长特征、根不同部位(主根、须根和剪口)As含量和根系分泌物中有机酸含量、可溶性糖含量和游离氨基酸含量的变化规律。结果表明:(1)株高、叶面积和生物量随着砷处理浓度的增加降低,砷处理浓度为260mg/kg时,根生物量降低26.47%,总生物量降低23.61%;(2)主根、须根和剪口砷平均含量分别0.38、2.51、0.44mg/kg。三七根不同部位砷含量依次为:须根剪口主根;(3)砷胁迫条件下,根系分泌物中柠檬酸和总有机酸含量随砷处理浓度的增加而增加,醋酸和琥珀酸含量随砷处理浓度的增加而降低,在砷≥80mg/kg时,根系不再分泌苹果酸和乳酸;(4)根系分泌物中可溶性糖和游离氨基酸含量随砷处理浓度的增加而增加。总之,二年生三七的生长、砷含量和根系分泌物的组成和含量受到砷胁迫的影响,As大于140mg/kg处理时,三七的生长受到抑制,As小于200mg/kg处理时,柠檬酸、可溶性糖和游离氨基酸含量随As处理浓度的增加而显著增加。     

The geometric distance and proper motion of the Triangulum Galaxy (M33)

We measured the angular rotation and proper motion of the Triangulum Galaxy (M33) with the Very Long Baseline Array by observing two H2O masers on opposite sides of the galaxy. By comparing the angular rotation rate with the inclination and rotation speed, we obtained a distance of 730 +/- 168 kiloparsecs. This distance is consistent with the most recent Cepheid distance measurement. M33 is moving with a velocity of 190 +/- 59 kilometers per second relative to the Milky Way. These measurements promise a method to determine dynamical models for the Local Group and the mass and dark-matter halos of M31, M33, and the Milky Way.