The flocculation of dissolved Fe,Mn, Al,Cu, Ni,Co and Cd during estuarine mixing

A laboratory experiment was carried out in which the flocculation products, formed from the mixing of filtered (0.4 μm) river water and seawater, were analysed. This study established that Fe, Mn, Al, Cu, Ni, Cd and Co have resolvable and well-defined estuarine chemistries. Copper, Ni, Mn and Co have salinity dependences of removal which are similar to those of dissolved Fe and humic acids. The amount of removal of the above trace metals increases between 0 and 15–18‰, after which little additional removal occurs. The extents of removal from river water are very different: Fe, 95%; Al, 20%; Cu, Ni, 40%; Co, 10%; Cd, 5% and Mn, 25–45%. The basic removal mechanism appears to be the estuarine flocculation of trace metals which exist, in part, in river water as colloids in association with colloidal humic acids and hydrous iron oxides. A qualitative model, based on this mechanism, supports the observations of this flocculation study.The results of this study give the most complete and consistent set of data presently available, from which to postulate the most important processes controlling the estuarine chemistry of trace metals. The generality of their behaviours still needs to be determined by future investigations.     

Trace element content of metals from L-group chondrites

Eight L- and one LL-group chondrites were selected for a major and trace element content study of their metals by instrumental neutron activation techniques. The elements Ni, Co, Fe, Cu, As, Ga, W, Au and Ir were determined. For each meteorite three metallic fractions were analyzed: (1) coarse, >100 mesh; (2) intermediate, 100–200 mesh; (3) fine, <200 mesh. The composition of the metals varies considerably with grain size, as a result of a preferential concentration of kamacite in the coarse and of taenite in the intermediate and fine fractions.A third metallic component, consisting of very fine plessitic inclusions, was observed in chondrules of equilibrated chondrite types 5 and 6. This component is probably responsible for the decrease of Ni, Cu, Ga and Au observed in the fine metallic fractions of the equilibrated chondrite types.W, as well as Ga, increases in the bulk metals with the petrologic type, suggesting that a substantial amount of this element, as already observed for Ga by previous authors, is not in the metal, but in some silicate phases in the lower metamorphic petrologic types 3 and 4.Ir is always concentrated in the fine metallic fractions of all meteorites, independent of petrologic type, suggesting the presence of a fine-grained metallic component enriched in this element.     

Geochemical processes controlling the relationship between Co,Mn, and Fe in early diagenetic deep-sea nodules

Early diagenetic manganese nodules from the northeast Pacific nodule belt and from the southeast Pacific (Peru Basin) show primary growth features of dendritic microtextures consisting of alternating laminae of crystalline 10-Åmanganate (A1 substance) and amorphous material which is composed of an intimate mixture of ferric hydroxide, silicate, and δ-MnO₂ (A2 substance). The formation of rhythmic sequences of A1 and A2 microlayers is explained by physico-chemical changes in the peneliquid sediment layer and in the microenvironment of the accreting nodule surface: (a) upward diffusion of Mn²⁺ in the interstitial water as a result of decay of organic matter and Mn mobilization; (b) oxidation of Mn²⁺ and formation of 10-Åmanganate in the upper part of the peneliquid sediment layer, leading to pH depression in the microenvironment of the nodule surface which decreases the mobility of silicate, resulting in formation of A2 layers; (c) restoration of pH and renewed precipitation of 10-Åmanganate.Based on data of 171 bulk analyses and on electron microprobe investigations, interelement relationships between Co, Mn, and Fe are pointed out. Fe and Co show a significant positive correlation (r = 0.84), while Mn and Co are poorly negatively correlated (r = ?0.21), assuming linear regression. The enrichment of Co within the amorphous A2 phase is attributed to specific surface adsorption and subsequent oxidation of Co²⁺ to Co³⁺ in the strong electric field of Si⁴⁺. Robust complexes of Co(III) and ≡ FeH₂SiO₄^? prevent most of the Co from being available for the 10-Åmanganate precipitation. Concerning the relation between Mn and Fe and Co respectively, the highest correlation coefficients are obtained using an inverse logarithmic regression. Under early diagenetic conditions, the concentration and precipitation of Mn²⁺ in the interstitial water depends on the redox gradient which is controlled by the amount of decomposing organic matter. The Nernst equation describes the relationship as a reciprocal logarithmic function. However, the quantities of colloidal ferric hydroxide and of dissolved silicate are not affected by variations of the redox potential. These different characteristics in the precipitation of Mn and the Fe- and Si-rich colloidal phase may cause the significantly negative logarithmic correlation of Mn versus Fe and Co, respectively.     

The geochemical behavior of refractory noble metals and lithophile trace elements in refractory inclusions in carbonaceous chondrites

Recent models of Ca, Al-rich inclusion (CAI) petrogenesis suggest that refractory inclusions may be residues of interstellar dust aggregates that were incompletely evaporated and partially melted in the solar nebula. These models, and the recent availability of new thermodynamic data, have led us to re-examine the traditional interpretation that lithophile refractory trace elements (LRTE) condensed as oxides in solid solution in refractory major condensates, while refractory noble metals (RNM) condensed as micron-sized nuggets of Pt-metal alloys. Calculations of LRTE-RNM alloy stability fields under nebular oxygen fugacities and partitioning experiments lead us to conclude that: (1) Ti, Zr, Nb, Hf, U, and Ta form stable alloys with RNM under nebular conditions; (2) the observation that metallic Zr, Nb, and Ta occur in some Pt-metal nuggets and grains is explained by the stability of these LRTE-RNM alloys under normal nebular oxygen fugacities; (3) metallic Ti, Hf, and U may also occur in some nuggets; (4) the lanthanides, the other actinides (Th, Pu), and Y do not form stable alloys, and thus probably do not occur alloyed with RNM; and (5) the partitioning of U (but not Th, Pu, or the REE) into RNM is a novel actinide and REE/actinide fractionation mechanism that is based on metal/silicate fractionation (rather than on the relative volatility of their oxides).We propose that micron-sized Pt-metal nuggets formed from smaller grains of RNM alloys and compounds during the evaporation and melting of primitive dust aggregates. This process would have been enhanced by: (1) the possibility that the RNM were present as compounds (especially with As and S) as well as metallic alloys in interstellar dust and in some primitive meteoritical material, since they often exhibit non-siderophile behavior; and (2) the fluxing of volatiles through CAI's during distillation. Microscopic nuggets are common in melilite chondrules, indicating that residence in a slowly-cooled silicate melt may have favored their formation. Cation diffusivity and variations in localf_O2 can explain why metallic LRTE-bearing nuggets are not common in CAI's (despite the relative stability of LRTE-RNM alloys). We propose that the lithophile component of Fremdlinge is enriched in super-refractory elements, and that Group II CAI's formed from Fremdlinge-poor dust. We interpret the Group II REE fractionation as a pre-solar event, and predict that Nd/Sm dating will yield an age greater than the canonical age of the solar system. If metal/silicate fractionation in a cold solar nebula can explain Group II REE patterns, the possibility that Group II CAI's are also distillation residues cannot be excluded.     

Cooling rates in the shock veins of chondrites: constraints on the (Mg, Fe)2SiO4 polymorph transformations

The occurrence of γ-phase, a high-pressure polymorph of olivine (α-phase), in the shock veins of Sixiangkou chondrite was due to a greater cooling rate (> 10 000°C·s^-1) in the veins. Because γ-phase partially reverted to β-phase and no back-transformation from β-phase to α-phase took place, the shock veins of Peace River chondrite with a cooling rate of 1 000–2 000δC·s^-1 contain a great amount of β-phase. In the shock veins of Mbale chondrite with a cooling rate of <500°C·s^-1, the majority of γ-phase reverted to α-phase. The heat dissipation in shock veins took place after a stage of shock compression of chondrite parent body, and the parent body was broken into fragmental pieces. Cooling rate in the shock veins constrained the back-transformations of (Mg, Fe)₂SiO₄ high-pressure polymorphs. Project of Chen and Xie supported by the National Natural Science Foundation of China (Grant No. 496720981, Natural Science Foundation of Guangdong Province (Grant No. 960500), and the Science Foundation of Academia Sinica for the returned scholars.     

The trace element chemistry of CaS in enstatite chondrites and some implications regarding its origin

Samples of the mineral oldhamite (CaS) were extracted from enstatite chondrites and analyzed by INAA. Prior to extraction, the petrologic setting of the grains was studied microscopically and their minor element contents determined by microprobe analyses. Minor element contents of CaS are known to vary and correlate with petrologic type, indicating secondary redistribution during metamorphism. For this reason, samples were chosen that displayed a range of minor element contents. The trace element contents determined in this study follow a similar pattern. The most primitive samples of CaS studied, contain virtually the entire inventory of the host meteorite's LREE and Eu plus 30–50% of the HREE inventory. In less primitive samples the LREE are less enriched although Eu remains highly concentrated in CaS. Several other elements, including lithophiles (Ba, Cs, Cr, Hf and Sc) and chalcophiles (Sb and Zn) are most enriched in more primitive CaS. The high concentrations of refractory elements, several of which have a tendency to form sulfides at high temperatures in a gas slightly more reducing than solar, lend support to the suggestion that CaS originated at high temperatures in a reduced region of the nebula. The high concentrations of volatile Cs, Sb and Zn indicate that with decreasing temperature CaS continued to interact with the nebular gas, which therefore must have had a low oxygen fugacity at low temperatures.     

Distribution of some heavy metals in the Gulf of Fos

Measurements of copper, lead, cadmium and zinc were determined using the differential pulse anodic stripping voltametry technique in a marine industrialized area, the Gulf of Fos, near Marseilles. Results show an important contamination of the whole area, with particularly high values near the coast. Comparing our results with those of the literature, we see that the Gulf of Fos is probably one of the most polluted areas in Europe.     

抚仙湖沉积物重金属时空变化与人为污染评价

分析了抚仙湖表层沉积物及沉积短岩芯中10种金属元素含量,结合沉积年代学,定量研究了Cr、Cu、Ni、Pb、Zn的污染特征及时空变化规律;参考沉积物质量基准与潜在生态风险指数法探讨了表层沉积物重金属的潜在生态风险.结果表明,表层沉积物中重金属含量具有一定的空间差异性,近岸地区重金属含量总体上高于湖心区;Pb、Zn含量自1980s中期以来逐渐增加,而Cr、Cu、Ni含量呈下降趋势.重金属富集系数与聚类分析结果表明,抚仙湖沉积物主要重金属污染元素为Pb、Zn,污染开始于1980s中期,并逐渐加重.表层沉积物中Pb、Zn富集系数分别为1.6~4.1和1.4~2.6,已达到弱—中等污染程度,北部湖区污染程度略高于南部湖区;除此之外,北部湖区近岸区域Cr污染程度也略高于其他湖区.除了大气沉降来源之外,抚仙湖沉积物重金属污染还可能与入湖河流输入有关.单因子生态风险指数表明,表层沉积物中Cr、Cu、Ni、Pb、Zn具有较低的潜在生态风险;而综合潜在生态风险指数表明,表层沉积物中重金属具有中等程度的潜在生态风险,这与根据沉积物质量基准所获得的评价结果一致.     

Sm-Nd isotopic evolution of chondrites and achondrites,II

The¹⁴⁷Sm¹⁴³Nd and¹⁴⁶Sm¹⁴²Nd isotope systematics have been investigated in five chondrites and the achondrites Moama and Angra dos Reis (ADOR). The new chondrite data and those we have reported before are all consistent with our previously reported reference values for CHUR (“chondritic uniform reservoir”) of (¹⁴³Nd/¹⁴⁴Nd)_CHUR⁰ = 0.511847 and (¹⁴⁷Sm/¹⁴⁴Nd)_CHUR⁰ = 0.1967. Most of the bulk chondrites analyzed have ¹⁴³Nd/¹⁴⁴Nd and ¹⁴⁷Sm/¹⁴⁴Nd within 0.5 ε-units and 0.15% of the CHUR values, respectively. This strongly suggests that the CHUR evolution is now known to within these error limits throughout the history of the solar system. The St. Severin chondrite yields an SmNd internal isochron age of T = 4.55 ± 0.33AE and an initial ε_Nd = 0.11 ? 0.26. Much larger variations in Sm/Nd ratios were measured in mineral separates of the Moama and ADOR achondrites. Thus, very precise ages of 4.46 ± 0.03AE and4.564 ± 0.037AE were obtained for these meteorites, respectively. The initial ε_Nd values obtained for Moama and ADOR are 0.03 ? 0.25and0.14 ? 0.20, respectively. The values obtained on these meteorites are fully consistent with the CHUR evolution curve. Initial ε_Nd data on terrestrial igneous and meta-igneous rocks demonstrates that positive initial ε_Nd values occur throughout the past 4 AE. This confirms our earlier report that a light rare earth element-depleted layer has existed throughout most of the Earth history and is the source of present-day mid-ocean ridge basalts. The inferred shape of the ε_Nd vs. age curve for the depleted mantle suggests profound changes in tectonic regimes with time; in particular, it suggests a much higher rate of recycling of continental materials into the mantle during the Archean as compared to later time periods.¹⁴⁶Sm¹⁴²Nd systematics of ADOR and Moama are supportive of the hypothesis that¹⁴⁶Sm was present in the early solar system and suggests a ¹⁴⁶Sm/¹⁴⁴Sm ratio of about 0.01 for the solar system ～ 4.56 AE ago. This inferred high¹⁴⁶Sm abundance cannot be explained as a late injection from a supernova and must be due to galactic nucleo-synthesis.     

Accretion of the ordinary chondrites

The narrow size distributions of silicate and metal particles in 19 unequilibrated ordinary chondrites and other textural properties of these meteorites strongly suggest that chondritic material was sorted before or during its accumulation in parent bodies. Gravitational sorting during accretion is possible, but the conditions which it requires are implausible. Aerodynamic sorting - exclusion of small and/or low-density particles from a planetesimal moving through a mixture of gas and dust - can account for the textures of ordinary chondrites. It may also explain observed variations of siderophile element contents among and within the three groups of ordinary chondrites.     

西藏纳木错及其入湖河流溶解有机碳和总氮浓度的季节变化

为深入理解纳木错湖水及入湖河流中溶解有机碳（DOC）和总氮（TN）浓度的季节变化特征及其影响因素,于2012-2013年不同季节对纳木错2个站点及流域内21条主要入湖河流进行采样及分析,采用统计学方法初步探讨纳木错水体和21条河流DOC和TN浓度季节变化特征.结果表明,河流DOC平均浓度范围为0.763~1.537 mg/L,TN平均浓度范围为0.179~0.387 mg/L.21条入湖河流DOC浓度在春末夏初和夏季达到高值,冬季为低值,TN浓度季节变化趋势大体上与DOC浓度相反.湖泊水体DOC和TN浓度范围分别为2.42~8.08和0.237~0.517 mg/L,明显分别高于河水中的浓度.湖泊DOC浓度季节变化趋势与河流一致,而TN浓度无明显的季节性变化.河水DOC浓度的季节变化和空间差异受控于河流的补给方式,湖水DOC浓度受湖泊内部藻类等水生植物活动和河流外源输入的影响.DOC等有机质的分解是影响纳木错流域湖水和河水TN浓度的重要原因.     

Distribution and ecological risk assessment of some heavy metals in coastal surface sediments along the Red Sea,Egypt

The ecological risk assessment for Al,Zn,Cu,Ni,V,Pb,Cd,and Hg in surface sediment collected from the Egyptian Red Sea coast was evaluated using the Geo-accumulation Index(I_(geo)).Sediment Enrichment Factor(SEF) and Potential Ecological Risk Index(PERI) methods.The predominant heavy metal,aluminum,showed high concentrations along both of Aqaba Gulf(4378.8 ± 2554.1 μg/g) and southern part of the Red Sea(2972.8 + 1527.5 μg/g).while it recorded the lowest concentration in Suez Gulf(829.7 ± 398.2 μg/g).The determined heavy metal concentrations had the order of Al Zn -Ni V Pb Cu Cd Hg.The statistical analyses showed some correlations among the heavy metals contents.Several international sediment quality guidelines were used to estimate the quality of the collected sediments.Interestingly,the recorded average heavy metals concentrations were lower than those of the permissible contents for sediment quality guidelines.The Geo-accumulation index calculations(I_(geo)) proved that the investigated region could be classified as an unpolluted area.Sediment Enrichment Factor(K_(SEF)) study showed high values in Suez Gulf region.The single pollution index analysis of heavy metals in the sediments(C~i_f) indicated that Al,Zn,V,and Pb were of natural origin,while Ni,Cd and Hg were seriously affected by human activities.Interestingly,amongst,all the determined heavy metals,Cd and Hg gave moderate ecological risk indicators.     

Chemical and physical studies of type 3 chondrites, VII. Annealing studies of the Dhajala H3.8 chondrite and the thermal history of chondrules and chondrites

Samples of the Dhajala H3.8 chondrite have been annealed for 10 hours at 600, 700, 800, 900 and 1000°C and at 1000°C for 1, 2, 20 and 100 h and their thermoluminescence (TL) properties measured. The TL sensitivity decreased by a factor of 2 after annealing at < 900°, but at higher temperatures fell by an order of magnitude. An abrupt increase in the temperature of the TL peak from 172 ± 9°Cto231 ± 8°C and a steady increase in the width of the peak from 169 ± 7°Cto212 ± 5°C were caused by the annealing treatment. The TL phosphor in Dhajala is thought to be feldspar predominantly in the high-temperature (disordered) form, but the present data indicate that a contribution from the low-temperature form is also present and that this low-temperature component is converted to the high form by the annealing treatment. The low-temperature feldspar is located in a few of the chondrules ( 20% of those separated from the meteorite) which are also noteworthy for having high TL sensitivities. These chondrules must have suffered greater crystallization of their mesostasis than the other chondrules, and equilibrated to lower temperatures. It is argued that, for compositional reasons, their mesostasis constituted less of a barrier to diffusion and therefore equilibration. Presumably the post-metamorphic cooling rate of the meteorite through the stability field of the low form was slow enough to permit some crystallization, and the width and temperature of the TL peaks for petrologic types 3.5–3.9 are somehow related to cooling rate. Based on TL, there is no indication of a correlation between petrologic type and cooling rate for types 3.5–3.9; this is not consistent with a simple, single internally heated meteorite parent body.     

Space-time variations in British Caledonian Granites: some geophysical correlations

The characteristics of 30 “granites” from the postulated Caledonian (Iapetus Ocean) suture zone of mainland Britain are discussed. Geophysical (gravity, aeromagnetic), geochemical (U/Pb and initial⁸⁷Sr/⁸⁶Sr) and isotopic age data indicate that these British Caledonian intrusions (390–600 Ma) can be divided into two distinct groups temporally, each of which is further subdivided spatially.The temporal division applies throughout the British province and separates a pre-Silurian (group 1) suite of low-volume, low-mobility magmas, which were intruded under compressive conditions, from a Siluro-Devonian (group 2) suite of large volume, mobile magmas intruded under tensional conditions.The spatial subdivisions of groups 1 and 2 are made between intrusions emplaced to either side of the postulated ENE-WSW Iapetus Ocean suture which runs through the Solway Firth. First, the group 1 granites northwest of the suture probably were produced by partial fusion involving Proterozoic continental crust (group 1N) whereas those to the southeast have isotopic characteristics simply indicating a mantle or ocean crustal source (group 1S). Second, the Siluro-Devonian granites, which were all derived largely at the expense of Caledonian mantle, have different aeromagnetic expressions depending on their position in the northwest (2N) or southeast (2S) Caledonides. These aeromagnetic characteristics are probably related to the differences in basement structure recently identified by seismic surveys and they provide further evidence for the former existence and Siluro-Devonian closure of Iapetus. Another significant implication may be that Proterozoic basement is lacking from beneath the region immediately adjacent to and southeast of the suture — southern Scotland and most of England.     

Total petroleum hydrocarbons and heavy metals in the surface sediments of Bohai Bay,China: Long-term variations in pollution status and adverse biological risk

Surface sediments collected from 2001 to 2011 were analyzed for total petroleum hydrocarbons (TPH) and five heavy metals. The sediment concentration ranges of TPH, Zn, Cu, Pb, Cd and Hg were 6.3–535 μg/g, 58–332 μg/g, 7.2–63 μg/g, 4.3–138 μg/g, 0–0.98 μg/g, and 0.10–0.68 μg/g, respectively. These results met the highest marine sediment quality standards in China, indicating that the sediment was fairly clean. However, based on the effects range-median (ERM) quotient method, the calculated values for all of the sampling sites were higher than 0.10, suggesting that there was a potential adverse biological risk in Bohai Bay. According to the calculated results, the biological risk decreased from 2001 to 2007 and increased afterwards. High-risk sites were mainly distributed along the coast. This study suggests that anthropogenic influences might be responsible for the potential risk of adverse biological effects from TPH and heavy metals in Bohai Bay.     

Acute toxicity of heavy metals to some marine larvae

The toxicity of copper, mercury and zinc to the larvae of oysters, shrimp, crab and lobsters has been examined over periods of up to 64 hours. Mercury was found to be more toxic than copper and zinc, which had similar levels of toxicity. Over the experimental period, the relationship between toxicity and concentration was linear. Larvae were from 14 to 1,000 times more susceptible than adults of the same species. The median lethal concentrations (LC₅₀) of each metal to the most sensitive species of larvae, tested over a 48 hour period, exceeded the concentrations found in natural sea water by a factor of 100. For longer test periods, the LC₅₀ would be considerably less and this factor would then be considerably reduced. Hence the continued addition of these metals to confined waters should give cause for concern.     

Determination of Cu,Fe, and Ni in Spices after Preconcentration on Diaion‐HP 20 Resin as Their Zincon Complexes

In this work, a new separation–preconcentration method was developed for the determination of trace amounts of Cu(II), Ni(II), and Fe(III) by flame atomic absorption spectrometry (FAAS). Analytes were complexed by using zincon (2‐[2‐[alpha(2‐hydroxy‐5‐sulfophenylazo) benzylidene] hydrazino] benzoic acid sodium salt). The analyte ions were quantitatively adsorbed on a Diaion HP‐20 resin at pH 5. The retained metal ions on the resin were eluted by acetone. The analytical parameters such as pH of the sample, eluent type and volume, sample volume, and flow rates of the solution and the eluent were investigated. The influences of concomitant ions on the recoveries of the analytes were also examined. The instrumental detection limits for the analytes after application of the presented solid‐phase extraction procedure were in the range of 0.72–1.41 µg/L. The validation of the presented procedure was checked by analyzing certified reference material of SRM1515 Apple Leaves. The procedure was performed by analyzing some spice samples.