Fractionation of dissolved organic matter affected by polyvalent metal cations

The purpose of the study was to evaluate the influence of polyvalent cations known to form complexes with natural organic substances on the operational fractionation of dissolved organic matter (DOM) using XAD-8 adsorber resin. Dissolved organic matter solutions from a forest floor were treated with increasing concentrations of polyvalent metal cations (Ca²⁺, Al³⁺, Fe³⁺) at different pH levels. Then the concentrations of total dissolved organic carbon (DOC) and the distribution between hydrophilic and hydrophobic DOC were determined. The concentrations of total DOC decreased slightly when the C/metal ratio was less than 10, especially for Al and Fe. Hydrophilic DOC increased and hydrophobic DOC decreased with increasing concentrations of metal cations. Effects increased in the order Ca<Al<Fe and were more pronounced at low DOC concentrations and high pH values. The reason for the reduction of the DOC concentrations seemed to be the formation of insoluble metal–DOM complexes, while soluble metal–DOM complexes may induce an alteration of the distribution between hydrophilic and hydrophobic DOC. Thus, the polyvalent cations and their concentration need to be considered when DOM fraction distributions, determined with XAD-8 resin, of different waters are compared, especially at low DOC contents and high pH.     

西南极乔治王岛冰芯研究——冰雪层定年、微粒记录及离子迁移

在分析南极乔治王岛冰帽大冰穹顶部降水和成冰条件的基础上,利用冰芯上部层物理特征参数确定的5个年层及其附近气象站相应的降水记录,结合多年降水资料将大冰穹45m冰芯划分为15个年层.应用此年层剖面,证实了微粒含量的两个异常峰值分别对应于1987年Deception岛和1980年的SealNunataks两次火山喷发.乔治王岛冰帽属于温性冰帽,大、小冰穹冰芯阴阳离子受沉积后融水渗浸淋溶作用的影响.对冰芯阴阳离子的淋溶次序分析显示,大冰穹为SO₄^2->Mg²⁺>Ca²⁺>K⁺>Cl^->Na⁺>NO₃^->Br^-,而小冰穹为Mg²⁺>Ca²⁺>SO₄^2->K⁺>Cl^->Br^->Na⁺.     

High‐Precision Measurement of Molybdenum Isotopic Compositions of Selected Geochemical Reference Materials

Here we describe high‐precision molybdenum isotopic composition measurements of geological reference materials, performed using multi‐collector inductively coupled plasma‐mass spectrometry (MC‐ICP‐MS). Purification of Mo for isotopic measurements was achieved by ion exchange chromatography using Bio‐Rad AG^® 1‐X8 anion exchange resin. Instrumental mass bias was corrected using ¹⁰⁰Mo‐⁹⁷Mo double spiking techniques. The precision under intermediate measurement conditions (eighteen measurement sessions over 20 months) in terms of δ^98/95Mo was 0.10‰ (2s). The measurement output was approximately four times more efficient than previous techniques, with no compromise in precision. The Mo isotopic compositions of seven geochemical reference materials, seawater (IAPSO), manganese nodules (NOD‐P‐1 and NOD‐A‐1), copper‐molybdenum ore (HV‐2), basalt (BCR‐2) and shale (SGR‐1b and SCo‐1), were measured. δ^98/95Mo values were obtained for IAPSO (2.25 ± 0.09‰), NOD‐P‐1 (?0.66 ± 0.05‰), NOD‐A‐1 (?0.48 ± 0.05‰), HV‐2 (?0.23 ± 0.10‰), BCR‐2 (0.21 ± 0.07‰), SCo‐1 (?0.24 ± 0.06‰) and SGR‐1b (0.63 ± 0.02‰) by calculating δ^98/95Mo relative to NIST SRM 3134 (0.25‰, 2s). The molybdenum isotopic compositions of IAPSO, NOD‐A‐1 and NOD‐P‐1 obtained in this study are within error of the compositions reported previously. Molybdenum isotopic compositions for BCR‐2, SCo‐1 and SGR‐1b are reported for the first time.     

Hydrochemistry of pampasic ponds in the lower stream bed of Salado River drainage basin, Argentina

Received: 3 May 1999 · Accepted: 13 July 1999     

Layer by Layer Assembly of Poly(Allylamine Hydrochloride)/Phosphate Ions and Poly(Sodium 4-Styrene Sulfonate) Membrane for Forward Osmosis Application

Based on the layer by layer(Lb L)assembly technology,the nano-scale composite membrane with excellent structure can be prepared by changing the polyelectrolyte and controlling the deposition conditions.Polyamines and phosphate ions(Pi)can be self-organized to form supramolecular systems which could be exploited to stabilize the interfacial architecture.The LbL membrane was made of the positively charged poly(allylamine hydrochloride)(PAH)self-organized with Pi and the negatively charged poly(sodium 4-styrene sulfonate)(PSS)alternatively on top of a poly(acrylonitrile)(PAN)substrate.Compared to the membrane without Pi,the membrane assembled by PAH/Pi improved forward of flux and reduced flux of salt.The concentration of PAH and PSS,deposition time,pH and number of layers showed significant influences on the performance of the membrane.In this experiment,we systematically investigated the preparation conditions and under the optimized conditions the prepared membrane exhibited high water fluxes of 13.5 L m^-2 h^-1 with corresponding salt to water flux,Js/Jv,ratio of 0.07 g L^-1 tested by forward osmosis when DI water as feed solution and 2 mol L^-1 MgCl2 as draw solution.     

On the impact of multiply charged heavy solar wind ions on the surface of Mercury, the Moon and Ceres

We have studied the impact of multiply charged solar wind O⁷⁺ and Fe⁹⁺ ions on the surfaces of Mercury, the Moon and on a Ceres-size asteroid using a quasi-neutral hybrid model.The simulations showed that heavy O⁷⁺ and Fe⁹⁺ ions impact on the surface of Mercury non-homogenously, the highest flux being near the magnetic cusps—much as in the case of impacting solar wind protons. However, in contrast to protons, the analyzed heavy ions do not create high ion impact flux regions near the open-closed magnetic field line boundary. Dawn-dusk asymmetry and the total ion impact flux were each found to increase with respect to the increasing mass per charge ratio for ions, suggesting that the Hermean magnetic field acts as a mass spectrometer for solar wind ions. The Moon, in contrast, does not have a global intrinsic magnetic field and, therefore, solar wind ions can freely impact on its surface when this body is in the solar wind. The same is true for a, non-magnetized, Ceres-size asteroid.The impact of multiply charged ions on a solid surface results in a large variety of physical processes, of often intimately inter-related atomic reactions, e.g. electron exchange between solid and approaching projectile, inelastic scattering of projectile, electronic excitation in the projectile and/or the solid, ejection of electrons, photons, neutral and iodized surface particles, and eventual slowing down and stopping of the projectile in the solid. The electron transfer process between impacting heavy ions and surface constituents can result in soft X-ray (E<1 keV) and extreme ultraviolet (EUV) photon emissions. These processes will eventually damage the target surface. Analysis of the hybrid Mercury model (HYB-Mercury) suggests that, at this planet the damaging processes result in non-homogenous ageing of the surface that is controlled by the intrinsic magnetic field of the planet and by the direction of the interplanetary magnetic field. In the corresponding Lunar model (HYB-Moon) and in the non-magnetized asteroid model (HYB-Ceres), surface ageing is demonstrated to take place on that side of the body that faces toward the flow of the solar wind.     

电气石微粉吸附水体中金属离子及其机理分析

研究了电气石微粉吸附水中Cu2＋、Pb2＋、Zn2＋的过程,讨论了吸附时间、粒度、用量和pH值等因素对吸附效果的影响,分析了电气石对含Cu2＋、Pb2＋、Zn2＋废水的吸附机理。电气石加工成超细粉体时,表面产生大量的不饱和键,在溶液中与水配位,使水发生解离生成羟基化表面,将重金属离子吸附到晶体负极,使局部金属离子浓度增高与电气石表面羟基离解而产生的氢氧根离子发生反应,形成各种沉淀或碱式盐析出,直到溶液中各种离子浓度达到平衡时为止。提出了凡是氢氧化物难溶于水的金属离子,理论上都可以使用电气石微粉进行吸附净化处理的观点。研究结果表明,电气石微粉对Cu2＋、Pb2＋、Zn2＋有较好的吸附效果。     

重金属离子对中华绒螯蟹肝胰脏和鳃丝SOD,CAT活力的影响

研究了 3种重金属离子 (Cu2 ,Zn2 ,Cd2 )对中华绒螯蟹肝胰脏和鳃丝 SOD,CAT活力的影响。实验结果表明 ,肝胰脏和鳃丝 SOD,CAT活力在 3种重金属离子作用下分别随取样时间变化显著 (P<0 .0 5 ) ,对 2种抗氧化酶活力的抑制均为肝胰脏 <鳃丝。 3种重金属离子在实验时间内对肝胰脏 2种抗氧化酶活力的影响呈峰值变化 ,低浓度组表现为促进作用 ,高浓度组在 96 h时为抑制作用 ;低浓度组在 72 h内能提高鳃丝 2种抗氧化酶活力 ,随后下降 ,至 96 h时表现为抑制作用 ,而高浓度组一直为明显的抑制作用 ,2种抗氧化酶活力表现出明显的时间、剂量效应关系。因此 ,肝胰脏和鳃丝SOD,CAT2种抗氧化酶可作为中华绒螯蟹毒理学的评价指标。     

地顶的地心距离及其变化

本文介绍了有关磁层中电离层离子起主要作用区域（地顶内区）的观测资料和磁层中电离层离子随地磁活动和太阳活动变化的观测资料,根据这些资料简单分析了上行离子的密度和通量密度及地顶的变化。