Extent of immobilisation of phosphate during aeration of nutrient-rich, anoxic groundwater

Nutrient-rich exfiltrating groundwater may impose a heavy phosphate load on surface water systems. However, iron oxides that bind PO₄ precipitate fast upon oxygenation at neutral pH and PO₄ may also become bound in Ca precipitates following upon pH increase, so load estimates based on conservative behaviour during exfiltration will be overestimates. Aeration experiments using natural groundwater were performed to characterise the immobilisation of PO₄ within one day after aeration started. Groundwaters having a wide variety in composition, were sampled in the coastal lowlands of the Western Netherlands. Three models were considered to describe the fast binding of PO₄ by Fe oxide type phases that form upon the oxygenation of dissolved Fe(II), each based on a different concept. The concepts were surface complexation, solid-solution precipitation and two-mineral precipitation. When the experimental data were compared with model results, all three models were found to be inadequate. Frequently, more immobilisation of PO₄ occurred than could be explained by binding to a Fe oxide type of phase alone. Uptake by Ca phosphates and/or Ca carbonates must additionally have played a role; alternatively, a non-ideal phase consisting of Ca, Fe and PO₄ precipitated upon oxygenation and CO₂ degassing. A predictive multiple regression model with two primary variables that reflect the driving forces for PO₄ immobilisation was deduced that describes immobilisation of phosphate after aeration of anoxic groundwater. The two primary variables are the log value of the groundwater Fe to PO₄ molar ratio and the saturation state for hydroxyapatite after the CO₂ degassing of groundwater. The model is useful for calculating the PO₄ load of surface water from exfiltration groundwater, taking into account fast immobilisation (<1 day) during exfiltration.     

Geochemical Process of Gas Hydrate Formation in the Nankai Trough Based on Chloride and Isotopic Anomalies in Interstitial Water

Abstract: Interstitial water expelled from gas hydrate-bearing and -free sediments in the Nankai Trough are analyzed in terms of Cl-, SO₄²-, δ¹⁸O and δD. The baselines for the Cl- concentration and δ¹⁸O value are close to seawater values (530 mM and 0%), indicating that the interstitial water is of seawater origin. The δD values decrease with depth, implying isotopic exchange of hydrogen between upwelling biogenic methane depleted in D and interstitial water. The Cl- concentrations in gas hydrate-bearing sediments are anomalously low, while the δ¹⁸O and δD values are both high, suggesting that the water forming these gas hydrates was poor in Cl- and enriched in ¹⁸O and D during gas hydrate formation. Calculation of the gas hydrate saturations using Cl "and δ¹⁸O anomalies gives results of up to 80 % in sand, and shows that the δ¹⁸O baseline is not consistent with the Cl" baseline. The δ¹⁸O baseline increases by +1% in gas hydrate-free clay and silt. This is considered to be caused by clustering of water molecules after gas hydrate dissociation in response to the upward migration of the base of gas hydrate stability, as indicated by the presence of a double bottom-simulating reflector at this site. The water clusters enriched in ¹⁸O are responsible for the increase in the δ¹⁸O baseline with normal Cl". The abrupt shallowing of the base of gas hydrate stability may induce the dissociation of gas hydrates and the accumulation of gases in the new stability zone, representing a geological process that increases gas hydrate saturation.     

海盐氯循环对输送污染物致酸的缓冲作用

着重研究海盐氯循环对输送污染物致酸的缓冲作用,通过对全球低污染点酸雨资料分析,初步结论是:海盐氯循环使经过海洋上空输送的致酸大气污染物转化为中性盐,这一机制缓冲了经过海洋上空输送的致酸前提物的酸性,使受体点降水中出现氯亏损、硫富集,并伴随有降水中氯亏损和H+离子浓度的负相关。在高氯亏损降水样品中,降水pH值一般大于5.0。硫同位素动力学分析表明,当降水pH值大于5.6氯亏损时,污染物在海洋上空输送过程中和海盐发生非均相反应的速率与其发生均相反应的速率接近。但这一机制仅适用沿海地区。     

Geochemical Evolution of Hydrothermal Fluids at the Daejang Cu–Zn–Pb Vein Deposit, Korea

Abstract: The Daejang mine is located within the Cretaceous Gyeongsang basin. Mineral paragenesis can be divided into four stages (stages I, II, III and IV) by major tectonic fracturing. Stages I, III and IV are economically barren. Stage II, at which the precipitation of major ore minerals occurred, is further divided into three substages with paragenetic time based on minor fractures and discernible mineral assemblages: substage IIa, marked by deposition of quartz and Fe–sulfides; substage IIb, by introduction of base-metal sulfides within carbonates and some quartz; substage IIc, by quartz and carbonates with various sulfosalts. Fluid inclusion data indicate a complex geochemical evolution of hydrothermal fluids. Both CO₂–rich and H₂O–rich fluids were trapped in fluid inclusions at stage I and substage IIa. It is suggested that a compositionally heterogeneous fluid was formed by fluid boiling and CO₂ immiscibility at temperatures of about 400° to 300°C. Composite lodes of base-metal sul–fides, carbonates and quartz at substage IIb were deposited in open spaces created by fracturing. The fracturing event prompted rapid decreases in pressure and temperature of residual fluids and resulted in retrograde fluid boiling at about 200 bars and 300°–250°C during substage IIb. The progressive loss of CO₂ by CO₂ effervescence and retrograde boiling from substage IIa and IIb fluids resulted in pH increase and related increase in carbonate activity, causing deposition of abundant carbonates. The change in pH also caused the decrease of stability of hydrogen sulfide with Cu, Zn and Pb chloride complexes (as main transporting agents at Daejang) and resulted in the pricipitation of base-metal minerals. Deposition of Ag– and Sb-bearing sul–fides and sulfosalts of substage IIc occurred at temperatures of about 250° to 150°C from a dominantly aqueous fluid with low salinity (down to 3. 0 equiv. wt % NaCl). At this substage, aqueous fluid formed by mixing with cooler and less saline meteoric groundwater. There is a systematic decrease in caculated δ¹⁸O_water values with the mineralization stage (and decreasing temperature) in the Daejang hydrothermal system, from values of about 11% for stage I, through about 4% for stages II and III, to about –3 per mil for stage IV. The result of stable isotope and fluid inclusion studies are interpreted to indicate progressive less evolved and/or unexchanged meteoric water influx of an early hydrothermal system formed by highly evolved meteoric waters.     

黑云母与氯化物热水溶液相互作用的实验研究

本文在500℃和1×108Pa条件下，利用冷封口高温高压水热系统和焊封金管技术实验研究了黑云母和Na－Ca－氯化物溶液的相互作用，着重考察反应不同时间的黑云母表面和溶液化学的变化。黑云母中的K、Fe和Si不同程度地进入溶液相，而溶液中原有的Na和Ca含量降低；SEM／EDAX和EMAX研究表明，反应后的黑云母边缘部分明显失去K和Fe，应得到相当数量的H2O和一些Ca。黑云母中Fe活化的控制反应可能是H+交代作用。     

煤系高岭岩制取氯化铝和水玻璃实验

本文讨论煤系高岭岩综合制取氯化铝和水玻璃的工艺路线及工艺条件，采用适当的酸浸工艺可使高岭岩的铝浸出率提高到接近100%，使酸渣中的SiO2含量提高到95%左右，其他杂质含量大大降低，为活性硅渣的利用提供保证，采用湿法工艺，加入适当助剂，可在缓和的反应条件下，使硅的转化率达到95%以上，制得合格的水玻璃产品。     

300℃时钯和铂氯络合物稳定性的实验研究

在控制氧逸度和酸度的条件下测定了３０℃时钯和铂氯络合物溶解度，将溶解度资料作用，求得它们的氯络合物种类分别为ＰｄＣｌ＾２－４和ＰｔＣｌ＾２－４，计算了相应反应式的平衡常数及推导了平衡常数与温度从属关系表达式，讨论了实验结果的地质意义。     

邻氯苯基荧光酮胶束光度法测定氮化硅中镁的研究

研究了在氯化十六烷基吡啶（ＣＰＣ）和乳化剂ＯＰ存在下，Ｍｇ与邻氯苯基荧光酮（ｏ－Ｃｌ－ＰＦ）的显色反应。在ｐＨ１２的碱性介质中，Ｍｇ（Ⅱ）与ｏ－Ｃｌ－ＰＦ形成１：３的蓝色配合物，其λ＿ｍａｘ＝６１２ｎｍ，表现摩尔吸光系数ε＿６１２＝１．３９×１０￣５Ｌ·ｍｏｌ￣－１·ｃｍ￣－１，Ｍｇ（Ⅱ）在０～０．２μｇ／ｍｌ范围内符合比尔定律。方法用于新陶瓷材料氮化硅（Ｓｉ＿３Ｎ＿４）中微量ＭｇＯ的测定，其结果与原子吸收光谱法相符。     

由鳕鱼排制备活性钙

为了充分利用鳕鱼排这一丰富的钙资源，本文对干鱼骨粉在不同的酸浓度、温度条件下，用盐酸、乳酸和乙酸提取骨钙的效果进行了研究。结果表明盐酸对鳕鱼鱼骨中钙的提取效果最好，可高达６０％以上；乳酸次之，提取率约为３０％；乙酸的提取率最低。以鱼骨制取的活性钙粉含钙３８．２７％，含磷为１７．７３％，Ｃａ／Ｐ比约为２：１。活性钙粉中Ｃｕ、Ｍｎ、Ｍｇ、Ｆｅ、Ｚｎ、Ｓｅ等微量元素在鱼骨活化处理后有一定的损失。     

Nitrate attenuation in soil and shallow groundwater under a bottomland hedgerow in a European farming landscape

In many agricultural areas, hedgerows give rise to strong expectations of reducing the inputs of excess nitrate to the groundwater and rivers. This study aims to analyse the spatial and seasonal influences of a hedgerow on nitrate dynamics in the soil and groundwater. Nitrate (NO₃^?) and chloride (Cl^?) concentrations were measured with spatially dense sampling in the unsaturated soil and in the groundwater along a transect intersecting a bottomland oak (Quercus rubor) hedgerow after the growing season and during the dormant season. We explain NO₃^? dynamics by using Cl^? as an index of tree‐root extension and water transfer. At the end of the growing season, NO₃^? is entirely absorbed by the trees over a large and deep volume corresponding to the rooting zone, where, in contrast Cl^? is highly concentrated due to root exclusion. However, these observed patterns in the soil have no influence on the deep groundwater composition at this season. During the dormant season, water transfer processes feeding the shallow groundwater layer are different upslope and downslope from the hedgerow in relation to the thickness of the unsaturated zone. Upslope, the shallow groundwater is fed by rainwater infiltration through the soil which favours Cl^? dilution. Right under the hedge and downslope, the rapid ascent of the groundwater near the ground surface prevents rainwater input and Cl^? dilution. Under the hedgerow the highest concentrations of Cl^? coincide with the absence of NO₃^? in the shallow groundwater layer and with high concentrations of dissolved organic carbon. The absence of NO₃^? during the dormant season seems to be due to denitrification in the hedgerow rooting zone when it is rapidly saturated by groundwater. Copyright © 2011 John Wiley & Sons, Ltd.