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11.
J.?GuoEmail author R.?D.?Vogt X.?Zhang Y.?Zhang H.?M.?Seip H.?Tang 《Environmental Geology》2004,45(8):1148-1153
Exchange reactions between Ca2+, H+ and Al species and their effects on the aluminium mobility in two Chinese acidic forest soils were studied. The study was based on a batch experiment using extractant solutions with different base cation (calcium) concentrations and pH. The experimental data showed that increased Ca2+ concentrations increased the release of soil hydrogen—and aluminium ions, especially from the more acid soil. In agreement with a cation exchange process, the treatment with Ca2+ extracts gave significantly decreased soil aluminium saturation (AlS) and increased calcium saturation (CaS) on the ion exchanger. Geochemical calculation using AlCHEMI program showed that activities of Al3+ in the extracts were all strongly under-saturated with respect to any gibbsite mineral in the studied pH region (i.e. below 4.1). There were instead apparently two different mechanisms controlling the activities of Al3+ in extracts. At pH between about 4.1 and 3.7, the Al3+ activity did not change significantly with pH. This is especially the case in the more acid soil. Apparently there are no sizeable pools available to release Al in this pH region. At pH below 3.7 (induced by higher Ca2+concentration) the activity of Al3+ increased with H+ though not in a pattern that complies with a gibbsite solubility control. An increase of base cation deposition would therefore mainly enhance the release of hydrogen ions between pH 4.1 and 3.7 and aluminium ions below pH 3.7 from Chinese mature acidic soils. This will cause an increased acidity of soil water in the short term and a decrease in the soil acidity in the long term. More attention should be paid to this fact in Chinese acid rain studies and control options. 相似文献
12.
Attenuation of Heavy Metals and Sulfate by Aluminium Precipitates in Acid Mine Drainage During the mixing of acid mine waters with nearly neutral tributaries, often precipitates are formed which are high in iron or aluminium. These precipitates cover the river bed for many kilometres. Near the town of Lehesten (Thuringian slate mining area), leachates of slate quarries and waste rock dumps contain high amounts of aluminium, sulfate, copper, nickel, zinc, manganese, and H+ ions as a result of the oxidation of incorporated pyrite. These leachates enter the brooks Loquitz, Kleine Sormitz, and Rehbach leading to the phenomenon named above. The contribution of the forming aluminium‐rich precipitates on the attenuation of sulfate and heavy metals by sorption or coprecipitation was studied by analysing the composition of water and sediment samples as well as samples of suspended matter. Sulfate is often considered as conservative tracer in acid mine drainage. However, sulfate does not behave conservatively in this system what might be explained by the adsorption of sulfate to the aluminium precipitates. Instead, conservative behaviour was found for calcium, potassium, chloride, zinc, manganese, and nickel. A formation of jurbanite can be excluded because of the low sulfate contents. The sulfate content of the sediment depends on the pH. At low pH values (4.8) the S/Al ratio corresponds to the theoretical ratio in basaluminite and decreases with rising pH. Sulfate is weakly bound to the solid phase and can easily be replaced by OH– ions. A formation of basaluminite is possible at low pH values with a fluent transition to aluminium hydroxide. Therefore the precipitates are assumed to consist predominantly of aluminium hydroxide with sulfate being adsorbed to the surface. 相似文献
13.
Gaotaigou borate deposit in Ji'an area, southeastern Jilin, is located in the easten end of Liaoning-Jilin (Liaoji)Proterozoic paleo-rift, which is a medium-sized deposit and makes up 67% of the total borate reserves in Jilin Province.The original borate ore bodies were formed by sedimentary exhalative process in Paleoproterozoic, but were activated and enriched by later metamorphism. In late stage of metamorphism, hydrothermal fluid of metamorphic origin made wallrocks be altered and the borate ore bodies be reformed. Ore bodies are strictly controlled by strata and their lithologies. In addition, the shape and spatial distribution of ore bodies are also defined by the Gaotaigou syncline. Combined with the ore-controlling factors and mineralizing features, it has been proposed that Gaotaigou borate deposit is a metamorphosed and hydrothermally altered sedimentary exhalative deposit. 相似文献
14.
Dissolved aluminium (Al) is generally at low concentrations in neutral freshwater due to its insolubility. However, a fall in pH resulting from acid deposition and mining alters the mobility of Al and so entry to adjacent neutral waters. The present study examines the environmental behaviour, cell-associated surface adsorption/absorption and toxicity of Al at neutral pH to the alga Chlamydomonas gigantea in the presence and absence of the key Al-binding ligand silica. We then examined transfer of Al from C. gigantea to the planktonic crustacean Daphnia pulex. Finally, the effect of Al on the elemental composition (and hence nutritional value) of the two organisms was compared to unexposed controls. C. gigantea increased the amount of Al in the algal culture medium. Binding of Al to extracellular glycoprotein is probably the reason why only one-third of the biosorbed Al was absorbed (accumulated) by C. gigantea. Aluminium concentrations between 50 and 500 μg l−1 reduced growth of C. gigantea at 16 days exposure to the metal. Silica reduced biosorption, accumulation and toxicity of Al by C. gigantea. The concentration of Al in D. pulex fed Al-contaminated C. gigantea for 16 days did not differ from those fed alga grown in the absence of added Al. C. gigantea contaminated with Al contained less sulphur, magnesium, potassium and sodium although only sulphur fell in D. pulex subsequently fed the contaminated alga. Chloride, calcium, iron and silicon were significantly higher in D. pulex. 相似文献
15.
A petrographic investigation revealed polyphase quartz cementation in the Finefrau Sandstone (Upper Carboniferous, Western Germany) and the Solling Sandstone (Lower Triassic, Central Germany). Three different cements could be distinguished in each sandstone based on their cathodoluminescence and trace element composition. The first quartz generation is suggested to have been formed during eogenesis due to dissolution and replacement of feldspar. The mesogenetic paragenesis comprises two generations of quartz and illite, which are accompanied by albite in the Solling Sandstone. Sharp luminescence zoning in quartz overgrowths points to distinct episodes of cementation in both sandstones. Significant amounts of Al, Li and H and traces of Ge and B have been detected in the quartz overgrowths. The Al‐content of the quartz cements in the Finefrau Sandstones exceeds that in the quartz cements in the Solling Sandstone by a factor of five. It is suggested that this compositional variation reflects the conditions in the pore‐water, such as temperature and pH. The Al‐concentration is generally correlated to the Li‐content with the exception of the latest quartz generation in the Finefrau Sandstones which is also most enriched in trace elements. The ratio of Li/Al varies between 0·11 and 0·25 in the two sandstones. The Li/H‐ratio, which ranges from 0·12 to 0·3, is controlled by the activity ratio of Li and H in the pore fluid. Clay minerals are the most important source for Li and high salinities favour the mobilization of Li during diagenesis. Thus, a relatively low salinity and low pH are responsible for the low Li/H‐ratio in the Finefrau Sandstone, while high salinity and neutral to alkaline pH results in a high Li/H‐ratio for the Solling Sandstone. The Ge‐contents are generally near the average of detrital quartz and indicate that pressure dissolution is a major source for quartz cementation. Different chemical compositions of distinct quartz generations indicate changes in the physico‐chemical conditions and point to mobilization of silica from different sources (for example, pressure solution and clay mineral transformations). 相似文献
16.
17.
XIAO Li-mei SUN Feng-yue 《东北亚地学研究》2005,8(1):65-71
Gaotaigou borate deposit in Ji'an area, southeastern Jilin, is located in the easten end of Liaoning-Jilin (Liaoji) Proterozoic paleo-rift, which is a medium-sized deposit and makes up 67% of the total borate reserves in Jilin Province. The original borate ore bodies were formed by sedimentary exhalative process in Paleoproterozoic, but were activated and enriched by later metamorphism. In late stage of metamorphism, hydrothermal fluid of metamorphic origin made wallrocks be altered and the borate ore bodies be reformed. Ore bodies are strictly controlled by strata and their lithologies. In addition, the shape and spatial distribution of ore bodies are also defined by the Gaotaigou syncline. Combined with the ore-controlling factors and mineralizing features, it has been proposed that Gaotaigou borate deposit is a metamorphosed and hydrothermally altered sedimentary exhalative deposit. 相似文献
18.
用电化学方法测量了Mg_2B_2O_5晶须增强AZ91D镁基复合材料在3.5%NaCl溶液中的开路电位、动电位极化曲线和交流阻抗,研究了晶须体积分数对镁合金基体耐腐蚀性能的影响,并利用SEM和XRD表征了腐蚀后复合材料表面的微观形貌和相组成。结果表明,随着Mg_2B_2O_5晶须体积分数的增加,AZ91D镁基复合材料的耐腐蚀性逐渐提高。当硼酸镁晶须的体积分数为35%时,材料的自腐蚀电位提高0.2V以上,自腐蚀流密度降低了1个数量级;SEM测试表明,复合材料表面生成了一层晶须增韧的腐蚀钝化膜,对基体起到保护作用。 相似文献
19.
20.
锌在示波极谱图上具有敏锐的切口,在pH为2~3的HCl-NaCl介质中,可用EDTA直接滴定铝。当滴加EDTA至切口消失时,即达到滴定终点。对红树植物体中铝的分析结果表明:此方法具有直观、操作简便、分析快速的优点,回收率相对误差在10%左右。几种红树体的不同部分铝的质量分数(干重计)分别是:叶为(6.69~29.9)×10~(-3),树干为(1.91~26.8)×10~(-3),常年生树枝为(5.54~29.8)×10~(-3). 相似文献